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Vickers (London) Patented Dynamo Regulator System Description

GENERAL DESCRIPTION OF THE SYSTEM

The text below is a transcription from patent no. 21157 of 1912. Many thanks to Robin Nelson for finding and researching this patent the number of which he discovered under our NB saloon no.461

Date claimed for patent under patents and designs Act 1907, being the date of first Foreign Application (in the USA) - 6th July 1912.
Date of application (in the United Kingdon), 17th September 1912
Accepted 10th April 1913

COMPLETE SPECIFICATION
Improvements in Regulators for Electric Train Lighting Systems and the like.

I Patrick Kennedy of 177 Belford Avenue, Brooklyn, State of New York, USA, Engineer, do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement:-

The object of the invention is to produce, for train lighting and like systems in which the resistance has to be varied by small increments over a wide range, a solenoid resistance regulator having such construction that the limited power of a small compact solenoid is effective, without the interposition of any intermediate or auxiliary mechanism, to impart to the contact arm resistance-varying movements of the desired amplitude, and with freedom from circuit interruptions or sparks due to the jar which is necessarily incident to the contemplated use, or due to poor contact arising from the collection of dirt or dust on the contact surfaces, or to improper order of separation of the contact arm from the compactly arranged resistance terminals.

NBR system

The construction of the invention differs from the known solenoid resistance regulators acting on carbon piles in the circumstance that by substituting a rolling contact between the resistance terminals and the contact arm, for the pressure contact between the surfaces of the elements of a carbon pile, a much more even gradation of resistance variation is obtained and the auxiliary tappet employed with a carbon pile is dispensed with.

The invention provides a direct acting solenoid resistance regulator, comprising a resistance divided into a sufficient number of sections to prevent objectionable variations of current in the controlled circuit upon passing from one resistance section to the next, compactly arranged terminals for the resistance sections a contact arm made up of a number of thin contact plates making yielding rolling contact with the said resistance terminals and spring loaded into close engagement therewith, a solenoid responsive to electrical variations in the circuit to be regulated and having a plunger operatively connected to the contact arm, and a dashpot for damping the movement of the solenoid plunger.

Other features of the invention will be hereafter described. In the accompanying drawings, which illustrate the preferred embodiment hereinafter of the invention.

  • Fig 1 is a central vertical section on the line 1-1 of fig 2.
  • Fig 2 is a top plan view partly broken away;
  • Fig 3 is a view of the contact arm and connections viewed from the right in Fig 1, and shows also in outline two of the resistance grids;
  • Fig 4 is a detail view, showing one of the blades and one of the spaces strips of which the contact arm is built up, and,
  • Fig 5 is a section on the line 5-5 of Fig 2, showing the manner in which the spring pressure is applied to the contact arm.

The solenoid proper is of ordinary construction, consisting of an outer shell made of iron, closed at one end by a cap b and at the other end by an annular plate c of iron, through which projects an iron tube or core d. The solenoid has an exciting winding, indicated at a1, the arrangement of which will depend upon the use to which the regulator is to be applied. That is to say, in a lamp regulator the exciting winding will be in a shunt across the lamp circuit, while in the case of a generator field resistance regulator the exciting winding will be made up of the field shunt, a winding in series with the load, and preferably an additional shunt winding for preventing an overcharge of the battery. Whatever arrangement of exciting winding may characterise the use of the solenoid, the binding posts b1 are provided for making the necessary connection. The stem c1 of the moveable core d1 passes loosely through the fixed core member d and is guided by a lubricating bushing e of graphite or the like. The moveable core d1 is preferably encased within a brass tube e1 and carries at the lower end a piston f preferably of graphite or the like, and moving in a piston chamber f1 in the lower end of the solenoid casing. Communication is established from one side of the piston f to the other by a by-pass g controlled by a screw valve g1. The piston f acts as a dash-pot and performs the important function of steadying the movement of the contact arm and preventing oscillations thereof upon sudden variations in the condition of the controlled electrical circuit as well as vibrations due to the mechanical jar which is incident to train lighting service. By means of the controlled bypass, the character of the dash-pot action may be regulated and because of the fact that the bypass has no opening to the exterior, through which dust or dirt might enter, the piston chamber may contain a lubricating fluid which will not become thickened with dirt.

NBR system

The resistance is preferably made up of a number of compactly arranged resistance grids h suitably connected in series and preferably arranged in two rows, so that the resistance varying effect of a movement of the contact arm may be increased. In the arrangement shown, the two sets of resistance grids are arranged in staggered relation to one another so that the grids of the two sets are cut into and cut out of circuit seriatim, whereby this increase of resistance varying effect is accomplished while maintaining the small gradations. The grids are securely held in a suitable support, as shown, and are exposed at the upper end to form contact surfaces, the exposed portions being preferably composed of a metal which has better conductivity than the material of the grids. It is important for the best regulation, that the material of these grids as well as the metal of which the solenoid windings are composed, shall have a low temperature co-efficient of resistance, and one of the known composition metals having such a low coefficient should be selected for the purpose. The important feature of the resistance element of the device is that the terminals should be compactly arranged so as to minimise the necessary movement of the contact arm, while individual sections should be of such a number and so brought into and out of circuit, that the resistance changes will be small increments which will not cause the lamps to flicker. No attempt has been made in the drawings to show the proper number of resistance elements employed, and it may well be to say that in practice there is contemplated the employment of say, 120 individual grids in a field regulator of standard construction whereas a less number, say about 90, is ordinarily sufficient for a lamp regulator.

A further important element of the combination is the contact arm i with the contact-making elements of the peculiar construction illustrated in Figs 1, 3 and 4. It has been found essential, if freedom of movement is to be combined with firm contact, that the contact surfaces should be pressed together as by a spring, and it has further been discovered that it is impossible to thus establish between the two plane surfaces, the close and uniform contact which is essential too prevent sparking when the contact arm moves over the compactly arranged contact terminals. If plane surfaces are employed, even small particles of dust on the surfaces will give rise to sparks, which so pit and roughen the surfaces that in a short time the apparatus becomes inoperative for any useful purpose. On the other hand, the use of thin plates of conducting material bound together to form a brush, and adapted upon yielding under the pressure to make a lateral wiping contact, as commonly used in circuit breakers, for example, is open to the defect, when applied to the present purpose, that the lateral wiping movement of the individual plates so increases the area of the surface in contact that it becomes impossible to introduce and remove seriatim the compactly arranged resistance elements, the wiping action giving rise to an improper order of introduction and removal of the elements, and contact sparking. These difficulties have been overcome in the present construction, in which the two contact portions or brushes of the contact arm are built up of a series of thin metal plates i1 separated by spacing strips i2 and embraced by jaw-like portions of the contact arm i, as shown in Fig 3. The plates i1 are deformed laterally, and preferably weakened, at a region between the contact edges and the portion embraced by the jaws of the arm, so that under pressure the individual plates will yield somewhat, and yet the contact edges of the plates are at all times normal to the surfaces of the resistance terminals. With this construction, the proper introduction and removal of the resistance elements is assured, since there is no lateral wiping action, and yet each plate i1, being capable of yielding individually, acts, under the pressure applied, as a knife edge, and cuts its own way to a good contact independently of all the other contact plates or blades.

The preferred manner of applying the spring pressure is illustrated in Figs 1 and 5 and comprises a blade spring k fastened to the frame of the regulator and engaging a stirrup k1 depending from the connecting position of the contact arm i. In this manner the pressure is applied at the centre of the contact arm and is evenly distributed to effect the best possible contact. It will be seen that the edges of the contact plates i1 are curved in any suitable arc or combination of arcs to obtain the proper shifting of the point of contact as the solenoid rises and falls.

In order to obtain the close regulations under all varying conditions incident to train lighting service, it is important, even with the arrangement of grids and contact arm thus described, to extend the accurate movement of the solenoid over as wide a range as practically possible, and to this end it greatly improves the apparatus if the variation in mechanical pull of the solenoid, due to a given change in electrical conditions, is equalised over the desired range of movement of the solenoid. This may be, and commonly is partially effected by making the surface at the air gap of the fixed and movable cores d and d1, conical shape: but in order to get the best results under the difficult conditions of service contemplated it is desirable to further bring about such equalisation of pull. To this end, there has been provided a spring acting on the solenoid plunger in such a manner as to resist the magnetic pull in increasing degree as the pull increases, the increasing effect of the spring acting in substantial proportion to the increasing pull of the solenoid. Such a construction is shown in Fig 1, in which the spring l presses downwardly upon an upward extension of the core c1, it having been found that the best results are obtained when the point of application of spring pressure is on, or substantially on the axis of the plunger. The effect of the spring is made to correspond to the varying effect of the magnetic pull by supporting the spring beneath cam l1 which is carefully shaped to give the desired increase of spring pressure as the pull increases. The shape of the cam can be determined either by experiment or by calculations and will differ for different solenoids, but the proper shape can easily be determinedby measuring the resultant total pull of the solenoid and so shaping the cam that this resultant pull is kept uniformor substantially so. In order that the apparatus may be set to respond to different values of current, or different normal conditions of electric circuit, there is provided the adjusting screw and nut indicated at m by which the average pressure of the spring on the plunger may be varied.

By the combination of the elements hereindescribed, it is possible to construct a regulator for train lighting systems which will establish the desired conditions of regulation with variations of not more than three per cent over the range of load variation from no lights, to the entire lighting system of the train or car, and with a variation of speed of the car from say, twenty miles per hour, at which point the automatic switch would be set to close the circuit of the generator, to ninety miles per hour, which may be taken as the maximum speed to be encounterd in ordinary service.

Having now particularly described and ascertained the nature of my said invention, and in what manner the same is to be performed, I declare that what I claim is:-

  • 1. A direct acting solenoid resistance regulator for train lighting systems comprising a resistance divided into a sufficient number of sections to prevent objectionable variations of current in the controlled circuit upon passing from one resistance section to the next, compactly arranged terminals for the resistance sections, a contact arm made up of a number of thin contact plates making yielding rolling contact with said resistence terminals and spring pressed into close engagement therewith, a solenoid responsive to electrical variations in the circuit to be regulated and having a plunger operatively connected to the contact arm, and a dash-pot for damping the movement of the solenoid plunger.
  • 2. A regulator according to claim 1 in which the thin contact plates are normal to the surface of the resistance terminals and are spaced apart and provided with deformed portions intermediate their contact edges and their bases permitting them to yield individually under pressure.
  • 3. A regulator according to claim 1 and 2 in which a spring acts upon the solenoid plunger in such manner as to resist the pull of the solenoid with a force substantially proportional thereto throughout a wide range of movement of the plunger.
  • 4. A regulator according to claim 3 in which means are provided for adjusting the resisting force of the spring.
  • 5. A regulator according to the foregoing claims in which the contact arm is pressed agains the contact terminals by a blade spring as k engaging a stirrup as k1.

Dated this 17th day of September 1912.

HASELTINE LAKE & Co.,
7&8 Southampton Buildings, London, England, and
60, Wall Street, New York City, USA.
Agents for the Applicant.