Drilling chuck

Claim 2

A chuck unit comprising a machine spindle adapted to be mounted on, and to be reciprocated in its axial direction by a machine tool, a tool spindle, means for guiding said tool spindle on said machine spindle so as to be slidable coaxially relative thereto, means on said tool spindle for mounting a tool thereon, a safety clutch having first and second clutch members adapted in one position to interengage with each other to connect said tool spindle to said machine spindle when said tool is in a proper condition when pressed in its axial direction against a workpiece, said clutch members adapted to disengage from each other when said tool is in an improper condition when pressed in its axial direction against a workpiece, and adjusting means for infinitely varying the strength of engagement between said clutch members so as normally to be in accordance with the axial back pressure exerted upon the free end of said proper tool by its engagement with said workpiece.

Claim 3

A chuck unit as defined in claim 1, in which said safety clutch is designed so that said clutch members will disengage from each other not only when said tool is in an improper condition when moved by said spindles against said workpiece, but also when said machine spindle is retracted at a certain speed from said workpiece but said tool on said tool spindle cannot be retracted at the same speed from said workpiece.

Claim 4

A chuck unit as defined in clAim 2, in which at least the front end of said machine spindle is tubular by having an axial bore and said tool spindle comprises two shank parts, one of said shank parts being thicker than the other and having an outer diameter substantially equal to the outer diameter of said machine spindle and having one end carrying said tool mounting means, and the other thinner shank part having an outer diameter substantially equal to the diameter of said bore in said machine spindle and being axially slidable within said bore.

Claim 5

A chuck unit as defined in claim 3, in which said safety clutch further comprises spring means acting upon said first clutch member for normally maintaining it in locking engagement with said second clutch member, said adjusting means being adapted to vary the effective strength of said spring means and the pressure exerted thereby upon said first clutch member.

Claim 6

A chuck unit as defined in claim 4, in which said adjusting means comprise an externally threaded first sleeve slipped over the end of said machine spindle, means for removably securing said first sleeve to said machine spindle, an adjusting sleeve having an internally threaded rear part adapted to be screwed over and axially along said first sleeve for varying the effective strength of said spring means, and a locking ring adapted to be screwed upon said first sleeve and against one end of said adjusting sleeve for maintaining it in its adjusted position.

Claim 7

A chuck unit as defined in claim 5, in which said adjusting sleeve has an internally smooth front part axially slidable over the rear end of said thicker shank part of said tool spindle and an annular internally projecting flange intermediate its front and rear parts and projecting toward said smaller shank part and its inner surface being axially slidable along said smaller shank part, the rear surface of said flange supporting the front end of said spring means.

Claim 8

A chuck unit as defined in claim 6, in which the front end surface of said tubular part of said machine spindle, the rear surface of said flange and the intermediate part of the wall of said adjusting sleeve together define a chamber around said thinner shank part of said tool spindle, a pair of pressure rings one behind the other in said chamber and having beveled surfaces at one side facing each other and also facing said thinner shank part, the rear side of the first of said rings being connected to said front surface of said tubular part, said tool spindle having an annular groove the wall of which forms one of said clutch members, the other clutch member consisting of a plurality of balls disposed between said pressure rings, said spring means also being disposed in said chamber and the other end of said spring means engaging upon the front side of the second of said pressure rings, said spring means being normally adapted to press said pressure rings toward each other to such an extent as to press said balls into said groove and thus to interengage said clutch members with each other when said adjusting sleeve is adjusted to compress said spring means so as to maintain said balls in said groove as long as said back pressure upon said tool does not exceed the force with which said spring means maintain parts of said balls in said groove, said tool spindle automatically ejecting said balls radially from said groove and forcing them entirely between said pressure rings when said back pressure exceeds said force or when said tool cannot be retracted at the same speed at which said machine spindle is retracted.

Claim 9

A chuck unit as defined in claim 7, in which, when said spring means are sufficiently released by said adjusting ring, said tool spindle may be easily withdrawn entirely from said machine spindle.

Claim 10

A chuck unit as defined in claim 1, further comprising indicating means for indicating the operative positions of said clutch members relative to each other.

Claim 11

A chuck unit as defined in claim 6, in which the wall of said adjusting sleeve is provideD with an aperture in its front end in front of said flange, and indicating means comprising an indicating member on said larger shank part adapted to be visible through said aperture so as to indicate the operative positions of said clutch members relative to each other when said tool spindle is appropriately shifted relative to said adjusting sleeve.

Claim 12

A chuck unit as defined in claim 10, in which said indicating means further comprise an indicating instrument including a Geiger tube mounted laterally at one side of and spaced from said adjusting sleeve, said indicating member containing a radioactive material adapted to act upon said Geiger tube through said aperture.

Claim 13

A chuck unit as defined in claim 10, in which said indicating member is adapted to emit light rays through said aperture.

Claim 14

A chuck unit as defined in claim 10, in which said indicating member is adapted to reflect light rays through said aperture.

Claim 15

A chuck unit as defined in claim 7, in which said annular groove has front and rear end walls spaced from each other at a distance greater than required for radially receiving the parts of said balls normally projecting into said groove so that said balls are movable in said groove in the axial direction of said tool spindle between said front and rear walls, and further comprising a compression spring inserted into said tubular part of said machine spindle and having one end acting upon the bottom of said tubular part and another end acting upon the rear end surface of said tool spindle so that, when said balls project into said groove, said tool spindle is axially slidable for said distance relative to said balls against the action of said compression spring.

Claim 16

A chuck unit as defined in claim 14, in which said internally smooth front part of said adjusting sleeve is omitted and said flange forms the front end of said adjusting sleeve, and further comprising indicating means for indicating the operative positions of said clutch members relative to each other, said indicating means comprising an annular outer flange on the rear end of said larger shank part of said tool spindle and having an outer diameter substantially equal to the outer diameter of said adjusting sleeve, said tool spindle when no axial back pressure is exerted upon said tool being maintained by said compression spring in a position in which said balls engage upon said rear wall of said groove so that an annular gap is formed between said inner flange and said outer flange, said indicating means further comprising an electronic switch mounted in a fixed position so that its free end is disposed opposite to and outside of said gap, said switch being actuated when a back pressure is exerted upon said tool so that said tool spindle is shifted toward the rear against the action of said compression spring until said balls engage upon said front wall of said groove and said outer flange is thereby moved to a position opposite to and in front of said free end of said switch.

Claim 17

A chuck unit as defined in claim 15, further comprising another annular member on said tool spindle in front of said outer flange and spaced by a second gap therefrom, said switch being again actuated when said back pressure upon said tool becomes excessive and said balls are forced out of said annular groove and said outer flange is moved so far toward the rear that said free end of said switch is disposed opposite to said second gap.