WO1986007232A1

WO1986007232A1 - Apparatus for positioning a circuit panel

Info

Publication number: WO1986007232A1
Application number: PCT/US1986/000998
Authority: WO
Inventors: Hans Hugo Ammann; Richard Frank Kovacs
Original assignee: American Telephone & Telegraph Company
Priority date: 1985-05-28
Filing date: 1986-05-07
Publication date: 1986-12-04

Abstract

A placement apparatus for positioning and securing a circuit panel on a work surface includes two gripping or engaging devices (102, 104) to engage two diagonally opposite corners of the panel and a mechanism (Fig. 6) for moving the engaging devices substantially in line with a diagonal line of the panel and apply pressure thereto to position the center point of the panel and coordinate axes originating thereat in registration with a center point and reference coordinate axes of the work surface.

Description

APPARATUS FOR POSITIONING A CIRCUIT PANEL

Field of the Invention This invention relates to the manufacture of circuit panels and more particularly to the positioning of circuit panels on a work surface in register with a reference coordinate system to permit operations to be accurately performed on the panel. Background of the Invention

In the production of circuit panels, many manufacturing operations on the panel are performed at different work stations. To assure that these operations produce results which are accurate with respect to the panel and to each other, the panel must be accurately positioned with respect to a reference coordinate system at each work station. Apparatus to accomplish this panel positioning must be consistently accurate and also accommodate dimensional variations that occur in the circuit panel during manufacture due to expansion, contraction, shear and other material instabilities. One class of existing techniques of aligning a panel with a work surface reference frame utilizes a plurality of slots cut into the circuit panel which fit over locating pins located on the work surface at each work station. Short comings of these and similar known techniques are that the panels are aligned relative to their edges only. Better accuracy is obtainable if the panels are aligned relative to their centers. This is accomplished by this invention. Summary of the Invention

A positioning apparatus for positioning a circuit panel on a work surface includes two synchronized engaging elements to engage two opposed angular features, and in the case of a rectangular panel, two diagonally opposite corners of the panel and a mechanism for synchronously and symmetrically moving the engaging elements in opposing directions with a trajectory of travel symmetrical with the reference frame origin of the work surface. With a rectangular panel, this trajectory of travel is similar to a diagonal line of the panel. The engaging elements apply the requisite forces to position and hold the panel on the work surface. The panel is centered so that the panel reference frame is in alignment- with the reference frame of the work surface and the tooling system. These forces are operative in particular to position the center point of the.panel and coordinate axes originating- thereat in alignment and registration with a center point and reference coordinate system of the work- surface. The engaging elements may be activated by any mechanism that can synchronously drive them in a symmetrical trajectory about the origin of the work surface reference frame. Brief Description of the Drawings

FIGS. 1 and 2 are schematic representations of panel positioning, schemes of the prior art;

FIG. 3 is a perspective view of a work table including a work surface having a system embodying the principles of the invention for accepting and positioning circuit panels thereon;

FIG. 4 is a perspective view of a work surface -upon which a circuit panel has been placed prior to its positioning for manufacturing operations; FIG. 5 is a perspective view of a work surface after the centering apparatus has properly positioned the circuit panel in register with the work surface coordinate system;

FIG. 6 is a cut away perspective of a centering mechanism to position and secure the panel on the work surface; FIG. 7 is a schematic representation of an alternative centering mechanism to position and secure the panel on a work surface; and

FIGS. 8 through 11 show schematic representations of alternate centering mechanisms that may be utilized in various embodiments of the invention. Detailed Description

Two prior known ways of positioning a -panel are shown in FIGS. 1 and 2, respectively. In FIG. 1 locating slots 1, 2 and 3 are cut into a panel 4. Slots 1, 2 and 3 fit over pins 5, 6 and 7 of the work surface 9 (shown in fragmented form) . The two horizontal slots 1 and 3 control the vertical positioning and angular positioning of the panel, and the vertical slot 2 controls its horizontal positioning. Since slots 1, 2 and 3 are all located along one edge of panel 4, it is apparent that the panel reference frame is along that edge as shown by axes 11 and 12 with the origin located at slot 6.

It is preferable to have the reference frame origin at the center of the panel to minimize worst case registration errors that result from linear deformations of the panel that occur during its manufacturing processing. One technique of moving the center of the reference frame to the center of the panel is to reposition and utilize slots located along all four edges, as disclosed in FIG. 2. Four slots 21, 22, 23 and 24 are located at the center of each edge of the panel 15. Slots 21, 22, 23 and 24 are positioned over pins 25, 26, 27 and 28 to locate the panel on a work surface 19. As shown in FIG. 2, the reference frame origin 17 now originates at the center of the panel. Hence, changes in linear dimensions of the panel are averaged in both orthogonal directions of the reference frame. However, a shear deformation of the panel is not accommodated by this technique. These panel locating techniques, being dependent on slots cut into the panel, consume a significant portion of the surface area of the circuit panel for locating purposes, an area which could otherwise be used for circuit paths or component location.

The work table 100 shown in FIG. 3 includes a planar work surface 101 for accepting a circuit panel thereon, and force applicators embodied as roller contacts 102, 103, 104 and 105, which move along elongated slots 110, as shown by the arrows 109, to engage diagonally opposite corners of a circuit panel. The work table 100 may be mounted as part of a manufacturing machine which performs machine operations on a circuit panel, and as such, has a reference coordinate system shown by origin 106 and axes 107 and 108 determined by the manufacturing operational devices (i.e., drills, etc.) of that machine. While the surface 101 is shown unbroken, it is to be understood that apertures may be provided to permit the emergence of machine tools or light through the surface.

A circuit panel 215 is shown as initially placed on the work surface 201 in FIG. 4. As shown, its coordinate system comprises an origin point 216 and axes 217 and 218,. which are shown displaced from the reference coordinate system of the work surface, which comprises origin point 206 and axes 207 and 208. As shown in FIG. 4, the roller contacts 202-205 have not yet fully engaged the circuit panel 215 so as to firmly grip it and accurately position it.

The circuit panel 315, shown in FIG. 5, is fully engaged by the roller contactors 302-305, which have moved inwardly along a line parallel to a diagonal 326 of the circuit panel to position it and also to firmly secure it to the work surface 301. Its origin point 316 and axes 317 and 318 are coincident with the reference origin and axes of the work surface. The roller contacts 302-305 make contact with panel edges, and apply forces perpendicular to the edges as shown by the arrows 332, 333, 334 and 335. The resultant force at each corner 319 and 320 of the panel appear as a force 329 and 330 substantially aligned along its diagonal line 326 and having balanced moments about the centroid point 316. These balanced moments and forces constrain the panel to be positioned so that its centroid and panel coordinates are in register with or aligned with the reference coordinates of the work surface 301. As shown, the roller contacts 302-305 which are mounted on carriage supports shown in FIG. 6, are permitted movement parallel to the diagonal 326 by slots 310 cut into the top planar surface of the work surface 301.

An illustrative meςhanism to supply the necessary movement and force to the roller contacts is shown included within the work table 400 in FIG. 6. The roller contacts 402-405 are shown positioned on two carriage mechanisms 441 and 442, each of which ride on track elements 433 and 434 respectively, to control lateral movement of the carriage mechanisms 441 and 442 to be substantially along and substantially coincident with a diagonal of the panel it is to position and secure.

Two roller contacts are mounted on top of each of the carriage mechanisms 441 and 442 and are designed to freely rotate so that they establish point contact with an edge of a circuit panel and apply forces in a direction perpendicular to the edge. Each carriage mechanism 441 and 442 is connected to an air cylinder and piston device 450 by a rod 448 and 449 respectively. Upon actuation of the cylinder 450, movement of the piston draws the two carriage mechanisms 441 and 442 toward one another. The cylinder 450 is connected by tubing 451 to a control mechanism 452, which may be automatically or manually (switch 453) actuated.

A continuous cable 455 is looped around two pulley wheels 456 and 457 located at diagonally opposite ends of the work table 400. The two carriage mechanisms 441 and 442 are connected to the cable loop 455 on the underside of the carriage mechanisms at points 461 and 462, respectively, on opposite sides of the diagonal line so that each carriage mechanism 441 and 442 is constrained to move in synchronism but with equal distance in opposite directions. The two carriage mechanisms 441 and 442 move toward one another by equal increments of distance until the circuit panel on the work surface is firmly secured in place. The roller contacts 402-405 shown may comprise roller bearings mounted on an axis perpendicular to the top surface of the carriage mechanism. They are positioned on the carriage so that when the circuit panel is secured,- the contact point of the roller contact makes contact with the edges of the panel at diagonally opposite corners of the panel at points equidistant from these corners. The track mechanism ^'433 and 434, may as shown, comprise a rail mechanism having a rectangular prism shape with the carriage mechanism having a channel undercarriage to fit over and engage the outer edges of the rail, thereby constraining its direction of motion along the line defined by the rail edges. Any other suitable pair of grippers which engage the panel on diagonal corners may also be employed. An alternative engaging mechanism embodying the principles of the invention is shown in FIG. 7.

In this particular embodiment, two stepper motor linear actuators 571 and 572 are mounted at diagonally opposed corners of a work surface 500. Stepper motor linear actuator 571 is mechanically connected to directly drive a panel engaging mechanism 581, and stepper motor linear actuator 572 is mechanically connected to drive panel engaging mechanism 582 through a force sensing mechanism 583. Both stepper motor linear actuators 571 and 572 are synchronously driven by the stepper motor controller 575 in response to commands from a control panel 576 by simultaneously applying the necessary drive pulses to the stepper motors 571 and 572, so that they simultaneously move or step the engaging members 581 and 582 along diagonal line 526 by equal increments of distance. Once a close command is activated at control panel 576, the stepper motor linear actuators 571 and 572 drive the two engaging members 581 and 582 toward each other until the force sensor 583 detects attainment of a preset force threshold and sends a signal to the stepper motor controller 575 to terminate applications of drive pulses to the stepper motor linear actuators 571 and 572. An open command reverses the stepper motor linear actuators 571 and 572 and . disengages the panel 501 from the engaging members 581 and 582.

In operation, a circuit panel 501 is placed on the work surface 500 with the engaging mechanisms 581 and 582 fully withdrawn. The stepper motor controller 575 is activated and, in turn, activates the stepper motor linear actuators 571 and 572 to drive the engaging members 581 and 582 toward each other to engage diagonally opposite corners of "the panel 501. When engaging mechanism 582 attains a certain application force threshold on the panel 501 as sensed by force sensor 583, a signal is applied to the stepper motor controller 575 to stop driving the stepper motor linear actuators 571 and 572. The circuit panel 501 remains secured to the work surface by the engaging members, 581 and 582 until the stepper motor controller 575 is commanded to reverse the stepper motor linear actuators 571 and 572 so that the engaging members 581 and 582 back off and are disengaged from the circuit panel 501.

The threshold at which the force sensor 583 is set is selected to assure that the circuit panel is properly secured to the work surface and further assure that the stepper motor linear actuators 571 and 572 are not overloaded thereby preserving synchronization between actuator position and the stepper motor control pulses.

Some alternative synchronous drive mechanisms suitable for application in various embodiments of the invention are disclosed in FIGS. 8-11.

The mechanism of FIG. 8 utilizes a crankshaft 801 driven by driver 802 to synchronously drive two carriage units 803 and 804 toward one another. A bias 805 supplies the necessary release force once the driver 802 is deactivated.

A rack and pinion mechanism is shown in FIG. 9 to synchronously drive two carriage elements 903 and 904. The pinion gear 901 drives two racks 905 and 906 which, in turn, are connected to the carriage mechanisms 903 and 904.

The scotch yoke mechanism of FIG. 10 utilizes two roller bearings 1001 and 1002 engaging the two yokes 1003 and 1004 to synchronously move the two carriages 1005 and 1006.

Two synchronized levers 1101 and 1102 are utilized to engage the circuit panel in FIG. 11.

Claims

Cla ims

1. Apparatus for positioning a circuit panel on a work surface

CHARACTERIZED BY: first and second corner engagement elements (103, 104) for engaging diagonally opposed first and second corners of a circuit panel placed on the work surface, a panel securing mechanism (FIG. 6) for synchronously moving the first and second engagement elements toward each other by equal distance in a line of travel aligned with a diagonal of the circuit panel.

2. Apparatus as defined in claim 1 wherein the panel securing mechanism includes first and second step motor linear actuators (571, 572) coupled to drive the first and second engagement elements respectively, control means (575) to synchronously drive the first and second step motor linear actuators, and a force sensor (583) to sense a force level applied by at least one of the first and second corner engagement elements.

3. Apparatus as defined in claim 1 wherein the first and second corner engagement elements each include first and second force application devices for applying a perpendicular force to a first and second edge adjacent to each of the first and second corners.

4. Apparatus as defined in claim 1 wherein the panel securing mechanism includes: a track mechanism for guiding a translation of the first and second engagement elements mounted thereon, and a driving mechanism for imparting motion to the first and second engagement elements by applying oppositely directed forces to the first and second engagement elements.

5. Apparatus as defined in claim 4 wherein the panel securing mechanism includes a displacement control mechanism for constraining the first and second corner engagement elements to move equal distances in opposite directions and including a continuous cable loop affixed to both the first and second corner engagement means.

6. Apparatus as defined in claim^' 3 wherein the first and second force application devices include first and second roller contacts each having their axis of rotation perpendicular to the plane of the work surface.

7. Apparatus as defined in claim 5 wherein the displacement control mechanism comprises first and second pulley wheels located adjacent diagonal opposite corners of the work surface and including a continuous cable loop wound around the first and second pulley wheels and being connected to the fi.rst and second corner engagement elements on opposite sides of a diagonal line joining the diagonally opposite corners respectively.