Clamping device for tool holder

A tool assembly includes a support body, a clamping device, and a tool holder clamped in a groove of the support body. A stopper block is disposed in the groove and abuts against the tool holder for positioning the tool holder along an axis. The stopper block is held in place by a wedge-type stopper clamp which applies a clamping force to the stopper block in a direction transversely of the axis. A wedge-type holder clamp is provided for applying a clamping force to the tool holder in a direction transversely of the axis. The stopper clamp is secured to the support body by a single fastening bolt, and the holder clamp is attached to the support body by a single fastening bolt. Each of the fastening bolts is provided with a part that forcefully pushes the respective clamp away from the support body in response to loosening of the fastening bolt. The arrangement is such that the tool holder can be inserted and removed without completely removing the holder clamp or its fastening bolt.

This application claims priority under 35 U.S.C. §§119 and/or 365 to Patent Application Serial No. 2002-311444 filed in Japan on Oct. 25, 2002; Patent Application No. 2002-329837 filed in Japan on Nov. 13, 2002; and Patent Application No. 2003-207909 filed in Japan on Aug. 19, 2003. The entire contents of those applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a clamping device for attaching a tool holder to various kinds of machine tools including a lathe, a numerical controlled lathe and an automatic copying lathe.

A conventional tool assembly101comprising a support body102and a plurality of tool holders111is depicted inFIG. 8. A clamping device for each tool holder111shown inFIG. 8is provided with a wedge-type holder clamping tool112having a plurality of fastening bolts114and one jack-up bolt113. A plurality of fastening bolts of the wedge-type holder clamping tool are fastened to the support body102, so that the tool holder can be connected to the support body via interaction between respective wedge surfaces (not shown) of the wedge-type holder clamping tool112and the support body, which interaction pushes the clamping tool112against the tool holder111. When the tool holder is to be removed from the clamping device, the jack-up bolt113that has been loosened in advance is screwed against the support body after the plural clamping bolts are loosened, so that the wedge surface of the wedge-type holder clamping tool is forcefully moved away from the wedge surface of the support body. Thus, the tool holder can be removed.

Various kinds of devices for simplifying attachment/removal of the tool holder are well known. A device for holding a tool holder shank in a machine tool is disclosed in Japanese Unexamined Patent Publication No. 2000-190110. The device releasably holds a holder shank of the tool holder to which a cutting insert is attached and a lock rod is provided on a base member. The attachment/removal structure between the holder shank and the lock rod is complicated and it is difficult to reduce the size of the device.

Japanese Unexamined Patent Publication No. 2001-300802 discloses a detachable securing mechanism of a cutting tool used in a comb-type tool rest of a machine tool such as a numerical controlled lathe. The mechanism is provided with a supporting member for supporting an arrangement of plural tools. The supporting member attaches the cutting tool to the comb-type tool rest of the machine tool by fastening a plurality of mounting bolts.

However, in the above conventional clamping device for a tool holder, it takes a long time to attach/remove the tool holder because it is required that a plurality of clamping bolts are fastened or loosened in attachment/removal of the tool holder.

Accordingly, there is a problem in miniaturization and simplification of the device because the structure of the device is complicated. In addition, it is difficult to repeatedly and accurately set the position of a top cutting edge because the placement of the cutting holder at a predetermined position must be visually checked.

In view of the above conventional prior art, the object of the present invention is to provide a clamping tool capable of reducing an attachment/removal time when one or plural tool holders, especially small tool holders, are attached to or removed from the machine tool such as the lathe, the numerical controlled lathe and the automatic copying lathe, and capable of improving the accuracy in positioning of the tool holder.

SUMMARY OF THE INVENTION

In a clamping device to which one or plural tool holders are attached, according to the present invention, the entire length of a wedge-type holder clamping tool for fastening the tool holder to the clamping device is shorter than that of a conventional clamping tool, and only one fastening bolt is provided on the wedge-type holder clamping tool. When the one fastening bolt is loosened, the clamping tool is forcefully displaced away from the support body, so that the tool holder can be attached to or removed from the clamping device. Preferably, this is done without completely removing the clamping tool or the fastening bolt.

With this structure, in the clamping device for the tool holder according to the present invention, the number of the fastening bolts can be reduced and a jack-up bolt can be dispensed with, and thus a miniaturization and simplification of the wedge-type holder clamping tool can be archived. In addition, the reduction of time required for attaching/removing the tool holder to/from the clamping device can be archived without modifying a tool holder generally and currently used.

Furthermore, in the clamping device to which the one or plural tool holders are attached, according to the present invention, the clamping device for the tool holder is provided with a stopper block provided at the rear end of the tool holder remotely of a cutting edge of the tool holder, and a wedge-type stopper clamping tool is provided for securing the stopper block to a predetermined position. Thus, the position of the tool holder can be accurately controlled when the tool holder is attached to the clamping device.

Furthermore, the wedge-type holder clamping tool according to the present invention is provided with a mounting bolt so that the tool holder can be attached to the clamping device with stability. The mounting bolt is replaced with an elastic mounting tool or a mounting bolt with an elastic mounting tool, so that the tool holder can be attached to the clamping device with further stability.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Depicted inFIG. 1(a-1) is a tool assembly comprising a support body1A, a tool holder5mounted in a groove1B of the support body, and a clamping device for clamping the tool holder. The tool holder carries a replaceable cutting insert5-1. In practice, there would be numerous tool holders with respective clamping devices, but only one tool holder is depicted herein. The clamping device includes a stopper block2disposed behind the tool holder for positioning the tool holder along an axis A, a wedge-type stopper clamping tool (stopper clamp)3for clamping the stopper block in place, a first fastener6for securing the clamping tool3to the support body1A, a wedge-type holder clamping tool (holder clamp)4for clamping the tool holder in place, and a second fastener7for securing the clamping tool4to the support body1A. The fastener6extends through a through-hole8′ formed in the stopper clamp3, and is secured in the support body1A by a thread connection. The fastener7is similarly attached. Thus, each fastener6,7has a threaded shank that can be directly threaded to the support body, or indirectly thereto as explained in connection withFIGS. 10–16.

With the above structure, the fastening bolts6,7are rotated in a fastening direction so that the wedge-type stopper clamping tool3and the wedge-type holder clamping tool4are fastened to the support body1A, respectively, and are rotated in a loosening direction so that the wedge-type stopper clamping tool3and the wedge-type holder clamping tool4are moved away from the support body1A, and thus the tool holder can be detachably attached to the support body.

In the support body1A (to which, for example, one tool holder is attached in the following embodiments) that is shown inFIGS. 1(a-1) and1(a-2), wedge surfaces12a,12bof the tool4and the support body1A engage one another to force the tool4downwardly against the tool holder5. Thus, a side face13of the wedge-type holder clamping tool4and a side face14of the tool holder5are clamped to each other by forces directed at right angles to the axis A and to a groove bottom (abutment surface)15of the support body1A. In the support body1A shown inFIGS. 1(b-1) and1(b-2), the side face13of the wedge-type holder clamping tool4is clamped, at an angle16, to the side face14of the tool holder5. To this end, the side face13of the tool holder must be oriented at an angle16shown inFIG. 1(b-2).

FIGS. 2(a),2(b) and2(c) show the clamping tool fastening bolt7. In these drawings, only the clamping tool fastening bolt7is shown. The stopper fastening bolt6can be formed into the same shape as that of clamping tool fastening bolt7. InFIG. 2(a), the clamping tool fastening bolt7is attached to the wedge-type holder clamping tool4. The fastening bolt is provided with, for example, an elastic element in the form of a ring17such as a lock washer or a spring washer. The elastic ring pushes the wedge-type holder clamping tool4(or the stopper clamping tool3in the case of the fastening bolt6) in a direction D away from the clamping device upon loosening the fastening bolt when the wedge-type stopper clamping tool3or the wedge-type holder clamping tool4is to be removed from the clamping device. Therefore, the wedge-type stopper clamping tool3or the wedge-type holder clamping tool4can be attached to or removed form the clamping device by the use of only one fastening bolt provided with the elastic ring. In order to attach the elastic ring to the fastening bolt, a slit10can be provided in the fastening bolt as shown inFIG. 2(b) and the elastic ring is attached to the slit as shown inFIG. 2(c).

Furthermore, as shown inFIG. 3, in lieu of using an elastic ring17, there can be used a fastening bolt7′ with left and right-hand screw threads, i.e., a left-hand thread7′-1and right-hand thread7′-2. When fastening bolts with the left and right-hand screws are used, the bolt through holes8′,9′ in the wedge-type stopper clamping tool3and the wedge-type holder clamping tool4are replaced with threaded holes having the same pitch as that of the corresponding thread of the corresponding thread of the fastening bolts. For example, the left-hand thread is used for the threaded holes of the wedge-type holder clamping tools3,4because the right-hand thread is used for the threaded holes of a conventional clamping device1(for example, a tool rest including an automatic copying lathe). Accordingly, for example, when the tool holder5is attached, the fastening bolt7′ with the left and right-hand screws is rotated in an attaching direction, so that the wedge-type holder clamping tool4is moved in a direction to clamp the tool holder5, so as to clamp the tool holder5to the support body1A. On the other hand, the fastening bolt7′ with the left and right-hand screws is rotated in a removing direction, so that the wedge-type holder clamping tool4is positively moved away from the tool holder5so as to remove the tool holder5from the support body1A. Similar to the above, when the stopper block2is secured by the wedge-type stopper clamping tool3, the block can be attached or removed by use of fastening bolt6with the left and right-hand screws. Thus, the wedge-type stopper clamping tool3or the wedge-type holder clamping tool4can be attached to or removed from the clamping device by use of only the fastening bolt with the left and right-hand screws. It will be appreciated that the device can be made smaller because the fastening bolt has no portion whose diameter is larger than the diameter of the threaded portions. Namely the clamping device can be applied to a tool holder having a small shaft.

The wedge-type holder clamping tool for attaching the tool holder to the clamping device with stability will be described below. In order to attach the tool holder to the clamping device with further stability, as shown inFIGS. 4(a-1) to4(c-2), the wedge-type holder clamping tool4is provided with pressing bolts18-1,18-2,18-3for pressing against the side face14, a top face or a corner19of the tool holder5.FIGS. 4(a-1) to4(b-2) show the pressing bolt for pressing against the side face14.FIGS. 4(c-1) and4(c-2) shows the pressing bolt for pressing against the corner19. As described above, the wedge-type holder clamping tool is provided with the pressing bolt so that the tool holder can be appropriately attached to the side face and the bottom face of the groove of the clamping device with stability.

In order to further accurately position the tool holder5in the axial direction thereof, according to the present invention, the stopper block2can be provided with an adjusting bolt20or a positioning bar23as adjusting means, as shown inFIGS. 5(a-1) to5(b-4). As shown inFIG. 5(a-1), the first adjusting bolt20extends through the stopper block2along the central axis thereof, and has a maximum length that is larger than the maximum length of the stopper block. The end face of the adjusting bolt that is in contact with the rear end of the tool holder has a diameter smaller than that of the adjusting bolt. The first adjusting bolt20positions the stopper block at a predetermined position by use of the wedge-type stopper clamping tool3. The adjusting bolt20provided in the stopper block2positions the tool holder at a predetermined position. As shown inFIG. 5(b-3), the second positioning bar23is inserted into a hole that extends through the stopper block2along the central axis thereof. The positioning bar23is secured and positioned by a securing bolt21and a positioning screw22that are engaged in threaded holes provided in one face of the stopper block. The second positioning bar23positions the stopper block at a predetermined position by use of the wedge-type stopper clamping tool3. As shown inFIG. 5(b-3), the chamfered end of the positioning bar23on the side of the bar that faces the tool holder is pressed against the tool holder to position the tool holder by use of the positioning screw22provided in the stopper block2. After that, the positioning bar23is secured by the securing bolt21. This enables the tool holder to be extremely accurately positioned at a predetermined position.

Another means for positioning the tool holder5in the axial direction thereof will be described below. As shown inFIGS. 6(a-1) to6(c-2), V-shaped cuts or recesses24are provided at a longitudinal corner of the tool holder5. In addition, the wedge-type holder clamping tool is provided with at least one pressing bolt18-1(inFIGS. 6(a-1)(a-2)), pressing bolt18-2(inFIGS. 6(b-1) (b-2)), and pressing bolt18-3(inFIGS. 6(c-1)(c-2)). At least one pressing bolt18-1,18-2,18-3is pressed against an inclined surface (near the stopper block) of the V-shaped cut24, so that the tool holder5can be pressed against the stopper block2at a predetermined pressure. The pressing bolt18-1is engaged toward the side face of the clamping device; the pressing bolt18-2is engaged toward the bottom face of the groove of the clamping device; and the pressing bolt18-3is engaged at a predetermined angle with respect to the side face and the bottom face of the groove of the clamping device. By means of any of the pressing bolts, the tool holder can be pressed against the side face and the bottom face of the groove of the clamping device. The top end of the pressing bolt18-1,18-2,18-3is shaped into a hemisphere or a cone corresponding to the V-shaped cut. However, if no cut is provided, the top end can be flat.

The wedge-type holder clamping tool that attaches the tool holder to the clamping device with further stability will be described below. In order to attach the tool holder to the clamping device with further stability, the wedge-type holder clamping tool4is provided with the elastic pressing tool or the pressing bolt with the elastic pressing tool in place of the pressing bolts shown inFIGS. 6(a-1) to6(c-2). Also, the elastic pressing tool or the pressing bolt with the elastic pressing tool is pressed against the side face14, the top face or the corner19of the tool holder5. As described above, the wedge-type holder clamping tool is provided with the elastic pressing tool or the pressing bolt with the elastic pressing tool, so that the tool holder can be appropriately attached to the side face and the bottom face of the groove of the clamping device with stability. A spring coil, an elastic rubber, a plate spring, a spring washer, a coned disc spring, a spring plunger screw or the like is used as the elastic pressing tool and in the pressing bolt with the elastic pressing tool. As an example of the elastic pressing tool and the pressing bolt with the elastic pressing tool, a spring plunger screw is shown inFIGS. 9(a–c). The spring plunger screw26is provided with: (i) a screw portion26-1that presses the tool holder against the abutment surfaces of the groove1B, (ii) a top end (having a round or flat end)26-2that abuts with the tool holder, (iii) a plug screw26-3that secures a spring, and (iv) a spring26-4that presses the tool holder via the top end thereof.

Means for positioning the tool holder5in the axial direction thereof by using the elastic pressing tool or the pressing bolt with the elastic pressing tool in place of the above pressing bolts will be described below. In such means, the V-shaped cuts24are provided at a longitudinal corner of the tool holder5shown inFIGS. 6(a-1) to6(c-2), and the wedge-type holder clamping tool is provided with at least one pressing bolt with the elastic pressing tool (for example, the spring plunger screw inFIGS. 9a-c) in place of the pressing bolts shown inFIGS. 6(a-1) to6(c-2). In such means, at least one pressing bolt with the elastic pressing tool is pressed against such an inclined surface (near the stopper block) of the V-shaped cut24, so that the tool holder5can be pressed against the stopper block2at a predetermined pressure. The pressing bolt with the elastic pressing tool used in place of the pressing bolt shown inFIGS. 6(a-1)(a-2) is engaged toward the side face of the clamping device; the pressing bolt with the elastic pressing tool used in place of the pressing bolt shown inFIGS. 6(b-1)(b-2) is engaged toward the bottom face of the groove of the clamping device; and the pressing bolt with the elastic pressing tool used in place of the pressing bolt shown inFIGS. 6(c-1)(c-2) is engaged at a predetermined angle with respect to the side face and the bottom face of the groove of the clamping device. By means of any of the pressing bolts with the elastic pressing tool (e.g., a spring plunger screw, a spring coil, an elastic rubber, a plate spring, a spring washer, a coned disc spring or the like), the tool holder can be pressed against the side face and the bottom face of the groove of the clamping device. The top end of the elastic pressing tool that abuts with the V-shaped cut24is shaped into a hemisphere or a cone corresponding to the V-shaped cut. However, if no cut is provided, the top end can be flat.

Furthermore, in the present invention, the attaching efficiency and the positioning of the tool holder5can be further improved by modifying a part of the tool holder5. As shown inFIGS. 7(a–c), in order to improve the attaching efficiency of the tool holder5, a chamfer25(e.g., a back taper, a truncated cone shape, spherical shape or plural combinations of the back taper, a truncated cone shape and a spherical shape) is provided on the rear end of the tool holder, so that the tool holder can be easily attached to the support body1A.

Furthermore, in the clamping device according to the present invention, a conventional long tool holder can be attached in place of the stopper block2, by using both the wedge-type stopper clamping tool3and the wedge-type holder clamping tool4.

The holder clamping tool4can be held in place as shown inFIGS. 10 and 11. As shown inFIG. 10, in the clamping device of the tool holder according to the present invention, the fastening bolt7of the wedge-type holder clamping tool4is attached to a spring nut121to define a thread connection. The spring nut121prevents the clamping tool fastening bolt7from being detached from the wedge-type holder clamping tool4, and the wedge-type holder clamping tool4is held between the nut121and a head of the bolt7.

As shown inFIG. 11, in the clamping device of the tool holder according to the present invention, the fastening bolt7of the wedge-type holder clamping tool4is fastened to a threaded sleeve-type nut122to define a thread connection. Rotation of the nut122is facilitated by a knurled ring123.

In each ofFIGS. 10 and 11, the holder clamping tool4has a slot9″ elongated in a direction transversely of the axis A and through which the bolt7passes. As a result, by loosening the bolt7and slightly displacing the holder clamping tool4out of the groove1B, the clamping tool4can be raised away from the tool holder in order to allow removal (or insertion) of the tool holder even while the fastening bolt7remains secured in the support body1A. Thus, with any structure having the feature described with reference toFIGS. 10 and 11, the tool holder4can be temporarily fastened without completely detaching the clamping tool fastening bolt7or the holder clamp4.

Other types of wedge-type holder clamping tools4which can temporarily fasten the tool holder5without fully detaching the clamping tool4or the fastening bolt7will be described below with reference toFIGS. 12 to 16, wherein a spring is provided which presses the holder clamp4against the tool holder5to hold the latter in place.

As shown inFIG. 12, in the clamping device of the tool holder according to the present invention, the fastening bolt7is fastened to the spring nut121. An upwardly extending spring mounting slit127is provided in the holder clamp4to one side of the elongated through hole9″ of the wedge-type holder clamping tool4. A biasing spring126extends into the slit so that a spring end126-1exerts an elastic biasing force in a direction to increase a distance between the clamping device and a wedge-type side face12aof the wedge-type holder clamping tool4, so that the holder clamping tool4presses against the holder5. Thus, the tool holder5remains temporarily fastened to the support body1A even while the clamping bolt fastening tool7is loosened but still secured to the support body1A. In that state, the tool holder5can be inserted or removed.

As shown inFIG. 13, the biasing spring128has an end128-1which exerts the elastic biasing force described above.

As shown inFIG. 14, the fastening bolt7is fastened to the sleeve nut122. A leaf spring124is provided in the wedge-type holder clamping tool4between the sleeve nut122and a wedge-type side face12aof the wedge-type holder clamping tool to temporarily fasten the tool holder5to the clamping device. Accordingly, the leaf spring124exerts an elastic force in a direction to increase a distance between the wedge-type side face12aand the sleeve nut122. Thus, the holder clamping tool4presses against the tool holder5, wherein the tool holder5remains temporarily fastened to the clamping device, even when the clamping bolt fastening tool7is loosened.

As shown inFIG. 15, a coil spring125having a fixed end is provided in place of the leaf spring124. Accordingly, the coil spring125having a fixed end exerts an elastic force in a direction to increase a distance between the wedge-type side face12aand the sleeve nut122, so that the tool holder5is temporarily fastened to the clamping device, when the clamping bolt fastening tool7is loosened.

As shown inFIG. 16, the wedge-type holder clamping tool4is provided with the sleeve nut122. A laterally biasing spring mounting slit131is provided in one of opposite side surface portions of the bolt through hole9″ of the wedge-type holder clamping tool4in the minor axis direction thereof. A laterally biasing spring129is mounted in the laterally biasing spring mounting slit. One end of the laterally biasing spring129is inserted into a hole132of the laterally biasing spring mounting slit, and the other end of the laterally biasing spring129is disposed between the clamping device fastening bolt7and the wedge-type side face12a. With this structure, the laterally biasing spring129exerts an elastic force in a direction to increase a distance between the wedge-type side face12aand the sleeve nut122, so that the tool holder5is temporarily fastened to the clamping device1, when the bolt7is loosened.

Therefore, with any structure described with reference toFIGS. 12 to 16, the tool holder5can be temporarily fastened without detaching the clamping device fastening bolt7from the wedge-type holder clamping tool4. The tool holder5can also be inserted and detached from the support body1A with the bolt7being loosened. Moreover, the features disclosed in connection withFIGS. 10–16can be employed in conjunction with a part which pushes the clamp in a direction away from the groove13upon loosening the bolt7, such as the elastic ring17.

EFFECT OF THE INVENTION

In the clamping device for the tool holder according to the present invention, the number of fastening bolts for the tool holder can be reduced; the jack-up screws can be dispensed with; and a miniaturization and the simplification of the wedge-type holder clamping tool can be achieved. Thus, the time required for attachment/removal of the tool holder can be reduced without modifying the tool holder and the clamping device for the tool holder that are currently used.

Furthermore, in the clamping device for the tool holder according to the present invention, the tool holder can be disposed at an accurate position, and can be repeatedly disposed at the same accurate position even when replaced. Also, in the clamping device for the tool holder according to the present invention, the tool holder can be temporarily fastened without being detached from the clamping device and without detaching the clamping tool fastening bolt from the wedge-type holder clamping tool when the tool holder is attached to and detached from the clamping device.