Tools – Wrench – screwdriver – or driver therefor – Machine
Patent
1985-10-25
1987-12-01
Olszewski, Robert P.
Tools
Wrench, screwdriver, or driver therefor
Machine
81 5744, 81 60, 81 583, B25B 1346
Patent
active
047096004
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a power screw driver with a power arm and a reaction arm, which can be rotated counterwise to one another around an axis, with finely graduated teeth, a rachet wheel that can be rotated around the axis, with a multi-toothed pawl that engages with this rachet wheel and that meshes with several teeth of the ratchet wheel in the meshing position when the power arm is rotating in one direction and when it is in the other rotational position the pawl slips over the teeth of the ratchet wheel, and with an hydraulic power cylinder, made of a cylinder and a piston that is attached between the two arms.
DESCRIPTION OF THE PRIOR ART
Such power screw drivers are known from several publications, for example, from DE-OS No. 30 08 381 (U.S. Pat. No. 4,440,046). In this prior art power screw driver, the cylinder bore is in the power arm; the piston is reinforced via an articulated arm at the reaction arm. On the basis of the ratchet wheel and the pawl having finely graduated toothing, small rotational angles of the power arm opposite the reaction arm are necessary in order to effect a rotary drive of the ratchet wheel. In this respect the toothing is designated as finely graduated if there are three or more teeth in an angular range of twenty degrees. This angular range is typical for the amount of angulation in the region of the power arm opposite the reaction arm.
In prior art power screw drivers the pawl is reinforced at the power arm via an articulated arm in a canal. Thus the reaction power train is unfavorable; it results is a long power train over and back, whereby a subsequent adjustment is necessitated via a grub screw.
One disadvantage of the prior art power screw driver is the relatively large number of individual parts of which it is made. Furthermore, the piston, which projects out of the force arm when it is swung out, must be protected against dirt. Unwanted dirt can also collect inside the piston that is open on one side and in which there is the articulated arm.
SUMMARY OF THE INVENTION
With the above as a starting point the purpose of the invention is to avoid the disadvantages of the power screw driver of the aforementioned type and to construct the known power screw driver in such a way that the most favorable power train possible is obtained between the hydraulic power cylinder and the ratchet wheel with as few individual parts as possible.
Starting the from the known power screw driver, this problem is solved by the fact that the power arm has a drive head that is located inside the cylinder bore and engages in the recess of the piston and that the cylinder bore is at a right angle to the connecting line of the axis and the drive head.
Thus a direct and compact power train is obviously obtained; the driving force of the piston, effecting the power arm, engages for all practical purposes in a ninety degree angle at the power arm, which can be constructed relatively simply. In the preferred embodiment the power train is symmetrical to a large degree; the piston is located in its mirror image to the connecting line between the axis and the drive head of the power arm. On the whole, a fairly closed construction is obtained in which the power arm is completely inside the reaction arm, which has a suitable recess for this.
In a particularly advantageous embodiment of the invention the piston has in the region of its recess at least one, preferably two, partially cylindrical, concave, first attachment surfaces whose center is located on the axis line. The drive head also has at least one, preferably convex, partially cylindrical, second attachment surfaces. The center point of this second attachment surface is displaced with respect to the movement of the power arm not only axially, as desired, but also somewhat radially. In order to keep this radial displacement as small as possible, it is averaged out on both sides of the axis line so that the center of the drive head in the mid-position of the power arm extends above the axis, whereas in the edge po
REFERENCES:
patent: 4137800 (1979-02-01), Austin
patent: 4201099 (1980-05-01), Junkers
patent: 4339968 (1982-07-01), Krieger
patent: 4409865 (1983-10-01), Krautter et al.
Blockisch Olaf
Frohn Gustav K.
Mierbach Hans-Bernd
Applied Power Inc.
Kile Bradford E.
Olszewski Robert P.
Vaught Bradley I.
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