Chucks or sockets – By centrifugal force – To counterbalance jaws
Reexamination Certificate
2000-04-10
2002-02-05
Bishop, Steven C. (Department: 3722)
Chucks or sockets
By centrifugal force
To counterbalance jaws
C279S121000, C279S123000
Reexamination Certificate
active
06343797
ABSTRACT:
The invention relates to a chuck comprising chuck jaws guided in a chuck body and inner jaws connected to said chuck jaws. The inner jaws can be engaged and disengaged with said chuck jaws directly or indirectly via a rack gear, and are connected through a wedge-type mechanism to a central drawing head which, in turn, is connected to a piston of a hydraulic cylinder assembled on the rearward side of a main spindle via a rod or pipe guided through a central hole of said main spindle.
Several chucks with great gripping force have been developed for serial and mass production. The wedge-type or lever-arm mechanism of such chucks can position the jaws only within a limited range, therefore the jaws should be adjusted or replaced in each case when the diameter of the work piece changes.
A further problem of known chucks relates to compensation of the centrifugal force exerting on the jaws. Gripping force of the jaws tends to steeply descend as rotational speed of the main spindle increases. Because of need for great gripping force it is necessary to keep developing the basic mechanism producing the gripping force.
Recent subtypes of known chuck structures can be classified according to above mentioned problems to be solved.
The most common mode to adjust chuck jaws to different diameters is the manual operation or human action, such as replacement of jaws followed by their orientation with a rack gear and their fixation by bolts.
Manually adjustable connection of jaws is described in DE Patent No. 1 288 872 of the Forkhardt Co. (Werkstatt und Bertieb 106, 173/11-895. oldal).
EP Patent No. 0166 887-A (Forkhardt) and EP Patent No. 0 318 360-A (Gamet Precision) describe a variety of solutions for quick manual replacement and adjustment of jaws.
One of the automated processes for replacing jaws is the robotic jaw replacement. A chuck construction suitable for such replacement is described in EP Patent No. 0 204 095 (S M W Schneider Weisshaupt GmbH). Use of such a chuck, however, requires voluminous and expensive jaw holders and robots.
A method for automatic jaw stepping is described In Hungarian patent applications No. 2737/86, filed on Aug. 29, 1986, and No. 1799/90, filed on Mar. 23, 1990. Inventions described in these documents do not solve the problem of centrifugal force compensation, either. Moreover, these inventions have not published yet.
DE Patent No. 3 726 773 (Röhm) and corresponding EP Patent No. 0 303 002-A also describe means for automatic jaw adjustment. Automatic compensation of the centrifugal force is not even reached by said inventions. Adjusting mechanism of the proposed chuck structure is operated by a hydraulic piston built in the chuck body, wherein introduction of the compressing medium requires special construction of the main spindle.
A chuck structure with compensation of the centrifugal force is described in EP Patent No. 0 349 742-A (Paul Forkhardt). The device comprises front jaws and rear jaws which are connected to each other through a double arm lever requiring a wide hole on the chuck body.
Another chuck structure with centrifugal force compensation is described in EP Patent No. 0 318 360 (Garnet Precision) and preceding FR Patent No. 87 16 243. In these documents no automatic jaw adjustment has been mentioned. Furthermore, in this chuck construction with lever arms there is a linear connection between the lever arms and the chuck jaws, which is disadvantageous with respect to the lifetime of the device.
Inventions relating to basic wedge-type mechanism are described in EP Patent No. 0 215 350-A and EP Patent No. 0 212 198-A (both by Forkhardt), wherein base jaws are positioned via keys accommodated on the side wall thereof, and in EP Patent No. 0 213 815-A (Pratt Burnard International Limited), wherein inclined cylindrical members are built in a hydraulic piston, wherein the cylindrical members are adapted for positioning the base jaws through a stud held by a bracket.
It is an object of the present invention to eliminate disadvantages of known chuck structures and to provide an improved chuck structure capable of automatically changing the diameter range of the chuck jaws and compensating the centrifugal force.
It is still a further object of the present invention to provide a chuck with a wedge-type mechanism capable of tolerating high load and improved switching mechanism for the automatic jaw adjustment, in particular, at solving safety engineering problems.
The aforesaid objects are achieved by the chuck according to the present invention, a basic sub-type of which comprises inner jaws having connector means guided axially and radially, and provided with a rack gear and a double locking device. The inner jaws are built together with counterweights for compensation of the centrifugal force, wherein the inner jaws and said counterweights are formed as a single integrated unit. The inner jaws comprise two heads located on opposite sides of the chuck structure axis, the narrower one of which is in the form of a connector means either provided directly with a rack gear or embedding a connector means provided with a rack gear and guided axially, whereas the wider one of said heads, which forms a counterweight on the opposite side, comprises a hole, the axis of which defines an acute angle with respect to the chuck structure axis. Respective heads of said inner jaws have equal dimensions between each other, wherein bridges between the respective heads are translated axially relatively to each other. The wedge-type mechanism connected to said central drawing head is arranged in such a way the central drawing head comprises three cylindrical studs fixed therein, the axis of which define an acute angle with respect to the chuck structure axis. The studs are connected into holes bored into said counterweights. There are bushings built into holes of the chuck body against respective chuck jaws, wherein the axis of said holes are parallel to the chuck structure axis. A stud segment with an axis in parallel to the chuck structure axis is guided in said bushings, wherein said stud segment and the respective cylindrical stud constitute a single integrated unit, or said stud segment is built together with the cylindrical stud.
Another embodiment of the chuck according to the present invention is the so called “by-passing” chuck. In this embodiment, the inner jaws comprise connector means guided axially and radially and provided with a rack gear and a double locking device. Each connector means has two cylindrical surfaces with a common axis but different diameter, wherein the larger cylindrical surface is guided in a hole comprising a wide control element, wherein said hole is bored into the face of said inner jaw, whereas the smaller cylindrical surface is guided in a hole bored into the narrower, rearward side of said inner jaw, and said counterweights for compensation of the centrifugal force are connected, through arms, to grooves formed on the side wall of said inner jaws. The longitudinal axis of said arms extend in parallel to the axis of rotation of the main spindle.
According to a preferred embodiment of the present invention, a first element of the double locking device of the chuck is a control ring guided turnably on the external surface of the chuck body Control elements in the form of control rollers and control members are secured to the control ring. A second element of the double locking device is a locking unit arranged between the control ring and the chuck body.
According to the above-mentioned embodiment of the present invention, the locking unit between the control ring and the chuck body is preferably formed as a locking pin guided axially in the control ring. When the control ring and the chuck body are locked, back side of the locking pin accommodates between locking surfaces arranged rigidly on the machine tool body. Preferably, the control ring of the chuck has a hole on its lateral surface into which a stud of a manually operated chuck wedge can be inserted. The chuck wedge has another stud connected to a surface which is adapted fo
Gaál József
Kertész József
Tajnafoi József
Bishop Steven C.
Kelemen Gabor J.
Venable
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