Robert Boschgmbh

Alfred Hettich

Karl Roll

Reinhold Stroezel

Manfred Kirn

Wilhelm W Schwarze

Hubert Stahl

Wolfgang Raidt

Werner Keil

Herbert Dieterle

A transducer arrangement for torque and/or angular displacement measurement, especially in power screwdrivers, operates in accordance with the eddy current principle. The transducer arrangement is constructed as a self-contained structural unit having its own transducer casing which is connected by appropriate coupling and connecting parts to the housing of the power screwdriver and to the driving and driven members of the screwdriver. A torsionally deformable member, especially shaft, is interposed between the driving and driven members, being connected thereto for joint rotation therewith. When torque is applied to the deformable member, its end portions are angularly displaced relative to one another. Two slotted members, especially sleeves, are respectively connected to the end portions of the deformable member for joint angular displacement therewith, and they influence the magnetic field in the vicinity of the deformable member in proportion to their relative angular displacement. The changes in the magnetic field are detected by an electric coil arrangement whose impedance changes accordingly, and the thus obtained signal is evaluated to obtain the magnitude of the applied torque. A cable connected to the coil arrangement and extending to the exterior of the casing through an opening provided in the latter is accommodated in a tube. The tube extends along a handgrip portion of the housing of the screwdriver to protect the hand of the user.

Transducer for torque and/or angular displacement measurement,

A screwdriver comprises a planetary gear carrier rotatably carrying a plurality of circumferentially displaced planet gears meshing with a pinion driven by the motor of the screwdriver and with teeth provided on the inner surface of a coupling element in form of a hollow cylinder surrounding the carrier. The coupling element is also provided at one end with coupling teeth axially displaced from the first-mentioned teeth. The coupling element is movable by a fluid-operated piston from a first position to which it is biased by springs, in which the coupling teeth thereon are in mesh with corresponding coupling teeth on the carrier to rotate with the same speed as the latter, to a second position in which the coupling teeth on the coupling element are in mesh with stationary teeth on a housing surrounding the carrier and the coupling element to hold the latter against rotation.

Motor-driven screwdriver

A power tool includes a motor and a motor switch movable between on and off settings. A transmission connects the motor to the tool holder of the power tool. The transmission includes a torque-responsive clutch arrangement which transmits torque below a preselected value in a first manner and torque above the preselected value in a different and distinguishable second manner. The torque-responsive clutch means undergoes an automatic change of torque transmission manner in response to a rise of transmitted torque past the preselected value. A turn-off arrangement mechanically detects the automatic change of the manner in which the clutch arrangement transmits torque and in response thereto automatically moves the motor switch from the on to the off setting. An override device is activatable by the user of the power tool for mechanically preventing the automatic turn-off arrangement from turning off the motor.

Power tool

A safety claw clutch wherein the adjacent end faces of driving and driven rotary clutch elements have alternating claws and recesses and the driven clutch element is biased axially against the driving clutch element by a spring. The bottom surfaces in the recesses of the clutch elements make a first acute angle with a plane which is normal to the common axis of the clutch elements and the front surfaces of claws of the driving clutch element (and hence the rear surfaces of claws of the driven clutch element) make with such plane a second acute angle which is larger than the first acute angle. The top surfaces of the claws are parallel to the respective bottom surfaces. Such configuration of the claws and recesses insures that the force which tends to reengage the clutch elements when the driving clutch element rotates relative to the driven clutch element upon disengagement of the clutch is a small fraction of the force which normally maintains the claws of the driving clutch element in the recesses of the driven clutch element and vice versa because the claws of the driving clutch element cannot enter the recesses of the driven clutch element.

Growing community of inventors

Stetten, Germany

Alfred Hettich