Rotary shafts – gudgeons – housings – and flexible couplings for ro – Torque transmitted via flexible element – Element is tube with slot through wall to provide flexibility
Patent
1991-03-18
1992-12-01
Stodola, Daniel P.
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Torque transmitted via flexible element
Element is tube with slot through wall to provide flexibility
F16D 350
Patent
active
051675820
DESCRIPTION:
BRIEF SUMMARY
This invention relates, in one aspect, to a flexible coupling of the type suitable for transmitting torque from one rotatable member to another and is particularly, though not exclusively, concerned with a flexible coupling for transmitting torque between driving and driven shafts in which there may be slight misalignments in the static and/or dynamic state.
There are many instances of use in which it is essential for a flexible coupling to be able to compensate automatically, by self-adjustment, for misalignment between driving and driven members, (and also to move laterally if required) and one of these uses includes the transmission of drives in industrial robots. Another use is in the formation of conductor lines on semi-conductor wafers, in which motors are used which drive suitable devices to form the lines, and in which extremely accurate control over the transmission of the drive is necessary, such drive normally including some form of flexible coupling.
One known type of flexible coupling comprises a generally cylindrical member which is of one-piece construction, and which has a single start helical spring configuration formed in the cylindrical member. The cylindrical member is hollow, having a substantial radial wall thickness, and the spring configuration extends radially inwardly from the outer periphery of the cylindrical member until the hollow interior of the member is reached. The spring configuration may be formed by machining (a "cut spring"), or by casting of the entire cylindrical member with the required spring configuration. This known coupling member therefore functions in the manner of a helical spring, even although the turns of the spring have substantial radial thickness, and therefore has an in-built tendency to "wind-up" as torque is transmitted from one end of the cylindrical member to the other and via the turns of the helical spring. Clearly, this can give rise to inaccuracies in the transmission of torque, especially when, for example, precise angular increments of rotation are required from one rotary member to another.
Therefore, while the known flexible coupling has the necessary flexibility, and resilience, to accommodate axial misalignments (and axial movements), and also variable torque transmission, it does not have sufficient stiffness to suit the requirements of some users, and particularly where there is a need for very accurate transmission of angular increments of drive.
Accordingly, there has developed a need to provide an improved design of flexible coupling which has sufficient flexibility and resilience to meet the requirements of a "flexible coupling", and yet which is able to transmit accurately i.e. without undue torsional deformation, rotation between an input and an output end of the coupling.
According to the invention there is provided a flexible coupling which comprises a hollow cylindrical body having an annular wall, and a helical spring configuration formed in the annular wall with the turns thereof each extending radially outwardly from the hollow interior of the cylindrical body to the outer periphery of the cylindrical body:
in which the helical spring configuration comprises at least two spring formations extending circumferentially and adjacent to each other around the axis of the cylindrical body, each formation extending in a continuous spiral from a start at one end portion of the cylindrical body to a finish at the opposite end portion.
In order to increase the strength of each spring formation at its start and finish (where it is joined to solid end pieces of the hollow cylindrical body), it is preferred to make the turns thicker (with respect to the axis of the body), than the remaining turns thereof.
By arranging at least two separate helical spring formations in the annular wall of the cylindrical body, a coupling is provided which is sufficiently flexible in the sense that it can absorb any axial misalignment between an input drive to an input end of the cylindrical body and an output drive from an output end of the cylindrical bod
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patent: 3390546 (1968-07-01), Jewell
patent: 3537275 (1970-11-01), Smith
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Darling John P.
Stodola Daniel P.
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