Abstract: A wheel-chair having a spring biased tiltable back-rest. The resilient force exerted on the back-rest by the spring is continuously adjustable to suit the actual person sitting in the chair. Preferably, the spring is a gas spring which is combined with a device reducing the effect of the gas spring when the back-rest is in its upright position and adds to its effect when the back-rest is adjacent or in its horizontal position.

Abstract: An electrical control or operation device for wheelchairs for invalids is provided, the wheelchair being driven and steered electrically. The device comprises two control means, each preferably consisting of two potentiometers, one of the control means controlling the speed forward and backward of the wheelchair, and the other control means controlling the direction of motion of the wheelchair. The two control means may be potentiometers or similar means and can be adjusted individually by one single lever. The body or casing of one of the two control means is fixed to the frame of the control device, and that of the other control means is mechanically connected to the control shaft of the first control means, whereas the control shaft of the second control means is mechanically connected to the lever.

Abstract: A method is provided of producing a moulding having a configuration corresponding to the surface configuration of a model. The method comprises the steps of bringing a gas-tight evacuatable container having at least one flexible wall portion in a position relative the configuration of the model such that the wall portion can be deformed to the contours of the model without cracking or creasing. A quantity of granular material is then poured into the container to deform the flexible wall portion to the shape of the model by pressure, whereafter at least a partial vacuum is created in the container to cause the granules to form a solid, persistent mass conforming to the shape of the model. The model is then removed while maintaining the condition of at least partial vacuum in the container.