Technical Field

The present invention relates to a device for the weighin of a vehicle which runs on a track, i.e. a rail vehicle such as a goods wagon. The invention relates in particula to a device enabling dynamic weighing.

Background Art

There has long been a substantial need for devices enabling the weighing of rail vehicles such as goods wagons with the necessary accuracy, especially in connection with industrial consignments and marshalling. As will be appreciated without further elaboration, it is preferable to be able to weigh dynamically, i.e. while th rail vehicle is in motion on a railway or other track.

There have been attempts to construct weighing devices fo the above field of application but the resulting constructions have been very complex, expensive and required extensive installation work, usually without providing the desired accuracy at least in relation to dynamic weighing.

Objects of the Invention

The objects of the present invention are to provide a weighing device which is simple, easy to install without substantial interference with the rail system, preferably very cheap and which provides accurate weighing results, even on a rail vehicle passing over the device at a relatively high velocity.

Summary of the Invention

The above objects are attained in a device which exhibits the features defined in the accompanying patent claims.

The device of the invention is thus based upon the insigh that load cells of a particular design can provide evalua tion amenable measurement signals if the load cells are placed under each rail in a rail pair against an under- lying transverse beam, which is conveniently shaped as a cross-tie or sleeper, the rails being fastened in conven¬ tional fashion to the transverse beam. The latter can tak the form of an ordinary cross-tie or sleeper in the rail system although of course a transverse beam specifically configured for load cell installation can be used. In the latter case, this special transverse beam advantageously replaces an ordinary cross-tie or sleeper.

The load cell is of a type having a substantial load receiving surface and an insubstantial height and is substantially insensitive to lateral load. Preferably, a pressure detecting fluid is disposed in the form of a thi layer between two steel plates which are best circular.

The load cells are advantageously of the type described i EP 0 342 305 Bl to which reference is made in relation to the details of a preferred load cell.

In accordance with the invention, means are further provided to controUably pre-bias the load cells. Such means can comprise an elastically deformable unit placed between the respective load cell and the underlying trans verse beam. The unit can advantageously be fluid pressure controlled, although the man skilled in the art will appreciate that it is possible to use other arrangements.

Controllable pre-biasing is advantageous from several aspects. Firstly, it enables compensating for load-relief rail heaving effects in connection with the passage of wheel pairs onto and away from the device. It is a matter of negotiating a "seesaw" effect which has proven to aris during wheel transit. Specifically, the wheel presses the rail downwardly so that in return it heaves upwardly some what a little further along in the direction of movement.

The pre-biasing of the invention results in better defi¬ nition of the output signal from the load cell.

Secondly, selective pre-biasing enables calibration of th respective load cells in connection with installation.

Thirdly, it enables selective readjustment of the cells a needed.

The load cells are advantageously arranged in a mounting plate which is simultaneously a rail anchor plate. In thi regard, the mounting plate can incorporate, or be arrange to accept, the abovementioned pre-bias unit.

As will be appreciated without further elaboration, the above discussed parts of the weighing device can be installed particularly easily and without significant disturbance to the rail system. In practice, installation can be regarded as an exchange of a cross-tie or sleeper.

Naturally, it also becomes possible to easily move the transverse beam arrangement with the load cells from one location to another.

The output signals from the load cells are input to evaluation means which can measure both the accumulated total weight and the load distribution between right and left sides. The evaluation is preferably effected in

accordance with the principles described in our Swedish patent application no. 9101569-3, relating to a method fo determining load measurements, to which reference is made for further details.

It will be appreciated that it is possible to set up more than one transverse beam arrangement, for instance three parallel spaced transverse beam-load cell arrangements connected to said evaluation means, the distance between the two outer arrangements conveniently exceeding the bogie inter-axle distance. The three arrangements can eac constitute an ordinary cross-tie or sleeper and be disposed with an ordinary cross-tie or sleeper interposed between the first and second, and second and third arrangements, respectively. In this embodiment, the weighing device can also be employed to advantage in static weighing.

An embodiment with several transverse beam-load cell arrangements means that the measurement span is extended which in turn means that deviations in the roundness of the wheels will produce detectable measurement signal variations. In other words, it also becomes possible to detect wheel faults, such as "flat wheels" and eccentri- city, using the device of the invention.

The invention will now be described in greater detail via an exemplary embodiment and with reference to the accompanying drawings.

Brief Description of the Drawings

Fig. 1 is a very schematic sectional view which illustra¬ tes the fundamental set-up of an embodiment of the device of the invention.

Fig. 2 is an enlarged partial sectional view which illust

rates the arrangement of a load cell in the device of Fig. 1.

Fig. 3 is a schematic view from above of a stretch of rail system illustrating the arrangement of a second embodiment of a weighing device in accordance with the invention.

Description of the Exemplary Embodiments

Fig. 1 depicts the manner in which a wheel pair 1 of a rail vehicle ride on two rails 3, 4 which are fastened to a transversely extending cross-tie 5 via anchor plates 7 mounted fast in the cross-tie. A pre-biased load cell unit is located between each of the respective rails and anchor plates, as shown in greater detail in Fig. 2. The load cell units 9 are connected via leads 11 to an evaluation unit 13 of electronic construction, located adjacent the rail system.

As is clear from Fig. 2, rail 3 is fastened to anchor plate 7 via rail fastener 15. Anchor plate 7 has an upwardly open cylindrical recess 17 of circular section, at the bottom of which a pre-bias unit 19 is secured. A cylindrical load cell 19 of circular section is movably disposed on top of the pre-bias unit 19. The load cell has a lower and an upper thin plate member with an intermediately disposed thin fluid layer 23 for pressure sensing. The output signal lead 11 connected to the load cell is not depicted but, bearing in mind its application, incorporates robust cabling, as will be readily apparent to the skilled artisan.

The rail 3 is supported, movably and elastically dampened, on the load cell 21 via a sheet metal disk 25 and a rubbe disk 27. An electrically insulting intermediate layer 29 is located between the rail 3 and its fastener 15.

The pre-bias unit 19, in principle, comprises an upper, load cell supporting plate member which is sealed relative to the bottom of the recess so as to enclose a small vo¬ lume of pressure fluid 31. This is in fluid communication with a controllable fluid pressure source 35 via conduit 33. As will be readily apparent, a change in this fluid pressure will mean a change in the pressure exerted by the pre-bias unit 19 from below against the overlying load cell.

In Fig. 3, an embodiment with three crossbeam-load cell arrangements in parallel disposition is illustrated connected cumulatively to the common evaluation unit 13. These crossbeam-load cell arrangements are set up as ordinary cross-ties in the rail system and are mutually separated by an intermediate ordinary cross-tie. In this fashion, the distance between the two outer arrangements becomes somewhat larger than the normal inter-axle distance in a bogie whose weight can thereby be simply measured.