Material or article handling – Elevator or hoist and loading or unloading means therefor – Grab
Reexamination Certificate
1998-08-12
2001-08-21
Werner, Frank E. (Department: 3652)
Material or article handling
Elevator or hoist and loading or unloading means therefor
Grab
C414S797000, C414S225010, C294S065000
Reexamination Certificate
active
06276891
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of vacuum driven circuit board pick up mechanisms. More specifically this invention relates to pick up mechanisms which are moved into contact with a work piece such as a circuit board and is attached thereto such that the work piece may be lifted away to another work area.
2. Description of the Related Art
Existing systems using vacuum usually apply pressure to a cylinder or equivalent device to move a pick up mechanism to engagement with a stack of circuit boards during a pick up cycle. However, the existing systems permit pressure from the cylinders to be applied directly to the stack of circuit boards and, in fact, to various vacuum cups or other devices which directly engage with the work piece. This can result in damage to the work piece, increases the stress on the pick up table and the vacuum assembly supporting the vacuum cups due to increased pressure and is replete with safety problems including the possibility of applying a crushing force to hands or other appendages of the workers using such equipment. In addition, because of the pressing of one board against a stack of boards, double feeding can result. That is, the picking up of two boards due to vacuum pressure between the two adjacent surfaces is increased by the increased pressure pressing the boards together which can evacuate any air between such surfaces the instant invention reduces the pressure applied to the stack of circuit board material, reduces the potential of material damage and be used to pick up a work piece from an uneven surface or from various different load height positions. It is also less likely to cause injury because the cylinder force is eliminated and the actual force applied to the work piece is minimized.
SUMMARY OF THE INVENTION
The current invention is characterized by a doubling acting air cylinder mounted at each end of the pick up mechanism which engages shafts mounted to a vacuum cup bar. The shaft of the vacuum cup pick up bar is slideably interconnected with a shaft guide mounted on the pick up mechanism frame. The shaft also slideably engages a shaft collar of a pneumatic cylinder body. Operation of the air cylinder causes the shaft collar to lower the respective guided shafts of the vacuum cup bar until the vacuum cups come in contact with the target circuit board. Further movement of the air cylinder body causes the shaft collar to slide down the guided shaft thereby eliminating any overrun of the air cylinder and eliminates any pressure of the cylinder being applied to the guided shaft, thereby preventing such pressure from being transmitted to the vacuum cup tray. The only force applied to the vacuum cup tray and therefore to the target circuit board is through the action of gravity. Vacuum is applied and the pick up mechanism then moves the body of the pneumatic cylinder upward. The shaft collar engages the end of the guided shaft which has a nut or a flanged end larger than the diameter of the guided shaft and the hole in the shaft collar, and lifts the vacuum cup bar along with the circuit board into another work location. In this way, the pneumatic cylinders move the vacuum cup bar up and down as required to engage, lift, transport and place individual ones of circuit boards from one place to another without damages. During such transport, the vacuum cups come in contact with a stack of circuit boards and vacuum bar travel stops while the cylinders continue to move to the full extent of stroke without applying additional pressure to the cups or to the circuit board materials. The pick up mechanism may then be moved to another location where the operation is reversed the vacuum is removed from the vacuum cups and the vacuum tray.
REFERENCES:
patent: 3834558 (1974-09-01), Bru
patent: 3884368 (1975-05-01), Ballard
patent: 4129328 (1978-12-01), Littell
patent: 5244343 (1993-09-01), Lockert
patent: 3-95022 (1991-04-01), None
Automated Manufacturing Technology, Inc.
Werner Frank E.
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