Work holders – Work-underlying support – Support mounting means
Reexamination Certificate
1999-10-04
2001-03-20
Watson, Robert C. (Department: 3723)
Work holders
Work-underlying support
Support mounting means
C269S025000, C269S266000, C269S296000
Reexamination Certificate
active
06202999
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of workpiece support devices. More particularly, the present invention provides a workpiece support device that enables an active creation of support surface recesses while enabling a very compact arrangement of the supporting rods.
BACKGROUND OF THE INVENTION
A workpiece support device can be formed by utilizing a plurality of parallel rods or pins, provided in an array of columns and rows with free ends of the rods or pins lying either in a plane which defines a support surface or alternatively retracted therefrom to form a recess in the support surface. A workpiece on which an operation is to be performed can be supported by the support surface even though it has projections or irregularities on the face which is towards the support surface since such projections or irregularities can be accommodated in the recesses formed by retracted ones of the rods. The workpiece may, for example, be a printed circuit board which already carries circuit components on one side thereof and the other side of which is to have an operation effected thereon such as a printing operation, solderflow to secure the circuit components in place or affixing of further circuit components.
In one embodiment of a device utilizing the prior art, the non-free end of each rod is coupled to a respective piston within a respective cylinder, with all cylinders in each row having their upper ends connected to a pressure source and their lower ends connected to a pressure source, both sources controlled by one respective solenoid valve, and with each rod controlled by a control means.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide for an improved workpiece support device. Furthermore, since a very large number of rods may be desirable, it is another object of the present invention to locate individual rods and mounting and moving means close together. Another object of the present invention is to provide for an array of support rods which can be set to an advanced position or a retracted position rapidly and reliably.
According to the invention, a workpiece support device comprises an array of rods in columns and rows with the free ends of the rods forming a support surface, in which support surface, recesses can be created by selectively retracting individual ones of the rods; wherein each rod is coupled to a respective piston within a respective cylinder, all the cylinders in each row have their upper ends connected to a medium pressure source via a common row valve and their lower ends connected to a high pressure source via a further common row valve; wherein a trigger piston is provided in the lower end of each cylinder and is movable between a raised position in which it allows the high pressure source to feed the bottom of the cylinder and a lowered position in which it closes off the feed from the high pressure source and allows feed to the bottom of the cylinder from a low pressure source connected to the bottom of the cylinders of each column by a common column valve; wherein each piston can be locked in an advanced position by differential pressure between the medium and high pressure sources and can be locked in a retracted position by causing that piston to hold the respective trigger piston in the lowered position.
The pressure sources are preferably pneumatic and, by choosing a suitable sequence of application of pressure to the upper end of the cylinder and the lower end of the cylinder from the low, medium and high pressure sources by the respective common column valves and common row valves, the pistons of the rows and columns can be set individually to advanced or retracted positions as desired.
Preferably, the common row valves feeding the upper ends of the cylinders and the common row valves feeding the lower ends of the cylinders are normally open valves and the common column valves feeding the lower ends of the cylinders are normally closed valves. Each common row valve, when not in its normal position, vents the portion of the cylinder to which it is connected to atmosphere.
The device can be set for a desired shape of workpiece by setting the cylinders of the rows individually and sequentially until all the rows required for the workpiece are set. Each row is set by energizing the common row valve supplying the upper end of the cylinders and the further common row valve supplying the lower end of the cylinders (thereby depressurizing the areas of the cylinder to which they are connected) and energizing the common column valve corresponding to cylinders required to be extended (thus applying air pressure to the lower end of the cylinder from the low pressure source). Such air applied by the common column valve depresses the trigger piston and raises the cylinder piston to the extended position of the rod. When the air pressure applied to the common column valve is removed and air pressure is again applied to the upper and lower row connections through the common row valve and the further common row valve, the high pressure to the lower connection raises the trigger piston and is applied to the underside of the main piston to force the rod to a fully extended position due to the differential pressure between the medium pressure source and the high pressure source.
In the columns in which the rod is not to be extended, the common column valve connected to the low pressure source at the lower end of the cylinder is not opened, the main piston is therefore not raised, and when the common row valve connected to the medium pressure source is opened, the main piston is forced downwardly and depresses the trigger piston closing the high pressure connection. The high pressure, when reconnected, is insufficient to raise the trigger piston against the downward force applied by the medium pressure to the main piston and the rod remains in the retracted position.
All cylinders may be reset to the retracted position by exhausting all the bottom connections while maintaining the air supply to the top connections and the pistons can then be set to advanced position or maintained in retracted position as desired. By the choice of valve types (either normally open or normally closed), it can be arranged so that when all the valves are de-energized, the apparatus maintains its current set up.
REFERENCES:
patent: 4506999 (1985-03-01), Robertson
patent: 5551677 (1996-09-01), Puettmer et al.
patent: 5609377 (1997-03-01), Tanaka
patent: 2 322 089 (1999-03-01), None
patent: WO 93 14907 (1993-08-01), None
patent: WO 95 03901 (1995-02-01), None
Pepper Richard Anthony
Wayman John Charles
Wigmore Richard
DEK Printing Machines Ltd.
Watson Robert C.
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