US3596682A

US3596682A - Friction letoff control

Info

Publication number: US3596682A
Application number: US777306A
Authority: US
Inventors: John H Nydam
Original assignee: North American Rockwell Corp
Current assignee: Draper Corp; Boeing North American Inc
Priority date: 1968-11-20
Filing date: 1968-11-20
Publication date: 1971-08-03
Anticipated expiration: 1988-08-03
Also published as: CH509219A; FR2023672A1; BE741939A; JPS4824107B1; DE1958075A1; GB1275606A

Abstract

A compensating follower device for a friction-type letoff actuated by variations in the angle at which a web of yarn or other wound material is withdrawn in going from a full to empty beam.

Description

United States Patent John H. Nydam Whltinsvllle, Mas.

Nov. 20, 1968 Aug. 3, 1971 North American Rockwell Corporation Pittsburgh, Pa.

Inventor Appl. No. Filed Patented Assignee FRICTION LETOFF CONTROL 7 Claims, 3 Drawing Figs.

US. 139/109 Int. Cl D03d 49/08 Field of Search... 242/156,

[56] References Cited UNITED STATES PATENTS 631,430 8/1899 Perham 139/106 2,472,548 6/1949 Schnell 242/7543 3,464,644 9/1969 Karamata et al 247175.43

FOREIGN PATENTS 1,292,845 3/1962 France l 39/109 931,493 8/1955 Germany 66/86 Primary Examinerl-lenry S. Jaudon Attomey-John R. Bronaugh ABSTRACT: A compensating follower device for a frictiontype letoff actuated by variations in the angle at which a web of yarn or other wound material is withdrawn in going from a full to empty beam.

Patented Aug. 3,1971

INVENTOR JOHN H.NYDAM AITORNEY FRICTION LETOFF CONTROL BACKGROUND OF THE INVENTION This invention pertains to letofi" mechanism for yarns or other continuous sheetlike material whereby the tension is controlled by retarding the rotative speed of the delivering beam.

More particularly this invention pertains to improved means for sensing a decreasing radius of the material and its resulting rotating speed requirements and for providing compensating reductions in the braking force to provide near-constant tension throughout an entire beam.

In friction letotTs presently known there are numerous means for maintaining an average tension throughout the duration of the complete beam. These means have generally provided a follower member of some sort which, through pivotal motion in bearing against the wound warp yarn as its diameter decreased, would permit increased rotation of the yarn beam. Yarn beam followers of this type presented a number of disadvantages due to the pressure required in holding them firmly upon the wound yarn. Followers have tended to bind because of loose yarn and lint, causing wear and the necessity for replacement. Adjustments have been required at intervals to maintain a constant reduction in pressure forces against the braking mechanism. These devices have not been fully automatic in applying a constant tension upon the warp yarns during the unwinding of a complete yarn beam.

SUMMARY OF THE INVENTION This invention provides a sensing device which follows and is pivoted by the web of yarns or other materials as they are unwound from a beam by tension applied by a takeup. A sensing wand, as shown in the drawing is supported by the warp yarns at a position between the yarn beam and a fixed roller. In the case of sheeting or paper or the like the wand might rest upon the upper surface, however, with thread or yarn it could be inserted as shown. With alternate groups of yarns running over and under the wand, it is both supported and urged downwardly by the web. The wand will follow the mean angle of declination taken by the sheet of yarn as the diameter upon the beam decreases without any further urging by springs or otherwise.

It is a general object of the invention to devise a letoff control follower which shall be simple and efficient, yet sensitive to minor angular movement caused by a decreasing warp supply.

It is a further object of the invention to devise a follower which shall be supported and movable by the tautly held yarns at a point away from the wound beam.

These and other objects of the invention will become apparent as further details are disclosed.

BRIEF DESCRIPTION OF THE DRAWING The invention will be described by reference to a specific embodiment thereof as illustrated in the accompanying figures of drawing, wherein:

FIG. 1 is a diagrammatic view in side elevation of the invention in relative position to known loom parts;

FIG. 2 is a front elevation of a portion of FIG. 1 as viewed from the left-hand side; and

FIG. 3 is a partial plan view ofFIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Now referring to the drawing, in FIG. 1 a letofi is shown in diagrammatic form as arranged for a weaving loom, however, the invention might be applied to machinery for unwinding other flat continuous material such as cloth or paper. A yarn beam 20, with only one of two beam heads 21 shown, is fully wound with a plurality of warp yarns 22. The warp yarns 22 are drawn over a roller 23 rotatable on a fixed shaft 24 which also pivotally supports a bellcrank lever 25. The lever 25 supports a whiproll 26 over which the warp yarns 22 are drawn with considerable tension by a takeup mechanism (not shown). The tension, which may be erratic for numerous reasons, will reciprocate the whiproll 26 and the lever 25 against some form of compressive force. As this mechanism is well known in the weaving art, it is not believed necessary to illustrate it further here. So far as a complete understanding of the invention is concerned, it is sufficient to state that the lever 25 may, under tension of the warp, be pivoted slightly in a counterclockwise direction as seen in FIG. 1.

At the lower end of the bellcrank lever 25 is a straight lever 27 pivoted near its center which has at one end a rigid connecting rod 28 pivotally fastened. Connecting rod 28 is also pivotally connected to one end of a sensing rod 29 which should have a polished surface and a generally round cross section. Another connecting rod 30 extends pivotally between the sensing rod 29 and the fixed shaft 24.

When used for letting ofi warp yarn, the sensing rod 29 may be inserted into the warp so that alternate groups of ends pass above and beneaththe horizontally extended rod as seen in FIG. 3. In this manner the sensing rod 29 is maintained in mean alignment with the warp as its angle to the horizontal changes in unwinding the beam 20 from full to empty. This angle is illustrated in FIG. 1 where the warp yarns 22 are numbered 22 as the beam is nearly exhausted. The tension of the warp yarns 22 will cause the sensing rod 29 to pivot in an are about the fixed shaft 24 and cause the connecting rod 28 to pivot the lever 27 to the dotted line position illustrated in FIG. 1. The sensing rod 29 is completely dependent upon the warp yarns 22 for movement and is sensitive to the slightest change in the letofi' angle followed by the yarn. The sensing rod may extend into the warp yarns a short distance as shown or may extend further or fully across the warp. It is believed that having the rod inserted into a portion of the warp yarns will be sufficient to efiect accurate let off in most instances.

At the lower end of the lever 27 a rod 31 is fastened for movement in a substantially horizontal plane when the lever 27 is pivoted. The rod 31 is encircled by a compression spring 32 having one of its ends restricted in position by an adjusting nut 33. The opposing end of rod 31 is loosely inserted through a hole in a brake lever 34 so that the spring 32 will bear against the brake lever 34 to a varying degree at all times. The brake lever 34 may be used in conjunction with a number of types of friction brakes suitable for application to a warp beam. In the disclosure herein, the brake used is a caliper type having a rotatable disc 35 in direct connection as by gearing (not shown) with the warp beam head 21. The disc 35 is positioned to rotate between a fluid actuated brake 36 wherein opposing brake shoes may be compressed against the disc with controlled pressure. Tubing 37 connects the brake 36 with a master-cylinder assembly 38 upon which the brake lever 34 is pivotally supported. The brake lever 34 is pivoted on the cylinder assembly 38 so that the greatest pressure or braking force is exerted when the lever 27 is in the solid line position of FIG. 1.

In operation the sensing rod 29 will gradually pivot downwardly as the warp diameter decreases until the dotted line positions of FIG. 1 are reached. As this downward movement takes place, a corresponding decrease in pressure is exerted upon the brake mechanism, which thus permits an increase in rotational speed to the yarn beam. The rate of the spring 32 determines the let off of warp yarn from full to empty beam as evidenced by the pivotal distance of the lever 27. Adjustment in the yarn tension at the start of a full beam through variation in the brake pressure is made by turning the adjusting nut 33 on the threaded portion of rod 31.

This invention provides a highly sensitive and efficient mechanism for controlling rate of warp let off, which is completely automatic throughout the full to empty beam range.

Iclaim:

1. A friction letoff control device for maintaining tension upon a sheet of continuous material defined by a plurality of warp yarns being drawn from a rotatable beam which comprises a. a brake mechanism for applying frictional restraint upon said beam,

b. a fixed member for supporting the material being drawn from said beam,

c. a sensing rod projecting into said material so that groups of warp yarns extend alternately beneath and above said sensing rod whereby said rod is supported and adapted to be influenced by the material suspended between said beam and said fixed member,

d. said sensing rod being supported by and angularly movable with the material extending from said beam, and

e. linkage means connecting said sensing rod with said brake mechanism.

2. The frictional letofi control device defined in claim 1 further comprising means for maintaining tension upon said sheet of continuous material.

3. The control device as set forth in claim 1, wherein said sensing rod is adapted to project only partially through the full width of the material.

4. The control device as set forth in claim 1, which further includes a reciprocating whiproll carried intermediate its ends by said fixed member, and wherein said linkage means is pivotally supported by one end of said whiproll lever.

5. The control device as set forth in claim 4, wherein said linkage means includes a. a pivotable lever supported by one end of said whiproll lever,

b. a rigid connecting link between said pivotable lever and said sensing rod, and

c. a brake-inducing rod pivotally connected with said pivotable lever and in active association with said brake mechanism.

6. The control device as set forth in claim 5, wherein said linkage means further includes a spring adjustably positioned upon said brake-inducing rod and adapted to bear compressively against said brake mechanism.

7. The control device as set forth in claim 6, wherein said brake mechanism includes a caliper-type disc brake in a controlling relationship with the rotatable beam, and a pressureforming master cylinder having fluid connection with said disc brake.

UNITED STATES PATENT OFFICE PO-IUSQ 5 CERTIFICATE OF CORRECTION Patent No. 3 596 682 I Dated August 3 197].

Inventor(s) John H. Nydam It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 1 after "whiproll" insert --1ever---.

Signed and sealed this 13th day of June 1972.

(SEAL) Attest:

R0 BERT GOTTSC HALK EDWARD M.FLEICHER,JR. Attesting Officer Commissioner of Patents

Claims

1. A friction letoff control device for maintaining tension upon a sheet of continuous material defined by a plurality of warp yarns being drawn from a rotatable beam which comprises a. a brake mechanism for applying frictional restraint upon said beam, b. a fixed member for supporting the material being drawn from said beam, c. a sensing rod projecting into said material so that groups of warp yarns extend alternately beneath and above said sensing rod whereby said rod is supported and adapted to be influenced by the material suspended between said beam and said fixed member, d. said sensing rod being supported by and angularly movable with the material extending from said beam, and e. linkage means connecting said sensing rod with said brake mechanism.

2. The frictional letoff control device defined in claim 1 further comprising means for maintaining tension upon said sheet of continuous material.

5. The control device as set forth in claim 4, wherein said linkage means includes a. a pivotable lever supported by one end of said whiproll lever, b. a rigid connecting link between said pivotable lever and said sensing rod, and c. a brake-inducing rod pivotally connected with said pivotable lever and in active association with said brake mechanism.

7. The control device as set forth in claim 6, wherein said brake mechanism includes a caliper-type disc brake in a controlling relationship with the rotatable beam, and a pressure-forming master cylinder having fluid connection with said disc brake.