Patent GB-436717-A (GB)
Title: Improvements in electromagnetic devices
IPC: H01F7/08
Filed: 1934-03-17
Abstract: 436,717. Electromagnets; oscillating motors; automatic regulators. HAUSRATH, H., 9, Wendtstrasse, Karlsruhe, Baden, Germany. March 17, 1934, No. 8488. [Classes 35 and 38 (iv)] [See also Group XXXVII] An electromagnet has an armature formed as a rocker, or rigidly attached to a rocker, which rolls on a guide curve comprising a continuous surface extending from a point near the polepieces of the electromagnet to a point remote from the polepieces. In the form shown in Fig. 1, a curved armature 4 carries at one end a pivoted pawl 30 spring pressed against a rack 32 which may operate automatic telephone selector mechanism. A return spring 11 is attached to this end of the armature and to an adjustable member 12, and the movement of the other end is limited by an adjustable stop 13 carried by a horizontal spring strip. The guide curve in this case is constituted by the straight upper edges of a pair of plates 3 adjustably screwed to the magnet yoke 1 at 22, 23. As the free end of the armature is attracted towards the magnet pole faces which are situated between the plates 3 just below the level of the guide curve, the fulcrum moves towards the left so that the leverage of the attractive force diminishes and that of the resisting force increases. Pins or springs 5 passing through slits 8 in side projections of the armature prevent displacement of the armature. The guide curve may be discontinued at a point short of the polepieces, or, if of convex form it may be continued as a straight line tangential to the curve, in which case the armature will pivot about this point. In Fig. 6, the curved upper edges of plates 43, 45 disposed one on each side of the magnet constitute the guide curve and the armature 49 is ground smooth and connected at the left to leaf springs 47 anchored at their other ends 46 to the plate. In the unattracted position shown in full lines, the springs lie against the under side of the armature and in the attracted position shown in dotted lines they conform to the shape of the guide curve. The leaf springs may be sufficiently wide to prevent displacement of the armature or the plates 43, 45 may be of magnetic material for this purpose. Flexible bands, chains, &c. may replace the springs, and in order to keep the armature in position, a spring 59 or additional pole extensions 63, 64 may be provided. In a modification, the springs are replaced by rods pivoted to the armature and connected at the right-hand end to the ends of a flat spring held at its centre. Fig. 8 shows a magnet 65 for use in alternating- current or continuous-current circuits. The frame 67 is U-shaped and the flat upper edges 74 constitute the guide curve for the curved armature plate 68. A pawl (not shown), acts on a rack passing through a slot 71 in the armature plate. The circuit of the magnet coil is interrupted at spring contacts 77, 79 and the armature is returned by a pair of springs such as 72 or by a single spring acting at the centre of the plate. To reduce the amplitude of vibration, the return spring may be such that it acts in the reverse direction when deflected beyond the normal position of rest. The guide curve may be grooved to receive flanges on the armature plate and the frame and armature plate may be of non- magnetic material. To minimize noise, the co-operating surfaces may be of elastic material. In the form shown in Fig. 10, the armature 103 is attached at one end to a return spring 105 which is unstressed in the position of rest, and at the other end is connected to a spring 108 and carries a weight 104. Arrangements of two electromagnets are described acting on a single armature carrying a pawl at each end and operating on two ratchet wheels geared together or carried on a single shaft. Fig. 13 shows a double electromagnet, the drive being taken from the centre of the armature 131. A driven disc 141 is toothed or is a friction disc preferably formed of metal foil and amber and is acted upon by a pivoted pawl 140. The lever 137 may be attached to the armature by a short stiff spring. The armature is connected to the magnet frame by tensioning bands shown by crosses and dots, which bands may be continuous with each other, and are preferably elastically connected to the armature ends. One of the bands may be flexible and non-resilient and the other a leaf spring. In order to reduce magnetic leakage, the two electromagnets may be separate and of U-shape, with each pole face in the vicinity of the guide curve. To reduce the reluctance, the polepieces may extend towards the centre. The exciting coils may be fed with alternating- current through rectifiers. Constructions are described employing three electromagnets having one or both poles in the guide curve. In these examples, the three windings may be connected in different circuits so that the apparatus may function as a measuring or regulating device or switch One winding may be for polarizing and others for driving. Fig. 21 shows a triple magnet in which the armature 177 is curved and carries a glass tube 179 in which a metal ball or bead of mercury 181 travels over a noble metal resistance 180 wound on a quartz or glass rod, or closes circuits. The sensitivity of the device is varied by altering the position of the centre of gravity or by varying the shape of the guide curve, and the damping of the movement of the mercury bead is controlled by the provision of a groove in the upper part of the tube. The apparatus may function as a quotient meter. A variable resistance such as a regulator or potentiometer which may be controlled in dependence upon a current, voltage or power is shown in Fig. 19, where the armature 165 of an electromagnet 163 is attached to conducting bars 167 which roll over a resistance coil 168. The sensitivity is varied by varying the tension of the spring 172, by loading the armature or rotating the base plate 161 to vary the effect of gravity. Fig. 23 shows a double magnet system 211, 221 for driving a shaft 220 in either direction. The shaft carries two ratchet wheels 219, 229 acted upon by pawls 218, 228 operated by the armatures 215, 225. Locking levers 231, 233 are magnetically controlled and operate in such a manner that when one of the magnets is in operation, the pawl of the other magnet is lifted clear of its co-operating ratchet wheel. The use of rolling armatures in electromagnetic sound reproducers is disclaimed and Specification 238,310, [Class 40 (iv)], is referred to.