US3630239A - Letoff for looms - Google Patents

Abstract

A constant warp tension letoff features an improved power path between the input shaft and letoff shaft which allows a considerable lessening of the force and tension which the transmission belt must exert on the variable cone pulleys of the letoff. A double-lead worm and gear at the letoff shaft reduces the torque which must be transmitted through the belt and cone pulley transmission. An improved weight lever mounting eliminates twisting of the weight lever which tends to cause binding. Excessive meshing of the lower worm and gear caused by heavy belt tension is eliminated.

Description

United States Patent [72] Inventors Felix E. Hooper; 2,786,491 3/1957 Hunt 139/110 Carlos Lee Owens, both of Greenville, S.C. 3,087,516 4/1963 Parks 139/110 [21] Appl. No. 5,720 3,156,267 11/1964 Hooper 139/110 [22] Filed Jan. 26, 1970 3,255,784 6/1966 Rothfuss et a1. 139/110 [45] Patented Dec. 28, 1971 3,320,979 5/1967 Owens .I. 139/1 10 [73] Ass'gnee gouthegnghchmery Company Primary Examiner-James Kee Chi reel" Attorney-B. P. Fishburne,Jr.

[54] LETQFF 5 4 21 ABSTRACT: A constant warp tension letoff features an imschlms rawmg proved power path between the input shaft and letoff shaft [52] [1.8. CI 139/110 which allows a considerable lessening of the force and tension [51] Int.Cl... D03d 49/06 which the transmission belt must exert on the variable cone [50] Field of Search 139/1 10, pulleys of the letoff. A double-lead worm and gear at the letoff 109 shaft reduces the torque which must be transmitted through the belt and cone pulley transmission. An improved weight [56] References Cited lever mounting eliminates twisting of the weight lever which UNITED STATES PATENTS tends to cause binding. Excessive meshing of the lower worm 2,755,824 7/1956 Hunt 139/1 10 and gear Caused by heavy tension is 2,775,263 12/1956 Rush 139/110 34 1 1 I 6% 1 1 (7/ K 2 i O} d5 .1 79 5: 1), I l u e1 1 l 7 78 29 v 1% 4i 1 a 4 ATE-P ,1 o e 7 58 TH 43 44 O l\ 7 45 \5 ao 39 41 47 a V J 42 Q PATtNTEnoiczmsn 31630.239

" sum 1 or 3 INVENTORS FELIX E. HOOPER CARLOS LEE OWENS ATTORNEY PATENTEUnc28t9n ajsaozas SHEET 2 OF 3 INVENTORS FELIX E. HOOPER CARLOS LEE (MENS BY KMW ATTORNEY PATENTED time 1971 sum 3 or 3 4 -333 6! [I C I RNVENTORS FELIX E. HOOPER CARLOS LEE OWENS ATTORNEY LETOFF FOR LOOMS BACKGROUND OF THE INVENTION The well-known Hunt letoff substantially in the forms disclosed by U.S. Pat. Nos. 2,786,491 and 3,255,784 has become the standard of the weaving industry around the world, and more than 140,000 of these Hunt letoffs are in use. Despite their wide acceptance and success, like all mechanisms the Hunt letoff has certain deficiencies which have come to light after long periods of operation. Among these deficiencies or defects is the tendency for the lower cone pulley and worm shaft to deflect upwardly under the relatively heavy tension force transmitted to this shaft by the belt which interconnects the upper and lower cone pulleys. In the existing letoff, the

bearings for this lower shaft are rather widely separated with the lower cone pulley and worm disposed intermediate the bearings. Consequently, upward deflection of the lower shaft under belt tension tends to cause excessive meshing of the worm and worm gear leading to the letoff shaft, the worm being in engagement with the bottom of the worm gear. This, in turn, causes friction and wear and over a long period of time restricts the efiiciency of operation of the entire letoff.

Another deficiency of the existing letoff resides in the pivot mounting of the weight lever, which lever sometimes has a tendency to bind on its pivot because of twisting.

With the above in mind, his the objective of the present invention to overcome and eliminate the deficiencies of the existing Hunt letoff and to improve the reliability, efi'rciency of operation, and the durability of the mechanism which has already proven to be highly satisfactory. In so doing, a letoff is provided in which constant and positive warp tension and control is maintained from full to empty beam, with added versatility for the widest range of fabrics.

Structurally, the improved letoff features a bottom cone pulley shaft which is separated from the worm shaft and the latter is moved overhead with respect to the letoff shaft and is interconnected with the bottom pulley shaft through a chain and sprocket drive. The two shafts are relatively short and their bearings are relatively close together and support the two shafts independently and rigidly. Belt tension effecting the bottom pulley shaft can have no effect whatsoever on the intermeshing of the worm .and gear and a consistent proper mesh can be maintained under all conditions of loading, the use of a double-lead worm and worm gear lessens the torque which must be transmitted and consequently relieves pressure on the belt transmission and actually reduces the force transmitted through the belt by as much as 3050percent in comparison to the existing mechanism. An improved bearing support for the weight lever wherein the latter is pivoted on both sides of the letoff frame fully eliminates twisting and binding. Other features and advantages of the invention will be apparent to those skilled in the art during the course of the following description.

BRIEF DESCRIPTION OF DRAWING FIGURES FIG. 1 is a fragmentary side elevation of a loom equipped with a letoff embodying the invention.

FIG. 2 is a view of the letoff along the axes of its pulley shafts, with parts in section.

FIG. 3 is a vertical section taken on line 3-3 of FIG. 1.

FIG. 4 is a fragmentary horizontal section taken on line 4- 4 of FIG. 1.

DETAILED DESCRIPTION Referring to the drawings in detail wherein like numerals designate like parts, the numeral designates one side frame of a weaving loom carrying a sturdybearing bracket 11 upon which the arbor 12 of the usual beam 13 is joumaled. The opposite end of the beam upon which the warps are wound is similarly supported on the other frame side of the loom.

The loom embodies a whip roll 14 over which the warps 15 pass under tension as they are gradually unwound from the beam during loom operation. The whip roll is cradled on mounting arms 16 at the opposite sides of the loom, carried by shafts l7, rockably mounted on brackets 18 rigid with the loom frame sides. Whip roll levers 19 are adjustably rigidly secured to the rockable shafts 17 in a well-known manner. The arms 16 and levers 19 are swingable vertically as a unit on the axes of shafts 17. The forward ends of the levers 19 connect with the letoff proper in a manner to be fully described.

The letoff proper comprises a rigid frame or plate 20 in the form of a casting upon which the principal components of the letoff are mounted. The frame 20 has an opening 21 receiving a hub portion 22 of a letoff shaft bearing and mounting bracket 23 having extensions 24 bolted to the loom frame side 10 at 25. The frame 20 is rigidly and adjustably mounted on the bracket 23 and supported bodily thereon substantially as shown and described in prior US. Pat. Nos. 2,786,491 and 3,255,784.

An input shaft 26 for the letoff near its top is supported in a bearing element 27 on the letoff frame 20 with its axis parallel to that of the beam arbor 12, FIG. 2. The input shaft 26 has an input sprocket gear 28 driven by a sprocket chain 29, in turn driven by the loom cam shaft, not shown. As shown in FIG. 2, the chain 29 is disposed between the letoff frame 20 and the adjacent loom frame side 10. On the opposite side of the letoff frame 20, the shaft 26 carries an input worm 30 meshing with an overhead worm gear 31 on the top cone pulley shaft 32, joumaled within bearings 33 and 34 carried integrally on the frame 20. This shaft 32 is perpendicular to the input shaft 26 and parallel to the loom frame side 10. At one end, it carries a hand wheel 35 and at theopposite end, a manual coupling means 36 substantially as shown in US. Pat. No. 2,786,49l. These details are unimportant to a full understanding of the present improvements.

The shaft 32 carries an upper cone pulley which embodies an axially movable cone disc 37 engaged by an endless transmission belt 38. A bottom cone pulley shaft 39 parallel to the shaft 32 is joumaled in bearings 40 and 41 integral with the frame 20 near its lower end. A lower cone pulley including an axially adjustable cone disc 42 is mounted on the shaft 39 and engaged by the belt 38 and it will be noted that the two adjustable discs 37 and 42 of the pulleys are in opposed relationship. The shaft 39 is a relatively short shaft andthe bearings 41 and 40 are rather closely spaced, rendering the shaft quite rigid under the tension force transmitted through the belt 38.

Somewhat above the shaft 39 and parallel thereto and extending beyond one end thereof is another short horizontal shaft 43 having a worm 44 thereon and being joumaled in sturdy bearings 45 mounted on the frame 20. The overlapping ends of the two shafts 43 and 39 carries sprocket gears 46 and 47 in vertical alignment and engaged by a short sprocket chain 48 lying outwardly of the adjacent bearing 45 and between this bearing and the belt 38.

The worm 44 meshes with and drives a worm gear 49 on a letoff shaft 50 joumaled upon the bracket 23, the latter having bearings 51 for the ends of the letoff shaft. A clutch or coupling means 52 is provided on the letoff shaft assembly for the purpose described in US. Pat. No. 2,786,491 but this forms no important part of the present invention and is conventional. An oil reservoir 53 within which the gear 49 operates is suitably secured to an extension of the frame 20.

Inwardly of the loom frame side 10, a spur gear 54 is secured to the letoff shaft 50 directly driving a larger gear 55 on the beam 13 and thus controlling the driving or turning of the beam to let off the warps thereon. It may be emphasized at this point that the provision of the two short shafts 39 and 43 with the interconnecting sprocket chain means 48 is a significant improvement or feature. The tension force through the belt 38 will cause little, if any, bending of the shaft 39, and due to the separation of the shaft 39 and 43, the tension force through the belt can have no effect on the shaft 43. In the prior art, as previously mentioned, a single-bottom pulley shaft was employed and the worm driving the letoff shaft was located at the bottom of the worm gearon the letoff shaft. The longer single shaft sometimes tended to bow upwardly under belt tension forces and wedge the worm too tightly into mesh with the worm gear, resulting in damage to the equipment.

The control components of the letoff include an improved weight lever 56 carrying weight 57 at its free end and having a main pivot shaft or pin 58 adjacent its other end. As shown in FIGS. 2 and 4, the pivot pin 58 is supported in a bearing part 59 on the frame and the weight lever has a U-shaped extremity 60 near its pivoted end having separated bearings 61 which receive the pin 58 and straddle the intermediate bearing part 59. This wide bearing support on the frame 20 in conjunction with an offset 62 in the weight lever stabilizes the weight lever and substantially eliminates twisting thereof and binding of the weight lever pivot which has been troublesome in the past.

The weight lever is counterbalanced by a generally vertical tension link 63 pivotally connected at its top to the lever 19 as indicated at 64. The lower end of tension link 63 is similarly connected to a cross pivot pin 65, HO. 4, which engages both arms of the U-shaped extremity 60. An upper control lever 66 is pivoted at 67 to a portion of the frame 20 and has an upper yoke 68 which engages a thrust collar 69 associated with the shiftable cone disc 37 to move the same axially. The control lever 66 has a lower extension 70 connected to an adjustable link 71 near the elevation of the weight lever 56 and the link 71 is pivotally connected at 72 to the upper arm 73 of a second control lever 74 having a lower yoke 75 engaging a thrust collar 76 on the shiftable cone disc 42 of the lower variable cone pulley. The control lever 74 is pivotally mounted on a pin 77 also anchored to the letoff frame 20. Another short substantially vertical link 78 interconnects a horizontal extension 79 of control lever 66 with the pivot pin 65 as shown clearly in FIGS. 1 and 3. The link 78 lies between the sides of U-shaped extremity 60 as shown in FIG. 4.

It may readily be seen that the effect of the weights 57 on the weight lever 56 pivoted at 58 is counteracted by the tension link 63, lever 19 and whip roll 14 pivoted at 17. As the diameter of the warp beam 13 decreases, a constant warp tension is maintained by the automatic operation of the letoff including the operation of the two interconnected control levers 66 and 74 which are tied into the weight lever 66 and tension link 63 through the common pivot pin 65. Thus, the diameters of the two cone pulleys will adjust or compensate automatically to maintain a constant tension on the warps 15 at all times. This mode of operation is disclosed fully in US. Pat.

No. 2,786,491 and need not be described further herein. As already stated, the present invention is concerned primarily with structural features of theletoff which improve its effciency, durability and versatility.

It is to be understood that the form of the invention herewith shown and described is to be taken as a preferred example of the same, and that various changes in the shape, size and arrangement of parts may be resorted to, without departing from the spirit of the invention or scope of the subjoined claims.

1. A letoff for a loom comprising a support frame attachable fixedly to a loom, an upper variable diameter pulley shaft journaled on said support frame on a fixed rotational axis, input drive means for said upper variable diameter pulley shaft operating while the loom is in operation, a lower variable diameter pulley shaft journaled on said support frame on a fixed rotational axis substantially parallel to the rotational axis of said upper pulley shaft and substantially in a common vertical plane therewith, variable diameter pulley transmission means including a transmission belt interconnecting said upper and lower shafts, yielding control linkage means for said transmission means having a connection with the whip roll of the loom, a letoff shaft journaled on the support frame on a fixed rotational axis near the elevation of said lower pulley shaft and spaced from one end of the lower pulley shaft, the rotational axes of the lower pulley shaft and said letoff shaft being substantially at right angles, said letofi shaft adapted to drive a warp beam ontheloom through gearing, a worm gear on said letoff shaft adapted to be driven, a drive shaft journaled upon said support frame above and parallel to the axis of the lower pulley shaft and disposed on a fixed rotational axis substantially at right angles to the axis of the letoff shaft spaced thereabove, a worm on said drive shaft in fixed meshed relation with the worm gear of the letoff shaft, adjacent end portions of said lower pulley shaft and drive shaft overlapping, and additional gearing drivingly interconnecting said overlapping end portions.

2. The structure of claim 1, and said additional gearing comprising a pair of sprocket gears on said overlapping end portions, and a sprocket chain engaging said sprocket gears.

37 The structure of claim 1, and a pair of bearings for said drive shaft on said support frame spaced closely on opposite sides of said worm, both said bearings disposed on one side of said additional gearing.

Claims (3)

1. A letoff for a loom comprising a support frame attachable fixedly to a loom, an upper variable diameter pulley shaft journaled on said support frame on a fixed rotational axis, input drive means for said upper variable diameter pulley shaft operating while the loom is in operation, a lower variable diameter pulley shaft journaled on said support frame on a fixed rotational axis substantially parallel to the rotational axis of said upper pulley shaft and substantially in a common vertical plane therewith, variable diameter pulley transmission means including a transmission belt interconnecting said upper and lower shafts, yielding control linkage means for said transmission means having a connection with the whip roll of the loom, a letoff shaft journaled on the support frame on a fixed rotational axis near the elevation of said lower pulley shaft and spaced from one end of the lower pulley shaft, the rotational axes of the lower pulley shaft and said letoff shaft being substantially at right angles, said letoff shaft adapted to drive a warp beam on the loom through gearing, a worm gear on said letoff shaft adapted to be driven, a drive shaft journaled upon said support frame above and parallel to the axis of the lower pulley shaft and disposed on a fixed rotational axis substantially at right angles to the axis of the letoff shaft spaced thereabove, a worm on said drive shaft in fixed meshed relation with the worm gear of the letoff shaft, adjacent end portions of said lower pulley shaft and drive shaft overlapping, and additional gearing drivingly interconnecting said overlapping end portions.

2. The structure of claim 1, and said additional gearing comprising a pair of sprocket gears on said overlapping end portions, and a sprocket chain engaging said sprocket gears.

3. The structure of claim 1, and a pair of bearings for said drive shaft on said support frame spaced closely on opposite sides of said worm, both said bearings disposed on one side of said additional gearing.

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