US 3374684 A
Description (OCR text may contain errors)
March 26, 1968 J. GREVEN CARRIAGE-RECIPROCATING STRUCTURE FOR A MACHINE SUCH AS A DRAWING MACHINE Filed Oct. 22, 1965 2 Sheets-Sheet 1 March 26, 1968 J GREVEN 3,374,684
CARRIAGE-RECIPROCATING STRUCTURE FOR A MACHINE SUCH AS A DRAWING MACHINE Filed Oct. 22, 1965 2 Sheets-Sheet 2 Fig. 4
United States Patent 3,374,684 A CARRIAGE-RECIPROCATING STRUCTURE FOR A MACHINE SUCH AS A DRAWING MACHINE Johann Graven, Aachen, Germany, assignor to Schumag Schumacher Metallwerke GmbH, Aachen, Germany, a
corporation of Germany Filed Oct. 22, 1965, Ser. No. 502,169 Claims priority, application Germany, Apr. 17, 1965, Sch 36,904 4 Claims. (Cl. 7456) ABSTRACT OF THE DISCLCSURE In a machine, carriage means cyclically movable along a given path first forwardly from a given starting position to a given end position and then rearwardly from the end position back to the starting position, a pair of camfollower rollers displaced one with respect to the other along the path and defining a given space between themselves, a pair of support means carried by the carriage means and respectively supporting the rollers for rotary movement, and elongated cam means extending through the space between the cam-follower rollers and between the latter and movable in a direction generally transverse to the path, the cam means having a pair of opposed camming faces engaging the cam-follower rollers and respectively cooperating therewith to provide by cooperation of one of the camming faces with one of the rollers forward movement of the carriage means and by cooperation of the other of the camming faces with the other of the rollers rearward movement of the carriage means, one of the support means which supports the cam-follower roller which cooperates with the cam means to provide rearward movement of the carirage means supporting the latter roller for resilient yieldable movement in the direction of movement of the carriage means.
SPECIFICATION My invention relates to machines which have carriages which must be reciprocated.
In particular, my invention relates to machines of this type which are used in connection with drawing opera tions, according to which metal will be drawn through suitable drawing dies so as to reduce the cross section of the treated metal.
With machines of this general type it is customary to provide carriages which move forwardly and rearwardly as the result of the cooperation between suitable cams and cam-follower rollers which are carried by the carriages.
Particularly in the case of drawing machines in which the treated material is continuously drawn through the drawing die, a uniform drawing speed is necessary. For this purpose the cams must be manufactured with great precision, and there must be absolutely no play between the camming surfaces and the cam-follower rollers which cooperate therewith.
With a known construction of this latter type the camfollower rollers are arranged for this reason in such a way that they can be adjusted. For this purpose the rollers are of a tapered or frustoconical configuration and are mounted axially one above the other between a pair of camming surfaces on a suitable stub shaft which is fixedly mounted only at one of its ends so that this shaft projects freely from its one fixed end. With this conventional construction the pair of camming surfaces provided for forward and rearward movement, respectively, are situated at different elevations so that one camming surface is capable of cooperating with one of the rollers on the stub shaft while the other camming surface is capable of cooperating with the other of the cam-follower rolls on the same stub shaft. By adjusting the axial positions of the cam-follower rollers on the shaft which carries them, it is possible as a result of the tapered configuration of the rollers, to eliminate any play which may develop.
The above conventional construction has several disadvantages. As a practical matter it is necessary to provide a certain amount of play for the cam-follower rollers at the camming surfaces with which they cooperate, as a result of manufacturing tolerances, so that at that location where the pair of mutually spaced camming surfaces are closest to each other jamming or undesirable gripping or seizing of the stub shaft and the plate of the carriage on which it is fixedly mounted can be avoided. Furthermore, the tapered configuration of the cam-follower rollers results in axial components of force which are transmitted to the cam-follower rollers from the camming surfaces, and these axial components of force are transmitted undesirably to the carriage itself. As a result of the latter forces the cariage must be constructed very robustly, so that it is essential to provide the carriage with a weight greater than would otherwise be the case. This additional weight acts in a highly undesirable manner with respect to the forces which accelerate the carriage and which are required to produce the movement thereof.
On the other hand, the stability of the drawing carriage and of the bearings for the cam-follower rollers are of extremely great importance so as to provide a reliable and faultless operation, particularly in those cases where the machine has a plurality of carriages and where the drawing operations are carried out at high speed. The abovediscussed conventional arrangement of tapered rollers on a stub shaft is only of limited utility in connection with the forward movement of the drawing carriage. Where large drawing forces greater than 10 tons, or even greater than 20 tons are present, the above conventional arrangement is no longer adequate. The mounting of the follower roller shaft so that it is fixedly supported only at one of its ends necessitates such a large and robust structure for the follower-roller shaft as well as for the fixed connection thereof to the carriage, that it is no longer possible to maintain the drawing carriage within reasonable acceptable dimensions. When the drawing operations are carried out at high speeds, it is essential to provide a drawing carriage of the smallest possible weight and to render those elements of the structure which absorb the forces better able to accept the large forces without increasing the weight of the components.
It is accordingly a primary object of my invention to provide a carriage-reciprocating structure of the above general type which will avoid all of the above drawbacks of the known structure.
Thus, it is in particular an object of my invention to provide a relatively simple rugged structure of light weight which nevertheless is very reliable in operation, even when high-speed drawing operations are encountered.
In addition it is an object of my invention to provide a structure of this type which is exceedingly compact and composed of a relatively small number of elements.
Furthermore, it is an object of my invention to provide a construction where while the'return movement of a carriage may, for example, be carried out at a higher speed than its forward movement, nevertheless the distance between cam-follower rollers is capable of being maintained substantially constant.
Primarily with the structure of my invention, the machine will include a carriage means movable from a given starting position forwardly along a given path to an end position and then rearwardly along this same path back to the starting position. A pair of cam-follower rollers 3 are provided with their axes of rotation spacedfrom each other .along the path of movement of the carriage means, and the pair of cam-follower rollers define between themselves a predetermined space. A support means is carried by the carriage means and supports the pair of cam-follower rollers for rotary movement. A single cam means extends through the space between the pair of cam-follower rollers and is movable in a direction generally transverse to the path along which the carriage means moves, and the single cam means which extends through the space between the pair of cam-follower rollers has forwardly and rearwardly directed camming faces respectively engaging the rollers to cooperate therewith for providing the forward and rearward movement of the carriage means. Preferably, the pair of cam-follower rollers are located in a common plane and the cam means is in the form of an elongated endless cam which is supported for rotary movement.
My invention is illustrated by way of example in the accompanying drawings which form part of this application, and in which:
FIG. 1 is a bottom plan view of a carriage means of my invention, FIG. 1 illustrating in phantom lines how the cam means cooperates with the structure carried by the carriage means;
FIG. 2 is a side elevation of the structure of FIG. 1 showing the cam means partly in a section taken along line 11-11 of FIG.'l in the direction of the arrows;
FIG. 3 is a developed view of the cam of FIGS. 1 and 2; and
FIG. 4 is a schematic side elevation showing how a pair of carriages of a drawing machine are controlled with the structure of my invention.
The carriage means 1 shown in the drawings is slideable along any suitable ways in a Well known manner so as to carry out a forward movement from a given starting position to a given end position and a rearward movement from this end position back to its starting position, during each operating cycle, and this cyclically repeating reciprocation of the carriage means 1 is represented by the double-headed arrow 10 in FIG. 1. Situated beneath the carriage means 1 are a pair of cam-follower roller-s 2 and 3. The carriage means 1 reciprocates in a given plane and the axes of the rollers 2 and 3 are parallel to each other and normal to the plane of the carriage means 1. The cam-follower roller 2 is the forward roller which participates in the forward movement of the carriage means 1, and it is supported for rotary movement by a support means 4 which is fixedly carried by the carriage means 1 and which provides a fixed mounting for the axis of rotation of the cam-follower roller 2. As is particularly apparent from FIG. 2, the support means 4 extends around the right peripheral portion of the roller 2, as viewed in FIG. 2, so that the support means 4 is situated both above and below the cam-follower roller 2 at both sides thereof, so that a very secure mounting of the cam-follower roller 2 at both of its sides is provided with the support means 4 of my invention. This support means 4 is fixedly connected directly with a bottom plate of the carriage means 1.
The support means which supports the rear cam-follower roller 3 for rotation, however, mounts the latter roller for yieldable resilient movement. For this purpose this latter support means includes an elongated lever 5 supported for pivotal movement by pivot pin 6 fixedly carried by the carriage means 1 and extending through a suitable bore in one end of the lever 5. The other end of the lever 5 is engaged by a spring assembly 7 made up of a stack or series of cup-shaped spring plates pressing one against the other and capable of having their force of compression adjusted by an adjusting screw 8, so that in this way the spring assembly 7 urges the lever 5 to turn in a counter-clockwise direction about the pivot 6, as viewed in FIG. 1. The lever 5 carries intermediate its ends the pivot 9 for the roller 3, and thus the roller 3 is urged toward the forward roller 2 by the spring means 7. The
axis of the pivot 9, which coincides with the axis of the roller 3, is thus capable of yielding rearwardly in response to a force sufficient to compress the spring assembly 7 so as to be capable of increasing the space between the rollers 2 and 3 when and if required.
It is to be noted that with the structure as thus far described the cam-follower rollers 2 and 3 are situated in a common plane which is parallel to the plane in which the carriage means 1 moves and moreover these rollers 2 and 3 are mounted with their axes displaced from each other along the path of movement of the carriage means 1 to an extent sufficient to provide a predetermined space between the rollers 2 .and 3. It is through this latter space that the cam means of my invention extends in a direction generally transverse to the path of movement of the carriage means 1, so that in this way a single cam can be provided with opposed camming faces respectively engaging the rollers 2 and 3.
The cam means of my invention includes a cam portion 11 which provides rearward movement of the carriage and a cam portion 11 which provides the forward movement of the carriage, and this cam is shown in one example most clearly in the developed view of FIG. 3. The cam portions 11 and 11' respectively have forward camming surfaces 12 and 12' which cooperate with the forward cam-follower roller 2 and rear camming faces 13 and 13 which cooperate with the rear cam-follower roller 3. The cam- -ming face 12 produces the forward movement of the carriage means 1, while the rear camming face 13 provides the return movement of the carriage means 1. As is particularly apparent from FIG. 3, the camming face 13 approaches the path of movement of the carriage means 1 to a far greater extent than the camming face 12' so that this camming face 13 is considerably steeper than the camming face 12' and thus will provide a return stroke for the carriage which requires less time than the forward stroke thereof. In addition, it is apparent that the thickness of the cam portion 11', because of its reduced steepness according to which it more closely approaches a direction precisely transverse to the path of movement of the carriage means 1, is greater than the thickness of the steeper cam portion 11 while also providing a substantially constant distance between the follower rollers 2 and 3. Furthermore, it is apparent that it is possible to provide a predetermined curvature for the camming faces 13 and 13' as well asfor the camming faces 12 and 12' both individually in and of themselves as well as in relation to each other, in such a way that while maintaining the distance between the rollers 2 and 3 constant throughout the entire operating cycle, nevertheless the desired acceleration and speed relationships for the carriage means can be provided and at the same time the thickness of the cam is great enough to produce the required strength. The cam portion 11 can be made hollow, as is particularly apparent from FIGS. 2 and 3, so that in this way the weight of the entire assembly can be reduced. Furthermore, FIG. 2 in particular clearly demonstrates how a rotary cam drum 14 forms part of the camming means and has its axis extending in the direction of movement of the carriage means 1 perpendicularly across the pair of parallel axes of the rollers 2 and 3 and parallel to the plane in which the carriage means 1 moves. In the particular example illustrated, the cam 11, 11' is integral with the hollow drum 14 and projects from the exterior surface thereof into the space between the follower rollers 2 and 3 so that the forward and rearward camming faces can respectively cooperate with these rollers 2 and 3.
As is apparent from FIG. 3, the follower rollers 2 3 engage the camming faces with completely different parts of their outer peripheries according to the angular position of the cam 11, 11'. This geometric factor must be taken into consideration in determining the curvature of the cam.
The prestressing of the spring assembly 7 is so chosen that when the machine operates at maximum drawing speed, which is to say when the carriage means 1 executes the largest number of operating cycles in a given period of time, the cam-follower roller 2 does not become separated from the cam at the crest or reversing point 19 where the camming faces 12 and 12' meet. In other words, during the return stroke of the carriage means 1 it should not be possible for the spring assembly 7 to be compressed to such an extent that the cam moves rearwardly out of contact with the forward cam-follower roller 2. Any inaccuracies in the camming faces 12, 12 and 13, 13' are compensated for by the elasticity of the spring assembly 7.
As may be seen from FIG. 4, in addition to the drawing carirage 1 with its cam-follower rollers 2 and 3, cam drum 14, and cam means 11, 11', there is a second drawing carriage 15 with its cam-follower rollers 16 and 17 which respectively correspond to the rollers 2 and 3 as well as with its cooperating cam drum 18 and cam 20 which corresponds to the cam drum 14 and cam 11, 11, respectively. As is apparent from FIG. 4, the pair of cams illustrated therein are angularly displaced with respect to each other in such a way that the pair of carriages 1 and 15 are out of phase in their cyclical movements, the cam drums 14 and 18 actually being shown at 180 out of phase relationship so that in this way the work can be continuously drawn-by being suceessively engaged in a known way with structure carried by the carriages 1 and 15. Thus, preciselywhen one of the carriages completes its forward drawing of the work and is about to perform its rearward stroke, the other carriage takes over and continues the forward drawing of the work without any interruption. This latter phase of the drawing operations are conventional and form no part of my invention.
While with a conventional construction where a pair of tapered cam-follower rollers are provided on a stub shaft it is necessary to provide a pair of axially spaced cams between which the cam-follower rollers are located with these rollers situated at different elevations so as not to conflict with each other, it will be noted that with the structure of my invention a single cam extends between the pair of cam-follower rollers. Thus, these rollers are located in the same plane, one behind the other in the direction of movement of the carriage. Any necessary adjustment of the rollers with the structure of my invention can easily be carried out by changing the position of one or both of the cam-follower rollers in the direction of movement of the carriage.
Furthermore, it is to be noted that the cam-follower rollers of my invention can take the form of simple rollers of cylindrical configuration, and any transmission of axial force components to the carriage itself is reliably avoided.
For these reasons experience has proved that the structure of my invention can be operated with very great precision. Therefore, the structure of my invention is particularly suited for drawing machines where the work material is continuously drawn through the drawing dies and where at least a pair of drawing carriages are provided to operate in a given phase relationship as pointed out above in connection with FIG. 4. Of course, it is possible to use for my invention fiat cams rather than cams which are carried by rotary drums, but the rotary drum support for the cam structure is preferred because of the advantages it provides in connection with the saving of space and the ease of mounting of the cam assembly.
Furthermore, because of the fact that both of the camfollower rollers are supported each at both of its sides, an extremely secure mounting of the cam-follower rollers is achieved. In this connection it is to be noted that the lever 5 also extends on both sides of the camfollower 3, as is the case with the support means 4, as pointed out above.
This supporting of each follower roller at both of its sides is relatively simple to carry out with the particular arrangement of my invention and provides the advantage of avoiding the necessity of structures which are too large and heavy, even when dealing with drawing forces on the .order 10 or 20 tons. As was indicated above, where the cam-follower rollers are mounted on a common stub shaft which is fixed at only one of its ends, the size of the parts is necessarily far too great to be of any practical value when dealing with relatively large drawing forces.
It is of course preferred to provide for the forward roller 2 a fixed mounting for its axis of rotation, since it is this forward roller which receives the greater force. During the forward movement of the carriage greater forces are encountered than during the return movement thereof, and therefore a fixed mounting of the axis of rotation of the forward cam-follower roller is preferred and makes the structure particularly suitable for drawing machines where relatively large forces are absorbed by these forward rollers of the drawing carriages.
While it is preferred to provide a fixed mounting for the axis of the forward roller, it is also preferred in accordance with my invention to provide the yieldable resilient mounting for the rear roller 3. Thus, the rear support means 59 will, as a result of the action of the spring assembly 7, provide constant engagement of both cam-follower rollers with the cam. Of course, the forces returning the carriage back to its starting position are considerably smaller than those acting on the carriage during its forward movement, and therefore by a suitable choice the magnitude of the spring force of the assembly 7 any possible inaccuracies in the movement of the carriage can be eliminated. Of course, it is to be remembered that a certain extent of inaccuracy in the return movement of the carriage can be accepted since the return movement need not be carried out with the same precision as the forward movement. In this way certain tolerances in the camming faces can be compensated. These cams are presently manufactured, in general, from a template on a suitable copying machine, and in spite of the greatest care in the manufacture of the cams, certain tolerances in the curvature of the cam faces and thus in the distance between the pair of camming faces cannot be avoided. These tolerances are compensated by the above-described yieldable, resilient mounting of the rear roller 3. Also, as a result of this construction wear resulting from long use of the structure will be compensated.
The particular construction according to which the rear roller is mounted on the lever 5 which is pivotally supported at one of its ends and which is acted upon by the spring assembly 7 at the other of its ends has proved in practice to be extremely stable and to be adequate for all of the requirements encountered by the machine in practice.
As was mentioned above, with the arrangement of my invention the cam-follower rollers 2 and 3 will be maintained at a constant distance from each other at all times. Thus, the less steep the cam, which is to say the more it approaches a line precisely perpendicular to the path of movement of the carriage, the greater the possible distance between the pair of forward and rearward camming faces from each other so that the greater the possible thickness of the cam itself and in fact at the cam portions which are of lesser steepness the thickness of the cam will approach the actual clearance between the pair of cam-follower rollers. However, where the cam is relatively steep, so that it approaches to a greater extent the direction of movement of the carriage, the distance between the pair of camming faces must be reduced and thus the thickness of the cam must be correspondingly reduced. By a proper choice of cam thickness it is possible to provide the structure of my invention according to which at all angular positions of the cam drum the cam will maintain the rollers at the same distance from each other. In this way any possible play between the cam-follower rollers and the camming faces is eliminated. The required variation in the thickness of the cam along its length can easily be calculated or. determined from drawings or from suitable tests.
Of course, with the structure of my invention the diameters of the rollers 2 and 3 as well as the distance therebetween, are so chosen that the pair of opposed camming faces at the steepest part of the cam will still be spaced from each other by a distance great enough to provide a cam at its steepest portion with a thickness sufficiently great toabsorb the forces which are encountered.
The greater the diameter of the cam-follower rollers, the smaller the possible thickness of the cam at the relatively steep portions thereof in relation to the thickness of a the cam at its portions of lesser steepness. With relatively large cam-follower roller diameters, it is therefore necessary by reason of this latter factor alone to provide under certain circumstances a distance between the rollers which is relatively large. With relatively large distances between the cam-follower rollers, however, it becomes necessary to provide a relatively large thickness of the cam at the portions thereof which are of lesser steepness.
However, bearing in mind the particular forces which will be encountered, it is possible to provide an optimum dimensioning of the parts. In this connection it is to be taken into consideration that the return stroke in general will take place at a faster rate than the forward stroke and therefore the part of the cam which produces the return stroke must be made particularly steep. On the other hand, the return stroke requires lesser power than the forward stroke, so that it is possible to provide an adequately robust cam structure even if the cam has a lesser thickness at its steeper portion which provides the quicker return of the carriage.
While various features of my invention are shown in combination with each other, it is of course apparent that they are of merit in and of themselves as well as in combination with the other features.
1. In a machine, carriage means cyclically movable along a given path first forwardly from a given starting position to a given end position and then rearwardly from said end position back to said starting position, a pair of cam-follower rollers displaced one with respect to the other along said path and defining a given space between themselves, a pair of support means carried by said carriage means and respectively supporting said .rollers for rotary movement, and elongated cam means extending through said space between said cam-follower rollers and between the latter and movable in a direction generally transverse to said path, said cam means having a pair of opposed camming faces engaging said cam-follower rollers and respectively cooperating therewith to provide by cooperation of one of said camming faces with one of said rollers forward movement of said carriage means and by cooperation of the other of said camming faces with the other of said rollers rearward movement of said carriage means, one of said support means which supports the cam-follower roller-which cooperates with said cam means to provide rearward movement of said carriage means supporting the latter roller for resilient -yieldable movement in the-direction of movement of said carriage means. I
2. In a machine as recited in claim 1, said one'support means including a lever turnable carrying said latter roller intermediate the ends of said lever, a pivot carried by said carriage means and supporting said leverfor turning movement adjacent one of said ends thereof and an adjustable spring assembly mounted on said carriage means and engaging the other of said ends of said lever for urging the cam follower roller carried thereby toward said cam means.
3. In-a machine, carriage means movable back and forth in a given plane from a given starting position forwardly to'a given end position and from said end position rearwardly back to said starting position, a rotary cam drum having an axis of rotation parallel to said plane in which said carriage means moves, said axis extending generally in the direction of movement of said carriage means and said rotary cam drum carrying at its exterior surface an endless cam of predetermined curvature which projects from the surface of said cam drum and which has a pair of opposed camming faces one of which is a forward camming face and is directed forwardly while the other camming face is a rear camming face and is directed rearwardly, a pair of cam-follower rollers respectively having axes parallel to each other and normal to the axis of said drum and said plane in which said carriage means moves, said cam-follower rollers being situated in a common plane parallel to the plane in which said car riage means moves and respectively engaging saidopposed camming faces with one of said rollers being a forward roller and engaging said forward camming face and the other of said rollers being a rear roller and engaging said rear camming face, and a pair of support means carried 'by said carriage means and respectively supporting said roller for rotary movement about their axes, at least the support means which support said forward roller for rotary movement maintaining the axis of said forward roller fixed with respect to said carriage means, the support means which supports said rear roller for rotary movement providing a yieldable resilient support for the axis of said rear roller.
4. In a machine as recited in claim 3, the endless cam which projects from said periphery of said drum having a curvature and a distance between said camming faces which maintains said rollers at a substantially constant distance from each other at all angular positions of said drum. Y
References Cited UNITED STATES PATENTS 1,808,083 6/1931 Tibbetts 74.-56 X 2,323,375 7/1943 Bugg 7456 X FOREIGN PATENTS FRED C. MATTERN, 1a., Primary Examiner.
W. S. RATLIFF, Assistant Examiner.