Patent GB-190318536-A (GB)
Title: Improved Means and Apparatus for Controlling Electric Motors.
Inventor: IMRAY OLIVER
Filed: 1903-08-27
Granted: 1904-08-11
Abstract: 18,536. Imray, O., [Bullock Electric Manufacturing Co.]. Aug. 27. Motors, controlling.-Relates to means, for controlling electric motors by changing the voltage applied thereto from a multiple-voltage system, wherein there is a quick break. Only one step is taken for each throw of the operating-handle. The generators 1, 1<1>, Fig. 1, are in series with one another, and supply different voltages ; e.g., the generator 1 may give 160 volts between the mains 3, 3<1>, and the generator 1<1> 20 volts between the mains 3<1>, 3". The armature of the motor to be regulated is indicated at 4, and its field winding at 5. The latter is connected across the mains 3, 3" with variable resistances 6. In the armature lead 9 is the resistance 9<a>, which may be short-circuited by a switch 10, having a soft iron arm 11 forming the core of the coil 12 and provided with a dash-pot arrangement consisting of a lower extension carrying a plunger 13 in a cylinder 14. The plunger is perforated, and is covered by a loosely-fitting flat ring 16 which normally closes the openings. The cylinder has openings 17 in its sides. When current passes in the coil 12, the piston slowly rises till just before the switch closes, when air enters beneath the piston through the openings 17, and the switch closes suddenly. When no current passes, the piston falls rapidly by gravity or spring pressure, air freely passing through the holes in the piston. The controller cylinder is formed of three insulated drums 18, 19, 20, the upper two being used for regulating the armature connections, and the lower the field resistances. The 'off' position is shown at 0, the forward positions by 2<a>, 2<b>, &c., and the backward positions by 3<a>, 3<b>, &c. For the position 2<a>, the path of the current is the main 3<11>, finger 1<b>, contacts 21, 22, finger 1<f>, lead 23, armature 3, lead 24, switch 10 (which is closed), leads 9, 25, finger 1<b>, contacts 26, 27, and finger 1<d> to the main 3<1>, thus subjecting the armature of the motor to the voltage of the generator 1'. At the same time, the field connections are the main 3, lead 7, field 5, finger 1‹, drum 26, finger 1<j>, and lead 8 to the main 3<11>, the full voltage of the mains 3, 3<11> passing while the resistances 6 are cut out. Further, the main 3<1> leads to the coil 12, finger 1<i>, drum 20, finger 1 <j>, lead 8, and main 3<11>, thus subjecting the coil 12 to the voltage of the generator 1<1>, and closing the switch. In the positions 2<b> and 2<c>, resistances are inserted in the field circuit. The positions 2<d>, 2<e>, and 2<f>, and the positions 2<g>, 2<h>, and 2<i>, correspond to the positions 2<a>, 2<b>, and 2<c>, except that, in the first group, the armature is subjected to the greater voltage of the generator 1, and in the latter to the combined voltages of the generators 1, 1<1>. In the position 2<j>, 2<k>, and 2<l> no further changes occur, except that more resistances are inserted in the field circuit. In passing from 2<c> to 2<d> and from 2<f> to 2<g> the switch 10 is opened, and the resistance 9<a> is inserted in series with the armature, whereby a too sudden rush of current is prevented. For reverse rotation, the first set of positions is 3<a>, 3<b>, 3<e>, when the current passes from the main 3<11>, finger 1<h>, contacts 36, 37, finger 1<g>, lead 9, switch 10, lead 24, armature leads 23, 38, finger 1<c>, contacts 39, 40, and finger 1<d> to the main 3<1>, the armature being subjected to the voltage of the generator 1<1> with the current reversed, while the field is the same as for the position 2<a>. In the second set of positions 3<d>, 3<c>, and 3<f>, the armature is subjected to the voltage of the generator; while, in the third set, it is subjected to the voltages of both generators. The resistances in the field circuit are varied as before. There are thus twelve forward speeds and nine reverse ones. The construction of the controller is shown in Fig. 2. A back-plate 49, secured to a support by lugs 50, carries arms 51 to which the top and bottom plates 53, 54 are secured. A suitable cover is placed over the whole device. The shaft 58 carries the three insulated brass drums 18, 19, 20. Each drum has an end plate 62. The contacts on the drums 18, 19 are screwed to lugs 67 integral with the drums. The drums 20 is cast in one piece, and consists of an outer cylinder of the shape shown connected to an inner supporting- cylinder 69 by ribs 70. The spring brass fingers are connected to metallic strips having fan-like extensions 78, and mounted on an insulating- support 74, made of maple soaked in paraffin. To confine and limit the spaces in which arching takes place, triangularly-shaped sheets of insulated materials 81 are supported between each set of contacts on the drums 18, 19, by the extensions 78 and by two vertical removable metal rods covered with fibre sleeves 84. On the top of the shaft is fixed an arm 85 having a pawl 86 carrying a steel plate which enters notches 90 in the rim of the top plate 53. The pawl has a lower extension 92 connected to the arm 85 by a spring 93, and an upper extension carrying a steel roller 96 having a beaded portion. At the opposite end of the arm is a depending lug 98, which engages a stop 99. The handle 100 is loosely mounted on the shaft 58, and its hub is surrounded by a spring 101, the projecting ends 102 of which engage projections 104, 105 from the handle and arm 85 respectively. The handle has side extensions, not shown, carrying rollers. The arm has upwardly-extending lugs 11<1>, which may engage with the projection 104. When the handle is turned, one end (depending upon the direction of turning), of the spring is carried round by the projection 104, the arm 85 remaining stationary. One of the rollers above mentioned then engages the bead of the roller 96, whereby the lug is forced inwards and the steel plate removed from its engaging-notch 90. The cylinder then turns suddenly under the action of the spring 101, giving a quick break. The spring 73 causes the plate to enter the adjacent notch. The handle must be turned a second time for a further change of speed.