Conveyors: power-driven – With means to facilitate working – treating – or inspecting... – Means to convey a palleted load back and forth between an...
Reexamination Certificate
2000-02-14
2001-08-14
Walsh, Donald P. (Department: 3651)
Conveyors: power-driven
With means to facilitate working, treating, or inspecting...
Means to convey a palleted load back and forth between an...
C198S346200
Reexamination Certificate
active
06273236
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to a pallet exchange apparatus for a machine tool. More particularly, it relates to a pallet exchange apparatus for automatically exchanging a pallet in an upright posture relative to a machine tool table.
2. Description of the Related Art
A machine tool often requires a pallet on which a work is set securely for machining with a machine tool. Where the machine tool uses such a pallet, the pallet carrying a work is fixed on the table of the machine tool before machining and then removed from the table after machining in order to replace it with another pallet with a new work.
In view of productivity and labor-saving in machining a large number of works, a pallet-utilizing machine tool is associated with a pallet exchange apparatus which provides an automatic pallet exchange function.
Typically, a conventional pallet exchange apparatus comprises a rotary arm which is rotatable in a vertical plane about a horizontal spindle, two pallet receivers each provided at a respective end of the rotary arm for removably receiving a pallet in the vertical plane of the rotary arm, and a setup stand for holding the pallet in an upright posture and transferring it onto a selected one of the pallet receivers. The pallet carries a work (normally made of a metal) which projects laterally from the vertical plane of the rotary arm when received by the relevant pallet receiver.
In operation of the conventional pallet exchange apparatus, the rotary arm first turns to a position where one of the pallet receivers (referred to as “first pallet receiver” just for convenience of description) is close to the machine tool table while the other pallet receiver (referred to as “second pallet receiver”) is close to the setup stand. In this position, the first pallet receiver receives an old pallet (because it carries a finished work) from the machine tool table, whereas the second pallet receiver receives a new pallet (because it carries a work which requires machining) from the setup stand. Then, the rotary arm turns by 180 degrees to bring the first pallet receiver close to the setup stand for replacement with another pallet at the setup stand while bringing the second pallet receiver close to the machine tool table for fixing the new pallet thereto.
In this way, the conventional pallet exchange apparatus provides an automatic pallet exchanging function for enhancing the productivity. However, the conventional pallet exchange apparatus still has the following disadvantages.
As described above, the work held by each pallet receiver projects laterally from the vertical plane of the rotary arm. Thus, the weight of the work acts to twist the rotary arm, which may cause a positional deviation of the pallet relative to the setup stand and/or the machine tool table to make automatic mounting of the pallet difficult. This problem is particularly remarkable when the weight of the work is large.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a pallet exchange apparatus which is capable of eliminating or reducing the above-described problems of the prior art pallet exchange apparatus.
According to a first aspect of the present invention, a pallet exchange apparatus for a machine tool comprises: a rotary support having a substantially horizontal support surface and rotatable about a substantially vertical axis; drive means for vertically moving and rotating the rotary support; a setup stand pivotable between a lying position for receiving a pallet and an upright position for transferring the received pallet onto the rotary support, the pallet carrying a work; and a plurality of pallet receivers each provided on the support surface of the rotary support for receiving the pallet in an erect posture from the setup stand which has been pivoted to the upright position.
Preferably, the pallet has a work carrying surface, and each of the pallet receivers receives the pallet with the work carrying surface directed toward the vertical axis.
Preferably, the pallet may have a follower roller, and each of the pallet receivers may have a guide mechanism for vertically guiding the follower roller of the pallet. More specifically, each of the pallet receivers may comprise a laterally spaced pair of brackets and a lateral support bar projecting upwardly from one of the paired brackets, and the lateral support bar may be provided with a guide groove serving as the guide mechanism.
Further, each of the brackets may also have an inwardly projecting pin for vertically fitting in a corner groove of the pallet.
Typically, the machine tool includes a table movable toward and away from the rotary support. In this case, each of the setup stand and the table may have an identical engaging mechanism for connection to the pallet. More specifically, the pallet may be provided with a plurality of guide recesses, the engaging mechanism may comprise a corresponding number of positioning rollers for removably fitting in the guide recesses of the pallet. Additionally or alternatively, the pallet may have a ring groove formed with a first coupling, whereas the engaging mechanism may comprise a second coupling for removable engagement with the first coupling.
In a preferred embodiment, the pallet has an outer ring groove formed with a first coupling, whereas the engaging mechanism comprises a second coupling for removable engagement with the first coupling. Further, the pallet is also provided with a plurality of inner guide recesses surrounded by the outer ring groove, whereas the engaging mechanism also comprises a corresponding number of positioning rollers for removably fitting in the inner guide recesses of the pallet.
Preferably, the drive means may comprise a vertical spindle fixed centrally to the rotary support for movement therewith. Further, the rotary support may be in the form of a rotary arm, in which case each of the pallet receivers may be provided at a respective end of the rotary arm.
According to a second aspect of the present invention, a pallet exchange apparatus for a machine tool comprises: a rotary support having a substantially horizontal support surface and rotatable about a substantially vertical axis; drive means for rotating the rotary support; and a plurality of pallet receivers each provided on the support surface of the rotary support for receiving a pallet in an erect posture, the pallet having a work carrying surface directed toward the vertical axis when received by each pallet receiver.
Other objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiment given with reference to the accompanying drawings.
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Higuchi Toshifumi
Sumida Tsuneto
Tanabe Yoji
Yasuda Yukihiko
Armstrong Westerman Hattori McLeland & Naughton LLP
Sharma Rashmi
Walsh Donald P.
Yasda Precision Tools K. K.
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