GB2188264A

GB2188264A - A clamping mechanism for tools

Info

Publication number: GB2188264A
Application number: GB08707259A
Authority: GB
Inventors: Karl-Friedrich Diener
Original assignee: SKF GmbH
Current assignee: SKF GmbH
Priority date: 1986-03-26
Filing date: 1987-03-26
Publication date: 1987-09-30
Anticipated expiration: 2007-03-26
Also published as: FR2596310A1; GB2188264B; DE3610143A1; IT8719562A0; GB8707259D0; IT1202620B

Abstract

A clamping mechanism comprises a shaft (10) having a bore (12), tool or tool holder (15), a plug (19) biased by a spring (23), the plug and tool holder being connected together in the manner of a bayonet fitting, first means (32, 34) allowing the tool holder (15) to be disconnected from and reconnected to the plug (19) and second means preventing rotation of the tool holder (15) with respect to the shaft (10). The plug (19) is rotatable in the bore (12) and the second means (30, 31) is positioned in the bore and comprises interengaging formations (30, 31) which are respectively fixed with respect to the shaft (10) and the tool holder (15). <IMAGE>

Description

SPECIFICATION Aclamping mechanism This invention is concerned with a clamping mechanism, such as a chuck, for holding tools, tool holdersandthe like.

Patent Specification GB 1152864 (Brundler) discloses a detachablequick-action chuck with tool holderwhich comprises a body having a bore opening at one end. A device, in this case the tool holder, is received in the open end. The body and the device have co-operating conical surfaces which axially and radially position the device with respect to the body. A plug or insert is disposed in the bore for movement therealong. A spring is-also disposed in the bore and biases the plug away from the open end of the bore.

The device and plug are structured and connected to each other in the manner of a bayonetfitting. First means allows the device to be disconnected from and re-connected to the plug and second means prevents rotation ofthedevicewith respecttothe body.

Actuation ofthefirst means causes the plug to move longitudinallyagainsttheforceofthespring. Because ofthe rotary construction ofthis first means, the plug is keyed with the body so that it can move longitudinally but not rotationally with respectto the body.

Afterthefirstmeans is actuated, then the device is disconnected by rotating it with respect to the plug and then withdrawing it longitudinallyfrom the body.

The action of the biassing spring clamps the device to the body and seats it firmly into the open end ofthe bore. The engagement of the conical surfaces provides a frictional connection resisting rotation of the device with respect to the body. The known construction also has a rockable lever mounted on the body at the end where the bore opens, and the device has a recess in its conical surface in which the lever engages when the device is aligned correctly. The engagement of the lever in the recess prevents rotation of the device with respecttothe body in either direction. In an alternative construction,the body has a radial screw-threaded bore and a screw engages in this and extends into the recess in the device. Every time the device isto be unclamped and disconnected, the lever orthe screw has to be disconnected.The lever or screw offersprotection only under limited torque and cannot entirely prevent rotation of the seating surfaces with respect to each other. This can lead to su bstantial wear ofthe surfaces, which can be quite rapid if there arefrequent changes ofthe device. As a consequencethedevice could be retained inaccurately and clamped unsatisfactorily with radial play. Also, as a result of shock loads, the lever or screw could shear leading to rotation of the device with respect to the body. The known construction also has a stop and/or engagement piece in the device to stop the device rotating with respect to the plug and becoming disconnected, since the plug is fixed rotationally with respectto the body.However, the stop and/or engagement piece can be dimensioned to shear as soon as the stress on the device exceeds a predetermined value. This can lead to the device becoming completely disconnected with the attendant risk of injury.

According to the invention a clamping mechanism comprises a body having a bore opening at one end of the body, a device received in the open end, the body and device having co-operating surfaces axially and radially positioning the device with respectto the body, a plug which is disposed in the bore for movementtherealong, a spring which is disposed in the bore and biases the plug away from the open end ofthe bore, the device and plug being structured and connected to each other in the manner of a bayonet fitting, first means allowing the device to be disconnected from and re-connected to the plug, and second means preventing rotation of the device with respect tothe body, wherein the plug is rotatable inthe bore and the second means is positioned within the bore and comprises interenagaging formations which are respectively fixed with respect to the body and device.

With such a construction, the device does not have to be rotated with respecttothe body to connect and disconnect it. The device simply has to be offered up and then the plug rotated to clamp the device to the body.

The interengaging formations can comprise a projection integrallyformed on an end face ofthe device engaging in a recess in the body, or the other way round. Thus the projection can have a relatively large cross-section whereby shearing off under shock loads is practically precluded. More than one projection and corresponding recess can be provided and they can be arranged annularly. Varioustypes of formation can be used,forexample, studs, blocks, teeth or radially extending projections which are disposed on radially extending and opposed surfaces.

Preferably, the interengaging formations are an interference fit with one another so precluding any play. The formation can be tapering orwedge-shaped so that a wedge-sha ped projection is an interference fit in a wedge-shaped recess, the corresponding surfaces being brought into firm contact by the biassing action ofthe spring.

Preferably, those of the interengaging formations that are fixed with respect to the device are provided by an annular memberwhich is produced separately from the device and is then fixed thereto, and preferably, those ofthe interengaging formations that are fixed with respect to the body are provided by an annular memberwhich is produced separately from the body and is then fixed thereto.

Such constructional features provide certain advantages in the production and assembly ofthe mechanism. Each annular member can befixed by,for example, a screw-threaded engagamentwith a cross pinorfixed by means of adhesive.

The annular memberwhich is fixed to the body can provide an abutmentforthe spring. The spring can, with othercomponents,thus be inserted into the bore in the body, and then the annular member can be fixed in place.

Preferably, the first means comprises a rod which extends in the bore for moving the plug longitudinally and rotationally, and a sleeve which extends in the boreforacting on the spring to allow free longitudinal movementofthe plug, the rod and the sleeve being operable independently from each other. In use of such a constructional feature, the sleeve is used to act onthespring and relieve the plug of load and allow it a certain amount of free longitudinal movement for disengagement of the interengaging formations of the second means.

Then the rod can be used, without abrasion of pressure surfaces and without rotating the spring or components ofthe spring so keeping wearto a minimum. Sincethe rod and the sleeve are operable independently of each other, the movements of each are sepa rate from the other and so do not interfere with each other, thereby reducing the risk of accidental erroneous movements.

Preferably, the sleeve is rotationally fixed with respectto the body so that the sleeve cannot accidently act rotationally on the rod. The sleeve can be secured rotationally in one of a number of known ways, forexample, by using longitudinal grooves and guide keys, splines and pins.

Advantageously, the plug and the rod can be fixed together so that they move rotationally and longitudi- nallywith each other and there is no play. The plug will be a highly stressed component made of a material having a higherqualitythanthatofthe rod. However, to disconnect and reconnectthe device reliably, transmission of movement from the rod to the plug should be directand without play.Theycan be screwed together and then a cross-pin inserted.

Preferably, the device and the plug have interengaging formations which are respectively fixed with respectto the device and plug and prevent rotation of one with respectto the other. If, for some reason, the second means preventing rotation ofthedevicewith respect to the bodywere to fail, thus resulting in rotation of the device with respect to the body, then the plug would rotate with the device. With the biassing force ofthe spring,the plug and the device would remain connected so preventing a possibly serious accident.

Preferably, those ofthe interengaging formations that are fixed with respect to the device are provided by an annular memberwhich is produced separately from the device and is then fixed thereto, and preferably, those of the interengaging formations that are fixed with respect to the plug are provided by an annular memberwhich is produced separately from the plug and is then fixed thereto. Such constructional features provide advantages in production and assemblyofthe mechanism.

Preferably, the interengaging formations are radial ly extending projections which are disposed on radially extending and opposed surfaces. For example, known types of teeth or Hi rth-type serrations are particularly advantageous.

In the accompanying drawings, Figure 1 is a longitudinal section through part of a clamping mechanism which clamps a tool; and Figure 2 is a section through partofinterengaging formations incorporated in the mechanism.

Referring to Figure 1 initially',the clamping mechanism comprises an elongate cylindrical body 10 mounted for rotation by two single row angular contact ball bearings 11. The body 10 has a longitudi nallyextending bore 12 which opensateach end ofthe body 10.Attheend shown,the bore 12 has a frusto-conical surface 13 converging inwardly of the body and from a flat radially extending end surface 14 ofthe body.Atool 15,forexample a milling cutter, is receivd in this open end and has a projection 16 with a frusto-conical surface 17 which extends from a flat radially extending flange surface 18 in accordance with DIN 55026 (March ~980~Machine Tools; Spindle Noses with Centering Taper and Flange; Dimensions). The surfaces 13,17 and 14,18 ofthe body a0 and tool 15 co-operate with each other and axiallyand radially position the tool 15 with respectto the body 10.

A cylindrisal plug 19 is disposed in the bore 12 for movementtherealeng. The plug 19 has an annular flange the end atthn--enclfurtherfrom thetool 15. Athrust washer 21 extendsarnund the plug 19 and abuts the flange 20. An annu larmember 22 is screwed into and fixed in a cylindrical portionofthe bore 12 extending from the frusto-conical surface 13, the plug 19 extending through the bore ofthe annnular member.

Aspring 23, comprising asetofconical orbelleville spring elements, isarranged inthe bore 112,around the plug 19 and between the th rustwasher 20 and the annular member 22.Thespring 23 biases the plug 19 away from the tool 15. The spring 23 extends in a reduced diameter portion of the bore 12 extending from the portion containing the member 22, which member abuts a shoulder ofthe bore.

The tool 15 and the plug 19 are connected together in the manner of a bayonetfitting. The end ofthe plug 19 opposite to that with the flange 20 has a reduced diameter section which is screw-threaded. An annular member 24 is screwed onto this end of the plug 19 and fixed in place by a radial cross-pin 25. The annular member 24 provides the plug 19 with two projections extending radially away from each other. The projection 16 of the tool 15 has a cylindrical socket 26 in its end face, which socket has a screw-threaded portion leading to a reduced diameter portion. An annular member 27 is screwed into the large diameter portion of the socket 26 and is fixed in place by an axial pin 28.

The annular member27hastwo radially extending slots for receiving the, radial projections ofthe annular member 24. The drawing shows the condition in which the tool 15 and p [ ug 19 have been rotated with respectto each otheraftertheendoftheplug having the annular member 24 has been received in the reduced diameter portion of the socket 26.

The radiaííy, extending and opposed faces of the two annular mernlAers24and 27 have interengaging formations 29 irrtheform of radially extending teeth.

These preventthetool 15 from rotating with respecttQ the plug 1,9~ The radiatly extending and opposed faces oftha-two annular members 22 and 27 have interengaging formations: the annular member 22 has three radially extending grooves 30 in its end face, which grooves are evenly angularly spaced from one another; and the annular member 27 hasthreecorresponding radial projections 31, which projections extend from the end face of the member and into the grooves 30.

These prevent rotation of the tool 15 with respect to the body 10.

The end ofthe plug 19 having the flange 20 has a screw-threaded bore in its end face. A rod 32 having a screw-threaded end is screwed into this bore and is fixed in place by a radial cross-pin 33. The rod 32 extends in the bore 12 and out from the other end (not shown) of the body 10 and is connected to an actuating mechanism (not shown). A sleeve 34 also extends in the bore 12 and outfromtheotherend of the body 10 and is also connected to an actuating mechanism (not shown). The rod 32 extendsthrough the bore of the sleeve 34.The sleeve 34 has two diametrically opposed radially outwardly extending pins 35 which engage in respective longitudinal grooves 36 in the bore 12so preventing the sleeve from rotating with respect to the body 10.

Acup-shaped piston 37 is disposed in the bore 12 in that portion containing the spring 23, the bore 12 having a further reduced diameter portion in which extendthe rod 32 andthe sleeve34. The base ofthe piston 37 has a bore through which the rod 32 passes.

The outer radially extending surface ofthe base ofthe piston 37 abuts the end of the sleeve 34 and faces the shoulder in the bore between the two portions. The inner radially extending surface ofthe base ofthe piston 37 faces the flanged end of the plug 19 and is axially spaced from it. The annular wall of the piston 37 extends aroundtheflange 20 ofthe plug 19, abuts the thrust washer 21 and is connected to it by screws 38. The plug 19 is freely rotatable with respect to the sleeve34and has limited longitudinal movementwith respect to the th rust washer 21 and the piston 37. The plug 19 can also rotate with respect to the piston 37 if frictional forces due to the spring 23 are overcome.

To release the tool 15, the sleeve 34 is moved towardsthetool 1 5 so that, byway of the piston 37 and the thrust washer 21, the spring 23 is longitudinally compressed. The piston 37 thus comes to abut the flange 20 ofthe plug 19 and an axial clearance is formed between the flange 20 and the washer 21. This relieves the plug 19 of axial tension, allows the plug to rotate freely and move longitudinally by the amount of the clearance. The rod 32 now moves the plug 19 longitudinally so that the interengaging teeth 29 ofthe annular members 24 and 27 become disengaged.

Then the rod 32 rotates the plug 19so that the projectionsontheannularmember24become aligned with the slots in the annular member 27. The tool 15 can now be simply withdrawn from the conical recess in the end of the body 10 with the projections 31 coming out ofthe grooves 30. Preferably, the rod 32 and the sleeve 34 are kept in that position for reconnectingthesametool 15 orfor connecting a different tool.

When reconnecting the tool 15, the rod 32 rotates the plug 19 so thatthe projections on the annular member24are notaligned with the slots in the annular member27. Then the sleeve 34 is moved awayfrom the tool 1 5 so that the spring 23 biases the plug 19 away from the tool so drawing the tool into the body 10 whereupon the teeth 29 interengage and the projections 31 extend into the groove 30 once more.

The rod 32,the plug 19 and the tool 15 have aligned central ducts for the supply of lubricant or coolant to the tool. If a radial branch extends to the conical surfaces 13 and 1 7 of the body 1 0 and tool 1 5, it can be used for blowing-offorventing.

In a modification, the sleeve 34 and the rod 32 can be connected so that the longitudinally displacement of the plug 19 is effected only by the sleeve 34, and the rod 32 is only used for rotating the plug.

Figure 2 shows a scrap-view in section ofthe annular members 22 and 27 with one ofthe grooves 30 and one of the projections 31. In cross-section, each groove 20 and projection 31 is an isosceles trapezium.

The projection 31 is an interference fit in the groove 30 with the groove 30 being deeper than the projection 31 is high. The dimensions are chosen so that when the surfaces 13, 17 and 14, 1 8 of the body 1 0 and tool 1 5 firmly engage one another, the projections 31 are wedged in the groove 30 within the elastic deformation rangeofthe materials of the two annular members 22 and 27.

Claims

1. Aclamping mechanism comprising a body having a bore opening at one end ofthe body, a device received in the open end, the body and device having co-operating surfaces axially and ra#dially positioning the device with respect to the body, a plug which is disposed in the bore for movement therealong, a spring which is disposed in the bore and biases the plug away from the open end ofthe bore,thedevice and plug being structured and connected to each otherinthemannerofa bayonetfitting, first means allowing the deviceto be disconnected from and reconnected to the plug, and second means prevent ing rotation of the device with respect to the body, wherein the plug is rotatable in the bore and the second means is positioned within the bore and comprises interengaging formations which are re spectively fixed with respect to the body and device.

2. A mechanism as claimed in Claim 1, wherein the interengaging formations are an interference fit with one another.

3. A mechanism as claimed in either preceding claim, wherein those of the interengaaging forma tions that are fixed with respectto the device are provided by an annular memberwhich is produced separately from the device and is then fixed thereto.

4. A mechanism as claimed in any preceding claim, wherein those ofthe interengaging formations that are fixed with respect to the body are provided by annular memberwhich is produced separately from the body and is then fixed thereto.

5. A mechanism as claimed in Claim 4,whereinthe annular memberwhich is fixed to the body provides an abutmentforthe spring.

6. A mechanism as claimed in any preceding claim,whereinthefirstmeanscomprisesa rod which extends in the bore for moving the plug longitudinally and rotationally, and a sleeve which extends in the boreforacting on thespring to allowfree longitudinal movementoftheplug,the rod andthe sleeve being operable independently from each other.

7. A mechanism as claimed in Claim 6, wherein the sleeve is rotationallyfixed with respecttothe body.

8. A mechanism as claimed in Claim 6 or7, wherein the plug and the rod are fixed together.

9. A mechanism as claimed in any preceding claim, wherein the device and the plug have interen gaging formations which are respectively fixed with respect to the device and plug and prevent rotation of one with respect to the other.

10. A mechanism as claimed in Claim 9, wherein those ofthe interengaging formations that are fixed with respect to the device are provided by an annular member which is produced separately from the device and is then fixed thereto.

11. Amechanism as claimed in Claim 9 or 10, wherein those ofthe interengaging formations that are fixed with respect to the plug are provided by an annular memberwhich is produced separatelyfrom the plug and is then fixed thereto.

12. A mechanism as claimed in any preceding claim, wherein the interengagementformations are radially extending projections which are disposed on radially extending and opposed surfaces.

13. A mechanism as claimed in any preceding claim, wherein the co-operating surfaces axially and radially positioning the device with respectto the bodyare conical and annular.

14. Aclamping mechanism substantially as herein described with reference to and as shown in the accompanying drawings.

15. Aclampingorgripping mechanismfortools, tool holders and the like, the latter being connected with a shaft via seating surfaces radially, axially to one another and coaxially in form-locking manner, in their other axial direction by the force of a spring and via an engagement means acting in peripheral direction, comprising a tension boltwhich is connected with the tool via a bayonetfastening, which is arranged axially movably in a bore of the shaft and which is axially braced in loading direction via the spring, and also comprising actuating means which load the spring, characterised in that the tension bolt is arranged for rotating movement and corresponding actuating means are provided for its axial and rotating movement, and in that in the vicinity of the seating surfaces between the tool and shaft there is provided at least one engagement means acting in form-locking and force-locking manner and connected immovably with the components.

16. A clamping mechanism as in Claim 15, characterised in that an engagement projection is arranged to engage, via its peripherally directed lateral surfaces, with an interference fit in forcelocking manner into a corresponding recessofthe shaftorthe like.

17. Aclamping mechanism as in Claim 16, characterised in that the recess is incorporated in a separate annular member secured in/on the shaft and serving as an axial abutmentforthe spring.

18. A clamping mechanism as in Claims 15 to 17, characterised in thatthe actuating means comprise an actuating rod, which effects the axial and rotating movementofthetension bolt, and a sliding sleeve which is guided coaxially in the shaft, which loads the spring and relievesthetension bolt.

19. Aclamping mechanism as in Claim 18, characterised in that the sliding sleeve is mounted in the shaft in a manner precluding relative rotation.

20. Aclamping mechanism as in Claim 19, characterised inthatthe actuating rod and the tension bolt form an assemblywhich is joined in form-locking manner in all directions.

21. Aclamping mechanism as in Claims 15 to 20, characterised in that between the tool and the tension boltthere is provided a form-locking connection which, in the clamped condition, acts in both directions of relative rotation.

22. A clamping mechanism as Claim 21, characterised in that the form-locking connecting takesthe form of end teeth disposed on the bayonet portions.

23. Aclamping mechanism asin Claims 15to22, characterised in that the bayontfastening comprises separate machine parts respectively connected with the tool and with the tension bolt.

24. Aclamping mechanism as in Claims 15to 23, characterised in that the seating surfaces take the form of a centering cone with a flange, in conformity with DIN 55 026.