Patent Publication Number: US-2021188548-A1

Title: Tray Feeder Tray Pulling Mechanism

Description:
RELATED APPLICATION 
     The present application claims priority to Israeli Patent Application No. 271654, filed on Dec. 22, 2019, and incorporated herein by reference in its entirety. 
     FIELD 
     The present invention relates to manufacturing, and in particular to an improved tray pulling mechanism. 
     BACKGROUND 
     Tray feeders are a common way to provide parts to an assembly station. In general, tray feeders are coupled to an assembly station, and loaded with a set of trays directly or using a dedicated cart, which may handle a certain number of trays. The trays move up and down within the tray feeder. 
     In one embodiment, the following prior art process is used to pull a tray with parts from the tray feeder to make the parts available to the assembly station. First, the tray feeder moves the trays in vertical direction and stops when the correct tray is in the “loading” position. Then, a needle or puller moves toward the tray puller. The tray to be pulled is lifted up, and the needle puller moves under it. The tray to be picked up is then dropped down onto the needle puller. The needle puller than moves back out, taking with it the selected tray. The process is repeated in reverse when a tray is returned to the tray feeder, after its use. This process takes approximately 15 seconds. This is a relatively long time and makes it inefficient to pull elements from multiple trays for assembly. 
     In another prior art configuration, trays are pulled by a dedicated gripper, which, after the correct tray reaches the “loading” position, approaches the tray, and then pulls it to the assembly area. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: 
         FIG. 1A  is an illustration of one embodiment of a tray feeder including the improved tray puller. 
         FIG. 1B  is a perspective view of one embodiment of the tray pulling portion of the tray feeder. 
         FIG. 1C  is a perspective view of the tray pulling portion of the tray feeder of  FIG. 1B . 
         FIG. 1D  is a front view of one embodiment of the tray array. 
         FIG. 1E  is a top view of one embodiment of the tray pulling portion of the tray feeder. 
         FIG. 1F  is a perspective view of one embodiment of the gripper used to pull the trays from the tray feeder. 
         FIG. 2  is a simplified diagram of some alternative configurations of the gripper. 
         FIG. 3  illustrates some alternative configurations of the tray including various tray grips. 
         FIG. 4  is a flowchart of one embodiment of using the tray puller. 
     
    
    
     DETAILED DESCRIPTION 
     Tray feeding systems allow the following functionality: 
     1) extracting of the trays of processed parts from tray feeder, 
     2) precise positioning of trays in the assembly station working area, 
     3) return of the emptied trays to the cart. 
     The improved tray feeding system allows a significant decrease of the overall process cycle time by eliminating a need of an array of trays or tray cart intermediate motion for releasing the returned tray, removing the gripping mechanism from the cart moving zone, return of the gripping mechanism and lowering the cart onto the gripping mechanism. This is accomplished by creating an improved design which allows a vertical motion of the trays while the gripping mechanism is prepositioned in the gripping area of the tray, and thus permits the nearly instantaneous removal of the tray when the vertical motion of the tray array stops, with the correct tray positioned in the loading position. 
     In one embodiment, each tray includes handles, which extend from the tray area. The handles may be any shape that has a gap in the middle and undercuts from both sides. The gap provides a path for the puller, which provides the motive power for the gripper. The undercuts are the areas where the gripper contacts the tray, to pull it. In one embodiment, the handles create a cavity which defines the gripping area, where the gripper is prepositioned when it is not pulling out a tray. The handles, in one embodiment, are integral with the tray. In one embodiment, the handles may be separately attached to the tray. 
     To pull out a tray, the gripper simply has to move, when the tray is correctly positioned for pulling. The gripper engages with the tray handle and pulls out the tray. To return the tray to the tray feeder, in one embodiment, after the gripper delivers the tray to the appropriate assembly location, the gripper pushes the tray back into an empty slot in the tray array. In one embodiment, the entirety of this process, from pulling out the tray to returning the gripper to the ready position can take less than 8 seconds, depending on the tray size and payload. 
     The following detailed description of embodiments of the invention makes reference to the accompanying drawings in which like references indicate similar elements, showing by way of illustration specific embodiments of practicing the invention. Description of these embodiments is in sufficient detail to enable those skilled in the art to practice the invention. One skilled in the art understands that other embodiments may be utilized and that logical, mechanical, electrical, functional and other changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. 
       FIG. 1A  is an illustration of one embodiment of a tray feeder including the improved tray puller. The tray feeder  100  is an apparatus that provides trays including parts to an assembly station. The assembly station may be a robotic assembly system. The tray feeder includes a tray array  110  with a number of trays which are moved vertically up and down. There is a loading position, from which a path to the assembly station extends. A tray in the “loading position” may be removed to be moved to the assembly station. In general, the tray feeder  100  has numerous trays, and the trays include parts used by the assembly system. The trays are tracked, and the appropriate tray with the parts needed next is pulled. 
       FIG. 1B  is a perspective view of one embodiment of the tray pulling portion of the tray feeder. For better visual representation the tray feeder itself has been removed, showing a “floating” tray array  110 . The trays in the tray array are moved up and down by the tray feeder (not shown). When the movement stops, the tray in the loading position  120  is removed. This is done by the gripper  150 . 
     Gripper  150  resides in the gripping area  145  defined by the tray handles  135 . In one embodiment, the gripper  150  is inserted into the tray feeder initially, and when it is not pulling out a selected tray  130  it is pre-positioned in the gripping area. The gripper does not impede the vertical movement of the trays in the tray array. The vertical movement stops when the correct tray is in the loading position. At that point, the gripper moves out, pulling with it the selected tray  130 . Because the gripper is pre-positioned in the gripping area, there is no wait time to move the gripper into position to remove the tray once the vertical movement stops. 
       FIG. 1C  is a perspective view of the tray pulling portion of the tray feeder of  FIG. 1B . This illustration shows the tray supports  165 , which support the sides of the selected tray  130  when is being pulled by gripper  150 . The puller  160 , in one embodiment, is a belt-based puller. The gripper  150  in one embodiment rides along a rail  180 . 
       FIG. 1D  is a front view of one embodiment of the tray array. As can be seen, the gripper  150  resides in the gripping area  145  of the tray array  110 . The front view shows the rail and puller associated with the gripper  150 . 
       FIG. 1E  is a top view of one embodiment of the tray pulling portion of the tray feeder. In this case, the tray array  110  shows only one tray, since the trays are vertically stacked. The gripper  150  is pre-positioned in the gripping area  145 . The portion of the path to the assembly station  115  is shown, as are the tray supports  165 . This is the configuration prior to the gripper  150  pulling out a selected tray. 
       FIG. 1F  is a perspective view of one embodiment of the gripper used to pull the trays from the tray feeder. The gripper  150  in one embodiment includes two gripper extensions  170 . The gripper extensions  170  are the portions of the gripper  150  that engage with the selected tray for pulling it out, and for returning it. In one embodiment, the gripper extensions  170  are regular bearings. In one embodiment, the shape of the undercut in the tray (the handles) and the shape of the gripper extensions engaging with the handle are closely matched. This means that the tray cannot slip. In another embodiment, the gripper extensions  170  have a non-slip exterior  175  to ensure that the tray does not slip. 
       FIG. 2  is a simplified diagram of some alternative configurations of the gripper. The purpose of the gripper is fit within the gripping area, and to have a secure grip on the tray for pulling the tray out of the tray feeder, to take the tray to the staging area for the assembly station, and for pushing the tray back into the tray feeder. The actual shape of the gripper is not limited. Some grippers may include a separate gripper extension extending from the sides of the gripper body, which engages with the tray. Others may have the body of the gripper serve that purpose. The actual shape of the gripper extensions is not limited. Any shape which can securely engage with a tray may be used. In one embodiment, the portion of the gripper which engages with the tray has a non-slip coating. In one embodiment, that coating is rubber. In one embodiment, the shape of the gripper extensions (or portion of the gripper which engages with the tray handles for pushing and pulling the tray) is closely matched to the shape of the handles of the tray. 
     In one embodiment, the space between the portion of the gripper that engages with the tray and the tray handles is less than a millimeter. In one embodiment, the space is between 0.1 mm and 1 mm. In one embodiment, the distance between the gripper and then handles is between 1 mm and 10 mm. In one embodiment, in such case, a tray fixation device is used at the assembly station to stabilize the tray while in use. After the gripper moves the tray to the work area in the assembly station, a tray fixation device is used to stabilize the tray, because the gap provides “play” and enables movement of the tray during use. So, in one embodiment, the tray is fixed in place with an additional device. In one embodiment, then the tolerances are sufficiently tight to keep the tray from having any play, the tray fixation device does not need to be used because the gripper provides stabilization for the tray. 
       FIG. 2  illustrates some exemplary shapes for the body of the gripper  220 ,  245 ,  765 , the gripper extensions  230 ,  250 , and the tray contact areas  235 ,  260 ,  265 ,  280 ,  285 . In one embodiment, the shape of the gripper extensions  230 ,  250  are closely matched to the undercut in the trays. In one embodiment, the tray contact areas have a non-slip coating to ensure that the gripper securely engages with the selected tray. In one embodiment, the gripper is designed such that the contact area of the gripper is in close proximity to the gripper handle when the gripper is positioned within the gripping area. This ensures that when the gripper starts moving, the tray moves with it, rather than having a collision between a moving gripper and the tray handle. These gripper shapes and configurations are merely exemplary, and one of skill in the art would understand that the shape of the gripper and gripper extensions is not limited by the shapes shown. Rather, any shape that provides sufficient contact area for the tray, and sufficient stability for pushing and pulling may be used. 
       FIG. 3  illustrates a simplified illustration of some alternative configurations of the tray including various tray handles or grips. The purpose of the tray is to provide a standard surface for carrying elements to an assembly station. The size of the tray is defined by the tray feeder&#39;s configuration. Each tray has a handle, and the cavity defined by the handles is the space where the gripper rests when no tray has been removed. Each tray includes a substantially identical handle, defining a substantially identical cavity. However, the actual shape of the handle and thus the shape of the gripping area is not limited. Any shape having an undercut with which the gripper can engage, and a gap enabling the puller to pull the gripper, may be used. The size of the handles may also vary, as long as they are sturdy enough to support the tray for pulling out. 
       FIG. 3  illustrates some exemplary handle configurations, including square handles  315 , extending from tray  310 . The handles  325  may be rounded, as shown in tray  320 . The handles  335  may be triangular as shown with tray  330 . The handles  345  may be cut into the tray rather than extending from the tray, as shown in tray  340 . The handles  355  may be quite thin, as shown in tray  350 . There may be more than one set of handles  365  as shown in tray  360 . For configurations with more than one handle, each handle has an associated gripper, and in one embodiment the grippers move in unison. These tray shapes are merely exemplary, and one of skill in the art would understand that the shape of the tray handles is not limited by the shapes shown. Rather, any shape that provides sufficient contact area for the gripper, and sufficient stability for pushing and pulling may be used. However, the tray shapes must be consistent within a tray loader, in one embodiment. 
       FIG. 4  is a flowchart of one embodiment of using the tray puller. The process starts when the tray feeder is initially assembled. The gripper is pre-positioned in the gripping area. The trays are loaded, at block  420 . In one embodiment, trays are loaded from above or below. 
     At block  430 , the tray feeder is operative, with trays loaded, and the tray gripper pre-positioned in the gripping area. 
     At block  440 , a request for a tray is received. The tray is identified, in one embodiment, by number or another identifier. The request, in one embodiment, is received from the assembly station which utilizes the parts on the trays. In one embodiment, the request may be generated automatically when a used tray (which may be empty or not) is returned to the tray array. For example, the sequence of trays may be pre-programmed/preset, and thus the tray feeder may automatically move the next tray in the assembly sequence to the loading position, when a tray is returned. 
     At block  450 , the tray array is moved vertically within the tray feeder, to position the requested tray in the loading position. The loading position is aligned with the path to the assembly station. 
     At block  460 , the gripper pulls out the tray in the loading position. This may occur very rapidly after the vertical movement stops. The gripper engages with the tray handles and pulls the tray to the correct position for the assembly station. In one embodiment, the puller is activated, which moves the gripper and thus the tray from the tray area, by receiving a signal from the tray feeder that the correct tray is in the loading position. In another embodiment, the puller is automatically activated when the vertical motion stops, without a separate signal. Because the gripper is prepositioned in the gripping area, there is no necessary delay prior to the removal of the tray, for moving the gripper into place. 
     At block  470 , upon reaching the destination, the tray gripper stops, remaining in place while the tray is in use. In one embodiment, the tray may be locked in place while it is in use. 
     At block  480 , when the tray is empty, or the use is ended, the gripper returns the tray to the tray feeder. In one embodiment, the now-empty tray is placed in the same slot from which it was removed, returning the gripper to the gripping area. In another embodiment, the tray may be returned to any empty slot in the tray feeder. This enables the substitution of a new tray arrays, while a tray is in use. If a tray array is substituted while a tray is in use, the new tray array includes one empty slot, into which the currently active tray is returned. In this way, the assembly process can continue without interruption, when the last tray has been pulled from a tray array. 
     The process continues to block  430 , with the gripper positioned in the gripping area, and ready to pull the next tray when a request is received. In this way, the system speeds up the tray pulling and returning process, by eliminating the period between when the vertical motion of the trays stops and when the gripper is ready to pull out the tray. In one embodiment, this reduction in takt time may be significant, especially if trays are pulled multiple times in a single assembly process. 
     In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.