Measuring and testing – Brake testing – Road test attachment or adjunct
Patent
1993-08-02
1995-05-02
Raevis, Robert
Measuring and testing
Brake testing
Road test attachment or adjunct
73862642, G01L 528
Patent
active
054109116
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/SE92/00096 filed Feb. 17, 1992.
TECHNICAL FIELD
This invention relates to a load cell for transmitting a signal depending on the force exerted thereon, comprising a housing, a rod, which is exposed to said force and extends into said housing, an elastic element between the housing and the rod, and a pressure responsive device for sensing the pressure in the elastic element and creating said signal. The invention also relates to the use of this load cell at a brake arrangement, especially but not exclusively for a rail vehicle.
TECHNICAL BACKGROUND
Load cells of the general type defined above are known in the art. One example is shown and described in EP-A-402 261. This load cell device has a plate-shaped chamber, which is filled with liquid but equally well could be filled with a silicon rubber disc or the like for transmitting a force to a piston of a pneumatic valve device for delivering a pneumatic signal depending on the force exerted on the liquid or disc. The internal arrangement of the device for exerting a compression force on the liquid or disc irrespective of whether the external force is pushing or pulling is comparatively complex and accordingly expensive and sensitive to disturbances.
Another similar device for measuring an axial force in either direction in a shaft is shown in EP-A-373 334, but here two separate elastic elements and pressure responsive devices (pressure transducers) are utilized for the two force directions, which is a complication.
A load cell of the type concerned may be used in many applications where a signal depending on a load or force is desirable, and no limitation of the present invention in this respect is intended.
However, the main purpose for the load cell according to the invention is to transmit a signal depending on the tangential brake force obtained in a brake arrangement, preferably at a rail vehicle, so that the brake force applied may be continuously or intermittently adopted to obtain a desired brake characteristic. In this way a feedback control system can be attained, which is of growing importance at modern rail vehicles.
THE INVENTION
A simple and reliable load cell of the type concerned, where signals related to both pushing and pulling forces may be transmitted, is according to the invention obtained in that the elastic element in the form of a rubber sleeve or disc is enclosed in an annular compartment formed by an annular recess in the housing and a corresponding recess in the rod and in that a ring is arranged at each end of the rubber sleeve or disc to transmit forces in the two axial directions of the rod to the rubber sleeve or disc from the respective end shoulders of the recess.
In a brake arrangement, either a block brake or disc brake, preferably for a rail vehicle, where a brake block or pad is brakingly applied against a wheel or disc, a load cell according to the invention may be mounted as a force transmitting element in the suspension means for the block or pad. In this way the tangential brake force (in either direction) in the wheel or disc may be measured, so that a certain force from a brake cylinder may be applied in order to give a certain tangential brake force.
BRIEF DESCRIPTION OF THE DRAWING
The invention will be described in further detail below reference being made to the accompanying drawings, in which
FIG. 1 is a partly sectional side view of a first embodiment of a load cell according to the invention,
FIGS. 2-4 are schetches to illustrate the use of load cells according to the invention in disc brake arrangements, and
FIG. 5 is a partly sectional view of a second embodiment of a load cell according to the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
A load cell 1 (as shown in FIG. 1) has a housing 2 (which may be cylindrical) and a cover 3 attached thereto by means of screws 4. The cover 3 is provided with an attachment hole 5.
The housing 2 has an inner, preferably cylindrical recess, which at its lower end is limited by a housing shoulder 2' and at its uppe
REFERENCES:
patent: 2063244 (1936-12-01), Gulliver
patent: 5036714 (1991-08-01), Christoffers et al.
patent: 5038605 (1991-08-01), Tews et al.
Brown Laurence R.
Raevis Robert
Sab Wabco Holdings BV
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