US3888095A

US3888095A - Stop motion assembly and method

Info

Publication number: US3888095A
Application number: US440138A
Authority: US
Inventors: Morris Philip
Original assignee: Philip Morris USA Inc
Priority date: 1973-03-16
Filing date: 1974-02-05
Publication date: 1975-06-10
Anticipated expiration: 1992-06-10
Also published as: CA1017160A; IT1015847B; BR7401988D0

Abstract

A stop motion assembly comprises a housing in which is mounted a retracting spiral spring tape having a terminal portion projecting from the housing, the tape continuously exerting a retracting force urging the terminal portion toward the housing. On the terminal portion is mounted a yarn vertex holder having spaced apart yarn guides for guiding the vertex of a yarn reach throughout the holder movement, the holder being movable away from a normal retracted position toward an extended position by an extending force, in excess of the retractng force, created by the vertex when normal yarn flow is undesirably impeded upstream of the holder, the retracting force automatically retracting the holder and the vertex to the normal position when elimination of the impediment reduces the extending force below the level of the retracting force. The housing contains a switch for actuating the stop motion control circuit of a knitting machine or the like and a sensor is pivotally mounted on the housing for sensing the position of the holder. The sensor automatically closes the switch when the extending force moves the holder from the normal position, without preventing the extending force from moving the holder toward the extended position after the switch has been closed, and automatically opens the switch when the retracting force returns the holder to the normal position. A releasable catch mounted on the housing prevents the holder from moving from the normal position until the extending force is at a predetermined level in excess of the retracting force.

Description

United States Patent 1 1 Philip STOP MOTION ASSEMBLY AND METHOD [76] Inventor: Morris Philip, 2519 Grand Ave,

Bronx, NY 10468 [22] Filed: Feb. 5, I974 [21] Appl. No.: 440,I38

Related U.S. Application Data [63] Continuation-impart of Ser. No. 341,957, March 16,

1973, abandoned.

[52] U.S. Cl. 66/163; 28/51; 57/81; ZOO/61.13; ZOO/61.18; 242/36 R [51] Int. Cl D04b 35/12 [58] Field of Search 66/157-164; 28/51; 57/81; ZOO/61.13, 61.14, 61.18; 340/259; 139/370; 242/36 R, 157 R, 147 R [56] References Cited UNITED STATES PATENTS 3,571,680 2/1971 Tellerman et a1 66/157 X 3,612,791 10/1971 Porter et a1 i l ZOO/61.18 3,713,308 [[1973 Levin i i i i i i 66/163 3,726,113 4/1973 Levin et al.... 66/163 3,795,120 3/1974 Levin 66/163 3,806,677 4/1974 Deniega et a1, ZOO/61.13 FOREIGN PATENTS OR APPLICATIONS 814,946 6/1959 United Kingdom a 66/161 1,029,717 3/1953 France 66/163 OTHER PUBLICATIONS Primary Examiner-James Kee Chi Attorney, Agent, or FirmMilt0n Osheroff 1 1 June 10, 1975 [57] ABSTRACT A stop motion assembly comprises a housing in which is mounted a retracting spiral spring tape having a terminal portion projecting from the housing, the tape continuously exerting a retracting force urging the terminal portion toward the housing. On the terminal portion is mounted a yarn vertex holder having spaced apart yarn guides for guiding the vertex of a yarn reach throughout the holder movement, the holder being movable away from a normal retracted position toward an extended position by an extending force, in excess of the retractng force, created by the vertex when normal yarn flow is undesirably impeded upstream of the holder, the retracting force automatically retracting the holder and the vertex to the normal position when elimination of the impediment re duces the extending force below the level of the retracting force. The housing contains a switch for actuating the stop motion control circuit of a knitting machine or the like and a sensor is pivotally mounted on the housing for sensing the position of the holder. The sensor automatically closes the switch when the extending force moves the holder from the normal position, without preventing the extending force from moving the holder toward the extended position after the switch has been closed, and automatically opens the switch when the retracting force returns the holder to the normal position. A releasable catch mounted on the housing prevents the holder from moving from the normal position until the extending force is at a predetermined level in excess of the retracting forcev 41 Claims, 6 Drawing Figures STOP MOTION ASSEMBLY AND METHOD CROSS REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of copending application Ser. No. 341,957, filed Mar. 16, 1973 now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention is directed to a stop motion assembly for use with, and to a method of controlling, the stop motion control circuit of a knitting machine or the like for actuating the stop motion control circuit when the normal flow of yarn is undesirably impeded upstream of the vertex of a flexed reach of traveling yarn.

2. Description of the Prior Art Machines such as knitting machines, or similar machines where one or more strands of yarn or similar material of indefinite length are drawn by the machine from a supply, are provided with a stop motion control circuit for stopping the machine when there is a fault or defect in the yarn flow to the machine. Such circuits are generally low voltage circuits which, when actuated, interrupt or terminate the positive drive of the machine. Generally, actuation of the circuit causes actuation of a solenoid or similar device which may either cause the opening of a switch to cut off power to the machine drive or cause the opening of a clutch mechanism to disengage the positive drive of the machine. Such stop motion control circuits, including the devices for interrupting the positive machine drive, are well known in the art and form no part of the invention. It is therefore considered not necessary to describe such circuits in detail, it merely being necessary to bear in mind that the actuation of the circuit causes cessation or interruption of the positive machine drive. In most installations, after the actuation of the stop motion control circuit causes interruption of the machine drive, subsequent deactuation of the circuit does not automatically cause reactivation of the machine drive. The machine drive would generally be manually reactivated.

One or more stop motion devices or assemblies are positioned in the path of each strand of yarn being drawn by the machine from the yarn supply, said devices detecting or sensing faults or defects in the flow of such strand. These devices normally contain a switch which is electrically connected to the stop motion control circuit. When the device senses a fault in the yarn flow, the switch in the device automatically closes to actuate the stop motion control circuit and actuation of the circuit causes termination of the positive machine drive. The fault is then eliminated, generally by the machine operator but sometimes the fault self-eliminates, and normal yarn flow is restored. The switch in the de vice is opened and positive machine drive is then restores, usually by the operator but sometimes automatically. and the machine resumes drawing the yarn.

Such stop motion devices, or stop motion boxes as they are sometimes called, sense one or more of three types of faults in the yarn flow. One type of fault is a break in the continuity of the strand caused by either tearing of the yarn or exhaustion of the yarn supply and this fault is sensed by what is generally called a yarn end detector. A second type of fault is an undesirable drop in the tension of the strand of yarn and this fault is sensed by what is generally called a slack detector. A third type of fault is an undesirable increase in the tension of the strand, as well as a complete cessation, stoppage, or blockage of yarn flow, and this fault is sensed by what is generally called a yarn tension detector. Some devices detect only one of these faults, while others detect several of them. The present invention is particularly directed to devices of the type for detecting the third type of fault, namely increase in yarn tension including stoppage of yarn flow.

It will be appreciated that because of the inherent nature of these machines there must be a time lag between the time the stop motion box actuates the stop motion control circuit after sensing the fault and the time the machine actually stops drawing the yarn. This time lag will hereinafter be called the inertial period and is caused by what may be called machine inertia. It is obvious that some time, no matter how small, must be consumed for the mechanical parts of the stop motion control circuit to move and that a still longer period of time is consumed for the machine to stop after positive drive ceases (flywheel effect). Even with the use of braking devices, it is impossible to stop the machine simultaneously with the closing of the switch in the stop motion box. With modern high speed machines such as circularknitting machines which draw appreciable lengths of yarn in very short periods of time, provision must be made to provide a sufficient length (called inertial slack) of yarn which can be drawn by the machine during this time lag in order to prevent the drawing of the yarn from breaking the yarn as a result of the increased tension or stoppage of the yarn flow. It is this problem with which the present in vention is particularly concerned.

The prior art stop motion boxes which sense increased yarn tension are generally similar in principle to those shown in US. Pat. Nos. 2,515,479 and 3,257,518. These devices comprise a support and a relatively short horizontally extending sensing arm of the order of between one and two inches in length, the inner end of the arm being pivotally mounted on the support about a horizontal pivot so that the outer end can pivot in a vertical plane between an upper horizontal position and a lower inclined position. The box is mounted above two spaced apart yarn guides for sensing the reach of yarn traveling between these guides. This reach is flexed to provide a vertex therein and the vertex is looped about the sensing arm intermediate its ends and guided thereby. If the reach were not flexed, so that the yarn could flow directly between the two guides, the reach would flow in a path which is called the base line of the guides.

The drawing of the yarn from the machine against the drag of the yarn flowing upstream of the vertex creates a tension in the reach of yarn tending to shorten the reach to provide an extending force tending to draw the vertex downwardly toward the base line. Tension means are provided in the box urging the sensing arm to the upper position and to maintain the arm in the upper position when the yarn flow and therefore the extending force is normal. When the flow of yarn upstream of the vertex is impeded to such an extent that the tension inthe reach is raised to an undesirable level, or to such an extent that the flow of yarn completely stops, the extending force created by the drawing of the yarn is sufficient to overcome the tension forces on the sensing arm and the sensing arm is then brought by the vertex to the lower position. During this movement of the sensing arm a switch in the box is closed to actuate the stop motion control circuit to terminate the positive drive of the machine. Because of machine inertia, as previously described, the machine continues drawing the yarn until the machine actually stops. Since usually the machine may draw at least several feet of yarn during this time period, and since the outer end of the arm only moves of the order of an inch or two between the upper and lower positions, the prior art boxes permit the vertex to slide off the sensing arm when the vertex has moved downwardly a distance of the order of one fourth to one inch to permit the vertex and the reach to freely fall toward the base line, thereby relieving the tension in the yarn reach and providing the necessary slack in the yarn for the machine to draw from the time the stop motion control circuit is actuated until the machine stops. lf the vertex were not released from the sensing arm, the drawing of the yarn by the machine would cause the yarn to tear. The stop motion box is spaced sufficiently above the base line to provide the necessary slack. After the vertex has been released from the arm, the tension force on the arm returns it to the upper position to open the switch in the box and deactuate the stop motion control circuit.

When the machine stops, the operator eliminates the impediment and then manually loops the vertex onto the outer end of the arm which is now back in the upper position and then restarts the machine. Returning the vertex to the sensing arm is a tedious and time consuming job. The stop motion box is located an appreciable distance above the machine, generally at least about ten feet from the floor, and the operator must use a stick called a yarn stick to loop the vertex onto the arm. Frequently, the drawing of the yarn by the machine, after the stop motion control circuit has been actuated, creates sufficient tension in the yarn to cause the impediment in the yarn flow to self-eliminate. Nevertheless, the vertex has already been released from the sensing arm and the operator must still return the vertex to the normal position. It is apparent that when the reach falls freely out of the stop motion box it is possible for the slack reach to become entangled with other strands of yarn adjacent thereto.

It has been proposed to greatly increase the length of the sensing arm to permit the outer end to move downwardly a sufficient distance to be able to hold the vertex throughout the movement and at the same time provide sufficient yarn for the machine to be able to continue drawing the yarn until the machine stopsv However, this would require that the yarn be pivoted about an axis transversely displaced from the path of movement of the vertex a distance greater than the maximum distance the vertex moves downwardly during the period of machine inertia. This proposal would produce an expensive, complicated stop motion device which would occupy a great deal of space transverse to the direction of the vertex movement and would eliminate the flexibility in the positioning of the stop motion device on the machine. It will be appreciated that at least 96 stop motion devices would have to be used with a circular knitting machine having 96 feeds and it would be extremely cumbersome and expensive, if not impossible, to have so many devices on such a machine. Such a proposal for lengthening the sensing arm therefore has only limited and expensive application. Furthermore. because of the rigidity of the sensing arm,

the vertex could only move on a very definite predetermined path. lt is frequently necessary to permit the vertex to move transversely to the general direction the vertex moves from the normal position toward the base line. US. Pat. Nos. 3,7l3,308 and 3,726,113 disclose devices utilizing sensing arms of increased length.

US. Pat. No. 3,57l,680 discloses a device wherein the guides for the yarn vertex are carried at the end of a tape which is wound on a roller geared to a reversible DC electric motor. When the yarn tension overcomes the resistance of the roller gears and motor rotor, the vertex will pull the end of the tape downwardly from its upper normal position to rotate the roller, gears and rotor, thereby unwinding the tape from the roller. Electric circuit control means are provided to permit the operator to select the direction in which the current flows through the motor so that the motor either tends to rotate the roller to wind up the tape, thus applying an upward force to the tape, or tends to rotate the roller to unwind the tape, thus applying a downward force to the tape. The control means also permits varying the current flow to vary the force exerted by the motor. By means of this control, the operator can operate the motor to move the tape either downwardly for gaining easy access to the guides for rethreading, etc., or upwardly so that the guides can be restored to their normal operating condition. Furthermore, in a normal operating position of the tape, the control means can be adjusted so as to apply to the tape a selected upward or downward force to adjust the resistance which the increased yarn tension will have to overcome to move the tape downwardly to activate the stop motion control circuit. The vertex in the normal position supports a pivotally mounted fly wire. Unwinding the tape frees the wire to swing out of the path of the vertex, whereupon the fly wire closes a switch which actuates the stop motion control circuit. When the yarn tension is reduced to normal, the operator operates the control means to move the tape upwardly to the normal position and manually pivots the fly wire to open the switch and position the wire on the vertex. Although this device eliminates the free falling vertex, it does not auto matically return the vertex to its normal position, nor does it eliminate the use of the yarn stick, since the latter must be used to reset the fly wire.

In US. Pat. No. 3,227,833 there is disclosed a device wherein the guide for the vertex guides and retains the vertex throughout the vertex movement. This vertex guide is mounted on the end of a rod which can reciprocate essentially in the path that the vertex moves when the yarn tension is increased. However, in this device movement of the rod, and therefore, the vertex, toward the base line is halted as soon as the switch is closed. The vertex guide is therefore not free to move during the period of machine inertia and drawing the yarn breaks the yarn. In this patent this reciprocating rod is supported by a transversely extending pivotable beam so that this construction inherently also has deficiencies of the previously described proposal for lengthening the sensing arm.

In US. Pat. No. 3,612,791 and German patent publication No. l,26l,267, there are disclosed stop motion devices wherein the vertex guide is mounted on a mov able holder which has a counterweight attached thereto to maintain the holder and the guide thereon in the normal position when yarn tension is normal. When the yarn tension increases above the normal the holder is moved, against the force of the counterweight, in a first direction away from the normal position and the stop motion control circuit is actuated. When the yarn tension drops below normal, the counterweight moves the holder away from the normal position in a direction opposite the first direction, and the stop motion control circuit is again actuated. When the yarn flow has been impeded to increase the yarn tension sufficiently to stop the machine, elimination of the impediment usually drops the yarn tension to below normal. Therefore, in these devices, the holder will not automatically return to the normal position since elimination of the impediment, when the machine is stopped, will cause the counterweight to move the holder from one side of the normal position to the other side and the stop motion control circuit will still remain actuated. Furthermore, these devices will occupy a great deal of space above the machine.

SUMMARY OF THE INVENTION The present invention is directed to solving the problems of the prior art. It is directed to a stop motion assembly wherein the vertex is always guided and retained by the vertex guide means of the assembly throughout the vertex movement, thereby eliminating the free falling reach of yarn during the period of machine inertia. The yarn reach is maintained taut throughout the movement of the vertex. The assembly automatically returns the vertex to the normal position after the impediment in the yarn flow has been eliminated, thereby eliminating the need for the operator to manually reloop the vertex about the sensing arm. The stop motion control circuit is also automatically deactuated, thereby eliminating the need for the yarn stick. The invention also provides a structure which eliminates the need for a long sensing arm extending transversely to the direction of vertex movement so that the assembly does not occupy any significant increased transverse space. The stop motion assembly of the invention can therefore be substantially as small as the stop motion box is described in Us. Pat. Nos. 2,5l5,479 and 3,257,5l8.

Briefly stated, to accomplish these and other purposes, the structure and method of the invention provide a continuous longitudinally lengthenableshortenable connection between the vertex guide and a support to mount the guide for longitudinal reciprocating movement between a normal guiding position and a terminal guiding position, the guide retaining and guiding the yarn vertex of the yarn reach being sensed throughout the guide movement. A retracting force is provided for urging the guide away from the terminal position toward the normal position, the retracting force being greater than the extending force created by the drawing of the yarn by the machine when the yarn flow is normal. When the yarn flow is impeded to the predetermined undesirable level, the extending force created by the drawing of the yarn exceeds the retracting force and moves the vertex guide away from the normal position toward the terminal position. The stop motion control circuit actuating switch is closed at the appropriate time without preventing the increased extending force from continuing to move the guide toward the terminal position, as the machine continues drawing yarn because of machine inertia, until the impediment self-eliminates or the machine stops drawing the yarn, whereby when the impediment is eliminated by self-elimination or otherwise to reduce the extending force to a level below that of the retracting force, the retracting force automatically returns the guide, guiding the vertex, to the normal position, the reach of yarn being sensed remaining taut by the interplay of the extending and retracting forces. The stop motion control circuit actuating switch is automatically reopened so that machine operation can be resumed.

According to a preferred aspect of the invention, the connection and the retracting force are provided by a spring actuated retracting spiral coil tape mounted on the support, the guide being mounted on the terminal portion of the tape. More preferably, the retracting spiral coil tape is a retracting spiral spring tape, that is, one in which at least some of the tape coils are resilient to provide the spring actuation, and most preferably is one in which all of the coils are resilient. Preferably, the guide is not released from the normal position until the extending force has been increased to a level greater than the minimum force needed to exceed the retracting force, so that the guide moves sufficiently freely after it has been released to reduce or relieve the tension in the yarn.

It is an object of the invention to provide an efficient stop motion assembly and method for providing adequate yarn slack during the inertial period and for automatically returning the yarn vertex to its normal posi tion after elimination of the impediment in the yarnflow.

It is a further object of the invention to provide a stop motion assembly and method wherein the stop motion control circuit is automatically actuated and deactuated.

It is a further object of the invention to provide an assembly and method wherein the yarn reach is maintained taut during the inertial period while minimizing the possibility of the yarn tearing.

These and other objects and aspects of the invention will be readily apparent from the description herein.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings,

FIG. 1 is a front elevation, substantially to scale, of the stop motion assembly of the invention, the front covers being partially broken away to show the elements inside the housing, the assembly being shown in the installed position relative to a fragmentary portion of the strand of yarn being sensed;

FIG. 2 is a horizontal cross section taken along the line 2-2 of FIG. 1',

FIG. 3 is an enlarged fragmentary cross section taken along the line 3-3 of FIG. 1;

FIG. 4 is an enlarged perspective view of the yarn vertex holder showing its attachment to a fragmentary portion of the tape;

FIG. 5 is a top elevation of the assembly;

FIG. 6 is a front elevation of a fragmentary portion of the catch chamber, without the cover, showing a modification.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring particularly to FIGS. 1-3, the illustrated embodiment of the stop motion assembly of the invention is provided with a support in the form of a generally U-shaped unitary enclosed casing or housing I for containing or supporting the various elements of the assembly. The housing 1 is fashioned in the form of three adjoining generally rectangular box-like covered chambers or compartments, namely, retractor chamber 2, catch chamber 3, and switch chamber 4.

Retractor chamber 2 has a back or bottom 5 from which extend forwardly directed upper end wall 6, lower end wall 7, left side wall 8 and right side wall 9, the walls defining the substantially square periphery of chamber 2. The walls are provided at spaced apart thickened locations with bores for threadedly receiving self-tapping screws 10 which removably secure cover plate 11 over the open front of chamber 2. In a similar manner, catch chamber 3 has a back or bottom 12 from which extend forwardly directed upper end wall 13, lower end wall 14, left side wall 15 and right side wall 16, the walls being provided at spaced apart thickened locations with bores for threadedly receiving selftapping screws 17 which removably secure cover plate 18 over the open front of chamber 3, the walls defining the generally oblong periphery of chamber 3, the longer dimension of the oblong being vertical. Switch chamber 4 has a back or bottom 19 from which extend forwardly directed upper end wall 20, lower end wall 21, left side wall 22, and right side wall 23, the walls being provided at spaced apart thickened locations with bores for threadedly receiving self-tapping screws 24 which removably secure cover plate 25 over the open front of chamber 4, the walls defining substantially square periphery of chamber 4.

Retractor chamber 2 is located above switch chamber 4 but offset to the right therefrom, the right hand portion of upper end wall of chamber 4 being con tiguous and integral with the left hand portion of lower end wall 7 of chamber 2, and the remainder of lower end wall 7 projecting to the right of right side wall 23 of chamber 4. Catch chamber 3 is to the right of retractor chamber 2 but offset downwardly therefrom, the lower portion of right side wall 9 of chamber 2 being contiguous and integral with the upper portion of left side wall 15 of chamber 3, and about the lower half of catch chamber 3 extending below lower end wall 7 of retractor chamber 2. As is readily apparent from FIG. 1, this arrangement provides the housing with its inverted U-shape. switch chamber 4 defining the left leg of the U, the lower portion of catch chamber 3 being spaced apart from switch chamber 4 and defining the right leg of the U, and retractor chamber 2 interconnecting the two legs. The space between the legs, namely, the space bounded by catch chamber 3, switch chamber 4 and retractor chamber 2, forms a recess or bay 26.

in the illustrated embodiment, the housing, except for the cover plates, is a single metal casting, the backs and walls of the chambers being integral. Obviously, the three chambers can be separately cast and then joined to provide a unitary housing. In the illustrated embodiment. back 5 of chamber 2 and back 12 of chamber 3 are coplanar (see FIGS. 3 and 5) as are the

covers

18 and 25, respectively, of these chambers. The depth of chamber 3 is therefore equal to that of chamber 2. Chamber 4 is somewhat deeper and as is readily apparent in FIG. 5, the

shallower chambers

2 and 3 are disposed substantially centrally of the depth of chamber 4. In other words, the medial plane 27 (shown in phantom) of the housing substantially coincides with the medial planes of the three chambers. Preferably, as illustrated, the chambers do not communicate with each other to prevent oil, lint, dust, etc., from passing from one chamber to the next.

Retractor chamber 2 is provided with a post or arbor 28 having a cylindrical head 29 and an externally threaded cylindrical shank 30, said shank extending rearwardly and coaxially from said head. The shank 30 has a diameter less than that of the head so that the junction of the shank and the head defines an annular shoulder 31 intermediate the length of the arbor 28. Back 5 of chamber 2 is provided with a smooth circular bore defining a bearing 32 for rotatably receiving therethrough shank 30, said bearing having a diameter less than the diameter of the shoulder 31. The arbor is positioned in chamber 2 with head 29 within the chamber and shank 30 extending through bearing 32 to project from the outer surface of back 5. A nut 33 is in threaded engagement with the external threads of the projecting part of shank 30, and when the nut is tightened against the outer surface of back 5, head 29 is urged rearwardly until shoulder 31 abuts the front or inner surface of back 5 around bearing 32 sufficiently to prevent arbor 28 from rotating about its axis. A transverse pin or key 34 is force fitted into a transverse bore in shank 30 rearwardly of nut 33 to act as a handle or key for rotating the arbor on its axis. When it is desired to rotate the arbor, nut 33 is loosened, the arbor is rotated by means of key 34 to the desired position, and the nut is again tightened to jam the shoulder 31 against back 5 to again immobilize the arbor against further rotation.

The head 29 is provided with a slot 35 extending diametrically therethrough from the front end of the head to about the shoulder 31. A slot 36 is provided in lower end wall 7 adjacent right side wall 9, said slot providing communication between the interior of chamber 2 and bay 26 adjacent catchchamber 3. A spirally wound retracting spring tape 37 is positioned in retractor chamber 2 about head 29, the innermost end 38 of the tape being received in slot 35 to fix said end to the head. The remainder of the tape is coiled about the head of the arbor withthe outermost coil of the tape terminating in a downwardly extending terminal tape portion 39 beginning at about 39, the exposed or lower or free end portion 40 of the terminal tape portion projecting or extending downwardly out of chamber 2 through slot 36 into bay 26, said exposed tape portion 40 being that portion of the tape extending out of the retractor chamber. As will be seen hereinafter, the amount of tape projecting out of chamber 2, the length of exposed tape portion 40, is variable so that the length of terminal tape portion 39 varies therewith. There may be a variation in the length of the part of terminal tape portion 39 in the chamber but this variation is relatively insignificant compared to the variation in the length of exposed tape portion 40.

Exposed tape portion 40 is provided with vertex guide means for retaining and receiving the vertex of the reach of traveling yarn being sensed by the stop motion assembly and in the illustrated embodiment, such vertex guide means is constituted by a yarn vertex holder 41 secured to the exposed tape portion 40 adjacent its free or terminal edge. The yarn vertex holder 41 (See FIG. 4) is constituted by two U-shaped members, a first or main U-shaped member 42 comprising a central web 43 from whose ends transversely extend laterally spaced apart opposed wings 44, and a second or auxiliary U-shaped member 45 comprising a central web 46 from whose upper end transversely extends a short upper arm 47 and from whose lower end transversely extends a longer lower arm 48 downwardly spaced apart from upper arm 47. As shown in FIG. 3, the length of central web 43 (the distance between wings 44) is greater than the width of tape 37 and the depth of

chambers

2 and 3, while the width of web 43 is slightly greater than the length of the web 46 (the distance between arms 47 and 48), The width of web 46 is about the same as the width of tape 37, the width of

arms

47 and 48 being slightly less than the width of the tape.

The U-shaped members and tape are assembled as shown in FIG. 4 by superposing web 46 on web 43 with the lower end of exposed tape portion 40 sandwiched between the webs, the tape extending upwardly from upper edge 49 of web 43. Rivets 50, passing through aligned bores in the superposed webs and tape, secure the U-shaped members to each other to constitute the yarn vertex holder 41 and to secure the holder to the tape end. Member 45 and the tape are positioned inside member 42 centrally between wings 44, the length of web 46 and the length of the terminal tape portion running perpendicular to the length of web 43. The upper surface of arm 47 is substantially aligned with upper edge 49 of web 43 with lower arm 48 and terminal edge of the tape not extending below the lower edge of web 43, whereby lower edge 51 provides the lowermost surface of the holder. When terminal tape portion 39 is of minimum length the holder 41 is in bay 26 in the holder's maximum retracted position (shown in solid lines in FIG. 1) and the posterior surface 52 of the holder is adjacent and substantially parallel to the exterior of left side wall of catch chamber 3, the wings 44 and

arms

47 and 48 extending transversely toward switch chamber 4, medial plane 27 passing through each arm to dispose the wings on opposite sides of the medial plane.

Each of wings 44 is provided with a yarn retaining and guiding yarn guide which, in the illustrated em bodiment, is constituted by a laterally extending ceramic guide eyelet or grommet 52 cemented into a seat or bore 54 near the end of its respective wing 44. It is apparent that the eyelet can be made of any conventional hard or wear-resistant material used in the art for such guide eyelets and that it can be fastened into its seat in any conventional manner.

Spiral spring tape 37 exerts a first or retracting force or tension which continuously attempts to retract exposed tape portion 40 into chamber 2, that is, continuously attempts to shorten the length of terminal tape portion 39 to bring the terminal edge of the tape closer to lower end wall 7. This resilient first force, acting in the direction of arrow 55, continuously urges the exposed tape portion 40 and therefore the yarn vertex holder 4I secured thereto in the direction of arrow 55 toward slot 36 in lower end wall 7 of the retractor chamber. In the illustrated embodiment, the tape is made of one length of resilient material such as spring steel and the tape in its unwound relaxed condition is normally substantially straight. When the tape has its innermost end 38 fixed in slot 35 or arbor head 29, and

is spirally wound or coiled in a plane about the arbor head with the coils increasing in diameter away from the arbor head, the resiliency of the metal causes the coils to continuously attempt to uncoil or expand in the plane of the spring to withdraw or retract exposed tape portion 40 in the direction of arrow and thereby continuously urges yarn vertex holder 41 in the direction of arrow 55 toward the outer or lower surface of lower end wall 7 of chamber 2. Retraction causes reduction of the length of the exposed tape portion so that it can be said that terminal tape portion 39 contracts in the direction of arrow 55. The width of the tape is less than the depth of chamber 2 to'minimize frictional contact between the tape edges and the inte' rior surfaces of the chamber.

The retracting spiral spring tape 37 is similar in structure to a clock mainspring or to the spring tape used in retractable metal measuring tapes, but it functions like the latter, rather than the former. In a clock mainspring the outer coil is fixed and during winding the inner end of the spring is rotated, thereby increasing the number of coils. As the mainspring unwinds, the number of coils decreases. On the contrary, in a retracting spiral spring tape, as well as in a retractable measuring tape, the inner end of the tape is fixed and the outer end is free, so that extension of the outer free end does not change the number of coils but merely reduces their diameter. Releasing the outer end permits the resiliency of the coils to increase the diameter of the coils to retract the outer end of the tape without changing the number of coils.

Stop means are provided to determine the maximum retracted position of holder 41, that is, the position wherein the length of the exposed tape portion is at its minimum. In the illustrated embodiment, such stop means are constituted by part of the upper surface of upper arm 47 and the portions of upper edge 49 of central web 43 which extend laterally from the edges of tape 37. When such stop means abut the lower exterior surface (that facinb bay 26) of chamber 2 adjacent slot 36, further retraction is prevented.

Although, in the illustrated embodiment, tape 37 is made of one length of spring steel, it obviously can he made of plural lengths (not shown) of such steel secured to each other. Alternatively, only the inner coils of the spring tape need be resilient and the outer coils can be made of any appropriate material, metal or nonmetal, which can be wound into a coil (not shown). Ob viously, in any of these constructions the tape need not be constructed as illustrated of a substantially elongated flat piece of material wider than the thickness. The tape can obviously be constituted by a single nar row strip, or strand, or wire, etc., or it can be constituted by a plurality of such strips or strands or wires, etc., laterally spaced apart or laterally abutting (not shown). IN all such retracting spiral spring tapes the number of coils remains constant as the tape is extended and retracted. In the preferred and illustrated embodiment, all of the tape coils are resilient.

The strength or level of the retracting force or tension provided by spring tape 37 can be varied by rotating the arbor 28. When it is desired to increase the spring tension, that is. increase the level of the retracting force acting in the direction of arrow 55, nut 33 is loosened, arbor 28 is turned by means of key 34 in the counterclockwise direction as seen in FIG. 1 until the desired degree of tension is obtained, and the nut 33 is then tightened. To reduce the tension, the arbor is rotated in the opposite direction. When the arbor is rotated to increase the tension the number of coils is increased and when rotated to reduce the tension the number of coils is decreased.

The tension in spring tape 37 should be at least strong enough for the retracting force, acting against a normal extending force exerted by the tension in the yarn reach being sensed (as will be later described), to retract the yarn vertex holder 41 to a normal retracted position, which is the maximum retracted position in the illustrated embodiment. It will be appreciated that if the normal retracted position is such that the holder is below the maximum retracted position with the stop means not abutting the lower exterior surface of chamher 2, the spring tape tension will have to be critically adjusted to stop retraction at precisely such a normal position, the retracting force continuously functioning only when the holder is away from (in a direction opposite arrow 55) such normal position. Such adjustment is difficult to obtain. in order to avoid the need for such critical adjustment, it is preferred to have the retracting force continuously acting on the holder all the time, even in the normal retracted position, and provide the positive stop means for determining the normal retracted position whereby the latter then coincides with the maximum retracted position. This is accomplished by providing sufficient tension in the spring tape to ex ceed the minimum necessary to retract the holder to the normal position. Therefore, it will be understood that the invention comprehends the retracting force continuously acting on the holder at least during the time the holder is away from the normal retracted position, and preferably, all the time. In either event, the retracting force will return the holder to the normal retracted position.

When a second or extending force, greater than and generally opposed to the first or retracting force, is ap plied to the yarn vertex holder 41 in the normal retracted position, the holder will be extended or moved away from lower end wall 7, in a direction generally opposite to that of arrow 55, toward a remote extended position 41A (in phantom in FIG. 1) outside of bay 26, the holder passing through an infinite number of intermediate positions, two of which are shown in the bay in phantom in 418 and 41C. This movement extends exposed tape portion 40 from the housing by expanding or lengthening it, thereby contracting or decreasing the diameter of the tape coils inside chamber 2 to increase the tension of the spring tape. Unless otherwise stopped, the second force will continue moving the holder away from the bay until the coils inside chamber 2 have been so contracted that no further contraction is possible so that there is an inherent maximum extended position beyond which holder 41 cannot be moved and in this position the exposed tape portion 40 is at its maximum length. By way of example, if the length of the tape is about 8 feet long, the length of exposed tape portion 40 will be about two-thirds of the length of the tape when the holder is in the maximum extended position.

When the extending force is eliminated or reduced to a level lower than that of the retracting force, the retracting force automatically retracts or moves the holder in the direction of arrow 55 to bring the holder to the normal retracted position. It will be apparent that the movement of the holder is essentially controlled by the interplay of the extending and retracting forces. The extending force urges the holder in a direction away from the normal retracted position toward the maximum extended position to cause extension of the exposed tape portion. On the other hand, the retracting force, at least when the holder is extended away from the normal retracted position, continuously urges the retraction of the exposed tape portion to urge the holder in a direction away from the maximum extended position toward the normal retracted position. Actual movement of the holder is determined by whichever of the two forces is greatest, unless other forces are interposed, such other force being interposed in the illustrated and preferred embodiment to restrain the start of the extending movement.

For purposes of orientation, the location of the maximum extended position is defined as being longitudinally remote from the normal retracted position. As a result, the extending and retracting forces act in a longitudinal direction, the holder during extension and retraction moves in a longitudinal direction, the exposed tape portion extends and retracts in a longitudinal direction, and the courses traced by the holder during extension and retraction extend longitudinally. The longitudinal direction is a general direction and therefore these definitions apply even though, as will be evident hereinafter, the holder does not necessarily move in a straight course during either extension or retraction and even through the extension course is not necessarily coincident or even parallel with the retraction course. In fact, in the illustrated embodiment, the courses are neither straight, nor coincident, nor parallel, although they are substantially so. Throughout thisapplication the word longitudinal is used in the sense defined herein unless the context clearly indicates otherwise.

Before proceeding to describe the remaining structure of the stop motion assembly, there will be described, by way of example, the manner in which the yarn reach being sensed by the assembly is retained and guided by yarn vertex holder 41. The housing 1 is provided with an exterior mounting ear 56 by which the assembly is secured in any conventional manner to an overhead mounting frame or bracket (not shown) of the stop motion control circuit (not shown), the assembly being mounted above an upstream main yarn guide G1 and adjacent downstream main yarn guide G2, guides G1 and G2 being mounted on the machine frame (not shown) or any other appropriate support. These guides are called main guides not because they are necessarily more important than any other guides, but because the yarn flowing between these guides defines the reach of yarn being sensed. When referring to one of these guides as being adjacent to the other guide it does not mean that they are necessarily close to each other. As a matter of fact, they can be spaced apart an appreciable distance both vertically and horizontally. Rather, it is meant that guide G2 is the next main guide through which the yarn flows after leaving guide G1, so that these guides are functionally adjacent.

The yarn flows in the direction indicated by arrows 57, directly or indirectly from a yarn supply (not shown), such as a yarn cone. through upstream main guide G1, then through the upstream holder guide 53, then through the downstream holder guide 53, then through downstream main guide G2, and finally directly or indirectly to the knitting machine (not shown) which draws the yarn from and through guide G2, thereby providing the force for moving or flowing the yarn through its path from the supply. By indirectly" it is meant that the yarn may first pass through structures conventionally interposed, as appropriate. in the path of yarn flow such as other guides, additional stop motion devices, tensioning devices, etc. (all not shown). An upstream location or element is one functionally closer, along the flow path of the yarn, to the yarn supply than is a corresponding downstream location or element. Either one of holder guides 53, depending upon the positioning of the stop motion assembly relative to guides G1 and G2 can be selected as the upstream holder guide with the other one being the downstream guide. In the illustrated example, the left hand holder guide 53, as seen in FIG. 3, is the upstream guide.

The reach of yarn traveling from guide G1 to guide G2 is the reach being sensed and is defined by an ascending or upstream branch Y1 extending from guide G1 to upstream guide 53, a yarn vertex Y2 extending beyond guides 53, and a descending or downstream branch Y3 extending from downstream guide 53 to guide G2, the yarn vertex being the portion of the reach retained and guided by the holder and is the portion of the reach where the reach is bent or flexed to change or reverse the direction from ascending to descending. In FIG. 1 branches Y1 and Y3 are shown in solid lines when the holder is in the normal retracted position and in phantom when the holder is in intermediate position 41C or extended position 41A, the branches not being shown when the holder is in intermediate position 418 for the purpose of clarity. The vertex Y2 is clearly shown in FIGS. 2 and 3.

The yarn is drawn by the machine from guide G2 against the drag of the yarn flowing upstream of upstream holder guide 53 to provide a tension in teh yarn reach when the yarn is being drawn. No matter how freely the yarn may flow from the supply there is always some tension in the yarn reach, even if merely from friction in the guides, although it may at times be very small, when the machine is operating properly. This tension in the yarn reach tends to shorten the yarn reach and this tendency to shorten the yarn urges vertex Y2 toward the base line B ofguides G1 and G2. The base line B, shown in phantom in FIG. 1, is the path which would be taken by the yarn reach, as the yarn travels from guide G] to guide G2, if the yarn were not retained and guided by holder guides 53. Since the vertex is continually retained and guided by holder guides 53, the urging of the vertex to move toward the base line constitutes the second or extending force on the vertex holder acting in a direction generally opposed to the direction of the retracting force exerted on the holder by spring tape 37. In other words, said extending force acts in a direction generally opposite that of arrow 55.

The strength of the extending force is therefore related to the tension in the yarn reach caused by the drawing of the yarn by the machine against the drag of the yarn flowing upstream of the vertex, said extending force increasing when the drag, and therefore the yarn tension, increases. When the extending force exceeds the retracting force, the holder will move longitudinally toward base line B and when the retracting force exceeds the extending force, the holder will move longitudinally toward the normal retracted position. When the yarn drag, and therefore the yarn flow, is normal, the retracting force exceeds the extending force and the holder will either bbe retained in the normal retracted position or, if the holder is away from the normal retracted position. it will be returned thereto. However,

when the yarn flow is impeded upstream of the vertex sufficiently to increase the extending force to a level greater than the retracting force, the extending force will move or extend the vertex, and therefore the holder, against the pull of the retracting force, toward base line B to an extended position. When the impediment is eliminated to reduce the extending force to a level below that of the retracting force, the holder will be retracted toward the normal retracted position. It is pointed out that usually most of the yarn drag occurs upstream of upstream main guide G] and usually when there is an impediment in the yarn flow, such impediment is also upstream of guide G1.

Because of the enclosed nature of guides 53, the vertex is never released from the holder throughout the holder movement except, of course, when the yarn breaks or is exhausted. Laterally spaced apart yarn guides 53 therefore define a laterally extending vertex guiding passageway or corridor 58 which retains and guides the vertex of the flexed reach throughout the movement of the holder and the holder therefore comprises a yarn vertex guide means for retaining and guiding the vertex throughout the movement.

It is preferable to provide means for preventing or restraining the extending force from moving the holder away from the normal retracted position until the extending force has been increased to a predetermined actuating level, which level is greater than the minimum force necessary to exceed the retracting force. Stated differently, such means prevents movement of the holder until the yarn flow has been impeded upstream of the vertex to such an extent that the tension in the yarn reach arrives at an undesirable level or to such an extent that the yarn flow upstream of the vertex is completely halted. In the illustrated embodiment, such a restraining means is provided by releasable catch 59 interposed between the holder and the base line.

Releasable catch 59, pivotally mounted in catch chamber 3, has a generally horizontal body portion 60, a tail piece 6] depending downwardly from the inner end of body 60, and an outwardly tapered nose portion 62 extending outwardly from the outer end of body 60. The nose portion 62 is composed of an upper bevel 63 and a lower bevel or lip 64. Upper bevel 63 extends obliquely downwardly and outwardly from the body and lower bevel or lip 64 depends obliquely downwardly and inwardly from the outer end of the upper bevel. A pair of laterally spaced apart ears 65 extend upwardly from the upper side of body near tail piece 61 and a headed bolt or pintle 66 having a threaded end 67 is journaled in aligned bores in cars and passed through washer or spacer 68 between the rear ear and back 12, the threaded end 67 being threaded through a threaded bore in chamber back 12. The pintle 66 is tightened sufficiently to secure catch 59 in the chamber 3 but not sufficiently to prevent the catch from pivoting around the pintle. A jam nut 69 is threaded onto the threaded end 67 projecting outside of the catch chamber to prevent the pintle from shaking loose. Left side wall 15 is provided with a slot or cutout 70 therethrough which provides communication between the interior of catch chamber 3 and bay 26, nose portion 62 extending outwardly through slot 70 into bay 26. Slot 70 extends downwardly from upper margin or stop surface 71 to lower margin 72.

A downwardly extending leaf or flat spring 73 has its upper end secured to the inside of right side wall 16 by means of screw 74 and the lower or free end 75 of the spring resiliently engages the lower end of tail piece 61 to constantly urge the catch to pivot upwardly (clockwise as viewed in FlG. 1) about pintle 68 until the upper surface of the catch adjacent the inner end of upper bevel 63 abuts stop surface 71 to prevent further upward movement. The catch in this upper position, which is the normal or locking position, is shown in solid lines in FIG. 1, body 60 being substantially horizontal. The catch is pivotable downwardly or counterclockwise against the resilient force of spring 73 to the lower or releasing position shown in phantom in FIG. 1. A tension adjusting threaded bolt 76 is threaded through a threaded bore in right side wall 16 so that the inner end 77 of the bolt presses against spring 73 intermediate its length, tightening or loosening the bolt varying the tension or resilient force applied by the spring against tail piece 61. A jam nut 78 serves to lock bolt 76 in its desired position to prevent the bolt from shaking loose.

When the catch is in the upper or locking position, nose portion 62 is in its uppermost position, and, because the body 60 is substantially horizontal and below the pintle axis, the nose portion extends substantially the maximum distance out of catch chamber 3 in bay 26 toward chamber 4. As the catch is pivoted downwardly, the nose portion also moves downwardly and withdraws or retracts away from chamber 4, into chamber 3, the length of slot 70, namely, the distance or spacing between stop surface 71 to lower margin 72, being sufficiently great for lower lip 64 of the nose portion to clear the lower margin as the nose portion retracts into chamber 3. When the yarn vertex holder is in the normal retracted position, which is the maximum retracted position in the illustrated embodiment, and the catch is in the locking position, as shown in solid lines in FIG. 1, the nose portion projects outwardly from chamber 3 sufficiently to project under the holder in bay 26 and particularly under lower edge 5] of web 43 of the holder. Although lower edge 51 can be vertically spaced apart from upper bevel 63, in the preferred and illustrated embodiment of the invention, lower edge 51 abuts upper bevel 63 near the latters inner end to snugly confine the holder between the catch and lower end wall 7 of the housing, preventing the holder from rattling.

It will be apparent, therefore, that the transverse projection of the catch nose portion under lower edge 51 of the holder will interfere with, or block movement of, the holder when the extending force exceeds the retracting force and therefore attempts to move the holder longitudinally from the normal retracted position in a direction opposite arrow 55. In order forthe extending force to be able to move the holder, the level of the extending force must exceed the sum of the retracting force and the upward force exerted on the catch by the tension of spring 73 in order to produce a force capable of moving the catch out of the blocking position. When the extending force has been increased to this level, the extending force is at the actuating level. The tension in spring 73 is appropriately adjusted to predetermine that the extending force be at the actuating level when the yarn flow has become impeded to an undesirable extent. The extending force at the actuating level will move the holder longitudinally to intermediate position 41B. During this movement the abutment of lower edge 51 of the holder and upper bevel 63 of the catch will cam or pivot the catch downwardly to cause retraction of the nose portion into catch chamber 3. When the holder is in intermediate position 418 the catch is in the releasing position wherein it has been withdrawn into chamber 3 sufficiently for lower edge 51 to clear or pass the outer extremity of the nose portion and the holder is free to cintinue moving toward extended position 41A. As soon as the holder arrives at the releasing position 418, the downward force on the catch is removed and the catch is free to be pivoted upwardly to the locking position by spring 73. As the catch is moving upwardly the nose portion is moving outwardly of chamber 3 so that its outer extremity will rub against the posterior 52 of the holder to push the holder in the direction of switch chamber 4. All this time the holder is still moving downwardly toward the base line so that when it arrives at intermediate position 41C (the switch actuating position), the holder, as well as exposed tape portion 40, have been slightly displaced away from catch chamber 3, the position of exposed tape portion 40 being shown in phantom.

The extending force continues to move the holder downwardly toward extended position 41A, the tape sliding along the outer extremity of the nose portion. When the level of the extending force is reduced below the level of the retracting force, the retracting force will then automatically urge holder 41 upwardly. During the upward movement the catch is in the upper locking position and therefore when the holder has been raised upwardly to about the level of 41B the holder will still be displaced closer to switch chamber 4 than it was in position 413. Nevertheless, the holder still can move upwardly until lower edge 51 passes the outer extremity of the nose portion and at that time the holder will move closer to chamber 3 to return the holder to the normal retracted position shown in solid lines in FIG. 1. The rivets 50 are substantially flush or smooth on the posterior 52 in order not to interfere withthe sliding of the nose portion against the holder posterior. The angle and shape of lower bevel 64 assists the passage of upper holder edge 49 past the nose portion during the retraction movement.

The holder does not pause at the intermediate positions and the movement is continuous during retraction and continuous during extension. It will be appreciated that in the illustrated embodiment the holder, as it moves between the normal retracted position and extended position 41A, does not move in a straight line either during extension or retraction. Furthermore, the course traced by the holder during extension does not exactly coincide with the course traced during retraction, although they generally coincide. It is also apparent, as shown in FIG. 1, that the exposed tape portion does not define a straight line when the holder is out of the bay, either during retraction or extension. Nevertheless, the movements, courses. etc.. are all longitudinal. The transverse flexibility of the tape readily permits the bow or bend in the exposed tape portion opposite the nose of the catch when the holder is out of the bay and this flexibility also permits the upwardly moving catch to move the holder transversely as the holder passes it.

An inwardly extending L-shaped flange 79 is provided on the inside of lower end wall 21 of switch chamber 4 and an insulator block 80 is provided with an L-shaped cutout or groove 81 generally corresponding in shape to the flange to be capable of snugly receiving the flange. The insulator block is slid into the chamber, flange 79 being received within cutout 81, so that the insulator block extends substantially the length of the interior of wall 21, the mating of the flange and cutout serving to fix the insulator block in the chamber.

Lower end wall 21 and the insulator block 80 are appropriately bored to provide bayonet socket 82 for receiving the base 83 of a bayonet base electrical bulb 84, said socket providing communication between the interior of chamber 4 and the exterior thereof through wall 21 and insulator block 80. The bulb 84 can be removably inserted into the socket so that the bulb globe is on the outside of the chamber with a portion of the bulb base 83 and central bulb contact 85 being inside the chamber. the base and central contact being electrically insulated from the housing.

Left side wall 22 is provided with a slot 86 providing communication between the interior and exterior of the chamber. An L-shaped insulator block 87 is provided with a horizontal short leg 88 and a vertical long leg 89 extending downwardly from the short leg. The short leg is provided with external grooves 90. The insulator block 87 is slid into the chamber so that the short leg passes through slot 86, the edges of the wall defining the slot being received in grooves 90 of the insulator. Long leg 89 is positioned against the interior of side wall 22 with the lower end of the leg abutting the adjacent end of insulator 80.

A resilient metal contact strip 9] inside of chamber 4 is electrically connected to a spring terminal clip 92 outside of chamber 4 by means ofa conductive rivet 93 passing through aligned bores in the clip. short leg 88 of the insulator 87, and the upper end of strip 91 in order to secure the clip and contact strip to each other and to secure them to. but insulated from, the housing. The free end of contact strip 91 is bent as shown in FIG. I to provide an electrical contact 94 making electrical contact with central bulb contact 85. A second resilient contact strip 95, near the back of chamber 4, is riveted intermediate its ends to insulator block 80 to insulate the contact strip from the housing. The left end 96 of contact strip 95 overlies and resiliently electrically contacts bulb base 83 while the other end of strip 96 is bent to provide electrical contact 97 which constitutes the fixed contact of a switch 98 inside chamber 4.

On switch chamber 4 there is pivotally mounted a yarn sensor 99 in the form of a wire bent into the shape shown in FIG. 2 to be successively constituted by a shaft 100, arm portion substantially perpendicular to the shaft, offset arm portion 102, first finger branch 103, laterally extending reverse curve 104, second finger branch 105, laterally extending connecting branch I06, and third finger branch I07 terminating in a free end. All the elements of the sensor lie in one plane with finger branches I03, I05, and 107 being substantially parallel to and laterally spaced apart from, each other. Finger branches I03 and 105 interconnected by reverse curve 104 constitute a first wide yarn sensing finger and finger branch 107 constitutes a second narrow yarn sensing finger to provide the sensor with two laterally spaced apart yarn sensing fingers connected to each other at their inner end by lateral connecting branch I06. It is apparent. therefore, that the sensor is constituted by a shaft at the inner end, laterally spaced apart sensing fingers at the outer end, the fingers being secured to the shaft by an arm defined by

arm portions

101 and 102. The length of the sensor is the distance from shaft to the outer extremities of the fingers defined by the outermost surfaces of reverse curve I04 and the free end of finger branch 107.

The shaft 100 is journaled in aligned bearing bores 109 in back 19 and 110 in cover plate 25, arm portion 101 being outside the back 19 and the free end of the shaft extending forwardly through cover plate 25, the shaft extending in a direction perpendicular to medial housing plane 27. The remainder of sensor 99 is outside of chamber 4, the angle of offset arm portion 102 positioning the sensing fingers in bay 26, the wide sensing finger being in back of the medial plane and the narrow sensing finger being in front of the medial plane. An eccentric collar 111 is positioned around shaft I00 adjacent the inner surface of back l9 and set screw 112 fixes the collar to the shaft for rotation therewith. This collar is fixed on the shaft before the cover plate is placed on the chamber and the collar prevents the shaft from sliding out ofits bearing bores. without interfering with the free rotation of the shaft. The shaft I00 is rotatably supported in bearings I09 and 110 to permit the sensing fingers to swing or pivot, in a direction parallel to the medial plane. about the axis of the shaft between at least an upper or normal position and at least a lower or switch actuating position. In the illustrated embodiment, the sensor in the upper position defines an angle of about 15 above the horizontal. as shown in solid lines in FIG. 1, and in the lower position defines an angle of about 15 below the horizontal. as shown in phantom at 99A in FIG. I.

Means are provided to furnish a force continuously urging the fingers to move away from their upper position toward their lower position, said force so moving the fingers except when the movement is otherwise prevented. In the illustrated embodiment. the shaft 100 is sufficiently freely rotatable in its bearings to permit the weight of the arm portions and the fingers to provide this force, the arm or fingers being weighted if necessary. In other words, gravity provides this force. and the sensor can therefore be called a drop wire.

During use of the stop motion assembly, there is relative longitudinal movement between the sensor, particularly the sensing fingers thereof, and the yarn vertex holder 41. In the preferred and illustrated form of the invention, it is desirable to avoid interference with such relative movement, and therefore the sensing fingers are spaced apart and shaped so as to avoid contact between any surface of the sensor and any surface of the holder regardless of the relative positions of the sensor and holder during normal operation of the device. The sensing fingers are capable of longitudinally passing between guide eyelets 53 and can therefore pass through laterally extending yarn guiding corridor 58, in the absence of yarn therein. In order to avoid such contact, the width of the lateral space between the fingers, namely, the lateral distance between finger branches and I07, exceeds the width of

arms

47 and 48. The total lateral width of the sensing fingers, namely, and lateral distance between finger branches 103 and I07, is less than the lateral distance between the inner opposed surfaces of guide eyelets 53. Lateral connecting branch I06 which interconnects the fingers at their inner end must be sufficiently remote from the outer end of the fingers to avoid contact between the connccting branch and the outer ends of

arms

47 and 48 of the holder.

The length of the sensor is such that its outer extremities do not extend to

webs

43 or 46 of the holder. Moreover, the sensor is sufficiently long for its outer extremities to be closer to chamber 3 than is corridor 58, at least when the holder is in bay 26. In other words, at least when the holder is adjacent to the sensing fingers, the fingers extend outwardly or transversely past the corridor toward chamber 3 to always lie across or tra verse the corridor, that is, either overlie, lie in or underlie the corridor.

The movable switch contact 113 of switch 98 is constituted by the arcuate eccentric surface of collar 111 opposed to fixed switch contact 97. Because of the eccentricity of contact 113, it is spaced away from contact 97 when the sensor is in the upper or normal position (in solid lines in FIG. 1) but abuts and makes contact with fixed contact 97 when the sensor is in the lower or switch actuating position 99A, such abutment preventing the sensor from moving below position 99A. Contacts 97 and 113 therefore define or constitute switch 98 which is closed and opened by the swinging movement of the sensor about the axis of its shaft.

The housing. the mounting ear, the sensor, and collar are all made of metal to be electrically conductive, the sensor shaft 100 being continuously in electrical connection with bearing

bores

109 and 110 to provide continuous electrical connection between switch contact 113 and the mounting ear. The stop motion control circuit (not shown) has one electrical branch grounded to the mounting frame (not shown) of the circuit so that this branch is in electrical contact with the housing when the mounting ear is secured to the mounting frame. The other branch of the stop motion control circuit is connected to wire 114 which is received in spring terminal clip 92. In thismanner the circuit in switch chamber 4 is electrically connected the stop mo tion control circuit. it will therefore be apparent that when the sensor moves from the normal upper position to position 99A, switch 98 is closed to complete and actuate the stop motion control circuit and effect termination of hthe positive drive (not shown) of the knitting machine while at the same time bulb 84 is illuminated to provide a visible signal indicating that the stop motion control circuit has been actuated by this particular stop motion assembly. When the sensor is moved upwardly to open switch 98, the bulb is extinguished and the stop motion control circuit, at least insofar as this particular stop motion assembly is concerned, is deactuated.

As previously described, the stop motion assembly is mounted above guides G1 and G2. At the beginning of the operation the holder 41 is in the normal retracted position with the vertex of the reach being sensed threaded therethrough, the sensing arms of sensor 99 overlying corridor 58 and resting on the vertex. This is the normal operating position and the positive machine drive can be commenced, the various elements remaining in the normal operating position as long as the yarn flow is normal. In the event the yarn breaks upstream of the corridor or the yarn supply is exhausted, the machine will draw the yarn out of the corridor. Since the corridor is now empty, there is nothing to prevent the force of gravity from pivoting the sensor to the switch actuating position 99A and the sensor will therefore move to this position to close switch 98 to actuate the stop motion control circuit to stop the positive drive of the machine and illuminate the bulb 84. The operator will then repair the broken yarn, or supply additional yarn from the supply, rethreading the yarn through the corridor with the sensor again overlying the corridor and resting on the vertex. The machine can then be restarted. When the assembly functions in the manner just described, it acts as an end detector for sensing continuity of the yarn. Although this is not the primary function of the assembly, it is a desirable ancillary function.

When the various elements are in the normal operating position and yarn flow upstream of the vertex is impeded sufficiently to increase the extending force to the actuating level, the extending force will move the holder toward the base line. During this downward movement the sensing fingers follow the vertex and remain in contact therewith (as shown by the position of the sensor in intermediate position 998 when the holder is in intermediate position 41B) until the holder arrives at intermediate position 41C. When the holder reaches position 41C the switch 98 is closed automatically to actuate the stop motion control circuit automatically and terminate the positive drive of the machine. Nevertheless, because of the machine inertia, the machine still continues drawing the yarn and the holder continues to move toward the base line, but the sensor does not drop below the switch actuating position 99A, since further movement is prevented by the closing of the switch. The holder stops its movement toward the base line either when the machine actually stops drawing the yarn or until the impediment is selfeliminated, whichever event occurs first. If the impediment has not been self-eliminated, the operator eliminates the impediment. As soon as the impediment is eliminated, by self-elimination or by manual elimination, the extending force is reduced below the level of the retracting force to permit the retracting force to automatically retract the holder to the normal retracted position. It will be apparent that during the retraction movement when the holder arrives at about the level of intermediate position 41C, the sensor overlies the corridor 58. Since the vertex is being guided by the corridor, the vertex will return the sensor to the upper normal position as the holder is returned to the normal retracted position. During this upward movement of the sensor switch 98 will be opened automatically to deactuate the stop motion control circuit automatically and extinguish the bulb. All the elements are therefore automatically returned to the normal operating position and positive machine drive can be resumed.

Although machines can be designed, and have been designed, so that deactuation of the stop motion control circuit automatically causes resumption of the positive machine drive, it is preferable and safer to have the operator manually start the positive machine drive after the stop motion control circuit has been deactuated. Virtually all of the conventional stop motion control circuits require manual resumption of positive machine drive, and therefore, unless otherwise clear from the context, in the remainder of the specification the assumption will be made that positive machine drive is manually resumed.

The causes of the yarn flow being impeded are well known. For example, the flow may be impeded by tangles in the yarn or knots in the yarn, such knots frequently becoming caught on a yarn guide. However.

most of the impediments are caused by interference with the yarn from freely coming off the yarn cone or tube. The cones or tubes are wound with varying ten sion and the yarn frequently lubricated and, of course, there are occasional knots. Because of this, the yarn frequently sticks or does not come freely off the cone or tube. Nevertheless, since the yarn is being drawn by the machine, the increase in tension caused by an impediment frequently is sufficient to jerk the yarn loose so that the impediment self-eliminates. In addition to such actual impediment to the yarn flow, because of the inherent nature of the yarns used in knitting, there are continual variations in yarn tension. These variations in tension caused by the nature of the yarn, as well as momentary impediments to the yarn flow which quickly self-eliminate, all fall within the normal operating range and it is not necessary to stop the machine operation during such fluctuations. It will therefore be appreciated that when reference is made to the normal level of yarn tension, yarn flow, yarn drag, or extending force, such normal level can be considered the base level wherein the yarn flows unimpeded and the extending force is less than the retracting force produced by spring tape 37, although continually during the normal operating conditions there will be momentary impediments wherein these levels will be raised above the base or normal level even to the extent of momentarily increasing the extending force to a level greater than the retracting force. These momentary fluctuations do not cause actuation of the stop motion control circuit and therefore can be disregarded. If the yarn flow is impeded sufficiently for the extending force to be raised to a level wherein it starts moving the holder toward the base line, but wherein the impediment self-eliminates before the holder reaches releasing position 418, the retracting force will return the holder to the normal retracted position and the stop motion control circuit will not be actuated. Such momentary activity is within the normal operating range.

If the impediment self-eliminates after actuation of the control circuit, the machine will eventually stop even though elimination of the impediment has permitted the retracting force to return the holder to the normal retracted position. The operator will only have to resume positive machine drive.

The purpose of the stop motion control system is to stop the machine when the yarn flow is impeded upstream of the vertex to a sustained predetermined undesirable level at which the machine should be stopped. This is the actuating level. The actuating level varies according to the nature of the yarn, machine, etc. This level is well known and can easily be predetermined by ordinary workers in the art. An undesirable level is obviously reached when the normal yarn flow is impeded sufficiently either to completely stop the yarn flow or to increase the yarn drag enoughto raise the tension in the yarn to a level at which the yarn is in danger of breaking if it continued to be drawn at this level. Since these are actually danger levels, the actuating level is usually established at a level below the danger level.

In stop motion devices, when the yarn flow is undesirably impeded, the vertex must move to prevent the continued drawing of the yarn by the machine from increasing the tension in the yarn to the breaking point and preferably, once the vertex has started its movement, it should move sufficiently freely to actually reduce or relieve the tension in the yarn to a level below the actuating level. The devices shown in US. Pat. Nos. 3,57l,680 and 3,6l2,79l and German patent publication No. l,26l,267 cannot provide such free movement.

In order for the stop motion assembly to operate, the elements of the assembly are so adjusted that at the ac tuating level the extending force exceeds the retracting force. Preferably, as shown in the illustrated embodiment, at the actuating level the extending force is greater than the minimum necessary to exceed the retracting force produced by coil spring 37, thereby reducing or relieving the tension in the yarn after the vertex has started its movement. It is for the reason that a releasing means such as catch 59 is preferably included since it can be adjusted not to release the holder until the extending force is greater than the minimum necessary to exceed the retracting force. Once the holder has been released, its movement toward the base line is resisted by a retracting force which is less than the extending force at the actuating level, and the vertex can therefore move sufficiently freely to reduce or relieve the tension in the yarn below the actuating level. After release, the holder will continue moving as long as the extending force exceeds the retracting force even though the extending force is below the actuating level.

It is emphasized that in most commercial installations, particularly those using high speed knitting machines, it is not merely preferable but commercially necessary for the vertex to move, virtually instantly, sufficiently freely to relieve or reduce the undesirable tension in the yarn, especially when the impediment is of such a nature that the yarn flow is completely stopped. If the undesirable tension is not swiftly relieved, the goods being knit will be damaged. The use of the catch provides such swift relief. In the illustrated embodiment, the catch releases the holder when it has moved from the normal position to the releasing position 418, a distance less than half an inch, and then the holder and the vertex guided thereby move freely toward the base line. Therefore, the undesirable tension in the yarn is relieved before the vertex has moved half an inch from the normal position. In other words, the undesirable tension is relieved even sooner than it is in commercial devices using the structure of US. Pat. Nos. 2,515,479 and 3,257,518.

It will appreciated that the retracting force can be adjusted so that it is just barely exceeded when the extending force is at the actuating level, and thus the catch 59 can be omitted (not shown), but such adjustment is not commercially desirable because it will not permit the vertex to move sufficiently freely to reduce or relieve the tension in the yarn below the actuating level, and in fact will permit the yarn tension to increase above the actuating level during the inertial period. This occurs because, when using a coil spring of the type described, the retracting force inherently increases as the holder moves towards the base line and this increase in the retracting force would interfere with the free movement of the holder towards the base line during the inertial period and permit the tension in the yarn to increase above the actuating level. The use of the catch overcomes these problems because it can be adjusted so that the extending force at the actuating level is in excess of the maximum retracting force exerted by the coil spring during the holder movement.

It is preferred that the retracting force be as small as possible to permit free movement of the holder toward the base line as soon as the holder has passed the releasing position 41B but at the same time be great enough to return the holder from its extended position when the extending force is within the normal level. With the retracting force so adjusted, the tension in spring 73 can be adjusted so that the catch prevents release of the holder from the normal position until the extending force is at the actuating level, and therefore the actuating level can be significantly in excess of the retracting force produced by coil spring 37. The strength of the retracting force is controlled not only by the rotation of arbor 28, but also by appropriate selection of the material or materials from which the spring coil is made, as well as the length of the spring coil.

Once the strength of the retracting force is adjusted to the desirable low but operative level, it will rarely have to be changed even when different types of yarns are used with the machine or different patterns are being knit. The actuating level can be controlled by adjusting the tension on spring 73. In fact, the level of the retracting force can generally be preset by the manufacturer of the stop motion assembly. It is therefore possible. when manufacturing the assembly, to eliminate key 34 and mount arbor 28 non-rotatably in the housing (not shown), so that the tension of the spring tape is predetermined by selecting its length, thickness, the materials from which it is made, and the number of times it is coiled around the arbor. In such a construction, if the operator desires to vary the tension of the tape, it is a simple matter to remove the cover from the box and appropriately increase or decrease the number of coils.

It is apparent that, during the period when the machine is drawing the yarn after actuation of the stop motion control circuit, the reach of yarn must be able to continuously shorten and continuously draw the vertex toward the base line. If the vertex could not continue moving, the drawing of the yarn by the machine would tear the yarn when the vertex stops moving. The distance the vertex moves toward the base line during the inertial period is called the inertial vertex movement distance and this distance must be long enough to provide the necessary inertial slack (the difference between the lengths ofthe yarn each at the beginning and end of the inertial period) for the machine to draw during this period. The length of the inertial slack needed depends upon the rapidity with which the machine stop and the rate at which the machine draws the yarn. The inertial vertex movement distance where is required to produce the necessary inertial slack for any particular installation depends upon the geometry of the relative locations of guides G1, G2 and the position of the stop motion assembly, that is, the length of upstream branch Y], the length of downstream branch Y3, and the angle between these branches. For most of the present day circular knitting machine installations, it will be adequate to provide for supplying about four feet of inertial slack. In most of these installations such sufficient inertial slack would be provided if the structure and location of the stop motion assembly can provide four feet of inertial movement distance. Generally, about two feet of vertex movement will be adequate. Therefore, the stop motion assembly should be mounted sufficiently remote from base line B for the position of the vertex guide means at the time the stop motion control circuit is actuated to be spaced longitudinally from the base line a distance at least equal to the inertial vertex movement distance. The aforesaid parameters are about the same as those involved when using a stop motion box of the type of U.S. Pat. No. 2,515,479.

To meet the foregoing requirements, tape 37 should be at least sufficiently long to permit the vertex to move the inertial vertex movement distance. Preferably, the tape is significantly longer than the minimum length necessary because the tension created by the tape increases greatly as the tape approaches its maximum extension. It has been found that a tape eight feet long will be adequate for most of the present day installations. However, if necessary a longer tape can be used and can still be accommodated in the same size housing as illustrated.

It is apparent that in every installation there is a limiting or terminal guiding position beyond which the vertex cannot be extended, this position being the base line. However, if the length of the tape is not sufficient to permit the vertex to reach the base line, the inherent maximum extended position determined by the length of the tape is the terminal guiding position. In a proper installation, unless there is a malfunction in the assem bly or a malfunction in the stop motion control circuit, the extending force will not bring the vertex to such terminal position, although an extending force urges the vertex toward such position.

In the illustrated embodiment, guide 53 is a complete annulus, thereby preventing the vertex from being released from the holder during the movement of the holder to provide vertex guide means retaining and guiding the vertex throughout the vertex movement. Obviously, other guide constructions can be used. For example, guide 53 and bore 54 need only be a partial annulus open at the top (not shown) and the vertex will still be retained and guided thereby throughout the vertex movement. Since the vertex is always retained and guided by the vertex guide means, the yarn reach being sensed will remain taut throughout the vertex movement because of the continuous interplay of the extending and retracting forces.

When stating that the yarn reach is kept taut during the vertex movement, there are obviously excluded those occasional times when there is a break in the continuity of the yarn of the reach, since at such times there is not reach. When the vertex is in the normal retracted position, because of the continual fluctuations in the yarn tension even under normal operating conditions, the yarn tension may intermittently momentarily drop to such an extent that there is momentarily no ten sion in the reach, so that it can be said that momentarily the tautness of the reach will be interrupted. However, these are just momentary interruptions and do not really effect the general tautness of the reach. However, it is possible for a fault to occur in the yarn flow where the tension is completely dropped to such a level or eliminated that the branches of the reach may go slack. If such a fault occurs, however, the reach would not go slack until the holder has been returned to the normal position. if the weight of the sensor is such that when such a slack creating fault occurs, the yarn of the vertex cannot sustain the sensor above the yarn corri dor, the sensor can move through the corridor pushing the yarn of the vertex downwardly until the sensor ar rives at the switch actuating position. In such a construction the present invention can also act as a slack detector. However, it has been found that slack detectors of this type are not particularly desirable or necessary. It is for this reason that the holder is provided with lower arm 48. When the slack occurs and the sensor starts moving downwardly, the yarn of the vertex will contact lower arm 48 to resist further downward movement. The friction of the yarn flowing through guides 53 and against lower arm 48 will prevent the sensor from moving to the switch actuating position.

Since the present invention is not particularly concerned with the handling of a slack creating fault in the yarn flow, the existence of such faults and the problems created thereby will not be considered hereafter in discussing the operation of the structure of the invention. Therefore, when referring to the reach as being kept taut during the vertex movement, the possibility of the reach going slack when the holder is in the normal retracted position is disregarded.

In the illustrated embodiment. the tape 37 is at least transversely flexible, that is, flexible in a direction transverse the length and plane of the tape. It may also be laterally flexible, that is, flexible in a direction parallel to the plane of hte tape but transverse to the length thereof. Even if not laterally flexible, the tape is at least somewhat twistablc because of the transverse flexibility and therefore the tape will permit the holder to move laterally to some extent. In view of this flexibility of the tape, the exposed tape portion will not significantly interfere with transverse or lateral movement of the holder throughout at least the major portion of the vertex movement when the vertex is out of the bay and past intermediate position 41C. Because of this freedom of movement of the holder the actual position of the holder during at least most of the holder movement is determined substantially only by the interplay of the extending and retracting forces. As will be understood from the subsequent discussion, there is a continual shift in the direction of each of the retracting force and the extending force during movement of the holder away from the normal position and back toward the normal position. In the preferred embodiment, the holder is free to move laterally, transversely or longitudinally as required by the interplay of the continually shifting forces.

In a typical exemplary installation such as diagrammatically shown in FIG. 1, a yarn cone would be positioned with its base about six feet from the floor and aligned with the axis of the cone. Guide G2 would be located about six feet from the floor and horizontally displaced from the axis of the cone about 2 feet. The stop motion assembly would be mounted at least about I l -l2 feet from the floor and be positioned in the vertical plane passing between guides GI and G2, or to the rear of this plane, or to the front of this plane. The medial plane of the assembly would normally be vertical and the medial plane would be aprallel to the vertical plane passing through guides GI and G2 or at any angle thereto. Furthermore, referring particularly to FIG. I, the assembly can be mounted so that the holder in the normal retracted position is located between vertical projections of guides G1 and G2 (as shown in this figure) or so that the holder in the normal position is to the left of the vertical projection of guide GI or to the right of the vertical projection of guide G2. It will be appreciated that the base line, branch Y1, vertex Y2, and branch Y3 may or may not be coplanar and if coplanar, the plane can be inclined relative to the vertical.

As the holder moves toward the base line, the relative length of branch Y1 relative to Y3 changes to cause a constant shift in the vertex. During the movement of the holder, as will be apparent from the ordinary laws of physics, the holder will move toward an equilibrium position to balance out the interplay of the forces. The shifting of the holder shifts the direction of the forces, thereby producing a dynamic interplay. From the foregoing it will be clear that even when disregarding the transverse shift in the holder created by catch 59, the holder will not move linearly during either of the retracting or extension movements but instead moves through a course which defines a significant curve and the curved course may be two dimensional or three dimensional. The extension and retraction curves do not coincide and will have a different shape. Despite this curve, it can be said that the courses are longitudinal, as the word longitudinal is being used herein. Although the holder reaches the base line during automatic proper operation, the operator may at times manually bring the holder to the base line. Despite the fact that the holder is never at the base line during proper automatic operation, it can be said that the extending force urges the holder longitudinally toward the base line and that the retracting force urges the holder longitudinally away from the base line.

It will be understood that the stopping location where the holder stage its movement when the machine stops drawing the yarn not only will vary from installation to installation, but will not necessarily be the same each time the yarn flow is impeded because of the nature of the impediments varies and there is a continual variation in the yarn itself. The courses traced by the vertex, and vertex holder, during each retraction and each extension are therefore not necessarily the same each time the holder moves because of the dynamic nature of the system. The swath or path bounded by the extension and retraction courses of the vertex (or vertex holder) and its longitudinal extension, may be considered as defining the movement path of the vertex (or the vertex holder).

Throughout the movement of the holder, exposed tape portion 40 substantially extends or lies in the movement path of the vertex, as well as the wider movement path of the holder. By substantially," it is meant that the exposed tape portion need not extend within the actual confines of the movement path, but can be outside and adjacent to the actual movement path. In the diagrammatic illustration of FIG. I, for example, the exposed tape portion lies outside the actual movement path of the vertex throughout the vertex movement but adjacent thereto.

In view of the freedom of movement provided the vertex, the various moving elements can efficiently accommodate themselves to the interplay of the forces acting thereon, thereby providing an economy in the occupied space, as well as avoiding extraneous strains on the yarn which might break the yarn. At the same time, this construction provides great flexibility for positioning the assembly. This is particularly important when the assemblies are to be used with a high speed multifeed knitting machine such as a 96 feeder, wherein space may be at a premium. Obviously, this construction avoids the disadvantages of having yarn vertex guide means secured to the support by a pivotally mounted arm. Because of the fixed length of the pivotally mounted arm, the vertex can only move in a definite predetermined path which would not be the natural path the vertex tends to take. The flexibility of location of the assembly provided by the invention, as well as the freedom of movement of the vertex, are provided by a conventional stop motion box of the type shown in US. Pat. No. 2,515,479, but such conven tional devices release the vertex and the reach at the beginning of the inertial period. The reach becomes slack and falls freely. This free fall not only creates the possibility of entanglements with adjacent yarns, but necessitates the manual restoration of the vertex to the box when the impediment has been removed.

The assembly need not be mounted above the base line, but it can be mounted to the side of the base line with the plane of the reach being essentially horizontal or it can be mounted upside down beneath the base line. In such cases, however, a slight modification will have to the made in the sensor to provide the force normally urging the sensor to move from the normal position to the switch actuating position. This can be done by having the sensor biased in the right direction by a tension spring (not shown) or by providing a counterweight (not shown) extending from the sensor shaft to permit gravity to provide the appropriate force when the assembly is mounted upside down. The base line can be at any angle relative to the longitudinal. It is merely necessary that the holder be located in such a position remote from the base line to create the tendency for the reach to draw the vertex toward the base line.

Spring 37 is a spring actuated retracting spiral coil tape, wherein, as has been described. the spring actuation is an inherent property of the tape resulting from the resiliency of at least some of the tape coils. The spring actuation can be supplied by means separate from the coil tape and the coil need not be spirally wound. For example, obviously, a construction similar to that of a window shade can be used. In such a window shade type construction (not shown) a nonresilient flexible tape has one end fixed to a rotatable arbor with the remainder of the tape, exclusive of the terminal portion, being helically or spirally wound around the arbor. A separate helical or spiral torsion spring or comparable torsion means supplies the torsion to urge the arbor to rotate to wind up the tape and cause the retraction.

It is necessary to provide mounting means for mounting the vertex guide means on the support for longitudinally reciprocating (not necessarily rectilinear) movement between a nromal guiding position and a terminal guiding position. This is provided by spring tape 37 in the illustrated embodiment. Many other mounting means can be used instead and some of the these will be briefly described. Since their construction is obvious. they will not be illustrated. One obvious substitute is a helical tension spring mounted within chamber 2 whose lower end passes through a slot 36 and is secured to the holder. Alternatively, a telescoping mount can have one end mounted on the support with the other end secured to the holder and resilient means can be supplied to urge the telescoping mount to the retracted position. In many installations the ceiling is sufficiently high to permit the use of a mounting means comprising a solid rod slidably mounted for vertical reciprocation, the lower end of the rod being attached to the holder and an appropriate compression or extension spring can urge the rod upwardly to the retracted position.

Both of the latter alternatives would limit the relatively free lateral and transverse movement of the holder obtained by the preferred embodiment, although some improvement in this freedom can be obtained by having the telescopic member or rod secured to the housing by a type of universal joint. The rod has the disadvantage that vertical space would be required above the housing, although in many applications this space is available. It will be apparent from the preceding discussion that it is most desirable to have a mounting means which is longitudinally lengthenable-shortenable (expansible-contractible) such as provided by coil tape 37, tension spring, or telescoping member, since such means retract into a space in or adjacent the support. The use of the tape is still further preferred because of the great freedom of movement provided the holder.

In addition to the advantages already described, there is another important reason why it is preferred that the mounting means be a retracting spiral spring tape. Retracting spiral spring tapes, and particularly those in which all the coils are resilient, have a very low starting inertia and are therefore more satisfactory and efficient under a wider variety of conditions than are other of the suggested types of mounting means. When the fault in the yarn flow is such that there is a gradual buildup in the yarn tension, the starting inertia of the mounting means does not create any particular problem. However, in most cases the fault in the yarn flow is of such a nature that there is virtually an instantaneous buildup of yarn tension and this is particularly true when the defect is such that the yarn is suddenly caught and completely stops the yarn flow. When such a fault occurs, the drawing of the yarn by the machine causes the vertex to jerk the holder toward the base line with such force that the yarn will tear if the holder does not immediately start moving to relieve the tension in the yarn. It is apparent that if the starting inertia of the mounting means resisting the downward movement of the yarn vertex holder is sufficiently high to prevent immediate starting of the holder movement, the jerking will tear the yarn. This is particularly true if the yarn is delicate.

With a spiral spring tape, at the moment that the holder starts its movement only the few outermost coils start rotating and therefore the movement of only a relatively small mass is involved. In addition, no bearings are involved and there is therefore practically no friction. It is for these reasons that a spiral spring tape has little starting inertia. Other suggested types of mounting means have a much greater starting inertia because movement of the holder would require the overcoming of much more friction and would require movement, either rectilinear or rotational. of a relatively much larger mass. This would be true even when using a retracting spiral tape wherein the spring actuation is supplied by means separate from the tape such as in the window-shade-like construction. In such a construction, the mass of the entire tape body and that of the rotatable arbor supporting the tape have to be rotated. This construction would also require bearings and therefore there would also be significant frictional forces to be overcome. The structures shown in US. Pat. Nos. 3,57 L680 and 3,61 2,79 l and German patent application No. l,26l ,267 all have highstarting inertia.

In order to maintain the vertex under the control of the interplay of the retracting and extending forces and maintain the reach taut during the vertex movement,

and at the same time avoid the shortcomings of the construction using a long pivotable sensing arm, it is a concept of the invention that the mounting means provide at least a portion of a continuous longitudinally lengthenable-shortenable connection between the vertex guide means (and therefore the vertex) and a reference connection location on the support throughout the vertex movement. A connection location is the location on a support wherein the connection, as one proceeds along the connection beginning at the vertex, first makes contact with the support or first passes through the support. In the illustrated embodiment, this connection location is slot 36 and the connection location remains the same throughout the vertex movement so that throughout the vertex movement exposed tape portion 40 always provides a connection between holder 41 and the slot. In this embodiment and the various alternatives suggested in the previous paragraph, the connection location is substantially constant throughout the vertex movement, and the connection between the vertex guide means and the connection location is continuous or unbroken. It is also emphasized that such connection provided by all of these alternatives actually lengthens and shortens, although the mounting means itself, as, for example, in the case of the solid rod alternative, may be offixed length. It is apparent that in the prior proposal involving the use of the elongated pivotally mounted sensor arm, the sensor arm provides a connection between the vertex guide means and the pivot but this connection is of constant length. By providing that the actual connection can lengthen or shorten longitudinally, that is, in the same general direction as the vertex moves, it is possible to provide the desirable construction permitting the economy in space transverse and lateral to the direction of movement. According to the preferred aspect of the invention, the connection substantially extends along the movement path and the lengthening and shortening is substantially along the movement path, bearing in mind that the movement path comprises not only the actual path bounded by the extension and retraction courses of the vertex or vertex holder, but also the longitudinal extension thereof. In other words, the connection is, in effect, a longitudinally lengthenableshortenable follower for the vertex and vertex guiding means.

The invention is sufficiently broad to encompass a construction wherein the connection location may vary during vertex movement and it is therefore desirable to provide a reference connection location and such reference connection location is a connection location at the time the vertex guide means is in the normal guiding position. For example, referring to FIG. 1, if the guide G2 were positioned further to the right from its illustrated position, exposed tape portion 40 would make contact with the lower left hand corner of chambeer 3 when the holder is in an extended position and this lower left-hand corner would be the connection location when the holder is in such a position. Nevertheless, it still can be said that there is a continuous connection between the holder and the slot with the tape portion between the holder and the corner being part of the connection and with the remainder of the connection being provided by either the portion of the housing between the corner and slot 36 or the piece of tape between the corner and the slot. It is therefore apparent that only a portion of the connection need be provided by the mounting means and that a portion of the connection can be provided by the support itself.

In the illustrated embodiments, the retracting force urges the holder away from the base line and toward the support, while the extending force urged the holder away from the support and toward the base line. Since the relative location of the support can obviously vary, the retracting force should be considered as a force which urges the holder away from the base line to the normal position (regardless of the location of the support) and the extending force should be considered a force which urges the holder away from the normal position and toward the base line (regardless of the location of the support). For example, it may be desirable to locate the stop motion assembly support adjacent the base line with the mounting means extending upwardly toward the vertex. In such a construction (not shown), the mounting means can be a telescopic member mounted on the support provided with resilient means continuously urging the telescopic member upwardly to its extended position to thereby urge the vertex holder at the upper end of the member away from the support. This force, continuously urging the holder away from the support, would provide the retracting force since it continuously urges the holder away from the base line. It will also be appreciated that the contin uous connection between the holder and the support shortens in the direction of the extending force when the extending force exceeds the retracting force, and lengthens in the direction of the retracting force when the retracting force exceeds the extending force, precisely the reverse of the previously described embodiments. Broadly, therefore, according to the invention, the lengthenable-shortenable connection lengthens in the general direction of the extending force during movement of the vertex guide means in one of the vertex guide movement directions and shortens in the gen eral direction of the retracting force during movement of the vertex guide means in the other of the vertex guide movement directions. In the preferred embodiment, however, the connection shortens in the general direction of the retracting force during the retraction movement away from the base line and lengthens in the general direction of the extending force during the extension movement toward the base line.

A modified form of the stop motion circuit actuating switch will now be described. In this modification, see FIG. 6, the catch chamber is slightly modified. ln modified catch chamber 3' there is mounted a catch 59 and spring 73, identical to those of FIG. 1. Chamber 3 is provided with a slot identical in construction with that of slot 70 in chamber 3, with nose portion 62 of the catch projecting through slot 70' out of the chamber. Right side wall 16' is provided with a slot 115 therethrough and an insulator 116 is mounted in slot 115. A resilient contact 7 inside the chamber is electrically and mechanically secured to a spring terminal clip 118 outside the chamber by rivet 119 passing through insulator 116, fixed Contact 7 and clip H8 being insulated from the housing. Wire 114', received in clip 118, provides a connection to the stop motion control circuit. Contact 117 is positioned adjacent free end of spring 73, said free end making contact with contact 117 just about the time the catch arrives at the lower or releasing position, said free end not making contact when the catch has been moved upwardly away from the releasing position. Since spring 73 is conductive and is connected to the housing, it will be apparent that spring 73 and contact 117 provide a switch which will actuate the stop motion control circuit when the catch has been moved to the releasing position.

Except for the changes just described, catch chamber 3' and the elements thereof are the same as that of catch chamber 3. The modification of FIG. 6 can be used together with the illustrated construction of switch chamber 4 and the elements thereof to provide the assembly with two means for actuating the stop motion control circuit. one means backing up the other in case of mechanical failure. However, it has been found that only one means is necessary. When the structure shown in FIG. 6 constitutes the sole sensing and switch means, the entire structure of switch chamber 4 can be eliminated and, if desired, a visible signal (not illustrated) can be included in the circuit provided by catch chamber 3'. it is preferred to have at least a sensor and switch arrangement comparable to that provided by chamber 4 because, as previously described, such con struction also provides a yarn end detection means.

It is the purpose of the present invention, as in prior art tension detectors, to initiate termination of positive drive of the machine, that is, actuate the stop motion control circuit, when the extending force reaches the actuating level. lf the circuit were actuated before the extending force reached the actuating level. the ma chine would continually be stopped unnecessarily. Therefore, by definition, the extending force must have reached the actuating level at the time the circuit was actuated (switch was closed). However, the circuit can be actuated after the extending force has reached the actuating level, provided precautions are taken to either maintain the extending force at the actuating level or to prevent it from substantially increasing from the actuating level. In the prior art devices and in the present invention, these precautions are effected by releasing the holder so that it is face to leave the normal guiding position.

As is well known in the art, the time span from the moment the yarn flow is impeded to the undesirable level to the moment the machine stops is very short. For example, in a high speed 30 inches circular knitting machine revolving at 20 revolutions per minute, the machine makes one revolution in 3 seconds. During one revolution a yarn feed may draw about 200 inches of yarn. Such a machine may make less than one-third of a revolution during the inertial period and less than a second will elapse from the moment the circuit is actuated to the moment the machine stops drawing. The entire action of the stop motion device is very rapid. In machines of this type the impediments to the yarn flow are usually of such a nature that there is an abrupt or rapid buildup of the tension in the yarn reach, rather than a gradual increase.

When, as in the illustrated embodiments, the switch is closed as a result of sensing the position of the holder guiding the vertex, the switch should not be closed when the holder is guiding the vertex in the normal guiding position. since this would result in the machine stopping when the yarn flow is in the normal range. The switch is closed when the holder guiding the vertex is moved from the normal guiding position to an intcrmcdiate position called the switch actuating position. In order for the holder to move to this intermediate position it must first be released from the normal position. It is considered as having been released from the nor mal position when it has moved sufficiently to start the action of the releasing means such as catch 59, although it may not be completely released until it has moved still further to position 418. This creates no problem because in most instances the abrupt increase in tension caused by the impediment will maintain the extending force at the actuating level from the time the catch begins to move downwardly until it arrives at its lowermost position. This intermediate switch actuating position may be spaced from the normal position or it may be contiguous thereto, although it is preferred that the intermediate switch actuating position be located past the point wherein the holder is completely released, as shown in the embodiment of FIG. 1. The intermediate position is not necessarily a precise point but may be a range as are all the other positions.

Referring back to the structure of chamber 3', it is obvious that the switch therein must be closed no later than the time the catch moves to its releasing position because after it arrives at this position it is not moved downwardly any further by the holder. To insure closing of the switch, spring 73 should make contact with fixed contact 117 at least momentarily before the holder is fully released from the catch. This embodiment therefore provides sensing means for actuating the switch before the holder is completely released.

In order to actuate the stop motion control circuit, sensing means are provided for sensing when the extending force has been increased to the actuating level and for closing the stop motion actuating switch in response thereto at a time not prior to the time the extending force increases to the actuating level. The sensing means of chamber 3' is responsive to the position of the vertex guide means for closing switch when the extending force moves the vertex guide means to the intermediate switch actuating position. In addition, it senses the position of the vertex guide means even when no vertex is being guided. This is not material. The sensing means of chamber 4 is responsive to the position of the vertex for closing the switch when the extending force moves the vertex from the normal guiding position to the intermediate switch actuating position. However, since the vertex is always retained and guided by the holder, it can be said that the sensor is also responsive to the position of the vertex guide means for closing the switch when the extending force moves the vertex guide means to the intermediate position. The sensing means of chamber 4 also senses the absence of the vertex and therefore performs the additional function of a yarn end detector. in the illustrated embodiments. therefore, the sensing means senses when the extending force increases to the actuating level by being responsive to the position of the holder guiding the vertex and therefore is also responsive to the position of the vertex, and other situations may be sensed as well.

It will be noted that the sensor and switch of chamber 3' only close the switch momentarily, since the switch reopens as soon as the catch moves upwardly. Because of the construction of the stop motion control circuit, it is not necessary to maintain the switch closed throughout the movement ofthe holder. It is only necessary for the switch to be momentarily closed. Once the circuit is actuated, the machine to comes to a halt and remains halted until the operator restarts it. However. to restart the machine the circuit must be deactivated and therefore the switch must be open. The

switch can be reopened at any time subsequent to its closing and preferably should be opened at a time no later than the time the holder guiding the vertex is returned to the normal position. It is apparent that if the automatic opening of the switch is delayed, by a time delaying mechanism or any other structure (not shown), so that the switch is opened later than about the time the holder is returned tothe normal position, the mechanism would still operate satisfactorily but there would be a loss of time before the machine can be restarted.

It is an essential concept of the invention that the holder be free to continue moving from its position at the time the switch is actuated toward the base line until the impediment is removed or the machine stops drawing yarn. It is therefore necessary for the sensor means to perform its sensing function and switch closing function without preventing the extending force from so moving the holder. It is noted that in the illustrated embodiment, once the holder has been fully released by the catch, it will continue its extending movement as long as the extending force is sufficiently above normal to exceed the retracting force, event though it may have dropped below the actuating level. [n this manner there is a minimum strain on the yarn. The extending force increases to the actuating level when the yarn flow is impeded upstream of the holder to a predetermined undesirable level, i.e., the impediment not only increases the yarn drag to an undesirable level, but may even increase the yarn drag to a still higher level, to the extent that the yarn may completely stop flowing. Since yarn drag generally implies that there is still movement, it may be said that when the yarn completely stops flowing, the yarn drag has been infinitely increased.

As has been pointed out, the drawing of the yarn against the drag of the yarn flow provides a tension in the yarn which tends to shorten the yarn reach so that the vertex exerts an extending force on the holder urging the holder toward the base line. Of course, conversely, when the holder is away from the normal position, the extending force is a force resisting the lengthening of the yarn reach and therefore resisting the movement of the holder toward the normal position by the retracting force. When the holder has been moved to an extended position and the machine has stopped drawing the yarn, the engagement of the yarn with the machine prevents the retracting force on the holder from drawing the yarn in an upstream direction through the downstream guide, and therefore, the retracting force is urging the holder toward the normal position against the resistance to the yarn flow upstream of the holder. The yarn reach is therefore still under tension so that the vertex still exerts the extending force opposing the retracting force but the extend ing force cannot exceed the retracting force as long as the machine is not drawing yarn. The system remains in equilibrium and the holderremains stationary as long as the resistance to yarn flow is sufficiently great to prevent the retracting force from exceeding the extending force. However, when the resistance to the yarn flow if reduced, as by elimination of the impediment by selfelimination or by the operator, to such a level that the resisting extending force is less than the retracting force, the retracting force automatically returns the holder to the normal position.

lt is apparent that, according to the invention, the retracting force cannot move the vertex past the normal position, in the direction away from the base line, to actuate the stop motion control circuit, no matter how much the level of the extending force is reduced below the level of the retracting force and even if the resisting extending force is completely eliminated. As previously described, the tension of the coil spring 37 can be adjusted so that it can just move the holder to the normal position, an adjustment which is difficult to obtain, and therefore positive stop means are preferably provided for preventing the retracting force from moving the holder past the normal position. In either event, the invention provides means preventing the retracting force from moving the vertex guide means past the normal position. This insures automatic return of the guide means to, but not past, the normal position when the impediment is eliminated, whether or not the machine is drawing yarn, and also insures that the vertex guide means is not moved past the normal position when the machine is stopped for any reason. The significance of this is obvious. As is well known, when the yarn is flowing normally, the yarn tension and the extending force increase as the speed of the knitting machine increases, because the frictional resistance to yarn flow increases. Conversely, when the machine is stopped and not drawing yarn, and the yarn is capable of flowing very freely, there would be substantially no friction and no resisting extending force. The machine must be capable of starting under such conditions and therefore the stop motion circuit must not be actuated; there cannot be any retracting force capable of moving the vertex past the normal position to actuate the stop motion control circuit.

The visible signal provided by bulb 84 is a convenience in assisting the operator in locating the particular yarn feed in which the impediment occurs. This is an optional convenience and may be eliminated, if so desired, by providing an permanent, direct connection (not shown) between contact strips 91 and 95.

Although the invention has been described particularly in connection with the yarn supply for a circular knitting machine, it is obviously applicable to other knitting machines and other similar machines wherein one or more strands of yarn, including filaments, strands, strips or similar material of indefinite length, are drawn by the machine from a supply.

In some knitting machines the drawing of the yarn is caused by the consumption of the yarn at the knitting stations. However, in other knitting machines there is interposed between the stop motion device and the knitting stations a positive feeding mechanism and itis such positive feeding mechanism which does the drawing of the yarn from the supply. In the context of this application, such positive feeding mechanisms are considered part of the knitting machine so that when reference is made to the machine drawing the yarn, such drawing can be effected by either knitting stations or the positive feeding mechanism.

I claim:

1. A method of controlling the stop motion control circuit of a knitting machine or the like when the normal yarn flow is undesirably impeded upstream of the vertex of a flexed reach of yarn traveling from an upstream yarn guide to an adjacent downstream guide by being drawn through the latter by said machine, said method comprising the steps of:

a. retaining and guiding said vertex with movable vertex guide means;

b. positioning said vertex guide means at a normal guiding position remote from the base line of said yarn guides so that drawing of the yarn against the drag of the yarn flowing upstream of said vertex guide means causes the vertex to exert an extending force acting on said vertex guide means urging said vertex guide means from said normal position toward said base line;

c. providing a retracting force generally opposed to said extending force continuously urging said vertex guide means, at least when said vertex guide means is away from said normal position, away from said base line toward said normal position, but preventing said retracting force from moving said vertex guide means past said normal position;

(1. normally operating said machine to draw said yarn through said downstream guide and maintaining said vertex guide means in said normal position with normal yarn flow;

e. when said normal yarn flow is impeded upstream of said vertex guide means to a predetermined undesirable level, thereby increasing said extending force to an actuating level at least sufficiently high to exceed said retracting force, releasing said vertex guide means to permit said increased extending force to move said vertex guide means toward said base line;

f. actuating the stop motion control circuit of said machine at a time not prior to the time the extend ing force increases to said actuating level while permitting said extending force to continue moving said vertex guide means toward said base line, as said machine continues drawing said yarn because of machine inertia, until either said impediment self-eliminates or said machine stops drawing said yarn;

g. eliminating said impediment if it has not been self eliminated, elimination of said impediment, by selfelimination or otherwise, reducing the extending force acting on said vertex guide means to a level below the level of said retracting force, to permit said retracting force to automatically return said vertex guide means to said normal position;

h. automatically deactuating said stop motion control circuit at a time subsequent to the time it was actuated;

i. continuously retaining and guiding said vertex with said vertex guide means throughout the foregoing steps to maintain said yarn reach taut;

j. maintaining a continuous connection between said vertex guide means and a reference connection location on a support throughout said vertex guide means movement, said connection being lengthened in the general direction of said extending force during movement of the vertex guide means in one of said vertex guide means movement directions and being shortened in the general direction of said retracting force during movement of the vertex guide means in the other of said vertex guide means movement directions;

k. and restarting said machine, to resume normal operation, after said vertex guide means has been returned to said normal position and said stop motion control circuit has been deactuated;

1. said normal position being sufficiently remote from said base line to provide adequate distance for said vertex guide means to continue moving toward said base line without reaching it until said machine stops drawing said yarn without selfelimination of the impediment after actuation of said stop motion control circuit.

2. A method according to claim 1, wherein said extending force at said actuating level is greater than the minimum force needed to exceed said retracting force and wherein said vertex guide means is not released from said normal position until said extending force has increased to said actuating level without preventing said extending force from subsequently moving said vertex guide means toward said base line as long as said extending force exceeds said retracting force.

3. A method according to claim 2, wherein said stop motion control circuit is actuated when said extending force has moved said guide means to a position intermediate said normal position and said base line.

4. A method according to claim 3, wherein said connection is lengthened during movement of said vertex guide means toward said base line and is shortened during movement of said vertex guide means away from said base line.

5. A method according to claim 4, wherein said retracting force is applied to said connection to urge contraction of said connection.

6. A method according to claim 5, wherein at least the portion of said connection which contracts and expands extends substantially along the movement path of said vertex guide means.

7. A method according to claim 6, wherein said retracting force is applied to said connection from a location on said support at least as remote from said base line as is said normal position.

8. A method according to claim 7, wherein at least a portion of said connection is at least transversely flexible.

9. A method of according to claim 8 wherein during at least the major portion of the movement of the vertex guide means between said intermediate position and said base line said vertex guide means is moved transversely substantially only by the interplay of said retracting and extending forces.

10. A method according to claim 9, wherein said stop motion control circuit is automatically deactuated at a time to later than about the time said vertex guide means is automatically returned to said normal position.

11. A method according to claim 10, wherein said stop motion control circuit is continuously actuated from the time said vertex guide means reaches said intermediate position until said vertex guide means is returned to said intermediate position.

12. A method according to claim 11, wherein a visible signal is actuated during actuation of said stop motion control circuit.

13. A method according to claim 5, wherein said retracting force and said connection are provided by means of a retracting spiral spring tape whose inner end is fixed to a support and whose outer portion carries said vertex guide means.

14. A method according to claim 13, wherein said stop motion control circuit is not actuated when said vertex guide means is retaining and guiding said vertex in said normal position.

Claims

1. A method of controlling the stop motion control circuit of a knitting machine or the like when the normal yarn flow is undesirably impeded upstream of the vertex of a flexed reach of yarn traveling from an upstream yarn guide to an adjacent downstream guide by being drawn through the latter by said machine, said method comprising the steps of: a. retaining and guiding said vertex with movable vertex guide means; b. positioning said vertex guide means at a normal guiding position remote from the base line of said yarn guides so that drawing of the yarn against the drag of the yarn flowing upstream of said vertex guide means causes the vertex to exert an extending force acting on said vertex guide means urging said vertex guide means from said normal position toward said base line; c. providing a retracting force generally opposed to said extending force continuously urging said vertex guide means, at least when said vertex guide means is away from said normal position, away from said base line toward said normal position, but preventing said retracting force from moving said vertex guide means past said normal position; d. normally operating said machine to draw said yarn through said downstream guide and maintaining said vertex guide means in said normal position with normal yarn flow; e. when said normal yarn flow is impeded upstream of said vertex guide means to a predetermined undesirable level, thereby increasing said extending force to an actuating level at least sufficiently high to exceed said retracting force, releasing said vertex guide means to permit said increased extending force to move said vertex guide means toward said base line; f. actuating the stop motion control circuit of said machine at a time not prior to the time the extending force increases to said actuating level while permitting said extending force to continue moving said vertex guide means toward said base line, as said machine continues drawing said yarn because of machine inertia, until either said impediment self-eliminates or said machine stops drawing said yarn; g. eliminating said impediment if it has not been selfeliminated, elimination of said impediment, by self-elimination or otherwise, reducing the extending force acting on said vertex guide means to a level below the level of said retracting force, to permit said retracting force to automatically return said vertex guide means to said normal position; h. automatically deactuating said stop motion control circuit at a time subsequent to the time it was actuated; i. continuously retaining and guiding said vertex with said vertex guide means throughout the foregoing steps to maintain said yarn reach taut; j. maintaining a continuous connection between said vertex guide means and a reference connection location on a support throughout said vertex guide means movement, said connection being lengthened in the general direction of said extending force during movement of the vertex guide means in one of said vertex guide means movement directions and being shortened in the general direction of said retracting force during movement of the vertex guide means in the other of said vertex guide means movement directions; k. and restarting said machine, to resume normal operation, after said vertex guide means has been returned to said normal position and said stop motion control circuit has been deactuated; 1. said normal position being sufficiently remote from said base line to provide adequate distance for said vertex guide means to continue moving toward said base line without reaching it until said machine stops drawing said yarn without selfelimination of the impediment after actuation of said stop motion control circuit.

15. A stop motion assembly for use with a stop motion control circuit of a knitting machine or the like for actuating said stop motion control circuit when the normal yarn flow is undesirably impeded upstream of the vertex of a flexed reach of yarn traveling from an upstream yarn guide to an adjacent downstream yarn guide by being drawn through the latter by said machine, said machine continuing to draw said yarn after actuation of the stop motion control circuit because of machine inertia, said assembly comprising: a. a support; b. movable vertex guide means for retaining and guiding the vertex of said reach of traveling yarn throughout the movement of said vertex guide means; c. mounting means for mounting said vertex guide means on said support for longitudinal reciprocating movement between a normal guiding position and a terminal guiding position and for providing at least a portion of a continuous longitudinally lengthenable-shortenable connection between said vertex guide means and a reference location on said support throughout said vertex guide means movement; d. means providing a retracting force continuously urging said vertex guide means, at least when said vertex guide means is away from said normal position, away from said terminal position toward said normal position; e. said vertex guide means being movable from said normal position toward said terminal position by an extending force exerted by said vertex, generally opposed to said retracting force, when the level of said extending force reaches an actuating level at least sufficiently high to exceed said retracting force, said retracting force automatically returning said vertex guide means to said normal position when said retracting force exceeds said extending force and said vertex guide means is away from said normal position; f. means preventing said retracting force from moving said vertex guide means past said normal position; g. switch means for actuating said stop motion control circuit, said circuit being actuated when said switch means is closed and being non-actuated when said switch means is open, said switch means being normally open; h. means for connecting said switch means to the stop motion control circuit of said machine; i. and sensor means for closing said switch means at a time not prior to the time said extending force increases to said actuating level while permitting said extending force to continue moving said vertex guide means toward said terminal position, as long as said extending force exceeds said retracting force, and for automatically opening said switch means at a time subsequent to the time it was closed; j. whereby when normal yarn flow is impeded upstream of said vertex guide means to increase the level of said extending force to said actuating level, said switch means is closed and said extending force moves said vertex guide means toward said terminal position, said extending force continuing to move said guide means toward said terminal position after said switch means closes as said machine continues drawing said yarn because of machine inertia until said impediment selfeliminates or said machine stops drawing said yarn, and when said impediment is eLiminated, by self-elimination or otherwise, to reduce the extending force to a level below the level of said retracting force, said retracting force automatically returns said vertex guide means guiding said vertex to said normal position, said switch means automatically opening at a time subsequent to the time it was closed.

16. An assembly according to claim 15, including means for preventing said extending force from moving said vertex guide means from said normal position until said extending force has been increased to a predetermined level greater than the minimum force needed to exceed said retracting force without preventing said extending force from subsequently moving said vertex guide means toward said terminal position as long as said extending force exceeds said retracting force, said predetermined level being said actuating level.

17. An assembly according to claim 16, wherein said sensor means closes said switch means when said extending force moves said vertex guide means to a switch actuating position intermediate said normal position and said terminal position.

18. An assembly according to claim 17, wherein said sensor means is responsive to the position of said vertex guide means for closing said switch means when said extending force means said vertex guide means from said normal position to said intermediate position.

19. An assembly according to claim 18, wherein said means exerting a retracting force comprises means acting on said mounting means to urge the shortening of said connection.

20. An assembly according to claim 19, wherein at least the longitudinally lengthenable-shortenable portion of said connection extends substantially along a movement path of said vertex guide means.

21. An assembly according to claim 20, wherein at least a portion of said connection is at least transversely flexible.

22. An assembly according to claim 21, wherein said assembly to substantially free of means restraining transverse movement of said vertex guide means during at least the major portion of the movement between said intermediate position and said terminal position.

23. An assembly according to claim 22, wherein said mounting means is longitudinally lengthenable and shortenable.

24. An assembly according to claim 20, wherein said mounting means comprises a telescopic member.

25. An assembly according to claim 20, wherein said mounting means and said means providing a retracting force are comprised by longitudinally resilient means.

26. An assembly according to claim 20, wherein said mounting means comprises a retracting coil tape having a terminal portion free to move away from said support, said vertex buide means being mounted on said terminal portion, said means providing a retracting force urging said coil tape to retract said terminal portion.

27. An assembly according to claim 26, wherein said coil tape is a spring actuated retracting spiral coil tape, said spring actuation providing said retracting force.

28. An assembly according to claim 27, wherein said coil tape is a retracting spiral spring tape whose inner end is secured to said support, at least some of the coils intermediate said inner end and terminal portion being resilient to provide said spring actuation.

29. An assembly according to claim 28, wherein said sensor means includes a sensor for sensing the position of the yarn vertex retained and guided by said vertex guide means as said vertex guide means moves from said normal position to said intermediate position.

30. An assembly according to claim 29, wherein said vertex guide means comprises laterally spaced apart yarn guides defining a laterally extending vertex guiding corridor for retaining and guiding the yarn vertex throughout the movement of said corridor between said normal guiding position and said terminal position.

31. An assembly according to claim 30, including means mounting said sensor on said support for movement between a normal sensing position adjacent said corridor in saId normal guiding position and a longitudinally spaced apart switch actuating sensing position adjacent said corridor in said intermediate position and for continuously urging said sensor from said normal sensing position toward said switch actuating sensing position; said sensor traversing said corridor throughout said sensor movement at least when said vertex guide means is in said normal guiding position, or said intermediate position, or in any position between; said sensor being longitudinally passable through said corridor, in the absence of yarn guided thereby, upon relative longitudinal movement between said sensor and said corridor; said sensor in said normal sensing position overlying said corridor whereby when said corridor is guiding said vertex said sensor will be urges against said vertex and will follow and sense said vertex as said corridor moves between said normal guiding position and said intermediate position, said sensor following said vertex being at said switch actuating sensing position when said corridor is at said intermediate position; said sensor opening said switch means in said normal sensing position and closing said switch means in said switch actuating sensing position.

32. An assembly according to claim 31, wherein said means for preventing said vertex guide means from moving from said normal guiding position comprises a catch pivotally mounted on said support for movement between a locking position wherein a catch portion is interposed in the course of movement of said vertex guide means from said normal position to said intermediate position and a releasing position wherein said catch portion is not so interposed, adjustable means urging said catch from said releasing position to said locking position, said catch being movable from said locking position to said releasing position by said vertex guide means when said extending force is at a predetermined level sufficiently high to overcome said retracting force and the force of said adjustable means, said interposed catch portion preventing said extending force from moving said vertex guide means from said normal position to said intermediate position when said extending force is below said predetermined level.

33. An assembly according to claim 32, wherein said adjustable means is a spring.

34. An assembly according to claim 15, wherein said sensor means automatically opens said switch means at least when said retracting force returns said vertex guide means retaining and guiding said vertex to said normal position.

35. An assembly according to claim 17, wherein said sensor means maintains said switch means closed as long as said vertex guide means is between said intermediate position and said terminal position.

36. An assembly according to claim 28, wherein said inner end of said tape is fixed to an arbor mounted on said support, said arbor being adjustably rotatable in order to vary the number of coils in said tape in order to preset the tension of said tape and thereby preset the retracting force provided thereby.

37. An assembly according to claim 28, wherein said inner end of said tape is non-rotatably mounted on said support.

38. An assembly accordin to claim 17, wherein said means for preventing said vertex guide means from moving from said normal guiding position comprises a catch pivotally mounted on said support for movement between a locking position wherein a catch portion is interposed in the course of movement of said vertex guide means from said normal position to said intermediate position and a releasing position wherein said catch portion is not so interposed, adjustable means urging said catch from said releasing position to said locking position, said catch being movable from said locking position to said releasing position by said vertex guide means when said extending force is at a predetermined level sufficiently high to overcome said retracting force and the force of said adjustable means, said interposed catch portion preventing said extending force From moving said vertex guide means from said normal position to said intermediate position when said extending force is below said predetemined level.

39. An assembly according to claim 28, wherein said means for preventing said vertex guide means from moving from said normal guiding position comprises a catch pivotally mounted on said support for movement between a locking position wherein a catch portion is interposed in the course of movement of said vertex guide means from said normal position to said intermediate position and a releasing position wherein said catch portion is not so interposed, adjustable means urging said catch from said releasing position to said locking position, said catch being movable from said locking position to said releasing position by said vertex guide means when said extending force is at a predetermined level sufficiently high to overcome said retracting force and the force of said adjustable means, said interposed catch portion preventing said extending force from moving said vertex guide means from said normal position to said intermediate position when said extending force is below said predetermined level.

40. An assembly according to claim 15, wherein said mounting means comprises a retracting spiral spring tape having an inner end secured to said support and an outer terminal portion free to move away from said support, said vertex guide means being mounted on said terminal portion, at least some of the tape coils intermediate said inner end and terminal portion being resilient to urge said spring tape to retract said terminal portion, thereby providing said retracting force.

41. An assembly according to claim 40, wherein said sensor means closes said switch means when said extending force moves said vertex guide means to a switch actuating position intermediate said normal position and said terminal position and automatically opens said switch means at least when said retracting force returns said vertex guide means retaining and guiding said vertex to said normal position.