Endless belt power transmission systems or components – Pulley with belt-receiving groove formed by drive faces on... – Speed responsive
Reexamination Certificate
1999-09-14
2001-06-19
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Pulley with belt-receiving groove formed by drive faces on...
Speed responsive
C474S008000, C474S100000, C474S085000
Reexamination Certificate
active
06248035
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a rotary device, which preferably is a pulley for use with an endless flexible drive element such as a belt, and whose effective diameter is variable in order to achieve a variable transmission ratio between the pulley and another pulley or pulleys with which the flexible drive element cooperates.
The invention has been devised in relation to such a pulley which comprises a pair of sheave members rotatable about an axis and supported for movement relative to one another in the direction along said axis, the sheave members having generally frusto-conical driving surfaces facing one another to define a generally V-section annular groove therebetween; and a drive ring disposed between the sheave members and having an external circumferential surface engagable by the drive belt and side surfaces engaging said facing generally frusto-conical driving surfaces of the sheave members, the drive ring being constrained between the sheave members and being able to assume an eccentric position relative thereto when permitted by the dimensions of the groove defined between the sheave members in accordance with the relative axial position thereof. Such a pulley will hereafter be referred to as a pulley of the kind specified.
In a pulley of the kind specified, as the distance between the driving surfaces of the sheave members increases (i.e. the V-section groove there between becomes wider) the drive ring is able to assume an increasingly eccentric position relative to tie sheave members and is caused to do so by the tension of the belt entrained around it. It may be the tension in the belt which causes the drive ring to assume an eccentric position and increase the distance between the sheave members. As the speed at which the drive ring is driven by the sheave members is dependent on the effective diameter at which they are engaged by the drive ring, the effective diameter of the pulley is decreased.
A pulley of the kind specified may be required to be used in the auxiliary drive system of an internal combustion engine for a motor vehicle. It is usual to arrange for the auxiliaries, which may comprise one or more of the following, namely an alternator, a water pump, a cooling fan, a power steering pump, an air conditioning pump, and so on, to be driven from the engine crank shaft by a belt. If a pulley of the kind specified is provided on the engine crank shaft, a variable transmission ratio may be provided between the crank shaft and the auxiliaries, so that the latter can be driven at a reasonably high speed when the engine is running slowly and yet not be over-speeded when the engine is being operated at its maximum speed. A means for maintaining the required tension in the drive belt or for causing a speed-dependent increase in belt tension, is, of course, additionally required when a pulley of the kind specified is thus used.
When a pulley of the kind specified is in use, it is a requirement that the drive ring should remain in a constant or substantially constant axial position, to maintain its alignment with the other pulley or pulleys with which the drive belt cooperates. It is the object of the present invention to provide a pulley of the kind specified with a convenient construction which enables this requirement to be met. In fulfilling this object, however, it will be appreciated as pointed out hereafter that the present invention is applicable to devices other than a pulley of the kind specified.
BRIEF SUMMARY OF THE INVENTION
According to one aspect of the present invention, we provide a rotary device comprising two elements supported for rotation about an axis and movable relative to one another along said axis, and diaphragm spring means urging said elements axially relative to one another, said diaphragm spring means having radially inner and outer portions connected respectively to said elements and being arranged so that said relative movement between said elements comprises movement thereof in opposite directions by the same or substantially the same distance as one another.
According to another aspect of the invention, we provide a rotary device comprising two elements supported for rotation about an axis and movable relative to one another along said axis, and diaphragm spring means urging said elements axially relative to one another, said diaphragm spring, means having a torque transmitting connection with each of said elements whereby torque can be transmitted therebetween.
Preferably, both aspects of the invention are provided together, and further preferably the diaphragm spring means provides for torque transmission between said axially movable elements and a driving component such as a shaft element on which they are supported.
The diaphragm spring means preferably comprises a diaphragm spring element having an annular portion and a plurality of fingers extending radially from the annular portion and circumferentially spaced thereabout. Preferably the fingers extend radially inwardly from the annular portion of the spring element, and are connected at or adjacent their free ends to one of the two axially movable elements of the device, whilst the other of the axially movable elements of the device is connected at or adjacent the outer periphery of the annular portion of the spring element.
To ensure that the two elements of the device undergo their relative axial movement about a reference position which is axially stationary or substantially stationary, the spring element of the device requires to be supported against axial movement about a part thereof which, in use, has an unchanged axial position when the inner and outer parts of the spring element move relative to one another.
Preferably the rotary device is a pulley, and the two elements comprise sheave members with generally frusto-conical surfaces facing one another to define a generally V-section annular groove therebetween.
The pulley may be one which cooperates directly with an endless flexible drive element whose cross-sectional shape includes portions which engage the generally frusto-conical surfaces of the sheave members directly, the effective diameter of tie pulley depending on the axial distance between the sheave members so that the drive element engages the sheave members at a greater or lesser radius depending on the axial position thereof.
Preferably, however, the pulley is a pulley of the kind specified, with a drive ring disposed between the sheave members and which is engaged by the drive element.
A rotary device, such as a pulley, according to the first aspect of the invention has the advantage that the spring means constituted by a diaphragm spring element serves the two purposes of urging the axially movable elements towards one another and controlling their relative movement so that they move by the same distance as one another in opposite directions. It is not necessary to provide, in addition to the spring means, a separate mechanism for the latter purpose.
If the spring element also provides for torque transmission between the sheave members of the pulley and a driving component, yet a further relative simplification in construction and manufacture can be achieved.
In the case where the diaphragm spring element does not provide for torque transmission between the sheave members of the pulley and a driving component such as a shaft element on which they are supported, there is required to be provided an alternative torque transmission means for such purpose. Such an alternative torque transmitting means may be arranged to provide, in the normal direction of torque transmission in use, an axial force which assists the diaphragm spring means in urging said elements axially towards one another.
Such an alternative torque transmission means may comprise cam and follower means associated with the shaft element or other driving component and with one of the axially movable elements.
REFERENCES:
patent: 2747420 (1956-05-01), Beck
patent: 3981205 (1976-09-01), Avramidis et al.
patent: 4365963 (1982-12-01), Thirion De Briel
patent: 46
Bucci David A.
Charles Marcus
GKN Technology Limited
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