US2565386A - Letoff motion - Google Patents

Description

H. T. MARCY LET OFF MOTION Aug. 21, 1951 4 Sheets-Sheet 1 Filed April 20, 1949 :3 EEE:

T70 SUMP FROM SUMP Ill-I225 JNVENTOR. HENRY TYLER MARCY uww / TOR/VEV 21 1951 H. T. MARCY 2,565,386

LET OFF MOTION Filed April 20, 1949 4 Sheets-Sheet 2 INVEN TOR. HENRY TYLER MARCY I i5 QibW ATTORNEY Aug. 21, 1951 H. T. MARCY 2,565,386

LET OFF MOTION Filed April 20, 1949 4 Sheets-Sheet 5 v Y HAP/D RELEASE 64 71 A SLOW RELEASE //\/l/E/\/7OR HENRY TYLER MARCY ATTORNEY 1, 1951 H. T. MARCY 2,565,386

LET OFF MOTION Filed April 20, 1949 4 Sheets-Sheet 4 90 H! IHIHHIII! I in 104 O r INVENTOR. HENRY TYLER MARCY F 7 Y/M4J%@ ATTORNEY Patented Aug. 21, 1951 LETOFF MQTION Henry Tyler Marcy, Staten Island, N .Y., assignor, by mesne assignments, to Steei and Alloy Tank Company, Newark, N. 5., a corporation of New Jersey Application April 20 1949, Serial No. 88,560

motions.

In a conventional loom, a let-ofi motion is employed to allow the necessary amount of warp yarn to be unwound from the warp beam and to maintain said yarn under tension during beat-up.

In prior art loom let off motions, as for example, those of the friction type, the warp beam is not positively driven but is driven against a predetermined frictional resistance by the tensional action of the warp yarn directly thereon. One of the many disadvantages of this type of 100111 let-off motion is that durin beat-up, when it is desirable to hold the warp beam, let-off may be effected by the beat-up tension of the warp yarn.

In one well known let-01f motion of the positive drive type, such as the Bartlett, the oscillations of the whip roll created by its tensional sensing action on the warp yarn sets a ratchet and pawl device into position to drive the warp beam, but the drive of the warp beam through said device is not initiated until a predetermined phase in the pick cycle is reached. Moreover, in such a let-off motion, the setting of the pawl and ratchet device determining the amount of let-off in each weaving cycle depends on the amplitude of oscillation of the whip roll. The

amount of let-off is therefore independent of the period during which the warp yarn remains under increased tension, and the rate of let-off is not susceptible of control. This type of letoff does not always maintain uniform conditions of tension in the warp yarn in successive cycles and must be provided with means compensating for reduction in the diameter of yarn mass on the warp beam as weaving operations proceed.

One object of the present invention is to provide a new and improved let-off process which does not have the disadvantages of the prior art let-off process above referred to. Another object of the present invention is to provide a new and improved let-off motion which is comparatively simple but nevertheles sensitive and accurate in operation, which is hydraulie in operation and control, which is operatable to produce better tensioning and weavin conditions during let-off and/or beat-up, which includes an oscillatory whip roll as a tension sensing device operatable with maximum of equilibrium and stability, which requires no compensation for variations in the size of the yarn mass on the warp beam, and which combines some of 2 the desirable features of both the frictional and positive drive type of let-off motions without some of their disadvantages.

Various other objects of the invention are apparent from the following particular description and from an inspection of the accompanying drawings, in which:

Fig. 1 is a diagrammatic layout of one form of let-off motion which can be employed to carry out the process of the present invention and which embodies the structural features of this invention;

Fig. 2 is a left side elevation of a part of a loom showin in connection therewith the let-on motion of Fig 1;

Fig. 3 is a section of the loom taken approximately along the lines 33 of Fig. 2;

Fig. 4 is a section of the main control valve of the let-off motion taken on lines 4-4 of Fig. 2 but showing said valve on a larger scale;

Fig. 5 is a somewhat diagrammatic perspective ShOWillg the irreversible drive transmission between the motor and the warp beam;

Fig. 6 is a diagrammatic layout of another form of let-off motion which can be employed to carry out the process of the present invention and which embodies certain structural features of this invention;

Fig. '7 is a left side elevation of a part of a loom showing in connection therewith the modified form of let-off motion of Fig. 6; and

Fig. 8 is a section of the loom taken approximately along the lines 88 of Fig. '7.

Referring to Figs. 1-5 of the drawings, the loom comprises a loom frame having loomsides iii, each being shown for purposes of illustration of the double-web type with inner frame plate ii and outer frame plate !2, as disclosed in copending application Serial No. 691,237, filed August 1'7, 1946, now Patent No. 2,533,128. These loomsides (only the left loomside being shown) support a warp beam l3 and an oscillatory whip roll it. The warp A (Fig. 2) is unwound from the warp beam 93, passes over the yieldably supported whip roll it: and is then directed towards 1e weaving instmmentalities in the usual manher. The tension of the warp A transmitted to the whip roll 54 causes oscillatory movement of said whip roll which in turn controls the let-off motion in the manner to be described.

For positively rotating the warp beam l3 and thereby unwinding the yarn therefrom, there is affixed to one end of the warp beam shaft, a beam head gear is driven by a let-off pinion I1 meshing therewith. The let-off pinion I1 is intermittently operated from a hydraulic motor it through a non-reversible speed reduction unit 29. A pump 2i continuously driven in a manner to be described, supplies working liquid from a sump or supply tank It to the hydraulic motor It. The delivery of the working liquid from the pump 2i to the hydraulic motor is is controlled by a valve 23 which in turn is controlled by the tension sensing deflections of the whip roll Hi.

The hydraulic motor !8 is lay-passed by the control valve 23 and the operation of said valve is basically to cause said motor to turn and thereby to cause the warp beam [3 to rotate when said valve is closed by the downward movement of the whip roll 14 and to cause said motor to stop or at least to turn at a slower rate when said valve is opened, as a result of the retractive deflecting movement of said whip roll. To assist in this operation, an automatic low pressure relief valve 25 is used on the downstream side of the hydraulic motor [8 to stop flow of the working liquid through said motor when the pressure drop across said motor is only sufiicient to force said liquid through the by-pass control valve 23.

A further control is advantageously used when it is desired that the hydraulic motor l3 runs at all times, but at two different speeds, for operation on light fabrics without beat-up. This control takes the form of an adjustable restriction or valve 26 placed in series with the control valve 23. The valve 26 may be adjusted to effect operation of the hydraulic motor is at one speed when the control valve 23 is opened and at a higher speed when the control valve 23 is closed, or may be adjusted so that the hydraulic motor cannot operate when the control valve 23 is open. The valve 26 may also be used to adjust the speed of rotation of the hydraulic motor [6 when the control valve 23 is open, so that rate of let-ofi may be controlled.

The embodiment of the present invention in its more specific aspects will now be described.

For yieldably supporting the whip roll 15, there is provided a whip roll shaft 3% journalled at its ends in universal bearings 3!, each carried at the upper end of a rod 32 retained in a bracket or clamp 33 afiixed to the inner face of the corresponding outer trame plate [2. The bracket 33 may be adjusted angularly to adjust the an gular position of the corresponding rod 32 and said rod may be adjusted lengthwise in said bracket, whereby the horizontal and elevational position of the whip roll shaft 38 may be adjusted, as described in copending application Serial No. 48,404, filed September 9, 1948, now

Patent No. 2,507,828.

The journal ends of the whip roll l4 are rotatably carried on one end of crank arms 34, the other end being affixed to the whip roll shaft 30. One end of the whip roll shaft has secured thereto one end of a crank arm 35 whose other end is pivotally secured to a valve stem 36 forming the operating part of the by-pass control valve 23.

With the whip roll support described, as the whip roll [Al is moved angularly about the axis of the whip roll shaft through its sensing contact with the yarn A, the resulting oscillatory movement of said shaft is transmitted to the crank arm 35, and this in turn moves the valve stem endwise to operate the by-pass control valve 23.

The by-pass control valve 23 comprises a casing or cylinder 45, pivotally mounted to the loomside It], to permit said casing to swing, when the whip r011 crank arm 35 is moved angularly. For

that purpose, the lower end of the valve casing 40 has secured thereto at diametrically opposite sides a pair of pivot pins 4| journalled in a bracket (not shown) afiixed to the outer loomside plate [2.

The valve casing 40, Fig. l, is closed at its lower end by a head 53 carrying the pivot pins 4| and at its upper end by a head 44 serving as a guide for a piston valve member 45 secured to the lower end of the valve stem 36. The upper head 44 is shown secured in position by the studs 46 and has a bore 41 for receiving the valve member 45 with a snug slide fit. The valve 23 is provided in the head 44 with a liquid inlet 48 which connects into a pipe 50 leading from the pump 2! and which leads to an annular recess 5| in the periphery of the valve bore 41.

The valve member 45 has a hollow 52 open at the bottom and defining a peripheral piston wall 49 with a series of ports or holes 53 through which flow communication is established between the inlet 48 and said hollow when said holes are in registry with the cylinder recess 5| in open position of the by-pass valve 23.

The valve casing 40 is provided with a liquid outlet 55 which connects with a return pipe 55 leading to the sump or supply tank l9.

In operation, when the tension on the warp yarn A is comparatively low, the whip roll 14 will be in elevated position and the by-pass valve 23 will be in open position with its ports 53 in registry with the cylinder recess 5i, thereby establishing flow communication between the inlet 48 and outlet 55. Under these conditions, little or no working liquid will flow through the hydraulic motor l8, according to the setting of the valve 26, thereby operating said motor at comparatively low speed Or maintaining said motor inoperative. When the tension on the warp yarn A has increased to a point where the whip roll I4 is depressed, the valve 23 will be operated correspondingly into closed position shown in Fig. 4. In this closed position, flow between the inlet 48 and outlet 55 is blocked. The pressure created thereby in the working liquid causes the liquid to flow freely through the hydraulic motor l8 and said motor to rotate from a state of rest or at an increased speed.

To render the operation of the whip roll l4 steady and free from excessive vibrations, especially during beat-up, there is provided in connection with the valve stem 36, a cushioning or dampening device comprising a piston in the valve casing 40 shown in the form of an inverted cup pressed against the piston valve member 45 by a coil spring 6|, one end of which extends into the hollow of said piston and bears thereagainst, the other end being seated on a platform 62 in said casing. A stud 63 threaded into the lower cylinder head 43 and impinging on the platform 62 serves to adjust the stress on the coil spring 6!.

To permit the operating liquid to escape from the hollow 52 of the piston valve member 45 to the outlet 55 the upper end of the piston 60 is provided with a series ofrecesses 64.

In connection with the dampening device described, there is provided a dash-pot mechanism, comprising a two-way valve l0 having pipe connections ll and 12 leading to chambers 13 and 14, respectively, on opposite sides of the piston 6B. The dash-pot valve may be of any well known type, to permit rapid flow of the liquid therethrough in one direction and slower liquid flow in the opposite direction, and in the specific form shown comprises a valvecasing [5 having a port or passage 16 in communication with the pipe :1], a port or passage 1-! in comanunication with the pipe 12, a valve .member 21.8 between said passages slidable along a .rod 30 threaded into ,a cap 8| topermitfadjustments in the .axial position of said rod and a spring :82 for urging the valve along said rod and into seating contact with a seat or shoulder 83 at one :end of the passage '16, as shown in .Fig. 4. The valve member 18 has an end sealing wall .84 which is adapted to seat against the shoulder 83 and recesses 85 extending radially from the bore .of .said valve member to its outer periphery. The rod 80 in seated position of the valvemember 18 extends away from the end wall .84 of said valve member to define an annular clear- .ance through which the liquid can flow .re-

.strictedly from the valve recesses 85 to the valve passage. 16, when the flow of liquid through the valve is from the pipe ll to the pipe 472. When the flow of liquid is in the opposite direction, the valve'member 758 .is moved away from its seat 83 against the action of the spring 82, thereby permitting free flow of liquid between the valve passages 16 and 11.

The dampening and dash-pot mechanisms .described restrict the speed of depressing :move- ,ment of the whip roll 14, since the liquid from the chamber 14 on one side of the piston 6!] discharges slowly through the dash-pot valve 10 when said chamber is collapsed by the transmission of said whip roll movement to said piston. These dampening and dash-pot mecha 'nisms, on the other hand, permit .free rapid retractive movement of the whip roll l4 limited only by the tension of the warp yarn A in contact therewith, and the piston 60 freely follows the piston valve member 45 during this retractive movement, clue to rapid release of the liq- :uid permitted from the chamber 13 on one side of said piston through the dash-pot valve l0 when said chamber is collapsed.

The working liquid of the system is desirably oil and can be employed to lubricate the relatively slidable parts of the valve 23. To that end, the cylinder head 4 has an oil duct 8.6 extending therealong and opening at one end into the chamber i3 and a passage Bl extending from said duct to an annular recess 88 in the periphery of the valve boredl.

The pump 2| may be of any suitable type, as for example, of the gear type, and is operated continuously from a pick cam shaft gear as through a sprocket and chain drive 91 The pick cam shaft gear 90 is in turn driven from the crank shaft gear 92 in the usual manner.

The pump .21 has an inlet pipe 93leading from the sump or supply tank l9 and an outlet pipe 94. The outlet pipe 94 has the branch pipe connection 59 leading to the inlet 48 of the by-pass valve 23, and a branch pipe connection 95 leading to the inlet-of the hydraulic motor I 8.

The hydraulic motor 18 may be of any suitable type, as far as some of the aspects of the invention are concerned, but is desirably of the gear type, and has an outlet pipe connection 36 leading F170 the sump tank l9 and provided with the low pressure relief valve 25 serving to stop or restrict flow of the working liquid through said motor when the by-pass control valve 23 is open. The output shaft 9'1 of the hydraulic motor it drives the let-oif pinion 1? through the non-reversible speed reduction unit 20, Fig. '5, which includes a worm and worm gear 98. The nonreversible speed reduction unit 20 permits positive drive of the warp beam l3 through the hydrualic motor l8, but looks said warp beam against rotation by the direct tensional action of the' warp yarn thereon.

Although the operation of the system described in Figs. 1-5 has been made apparent, it is now summarized.

During certain periods ofseach Weaving cycle, when the tension on .therwarp yarn Ais lowest, the whip roll Hi will be in elevated position under the expansive action of the spring 6|, so that any slack in the-warp yarnis taken up. Under these conditions, the by-pass valve 23 .is open and the .pump .21 operating continuously, is forcing liquid through the outlet pipe .94, through the branch pipe 59, through the open valve .23, and through the pipe 56 to the sump t9. Little or no liquid flows from the pump 2,! through the other branch pipe "and through the hydraulic :motor L8, so that said motor is either inactive or operating at a comparatively low speed, according'to'thesetting of the restrictivehand valve 26 or-of itheautomatic relief valve 25.

As :the warp yarn A is tightened by the opening of the shed, the whip roll I4 will be pulled down by said yarn, thus relieving the tension on said yarn. This depressing movement of the roll M is transmitted Ito the'piston valve mem- 'ber 45 of the by-pass valve 23 against the action of the spring bl, until said valve .member .is in the closed position shown in Fig. 4. During this movement of the valve member 45 towards closed position,.theliquid in the chamber M is discharging through the pipe .12, through the restricting dash-pot valve l'il, through the pipe H .and into thechamber ltlfor discharge into the outletline '56.

With the bypass valve 23 closed as indicated, the liquid from the pump 2! will be all .iorced through the hydraulic motor [8, thereby causing said motor to rotate from a-state of rest or at a greatly increasedspeed. Through the transmission 20, the warp beam |.3.is turned :and the required yarn is let-off from said warp beam.

The whip roll support, the dash-pot mechanism 16] and the dampening l'mechanism Bit, 'Bl associated therewith are such as to prevent letoif during beat-up, and to prevent excessive adeflection of the whip roll H! at that time. Before beat-up, the tension of the warp yarn will have decreased sufficiently to cause the by-pass valve 23 to open. This opening operation'of the by-pass -va1ve 23 ise'fiected comparatively quickly, since the dash-pot valve it permits rapid release of the liquid therethrough during movement of said valve towards open position. However, any tendency to open the by-pass valve 23 during beat-up is resisted not only by the spring -51 but is delayed by the restriction in the flow of the liquid through the dash-pot valve ll) from "the collapsing chamber M.

The basic reason why a deflecting whip roll at the time of beat-up is undesirable is believed to be the need for packing of fill threads "before cloth buckling as the reed forces its way into the =fell of the cloth. If the reed finds that the fell of the cloth yields due to a spring supported whip roll, then the-excess forces'needed for fillthread packing cannot be established with small motions of the reed into the fell or the cloth. Since the packing of the fill thread in the cloth must be resisted by the cloth itself, conditions for efficient packing are good only until the cloth has buckled. This buckling takes place after a, very short distance of reed travel into the fell of the cloth. Because of the radical difference in interthread friction between cotton and rayon, this phenomena is obviously much more important in weaving heavy cottons than in weaving heavy rayons.

With the arrangement of the present invention, the loom may be operated successfully under the following conditions 1. When the loom is running on light fabrics without beat-up.

2. When the loom must stop suddenly.

3. When the loom is running under high beatup conditions.

Condition 1.When the loom is running with light fabrics of very low pick count and without beat-up, the hydraulic motor 58 may have two speeds, this being arranged by the proper setting of the valve 23. The maximum speed of this motor 18 occurs when the tension in the warp yarn is high enough to close the by-pass valve 23, and the minimum speed may be zero or may be adjusted to comparatively low speed by the proper setting of the valve. The use of the low speed in the hydraulic motor 58 alleviates the requirements on the main control by-pass valve 23 in the by-pass line 53 and lessens capacity requirements of the pump 2% when weaving goods of low pick count. The use of a nonreversible worm gear transmission from the hydraulic motor [8 to the warp beam l3 prevents the warp beam from pulling said hydraulic motor. The torque requiredfrom the hydraulic motor I8 is only that necessary to overcome static friction inherent in the gear transmission 25.

Condition 2.When the loom must stop suddenly, as for example, due to warp or to fill breakage or loom bang-off, the pump 2! stops, so that the hydraulic motor l8 also stops. Since there is a non-reversible worm gear drive 28 from the hydraulic motor Hi to the warp beam [3, the Warp is held. This operation obviates the necessity for disconnecting the let-off and prevents lines in the cloth due to starting and stopping of the let-off motion. Means may be provided, as for example, a disengageable clutch in the drive between the hydraulic motor l8 and the warp beam l3 to permit the warp beam to turn for trimming or warp adjustments, when the loom is stopped and the hydraulic motor :8 is not operating.

Condition 3.When the loom is running on high density fabrics, the let-01f motion operates only briefly during each pick cycle. Under these conditions, the spring loading of the whip roll 14, and the use of the dash-pot valve 79 becomes important. The hydraulic motor l8 functions as long as the by-pass valve 23 is closed, Since the actual quantity of let-01f during each pick cycle is small compared to the beat-up distance, and since there is little or no let-on during beat-up, excessive beat-up distance is avoided. This beatup distance is the length of travel of the reed at the fell of the cloth between the time it first exerts force in packing the fill thread and the time it reaches front center position and especially in the weaving of fabrics of high density should be as small as possible.

It should be noted that with the mechanism of the present invention, the operation of the let-01f is entirely and directly responsive to the tension of the warp yarn and is not directly dependent on or initiated directly by the timing of the pick cycle, as in well known let-off motions such as the Bartlett let-01f. Moreover, the

amount of let-off during each cycle is not dependent on the amplitude of deflection of the whip roll, as in the Bartlett let-off. The period of letoff 'is dependent on the period during which the warp yarn is maintained under let-off tension. The speed of warp let-off is determined by the quantity of working liquid pumped and the gear ratio between the hydraulic motor I8 and the warp beam l3.

It should also be noted that with the mechanism of the present invention, since the operation of the let-off is entirely and directly responsive to the tension of the warp yarn, no mechanism compensating for changes in the diameter of the mass of yarn on the warp beam is necessary.

In Figs. 6, '7 and 8 is shown a simplified hydraulically controlled let-off motion embodying the present invention. In this form of the invention, the by-pass valve 23a may consist of a simple casing 49a with an inlet port 48a and an outlet port 55a controlled by a piston valve member 55a operated through deflections in the whip roll Ma.

The yieldable whip roll mount and the connection between the whip roll Ma and the bypass valve 23a comprises a whip roll shaft 39a journalled at its ends in universal bearings 31a each carried at the upper end of a rod 32a adjustably retained in a bracket or clamp 33a which is affixed to the inner face of the corresponding outer frame plate Na and which can be angularly adjusted as in the construction of Figs. 15. The journal ends of the whip roll Ma are rotatably carried on the crank arms 34a at one end thereof, the other ends of said crank arms being afiiXed to the Whip roll shaft 30a. One end of the whip roll shaft 30a has secured thereto one end of a crank arm 35a, the other end being pivotally connected to one end of a link lilll shown in the form of a turnbuckle. The other end of the link Hill is pivotally secured to one end of a lever i2! pivotally supported intermediate its ends to the loomside frame plate l2a by mounts [02. The other end of the lever If]! is connected to the valve stem 36a of the lay-pass valve 23a through a short link I83.

To spring load the whip roll [4a, the whip roll shaft 3011 has connected thereto a crank arm M which in turn is connected b an adjusting bar I05 to a coil spring Sla anchored to the loomside frame plate I la.

The remainder of the system of Figs. 6, 7 and 8 is similar to that of Figs. 15, the pump outlet line 94a, branch lines 95a and 50a and valve outlet line 56a corresponding to the lines 94, 95, 50 and 56 respectively of Figs. 15. The operation of the system of Figs. 6, '7 and 8 is similar to that described in connection with the system of Figs. 1-5.

While the invention has been described with particular reference to specific embodiments, it is to be understood that it is not to be limited thereto but is to be construed broadly and re stricted solely by the scope of the appended claims.

What is claimed is:

1. In a loom having a warp beam and operatable through recurrent weaving cycles, the combination comprising a conduit system, a pump in said system for circulating liquid therethrough, a hydraulic motor in said system in series with said pump, a drive connection between said motor and said warp beam, means for operating said pump continuously, a valve by-passing said motor, whereby said motor is operated at increased speed when said valve is closed, and means for closing said. valve during a period of each cycle when the tension of the Warp yarn exceeds a predetermined value and for opening said valve during the remaining period of each cycle when the tension is restored to a lower value. v

2. In a loom, the combination as described in claim 1, comprising a whip roll over which the Warp yarn is adapted to pass from the warp beam, means mounting said whip roll for oscillatory movement in response to the tension of said yarn, and means responsive to the deflections of said whip roll for operating said by-pass valve into and out of closed position.

3. In a loom operatable through recurrent weaving cycles, the combination comprising a whip roll over which the warp yarn is adapted to pass from a warp beam, means mounting said whip roll for oscillatory movement in response to the tension of said yarn, means operatable while said whip roll is deflected beyond predetermined position by an increase in tension during each of said cycles for letting-off yarn from said warp beam, and a dash-pot mechanism for re tarding deflecting movement of said whip roll towards said predetermined position caused by increasing tension of said warp yarn.

4. In a loom, the combination as described in claim 3, said dash-pot mechanism being of the two-way orifice type to retard deflecting movement of said whip roll in one direction while permitting free return of said whip roll in the opposite direction.

5. In a loom, the combination as described in claim 3, comprising spring means assisting said dash-pot mechanism in resisting movement of said whip roll towards said predetermined position and resiliently loading said whip roll.

6. In a loom having a warp beam and operatable through recurrent weaving cycles, the combination comprising a conduit system, a pump in said system for circulating liquid therethrough, a hydraulic motor in said system in series with said pump, a drive connection between said motor and said warp beam, means for operating said pump continuously, a valve by-passing said motor, whereby said motor is operated at increased speed when said valve is closed, a pressure regulating valve in said system adjustable to allow some working liquid in said system to run said hydraulic motor but at a reduced speed when said by-pass valve is open, or adjustable to prevent working liquid in said system from running said hydraulic motor when when said bypass valve is open, and means for closing said valve during a period of each cycle when the tension of the warp yarn exceeds a predetermined value and for opening said valve during the remaining period of each cycle when the tension is restored to a lower value.

7. In a loom having a warp beam and operatable through recurrent weaving cycles, the combination comprising a whip roll over which the warp yarn is adapted to pass from a warp beam, means mounting said whip roll for oscillatory movement in response to the tension of said yarn, a spring loading said whip roll, a conduit system, a pump in said system for circulating liquid therethrough, means for continuously operating l0 said pump from the main drive of the loom, a hydraulic motor in said system in series with said pump, an irreversible drive connection between said motor and said warp beam, a valve by-passing said motor, whereby said motor is operated at increased speed when said valve is closed, and a connection between said whip roll and said valve to operate said valve in accordance with the deflections of said whip roll.

8. In a loom having a warp beam and operaable through recurrent weaving cycles, the combination comprising a whip roll over which the warp yarn is adapted to pass from said warp beam, means mounting said whip roll for oscillatory movement in response to the tension of said yarn, a motor for driving said warp beam for let-ofi operations, a valve for controlling the operation of said motor and comprising a valve casing, a piston valve member in said casing operable into open and closed position by the deflecting movements of said whip roll, and a con" nection between said whip roll and said valve to operate said valve in accordance with the deflections of said whip roll, said connection comprising a coil spring in said valve casing operating on said valve member to spring-load said Whip roll.

9. In a loom having a warp beam and operable through recurrent weaving cycles, the combination comprising a whip roll over which the warp yarn is adapted to pass from said warp beam, means mounting said whip roll for oscillatory movement in response to the tension of said yarn, a motor for driving said warp beam for let-off operations, a valve for controlling the operation of said motor, said valve comprising a valve casing, a piston valve member in said casing operable into open and closed position by the deflecting movements of said whip roll, and a connection between said whip roll and said valve to operate said valve in accordance with the deflections of said whip roll, said connection comprising a piston movable with said valve member in said casing and defining a pair of chambers in said casing on opposite sides of said piston, said chambers containing liquid, a pipe connection between said chambers, and a dashpot two-way orifice valve in said pipe connection permitting free piston movement in one direction created by deflection of the whip roll under the influence of the increasing tension of the warp yarn and retarding movement of said piston in the opposite direction.

HE NRY TYLER MARCY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 807,721 Carver Dec. 19, 1905 1,391,435 Weissenborn Sept. 20, 1921 1,463,966 Northrop Aug. 7, 1923 1,666,835 Ruhren Apr. 1'7, 1928 2,529,241 Bassist Nov. 7, 1950 FOREIGN PATENTS Number Country Date 624.6%2 Germany Jan. 25, 1936

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