Chucks or sockets – With fluid-pressure actuator – Socket type
Reexamination Certificate
1999-07-29
2001-08-14
Bishop, Steven C. (Department: 3722)
Chucks or sockets
With fluid-pressure actuator
Socket type
C092S169100, C092S171100, C092S13000R, C269S309000, C409S225000
Reexamination Certificate
active
06273434
ABSTRACT:
The present invention concerns a method for manufacture and assembly as well as a capless quick-grip cylinder manufactured by this method with a feed nipple for clamping a carrier plate, also called a pallet, which on a machine tool serves to fix work pieces.
To allow a quick overview of the relationships with the technological background, the following statements are made.
Quick-grip cylinders are needed for clamping devices for clamping work pieces on carrier plates for machine tools. A quick-grip cylinder of this kind is known, for example, from DE-U-296 15 613 by the present applicant. Such a quick-grip cylinder is distinguished in that in an open-topped housing are formed the seats for support of the clamping springs and that the housing is closed off at the top by an associated cap. The cap has a central recess in which, sealed and flush, the feed nipple is slidable in an axial direction under hydraulic action.
The use of a housing for the quick-grip cylinder with an associated cap does however have drawbacks.
Manufacture of the cap requires elaborate machining steps, for the cap must be machined with high precision as a single component; it needs corresponding through-bores extending all round the periphery and distributed over the circumference. Further, it needs high-precision machining at the outer circumference and on an associated shoulder, so that it can be pressed with excess size, with accurate fit, into the open-topped recess of the housing. Therefore a press fit is used, which is linked to suitably high-precision machining of the open-topped housing and associated cap.
Further, there is an axial shoulder which must be machined correspondingly at its outer circumference, because this shoulder must fit snugly against the inner wall of the cylinder with high precision. Further, a recess must be provided in this shoulder, in which an O-ring is laid so that the cap fits sealingly against the cylinder wall of the housing.
There are several known embodiments for connection of the cap to the housing of the quick-grip cylinder.
In a first known embodiment the cap is designed to sit on the housing of the quick-grip cylinder, i.e. the quick-grip cylinder forms an upwardly extended axial attachment on the end of which the cap is placed and screwed fast with corresponding threaded bores. The drawback is that the feed force of the feed nipple passing through the cap can be so great that the cap is deformed.
Since the total height of the quick-grip cylinder (the height of the housing of the cylinder and cap) is precisely fixed, an accumulation of errors can arise if the two heights do not tally.
In another embodiment it is provided that the cap is inserted in an associated open-topped recess of the housing, this recess comprising a peripheral edge, the edge protruding slightly above the surface of the cap. The cap is therefore, as shown in the above-mentioned utility model, encompassed and held in mating relationship by the peripheral edge.
Here, of course, inadmissible deformation of the cap due to a high feed force of the feed nipple is avoided, but the mounting pallet itself is not prevented from warping when the mounting pallet is mounted on the cap and in turn holds a work piece. Similarly there is the risk that, when the work piece is placed directly on the cap, the clamping force which is applied to the work piece by the feed nipple is transmitted via the cap, which then in turn can bend inadmissibly.
Furthermore the assembly of such a quick-grip cylinder is relatively elaborate because first of all with the cap removed the springs must be inserted in the open-topped recess of the housing of the quick-grip cylinder. The springs are here fitted so as to be first inserted in the housing of the quick-grip cylinder in the relaxed state. Then the cap is placed on top and, under the action of a press which acts on the upper side of the cap, the latter is pressed inwards into the housing of the quick-grip cylinder against the force of the springs. Then the cap is screwed to the housing of the quick-grip cylinder with the assembly screws arranged peripherally on the cap.
But with this arrangement there is the drawback that the cap is connected to the housing of the quick-grip cylinder only under force of pressure, which can lead to certain parts on the quick-grip cylinder being damaged while the cap is pressed in. Also the through-bores in the cap must be made to correspond to the associated threaded bores in the housing of the quick-grip cylinder with accurate fitting under the action of force of pressure, in order to allow assembly of the cap at all.
The assembly screws used for connection of the cap to the housing of the quick-grip cylinder have the added drawback that, as a result, valuable area on the surface of the cap is lost, which could be used e.g. for the arrangement of blow-out grooves or blow-out bores. These blow-out bores must then be formed in the cap outside the corresponding fixing bores, which is associated with increased manufacturing costs, and also with a weakening of the material thickness of the cap.
It is therefore the object of the invention to develop a method for the assembly of a quick-grip cylinder, and to design a quick-grip cylinder made by the method, in such a way that a construction of the quick-grip cylinder which is substantially simpler, cheaper, capable of taking higher loads and operationally reliable, is ensured.
The essential point with the present method is that the quick-grip cylinder is assembled from the piston side (that is, the bottom side, and no longer from above, from the side of the cylinder opening.
In a first step, therefore, first the relaxed springs are inserted in their associated recesses in the open-bottomed cylinder housing, in a second step the piston is then inserted in the cylinder chamber, and in a third step a bottom is laid in the open-bottomed recess of the cylinder housing, in a fourth step with a press this bottom is pressed into the cylinder housing until it reaches a stop fixed to the housing, and in a sixth step to prevent sliding of the bottom in an axial direction—seen outwards—a Seeger ring which fixes the cap to the cylinder housing is inserted, in a seventh step the pressure is removed from the bottom, which accordingly moves downwards in an axial direction under the force of the springs, and is applied to the stop fixed to the housing.
All the directions of motion described above (upward and downward) are here referred to a practical example which shows the quick-grip cylinder in its working position.
These directions are however to be transposed in an analogous manner when the quick-grip cylinder is turned over for assembly purposes, so that its bottom side faces upwards.
It is therefore again emphasised that the directions of motion given here refer to when the quick-grip cylinder is in its operative state.
It is therefore an essential characteristic of the invention that a cap on the upper side of the quick-grip cylinder is completely eliminated, because the upper side of the cylinder housing simultaneously forms the cap. A corresponding cap on the upper side is therefore completely eliminated. Instead, a bottom inserted on the lower side is used, which has substantial advantages over the state of the art. For a bottom of this kind does not have to be made precisely at all, because no clamping forces act on it at all. It must only take up the oil pressure, because it is the bottom boundary of the cylinder housing and subject to oil pressure on its surface. Accordingly there is no longer any danger of this cap being warped by inadmissibly high clamping forces.
With the technical instruction given, there are therefore several advantages simultaneously.
Because a cap on the upper side is eliminated and the corresponding screws are no longer necessary, the drawback that the cap could warp under the action of the clamping force is also eliminated. The portion of the cylinder housing on the upper side, the top region, can be made so thick that warping of this region no longer has to be feared.
Another
Bishop Steven C.
Knobbe Martens Olson & Bear LLP
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