GB2113124A - Gripping jaw for machine tool rotary chucks - Google Patents

Abstract

A gripping jaw (1) has a bearing surface (3) and a stop surface (4) defining a recess for receiving a gripping insert (5). The gripping insert (5) is retained in the jaw (1) by a screw (6) extending through an oversize bore in the insert, the longitudinal axis (6a) of which screw extends at an acute angle to the bearing surface (3). <IMAGE>

Description

SPECIFICATION Gripping jaw The invention relates to a gripping jaw for gripping devices, in particular rotary chucks, comprising a replaceable gripping insert which is supported in the gripping jaw against a bearing surface thereof which is inclined to the gripping direction, and against a stop surface thereof which extends at an angle to this latter surface, and is protected against falling out by at least one retention element which does not hinder the automatic adjustment of the gripping insert relative to the gripping jaw.

Gripping jaws provided with gripping inserts are known in various embodiments. In addition to hard metal-clad gripping inserts, there are replaceable hard gripping claws which are fixed by screws either to the gripping surface of the gripping jaw or in a recess provided in the gripping surface.

The known embodiments of such gripping jaws have the drawback that the position of the gripping inserts is determined by their fixing screws, the strength of which is limited, so that frequently the necessary precision cannot be attained or the high power required for heavy machining cannot be transmitted.

In order to provide a gripping jaw, of which the gripping insert can be exactly positioned in the gripping jaw and can be retained both in an axial and radial direction in its given position in the gripping jaw, it has already been proposed to support the gripping insert in the gripping jaw against a bearing surface inclined to the gripping direction, and against a stop surface extending at an angle thereto.

By means of this proposal, the gripping insert is retained in a radial and axial direction in its given position by the gripping force alone, as it is slid along the inclined bearing surface until it makes contact with the stop surface which extends at an angle thereto, and thus assumes its given position under the action of the gripping force. Moreover, there is the advantage that in order to grip different work pieces, it is not necessary to replace complete false jaws, but only the gripping inserts, which because of their small volume can be produced from high-value material and be adapted to the respective gripping application.

If the gripping inserts grip over the bearing surface of the gripping jaws by means of lateral clip-type appendices, they automatically orientate themselves relative to the gripping jaw when substituted. It is only necessary to mount the gripping insert on the inclined bearing surface, whereupon the laterally projecting appendices determine the position transverse to the gripping jaw, and the final position of the gripping insert relative to the gripping jaw is attained by applying pressure in the gripping direction. Because of the form-locked connection which is thus attained between the gripping insert and gripping jaw, it is possible to transmit a high torque for high metal removal rates.

In order to protect the gripping inserts from falling out, in particular when a rotary chuck is at rest, each gripping insert is retained by at least one retention element which does not hinder the automatic adjustment of the gripping insert relative to the gripping jaw. Preferred retention elements are screws or pins. By overdimensioning both the bore through which the screw shank passes and the recess for the screw head, the screw or pin is allowed to retain the gripping insert on the gripping jaw, but without presenting any hindrance to the automatic orientation of the gripping insert relative to the bearing surface and stop surface.

In the practical operation of the presently described initially defined clamping jaw, it has appeared that the operating personnel fully tighten the screws acting as the retention element by means of which the gripping inserts are merely retained on the gripping jaws against falling out, due to a misunderstanding of their purpose because they believed that it is necessary to fully tighten them in order to transmit the required torque. In order to exclude any possibility of hindering the automatic orientation of the gripping insert when the screws acting as the retention element are fully tightened in this manner, the position of the retention element assumes special importance.

The object of the invention is therefore to improve a gripping jaw of the initially described type in such a manner that no hindrance to the automatic orientation of the gripping insert relative to the gripping jaw arises even if the retention element is fully tightened.

This object is attained according to the invention in that the longitudinal axis of the retention element extends at an acute angle to the bearing surface. By this means, it is assured that even if the retention element should exert a pulling action on the gripping insert, for example due to the fact that the screw serving as the retention element has been too fully tightened, the automatic orientation of the gripping insert relative to the bearing surface and stop surface is not hindered, due to the fact that the action of the retention element, which substantially coincides with the longitudinal axis of the retention element, pulls the gripping insert both against the bearing surface and against the stop surface.Thus by virtue of the retention element positioning according to the invention, any hindrance or unattainability in orientating the gripping insert exclusively in accordance with the bearing surface and stop surface is prevented.

According to a preferred embodiment, the longitudinal axis of the retention element can extend in a direction radial to the gripping jaw, because the bearing surface is inclined to the gripping direction. According to a further characteristic of the invention, a particularly satisfactory positioning of the retention element is attained if the longitudinal axis of the retention element extends at an acute angle both to the bearing surface and to the stop surface. In this case, if the retention element exerts a pulling action, the gripping insert is pulled into the acute angled corner formed by the bearing surface and stop surface, so that no gap can arise either between the gripping insert and bearing surface or between the gripping insert and stop surface.

The drawing shows a side view of one embodiment of the gripping jaw according to the invention.

The embodiment illustrated on the drawing shows a gripping jaw 1 for a rotary chuck, and provided on its rear end with trapezoidal toothing 2 so that it can be adjusted relative to a holding drive fixture. The chuck and drive for the gripping jaw 1 are not shown on the drawing.

A recess is provided in the gripping surface of the gripping jaw 1, and comprises a bearing surface 3 inclined to the radially extending gripping direction, and a stop surface 4 which extends at an angle to this latter surface. The inclination of the bearing surface 3 is such a gripping insert 5 provided with a corresponding counter-surface is slid by the gripping force along the bearing surface 3 until it comes into contact with the stop surface 4. In this manner, the position of the gripping insert 5 is determined both in the axial and in the radial direction.

The gripping insert 5 comprises lateral appendices which grip over the bearing surface of the gripping jaw in the manner of clips. These appendices are not shown on the drawing.

The drawing does show however that the gripping surface of the gripping insert 5 is formed from claw-like jutting projections, of which the tips lie on a circular arc which is concave to the gripping jaw 1 in the case of external gripping, and on a circular arc which is convex to the gripping jaw 1 in the case of internal gripping.

A screw 6 is provided in order to retain the gripping insert 5 in the gripping jaw 1 when there is no workpiece W present, and in particular when the chuck is stationary. The bore provided in the gripping insert 5 for the screw 6 has a greater diameter than the screw shank. The recess provided in the gripping insert 5 for the head of the screw 6 is also dimensioned so that the automatic position setting of the gripping insert 5 relative to the gripping jaw 1 is not impaired by the screw 6.

The longitudinal axis 6a of the screw 6 shown on the drawing with full lines extends at an acute angle 8 to the bearing surface 3. Two further possibilities for the positioning of the screw 6 in the gripping jaw 1 are shown by dashed and dotted lines. These illustrated positions show that even in these two extreme cases, the longitudinal axis 6a of the screw 6 extends at an acute angle 8 to the bearing surface 3. This is thus also the case when the screw 6 extends in a radial direction.

The position of the screw 6 shown in full lines indicates that the longitudinal axis 6a of the screw 6 also extends at an acute angle 9 to the contact surface 4 provided it is inclined slightly away from the radial direction towards the direction of the trapezoidal toothing 2 of the gripping jaw 1. By this means, if the screw 6 which passes slackly through the gripping insert 5 is tightened too fully, then the gripping insert 5 is pulled into the corner of the gripping jaw 1 formed by the bearing surface 3 and stop surface 4.

In order to enable an axial position to be defined for the work piece W which is independent of the respective construction of the gripping jaw 1, a stop pin 7 is provided. This is screwed into the gripping jaw 1 in an axial direction and its end surface serves as a contact surface for the work piece W. If the axial position of the work piece W relative to the gripping jaw 1 is to be changed, then the stop pin 7 can be substituted, or can be shortened in terms of its axial length. For this purpose it is preferably constructed of a machinable material.

Claims (4)

1. A gripping jaw for gripping devices, in particular rotary chucks, comprising a replaceable gripping insert which is supported in the gripping jaw against a bearing surface thereof which is inclined to the gripping direction, and against a stop surface thereof which extends at an angle to this latter surface, and is protected against falling out by at least one retention element which does not hinder the automatic adjustment of the gripping insert relative to the gripping jaw, characterised in that the longitudinal axis (6a) of the retention element (6) extends at an acute angle (8) to the bearing surface.

2. A gripping jaw as claimed in claim 1, characterised in that the longitudinal axis (6a) of the retention element (6) extends at an acute angle (8 and 9 respectively) both to the bearing surface (3) and to the stop surface (4).

3. A gripping jaw comprising a housing, a gripping jaw insert adapted to be received in a recess in the housing with surfaces of the insert adjacent a bearing surface and a stop surface defining the recess in the housing, the bearing and stop surfaces being disposed such that during rotation of the gripping jaw, the insert is automatically positioned with respect to the housing, and retention means for holding said insert in the housing without preventing said automatic positioning.

4. A gripping jaw substantially as herein described with reference to the accompanying drawing.