Abstract:
An apparatus for retention and release of pallets used in a production line system comprising pallets, means for advancing pallets, latching means, rolling means, and a rail member, wherein the latching means are pivotally coupled to the advancing means to allow pivoting of the latching means about a horizontal axis, the rolling means are affixed to the latching means, and the rail member is adapted to exert an upward force on the rolling means during advancement of the pallet for causing pivotal rotation of the latching means for sequential release of each pallet when removal of the pallet is desired.

Description:
This application claims benefit of provisional application No. 60,068,749 filed Dec. 24, 1997. 
    
    
     FIELD OF INVENTION 
     The present invention relates to the field of conveyor systems and, more particularly, relates to a pallet retention and release system for use with a conveyor chain which transports a variety of workpieces. 
     BACKGROUND OF INVENTION 
     Pallet conveyor systems are used in connection with production line systems, for example, in connection with high production grinding machines, which grind internal combustion engine blocks to transport workpieces between successive workstations enabling different operations to be performed on the workpieces and to reduce efficiency losses in handling the workpieces between the workstations. Workpieces which are handled in this manner can be placed on pallets, which are mounted on master platens which are mounted on a conveyor chain. The conveyor chain thus can transport the workpieces from workstation to workstation, enabling required operations to be performed at each workstation. 
     Most production line systems are designed to enable operations on a variety of workpieces of different dimensions to be performed. All workpieces cannot be mated to the same pallet if it is intended to handle such workpieces using a pallet conveyor system. Rather, because of dimensional differences between workpieces, each type of workpiece to be produced on a high production line often requires its own separate and unique pallet. Accordingly, when production systems must change-over to different workpieces, the conveyor system&#39;s pallets must be removed and replaced. In some circumstances, adjustments can be made to a pallet so that it can accommodate the new workpiece. 
     At other times, operations must be performed on workpieces at workstations remote from the conveyor chain and the workpiece must be removed from the conveyor chain. Once the operations are completed, it may be necessary to return the workpieces to the conveyor chain. In those cases, the pallet is removed with the workpieces from the conveyor chain and returned with the workpiece to the conveyor chain upon completion of the desired operation. 
     Pallet removal from the conveyor chain during change-over or otherwise is a time-intensive operation which causes losses to production efficiency. In removing pallets from the conveyor chain, fasteners must be manually loosened before the pallet is removed, and re-tightened when it or a new pallet is mounted back on the conveyor. 
     Accordingly, there exists a real need in the art for a pallet retention and release system which reduces the manual labour required during pallet removal and replacement and thereby reduces the time required. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a pallet retention and release system which obviates or mitigates at least one of the disadvantages of the prior art. 
     In a first aspect of the present invention, there is provided a pallet retention and release system including pallets for supporting workpieces, means for advancing the pallets, an apparatus for securing the pallets to the advancing means comprising latching means, and rolling means, and a rail member. 
     The latching means can be pivotally coupled to the advancing means to allow pivoting of the latching means about an axis having a first orientation for releasably engaging a pallet, the rolling means is affixed to the latching means, and the rail member is adapted to be engaged by the rolling means to exert a force in a direction perpendicular to the first orientation on the rolling means during advancement of the pallet in a pallet changeover area for causing pivotal rotation of the latching means for disengaging said pallet when removal of the pallet is desired. The rail member is also disengageable from the rolling means so that the latching means secure the pallet to the advancing means. 
     In the alternative, removal of the pallet can be effected while the pallet is stationary in the pallet changeover area. The rail member can exert a force perpendicular to the first orientation on the rolling means while the pallet is stationary, thereby causing pivotal rotation of the latching means for disengaging said pallet when removal of the pallet is desired. 
     In a preferred embodiment, the latching means are urged by spring means into slidable engagement with the pallet. Engagement of the rolling means by the rail member urges the latching means in an upward direction, overcoming the downward forces of the spring means, causing pivotal rotation of the latching means, and thereby releasing the latching means from engagement with the pallet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Further objects and advantages will appear from the following detailed description of the invention, taken together with the following drawings, in which: 
     FIG. 1 is a top view of an embodiment of a pallet retention and release system; 
     FIG. 2 is a transverse section, partly in elevation, taken along line  2 — 2  of FIG. 3; 
     FIG. 3 is a top view of the master platen shown in FIG. 2; 
     FIG. 4 is a side view of the master platen, the pallet, the latching means, the rolling means and the rail member shown in FIG. 2, showing the pallet in secured relationship with the master platen; 
     FIG. 5 is a side view, partly in section, taken along line  5 — 5  of FIG. 3, showing the rail member in the “down” condition; 
     FIG. 6 is a side view corresponding to FIG. 5, showing the rail member in the “up” condition; 
     FIG. 7 is an enlarged top view of the pallet retention and release system shown in FIG. 1, showing a rail release member; and 
     FIG. 8 is a side view of the rail release assembly of FIG. 7, showing three assemblies in series, showing each of the pallets in an unsecured relationship with the respective master platen. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following discussion refers to a single master platen and a single pallet, but it is generally understood that the discussion extends to a plurality of similar master platens and pallets, each of which co-operates with the same pallet retention and release system. 
     An embodiment of a pallet retention and release system is shown in FIGS. 1 and 2. As shown in FIG. 2, one embodiment of the invention includes a pair of equispaced conveyor chains  10 , a master platen  20  and a pallet  30 . The lower surface  40  of the platen  20  is specifically adapted to be secured to the conveyor chains  10  for purposes of transporting a workpiece (not shown) between workstations, such workpiece being supported by a corresponding pallet  30  which is mounted to the upper surface  45  of the master platen  20 . 
     Referring to FIGS. 1,  2 ,  3 ,  4 ,  5  and  6 , the pallet  30  is secured to the upper surface  45  of the master platen  20  with at least one latch assembly  70 . The latch assembly  70  is capable of assuming open and closed conditions. 
     The latch assembly  70  is pivotally coupled to an upright member  72 , which is secured to the master platen  20 , by means of a connecting bolt  74  which permits pivotal rotation of the latch assembly  70  about a horizontal axis  75 , about which the connecting bolt  74  is centered. A nut  76  is threadably received by the connecting bolt  74 . Although the description herein will proceed with reference to the latch assembly  70  pivoting about the horizontal axis  75 , it will be understood that the latch assembly  70  need not pivot about a horizontal axis, but can pivot about an axis which is vertical or which is oriented at an angle between horizontal and vertical. 
     The latch assembly  70  includes a lever  80  with upper  90  and lower  100  ends in substantially right-angled relationship with each other. The upper end  90  of the lever  80  terminates in a hardened locking wedge  105  whose lower surface  110  extends outward from and in substantially perpendicular relationship with the lever  80 . The lower surface  110  of the locking wedge  105  is adapted to slidably engage a hardened button  37  located on the upper surface  35  of the pallet  30  when the latch assembly  70  is in the closed position, thereby securing the pallet  30  to the master platen  20 . 
     Particularly referring to FIGS. 5 and 6, associated with the lower end  100  of the lever  80  are rolling means  120 , oriented in parallel relationship with the direction of travel of the conveyor chains  10 . The rolling means  120  are adapted to engage a release rail assembly  130 . 
     FIG. 1 shows a plan view of a series of pallets  30 , the conveyor chains  10 , a series of latch assemblies  70 , and the release rail assembly  130 . Each latch assembly  70  is shown in the closed position in FIG.  1 . 
     In a preferred embodiment, associated with the latch assembly  70  is a spring  140 , secured at either end to each of a spring housing assembly  145  and lever  80  respectively, which urges the lower end  100  of the lever  80  in a downward direction. In order for the lever  80  to pivot about the horizontal axis  75 , thereby opening the latch assembly  70 , sufficient upward forces must be applied to the lever  80  to overcome the action of the spring  140 . The configuration of the lever  80  is such that upward forces acting upon the wedge  105 , when a workpiece is being ground, are taken through the lever  80 &#39;s pivot point, i.e., the horizontal axis  75 . 
     In an alternative embodiment, a stop bar  150  can be used, as shown in FIG. 5. A stop bar  150  can be used where the spring  140  is secured in captive arrangement between the master platen  20  and rolling means  120 . The a stop bar  150  is associated with the latch assembly  70  to prevent counterclockwise pivoting (as viewed in FIGS. 5 and 6) of the lever  80  about a horizontal axis. The stop bar  150  is secured to the front surface of the upright member  72  which is secured to the lower surface  40  of the master platen  20  and extends outward, intersecting the path of the lever  80  should it pivot in the counterclockwise direction about a horizontal axis. If nothing is mounted on the upper surface  45  of the master platen  20 , the force of the spring  140  urges the lower end  100  of the lever  80  in a downward direction. Without the stop bar  150 , the lever  80  would pivot, resulting in downward displacement of the lower end  100 , eventually causing the spring  140  to decouple from the latch assembly  70 . 
     Referring to FIGS. 5,  6 ,  7  and  8 , associated with the opening of the latch assembly  70  is the release rail assembly  130  which is only engaged by the rolling means  120  when pallet  30  removal is desirable, and more particularly, in the pallet changeover area  300 . In this respect, the release rail assembly  130  is capable of assuming “up” and “down” conditions. Preferably, the release rail assembly  130  includes a longitudinally elongated rail member  160  having upper  170  and lower surfaces  175  and two ends  180   185 , adapted to facilitate rolling of the rolling means  120  from the first end  180  of the upper surface  170  to the opposite end  185  thereof. The upper surface  170  includes an upward sloping portion at the first (i.e., leading) end  180  thereof adapted to be the point of initial engagement with the rolling means  120  when the release rail assembly  130  is in the “up” condition. The upper surface  170  also includes a downward sloping portion at the second end  185  thereof adapted to permit the rolling means  120  to roll off the rail member  160  as the conveyor chain  10  advances. Preferably associated with the release rail assembly  130  are actuating means  210 , for example, a double-acting hydraulic cylinder containing a non-compressible fluid, for changing the position of the release rail assembly  130  from the “down” to the “up” condition and vice-versa. 
     In operation, to effect removal of the pallet  30 , the pallet  30  and associated master platen  20  can be advancing with the conveyor chains  10  within the pallet changeover area  300  with the release rail assembly  130  in the “up” condition. As the master platen  20  travels above the release rail assembly  130 , the rolling means  120  engage and climb the first end  180  of the upper surface  170  of the rail member  160 . The rail member  160  exerts an upward force on the rolling means  120 , overcoming the downwards force of the spring  140 , causing the lever  80  to pivot in a counter-clockwise direction (as viewed in FIGS. 5 and 6) about the horizontal axis  75 , thereby disengaging the locking wedge  105  from the hardened button  37  on the upper surface  35  of the pallet  30  and opening the latch assembly  70 . Once the wedge  105  is disposed outside the region of space above the upper surface  35  of the pallet  30 , the pallet  30  is uncoupled from the master platen  20 . At that point, movement of the conveyor chains  10  is stopped, permitting removal of the pallet  30  from the upper surface  45  of the master platen  20 . 
     In the alternative, removal of the pallet  30  can be effected while the pallet is stationary in the pallet changeover area  300 . The release rail assembly  130  can be raised by actuating means  210 , resulting in rail member  160  exerting an upward force on rolling means  120 , overcoming the downward force of the spring  140 . This causes the lever  80  to pivot in a counter-clockwise direction (as viewed in FIGS. 5 and 6) about the horizontal axis  75 , thereby disengaging the wedge  105  from the hardened button  37  on the upper surface  35  of the pallet  30  and opening the latch assembly  70 . Once the wedge  105  is disposed outside the region of space above the upper surface  35  of the pallet  30 , the pallet  30  is uncoupled from the master platen  20 , thereby permitting removal of the pallet  30  from the upper surface  45  of the master platen  20 . 
     To secure a new pallet (or re-secure the old pallet) to the master platen  20  in the pallet change-over area  300 , the conveyor chains  10  must be stationary, the region of space above the upper surface  45  of the master platen  20  defined by the perimeter of the master platen  20  must be free, and the release rail assembly  130  must be in the “up” condition. The pallet  30  is first mounted on the upper surface  45  of the master platen  20 , and then he conveyor chains  10  are engaged to move forwards. As the conveyor chains  10  move forwards, the rolling means  120  move in contact with the rail member  160  and eventually roll off the second end  185  of the rail member  160 . In doing so, the spring  140  urges the rolling means  120  in a downward direction, causing the lever  80  to pivot in a counter-clockwise direction (as viewed in FIGS.  5  and  6 ) about the horizontal axis  75 , thereby causing slidable engagement of the wedge  105  with the hardened button  37  and upper surface  35  of the pallet  30 , and thereby securing the pallet  30  to the master platen  20 . 
     Preferably, a hardened clamping button  37  is coupled to the upper surface  35  of the pallet  30  and is adapted to be slidably engaged to the wedge  105  as shown in FIG.  6 . Frequent opening and closing of the latch assembly  70  causes excessive wear to the upper surface  35  of the pallet  30 . Accordingly, it is preferable to provide a removable part, such as the hardened clamping button  37 , for slidable engagement with the wedge  105 . 
     Referring to FIG. 2, in a further preferred embodiment, a wear rail  190  is further associated with the rolling means  120  to prevent inadvertent opening of the latch assembly  70 . The wear rail  190  has a lower surface  200  adapted to remain in sliding contact with the upper edge  125  of the roller means  120  during movement of the master platen  20  by the conveyor chains  10 , except when it is necessary to remove pallets  30  in the pallet change-over area  300 . In this respect, the lower surface  200  of the wear rail  190  constrains upward movement of the roller means  120 , and thereby prevents inadvertent opening of the latch assembly  70  when unanticipated forces act upward on the lower end  100  of the lever  80 . Because the configuration of the lever  80  is such that upward forces acting upon the wedge  105  are taken through the horizontal axis  75 , the spring  140  is not required to withstand such upward forces. 
     Although the disclosure describes and illustrates preferred embodiments of the invention, it is to be understood that the invention is not limited to these particular embodiments. Many variations and modifications will now occur to those skilled in the art.