Expansible chamber devices – With releasable stop or latch means to prevent movement of... – Means includes element interfitting between working member...
Patent
1995-01-03
1996-06-04
Lopez, F. Daniel
Expansible chamber devices
With releasable stop or latch means to prevent movement of...
Means includes element interfitting between working member...
60406, F15B 1526
Patent
active
055223036
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a machine tool comprising a headstock, at least one tool changer adapted to move production tools between a magazine position and a working position, and at least one fluid power drive cylinder associated with the tool changer as a drive unit, said cylinder having a cylinder housing, in which an axially moving piston is arranged.
A machine tool of this type is for instance disclosed in the European patent publication 0 205 030 A2. The drive cylinder is in this case dependent, the piston rod connected with the piston being directed vertically downward therefrom and bearing the object to be manipulated, generally a production tool. When the machine tool is not in the operative condition the drive cylinder is in a withdrawn position, the drive piston assuming an end of stroke position near the upper terminating wall of the cylinder housing. During long periods in which the drive cylinder is not used, this length of the stroke is not constant. Owing to a reduction in the operating pressure the piston tends to move down, under the constant weight acting on it, toward the extended position of the drive cylinder. Apart from dangers with may arise, this may also lead to impairment of function of the machine tools equipped with the drive cylinder. Therefore so far attempts have been made to evolve external and intricate support structure in order to lock the drive cylinder during idle times.
In known machine tools there is furthermore the disadvantage that the power valves and any pilot valves must be arranged on the machine tools themselves so that during the final assembly of such machine tools arranging piping and wiring is complex, for the pneumatic and also for the electrical systems.
Taking this as a starting point one object of the present invention is to so improve on a machine tool of the type initially mentioned that, while maintaining a generally compact design the drive piston can be reliably locked during idle times with the result that when the machine tool is put into use again no dangerous situations occur. Furthermore low-wear operation is to be possible.
In accordance with the invention this object is to be attained by the provision of a locking mechanism on the drive cylinder, which is adapted to mechanically lock in relation to the housing if a release pressure of the piston should drop.
In case of need, that is to say, if the release pressure should fail, the locking mechanism ensures mechanical locking of the drive piston in relation to the housing so that the piston is prevented from moving out of the end of stroke position it previously reached.
Further advantageous forms of the invention are recited in the dependent claims.
If the locking device is integrated in the drive cylinder and, as is preferred, the release pressure is the operating pressure of the drive cylinder, final assembly of the novel machine tool becomes very simple. In fact it is merely necessary to arrange one fluid power line running to the drive unit, via which both the operating pressure and also the release pressure for the locking device is supplied. If the operating pressure should drop, and accordingly the release pressure, in the novel machine tool the tool changers located in the end of stroke setting will be mechanically locked so that they are not able to move downward. This involves the advantage that when the novel machine tool is turned off or there is a failure of the compressed air supply the tool changers are not able to "sag", something which would lead to a dangerous or a confused operational situation.
The locking action is preferably only effective if the drive cylinder is outside the ready for operation condition so that it is merely during short machine related idle times that no locking is necessary. This may be ensured by always having a sufficient level of release pressure, which maintains the second transversely moving locking part in a release setting. It is only when the release pressure sinks to below a certain and more particularly predetermined value that, acted upon
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Grund Peter
Preussler Udo
Stoll Kurt
Chiron-Werke GmbH & Co. KG
Festo KG of Ruiter
Lopez F. Daniel
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