US3480048A - Fill break detector for a loom - Google Patents

Description

Nov. 25, 1969 P. E. BLOCK 3,480,048

FILL BREAK DETECTOR FOR A LOOM Filed Feb. 12, 1968 5 Sheets-Sheet 1 l/ 9 owe MWOC o l-Proms; Yw

P. E. BLOCK Nov. 25, 1969 FILL BREAK DETECTOR FOR A LOOM l/ /Oc wag @J O QTTOIQIOELYf & MVEIIQTO aul 6:.

3 Sheets-Sheet I Filed Feb. 12, 1968 Nov. 25, 1969 P. E. BLOCK FILL BREAK DETECTOR FOR A LOOM 3 Sheets-Sheet 3 Filed Feb. 12, 1968 mavaw-vm 7 0w! 6. filocli,

W MM @w-rar-zmsvf United States Patent 3,480,048 FILL BREAK DETECTOR FUR A LOOM Paul E. Block, South Beloit, Ill., assignor to Warner Electric Brake & Clutch Company, South Beloit, 111., a corporation of Delaware Filed Feb. 12, 1968, Ser. No. 704,623 Int. Cl. D0311 51/18, 51/44, 51/28 US. Cl. 139374 6 Claims ABSTRACT OF THE DISCLOSURE For stopping a loom in the absence of a filling thread, a fill break detector includes a feeler normally projecting into the path of a reciprocating shuttle in resting engagement with the thread last drawn from the shuttle and adapted to be retracted clear of the path by a cam before the next pass of the shuttle. After each such pass, the feeler is returned to the path and, if a correctly tensioned filling thread is not present to limit the return of the feeler, the latter falls to an abnormal position causing one electrical terminal on the feeler to contact a second terminal on the cam and thereby produce an electric signal indicating the thread absence. A circuit including the two terminals responds to the signal to stop the loom by energizing an electromagnetic brake and de-energizing an electromagnetic clutch interposed in the loom drive.

This invention relates to a fill break detector for automatically stopping a loom upon sensing the absence of a filling thread which normally trails out behind a shuttle and is weaved through warp threads as the shuttle reciprocates back and forth in a predetermined path along an oscillating lay.

A typical fill break detector includes a feeler normally projecting into the path of the shuttle and resting on the filling thread last drawn from the shuttle. Upon each pass of the shuttle along the lay, a reciprocating cam retracts the feeler out of the path to clear the shuttle. Thereafter, the feeler is returned to the path to rest upon the newly laid thread and, when the latter is present and correctly tensioned, such engagement stops movement of the feeler in a normal sensing position. If the filling thread is absent, i.e., missing or broken, the returning feeler is not stopped in its normal sensing position but is permitted to advance to an abnormal position beyond the sensing position. Movement of the feeler to the latter position is detected and is utilized to initiate stoppage of the loom before substantial beating of the warp threads takes place without a filling thread or with a broken filling thread.

It is the aim of the present invention to provide a fill break detector which is capable of responding much faster to movement of the feeler to the abnormal position than existing detectors of the same general type, which is capable of stopping the loom almost instantaneously when the feeler senses that the filling thread is absent, and which, at the same time, may be constructed by making a simple addition to existing detectors eliminating the need of a substantial number of parts necessary to the operation of such existing detectors.

These and other objects and advantages of the invention will become apparent as the following description proceeds with reference to the accompanying drawings, in which:

FIGURE 1 is a fragmentary perspective view schematically showing an exemplary loom equipped with a fill break detector embodying the novel features of the present invention;

FIG. 2 is an enlarged fragmentary cross-section taken substantially along the line 22 of FIG. 1;

ice

FIG. 4 is a fragmentary cross-section taken substantially along the line 4-4 of FIG. 2;

FIG. 5 is a fragmentary view of parts illustrated in FIG. 4 and showing such parts in moved positions;

FIG. 6 is a perspective view of the fill break detector and showing the feeler in the abnormal position;

FIG. 6a is a view similar to FIG. 5 but showing the parts in still other positions;

FIG. 7 is an enlarged fragmentary cross-section taken substantially along the line 77 of FIG. 6;

FIG. 8 is a simplified, diagrammatic illustration of an arrangement for selectively driving and stopping the loom by means of a controlled electromagnetic clutch and brake; and

FIG. 9 is a schematic diagram of a control circuit for selectively energizing and de-energizing the windings of the clutch and brake and responsive to movement of the feeler to the abnormal position.

While the invention has been shown and will be described in some detail with reference to a particular embodiment thereof, there is no intention that it thus be limited to such detail. On the contrary, it is intended here to cover all modifications, alternatives and equivalents falling within the spirit and scope of the invention as expressed in the appended claims.

For purposes of illustration, the invention is shown in the drawings embodied in an automatic 100m of well known construction in which a pair of swinging picker sticks 10 (FIG. 1) are operated alternately to propel a reciprocable shuttle 11 back and forth along an oscillating lay 13 adapted to be advanced and retracted through forward and return strokes in timed relation with the reciprocation of the shuttle. The shuttle carries a bobbin (not shown) of yarn, thread or other filamentary material and begins one pass along the lay during each return stroke of the latter, one or more strands 14 (FIGS. 2 and 4) of the material trailing out behind and following the flight of the shuttle to fill the shed 15 (FIG. 2) of a series of warp threads 16 drawn across the lay in a conventional manner. The strand or strands 14 laid by the shuttle is customarily called the filling thread, which is weaved through the warp threads as the shuttle executes its flight and then is beaten into place during the forward or beat-up stroke of the lay by a reed 17 (FIG. 1) located above and movable with the lay.

The picker sticks 10 and the lay 13 are pivotally mounted at 20 and 21 on a suitable frame 19 (FIG. 1), and are actuated by an electric motor 23 connected through gears 24, 25 to rotate a shaft 26. The latter is selectively coupled to main drive shaft 27 by engagement or disengagement of an electromagnetic clutch CL having cooperating elements 29 and 30 (FIG. 8) which are drivingly connected in response to energization of a clutch winding CW. An electromagnetic brake BR is interposed in the drive with one of its engageable elements 31 connected to the shaft 27, and with the other such element 33 stationarily anchored to the frame 19. When the brake elements 31 and 33 are engaged or coupled, a retarding force is exerted on the shaft 27 and the latter is stopped. The electromagnetic brake BR is actuated or de-actuated in response to energization or de-energization of an associated brake winding BW.

To oscillate the lay 13, a pair of cranks 34 (FIG. 1) rotatable with the main drive shaft 27 are coupled to connecting rods 35 which in turn are attached to the lay to rock the latter about the pivots 21 in response to rotation of the shaft. Swinging of the picker sticks 10 in timed relation with the oscillation of the lay is effected by a shaft 36 connected to the main shaft 27 via gears 37 and 39 and carrying two angularly olfset cams 40 which alternately engage followers 41 on the ends of pivoted linkages 43 coupled to the picker sticks.

In the event the shuttle 11 fails to lay a complete, correctly tensioned filling thread 14 through the shed 15 of the warp threads 16, the drive to the loom is terminated automatically to preclude beat-up of the warp threads without a filling thread or with a defective filling thread in the shed. For this purpose, a fill break detector 44 (FIGS. 1 and 6) is positioned on the lay 13 to sense the presence of the filling thread 14 and, if the thread is absent (e.g. broken, missing or too loosely tensioned), the detector responds to such absence and acts to initiate interruption of the loom drive.

In mechanical construction, the preferred but exemplary fill break detector 44 disclosed herein is, in many respects, similar to those incorporated in the Model X-3 looms manufactured and sold by the Draper Corporation of Hopedale, Mass. The mechanical elements include a feeler 45 formed by a series of elongated prongs projecting radially from a hub 46 (FIG. 4) and disposed between the legs 47 of a center fork 49 attached to the forward side of the lay 13 by screws 50 (FIG. 2). The hub is fast on a horizontal pin 51 spanning the legs of the fork and rotatably journaled therein to mount the feeler 45 for up and down swinging relative to the fork.

Normally, the feeler 45 overlies the top surface of the lay 13 and is biased to project into the path of the shuttle 11 in resting engagement with the filling thread 14 last drawn from the shuttle. Upon each pass of the shuttle along the lay, the feeler is swung upwardly about the axis of the pin 51 to a clear or retracted position (shown in phantom in FIG. 2) disposed out of the path of the shuttle to permit free movement of the latter. After the shuttle passes, the feeler is swung downwardly about the axis of the pin and is returned into the shuttle path to rest upon the newly laid filling thread. With such thread present and properly tensioned, downward swinging of the feeler is stopped in a normal sensing position shown in full in FIG. 2 by engagement of the free end portion of the feeler with the taut thread. If, however, the thread is broken, missing or otherwise absent, the feeler continues to swing downwardly beyond the normal sensing position and advances to an abnormal position (FIG. 6) since a normal filling thread is not present to restrain such further downward swinging. Movement of the feeler to the abnormal position thus indicates thread absence.

The feeler 45 is retracted out of and returned to the path of the shuttle 11 as a cam 53 (FIGS. 4 and 6) moves into and out of camming engagement with a follower which herein comprises an elongated finger or crank 54 preferably but not necessarily attached on one end of the pin 51 and projecting inwardly toward the lay 13. The cam 53 is simply a metal plate fastened to a base 55 by screws 56 and formed on its upper margin with an upwardly opening notch 57 receiving the crank 54. One side wall of the notch (the right wall as viewed in FIG. 4) is inclined upwardly to define a cam surface 59 engageable with the crank 54 to lift the latter upwardly and thereby retract the feeler 45 as the cam is moved to the left to a first position (FIG. Upon return of the cam to the right to a second position (FIG. 4), the crank is free to ride downwardly along the inclined cam surface 59 and then into the notch 57, permitting the feeler to swing downwardly under the urging of a return spring 60 (FIGS. 2 and 4) anchored between the center fork 49 and the end of the pin 51 opposite the crank 54. The spring force biasing the feeler is sufficient to swing the latter downwardly to its abnormal position in the absence of the filling thread 14 but is not great enough to cause adverse deflection of a normally tensioned thread.

Lateral movement of the cam 53 toward and away from the crank 54 (i.e., in a direction parallel to the lengthwise dimension of the lay 13) is produced by reciprocating a rod 61 (FIGS. 1 and 6) extending along the forward side of the lay 13 and carrying the cam base 55, the latter being formed with a bearing lug 63 near its lower end and being anchored to the rod by set screws 64 (FIG. 4).

The rod is slidably mounted within a guide bracket 65 (FIG. 1) attached to the left end portion of the lay, a bearing lug 66 (FIG. 4) formed on the lower portion of the center fork 49, and a second guide bracket 67 (FIG. 1) fastened to the right end portion of the lay. Near its left end, the rod 61 carries a collar 69 (FIG. 3) positioned for engagement with one arm 70 of a bell crank 71 which is pivotally mounted at 73 on the forward side of the lay. A push rod 74 is connected at its upper end to the other arm 75 of the bell crank and is pivoted at its lower end to a pin 76 (FIG. 1) disposed forwardly of the pivot axis 21 of the lay and mounted on a second bracket 77 attached to the frame 19.

With this arrangement, oscillation of the lay 13 acts through the push rod 74 and causes back and forth rocking of the hell crank 71 to move the arm 70 into and out of engagement with the collar 69. As the bell crank rocks counterclockwise about the pivot 73, the arm 70 engages the collar to shift the rod 61 and the cam 53 to the left, (as viewed in FIG. 4), thereby causing the cam surface 59 to engage the crank 54 and lift the feeler 45 upwardly against the bias of the spring 60 and out of the path of the shuttle 11. When the bell crank 71 is rocked clockwise (FIG. 3), the rod 61 and the cam 53 are returned to the right by a coil spring 79 (FIG. 1) telescoped over the rod and compressed between the guide bracket 67 and a collar 80 carried on the right end portion of the rod. With movement of the cam to the right, the crank 54 rides downwardly into the notch 57, and stops well above the bottom thereof as shown in FIG. 4 when the feeler 45 engages a tensioned filling thread 14 and stops in its normal sensing position. In the absence of the filling thread, the crank continues to move downwardly to a lower position (FIG. 6a) just above the bottom of the notch as the feeler moves downwardly past the sensing position and swings to its abnormal position.

In accordance with the primary aspect of the present invention, an electrical signal is produced essentially at the exact instant the feeler 45 first detects the thread absence and is created directly in response to movement of the feeler to the abnormal position. For this purpose, a first electrical terminal 83 is carried by and is movable with the feeler 45 and is normally spaced from a second terminal 84 located to be contacted by the first terminal only when the feeler swings downwardly to the abnormal position. In response to such swinging, the two terminals immediately engage one another to close a circuit and thereby produce a signal indicative of thread absence.

To simplify the construction of the detector 44, the first terminal 83 is formed as part of the feeler 45 itself and, in the preferred embodiment, such terminal is constituted by the free end of the crank 54 which is used in a mechanical sense to oscillate the feeler 45. The crank 54 is made of conductive metal and resides at ground potential by virtue of being connected via the center fork 49 and the rod 61 to the loom frame 19. The second terminal 84 is formed physically by a conductive plate 89 (FIGS. 6 and 7) having a lower mounting portion 91 attached to the outer side of the cam 53 by the same screws 56 which fasten the cam to the base 55. Two nonconductive spacers 93 (FIG. 7) are disposed on opposite sides of the mounting portion 91, and non-conductive washers 94 surround the scews 56 to insulate the plate 89 electrically from the cam and the screws. Electrical connection is made to the terminal plate 89 by a wire lead 94a (FIG. 4) having an eyelet fastened to the plate by a suitable screw.

As shown in FIG. 4, the terminal 84 comprises a pointed projection formed on an upper corner of the conductive plate 89 and positioned jut above the bottom of the notch 57 near the lower portion of the inclined cam surface 59. When the feeler 45 is retracted upwardly out of the shuttle path to its clear position, the first terminal 83 formed by the free end of the crank 54 is located on the extreme upper portion of the cam surface 59 and, as

shown in FIG. 5, is spaced well above the second terminal 84 formed by the pointed projection on the plate 89. Upon downward swinging of the feeler, the crank 54 rides downwardly into the notch 57 but it is stopped short of contacting the pointed projection as shown in FIG. 4 so long as a normally tensioned filling thread 14 is present to stop the feeler in its normal sensing position. However, continued downward swinging of the feeler to the abnormal position in the absence of the filling thread causes the crank 54 to fall deeper into the notch and into contact with the pointed projection on the plate 89 (see FIGS. 6 and 6a), thereby engaging the first and second terminals 83, 84 and completing an electrical circuit (to be described) in which they are connected. The signal thus is produced by engagement of the two terminals immediately when the feeler 45 detects the thread absence and falls to the abnormal position. Since the terminals are held out of contact when the feeler is disposed in both its retracted and normal positions, the signal is produced only when the feeler detects the thread absence and is permitted to swing to its abnormal position.

The brake BR is energized and the clutch CL is deenergized in response to the signal produced by engagement of the terminals 83 and 84. For this purpose, the terminals and the clutch and brake windings CW, BW are connected into an exemplary circuit 96 (FIG. 9) which is similar in many respects to that disclosed in US. patent application Ser. No. 585,577, filed Oct. 10, 1966, in the name of Roger C. Brendemuehl and assigned to the assignee of the present application. As shown, the clutch winding CW and the brake winding BW are connected through respective silicon controlled rectifiers (SCRs) 95, 95' across first and second conductors or voltage sup ply lines L1 and L2 leading from a suitable DC. voltage source, here shown as a 30 volt battery 99. The line L1 is grounded to the loom frame 19 and resides at a reference or ground potential, and the line L2 is thus a 30 volt supply line. Each of the SCRs 95 and 95' is poled to conduct current through its anode-cathode path from the ground line L1 to the negative line L2. The SCR 95 may be triggered into its conductive state to excite the clutch winding CL by momentary closure of a start switch S1, thereby connecting a voltage divider formed by resistors 97, 98 across the supply lines L1, L2. The gate g of the SCR 95 is connected to the junction between the resistors 97, 98 so that even momentary closure of the switch S1 creates a voltage pulse making the gate g positive relative to the SCR cathode, and thus triggers the SCR 95 into its conductive state. As is well known, once an SCR has been triggered into conduction, it will continue to conduct current across its anode-cathode path even though the enabling gate signal is removed, and until the anode-cathode potential is reduced to zero or is reversed in polarity.

Similarly, the SCR 95' may be triggered into its conductive state to excite the brake winding BW by momentary closure of a stop switch S2 to connect a voltage divider formed by resistors 97' and 98 between the lines L1 and L2 so that a momentary pulse is applied to the gate g making the latter positive with respect to its associated cathode. To de-energize the brake BR whenever the clutch CL is energized, and vice versa, one SCR (95, 95') is always turned off when the other SCR is triggered on. For this purpose, a switching capacitor 100 is connected between the anodes of the SCR 95 and the SCR 95'. As explained in more detail in the above-identified Brendemuehl application, the capacitor turns off the SCR 95 by reversing the polarity of the voltage between its anode and cathode each time the SCR 95 is triggered. Similarly, the capacitor momentarily reverses the polarity of the voltage between the anode and the cathode of the SCR 95 and causes the latter to turn off each time the SCR 95' is triggered. In this way, the cluch CL and the brake BW will be complementally actuated since triggering of the SCR 95 (by momentary closure of the start switch S1) will initiate excitation of the clutch winding CW with simultaneous de-energization of the brake winding BW. In a like manner, triggering of the SCR 95 (by momentary closure of the stop switch S2) will initiate excitation of the brake winding BW while simultaneously de-energizing the clutch win-ding CW.

In carrying out the present invention, the signal produced by closure of the terminals 83, 84 in response to detection of the absence of the thread 14 is utilized to stop the loom drive. This is accomplished quite simply and with a minimum of physical elements by connecting the terminals 83, 84 in parallel with the stop switch S2 in the circuit of FIG. 9. The terminal 83 is at ground potential and thus connected to the line L1; and the lead 94a is simply connected to the junction between the switch S2 and the resistor 97'. The terminals 83, 84 are thus in a series circuit with resistors 97, 98' between voltage supply lines L1, L2. Thus, no current flows through the voltage divider 97, 98' in those instances when both the switch S2 is open and the terminals 83, 84 are out of engagement. But when the clutch coil CW is excited and the loom is operating by drive through the engaged clutch CL, momentary contact of the detector terminals 83, 84 will produce signal current through the divider 97', 98 from the line L1 to the line L2, thereby triggering SCR and turning SCR 95 off to disengage the clutch CL and engage the brake BR.

With the foregoing arrangement, the loom may be conditioned for operation by closure of a main switch S3 in the line L2 to connect the voltage source 99. After the drive motor 23 has been started, the start switch S1 is momentarily closed to set the SCR 95 and the SCR 95' in their conductive and non-conductive states, respectively, and thereby energize the clutch winding CW and de-energize the brake winding BW to allow rotation of the drive shaft 27, 36. During normal operation of the loom, the detector terminal 83 remains out of contact with the terminal 84 as long as normally tensioned filling threads 14 are being drawn from the shuttle 11. If a filling thread should happen to be absent, the feeler 45 immediately swings downwardly to its abnormal position allowing the terminal 83 to fall into contact with the terminal 84 and instantaneously trigger the SCR 95. This results in the immediate energization of the brake winding BW and de-energization of the clutch winding CW to stop the loom well before the lay 13 reaches the end of its subsequent forward stroke and causes beating of the threads. The operator may stop the loom at any time independently of the condition of the terminals 83, 84 by closing the stop switch S2 and, whenever the loom is to be shut down and idle, the main switch S3 may be opened to disconnect the voltage source 99 so that neither of the windings CW or BW is excited.

From the foregoing, it will be apparent that the present invention brings to the art an improved fill break detector capable of stopping the loom immediately in response to the sensing of the absence of a filling thread and without the delays heretofore resulting from the mechanical transmission of the motion of the feeler. The invention may be readily incorporated in detectors presently being manufactured simply by adding a conductive plate 89 to the cam 53 and by providing appropriate circuitry to the electromagnetic clutch and brake. This not only reduces the response time of the detector but also simplifies its overall construction since various linkages for transmitting the motion of the feeler then may be eliminated.

I claim as my invention:

1. In a loom having an oscillating lay, a shuttle carrying a filling thread and reciprocable back and forth on the lay along a predetermined path with the thread following the flight of the shuttle, a feeler mounted for movement into and out of said path, means for retracting said feeler to a clear position out of said path while the shuttle passes thereby and for thereafter returning said feeler into said path to engage the thread drawn from the shuttle during such pass, said feeler being stopped in a normal sensing position by such thread when the latter is present and being permitted to advances beyond said sensing position to an abnormal position when such thread is absent, the improvement comprising a first electrical terminal carried by said feeler, a second electrical terminal mounted adjacent said feeler and spaced to be contacted by said first terminal only when said feeler reaches said abnormal position, elec trical circuit means, including said first and second terminals and responsive to engagement thereof, for electrically signaling thread absence, said first terminal comprising a cam follower carried by and movable with said feeler, said means for retracting said feeler comprising a reciprocating cam movable relative to said feeler in timed relation with the reciprocation of said shuttle and engageable with said follower to move the feeler to said clear position, and said second terminal being carried on said cam and being free of contact with said follower when said feeler is in said sensing and clear positions while being engaged with said follower when said feeler is in said abnormal position.

2. In a loom having a lay, a shuttle carrying a filling thread and reciprocable back and forth on the lay along a predetermined path with the thread trailing out behind the shuttle, a feeler mounted for movement into and out of said path and biased into the path, a cam movable to a first position to engage and retract said feeler clear of said path while said shuttle passes by the feeler, said cam being movable to a second position to release said feeler for movement into said path after each pass of said shuttle to engage the thread last drawn from the shuttle, said feeler being stopped in a normal sensing position by such thread when the latter is present and being permitted to advance beyond said sensing position to an abnormal position when such thread is absent, the improvement comprising a first electrical terminal carried by said feeler, a second electrical terminal mounted on but insulated from said cam and located to be contacted by said first terminal only when the feeler moves to said abnormal position and said cam is in said second position, and electrical circuit means, including said first and second terminals and responsive to engagement thereof, for electrically signaling said thread absence.

3. In a loom having an oscillating lay, a shuttle carrying a filling thread and reciprocable back and forth on the lay along a predetermined path with the thread following the flight of the shuttle, a rotatably driven shaft connected to propel said shuttle back and forth along said lay and to oscillate the lay in timed relation, an electromagnetic brake energizable to exert a retarding force on said shaft, an electromagnetic clutch de-energizable to interrupt the transmission of driving torque to said shaft, a feeler oscillating with and mounted for up and down swinging movement on said lay and biased to swing downwardly into said path, a follower carried by said feeler, a cam movable to a first position to engage said follower and swing said feeler upwardly out of said path while said shuttle passes by the feeler, said cam being movable to a second position to release said feeler for downward swinging into said path after each pass of said shuttle to engage the thread last drawn from the shuttle, said feeler being stopped in a normal sensing position by such thread when the latter is present and being permitted to swing downwardly beyond said sensing position to an abnormal position when such thread is absent, the improvement comprising, means on said cam engageable with said follower only when said feeler swings downwardly to said abnormal position and operable as an incident to such engagement to produce an electrical signal, and means responsive to said signal for energizing said brake and deenergizing said clutch.

4. In a loom having an oscillating lay, a shuttle carrying a filling thread and reciprocable back and forth on the lay along a predetermined path with the thread following the flight of the shuttle, a rotatably driven shaft connected to propel said shuttle back and forth along said lay and to oscillate the lay in timed relation, an electromagnetic brake energizable in response to an electrical signal to exert a retarding force on said shaft, an electromagnetic clutch de-energiza'ble in response to an electrical signal to interrupt the transmission of driving torque to said shaft, a feeler oscillating with and mounted for up and down swinging movement on said lay and biased to swing downwardly into said path, a follower carried by said feeler, a cam movable to a first position to engage said follower and swing said feeler upwardly to a clear position out of said path while said shuttle passes thereby, said cam being movable to a second position to release said feeler for downward swinging into said path after each pass of said shuttle to engage the thread last drawn from the shuttle, said feeler being stopped in a normal sensing position by such thread when the latter is present and being permitted to swing downwardly beyond said sensing position to an abnormal position when such thread is absent, the improvement comprising, a normally open electrical circuit having a first terminal carried on said cam, said circuit including a second terminal on said follower in spaced relation with said first terminal when said feeler is in said clear and sensing positions and movable into contact with said first terminal directly in response tov swinging of said feeler to said abnormal position, thereby to close said circuit and to produce an electrical signal indicative of the thread absence, and means responsive to said signal for energizing said brake and de-energizing said clutch.

5. A loom as defined in claim 4 in which said cam is formed with an upwardly inclined cam surface and in which said first terminal is located near the lower portion of said cam surface, said follower and said second terminal comprising an elongated finger of conductive material riding on said cam surface and held above said first terminal by engagement of said feeler with said thread when the feeler is in said sensing position, said surface being shaped to cam said finger upwardly to swing said feeler to said clear position and being shaped to leave said finger free to fall downwardly into contact with said first terminal when said feeler swings downwardly to said abnormal position in the absence of said thread.

6. A loom as defined in claim 5 in which said circuit includes an electrical power source having one side connected to said finger, said first terminal being connected to the other side of said power source and being insulated electrically from said cam and said inclined cam surface.

References Cited UNITED STATES PATENTS 3,373,773 3/1968 Balentine et al. 139336 FOREIGN PATENTS 1,009,546 3/1952 France. 1,140,614- 3/1957 France.

830,780 7/ 1949 Germany.

HENRY S. JAUDON, Primary Examiner

Images