Patent Application
20050116428
The present invention relates to a tool holder for a rotary hammer.
Such tool holders generally have a main tube like body with an open forward end within which a chisel tool or drill bit may be inserted. The tool or bit is generally formed with at least one axially extending closed groove towards the rearward end of the tool shank. The tube like body of the tool holder is generally formed with at least one through hole, within the or each of which is located a locking body. The locking body is arranged so that it can be radially displaced between a radially inward locked position and a radially outward unlocked position. The locking body is generally held in the locked position by a locking ring of the tool holder, and in the locked position the locking body engages within the closed groove of the tool or bit. The closed groove is generally axially longer than the locking body and so the tool or bit is locked in the tool holder main body so as to be able to reciprocate by a limited amount with respect to the tool holder body. In the unlocked position, the locking body can disengage the closed groove in the tool or bit and a tool or bit can be removed from or inserted into the tool holder.
In addition to the at least one axial groove closed at both ends, the tools or bits insertable in such a tool holder generally have at least one further axial driving groove offset with respect to the axial closed groove or grooves. The further driving groove or grooves are each open at the rear end of the shank of the tool or bit and when the tool or bit is inserted into the tool holder the driving groove or grooves are each engaged by an axial driving rib of the holder body, by means of which the torque for rotation of the tool or bit is transferred to the tool or bit. Such drill bits are known, for example, as so-called SDS-Plus and SDS-Max drill bits.
The axial driving ribs of the tool holder are generally formed on the tool holder and extend radially inwardly of the inner surface of the tool holder main body. When the hammer to which the tool holder is fitted is used in a hammering mode, the tool or bit reciprocates and so the axial driving groove, which engages the axial driving rib reciprocates with respect to the driving spline causing a considerable amount of wear, especially in a rotary hammer mode in which torque is transmitted from the driving rib to the driving groove. The wear means that the tool holder may have to be replaced by a new tool holder after prolonged use of the tool holder.
This problem has been addressed in U.S. Pat. No. 5,700,018 by replacing the driving ribs with driving elements shaped as rolling bodies, such as cylinders, which rolling bodies are mounted within the tool holder main body so that a portion of the rolling body extends radially inwardly of the inner surface of the tool holder main body. The rolling bodies are arranged to engage corresponding driving grooves of a tool or bit in order to transmit torque. The rolling bodies are mounted within the tool holder body in such a way that they are able to roll along the driving grooves of the tool or bit as the tool or bit reciprocates within the tool holder. This rolling movement of the rolling bodies reduces wear on the rolling bodies and so extends the life of the tool holder. A problem with this is that a non-standard tool or bit is required with driving grooves specially shaped to engage the rolling bodies.
The same problem has also been addressed in EP335,795 and DE199 58 342. In EP335,795 a driving rib insert of hard material is fitted into a corresponding recess in the tool holder body. The recess extends radially from the inner to the outer surface of the tool holder main body and is formed as rectangular opening with outwardly tapering sides. The tapering of the recess prevents the insert from falling into the inside of the tool holder body. The insert is locked in place by a locking ring of the tool holder. The insert is formed with an axially extending driving rib, which when the insert is fitted into the recess, extends radially inwardly of the inner surface of the tool holder body. Thus, the rib is engageable with the driving groves of a standard type of tool or bit. While EP335,795 provides hard wearing driving ribs, the recess in the tool holder main body is of complex shape and relatively difficult to machine.
In DE199 58 342 a driving rib insert of hard material is fitted into the tool holder main body by machining in the walls of the tool holder main body recesses extending axially along the body, which recesses communicate with the central opening of the main body. The insert is then slideably inserted into the axially extending recesses. The insert is formed at its rearward end with a driving rib which extends radially inwardly of the inner surface of the main body so as to be engageable with a driving groove of a conventional tool or bit. The insert is fixed in place by for example, welding, adhesion or soldering. Again, DE199 58 342 provides hardened driving ribs, however, the axially extending recesses undermine the structural strength of the forward end of the tool holder main body. Also, the driving insert is subject to axial vibration due to the relative reciprocation between the driving groove and the rib, which can weaken the fixing between the insert and the tool holder body. The driving insert is a relatively large part, and as it is made of carbide material then it is relatively expensive.
The object of the invention is to produce a tool holder with driving ribs which are wear resistant, robust and enable a simple construction of the tool holder.
According to a first aspect of the present invention there is provided a tool holder for a rotary hammer, comprising:
The additional through holes for receiving the inserts are formed by simply drilling two or more axially offset circular cross sectioned through holes through the wall of the tool holder main body (holder body). The same drilling tool can be used for drilling each circular cross sectioned hole, with the tool or the holder body being moved axially between drilling operations. For longer driving ribs a greater number of circular cross-sectioned holes can be drilled in order to minimise the circumference of the additional holes in order to maintain the structural strength of the holder body. The circular cross-sectioned holes may each have the same diameter.
The overlapping axially offset circular through holes may be circumferentially aligned on the holder body, this enables the maximum length of axially extending driving rib to be achieved for a set diameter of through hole. Further, the or each additional through hole may be circumferentially offset with respect to the or each through hole for receiving a locking body in order to correspond to one of the standard tool or bit shank configurations.
In one embodiment the or each additional through hole is formed by two overlapping axially offset circular cross-sectioned through holes.
In order to simplify the drilling of the circular through holes each circular cross-sectioned hole may have a cross-section with a constant diameter from the radially outer to the radially inner surface of the holder body.
The or each insert may be secured in the corresponding additional through hole in the holder body by any convenient method, for example by adhesion, press fitting, soldering or welding, for example laser welding.
The hardened metal rib may be separate from the insert and fixed to the insert, which insert may be made out of a different material. In one embodiment the or each rib is formed integrally with the insert and the insert is made of hardened metal. The hardened metal may, for example, be a metal which is harder than the material making up the spindle, such as carbide material.
In one embodiment the base of the or each insert is shaped like a number, corresponding to the number of circular cross-sectioned holes, of overlapping solid cylinders arranged side by side with their axes parallel. Where there are two circular through holes, the base will have an end face shaped as two overlapping circles with a waist and the rib may extends lengthwise across said end face. In one embodiment the rib does not extend, axially or circumferentially (with respect to the holder body, when the insert is fitted in the holder body) beyond the end face of the base. This means that the width of the rib (in the circumferential direction with respect to the holder body, when the insert is fitted in the holder body) defines a minimum width for the waist portion of the end surface.
According to a second aspect of the present invention there is provided a tube like tool holder main body of a tool holder suitable for a rotary hammer formed with at least one through hole suitable for receiving a corresponding locking body of a tool holder and formed with at least one additional through hole suitable for receiving at least one hardened metal driving rib insert of a tool holder characterised in that the or each additional through hole is formed by at least two overlapping axially offset circular cross-sectioned through holes. A tool holder incorporating the holder body will have the same advantages as the tool holder according to the first aspect of the present invention. The holder body may have the subsidiary features described above in relation to the holder body of the tool holder according to the first aspect of the present invention.
According to a third aspect of the present invention there is provided a driving rib insert for the holder body described above comprising at least one hardened metal driving rib located on a base of the insert which base is shaped to fit a corresponding additional through hole in the holder body so that the rib extends axially and radially inwardly of the radially inward facing surface of the holder body. A tool holder incorporating the driving rib insert will have the same advantages as the tool holder according to the first aspect of the present invention. The driving rib insert may have the subsidiary features described above in relation to the driving rib insert of the tool holder according to the first aspect of the present invention.
According to a fourth aspect of the present invention there is provided a method of securing a driving rib insert as described above to a holder body as described above, comprising the steps of;
According to a fifth aspect of the present invention there is provided a method of forming the additional through holes in a holder body as described above comprising the steps of:
The invention is explained in detail in the following with reference to the Figures illustrating an exemplary embodiment.
The tool holder 1 shown in
On the front end of the housing part 2 there is seated an alignment sleeve 6, which, in a manner not shown specifically, is in interlocking engagement with the housing part 2 and is in interlocking engagement with the holder body 10, so that the latter is held locked against rotation relative to the housing part 2 and hence relative to the hammer. The sleeve 6 can be actuated, in a manner which is known in the art, so as to alter the orientation of a chisel tool fitted within the tool holder 1 with respect to the housing part 2.
In the front region of the tool holder main body 10, on opposite sides in the wall of the holder body there are formed axially extending through-openings 11, in which locking members 12, which can comprise, for example, sintered shaped bodies, are located. The locking members 12 are inserted into the through-openings 11 in such a way, and their cross-sectional shape and the cross-sectional shape of the receiving openings 11 are so matched to one another, that the locking members 12 can be displaced between a radially inner and a radially outer position, but so that when there is no tool or bit shank 30 inserted in the receiving opening 10, the locking members 12 are not able to fall radially inwards right through the receiving openings 11.
The locking members 12 co-operate with a supporting ring 16. An outer spring 20 acts on the rear side of the supporting ring 16 and so the supporting ring 16 is consequently always spring-loaded in the forward direction. An inner spring 21 is arranged with its front end abutting a washer 22 which, in the position shown in
As can best be seen in
A driving rib insert 42 made of carbide material is inserted into each through hole 40. Each driving rib insert is formed with a base 44 shaped as two cylinders arranged side by side with the axes of the cylinders parallel and with the adjacent edges of the cylinders overlapping. The diameter of each cylinder 44a, 44b is the same as the diameter of the overlapping through holes 40a, 40b and so the base 44 of the insert fits the through hole 40. The base 44 is secured in the through hole, for example by press-fitting, adhesion, soldering or welding. A driving rib 46 is formed across one end face of the base 44 so as to extend over an end face of each of the overlapping cylinders 44a, 44b forming the base. When the base 44 is fitted within the recess 40 the driving rib 46 extends axially and extends radially inwardly of the inner surface of the holder body 10. The rib 46 does not extend, axially or circumferentially (with respect to the holder body, when the insert is fitted in the holder body) beyond the end face of the base. Accordingly, the width of the rib (in the circumferential direction with respect to the holder body, when the insert is fitted in the holder body) defines a minimum width (W) for the waist portion 45 of the end surface.
The shank 30 of a tool or bit is formed with two opposing axial grooves 4 closed at both ends and with two opposing axial driving grooves, open at the rearward end of the shank and circumferentially offset with respect to the closed grooves. Such tools are well known in the art, for example under the SDS Plus or SDS Max designation. When the tool or bit is fitted within the tool holder 1, the radially inner portions of the locking members 12 extend into the axially closed grooves 11, and the locking members 12 are braced against radial outward displacement by supporting ring 16. The driving grooves in the shank 30 engage the driving ribs 46 of the inserts 42 so as to transmit torque between the holder body 10 and the tool or bit when the tool holder 1 is rotatingly driven. In operation in hammer mode, the tool or bit is able to move back and forth in the usual manner, commensurate with the axial extent of the axial grooves 4, but is held by the locking members 12 to prevent it from escaping from the receiving opening of the holder body 10.
To remove the tool or bit 30 from the tool holder 1, the user displaces the adjusting sleeve 23 by hand against the force of the outer spring 20 and the inner spring 21 out of the position shown in the upper half of
In the position illustrated in the lower half of
If the shank 30 of a tool or bit is inserted into the receiving opening of the holder body 10 then the rear end of the shank 30 comes into contact with the front end of the locking members 12. As the chisel shank 3 is introduced further, it displaces the locking members 12 axially rearwards the locking members 12 are able to yield radially outwards and move behind the supporting ring 16. In this position of the locking members 12, the rear end of the chisel shank 3 can slide past the locking members 12, until the locking members 12 are again located entirely in the region of the axial grooves 4 of the shank 30. Once this position has been reached, the pressure of the inner spring 21 causes the washer 22, and hence the locking members 12, to be displaced forwards again into the position shown in the upper half of
| Number | Date | Country | Kind |
|---|---|---|---|
| GB 0226524.7 | Nov 2002 | GB | national |
