DE102005020829A1 - Cordless power tool such as screwdriver, activates switch-off function when sudden increase in speed or sudden drop in torque occurs - Google Patents

Abstract

The power tool includes a drive arranged in a housing. An automatic switch-off function is activated when the rotation speed suddenly increases and/or the torque suddenly falls. The drive may have an active brake which is activated by the switch-off function. An independent claim is included for a method of operating a cordless power tool.

Description

State of technology

The The invention is based on a rechargeable batteries operable Electric machine tool and a method for operating a Such power tool according to the preambles of the independent claims.

With rechargeable batteries operable power tools are widely known. Such devices are in a wide range Range offered, from the smallest and cheapest cordless screwdrivers up to an upper performance class of cordless rotary hammers. Small cordless screwdrivers As a rule, they are only suitable for tightening screws. Also in the upper power class can Such power tools usually for tightening screws be used.

Cordless Screwdriver are currently being used in home improvement to tighten screws. It is often not enough Force exerted on the cordless screwdriver. This can lead to an unfavorable slippage come a screwing. By slipping loses The cordless screwdriver has the counterforce needed for tightening the screw is required. The slippage leads to a disadvantageous leaps and bounds Increase in the speed or to a sudden drop in torque. The slipping can both the screw and a Damage the head of the screw. This damage can complete destruction lead from screw top or screw head.

Advantages of invention

at an inventive with rechargeable batteries operable power tool is at a sudden increase in the speed and / or at a sudden Drop in torque can be activated an automatic shutdown function. This has the advantage that the unfavorable ones described above Consequences of slipping through a screw attachment prevented can be. By the activation according to the invention The shut-off function becomes both the screw attachment and the screw head from damage or before a complete destruction protected. This advantageously results in cost savings because the screw attachments damaged less often and therefore need not be replaced. Also with the screw material is handled gently.

The Shutdown can be done by immediately switching off the power tool or the drive motor triggered be and can be solved after a tightening again, if the screw head undamaged is. In a preferred embodiment An active brake of the drive is provided, the switching function from the Ab activated, for example by friction. This is the power tool even faster to a halt, so that by slipping caused damage be actively prevented.

at a method according to the invention for Operating a powered with rechargeable batteries power tool is at a sudden increase in speed and / or a sudden drop in torque an automatic shutdown function activated to deactivate the drive. Advantageously damage, which are caused by slipping, as low as possible held.

Prefers is during a normal operation of the sudden increase in speed and / or the sudden drop in torque detected automatically, whereupon expediently the speed as fast as possible is reduced to zero. This can be achieved by: the drive is deactivated by breaking a power supply. This has an immediate shutdown of the power tool, for example, the cordless screwdriver, the result.

In a preferred embodiment the drive is actively decelerated. In particular, this can be a brake to be activated. This can be achieved, an even faster Decrease in speed to zero.

The Switch-off function can be deactivated by releasing an on-off switch become. The procedure of the procedure is then as follows: At usual Operation with the power tool according to the invention, For example, in a cordless screwdriver, is in a normal operation worked. Once slipping during normal operation of Cordless screwdriver is detected, the function of the invention triggered as described above be used to reduce the speed to zero. Then the Operator release the on / off switch to the cordless screwdriver with his Put the screw attachment back on a screw head. By the release of the on-off switch is the shutdown function conveniently been finished, and the cordless screwdriver can be repeated by pressing the On-off switch to start working again in normal operation. The shutdown function can thus by pressing the on-off switch be deactivated.

Of the described sudden increase in the speed or the erratic Waste torque can not only slipping, but also at other events with similar ones Follow during a normal operation of a power tool occur, for example in a drilling operation when a drill penetrates into a cavity or in a wall layer having a much lower density as the previously pierced outer layer. In such events in the drilling operation is the shutdown function according to the invention unfavorable, because it must be rescheduled to continue drilling. It can therefore be provided that the shutdown disabled in drilling mode is, for example, by a toggle switch on the device.

Claims (9)

Can be operated with rechargeable batteries power tool, comprising a arranged in a housing drive, characterized in that at sudden increase in speed and / or sudden drop in torque, an automatic shut-off is activated. Electric machine tool according to claim 1, characterized characterized in that an active brake of the drive by the shutdown function is activatable. Method of operating a rechargeable Battery-operated power tool, characterized that at a sudden increase in the speed and / or a sudden Drop of torque an automatic shutdown function to disable of the drive is activated. Method according to claim 3, characterized that the drive is disabled by canceling a power supply. Method according to claim 3 or 4, characterized that the drive is actively decelerated. Method according to one of claims 3 to 5, characterized that the sudden increase in speed and / or the erratic Drop of torque automatically is recognized. Method according to one of claims 3 to 6, characterized the shutdown function activates a brake of the drive. Method according to one of claims 3 to 7, characterized that the shutdown function by releasing an on-off switch is deactivated. Method according to one of claims 3 to 8, characterized that after the deactivation of the shutdown function normal operation by pressing of the on-off switch is resumed.