NZ604986B - Hand tool - Google Patents

Abstract

604986 Disclosed is a hand tool (1), such as a drill or rotary hammer, with an electric motor (3) for rotationally driving a member (2) to be driven. The hand tool comprises means (6) for detecting the rotation of the tool, including a gyroscopic sensor. These means detect a blockage of the tool which then activates a means (5) for slowing down the motor. The means for slowing down the motor includes a contactor (14) arranged to insulate the engine from its electric supply and transform it into a current generator wherein the current is reinjected in inverse polarity into the engine. Thus, momentary regenerative braking is caused upon a blockage of the tool. which then activates a means (5) for slowing down the motor. The means for slowing down the motor includes a contactor (14) arranged to insulate the engine from its electric supply and transform it into a current generator wherein the current is reinjected in inverse polarity into the engine. Thus, momentary regenerative braking is caused upon a blockage of the tool.

Description

HAND TOOL This invention relates to hand tools ed with an electric engine, for rotationally driving an anchoring, drilling or fastening member. The tools may be drills, screwing machines, millstones, or other rotary s.

With such tools, the risk could occur that the member to be rotationally driven gets suddenly blocked, for example, when a drill bit of a drill strikes a metal part. Consequently, it is the tool which is driven in rotation and which is able to hurt the operator's hand or arm.

From document US 2004/0104034, a hand tool is known, sing, between the engine and the member to be driven, a safety clutch controlled by a torque active control safety module, comprising a detector being sensitive to an angular shift, and cutting the driving of the engine when the member to be driven no longer moves.

Such a prior art tool, however, has the drawback of having quite a short life.

According to the invention there is provided a hand tool with an electric engine for rotationally driving a member, to be driven, the tool comprising means for slowing down the engine and means for ing on of the tool so as to control the slowing down means of the engine, the tool comprising a contactor ed for ting the engine from its electric supply and for transforming the engine into a current generator of which the current is re-injected in inverse polarity into the engine.

' Thus, instead of stopping the g of the engine, the engine is only slowed considerably improving the life of the tool. Moreover, the engine becomes a current generator. The generated current is re-injected in inverse polarity into the engine, thereby ensuring a fast slowing down in the tool rotation.

Advantageously, the means for ing the rotational g of the tool comprise a gyroscopic detector.

This invention will be better understood using the following description, provided by way of non—limiting example, of a hand tool according to a preferred embodiment with reference to the single figure showing a functional block diagram, with its electric engine for driving a member to be driven and its control module for slowing down the engine, in the case of the rotation being blocked for the member to be driven.

With reference to the Fig, a hand tool 1, here, but actually as an example, a rotary hammer adapted to rotationally drive a drill bit 2, and a control module 4, intended to prevent the tool from rotating when the drill bit 2 suddenly gets d, as a ,. for example, of the same meeting a metallic part upon the drilling operation.

The control module 4 comprises a block 5 for slowing down the engine 3 and means for detecting the rotational driving of the tool 1 controlling the slowing down block 5. The ing means here comprise a gyroscopic sensor 6 substantially arranged along the rotation axis 7 of the tool. An electronic filter 8 is connected with the output of the gyroscope 6 for removing the noise generated by the normal operation of the tool. The slowing down block 5 is connected to the output of the filter 8.

As soon as the tool is started, the gyroscope 6 could detect the rotation of the tool.

The output signal of the filter 8 as well as that of a quartz 9 are received in a calculator 10 of 1O a. microcontroller ll delivering, in. , a signal V(9)being representative of the rotation speed of the tool. The signal v(e) is compared, in a comparator 12, to a signal being representative of a threshold speed V (5). Such a speed V (s) could be determined. by a software part 13 embedded into the microcontroller 11. The output signal of the comparator 12 is sent to a tor 14 being active as soon as v (e) >V (s) The contactor 14 is connected to the engine 3. The activation of the contactor l4 tes the engine from its electric supply. Thus, the engine becomes a current generator. The generated current is re—injected in inverse polarity into the engine, thereby ensuring a fast, even sudden, slowing down of the tool.

Such an action of insulation and phase ion of the engine could occur on a field effect transistor FET of the engine.

It should be noticed that the activation of the transistor FET should be as fast as possible. This is why, as a contactor, an electromechanical contactor is red having a very fast reaction. In addition, this is a particularly robust equipment material. Thus, it could be hoped that the tool is onally driven on less than one quarter of revolution.

The just described assembly is thus a slowing down module. It could be arranged on any electric engine tool, on which an unexpected rotational blocking could occur. The risks of accident of the type fracture or sprain at the level of operators' arms are thereby restricted.

The ion has been bed by way of non—limiting example only and many modifications and variations may be made thereto without ing from the spirit and scope of the invention. Throughout this specification and the claims which follow, unless the context requires otherwise, the word ise”, and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims (3)

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:
1. l. A hand tool with an electric engine for onally driving a member to be driven, the tool sing means for slowing 5 down the engine and means for ing rotation of the tool so as to control the g down means of the engine, the tool comprising a contactor arranged for insulating the engine from its electric supply and for transforming the engine into a current generator of which the current is re—injected in inverse polarity 10 into the engine.
2. 2. The hand tool according to claim 1, wherein the means for detecting the rotational driving of the tool comprise a gyroscopic detector.
3. 3. The hand tool according to claim 1, wherein the contactor is an electromechanical contactor. nil1 N