Improved apparatus for holding tools

Abstract: An improved tool holding apparatus including a collet chuck or a steel ball chuck that clamps a pull bolt (13), which defines the forward end portion of a tool, by resilient force applied thereto from a coned disc spring (36). The tool holding apparatus further includes a temporarily clamping device (33,34) which is buried in a sleeve to clamp the pull bolt temporarily. Clamping force applied by the temporarily clamping device is set at such a level that an arm can draw the tool from a main spindle by gripping the rear end portion (11) of the tool.

Description: The present invention relates to an apparatus for sequentially changing tools and holding a tool to be used in a machine tool that uses a plurality of tools. In general, a plurality of tools are used in the operation of a machine tool. Since the tool operating position is limited, a tool changing operation is required inevitably. Generally, at least 10 different tools are changed from one to another. In an extreme case, more than 100 different tools must be changed. A tool holding apparatus, which has heretofore been used, employs an arrangement such as that shown in Figs. 1(a) and 1(b) of the accompanying drawings. That is, a pull bolt 13, which defines the forward end portion of a tool 1, is clamped by using a collet chuck 32 or a steel ball chuck 32, which is disposed inside a sleeve 31, thereby holding the tool 1. To release the tool 1, it is unclamped by the forward (leftward as viewed in Fig. 1) movement of coned disc springs 36 and a drawbar 35. Needless to say, the above-described clamping is extremely strong, so that it is impossible to draw the tool 1 from a main spindle 3 by gripping the rear end portion 11 of the tool 1 with an arm 2. In the prior art, the operation of changing the tool 1 is carried out in the following sequence: 1 ○ The arm 2, which faces the tool holding apparatus, is rotated to grip the tool 1, which has already been used, at the rear end portion 11. 2 ○ The drawbar 35 is moved forwardly on the basis of the resilient force from the coned disc springs 36 under the control of a hydraulic cylinder (not shown), thereby releasing the tool 1 from the clamping that has been effected to the pull bolt 13 by the action of the collet chuck 32 or the steel ball chuck 32. 3 ○ The tool 1 is drawn from the main spindle 3. 4 ○ The arm 2 is rotated so that a tool 1 which is to be newly used comes to the position of the main spindle 3. 5 ○ The tool 1, which is to be newly used, is inserted into the main spindle 3 and the magazine. 6 ○ The drawbar 35 is moved backwardly to allow the collet chuck 32 or the steel ball chuck 32 to clamp the pull bolt 13 of the tool 1. 7 ○ The arm 2 is made to stop gripping the rear end portion 11 of the tool 1 and then rotated to move away. The reason why the operation 2 ○ is carried out after the operation 1 ○ is that the tool 1 may fall if it is released from the clamping in the main spindle 3, as in the operation 2 ○, before the arm 2 grips the tool 1 according to the procedure 1 ○. Further, the reason why the operation 7 ○ is carried out after the operation 6 ○ is that the tool 1 may fall unless the tool 1 is completely clamped by the operation 6 ○ before the rear end portion 11 of the tool 1 is ungripped as stated in 7 ○; therefore, the arm 2 cannot be released from the tool gripping condition before the tool 1 is satisfactorily clamped. However, it takes an extra time in the tool changing operation to carry out the operations 1 ○ and 2 ○, and the operations 6 ○ and 7 ○, serially. As the number of tools 1 which need to be changed increases, the dead time in the machining process increases unavoidably. It is an object of the present invention to overcome the above-described disadvantage of the prior art and to provide an improved apparatus for holding tools, which makes it possible to carry out simultaneously the steps 1 ○ and 2 ○, and the steps 6 ○ and 7 ○. EP-A-0262368 discloses a tool changing apparatus with a temporary clamping device. EP-A-0262368 discloses tool holding apparatus which clamps a pull bolt that defines a forward end portion of a tool by using a clamping force based on a coned disc spring and a drawbar, which is applied to a collet chuck in a sleeve, wherein the apparatus comprises: a collet chuck, which is engaged with the coned disc spring and the drawbar, to clamp said pull bolt; and a temporary clamping device for clamping a tool temporarily without engaging with either said coned disc spring or said drawbar, thereby temporarily clamping said pull bolt, wherein said temporary clamping device comprises a contact member having a smoothly curved face, and an elastic spring which extends radially. To attain the above-described object, the present invention provides a tool holding apparatus which clamps a pull bolt that defines a forward end portion of a tool by using a clamping force based on a coned disc spring and a drawbar, which is applied to a collet chuck or a steel ball chuck in a sleeve, wherein the apparatus comprises: a collet chuck or a steel ball chuck, which is engaged with the coned disc spring and the drawbar, to clamp said pull bolt; and a temporary clamping device for clamping a tool temporarily without engaging with either said coned disc spring or said drawbar, thereby temporarily clamping said pull bolt, wherein said temporary clamping device comprises a plurality of units each including at least one steel ball, a contact member having a smoothly curved face, and an elastic spring, which are buried in a sleeve so that said elastic spring is extended and contracted in the same direction as that in which said tool is inserted and removed, thereby moving said steel ball in the same direction so as to slide into contact with said contact member, and thus causing a part of said contact member to project from and withdraw into an inner wall of said sleeve. In the accompanying drawings:- Figs. 1(a) and 1(b) are sectional side views showing the arrangement of a conventional tool holding apparatus. Figs. 2(a) and 2(b) are a longitudinal sectional side view showing the arrangement of an embodiment of the present invention, and a transverse side view showing the arrangement of a chuck and steel balls. Fig. 3 is a fragmentary side view showing an arrangement in which a pin whose distal end is in the form of a smoothly curved projection is used as one of two steel balls used in the embodiment of figs 2(a) and 2(b). In this application also, the clamping force with which a tool is clamped by a collet chuck or a steel ball chuck, which is engaged with coned disc springs and a drawbar, is so strong that the tool will not come off the main spindle even if it is pulled backwardly by gripping the rear end portion thereof with the human hand or an arm. On the other hand, in the stage where the tool has been released from the clamping by advancing the drawbar on the basis of the resilient force from the coned disc springs, clamping members, e.g., steel balls, which are engaged with respective elastic springs clamp the pull bolt provided at the forward end of the tool. However, the object of the clamping by the elastic springs and the clamping members is to clamp the tool temporarily. Therefore, the clamping force for this purpose is considerably weak in comparison to that for the clamping by the collet chuck or steel ball chuck, and it is set at such a level that the tool can be readily released when drawn by gripping the rear end portion thereof. In such a temporary clamping stage, the operation 1 ○ of gripping the tool with the arm and the operation 2 ○ of releasing the tool from the clamping can be carried out simultaneously. Similarly, a tool that is newly inserted can be temporarily clamped by the elastic springs and the steel balls to such an extent that the tool will not come off accidentally, before the pull bolt of the tool is firmly clamped with the collet chuck on the basis of the coned disc springs by moving the drawbar backwardly. Therefore, it is possible to carry out simultaneously the operation 6 ○, in which the pull bolt of the tool is clamped with the collet chuck or steel ball chuck, and the operation 7 ○, in which the arm is made to stop gripping the holder portion of the tool and then rotated to move away. In other words, the temporary clamping by the elastic springs and the steel balls engaged therewith makes it possible to carry out the operations 1 ○ and 2 ○, and the operations 6 ○ and 7 ○, simultaneously. Thus, it becomes possible to reduce the time required for changing tools in comparison to the time required in the prior art (by about 20% according to the actual measurement). It should be noted that temporary clamping that is applied to such an extent that the tool can be drawn out with the arm, as described above, depends on the compressive force of the elastic springs and the configuration of the clamping members. However, it is required for the clamping members to have a distal end portion which is in the form of a smoothly curved projection, with a view to allowing the clamping members to come off the tool smoothly when the arm draws it by gripping the rear end portion thereof. Figs. 2(a) and 2(b) show an embodiment in which steel balls 33 are used as clamping members that temporarily clamp the pull bolt, in units each including two steel balls 33 and one elastic spring 34, which are buried in the sleeve 31, so that the elastic spring 34 moves one steel ball 33 in the same direction as that in which the tool 1 is inserted and removed, and this steel ball 33 slides in contact with that end portion of the other steel ball 33 which is closer to the inner side of the sleeve 31, thereby causing a part of the second steel ball 33 to project from and withdraw from the inner wall of the sleeve 31. In this case, the clamping force that is applied through the steel balls 33 is set at such a level that the tool can be released from the clamping when the arm draws it backwardly (away from the main spindle 3) by gripping the rear end portion 11 of the tool. In Figs. 2(a) and 2(b) a collet chuck 32 is used as a chuck that is engaged with a coned disc spring 36 and a drawbar 35, it should be noted that a steel ball chuck can also be used in the same way. Although the foregoing embodiment uses steel balls the clamping members are not necessarily limited to this embodiment. Pins may be used in the embodiment as clamping members. Further, it is possible to use a pin whose distal end is in the form of a smoothly curved projection as one of the two steel balls used in the embodiment, as shown in Fig. 3. In the embodiment of the present invention, arranged as described above, the steps 1 ○ and 2 ○, and the steps 6 ○ and 7 ○, can be carried out simultaneously. Therefore, the time required for changing tools can be shortened correspondingly. Accordingly, the embodiment of the invention of this application is applied even more advantageously to a complicated process which needs to change tools frequently. Since such a complicated process can be realized with a relatively simple arrangement, such as that shown in Figs. 2(a) and 2(b), the value of the invention of this application is deemed to be extremely high from the economic viewpoint as well.

Claims: A tool holding apparatus which clamps a pull bolt that defines a forward end portion of a tool by using a clamping force based on a coned disc spring (36) and a drawbar (35), which is applied to a collet chuck (32) or a steel ball chuck in a sleeve, wherein the apparatus comprises: a collet chuck or a steel ball chuck, which is engaged with the coned disc spring and the drawbar, to clamp said pull bolt; and a temporary clamping device for clamping a tool temporarily without engaging with either said coned disc spring or said drawbar, thereby temporarily clamping said pull bolt, wherein said temporary clamping device comprises a plurality of units each including at least one steel ball (33), a contact member (33) having a smoothly curved face, and an elastic spring (34), which are buried in a sleeve so that said elastic spring is extended and contracted in the same direction as that in which said tool is inserted and removed, thereby moving said steel ball in the same direction so as to slide into contact with said contact member, and thus causing a part of said contact member to project from and withdraw into an inner wall of said sleeve. An apparatus according to claim 1, wherein said contact member (33) is a steel ball.

Inventors: HORIKAWA YOSHIHARU, MATSUSHIMA TAKANORI, YOKOI SHINICHI, HORIKAWA, YOSHIHARU, MATSUSHIMA, TAKANORI, YOKOI, SHINICHI
Applicants: MATSURA MANUFACTURING CO LTD, MATSUURA MANUFACTURING CO., LTD.
Application year: 1993
Main classification: B23Q3
IPC codes: B23B31