Patent SE-339591-B (SE)
Inventor: WILKES D
IPC: H01H35/14
Filed: 1968-05-21
Abstract: 1,181,636. Inertia switches; variable resistors. UNITED STATES ATOMIC ENERGY COMMISSION. 26 Feb., 1968 [29 May, 1967], No. 9090/68. Headings H1N and HIS. [Also in Divisions F1, F2, F3 and G1] A device 42 for eliminating or minimizing sliding friction between relatively moving parts in electro-mechanical and mechanical devices comprises a housing with walls 48, 50 spaced apart a distance less than the sum of the diameters of a pair of rollers 44, 46 urged toward parallel relationship by the tension in a flexible band 52 supported intermediate the walls with a portion disposed between and partially encompassing the rollers for providing rolling movement of the rollers and band along the housing walls. It appears that if the band parameters W (width), E (modulus of elasticity) and h (thickness) are equal at the lines of contact 54, 56 the device will be in a state of equilibrium in the absence of external forces. However, if, for example, the width of band contact is greater at the line 56 than at the line 54, the tension in-the band produces a force bias in the direction of the arrow in Fig. 2. Twelve alternative tension band configurations are shown applicable to the device of Fig. 2, with force diagrams illustrating the force bias functions they would produce simulating e.g. types of springs with positive or negative spring constants or both. While the overall width of the band may be varied, it is preferable to keep the width uniform and to vary the contact width by means of cut-outs, suitably shaped. Cut-outs can also provide a detent or latching action. The tension band may be made from a wide range of flexible materials including plastics, metals, alloys, laminates, insulators and viscoelastic materials and examples are given of conductors forming switch contacts embedded in the band. A temperature sensitive bi-metallic tension band may be used. To provide flexibility and shock resistance whilst maintaining tension, ring or maze type cut-outs or corrugations may be provided at the ends of the band or it may be made of elastic material. For instrumentation purposes a width of 0À0002 to 0.004 inches is suggested. The rollers may be solid or hollow of any cylindrical shape such as a right circular cylinder or right prism and they may be coated with metal or insulating materials. The guide walls may be insulating or conducting and their profiles may be various shapes. The devices may be constructed using microminiature modular techniques. In an accelerator or "G" switch, Figs. 6, 8, a screw 110 presets the initial position of rollers 80, 82 by engaging a tongue 108 in the band 96 formed by cut-out 104 and if the housing is submitted to an acceleration towards the left sufficient for the inertia forces of the system to exceed the negative force bias generated by the cut-out 100 the rollers 80, 82 and band 96 will begin to roll but will return to initial position when the acceleration ceases unless it is maintained long enough for the contact line between roller 80 and wall 84 to move past cut-out 100 and the contact line between roller 82 and wall 86 to move over cut-out 101, which will reverse the bias force and lock the system with tongue 106 in contact with electrical contact 112. The accelerometer or "G"-switch, Fig. 9, is modified to measure velocity change as well as acceleration by providing a second band 136 and pair of rollers 124, 126, the roller 126 with an orifice 138 aligned with an orifice 140 in the band 136. The band 136 is of uniform width along its whole length while the band 146 and rollers 142, 144 are similar to those shown in Fig. 6 and the force bias in band 146 holds both sets in initial position. The interior is filled with damping fluid (liquid or gas) and when an acceleration is applied the right-hand set behaves as before while the left-hand set also rolls, without an opposing bias force, at a rate dependent on the flow through orifices 138, 140, which thus integrates the acceleration with respect to time. A doubly integrating accelerometer may be made by attaching a pair of large diameter flywheels to rotatable members of unequal diameter, Fig. 12 (not shown), and one or more G-force levels may be sensed with a device described with reference to Fig. 10 (not shown). An electrical potentiometer and function generator 230, Fig. 13, comprises a pair of hollow rollers 226, 228, held parallel between guide walls by tension in a band 238 of conducting material. An insulating layer 246 separates two resistance wires 242, 244, connected to a power source and utilization means. When the rollers 226, 228 and band 238 roll along the guideway, e.g. under the influence of an acceleration force, a varying resistance loop is established. If one wire 242 or 244 is curved with respect to the other, the linear movement of the band 238 along the wires may generate any desired function of resistance with respect to time or other variable related to roller displacement.