US2090342A - Starting apparatus for internal combustion engines - Google Patents

Description

Aug. 17, 1937. 2,090,342

STARTING APPARATUS FOR INTERNAL COMBUSTION ENGINES A. CALLSEN Filed March 23, 1936 Patented Au 17, 1937 STARTING APPARATUS FOR-INTERNAL COMBUSTION ENGINES Albert Callsen, Stuttgart, Germany, assignor to Robert Bosch Aktiengcsellschaft, Stuttgart,

Germany Application March 23, 1936, Serial No. 70,466 In Germany April 5, 1935 4 Claims.

The present invention relates to starting apparatus for internal combustion engines, wherein the pressure produced in a cylinder by explosion gases acts on a piston, which rotates a driving 5 member, for instance a'dog or claw, which can be brought into engagement with a part of the engine to be started.

In apparatus of this kind the difficulty exists in that the thrust of the piston produced by the explosion gases. for instance, from a cartridge, is greatest directly after the explosion, whilst the acceleration of the masses, such as the crank-shaft and pistons. in the engine is greatest on being started from rest. Accordingly the torque required to be exerted by the driving member is greatest at the instant of starting. Too great a strain on the parts of the piston and driving member which transmit the pressure of the gases from the piston to the driving memher can be avoided by making the lever arm,

with which the piston acts on the driving member, large. This necessitates, however, a large piston stroke and thus a great increase in the cost of the apparatus and the driving medium.

If the lever arm is made small, the power-transmitting parts such as a toothed pinion and rackbar or a traction. cord, cannot withstand the stresses.

These drawbacks are avoided according to the invention, by varying the lever arm thrust of the piston on the driving member, the said lever arm thrust being greater at the beginning of the starting operation than in the succeeding rotary movement of the driving member.

Twoexamples of construction of the invention are diagrammatically shown in the drawing, in which: A. v Figure 1 shows a starting apparatus partly in section.

Figure 2 is a section on the line 2-2 of Figure 1.

Figure 3 shows the position. I

Figure 4 shows a second form of construction.

apparatus in a special i, in which is a piston 2, which is moved by compressed gases, that can be produced, for instance, by firing a cartridge. To the piston is connected a toothed rackbar 3 which on the forward stroke of the piston comes in engagement with a toothed pinion 4. This toothed pinion is keyed on a hollow shaft 5, which is mounted in bearings H in the gear-box 9, and in this hollow shaft a clutch-dog 6 is longitudinally movable but prevented from rotating.

The starting apparatus consists of a cylinder Stops I are provided on the toothed pinion, on which stops a driving member I can act, the said driving member being formed as a yoke, which is rotatably mounted on the hollow shaft 5, and

engages over the pinion. An extension I! provided at the free end of the rackbar acts on the yoke, and projects in the direction of movement of the rackbar so far beyond the teeth thereof that on the forward stroke of the piston the extension bears on the yoke before the teeth on the rackbar engage in the pinion. A stop III is provided on the gear-box 9 to limit the rotary movement of the yoke.

The apparatus works in the To start the crank-shaft II, the driver puts thedog 6 into engagement with the dog ii of crank-shaft. He then explodes a cartridge, inserted in the chamber i3. The compressed gases evolved by firing the cartridge drive the piston 2 forward in the cylinder. On this movement of the piston, the extension l2 of the rackbar 3 first acts on the yoke 8, which by means of the stop 1 transmits the force exerted on it to the toothed pinion I and the dog 6 coupled thereto. After a rotation of the pinion and yoke, of say the teeth of the rackbar come into engagement with the pinion 4, while the extension i2 thus comes out of enga now the force of the pi slides past over the yoke, and

gement with it, so that ston is conveyed to the pinion only by the teeth of the rackbar. After the full stroke of the piston 2 (Figure 3) the pinion 4 has made a full rotation. The spring l6 arranged in the cylinder force's back the piston 2, and thus at the 4 and the yoke same time the pinion 8, into its initial position.

The maximum point of torque in the starting of an engine by compressed gases lies in the region of the first quarter revolution of the crank-shaft. In this re gion the piston acts on the dog 6 with the large lever arm of the yoke 8. After passing this point the torque quickly drops, because the acceleration of the masses in the engine slackens. now be transmitted by and the toothed pinion This smaller torque can the teeth of the rackbar without the strain 0 the teeth reaching an injurious degree.

In Figure 4 a second is shown. In this, instead a drum II is employed example of construction of a toothed pinion, round which a cord ll following way:

with the lever 8, the whole thrust of the piston is transmitted only'by the cord and the spring.

The advantage of the invention is that, without overloading the transmission members (teeth), the size of the cylinder can be kept small and thereby the starting apparatus can be made cheaply and is serviceable in practice,

I declare that what I claim is:

4 1. A starting apparatus for internal combustion engines comprising a pinion adapted for coupling to a moving part of the engine to be started, a lever, pin means on said pinion for engagement by said lever to couple said lever with said pinion a cylinder, a piston displaceable in said cylinder for starting said engine, a rack bar carried by said piston and means projecting beyond the free end of said rack bar to engage with said lever at a part farther away from the axis of said pinion than the point of inter-engagement of the teeth of said rack bar with the teeth of said pinion.

2. Astarting apparatus for internal combustion engines comprising a pinion adapted for coupling to a moving part of the engine to be started, a yoke shaped lever pivotally mounted about the axis of said pinion, pin means carriedv by said lever to rotate said pinion on angular displacement of said yoke shaped lever, a cylinder, a piston displaceable in said cylinder for starting said" engine, a rack bar carried bysaid-piston and means projecting beyond the free end of said.

rack bar to engage with said lever at a part farther away from theaxis of said pinion than the to couple said pinion therewith, a cylinder; a

piston displaceable within said cylinder for starting. said engine, a rack bar carried by said piston and an extension of said rack-bar which projects forwardly beyond the free end of said rack bar in the direction of thrust of said piston and is located at a greater distance from the axis of said pinion than the teeth of said rack bar to provide a diflerential torque on said pinion when said extension engages with said lever at the commencement of movement of said piston than subsequently thereto when the rack bar of said piston engages with the teeth of said piston.

4. A starting apparatus as claimed in claim 3 wherein means are provided for limiting the angular displacement of said lever ami to substantially 60 and for limitingthe total displacement of said pinion to one complete revolution duringv which the pin carried by said pinion travels from one side of said lever arm to the other.

ALBERT CALI-BEN.

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