GB2069406A

GB2069406A - Mounting of a keyhole-saw blade

Info

Publication number: GB2069406A
Application number: GB8103440A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1980-02-20
Filing date: 1981-02-04
Publication date: 1981-08-26
Also published as: ES267107U; CH651489A5; IT1135545B; IT8119861A0; NL8100781A; GB2069406B; FR2475959B1; JPS56133101A; ES267107Y; DE3006299A1; FR2475959A1; BR8101013A

Abstract

The blade 5 is clamped to the end 9 of the reciprocating shaft by a rotatable sleeve 14 provided with a clamping disc 15 having a recess 24 in which a clamping jaw 28 is accommodated when the sleeve is rotated to a position for removing a blade. An auxiliary groove 11 is provided in the end of the shaft 9 to facilitate removal of broken-off saw blade ends 6. The sleeve (14) is made of metal or plastics with the disc 15 being moulded therein so that the disc is rigidly secured to the sleeve. <IMAGE>

Description

SPECIFICATION A keyhole-saw State of the Art The invention originates from a keyhole-saw according to the preamble to the main claim. Such keyhole-saws have already been known from German patent specification 960 503 and German patent specification 1 041 236. In those, the keyhole-saw blades are retained in their mount positively and in addition by clamping with clamping screws. Moreover, the clamping screws can act radially or axially on the clamped keyholesaw blade. The clamping screws which are used can only be reached and tightened and loosened by means of a tool. If clamping screws of this kind are damaged they may only be removed by a partial dismantling of the hand machine tool and replaced by new clamping screws. Due to the high possibility of damage, for example to the screw slot, of an invisible screw, the replacement is necessary comparatively often.Thus, the servicing and maintenance of such a key-hole saw is considerable and time-consuming. A further disadvantage of the mounts of such key-hole saws can be seen in the fact that the removal of broken saw blade clamped ends is very difficult when the broken off piece does not project out of the mount.

Domestic workers less trained as craftsmen in particular are then faced with an almost insoluble problem.

Advantages of the Invention As opposed to this, the keyhole-saw in accordance with the invention comprising the characterising features of the main claim has the advantage of a very robust construction and very easy and simple serviceability. Due to the sleeve which is accessible from the outside and the clamping disc associated therewith, keyhole-saw blades can be ridigly clamped or released in their positively acting mount by a simple rotation of the sleeve.

Advantageous further developments and improvements of the keyhole-saw set forth in the main claim are made possible by the measures set forth in the sub-claims. The clamping jaw which is used and which is inserted in a recess at the end of the reciprocating shaft between the saw blade clamp end and the clamping disc, is especially advantageous for a reliable mount free from wear.

The auxiliary groove provided in the reciprocating shaft end for removing broken sawblade clamped ends is a simple but very effective further development of the subject matter of the invention. Finally, the use of light metal or plastics for the production of the sleeve receiving the clamping disc made possible by the construction of the mount for the saw blade in accordance with the invention, is also of advantage. The masses reciprocated by the shaft are doubtless reduced thereby.

Drawing An embodiment of the subject matter of the invention is illustrated in the drawing and is described in detail in the following specification.

Figure 1 shows a perspective representation of a keyhole-saw constructed in accordance with the invention, Figure 2 is a section through the mount for the keyhole-saw blades in accordance with the invention, Figure 3 is a plan view of Figure 2 according to the section A-A, Figure 4 is a side view of Figure 2 seen from the right in section and Figure 5 is a variant of a sleeve pushed over the end of the reciprocating shaft and provided with another solution for securing the said sleeve to the end of the reciprocating shaft.

Description of the Embodiment A keyhole-saw 1 provided with a support and guide plate 2 and a reciprocating shaft 3 is provided at the end of the reciprocating shaft 3 with a mount 4. The end of the shaft 3 and the mount 4 accommodate a keyhole-saw blade. The clamping end of the keyhole-saw blade 5 referenced 6 has lugs 7 and 8 on its edges. The shaft 3 has a shaft end 9 which is provided with a recess 10 with an auxiliary groove 11 at its base.

Recesses 12 and 13 which are designed to receive the lugs 7 and 8 on the clamping end of the keyhole-saw blade and are matched in crosssection for this purpose, are machined in the side walls of the recess 10. Finally, the end 9 of the shaft is so designed that it can receive a sleeve 14 which is rotatable but is secured against axial displacement. The sleeve 14 is made from light metal or plastics material and accommodates a moulded-in clamping disc 15. The arrangement of the sleeve 14 (Figure 2) is pushed over the shaft 3 from above, in the representation, and engages by way of an abutment surface 16 a corresponding step 17 on the end 9 of the shaft. A disc 19 which is inserted in the clamping sleeve 14 and is retained in the said recess 20 by a snap ring 21, engages the end surface 18 of the end 9 of the shaft.Moreover, the snap ring engages in an annular groove 22 in the sleeve 14. The clamping disc 15 has a bore 23 by which it is pushed over the end 9 of the shaft like the sleeve 14. The bore 23 is widened by a recess 24. The recess 24 forms abutment surfaces 25 and 26 and a clamping surface 27. The abutment surfaces 25 and 26 and the clamping surface 27 are matched in shape to the back of a clamping jaw 28 which is likewise inserted in the recess 10 in the end 9 of the shaft for clamping the clamped end 6 of the keyhole-saw blade and is retained in the recess by the disc 19. On rotating the sleeve 14 in the direction of the arrow 29, the clamping surface 27 moves out of the position illustrated in dotted lines in Figure 3 against the back of the clamping jaw 28 raised from the clamping end of the keyholesaw blade and urges the clamping jaw 28 into a clamping position.When the sleeve 14 and with it the clamping disc 15 has been rotated through 90C in the direction of the arrow 29, the keyholesaw blade 5 is rigidly clamped and this clamping position is secured by inherent friction between the back of the clamping jaw 28 and the wall of the bore 23. In order to release the clamping connection, the sleeve 14 together with the clamping disc 15 is rotated in the opposite direction as is shown by an arrow 30. The clamping jaw 28 is released and together with its side surface facing the abutment surfaces 25 and 26 forms a limitation of the said rotary movement.

The keyhole-saw blade 5 can then be removed.

In the case where the clamping end 6 of the keyhole-saw blade is broken off so short that it no longer projects beyond the end 18 of the end 9 of the shaft it can nevertheless be easily removed. A scriber or another suitable pin is simply pushed into the auxiliary groove 11 and forces the clamping end of the sawblade out of its positive connection between the lugs 7 and 8 and the recesses 12 and 13. The vanes 31 formed on the sleeve 14 makes the sleeve 14 more non-slip. This can of course be produced in some other desired known manner.

The mount 4 can operate in the same manner when the connection between the end 9 of the shaft and the sleeve surrounding it is selected in accordance with the example of Figure 5 where a sleeve 32 can be pushed over the end 9 of the reciprocating shaft with the keyhole-saw 1 otherwise completely assembled. For this purpose, the end 9 of the shaft is provided with an annular groove 33 which is arranged opposite an annular groove 34 in the sleeve 32 provided with an inserted snap ring 35. A shoulder 36 on the sleeve 32 serves as an abutment for the end 1 8 and for simultaneously securing the clamping jaw 28 in the recess 10.

Claims

1. A keyhole-saw, especially a motor driven keyhole-saw designed as a hand tool comprising a mount for the positive reception of an appropriately shaped clamping end of a keyholesaw blade and a clamping device for the keyholesaw blades, characterised in that it has a clamping disc for rigidly clamping the clamping end of the keyhole-saw blade, connected to a sleeve accessible from the outside, rotatable on the end of the reciprocating shaft and secured against axial displacement.

2. A keyhole-saw according to claim 1 characterised in that a clamping jaw which is inserted in a recess at the end of the reciprocating shaft between the clamping end of the keyholesaw blade and the clamping disc, is provided as a mount for the keyhole-saw blades.

3. A keyhole-saw according to one of claims 1 and 2 characterised in that an auxiliary groove is provided in the end of the reciprocating shaft for removing broken-off clamping ends of keyholesaw blades.

4. A keyhole-saw according to one of claims 1 to 3 characterised in that the projections or recesses for producing the positive connection between the reciprocating shaft and the keyholesaw blade are formed in the end of the reciprocating shaft.

5. A keyhole-saw according to one of claims 1 to 3 characterised in that the projections or recesses for producing the positive connection between the reciprocating shaft and the keyholesaw blade are formed in the clamping jaw.

6. A keyhole-saw according to one of claims 1 to 3 characterised in that the projections or recesses for producing the positive connection between the reciprocating shaft and the keyholesaw blade are formed in the end of the reciprocating shaft and the clamping jaw.

7. A keyhole-saw according to one of claims 1 to 6 characterised in that the sleeve is made from light metal or plastics material and the clamping disc is preferably moulded into the sleeve.

8. A keyhole-saw substantially as herein described with reference to Figures 1 to 4 or Figure 5 of the accompanying drawings.