Cutting by use of rotating axially moving tool – With means to apply transient – fluent medium to work or product
Reissue Patent
1999-10-20
2001-12-25
Bishop, Steven C. (Department: 3722)
Cutting by use of rotating axially moving tool
With means to apply transient, fluent medium to work or product
C279S020000, C279S046400, C279S046900, C408S057000
Reissue Patent
active
RE037484
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a clamping device between a tool shank and a machine tool. The invention relates in particular to a clamping device for cutting tools with an internal coolant supply.
The cutting principally of metals on machine tools (drills, millers, lathes) is carried out using, inter alia, cutting tools which feed the coolant directly to the cutting edge through a bore in the tool shank in order to lengthen the service life of the tool and improve its cutting capacity.
Such cutting tools usually have a round shank which is clamped in the tool holder by means of a suitable collet chuck or clamping sleeve, provided with slots for flexibility, and is thus secured against twisting. As these cutting tools with an internal coolant supply can easily be made to rotate at speeds of 40,000 rpm, enhanced cooling of the operation is essential. To improve the cooling, the pressure at which the coolant is injected is therefore increased to as much as 50 bar or more. Now, if a tool with an internal coolant supply is connected to the machine tool by means of a collet chuck or clamping sleeve, a large part of the cooling fluid is lost through the slots in the unsealed collet chuck or clamping sleeve.
To prevent this, the slots in the collet chuck or clamping sleeve have hitherto been filled with an elastic compound such as rubber, although the chucking capacity was then lost, or the tensioning nut was sealed by means of a washer, a solid sealing ring or a packing, or rubber pegs were inserted in specially made bores in the slots in the collet chuck or clamping sleeve. The disadvantages of these variants are that for every shaft or tool shank diameter there must be a washer of corresponding diameter or a packing available, and that the sealing rings or rubber pegs are no longer certain to form a seal at today's high cooling fluid pressures and are attacked by the various coolants. The greatest disadvantage of these variants, however, is that a collet chuck or clamping sleeve which had to be sealed required additional components.
The object of the invention is therefore to provide a clamping device which forms a perfect seal against the escape of fluids from machine tools, even at high pressures of up to 150 atm, and substantially retains its flexibility, and which is effective without additional sealing components and can nevertheless be used in conventional machine tools.
SUMMARY OF THE INVENTION
Based on a device of the type described at the outset, the aforesaid object is achieved according to the invention by the provision of a collet chuck or clamping sleeve whose non-through parts of the radial slots or intermediate slots are fixed on the one hand to the tool shank and on the other hand at least partially to the collet chuck or clamping sleeve housing in such a way as to form a coolant barrier together with the tool shank and the collet chuck housing. Radial pressure on the external contour of the collet chuck or clamping sleeve, or axial pressure by means of a tensioning nut in the case of a conical collet chuck, forms coolant-tight metal—metal seals between tool shank, collet chuck or clamping sleeve and collet chuck or clamping sleeve housing, so the pressurized coolant can only escape in the tool direction via the bore provided for this purpose in the tool shank.
Alternatively, the embodiment with slots open on the machine side can be avoided by using intermediate slots closed on both sides. Again, with this embodiment of the invention, the coolant can only escape in the cutting tool direction via the bore provided for this purpose in the tool shank.
It is preferable to use double-slotted collet chucks, the distinguishing feature of which is that the slots are cut into the collet chucks alternately from the opposite sides, although it is also possible to use collet chucks with intermediate slots, i.e. with slots which are closed at both ends of the collet chuck or clamping sleeve. Advantageously, such a collet chuck or clamping sleeve then only has slots open on the cutting tool side, so there are no longer any tightness problems on the machine side because there are no open slots. To improve the flexibility of these collet chucks or clamping sleeves as well, it is advantageously possible to provide them additionally with an outflow.
The collet chucks or clamping sleeves are conventionally made of hardened spring steel, tool steel or beryllium bronze so that the radial slots give them a degree of flexibility when mechanical or hydraulic pressure is applied. Their shape can be either that of a cylinder or that of a cone, double cone or cone/cylinder combination.
The collet chucks or clamping sleeves can have a bore at the machine end if the tool shank has a small diameter, this usually being unnecessary in the case of tool shanks of larger diameter.
Examples are illustrated in greater detail with the aid of the Figures below.
REFERENCES:
patent: 4423880 (1984-01-01), Kosmowski
patent: 4725064 (1988-02-01), Glimpel et al.
patent: 4817972 (1989-04-01), Kubo et al.
patent: 5028178 (1991-07-01), Ronen
patent: 5405220 (1995-04-01), Ishikawa
patent: 2139437 (1972-10-01), None
patent: 3600445 (1986-07-01), None
Bishop Steven C.
Bryan Cave LLP
Rego-Fix AG
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