Abstract:
A mechanism for forming thin metallic skin enclosures from blanks. The apparatus includes a forming assembly including a plurality of die stations. The stations are stepped farther away from an axis in a direction of which blanks being processed are positioned at a plurality of die stations. Grippers spaced along the axis and away from the axis at distances substantially the same as are die stations are carried by the transfer assembly. An actuator is used to move the transfer assembly reciprocally in directions generally parallel to the axis between first and second axial positions. A ram is provided to move the transfer assembly between first and second stepped positions relative to the axis.

Description:
TECHNICAL FIELD 
     The present invention deals broadly with the field of tool and die technology. More narrowly, however, it deals with the forming of multiple, thin metallic skin enclosures from blanks. Even more narrowly, it deals with forming cases defined by a thin metallic skin. A specific focus of the invention is an apparatus and method for forming battery casings by progressively stamping a plurality of blanks at sequenced die stations. 
     BACKGROUND OF THE INVENTION 
     Various machines are known in the prior art for progressively forming blanks by passing them through sequential die stations until they conform to a desired size and shape. Successive draws take an initially flat blank of metal and deform it in such a manner so as to prevent wrinkles and cracks from forming in the blank. This is true even though its shape is changed to one that is intended depending upon the particular application to which the work piece is to be put. The ultimate application may be a medical enclosure for a defibrillator or a pacemaker. 
     Prior art structures employ tools for each individual draw. In some instances, the case needs to be washed and annealed in order to maintain a sufficient degree of pliability for the next successive draw. The time element can be critical in going from draw to draw. Depending upon the number of draws necessary and the treatment between draws, it can take several weeks to complete a particular work piece. 
     The specific process typically utilized in the prior art passes parts in what is known as a common pass line. In such a methodology, all the presses are in the same horizontal plane. All the tooling has to be in that horizontal plane, and the work pieces are inserted into the draw tool and extracted from the draw tool from the same surface. Such methodology substantially effects drawing the work piece twice because the metal passes twice over the surfaces that actually effect deformation. Such a process can reduce quality by deforming the work piece to push back out a tool. By doing so, a geometry change can occur. 
     As was previously discussed, time can be an important factor. In one application of such a methodology, a period of time of 45 minutes between draws can be excessive. There is a natural tendency to allow a quantity of work pieces to build up at one machine before they are passed to the next machine. Similarly, because of break time and shift changes, parts may sit unattended for in excess of 45 minutes. 
     It is to these dictates and shortcomings of the prior art that the present invention is directed. It includes apparatus and methods for sequentially forming a plurality of thin metallic skin structures which solve problems in the prior art. 
     SUMMARY OF THE INVENTION 
     The present invention focuses upon both apparatus and methods. It includes apparatus for forming a plurality of enclosures having thin metallic walls. Such enclosures are formed by sequencing a plurality of blanks through progressive die stations. The apparatus includes a forming assembly which has a plurality of die stations spaced along an axis. The stations are stepped serially farther away from the axis in a direction perpendicular to the direction of movement of the blanks along the axis. The stations serve to progressively form the blanks as they are sequentially transferred in the direction of movement along the axis and from one station to another. A transfer assembly mounts a plurality of gripping means for gripping the blanks to transfer them from one station to the next. Such gripping means are spaced from each other along the axis and are serially stepped away from the axis at distances substantially the same as are the die stations. Actuator means to effect movement of the transfer assembly reciprocally in directions generally parallel to the axis are provided. The actuator means move the transfer assembly between a first axial position, in which the gripping means are registered with corresponding die stations, and a second axial position, in which each gripping means is registered with a die station adjacent the station with which it is registered when the transfer assembly is in its first position, advanced in a direction of movement from the first position. Also provided is a ram which moves the transfer assembly between a first stepped position in which the gripping means are withdrawn from the die stations, and a second stepped position, in which the gripping means engage blanks at the die stations. 
     The actuator means by which the transfer assembly is moved between its first and second axial positions can be pneumatic in nature. By employing a system so constructed, the transfer assembly can be efficiently moved between its first and second axial positions. 
     Similarly, pneumatic means can be provided to operate the ram in moving the transfer assembly between the first stepped position and the second stepped position. Again, it has been found that such a ram can be optimally operated to accomplish its intended goals. 
     The present invention is thus an improved apparatus and method for forming multiple metallic enclosures from blanks. More specific features and advantages obtained in view of those features will become apparent with reference to the appended DETAILED DESCRIPTION OF THE INVENTION, appended claims and accompanying drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a work piece after a first draw at a die station; 
         FIG. 2  is a perspective view of a work piece after a second draw at a die station; 
         FIG. 3  is a perspective view of a work piece after a third draw at a die station; 
         FIG. 4  is a perspective view of a work piece after a fourth and final draw at a die station; 
         FIG. 5  is a simplified side elevational view of an apparatus in accordance with the present invention with a transfer assembly in its first axial position and its first stepped position; 
         FIG. 6  is a view similar to  FIG. 5  but in more detail; 
         FIG. 7  is an enlarged view illustrating a die station; 
         FIG. 8  is a view similar to  FIG. 6  with the transfer assembly in a first axial position and a second stepped position; 
         FIG. 9  is a view similar to  FIG. 8  but with a ram retracting the transfer assembly back toward its first stepped position; 
         FIG. 10  is a top plan view illustrating a set of grippers gripping a work piece; 
         FIG. 11  is a view similar to  FIG. 10  showing the set of grippers releasing the work piece; and 
         FIG. 12  is a view similar to  FIG. 6  with the transfer assembly in its second axial position and its first stepped position. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawing figures wherein like reference numerals denote like elements throughout the several views,  FIGS. 6 ,  8 - 9  and  12  illustrate an apparatus  20  in accordance with the present invention.  FIG. 5  is a simplified illustration of the apparatus  20  of  FIGS. 6 ,  8 - 9  and  12 . Initial discussion is made with reference to  FIG. 5 . That figure illustrates a base  22  which mounts a forming assembly  24 . The assembly  24  is elongated along an axis  26 . The axis  26  extends in a direction of movement of work pieces  28  through a plurality of die stations  30  spaced along the axis  26  of the base  22 . 
     Each die station  30  mounts a tool  32  which, when work pieces  28  are successively processed through from station to station, the shape of a work piece will be progressively more conformed to an intended shape and size. As seen in  FIG. 5 , the tools  32 , moving in a right-to-left direction in that figure, are successively smaller in cross-section. 
       FIGS. 1-4  illustrate the size and shape of a work piece blank  28  as it proceeds in a direction of the axis  26  from station to station. The work piece  28  being formed, as illustrated by  FIGS. 1-4 , is a casing for use in an implantable medical device. While the figures do not illustrate the specific shape of tools  32  to achieve the shape and size of the work piece illustrated in  FIGS. 1-4 , it will be understood that any shaped sequentially processing tools to achieve a particular constructed work piece can be utilized. It should also be understood, of course, that a die  34 , cooperating with a particular tool  32 , would also be utilized in the forming process. 
       FIG. 5  illustrates a stepping of sequenced stations  30  wherein they are defined serially farther away from the axis  26  in a direction generally perpendicular to the direction of movement of the work pieces  28  along the axis  26 . Such stepping is for a purpose as will be discussed hereinafter. 
     The figures also illustrate a transfer assembly  36  which mounts a pair of gripping fingers  38  and a die structure corresponding to a tool at a die station  30 . It is the cooperation of the tool  32  and its corresponding die  34  which effects processing of a work piece  28  at a particular station  30 . As will be seen in the figures, the finger gripping means  38  corresponding to a particular die station  30  are stepped from an adjacent station in an amount similar to the distance at which the die stations  30  are stepped from the axis  26 . 
     The gripping means structures are positioned on a platen  40 . The platen  40  is carried by a series of telescoping mounts  42  which allow for the transfer assembly  36  to move from a position wherein the gripping means is withdrawn from engagement of the corresponding tool, to another position wherein the gripping means engage a corresponding tool to effect sequential formation of the work pieces  28 . A ram  44  is provided to mount the transfer assembly  36  for movement between the first, withdrawn position, and the second, extended position. 
     As will be apparent, the die structures  34  are ganged. That is, they are fixed with respect to each other in a defined spatial relationship. 
     The transfer assembly  36  is also mounted for movement in a direction along the axis  26 . Movement is between a first position and a second position. When the transfer assembly  36  is in its first position, the various gripping means  38  assemblies are substantially registered with their corresponding tools  32  at the die stations  30 . When the transfer assembly  36  is in its second axial position, the gripping means assemblies are generally registered with a die station and its corresponding tool spaced one station to the left (as viewed in  FIG. 5 ). This second axial position of the transfer assembly  36  is illustrated in  FIG. 12 . 
     It will be understood that actuator means for moving the transfer assembly  36  reciprocally in an axial direction between its first and second positions, and movement of the transfer assembly  36  by the ram  44  in a direction generally perpendicular to axial movement can be accomplished by an actuator  46  of any appropriate means. It has been found that a pneumatic actuation means is appropriate. 
     In operation, an initially structured work piece  28 , as illustrated in  FIG. 6 , is placed over the tool  32  at the first station. Such positioning of the work piece  28  can be accomplished either manually or by employment of a mechanical transfer structure (not shown). The transfer assembly  36  is initially in its first positions both axially and in a direction stepped perpendicular to axial movement. The first movement of the transfer assembly  36  is accomplished by actuating the ram  44  to move the transfer assembly  36  from its first stepped position to the second stepped position. This movement will cause forming to be brought to bear upon the work piece in the first station (that is, in the right-most station as viewed in the figures). 
     When this forming process is completed, the ram  44  withdraws the transfer assembly  36  to the first stepped position. As withdrawal of the ram  44  proceeds, a stripper  48 , shown in  FIG. 7 , will facilitate removal of the work piece  28  from the tool  32 , and a pair of fingers  38  of gripping means will grasp the work piece  28  to hold it as the transfer assembly  36  is cycled. 
     When the transfer assembly is withdrawn to its first stepped position, actuation means then function to move the assembly  36  in an axial direction to a location wherein the gripping means  38  holding the work piece  28  becomes substantially registered with the second die station. Such a station is the one immediately adjacent the first station at which processing has already occurred. With the transfer assembly  36  in this position, another blank, which can be pre-processed, is placed over the tool  32  in the first station. The ram  44  then moves the transfer assembly  36 , after the fingers  38  having released the first work piece at the second die station, back to its first stepped position. As will be able to be seen, two stations now hold sequentially-processed work pieces  28  over their respective tools  32 . The ram  44  then moves the corresponding dies  34  in a downward direction to process the work pieces  28  in the first and second stations. Subsequent insertion of a pre-processed work piece at Station  1  as previously processed blanks have moved on to subsequent stations will allow for sequential processing of the work pieces in third and fourth stations. 
     It will be understood that, while four stations are shown in the various figures, a number greater or smaller than four is within the contemplation of the invention. Circumstances might, in fact, dictate six or more stations for processing. 
       FIGS. 10 and 11  illustrate, in plan, the functioning of gasping fingers.  FIG. 10  illustrates the fingers closed onto the workpiece with which the fingers are cooperating.  FIG. 11  shows the fingers in their release mode. Actuation of the fingers is, of course, coordinated with the positioning of the transfer assembly. Opening and closing of the fingers can be accomplished by mechanical means, a pneumatic system, etc. 
     It will be understood that this disclosure, in many respects, is only illustrative. Changes may be made in details, particularly in matters of shape, size, material, and arrangement of parts without exceeding the scope of the invention. Accordingly, the scope of the invention is as defined in the language of the appended claims.