Endless belt power transmission systems or components – Pulley with belt-receiving groove formed by drive faces on... – Speed responsive
Reexamination Certificate
1999-06-07
2001-02-13
Marmor, Charles A (Department: 3681)
Endless belt power transmission systems or components
Pulley with belt-receiving groove formed by drive faces on...
Speed responsive
C474S008000, C474S084000
Reexamination Certificate
active
06186916
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a pulley of a variable speed transmission of the V pulley and trapezoidal belt type, as well as the endless transmission incorporating such a pulley.
It relates more particularly to a relay pulley for the endless transmission of power at variable speed, between a drive pulley of a first endless transmission with a trapezoidal belt and a driven pulley of a second endless transmission with a trapezoidal belt, said relay pulley being constituted by a rotatable hub carrying, between two fixed external plates, at least one axially movable member on said hub to delimit, with the fixed plates, two parallel grooves of variable dimension adapted to receive respectively a belt of the first or respectively of the second endless belt transmission.
BACKGROUND OF THE INVENTION
The principle of operation of such a transmission is well known. Thus, the V grooves of the relay pulley are of variable size because of the displacement of the movable member axially on the hub of the relay pulley. Each relative displacement of the drive, driven and relay pulleys relative to each other gives rise to an external or internal radial displacement of the belt of one of the transmissions in one of the grooves of the relay pulley and substantially simultaneously of a directly proportional radial displacement in a reverse direction of the belt of the other transmission in the other groove under the action of the displacement of said movable member. This variation of the diameter of engagement of the belts in the grooves of the relay pulley generates the desired speed change.
The principal drawbacks encountered in this type of transmission are high wear of the belts and of the assembly of members constituting the transmission, as well as large power loss by friction such that the overall output of the transmission is mediocre. To permit a reduction in wear of the constituent members of this transmission and correspondingly to increase the output of the transmission, it is necessary that the belts of the two transmissions be slightly stretched when the engine stops and that their tension increases proportionately to the increase of the couple transmitted. Because of this problem, a certain number of manufacturers have designed tensioning devices for the belt at the moment of starting the transmission. However, none of these devices is satisfactory to the extent that all these devices include fragile parts, in particular springs, as again shown in U.S. Pat. No. 4,176,560, or tensioning rollers.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a relay pulley for a transmission of the recited type, whose design permits tension and automatic loosening of the belts of each of the transmissions as a function of the transmitted couple, including in the absence of resilient return members, such as springs, or tensioning elements, such as rollers, and without reducing the speed range of said transmission.
Another object of the present invention is to provide a relay pulley whose design permits, despite its simplicity, automatic accommodation of wear of the pulley of each transmission and quasi-simultaneous adjustment of the tension of the two belts.
Another object of the present invention is to provide a relay pulley whose design permits making it of pieces of synthetic material without undergoing deformation of the constituent elements of said pulley with time.
Another object of the present invention is to provide an endless variable speed transmission whose design permits obtaining a compact, reliable, certain transmission and at low cost, whose overall output is improved.
To this end, the invention has for its object a relay pulley for the endless power transmission with variable speed between a drive pulley and a first endless transmission with a belt and a driven pulley of a second endless transmission with a belt, said relay pulley being constituted by a rotatable hub carrying, between two external plates fixed to said hub, at least one member movable axially on said hub to delimit, with the axially fixed plates, two parallel grooves of variable dimension adapted to receive respectively a belt of the first or respectively of the second endless belt transmission, characterized in that the axially movable members constituted by at least two hollow plates mounted on the rotatable hub, these plates confronting bearing surfaces in sliding contact, said bearing surfaces being arranged to permit, during angular displacement of at least one of the blades, as a function of the couple transmitted by the belt from at least one of the transmissions, the approach or respectively the spacing of the confronting movable plates so as to ensure, by co-action with the fixed external plates, an automatic tensioning or relaxing of the belts of the first and second transmissions.
In accordance with the invention, the possibility of replacement of fragile members such as springs or tensioning rollers by simple bearing surfaces permits obtaining an automatic tensioning or respectively relaxation of the belts of each of the transmissions, this adjustment taking place instantaneously and proportionally to the couple transmitted, such that the belts have high tension only when this is necessary for the good operation of the transmission. As a result, there is an absence of wear of the constituent members of the relay pulley. But conversely, this design permits, because of a progressive tensioning of the belts proportionally to the couple transmitted, curing or retarding the play due to wear of any one of the belts.
The invention also has for its object an endless power transmission with variable speed, between a drive pulley, a relay pulley and a driven pulley, characterized in that the relay pulley of the type recited above and the driven pulley are disposed in a transmission housing to form a monobloc assembly, the relay pulley being connected to the transmission housing by a control member of the position of the hub of the relay pulley.
REFERENCES:
patent: 3786688 (1974-01-01), Svenson
patent: 4270906 (1981-06-01), Kraft et al.
patent: 4962636 (1990-10-01), Sampei et al.
patent: 5403240 (1995-04-01), Smith et al.
patent: 60-048032 (1983-08-01), None
France Reducteurs
Marmor Charles A
Waddell Tisha D.
Young & Thompson
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