Abstract:
A transfer device combines an advance-return drive mechanism and a clamp-unclamp drive mechanism. The transfer device operates from only one side of a press to position both drive mechanisms above a pair of feed bars thereby greatly reducing spatial constraints and costs and enabling an increase in speed. The feed bars operate to process a work piece along a process direction. The feed bars are cantilevered from the transfer device for easy use with a press, raw materials feeder, and product gatherer.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a transfer device for a press having multiple processing stages. More specifically, the present invention relates to a transfer device that conducts progressive processing on an upstream side, separates a product from a product skeleton on the way, and thereafter conducts transfer processing on a downstream side. 
     2. Description of the Related Art 
     In recent years, productivity improvements have required pressing and processing increasingly complex shapes. Additionally, manufacturers have demanded increased precision, reduced up-front equipment costs, increased processing speed, and reduced installation and operation space. 
     As one example of this demand, a plurality of processing steps are now frequently required for a single press. In this example, a production format calls for progressive processing on an upstream side and transfer processing on a downstream side. In this production format, a general transfer device is often used since only the transfer process is conducted with great frequency. In this type of general transfer device, a unit case houses a drive mechanism module for feed bars installed on both sides of the press. In this type of general transfer device, the unit cases that control the feed bars are installed below the feed bars creating transfer problems. 
     Where transfer processing frequency is low and progressive processing frequency is high, the above described general transfer device of the prior art is inadequate. Here, when a unit case is installed on an upstream side surface of the press, the distance from a material supply opening of a coil feeder to a first processing stage is long. This type of construction results in increased waste after processing is conduced. The increased waste increases costs. 
     Further, the long distance reduces feeding precision and negatively effects processing precision. This construction requests unit cases provided on each side of the processing area and necessitates speciality manufacturing, thus increasing costs. 
     Finally, since the unit cases are installed below the feed bars, space for conveyor equipment, product removal equipment, and a product receiving equipment is reduced. 
     OBJECTS AND SUMMARY OF THE PRESENT INVENTION 
     It is an object of the present invention to provide a transfer device with improved productivity, reduced installation space, and reduced costs of production and purchase. 
     It is another object of the present invention to provide a transfer device with a unit case positioned above feed bars to increase space availability, speed processing, and reduce waste. 
     It is another object of the present invention to provide a transfer device with a unit case on only one side of a press to increase space, reduce costs, and increase supply and process precision. 
     It is another object of the present invention to provide a transfer device with feed bars supported on only one side. 
     It is another object of the present invention to provide a transfer device with a unit case that internalizes and protects a drive mechanism module. 
     It is another object of the present invention to provide a transfer device that easily accommodates a removal conveyor. 
     It is another object of the present invention to provide a transfer device that includes a drive mechanism combining an advance-return drive mechanism and a clamp-unclamp drive mechanism. 
     It is another object of the present invention to provide a transfer device that accommodates a safety sensor to prevent damage to the device upon an error in transfer. 
     Briefly stated, the present invention relates to a transfer device that combines an advance-return drive mechanism and a clamp-unclamp drive mechanism. The transfer device operates from only one side of a press and positions both drive mechanisms above a pair of feed bars greatly reducing all spacial constraints and costs. The feed bars operate to process a work piece along a process direction. The feed bars cantilever from the transfer device for easy use with a press and raw materials feeder or product gatherer. 
     According to an embodiment of the present invention, there is provided, a transfer device, conducting multiple processing steps along a process direction of a press, comprising: means for driving the transfer device, means for feeding an external workpiece along the process direction, the feeding means cantilevered from one side of the driving means, the feeding means below the driving means, the driving means including a first and second operating means, the first operating means controlling the feeding means along the processing direction, a second operating means controlling feeding means perpendicular to the processing direction, and the first and second operating means operating together whereby the transfer device processes the external workpiece from an upstream side to a downstream side and is simplified and reduced in cost and size. 
     According to another embodiment of the present invention, there is provided, a transfer device wherein: the driving means operates on a first side of the press, the feeding means extends below the driving means, the first operating means controls the feeding means in an advance-return motion, and the second operating means controls the feeding means in a clamp-unclamp motion. 
     According to another embodiment of the present invention, there is provided, a transfer device, further comprising: slider means for slidably directing the feed bars in the advance-return motion. 
     According to another embodiment of the present invention, there is provided a transfer device, further comprising: a bushing, a nut, and a slider on the slider means, the slider and the bushing perpendicular to the feeding means, at least one guide shaft slidably supporting the bushing and the slider in the advance-return motion, a first ball screw shaft extending parallel to the feed bars, the nut threadably engaging the first ball screw shaft, a first drive source rotatably engages the first ball screw shaft, and the nut rotatively controls the slider in the advance-return motion whereby the external work piece processes along the process direction. 
     According to another embodiment of the present invention, there is provided a transfer device, further comprising: cart means for slidably supporting the feeding means in the advance return motion and conducting the clamp-unclamp motion whereby the external work piece processes along the process direction. 
     According to another embodiment of the present invention, there is provided a transfer device, further comprising: at least first and second carts in the cart means, a second ball screw shaft extending perpendicular to the feeding means between the first and second carts, the second ball screw shaft being reverse threaded at a midpoint to the process direction, a second nut on each cart, each second nut threadably engaging the second ball screw shaft, and a second drive source rotatably engaging the second ball screw shaft and rotatably controlling each cart and the feeding means in the clamp-unclamp motion whereby the external work piece processes along the process direction. 
     According to another embodiment of the present invention, there is provided a transfer device further comprising: an end plate affixed to an inside portion of each the cart, a spring resiliently retained between each second nut and each end plate, the second ball screw shaft extending through each end plate and each spring, a first bracket affixed to the cart opposite each end plate, and the springs providing a spring force through the second nut to the first bracket whereby the spring resiliently urges the second nut against the first bracket. 
     According to another embodiment of the present invention, there is provided a transfer device, further comprising: sensor means for detecting a separation between the first bracket and the second nut, control means for controlling the press and the transfer device, the sensor means producing a signal to the control means on the separation, and the control means detecting the signal and stopping the press and the transfer device whereby damage to the drive mechanism and the feed bars is eliminated and costs are reduced. 
     According to another embodiment of the present invention, there is provided a transfer device, further comprising: sensor means for detecting a failure to operate the feeding means, control means for controlling the press and the transfer device, the sensor means producing a signal to the control means on the failure to operate, and the control means detecting the signal and stopping the press and the transfer device whereby damage to the driving means and the feeding means is eliminated and costs are reduced. 
     According to another embodiment of the present invention, there is provided a transfer device, conducting multiple processing steps along a process direction of a press, comprising: a drive mechanism having a case, a pair of feed bars cantilevered from one side of the drive mechanism, the feed bars cantilevered in the processing direction, the feed bars extending below drive means, the drive mechanism including a first and second operating means, the first operating means operating the feed bars along the processing direction in an advance-return motion, a second operating means operating the feed bars perpendicular to the processing direction in a clamp-unclamp motion, and the drive mechanism on a first side of the press and driving the first and second operating means whereby the feed bars processes an external workpiece along the processing direction and the transfer device is simplified and reduced in size. 
     According to another embodiment of the present invention, there is provided a transfer device, further comprising: a slider slidably supporting the feed bars in the advance-return motion, the slider including a bushing and a nut, the slider and the bushing perpendicular to the feed bars, at least one guide shaft slidably supporting the bushing and the slider in the advance-return motion, a first ball screw shaft extending parallel to the feed bars, the nut threadably engaging the first ball screw shaft, a first drive source rotatably engages the first ball screw shaft and the nut rotatively controls the slider in the advance-return motion whereby the external work piece processes along the process direction. 
     According to another embodiment of the present invention, there is provided a transfer device, further comprising: a cart slidably supports each feed bar in the advance-return motion, a second ball screw shaft extending perpendicular to the feed bars to each cart, the second ball screw shaft being reverse threaded at a midpoint to the process direction, a second nut on each cart, the second nuts threadably engaging the second ball screw shaft, and a second drive source rotatably engages the second ball screw shaft and the second nuts rotatably control the carts and the feed bars in the clamp-unclamp motion whereby the external work piece processes along the process direction. 
     According to another embodiment of the present invention, there is provided a transfer device, further comprising: an end plate affixed to an inside portion of each cart, a spring resiliently retained between each second nut and each end plate, the second ball screw shaft extending through each end plate and each spring, a first bracket affixed to the cart opposite each end plate, and the springs urging a spring force through the second nut to the first bracket whereby the second nut is resiliently urged against the first bracket. 
     According to another embodiment of the present invention, there is provided a transfer device, further comprising: a sensor, a control means for controlling the press and the transfer device, the sensor detecting a separation between the first bracket and the second nut, the sensor producing a signal to the control means on the separation, and the control means detecting the signal and stopping the press and the transfer device whereby damage to the drive mechanism and the feed bars is eliminated and costs are reduced. 
     According to another embodiment of the present invention, there is provided a transfer device, for use in press that conducts pressing by a plurality of processing steps along a feed direction, comprising: a pair of feed bars extending parallel to a feed direction, a drive module, the drive module being of a type that drives the feed bars to conduct transporting motions of a workpiece, the drive module being of a type that supports one end of the feed bars, a unit case that internalizes the drive mechanism module, the unit case on one side surface of the press, and the unit case above the feed bars whereby the transfer device is made smaller, at a reduced cost, while increasing precision and efficiency. 
     According to another embodiment of the present invention, there is provided a transfer device, further comprising: the drive module includes an advance-return drive module and a clamp-unclamp drive module, the advance-return drive module being of a type operating the feed bars along the feed direction, the clamp-unclamp drive module being of a type operating the feed bars perpendicular to the feed direction, and the drive module coordinating the advance-return drive module and the clamp-unclamp drive module whereby transfer device moves an external work piece along the feed direction. 
     According to another embodiment of the present invention, there is provided a transfer device, further comprising: a slider that slidably supports the feed bars in the feed direction, a bushing on the slider, a guide shaft slidably joined to the bushing and the slider, the guide shaft slidably supports the slider along the feed direction, a first ball screw shaft, a first nut on the slider, the first nut threadably engages the first ball screw shaft, and a first drive source rotatably controlling the first ball screw shaft and the slider whereby the advance-return drive module operates and transfers the external work piece along the feed direction. 
     According to another embodiment of the present invention, there is provided a transfer device, further comprising: at least one cart, the cart slidably supports each the feed bars along the feed direction, a second nut operably attached to each the cart, a second ball screw shaft perpendicular to the feed direction, the second ball screw shaft threadably engages each the second nut, the second ball screw shaft reverse threaded about a center line of the feed direction, and a second drive source rotatably controlling the second ball screw shaft and each cart whereby the clamp-unclamp module operates and transfers the external work piece along the feed direction. 
     According to another embodiment of the present invention, there is provided a transfer device, further comprising: an end plate, the end plate affixed to each the cart, a spring on the second ball screw shaft, the spring resiliently retained on between the each end plate and each the second nut, a bracket, the bracket affixed opposite the end plate on the cart, the springs resiliently urging each second nut against each bracket, and a sensor being of a type that detects a separation of the second nut from the bracket and sends a signal that stops the transfer device and the press whereby the transfer device and the press are protected from damage. 
     According to another embodiment of the present invention, there is provided a transfer device, wherein: a coil feeder is on an upstream side of the press, the transfer device is on a downstream side of the press, and the transfer device progressively transfers an external work piece from the coil feeder through the press to an offload station whereby the transfer device increases operational precision, minimizes operational costs, reduces the equipment size, and reduces waste material. 
     The above, and other objects, features, and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 is a front view of an embodiment of the present invention. 
     FIG. 2 is cross-section along line  2 — 2  of FIG.  1 . 
     FIG. 3 is a right side view of FIG.  1 . 
     FIG. 4 is a cross-section along line  4 — 4  of FIG.  1 . 
     FIG. 5 is a detailed drawing of a section of FIG.  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, a press  2  includes a bed  3  and a bolster  4 , opposite a slide  6 . A portion of a column  5  guides a slide  6  during operation. A transfer device  1  is positioned at one side of press  2 . 
     During operation, a die (not shown) is positioned between slide  6  and bolster  4 . A coil feeder (not shown) is positioned on the opposite side of press  2  from transfer device  1 . The coil feeder provides raw material for processing. 
     The die includes multiple processing steps. Progressive processing is conducted on an upstream side and transfer processing is conducted on a downstream side. In operation, the supplied coil material is progressively processed on the upstream side to an intermediate step, where a product and skeleton are separated, and the product is thereafter transfer processed on the downstream side. 
     A conveyor  11  is positioned below transfer device  1 . In a final processing step, a product is placed on top of conveyor  11 . Conveyor  11  moves the product to the outside of press  2  for removal and later processing. 
     A unit case  7  is on one side (right shown) of press  2 . A drive mechanism module  8  is internalized in unit case  7 . Drive mechanism module  8  actuates a pair of feed bars  9 . Drive mechanism module  8  includes an advance return drive mechanism module  50  that drives feed bars  9  in an advance-return motion. Drive mechanism module  8  also includes a clamp-unclamp drive mechanism module  100  that drives feed bars  9  in a clamp-unclamp motion. 
     A cover  7   a  is on unit case  7 . Feed bars  9  extend in a cantilever manner from transfer device  1 . Receiving stands  10  may be optionally provided to support the ends of feed bars  9  but are not required in a preferred embodiment. Receiving stands  10  are not required for operation but may be included to provide additional security and support in heavy operating situations. 
     A servo motor  51  is on top of unit case  7 . Servo motor  51  is a drive source for advance return drive mechanism module  50 . A pulley  52  is provided on a drive shaft of servo motor  51 . 
     A ball screw shaft  53  is in unit case  7 . Ball screw shaft  53  is parallel with the advance-return direction (to the left-right in FIGS.  1  and  2 ). Ball screw shaft  53  is supported by a bearing  54   a  and a bearing  54   b  provided on unit case  7 . 
     A pulley  55  is affixed to one end of ball screw shaft  53 . A belt  56  connects pulley  55  to pulley  52 . A drive force of servo motor  51  is transferred to ball screw shaft  53  by belt  56  and pulleys  52 ,  55 . A slider  57  is included in advance return drive mechanism module  50 . 
     Two guide shafts  60  are in unit case  7  parallel to the advance and return direction of feed bars  9 , as will be explained. 
     Additionally referring now to FIG. 3, a nut  58  is affixed to the center of an upper part of slider  57 . Nut  58  and ball screw shaft  53  are screwed together. A guide module  57   a  and a guide module  57   a  are on both sides of nut  58 . Guide modules  57   a  include a central hole (not shown). A bushing  59  and a bushing  59  are in the central holes passing through guide modules  57   a.    
     Guide shafts  60  are parallel to the direction of advance and return movement in unit case  7  and serve to guide bushings  59  and guide parts  57   a  during operation. Bushings  59 , in guide parts  57   a , are slidably joined to guide shafts  60 . It should be understood, that additional guide shafts  60 , and operating elements may be provided depending upon manufacturer need and processing demand. 
     A groove  57   b  is on a lower part of slider  57 , in parallel with the clamp-unclamp direction. Lower parts of a pair of holders  61  operably affix the ends of feed bars  9 . The upper parts of holders  61  are slidably supported in the clamp-unclamp direction by groove  57   b.    
     Additionally referring to FIG. 4, a servo motor  101  is on a top portion of unit case  7 . Servo motor  101  serves as a drive source for clamp-unclamp drive mechanism  100 . A pulley  102  is on a drive shaft of servo motor  101 . 
     A ball screw shaft  103  is in unit case  7  in a direction parallel to the clamp-unclamp direction. Ball screw shaft  103  is operably supported on both ends by a bearing  104   a  and a bearing  104   b . A pulley  105  is on one end of ball screw shaft  103 . A belt  106  connects pulley  105  and pulley  102 . Belt  106  transmits the drive force of servo motor  101  to ball screw shaft  103 . The direction of threading on ball screw shaft  103  changes to an opposite direction at a midpoint to the feed direction shown in FIG.  2  and assists the clamp-unclamp operation, as will be explained. 
     Carts  107  are on clamp-unclamp drive mechanism module  100 . Joining parts  107   a  are on an upper part of carts  107 . Joining parts  107   a  include a through hole. Cam followers  115  are on a lower parts of cars  107 . Cam followers  115  guide feed bars  9  in the advance-return direction, as will be explained. 
     Additionally referring now to FIG. 5, a nuts  108  and ball screw shaft  103  are screwed together. Nuts  108  slidably join with the hole in joining parts  107   a.    
     A pair of springs  110  are provided between nuts  108  and end plates  109 . End plates  109  are affixed to the side surface of the inner side of joining parts  107   a . Brackets  112  are affixed on the side surface of the outer side of joining parts  107   a , by spacers  111 . Spacers  111  are hollow, as will be explained. 
     Spacers  111  pass through holes  108   b  on flange parts  108   a  of nuts  108 . Bolts  113 , tighten and sandwich spacers  111  between the side surface of the outside of carts  107  and brackets  112 . Holes  108   b  have an inside diameter slightly larger than the diameter of spacers  111  to allow operation of a safety sensor, as will be explained. Bolts  113  are inserted in spacers  111  and placed in a radiating manner. 
     The extending spring force of springs  110  maintains contact between the side surfaces on the outside of flange parts  108   a  of nuts  108  are in contact with brackets  112 . It is to be understood, that the outward movement of nuts  108  is restricted by brackets  112 . Springs  110  are compressed between nuts  108  and end plates  109 . 
     At least one sensor  114  is affixed to brackets  112 . In the present embodiment, multiple sensors  114  are proximity switches. Holes  112   a  are on brackets  112  and accommodate sensors  114 . Sensors  114  measure the distance from sensors  114  to the surface where flange parts  108   a  contact brackets  112 . 
     The movement of nuts  108 , defined as flange parts  108   a  separating from brackets  112 , can be detected by sensors  114 . It is to be understood, that as long as sensors  114  can detect the movement of nuts  108  the specific type or position of sensor  114  is not critical. 
     It is to be understood that in advance-return mechanism module  50 , during advance-return motion, ball screw shaft  53  rotates via belt  56  in a direction dictated by servo motor  51 . Thereupon, nut  58  moves in the direction indicated, and, slider  57  also moves along guide shaft  60  in the same direction. Holders  61  move in a similar manner. Feed bars  9  conduct an advancing motion (or a returning motion). During the advance or retreat motion, cam followers  115 , on the lower parts of carts  107  guide feed bars  9 . 
     It is to be understood that in clamp-unclamp mechanism module  100 , during clamp-unclamp motion, ball screw shaft  103  rotates via belt  106  in a direction controlled by servo motor  101 . Since the direction of the threading on ball screw shaft  103  changes at the midpoint in the feed direction, nuts  108  move closer to each other. In the opposite direction, nuts  108  move further away from each other. The motion of nuts  108  dictates the motion of carts  107 . Feed bars  9  are fixed in the clamp-unclamp direction by cam followers  115 . As a result, feed bars  9  conduct a clamping or unclamping motion. In parallel with the this motion, holders  61  also move relative to each other along groove  57   b.    
     With the above construction and motions, transfer device  1  can transport a workpiece through a work process. In the present invention, the advance-return motion and the clamp-unclamp motion are combined to securely transport a work piece from an upstream to a downstream side of a work process. 
     In the clamp motion described above, the workpiece is gripped, and the feed bars are advanced, and the workpiece is transported one pitch distance. By the unclamping motion, the workpiece is released and is pressed. The feed bars are then returned to their original positions. This series of clamp-unclamp motions is repeated throughout the process. 
     It is to be understood that the present invention may transport work pieces of variable weight and size. Feed bars  9  are designed to accommodate generous sizes and shapes. Holders  61  operate to support feed bars  9  during regular operation. If holders  61  cannot support feed bars  9 , by reason of work piece weight, it may be beneficial to the process to additionally provide receiving stands  10  upon customer request. Receiving stands extend from a top of bolster  4  below the area near the end of feed bars  9 . Receiving stands  10  slidably support the ends of feed bars  9 . 
     It is to be understood, that the length of feed bars  9  is shown at an intermediate point in the die area. During normal operation a coil feeder (not shown) or other feeder is on the upstream side of transfer device  1 . Progressive processing is conducted on the upstream side, and transfer processing is conducted on the downstream side. 
     With the current transfer device  1 , since there is no second unit case  7  on the upstream side, the distance from a material supply opening, from a coil feeder to the die area is shortened. As a result, the amount of residual material at completion of processing is reduced. Further, the shortened supply distance enables precise materials supply. 
     Furthermore, because space is available below unit case  7 , the removal of the product can also be conducted easily by placing product removal conveyor  11  below unit case  7 . This enables close association between transfer device  1  and conveyor  11  and further reduces the equipment footprint. This reduction in footprint means that more presses  2  may be positioned close together and small floor space utilized for the same output. 
     During a clamping motion, a foreign object may be inappropriately positioned between feed bars  9 . This situation most frequently occurs during die adjustment when feed bars  9  or fingers (not shown) on feed bars  9  contact the dies. This situation may also occur where a product is in appropriately misplaced in transfer device  1 . 
     Where a foreign object is between feed bars  9 , feed bars  9  can no longer move. As a result, carts  107  can no longer move. However, since servo motor  101  continues to operate, ball screw shaft  103  tries to rotate. Due to the rotation of ball screw shaft  103 , nuts  108  try to move closer to each other. Because carts  107  do not move, only nuts  108  move opposing the expanding force of springs  110  that are trying to extend. 
     Thereupon, the surface, where flange parts  108   a  contact brackets  112 , separates from brackets  112 . A distance H is defined as the distance nuts  108  move when a foreign object blocks the movement of carts  107 . Distance H is detected by sensors  114  that generate a detection signal. The detection signal is sent to a control device (not shown) of transfer device  1  and press  2 . The control device immediately stops transfer device  1  and press  2 . As a result, damage is the mechanical structures of transfer device  1 , particularly drive mechanism module  8  and feed bars  9 , is prevented. 
     It is to be understood, that through the combination of reduced equipment needs and reduced failure rates, equipment costs are greatly reduced. Specifically, compared to related art, the manufacturing cost of unit case  7 , attachment stays, other equipment, and failure losses is halved. This is a surprising result since total costs are seldom so dramatically reduceable. 
     It is to be further understood that since unit case  7  is positioned above feed bars  9 , a product removal conveyor  11  or product removal by loading of the products by a bucket or cart is easily conducted. The simplified removal further increased final product precision and reduces failure rates by enabling quick removal of the final product and any residual material in press  2 . 
     It is to be further understood that the simplified transfer device  1  of the present invention is only one side of press  2 , it greatly reduces overall size, eases repairs, and increases precision without any of the detractions of the related art described above. This great reduction in size, ease of repair and increase of precision is additionally surprising. 
     Although only a single or few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiment(s) without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described or suggested herein as performing the recited function and not only structural equivalents but also equivalent structures. Thus although a nail and screw may not be structural equivalents in that a nail relies entirely on friction between a wooden part and a cylindrical surface whereas a screw&#39;s helical surface positively engages the wooden part, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. 
     Having described preferred embodiments of the invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.