Chucks or sockets – Socket type – Self-centering of floating
Patent
1993-04-19
1994-08-30
Bishop, Steven C.
Chucks or sockets
Socket type
Self-centering of floating
464102, B23B 3102
Patent
active
053420691
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a tool holder for machine tools with a mounting portion on the machine side and on the tool side and with a coupling device which rotationally fixedly connects the mounting portions together with a radial clearance and which is supported on both sides in the axial direction via rolling bodies and has a radially movable coupling disc with at least two radial slots extending perpendicularly to one another, an axial carrier on the one mounting portion engaging in the one slot and an axial carrier on the other mounting portion engaging in the other slot.
Such tool holders are always used where existing bores must be machined with high precision. For instance, they are used to receive thread cutting tools and, first and foremost, reamers. The coupling device, which is also known under the name Oldham coupling, compensates for any axial offset between the tool and the bore to be machined using the radial clearance ensured by the coupling device between the mounting portion secured to the machine tool and the mounting portion accommodating the tool. The rolling bodies serve to make these radial movements easy to perform. In the case in which the tool is stationary and the workpiece rotates there is only a single adjusting movement per bore. In the reverse case every rotation of the tool causes a cyclical adjustment movement.
In a known tool holder of the type referred to above (DE-B 1256039) the rolling bodies are constructed as balls. Balls have excellent running characteristics. However, they are associated with the disadvantage that the axial forces which occur must be transmitted by point contact. These axial forces are considerable, caused by the high feed speeds with which modern machine tools operate. Under these loads the balls damage the associated opposing surfaces but over very small regions since the radial movements are small. The ease of movement of the coupling thus decreases. In extreme cases complete jamming occurs.
In order to prevent this a further known tool holder (DE-C 3425869) uses a coupling disc whose axial surfaces are constructed as sliding surfaces. This coupling operates practically without wear, its ease of movement for the machining of steel and other metals of comparable hardness being easily sufficient. It has, however, been found that difficulties can arise when machining metals of lesser hardness, for instance with light metals such as aluminium and alloys thereof. If, in this case, the radial adjustment movement is delayed even slightly, inaccuracies occur, at least in the entry region of the bore. Such inaccuracies can not be tolerated in, for instance, aerospace technology, for instance when reaming rivet holes.
It is thus the object of the invention to provide an apparatus of the type referred to above which operates substantially without wear and possesses a high degree of ease of movement for long periods of operation.
In order to solve this object the tool holder in accordance with the invention is characterised in that the rolling bodies are constructed as rollers.
It has been found that changing over from the point contact of balls to the line contact of rollers is sufficient to transmit even extreme axial forces without damaging the flat running surfaces, even for long periods of use.
Surprisingly, it has been found that this is substantially independent of the orientation of the rollers. Even if the rollers perform sliding movements the running surfaces remain undamaged. Of principal importance is that the ease of movement of the radial compensation is only insubstantially impaired.
It is thus possible in a further embodiment of the invention to arrange the rollers in recesses in the coupling disc whereby sliding movements of the rollers necessarily occur in certain directions of movement.
The rollers are preferably aligned parallel to one another.
In an alternative, which is also preferred, the rollers are aligned parallel to one another in sets. For this purpose the axes of the rollers can be orientated in the peripheral direction or in the
REFERENCES:
patent: 3072417 (1963-01-01), Ziegler
patent: 3454283 (1969-07-01), Benjamin et al.
patent: 5013054 (1991-05-01), Burnet
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