Machine element or mechanism – Mechanical movements – Rotary to intermittent unidirectional motion
Patent
1994-01-13
1996-02-20
Ta, Khoi Q.
Machine element or mechanism
Mechanical movements
Rotary to intermittent unidirectional motion
475170, F16H 2916, B62M 908
Patent
active
054920264
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a continuously adjustable transmission, which comprises a number of arms, one end of which is pivotably connected to a rotatably arranged first member to be driven from the outside or by the transmission itself, and of which the other end acts on a second rotatably arranged member, the axes of rotation of the arms being parallel to the axes of rotation of the members and being evenly distributed about a circle, in which the part of the second member being acted upon by the arms lies at a radial distance from the circle on which the axes of rotation of the arms are situated, both members having been arranged such that they are movable in relation to each other between a concentric position in which the transmission ratio is 1:1 and an eccentric position for obtaining another transmission ratio.
Such a transmission is known from NL-A-8900501. In this known device, the arms are also pivotably connected to the second member and executed telescopically for being able to accommodate the differences in length occurring in the eccentric position of both members. Only when they have their minimal lengths, they will be active for transmission of forces. Further, each arm with its related parts is situated in a separate plane, so that the transmission takes up a lot of space and comprises many parts.
The invention intends to remove these disadvantages and to that end provides that a number of arms are situated in a same radial plane and that each of the arm-ends acting on the second member has at the end concerned been provided with an elongated clamping member rotatably connected with the arm through an axially extending shaft, which clamping member has been accommodated in a ring-shaped slot made in the second member, with parts of the clamping member engaging the two opposite, substantially cylindrical walls of the slot by means of spring force, while the center of rotation between a clamping member and the corresponding arm is positioned such and the clamping member is formed such, that under certain conditions, the clamping member establishes a fixed connection between the arm and the second member, as a result of clamping.
The spring force exerted on a clamping member need only be sufficient for keeping the parts concerned of the clamping member in contact with the walls of the slot and therefore can be small. When the clamping member is not active, it will easily slide along the walls of the slot, which only produce a small frictional resistance.
For a most suitable distribution of forces exerted on the various parts it can be provided that the clamping member extends at both sides of the corresponding arm and that each of the parts present at both sides of the arm is situated in a slot of the second member.
Through this it is achieved, that the arm is only under tension or pressure and that only a radially directed force is exerted on the clamping member.
In order to obtain a still better clamping of a clamping member in the slot of the second member, it can be provided that at least one of the walls of the slot, seen in cross section, has a V-shape such that the clamping member is accommodated in the V-shaped part.
According to a development of the invention, the spring force by which the clamping member engages the walls of the slot, can be created by means of a tension or compression spring situated between the clamping member and the corresponding arm.
Owing to the fact, that the arm and the clamping member at a transmission ratio other than 1:1 will take up a continually varying position in relation to each other, the spring force will likewise change continuously.
When this would cause difficulties, it can be provided that the clamping member consists of two sections, with the one section near one end being pivotally connected to the arm and near the other end to the other section, in which the pivoting point between the sections is situated between the walls of the slot and a spring is present between the sections for pressing each of the sections against the corresponding wall
REFERENCES:
patent: 1945702 (1934-02-01), Pitter
patent: 2677968 (1951-04-01), Hubner
patent: 3892139 (1975-07-01), Harris
patent: 5029486 (1991-07-01), Mercat
patent: 5048358 (1991-09-01), Shook
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