Tool chucking apparatus

A tool chucking apparatus to hold a machining cutter or tool includes a holding member and a fastening member that are coupled together to form a grip space inside to hold a collet. The collet has a plurality of pawl structures with a plurality of elastic slots formed thereon. When the holding member and the fastening member are coupled, the collet has one end tightly held in the holding member and the other end tightly held in the fastening member. Hence the two ends of the collet contract the elastic slots to tightly grip the cutter or tool. As a result, machining precision improves, safety enhances and the life span of the cutter or tool increases.

FIELD OF THE INVENTION

The present invention relates to a tool chucking apparatus and particularly to a chucking apparatus to firmly hold a tool.

BACKGROUND OF THE INVENTION

These days precision metal machining such as drilling, tapping, boring, milling, cutting of inner or outer diameters or surface grinding usually relies on CNC (Computer Numerical Control) machine tools in cooperation with a plurality of cutters or tools. Those cutters or tools mostly have an elongated stem connecting to a driving spindle of the CNC machine tools through a chucking apparatus or chucking structure. The driving spindle rotates in high speed to drive the cutters or tools held by the chucking apparatus to perform machining on a targeted object.

Hence the holding condition of the chucking apparatus on the cutters or tools directly affects the machining precision of the targeted object. If clamping is not tight enough during high speed rotation of the machining tool idle rotation of the cutters or tools occurs. Referring toFIG. 1, a conventional chucking apparatus mainly includes a fastening member1, a collet2and a holding member3. The holding member3is connected to a driving spindle (not shown in the drawing) of a machining tool, and has a housing space4to hold the collet2to form a tight coupling. The collet2is a hollow conical element and has a plurality of conical pawl structures5formed in an annular manner with a center passage6. The pawl structures5are elastic. When a cutter or tool is inserted into the collet2the inner diameter of the center passage6can be adjusted accordingly. The fastening member1and the holding member3have respectively a corresponding screw thread7and7′ for screwing together to firmly hold the collet2. In addition, as the collet2has the pawl structures5, when the holding member3and the fastening member1are screwed together, the pawl structures5are forced and shrunk inwards to strengthen coupling of the cutter or tool to increase the firmness of machining and enhance the machining precision of the targeted object.

The collet2equipped with the pawl structures5to hold the cutter or tool has many advantages, such as it can hold cutters or tools of varying sizes and specifications. Moreover, when the holding member3and the fastening member1are screwed together, they automatically clamp the cutter or tool in an optimal condition. However, when the conical top of the collet2is moved towards the holding member3it mainly holds the distal end of the cutter or tool. Due to the targeted object to receive machining usually is a hard article such as metal, and the driving spindle (not shown in the drawing) of the machining tool rotates at high speeds, with the collet2holding the cutter or tool at the distal end, only the distal end receives the force, hence the cutter or tool is not being held and fastened securely. Loosening or slipping of the cutter could take place during machining process. Moreover, as the cutter or tool has an excessive portion exposed outside the collet2, when a great force is applied or the forcing angle is not applied vertically, the cutter or tool could be skewed. As a result, machining precision suffers. It could even cause damage of the collet2or the machining tool and result in a great loss of cost.

U.S. Pat. No. 1,953,637 discloses a chuck which has a shell, a nut coupling with the shell and a stem running through the nut and movable relative to the nut. The stem has a plurality of springs to couple with a plurality of jaws. The jaws are held in the shell. The stem moves towards the shell to push the jaws through the springs so that the jaws butt the inner wall of the shell and the front end thereof can grip a cutter. However, when the jaws butt the inner wall of the shell, the rear end of the jaws (namely one end connecting to the spring) is merely braced by the elasticity of the spring. The rear end of the jaws cannot firmly grip the cutter, and the cutter is not firmly held. When the cutter performs machining to a work piece, cutter wobbling could occur due to infirm holding. This could cause poor precision of machining and produce rough edges on the work piece. The cutter could even be thrown out during high speed operation. Not only the cutter or work piece could be damaged, it also creates a serious concern on user's safety.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide a tool chucking apparatus to enhance holding firmness of a cutter or tool on a machining tool during machining for a targeted metal to prevent suffering of precision or damage of the machining cutter or tool, and also reduce rough edges and facilitate machining of tough machining material. To achieve the foregoing object the tool chucking apparatus of the invention includes a holding member and a fastening member. The holding member has one end coupled with the fastening member to form a grip space inside. The holding member has a first contact surface in the grip space, and the fastening member has a second contact surface. The grip space tightly holds a collet inside. The collet and holding member and fastening member are coupled tightly together to form a holding passage, and hold the cutter or tool through the collet. The collet has a plurality of pawl structures which are spaced in an annular manner and formed in a conical structure with a plurality of elastic slots. The pawl structures are elastic and can adjust the inner diameter according to the cutter or tool. The pawl structures have a third contact surface and a fourth contact surface. When the pawl structures are coupled with the holding member and fastening member, the third contact surface is tightly in contact with the first contact surface, and the fourth contact surface is tightly in contact with the second contact surface, so that the collet and holding member and fastening member form a compact coupling to firmly grip the cutter or tool. Thereby the cutter or tool can be firmly gripped and prevented from loosening during machining process. Moreover, the conical structure has a top end facing the fastening member to allow the cutter or tool to be inserted deeply into the chucking apparatus without exposing too much outside the chucking apparatus. As a result, the cutter or tool can be held firmer to improve machining precision on the targeted metal. Safety and the life span of the cutter are enhanced. In addition, the fastening member and the holding member have respectively a coupling structure corresponding to each other. The fastening member further has an encasing portion extended towards the holding member. The holding member and the encasing portion have respectively a fifth contact surface and a sixth contact surface corresponding to and tightly in contact with each other to increase concentricity of the holding member and the fastening member to further improve steadiness of the chucking apparatus during operation of the machining tool.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Please refer toFIGS. 2,3and4, the tool chucking apparatus according to the invention aims to couple a machining tool (not shown in the drawings) with a machining cutter or tool (also not shown in the drawings), and to be connected to a driving spindle (not shown in the drawings) of the machining tool so that the machining tool can drive the cutter or tool held by the tool chucking apparatus to rotate at high speed to do machining on a targeted object (not shown in the drawings). The tool chucking apparatus of the invention includes a holding member10and a fastening member20coupling with the holding member10to form a grip space25inside to hold a collet30tightly. The holding member10has one end connecting to the driving spindle and another end forming a first screw thread11. The fastening member20has a second screw thread22corresponding to the first screw thread11that can engage with each other to form a tight fastening between the fastening member20and the holding member10(in an embodiment of the invention coupling of the fastening member20and the holding member10is accomplished through the screw threads, but it is not the main feature of the invention). The holding member10has a first contact surface12in the grip space25, and the fastening member20has a second contact surface26. The first contact surface12and the second contact surface26respectively form a grip angle in the grip space25. To prevent the holding member10and fastening member20from loosening during the high speed rotation at least one through threaded passage23may be formed at the coupling juncture thereof to receive at least one corresponding bolt24. Hence after the holding member10, fastening member20and collet30are coupled together, a passage is formed in the center to receive a machining cutter or tool.

The collet30is the main holding structure of the cutter or tool. It has a plurality of pawl structures31arranged in a conical structure. The pawl structures31have a third contact surface312at one end corresponding to the first contact surface12and a fourth contact surface311at the other end corresponding to the second contact surface26. Furthermore, the pawl structures31are formed in an annular manner with a plurality of elastic slots32and33formed thereon and spaced from one another so that the pawl structures31can provide the collet30with desired elasticity. When the cutter or tool of varying specifications is inserted, the pawl structures31can adjust the inner diameter thereof. The elastic slots33correspond to the third contact surface312and have openings facing the direction of the third contact surface312. The other elastic slots32correspond to the fourth contact surface311and have other openings facing the direction of the fourth contact surface311.

Also referring toFIGS. 5A and 5B, for assembly, first dispose the collet30in the grip space25; couple the holding member10and the fastening member20by screwing the first and second screw threads11and22so that the first contact surface12butts the third contact surface312, and the second contact surface26butts the fourth contact surface311; with the first and second screw threads11and22screwing deeper, the grip angles of the first and second contact surfaces12and26push the collet30moving towards the second contact surface26, and the elastic slots32and33are squeezed to shrink, hence two ends of the pawl structures31contract inwards and the third contact surface312and the first contact surface12form a closed contact, and the fourth contact surface311and the second contact surface26also form a closed contact, as a result, the collet30and the holding member10and fastening member20form a compact coupling to tightly grip the cutter. The collet30has two ends providing double grip forces for the cutter. Therefore, the cutter is less likely loosening off during high speed machining operation. This not only can improve machining precision and eliminate rough edges of the work piece, also can prevent the cutter from being thrown out and enhance safety and the life span of the cutter. Moreover, differs from the conventional structure that has the top end of the conical structure of the collet30facing the holding member10or driving spindle, the conical structure of the collet30of the invention has the top end facing the fastening member20. Thereby the machining cutter or tool can be held deeper in the tool chucking apparatus without exposing too much outside. Such a design increases the contact area of the cutter or tool and the tool chucking apparatus, and reduces the impact of external forces. Thus machining precision of the cutter or tool on the targeted object improves significantly.

In addition, the fastening member20has an encasing portion27extended towards the holding member10to encase one end of the holding member10. The encasing portion aims to increase the coupling firmness of the holding member10and the bottom end of the collet30. Moreover, the holding member10and the encasing portion27have respectively a fifth contact surface13and a sixth contact surface28corresponding to each other to form a closed contact, thereby to enhance concentricity of coupling of the holding member10and the fastening member20. This also enhances machining steadiness and precision.

As previously discussed, after the holding member10and the fastening member20are coupled together, the third contact surface312of the collet30and the first contact surface12of the holding member10form a closed contact, and the fourth contact surface311of the collet30and the second contact surface26of the fastening member20form a closed contact, so that the collet30and the holding member10and the fastening member20form a compact coupling to tightly grip the cutter. As a result, machining precision and safety improve, and the life span of the cutter also increases.