US3138243A - Drawing apparatus - Google Patents

Description

J n 2 9 s. A. OAKLEY DRAWING APPARATUS 3 Sheets-Sheet 1 Filed April 2, 1962 INVENTOR. 57524 //\/e ,4. OAKLEY BY mum, M/emwgp, faIIM/ MM 44m ArroeMe Y6 June 23, 1964 s. A. OAKLEY DRAWING APPARATUS 3 Sheets-Sheet 2 Filed April 2, 1962 Y i z w W a n 6 M0 M E \V\\\ w% R M m m 6 f W/JJ4 WWW M 1 v w m mm R Q m 4 fl? a W k M %JA/ 244 m W w 1% Q 1 k V/ V M June 23, 1964 s. A. OAKL-EY 3,138,243

DRAWING APPARATUS Filed April 2, 1962 3 Sheets-Sheet 3 INVENTOR.

Arron/5Y5 By firenu/yq .4. UAALEY Won, filelnaim, (di Wm! MA United States Patent 3,133,243 DRAWING APPARATUS Sterling A. Oakley, Lincolnwood', lll., assignor to Oakley Industries, Incorporated, Skokie, 111., a corporation of Illinois Filed Apr. 2, 1962, Ser. No. 184,371 7 Claims. (Cl. 205-3) The present invention relates to drawing apparatus and more particularly to apparatus for drawing wirelike material through a draw die for reducing the diameter thereof. The invention has particular application to the drawing of miniature metal tubing such as is used for hypodermic needles.

The great increase in the number of hypodermic needles required during recent years and the difficulty of sterilizing hypodermic needles in the field for initial and reuse makes it desirable that hypodermic needles be produced quickly and readily at low cost so that they may be shipped sterile and discarded after use. Accordingly, it is desirable to provide a drawing apparatus which will very rapidly draw hypodermic tubing, as well as tubing for other uses, to a desired size.

In one particular drawing method the outside diameter of the hypodermic needle tubing is drawn in a plurality of steps from an outside diameter of, for example, fifty thousandths of an inch to twenty thousandths of an inch.

'The tubing is drawn in a continuous operation passing through a series of substantially identical drawing apparatus, each of which is provided with a difiierently sized drawing die so as to provide the desired reduction in the outside diameter. The hypodermic needle tubing passes continuously between successive drawing apparatus. A thyratron motor or other control is used to regulate the slack between the successive drawing apparatus. If desired, the tubing can be annealed between the drawing passes.

Accordingly, one object of the present invention is to provide new and improved apparatus for drawing wirelike material, such as hypodermic needle tubing and the like.

A further object of the present invention is to provide a new and improved drawing apparatus which will rapidly draw hypodermic needle tubing through a drawing die to reduce the outside diameter thereof.

Yet a further object of the present invention is to provide a new and improved propelling apparatus for griving hypodermic needle tubing through a drawing Further objects and advantages of the present invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In accordance with the present invention, there is provided an improved drawing apparatus wherein hypodermic needle tubing or similar wirelike material is drawn through a draw die mounted on the supprt of the apparatus. The apparatus includes a propelling device which is effective to move the material through the draw die. The propelling device includes a rotatably mounted shaft carrying a positive displacement cam means. Propelling units are provided in each propelling device, each propelling unit is slidably mounted on the support of the apparatus for reciprocating movement relative to the draw die, and including means for gripping the material when the propelling unit is reciprocally moved in a first direction, and means for releasing the material when the propelling unit is moved in the opposite direction. A cam follower operatively associated with the cam means is effective for reciprocating each propelling unit.

Patented June 23, 1964 Each of the propelling units includes a rectangular gripper frame, which carries a pair of spaced backing blocks. Each of the backing blocks is provided with one or more surfaces opposed to the surfaces of the other blocks and each having a small angular outward inclination in the direction of movement of the propelling units. A pair of movable gripping jaws are positioned between the backing blocks and each jaw is provided with an inclined surface confronting a respective one of the inclined surfaces in the backing blocks. The inclined surfaces of the jaws are provided with a slightly smaller inclination in the same direction as the associated inclined surface of the backing blocks so that a wedge-shaped area is formed between respective pairs of confronting surfaces. Roller means, such as balls or rollers, are positioned in each of the wedge-shaped areas spacing the respective pairs of confronting surfaces. The diiference in the angular inclination of the surfaces in the backing block and gripping jaws forms a wedge to provide a squeeze for the roller means. In this manner, the gripping jaws and hacking blocks function as an over-riding clutch.

In operation, movement of the propelling unit in a first direction causes the tubing positioned between the jaws to frictionally move the jaws a minute distance opposite to the direction of movement of the gripper frame relative thereto. Such movement is effective to cause the roller means to wedge between the respective pairs of confronting surfaces to move the gripper jaws toward each other to engage and frictionally hold the tubing. In order to assure a positive grip of the roller at all times, the gripper jaws are continuously biased into a tube gripping position by very light springs.

For a better understanding of the present invention. reference may be had to the accompanying drawings wherein:

FIG. 1 is a somewhat schematic, plan view, illustrating a series of drawing devices for sequentially treating tubing according to the present invention;

FIG. 2 is an enlarged sectional view taken on line 22 of FIG. 1;

FIG. 3 is a sectional view taken on line 33 of FIG. 2, assuming that FIG. 2 illustrates the entire structure;

FIG. 4 is a fragmentary sectional view taken on line 4-4 of FIG. 2, again assuming that FIG. 2 shows the entire structure illustrating operation during the return stroke;

FIG. 5 is a fragmentary view of a portion of FIG. 4 but illustrating the propelling unit during the return stroke; and

FIG. 6 is an exploded isometric view of one of the propelling units.

Referring now to the drawings, there is provided an improved drawing apparatus, generally indicated at 10, for drawing tubing 11 or other wirelike material to reduce the outside diameter thereof. As illustrated in FIG. 1, there is shown a plurality of such drawing devices 10a, 10b and 10c serially arranged in a continuous drawing sequence to reduce the diameter of the tubing 11 in a plurality of steps; the tubing 11 passing through the first one Itia of the drawing devices, then through the second one 10b of the drawing devices and finally through the third one of the drawing devices. Obviously many more stages may be employed, if desired. Each of the drawing devices 10a, 10b and lilc, is individually driven by a prime mover, here schematically illustrated as an electric motor 12. Each of the electric motors 12 is driven at a predetermined rate in synchronism with the other motors of the series to maintain a desired slack in the tubing 11 between the adjacent drawing devices ltla, 10b and 10c, as determined by a thyratron motor or similar control (not shown). It should be understood that the drawing devices 10a, 10b and 10c might be stacked one above the other if desired, whereby an operator is required at each end to feed the various stages thereof.

Referring now specifically to the individual drawing device 101), as best illustrated in FIGS. 2 and 3, it, like the other devices a and the includes a chassis or support 13 formed of a base plate 14, a pair of side plates 15 and 16 (FIG. 3), and a pair of end plates 17 and 18. The upper end of the support 13 is held in proper spaced relation by a pair of end spacers 21 and 22 and a center spacer 23. A pair of spaced cover plates 19 form the top of the support 13. The support 13, as best described, forms a generally box-shaped frame, open at the top. The end plates 17 and 13 are each provided with an aperture 24 and 25, respectively. A shaft 26 is supported in the apertures 24 and in suitable bearing means 27 and 23 and is secured in place against axial movement by suitable lock means and a lock nut 31. The end of the shaft 26, which extends through the end plate 18 is enclosed by an end cover and die holder 32 so as to enclose the bearing 28 and form an oil seal with the support 13. The other end of the shaft 26 extends externally of the support 13 through the end plate 17 and is provided with a key slot 33 or other means for providing a driving connection with a respective one of the motors 12. An oil seal cartridge 34 is secured to the end plate 17 to protect the bearing 27.

To reduce the outside diameter of the tubing 11, there is provided a draw die 35, FIG. 2, positioned in a counterbore 36 in the end cover and die holder 32. A set screw 37 extends through the top wall of the end cover 32 to lock the draw die 3 in place. The draw die includes a die frame 40 carrying a hardened die portion 41 and provided with a tube opening 42 of the desired diameter, so that as the tubing 11 is drawn through the tube opening 42 to the right, as viewed in FIG. 2, the tubing 11. is reduced to the diameter of the tube opening 42.

In accordance with an important feature of the present invention, the tubing 11 is drawn through the draw die 35 by an improved propelling apparatus. As best illustrated in FIGS. 2 and 3, the propelling apparatus includes a plurality of propelling units 46 and 47, each operatively driven by a respective one of a pair of drum earns 44 and 45 through an associated one of a pair of cam followers 5:) and 51, respectively. The drum cams 44 and 45 are fixedly secured to the shaft 26 in any suitable manner, for example, by a key 26a, FIG. 3. A pair of nuts 49 cooperate with a threaded portion 43 of the shaft 26 to clamp and lock the drum cams 44 and 45 longitudinally on the shaft 26 and a spacer positioned between the drum cans 44 and 45 is effective to maintain the drum cams in proper spaced relation with each other.

Each of the drum cams 4-4 and 45 are identical, except for their positioning on the shaft 26, and, therefore, only the drum cam 45 is herein described in detail. The drum cam 45 is formed of a cylindrical cam member 52 provided with a circumferential cam groove 53 in its side wall for receiving a roller following portion 54 of the cam follower 51. The cam groove 53 on the cam 45 is cut to advance the cam follower 51 (and therefore the propelling unit 47) in a first longitudinal direction to the right, as viewed in FIG. 2, at substantially constant speed during one-half of the rotation of the shaft 26 and to return the cam follower 51 to its initial starting position during a second half of the rotation of the shaft 26 to provide a return stroke for the propelling unit 47. The drum cams 44 and 45, however, are angularly displaced by one hundred eighty degrees with respect to each other so that while one of the drum earns 45 is effective to advance its respective propelling units 47 into an advancing stroke, the other drum cam 44 is returning its associated propelling unit 46 to its starting position. Accordingly, one of the drum cams 44 and 45 is continuously driving its associated propelling unit 46 or 47 in a tube advancing direction at a substantially constant velocity;

A. the other cam during this time is moving its associated propelling unit through its return stroke to its beginning position.

-For guiding each of the propelling units 46 and 47 for reciprocating movement relative to the draw die 35 and relative to each other, the support 13 of the drawing device it is provided with a pair of spaced gib rails 53 on each side adjacent the top of the side plates 15 and 16 which together form a pair of opposing track or guide means 59 (FIG. 3). Each of the propelling units 46 and 47 are similar, except for being complementary in action, i.e., the propelling unit 46 may be termed as a right-hand unit and the propelling unit 47 may be termed as a lefthand unit. The components of each of the propelling units 46 and 47 are identical except for a reversal of parts thereof. Each of the propelling units 46 and 47 are guided along the track 59 by a guide base 60 (see also FIG. 6) whose side edges 60a fit between the gib rails 58 in sliding relation therewith. Each of the cam followers 5i) and 51 are provided with a shank portion 61 which fits through an aperture 62 on a follower plate 63 fixedly secured below the guide base 60 and slidably positioned between the lower ones of the gib rails 58. A not 64 disposed in an aperture 65 in the respective one of the guide bases 60 is threaded on the shank portion 61 to maintain the cam followers 50 and 51 secured in fixed relation to the follower plate 63 and the guide base 60.

So that the propelling units 46 or 47 are effective to grip and pull the tubing 11 through the draw die 35 when these propelling units are driven in their advancing stroke, and to release the tubing 11 during its return stroke, each of the propelling units 46 and 47 is provided with gripping means which are effective to grip or release the tubing 11 in response to the direction of movement of the propelling unit. As best illustrated in FIGS. 4, 5 and 6, the gripping means includes a rectangular gripper frame 69 fixedly secured to the top of the guide base 60 and slidably positioned between the upper of the gib rails 58. The gripper frame 69 is provided with a pair of longitudinally aligned apertures 70 which are longitudinally aligned with the tube opening 42 in the draw die 35 and through which the tubing 11 is directed. The gripper frame 69 forms a rectangular central opening 71 in which are positioned a pair of backing blocks 72 and 73 and a pair of gripper jaws 74 and 75. The backing blocks '72 and 73 and the gripper jaws 74 and 75 are enclosed within the gripper frame 69 by a cover plate 76. A plurality of fasteners, here shown as screws 77, secure the guide base 60, follower plate 63, gripper frame 69 and cover plate 76 in fixed relation.

In order to provide for the automatic gripping action of the tubing 11 by the gripper jaws 74 and 75, the backing blocks 72 and 73 are fixedly secured in the opening 71 in spaced apart relation by a plurality of studs 78 which extend through the sides of the gripper frame 69 and thread into the respective backing blocks 72 and 73, and the gripper jaws 74 and 75 are spaced inwardly between the adjacent backing blocks 72 and 73 by a plurality of roller means, such as the illustrated roller pins 31, 82 and 83. The backing block 72 is provided on its inner surface near its longitudinal cenfor with a recessed surface 84 having a small angular inclination in the direction of reciprocation of the propelling unit 46, the inclination of the surface 84 being forwardly and outwardly of the propelling unit 46 in the direction of advancement of the tubing 11. Moreover, the backing block 73 is provided with a pair of spaced, similarly inclined surfaces 85 and 86, inclined forwardly and outwardly relative to the direction of advancement of the tubing 11 and which are opposed to the first inclined surface 84 in the backing block 72. Each of the gripping jaws is provided with inclined surfaces confronting the adjacent one or ones of the inclined surfaces 84, 85 and 86. Specifically, the gripper jaw 74 '2) is provided with an inclined surface 87 inclined forwardly and outwardly relative to the direction of advancement of the tubing 11 and the gripper jaw 75 is provided with inclined surfaces 88 and 89 confronting the respective inclined surfaces 85 and 86 and inclined forwardly and outwardly relative to the direction of advancement of the tubing 11. The inclination of the surfaces 84, 85 and 86 in the backing blocks 72 and 73 is small, forming a small acute angle relative to the longitudinal direction of advancement of the tubing 11, and, specifically in one embodiment, formed an angle of seven degrees with the longitudinal, as indicated by the angle X in FIG. 4. The inclination of the surfaces 87, 88

and 89 in the gripping jaws 74 and 75 is slightly less than the inclination of the surfaces 84, 85 and 86 in the backing blocks 72 and 73 and, in one specific embodiment, these surfaces 87, 88 and 89 form an acute angle Y with the longitudinal of five degrees. It will be seen, therefore, that the respective confronting surfaces 84 and 87, 85 and 88, and 86 and 89 each form a wedgeshaped area whose sides form an angle Z, FIG. 4, of two degrees with each other and which are inclined as the surfaces of a frustrum of an obtuse wedge. The pairs of inclined surfaces 84 and 87, 85 and 88, and 86 and 89, are spaced by the respective roller pins 81, 82 and 83, which wedge between the confronting inclined surfaces during an advance stroke in a manner similar to the action of an overriding clutch.

To provide for the gripping of the tubing 11 by the gripper jaws 74 and 75, each of the jaws 74 and 75 is provided with a substantially semicylindrical central recess 91 and 92, respectively, which circumscribes the tubing 11 to engage and grip the tubing. Moreover, the gripper jaws 74 and 75 are slightly shorter than the length of the opening 71 in the gripper frame 69 so that friction of the tubing 11 in the recesses 91 and 92 will be effective to pull the gripper jaws 72 and 73 rearwardly when the propelling unit 76 is in an advancing stroke, as indicated in FIG. 4, to cause the roller pins 81, 82 and 83 to wedge in the two-degree inclined wedge formed by the respective inclined surfaces. Accordingly, the gripper jaws will be moved toward each other to grip the tubing 11. A pair of very light pressure springs 93 lightly bias the gripper jaws 74 and 75 rearwardly with reference to the gripper frame 69 in order to insure an initial friction between the gripper jaws 74 and 75 and the tubing 11 when the propelling unit 46 begins an advance stroke. It will be appreciated that when the propelling unit 46 is in a return stroke, the bias of the springs 93 will be overcome by the frictional resistance between the tubing '11 and the gripper jaws 74 and 75 and the pins 81, 82

and 83 will move down the inclined wedge areas to release the tubing 11.

From the above-detailed description the operation of the improved drawing device is believed clear. However, briefly, it will be appreciated that the tubing or other similar wirelike material which is to be reduced in outside diameter is pulled through a draw die 35 by the action of the propelling units 46 and 47. The propelling units are reciprocated relative to the drawing die 35 by the drum cams 44 and 45 rotated through the shaft 26. The drum cams are each provided with the cam tracks 53 and are effective to sequentially move the respective propelling units 46 and 47 alternately through a tube advancing stroke, so that the tube 11 is moved to the right as viewed in FIGS. 1, 2 and 4, and then through a return stroke. By superimposing the action of the pair of propelling units 46 and 47 onto the tubing 11, one of the propelling units 46 and 47 is at all times in the advancing stroke so that the tube 11 is pulled continuously through the die 35 by the action of one or the other of the propelling units. The propelling units include the gripper jaws 74 and 75 which, in association with the backing blocks 72 and 73 through the action of the roller pins 81, 82 and 83, act as an overriding clutch. The roller pins 81, 82 and 83 space the gripper jaws 74 and from the backing blocks 72 and 73 along pairs of confronting surfaces which are inclined relative to each other. When one of the propelling units, for example, propelling unit 46, is advanced to the right, as viewed in FIGS. 1, 2 and 4, the springs 93 are effective to bias the gripper jaws 74 and 75 to the left so that the roller pins 81, 82 and 83 are effective to bias the gripper jaws 74 and 75 toward each other so as to grip the tube 11 and to draw the tube llthrough the draw die 35. However, once the propelling unit 46 has completed its advance stroke and begins its return stroke, as indicated in FIG. 5, the frictional force of the tube 11 against the gripper jaws is effective to move the gripper jaws 74 and 75 to the right against the return bias of the springs 93 and the roller pins 81, 82 and 83 move down the inclined wedge so that the gripper jaws 74 and 75 move outwardly from each other out of gripping engagement with the tubing 11. It will be appreciated that the tube 11 then is free to slide along the recesses 91 and 92 in the gripper jaws 74 and 75.

It has been found that supporting the gripping jaws 74 and 75 at a total of three points, by the three roller pins 81, 82 and 83, is advantageous in that the pressure on the jaws 74 and 75 at each end is equalized whereas if each 'of the jaws 74 and 75 were supported from the respective backing blocks 72 and 73 by two pins, one end might tend to grip tightly while the other end would be loose. Moreover, the springs are advantageous in that they give an initial friction in the advance stroke but are sufficiently light so as to prevent a wedging action between the roller pins 81, 82 and 83 during the return stroke. Moreover, providing an obtuse and inclined wedge area with a two-degree differential between the respective confronting inclined surfaces 84 and 87, 85 and 88, and 86 and 89 is advantageous in facilitating release thereof, whereas a two-degree incline of a lightweight Wedge could present difficulty in release when the propelling units are in their return stroke.

Although the present invention has been described in connection with a single embodiment thereof, it is obvious that numerous other embodiments may be devised by those skilled in the art. It is intended, therefore, in the appended claims to cover all such embodiments as fall within the true spirit and scope of this invention.

What is claimed as new and is desired to be secured by Letters Patent of the United States is:

1. A propelling apparatus for driving wirelike material through a draw die and comprising a support including guide means; a shaft rotatably mounted on said support; a pair of drum cams carried on said shaft having cam tracks in their surface disposed one hundred eighty degrees out of phase with each other; a pair of propelling units each provided with guide means cooperatively associated with the first-mentioned guide means for guiding the respective propelling units in aligned reciprocating relation; a pair of cam follower means each drivingly connected to a respective one of said propelling units and each operatively associated with a respective one of said cam tracks for reciprocating said propelling units in response to rotation of said shaft; each of said propelling units including a rectangular gripper frame, means carried by said frame including a plurality of spaced opposed surfaces each having a small angular inclination in the direction of reciprocation of said units, a pair of' movable gripping jaws positioned between said spaced surfaces each having confronting surfaces to respective ones of the first-mentioned opposed surfaces and provided with material gripping means, said surfaces of said jaws having a slightly smaller angular inclination in the same direction as said first-mentioned opposed surfaces to form wedgeshaped areas between respective pairs of confronting surfaces, and roller means positioned in each of said wedgeshaped areas spacing said respective pairs of confronting surfaces.

and additionally including means exerting a light bias on jaws biasing them in a direction to wedge the roller means between respective confronting surfaces.

3. A propelling unit as set forth in claim 1 above Wherein the inclination of each of said confronting surfaces is in the same direction.

4. A propelling apparatus for driving wirelike material through a draw die and comprising a support including guide means; a shaft rotatably mounted on said support; a pair of positive displacement cams carried on said shaft having cam tracks disposed one hundred eighty degrees out of phase with each other; a pair of propelling units each provided with guide means cooperatively associated with the first-mentioned guide means for guiding the respective propelling units in aligned reciprocating relation; 21 pair of cam follower means each drivingly connected to a respective one of said propelling units and each operatively associated with a respective one of said cam tracks for reciprocating said propelling units in response to rotation of said shaft; each of said propelling units including a gripper frame, means carried by said frame including a plurality of opposed surfaces each having a small angular inclination, a pair of movable gripping jaws each having confronting surfaces to respective ones of the first-mentioned opposed surfaces and having a different angular inclination to form wedge-shaped areas between respective pairs of confronting surfaces, roller means positioned in each of said wedge-shaped areas spacing said respective pairs of confronting surfaces, and biasing means urging said gripping jaws in a direction to wedge respective roller means between respective confronting surfaces.

5. A propelling unit as set forth in claim 4 above wherein said area is in the shape of a frustrum of an obtuse wedge.

6. A propelling apparatus for driving Wirelike material through a draw die and comprising a support including guide means; a shaft rotatably mounted on said support; a pair of drum cams carried on said shaft having cam tracks in their surface disposed one hundred eighty degrees out of phase with each other; a pair of propelling units each provided with guide means cooperatively associated with the first-mentioned guide means for guiding the respective propelling units in aligned reciprocating relation; a pair of cam follower means each drivingly connected to a respective one of said propelling units and each operatively associated with a respective one of said cam tracks for reciprocating said propelling units in response to rotation of said shaft; each of said propelling units including a gripper frame, means carried by said frame including a plurality of opposed surfaces each hav ing angular inclination of approximately seven degrees in the direction of reciprocation of said units, a pair of movable gripping jaws each having confronting surfaces to respective ones of the first-mentioned opposed surfaces and having an angular inclination of approximately five degrees in the same direction as said first-mentioned opposed surfaces to form wedge-shaped areas between respective pairs of confronting surfaces whose sides form an angle of approximately two degrees with each other, roller means positioned in each of said wedgeshaped areas spacing said respective pairs of confronting surfaces, and biasing means urging said gripping jaws in a direction to wedge respective roller means between respective confronting surfaces, to form an overriding clutch type connection between said gripping jaws and said gripper frame.

7. Drawing apparatus for reducing the diameter of hydraulic needle tubing and similar wirelike material comprising a support, a draw die carried by said support, a shaft rotatabiy mounted on said support, a pair of positive cam means carried by said shaft, a pair of propelling units slidably mounted on said support for reciprocating movement relative to said draw die and each associated with a respective one of said cam means, each of said propelling units including a rectangular gripper frame, means carried by said frame including a plurality of opposed surfaces each having a small angular inclination in the direction of reciprocation of said units, a pair of movable gripping jaws each having confronting surfaces to respective ones of the first-mentioned opposed surfaces and provided with material gripping means aligned with said draw die, said surfaces of said jaws having a slightly smaller angular inclination in the same direction as the said first-mentioned opposed surfaces to form wedgeshaped areas between respective pairs of confronting surfaces, roller means positioned in each of said wedge-shaped areas spacing said respective pairs of confronting surfaces, and a pair of cam follower means each operatively associated with one of said cam means for reciprocating a respective one of said propc ling units.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. A PROPELLING APPARATUS FOR DRIVING WIRELIKE MATERIAL THROUGH A DRAW DIE AND COMPRISING A SUPPORT INCLUDING GUIDE MEANS; A SHAFT ROTATABLY MOUNTED ON SAID SUPPORT; A PAIR OF DRUM CAMS CARRIED ON SAID SHAFT HAVING CAM TRACKS IN THEIR SURFACE DISPOSED ONE HUNDRED EIGHTY DEGREES OUT OF PHASE WITH EACH OTHER; A PAIR OF PROPELLING UNITS EACH PROVIDED WITH GUIDE MEANS COOPERATIVELY ASSOCIATED WITH THE FIRST-MENTIONED GUIDE MEANS FOR GUIDING THE RESPECTIVE PROPELLING UNITS IN ALIGNED RECIPROCATING RELATION; A PAIR OF CAM FOLLOWER MEANS EACH DRIVINGLY CONNECTED TO A RESPECTIVE ONE OF SAID PROPELLING UNITS AND EACH OPERATIVELY ASSOCIATED WITH A RESPECTIVE ONE OF SAID CAM TRACKS FOR RECIPROCATING SAID PROPELLING UNITS IN RESPONSE TO ROTATION OF SAID SHAFT; EACH OF SAID PROPELLING UNITS INCLUDING A RECTANGULAR GRIPPER FRAME, MEANS CARRIED BY SAID FRAME INCLUDING A PLURALITY OF SPACED OPPOSED SURFACES EACH HAVING A SMALL ANGULAR INCLINATION IN THE DIRECTION OF RECIPROCATION OF SAID UNITS, A PAIR OF MOVABLE GRIPPING JAWS POSITIONED BETWEEN SAID SPACED SURFACES EACH HAVING CONFRONTING SURFACES TO RESPECTIVE ONES OF THE FIRST-MENTIONED OPPOSED SURFACES AND PROVIDED WITH MATERIAL GRIPPING MEANS, SAID SURFACES OF SAID JAWS HAVING A SLIGHTLY SMALLER ANGULAR INCLINATION IN THE SAME DIRECTION AS SAID FIRST-MENTIONED OPPOSED SURFACES TO FORM WEDGESHAPED AREAS BETWEEN RESPECTIVE PAIRS OF CONFRONTING SURFACES, AND ROLLER MEANS POSITIONED IN EACH OF SAID WEDGESHAPED AREAS SPACING SAID RESPECTIVE PAIRS OF CONFRONTING SURFACES.

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