Conveyors: power-driven – Conveyor system for moving a specific load as a separate unit – System includes a load supported by a conveyor portion which...
Reexamination Certificate
1999-02-22
2001-10-16
Krizek, Janice L. (Department: 3652)
Conveyors: power-driven
Conveyor system for moving a specific load as a separate unit
System includes a load supported by a conveyor portion which...
C198S832100
Reexamination Certificate
active
06302261
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an indexing apparatus having a plurality of work platens or pallets movable through successive workstations. More particularly, the present invention relates to methods and apparatus for safely coupling the platens to a drive assembly during operation of the apparatus. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Related Art
It is known in the indexer art that endless conveyors containing a plurality of platforms (also described herein as platens or pallets) can be used to move workpieces on the platens through the various workstations. It is also known to use such apparatus in the screen printing art. However, problems with multi-color printers of the related art arise from the fact that such printers have a fixed configuration with a fixed number of printing stations printing a fixed number of colors. If additional colors are to be printed, the workpieces, in the typical case a print substrate, must be run through the same or a different printer having the additional colors. This greatly limits productivity.
Other deficiencies associated with indexing apparatus used with printers of the related art result from the shear size and massiveness of the related art printing apparatus. In particular, it is noted that printing apparatus of this type can be almost 40 feet long and weigh on the order of 20,000 pounds. The sheer size and weight of such apparatus give rise to the danger that the apparatus operators can be seriously injured due to (1) equipment failure; (2) the inadvertent introduction of foreign objects into the apparatus; and/or (3) partial or complete entrapment in the apparatus. Moreover, even minor malfunctions of such machinery can lead to operator injury and/or additional damage to the apparatus itself. For example, decoupling of the platens from the drive assembly in a conventional indexer can easily lead to a “pile-up” of platens before the apparatus can be manually shut-down.
Traditionally, efforts to reduce or eliminate such dangers have focused the use of shear pins which mechanically couple the platens and the associated drive assembly. Basically, such shear pins provide a replaceable “weak link” in the system so that the damage caused by many apparatus failures will be limited to breakage of the shear pin. For example, inadvertent placement of a foreign object into the path of the platens will merely stop movement of the platen and break the shear pin. Since such a foreign object may be an operator's appendage, use of the shear pin may very well save the operator from serious injury.
The shear pin arrangements of the related art, however, suffer from many deficiencies. First, each time a shear pin serves its purpose of preventing substantial damage, the shear pin must be replaced. Depending on the particular circumstances, this may entail an extensive, expensive and lengthy procedure. Naturally, in the event that the shear pin breaks due to a very minor malfunction, the cost of replacing the shear pin can greatly exceed the damage which the shear pin actually prevented. Second, conventional shear pin arrangements cannot prevent damage resulting from a “pile-up” of platens once one shear pin has broken. In other words, indexing apparatus of the type discussed herein tend to be subjected to a “domino effect” once damage begins to occur. Conventional shear pin arrangements simply lack the ability to prevent consequential damage of this sort. Thus, conventional procedures require an operator to manually shut the apparatus down. This, however, requires a relatively long period of time during which simply unnecessary damage often occurs.
Accordingly, there remains a need in the art for improved indexing apparatus for use with a multi-station apparatus which can be combined, broken apart and reconfigured as desired while still providing a fast and effective safety mechanism for minimizing operator injury as well as damage to the apparatus itself.
There remains a further need in the art for an indexing apparatus which employs an improved safety coupling assembly which is capable of quickly and automatically shutting-down the apparatus in the event of a malfunction or operator injury.
There remains still another need in the art for an indexing apparatus utilizing an improved indexing apparatus which is capable of long term repeated use without suffering significant degradation in performance.
There is yet another need in the art for an improved indexing apparatus which prevents unnecessary consequential damage to the apparatus by eliminating further advancement of the platens in the event of apparatus failure.
SUMMARY OF THE INVENTION
Therefore, one object of the present invention is to provide an improved indexing apparatus having at least one platen and a plurality of workstations for advancing a workpiece through the workstations, the apparatus including at least one detented safety coupling for selectively coupling and decoupling of the platens.
A further object of the present invention is to provide an improved indexing apparatus having a modular arrangement of workstations whereby the number of workstations can be easily selected and changed including concommitent changes in the safety coupling assembly.
Still another object of the present invention is to provide an improved indexing apparatus for advancing at least one platen through a plurality of workstations wherein the apparatus includes a safety coupling assembly which prevents further advancement of the platen in the event of apparatus failure.
Yet another object of the present invention is to provide novel and improved indexing apparatus for sequentially advancing a workpiece through a plurality of workstations.
These and other objects and advantages of the present invention are provided by a detented safety coupling assembly for use with an indexing apparatus for advancing a workpiece through a series of workstations. The indexing apparatus may include a plurality of workstations arranged in spaced relationship, at least one pallet which supports the workpiece as it passes through the workstations and a drive assembly for moving the pallet through the workstations. The safety coupling assembly releasably couples the drive assembly and the pallet such that movement of the drive assembly causes corresponding movement of the pallet when the forces acting on the coupling assembly do not exceed a predetermined value. The coupling assembly ceases to couple the drive assembly and the pallet, without breakage, when the forces acting on the coupling assembly exceed a predetermined value. The safety coupling assembly also provides the capability of automatically and nearly instantaneously shutting-down the indexing apparatus in the event of failure.
In a preferred embodiment, the safety coupling assembly includes a drag-link pin movably attached to the drive assembly of the apparatus and a detented engagement assembly (such as a spring-loaded ball plunger) affixed to the pallet of the apparatus, the engagement assembly releasably engaging the drag-link pin. The drag-link pin is preferably attached to the drive assembly with a coupling pin which also defines a pivot point about which the drag-link pin may rotate. Moreover, means can be provided for rotating the drag-link pin about the pivot point when the engagement assembly becomes decoupled from the drag-link pin. In this manner, a portion of the drag-link pin can act as a flag which indicates that an error has occurred and that the apparatus should be shut-down.
Such an error can be detected by a light emitter/detector assembly such as a focused diode laser with a companion detector. Once an error has been detected, the apparatus can be automatically shut-down by a centralized controller. Since the coupling assembly is detented, both operator injury and apparatus damage can be avoided without any breakage of the apparatus whatsoever. Additionally, damage cause
Gilberti Joseph J.
Todd Gary C.
Alix Yale & Ristas, LLP
Gilberti Joseph J.
Krizek Janice L.
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