This invention relates to power tools and particularly to an application mechanism for a power tool of the type comprising a housing, a motor mounted in said housing, a gearbox having an input end mounted on said motor and an output end adjacent an aperture in the housing, the gearbox being epicyclical and including a torque control ring which, when held stationery with respect to said housing, permits the gearbox to transmit torque and which, when permitted to rotate in the housing, disables torque transmission by the gearbox.
In such power tools it is known to dispose an application mechanism on the output end of the gearbox, which mechanism comprises a resiliently biased, adjustable actuating means mounted on said body to selectively engage said torque control clutch ring.
Adjustment of the actuating means varies the engagement with said torque control clutch ring thereby varying the torque at which it begins to slip and at which transmission by the gearbox to its output shaft is stopped.
It is also known to lock the torque control ring so that it is not employed and so that no torque limitation is provided. In this instance, it is also known to dispose an application mechanism on the output end of the gearbox, which mechanism comprises a hammer arrangement whereby oscillating axial vibration can selectively be imposed on the rotary drive supplied by the gearbox.
Finally, it is also known from DE 4038502 to provide an arrangement as first described above, i.e. a tool having a torque control mechanism mounted on the output end of the gearbox, but where a hammer mechanism is added on the front end of the torque control mechanism. Such an arrangement is versatile because it can be employed in various different ways. However, it suffers from being somewhat long having first a motor, then a gearbox, then a torque control mechanism, then a hammer mechanism, all one after the other.
It is also known to employ electronic torque control whereby the torque applied is fed back to an electronic control module and, if the applied torque exceeds the torque preset in the control module, power is disconnected from the motor. Thus if a hammer mechanism is on the front of the gearbox there is no penalty in terms of compactness in providing both torque control and a hammer facility but, of course, the electronics do add cost and complexity.
It is therefore, an object of the present invention to provide a power tool which has this versatility and yet remains compact but which is still simple and relatively inexpensive.
In accordance with the present invention there is provided a power tool comprising a housing, a motor mounted in said housing, a gearbox having an input end mounted on said motor and an output end adjacent an aperture in the housing, the gearbox being epicyclical and including a torque control ring which, when held stationery with respect to said housing, permits the gearbox to transmit torque and which, when permitted to rotate in the housing, disables torque transmission by the gearbox; and an application mechanism driven by said gearbox, which mechanism comprises:
a) a substantially cylindrical hollow body;
b) a chuck drive spindle journalled in said body and defining therebetween an annular space;
c) means limiting axial movement of said spindle in said body towards said gearbox;
d) a rotary ratchet plate fixed on said spindle;
e) a facing fixed ratchet plate in said body;
f) means to engage said ratchet plates together such that on rotation of the spindle a reciprocating action is imposed thereon, said means including a lever projecting through a slot in said body;
g) resiliently biased, adjustable actuating means mounted on said body to selectively engage said torque control clutch ring, said lever projecting through said actuating means.