Machine element or mechanism – Flexible sealing diaphragm attached to moving rod and to casing – Longitudinally reciprocating rod
Patent
1991-11-08
1993-01-12
Herrmann, Allan D.
Machine element or mechanism
Flexible sealing diaphragm attached to moving rod and to casing
Longitudinally reciprocating rod
74 63, 74570, 251251, F16H 2504, F16K 4110, F16K 3152
Patent
active
051780240
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
METAL BELLOWS TYPE SEALED ROTARY TRANSMISSION DEVICE
The invention concerns a metal bellows type sealed rotary transmission device, in particular a device of this kind adapted to control a valve, in particular a quarter-turn valve of the type used for remote control in industrial installations.
The invention is more particularly concerned with an arrangement that is simple and easy to manufacture in which the bellows is effectively protected against torsion, especially if an excessively high resisting torque is applied to one shaft or if one shaft is accidentally jammed.
DESCRIPTION OF THE PRIOR ART
Numerous metal bellows type sealed transmission devices are known. In one such known device the bellows is placed around a receiver shaft controlling a valve mechanism, for example. The bellows provides isolation between this mechanism and the external environment so that, should a leak occur along the shaft, the fluid (which may be hazardous) cannot escape to the exterior.
For example, French patent application No 87.09402 now French Patent No. 2,617,567 and which corresponds to U.S. Pat. No. 4,892,010, by the same applicant describes a device in which the respective axial ends of the bellows are welded and sealed to a fixed part of the transmission device casing and a mobile transfer member inside the casing coupled to the receiver shaft and to the control shaft. For the bellows to be durable it is essential, as previously mentioned, that no torsion is applied to it. For this reason, in this prior art device the transfer member is constrained to move strictly in "circular translation". This movement is obtained positively by an appropriate kinematic coupling between the assembled parts. However, some parts of the device described are difficult to manufacture and the design principle adopted requires a physical offset between the control shaft and the receiver shaft which are disposed at opposite axial ends of the device casing and are parallel to each other. It is not possible to design a device of this kind with the control shaft and the receiver shaft aligned with each other.
A main object of the invention is to propose another bellows type sealed transmission device which comprises only a small number of easily manufactured parts and in which an appropriate kinematic coupling of the moving parts, to protect the bellows against torsion, is obtained as a "result" of mechanical interdiction means associated with the transfer member.
Another object of the invention is to propose a sealed transmission device in which said appropriate kinematic coupling does not require the control shaft and the receiver shaft to be physically offset parallel to each other.
SUMMARY OF THE INVENTION
To be more precise, the invention consists in a bellows type sealed rotary transmission device comprising a control shaft and a parallel receiver shaft, of the type in which said bellows surrounds one shaft and is fixed and sealed at one end to a fixed casing and at the other end to a transfer member mobile in said casing and coupled to the two shafts by respective eccentric linkages, characterized in that said transfer member is able to move in translation perpendicularly to the parallel shafts because it is guided by a tilting member articulated about an axis transverse to the lengthwise direction of said casing by two aligned journals perpendicular to said two shafts.
In a system of this kind torsion of the bellows is avoided (especially if one of the shafts is jammed) by the coupling between the transfer member and the tilting member, the latter being attached to the wall of the casing. If the device is used to control a valve, the shaft surrounded by the bellows constitutes a receiver shaft of the transmission device, the other shaft constituting a control shaft.
In one possible embodiment said tilting member is a crankshaft slidably inserted through a transverse bore in the transfer member so that said transfer member slides on said crankshaft. This latter comprises two said journals offset
REFERENCES:
patent: 2137303 (1938-11-01), Nelson
patent: 4892010 (1990-01-01), Pottier et al.
Leclaire Remy
Pottier Daniel
Carvellas Perry
Herrmann Allan D.
NORMETEX
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