US1876809A - Air starting system for internal combustion engines - Google Patents

Description

Sept. 13, 1932. w, W 1,876,809

AIR'STARTING SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed .March 11. 1926 I am re pus/7 r0 INVENTOR a 5M qzwwfi ATTORNEYS Patented Sept. 13, 1932 ire STATES PATENT OFFICE j WILLIAM HARD, F GROTON, CONNECTICUT, ASSIGNOR TO ELECT-341C BQAT. 0F GRO'ION', CGNN'ECTIECUT,.A CORPORATTQN OF JERSEY V A B STAR N E013 INTERNAL QMBIISTION App ication at. Maren 11. 192.6. sena no. 93.8.89.

This invention relates to internal combustion engines and has to do more particularly with mechanism for starting engines of the heavy duty type of which the Diesel engine is an example. i

In such engines, the moving masses are so large that provision must be made for getting the engine approximately up to speed before ignition takes place, and it is customary to provide means by which the engine may be operated by compressed air during the starting period. Ordinarilya separate, starting valve is provided, the operation of which is accomplished by means of a separate cam on the ma n cam shaft of the engine. 7 When the engine is to be started, starting air, is introduced into the cylinder above the piston through the valve, and the piston is forced downwardlyin the usual way, the admission of starting air at the appropriate inst-ant being controlled by the starting valve, and the air exhausting through the usual exhaust valve. The actuation of the starting air valve by means ofa separate cam somewhat complicates the design of the engineand addsuto the cost of construction but heretofore this has. been standard commercial practice.

The object of the present invention is to simplify the engine with reference particularly tothe startingmechanism and in an engine in which the invention'is embodied the cam by which the combustion air inlet valve is actuated serves also to actuate the valve controlling the admission of air used in starting. In the new starting apparatus, mechanism is provided by which the starting air valve is opened and closed at the appropriate instants, and the mechanism is such that it may beautomaticallyrendered operative by the action of the air used for starting. Accordingly, when the engine is tobe put into operation, the attendant simply opens a single valve controlling the supply of starting air, and the engine begins to. turn over. Then the engine is movingapproximately at normal speed, the starting air is cut oft, and normal fuel operation is begun. Immediately upon'the cutting 0110f; the-starting air, the starting mechanism is rendered" inoperative automatically and remains idle until another starting operation is to. begin."

In another form of embodiment of the invention, the starting mechanism is put into operation when desired by the attendant. In this form connections are provided by which the openiing' by the attendant of thecontrol valve'for the starting air places the starting mechanism in operative position.

I For a better understanding of the invention reference may be made" to the accom panying drawing; in which Fig. l is a see- ;tional View, largely diagrammatic, showing the starting valve and its actuating mechanism in-the"positions they assume during the working periods of the engine Fig. 2 is a, detail view in elevation of certain 01* the parts shown in Fig. "1; Fig. 3 is a view: similar to Fig. 1', in which the parts are int-he positions they assume when the engine isabout to be started -Fig. 4: is a view similar to Fig. 3', but 7 showing the parts, in the positions they as: sume at a later point in the cycle; Fig, 5 is a view showingthe combustion 'airfinlet cam profile and indicating that'part of the cam used for starting purposes; Fig. 6. is

aview similar to Fig. 1 showing mechanical meansv for bringing the starting mechanism into action and Fig. 7 is a view similar to Fig; 6 showing the parts in slightly altered position.

Upon reference to the drawing, the mechanism for starting will be seen to include a rocker arm 10 pivotally mounted on a pin 11 in a bracket 12 secured ,to. a convenient part of the engine. The rocker arm 10, car

'ries a roller 13 at one end which may ,ride

on the usual cam 14 for actuatingthe'combustion air inlet valve of the engine. The

'combustion'air inlet valve (not shown) is of the usual type and is operated .by a. push rod 15 having a roller 16 riding on'the cam 14:. The cam is fasten the usual cam shaft 17 driven from the main shaft of the engine in any convenient manner.

The rocker arm 10 is preferably formed with a tubular central portion 18 enclosing the pin 11 and theextension' 19 therefrom near one end carries the roller 13. Anextension 20 from a point near the other end 0f the central portion has a seat 21 in which may rest the end of a push rod 22 which carries the starting air timing valve 23 on its other end, this arrangement being desirable to render the parts accessible. The air timing valve 23 lies in a chamber 24 of a casing 25. In this casing is a chamber 26 which receives the starting air from a tank (not shown) through the conduit 27, the flow through which is controlled by the starting air supply valve 28, manually operated. The air timing valve 23 extends through chamber 26 into chamber 24 and may be seated to close the port 29 through which the chambers are in communication. The air timing valve 23 carries a cylindrical member 30 spaced from the head, the end of this member lying within the chamber 26. The area of this end of the member is greater than the under surface of the head and the head and member together form an unbalanced air timing valve, such that, upon introduction of air under pressure into the chamber 26 from the line 27, the air acting on the unequal surfaces of the air timing valve 23 will tend to force this valve downwardly, closing the port 29 as shown in. Fig. 3. Such movement of the valve 23 is resisted by the spring 31, encircling the push rod and bearing at one end against a collar 32 fast on the rod and at the other against the .cam shaft housing 33.

From the chamber 24, a passage 34 leads to the interior of the cylinder represented at 35. A port 36 in a Wall of the chamber 24 affords communicationtothepassage,andavalve consisting of a head 37 and a stem 38 prevents the return flow of air through the port 36. The head 37 of the valve lies in the passage, and the stem 38 extends across the chamber 24 and through the opposite wall thereof. A spring 39 encircling the exposed part of the stem bears at one end against an adjustment nut 40 on the end of the stem and at the other against a bushing 41 threaded into the wall of the chamber, the stem passing through the bushin The spring 39 normally holds the valve 3! seated to close the port and the bushing 41 contains suitable packing to prevent the escape of air around the stem.

The mechanism is shown in Fig. 1 with the parts in their inoperative positions. The starting air timing valve 23 is off its seat, the push rod 22 being forced upwardly by spring 31, and the roller 13 is out of contact with the cam 14, the rocker arm being balanced so that it will assume this position when free to do so. When the engine is to be started, the a tendant opens the air valve 28, and air flows into chamber 26, forcing the unbalanced starting air timing valve downwardly a slight distance until the roller 13 bears against the high point of the cam 14. In this position of the valve the port 29 remains open as shown in Fig. 4 and air flows through chamber 26 and port 29 into chamber 24,

where it unseats valve 37 and flows through the passage 34 into the engine cylinder. The air acts on the piston 35 forcing it downwardly, which causes the main shaft to turn, and to cause a rotation of the cam shaft which will bring a low point on cam 14 in contact with the roller 13. hen this happens, the unbalanced forces on the air starting timing valve result in the valve seating to close port 29 as shown in Fig. 3, thus cutting off the flow of air to the cylinder and exhaust takes place. When the cam shaft returns to the position shown in Fig. 1, the air starting timing valve is again opened to admit starting air to the cylinder and the cycle of operations is repeated.

Directly after fuel operation of the engine begins, the starting air supply valve 28 is closed, and as the air pressure within the chamber 26 is dissipated, the air starting timing valve is held open by spring 31, the roller 13 lying free of the cam 14. Return flow of gases through the passage 34 during operation of the engine is prevented by valve 37. This valve 37 also prevents increase in the clearance volume of the working cylinder during the operation of the engine, which would occur if this valve were not present because the engine cylinder would be in direct connection with chambers 24 and 26 and pipe 27 when valve 23 is open. Valve 37 is held seated by its spring 39 at all times except when valve 23 is openduring the starting period.

During the following revolution of the cam shaft, after the starting air supply valve 28 has been closed, the valve 23 is opened by cam 14, thus connecting chamber 24 with chamber 26 and pipe 27 and causing the starting air to flow from chamber 26 and pipe 27 with a consequent drop in pressure. During the next intake or exhaust stroke of the engine piston, the pressure in the cylinder falls .below the pressure of the air in chamber 24 so that Valve 37 is overbalanced by the starting air to allow this air to flow into the engine cylinder. This process is repeated until the air pressure is equalized and spring 39 closes valve 37 and spring 31 holds valve 23 open. This condition obtains in several revolutions of the cam shaft and takes place so rapidly as to be undiscernible.

In the form of embodiment of the invention illustrated in Figs. 6 and 7 the device is manually brought into operation at the same instant that the starting air supply valve 28 is opened. It includes the rocker arm 10, the bracket 12 and the roller 13 which may ride on the usual cam 14 for actuating the inlet valve of the engine. A pivot pin 42 is mounted eccentrically in bracket 12 and has a lever 43 mounted on one end. This lever 43 is connected by a link 44 to the operating lever 46 of the starting air supply valve 28. The push rod 22 carries at its end a valve 23 mitted to chamber 26 through conduit 27 by the attendant opening valve 28, the rocker arm 10 is raised into contact with cam 14 and when valve 28 is closed the rocker arm is lowered out of contact simultaneously. In the operative position of the rocker arm, the valve 23 is held on its seat by spring 45 and prevents return flow of gases from the cylinder during the running of the engine.

The starting apparatus may be used either with single or multi-cylinder engines of the four-cycle type. In multi-cylinder engines, when the engine comes to rest, there will ordinarily be one inlet cam in a position such that it will hold the valve 23 off its seat when air is admitted to chamber 26 through valve 28. In single cylinder engines, it may be necessary to jack the engine over in the usual way to the desired position before starting.

In Fig. 5 there is shown a profile of the inlet cam, showing the portions of its profile used for actuating the combustion air inlet and starting air valves. The cam is so arranged that it holds the combustion air inlet air valve open through a portion of its surface equal to about 112 /5 of its revolution while the starting air valveis held open through about of the revolution of the cam. The rollers through which the valves are actuated engage the cam about 180 apart.

With this arrangement, during the suction stroke of the engine piston, the combustion air inlet valve is held open from a point about 22 prior to top center to a point about 22 beyond bottom center,- or through an arc of 225 of crank shaft travel corresponding to 112 of cam shaft travel. The compression stroke continues from this point to a point 20 following the next top center position, or through an arc of 177 equivalent to 88 of cam shaft travel. The explosion stroke during which the, starting air valve is open corresponds to 140 of main crank shaft travel, equivalent to 7 0 of cam shaft travel, and the exhaust valve opens 20 prior to bottom center and remains open while the crank shaft travels 17 7 equivalent to 88 ,4 of cam shaft movement. With this arrangement, a very eflicient eflort is obtained and the starting air is used with great economy.

I claim:

1. In an internal combustion engine having an inlet valve, the combination of a cam shaft, a cam thereon for operating the inlet valve of the engine, a chamber, a normally closed starting air valve between the chamber and the cylinder, an air-line leading to the chamber for supplying starting air, a secon starting air valve controlling the flow of air from the air-line to the chamber, a piston rigidly connected with said second starting air valve, the movement of said piston and said second starting air valve being controlled by air pressure in the line, and connections between the piston and the cam, effective upon air pressure being admitted to the air-line, to cause said cam to open the second starting air valve, said first starting air valve being opened by air pressure in the chamber.

2. In an internal combustion engine having an inlet valve, the combination of a cam shaft, a cam thereon for operating the inlet valve of the engine, a chamber, a normally closed Y starting air valve between the chamber and the cylinder, an air-line leading to the cham-- ber for supplying starting air, an unbalanced valve controlling the flow of air from the air-line to the chamber comprising a piston rigidly connected therewith, said valve being normally held open, the movement of said unbalanced valve being controlled by air pressure in the line, and connections between the piston and the cam, effective upon air pressure being admitted to the air-line, to cause said cam to open the unbalanced valve, saidfirst mentioned air valve being opened by air pressure in the chamber.

In testimony whereof I aifix my signature.

WILLIAM WARD.

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