|Title of Invention||
|Abstract||The invention concerns about a clamping device, for connecting a tool head (12) and a tool holder (10) in machine tools, with an interchangeable tool head (12), which has a cylindrical or at least partly conical receiving spigot (13), which operates with a correspondingly designed receiving bore (11) of the tool holder (10), whereby, for the clamping by means of an axially movable clamping rod (15), clamping elements (14) can be moved radially towards outside in recesses (37) of the tool head (12), and the clamping rod (15) has a cross-hole (32), in which a rotatable eccentric shaft (18) is guided along the contour of the cross-hole (32) and the axial movement of the clamping rod (15) is effected by the rotation of the eccentric shaft (18). According to the invention, the cross-hole (32) has an oval shaped cross-section, which simultaneously defmes the axial clamping path as the rotation-limiting stop.|
The invention concerns with a clamping device for connecting a tool head and a tool holder in machine tools with an interchangeable tool head, which has a cylindrical or at least partly tapered adaptor spigot, which joins a correspondingly built adaptor bore of the tool holder, whereby, for the clamping action by means of an axially moving clamping rods, clamping elements can be moved radially towards outside in recesses of the tool head, and the clamping rod has a cross hole, in which a rotatable eccentric shaft is leading along the convex surface of the cross hole and the axial movement of the clamping rod can be realized by the rotation of the eccentric shaft.
One such clamping device is known, for example, from Indian Patent Application No. 515/DEL/95. The eccentric shaft consists of variously formed regions, which drive the clamping rod correspondingly as per the movement of the eccentric shaft in the tool holder, either towards backwards or forwards, i.e., an axial movement of the clamping rod is achieved. The clamping rod, which is designed essentially cylindrical, possesses in the front region of the cylindrical surface recesses, in which clamping elements formed as balls can "slide in". If the clamping rod is pulled back by the movement of the eccentric shaft towards backwards, then the clamping balls which leave the deeper regions of the chip trough are driven radially outwards, where after they reach the corresponding bores of the adaptor spigot built in the cylindrical shape, whereby, the tool head and the tool holder are clamped against one another. For releasing the clamping, the clamping rod is moved towards, forwards in the opposite direction, whereby the balls are moved towards inside as clamping elements in the reverse direction, so that the cylinder-shaped adaptor spigot is set free again. The tool head can be drawn from the tool holder.
The clamping rod is preloaded at the rear over a spring, which acts on a ring element at the rear with the spring force, whereby the front face of the ring element lying opposite serves as the working surface for a part of the eccentric shaft.
The limits of the rotary angle of the eccentric shaft serves a circumferential limiting stop groove in the head of the clamping shaft in the eccentric shaft. In this groove, a pin is engaged, so that the clamping shaft is rotatable only over the angle, over which the
circumferential groove extends. The disadvantages of the design represented and described in Indian Patent Application No. 515/DEL/95 are that, last but not least due to the stopper pin and the ring, the entire clamping device design consists of one of the many individual parts, which can be clamped against each other, so that an integral clamping movement can no more be carried out. Further, with the present design version, there is also no compact and slender design possible.
Similar clamping systems are described in DE 30 07 440 Al and DE 36 02 247 Al, in which, instead of clamping balls, clamping pins (DE 30 07 440 Al) or clamping jaws (DE 36 02 247 Al) are used. Here also, a longitudinally moveable clamping rod is used during clamping, which drives the clamping elements radially towards outside over various design details, where they engage into correspondingly provided recesses of the complementary details in the clamped portion.
The purpose of the present invention is to produce a clamping device, which produces a slender and compact construction with minimum number of parts and which ensures safe working and is free from failure.
This purpose is achieved by the clamping device of the present invention, which is characterized by the provision of a cross hole that produces an oval - shaped cross section, which determines simultaneously the rotary limit stop of the axial clamping path. By this action, firstly the expensive construction of the limiting stops of the rotary movement along with the circumferential groove and the pin engaging therein in the clamping shaft head is saved, which considerably simplifies the construction of the clamping device, and makes it fault-free. However, there is the risk of jamming of the stopper pin or its breakage. The clamping shaft used with the eccentric shaft can be designed to be considerably shorter. Further, only a single eccentric shaft with a constant diameter over its total longitudinal axis is to be provided, which determines an advancing or retracting movement, corresponding to the rotary movement from stopper to stopper. By this stopper limit, the clamping path is determined clearly, simultaneously with the prescribed value of eccentricity.
Also intermediate links, like the ring as per the theory of Indian Patent Application No. 515/DEL/95, can be eliminated, since the eccentric shaft influences directly on the clamping rod.
Further developments about the invention are presented in the sub-claims.
Thus, preferably, the clamping rod is preloaded at the rear against a disk spring pack, which is considerably sturdier than the helical spring, which is used thus for as per current designs. As per another version of the design, the clamping rod is divided into a clamping bar with clamping cavities and a clamping blot, which has the cross hole for receiving the eccentric shaft, and whose frontal tapered front face lies against a rear front cavity of the clamping bar. Preferably, the clamping bar can be moved axially in a canister connected with the tool holder housing. The design version described earlier has the advantage that the entire clamping system can be designed as a damped clamping cartridge.
Further developments of the invention, as well as the advantages that can be obtained, can be seen from the drawings given in the version examples. They are as follows;
The schematic construction of the clamping device in a sectional perspective view.
The basic body of the tool holder.
A canister for introducing in the basic body.
The clamping rod.
A clamping bolt in a perspective view.
The same clamping bolt in plan view.
Fig,7a to 7c:
The same clamping bolt in plan view with three different eccentric positions.
The clamping shaft with the eccentric shaft in side view.
A tool head in side view.
The part belonging to the tool holder in exploded view.
The core piece of the clamping device is, the tool holder with a basic body 10, which has a locating bore 11 (see Fig. 2), which a tool head 12 as per Fig. 9 can be introduced. The tool head 12 has a spigot 13, whose outer profile corresponds to the inner profile of the locating bore 11. The clamping balls 14 serve as clamping elements, which can be moved over a clamping rod 15 with cavity 16 radially towards outside, where they protrude towards outside radially through a recess in a canister 17 in which the clamping rod 15 is introduced, and where they engage in the recesses 37 of the spigot built in the form of a hollow body. An eccentric shaft 18 of a clamping shaft 19 serves for the longitudinal axial motion, the shaft 19 rotating over an interlocking movement. This eccentric shaft 18 admits (directly or indirectly) the clamping rod 15 against the force of a disk spring pack 20. The bolt 21 serves for the torque transmission. To compete, a coolant supply hole is shown partly, rotated by 90 deg.
The basic body 10 has a frontal ring arrangement 23, against which the ring-shaped front face 24 of the tool head lies flat in the clamped condition. In the rear region of the housing extends a shank, which has a hole 25, in which is guided the clamping shaft rotatably. The clamping shaft 19 stays perpendicular to the clampmg rod 15. As can be seen from Fig. 3, a canister 11 is used in the basic body 10, whose front end has holes 26, through which the clamping balls 14 can protrude out radially towards outside. The canister has another hole 27, which coincides with the hole 25, and in which the clamping shaft 19 is likewise guided.
The entire clamping shaft, in the present case, is made in two parts, and consists of a clamping bar 28, which has a pushing face 29 for the pressing (loosening) of the tool head. At the cylindrical contour of the clamping bar, there are cavities 30 on the convex surface on opposite sides, which serve as guides and whose sizes accommodate the sizes of the clamping balls 14. As can be seen from the representation by dotted lines in Fig, 4, the clamping balls 14 can slide in at opposite sides in the cavities provided therein, if the clamping rod or the clamping bar 28 takes up a first longitudinal axial position moving towards forward. If the clamping rod, pulled in the canister 17 towards backward longitudinal axially, then the balls, limited by the hole 26, is held in place, whereby they are driven radially towards outside along the cavities which become narrower and shallower towards the front, so that they engage in the openings 18 of the tool head 12. The rear portion of the clamping bar is designed as a hollow body 31, which serves for accepting the clamping bolt 33 (see Fig. 5). In the clamping bolt, there is an oval-shaped opening 34 in its head 35, whose front side 36 is designed in the shape of a truncated cone and presses against the rear side of the clamping bar 28. The bore 34 oval-shaped in the cross-section is penetrated by the eccentric shaft 18, which is lead simultaneously into the longitudinal hole 34. By rotating the clamping shaft 19, and limited by the eccentricity of the diameter of the eccentric shaft 18, a longitudinal axial movement of the clamping bolt 33 is determined, whose rear-sided face 37 lies contiguous against the spring pack 20, i.e., it gets preloaded by this. While the width of the bore 34 corresponds somewhat to the eccentric shaft 18, the length of this bore is designed to be bigger, where by the eccentric shaft 18, correspondingly as per the rotation of the clamping shaft, passes through the positions represented in Figs. 7a to 7c* In the beginning, the eccentric shaft is found in the indicated lower region of the bore 34. Through a 90-deg, rotation to the position represented in Fig. 7b, the eccentric shaft 18 "wanders" in the longitudinal hole 34, whereby the clamping bolt 33 experiences a thrust which can be recognized by the length difference from LI to L2. By rotating the clamping shaft 19 up to an angle of 180 deg., the pushing movement continues to the indicated longitudinal axial dimension L3; in this position, the eccentric shaft has reached again the lower position in the longitudinal hole 34. Further rotation of the clamping shaft over 180 deg., outside is not possible, since, the clamping shaft 19 due to its fixing by the bores 25 or 27, and since the
eccentric shaft 18 due to its guidance for the clamping bolt 33 in the cylindrical portion 31, do not allow any alternate movement that is possible over the 180 deg. angle. For releasing the clamping device, the clamping shaft 19 or the eccentric shaft 18 is turned back by180 deg,
The special advantage of the present clamping device consists in the use of minimum number of parts, whereby the clamping bolt itself serves, over its oval-shaped opening 34, as rotation-limiting stop for the clamping shaft 19 or the eccentric shaft 18.
1. Clamping device, for connecting a tool head (12) and a tool holder (10) in machine tools, with an interchangeable tool head (12), which has a cylindrical or at least partly conical receiving spigot (13), which operates with a correspondingly designed receiving bore (11) of the tool holder (10), whereby, for the clamping by means of an axially movable clamping rod (15), clamping elements (14) can be moved radially towards outside in recesses (37) of the tool head (12), and the clamping rod (15) has a cross-hole (32), in which a rotatable eccentric shaft (18) is guided along the contour of the cross-hole (32), and the axial movement of the clamping rod (15) is effected by the rotation of the eccentric shaft (18), characterized in that the cross-hole (32) has an oval-shaped cross-section, which determines simultaneously the rotary limit stop of the axial clamping path.
2. Clamping device as claimed in claim 1, wherein the clamping rod (15) is preloaded at its rear against a disk spring pack (20).
3. Clamping device as claimed in claim 1 or 2, wherein the clamping rod consists of a clamping bar (28) with clamping cavities (30) and a clamping bolt (33), which has the cross-hole (32) for receiving the eccentric shaft (18), and whose frontal tapered front face (36) lies contiguous to a rear front cavity of the clamping bar (28).
4. Clamping device as claimed in claim 3, wherein the clamping bar (28) is guided
axially movable in a canister (17) connected with the tool holder housing (10).
|Indian Patent Application Number||1851/MAS/1998|
|PG Journal Number||07/2008|
|Date of Filing||18-Aug-1998|
|Name of Patentee||WIDIA GMBH|
|Applicant Address||MUNCHENER STRASSE 90, D-45145, ESSEN,|
|PCT International Classification Number||B 23 B 29/00|
|PCT International Application Number||N/A|
|PCT International Filing date|