Gear cutting – milling – or planing – Milling – With means to control temperature or lubricate
Reexamination Certificate
2001-06-21
2003-11-18
Wellington, A. L. (Department: 3722)
Gear cutting, milling, or planing
Milling
With means to control temperature or lubricate
C409S234000, C408S057000, C408S059000
Reexamination Certificate
active
06648565
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coolant tube for a holder for a tool having a tapered hollow shaft with an upper opening for clamping into a tool receptacle, wherein the coolant tube is arranged in the interior of the tapered hollow shaft for supply of coolants to the tool, and the coolant tube has an inlet opening for coolants, said inlet opening facing the upper opening, and an upper tube section which, when the holder is clamped in the tool receptacle, projects into a supply tube for coolants, said supply tube overlapping the coolant tube at least partially, whereby a covering is provided for the inlet opening, which prevents chips from entering into the coolant tube.
The invention further concerns a holder having a coolant tube of this kind.
2. Related Prior Art
Such a holder with coolant tube is known from DE 196 21 240 A1.
These holders, which are also called HSK tool holders, consist substantially of three sections, namely the tapered hollow shaft, adjoining which at the bottom is a thickened collar on which gripper grooves for automatic tool changing mechanisms are provided. Adjoining said collar at the bottom is a holding shaft onto which a variety of tools can be attached. Since some of said tools in operation must be cooled with coolant, a centered, stepped threaded hole is provided in the interior of the tapered hollow shaft into which hole a coolant tube can be threaded. Said coolant tube has a central coolant conduit through which the coolant coming from the machine tool arrives at the respective tool.
Tool holders of this kind, or HSK tool holders, are standardized, they can be fitted with various tools and then clamped into a tool receptacle, which is provided in a spindle of a machine tool and has an opening complementary to the tapered hollow shaft.
The tapered hollow shaft is equipped with an upper opening through which jaw segments and the draw-in taper of a clamping system can engage into the interior of the tapered hollow shaft. Clamping of the tapered hollow shaft into the receptacle is accomplished by the fact that the jaw segments, in their released position, are first swung inward and inserted, together with the draw-in taper, through the opening into the tapered hollow shaft. The draw-in taper is then pulled partly back out of the tapered hollow shaft via its draw-in rod, thereby pressing the jaw segments outward in their clamping position, in which they rest against the interior of the tapered hollow shaft and clamp the latter nonrotatably to the spindle.
When the holder is inserted into the tool receptacle, the coolant tube enters a centered bore, provided in the draw-in taper and the draw-in bar, through which coolant is then delivered during operation. Provided in the front region of said bore is a sealing ring, preferably an O-ring, which comes into contact with the cylindrical outer enveloping surface of the coolant tube.
In machine tools, problems repeatedly occur in connection with the supply of coolant to the tools. Coolant supply is often interrupted by clogged coolant conduits in the tools themselves or influenced disadvantageously by the fact that the seal between the coolant tube and the coolant delivery system on the machine tool becomes leaky, so that coolant pressure declines and is no longer sufficient to push coolant into the small coolant conduits in the tools. A diminution in the coolant supply due to clogged coolant conduits or a leaking seal often leads, however, to overheating and thus to damage of the tool, so that frequent cleaning of the holder, the coolant tube, and the tools with which the holders are fitted, is necessary. In addition, the sealing ring on the machine tool must be replaced at relatively short intervals. If these time- and wage-intensive actions are omitted, the operational reliability of the machine tools equipped with the holders is reduced.
In the case of the coolant tube mentioned in DE 196 21 240 A1, the problem is remedied by providing a cover for the inlet opening which prevents chips from entering into the coolant tube.
Said cover is designed as a sieve, which rests on a shoulder of the coolant conduit running lengthwise through the coolant tube and which is held by a toothed ring in the upper widened diameter of the coolant conduit.
In operation, it turned out that due to wrong mounting or the pulsating coolant the toothed ring falls out or the sieve is jackknifed, so that the desired protection effect gets lost.
Moreover, it was realized that the sieve is dissolved which also results in a loss of the protection effect.
Therefore, in EP 0 925 869 A2, a further development is described, in which at the top of the coolant tube an insert is arranged on which various sieves are provided. Said insert is held by a toothed ring in the coolant conduit.
By a sequence of fine sieves which are supported by coarser sieves it shall be prevented that the fine sieve is pushed into the coolant conduit.
It has turned out, however, that here, too, the toothed ring falls out or due to mounting problems the insert and/or the toothed ring are wrongly inserted or get lost already on transport, so that the desired protection effect is not reached.
In view of the above, it is an object of the present invention to improve the coolant tube in such a way that the disadvantages mentioned above are avoided. In particular, the operational safety of a machine tool with a constructively simple design and equipped with a holder with a coolant tube, as mentioned at the outset, is to be ameliorated.
SUMMARY OF THE INVENTION
According to the invention, this object is achieved with the holder and the coolant tube mentioned at the outset by providing in the coolant tube an exchangeable insert tube which holds the cover.
The object of the invention is in that way completely achieved.
The insert tube, which preferably runs through the coolant tube in its complete length, diminishes the clear width of the coolant conduit, so that it was originally assumed that the pressure applied to the cover was enforced and, thus, the danger of malfunction increased. In contrast, it turned out, however, that this was not the case. It turned out, namely, that, via the insert tube, a distinctively better support of the cover can be achieved, which now e.g. can be inserted between the upper end of the coolant tube and the insert tube, so that a toothed ring is not necessary any more.
It turned out, namely, that the toothed ring, which is used in the prior art for fixation of the cover, is one of the reasons for detaching covers. The toothed ring can namely not, as assumed, get jammed in such a way at the surface of the coolant tube that it is fixed in a safe position. The coolant tube is namely manufactured from hardened metal, so that the toothed ring cannot penetrate into the hardened surface.
Since the coolant tube is now completely interspersed by an insert tube, the clear width of the coolant conduit is reduced on the whole length of the coolant tube compared with the prior art, which, however, against all expectations, has neither resulted into problems.
It turned out, namely, that with the counter pressure of 70 bar occurring in operation, the transporting capacity of the coolant pump of 201/min still passes through the coolant tube, so that a sufficient coolant flux is ensured. If the tube, however, is run without counter pressure, so to speak in no-load operation, the transporting capacity is distinctively diminished by the insert tube additionally provided, what, originally, seemed to be against the use of such an insert tube. It turned out, however,—as mentioned—that the reduction of the cross-section of the coolant conduit is no problem during operation.
In a further development it is preferred if the coolant tube has on its top a rim which protrudes to the inner side.
This proceeding has the advantage that the cover is jammed between the protruding rim of the coolant tube and the insert tube, so that it is held in a safe position and cannot be detached. Another advantage is that the cov
Cadugan Erica E
Chiron-Werke GmbH & Co. KG
Weingarten Schurgin, Gagnebin & Lebovici LLP
Wellington A. L.
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