Abstract:
A press ( 10 ) for operating a tooling unit in the performance of a manufacturing operation, such as crimping terminals onto a conductor. The press is adapted for attachment to the frame of a host machine ( 12 ), such as a lead maker, and for receiving a tooling unit, such as a terminal applicator ( 52 ). The press ( 10 ) includes a frame ( 13 ), a carriage ( 20 ) arranged for reciprocating motion with respect to the frame ( 13 ) and a ram ( 110 ) in sliding engagement with and carried by the carriage ( 20 ). A relatively low powered actuator ( 22 ) causes the ram ( 100 ) to move through a first incremental amount of movement during the first portion of the crimp cycle and a second, more powerful, actuator ( 80 ) causes the carriage ( 20 ) and ream ( 110 ) assembly to move through a second incremental amount of movement to complete the crimp cycle.

Description:
This application is a 371 of PCT/US97/12471, filed Jul. 15, 1997, which claims benefit of Provisional No. 60/021,843, filed Jul. 16, 1997. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a press for operating a tooling unit in the manufacture of articles such as electrical leads, and more particularly to such a press having a ram that moves through a power stroke in two incremental steps. 
     BACKGROUND OF THE INVENTION 
     Terminal applicators are commonly used in the electrical connector industry to attach terminals to electrical conductors. These terminal applicators are operated by means of a press that provides the power to actuate the applicator ram and effect the crimping of the terminal onto the conductor. Such presses include a frame, a ram arranged to undergo reciprocating motion toward and away from a platen, and a power source, such as an electric motor. The terminal applicator is secured to the platen and the ram of the applicator is coupled to and carried by the ram of the press. Typically, the electric motor is run continuously to drive a rotating flywheel which is coupled to a single revolution clutch mechanism that drives a crank coupled to the press ram. When the clutch is tripped the press ram is made to reciprocate one cycle. Such a press is disclosed in U.S. Pat. No. 3,343,398. While this press utilizes a moderately sized electric motor for power, it also requires a rather large and massive flywheel, crank, and clutch mechanism. Another approach is a press for a terminal applicator that utilizes an electric motor that is coupled to a ram crank by means of a drive belt. The press includes a control system that energizes the electric motor only when the ram is to be cycled. At other times the motor drive shaft is stationary. This press, of course, requires a rather large and powerful motor and relatively complex motor controller. Such a motor controller is disclosed in U.S. Pat. No. 5,449,990 which issued Sep. 12, 1995 to Bowling et al. Both of these types of presses require that the press crank and ram mechanism be strong and able to accommodate the high forces required to crimp a terminal onto a conductor. As a result, the mechanisms of these presses tend to be bulky and massive, and tend to undergo substantial wear during use. Because of the tendency for these presses to be bulky, the host machines that receive these presses must themselves be larger than would otherwise be necessary. 
     In U.S. Pat. No. 3,783,662 is disclosed a magnetically actuated die closing apparatus and a control circuit therefor, utilizing reciprocating movement of a ram that is effected by energizing of the coils in a pair of electromagnets and a spring member acting in a reverse direction. The electromagnets thereby form an actuator coupled to the ram for effecting a first and a second incremental amount of movement in a first direction. Stopping of the first movement and initiation of the second movement is determined by a switch assembly mounted on the magnets. 
     What is needed is a press for operating a tooling unit, such as a terminal applicator, in the manufacture of articles wherein the press utilizes relatively light actuating components that are inexpensive to manufacture. The press should be compact for easy adaptation to host machines of relatively small size. 
     SUMMARY OF THE INVENTION 
     A press is provided for operating a tooling unit in the performance of a manufacturing operation. The press includes a frame having a platen attached thereto for receiving the tooling unit. A ram is coupled to the frame and arranged to undergo reciprocating movement in a first direction along a ram axis toward the platen a specific distance in two incremental amounts, and in a second opposite direction along the ram axis, thereby effecting the operation of the tooling unit. A first actuator is coupled to the ram for effecting a first of the two incremental amounts of movement of the ram in the first direction, while a second actuator is coupled to the ram for effecting a second of the two incremental amounts of movement of the ram in the first direction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will now be described with reference to the accompanying drawings, in which: 
     FIG. 1 is an isometric view of a press incorporating the teachings of the present invention; 
     FIGS. 2 and 3 are front and side views, respectively, of the press shown in FIG. 1; 
     FIG. 4 is a cross-sectional view taken along the lines  4 — 4  in FIG. 3; 
     FIG. 5 is a cross-sectional view taken along the lines  5 — 5  in FIG. 2; 
     FIG. 6 is an exploded parts view of the actuator shown in FIG. 5; 
     FIG. 7 is a cross-sectional view taken along the lines  7 — 7  in FIG. 3; 
     FIGS. 8 and 9 are front views similar to that of FIG. 2 showing the press in various stages of operation; 
     FIG. 10 is a graph illustrating current usage of the electromagnet and ram position with respect to time during the operation of the press; and 
     FIG. 11 is a block diagram showing the main functional elements of the magnet coil drive circuit. 
    
    
     DETAILED DESCRIPTION 
     A press  10  is shown in FIG. 1 attached to a host machine  12 , the press  10  having a frame  13  consisting of a bolster plate  14  and mounting flanges  15  cast integral thereto, and a carriage  20 . Alternatively, the frame may consist of a bolster plate with a mounting plate screwed to its underside to form the mounting flanges. The carriage  20  includes a first actuator  22 , two parallel rods  24 , and a flange  26 . The flange  26  has a pair of spaced bosses  28  having holes through which the lower ends of the rods  24  extend, as viewed in FIG.  1 . Two pins  30  extend through holes in the two bosses  28  and the rods  24  to rigidly secure the rods to the flange  26 . The opposite ends of the rods  24  extend into blind holes formed in the bottom side of a block  32  and are rigidly secured by means of screws  34  which extend through counterbored holes in the top side of the block and into threaded holes formed in the ends of the rods, as shown in FIG.  1 . The two rods  24  extend through bushings  36  that are arranged in the bolster plate  14  to permit reciprocating movement of the carriage  20  with respect to the frame  13  in a direction that is parallel to the longitudinal axes of the rods  24 , as indicated by the arrow  38  in FIG.  2 . That is, the first actuator  22 , the two rods  24 , and the flange  26  form a rigid unit that is free to move in the two directions indicated by the arrow  38 . Two clamp bars  44  and screws  46  that are threaded into the host machine  12  secure the mounting plate  40  and bolster plate  14  to the host machine. A tooling unit mounting plate  48  is secured to the top of the bolster plate  14  by means of screws  50 . The mounting plate  48  includes the usual clamps and locating surfaces, not shown, for accurately positioning and securing the tooling unit, in the present example a terminal applicator  52  shown in phantom lines in FIG.  2 . 
     A center post  56  extends downwardly, as viewed in FIG. 4, from the bolster plate  14 , through a bearing  54  pressed into a central hole in the flange  26 , through a thrust washer  57  and compression spring  72 , to a base plate  58 . A screw  60  extending upwardly through a counterbored hole in the base plate and into a threaded hole in the end of the center post  56  secures the center post to the base plate. An electromagnet  62  having an electric magnet coil  64  and poll face  66  is attached to the base plate  58  with suitable screws, the poll face  66  opposing the flange  26 . A magnet plate  68  having an attraction face  70  is attached to the flange  26  with suitable screws so that the attraction face is directly opposed to the poll face of the electromagnet, as shown in FIG.  4 . The electromagnet  62  has a close clearance hole through which the center post  56  extends, while the magnet plate  68  includes a larger central hole through which the center post  56  extends for loosely receiving the compression spring  72 . The compression spring  72  pushes against the poll face  66  and the thrust washer  57  to urge the flange  26  and the carriage  22  away from the electromagnet  62  to create the gap  74  between the attraction face  70  and the poll face  66 , as shown in FIG. 4. A collar  76  is arranged around the center post  56  and secured in place by means of a pin  78  extending through a hole in the collar and center post. The collar is positioned with respect to the center post to provide a gap  74  of a desired dimension, of about 4.826 (0.190 inch) in the present example. As will be explained below, when the coil  64  of the electromagnet is energized the attraction face  70  is pulled against the poll face  66  thereby closing the gap  74  to zero. The magnet plate  68 , electromagnet  62 , and associated energizing circuitry are referred to herein as the second actuator  80 . 
     A flanged sleeve  82  is disposed in a counterbored hole  84  formed in the under surface of the bolster plate  14 , as best seen in FIG. 4, and is held in place by screws  86  that are threaded into holes in the bolster plate  14 . The hole  84  is a blind hole having a square bottom. A jack screw  88  is positioned within the bore  84  between the end of the flanged sleeve  82  and the flat bottom of the bore with clearance so that the jack screw is free to rotate. The jack screw includes a threaded end  90  that is in threaded engagement with a threaded hole  92  formed in the end of the center post  56  opposite the end attached to the base plate. As the jack screw  88  is turned in one direction the center post  56  is forced to move away from the jack screw axially in a direction toward the base plate  58  and when turned in the other direction the center post  56  is forced to move further into the flanged sleeve toward the jack screw. This has the effect of moving the entire carriage  22 , magnet plate  68 , electromagnet  62 , and base plate  58 , with respect to the frame  13 , without altering the dimension of the gap  74 , for a purpose that will be explained. The bolster plate  14  includes a radiused periphery portion  96  that is concentric with the bore  84 , as shown in FIG.  1 . An elongated slot  98  extends through the radiused portion  96  and into the bore  84 . A screw  100  extends through the elongated slot  98  and into a threaded hole formed in the jack screw  88 . When it is desired to adjust the axial position of the center post  56 , the screw  100  is loosened, the jack screw is rotated by moving the screw  100  within the elongated slot  98  to the desired position indicated by indices  102  formed on the radiused portion  96 , and the screw is then tightened against the radiused portion to lock the center post in place. 
     As shown in FIGS. 5 and 6, the first actuator  22  includes the block  32  which has a cutout  108  formed in one face thereof between the two rods  24 . A ram  110  having a ram plate  112  is arranged so that the ram plate and two cam plates  114  and  116 , one cam plate on each side of the ram plate, are disposed within the cutout  110 . A pair of spacer block  117  are arranged on each side of the ram plate  112  between the two cam plates  114  and  116 . Two pins  113 , pressed into holes in the block  32 , extend through holes  115  formed through the two cam plates and two spacer blocks to position the cam plates within the cutout  108 . The assembly is held together by four screws  120  extending through clearance holes  122  in the cover plate and into threaded holes  124  in the block  32 . The thicknesses of the ram plate  112  and the two spacer blocks  117  are chosen so that the ram plate is free to slide vertically between the two cam plates  114  and  116 , in the directions indicated by the arrow  38  in FIG. 2, without appreciable lateral play. An air powered rotary actuator  126 , or other suitable rotary actuator, is attached to the block  32  by means of suitable screws. The actuator  126  has an output shaft  128  that is keyed to a crank  130  having an outside diameter that rotates in a bore  132  formed in the block  32 . A crank pin  134  projects from the crank  130  and extends through an arcuate cam track  136 , or circular opening, formed in each of the two cam plates  114  and  116 . The cam tracks  136  are sized to closely receive the crank pin with little play and are concentric with the bore  132 . Each end of the cam tracks  136  terminate on the left side of a vertical centerline  138 , as viewed in FIG. 7, and extends through an angle of about 200 degrees, the major portion of the cam track being on the right side of the vertical centerline  138 . The vertical centerline  138  intersects the axis of the bore  132  and defines an axis of reciprocating motion of the ram  110  in the directions indicated by the arrow  38  in FIG.  2 . The cam tracks  136  are constructed in this way for a purpose that will be explained below. The ram plate  112  includes a rectangularly shaped slot  144  containing a slide block  146 . The slide block  146  is retained within the slot between the two cam plates  114  and  116  and is free to slide laterally within the slot with respect to the vertical centerline  138 . A hole  148  is formed through the slide block  146 , the crank pin  134  extending through the hole. As the rotary actuator  126  rotates the crank  130 , the crank pin  134  causes the slide block  146  to slide laterally within the slot  144  and thereby causes the ram plate  112  to move in one of the directions indicated by the arrow  38  in FIG.  2 . The ram  110  includes a guide block  150  attached to one end of the ram plate  112 . The guide block includes bushings  36  disposed in opposite ends thereof, as best seen in FIG.  6 . The rods  24  extend through the two bushings to support and guide the ram  110  during its reciprocating movement in the directions indicated by the arrow  38  in FIG. 2. A coupling  152  is attached to the guide block  150  and includes a T-slot  154  for coupling to the ram of the terminal applicator  52  in the usual manner for operation thereof. 
     The operation of the two stage press  10  will now be described with reference to FIGS. 2, and  7  through  11 . FIG. 2 depicts the press  10  prior to beginning the crimping operation, with the press ram  110  fully retracted. The attraction surface  70  is spaced from the poll face  66  with a gap distance  74  and the crank pin  134  is in the upper portion of the cam track  136  on the left side of the vertical centerline  138 , as shown in solid lines in FIG.  7 . Note that this is an over center condition for the crank pin  134  thereby preventing the applicator ram  110  from falling downward toward the bolster plate  14  under the influence of gravity. The actual amount that the crank pin  134  is over center is unimportant, it only being necessary that the axis of the crank pin be to the left side of the vertical centerline  138 . That is, a major portion of the crank pin is to the left said of the vertical centerline  138 . To begin the operating cycle, the rotary actuator  126  is energized so that the crank  130  is caused to rotate clockwise, as viewed in FIG.  7 . As the crank rotates the crank pin  134  tracks within the cam track of both cam plates  114  and  116  causing the slide block  146  to follow within the slot  144 , thereby causing the ram plate  112  to move downwardly toward the bolster plate  14 . Movement continues until the crank pin  134  has rotated as far clockwise as possible to the position shown in FIG.  8  and the press ram  110  is fully extended as shown. Note that the crank pin  134  is now in the lower portion of the cam track  136  and to the left of the vertical centerline  138 , as shown in phantom lines at  160  in FIG.  7 . Again the crank pin  134  is in an over center position for a purpose that will be explained. As explained above, the actual amount that the crank pin  134  is over center is unimportant, it only being necessary that a major portion or the axis of the crank pin be to the left side of the vertical centerline  138 . The movement of the press ram  110  from the position shown in FIG. 2 to the position shown in FIG. 8 is referred to herein as the first incremental amount of movement and represents about 88 percent of the total movement of the press ram required to operate the terminal applicator  52 . In the present example the first incremental amount of movement is about 36.44 mm (1.435 inches). During this movement the applicator ram is caused to move toward a terminal to be crimped onto a conductor, however it does not begin crimping the terminal. Also during this movement the applicator ram, which is coupled to a feed mechanism, causes the feed mechanism to feed a terminal into alignment with the crimp tooling preparatory to performing the crimping operation. Very little power is required to rotate the crank pin  134  because the only functions being performed during this first incremental amount of movement is to operate the terminal feed mechanism. 
     At this point of the operating cycle of the press  10 , the attraction surface  70  is still spaced from the poll face  66  with a gap distance  74 . The magnet coil  64  is then energized by means of a control circuit shown in FIG.  11 . The control circuit includes a rectifier  164  interconnected to a pulse width modulation controller  166  and a current sensor  168 . A standard power source provides 120 volts AC to the rectifier which rectifies the current and outputs 170 volts DC into the pulse width modulation controller  166 . The operation of the control circuit will be best understood with reference to FIG. 10 which shows a current graph  172  and a position graph  174  with their X axes in vertical alignment, the X axes being time. The current graph  172  depicts the amount of current passing through the magnet coil  64  and the position graph  174  depicts the position of the press ram  110  during movement of the attraction face  70  toward the poll face  66 . This movement will be referred to herein as the second incremental amount of movement. To begin, the controller  166  outputs a maximum pulse width so that the current available to the magnet coil  64  is a maximum, as shown at  176  in FIG.  10 . As the current builds in the magnet coil  64  it reaches a high value at the point  178 . At this point in time the carriage  20  and attached magnet plate  68  begin to move downwardly against the upward bias of the spring  72  toward the poll face  66  as indicated at 180 thereby causing the current flow through the magnet coil  64  to peak and begin falling off as indicated at  182 . The current sensor  168  senses the current fall off and signals the pulse width modulation controller  166  to reduce the pulse width of the current passing through the magnet coil  64  to a minimum. This minimum current is maintained at a sufficient level to assure continued downward movement of the carriage  20 . By minimizing the current flow there is less of a tendency for the magnet plate  68  to violently strike the electromagnet  62 . As downward movement of the carriage continues, the tooling on the end of the applicator ram first engages the terminal to be crimped. This results in a resistance to the downward movement of the carriage  20  and causes an increase in the current passing through the magnet coil  64  as indicated at  184  in FIG.  10 . The current sensor  168  senses the current increase and signals the pulse width modulation controller  166  to increase the pulse width of the current passing through the magnet coil  64  to a maximum to provide maximum crimping force to the crimping tooling. At this point the gap  74  is reduced to zero and the magnet face  70  is against the poll face  66 , as shown in FIG.  9 . During this second incremental movement, a force of about 5000 pounds is produced at the crimp tooling. This maximum pulse width current is maintained for a specific time period and at the point indicated at  186  in FIG. 10 is cut off. The compressed spring  72  then causes the carriage  20  to move upwardly away from the electromagnet  62  until the flange  26  engages the collar  76 , to the position shown in FIG.  8 . This upward movement of the carriage is indicated at  188  in FIG.  10 . The rotary actuator  126  is then energized to rotate the crank  130  in a counterclockwise direction so that the crank pin  134  tracks within the cam track of both cam plates  114  and  116  causing the slide block  146  to follow within the slot  144 , thereby causing the ram plate  112  to move upwardly away from the bolster plate  14 . Movement continues until the crank pin  134  has rotated as far counterclockwise as possible to the position shown in solid lines in FIG.  7  and the press ram  110  is fully retracted as shown in FIG.  2 . Note that the crank pin  134  is now in the upper portion of the cam track  136  and to the over center position left of the vertical centerline  138 . 
     As will be appreciated by those skilled in the art, this relatively large crimp force of 5000 pounds generated by the second actuator  80  during the second incremental amount of movement is transferred from the ram of the terminal applicator  52  to the press ram  110 , the slide block  146 , and the crank pin  134  to the cam plates  114  and  116 . Because the crank pin  134  is in an over center position within the cam track  136 , all of the forces through the crank pin are in shear. For this reason the first actuator  22  and its component parts can be relatively light in weight and structure. The second actuator  80  is large enough to provide the relatively high crimp force of 1,865 kg (5000 pounds) but need only have a relatively short stroke of about 4.826 mm (0.190 inch). While the first actuator  22  has a relatively long stroke of about 1.435 inches it need only provide a relatively small force to operate the feed mechanism of the terminal applicator. 
     An advantage of the present invention is that the press produces a relatively high crimp force while utilizing relatively light actuating components that are inexpensive to manufacture. Additionally the press is compact for easy adaptation to host machines of relatively small size.