Power-driven screwdriver

Details Power-driven screwdriver Power-driven screwdriver

2002-05-14

2004-04-06

Wilson, Lee D. (Department: 3723)

Tools

Wrench, screwdriver, or driver therefor

Machine

C081S057290

Reexamination Certificate

active

06715380

ABSTRACT:

This application claims priority of pending German Patent Application Nos. 101 24 569.6, 101 24 571.8, 101 24 572.6 and 101 24 573.4 all filed on May 14, 2001.
BACKGROUND OF THE INVENTION
The invention relates to a power-driven screw drive comprising a housing having a main housing within which a drive, a reduction gear coupled therewith and a spindle received therein are supported, further comprising an angle head having a tool spindle for driving a tool, the tool spindle driven by the spindle and arranged at an angle thereto, and further comprising an angle head housing that is connected adjustably with the main housing via an adjusting device.
Such a screw drive is known from EP 0 691 185 A1.
From WO 99/16858, a power screwdriver having a torque limiting coupling releasing torque-dependently is known comprising a first coupling part, a second coupling part, a spring element for axially biasing both coupling parts against each other, and further having at least one roll body rolling between both coupling parts, the at least one roll body coupling both coupling parts when driving the screwdriver up to a preset release moment, when tightening a screw.
Angle-type screwdrivers having an adjustable angle head within which a tool spindle for driving a tool is received at an angle to a spindle driven by a gear, have several advantages with respect to other power-driven screwdrivers the tool receptacle of which is received directly on the spindle and which are thus oriented in the longitudinal direction of the screwdriver. On the one hand, the possibility for adjusting the tool head allows different operating positions, allowing in many cases a more economic operation, even under confined conditions. On the other hand, the reaction moment received by the screwdriver during tightening and loosening of screws does not lead to a turning of the screwdriver about its longitudinal axis, but to a pivoting of the screwdriver about the angle head. Such pivot movements can be controlled by the operator much easier than a rotation of the screwdriver about its longitudinal axis.
The angle-type screwdriver known from EP 0 691 185 A1 mentioned at the outset, comprises a rotatable angle head which is connected to a main housing of the angle-type screwdriver by a screw connection. Within the main housing, a drive and a reduction gear of the angle-type screwdriver are supported fixedly against rotation. The screw connection is arranged directly at the transition from the angle head to the main housing and is secured by a securing nut against unintentional rotation. When operating the angle-type screwdriver between the angle head and the main housing part, relatively large torques may occur. Therefore, there is an additional retention against rotation by providing a locking pin. In a locking position, the locking pin extends through bores within which the angle head and the main housing extend in radial direction in the region of the screw connection. In this way, the angle head can be locked fixedly against rotation with respect to the main housing in several positions, so that the angle head cannot change its position unintentionally when operating the angle-type screwdriver.
SUMMARY OF THE INVENTION
It is a first object of the invention to provide an improved angle-type screwdriver allowing for a relative rotation between the angle head and the main housing a particularly simple and cost-effective way.
It is a second object of the invention to allow an easy adjustment of the angle head with respect to the housing even during operation of the angle-type screwdriver.
It is a third object of the invention to provide an angle-type screwdriver having a torque limiting coupling having high reliability and low wear during operation.
It is another object of the invention to provide a power screwdriver allowing for a precise adjusting for the tightening torque of a screw.
It is still a further object of the invention to provide a power screwdriver of high reliability having a torque limiting coupling with low wear in operation.
These and other objects are solved by the invention by the fact that the reduction gear comprises a reaction part receiving a reaction moment with respect to the spindle, the reaction part being connected with the angle head housing fixedly against rotation and being coupled to the drive adjustably.
The reduction gear may be any gear suitable for transmitting torque from an input end to an end and having a transmission ratio of less than one, which means that there will be a lower output than input speed. A reduction gear will transmit a higher torque at its output end than it receives at its input end. The reaction torque resulting therefrom is received by a part which is called reaction part and which must be somehow supported externally. If the reaction part would not be supported externally, than the reaction part would freely rotate, when the input end is driven. Thus the reduction gear would not transmit the desired torque at its output end.
The reduction gear could for instance be a spur gear received within a gear housing, the gear housing forming the reaction part. Or the reduction gear may be a planetary gear comprising a hollow wheel within which planetary wheels and at least one sun wheel are received. The hollow wheel would then form the reaction part. Also any other type of gear can be used.
According to the invention, the connection of the reaction part with the angle head housing in a way fixedly against rotation while also coupling to the drive via an adjustment means leads to the consequence that the reaction part is connected to the angle head housing fixedly against rotation even when the adjustment device is completely released and thus the angle head can be rotated with respect to the main housing. By contrast, in prior art angle-type screwdrivers, the reaction part is always directly connected with the drive or with a housing part fixed thereto, without any adjustment possibility. The different connection of the reaction part with the two parts of the angle-type screwdriver that are adjustable thereto has important implications with respect to the torques that act between the angle head housing and the main housing and which must be absorbed by the adjusting device in operation.
For illustration, it may be assumed that the spindle is blocked by a screw that has been fully tightened so that the torque exerted by the drive must be fully absorbed between the housing parts of the angle-type grinder. In this case, the torque exerted by the drive operates between the drive and the reduction gear, on the one hand by a spindle section lying therebetween, and on the other hand, as a counter torque, between the housing parts which are connected with the reaction part of the reduction gear and with the drive, respectively. This torque is reduced by the reducing factor of the reduction gear with respect to the torque that acts between the reduction gear and the angle head. Thereby, the adjustment device can be constructed much simpler and not as sturdy as the adjustment devices necessary in prior art designs which allow an adjustable connection between the reaction part of the reduction gear and the angle head housing.
Due to the small torque that must be absorbed by the adjustment device, it is even possible to adjust the angle head during operation of the angle-type screwdriver or when the screw is fully tightened or blocked.
Any locking nuts or additional locking mechanisms become superfluous in this way. By contrast, it is sufficient to design the adjustment device as a simple screw connection. Alternatively, or in addition thereto, it is of course possible, to provide a locking mechanism, for instance if pre-defined relative positions between the angle head and the main housing are desired. However, such a locking mechanism is not necessary in view of the torque to be transmitted. However, if such a locking mechanism is desired, the mechanism may be very simple and light, since it must not absorb any considerable torque.
Of course, corresponding considerations are v

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