US3065518A - Power stop controls - Google Patents

Description

NOV. 27, 1962 NEAL ETAL 3,065,518

POWER STOP CONTROLS Filed March 50, 1959 2 hee s-Sheet 1 Fig.1. 5

l3 i l6-\ m if 35 34 J 1 r II--' I B d" 4!] F an 42 22 v l I C as i J 1 c A Py- B i r "1' 1 v INVENTORS RICHARD D. NEAL CARROLL W. CROMWELLJR BY wAz-m Nov. 27, 1962 Filed March 50, 1959 R. D. NEAL ETAL 3,065,518

POWER STOP CONTROLS 2 Sheets-Sheet 2 INVENTORS RICHARD D. NEAL CARROLL W. CROMWELL,JR

BY am ATT NE 3,065,518 POWER STGP CONTROLS Richard 1). Neal and Carroll W. Cromwell, Jr., Asheville, N.C., assignors to American Enka Corporation, Erika, N.., a corporation of Delaware Filed Mar. 30, 1959, Ser. No. 803,002 14 Claims. (Cl. 285l) This invention relates in general to the feeding of yarn, threads, strands, etc., of indefinite lengths under controlled conditions and more particularly to a novel means for interrupting the feed in response to a sudden increase in tension on the running yarn.

While not limited to such, the present invention is particularly applicable to the winding of a plurality of yarns into warp form on a single beam or yarn take-up, and will be specifically described in connection with that operation.

It is desirable, and practically essential from the standpoint of salability, that the plurality of ends forming a warp be collected on the beam under uniform conditions. Any increase in tension on any one of these ends will cause uneven winding at the take-up means, which introduces difficult handling problems in subsequent processing of the packaged yarn. Sudden increases in tension are generally caused by irregularities in formation of the cakes, cones, or other yarn packages which supply singles to the warping creel. In yarn supplied from cakes, for example, plucks are often formed from uneven shrinkage of the cakes during washing and drying. Additionally, defects may be produced from overwinds or underwinds during initial supply package formation, or uneven distribution of finish on the yarn may produce tension increases because of the resulting variation in friction.

The warp forming problem described briefly above is well known in the textile field. Moreover, many attempts have been made to obviate this problem by detecting any sudden increase in tension and automatically interrupting yarn feed in response thereto. These known stop motion or knock-off devices generally employ either the normal effect of gravity on a weighted member, or spring-biased levers, or both. Such devices are designed to stop the feed of yarn immediately upon increase in yarn tension to a given level so that the cause of tension increase may be located and corrected before continuing collection of the yarn.

While the known stop motion devices are theoretically sound, there are many disadvantages to operation of the same. With a device utilizing the spring bias principle, for example, each operating position must be set individually. A standard warper creel employes thousands of yarn ends, and yarn control positions, which means that a considerable amount of man hours is required for initial setting of the controls. Moreover, the springs weaken and the settings accordingly drift upon extended use, which means that a substantial amount of time is required to maintain the controls in proper adjust-ment.

The stop motion devices of the gravity type usually employ a weight or weighted arm which counterbalances tension in the running yarn and which is displaced in response to tension variations to interrupt the yarn feed motor circuit. Inasmuch as the inertia of the weight or weighted arm must be overcome before any shifting can result, these devices have proved less sensitive to change in tension than required in commercial operations to protect the physical and chemical characteristics of the yarn. In other words, the mass necessary to counterbalance running tension in the yarn inherently reduces sensitivity and precludes immediate activation in response to tension variation. Another disadvantage of the grav- 3,%5 ,5 l8 Patented Nov. 27, 1962 igC ity mechanism is that each device of the thousands employed must be set individually.

One of the primary objects of this invention is to provide a stop motion, or knock-off device for running yarn not having the disadvantages of known systems such as described above.

Another object of the present invention is to provide a stop motion system affording simultaneous and equal tension level adjustment of a plurality of units.

Still another object of this invention is to provide a stop motion device for running yarn which may be easily and quickly adjusted to desired knock-off tension, and which will maintain the initial tension level until subsequently readjusted.

A further object of the present invention is to provide a stop motion device which requires a minimum of servlClIlg.

An additional object of this invention is to provide a low pass knock-off device having very little inertia and internal friction and which may be activated immediately upon increase in tension to a predetermined level on yarn running therethrough.

Another object of the present invention is to provide a stop motion device which is adjustable over a wide range of tensions in order to accommodate various types of running yarn.

Still another object of this invention is to provide a stop motion device which also functions to impart desired tension to running yarn.

A further object of the present invention is to provide a novel electromagnetic yarn tensioning device which also operates to interrupt yarn feed immediately upon increase in tension above a predetermined level.

A more specific object of this invention is to provide an electromagnetic warp tension device which will uniformly tension a plurality of yarns fed to a warping machine and which will interrupt operation of the warping machine immediately upon increase in tension on any of the running lengths of yarn.

The foregoing objects may be accomplished in accordance with the present invention by utilizing a normally energized electromagnetic device for maintaining a secondary or control circuit in an inactive or inoperative state, by displacing running yarn laterally from an established rectilinear path in operative contact with said device so that at least a component of the yarn tension tends to render said secondary circuit operative, but is unable to do so until the electromagnetic force is overcome, by suitably connecting said secondary circuit to the primary yarn feed motor circuit so that actuation of the former will interrupt the latter, and by adjusting the voltage in the coil of the electromagnetic device so that the force developed thereby will correspond with, or counterbalance, normal yarn tension. An increase in yarn tension above the adjusted level will immediately unbalance the system, or overcome the electromagnetic force, and render the secondary circuit operative, which will interrupt the primary circuit and instantaneously discontinue the feeding operation. It is preferred that the force developed by the energized electromagnetic device also be utilized to impart primary tension to the running yarn.

Gther objects and advantages will become apparent upon study of the following detailed disclosure taken in conjunction with the accompanying drawings, wherein FIGURE 1 is a circuit diagram illustrating schematically a series or group of electromagnetic stop motion devices, a secondary or control circuit activated thereby, and a normally closed feed motor circuit which is opened in response to activation of the secondary circuit;

FIGURE 2 is an elevational view, partly in section and partly schematic, showing the passage of yarn from a supply source to a war-ping beam, and illustrating a preferred stop motion device which also functions to tension yarn;

FIGURE 3 is an elevational view of an alternative stop motion device which functions only to interrupt the feed of yarn passing therethrough in response to increase in yarn tension; and 1 FIGURE 4 is a perspective view of the combination stop motion-tension device shown diagrammatically in FIGURES 1 and 2.

The component parts of a single combination stop motion-primary tension device will now be described with particular attention to FIGURES 2 and 4, it being understood that corresponding elements will be identified by like reference numerals throughout the specification and drawings. Moreover, it should also be understood that the additional devices 11 and 12 shown in FIGURE 1 may be and preferably are of identical construction to the device 10. i

The device 10 consists of an electromagnetic head 13 which may be mounted in any convenient manner to subframe 14. The sub-frame in turn is supported by a warper creel (not shown) or any other framework with which the device is to be used. Electromagnetic head 13, which contains a coil or winding (not shown), is commercially available and will not be described in detail. Mounting post 15 is fixed to and extends normal from the plane of the coil enclosed within head 13 and, in this embodiment, supports head 13 from sub-frame 14.

An apertured tension disc 16 formed from magnetic material is slidably and rotatably mounted over post 15. In the modification presently described, this disc performs a dual function. Upon inspection of FIGURE 2, it will be seen that the yarn or thread 17 to be controlled passes between the disc 16 and head 13. When the coil within head 13 is energized, disc 16 is urged against yarn 17, which produces a frictional drag or resistance to passage, thereby imparting considerable tension, depending on energization of the coil. The disc 16 also is conductive, and serves the additional function of activating a secondary or control circuit now to be described.

Attention is directed to the fact that electromagnetic head 13 is mounted in an inverted position from that heretofore suggested. With this mounting the normal effect of gravity is utilized to urge the disc away from the head. Although this arrangement is not essential from a theoretical standpoint, the same, practically speaking, is very important to the present invention. Displacement of disc 16 away from head 13 activates the secondary circuit, as will be more fully explained infra. An undesired increase in yarn tension is used to physically displace the disc. It is necessary, therefore, that the weight of this disc be kept at a minimum, else too great a knock-off tension would be required to overcome the inertia thereof. If a substantially weightless disc could be obtained, a slight increase in yarn tension would be sufficient to displace the same, and the head 13 could be mounted in any position desired. Since weightless discs are not available, however, it has been found that the force of gravity should be utilized to assist disc knock-off and reduce that increased yarn tension required to interrupt the yarn feed motor circuit. A more satisfactory operation thus is obtained, since the sensitivity of the stop motion device is inversely proportionalto the incremental tension required to displace disc 16.

With attention now directed to FIGURES 1 and 2, it can be seen that four independent but definitely interrelated circuits have been illustrated. Reference letter A represents a steady or pulsating source, or combination of both, of direct or alternating current used solely for energizing the coils within. electromagnetic heads 10, 11 and 12. These heads are wired in parallel to power leads 18, 26 in this embodiment, although it should be understood that a series connection could be usedequally effectively. A potentiometer 21 is advantageously provided intermediate the coils and source of current A to enable simultaneous and uniform adjustment of the force generated by each of the heads 10, 11,12. If simultaneous adjustment is not desired, individual potentiometers could of course be provided for each head. This force determines not only the primary tension imparted to the running yarn 17 but also the amount of additional or knock-off tension required to inactivate the feed of yarn. Usually, from 15 to 250 ma. current, at from 1 to 20 volts, is sufficient for the purposes described.

Reference letter,B represents, and may also be used to identify the source'of current provided for, the secondary or control circuit. This secondary circuit is utilized to energize relay 22 which, upon energization, opens the primary yarn feed motor circuit indicated at C. Power leads 2.3, 24, which form the secondary circuit B, connect at one end to a suitable source of current such as 6.3 volts, alternating or direct, and connect at the opposite ends to additional stop motion-tension devices, neither of which are shown.

Primary circuit C is represented by power leads 25, 26 which supply yarn feed motor 27 with either or 220 v. A.C., depending upon the type of processing to which yarn 17 is subjected. This circuit as shown is provided with two relay-operated switches 28, 30, to be described more fully hereinafter, and a manual on-off switch 31. It should be understood, however, that additional switches 28 will be required,one for each of the stop motion tension systems provided. One complete system, as used here, .is represented by a plurality of individual units or devices such as 10, 11, 12. Moreover, where cost and space requirements are of no consequence, it may be practicable to provide a relay 22 for each of the devices 10, 11, 12. It has been found expedient, however, to wire the system in such a manner that a plurality of devices operate the same relay. Although three of these devices operate relay 22 in the diagram illustrated, it will be apparent that any other number could be connected in the manner described; It will become obvious hereinafter, however, that the most desirable arrangement would employ one relay 22 for each stop motion-tension device.

Returning for the moment to FIGURE 1, the fourth independent but interrelated circuit is represented by reference letter D. This circuit is provided on a conventional warping machine for the purpose of interrupting the warping operation immediately upon determination that one or more of the ends or filaments fed to the collecting beam has been broken. The break detector circuit D may employ a photo-electric scanner and receiver placed on opposite sides of the, warp, or drop wire stop motion, or any known system indicated simply by numeral 32 in FIGURE 2, and operatively connected to a relay such as 33 (see also FIGURE 1). Upon detection of a broken filamentor end, the unit 32 functions to energize relay 33 and thereby open switch 30, which interrupts yarn feed immediately. This circuit, per se, forms no part of the present invention and is included here merely to illustrate that the novel stop motion system which constitutes the subject matter of this application is supplementary to, and not in lieu of, known mechanisms for opening feed motor circuits in response to yarn breakage. It can be seen from these figures that both secondary or control circuit B and break detector'circuit D are operatively connected to, and function to open, the primary or yarn feed motor circuit C.

A pair of contacts 34, ,35 is associated with each of the devices 10, 11, 12, and the discs 16 mounted on the posts 15 thereof. These contacts may be supported in an insulated condition from a sub-frame 14, as shown, or in any other manner desired. Contact 34 is connected through conductor 36 to power lead 24 of control circuit B, as illustrated in FIGURE 1,-while contact 35 is connected through conductor 37 and pilot light 38 to the remaining power lead 23 of circuit B. Relay 2,2 is Wired through conductors 40, 41 in parallel with the pilot light and consequently is operated simul taneously therewith. It can be seen from this circuit diagram that displacement of disc 16 results in energization of relay 22 and concomitant interruption of primary circuit C.

Increased yarn tension of any magnitude or duration above a predetermined level is detrimental to the warping operation. Consequently, it is desired that even a momentary tension increase above the knock-01f level be detected and the cause of such be corrected prior to resuming yarn feed. While a sudden increase of short duration might temporarily dislodge one side of disc 16 sutficiently to short out contacts 34, 35, such momentary increases usually would not completely displace the disc from head 13, and primary circuit C would be inteirupted temporarily only unless other measures were taken. Accordingly, a lock-in circuit consisting of switch 42 and conductor 43 is provided to lock relay 22 in energized condition from a momentary shorting only of contacts 34, 35. The result of this lock-in is sustained inactivation of the primary circuit C (until manually reset) even from a brushing of contacts 34, 35 by disc 16.

The secondary circuit B operates in the following manner. Closing of contacts 34, 35 establishes continuity from power lead 24 through conductors 36, 37, and 41 to relay 22, and from this relay through connector 40 to the remaining power lead 23. A circuit also is completed through pilot light 38 which locates the source of diificulty for the creel operator. Energization of relay 22 from leads 23, 24 operates to shift switch 28 to open position, thereby interrupting primary circuit C. The normally open lock-in switch 42, Which is mechanically connected to switch 28, is shifted to closed position, thereby establishing the lock-in circuit through conductors 43, 40. Subsequent opening of the contacts 34, 35 therefore will not reactivate the primary circuit C. Consequently, even though the tension increase on yarn 17 might have been of a momentary nature only, yarn feed will be discontinued until the source of difiiculty can be located and obviated.

After correction of the tension problem the stop motion-tension system must be reset so that yarn feed may be resumed. This may be accomplished by temporarily opening normally closed reset switch 44. It will be obvious, however, that disc 16 must be restored to operative position prior to resetting, if the same has been completely displaced from the magnetic field within head 13 by the increase in 'yarn tension.

Operation of the preferred embodiment will now be summarized with particular attention to FIGURE 2, which figure shows only enough details of the circuit to enable a complete understanding of this invention. Yarn is withdrawn from a supply package 45 by take-up means 46 which, in this instance, is a beam for collecting a warp of individual ends. Although only one end is shown in FIGURE 2, it will be understood that a plurality of yarns 17, and a plurality of stop motiontension devices are required to fill beam 46. Beam 46 is driven by motor 27 in a manner known to this art. Moreover, the operation of photo-electric scanner and receiver 32 also is known and will not be described further.

Yarn 17 may be passed through a preliminary tension device 47, electromagnetic or otherwise, if found to be necessary or desirable, after which it is introduced into the stop motion-tension unit 10 in a plane parallel to the face of head 13. Usually the yarn passes about 270 about mounting post 15, as illustrated in FIGURE 4, before discharging therefrom. As stated earlier, yarn 17 passes between disc 16 and head 13 so that the magnetic force urging the disc against the head will also serve to tension the yarn. The disc 16 usually rotates during operation, which promotes uniformity of tension.

It is essential that yarn 17 be introduced and/or withdrawn from the device it in such a manner that at least a component of the tensional force developed therein will function to urge disc 16 away from head 13.

'48 mounted so that the yarn extending between it and the disc 16 forms an angle alpha with an imaginary horizontal plane, or with the plane of yarn running from guide 48 to the warper. The knock-elf tension level and the ratio of yarn tension to knock-off tension are dependent upon the magnitude of angle alpha. Although an angle alpha of between 35 and 40 degrees has proved satisfactory for most purposes, the angle theoretically may lie anywhere between about 1 and degrees. It is preferred that guide 48 be adjustably mounted, as indicated by the arrow, so that this angle may be changed when desired to accommodate various types of yarns, various yarn tensions, and various ratios of primary tension to knock-off tension.

In some operations it might be desirable not only to withdraw yarn from but also to introduce the same to device 10 at an angle. Accordingly, thread guide 50, which may also be adjustably mounted as indicated by the arrow, has been provided to deflect yarn from supply package 45 through the dashed line path to the stop motion-tension device. The angle of approach, beta, is determined by the same conditions as, and may correspond generally to, the angle alpha discussed above.

A modification of the device described hereinabove will now be discussed with attention directed to FIG- URE 3. As can be seen from an inspection of that figure, the stop motion or knock-0E device 51 functions only to interrupt operation of the yarn feed motor circuit and does not directly, or primarily, tension the running yarn. Stop motion device 51 is provided with an electromagnetic head 13, similar to that used with the previously described embodiment except for a central aperture, which is electrically connected to the source of current A either in series or parallel with additional devices. This unit difliers slightly from the device shown in FIGURE 4, however, in that mounting post 52 is supported for limited longitudinal movement through the aperture head 13 and relative to the coil (not shown) enclosed thereby.

A washer 53 of magnetic material is fixed to post 52 and limits upward movement, whereas an electrical disclike contact 54 fixed to the upper end of post 52 limits downward movement. The movable contact 54 cooperates with stationary contact 55, which is fixed to the upper side of head 13, to activate or close control circuit B, indicated in this figure only by a bracket. The lower end of post 52 terminates in a thread guide 56 through which yarn 17 is passed, either at an angle beta from guide 50, as indicated in solid lines, or normal to the mounted post, as indicated in dotted lines. The yarn is withdrawn from guide 56 at an angle alpha and passed, under guide 48. The two positioning guides 48, 50 correspond to the identical guides described above. The head 13 may be stationarily supported on a subframe (not shown) similar to 14 shown in FIGURE 4. A separate tension device 57, which may be electromagnetic or otherwise, is provided for imparting running tension to the yarn 17.

Except for the single rather than dual function, device 51 operates quite similar to devices 10, 11 and 12. Yarn 17 is withdrawn from a supply package such as 45 by feeding or collecting means such as beam 46 (see FIG- URE 2). The yarn passes from the supply package through the tension device 57, under guide 50 (if angular introduction is desired), through guide 56 on mounting post 52, and under guide 48. The coil within head 13 is energized from circuit A, and the magnetic attraction resulting from this raises post 52 until washer 53 rests aaginst the lower side of the head. In this position contacts 54, 55 are separated, as shown, and control circuit B is inoperative. The force generated to maintain post 52 in a raised position may be adjusted through a potentiometer such as 21, FIGURE 1, which of course deterthe same function.

of head 13. The axial spacing of washer 53 and movable contact 54 is so chosen that a slight downward movement of washer 53 will result in closing the circuit B through contacts 54, 55. Activation of circuit B results .in interrupting yarn feed means circuit C in the same manner discussed with respect to FIGURE 1. Preferably, the magnetic force urging post 52 upwardly should exactly counterbalance the vertical component of tension in the running yarn coupled with the effect of gravity on the movable elements. As a result of this, any increase in tension on the running yarn will increase the vertical component of force represented by the arrow, and unbalance the system. A suitable lock-in circuit and reset switch should be provided. Consequently, even a momen-tary unbalance is sufficient to inactivate circuit C, as explained earlier.

There are many alternatives to the preferred arrangements described supra. The angle of approach and discharge of yarn to the stop motion-tension device is unlimited insofar as concerns tensioning, and any angle from about 1 to 90 is satisfactory for knock-off purposes, depending upon tensions, breaking strength, etc, mentioned above. Moreover, any positioning of the device should result in satisfactory operation as long as an incremental increase in tension in sufficient to displace the secondary circuit activating means 16 or 54, 55. As stated above, however, it is more practical to mount head 13 in an inverted position so that the normal force of gravity will assist tension increase in shifting means 16 or 54, 55. Quick activation of control circuit B is obtained through use of an electromagnetic head 13 because the force acting on means 16 or 54, 55 decreases very rapidly, or in proportion to the square of the distance of this means from the head 13. Consequently, gravity, tension and decreased magnetic force contribute mutually to quick operation of the circuit B Whenever the preset knock-d tension level is exceeded.

' It may be desirable in some instances to provide a pulsating current for energizing circuit A. This pulsating current of coursewill vary from high current to low current periodically. With proper circuit design, it should be possible to utilize the average of high and low current for tension purposes, while permitting knock-01f only at the low portion of pulses, thereby enabling a more slight incremental increase to produce interruption of circuit C. With either steady or pulsating current supplied to electromagnetic heads 13, however, the knock-off tension range may be varied through potentiometer 21 from a fractional gram to several times the primary tension imparted to the running yarn. Moreover, in certain operationsit may also be desirable to introduce yarn to the control unit at an angle and to withdraw the yarn therefrom in a plane parallel to the tensioning head. With such an arrangement an even slighter percentage tension increase should activate control circuit B since the primary yarn tension is lower at the introduction side than at the Withdrawal side.

Additionally, it may be desired to utilize one electromagnetic coil for stop motion purposes and another coil for tensioning. Such an arrangement would correspond to that shown in FIGURE 3, with device 57 being an electromagnetic tensioning head. This system has the ing post, whereas the preferred arrangement shown in FIGURE 2 requires only onepost for both stop motion and tension control. 7 w

Although a conventional circular disc has been described in connection with the preferred embodimenn it is of course obvious that any type'of magnetic armature, such as a flat plate, apertured or otherwise, would 'serve Moreover, contacts 34, 35 were selected primarily for illustrative purposes and other means,

such as microswitches, could be used equally advanta- 16 while preventing play therebetween, it may be found necessary to reduce the diameter of the post 15 immediately below' the normal operating position of the disc. This construction also would permit slight pivotal movement of the disc about either a real "or imaginary pivot point, which would enable activation of secondary circuit B from an even slighter increase in tension.

While the stop motion-tensioning devices illustrated herein have been described particularly in connection with a warping operation, it will be apparent that the same could be used with any yarn feeding process such as coning, rewinding, draw-twisting, etc. Moreover, the invention will operate equally etfectively with any typefiber, whether the same be natural, artificial or synthetic, and fibers of any denier and/or breaking strength may be controlled by proper manipulation of potentiometer 21.

Inasmuch as other alternatives will become obvious to those skilled in this art, it is intended that the present invention be limited in scope only to the extent set forth in the following claims.

What is claimed is:

l. A power stop control comprising an apertured electromagnetic head, means permitting adjustable energization of said head, an elongated mounting post positioned within the aperture of said head and movable between an operative and an inoperative position, said post normally being held in operative position by the magnetic force of said head, a first electrical contact supported by one end of said post, a second electrical contact supported by said head, and a control circuit energized by closing of said electrical contacts upon movement of said mounting post from operative to inoperative position.

2. In combination with a warping operation having means for withdrawing a plurality of yarns through a rectilinear path, a plurality of apertured electromagnetic heads, means for adjustably energizing said heads, an elongated mounting post having a thread guide on one end thereof positioned Within the aperture of each head and movable between an operative and an inoperative position, said posts normally being held in operative position by the magnetic end of each mounting post, said thread guides functioning in operative position of said mounting post to displace said yarns laterally from said rectilinear path while in inoperative position of said post permitting limited lateral movement toward said path, a first electrical contact fixed to the other end of each mounting post, a cooperating second electrical contact fixed to each of said heads, and a control circuit common to all of said contacts and operative upon closing of any cooperating pair thereof upon movement of said post to inoperative position for interrupting the feed of yarn, whereby an undesired increase in tension on any single yarn fed may instantly terminate said warping operation.

3. A warping operation as set forth in claim 2 and further including means for individually tensioning said yarns prior to passage through the thread guides on respective mounting posts.

4. A power stop control comprising an electromagnetic yarn tensioning head, a mounting post extending from said head, an apertured tensioning disc slidably mounted between operative and inoperaive positions on said post, means for energizing said electromagnetic head and urging said disc into operative poistion, and a control circuit energized in response to movement of said tensioning disc into inoperative position.

5. A power stop control comprising a sub-frame, an electro-mag etic yarn tensioning head supported on said sub-frame, a mounting post extending from said head, an apertured tensioning disc slidably mounted between operative and inoperative positions on said post, means for energizing said electromagnetic head and for urging said disc into operative position, a pair of normally open electrical contacts supported by said sub-frame adjacent to said tensioning disc and adapted tobe closed upon movement of said disc to inoperative position, and a control circuit operative in response to closing of said contacts by said tensioning disc.

6 A stop motion-tensioning system comprising a plur'ality of electromagetic yarn tensioning heads, a mounting post secured to and extending from each of said heads, an apertured tensioning disc slidably mounted between operative and inoperative positions on each of said posts, means for simultaneously adjustably energizing said electromagnetic heads and urging said discs into operative position against respective heads, a pair of contacts positioned adjacent each disc and adapted to be closed upon shifting of a respective disc into inoperative position, a normally energized primary circuit the function of which is to be controlled, a control circuit common to all tensioning heads and activated upon closing of any pair of contacts for interrupting said primary circuit, and means including said tensioning discs for energizing said control circuit and thereby interrupting said primary circuit.

7. In combination with a yarn processing device having means for feeding yarn through a rectilinear path, a stop motion-tensioning device comprising an electromagnetic tensioning head mounted laterally of said rectilinear path a mounting post extending from said head in the direction of said path, an apertured tensioning disc slidably supported on said post between operative and inoperative positions, said disc in operative position tensioning said yarn and displacing the same laterally outside said path, means for energizing said head and urging said disc into operative position, a pair of electrical contacts mounted adjacent said post and adapted to be closed upon move ment of said disc into inoperative position, a normally deenergized control circuit connected to said contacts and adapted to interrupt the feed of yarn upon activation thereof, and means for adjusting the energization of said head to a predetermined tension level whereby an increase in yarn tension thereabove will shift said disc into inoperative position, close said pair of contacts, activate said control circuit and interrupt the feed of yarn.

8. A stop motion-tensioning device as set forth in claim 7 and further comprising means operating upon activation of said control circuit for visually indicating the condition of that circuit.

9. A stop motion-tensioning device as set forth in claim 7 and further comprising a lock-in circuit whereby only temporary closing of said pair of contacts will interrupt the feed of yarn until the control circuit is manually deenergized.

10. In combination with a warping operation having means for withdrawing a plurality of yarns through a rectilinear path and collecting the same on a beam, a plurality of electromagnetic tensioning heads laterally displaced from said rectilinear path, a mounting post extending toward said path from each of said heads, an apertured tensioning disc slidably supported on each of said posts between an operative and an inoperative position, each disc in operative position tensioning a single yarn and displacing the same laterally outside said path, means for simultaneously energizing said heads and urging said discs into operative position, a pair of electrical contacts mounted adjacent each post and adapted to be closed upon movement of a respective disc into inoperative position, a normally de-energized control circuit connected to each pair of contacts and adapted to interrupt the feed of yarn upon activation thereof, and means for simultaneously adjusting the energization of said heads to a predetermined tension level whereby an increase in tension on any single yarn above this level will shift a disc into inoperative position, close a corresponding pair of contacts, activate said control circuit and interrupt he feed of yarn.

11. In combination, an electromagnetic tensioning head, a yarn tensioning disc normally urged by magnetic force toward said head for tensioning yarn passed therebetween, means for feeding yarn between said disc and head and for withdrawing the same therefrom at an angle, electrical means for controlling the tension imparted to said yarn by said disc and head, and means operating in response to tension increase above the control level for interrupting the feed of yarn.

12. The device as set forth in claim 11 wherein said yarn is also introduced to the tensioning head at an angle.

13. A power stop control comprising a sub-frame, an electromagnetic yarn tensioning head supported on said sub-frame, a mounting post extending from said head, an apertured tensioning disc slidably mounted between operative and inoperative positions on said post, means permitting energization of said electromagnetic head for urging said disc into operative position, and a pair of normally open electrical contacts supported by said subframe adjacent to said tensioning disc and adapted to be closed upon movement of said disc to inoperative position for activating a control circuit.

14. A power stop control comprising an electromagnetic yarn tensioning head, a mounting post secured to and extending outwardly from said electromagnetic head, an apertured tensioning disc of magnetizable material supported by and slidably mounted on said post between an operative position adjacent said electromagnetic head and an inoperative position remote from said electromagnetic head, power leads permitting energization of said electromagnetic head resulting in retention through electromagnetic force of said tensioning disc in operative position adjacent said electromagnetic head, and switch means supported adjacent said mounting post opposite said tensioning disc from said electromagnetic head for inactivating a control circuit in response to movement of said tensioning disc into an inoperative position while permitting activation of said control circuit when said tensioning disc is maintained in operative position by energization of said electromagnetic head.

References Cited in the file of this patent UNITED STATES PATENTS 2,140,087 Newell Dec. 13, 1938 2,705,362 Roughsedge Apr. 5, 1955 2,825,119 Heifelfinger et al. Mar. 4, 1958 2,844,860 Ayars et al. July 29, 1958 2,907,535 Mindheirn et al. Oct. 6, 1959

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