Patent GB-1474239-A (GB)
Title: Weighing apparatus for truck and vehicle loads
IPC: G01D5/26
Filed: 1974-05-22
Abstract: 1474239 Measuring weight photo-electrically; weighing dynamometers M A ASKEW 22 May 1974 [1 June 1973] 22934/74 Headings G1A and G1W Apparatus for indicating the weight of a vehicle load comprises: a sensor arm operable in conjunction with a spindle between a moving part and a stationary part of the vehicle, for sensing the distance between the relatively movable parts of the vehicle; a transducer unit providing an electricallyoperated display responsive to the distance and including a light source, a shutter mounted on the spindle and rotatable in response to changes in the distance, and a photo-cell sensing variations in light responsive to rotation of the shutter, the source, shutter and photo-cell being enclosed in a lighttight chamber; and display means for indicating the weight. The distance sensing means preferably includes a sensor arm having two end portions joined by a spring, and is provided with screw-thread adjustment of length. A transducer mounting plate 29, Fig. 1 attached by U-bolts to a bar 6 mounted on the vehicle chassis (not shown), carries a spindle 14 rotatable in sealed bearings and coupled by a toggle arm 11 to a sensor arm 2, of which the other end is pivoted on a plate 9 attached to a vehicle axle (not shown). Relative motion between the chassis and axle, e.g. following the imposition of a load, causes the spindle 14 to rotate, carrying with it an eccentric circular shutter 23 in a light-tight can 22. A lamp 46 in a dirt-proof can 32 illuminates a slot 25 behind the periphery of the shutter 23, the emergent light being variably obscured by the shutter 23 before falling on a photo-resistor 27. The sensor arm 2 includes rigid end portions 15, 15a pivoted by ball-and-socket joints 19, 13 to the plate 9 and the toggle arm 11 respectively. Oppositely threaded portions 16, 16a of the end portions 15, 15a are attached by nuts 18, 18a and guides 12, 12a to the ends of an expansion spring 17, the spring 17 being resiliently yieldable by tension or buckling to protect the apparatus from excessive displacements. Buckling of the spring 17 is assisted by curvature in the end portion 15a, which provides components of force out of line with the axis of the spring. Mechanical adjustment is provided: by rotation of the spring 17 causing turnbuckle action in the sensor arm 2; by altering the point of attachment of the joint 13 (e.g. to 20); and by rotating the spindle 14 in a forked clamping end of the toggle arm 11. Rotation of the toggle arm 11 is limited by stop arms 21, 21a. The lamp L 1  Fig. 4 is supplied with voltage from a 24v. or 12v. vehicle supply connected at a terminal T 1  or T 2  and reduced by an integrated stabilizing circuit I.C. to a value somewhat below the lamp rated voltage. The photo-resistor LDR is connected via an adjustment resistor R 5  and a potentiometer resistor R 2  in series with a display M. An adjustable potential picked off R 2  at X 2  determines the point of oscillation of a regenerative circuit B which energizes a loudspeaker Sp if the maximum safe load is exceeded. A plurality of transducers positioned at respective axles of the vehicle may be selected by the ganged switch S 2 , S 2 T 2 .