US2661774A

US2661774A - Device for maintaining the tension in the warp threads of a loom uniform

Info

Publication number: US2661774A
Application number: US224357A
Authority: US
Inventors: George W Kretzschmar
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-05-03
Filing date: 1951-05-03
Publication date: 1953-12-08
Anticipated expiration: 1970-12-08

Description

Dec. 8, 1953 w KRETZSCHMAR 2,661,774

DEVICE FOR MAINTAINING THE TENSION IN THE WARP THREADS OF A LOOM UNIFORM Filed May 3, 1951 4 Sheets-Sheet 1 7 INVENTOR. GEORGE w. mzrzscm/ue ATTOQMEKB Dec. 8, 1953 G. w. KRETZSCHMAR 2,661,774

7 DEVICE FOR MAINTAINING THE TENSION IN THE WARP THREADS OF A LOOM UNIFORM Filed May 3, 1951 4 Sheets-Sheet 2 INVENTOR. 6501265 PV. IZQE TZSCHMAB OLJNL,

A 7' TOQNE Y5 Dec. 8, 1953 s. w. KRETZSCHMAR 2,661,774

DEVICE FOR MAINTAINING THE TENSION IN THE WARP THREADS OF A LOOM UNIFORM Filed May 3, 1951 4 SheecQs-Sheet 3 Fig.5

' I "III'I'I'II" INVENTOR. 69 79 650.426;- w. KAETZSCHMAIQ ysybwkfglw ATZ'OQNEYS G. W. KRETZSCHMAR DEVICE FOR MAINTAINING THE TENSION IN I THE WARP THREADS OF A LOOM UNIFORM 4 Sheets-Sheet 4 IN V EN TOR.

m m E M N H R C O n W m A K mv M Dec. 8, 1953 Filed May 3, 1951 in-1. 52 u f n} u llll l I Patented Dec. 8, 1953 DEVICE FOR MAINTAINING THE TENSION IN THE WARP THREADS OF A LOOM UNI- FORM George W. Kretzschmar, Ridgewood, N. J. Application May 3, 1951, Serial No. 224,357

9 Claims.

This invention relates to looms and, more particularly, to a device for letting off the warp from a warp beam under an initial tension which has been preset for the particular quality of the goods to be woven.

In applicants copending application, Serial Number 181,663, filed August 26, 1950, there was illustrated and described a tension unit for letting off the warp from the beam under uniform tension regardless of the diameter, width, or weight of the beam. In the tension unit there was also illustrated and described in detail a full floating whip roller against each end of which a hydraulically deflected compression spring exerts an equal pressure regardless of the out of horizontal position of one end of the roller relative to the other. The tension unit is designed to prevent or to eliminate in a woven cloth defects from side to side which arise from uneven tension across the warp or any portion thereof. Subsequently it was found desirable to include a new visible means for determining the average amount of spring deflection or pressure on the ends of the floating whip roller. It was also found desirable to transmit the up and down or reciprocal movement of the whip roller from an average position thereon to a control arm actuating a signal light and to incorporate in the control arm means for adjusting the let off from the warp beam with the loom in motion. It was also i found desirable to provide means in coaction with the control arm for letting off the warp from the warp beam with each and every stroke (pick) of the loom in approximately the exact amount required for each stroke or pick, and means for releasing all the tension or for Varying the tension on the warp of a loom at rest.

It is an object of the instant invention to provide a device which will let off the warp under uniform tension regardless of the diameter, width, or weight of the warp beam.

A further object is to provide a device for maintaining a uniform tension in the warp threads during the entire letting oif of the warp from a full beam to an empty one.

Another object is to provide a floating whip roller against each end of which a hydraulically deflected compression spring exerts an equal pressure, regardless of the position (up or down) of either end, to press the whip roller against the warp at any position thereof with equal pressure and to impart therein uniform tension.

Still another object is to transpose the motion from an average position of the tension imparting mechanism to a control arm for actuating a signal light and for guiding a control rod the position of which determines the amount of let off.

It is also an object of the instant invention to provide means for letting off the warp from a warp beam with each and every stroke of the loom (pick) and approximately in the exact amount required for each pick. I

An additional object is to provide means to signal with a light whenever the tension on the warp changes within presetlimits whether the loom be in operation or at rest.

Still another object is to provide a visible graduated scale for reading the average amount of spring deflection against the whip roller in the tension unit or the tension on the warp.

t is moreover an object of the instant invention to provide means for manually releasing all tension on the warp on a loom at rest.

A further object is to provide means on a loom at rest for manually increasing or decreasing the warp tension when the warp has stretched or shrunk and without interfering with the preset spring pressure.

Other objects of the instant invention will become apparent in the course of the following specification.

In the attainment of these objectives, the desired tension in the warp is maintained uniform by a tension unit, a warp beam let off mechanism in operable engagement with the tension unit, and a full floating warp beam in operable engagement with the let ofi mechanism. The tension unit was described in detail in the p=reviously mentioned copending application, Serial Number 181,663, and is designed to let off the warp thread from a full to an empty beam under uniform tension. As described in the copending application, the tension unit isconstituted in part of a full floating whip roller under upwardly directed preset pressure against the warp for the quality of the goods to be woven, the pressure being attained by' hydraulically operated compression springs. In the copending application, a pressure gauge in the hydraulic fluid line provides a means for reading the pressure of the fluid against pistons which deflect the springs. In subject application, new means have been provided for reading directly the pressure of'pre designed springs against the whip roller by the deflection of the springs. The tension unit of subject application further differs from the unit in the copending application by providing a means for transmitting th reciprocal movements of the whip roller from the average position to a coni: trol arm in operable engagement with a signal light for indicating the variation of the tension beyond predetermined limits, the means being also in operable engagement with the let off mechanism. The let off mechanism for the warp thread is in operable engagement with both the control arm and the lay leg or stroking mechanism of the loom and incorporates a multiple pawl mechanism for a very fine let ofi of the warp. To even further maintain the tension in the warp uniform, there is employed known full floating rotatable supports for the beam in operable engagement with the let oif mechanism.

The invention will appear more clearly from the following detailed description when taken in conjunction with the accompanying drawings showing by way of example the preferred embodiments of the inventive concept.

In the drawings:

Figure l is a side elevational view in part section of the tension unit, the mechanism for maintaining the tension roller of the tension unit un der uniform pressure against the warp and the let-off mechanism;

Figure 2 is a front elevational view of the mechanism shown in Figure 1;

Figure 3 is a top view of the mechanism shown in Figure 1;

Figure 4 is an elevational view taken in the direction of 4-4 of Figure 3;

Figure 5 is a sectional view along 55 of Figure 2;

Figure 6 is a sectional view along 6-6 of Figure 1;

Figure 7 is an enlarged fragmentary elevational view of the multiple pawls controlling the magnitude of the warp let off from the beam with each pick;

Figure 8 is a fragmentary top plan view of the multiple pawls shown in Figure 7;

Figure 9 is an elevational view of one of the improved covers constituting a part of the mechanism for maintaining both ends of the whip roller of the tension unit under uniform pressure against the warp;

Figure 10 is a fragmentary perspective View of one end of the full floating warp beam;

Figure 11 is a fragmentary perspective View of the control arm of the tension unit for controlling the length of the warp let oif from the warp beam, and for closing the circuit to an electric light when the tension variations in the warp exceed predetermined limits; and

Figure 12 is a diagrammatic view of the mechanism for maintaining uniform pressure on both ends of the full floating whip roller irrespective of the out of horizontal position of the roller.

Referring now in greater detail to the drawings where like reference numerals indicate like parts, reference numeral l0 indicates the warp stand, H the tension unit, l2 the warp beam, [3 the let off mechanism for the warp beam, [4 the tension adjusting mechanism for the tension unit, and 15 the tension signal light.

The warp stand i0 is located at the warp end of a loom (not shown) and is constituted of the spaced side members 16 and I! (Fig. 3) which are designed, when fastened to the end of the loom, to support the warp beam and the tension control devices in a manner hereinafter described. Any suitable means may be used for attaching the side members to the end of the loom.

At the top of the stand I 9 is the tension unit H as most clearly shown in Figures 1, 2, 3, and 5. The tension unit H is constituted of the similar end housings I3 at the top of each side of the warp stand and above the warp beam 12. Each end housing has spaced side and end members, a closed top, and an open bottom (Figs. 1 and. 2). Each housing further has formed through the side members, the aligned openings 23 and 24 (Fig. 2) adjacent the outer end or front of the unit and similar aligned

openings

21 and 28 equally spaced inwardly and upwardly from the openings 23 and 24. In the aligned openings 23 and 24 are any suitable bearings as illustrated. Rotatably supported by the bearings in the aligned openings 23 and 24 of each housing is the shaft 29 which, in turn, is rotatably inserted through the tension roller 39. Rotatably supporting the shaft 29 above the side members of the stand are the similar adjustable brackets! (Fig. 2), one on each side of each side member. Each bracket of each pair has formed therethrough near the bottom a similar longitudinal slot 22 (Fig, 1) through which like fasteners 2! are inserted as well as through a registered opening (not shown) in the side member between the brackets. In the ends of each pair of brackets extended above the stand are a pair of aligned Openings 25 and 26 (Fig. 2) equipped with bearings for the rotatable support of the ends of the shaft 29 when suitably aligned with the openings 23 and 24 in each end housing. Rotatably inserted through the previously mentioned openings 2'! and 28 in each end housing is the shaft 3| of the whip roller 32. The inwardly directed ends of each housing are secured together by a light flexible channel member or tie rod 33 (Figs. 1 and 5) with the channel directed toward the tension roller 30 or otherwise. Any known means may be used for attaching the channel member to the ends of the housing. By the construction described, both

rollers

30 and 32 are rotatable and the whip roller '32 and the end housings l8 pivotal about the shaft 29 of the tension roller within the limits of the housings and the stops 29a (Fig. l) integrally formed with each end housing and coacting with the adjustable brackets l9. Also by virtue of the construction described in detail in copending application, Serial Number 181,663, when the warp is drawn over the tension and whip rollers from the warp beam, the angle formed by the whip roller with the tension roller for any diameter of warp beam remains constant because of the parallelogram of forces.

Fastened to one end of the shaft 29 of the tension roller 30 by any suitable means 20 is a control arm 34 (Fig. 3) which is extended inwardly under the channel member or tie rod 33 (Fig. 5). As shown especially in Figure 11, the control arm 34 terminates at the free end in an upturned portion which has on one side an integrally formed electrical contact 34a. Transversely disposed through the contact 34a and adjustable therein relative thereto is another electrical contact 35. Both

contacts

34a and 35 may be designated as movable contacts. Coacting with the movable contacts is a stationary or third contact 36 (Fig. 11) in the circuit of the signal light I 5, the circuit for which is well known but not shown. Both the light and the third or stationary contact are attached in a known manner to a side member of the stand and the stationary contact may be made adjustable. On the side of the arm 34 opposite the movable electrical contacts is a member or eye which has inserted therein a ball joint 35b for the slidable insertion of the later described sleeve 64 which regulates the magnitude of the let off.

To more evenly distribute the forces acting on the tension unit and to operate the control arm 34, a compensating rigid brace 42 (Fig.3) has been incorporated in the tension unit. The brace 42 is of U-shape as illustrated with the forwardly directed

end extremities

43 and 44 of the side portions 43a and l-ia, respectively, attached to opposite ends of the shaft 29 of the tension roller 30. The side portions 43a and tea are then extended rearwardly under the whip roller 32 with the integrally formed bottom or horizontal portion 45 adjacent the channel member or tie rod 33 on the side of the roller 32 as further illustrated. Substantially at the center of the bottom portion 45 is a pin 45 extended rearwardly and pivotally fitted into the flexible channel member. By virtue of the described construction, the whip roller is full floating and one end may be tilted above the other without varying the pressure against the warp threads as later shown. As the warp beam decreases in diameter, the movement of the pin 48 is gradually downward.

To maintain the hull floating whip roller 32 at a predetermined upwardly directed uniform pressure against all of the warp, there was described in applicants aforementioned copending application, Serial Number 181,663, a visible and balanced tension control device in which reciprocal pistons in operable engagement with springs in turn in operable engagement with the ends of the whip roller regulate the pressure of the roller against the warp and maintain the tension therein constalnt, the pressure being preset in accordance with the quality of the goods to be woven. As illustrated in Figure 12, the construction adopted involves a master cylinder 38 in operable engagement with the pistons 3? of the slave cylinders through the medium of a hydraulic fluid. Predesigned compression springs are disposed between the land of the piston and the ends of the shaft 3|. By turning the head of the master cylinder 38 down into the cylinder the hydraulic fluid is expelled simultaneously into both slave cylinders to give an equal preselected pressure on both ends of the shaft. However, the shaft 3| will not always be in a horizontal position because of (l) defective beams and beam gudgeons; (2) uneven warping; (3) misalignment of the take-up and whip rollers; (4) unbalanced action of the lay leg; (5) wear and tear on bearings, pivots, and

cranks; etc. However, irrespective of the out of horizontal position of the shaft 3! the pressure of the springs thereagainst will not vary since the forcing of the fluid out of the left hand slave cylinder shown in Figure 12 will in turn force the fluid into the right hand slave cylinder to keep the pressure constant, the master cylinder remaining unchanged. In subject application, the visible and balanced tension control device is identical with the mechanism described and illustrated in the copending application except that the cover or guide 37a (Fig. 9) for the pistons and springs have formed therein a longitudinal open ing 39. Along one edge of the opening 39 is a graduated scale 40, graduated in fractions of an inch or pounds of pressure and correlated with the spring deflection so that as the index line on mark i! on the land of the piston supporting one end of the spring moves along the scale, a direct reading of the pressure on the whip roller at each end is visible.

In operable engagement with the control arm I 34 of the tension unit is the let off mechanism l3 for the threads of the warp beam E2. The warp beam let off mechanism is con tituted as follows: Through one of the side members of the warp stand I0 an opening 420/, (Fig. 2) is made and through the opening is a portion of a housing 43b attached in a known manner to the side member. Rotatably and horizontally inserted in the housing and parallel to the axis of the warp beam isthe helical gear bushing 45a, the outer end of which is extended beyond the end of the housing and externally threaded as shown in Figure 6. Threaded on the extended end of the bushing is the ratchet gear 4511. Through the bushing 45a is rotatably inserted the shaft 42', the ends of which protrude beyond the ends of the bushing. On the inner extended end of the shaft 4'! is keyed the spur gear 48 in operable engagement with the later described vertical rack 6! which, in turn, is in operable engagement with the later described sleeve d4, reciprocally inserted in the arm 34. Rotatably secured over the outer extended ends of both the bushing and the shaft 47 is the stroke lever 49 of inverted U-shape. Pivotally attached to one side of the inverted U-shaped lever substantially adjacent the horizontal or upwardly positioned bottom portion and on the outside, is the stroke arm 50 (Figs. 2 and 7), the opposite end of the stroke arm being in operable engagement with the lay leg or stroln'ng mechanism of the loom (not shown). In operable engagement with the stroke lever 49 is the pawl lever 5! secured to the shaft 4! and on which are pivotally mounted and forwardly extended over the teeth of the ratchet gear 46a the

multiple pawls

52, 53, and 54. It will be noted in Figure 8 especially that each pawl is of difierent length so that the ratchet gear 46a may have a minimum number of teeth which in any position of the gear teeth will engage at least one thereof. The length of the pawls is dependent upon the circular pitch of the teeth divided by the number of pawls, that is the pawl of intermediate length (Fig. 8) is made shorter by one third of the circular pitch than the pawl of greatest length and the pawl of shortest length is shorter than the pawl of intermediate length by one-third of the circular pitch. Thus, by using multiple pawls the ratchet gear 360, can have teeth of sufficient body to withstand long wear while the let oif resulting from the rotation of the ratchet gear by the pawls can be made very fine.

On the inner surface of the ratchet gear 45a is a pulley (Fig. 6) around a part of which the brake band 56 is passed, One end of the band is anchored in the brake support 5'! (Fig. 1),.

which is a part of or attached to the side member H5. The opposite end of the band is held under tension by the pin 55! slidably inserted through a screw 58 threaded through the support 51 with the head of the pin held in spaced rela-- tionship with the head of the screw by the spring 50.

As aforementioned, the spur gear 43 keyed to the inner end of the shaft 47 is in operable en gagement with the rack 6i maintained reciprocal in a vertical position in a slideway at the back of the housing (Fig. 5), One end of a rod 62 s pivotally attached to the top of the rack 5! by any suitable pin es. The rod is then extended upwardly from the rack for threaded attachment in the bottom of the previously mentioned sleeve 64 (Fig. 5). The sleeve 54 extends vertically through a ball joint 35?) in the eye 65 on the control arm 3 and terminates in a knob at the top which when turned will move the rod and rack up or down to turn the shaft 41 and vary the spacing of the pawl lever 5i relative to the stroke lever 59 to control the magnitude of the thread let ofi from the warp beam. It is to be noted that the stroke of lever 49 as actuated by the arm 50 in operable engagement with the lay leg or stroking mechanism of the 100m is constant and that pawl lever 51 and spur gear 43 are secured to the shaft 41. The rack 61 is in mesh with the gear 48 and is pivotally connected at the top to one end of the rod 62. The opposite end of the rod 52 is threaded into the sleeve 54 so that it can be made longer or shorter. The knob-like top of the sleeve 65 comes to rest on the ball joint 35?) with each stroke of the loom. Thus, the length of the rod 52 can be varied to determine the position of the pawl lever i While the turning of the knob is a manual operation, it will be noted that the control of the let off is also auto matic. For example, suppose the tension in the warp becomes sufficiently increased to pivot the tension unit it and the control arm 34 downwardly. In the lowered position, the sleeve 6:; will drop downwardly also to a lower position until stopped by the knob-like top thereof. In the lowered position of the sleeve E4, the spacing between the pawl lever ii and the stroke lever 49 will be decreased so that the

pawls

52, 53 and 54 will be moved to a position to let off more warp as shown in the following paragraph to restore the uniform tension.

By the previously described construction, the helical gear bushing ifia will be rotated in one direction by the ratchet gear dta in turn operated by the pawls in accordance with the required let off. On the bushing and in the housing 63b is the gear 55a in operable engagement with a gear 65 turning with a. rotatably mounted worm and helical gear shaft 66 which is in operable engagement with the worm gear 58 attached to the end of the warp beam 12 in a manner subsequently described. One end of the shaft 65 protruding through the housing terminates in a square head fil for the releasable attachment of a manually operated wrench or crank which is not shown.

Since warp beams as a rule are not mechanically perfect, the gudgeon 69 at each end of the beam is rotatably supported by a self-aligning coupling of known design. In brief, the gudgeon fi is fastened in the end of the warp beam in the usual manner and protrudes through the open end of a barrel Til (Fig. also fastened to the end of the warp beam. Secured to the inner surface of the barrel and also protruding through the open end thereof are two spaced lugs H and '12. Coacting with the lugs is a plate i3 having the inwardly directed slots is and '15 and the outwardly directed protuberances I6 and 11. The protuberances l5 and 11 coact with spaced slots 80 in the worm gear 68 in the rotation of the warp beam while a ring "18 attached to the ends of the lugs holds the plate in position. The extremities of the gudgeons are supported by the floating bushings 8i, Each bushing has an outer race 32 horizontally disposed through each of the stand side members (Fig. 6) and in which it is attached by welding or the like. In the inner surface of the outer race is a recess of arcuate cross section on either side of the vertical center line. An inner race 83 is attached on the end of the gudgeon, the inner race being enlarged on the outer surface to provide a surface coacting with the recess of the inner race. The self-aligning coupling previously described is designed for the end of the warp beam having the worm gear 68. It is to be understood, however, that there is a self-aligning coupling for both ends of the beam, but since the let-ofi mecha nism is applied to only one end, the plate 13 for the opposite end may be of more simple construction.

In operation:

With the tension adjusting devices assembled in the manner previously described, the tension adjusting mechanism I4 is set by the use of the graduated scales of each slave cylinder to read the average amount of spring deflection or tension in the warp required for the particular quality of the goods to be woven and is never changed during the entire letting oil of the warp. Where a plurality of looms are used for weaving goods of the same quality, the deflection of the springs are hydraulically set to the same scale reading and the weaves will all have the same warp tension. For a pickup, that is, the removal of the filling threads, the loom is stopped and all tension released on the warp by turning the square head Bl of the shaft 66 clockwise until the end housings 29a are stopped by the adjustable brackets l9. To reset the tension to the operating warp tension, the

pawls

52, 53, and 54 are lifted upwardly out of engagement with the teeth of the ratchet gear 46a, and the shaft 66 turned counterclockwise until the signal light l5 goes out which gives a simple and novel method for pickouts. The stroke lever 49 has a constant stroke and pushes the pawl lever SI for a part of the constant stroke while the stroke of the pawl lever 51 is determined by the position of the knob-like top of the sleeve 64 resting on the ball joint 35b for operating the ratchet gear Mic with the

pawls

52, 53, and 54. To manually increase or decrease the warp tension, without changing the hydraulically preset spring pressure against the whi roller, on a loom at rest, the pawls are lifted and the shaft 66 is turned counterclockwise until one of the

movable contacts

34a and 35 is disengaged from the stationary contact 36, as the case may be, and the signal light [5 goes out when increasing the tension, and clockwise until the signal light l5 goes out when decreasing the tension. In a loom either at rest or in motion, the signal light out means that the warp is under the initial or exact tension to which the warp has been set. In a loom in motion, the light on calls for a manual adjustment of the sleeve 64 to vary the spacing of the pawl lever from the stroke lever for more or less let oil as required. In a loom at rest, the light on calls for an increase or decrease of warp tension by means of manually rotating the shaft 66.

It is obvious that the mechanisms hereinbefore described and illustrated are subject to wide variations and modifications within the scope of the appended claims.

What is claimed is:

l. A tension unit for the thread from the warp beam of a loom, the unit comprising two end housings, each end housing comprising spaced parallel side and end members and a top member, the bottom of each housing being open and the members being secured along corresponding edges, the side members of each housing having a pair of aligned openings formed therein adj acent the outer end and a second pair of aligned openings formed therein adjacent the inner end, the second pair of openings being equally spaced from and above the first pair, a tension roller shaft rotatably disposed through the first pair of aligned openings in each housing, a tension roller for the warp thread from the beam rotatably disposed on'the shaft, a whip roller forthe warp thread from the tension roller rotatably disposed between the second pair of aligned open ings of each housing, means for rotatably mounting the war beam adjacent the warp end of the loom, means coacting with the shaft of the tension roller for pivotally securing the end-housings on opposite sides of the loom with the whip roller adjacent the end of the 100111 and the rollers above and parallel to the warp beam, a flexible tie rod disposed on the inner ends of the housings, means for distributing the forces acting'on the tie rod to the shaft of the tension roller, means for maintaining the whip roller under tension against the warp threads, and signal means coacting with the shaft of the tension roller to indicate when the pressure of the whip roller against the warp thread exceeds predetermined limits.

2. A tension unit according to claim 1 in which the means coacting with the shaft of the tension roller for pivotally securing the end housings on opposite sides of the loom with the whip roller adjacent the end of the loom and the rollers above and parallel to the warp beam comprises a stand for the warp beam and the tension unit, the stand comprising spaced parallel side members disposed on opposite sides of the loom at the warp end, means for rotatably securing the warp beam between the side members, at least one bracket adjustably disposed on each side member of the stand, the bracket extending upwardly above the side member through the open bottom of the corresponding end housing, the upwardly extended end of the bracket having an opening formed therein for the rotatable insertion of the shaft of the tension roller.

3. A tension unit according to claim 1 in which the means for distributing the forces acting on the tie rod to the shaft of the tension roller comprises a rigid compensating brace of U-shape, the ends of the side portions of the U-shape brace being secured to the shaft of the tension roller intermediate the end housing and the roller at each end thereof, the bottom portion of the U- shaped brace being adjacent the tie rod on the side of the whip roller, and means for pivotally securing the bottom portion to the tie rod substantially at the center of each.

4. A tension unit according to claim 1 in which the signal means coacting with the shaft of the tension roller to indicate when the pressure of the whip roller against the warp thread exceeds predetermined limits comprises a control arm disposed on the shaft of the tension roller, the arm extending inwardly under the tie rod and thence upwardly, a movable electrical contact disposed on one side of the upwardly extended portion of the arm, a second movable electrical contact transversely and adjustably disposed through the first, a stationary contact disposed on the stand and coacting with the movable contacts, an electric light lamp disposed on the stand, and a normally open electric circuit between the contacts and the lamp.

5. In a loom having a full floating whip roller maintained at a predetermined pressure against the warp thread by hydraulic spring deflection against the roller at both ends, the springs being actuated by the lands of pistons controlled by a hydraulic fluid from a master cylinder; the improvements comprising a cover for each spring and piston, the cover having a longitudinal opening formed therein, the opening having a graduated scale along one longitudinal edge, and the 10 land of the piston having an index mark coacting with the scale.

6. A positive let on" mechanism for the warp thread from the warp beam of a loom, the beam having a gudgeon, the loom having a stroking mechanism, a tension unit, and stand supporting the tension unit and beam, and the tension unit having a control arm equipped with a ball joint; the let off mechanism comprising a housing disposed through one side of the stand, a helical gear bushing rotatably disposed through the housing at one side of and parallel to the beam, the outer end of the bushing being extended beyond the stand and the housing, a ratchet gear disposed on the outer end of the bushing, and pawl means in operable engagement with the stroking mechanism of the loom for rotating the ratchet gear in one direction; the let off mechanism further comprising a shaft rotatably disposed through the bushing and extended beyond the ends thereof, a spur gear keyed to the extended inner end of the shaft, a vertical rack reciprocally disposed in the housing and in operable engagement with the spur gear, and means coacting with the rack and the ball joint for varying the spacing of the pawls relative to a tooth of the ratchet gear; the let oif mechanism further comprising a worm and hellcal gear shaft rotatably and horizontally disposed through the housing at a right angle to and in operable engagement with the helical gear bushing, one end of the worm and helical gear shaft being extended through the housing, and means for manually rotating the extended end; the let-off mechanism further comprising a worm gear for the gudgeon of the warp beam in operable engagement with the worm and helical gear shaft, the worm gear having a central circular opening and the opening having two spaced slots formed in the rim thereof, and means coacting with the slots to form a universal joint between the worm gear and the warp beam.

7. A let off mechanism for the warp threadfrom the warp beam of a loom according to claim 6 in which the pawl means in operable engagement with the stroking mechanism of the loom for rotating the ratchet gear in one direction comprises in combination an inverted U-shaped stroke lever, one end of the lever being rotatably disposed on the extended outer end of the shaft through the bushing and the other end rotatably disposed on the extended outer end of the bushing, means intermediate the stroking mechanism of the loom and the outside surface of the inverted bottom portion of the U-shaped lever for reciprocating the lever, a pawl lever of inverted L-shape keyed to the extended outer end of the shaft through the bushing, the inverted bottom portion of the L-shaped lever coacting with the inverted bottom portion of the stroke lever, a plurality of pawls p-ivotally disposed on the inverted bottom portion of the L-shaped lever, the V pawls being directed toward the warp beam and in operable engagement with the teeth of the ratchet gear, each pawl being of different length, the length of each pawl following the pawl of greatest length being shorter than the preceding pawl by a distance equal to the circular pitch of the ratchet gear divided by the number of pawls.

8. A let olf mechanism for the warp thread from the warp beam of a loom according to' claim 6 in which the means coacting with the rack and the ball joint for varying the spacing of the pawls relative to a tooth of the ratchet gear comprises an adjustable control rod, means for pivotally securing one end of the rod to the top of the rack, the opposite end of the rod being extended upwardly to the control arm and externally threaded, a sleeve slidably disposed through the ball joint, the bottom of the sleeve having a threaded opening formed therein for the threaded attachment of the threaded end of the rod, and the top of the sleeve having formed thereon a knob coacting with the ball joint.

9. A let off mechanism for the warp thread from the warp beam of a loo-m according to claim 6 in which the ratchet gear has a pulley formed on the inner surface thereof, a brake band disposed substantially around the pulley, means for anchoring one end of the brake band to the stand, and means for adjustably anchoring the opposite end to the stand adjacent the anchored end.

GEORGE W. KRETZSC'HMAR.

References Cited in the file of this patent UNITED STATES PATENTS Number 5 1,705,637 2,305,422 2,398,547 2,398,925 2,450,488 2,507,828 2,565,386

15 Number Name Date Deleu Mar. 19, 1929 Herard, Jr. Dec. 15, 1942 Moess inger Apr. 16, 19h; Darwin Apr. 23, 1946 SGhedin Oct. 5, 1948 Stephensen et al. May 16, 1950 Marcy Aug. 21, 1951 FORETGN PATENTS Country Date Great Britain s Aug. 12, 1926