US2688680A - Speed control for wire drawing blocks - Google Patents

Description

Sept. 7, 1954 J. E. CROTTY 2,688,680

SPEED CONTROL FOR WIRE DRAWING BLOCKS A TTOENEYS Sept. 7, 1954 J. E. CROTTY SPEED CONTROL FOR WIRE: DRAWING BLOCKS 2 Sheets-Sheet 2 Filed April 6, 1950 INVENTOR. .TAC/f EDWARD CEOTTY A TTOE'NEYS Patented Sept. 7, 1954 SPEED CONTROL FOR BLOCK WIRE DRAWING S Jack E. Crotty, Youngstown, iOhio, assignor to The Aetna-Standard Engineering Company, Youngstown, Ohio, a corporation of Ohio Application April 6, 1950, Serial No. 154,369

3 Claims.

This invention relates to automatic speed controls for wire drawing machines.

In Patent No. 2,272,192, issued February 10, 1942, to the assignee of this application, there is described an automatic speed control for wire drawing machines of the type in which wire is allowed to accumulate on each block of the machine and is then withdrawn from each of the blocks in a generally axial direction. The wire has engagement with a movable guide as it is withdrawn from the block, and the movement of the guide is utilized to operate a rheostat to control the speed of the block. In the application of Edward J. P. Fisher, Serial No. 112,506, filed August 26, 1949, and also assigned to the assigneee of the present application, the movements of the guide of the nishing block of a wire drawing apparatus are utilized to operate a rheostat to control the speed of a spooler in which the wire withdrawn from the finishing block is wound on spools or reels. The devices of the said patent and application have been successful in use, but for some purposes, and particularly where ne wire is being drawn at very high speeds, the specic controls utilized to control the speeds of the motors are not sufliciently accurate, and in some instances undesirable hunting has resulted.

The present invention has for its object the provision of an improved control for wire drawing apparatus in which finer adjustments of the speeds of the motors are possible and in which the above noted difficulties are eliminated. The invention is described herein as it is applied to the control of the speed of the motor driving a block of a wire drawing machine, but the application of the invention to an installation embodying a spooler control such as shown in the aforesaid Fisher application will be evident to those skilled in the art, and it is to be understood that the invention is not limited to the control of the speed of the wire drawing blocks and that the invention may be applied to other uses and purposes.

In the aforesaid Fisher patent and application, the motor speed control is effected by rotation of the guide over which the wire is withdrawn from the block, the guide rotating in one direction when Wire is being withdrawn from the block at a speed less than the speed at which it is being drawn onto the block and rotating in the opposite direction when wire is being withdrawn from the block at a speed greater than the speed at which it is being drawn onto the block. The guide is stationary when the speeds are equal. The movement of the guide is transmitted through suitable driving connections such as gearing and chains to a rheostat of conventional drum type, a single revolution of the rheostat covering the entire speed range of the motor. With this type of construction, the steps oi the rheostat necessarily give relatively coarse adjustment of the motor speed with the result that in some installations the motor speed cannot be adjusted to conform precisely to the desired speed, the control is not as accurate as desired, hunting occurs, and the motor speed is constantly changing. The difficulties are particularly noticeable in high speed drawing of ne wire.

Briefly the present invention overcomes these difliculties by providing two rheostats for controlling the speed of the motor, one rheostat eecting fine adjustment of the motor speed and the other rheostat effecting coarse adjustment of the motor speed. Both of the rheostats are operated by the movement of the guide but the arrangement is such that all of the speed adjustment available by the line adjstment rheostat is utilized before the coarse adjustment rheostat comes into play. Thus, the amount of speed adjustment is correlated with the amount of adjustment required. Smooth operation is obtained at high speeds and hunting is substantially eliminated.

Referring to the drawings, Figure l is an elevation, of a wire drawing unit embodying my invention; Figure 2 is a plan view of the unit shown in Figure 1; Figure 3 is a vertical sectional view of the unit shown in Figure l, the section being taken as indicated by the line 3-3 of Figure l; and Figure 4 is an enlarged horizontal sectional view of the rheostats and their operating mechanism taken as indicated by line 4-4 of Figure 3,

Referring now to Figures 1 and 2 of the drawings, a wire drawing unit embodying my invention is indicated in general at l0. Such a unit may be used by itself to perform a single drawing operation on wire or a plurality of units may be used in tandem to provide a continuous wire drawing apparatus adapted to perform a series of drawing operations. The unit preferably is constructed generally in accordance with the disclosure of the aforesaid Fisher Patent No. 2,272,- 192 and comprises a suitable frame structure or base Il upon which the die box l2 is mounted; the die box l2 supports the die I4. The base il also supports the block or drum l5 which functions to draw the wire W through the die. The block l5 is driven by a variable speed motor I6 3 mounted on the base Il in back of the block. The drive may be through any convenient means such as that shown in Figure 3 comprising the pinion I1, gear I8 and pinion I9 mounted on countershaft and gear 2l at the lower end of shaft 22 which drives block l5.

The wire drawn through the die is wrapped around the block a number of times and is withdrawn from lthe block in a generally axial direction over the guide pulley 25 carried by an arm or bracket 25 extending from the hub 21 of gear 28. Hub 21 is supported by bearings 25 on shaft which is coaxial with shaft 22 and block l5, The gear 28 and hence the arm 23 and pulley 25 are urged to rotate about the shaft 30 in the direction of rotation of the block I5 (counterclockwise in Figure 2) by friction drive means consisting of brake bands or shoes 32 which engage the cylindrical surface of a friction drum 33 that is secured to block I5 for rotation therewith. Thus, the guide pulley 25 is frictionally urged to rotate in the direction of rotation of the block I5, and this rotation is resisted because of the engagement of the guide pulley with the wire.

From the guide pulley 25 the wire is led over the upper guide pulley 35 and thence downwardly to guide pulley 36 mounted on the base, from which pulley it may be led to a subsequent operation such as the die of another wire drawing unit or to a spooler or the like.

In a machine of this type, the wire drawn through the ydie 14 is wrapped tightly around the lower portion `of block l5. As more wire is drawn onto the block, the turns of wire around the lower portion move upwardly and turns of wire accumulate on the upper portion of the block which is tapered toward the top as a frustum of a cone. It is .a characteristic of machines of this type that the guide pulley over which the wire is withdrawn remains stationary so long as the wire is withdrawn from the block at the same rate of speed -that it is drawn onto the block. However, when the speed of withdrawal is less than the speed at which the wire is drawn onto the block, the guide pulley 25, arm 26 and gear 28 rotate bodily in the direction of rotation of the block, i. e., more turns of wire are being accumulated on the block. On the other hand, when the speed of withdrawal is greater than the speed at which the wire is drawn onto the block, the guide 25, bracket 26 and gear 2E rotate in a direction opposite to the direction of rotation of the block, i. e., the more rapid withdrawal of wire from the block reduces the number of turns of wire on the block. As described in the aforesaid patent, this rotational movement of the guide may be utilized to control the speed of the motor driving the block, or as described in the application, may be utilized to control .the speed of a subsequent operation such as a spooler.

In order to transmit the movements of the guide 25 and gear 28 Ito rheostats for controlling the speed of the motor l5, gear 28 meshes with gear 38 which is mounted on a short shaft supported on the back plate 39 projecting upwardly from the base I I. Sprocket 40 rotates with gear 38 and drives chain 4l which in turn drives sprocket 42. Sprocket 42 is carried on bearings 43 mounted on shaft 44 and thus is freely rotatable with respect to shaft 44; the sprocket 42, however, carries a ydrum or flange 45 engaged by brake band 46 tensioned around ange 45 by spring 41. The brake band 46 is adapted to drive shaft 44 through arm 48 to which the ends of the brake band are secured. Thus, shaft 44 is rotated as a result of rotation of pulley 25 about the axis of the block l5 through the friction drive provided by the brake band 46, the friction drive furnishing a slip connection to permit continued rotation of the guide pulley 25 without damage to the parts even though the shaft 44 is prevented from rotation. These elements may be constructed and arranged as described in greater detail in the aforesaid Fisher patent.

In order to provide for fine adjustment of the speed of motor i5, a Vernier rheostat 5l) is supported by a welded box-like structure made up of plates 5l and 52 extending rearwardly from the back plate 39, and transversely extending plates 53 and 54. The shaft 55 of rheostat 50 is coaxial with shaft 44 and is arranged to be rotated by shaft 44 through the lost-motion coupling 56. Preferably coupling 56 has sufficient play in it to permit the guide pulley 25 to rotate about the shaft 3! through an angle of about 15 without transmitting any rotation from shaft 44 to the shaft 55 of the rheostat 55.

The contact arm 58 of Vernier rheostat 55 is mounted on and rotates with shaft 55; the end of the contact arm engages the resistance element 59 of the rheostat, a stop 3Q being provided at the ends of the resistance element so that when the contact blade is positioned at the stop at one side thereof, all of the resistance is out into the circuit, and when it is positioned against the stop at the other side thereof, all of the resistance is cut out of the circuit. While various 7 motor speed control systems can be employed with a rheostat to effect the desired variation in speed, the preferred form is to employ a shunt wound motor and to utilize the Vernier rheostat 50 to control the resistance of the shunt field. The rheostat 50, however, is of comparatively low resistance and can control the speed of the motor through only a fraction of its entire speed range. Thus, the vernier rheostat 50 is utilized to make ne adjustments of the motor speed with relatively large movements of the guide pulley 25.

In order to provide for adjustment of the speed of the motor throughout the desired range, a master rheostat 54 is provided. This rheostat preferably is mounted immediately behind and concentric with rheostat 5U, the housing S5 of the master rheostat being fixed to plate 54 as by welding. The master rheostat 34 is provided with a plurality of resistors 56 arranged in annular fashion and supported by the face plate 51 which carries on its opposite side the contact points 58. Resistance is cut in or out by movement of the contact arm 58, the contact arm being rotated by shaft 15, a high and low end stop 1I being employed between the two end contact points 6B. The capacity of the master rheostat `64 is such that it can control the speed of the motor throughout the usable speed range in steps determined by the number of contact points 68; in a typical installation, there may be, for example, iifty contact points 5S with the resistance arranged in known manner to Asecure equal changes in motor R. P. M. for each step. The master rheostat thus provides coarse adjustment of the motor speed, while finer adjustment is `provided by the Vernier rheostat 59. Preferably the total resistance of the Vernier rheostat is in excess of the resistance cut in by any single step of :the master rheostat 54.

In order to provide for the automatic operation of master rheostat 54 in instances where the assenso speed correction available through .the operation of Vernier rheostat y5l] is insuicient, the Vresistance `element 59 of the Vernier rheostat `5I) is mounted upon a plate 12 lwhich is in turn carried by shaft I .of master rheostat 64. The friction of the master rheostat 64 is greater than the friction vof the Vernier rheostat. With this arrangement, minor speed adjustments are made by the Vernier rheostat withoutv change in the adjustment of the master rheostat.. jIf, however, the speed adjustment required is too great to be accomplished by the Vernier rheostat, the .guide Dlllley 25 continues to rotate after the Contact arm 58 of Vernier rheostat 50 has come into engagement with stop 60. Continued rotation of the guide pulley after this has occurred will result in bodily rotation of the entire Vernier rheostat 50. Inasmuch as the Vernier rheostat is mounted on plate 12, rotation of shaft 'l0 thereupon occurs and contact arm 69 of the master rheostat 64 is moved to vary the resistance of rheostat 64 to correct the speed of motor I6. As soon as the correction is completed, the swinging movement of guide pulley 25 about the axis of block I stops, and the rotation of shafts 55 and I0 stops.

If, by reason of the comparatively large steps in master rheostat 64, the apparatus should make a greater correction than required, then pulley 25 will swing about the axis of the block I5 in the opposite direction and this correcting movement will be transmitted to rheostat 50. Vernier rheostat 50 has suiicient capacity to make the required final adjustment inasmuch as its complete resistance can be cut in or out as required before any reverse movement of shaft 'I0 of rheostat 64 takes place, and the change in Vernier resistance is greater than the difference in resistance between any pair of successive contact points 68 of rheostat 64. The Vernier rheostat thus in effect acts as a kind of lost-motion coupling between the guide pulley 25 and the master rheostat 64, always making its given correction before the master rheostat can operate to produce a greater correction in the speed of the motor.

Thus, with this apparatus, small swings of guide pulley 25 have no effect on either rheostat because of the lost motion provided by coupling 56. Larger movements of the guide pulley operate the Vernier rheostat. Ordinarily, after the machine has settled down in its operation, the Vernier rheostat is sufficient to eifect the desired control and to maintain the number of turns accumulated on the block I5 substantially constant. When the machine is started or when operating conditions change to such an extent that a greater adjustment is desired, then the master rheostat 64 comes into play, but only after the adjustment provided by the Vernier rheostat has proved to be insufficient. Overcorrection, if any, ordinarily is corrected by the Vernier rheostat. Thus, unnecessary adjustments of motor speed are eliminated, hunting is prevented, and stable operation is obtained.

For manual adjustment of the motor speed, hand wheel I5 is provided adjacent the front of the machine. This is mounted on shaft 'IB which carries sprocket 'II and drives sprocket 'I8 through chain 19. Sprocket I8 is keyed to shaft 44; hand wheel 'I5 thus controls the rheostats through the lost-motion coupling 56. When the control of the motor speed is effected by hand wheel 15, contact 58 of Vernier rheostat 50 must be brought into engagement with one side or the .other of stop 6l before the master rheostat can be adjusted.

In order to provide immediate .adjustment of the master rheostat, a khand wheel 80 is mounted on the rear end .of shaft 1.0. Operation of this hand wheel -moves 4the contact arm 69 of master rheostat 164 immediately and simultaneously moves the housing .of the AVernier rheostat 50. Hand wheel is useful for making prompt .coarse adjustments of the speed of the motor I6.

From the foregoing ldescription of a preferred form of my apparatus, it vwill be seen that I have provided a simple and effective .apparatus to control the speed `of the block `cf a wire drawing machine. The apparatus provides consistently accurate speed control, and permits finer adjustments of speed while Virtually eliminating the occurrence of hunting. Such control has been found to be particularly useful for drawing fine wire at high speeds. It is to be understood, of course, that while the invention is described as applied to control of the speed of the motor which drives a wire drawing block, it could with equal ease be applied in controlling the speed of a spooler which takes the wire directly from the finishing block of a wire drawing machine.

Those skilled in the art will appreciate that various changes and modifications may be made in my apparatus without departing from the spirit or scope of my invention. Therefore, it is to be understood that the foregoing description of a preferred form 0f my invention is given merely by way of example and not by Way of limitation. It is intended that the invention shall be covered by appropriate expression in the appended claims.

I claim:

1. In combination, a ne adjustment rheostat and a coarse adjustment rheostat, each rheostat having a housing and a shaft rotatable with respect to the housing for effecting adjustment of the rheostat, the ne adjustment rheostat and the coarse adjustment rheostat being coaxially mounted, the fine adjustment rheostat having stop means for stopping rotation of the shaft thereof with respect to the housing thereof at either end of the range of adjustment thereof, the housing of the line adjustment rheostat being mounted on the shaft of the coarse adjustment rheostat and the housing of the coarse adjustment rheostat being fixed, whereby continued rotation of the shaft of the ne adjustment rheostat after said stop means has stopped rotation thereof with respect to the housing of the fine adjustment rheostat causes the housing of the nne adjustment rheostat to rotate, thereby rotating the shaft of the coarse adjustment rheostat with respect to the housing of the coarse adjustment rheostat, the friction between the shaft and the housing of the coarse adjustment rheostat being greater than the friction between the shaft and the housing of the ne adjustment rheostat.

2. In combination, a fine adjustment rheostat and a coarse adjustment rheostat, each rheostat having a housing and a shaft rotatable with respect to the housing for effecting adjustment of the rheostat, the fine adjustment rheostat having stop means for stopping rotation of the shaft thereof with respect to the housing thereof at either end of the range of adjustment thereof, the housing of the fine adjustment rheostat being rotatably mounted and operatively connected to the shaft of the coarse adjustment rheostat and the housing of the coarse adjustment rheostat being fixed, whereby continued rotation of the shaft of the ne adjustment rheostat after said stop means has stopped rotation thereof with respect to the 'housing of the fine adjustment rheostat causes the housing of the fine adjustment rheostat to rotate, thereby rotating the shaft of the coarse adjustment rheostat with respect to the housing of the coarse adjustment rheostat.

3. In an apparatus of the type described, a ne adjustment rheostat comprising a housing, a shaft rotatable with respect to the housing for adjusting the rheostat and stop means associated with said shaft and housing for stopping the rotation of said shaft with respect to said housing, said 'housing being rotatably mounted whereby said housing rotates with said shaft upon engagement of said stop means, a coarse adjustment rheostat and operative connections between said coarse adjustment rheostat and said housing whereby continued rotation of said shaft operates said coarse adjustment rheostat after said stop means has stopped rotation of said shaft with respect to said housing.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,351,019 Boothman Aug. 31, 1920 2,176,090 McAllister et a1 Oct. 17, 1939 2,272,192 Fisher Feb. 10, 1942 2,473,409 Beechlyn June 14, 1949

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