Tool clamping mechanism for a power tool

Details Tool clamping mechanism for a power tool Tool clamping mechanism for a power tool

1998-07-14

2001-10-30

Rachuba, M. (Department: 3724)

Cutlery

Cutting tools

Saw

C083S699210

Reexamination Certificate

active

06308425

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a clamping mechanism for power tools.
EP 0623413 A1 discloses a blade clamping mechanism for a power tool in which a rotating collar forces two balls inwards to hold ears formed on the saw blade, but this has the disadvantage that the blade is not automatically centralised. There is further disclosed in EP 0544129 B1 a blade clamping mechanism in which a rotating collar engages with a screw thread on the outside of a plunger, pulling ears formed on the saw blade up into Ve notches cut into the bottom of the plunger. This mechanism automatically centralises the blade, but has the disadvantage that it does not latch in the open position when no blade is present.
SUMMARY OF THE INVENTION
According to an embodiment of the invention at present preferred, there is provided a power tool having a clamping mechanism for a removable operating member, the clamping mechanism including a locking member which is rotatable about an axis parallel to the insertion direction of the operating member between an open position in which the operating member may be inserted into the tool and a closed position in which removal of the operating member is prevented, and means for latching the locking member in the open position when no operating member is present. In the case of a jig saw, the operating member would usually be a saw blade.
The power tool of the above described embodiment has the advantage that the clamping mechanism remains in the open configuration when no operating member is present and is ready to receive a new operating member which can be simply pushed in. The user does not, therefore, need to hold a button or switch whilst inserting the operating member as is necessary with presently known mechanisms. As will become clear from the following, the operating member may be removed from the mechanism by the user rotating the locking member to its open rotational position whereupon the operating member simply drops out of the mechanism. This has the advantage that the user has only to make a small movement to release the operating member from the clamping mechanism.
In a development of the invention, the latching means comprise at least one projection movable in the direction opposite to the insertion direction to engage one or more cooperating recesses in the locking member. The locking member is preferably carried on a plunger extending from the tool and the latching means is preferably formed on a keeper which is slidably mounted in the plunger. Each projection may be in the form at least one leg extending from the bottom of the keeper towards the locking member. The keeper is also advantageously biassed towards the locking member, preferably by a compression spring.
One or more v-shaped grooves may be formed in the keeper for guiding the operating member and additionally, the plunger could have at least one v-shaped groove for receiving a corresponding projection on the operating member. The locking member advantageously comprises a washer through which the operating member may be inserted, preferably having at least one slot for receiving a projection on the operating member whereby the operating member is captured on rotation of the washer. In one embodiment, at least one, and preferably two cam surfaces or ramps are formed on the washer for driving the operating member into the tool on rotation of the washer by engagement with the or each projection on the operating member. In the case of two cam surfaces, it is advantageous for each cam surface to engage its associated projection at a different angular position of the washer, so that the force necessary to rotate the washer is reduced. The locking member is additionally biassed towards its closed position, for example by the action of a torsion spring.
According to another aspect of the present invention there is provided a power tool having a clamping mechanism for a removable operating member including a plunger extending from the tool for receiving the operating member having one or more V-shaped notches for receiving a corresponding projection on the operating member and means for driving the operating member into the tool to centre the projection(s) in the notch(es) to centre the operating member.
The driving means preferably comprise a rotatable member having one or more cam surfaces for engaging the projections on the operating member.


REFERENCES:
patent: 2617166 (1952-11-01), Kaufmann
patent: 4528753 (1985-07-01), Kuhlmann et al.
patent: 5306025 (1994-04-01), Langhoff
patent: 5433457 (1995-07-01), Wright
patent: 5634277 (1997-06-01), Wada et al.
patent: 0 623 413 a1 (1994-11-01), None
patent: 0 544 129 B1 (1995-01-01), None

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