Machine element or mechanism – Mechanical movements – Reciprocating or oscillating to or from alternating rotary
Reexamination Certificate
1999-10-26
2001-07-03
Herrmann, Allan D. (Department: 3682)
Machine element or mechanism
Mechanical movements
Reciprocating or oscillating to or from alternating rotary
C074S424830, C074S09900A
Reexamination Certificate
active
06253632
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of motion transforming devices with electric motor and velocity reducing screw-and-nut transmission, located in a tube.
BACKGROUND OF THE INVENTION
Motion transforming device with screw-and-nut transmission is described for instance in a German Patent DE 3121136. State of the art of motors in a tube and screw-and-nut transmissions is represented by following patents: GB 857,203, DE1 957658, U.S. Pat. No. 2,818,743 a U.S. Pat. No. 4,723,453. Existing motors in a tube use screw transmission where both guide and driving nuts are manufactured by milling of both axial and helical groove on tube and both guide and driving nuts are coaxial.
Disadvantage of such an arrangement is in that it cannot work at high specific torques, related to the cross-section of the transmission. Otherwise, there are motors in a tube used with planetary gearbox, however, they have the same disadvantage.
SUMMARY OF THE INVENTION
The present invention avoids mentioned disadvantages of the prior art.
Motion transforming apparatus transforming an angular motion into an angular function thereof, comprising an electric motor that is placed in a tube and has an output that is coupled to a screw transmission which includes two screws with different pitches and two nuts and a guide mechanism, according to the invention has the output of the electric motor coupled to a driving screw transmission which includes a driving screw and a driving nut cooperating with one another, whereby one of said driving screw and driving nut is rotatably connected to said output and the other end of said driving screw and said driving nut being arranged non-rotatably but axially movable, said non-rotatably but axially movable driving screw or driving nut being drivingly connected to a guide rod so as to impart a non-rotatable but axial motion to said guide rod, said guide rod being linearly guided in a guide mechanism and connected to a driven screw so as to form a single piece therewith, said non-rotatable but axial movable driven screw cooperating with a rotatable but axially immovable driven nut whereby said linear motion-of said guide rod and said driven screw imparts via its pitch in turn a rotational motion to said rotatable but axially immovable driven nut, said electric motor, said driving screw, said driving nut, said guide rod, said driven screw, said driven nut and said guide mechanism being arranged in-line on a common axis in a stationary tube, said electric motor being fixed at one end of said stationary tube and said driven nut being rotatably but axially immovable coupled to the other end of said stationary tube, said driving and driven screw having different pitches, whereby the pitch of said driven screw is high enough that the whole screw transmission is self-locking with respect to an external torque.
In one possible embodiment of the invention, the said guide mechanism serving to linearly guide the said guide rod, is an immovable guide profile fixed to the internal side of the said stationary tube.
In another possible embodiment of the invention, the said guide mechanism is composed of two rotatable wheels, carried on an axle fixed to an end of the said guide rod and perpendicular thereto, said rotatable wheels being linearly movable in an immovable guide profile fixed to the internal side of the said stationary tube.
Arrangement of the motor and the screw transmission according to the invention enables to maximize the torque of the apparatus in relation to given cross-section of the tube, as the guide and driven rod, the guide mechanism and the driven nut can be made just fill-in the cross-section of the tube. The self-locking transmission protects the driving screw and the electric motor against external torque.
The driven screw and the guide rod can be manufactured of a single piece of the same cross-section, e.g. trihedral to octagonal rod and/or of a rod with two- to eight grooves, while the screw can be manufactured on a part of the rod by hot or cold twisting. Manufacturing of driven screw by forming a part of the guide rod is quick and easy.
Use of standard profile rods, especially square, enables to use also standard tools for manufacturing of nuts. It reduces price substantially.
The guide mechanism of the driven screw is a guide profile corresponding to at least trihedral rod placed in it or, for reduction of friction, it is represented by at least two rotatable wheels placed on axles which are fixed at the end of the driven screw perpendicularly to the longitudinal axis of the driven screw, said wheels being placed in the guide profile which is manufactured in the tube co-axially with the longitudinal axis of the driven screw.
The coupling element located at one end of the driving screw enables to compensate misalignment between the driving screw and the guide rod. It enables to increase manufacturing tolerances.
Use of driving ball screws substantially increases mechanical efficiency of the apparatus.
Use of the electric motor with a hollow axle reduces the design length of the apparatus. Use of the electric motor with gearbox enables to increase transmission ratio of the apparatus. Use of the auxiliary output tube on the driven nut enables easy attachment to a driven device.
REFERENCES:
patent: 2144447 (1939-01-01), Barnhart
patent: 2818743 (1958-01-01), Zatsky
patent: 3121345 (1964-02-01), Zeigler et al.
patent: 3184214 (1965-05-01), King
patent: 3391722 (1968-07-01), Ligh
patent: 4350460 (1982-09-01), Schmelzer et al.
patent: 4723453 (1988-02-01), Kannapan et al.
patent: 5622078 (1997-04-01), Mattson
patent: 1957658 (1970-11-01), None
patent: 3121136 (1982-12-01), None
patent: 0163602 (1985-12-01), None
patent: 0509362 (1992-10-01), None
patent: 2161491 (1973-07-01), None
patent: 857203 (1960-12-01), None
Burns Doane Swecker & Mathis L.L.P.
Herrmann Allan D.
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