US2973617A

US2973617A - Device for monitoring the continuity of yarns, rovings and the like

Info

Publication number: US2973617A
Application number: US715955A
Authority: US
Inventors: Weinberger Jan Viteslav
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-02-18
Filing date: 1958-02-18
Publication date: 1961-03-07
Anticipated expiration: 1978-03-07

Description

March 7, 1961 J v wElNBERGER 2,973,617

DEVICE FOR MONITORING THE CONTINUITY 0F YARNS, ROVINGS AND THE LIKE Filed Feb. 18, 1958 2 Sheets-Sheet 1 i F5 INVENTOR JAN u WE/NBERGER y RLIW U AGENT March 7, 1. 6 J. v. WEINBERGER ,973,617 A DEVICE FOR MONITORING THE CONTINUITY 0F YARNS, ROVINGS AND THE LIKE Filed Feb. 18, 1958 2 Sheets-Sheet 2 v lNVENTOR JAN 1 WE/NBERGER 5 RXJW AGENT DEVICE FOR MONITORING THE CONTINUITY OF YARNS, ROVINGS AND THE LIKE Jan Viteslav Weinberger, 255 Metcalfe St, Apt. 11, Ottawa, Ontario, Canada Filed Feb. 18, 1958, Ser, No. 715,955 7 Claims. (Cl. 51-86) This specification describes an invention in devices for monitoring the condition of a thread or strand, and in particular sets forth an invention in a device for testing the continuity of a weak or vulnerable'yarn or roving body and for giving an indication when a discontinuity in such body occurs.

The subject invention has a primary utility in the field of textile manufactures, and specifically applies to wrapping, winding, twisting; pairing or other operations dealing with two or more yarns, filaments, rovings or thread bodies, where the discontinuity of any one or more of the component bodies would degrade an ultimate product woven or knitted therefrom. The processing of defective yarns wherein one or more component bodies is inadvertently omitted may result in visible flaws, particularly upon dyeing of the fabrics if the component threads have dissimilar affinities to the dyestuff. Whenever a discontinuity of a monitored thread occurs, it is highly desirable that the event be immediately detected and the operation completely stopped, as by shutting down a machine drive or by cutting all corn: panion threads or rovings, in order to prevent manufacture of defective product.

In certain operations one or more of the threads or rovings may be the weaker and hence may require continuous supervision to detect a discontinuity arising from excessive tension; however any component thread or yarn, as fed to a spindle or other operative part from conventional spools or bobbins carrying finite lengths of the material, will automatically become discontinuous as the spool or bobbin becomes empty. Accordingly, for either event the action of the monitor should be the positive shut-down of the operation or the severing of all companion threads to terminate the operation until restored.

Embodiments of the present invention have utility for the detecting of a break or discontinuity of a thread or roving, and for giving notice thereof to an operator or attendant responsible for monitoring such events, Preferred embodiments additionally include means to effect a significant change in the condition or state of an elec trical circuit whereby evidence of the event may be manitested at a remote location, and automatic controls may be. activated accordingly to shut down the operation or otherwise take corrective action.

To this end and in accordance with the invention, in a device of the kind referred to a pendulous body having one stable rest position with respect to a substantially horizontal axis of rotation is inverted to an unstable rest position in which it is maintained by the resistance to deflection of a roving or yarn body extending between spaced guides; in the event that the roving or yarn therebetween becomes discontinuous, the pendulous body is released. Under the force of gravity the pendulous body-thereupon swings about the axis of rotation to produce a mechanical indication of the'event by its change of position, and acquires kinetic energy in its fall.

Patented Mar. 7, 1961 In my preferred embodiment the device includes means for using the kinetic energy of the pendulous body to effect a severing of the companion threads or yarns, either by pressing the threads against a stationary knife edge or by swinging a blade to slice across the threads.

An electrical contact-making device is preferably actuated either directly by the body or indirectly .by an extension or arm fixed to the body, to alter the state;

or condition of an electrical circuit which includes the switch contacts. Any of a wide variety of electrical circuit arrangements and indicator elements maybe associated with the switch whereby to transmit information of the event remotely; For example, a multitude of such monitor devices may be electrically connected to respective bulbs in a monitorpanel, the state of each particular bulb corresponding to the cocked or released position of its associated detector.

In carrying the invention into effect, a device for monitoring the continuity of a yarn or a roving is mounted between a source spool and the combining unit which operates on the roving together with one or more com-' panion threads, the device having at least a pair of smooth supports between which the yarn or roving passes; a pendulous body pivotable about a horizontal axis in thedevice is disposed in an unstable position with its centre of mass above and laterally offset from a vertical through the axis, and is maintained in such inverted position by the opposing force against a fork or a finger fixed to the body presented by a yarn or roving extending the supports. The force tending to deflect the yarn or roving is so adjusted by choosing the position of the centre of mass with respect to its pivot axis that the tension developed does not cause the monitored body to break or to deform, Lays of a companion thread or threads are arranged and supported between eyelets or guides so that they cross the arcuate path along which a knife fixed to the pendulous body, as by means of a blade holder, moves when the body swings about itsrotational axis. In the event of a discontinuity in the roving appearing between the supports, the pendulous body swings around its axis and the potential energy of the mass is transformed into kinetic energy. By'

suitably choosing the dimensions and mass of the body, the kinetic energy developed may be adequate to cause the knife edge to sever the companion thread or threads. At the same time an electrical circuit may be closed, as

by impact of the pendulous body with a switch-contact by study of the follOwing description of its preferred embodiments which are illustrated in the accompanying figures of drawing, and wherein: Y

Fig. 1 is a frontal perspective view of an assembled monitor device in use, for detecting a break in a roving body and for severing a companion thread if such break occurs;

Fig; 2 is a vertical section through the device taken on the line 2-2 of Fig. 1 to illustrate the support of a mass in an inverted position, resting against a roving or yarn;

Fig. 3 is a front elevation view of a slotted mounting frame in somewhat reduced scale;

Fig. 4 is a composite vertical section taken on the line 4-4 of the device of Fig. 1 as viewed from the right;

Fig. 5 shows the manner of frictionally locking the p u s body of th device in Fig- Fig. 6 shows the two-part housing employed in constructing the device in disassembled relation;

Fig. 7 is a projection view of the device of Fig. 1 along a radius indicated by the arrow 7, and showing the lay of a companion thread with respect to a movable knife blade;

Fig. 8 isa frontal perspective view of an alternative embodiment wherein a semaphore arm or telltale rises to indicate a break detected in a roving or yarn;

Fig. 9 is a view similar to that of Fig. 8 with the front housing removed;

Fig. 10 is a front view of the device of Fig. 8 showing the monitor device after it has severed a companion thread in response to a discontinuity of a roving; and,

Fig. 11 is a radial projection directed through the axis of rotation of the pendulous body looking toward the knife blade, the latter being in a position just prior to severing a lay of companion thread.

Referring to the drawing, a monitor device as in Fig. 1 generally designatedlO is afiixed to a support bracket 14 which in turn depends from a machine frame 15, as for example a support rack in a textiles plant upon which an array of spools or bobbins such as 16 are located. A roving 17, which may for example be a relatively weak unspun body of staple such as cotton, passes through the monitor 10 from the rear to the front through a pair of

eyelets

18, 19, and is partly surrounded by a channel guide 38. A pair of

prongs

37 and 41, movable within the channel guide through the

slots

39 and 40 formed therein, are arranged as will be described in greater detail hereinafter, to exert a slight and adjustable force against the roving as it moves through the device.

Referring additionally to Figure 2 showing the device in typical operation, the monitor includes a housing comprising a front vertical wall 11 spaced from a parallel similarly shaped back wall 13 and integrally joined therewith by an end wall 65, disposed normally to both. As may be more readily understood by referring additionally to Figure 6, the aforesaid walls may be conveniently fabricated from a single piece of sheet metal folded by two right angle bends defining the joining end wall 65 and including a tab 42 extending from the said end wall and having a width slightly less than that of wall 65.-

The tab is bent over at 90 degrees with respect to the end wall and is arranged to be freely deflectable between the front and the back walls. Suitable material for the housing is a stainless steel or other strong and relatively noncorroding metal.

A body 20 comprising a mass of metal or other relatively dense material is eccentrically mounted upon a pivot axis 21, the axis being generally horizontal when the monitor is in operative position. The pair of

prongs

37 and 41, made of a suitable stiff and relatively hard material, or having a hard surface material coating, are secured as by a press fit into holes drilled into the body 20; In normal monitoring operation, the centre of mass of the.body 20 including its knifeblade holder 22, is above and slightly to the side of a vertical plane passed through the axis of rotation in axle 21, so as to produce a small couple tending toproduce a clockwise rotation as viewed in Fig. 2. A force is exerted by the prongs against the roving 17, which is'pressed against the inner face of the guide channel 38. Adjustment of the amount of force is possible by bodily rotating the monitor about a horizontal axis in either a clockwise or an anti-clockwise direction, after loosening the fastening nuts of. bolts 60 securing it in the

slots

35 and 36 of mounting bracket 14, shown in Fig. 3. When the relative positions of the axis of'rotation of axle 21 and the center of mass of the pendulous body 20 are suitably related, the nuts 48 engaging the ends of an upper and a lower mounting bolt 60 are flanges 58, along the greater part of its length, and is terminated by a U-shaped slotted guide channel 38 having a width substantially equal to the over-all width of the end wall as measured between the outer faces of the flanges 58. The

slots

39, 40, lie in planes parallel with the

walls

11 and 13, and have a width sufficient to pass

prongs

37 and 41 freely therethrough. The lower marginal portions of the U-shaped channel may be relieved, as will appear from Fig. 4, to avoid interference with the

ceramic guides

18, 19. A series of oppositely disposed holes 62 are provided in the pairs of

parallel tabs

55, 56, and 57, which are integral with the flanges 58. When the end wall is fitted between the open ends of the

side walls

11 and 13, registering holes 61 formed in the latter align with the holes 62 to receive through bolts 60 to provide a sturdy assembly. The front wall 11 has an arcuate slot 50 formed therein concentric with the central hole 49, in which axle support bolt 47 is received, A pair of circular apertures 52 and 53 respectively are formed in opposite sides of the monitor in

walls

11 and 13 to receive ceramic or other hard-

surface guide eyelets

18 and 19. A pair of slots are formed between the outer margins of the side walls and the said circular apertures to permit inserting a roving.

Mounted upon the front wall of the monitor are a pair of thread guides or

pigtails

25 and 26, located in holes 63 respectively radially inwardly of and radially outwardly of the arcuate slot 50. A tensioning device including tension adjustment discs 27 is supported on the front wall in the hole 64.

Referring additionally to Figure 7, a knife blade 23 is supported in a carrier 22, the latter being a relatively stiff sheet metal body attached to the front face of the pendulus body 20 and extending through the slot in the front Wall 11. The slot 51 which extends radially inwardly from the arcuate slot 50 is provided topermit assembly by a mounting tab integral with the knife blade carrier through the front wall.

' The knife blade 23 is inclined with respect to the front Wall 11 and is mounted with its cutting edge facing towards a guide aperture in the carrier bounded on one side by the lug 31. An arm or handle 30 extends from the holder 22, and is inclined outwardly and foivvardly from the wall 11 for the purpose'o-f manipulating the pendulous body 20.

A companion filament or thread 24 is threaded through the guide 25, between the tensioning discs 27 and through the other guide 26, and thence is led to an operative device (not shown) such as a machine for manufacturing a core yarn. In general the monitor will be used with a roving 17 and a thread 24 of greatly dissimilar strength properties, the thread being 'for example one or more continuous filaments of a polyamide generally known as nylon, of much greater strength and resilience as compared with an unspun roving 17. A tensioning device of conventional form comprising a pair of discs 27, which are compressed by a spring 28 adjustable by means of the locking nuts 29, controls the tension in a lay of thread passing from the discs 27 to the guide 26. This lay is arranged to cross an arcuate path traversed by the knife blade 23, so that when the latter moves with pendulous body 20 through the limit of its swing, the filament 24- will be severed.

An electrical switch 33, for example a microswitch having a pair of circuit leads 34 and an actuator lever 32, is supported' upon the end wall 65 and is disposed so that at the conclusion of the swing produced by release of the pendulous body 20, the lug 31 on the knife blade carrier strikes the lever.32 to changethe circuit condition of the switch. g I

Where the strands 24 are. relatively tough or of con-- siderable diameter, a relatively larger magnitude ofkinetic energy must be provided bythe pendulous body to perform the work of cutting. The body 20 may F J therefore be suitable shaped to dispose the greater part of its mass as far radially outwardly of its axis as prac-" tical. At will be observed in Figs. 2 and 3, part of the mass is disposed'at a distance radially greater than that of the knife blade carrier 22. Since the knife blade 23 is disposed at an angle to the vertical plane, the resistance offered by filaments 24 when undergoing the outting action tends to deflect the carrier 22 outwardly away from the wall 11, and hence to produce a thrust on the axle 21. In order to provide a sturdy, reliable and lowfriction bearing, the axle 21 is preferably made in the form of a threaded rod having a bolt head 43 formed on one end and of a total length equal to the separation of the

walls

11 and 13. The pitch of the thread is preferably chosen to be a National Fine standard V thread, to co-operate with a corresponding internal thread in a transverse hole in body 20, as a class of fit toprovide for free relative rotation without undue looseness of the parts. An axial bore is formed throughout the entire length of the rod. The width of the pendulous body 20 is arranged to be less than the threaded length of the rod.

To assemble the monitor, the axle 21 is threaded into the transverse bore in the pendulous body 20 and the body with its

prongs

37 and 41 affixed is inserted between the

Walls

11 and 13 prior to the assembly of end wall 12. Bolt 47 is passed through the front wall hole 49 and through the bore in axle 21, passing through a corresponding hole in the back vertical wall, and the axle is secured by tightening nut 46 on the lock washer 45 against the rear wall 13. The relative distance of the pendulous body 20 with respect to the rear wall may be adjusted by turning the axle 21 as by means of a wrench engaging the bolt head 43. The end wall 12 is inserted and secured as described hereinbefore, and the rear and front

roving guides

18 and 19 are fixed in the holes 52 and 53 as by means of spring clips (not shown) or by use of a resilient cement.

Prior to the insertion of the roving 17, the handle 30 is rotated to the left, until the

prongs

37 and 41 pass under the curved lip 54 formed on the end of spring tab 42, and frictionally engage and seat in the recess 59 on that is, the prongs are forced in a clockwise direction out of the recess 59 and are gently brought to bear against the roving 17.

The monitor device described may be used with any roving having sufficient coherence to be led from a bobbin and handled in conventional textiles manufacturing operations. Inasmuch as the monitor device imposes a small but measurable friction load upon the roving, .under certain low humidity conditions the generation of static electricity may result. Fibres of the thermoplastic group have a very low natural regain a term referring to the water content at 68 percent relative humidity and at a temperature in the range 68 to 72 degrees F. Staples made of such fibres are inclined to develop static electricity in handling, unless treated by special finishes, due to the low hydroscopic water content. Where a roving of such staple is subjected to friction, the generation of static electricity at a given low relative humidity is less severe if'the area in bearing subject to rubbing pressure is reduced, as by the arrangement of hook guides incorporated in the device shown in Figs. 8 to 11. In the alternative embodiment described with reference to these figures, the set of hooks 6? of relatively small diameter are substituted in lieu of the guide channel 38 of the embodiment described hereinbefore.

Referring'to Figs. 8 to 11 of the drawing, an alternative monitor device according to the invention includes a housing comprising a front wall 11 spaced from a vertical back plate 13 by a generally arcuate flange 12, to

which the back plate is detachably secured as by screws engaging'the tabs 74 bent from the margins of the wall 131 A pendulous body 20 is rotatably mounted upon an axle 21 which has an intermediate threaded larger diameter portion of a length substantially equal to the spacing of the walls, and coaxial end portions '77 of reduced'diameter. The ends '77 protrude through holes H1 the plates on assembly, and the axle is firmly secured within the housing by nuts 68 engaging the threads thereof to clamp the walls againstthe shoulders formed at the stepped diameters.

The pendulous body 20 is preferably a high density metal block, which is bored and threaded to engage the thread on axle 21, and to swing freely thereon without objectionable end play or looseness. The axis of the bore is displaced from the centre of mass of the body to provide an effective moment arm and is preferably located near the outer margin of the body. The width of the body is made, sufliciently less than the spacing between the

walls

11 and 13 so that throughout approximately degrees of swing the pendulous body remains clear of the walls.

An actuating lever arm and indicator 30 formed of sheet metal is secured to the body 20 by suitable fastening means (not shown), and has a length sufficient to extend beyond the housing, moving in the slot 66 in the flange 12. A knife support arm 22, preferably integral with the lever arm 30, extends from the pendulous body 20 generally parallel with the axis of rotation, and protrudes the arcuate slot 50' in the front wall 11 sufficiently to expose the knife blade 23 and the aperture between lug 31 and the toe 67. The slot 50 is somewhat more than 180 degrees in circumference.

Referring to Figs. 9 and 10, a smoothly faired and rounded aperture 70 is formed in the top margin of the rear wall 13 and a similar fairednaperture is formed directly opposite along the boundary between the front wall 11 and the flange 12*. Apertures 70 take the form of short semi-cylindric sleeves having bell-mouth ends,

facing towards each other, the flange 12 being discon-' tinuous at this point. A roving or yarn 17 to be monitored is laid across the two apertures, passing from the back to front as shown in Figs. 8 and 9, although the direction of travel is immaterial. A protective shield 12a is formed by bending flange 12 outwardly at the left of the apertures 70, the free edge of the shield being preferably curved upwardly to permit feeding a roving into the supports.

One or more hooks, and preferably a group of three hooks designated 69, disposed between the inner edges of the apertures 70, are equally spaced apart and have their free ends upcurved and bent in arcs centered on the longitudinal axis of the apertures. The stem portions of the hooks are preferably disposed not lower than the margins of the apertures '70 so that a roving body 17 laid therein lies supported uniformly with its axis substantially straight. The stems of the hooks are adjustably secured between upper and lower blocks 71, which are secured together by detachable fastener means. The lower of the pair of blocks is mounted to the back plate 13 as by fastening screws (not shown).

A two-pronged fork having parallel rod-

like prongs

37 and 41 extending upwardly and secured adjustably in any suitable manner to the pendulous body 20, presses against a span of roving or yarn 17 laid upon the hooks 69, exerting a slight force tending to deflect the roving or yarn to the right. In the detecting position, the centre of mass of body 21) lies above and slightly to the right of a vertical axial plane passing through the axle 21, to produce a relatively weak couple tending to revolve the pendulous body in a clockwise direction. The spacing between the hooks 69 will be so adjusted generally that the pressures of

prongs

37 and 41 which are centred 7 The frictional load exerted by the prongs should generally be kept to a value which will not increase the tension required to overcome friction of the roving against its supports by an amount sufiicient to break or deform the roving or yarn. Furthermore, when the roving is stationary, the force exerted by the prongs should not be so large as to deflect its unsupported spans to such an extent that when the roving is again pulled through the device it becomes deformed or ruptured due to increased friction. Inasmuch as the body is essentially an inverted pendulum, any clockwise rotation due to sagging. of the roving 17 between the hooks would astatically increase the force exerted by the prongs. Therefore, for any given roving, the spread of hooks 69 should be insuflicient to allow objectionable initial sag. The manner of adjusting the magnitude of the force exerted by the prongs is as described with reference to Figs. 1 to 7, the inclination of the device as a whole being adjusted with reference to a plumb line or reference vertical for which purpose the indicia 73 on the front wall 11 is provided. The prong pressure may be gauged as by a test instrument, or visually by observing its effect on a sample roving or yarn.

A companion thread or thread group, generally designated 24, is fed through the upper guide to a tensioning device including the discs 27, and thence through the lower thread guide 26, all of the parts being mounted on the front wall 11 of the housing. From the lower guide the threads are led to the operative part or spindle (not shown), the tension in this portion being adjusted by the compression of spring 28 by means of wing nut 72 forming part of the tensioning device. The lay of threads is disposed parallel with the front wall 11 and spaced therefrom so as to be intersected by the arcuate path traversed by the knife 23, carried by the knife support arm 22.

After release of the pendulous body 20, the final condition is as shown in Fig. 10, wherein the body 20 is swung down through an arc of about 180 degrees, and the toe 67 of the blade support arm 22 has struck the switch lever 32 with a force sufficient to deflect it and to actuate contact-making elements within the switch 33. Accordingly the circuit between the conductors 34 is either completed or opened, the change of electrical state constituting an indication of the event.

Referring additionally to Fig. 11, the cutting action of knife 23 on the threads 24 will be seen to include a deflection of the threads along the length of the blade edge, until the elfect of pressure and relative motion therebetween has severed all fibers or filaments. The exact angle of inclination of the knife 23 with respect to the front wall 11 is not critical, an angle of 60 degrees therebetween being effective, for severing most textile threads.

While throughout the foregoing description the sev ering of companion textile threads has been exemplified, it is to be understood that the invention is not necessarily limited to the particular field of textiles. Indeed, the usefulness of the monitor device extends to all related fields wherever it is required to produce information of a discontinuity of a filamentary body. For example, in the wrapping of a core wire or rod with a fine diameter filamentary body, as in the manufacture of certain grades of music wire and strings for musical stringed instruments, the monitor device may be employed to change the state of an electrical circuit whenever a break in the filament passes the

prongs

37 and 41. In certain such applications it may additionally be desirable to cut a companion filament, which need not necessarily be a core filament, by the action of a knife blade as described.

It is irrelevant to the operability of the monitoring device whether the monitor body 17 is static or stationary for long periods of time, and is only drawn through the device in response tosome causatory action, to present a discontinuity between the

hooks

37 and 41, with consequent release of body 20 and concomitant actuation of switch device 33. Accordingly, embodiments of the invention may be used for the protection of property and to give warning of intrusion within a protected space, by arranging that a strand 17 has a relatively weak zone which will be ruptured as a result of a disturbance of a camouflaged trip thread secured to an end of the strand, so as to pull the discontinuity through the hooks, and thereby cause release of the body 20.

In the device of Fig. 8, to restore the device to monitoring position, the lever arm 30 is first swung to an extreme anti-clockwise position which causes the

prongs

37, 41 to approach the blocks 71, and a spring latch 76 is deflected by the prong 41, to cause a shoulder of the latch to hold the prong. After the roving or yarn 17 has been laid into hooks 69, the prong 41 is released by carefully actuating arm 30 and rotating it clockwise to bring the prong to rest against the side of the roving.

It will be obvious, it is believed, that numerous modifications of form, and departures of the exemplary embodiments described hereinbefore may be effected, without departing from the scope of the invention as defined in the appended claims.

I claim:

1. A device for monitoring the continuity of a yarn or roving comprising a frame, U-shaped channel means in the frame for guiding a span of said yarn or roving therealong, a plurality of slots formed transversely in the sides and bottom of said channel and spaced along the length of said channel, a pendulous body having a bore therein, the axis of said bore being offset from the center of mass of said body, a shaft fixed transversely in the frame and passing through the bore for journalling said body for rotation about said axis, a plurality of prongs having a common tangent plane parallel with said axis fixed in said body and having paths of arcuate movement passing through respective slots, means for supporting said frame so that said body has its center of mass above said axis, whereby said span opposes. passage of said prongs through said slots while said yarn or roving means continuous along said channel, and whereby said body is releasable to be rotated to pendulous position under the force of gravity when said slots are not bridged by said yarn or roving.

2. A device as in claim 1 wherein said body carries a visual indicator arm and switch means are disposed on the frame in the path of movement of said arm for actuation thereby when said prongs pass through said slots during descent of said body to pendulous position.

3. A device as in claim 1 including a cutting blade carried by said body, and a pair of eyelets fixed in said frame for guiding a lay of a companion strand, said lay being in the path of movement of said blade and disposed for severance thereby when said prongs pass through said slots during descent of said body to pendulous position.

4. A device as claimed in claim 1 further including a flat spring latch secured by one end in said frame and having a latch portion disposed in the path of movement of said prongs for displacement thereby for releasably holding said body inverted and angularly displaced from its operative inverted position with said prongs exterior of said slots.

5. A device for monitoring the continuity of a yarn or roving comprising a sheet metal frame having spaced parallel side walls joined by end walls, an arcuate slot formed in one side wall, opposed openings in said side walls, a U-shaped open guide channel formed in an end wall having a curved bottom portion extending between said side walls, a pair of split ring roving guides supported in said opening coaxially with said bottom portion of said channel for supporting a span of yarn or roving guided therealong, a weighted body having a bore, an axle fixed in the frame and engaging said bore for namely journalling said body to rotate about an axis parallel with the length of said channel, prong means carried by said body, said body having its center of mass displaced from said axis in the direction of said prong means, spaced slots opening in said bottom portion in the path of movement of said prongs to freely pass said prong means therethrough, an indicator arm fixed to said body extending through said arcuate slot, and means to support said frame whereby when said body is inverted with said prong means above said axis said pnong means apply pressure transversely of portions of said span bridging said slots so that upon removal of said span from said channel said body is releaed to fall to pendulous position.

6. The device claimed in claim 5 wherein said indicator arm carries a knife blade, and thread guide means supported on said arcuately slotted side wall present a lay of thread across the path of said blade for severance thereby when said body falls upon release of said prong means to said pendulous position.

7. The device claimed in claim 6 further including electrical switch means supported on said side wall and disposed to be actuated by said indicator arm when said body fallsto said pendulous position.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No; 2,973,617 March 7, 1961 Jan Viteslav Weinberger It is hereby certified'that error appears in the above numbered paten't requiring correction and that the said Letters Patent should read as corrected below.

Column 8 line 42, for "means" read remains column 9 line 13, for ""releaed read released Signed and sealed this 8th day of August 1961.

SEA L) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents