Gear cutting – milling – or planing – Milling – Cutter spindle or spindle support
Patent
1994-05-18
1996-01-30
Howell, Daniel W.
Gear cutting, milling, or planing
Milling
Cutter spindle or spindle support
409135, B23Q 1112
Patent
active
054876311
DESCRIPTION:
BRIEF SUMMARY
This invention relates to machine tool spindles which support a cutting tool at one end and are journalled in bearings.
BACKGROUND OF THE INVENTION
It is conventional to supply a coolant/rinsing fluid, such as suds, to a tool and it is important to prevent that fluid from reaching the bearings. It also is conventional to supply lubricant to the bearings and it also is desirable to prevent that lubricant leaking externally. So one or more seals are interposed between the bearings and cutting tool. This creates problems.
It is usual to employ wiping seals which maintain contact between rotating and non-rotating parts even when the rotation ceases. The wiping seal has to be resiliently held in place. It is known to use so-called V -rings which comprise a ring to fit tightly on the spindle and an integral radial flange, made from a slightly resilient material such as a suitable plastic or rubber. However, the wiping creates friction, which leads to temperature increase and this can lead to inaccuracy in the machining operation because the spindle center positions will vary between cold and hot dimensions. Sometimes the shaft needs to be locally hardened or provided with for example ceramic surfaces as a seal component and to reduce wear and that also is expensive.
Labyrinth seals are often employed to avoid friction and its consequent heat and wear but multiple component labyrinths complicate the design, increase expense, and require additional length which is a disadvantage in many designs.
Another well known seal system employs radially extending flanges freely located so that liquid--lubricant or coolant--creeping along the spindle will reach the flange and be thrown off by centrifugal force into an annular collector space. But these, like labyrinth seals are primarily and sometimes exclusively useful when the spindle is in use. When stopped for any reason, undesired flow can occur from liquids already in place.
So the object of the .invention is to provide an improved and simplified design.
SUMMARY OF THE INVENTION
According to the invention, a machine tool spindle comprises at least one wiping seal between the spindle and a fixed non-rotating part arranged to be displaced from contact with the said fixed part by an applied fluid pressure so as to avoid friction when so displaced.
The applied fluid pressure may be a purging gas The effect of the purging gas may be not only to displace the parts to a non-contacting and hence non-friction position, but also to enable the flange to be used to throw off fluid by centrifugal force, and drain passages may be provided for such fluids.
Hence, when there is no purge gas the seal is a contact seal. When there is purge gas, the gas flow will prevent liquid flow in the counter-current direction through the seal, and when there is purge gas and spindle (including the seal) rotation, the seal can act to throw off liquid which reaches it.
Preferably a pair of such seals are arranged to contact opposite faces of a common fixed component through which the purge gas is fed and these may be oppositely inclined to form a V shape. The gas may be air.
THE DRAWINGS
One presently preferred embodiment of the invention is now more particularly described with reference to the accompanying drawing wherein the sole figure is a fragmentary sectional elevation of a single spindle assembly. Those skilled in the machine tool art will recognise that multi-spindle assemblies are usual, and will realise that the invention may be employed on each and all of them.
DETAILED DESCRIPTION
In the drawing, the spindle is indicated by the reference numeral 10 and end 12 is adapted in known manner (not shown) to carry the cutting tool (aot shown). Bearings, diagrammatically indicated by the references 14, 16, journal the spindle in support structure of the assembly for rotation about the longitudinal axis of the spindle.
In this embodiment the spindle has a pair of shallow peripheral grooves 18, 20. Each groove supports a V -ring 22, 24 comprising a ring unitary with a radial flange or leg
REFERENCES:
patent: 5290130 (1994-03-01), Beretta
Howell Daniel W.
Systematic Drill Head Co. Ltd.
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