Diaphragm chuck

A diaphragm chuck with an operating element inserted in a chuck body and axially movable in relation to the chuck body, a diaphragm attached to a free end of the operating element with the diaphragm secured to the chuck body by its outer circumference, three base jaws in driving connection with the diaphragm, on each of which a centering surface is disposed in a concentric alignment with the axis of the operating element, three clamping jaws attached to the corresponding base jaws, by which a gear to be machined can be clamped and which make contact with the centering surface, and clamping pins, each allocated to one of the clamping jaws, radially aligned and arranged between two teeth of the gear in the clamped condition, such that the diaphragm chucks reliably clamps differently sized gears and gears with different numbers of teeth between the three clamping jaws.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a diaphragm chuck.

2. Description of the Prior Art

Diaphragm chucks of this type are described in EP 1 837 108 B1 and EP 1 757 392 B1. A diaphragm attached to an operating element is tilted outwards in an area where it is attached to the chuck body, as a result of which a swivelling movement of a base jaw attached to a machine occurs in a radially outward direction. The operating element is configured, for example, as a pneumatically or hydraulically operated piston with a piston rod attached thereto, which is moved in the direction of a workpiece to be clamped, in order to open base jaws and clamping jaws attached thereto, with the effect that a workpiece can be removed from the clamping jaws, or a new workpiece to be machined can be inserted between the clamping jaws.

Although diaphragm chucks of this kind have proven themselves in practice, they do suffer from the disadvantage that the clamping jaws and the base jaws on the chuck body must be reconfigured for each workpiece that is to be machined, because the radial stroke of the clamping and base jaws is only a few millimeters as the diaphragms only move through an extremely small advance and opening stroke. In particular, if gears are to be clamping in the diaphragm chuck for machining, then different base and clamping jaw arrangements have to be mounted on the chuck body for each geometrical dimension of the particular gear. If, for example, the base circle of the gear is reduced or increased in size whilst maintaining a constant pitch, then the clamping jaw/base jaw arrangement system intended for a particular base circle cannot be used, because the distance between the clamping pins and the gear to be clamped ends up too large or too small with the effect that no clamping force can be generated, or the clamping pins make contact with the gear before the diaphragm has been moved back to its initial position in order to generate the clamping force.

As a result, companies which wish to use such diaphragm chucks need to have a corresponding clamping jaw/base jaw unit for almost every geometry of gears to be machined, so that there will be a unit adapted geometrically accurately to the particular gear to be machined.

SUMMARY OF THE INVENTION

An object of the present invention is, therefore, to improve a diaphragm chuck of the aforementioned type by enabling it reliably to clamp differently sized gears and gears with different numbers of teeth (i.e. different tooth pitches) between the three clamping jaws.

Centering grooves worked into a base element and corresponding clamping jaws can be aligned by means of keys that are inserted in the grooves, with the effect that distances can be adjusted in the circumferential direction between the three clamping jaws and the geometrical outer contour of the gear to be clamped, and in relation to the pitch (i.e. the number of teeth on the gear wheel), without the need for exchanging the clamping jaws or the base jaws. The assembly of the clamping jaw and base jaw can therefore be used for gears with different pitch values and differently sized base circles, because not only can the clamping jaws be aligned concentrically about the middle point of the chuck but also the radial distance between the heads of clamping pins can be adjusted variably within a certain range of dimensions.

Furthermore, it is advantageous for the heads of the clamping pins to be able to be adjusted to the geometry of the teeth, in particular to the geometry of two adjacent flanks of teeth, in such a way that the heads end up in contact between the two adjacent tooth flanks and therefore clamp the gear reliably.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A,1B and1C show a diaphragm chuck1with a chuck body2in which an operating element3is mounted in a central and axially movable arrangement. The operating element3can be configured, for example, as a hydraulically or pneumatically operated piston with a piston rod attached to it. The operating element3runs in alignment with an axis10of the chuck body2. A free end4of the operating element3is provided a diaphragm5connected to it in a drivable arrangement. An outer circumference6of the diaphragm5is attached to the chuck body2, with the effect that the stroke movements, i.e. the axial movements of the operating element3, are parallel to the axis10of the chuck body2and result in a deflection of the diaphragm5.

Three base jaws7,8and9are attached to the diaphragm5at an angle of 120° in relation to one another, with the effect that deflections of the diaphragm5lead to the base jaws7,8and9being swivelled radially outwards or inwards. A clamping jaw12,13and14is attached to each of the base jaws7,8and9, which guarantees that the three clamping jaws12,13and14carry out the radial tilting movements of the base jaws7,8and9. The position of the clamping jaws12,13and14can be variably adjusted—as explained below—in relation to the corresponding base jaws7,8,9.

A gear20should be able to be clamped by the clamping jaws7,8and9. The clamping jaws12,13and14are aligned at an angle of about 120° in relation to one another. However, it is also feasible for more than three clamping jaws12,13and14, as well as more than three base jaws7,8and9, to be attached to the diaphragm5.

It is necessary for the three clamping jaws12,13and14to have an exactly equally sized distance in relation to the axis10of the chuck body2or the middle point11of chuck body2, which should run in alignment with the middle point of the gear20to be clamped, in order to achieve machining and clamping of the gear20which is, if possible, free from tolerance. For this purpose, a centering surface18is worked on each of the base jaws7,8and9concentrically about the middle point11, with the radial distance of the centering surface18in relation to the axis10or the middle point11having the same size. The corresponding clamping jaw12,13or14should be in contact with the centering surface18when installed, and be held by this centering surface18in a radial direction in the form of a stop, with the effect that the radial distance of the three clamping jaws12,13and14in relation to the axis10or the middle point11is also of the same size.

To achieve this, each of the base jaws7,8and9is provided with a hole27, a detent guide28, a compression spring29, and a detent pin30inserted in it. The compression spring29presses the detent pin30out of the base jaw7,8or9in such a way that the detent pin30projects from the plane formed by the corresponding base jaw7,8or9. A wedge-shaped or pyramid-shaped groove31is worked into the corresponding clamping jaws12,13or14, and this groove31must be aligned with the detent pin30. The detent pin30projects into the corresponding groove31. The inclined plane of the groove31gives rise to a force component running radially outwards and by means of which the corresponding clamping jaw12,13or14is pressed in the direction of the centering surface18of the corresponding base jaw7,8or9, with the effect that the clamping jaws12,13or14make contact with the centering surface18.

A concentrically or arc-shaped slot15aligned about the middle point11is worked into each of the clamping jaws12,13and14, and a retaining screw17is inserted through the slot15. One or more threaded holes16is/are provided in the corresponding base jaws7,8or9, with the effect that the clamping jaws12,13or14are held in the threaded hole16of the base jaw7,8or9by means of the retaining screw17.

Each of the clamping jaws12,13and14is provided with a through-hole33running radially, with a clamping pin19inserted in it. The head32of the clamping pin19is arranged between two teeth20′ of the gear20. This can be seen in particular inFIGS. 1A,1B and1C. The external contour of the head32is adapted to the distances between the teeth20′, with the effect that the head32makes contact with the tooth flanks20″ of the gear20when clamped.

Furthermore, the radial distance of the head32of the corresponding clamping pin19can be changed by means of a setscrew36screwed into the through-hole33because the setscrew36pushes a ball35against the end of the clamping pin19, with the effect that this can be moved against the force of a compression spring34inserted between the setscrew36and the clamping pin19. The setscrew36, the ball35and the clamping pin19form a common subassembly, with the effect that when the setscrew36is screwed in, the clamping pin19is pushed out of the clamping jaws12,13or14and, when the setscrew36is screwed out, the clamping pin19is moved inwards in the direction of the clamping jaws12,13or14.

Due to the radial setting options of the clamping pins19, it is possible to insert differently sized gears20between the three clamping pins19.

Normally, the diaphragm5is deflected by the operating element3; the operating element3is therefore moved in the direction of the gear20that is to be clamped. The stroke movement of the operating element3is about one mm, as a result of which the diaphragm5is deflected by about the same swivelling travel. The movement of the diaphragm5causes the clamping jaws12,13and14, as well as the base jaws7,8and9, to move in the radial direction, with the effect that the radial distance between the heads32of the clamping pins19is increased. The gear20to be machined can be inserted in the corresponding way. The operator must adjust the diaphragm chuck1in such a way that initially the operating element3is moved back towards its initial position. Following a stroke travel of about 0.8 mm, the heads32of the clamping pins19should secure the gear20to be clamped exactly centrally, with the effect that the middle point of the gear20and the axis10are in alignment with one another. The remaining stroke travel of 0.2 mm is required for the diaphragm5to establish a corresponding preload force by means of which the clamping force of the clamping pins19is generated. In addition, the operating element3can also be pushed or moved actively further back so that additionally a clamping force acts on the gear20by means of the clamping pins19. The setscrew36of the clamping pins19must be changed in order for this setting position or clamping position to be found.

The gears20to be machined can have a different number of teeth (referred to as the pitch (T)) even if the base circle diameter is the same, therefore it is necessary for the concentric position of the clamping jaws12,13and14to be able to be aligned in relation to the middle point11in order to enable the three clamping pins19to engage between two teeth20′.

FIGS. 2,3A,3B,3C,4,5A and5B in particular show the positioning of the clamping jaws12,13and14in relation to the different pitch (T) of the gears20to be machined. Each of the base jaws7,8and9has a centering groove21worked into it; each of the clamping jaws12,13and14also has a centering groove21provided in it. If, for example, the pitch (T) can be divided by the factor three, then the centering grooves21of the base jaws7,8and9and the clamping jaws12,13and14must be aligned with one another exactly. Flush alignment of the centering grooves21of the base jaws7,8and9and of the clamping jaws12,13and14can be achieved using three keys22,23and24, shown inFIG. 5B. The three keys22,23and24have a T-shaped cross section. The keys23and24of the clamping jaws13and14are aligned offset from one another in a mirror-image arrangement.

Each of the keys22,23and24is held in a threaded hole26worked into the corresponding base jaws7,8or9by means of a screw25.

If a gear20with, for example, thirty-one teeth must be clamped, then the clamping jaw12can be secured on the base jaw7, as before, using a T-shaped key22. The number of teeth between the clamping jaw12and the clamping jaw13should be ten, with the effect that the clamping jaw13must be moved out of the position shown inFIG. 5Bin the direction of the clamping jaw12. The key23is now configured with an S-shaped cross section, with the effect that the centering grooves21in the base jaw8are aligned so they are laterally offset in relation to the centering groove21of the clamping jaw13.

The total of thirty-one teeth20′ of the gear20should be arranged between the clamping jaw13and the clamping jaw14, with the effect that the clamping jaw14must be moved further away from the clamping jaw13. This is achieved in that an S-shaped key24is inserted into the centering groove21of the base jaw9and of the clamping jaw14, in which case the key24is arranged so it is offset in a mirror-image arrangement in relation to the key23. This means there are ten of the total of thirty-one teeth20′ between the clamping jaw12and the clamping jaw13/clamping jaw14, and eleven of the total of thirty-one teeth20′ between the clamping jaws13and14, shown inFIG. 2.

If a gear20with thirty-two teeth20′ should be clamped on the diaphragm chuck1, then the positions of the clamping jaws13and14must be changed so that the distance between the clamping jaw12and the clamping jaw13, or between the clamping jaw12and the clamping jaw14, is increased to a total of eleven out of the thirty-two teeth20′, and therefore ten of the total of thirty-two teeth20′ are arranged between the two adjacent clamping jaws13and14.FIG. 5Ashows that the keys23and24have an S-shaped design and are offset from one another in a mirror-image arrangement. The leg of the key23projecting into the centering groove21of the base jaw8and the leg of the key24projecting into the centering groove21of the clamping jaw14face one another in this case.

The T-shaped or S-shaped cross-sectional shape of the keys22,23and24therefore enables the concentric position of the clamping jaws12,13and14to be adapted to the pitch (T) of the gear20that is to be clamped.

FIGS. 3A,3B and3C in particular, show the arrangement of the corresponding keys22,23and24in the base jaw7,8and9or the clamping jaw12,13and14.