Abstract:
Panels are positioned relative to a pattern by moving the pattern onto a registration mechanism having contact elements, engaging contact areas on the pattern with contact elements by moving the contact elements synchronously and equidistantly while allowing the registration mechanism to move as the elements engage the contact areas, locking the position of the registration mechanism, and engaging contact areas on sequential panels by moving the contact elements of the locked registration mechanism synchronously and equidistantly to contact areas on one panel after the other.

Description:
This is a divisional application of Ser. No. 08/581,644 filed Dec. 28, 1995, now U.S. Pat. No 5,862,583. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to methods and apparatuses for positioning panels on a work surface in register with a tool to permit accurate operations on the panel, and particularly to methods of positioning printed circuit panels relative to stencil or screen printing patterns. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 4,793,052 illustrates, methods and apparatuses for positioning panels, such as printed circuit panels, on a work surface. A registration mechanism displaces engaging member, such as locating pins, equidistantly and synchronously in opposite directions into engagement with contact areas, such as locating slots or holes in the panel, to fix the panel position relative to the work surface so that a tool can perform its function with respect to the panel. 
     Often, the tool operating on the panels, such as a frame holding a printing pattern, must move repetitively with great accuracy relative to successive panels mounted on the work face to complete the processing on each panel. Such tools must also operate in registry with the panels. However, the weight of the tool or the complexity of its mounting and movement makes registration of the tool with the panels or the co-ordinates of the panels difficult. 
     SUMMARY OF THE INVENTION 
     According to an embodiment of the invention, the registration mechanism that contains and moves the pins is itself movable relative to the workface, and the registration mechanism is moved into registry with the tool by engaging the mechanism&#39;s engagement elements with contact areas on the tool and then fixing the registration mechanism in position relative to the tool operating position, before registering the panel with the tool. 
     The various features of novelty which characterize the invention are pointed out with specificity in the claims forming a part of this specification. Objects and advantages of the invention will become evident from the following detailed description when read in light of the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a somewhat schematic perspective of a work station embodying features of the invention. 
     FIG. 2 is a plan-view of a work face and registration mechanism in FIG.  1 . 
     FIG. 3 is another view of the work station in FIG. 1 showing a panel in position on the work face. 
     FIG. 4 is a plan view of the work face in FIGS. 2 and 3 with the panel in position on the work face. 
     FIG. 5 is a plan schematic showing relationship of holes it various members of FIGS. 1 to  4 . 
     FIG. 6 is a plan view showing another embodiment of the invention. 
     FIG. 7 is a perspective view of a board center registration (BCR) mechanism for use in the device of FIGS. 1 to  4 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1 to  4 , where like parts are designated with like reference characters, show an embodiment of the invention. Here, a frame FR 1  fixedly holds a pattern PA 1  and a frame control FC 1  moves the frame and the pattern vertically down against a work table WT 1  with a workface WF 1 . A board center registration (BCR) mechanism BE 1  under the workface WF 1  projects engaging elements illustratively in the form of vertical locating pins PI 1 , PI 2 , PI 3 , and PI 4  through respective larger openings OP 1 , OP 2 , OP 3 , and OP 4  in the work table WT 1 . When the pattern PA 1  is against the workface WF 1 , the pins PI 1 , PI 2 , PI 3 , and PI 4  also project through tooling features or slots illustratively in the form of holes HO 1 , HO 2 , HO 3 , and HO 4 , larger than the pins, in the pattern PA 1 . 
     BCR mechanisms such as BE 1  are described in U.S. Pat. No. 4,793,052. The BCR mechanism BE 1  moves the vertical pins PI 1 , PI 2 , and PI 3 , PI 4  horizontally parallel to an axis HX 1 -HX 2 . The latter pass through the central portion of the workface WF 1  and pattern PA 1  when the pattern PA 1  is on the workface WF 1  and also passes between the pins PI 1  and PI 2  and between the pins PI 3  and PI 4 . The BCR tool simultaneously moves the pins PI 1  and PI 2 , in a direction opposite to the pins PI 3  and PI 4 , and in equidistant amounts, about a horizontal axis HY 1 -HY 2  transverse to the axis HX 1 -HX 2 . The latter passes through the central portion at the workface WF 1  and pattern PA when the latter is down against the workface WF 1 . 
     The holes HO 1 , HO 2 , HO 3 , and HO 4  are arranged relative to the pins PI 2 , PI 2 , PI 3 , and PI 4  so that when the BCR mechanism BE 1  moves the pins PI 1 , PI 2 , and PI 3 , PI 4  synchronously and equidistantly outward parallel to the axis HX 1 -HX 2 , the pins forcibly engage localized areas of the holes HO 1  to HO 4  as shown in FIG.  2 . The openings OP 1  to OP 4  are sufficiently large to permit engagement between the pins PI 1  to PI 4  and HO 1  to HO 4 . Specifically in the engaged positions, the pin PI 1  engages the Northwest area of the hole HO 1 , the pin PI 2  engages the Southwest HO 2 , the pin PI 3  engages the Northeast area of hole HO 3 , and the pin PI 4  engages the Southeast area of the hole HO 4 . 
     The BCR mechanism BE 1  under the worktable WT 1  floats horizontally, for example, on supports SU 1  and SU 2  relative to the worktable along both axes HX 1 -HX 2  and HY 1 -HY 2 . To achieve registration of the BCR tool BE 1  and the pattern PA 1 , i.e. in order for the engagement of pins PI 1  to PI 4  to forcibly engage the contact areas of holes HO 1  to HO 4  as shown in FIG. 2, the BCR mechanism moves relative to the worktable WT 1 . When such registration, i.e. such engagement between the pins PI 1  to PI 4  and edges of the holes HO 1  to HO 4  occurs, schematically shown locking members LO 1  and LO 2  on the supports SU 1  and SU 2  lock the horizontally floating BCR tool BE 1  in position on the worktable WT 1 . This fixes the position of the BCR mechanism BE 1  relative to the pattern PA 1  fixed on the frame FR 1 . In this position the BCR mechanism BE 1  and the pattern are in registration. 
     The BCR mechanism BE 1  now withdraws the pins PI 1  to PI 4  inwardly toward the center axis HY 1 -HY 2  synchronously and equidistantly and the frame control FC 1  lifts the frame FR 1  and the pattern PA 1  from the workface WF 1 . Manual or automatic means then place a panel PN 1  to be oriented on the workface WF 1 , as shown in FIG. 3, so that panel tooling features in the form of panel holes PH 1 , PH 2 , PH 3 , and PH 4  receive the pins PI 1 , PI 2 , PI 3 , and PI 4  respectively. The panel holes PH 1  to PH 4  are larger than the pins PI 1  to PI 4  so the pins slip easily into the holes. Suitable means prevent the panel from being placed upside-down or backwards about either axis HX 1 -HX 2  or HY 1 -HY 2 . For this purpose, according to one embodiment, the pins PI 1  to PI 4  are offset from each other unsymmetrically about the respective axes. Also the holes HO 1  to HO 4  and panel holes PH 1  to PH 4  and the pins PI 1  to PI 4  are congruently offset about the axes HX 1 -HX 2 , and HY 1 -HY 2 . 
     According to another embodiment of the invention, the pins PI 1  to PI 4  are located symmetrically. However, preferably, in such an embodiment, a separate projection or other device prevents the panel from being place upside down or backwards. 
     The BCR mechanism now moves the pins PI 1  to PI 4  synchronously and equidistantly outwardly parallel to the axis HX 1 -HX 2 . The panel holes PH 1  to PH 4  are sized and arranged so that synchronous equidistant outward movement of the pins PI 1  to PI 4  parallel to the axis HX 1 -HX 2  ultimately results in forcible engagement of the pins PI 1  to PI 4  with respective Northwest, Southwest, Northeast, and Southeast regions of the panel holes PH 1  to PH 4  as shown in FIG.  4 . The outward movement of the pins PI 1  to PI 4  on the BCR mechanism BE 1 , now secured to the worktable WT 1 , moves the panel PN 1  into registration with the pattern PA 1 . To prevent subsequent interference of pins PI 1  to PI 4  with the holes HO 1  to HO 4 , the holes HO 1 , HO 2  are further from the holes HO 3 , HO 4  than are the holes PH 1 , PH 2  from the holes PH 3 , PH 4 . FIG. 5 illustrates this relative distribution of holes. Alternatively, the holes HO 1  to HO 4  are larger than the holes PH 1  to PH 4 . According to another embodiment, the pins do not protrude above the panel PN 1 . 
     The control FC 1  now moves the frame FR 1  and the pattern PA 1  down into contact or other operating position relative to the panel PN 1  and the operation, such as printing, proceeds. The further outward position of the holes HO 1 , HO 2  from the holes HO 3 , HO 4  than the holes PH 1 , PH 2  from the holes PH 3 , PH 4  avoids any interference between the pins PI 1  to PI 4  with the holes HO 1  to HO 4 . 
     After completion of the operation the control FC 1  lifts the frame FR 1 , the BCR mechanism BE 1  moves the pins PI 1 , PI 2 , and PI 3 , P 14  synchronously and equidistantly inward parallel to the axis HX 1 -HX 2  to release the patterned panel, and the patterned panel PN 1  is then removed. The work face WF 1  then receives the next panel PN 1 , the BCR mechanism BE 1  moves the pins PI 1 , PI 2 , and PI 3 , PI 4  synchronously and equidistantly outward parallel to the axis HX 1 -HX 2 , the pins forcibly engage localized areas in the holes PH 1  to PH 4  of the next panel PA 1 . The control FC 1  lowers the frame FR 1  and the pattern PA 1 , and the operation is repeated. The control FC 1  then lifts the frame FR 1  the BCR mechanism BE 1  moves the pins PI 1 , PI 2 , and PI 3 , PI 4  synchronously and equidistantly inward parallel to the axis HX 1 -HX 2 , and the panel PA 1  is removed. The entire procedure is then repeated continuously. 
     According to another embodiment of the invention, the pins PI 1  to PI 4  are arranged to move inwardly relative to the holes HO 1  to HO 4  and the panel holes PH 1  to PH 4  to position the BCR mechanism. BE 1  and the panels PN 1 . This is shown in FIG.  6 . 
     A BCR mechanism BE 1  is shown in FIG.  7 . U.S. Pat. No. 4,793,105 shows another BCR mechanism. 
     The registration holes PH 1  to PH 4  in the panels PN 1  are formed in the same operation and at the same time to assure subsequent accuracy of positioning. Separately, the holes HO 1  to HO 4  in the pattern PA 1  are formed in the same operation and at the same time to assure subsequent accuracy of positioning. For the pattern, this is all done at the time the pattern is created, the latter by means such as etching. This ensures proper alignment of registration of features and registration holes. 
     According to an embodiment of the invention, the pattern PA 1  is a stencil for placing solder paste on the panel PN 1  in the form of a printed circuit board. In that case, solder paste is then placed on the PC board through the stencil. The solder paste is then processed in the usual manner, the stencil raised, the board released by the pins, the board removed, and the process repeated with a new panel. 
     During setup the contact points on the pins are inboard of the contact pins points on the holes PH 1  to PH 4  and HO 1  to HO 4 . This avoids interference. 
     According to an embodiment of the invention, the holes HO 1  to HO 4  are concentric but are sufficiently larger to prevent interference. 
     According to another embodiment of the invention, the pins PI 1  to PI 4  engage the holes HO 1  to HO 4  by moving inwardly. According to another embodiment of the invention, the holes may be of different sizes as long as they are large enough to permit the pins to pass through. 
     While embodiments of the invention have been described in detail, it will be evident to those skilled in the art, that the invention may be embodied otherwise without departing from its spirit and scope.