From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Patent specification for an improved electric starter system with an auxiliary battery to boost the main battery.
| Identifier | ExFiles\Box 147\2\ scan0307 | |
| Date | 1st March 1939 guessed | |
| 2 which may be quite small and equivalent or substantially so to the aforesaid momentary voltage drop across the main battery, may comprise dry cells or consist 5 of a small accumulator. In some instances a flash-lamp battery may be found sufficient for the intended purpose. However, any suitable type of battery which gives a direct current may 10 be employed. The improved electric starter system, as in most systems of this general character, may conveniently be of the single pole type with earth return. 15 In a system constituting a particularly simple and comparatively inexpensive embodiment of this invention, the conventional starter switch has associated therewith an auxiliary switch of any 20 suitable type which is adapted, upon closure of the starter switch, to be closed to bring the auxiliary battery into the circuit and in series with the main battery to boost up the latter. 25 In the preferred arrangement, however, there is provided for bringing the auxiliary battery into circuit with the main battery a switch which is independent of the conventional starter 30 switch and arranged to be closed by any suitable relay such as an electro-magnetic device which latter is in circuit with and adapted to be excited upon closure of said starter switch. 35 If desired provision may also be made in the improved system as will be hereinafter more fully described whereby the auxiliary battery can be charged from the main battery, but in such a system it 40 would be necessary to insert a comparatively high resistance in circuit with the auxiliary battery or to provide some equivalent arrangement so as to allow only a small or a trickle charge to the 45 latter. In this way the auxiliary battery can be kept fully charged in an automatic manner so that it is always in a condition to give its maximum output during starting. 50 In order that the invention may be more clearly understood and readily carried into practical effect, some specific examples thereof will now be described with reference to the accompanying 55 drawings, wherein, Figure 1 is an electrical diagram representing one specific embodiment of the invention wherein the switch for bringing the auxiliary battery into circuit 60 with the main battery, and vice versa, is operated from the conventional starter switch. Figure 2 is a similar diagram illustrating another arrangement in which 65 closure of the starter switch effects opera-tion of a relay device for the purpose here-inbefore mentioned. Figure 3 shows a somewhat similar system to that shown in Figure 2 but one 70 in which provision is made for automatically charging the auxiliary battery. Like parts are designated by similar reference characters throughout the drawings. 75 In the drawings, 1 represents the main battery, 2 the ignition switch which is conveniently operated by an ignition key, 3 the ignition coil, 4 the starter switch and 5 the engine starting motor. 80 Referring to Figure 1, which shows a simple and inexpensive arrangement, it will be seen that the electrical system is of the single pole type with leads to earth at the appropriate points 6, 7 and 8. The 85 starter switch 4 is of conventional form besides being spring or equivalently loaded and is operable by a button 9 which, in the case of a motor car, is arranged on the dashboard for ready 90 access. When the said button is said depressed the starter switch is moved into contactual relationship with a contact 10 whereby the starter circuit is closed so that current from the battery 1 flows 95 through the switch to the starting motor and thence to earth at 7. Mechanically connected to or with the starter switch as, for instance, by means of an insulated connection 11, is an auxiliary switch 12. 100 This auxiliary switch therefore follows the movements of the starter switch 4 and when the latter is open the auxiliary switch co-operates with a contact 13 so as to provide, when the ignition switch 2 is 105 closed, the primary ignition circuit which is from earth at 6, through the main battery 1, the switch 12, the primary winding (not shown) of the coil 3 and thence back to earth at 8. A branch of 110 the secondary ignition circuit is indicated at 14 and, in accordance with customary practice, said circuit conveniently includes a revolving distributor or a commutator form of contact-maker from which the high tension output of the coil 115 3, supplied by its secondary winding, is led to the sparking plugs. When, however, the starter switch 4 is closed the auxiliary switch 12 is moved away from the contact 13 and into 120 contactual relation with another contact 15 with the result that—assuming the ignition switch to be closed—an auxiliary battery 16 which is wired in series with the main battery 1 is temporarily brought 125 into the primary ignition circuit. In this way the battery 1 is boosted up by the auxiliary battery, during starting, so that maximum voltage is immediately applied 130 to the coil 3. When the engine has been started up and the starter button 9 is released to open the switch 4, the switch 12 is automatically transferred from the contact 15 to the contact 13 as a conse- 5 quence of which the auxiliary battery is cut out of circuit. Upon the starter switch being opened, moreover, the motor 5 is also cut out and the full voltage of the main battery 1 is then available for igni- 10 tion purposes. If the main battery is rated at, say, 12 volts then the voltage drop upon closure of the starter switch would be approximately 4 1/2 volts. Assuming then that the ignition coil is 15 designed to take 12 volts and no means were provided to boost up the battery during starting then the voltage applied to the coil would only be 7 1/2 volts. To remedy this an auxiliary battery of about 20 4 1/2 volts arranged as shown would be necessary. It is to be understood, however, that these figures are given merely by way of example and may be varied according to requirements. 25 The general layout of the system shown in Figure 2 is similar to that just described but in this case a switch 17 which is independent of the conventional starter switch 4 is provided for bringing 30 the auxiliary battery 16 into and cutting it out from the primary ignition circuit as and when required. For operating the switch 17 there is provided a relay 18 which is wired in circuit with the starter 35 switch 4. This relay may conveniently take the form of an electro-magnetic device, whereby upon closure of the starter switch 4 current from the main battery 1 excites the said device and 40 attracts the switch 17 which thereupon moves from a contact 19 into contactual relationship with another contact 20 temporarily to bring the auxiliary battery 16 into the primary ignition circuit, that is 45 to say, into series with the main battery 1. When, however, the starter switch is opened, upon the engine starting, the excitation of the relay 18 ceases so that the switch 17 moves over from the con- 50 tact 20 to the contact 19 thereby cutting out the auxiliary battery 16. It is thought that from the foregoing description of Figure 2 the circuits and paths of the current in the example last 55 described will be evident without further elaboration. The resistance of the relay device, which is earthed at 21, may conveniently be in the region of 100 ohms. 60 Now, in both of the arrangements shown in Figures 1 and 2 it is not possible to charge the auxiliary battery automatically. Consequently if the battery is a dry one it has to be changed 65 from time to time, or if it is in the form of an accumulator it is necessary when it runs down to take it out of circuit and charge it up for further use. In some cases this may not be found to be a serious 70 disadvantage, but it may sometimes be desirable as hereinbefore mentioned to provide in the improved system means whereby the auxiliary battery can be charged automatically from the main 75 battery. For instance, when the main battery is being charged current therefrom, suitably reduced by passage through a high resistance, may be passed through the auxiliary battery from the 80 positive to the negative terminals thereof for charging purposes. Most electric starter systems of the character concerned have provided in conjunction therewith a charging circuit including a dynamo and 85 an automatic cut out device whereby at a predetermined engine speed a charging current is passed through the battery to charge it up. In such a system, therefore, the same current could be caused to 90 pass also through a high resistance to reduce its value and thence through the auxiliary battery. A resistance of about 100 ohms to reduce the value of the current from 10—15 amperes to about 1/2 95 Ampere would be suitable for this purpose. Alternatively, and by arranging the ignition switch at an appropriate point in the circuit, the auxiliary battery may receive a trickle charge from the main 100 battery, in which instance said auxiliary battery would be permanently on charge. An example of a system wherein provision is made for charging the auxiliary battery automatically will now be 105 described with reference to Figure 3. Since, however, the system illustrated in this figure is, so far as starting and ignition is concerned, the same as that shown in Figure 2, only so much of Figure 3 as 110 is necessary to emphasise the differences will be described. Whenever the relay 18 is excited by reason of closure of the starter switch 4, the switch 17 for bringing into the primary ignition circuit the 115 auxiliary battery 16 is moved from a contact 21¹ into contactual relation with another contact 22. In this example the said switch 17 is mechanically connected, as by means of insulated connections 23 and 120 24, to two additional switches 25 and 26 the purpose of which is to control the cutting in and out of a high resistance 27 employed for the purpose aforesaid and also to determine the direction of current 125 flow through the auxiliary battery. In this respect it will be understood, of course, that during starting, i.e. whenever the switch 4 is closed, the path of the current from the main battery 1 must 130 be such that it flows through the auxili- | ||