US3643497A

US3643497A - Tensile loading apparatus for moving wire

Info

Publication number: US3643497A
Application number: US812971A
Authority: US
Inventors: George W Lecompte
Original assignee: Hughes Aircraft Co
Current assignee: Raytheon Co
Priority date: 1969-04-01
Filing date: 1969-04-01
Publication date: 1972-02-22
Anticipated expiration: 1989-02-22
Also published as: FR2038096A1; NO126346B; SE355077B; NL6919697A; BE743912A; DE1963120B2; DE1963120A1; JPS4919829B1; GB1290193A

Abstract

Apparatus for testing the tensile strength of moving wire without subjecting wire at the supply coil or other source to high tension, comprising a main pulley with two grooves and a free pulley biased away from the main pulley for leading wire in a loop from one main pulley groove to the other. Guides for guiding wire to and away from the main pulley assure a 180* wire wrap about each main pulley groove. This permits a high-testing tension to exist in the loop that extends about the free pulley, while only a low tension exists prior to entering on the main pulley and after leaving it.

Description

Sits no H 1 9 9 LeCompte 1 Web, 2, 1972 [54] TENSILE LUADING APPARATlUfi FUR FOREIGN PATENTS OR APPLICATIONS MUVING WHRE [72] Inventor: George W. LeCompte, Rockville, Md.

[73] Assignee: Hughes Aircratt Company, Culver City,

Calif.

[22] Filed: Apr. 1, 1969 [21] Appl. No.: 812,971

[52] US. Cl ..73/95.5, 226/195, 226/1 1,

[51] lint. Cl. ..G01n BIN [58] Field of Search ..73/95.5, 143, 144, 158; 226/195, 144; 242/155 [56] References Citedl UNITED STATES PATENTS 3,051,362 8/1962 Shook ..226/44 841,255 7/1960 GreatBritain ..73/95.5

Primary Examiner-Samuel Feinberg AttorneyW. l-l. MacAllister, Jr. and Lawrence V. Link, Jr.

[571 STCT Apparatus for testing the tensile strength of moving wire without subjecting wire at the supply coil or other source to high tension, comprising a main pullley with two grooves and a free pulley biased away from the main pulley for leading wire in a loop from one main pulley groove to the other. Guides for guiding wire to and away from the main pulley assure a 180 wire wrap about each main pulley groove. This permits a hightesting tension to exist in the loop that extends about the free pulley, while only a low tension exists prior to entering on the main pulley and after leaving it.

1 1 Claims, 6 Drawing Figures $HEU 1 OF @eozcaa m 5 COMPTE XNVENTOR.

QTT QJEVS TEST LOAD mmmnm m2 EWBAE A9? SHEET 2 OF 3 INVENTOR @502612 W0 is @OMPTE TlENfillLlE LOADTNG AlPlPAlPtATlUS ll Olit MOVIING WlllltE BACKGROUND OF THE TNVENTION 1. Field of the invention This invention relates to apparatus for testing and handling wire and other elongated material.

2. Description of the Prior Art The testing of long lengths of wire to assure at least a predetermined tensile strength, can be performed by running the wire along a path where it is subjected to a predetermined high tension. Such testing is preferably performed in the course of some other handling operation, such as during manufacture when the wire is wound into coils, or during the winding of wire from a supply coil onto an end use product such as a bobbin. However, the testing tension is generally much higher than the tension which can be applied to a supply coil or other source of wire, or which can be applied to the bobbin or other means for taking up the wire.

OBJECTS AND SUMMARY OF THE llNVENTlON An object of the present invention is to provide apparatus for facilitating the tensile testing of long lengths of wire or the like.

Another object is to provide apparatus for subjecting a continually moving wire to a high tension without subjecting the source of the wire or the means for taking up the wire to high wire tension.

In accordance with the present invention, apparatus for testing wire or other elongated material is provided which applies a high tension to a small interval of the wire without subjecting the rest of the wire to a high tension. The apparatus includes a main pulley with at least two grooves and a free pulley for leading wire in a loop from one main pulley groove to the other. Guides are included which guide wire to and away from the main pulley to assure a large wire wrap, such as 180, about each main pulley groove before the wire extends to the free pulley. The free pulley is pulled away from the main pulley by a high test force. This results in a wire loop extending from the main pulley around the free pulley being subjected to a high test tension. However, only a low tension exists in wire initially entering upon and finally leaving the main pulley. A large difference in tension exists without wire slipping on the main pulley grooves because of the large wire wrap, such as 180, about each pulley groove.

The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a perspective view of wire-testing apparatus constructed in accordance with the invention;

FIG. 2 is a partial perspective view of wire-testing apparatus constructed in accordance with another embodiment of the invention;

FIG. 3 is a partial sectional view taken on the line 3-3 of FIG. 2;

FIG. 4 is a front elevation view of wire-testing apparatus constructed in accordance with still another embodiment of the invention;

FIG. 5 is a plan view of the apparatus of FllG. 4; and

FIG. 6 is a partial front elevation view of yet another embodiment of the invention useful for applying bending stresses to wire.

DESCRIIPTION OF THE PREFERRED EMBODIMENTS FIG. ll illustrates wire-testing apparatus for subjecting a continually moving wire 110 to a testing tension which will break any weak portion of the wire. An example of a situation where such testing may be performed is in the movement of control wire from a large supply coil onto a bobbin that is to be placed in a missile launcher. Such wire trails behind a missile and transmits signals that steer the missile to the target. While previous quality testing has been performed, a final tensile test is considered desirable. A high tensile testing load could be applied to the wire by merely winding it tightly on the bobbin. However, a relatively low tension such as 0.5 pound must be used in winding the wire onto the bobbin for facilitating its use, and also in removing wire from the supply coil to prevent stoppages. The wire-testing apparatus of the invention subjects an interval of the moving wire to a high testing ten sion such as 5 pounds, but isolates the rest of the wire from this tension.

The testing apparatus comprises a frame 112 with four wheels or pulleys M, llti, llh and 20 thereon. All pulleys are idler pulleys, no motor being required to operate this embodiment of the invention. Pulley lid is the main pulley, which is rotatably mounted on a shaft 22 that is fixed to the frame. Pulley Ed is a free pulley, which is mounted on a shaft 2d. The shaft 2d is held by a mount 26 which is free to move toward and away from the main pulley. A weight 2% urges the free pulley away from the main pulley to subject the wire loop extending between them to a high tensile load. Pulleys M and T6 are guide pulleys for guiding the wire onto and away from the main pulley, and they are rotatably mounted on

shafts

30 and 32 that are fixed to the frame.

The main pulley has two parallel grooves 34- and 36, while the other pulleys M, 116 and 20 have only single grooves 38, 450 and 42, respectively. The wire extends from the supply coil around the guide pulley lid, then around the first main pulley groove 1%, then around the free pulley 2%, then l80 around the second main pulley groove 36, and then around the guide pulley llh to the bobbin. it may be noted that the axes of rotation of the main and free pulleys lit and 20 are not parallel, since the free pulley must direct wire between the two main pulley grooves.

The weight 28 that is attached to the mount, places the interval of wire 1101, which extends between the main and free pulleys, under a testing tension. The wire at lldl is under a tension AT which is one-half the force T applied by the weight 28 (plus the weight of the mount and pulley) to the free pulley. The portions of wire extending from the supply coil around the guide pulley M, and up to the main pulley iii are all under the relatively low tension which is used in winding. Similarly, the portions of wire extending from the main pulley, around the guide pulley 16, and to the bobbin are under a low tension approximately equal to the tension of wire extending around the other guide pulley M. About the only difference in tension in wire entering and leaving the testing apparatus is that difference required to overcome friction of the four pulleys of the wire-testing apparatus, which is very low.

The large difference in tension between the wire portion lltlM, which approaches the main pulley, and the portion ltil, which is leaving the first main pulley groove 3d tends to cause slippage of the wire over the main pulley. This is resisted by friction between the wire and first main pulley groove. The difference in tension which can be tolerated is approximated by the well ltnown formula I /Fae? where F is the wire tension after leaving the pulley (which is 5 pounds in the above example), F is the tension prior to entering on the pulley (which is 0.5 pound in the above example), e is the base for natural logarithms (approximately 2.718), 1.4 is the coefficient of friction between the wire and pulley surface materials, and 9 is the angle of wire wrap around the pulley (about 180, or w radians, in the above example). in the above example, where a ratio of tensions of 10 to 1 is employed, an effective coefficient of friction of about 0.5 is required to prevent slippage on an ordinary pulley groove of flat or large radius cross section. Of course, the above also applies to the wire portions leaving and approaching the second main pulley groove. Generally a large wrap at least on the order of 180 is required to enable the maintenance of an appreciable tension ratio. it should be noted that no appreciable change in wire tension occurs around the free pulley 2%. Accordingly, instead of employing a rotating member as the free pulley means, or free wire engaging means, a slider member can be used. Such a slider member is preferably of low friction, and may be made of materials such as Teflon for light duty applications or of polished synthetic sapphire for long wear.

When the wire-testing apparatus is used, the wire tends to creep over the

main pulley grooves

34 and 36 to cause a continual lengthening of the wire loop portion 101 extending from the main pulley to the free pulley 20. This is due to the change in tension around the main pulley grooves which is accompanied by a change in elongation. In the apparatus of FIG. 1, elongation of the loop portion 10I generally requires that a substantial distance be provided under the weight 28 to allow it to move down, and that the weight be raised and the wire pulled through to reduce the loop after a period of use.

FIG. 2 illustrates another embodiment of the invention which enables a large ratio between the testing tension and the tension of the wire both when it is originally received and when it finally leaves the testing apparatus. While a high tension ratio can be maintained without slippage by using a main pulley with soft rubber or the like at the grooves, such materials generally wear rapidly, and the tension ratio is still limited to a moderate level. The apparatus of FIG. 2 enables a high ratio to be employed with pulleys of only moderate coefficient of friction.

In the apparatus of FIG. 2, wire 50 moves around seven pulleys of a wire-testing machine. The pulleys include two guide pulleys 52 and 54 for guiding wire entering and leaving the apparatus, two

main pulleys

56 and 58 which receive wire from the guide pulleys, and three

free pulleys

60, 62 and 64. The guide pulleys S2 and 54 and

main pulleys

56 and 58 are mounted for free rotation on a frame, the frame not shown in order to aid clarity. The

main pulleys

56 and 58 are rotatably fixed to a shaft 66 so they rotate together, the shaft 66 being rotatably mounted on the frame. The free pulleys 60, 62 and 64 are rotatably mounted on individual mounts, of the type shown at 26 in FIG. I, to enable movement toward and away from the main pulleys. Biasing means such as weights or springs are coupled to the mounts to pull the free pulleys away from the main pulleys, the biasing means being indicated by

arrows

68, 70 and 72 for

pulleys

60, 6 and 62, respectively.

The wire 50 follows a path from the wire source around guide pulley 52, then 180 around a first main pulley groove 74, then around free pulley 60, and then 180 around a second main pulley groove 76. The wire then continues around primary free pulley 62, then 180 around third main pulley groove 78, then around free pulley 64, then 180 around fourth main pulley groove 80, and then around the guide pulley 54 to the wire receiving means. The free pulleys 60 and 64 are intermediate free pulleys which are used to step up or step down the wire tension to a level in between the lowest tension existing at the guide pulleys 52 and 54 and the highest tension ex isting at the primary free pulley 62. Thus, the wire portions 50L and 50M at the guide pulleys 52 and 54 are at a low tension, such as 0.5 pound. The wire portions SON and 50? at the intermediate

free pulleys

60 and 64 are at an intermediate tension, such as 1.5 pounds, which may be applied by employing weights at 68 and 70 of 3 pounds each. The wire portion 500 at the primary free pulley is under the test tension, such as 5 pounds, which may be realized by applying a weight at 72 of pounds.

In the apparatus of FIG. 2, wire creep occurs over the

main pulleys

58 and 56, which tends to increase the length of the wire loop portion 500 that extends to the primary free pulley 62. There can also be a tendency for creep to occur in the

wire portions

50N and 50? which extend around the intermediate free pulleys. If the intermediate load 68 is small, so that the creep at groove 76 is faster than the creep at groove 74, intermediate free pulley 60 will tend to move upward toward the main pulley 56. If the intermediate load 68 is large, so that the creep at groove 76 is slower than the creep at groove 74, intermediate free pulley 60 will tend to move downward away from the main pulley 56. If the intermediate pulley 60 is rotatably mounted at a fixed distance from the main pulley $6, the intermediate load will be self-regulating, seeking a value that results in equal creep rates at the

main pulley grooves

74 and 76. Thus the tension increments associated with these two passes over the main pulley will be approximately equal. The use of intennediate pulleys permits the effective angle of wrap on the main pulley to be increased, providing a higher tension ratio with a given coefficient of friction. It avoids sideslip and abrasion inherent in a conventional multiwrap capstan where there are no distinct grooves.

An additional technique for increasing tension ratio at the main pulley is the use of a V-shaped groove. FIG. 3 illustrates the V-shape of the grooves in the pulley 56. The V-shaped groove increases the normal force acting between the wire, or other round strand, and the sides of the pulley which it contacts. This normal force can be increased by decreasing the angle A of the groove, thereby increasing the effective coefficient of friction. However, if the angle is decreased until it is very narrow, the wire tends to be trapped in the V-groove or damaged by the increased normal force. The V-groove pulley can be constructed as a stack of disks 56X, 56Y, and 562, each having beveled edges, as shown in FIG. 33. This design facilitates precise fabrication and permits disassembly for cleaning.

FIGS. 4 and 5 illustrate still another embodiment of the invention wherein provisions are made to take up the elongations in the loop of wire subjected to the test tension. The wire I00 extends around two guide pulleys W2 and MM, two

main pulleys

106 and 108, two intermediate pulleys Iillb, and H4, and one free pulley H2. The guide pulleys 102, MM, main pulleys 106, I08 and intermediate pulleys 1110, 1143 are rotatably mounted on a frame 116. The free pulley H2 is mounted on a lever 126 that is pivotally mounted at 12$ on the frame I M. A weight 134 suspended from the opposite end of the lever 1126 biases the primary free pulley 112 away from the main pulleys. Each of the main pulleys has three grooves, while each of the intermediate pulleys has two grooves, to permit a higher ratio of tension. Where such a high ratio is not required, only two pulley grooves per main pulley and one groove per intermediate pulley can be employed.

In order to prevent excessive lengthening of the wire loop extending to and around the free pulley 112, by reason of creep, a differential drive 132 is provided. The drive comprises a pair of

bevel gears

134 and 136 fixed to the main pulleys I06, 108, respectively, and a differential gear I38 that is engaged with the two bevel gears. The differential gear is rotatably mounted on a support 140. A gear head motor 142 has a shaft 144 that extends through holes in the main pulley I08 and frame, and is fixed to the differential gear support M0.

As the wire I00 moves through the testing apparatus, the main pulleys 1106 and 108 rotate at the same speed, but in opposite directions as shown by arrows M6 and M8. (They must rotate at the same peripheral speed, which is achieved by identical speeds for pulleys of the same diameter.) As a result, the differential gear 138 does not translate about the axis M1 of the motor shaft, and the gear support Mil remains stationary without affecting the operation of the testing apparatus. After a period of use of the apparatus, during which time the free pulley 112 moves down due to wire creep, the lever 126 contacts a button on a switch sensor 152. The sensor 1152 thereupon causes energization of the motor M2 for a brief period. The motor 142 slowly turns shaft 144 in the direction of arrow 154, causing the differential gear support 140, and the differential gear 138 thereon, to rotate around the motor axis. This results in the main pulley 1% turning more slowly than the other main pulley me, which shortens the wire loop around the free pulley. As a result, the free pulley I12 moves up to decrease the distance between it and the main pulleys.

In some situations it is desirable to subject the wire to a bending stress test as well as a tensile test. A bending test can be performed on the continuously moving wire by forcing it around a small diameter wheel while it is under substantial tension. The apparatus of FEG. 6 illustrates part of a tension and bending tester, comprising a pair of main pulleys MW, 162 and a free pulley apparatus lo l. Guiding pulley apparatus (not shown) of the type described above leads wire to and from the main pulleys. A weight indicated by arrow lied biases the free pulley apparatus away from the main pulleys. instead of using one free pulley, a pair of pulleys lltili and 117i) is used. A small diameter bending test pulley T72 is mounted on the free pulley apparatus. Retaining flanges ll'73 are mounted at either end of the bending test pulley to keep the wire thereon. The wire is subjected to a high bending stress as it passes over the bending test pulley, the bending stress depending upon the tension in the wire (which is one-half the weight ins and the diameter of the test pulley T72. instead of employing the two free pulleys lab and 17b, the test pulley 1172 can be used with a single free pulley. However, the wire wrap about the test pul ley then varies slightly as the free pulley moves up and down.

Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.

What is claimed is: l. Apparatus for applying bending stress and tension to a limited interval of moving wire means comprising:

pulley means with first and second grooves; wire-engaging means for leading said wire means from said first groove to said second groove; means for biasing apart said pulley means and wire-engaging means to subject the interval of said wire means extending between them to an increased tension; and bending test pulley means disposed along said interval of said wire means extending between said first and second grooves, for guiding said wire means in a small radius path. 2. Apparatus for subjecting an interval of moving elongated material to a predetermined tension comprising:

a frame; first and second main pulley means rotatably mounted on said frame; free wire engaging means oriented to lead said material between said first and second main pulley means; means for biasing said free wire engaging means away from said main pulley means; means for guiding said elongated material onto said first main pulley means for at least on the order of 180 wrap thereabout prior to extension to said wire-engaging means; said first main pulley means having first and second grooves, with said first groove positioned to receive elongated material from said means for guiding material onto said first main pulley means, and said second groove positioned to deliver said elongated material to said wire-engaging means; and intermediate pulley means for guiding said elongated material from said first groove to said second groove; and means for guiding said elongated material oil from said second main pulley means at a position relative to said wire-engaging means for at least on the order of 180 wrap about said second main pulley means. 3-. The apparatus of claim 2 further comprising coupling means for coupling said first and second main pulley means for rotation in opposite directions at approximately the same guiding said material in a small radius path.

n. Apparatus for testing wire and hire elongated material comprising:

a frame;

first and second main pulleys rotatably mounted on said frame;

a free pulley;

mount means for rotatably supporting said free pulley;

means for biasing said mount means away from said main pulleys; means for guiding said elongated material to said first pulley for movement at least partially thereabout prior to moving to said free pulley, and for guiding said material from said second pulley, said means for guiding positioned for rotation of said main pulleys in opposite direction; and

coupling means for coupling said first and second pulleys for rotation in opposite directions at approximately the same peripheral speed.

7. The apparatus of claim 6 wherein said first main pulley has first and second grooves, with said first groove positioned to receive elongated material from said means for guiding material to said first pulley and said second groove positioned to deliver said elongated material to said free pulley; and including intermediate pulley means for guiding said elongated material from said first groove to said second groove.

The apparatus of claim 7 wherein said second main pulley has first and second grooves, with said first groove on said second pulley positioned to receive said elongated material from said free pulley, and said second groove on said second pulley positioned for delivering said material to said means for guiding said material from said second pulley; and further comprising second intermediate pulley means for guiding said elongated material from said first groove to said second groove of said second main pulleyv 9. The apparatus described in claim s including:

means connected to said coupling means for varying the relative speed of said first and second pulleys to shorten the length of wire extending to and about said free pulley.

llll. The apparatus of claim a wherein said coupling means includes differential gear means coupled to said first and second main pulleys, support means for rotatably mounting said differential gear means, motor means for rotating said support means, and means responsive to the relative position of said free pulley and mount means for controlling said motor means to cause the length of material extending to and from said free pulley to be maintained at less than a preselected value.

Ill. The apparatus of claim ill further comprising bending test pulley means disposed along the interval of said elongated material extending between said first and second main pulley for guiding said material in a small radius path.

Claims

1. Apparatus for applying bending stress and tension to a limited interval of moving wire means comprising: pulley means with first and second grooves; wire-engaging means for leading said wire means from said first groove to said second groove; means for biasing apart said pulley means and wire-engaging means to subject the interval of said wire means extending between them to an increased tension; and bending test pulley means disposed along said interval of said wire means extending between said first and second grooves, for guiding said wire means in a small radius path.

2. ApParatus for subjecting an interval of moving elongated material to a predetermined tension comprising: a frame; first and second main pulley means rotatably mounted on said frame; free wire engaging means oriented to lead said material between said first and second main pulley means; means for biasing said free wire engaging means away from said main pulley means; means for guiding said elongated material onto said first main pulley means for at least on the order of 180* wrap thereabout prior to extension to said wire-engaging means; said first main pulley means having first and second grooves, with said first groove positioned to receive elongated material from said means for guiding material onto said first main pulley means, and said second groove positioned to deliver said elongated material to said wire-engaging means; and intermediate pulley means for guiding said elongated material from said first groove to said second groove; and means for guiding said elongated material off from said second main pulley means at a position relative to said wire-engaging means for at least on the order of 180* wrap about said second main pulley means.

3. The apparatus of claim 2 further comprising coupling means for coupling said first and second main pulley means for rotation in opposite directions at approximately the same peripheral speed.

4. The apparatus of claim 3 wherein said coupling means comprises differential gear means coupled to said first and second main pulley means, support means for rotatably supporting said differential gear means, motor means for rotating said support means, and means responsive to the relative positions of said free wire engaging means for controlling said motor means.

5. The apparatus of claim 2 further comprising bending-test pulley means disposed along the interval of said material extending between said first and second main pulley means, for guiding said material in a small radius path.

6. Apparatus for testing wire and like elongated material comprising: a frame; first and second main pulleys rotatably mounted on said frame; a free pulley; mount means for rotatably supporting said free pulley; means for biasing said mount means away from said main pulleys; means for guiding said elongated material to said first pulley for movement at least partially thereabout prior to moving to said free pulley, and for guiding said material from said second pulley, said means for guiding positioned for rotation of said main pulleys in opposite direction; and coupling means for coupling said first and second pulleys for rotation in opposite directions at approximately the same peripheral speed.

8. The apparatus of claim 7 wherein said second main pulley has first and second grooves, with said first groove on said second pulley positioned to receive said elongated material from said free pulley, and said second groove on said second pulley positioned for delivering said material to said means for guiding said material from said second pulley; and further comprising second intermediate pulley means for guiding said elongated material from said first groove to said second groove of said second main pulley.

9. The apparatus described in claim 6 including: means connected to said coupling means for varying the relative speed of said first and second pulleys to shorten the length of wire extending to and about said free pulley.

10. The apparatus of claim 6 wherein said coupling means includes differential gear means coupled To said first and second main pulleys, support means for rotatably mounting said differential gear means, motor means for rotating said support means, and means responsive to the relative position of said free pulley and mount means for controlling said motor means to cause the length of material extending to and from said free pulley to be maintained at less than a preselected value.

11. The apparatus of claim 10 further comprising bending-test pulley means disposed along the interval of said elongated material extending between said first and second main pulley for guiding said material in a small radius path.