US2552256A - Starter system for diesel engines - Google Patents

Description

y 8, 1951 G. D. CERF 2,552,256

STARTER SYSTEM FOR DIESEL ENGINES Filed Feb. 3, 1950 2 Sheets-Sheet 1 [IA I 'IIIIIIIIII IIIII/I/I I GasZ-avwD. Cerf May 8, 1951 G. D. CERF STARTER SYSTEM FOR DIESEL ENGINES 2 Sheets-Sheet 2 Filed Feb. 3, 1950 l I J INVENTOR Gustave l). CerF y N t 6! 44 l kw ATTORNEY Patented May 8, 1 951 STARTER SYSTEM FOR DIESEL ENGINES Gustave D. Cerf, Livingston, N. J., assignor to Thomas A. Edison, Incorporated, West'orange, N. J., a corporation of New Jersey Application February 3, 1950, Serial No. 142,107

This application is a continuation-impart of my pending application Serial No. 26,685, filed May 12, 1948, now abandoned.

This invention relates to starter systems for Diesel engines which utilize one or more glow,

plugs for igniting the fuel-air charges to the cylinders when the engine is cold, and more particularly the invention relates to starter systems for Diesel engines which are adapted to delay the turning of theengine, if the engine is cold, until the temperature in the immediate vicinity of each glow plug reaches a suitable value to cause effective ignition.

Great difliculties are frequently experienced in starting Diesel engines while cold since cold engines absorb such a great amount of heat from the compressed gases during the compression stroke that the compression temperature in the combustion chambers does not rise high enough to cause ignition. If ignition fails, or is late so that only partial combustion occurs, serious damaging efiects to the engine may occur such as destructive pounding and hammering of the working parts and bearings.

These difficulties are now commonly overcome by the use of glow plugs. These plugs are generally the shape of spark plugs, and are threaded into the engine block so that the active elements thereof extend into the combustion chambers, but the active elements are in the form of straight or coiled wires which are electrically heated to a temperature of the order of 1700 F.

These glow plugs must be supplied with electric heating current for an initial period, depending on the ambient temperature, before they become hot enough to cause effective ignition Also they should be left energized for a short while after the engine firing begins and should then be disconnected from their heating current supply. An object of my invention is to provide a control system which is adapted to carry out these and other important steps to assure proper starting of Diesel engines and to maintain the engines running smoothly, regardless of the ambient temperature, until the engines reach normal operating temperature.

Another object is to provide such a starting system for Diesel engines which is arranged so that the operator is required to perform only simple and normal manipulations similar to the common procedure in starting engines generally.

It is another object of my invention to provide a starter system for Diesel engines which is substantially free from possible human error.

It is another object to provide a starter sys- 16 Claims. (Cl. 123-179) tem adapted to carry out the steps of starting a Diesel engine in proper relation.

It is another object to provide a starter system of the character mentioned which is adapted to vary the preliminary period of energization of the glow plugs in accordance with the ambient temperature so that the glow plugs are rendered effective in all seasons of the year before the starter per se is put in operation.

Another object is to provide such starter system which will maintain the glow plugs energized for a limited period following the starting of the time and sequence engine.

Still another object is to provide such starter system which, if the engine is already at a proper starting temperature, will put the starter per se in operation immediately as soon as the starter system is turned on.

Still another object is to provide a compact control unit for starter systems for Diesel engines which is arranged for convenient manual operation.

Other objects of my invention will be apparent from the following description and the appended claims.

In the description of my invention reference is had to the accompanying drawings, of which:

Figure 1 is a view showing diagrammatically the circuits and mechanism, with parts of the latter in section, of one embodiment of a starter system for Diesel engines according to my invention;

Figure 2 is a fractional view to show a modification of this embodiment; and

Figure 3 is a view similar to Figure 1 showing a second embodiment of my invention.

In Figure 1 a Diesel engine H] is shown having a crank shaft H and cylinders I! of which four are indicated by dash lines. An electric starter I3 for this engine has a coupling to the crank shaft represented diagrammatically by dash lines l4 and has an energizing circuit I5 connected to ground at l6. One glow plug I7 is provided for each cylinder, each being shown diagrammatically in the accompanying figure as having a coiled heating element in a combustion chamber of a cylinder of theengine. These plugs may be connected either in series or parallel, a parallel connection being shown wherein one end of the heating element of each plug is grounded at I8 and. the other end of each heating element is connected to an energizing circuit Hi.

The present control system for starting the engine I0 comprises a relay 2!] for controlling the energizing circuit I5 of the starter l3 and a relay 2| for controlling the energizing circuit IQ of the glow plugs ll. Each of these relays comprises an energizable coil and a pair of contacts one of which is operated when the respective coil is energized. The circuit l5 serially includes the contacts of the relay 2B and a source of potential, typically a battery 22 having one end grounded as at 23. Similarly, the circuit l9 serially includes the contacts of the relay 2| and the same battery 22.

A control unit 24 is provided which comprises a case 25 made as of suitable plastic or metal. Mounted on the front face, of this case are two on-ofl controls: (1) a single circuit on-off locking switch 26 adapted to be operated between Off and On (i. e., open and closed) positions by a key 2': which is removable when the switch is in Off position, and (2) an on-oif multiple switch 28 push-operable into On position and comprising three pairs of spaced contacts 29, 30 and 31 and respective bridging members 32, the bridging members being all carried by one bar 33 mounted on a plunger 34 which slides in a bearing 35 of the case. On the front end of this plunger there is a knob 36 and between this knob and the case there is a compression spring 31' which normally holds the switch in an off position wherein the bridging members are disengaged from the respective pairs of contacts 29-3 I. When the knob 36 is depressed the contacts of each pair 29-3l are interconnected by the respective bridging member.

The switch 26 is a master on-off control for the system and has one contact thereof connected by a wire 38 to a terminal 39 which in turn is connected by a lead 43 to the positive side of the battery 22. This circuit carries the operating current for the entire controlling part of the starter system. The other contact of this master switch is connected by a lead 4| to both a heating coil 22 and associated movable switch arm 43 of a thermal relay 44 which is preferably of the encased-evacuated type, this being a form of time-delay switch as will appear. The other end of the heating coil 42 is connected by a lead to one of the pair of contacts 29, the other contact of this pair being connected by a lead 46 to a terminal 41 which is in turn connected by a lead 48 to the coil of the relay 2|. The other end of the coil of this relay 2| is grounded at 49. Thus, upon turning the key switch 26 to its On position and then holding the knob 35 depressed so as to maintain the switch 28 also in its On position, the heating coil. 42 of the relay 44 and the coil of the relay 2| are connected in series across the battery 22. As soon as the relay 2| is so connected to the battery 22 it is operated to close the energizing circuit l9 and start the heating of the glow plugs l'l. Energization of the heating coil 42 is also started immediately but such energization is required for an interval from a minimum of about ten seconds when the ambient is approximately at room temperature to a maximum of about forty-five seconds when the ambient is at a very cold temperature. This interval of energization required to operate the relayi. e., to close the switch arm 43 with an associated semistationary arm is referred to as its operate time. It is this operate time of the thermal relay 44 that determines thepreliminary period of heating of the glow plugs before the starter I3 is put into operation, as will be herein next understood.

The semistationary switch arm 50 of the relay M is connected by a lead 5| to one of the pair of contacts 33. The other of this pair of contacts is connected by a lead 52 to a terminal 53 and this terminal is connected by a lead 54 to one end of the coil of the starter control relay 20, the other end of this coil being grounded at 55. This circuit from the switch arm 58 to ground 55 is a start-stop control circuit for the starter I3. Upon the operator continuing to hold the switch 28 in its On position after the key switch 25 is turned on-which he is to do until the engine is startedthe contacts of the thermal relay 44 will close at the expiration of the operate time of this relay and will thereby connect the starter control relay 20 across the battery 22 to cause the energizing circuit l5 to be closed and the starter 13 to be put into operation. When the engine starts running, the operator will remove his hand from the knob 3'5 to allow the spring 3'! to return the push switch 28 to Off position. Since the contacts 33 are opened as the push switch is so returned, the energizing circuit of the starter control relay 28 is immediately broken and the starter I3 is stopped. It is desired though that the glow plugs be kept energized for a short interval after the engine has started in order to assure continued running of the engine. For this purpose an energizing circuit for the relay 2| is maintained after the push switch 28 is released so long as the contacts of the thermal relay M are closed. The interval during which continued energization of the glow plugs is desired is typically about twenty seconds. Accordingly, the thermal relay 44 is chosen to have a release time of this length of interval. This continued energizing circuit for the relay 2| is completed by way of a contact 56, which makes with that one of the contacts 30 connected to the lead 5| when the push switch 28 is released, and a resistor 51 connected to the lead 46. The time of engagement of the contact 56 with the contact 30 just mentioned is to overlap momentarily the time of bridging of the contacts 30 by the respective bridging member 32 as the push switch 28 is released. Since the contacts 29 are interconnected during this interval an energizing circuit for the relay 2| is maintained continuously as the switch 28 is released. For instance, when the knob 36 is fully depressed the energizing circuit for the relay 2| is by way of the heating coil 42 and contacts 29. During the mentioned momentary time overlap as the knob 36 is released, the energizing circuit for the relay 2| is completed both by way of the circuit just mentioned and by way of the circuit including the switch arms 435- l, contacts 3056 and the resistor 51; and when the knob 36 is fully released the energizing circuit is only by way of the latter circuit. The resistor 52' is included as a voltage cut-down resistor to limit, among other things hereinafter explained, the current to the relay 2| during the release time of the relay 44 following the return of the switch 28 to Off position.

Because of the momentary bridging of the contacts 30 while one thereof is connected to the contact 56, there is a momentary circuit set up, as the push switch 28 is depressed, to supply current to the starter relay 20. This circuit is from the battery 22 by way of the leads 40 and 38, switch 26, coil 42 of the relay 44, contacts 29, resistor 51, contact 56, contact 30, and the leads 52 and 54 to the starter relay 29. This is an undesired circuit and in order that the current therein will not be sufiicient to operate the relay 20 the resistor 51 is made large, say several times the'resistance of the coil 42. The use of such relatively large resistance will however not prevent the relay 2| from being held operated, after the push switch 28 is released, by the circuit hereinbefore described including the contact 56 and resistance 51, since the current required to hold the relay 2| operated is approximately only 30% of the current required to operate the relay.

An important feature of the apparatus hereinabove described is that the operate time of the thermal relay 44 varies with the ambient temperature to cause the preliminary heating of the plugs to be longer when the ambient temperature is colder, and vice versa. Thus, the thermal relay controls the preliminary heating period so .as to tend to bring the immediate vicinity of each plug always to a proper temperature for igniting the fuel-air charges to the respective cylinders in all seasons of the year before the starter I3 is put into operation.

In the event that the engine is already at a proper starting temperature when the key switch 26 is turned on, a thermostat 5 8 is provided and arranged to cause the starter l3 to be put immediately into operation. This thermostat is placed at any suitable place in or on the engine as, for instance, in a well 59 of the engine block. The thermostat is arranged to be open at cold temperatures and to close when the temperature of "the engine block reaches a threshold value at or above which the engine will readily start when turned over by the starter l3. One switch arm of this thermostat is connected to the battery 22 by way of the leads 4D and 38, the key switch 26, and a lead 64. The other switch arm of this thermostat is connected by a lead 65 to a terminal 65 of the control unit 24 and thence by a lead 61 to one of the contacts 3|, the other of these contacts being connected by a lead 69 to the leads 52 and 54 running to the starter control relay 20. Thus, if the thermostat 58 is closed an energizing circuit for the starter relay 29 is provided as soon as the key switch 26 is turned on and the push switch 28 is depressed.

In a modification of the push switch 28 shown in Figure 2 and now referred to as 28a, one of the bridging members 32athe one associated with the contact pair 29is carried by a pin 69 which is slidably mounted in a bar 33 for movement relative thereto in directions of movement of the plunger 34. This pin 69 has a head 6| on the end thereof and between this head and the bar 33 there is a compression spring 62 which normally holds the bridging member lightly against the bar 33. The bridging member 32a is shorter than the other bridging members 32 so that, when the switch 28a. is moved to On position, it will not interconnect the associated contacts 29 until after the contacts of the pairs 39 and 3| are respectively interconnected. When the switch 28a is in fully On position, the bridging member 32a is gripped releasably by the contacts 29 engaging an annular groove 93 of this bridging member. By so gripping the bridging member 32av the same is held momentarily between the contacts 29 as the switch 28a is released, with the spring 92 being compressed, until the other bridging members 32 are fully disengaged from the respective contact pairs 39 and 3|. The advantage in so delaying the interconnecting of the contacts 29 until after the contacts of the pairs 30 and 3| are bridged by the respective bridging members, as the switch 28a is moved to On position, is that the contact 56 is disengaged from the associated contact 30 before the contacts 29 are interconnected, with the result that the momentary leakage circuit to the starter relay 2|], hereinbefore described, no longer exists. The advantage in delaying the breaking of the contacts 29 from each other until after the contacts of the pairs 39 and 3| are respectively broken is that the contact 59 is reengaged'with the associated contact 30 before the contacts 29 are broken and thus there is provided a continuous energizing circuit for the glow-plug control relay 2| as the switch 28a is released. For instance, during the initial partof the release movement of the switch 28a the energizing circuit for the relay 2| is completed by way of the coil 42 and contacts 29, and dur ing a latter portion of this initial part of the release movement and during the remainder of the release movement of the switch 280. an energizing circuit for the relay 2| is completed by way of the switch arms 43-59, contacts 3|l-.5 6 and resistance 51. Since there is in this .arrangement no possible leakage circuit to the starter control relay 29, the resistance 51 may have a smaller value than that above described typically, a value equal approximately to the effective resistance of the coil 42so that normal energizing current for the relay 2| is maintained during the release time of the thermal relay-44 following the release of the switch 28a. to Off position.

The second embodiment of my invention, shown in Figure 3, differs from my first embodiment principally by a rewiring of the circuit in the control unit 24. In describing this second embodi- -ment, those parts and components which are the same as in my first embodiment are given the same reference characters, those parts which have been modified but which are still similar to the corresponding parts of the first embodiment are given the reference characters of the latter increased by IOU, and those parts which are entirely new are given new reference characters.

The control unit, now referred to as I24, com.-

, prises the key-operable master switch 26, a

modified push-operable switch I28 and the nor:- mally-open thermal relay 44. The switch I28 differs from the foregoing switch 28 of my first embodiment by having a bridgin member |32 associated with the contacts 3|, which is shorter than the other two bridging members 32. The purpose of this modification in the multiple switch is to delay the closing of the contacts 3| until the auxiliary contact 56 has broken with th associated contact 39 as the push button 36 is depressed, and to open the contacts 3| before this auxiliary contact re-makes with the associated contact 30 as the push button 36 is released, the reason for this action being hereinafter fully explained.

When only the master switch 26 is closed, no circuit of thestarting system is normally completed, an exception being when the thermal re lay 44 is closed. This exception will normally not occur unless the master switch is closed while the thermal relay is still under the heating influence of the starter l3 from a previous starting attempt. However, as the button 39 is next depressed, the glow-plug control relay 2| is energized as soon as the contacts 30 are bridged by the member 32 by way of the circuit leading from ground 23 through battery 22, lead lines 49 and 38, switch 26, lead line 19, contacts 39 by way of bridging member 32, lead lines 1| and 48, and the relay 2| to ground at 49. As soon as the coilof the relay 2| is energized it closes the line ill to supply heating current to the glow plugs from the battery 22-. With the closing of the contacts 29, which occurs simultaneously as the contacts 30 are closed, the heater winding 42 or the thermal relay 44 is connected in shunt with the coil of the relay 2| by way of the lead line: 46, the contacts 29=and respective bridging member 32, a lead line 12, the heater winding 42: and a. lead line 13 to ground at 14. Thus, the heater winding of the thermal relay 44 is energized as soon as heating currentis supplied to the glow plugs. By placing the heater winding 42 in parallel with the coil of the relay 2|, the heater winding and relay coil can be designed independentl of one another for most efficient operation in the system.

As: is true with my first embodiment, the operator is to hold the button 36. depressed until the starter. I3 is put into operation and the engine is running under its own power. The energization of the starter |-3 occurs at the expiration of. the'operate time of therelay 44. For instance, when the contacts 43 and. 5|] of the thermal relay "are closed, an energizing circuit for the starter control relay 20 is closed by way of the battery 22 through the master switch 26, the contacts 43 and 50, the lead lines 15 and 61, the contacts 3| through the bridging. member |32, and the lead line 53 to the coil of the relay 23.

It is normally desired, as explained hereinbefore in connection with my first embodiment, that the glow plugs remain energized after the push button 36 is released until the engine runs smoothly under its own power. For this purpose, the auxiliary contact 56 is closed with one of the contacts 30 when the push button 36 is released and is disconnected from this contact 30 when the push button is depressed. After release or the push button 36, and until. the bimetal strip of the thermal relay 44 is cooled sufficiently to open the contacts 43 and 50, the glow-plug control relay 2| is kept energized by way of the circuit leading from the master switch 26 through the thermal relay 44, a lead line '16 serially including a normally-closed thermostat Tl hereinafter explained, the contacts 56 and 30 and the lead lines H and 48 to the coil of the relay 2|.

In order that there will not occur any momentary interruption in the energization of the relay 2| as the push-button 36 is released, the

auxiliary contact 56 is adapted to make with the associated contact 30 before the associated bridging member 32 breaks with the contacts 30-. There is accordingly an instant, when the push-button 36' is depressed, wherein both contacts 30' are interconnected by an associated bridging member 32 and one of these contacts is concurrently connected to the auxiliary contact 56. In order that at this instant there will not occur a momentary energization of the starter control relay 2|) by way of a circuit leading from the master switch '25 through the lead line 1|], contacts 303il through bridging member 32, contact 5.6, lead line 16, thermostat '11, lead lines 15 and 61, contacts 3| through the respective bridging member I32 and the lead line 53 to the starter control relay, the bridging member |32 associated with the contacts 3| is made shorter than the other bridging members 32, to prevent the contacts 3| from being closed until the auxiliary contact 56 is broken with the associated contact 30, as hereinbefore explained. There is accordingly in this embodiment a complete avoidance of any leakage current to the starter relay.

The temperature-time delay characteristic normally required of the thermal relay 44' is such that the contacts 43-58 are open under all ambient temperatures encountered in the field. However, sometimes it is desired to have such fast-decreasing time delays with rising ambient temperature that the contacts 43-58 will close at the higher ambient temperatures sometimes encountered in the field. This would mean that at these higher ambient temperatures the glow plugs would be energized continuously so long as the master switch 25 is closedby way of the circuit leading from the switch 26 through the thermal relay 44, lead line 16, contacts 56 and 30 and the lead lines H and 48-unless some preventive device is provided. Such preventive device is the thermostat TI serially included in the lead line '16. This thermostat is arranged to be open at all temperatures above the ambient temperature at which the thermal relay closes; pref erably, for safety reasons, the thermostat should be open also through a small temperature range, say 10 F., extending below the closing temperature of the thermal relay 44. Thus, if the master switch 26 is closed when the ambient temperature is at or above the closing temperature of the thermal relay; no immediate action will take place. However, on next depressing the pushbutton 36, the starter relay 28 will be immediately energized to cause the starter it to crank the engine, theenergizing circuit for the starter relay being through the thermal relay 44, lead lines 75 and 61, contacts 3| through the bridging member I32, and the lead line 53 to the relay 2!]. This energizing circuit of the starter relay 23 is however broken by the opening of the contacts 3| as soon as the switch button 36 is released. This is permissible. since it is generally unnecessary to maintain the glow plugs heated after the engine has started when the ambient is at the high temperature just mentioned.

At ambient temperatures in the range between the opening temperature of the thermostat H and the closing temperature of the thermal relay 44, a short time interval equal to the operate time of the relay 44 will transpire after the button 36 is depressed before the starter relay 23 is energized, this being the same whether or not the thermostat is open or closed; however, with the thermostat I! being now open the energization of the glow-plug control relay 2| is stopped immediately as soon as the push button 36 is released. This, likewise, is permissible when the ambient is in this higher temperature range.

To take care of the requirement of immediate starting, when in cold weather the engine is at operating temperature, another thermostat '58 is mounted in a water jacket or well 59 of the engine, as hereinbefore explained in connection with my first embodiment. This thermostat closes when the engine reaches a temperature at which it can be started satisfactorily without the help of the new plugs. When this thermostat is closed, the coil of the starter relay 28 is energized, to cause the engine to be cranked, as soon as the master switch 26 is closed. and the button 36 is depressed, the starting circuit being by way of the switch 26, lead line It, contacts 3|! through the bridging member 32, lead lines H and 48, a lead line 18, thermostat 58, lead lines and 61, contacts 3i through the bridging member I32 and the lead line 53 to the starter relay 28.

The embodiments of my invention hereinabove described are intended to be illustrative and not limitative of my invention since the same are subject to changes and modifications without dethe combination of an on-off control means;

means rendered effective by said on-off control means when the same is placed in On position for energizing said glow plug; timing means connected to said on-ofi control means for energization when the control means is in On position, said timing means being adapted to be moved to an operated position at the expiration of a predetermined interval of energization thereof; and start-stop means for said starter operably including said on-off control means and said timing means and effective to render said starter operative when said on-ofi control means is in On position and said timing means is simultaneously in its operated position.

2. The combination set forth in claim 1 wherein said timing means is responsive to ambient temperature to cause said time interval of energization of said glow plug to be longer for colder ambient temperatures than it is for warmer ambient temperatures.

3. The combination set forth in claim 1 wherein said on-off control means comprises two independently-operable on-ofi control devices, and wherein said glow plug is energized and said timing means is put in operation only when both of said control devices are placed in their respective On positions.

4. The combination set forth in claim 1 including a thermostat thermally associated with said engine and operatively connected with said startstop means for causing said starter to be put immediately into operation upon said control means being placed in On position while the temperature of said engine is above a predetermined threshold value.

5. In a control system for starting a Diesel engine including a glow plug for igniting the fuel-air charges to a cylinder of the engine when the engine is cold, and a starter for the engine: the combination of a key-operable on-oif control device; a push-type on-off control device biased into Off position; means controlled by said control devices to cause energization of said glow plug when both of said devices are in respective On positions; a timing device; means for energizing said timing device when both said control devices are in respective On positions, said timing device being adapted to operate at a time interval following the start of energization thereof; and means controlled jointly by said timing device and said push-type control device and effective when said push-type control device is held in On position and said timing device is operated to render said starter effective.

6. In a control system for starting a Diesel engine: the combination of a glow plug for igniting the fuel-air charges to a cylinder of said engine when the engine is cold; an electric starter for said engine; a switch device operable into On and Off positions; a multiple switch device normally held in Off position; a thermal relay adapted to operate at a time interval following the start of energization thereof; circuit means controlled by said switch devices for supplying energizing current both to said glow plugs and to said thermal relay while both of said 10.. switch devices are in 011 positions; and circuit means, rendered effective by said thermal relay at the instant of operation thereof, for placing said starter in operation.

7. The combination set forth in claim 6 in-" cluding a thermostat associated with said engine and closed only when the temperature of the engine is above a predetermined threshold value, and a circuit including said thermostat and a switch element of said multiple switch device for causing said starter to be put in operation when both of said switch devices are in respective On positions and the temperature of said engine above said threshold value. I

8. In a control system for starting a Diesel engine including a glow plug for igniting the fuelair charges to a cylinder of the engine when the engine is cold, and a starter for the engine: the combination of a first relay controlling energization of said glow plug; a second relay for controlling energization ofsaid starter; a switch device operable into On and Off positions; a multiple switch device normally held in Off position; an energizing circuit for said first relay rendered closed by said switch devices only when the same are in respective On positions; a thermal relay having a heating coil arranged in said system to be energized when both of said switch devices are in respective On positions, said thermal relay having a pair of contacts adapted to close at the expiration of a time interval following the start of energization thereof; and a circuit including said contacts and a switch element of said multiple switch device for sup-- plying current to saidsecond relay to place said starter in operation at the'expiration' of said time interval following operation of both of said switch devices into respective On positions,

said last-stated circuit being opened to cause said starter to be rendered inoperative upon releaseof said multiple switch device.

9. The combination set forth in claim 8 com prising another circuit including said contacts and a switch element of said multiple switch device for supplying energizing current to said first relay while said contacts are closed and said multiple switch device is in 01f position; and thermostatic means responsive to ambient temperature and associated with said last-stated circuit for disabling this circuit when the ambient temperature is above a predetermined value.

10. The combination set forth in claim 8 where'- in said energizing circuit serially includes said heating coil of said thermal relay, comprising a second energizing circuit for said first relay, said second energizing circuit excluding said heating coil and including said relay contacts and the second pair of contacts of said multiple switch device, said second pair of contacts being closed when said multiple switch device is in Off position, and said switch device being adapted to cause both said first and second pairs of contacts thereof to be closed momentarily at the same time as said switch device is moved between Off and On positions.

11. The combination set forth in claim 8 including a thermostat associated with said engine and closed when the temperature of the engine is above a predetermined value; and including another circuit for supplying current to said second relay, said other current-supplying circuit being rendered closed only when both said switch devices are in respective On positions and said thermostat is closed.

12. In a control system for starting a Diesel amazes engine including a glow plug for igniting the fuel-air charges to a cylinder of the engine when the: engine is cold, and a starter for the engine: the combination of a first relay controlling energization of said glow plug; a second relay for controlling energization of said starter; a switch device key-operable into On and Off positions; a push-type switch device normally held in Oil position and including three pairs of contacts respectively closed when said switch device is held in On position; a thermal relay having a heating coil and normally-open contacts said relay being adapted to close said contacts at the expiration of a time interval follow ing thestart of energization of said heating coil; an energizing circuit for said first relay andheating coil of said thermal relay, said energizing circuit serially including said key-operable switch device and a pair of contact of said push-type switch device; an energizing circuit for said second relay serially including said contacts of said thermal relay and a second pair of contacts of said push-type switch device; a thermostat as sociated with said engine; and a second energizing circuit for said second relay serially iii-- eluding said key-operable switch device, said thermostat and a third pair of contacts of said push-type switch device.

13. In a control system for starting a Diesel engine including a glow plug for igniting the fuel-air charges to acylinder of the engine when the engine is cold, and a starter for the engine: thecombination of a first on-ofi master control device; a second on-ofi auxiliary control device; means rendered effective when both of said con trol devices are in respective On positions tocause energization of said glow plug; timing means adapted to move to operated position at the expiration of a first interval of energization thereof and to return to unopera pos on t the expiration of a second interval following the stopping of the energization thereof; means for energizing said timing means as both of said onofi control device are moved to On positions; start-stop means for said starter operatively including said timing means and both of said onoil control devices, said start-stop means being adapted to render said starter operative. when both-of said on-off control devices are in On positions and said timing means is in operated position, and to stop said starter as said second control device is moved to .Ofi" position; and means controlled jointly by said timing means and said control devices for maintaining energization of said glow plug following return of said second control device to Ofi position until said. timing means is restored to unoperated position.

14. The combination set forth. in claim 13} in-- cluding thermostatic, means, responsive to the ambient temperature and operatively associated latter when the ambient temperature is above a predetermined value.

15. In a control system for starting a Diesel engine including a glow plug for igniting the fuel-air charges to a cylinder of the engine when the engine is cold, and a starter for the engine: the combination of a first relay controlling energization of said glow plug; a second relay for controlling energization of said starter; a switch device key-operable into On and Off positions; a push-type switch device normally held in Ofi position and including three pairs of contacts respectively closed when said switch device is held in On position; a thermal relay having a heating coil and normally-open contacts, said relay being adapted to close said contacts at the expiration of a time interval following the start of energization of said heating coil; an energizing circuit for said first relay and heating coil of said thermal relay, said energizing circuit serially including said key-operable switch device and a pair of contacts of said pushtype switch device; and an energizing circuit for said second relay serially including said contacts of said thermal relay and a second pair of contacts of said push-type switch device.

16. In a control system for starting a Diesel engine including a glow plug for igniting the fuel-air charges to a cylinder of the engine when the engine is cold, and a starter for the engine: the combination of a first switch device; a. second switch device biased into open position; an energizing circuit for said glow plug controlled by said switch devices and rendered closed when both of said devices are in respective closed positions; a currcnt-energizable timing device including a. switch operable into. closed position atv the expiration of a first time interval of energization of said timing device and into open position at the expiration of .a second time interval following stopping of .energization of .said timing device; an energizing circuit for said timing device rendered closed when both of said switch devices are in respective closed positions; circuit control means serially including said time-operated switch and switch contacts. of both of said switch devices for placing said starter in operation at the. expiration of said first time interval following the closing of both of said switch devices and for stopping said starter upon release of said second switch device; and circuit means including said time-operated switch for maintaining energization of said glow plug for the duration of said econd time interval following said release of said second switch device.

GUSTAVE D. CERF.

No references cited.

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