GB1574591A

GB1574591A - Adapter collet with oppositely directed slit- incisions

Info

Publication number: GB1574591A
Application number: GB13089/78A
Authority: GB
Original assignee: Emuge Werk Richard Glimpel GmbH and Co KG Fabrik fuer Praezisionswerkzeuge
Current assignee: Emuge Werk Richard Glimpel GmbH and Co KG Fabrik fuer Praezisionswerkzeuge
Priority date: 1977-04-06
Filing date: 1978-04-04
Publication date: 1980-09-10
Also published as: DE2715418B2; FR2386712B1; DE2715418C3; DE2715418A1; IT1093565B; IT7821975A0; FR2386712A1

Description

(54) ADAPTOR COLLET WITH OPPOSITELY DIRECTED SLIT-INCISIONS (71) We, EMUGE-WERK RICHARD GLIMPEL FABRIK FUR PRAZISIONSWERK ZEUGE vormals Moschkau & Glimpel, an Offene Handelsgesellschaft, of 8560 Lauf ad. Pegnitz, Nurnberger Strasse, 100 Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention concerns an adapter collet for a chuck of the kind comprising a deformation zone provided with at least two oppositely directed slit-incisions.

In an existing adapter collet of this kind (U.S. Patent Specification No. 3,111,327), wherein the taper is provided in the form of a saw-tooth thread, the slits extend in the longitudinal direction of the collet and are evenly spaced over the circumference thereof with equal distances between adjacent slits, so that a single deformation zone is created which extends over the entire circumference of the collet. When such a collet is tensioned, the radially outward movement of the collet strip between adjacent slits will not be directed precisely parallel to itself, but the strip will twist and occupy an oblique position relative to the central collet axis. This twisting of the collet strip has an adverse effect with regard to the clamping accuracy and true rotation characteristics achievable in a collet of this type.

The present invention therefore aims to provide an adapter collet of the kind specified with improved precision of clamping accuracy and true rotaton owing to the provision of a collet strip between adjacent slit incisions which moves radially outwards precisely parallel with itself under the application of tension.

According to the invention there is provided an adapter collet for a chuck, comprising a deformation zone with at least two oppositely directed, longitudinally extending slit incisions, a slit-free bearing zone provided next to the deformation zone and laterally adjacent thereto, said bearing zone being at least twice as wide circumferentially as the distance between adjacent slits in the deformation zone, and the bearing zone being provided with a tapered surface portion to effect a tensioning or clamping see- tion to effect a tensioning or clamping action of the collet, in use.

The slit-free bearing zone provides a collet strip which, because of its greater width, cannot twist under tension and is therefore radially outwardly displaced pre- cisely parallel to itself to engage in pre cisely this condition with the part or object to be clamped in the chuck, wih the result that the collet according to this invention is capable of achieving very considerably improved clamping accuracy and truerunning precision. An essential factor for the achievement of this result is the relatively oppositely directed, i.e. overlapping dispositioin of the slits and this effect cannot be obtained with a unilaterally slit collet wherein the incisions all start at the satne collet end or side, simply by sub-dividing such a collet into bearing and deformation zones.

Preferably the tapered surface portion is provided by means of an internal sawtooth thread of the collet, because, owing to such a thread, the collet is of identical form at either end thereof which means identical expansion behaviour at both collet ends. On the other hand, if the taper is obtained by a processive conical increase of wall thickness over the whole length of the collet, the wall thickness difference between the two collet ends will be extreme and this has an adverse effect on clamping and truerotation accuracy and may even cause twisting of the slit-free, wider bearing zone.

It is partciularly convenient and advantageous for the purpose of this invention if at least two deformation zones are provided which are evenly spaced over the circumference of the collet and relatively separated by bearing zones. A greater number,, e.g.

three, of deformation zones and bearing zones will also improve clamping and truerotation precision of the collet.

It is further of special advantage to provide an even number of slits for each deformation zone, as this will result in symmetrical conditions at both ends of the collet.

Moreover, it is particularly advantageous for the purposes of this invention if the deformation zone is of constant thickness forming a recessed region over the length of the collet. With such an arrangement three is no taper in the region of the deformation zone and the elastic characteristics of the deforming zone can be far more accurately predetermined than this would be possible with a taper in the region of the deformation zone. It is not possible to achieve this kind of control regarding the elastic characteristics of the collet simply by partly eliminating the taper configuration next to the slits. The - important factor is here the oppositely directed disposition of the slits, the grouping - of the slits in a deformation zone, and the constant thickness in the whole of this deformation zone, including the joints at both collet ends.

With special advantage, in such an arrangement the bearing zone thickness dimension will be greater than the thickness of the deformation zone. Such an arrangement permits the production of collets presenting like elastic characteristics for like walL- thickness dimensions of the deformation zone but adapted, by virtue of different wall thicknesses in their bearing zones, i.e. different clamping diameters, for application to part of different dimensions.

In a particularly convenient and advantageous embodiment of this invention the bearing zone is provided with a profile.

This allows so-called profile clamping engagement, that is to say clamping of parts wherein the areas which are engaged with the collet are not cylindrical but of any other, non-cylindrical form, the collet protile being nattirally adapted to such deviation.

A preferred embodiment of the invention is illustrated by way of example in the accompanying drawings, wherein: Figure 1 is a top view or plan of a developed projection of a collet with oppositely directed slits constructed in accordance with the invention, and Figure 2 is an end view of the collet of Fig. 1.

A chuck collet as shown in the drawings is an essentially elongated cylindrical shape circumferentially subdivided into three identical bearing zones 1 and three identical deformation zones 2 which are arranged in alternate succession. Each deformation zone 2 comprises two relatively oppositely directed rectilinear slits 3 parallel with one another and with the central collet axis, each slit starting at one end of the collet and ending in spaced relationship with the other collet end in an enlarged opening 4, the arrangement being such that in each case one slit longitudinally overlaps the space between the terminal enlarged hole of the other slit and the associated collet end. The deformation zone 2 further comprises a narrow marginal strip on each side of the two slits 3. Between the two slits 3 of ecah deformation zone there is a narrow strip 5 attached to the rest of the collet at the two joints 6 within the deformation zone 2. Each bearing zone 1 is at least twice as wide as the strip 5, between slits 3.

Internally the collet comprises a taper for expansion by axial displacement in the form of a saw-tooth thread 7 which is interrupted in the region of each deformation zone 2 and consequently extends only over the regions of the bearing zones 1. In other words, the collet internally comprises a groove-like recess 8 in the region of each deformation zone, which extends over the length of the collet. The wall thickness of the collet is considerably greater in region of the bearing zones, irrespectively of the sawtooth thread 7, than in the region of the deformation zones, so that the outside of the collet in the region of the deformation zones 2 presents groove-like recesses 9 extending over the length of the collet.

The illustrated embodiment of the invention is designed for internal clamping or chuck application. Obviously however the invention is also applicable to an exterior collet or clamping sleeve for external clamping engagement during fitting in chucks, in which case the clamping engagement face of the bearing zone would be on the inside and the taper, that is to say, the saw-tooth thread, for example, on the outside.

WHAT WE CLAIM IS: I. An adapter collet for a chuck, comprising a deformation zone with at least two oppositely directed, longitudinally extending slit incisions, a slit-free bearing zone provided next to the deformation zone and laterally adjacent thereto, said bearing zone being at least twice as wide circumferentially as the distance between adjacent slits in the deformation zone, and the bearing zone being provided with a tapered surface portion to ecect a tensioning or clamping action of the collet, in use.

2. An adapter collet as claimed in claim 1, wherein there are provided at least two circumferentially evenly spared deformation zones whirh are relatively separated by bearing zones.

3. An adapter collet as claimed in claim 1 or claim 2, wherein an even number of slits are provided for each deformation zone.

4. An adapter collet as claimed in any one of the preceding claims, wherein the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

It is further of special advantage to provide an even number of slits for each deformation zone, as this will result in symmetrical conditions at both ends of the collet.

Moreover, it is particularly advantageous for the purposes of this invention if the deformation zone is of constant thickness forming a recessed region over the length of the collet. With such an arrangement three is no taper in the region of the deformation zone and the elastic characteristics of the deforming zone can be far more accurately predetermined than this would be possible with a taper in the region of the deformation zone. It is not possible to achieve this kind of control regarding the elastic characteristics of the collet simply by partly eliminating the taper configuration next to the slits. The - important factor is here the oppositely directed disposition of the slits, the grouping - of the slits in a deformation zone, and the constant thickness in the whole of this deformation zone, including the joints at both collet ends.

With special advantage, in such an arrangement the bearing zone thickness dimension will be greater than the thickness of the deformation zone. Such an arrangement permits the production of collets presenting like elastic characteristics for like walL- thickness dimensions of the deformation zone but adapted, by virtue of different wall thicknesses in their bearing zones, i.e. different clamping diameters, for application to part of different dimensions.

In a particularly convenient and advantageous embodiment of this invention the bearing zone is provided with a profile.

This allows so-called profile clamping engagement, that is to say clamping of parts wherein the areas which are engaged with the collet are not cylindrical but of any other, non-cylindrical form, the collet protile being nattirally adapted to such deviation.

A preferred embodiment of the invention is illustrated by way of example in the accompanying drawings, wherein: Figure 1 is a top view or plan of a developed projection of a collet with oppositely directed slits constructed in accordance with the invention, and Figure 2 is an end view of the collet of Fig. 1.

A chuck collet as shown in the drawings is an essentially elongated cylindrical shape circumferentially subdivided into three identical bearing zones 1 and three identical deformation zones 2 which are arranged in alternate succession. Each deformation zone 2 comprises two relatively oppositely directed rectilinear slits 3 parallel with one another and with the central collet axis, each slit starting at one end of the collet and ending in spaced relationship with the other collet end in an enlarged opening 4, the arrangement being such that in each case one slit longitudinally overlaps the space between the terminal enlarged hole of the other slit and the associated collet end. The deformation zone 2 further comprises a narrow marginal strip on each side of the two slits 3. Between the two slits 3 of ecah deformation zone there is a narrow strip 5 attached to the rest of the collet at the two joints 6 within the deformation zone 2. Each bearing zone 1 is at least twice as wide as the strip 5, between slits 3.

Internally the collet comprises a taper for expansion by axial displacement in the form of a saw-tooth thread 7 which is interrupted in the region of each deformation zone 2 and consequently extends only over the regions of the bearing zones 1. In other words, the collet internally comprises a groove-like recess 8 in the region of each deformation zone, which extends over the length of the collet. The wall thickness of the collet is considerably greater in region of the bearing zones, irrespectively of the sawtooth thread 7, than in the region of the deformation zones, so that the outside of the collet in the region of the deformation zones 2 presents groove-like recesses 9 extending over the length of the collet.

The illustrated embodiment of the invention is designed for internal clamping or chuck application. Obviously however the invention is also applicable to an exterior collet or clamping sleeve for external clamping engagement during fitting in chucks, in which case the clamping engagement face of the bearing zone would be on the inside and the taper, that is to say, the saw-tooth thread, for example, on the outside.

WHAT WE CLAIM IS: I. An adapter collet for a chuck, comprising a deformation zone with at least two oppositely directed, longitudinally extending slit incisions, a slit-free bearing zone provided next to the deformation zone and laterally adjacent thereto, said bearing zone being at least twice as wide circumferentially as the distance between adjacent slits in the deformation zone, and the bearing zone being provided with a tapered surface portion to ecect a tensioning or clamping action of the collet, in use.
2. An adapter collet as claimed in claim 1, wherein there are provided at least two circumferentially evenly spared deformation zones whirh are relatively separated by bearing zones.
3. An adapter collet as claimed in claim 1 or claim 2, wherein an even number of slits are provided for each deformation zone.
4. An adapter collet as claimed in any one of the preceding claims, wherein the

wall thickness of the deformatino zone is constant over the length of the collet to foriji a recess area.
5. An adapter collet as claimed in any one of claims 1 to 4, wherein the wall thickness of the bearing zone is greater than the wall thickness of the deformation zone.
6. An adapter collet as claimed in any one of the preceding claims wherein said tapered surface portion is provided on one of the interior and exterior surfaces of said bearing zone and the other of said interior and exterior surface is provided with a non-cylindrical profile, to which, in use, a member can be clamped to engage the collet.
7. An adapter collet as claimed in any one of the preceding claims, wherein said taper is provided by a saw-tooth thread.
8. An adapter collet as claimed in claim 7, wherein said thread is provided on the inside of the collet.
9. An adapter collet substantially as hereinbefore described with reference to and as shown in the accompanying drawings.