GB2107537A - Improvements in model train systems - Google Patents

Abstract

A two locomotive model railway system is described having two rails (12, 14) in which each locomotive is equipped with a current rectifying device (22; 28) connected in series with an electric motor winding (20; 28) wherein electric current pulses of one polarity from an alternating supply (36) are directed to the one motor and pulses of opposite polarity are directed to the other motor, and the means current to either motor is controllable to vary the speed of the motor independently of the other. Current control may be by variable resistor (48 or 50), variable transformer, or by thyristor or triac based rectifying circuits. Smoothing capacitors (24; 30) serve to iron out short-term variations in the current supplied to the rails. The system allows the locomotives to be driven in one direction only. <IMAGE>

Description

SPECIFICATION Improvement in model train systems This invention relates generally to a model train system and, in particular, to an arrangement for controlling the speed of two locomotives independently, which locomotives may run on a single track.

Known model train systems on which two or more locomotives may be driven simultaneously usually entail the use of track components such as points, crossovers etc, which can be employed to isolate one part of the track from another, eg an inner track circuit from an outer track circuit. The respective controllers for the locomotives relate to the corresponding parts of the track which can be isolated from one another. If two locomotives are brought onto the same part of the track, they both fall under the control of one controller, and their speeds cannot then be independently controlled.

Control arrangements have been proposed which enable independent speed control of two locomotives on a single track, but hitherto these have been complex and expensive.

It is an object of this invention to provide an improved model railway system which enables independent speed control of two locomotives on a single continuous track circuit in a simple and inexpensive manner.

According to one aspect of the invention, there is provided a model railway system which comprises a track fed with low voltage alternating current between the two rails, two locomotives having respective pick-up shoes and electric motors, each with a rectifying means in series with the motor winding, the motor windings and rectifying means being arranged so that each locomotive will be driven in the same direction along the track, one by positive half cycles of the track current and one by negative half cycles thereof, and two speed controllers, one for each locomotive, through which a power circuit to the track is completed, the controllers each including a rectifying means and an adjuster to enable the amplitudes to the positive half cycles and of the negative half cycles fed to the track to be varied independently of one another.

It will be appreciated that, with the speed control arrangement according to the invention, the facility to reverse the locomotives is dispensed with, but in practice this is not materially disadvantageous, and generally results in a reduction in the number of derailments and other accidents. However, as the locomotives can only be driven forwardly, continuous track loops must be employed throughout, with sidings and extensions which allways return to the main track circuit(s).

Although dead ends must be avoided, openended sidings and extensions can be equipped with the usual track isolation facilities, eg at the points.

According to another aspect of the invention, there is provided a locomotive for the above described system, which locomotive has a rectifying means, such as a block diode, in series with the motor winding. The motor itself may be of the standard or the ringfield type, preferably with a smoothing capacitor connected in parallel with the winding to prevent any possible jerkiness which might arise from the pulsed power supply (positive or negative half cycles usually at 50 Hz).

According to yet another aspect of the invention, there is provided a speed controller for the above described system, which controller is connectible between a low voltage (eg 1 2 volts) a.c. power supply and the track and includes a rectifying means such as a blocking diode and an adjuster such as a variable resistor for varying the amplitude of the positive half cycles (or negative half cycles) transmitted to the track independently of the negative half cycles (or positive half cycles).

Power will usually be derived from the mains supply via a step-down transformer and it is alternatively possible to employ a split secondary winding or dual secondary windings with adjusters constituted by variable tappings on the two sides of the split (eg centre-tapped) secondary winding or on the two separate secondary windings.

Yet again, the adjusters may act in conventional V age control thyrister or triac circuits, and the rectifying means may then be incorporated in these circuits. The two last mentioned possibilities for speed control have the advantage over variable resistors for reducing energy loss due to production of heat.

According to yet another aspect of the invention, there is provided an adaptor set for converting a conventional track system in which two independent controllers provide independent d.c. supplies for running independent locomotives, into a system as hereinbefore described in accordance with the invention, which adaptor set comprises first and second circuit means adapted to chop the two d.c. outputs from the two controllers to provide alternatively positive and negative going pulses for supply to the track input sockets for connection of each existing controller to the input of the adaptor set, and output sockets for connection of the adaptor output to the track through conductors so that one of the controllers serves to control the amplitude of the positive going pulses fed to the track and the other controller serves to control the amplitudes of the negative going pulses supplied to the track. A pair of conventional locomotives may readily and inexpensively be converted to run on the converted track systems by the connection of a blocking diode in series with and a smoothing capacitor in par allel with the motor winding. When fitting the additional components, the winding of one locomotive may if necessary be reversed to ensure that both locomotives run forwardly.

A practical arrangement in accordance with the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 diagrammatically illustrates a model train system having respective, independent speed controllers for two locomotives running on a single track, and Figure 2 is a waveform diagram for the system.

A typical conventional model train system has two electrically isolatable tracks supplied with direct current through a transformer unit which includes a block rectifier bridged by a smoothing capacitor. The output of the transformer is taken to the two tracks through respective speed controllers, typically variable resistors, which vary the magnitudes of the d.c. voltages applied between the rails of the respective tracks.

In contrast, the system in accordance with the present invention is shown in Fig. 1. A single track, generally designated 10, is supplied with low voltage alternating current between its two rails 1 2 and 14. A first locomotive on the track is generally designated 1 6 and a second locomotive on the same track is referenced 18. Motor winding 20 of locomotive 1 6 has a blocking diode 22 connected in series therewith and smoothing capacitor 24 connected in parallel therewith. Motor winding 26 of locomotive 18 has a blocking diode 28 connected in series therewith and a smoothing capacitor 30 connected in parallel therewith. It will be noted the diode 22 of locomotive 1 6 is oppositely directed to diode 28 of locomotive 18.

As the track 10 is supplied with alternating current, locomotive 1 6 will be driven by the positive half cycles or pulses or current passed through the diode 22, while locomotive 1 8 will be driven by the negative half cycles or pulses of current passed by oppositely directed diode 28. In order to prevent the second locomotive 18 being driven rearwardly as as compared to the forward drive of the first locomotive 16, the winding 26 of locomotive 18 is reversed in sense relative to the winding 20 of locomotive 16.

Speed control of the locomotives 1 6 and 18 requires the facility of independent regulation of the amplitudes of the positive and negative half cycles of current. For this purpose, two controllers generally referenced 32 and 34, the controlller 32 for locomotive 16 and the controller 34 for locomotive 18, are provided. Each controller is connected to one side of the secondary winding 36 of a stepdown a.c. transformer 38 the primary winding 40 of which is connected across the normal domestic a.c. (240 V, 50 Hz) mains electricity supply. The secondary windings 36 typcially provides a 1 2 V, 50 Hz, a.c. output, and the other side of said winding 36 is connected through an overload device 42 to one rail 1 2 of the track 10.The power circuit for positive and negative is completed by connections from the controllers 32 and 34 to both rails 12 and 14 of the track 10. In Fig. 1,the solid line arrows indicate the direction of current flow during positive half cycles of current and the dashed line arrows indicate the direction of current flow during negative half cycles. Each controller 32, 34 comprises a blocking diode, respectively 44 and 46, and a variable resistor, respectively 48 and 50.

Diode 44 is oppositely directed to diode 46, so that controller 32 will only pass positive half cycles of current operative to drive locomotive 1 6 and controller 34 will only pass negative half cycles of current operative to drive locomotive 1 8.

Fig. 2 is a waveform diagram illustrating the voltages available across the rails 12 and 14 of the track to drive the locomotives.

Positive cycles 52 are shown gradually being reduced in amplitude by the adjuster of variable resistors 48 of controller 32 in order to slow down the locomotive 16, whilst negative cycles 54 are shown gradually being increased in amplitude by the adjuster of variable resistor 50 of controller 34 in order to speed up the locomotive 18. At point 56, both locomotives have been stopped by simultaneously moving both adjusters to the 'off' positions 58, 60 indicated in Fig. 1. It is obviously possible, however, to stop either one locomotive whilst continuing to drive the other.

As previously explained, it is not materially disadvantageous that the locomotives cannot be rearwardly driven provided that a track layout is employed in which all sidings and extensions loops, isolatable or not, return to the main track.

Various modifications of the arrangement are possible within the scope of the invention as hereinbefore defined. For example, to reduce energy loss due to heat production, the controllers may enable speed variation by means of adjustable tappings on a split secondary or dual secondary winding of the stepdown transformer or, alternatively, thyristor or triac speed control may be employed.

It is also within the scope of the invention to provide an adaptor set for converting a conventional model train system into a system in accordance with the invention. This requires the insertion of an adaptor set between the conventional controller which incorporates a transformer and rectifying unit together with the usual speed controllers (which normally provide two independently controlled d.c. outputs) and the track. The adaptor set includes synchronised high speed switching devices, typically solid state switching circuits, to pro vide at a first output a series of positive going pulses and at a second output a series of negative going pulses, the pulses being supplied synchronously out of phase to the track.

Conveniently the two outputs are combined within the adaptor to form a composite electrical current for supply to the tracks, made up of controlled amplitude positive and negative going pulses. By providing appropriate diodes in the locomotives and reversing the windings on one of the locomotive engines, so one will respond to one of the controllers and the other to the other controller. Smoothing capacitors may be employed in the locomotives to advantage.

Claims (14)

1. A model railway system comprising a two-rail track fed with low voltage alternating current between the two rails which includes: two locomotives having respective pick-up shoes and electric motors, each with a rectifying means in series with the motor winding, the motor windings and rectifying means in series with the motor winding, the motor windings and rectifying means being arranged so that each locomotive will be driven in the same direction along the track, one by positive half cycles of the track current and one by negative half cycles thereof, and two speed controllers, one for each locomotive, through which a power circuit to the track is completed, the controllers each including a rectifying means and an adjuster to enable the amplitudes of the positive half cycles and of the negative half cycles fed to the track to be varied independently of one another.

2. A locomotive pair for a model railway system as claimed in claim 1 in which the rectifying means connected in series with motor winding of one locomotive is connected oppositely to that in the other locomotive.

3. A locomotive pair as claimed in claim 2 wherein each motor is of the ringfield type.

4. A locomotive pair as claimed in claim 2 or 3 wherein a smoothing capacitor is connected in parallel with the winding.

5. A locomotive for use in a model railway as claimed in claim 1 wherein the rectifying means in series with the motor is a blocking diode.

6. A speed controller for a model railway system as claimed in claim 1 which is connectable between a low voltage a.c. power supply and the track and which includes a rectifying means and a variable resistor for varying the amplitude of half'cycles of current of one polarity independently of the half cycles of opposite polarity.

7. A speed controller for a model railway system as claimed in claim 1 which is derived from an electricity supply main via a stepdown transformer having a centre-tapped secondary winding or two similar secondary windings and current variation and therefore speed variation is obtained by selecting between tappings on the two sides of the centretap or on the two separate secondary windings.

8. A speed controller for a model railway system as claimed in claim 1 wherein the rectifying means includes a thyristor and voltage control is achieved in known manner by controlling the firing of the thyristor.

9. A speed controller for a model railway system as claimed in claim 1 wherein the rectifying means includes a triac and voltage control is achieved in known manner by controlling the firing of the triac.

1 0. An adaptor set for converting a conventional model railway track system of the tyoe in which two independent controllers provide independent d.c. supplies for independently driving two locootives, into a model railway system as claimed in claim 1, which adaptor set comprises first and second circuit means adapted to chop the two d.c. outputs of the two independent controllers to provide alternately positive and negative going pulses for supply to the track, input sockets for connection for each existing controller to the input of the adaptor set, and output sockets for connection of the adaptor set to the track through conductors such that one of the controllers serves to control the amplitude of the positive going pulses to the track and the other controller serves to control the amplitude of negative going pulses to the track.

11. An adaptor as claimed in claim 10 which includes synchronised high speed switching devices, to provide at a first output a series of positive going pulses and at a second output a series of negative going pulses, the pulses being supplied synchronously but out of phase to the two lines of the track, as a composite electrical current made up of controlled amplitude positive and negative going pulses.

1 2. A model railway system constructed arranged and adapted to operate substantially as herein described with reference to the accompanying drawings.

1 3. A locomotive for a model railway system constructed arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.

14. An adaptor set for converting a conventional model railway track system into one as claimed in claim 1 wherein each adaptor is constructed and arranged substantially as herein described with reference to Fig. 19 of the accompanying drawings.