Machine element or mechanism – Mechanical movements – Reciprocating or oscillating to intermittent unidirectional...
Patent
1992-07-23
1993-08-03
Herrmann, Allan D.
Machine element or mechanism
Mechanical movements
Reciprocating or oscillating to intermittent unidirectional...
188 721, 188163, 188196F, 310 26, F16H 2702, F16D 6527
Patent
active
052318877
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a device in a force actuator for transforming a reciprocating axial movement of a drive member to an axial movement in an application direction of a push rod coaxial therewith.
TECHNICAL BACKGROUND
In a number of different ways it is possible to accomplish a reciprocating movement or force, which it may be desirable to transform into a undirectional movement or force. A relatively recently developed technique is to utilize materials having magnetostrictive properties. Magnetostriction means that a material change its dimensions when exposed to a magnetic field.
Materials with such properties are typically alloys with rare earth metals, an alloy with terbium and iron being available under the name Terfenol. This material Terfenol has a very high magnetostriction, namely up to 0.2% at a magnetic field with a field strength of appr. 3000 oersted, and a very fast response.
Due to the magnetostriction a Terfenol rod exposed to a pulsating magnetic field and prestressed for accomplishing a return to original shape will have a reciprocating length and accordingly exert a reciprocating force.
In order to utilize this oscillating movement or force in a practical force actuator this movement has to be transformed into a unidirectional movement of a push rod or the like in the actuator.
THE INVENTION
In a force actuator of the kink described above this may according to the invention be accomplished in that the drive member and the push rod are connected by means of a connection member, which is in self-locking thread engagement with the drive member and/or the push rod and is subjected to a torque for its rotation during the idle stroke of the reciprocating movement in the direction for advancing the push rod in the application direction.
In a first practical embodiment a connection ring is in thread engagement with external threads on the drive member and is subjected to a torque exerted by a prestressed spring. In a preferred embodiment the connection ring is in thread engagement with oppositely directed threads on the drive member and the push rod.
In a second practical embodiment a connection rod is in thread engagement with oppositely directed internal threads in the drive member and the push rod and is subjected to a torque excerted by a prestressed spring.
In these embodiments a clock or spiral spring is arranged between the connection member and an outer ring, which is rotatable, preferably my means of an electric motor, for prestressing the spring.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in further detail below reference being made to the accompanying drawings, in which
FIG. 1 shows a rather simple embodiment of a disc brake with a actuator illustrating the principle underlying the invention,
FIG. 2 is a side-view, mostly in section, of a preferred embodiment of an actuator including a movement transforming device according to the invention, and
FIGS. 3 and 4 are side-views, partly in section, of two modified devices according to the invention.
DETAILED DESCRIPTION OF EMBODIMENTS
FIG. 1 shows a simple disc brake arrangement, which is more intended to illustrate a principle than a practical embodiment.
The arrangement is intended to brake a rotating disc 1 by means of brake pads 2 arranged at the ends of two caliper levers 3 and 4 pivotally attached to each other at 5. The braking action is obtained by pushing the ends of the levers 3 and 4 opposite the pads 2 apart.
In the simple arrangement according to FIG. 1 this is accomplished by an electric coil 6 surrounding a rod 7 of the material called Terfenol, with the characteristics to prolong itself up to say 0.2% of its length when subjected to a certain magnetic field (from the coil 6). The rod 7 is connected to the lever 3 to the left in FIG. 1 and cooperates with the lever 4 to the right via a wedge 8. The wedge 8 is biassed upwards by a compression spring 9 and cooperates with a wedge surface in the lever 9.
The coil 6 is electrically activated in a pulsating manner. The mass
REFERENCES:
patent: 3543888 (1970-12-01), Erdmann
patent: 4334602 (1982-06-01), Armour et al.
patent: 4854424 (1989-08-01), Yamatoh et al.
patent: 4927334 (1990-05-01), Engdahl et al.
patent: 4953668 (1990-09-01), Severinsson
Arvidsson Thomas
Westgren Leif
Brown Laurence R.
Herrmann Allan D.
SAB Wabco Holdings B.V.
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