Clamping device

Description

The description is 14 pages long (including 10 pages of illustrations). Figure 3 HU 225 749 B1 The invention relates to a clamping device for releasably clamping the stem portion of an insertable element in a clamping device. The clamping device has a clamping element in which an insertion hole formed by the interaction of a receiving bore portion with a circular cross-section and a fixing bore portion with a circular cross-section is formed, and the diameter of the receiving bore portion is larger than the diameter of the stem portion, and the diameter of the fixing bore portion is smaller than the diameter of the stem portion, and the fixing bore portion is provided with a clamping surface for clamping the stem portion forced from the receiving bore portion into the fixing bore portion. A general application of clamping devices is to releasably clamp cutting tools (which constitute the insertable member) into a tool holder (which constitutes the clamping device). JP 7-9212 discloses a side-locking tool holder, the insertion hole of which is formed by combining a receiving bore portion and a fixing bore portion. The receiving bore portion and the fixing bore portion have a common longitudinal axis and radii r' and r, respectively, where r'>R and >r, and R is the radius of a straight cylindrical shank of a cutting tool. The receiving bore portion encloses an arc angle of about 180° so that the cutting tool can be freely slid into and withdrawn from it, and the cutting tool can be forcibly transferred from the receiving bore portion to the fixing bore portion. The disadvantage of this tool holder is that the arc angle of the fixing hole portion is less than 180°, which reduces the gripping ability of the fixing hole portion, which adversely affects stability during the cutting operation. JP 59 059303 (D1) discloses a tool holder mechanism having a cylindrical head bore formed by combining a true cylindrical section and a tapered grooved section. A tool holder can be freely slidably inserted and withdrawn from the head bore and clamped therein by being urged toward a pair of axially extending connecting lines located between the cylindrical section and the grooved section when the tool holder moves from the cylindrical section toward the grooved section under the action of a clamping rod. The clamping force is maintained for as long as the tool holder is to be clamped in the head bore. The object of the invention is to eliminate the above shortcomings. According to the invention, this is achieved by a clamping device which serves to releasably clamp the stem part of the element that can be inserted into the clamping device, and the clamping device has a clamping element in which an insertion hole formed by the interaction of a receiving bore part with a circular cross-section and a fixing bore part with a circular cross-section is formed, and the diameter of the receiving bore part is larger than the diameter of the stem part, and the diameter of the fixing bore part is smaller than the diameter of the stem part, and the fixing bore part is provided with a clamping surface for clamping the stem part forced from the receiving bore part into the fixing bore part, and the angle of curvature of the clamping surface in at least one plane perpendicular to the longitudinal axis of the fixing bore part is greater than 180°. The longitudinal axes are preferably in the same plane. The longitudinal axes are preferably parallel to each other and spaced apart. The receiving bore portion and the fixing bore portion advantageously have a straight circular cylindrical shape. The receiving bore portion preferably has the shape of a straight circular cylinder and the fixing bore portion has the shape of a straight truncated cone. The clamping element preferably has an outer tubular part and an inner tubular core part in which the insertion hole is arranged, and the outer tubular part and the inner tubular core part are made of different materials. The clamping device preferably has a guide stop surface for axially supporting the insertable element, and is further provided with a clamping screw that can be fitted to an inclined surface formed on the insertable element for forcibly moving the insertable element from the receiving bore portion to the fixing bore portion and simultaneously clamping it axially to the guide stop surface. The longitudinal axes preferably intersect each other. In the preferred embodiments, the diameter of the receiving bore portion is D-|, the smallest value of which is larger than the diameter Do of the shank portion of the insert, while the largest diameter D2 of the fixing bore portion is smaller than Do. Furthermore, in one embodiment, the two longitudinal axes are spaced apart by D3, while in another embodiment, the two longitudinal axes are at an angle γ to each other. The invention will be described in more detail with reference to the drawings, which show an exemplary embodiment of the clamping device according to the invention. Figure 1 is a perspective view, partially cut away, of a tool holder clamping device for releasably securing a tool holder. Figure 2 shows a section taken along line 11 of the tool holder clamping device according to Figure 1 in the initial insertion position. Figure 3 shows a section taken along line 11 of the tool holder clamping device according to Figure 1 in the clamped position. Figure 4 shows a perspective view of a tool holder for releasably clamping a cutting tool. Figure 5 is a top view of the tool holder of Figure 4. Figure 6 is a cross-section of the tool holder according to Figure 4 taken along line II-II. Figure 7 shows a perspective view of a part of a tool holder and a wrench for loosening or tightening the clamping nut of the tool holder. Figure 8 shows a perspective view of the wrench of Figure 7. Figure 9A shows a cross-section of the wrench of Figure 8 taken along line II-II. Figure 9B shows a cross-section of the wrench of Figure 8 taken along line IV—IV. Figure 9C shows a cross-section of the wrench of Figure 7 taken along line VV. HU 225 749 B1 Figure 10A shows a perspective view of the wrench of Figure 7 together with the tool holder in an initial insertion position. Figure 10B shows the wrench of Figure 10A in longitudinal section, in the initial insertion position. Figure 11A shows a perspective view of the wrench of Figure 7 together with the tool holder in a clamped position. Figure 11B shows the wrench of Figure 7 in longitudinal section with the tool holder in the clamped position. Figure 12A shows a cross-section of the side-locking tool holder of Figure 4 taken along line ll-ll for radial clamping of the tool holder. Figure 12B shows a cross-section of the side-locking tool holder of Figure 4 taken along line ll-ll for axial clamping of the tool holder. The tool holder clamping device 1 shown in Figures 1-3 (which forms the clamping structure) comprises an L-shaped mounting frame 2, the horizontal mounting element 3 of which is suitable for mounting the tool holder clamping device 1 on a workbench 4 by means of a pair of clamping screws 5A and 5B, and a vertically standing support 7 on which a clamping element 8 is mounted. The clamping element 8 can releasably clamp a tool holder 9 (which is the insertable element), which can be any type of tool holder, for example an HSK type tool holder having a straight, cylindrical shank 10 of diameter Do. The clamping element 8 has an insertion bore 11 in which there is an intermediate support shoulder 13 on which the lower stop surface 14 of the shank 10 rests. The tool holder 9 is secured in the upper support part of the insertion hole 11, above the support shoulder 13, by means of a fixing device which has a bushing 17 and which rests against the shank part 10. As shown in Figures 2 and 3, the upper support portion 15 is formed by combining a straight cylindrical receiving bore portion 19A and a fixing bore portion 19B, which are located closer and further away from the fixing means 16, respectively. The receiving bore portion 19A and the fixing bore portion 19B have diameters D1 and D2, respectively, and their parallel longitudinal axes 20A and 20B are spaced apart by a distance D3. The inner surfaces of the receiving bore portion 19A and the fixing bore portion 19B intersect each other along interaction lines (not shown in the drawing) which define a clamping surface 21 of the fixing bore portion 19B having a substantially semicircular cross-section and an arc angle greater than 180°. In use, the clamping device 16 is initially unscrewed from the clamping element 8 so that the shank portion 10 of the tool holder 9 can be easily inserted into the receiving bore portion 19A (see Figure 2). The clamping device 16 is then screwed into the clamping element 8 so that its bushing 17 presses against the shank portion 10 of the tool holder 9, whereby it is tightly received by the forced expansion of the clamping bore portion 19B. Once clamped, a new cutting tool can be clamped into the cutting tool receiving bore 22 of the tool holder 9 or the worn cutting tool can be replaced. Finally, the clamping device 16 is unscrewed and the tool holder 9 is forced back into the receiving bore portion 19A by hand, from where it can be easily slid back. The return to the receiving bore portion 19A can be clearly felt by a click when the tool holder 9 passes through the connection lines between the receiving bore portion 19A and the fixing bore portion 19B. Figures 4-6 show a side-locking tool holder 25 (which forms the clamping mechanism) which consists of two parts, an outer tubular part 25A and an inner tubular core part 25B, in which an insertion hole 26 is provided for releasably clamping a straight cylindrical shank 28 cutting tool 27 - which forms the insertable element - by means of a transverse clamping screw 29 which rests thereon. The part 25A and the core part 25B are made of different materials so as to damp the vibration of the tool, for example the part 25A may be made of steel, while the core part 25B may be made of cast iron. The insertion hole 26 is similar to the insertion hole 11 in that it is formed by combining a receiving hole portion 31A and a fixing hole portion 31B, the longitudinal axes 32A and 32B of which are parallel and offset from each other (see FIGS. 5 and 6). 6). However, since the insertion hole 26 is closed at one end, the open end is more subject to forced expansion than the closed end, so if the fixing hole portion 31B is cylindrical, the clamping force exerted by it will not be uniform. In order to ensure that the straight cylindrical stem 28 is clamped with uniform force along the entire length of the fixing hole portion 31B, this fixing hole portion 31B has a straight truncated conical shape instead of a cylindrical shape. The cross-section of the fixing hole portion 31B perpendicular to the axis 32B is larger at the closed end than at the open end. The inner surfaces of the receiving hole portion 31A and the fixing hole portion 31B intersect along the connecting lines 33A and 33B. Due to the above-described truncated cone shape, the same clamping ability is obtained along the entire length of the clamping bore portion 31B, so that the arc angle of its clamping surface 33 will be the same at both ends when the cutting tool 27 is clamped in the clamping bore portion 31B. The application of the tool holder 25 for clamping the cutting tool 27 is similar to the tool holder clamping device 1. As an example, the tool holder 25, which is used for a cutting tool 27 with a shank diameter of Do=2O.OO mm, has the dimensions of the insertion hole 26 determined by the following hole triple: D-|=20.07 mm, D2=19.985 mm D2=19, 995 mm, D3=1 mm. In this case, when the cutting tool 27 is clamped in the clamping hole portion 31B, the arc angle of the clamping surface 33 will be about 18Γ at both ends of the clamping hole portion 31B. Figures 7-11 show a wrench 35 (which forms the clamping mechanism) and whose elongated arm 36 terminates in a wrench head 37, with which HU 225 749 The straight cylindrical clamping nut 39 (which forms the shank part) of the tool holder Β1 (which forms the insertable element) can be loosened or tightened, and has a diameter of Do. The wrench head 37 has an insertion hole 40, which is formed by combining a straight, cylindrical fixing hole part 41B with a diameter of D2 and an inclined, cylindrical receiving hole part 41A with a diameter of Dt, the longitudinal axes 43B and 43A of which make an angle γ with each other (see Figs. 8 and 9A). The longitudinal axes 43A and 43B intersect at the centers of the receiving bore portion 41A and the fixing bore portion 41B so that their surfaces intersect along a pair of semicircular connection lines 44A and 44B, and thus define the receiving bore portion 41A with a pair of semicircular surfaces 45A and 45B. In use, the wrench 35 is initially tilted relative to the vertically held tool holder 38 so that it can be slid onto it so that the clamping nut 39 is seated in the receiving bore portion 41A (see Figs. 10A and 10B). The wrench 35 is then rotated clockwise relative to the tool holder, as indicated by the dashed arrow in Fig. 10B, to force the clamping nut into the mounting bore portion 41B and thereby clamp the wrench 35 onto the clamping nut 39. In this position, the wrench 35 is rotated about the axis 43B, thereby releasing the clamping nut 39 (see Figs. 11A and 11B). The worn cutting tool can then be replaced with a new cutting tool and the clamping nut 39 can be tightened by rotating the wrench 35 counterclockwise about the axis 43B relative to the tool holder 38.After tightening the clamping nut 39 again, the wrench 35 is rotated counterclockwise in the direction opposite to the arrow shown in the dashed line in Fig. 10B. As a result, the contact between the clamping nut 39 and the fixing hole portion 41B is eliminated and the wrench 35 can be removed upward from the tool holder 38. Many modifications can be made to the above-described embodiment without departing from the scope of the invention, for example, the longitudinal axes of the receiving bore portion 19A and the fixing bore portion 19B of the insertion bore 11 do not have to lie in a single plane as long as the insertable element can be placed between them. In addition, as shown in Figs. 12A and 12B, a side-locking tool holder 25 may be used for a cutting tool 42 having a groove 42A, and the inclined surface thereof engages with the clamping screw 29 of the tool holder to force the cutting tool 42 from the receiving bore portion 31A to the fixing bore portion 31B by the radial component Fsr of the clamping force Fs of the screw, while forcing the cutting tool 42 toward the stop surface 30 of the tool holder guide in the axial direction by the axial component Fsa of the clamping force Fs, thereby securely clamping the cutting tool 42. The groove 42A may be shallow (see FIG. 12A), where F2>F1, suitable for a turning tool, for example, or it may be deep (see FIG. 12B), where F2=F1, suitable for a drilling or milling tool, for example, where F3 and F2 are axial clamping forces.

Claims

PATENT CLAIMS 1. A clamping device for releasably clamping a stem portion (10) of an insertable element in a clamping device, wherein the clamping device has a clamping element (8) in which an insertion hole (11) formed by the interaction of a receiving bore portion (19A, 31 A) with a circular cross-section and a fixing bore portion (19B, 31B) with a circular cross-section is formed, and the diameter (Ο4) of the receiving bore portion (19A, 31 A) is larger than the diameter (Do) of the stem portion (10), and the diameter (D2) of the fixing bore portion (19B, 31B) is smaller than the diameter (Do) of the stem portion (10), and the fixing bore portion (19B, 31B) extends from the receiving bore portion (19A, 31 A) to the fixing bore portion (19B, 31B) has a clamping surface (21) for fixing a forced stem part (10), characterized in that the arc angle of the clamping surface (21) in at least one plane perpendicular to the longitudinal axis (20B, 43B) of the fixing bore part (19B, 31B) is greater than 180°.

2. Clamping device according to claim 1, characterized in that the longitudinal axes (20A, 20B, 43A, 43B) are in the same plane.

3. Clamping device according to claim 2, characterized in that the longitudinal axes (20A, 20B, 43A, 43B) are parallel to each other and have a distance (D3) between them.

4. The clamping device according to claim 3, characterized in that the receiving bore portion (19A, 31A) and the fixing bore portion (19B, 31B) have a straight circular cylindrical shape.

5. The clamping device according to claim 3, characterized in that the receiving bore portion (19A, 31A) has a straight circular cylindrical shape and the fixing bore portion (19B, 31B) has a straight truncated conical shape.

6. The clamping device according to any one of claims 1-5, characterized in that the clamping element (8) has an outer tubular part (25A) and an inner tubular core part (25B) in which the insertion hole (11) is arranged, and further that the outer tubular part (25A) and the inner tubular core part (25B) are made of different materials.

7. The clamping device according to any one of claims 1-6, characterized in that it has a guide stop surface (30) for axially supporting the insertable element, and is further provided with a clamping screw (29) that can be fitted to an inclined surface formed on the insertable element for forcibly moving the insertable element from the receiving bore portion (31A) to the fixing bore portion (31B) and simultaneously clamping it axially to the guide stop surface (30).

9. The clamping device according to claim 2, characterized in that the longitudinal axes (43A, 43B) intersect.