Gear cutting – milling – or planing – Milling – Process
Reexamination Certificate
2001-09-14
2002-09-24
Briggs, William (Department: 3722)
Gear cutting, milling, or planing
Milling
Process
C144S252100, C409S137000
Reexamination Certificate
active
06454499
ABSTRACT:
BACKGROUND DESCRIPTION
1. Field of the Invention
The present invention relates to a device for machining workpieces, more particularly workpieces of wood-based materials, plastics or the like. invention relates furthermore to a method of machining workpieces by means of such a device.
2. Prior Art
Known from DE 195 09 933 C
1
is a chip removing, rotating tool for machining workpieces, more particularly workpieces of wood-based materials, plastics or the like, which is configured substantially as a hollow body and comprises at least one cutter at its outer circumference. A portion of the tool adjoining each cutter is penetrated by a chip receiving opening for communicating the chips into a cavity, namely a quill shaft of the tool, i.e. the tool featuring internal chip removal. To assist removal of the chips materializing in operation of this tool it is possible to pass an air stream longitudinally, i.e. axially, through the quill shaft of the tool. Furthermore evident from this reference document is that chip removal may be additionally assisted by a conical configuration of the quill shaft of the tool.
In devices including the type of tool as described above a very high proportion of the resulting chips gains access to the cavity within the tool. Where wood-based materials are concerned, this proportion may be as high as approx. 95% to approx. 98% of the resulting chips.
Accordingly, chip removal or chip exhaust from the tool is especially of importance.
Experience has shown, however, that in conventional devices comprising tools with internal chip removal the chips can only be exhausted at a very high energy expense. For example, the energy requirement for such exhaust systems in woodworking operations is on an average between approx. 30% and approx. 50% of total electrical power consumption per year. This is why it would be desirable and good practice from both a technical and costeffective consideration to reduce the energy consumption for such exhaust systems.
In tools incorporating internal chip removal, a chip separated from the workpiece is usually accelerated by the cutter and moves through the chip receiving opening into the tool cavity. Due to the tool rotating, the air mass accommodated in the cavity is exposed to a centrifugal effect, however, as a result of which the entrained air tends to emerge outwardly from the chip receiving opening, i.e. the air mass flows in a direction which is precisely opposite to the direction of movement or trajectory of the chips entering the tool. This obstructs the movement of the chips into the tool cavity and the chips are decelerated or even directed back out of the chip receiving opening, it being particularly large chips that suffer from this disadvantageous effect. It is these unwanted effects that may result in chip removal being detrimented or even in the chip receiving opening becoming blocked which aggravates tool wear. Chips having regained access to the outer side of the tool or chips failing to be handled by the chip receiving opening and/or exhaust may, in addition, be multiply cut unnecessarily at the machining site of the tool, this likewise aggravating tool wear, resulting in reduced tool life and, last-but-not-least, in higher pollution of the ambient air.
In addition, chips having gained access to the tool cavity, but greatly decelerated are forced outwardly by the centrifugal force against the inner wall the tool cavity where they may accumulate and even become cemented. This substantially hampers chip removal and may even result in the tool becoming unbalanced which particularly at high tool rotating speeds is detrimental to operational safety.
Chips which are not removed and/or even regain access to the chip receiving opening may in addition accumulate or build up at the surface of the workpiece and cause undesirable chip marks, it being particularly multiply cut chips that result in ugly marking of the workpiece where softish materials are concerned, such as, for example, wood-based materials or plastics. This results in a reduction in workpiece quality which is, of course, undesirable.
This is why devices of the aforementioned kind equipped with tools, having internal chip guidance, require for satisfactory chip removal external high-power exhaust means for high exhaust velocities especially for high cutting speeds and rotary speeds, resulting, however, not only in a corresponding high power requirement but also causing a noise nuisance due to such exhaust systems.
However, the type of tool used as such has also proven to be a considerable source of noise. Thus, conventional tools, having internal chip removal, generate high noise emissions involving screeching and/or pulsating acoustic oscillations experienced by operators of the device to be extremely unpleasant, it thus also being desirable to reduce the noise emission produced by the device including its tools.
SUMMARY OF THE INVENTION
The objective or the technical problem forming the basis of the present invention is to provide a suitable device and a suitable method for machining workpieces which permit improved chip removal for a lower exhaust capacity and a reduced noise emission.
This technical problem is solved by a device in accordance with the invention having the features of claim
1
.
This device for machining workpieces, more particularly workpieces of wood-based materials, plastics or the like comprises
at least one chip removing, rotating tool configured substantially as a hollow body including at least one cutter, a portion of the tool adjoining the cutter being penetrated by a chip receiving opening for communicating chips into a tool cavity; and
an exhaust means including a stationary exhaust housing configured substantially as a hollow body communicating with or protruding into the tool cavity at least in part and in connection with at least one exhaust air source;
the portion of the exhaust housing communicating with the tool cavity comprising in the region of an effective site of the tool assigned to the cutter at least one chip communicating window porting into an exhaust passage of the exhaust housing; and
the exhaust passage comprising in an exhaust passage section upstream of the chip communicating window, relative to the exhaust direction, at least one auxiliary air infeed opening.
The tool of the device in accordance with the invention, which is to be classified as a tool having internal chip removal, may be configured one-part or multi-part. A multi-part tool may comprise, for example, a one-part or multi-part thin-walled quill body for connecting to a tool shaft or spindle and/or other components of the tool. The tool is formed preferably rotationally symmetrical, although the invention is not restricted to this configuration, however.
The at least one cutter of the tool, which may be a geometrically defined, straight, profiled or regular or irregular shaped cutter may be an integral part of the tool or, however, a separate part of the tool. The cutter may be configured more particularly interchangeable, the tool in this case expediently featuring a suitable quick-change means. The number of tool cutters depends on the application in each case.
Instead of a single cutter, it is, of course, just as possible that two or more cutters find application. The cutters are preferably applied to the radial outer circumference of the tool. However, the tool may also comprise in addition facing cutters.
The exhaust housing may be one-part or multi-part. As already mentioned above, the exhaust housing is arranged stationary. More particularly, the part of the exhaust housing communicating with or protruding into the tool cavity at least in part may be adjustable as regards its stationary arrangement, however. The part of the exhaust housing communicating with or protruding into the tool cavity is preferably formed rotationally symmetrical at its sections located opposite the inner wall the tool cavity. It is, however, expressly to be noted that the invention is not restricted to this configuration. The part communicating with the cavity m
Fischer Roland
Gittel Hans-Juergen
Kalmbach Kurt
Kalmbach Wilhelm
Oertel Michael
Berkowitz Marvin C.
Briggs William
Ledermann GmbH
Nath Gary M.
Nath & Associates PLLC
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