US3929169A

US3929169A - Thread brake

Info

Publication number: US3929169A
Application number: US457235A
Authority: US
Inventors: Erwin Pfarrwaller
Original assignee: Sulzer AG
Current assignee: Sulzer AG
Priority date: 1973-04-03
Filing date: 1974-04-02
Publication date: 1975-12-30
Anticipated expiration: 1992-12-30
Also published as: CH564478A5; JPS49126938A; JPS5327393B2; AT324978B

Abstract

The thread brake has two oppositely disposed braking surfaces at least one of which has an indentation to limit lateral movement of the thread during braking. The indentation can be of uniform groove shape and of a depth less than the thickness of a thread or can have a transition zone formed by a chamfered wall which merges on an obtuse angle into the braking surface.

Description

United States Patent [1 1 UNITED STATES PATENTS 1/1949 Houseman 188/652 Pfarrwaller 51 Dec. 30, 1975 [54] THREAD BRAKE 2,608,845 9/1952 Brown 66/145 1 Inventor: Erwin Harman, wimwhw, i'lil'ifi 211322 fifiill'lgzzijij la /.22

Switzerland [73] Assignee: Sulzer Brothers Limited wintenhur' Switzerland Primary Exammer-l-lenry S. .laudon Attorney, Agent, or Firm-Kenyon & Kenyon Rally [22] Filed: Apr. 2, I974 Carr & Chapin [21] Appl. No.: 457,235

[30] Foreign Applic'ation Priority Data [57] ABSTRACT Apr. 3, 1973 Switzerland 4723/73 The thread brake has two oppositely disposed braking surfaces at least one of which has an indentation to gg fg lgg limit lateral movement of the thread during braking. The indentation can be of uniform groove shape and [58] Field of Search 139/122 R, 122 H, 194;

H25 226/195 [88/651 65 2 65 3 of a depth less than the thickness ofa thread or can 65 A have a transition zone formed by a chamfered wall which merges on an obtuse angle into the braking sur- [56] References Cited face 10 Claims, 6 Drawing Figures US. Patent Dec. 30, 1975 Sheet 1 0f 2 3,929,169

US. Patent Dec. 30, 1975 Sheet 2 of2 3,929,169

THREAD BRAKE This invention relates to a thread brake and particularly to a thread brake for use in braking weft threads in a loom.

Heretofore, various types of thread brakes have been known for braking threads during travel, for example in textile machines such as looms. Generally, the thread brakes have been constructed with two brake members having overlapping braking surfaces which are adapted to decelerate a thread that runs between the surfaces. However, in thread brakes of this kind it is possible for the thread which is gripped by the brake members, particularly if the thread passes through the brake members intermittently to deviate laterally during braking. As a result, in many instances, the threads have become positioned outside the braking position and become loose. This may be caused by the unavoidable minor deviations of parallelity in the braking surfaces, particularly in conjunction with vibrations of the brake members of thread brakes which are disposed in an operating machine.

A thread which emerges laterally from the brake gap between two braking surfaces is frequently unable to re-enter between the brake members. Thus, the thread cannot be braked in a subsequent thread motion and causes an operational breakdown. Any such misalignment of a stationary thread is particularly detrimental in machines, for example looms, whose elements operate reliably only if the thread remains taut. For example, the transfer of thread between a thread supply means and a shuttle may be detrimentally affected or rendered impossible in gripper-type shuttle loom.

Accordingly, it is an object of the invention to ensure reliable gripping of a thread in a thread brake. It is another object of the invention to impose as small as possible a stress on a thread which is periodically braked to a stop during travel.

It is another object of the invention to prevent a lateral deviation of a thread out of a thread brake during operation of the brake.

Briefly, the invention provides a thread brake which has a pair of brake members, each of which has a braking surface, with an indentation in at least one of the braking surfaces. The indentation is disposed laterally of the path which a thread takes in passing longitudinally between the braking surfaces and is sized to receive the thread. The thread section that is disposed between the braking surfaces is therefore able to travel laterally only within a precisely defined range before being caught in the indentation.

In one embodiment particularly intended for the deceleration of taut threads with an accurately defined thread run, the indentation has the form of a groove that extends substantially parallel to the path of the thread.

In order to ensure a constant deceleration of the thread, i.e. even for a thread that has already been laterally displaced, it is appropriate if the depth of the indentation is less than the thickness of the thread that has to be decelerated.

In a further embodiment, the transition zone between the braking surface and the indentation is constructed so as to avoid additional stressing of the thread, particularly during each recommencement of the thread motion after a stoppage. For example, the wall of the indentation nearest to the braking position is cham- 2 fered or otherwise formed to merge on an obtuse angle into the braking surface.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 diagrammatically illustrates a thread brake of the invention in an open position, shown partially as a longitudinal section;

FIG. 2 illustrates a horizontal sectional view taken along line II-II of FIG. 1;

FIG. 3 illustrates a view of the thread brake according to FIG. 1 in a braking position;

FIG. 4 illustrates a cross-sectional view taken along line IV-IV of FIG. 2;

FIG. 5 illustrates a modified thread brake according to the invention; and

FIG. 6 illustrates a further modified yarn brake according to the invention.

Referring to FIG. 1, the thread brake has a flexible brake member 1 and a rigid brake member 2 which cooperates with each other to brake a thread 19 passing longitudinally therebetween in a predetermined path. The brake member 1 comprises a flexible strip 3, for example a steel band, both ends of which are secured to

holders

4, 5 each of which is provided with an

eyelet

4a, 5a respectively, for passage of the thread 19. The holder 4 is mounted on a support member 6 of a loom (not shown) and the holder 5 is disposed on an arm 8 which is pivotable in the direction indicated by an arrow 7 and is situated on a shaft 9 that is associated with the drive (not shown) of the loom.

The brake member 2 comprises a plate which is disposed on a shaft 11 and one side of the brake member 2 forms a cylindrically curved smooth braking surface 12. This surface 12 overlaps a corresponding smooth braking surface 10 on the strip 3 as indicated in FIGS. 2 and 4. The shaft 11 is axially slidably guided in the directions indicated by an arrow 14 in a bearing 13 that is disposed on the loom (not shown). The shaft 11 is provided with a collar 15 on which a compression spring 16 acts that bears on the bearing 13. The compression spring 16 causes the end of the shaft 11 to be thrust against a cam 17 which is mounted on a shaft 18 that is associated with the loom drive (not shown).

The thread 19 is supplied from a supply reel (not shown) through the eyelet 4a to pass between the

brake members

1, 2 and exit through the eyelet 5a. For example, the thread 19 is a weft thread of the loom which is guided downstream of the eyelet 5a, as indicated by the arrow 20, to a weft picking device (not shown) and is intermittently transferred by the picking device into a shed. The thread is kept tensioned between every two weft picks by means of a thread tensioner (not shown) that is disposed between the supply reel (not shown) and the

thread brake members

1, 2.

Referring to FIGS. 2 and 4, in order to limit lateral movement of the thread 19, the braking smooth surface 11 of the rigid brake member 2 is provided with two

indentations

21, 21a which define the brake position and extend in laterally spaced parallel planes to the direct thread path defined by the

eyelets

4a and 5a. These

indentations

21, 21a are provided on both sides of the smooth portion of the brake surface 11 which defines the thread path and have a groove-shaped cross-section of a depth h (FIG. 4) which is less than the thickness of the thread 19 which is to be decelerated. Each

indentation

21, 21a has a wall 22 nearest to the thread path which is chamfered and merges on an obtuse angle into the braking surface 12.

The thread brake (1, 2) is adjusted so that when the brake is in the open position (FIG. I), the brake member 2 is maintained at a distance from the taut strip 3 that will permit unobstructed passage of the thread 19, for example while the thread is being picked as a weft. In the end phase of the weft picking operation, the brake member 2 is guided into the position 2' (FIG. 3) through a half rotation of the cam 17 which is controlled by the loom drive. This causes the strip 3 to be flexed into the position 3' by a simultaneous pivoting motion of the arm 8 so that the strip 3 together with the thread 19 hugs the brake member 2. The thread 19 is then decelerated between the smooth portions of the two

brake surfaces

10, 12 by friction and is finally braked to a stop. After a predefined period of time, the brake member 2 is guided back into the position shown in FIG. I by a further half rotation of the cam 17 so that the thread 19 is released, for example for a succeeding weft picking motion.

For the reasons mentioned initially, the part of the stationary thread 19 which is gripped in the closed thread brake has the tendency of deviating laterally from the brake position which is disposed in the direct thread path. Accordingly, the thread portion disposed between the eyelets 4a, a is curvilinearly deflected into the position 19' (FIG. 2) particularly in the course of prolonged braking, for example in multiple weft looms with an alternating weft picking motion, and finally passes via a chamfered wall 22 into the zone of the

indentation

21 or 21a in which the thread 19 is caught.

Owing to the depth h of the

indentation

21, 21a being less than the thread thickness and because of the contact force of the brake member 2 or the elasticity of the strip 3, the thread section is retained in the

indentation

21, 21a and is released only when the thread brake is released. The chamfered walls 22 of the

indentations

21, 21a facilitate the reception and release of the thread section so that, in practice, the thread is not subjected to any additional stresses.

Referring to FIG. 5, wherein like reference characters indicate like parts as above, the brake member can also be made with a flexible brake member 1 which has each end mounted on a stationary support member 25 to cooperate with a brake member 26 which is mounted on a holder 28 that is pivotable in the directions indicated by an arrow 27. The holder 28 is disposed on a shaft 29 that is controlled by the loom drive (not shown). The brake member 26 has a smooth substantially plane braking surface which is provided with two parallel indentations 32, 32a that extend over the entire length of the member 26. These indentations 32, 32a are constructed as half round grooves, the depth h of which is less than the thickness of the thread I9.

Pivoting motions derived from the loom drive cause the brake member 26 to be moved against the thread 19 into the brake position illustrated in FIG. 5 or to be moved out of this position into a release position in which the thread 19 is released. Flexing of the strip3 under the action of the brake member 26 during the braking operation is only slight or does not take place at all. Accordingly, only slight pivoting motion need be imparted to the holder 28 via the shaft 29 and braking becomes stronger. The flattened piece of the thread which moves laterally into the position 19' moves into the indentation 32 or 32a and is retained until the thread brake is lifted.

As shown, it is possible to dispense with a special construction of the transition zone between the brake surface 31 and the associated walls of the indentations 32, 32a in favor of a simpler construction or manufacture of the brake member 26.

Referring to FIG. 6, wherein like reference characters indicate like parts as above, the thread brake may also be constructed of two plate shaped

brake members

35, 36 with smooth plane braking surfaces 37, 38, respectively. The brake member 35 is provided with a single groove-shaped indentation 39 for accommodating the thread portion that is displaced laterally into the position 19'. In addition, a guide strip 40 is provided on an opposite side of the thread path to limit any lateral motion of the thread 19 in the other direction. As shown, the guide strip 40 is in laterally spaced relation to the edge of the brake member 35 and is mounted adjacent to the brake member 36. The brake member 39 is disposed on a resilient base 41 on a support member 42 of the machine. The brake member 35 is mounted on a shaft 11 which is movably supported in the directions indicated by the arrow 14 in the manner already described hereinbefore and is guided via the cam 17 into the brake position illustrated in FIG. 6 or into a released position in which the thread 19 is released.

Other embodiments of the invention are also possible. For example, the indentation for accommodating the thread may be provided in the braking surface of a flexible brake member. The flexible brake member may also be constructed of a material other than steel, for example light alloy, titanium or a plastics material and may also be provided with a covering of wear resistant material. Furthermore, each of the two cooperating brake members may have an indentation.

The invention can also be applied to thread brakes with other cooperating brake members, for example brake jaws.

Instead of providing a groove-shaped indentation, one of the braking surfaces may also have an indentation of a different shape, for example a bore suitable for accommodating the thread and also disposed in a laterally spaced parallel plane to the normal thread path to retain a thread within the limits of the brake members.

The thread brake of the invention can be employed for other textile machines in addition to looms and is particularly advantageous for machines with thread brakes for threads which run intermittently.

What is claimed is:

I. A thread brake comprising a pair of brake members for movement against each other for braking a thread passing longitudinally therebetween in a predetermined path, each brake member having a smooth braking surface opposite each other to define said path therebetween, and an indentation in at least one of said braking surfaces disposed in a laterally spaced parallel plane to said path, said indentation being sized to receive a braked thread therein to retain the thread within the limits of said brake members.

2. A thread brake as set forth in claim 1 wherein said indentation is groove-shaped in cross-section and extends longitudinally of said one braking surface parallel to said path.

3. A thread brake as set forth in claim 2 wherein said indentation is of a depth less than the thickness of the braked thread.

4. A thread brake comprising a pair of brake members, each said member having a smooth braking surface disposed opposite a smooth braking surface on the other said member to define a thread path therebetween; and an indentation in at least one of said braking surfaces for receiving a braked thread to limit lateral movement of the thread relative to said braking surfaces during closing of said surfaces relative to each other said indentation being disposed parallel and in laterally spaced relation to said path.

5. A thread brake as set forth in claim 4 which further comprises a guide strip on one side of a thread path passing between said brake members opposite said indentation, said strip being disposed in laterally spaced relation to one brake member and mounted adjacent the other brake member to limit lateral movement of the thread relative to said braking surfaces.

6. A thread brake as set forth in claim 4 wherein said indentation is of semi-circular cross-sectional shape.

7. A thread brake as set forth in claim 4 wherein one of said brake members is a flexible strip.

8. A thread brake comprising a pair of brake members for braking a thread passing longitudinally therebetween in a predetermined path, each brake member having a braking surface opposite each other, and an indentation in at least one of said braking surfaces disposed laterally of said path, said indentation being sized to receive a braked thread therein and including a wall on a side nearest a braking position merging into said one braking surface at an obtuse angle.

9. A thread brake comprising a pair of brake members, each said member having a braking surface disposed opposite a braking surface on the other said member; and two indentations in at least one of said braking surfaces spaced on either side of a thread path passing between said brake members for receiving a braked thread to limit lateral movement of the thread relative to said braking surfaces during closing of said surfaces relative to each other.

10. A thread brake comprising a pair of brake members, each said member having a braking surface disposed opposite a braking surface on the other said member; and an indentation in at least one of said braking surfaces for receiving a braked thread to limit lateral movement of the thread relative to said braking surfaces during closing of said surfaces relative to each other, said indentation being of groove-shaped crosssection and including a chamfered wall nearest a thread path passing between said brake members, said wall merging on an obtuse angle into said one braking surface.

It l=

Claims

1. A thread brake comprising a pair of brake members for movement against each other for braking a thread passing longitudinally therebetween in a predetermined path, each brake member having a smooth braking surface opposite each other to define said path therebetween, and an indentation in at least one of said braking surfaces disposed in a laterally spaced parallel plane to said path, said indentation being sized to receive a braked thread therein to retain the thread within the limits of said brake members.

10. A thread brake comprising a pair of brake members, each said member having a braking surface disposed opposite a braking surface on the other said member; and an indentation in at least one of said braking surfaces for receiving a braked thread to limit lateral movement of the thread relative to said braking surfaces during closing of said surfaces relative to each other, said indentation being of groove-shaped cross-section and including a chamfered wall nearest a thread path passing between said brake members, said wall merging on an obtuse angle into said one braking surface.