US 2947300 A
Description (OCR text may contain errors)
Aug. 2, 1960 R. L. TRAPP STARTER-CONTROLLED ENGINE COMPRESSION RELIEF Filed May 31, 1957 3 Sheets-Sheet 1 77 lzqfilg i INVENTOR. E0552?" 4. 24%
g 2, 1960 R. L. TRAPP STARTER-CONTROLLED ENGINE COMPRESSION RELIEF Filed May 31, 1957 3 Sheets-Sheet 2 Ir mglllllllllllll/m Aug. 2, 1960 R. 1.. TRAPP STARTER-CONTROLLED ENGINE COMPRESSION RELIEF Filed May 31, 1957 3 Sheets-Sheet 3 I .p R 5 mm a 2 m N T I. 4 A H k I W V 'for an engine having a recoil starter.
a wheel continues to actuate the pistons.
"United States Patent Zi,-?,30 Patented Aug. 2,- 1960 7 STARTER-CONTROLLED EN GINE COMPRESSION RELIEF Filed May 31, 1957, Ser. No. 662,671 14 Claims. (Cl. 123-482) 'This invention relates to a starter-controlled engine "compression relief.
The invention is applicable to any internal combustion engine, whether two-cycle or four-cycle. It is illustrated .in connection with a two-cycle engine such as is conventitionally employed in most outboard motors.
'There have been many devices proposed for the relief of high compression to facilitate starting an engine. The ;present device accomplishes this objective automatically Several embodiments are disclosed, all of which depend on the operation of the starter to open the relief valve.
In one embodiment, the starting pulley has a cam track 'which guides a cam follower to a position in which compression is relieved during rotation of the pulley in a r starting direction, the track having a switching arrangerment for closing the relief valve as soon as the rewinding operation commences. Since the flywheel will continue to actuate the pistonsd-uring this period, the device functions to enable the operator to establish flywheel rotation with minimum resistance attributable to compression, starting being facilitated by restoration of full compresr sion as soon as maximum speed has been attained.
In a second embodiment, the starting cord it trained about a yieldable pulley connected with the valve to I open the valve when'the pulley yields in response to tension on the cord. When the tension on the cord is re- "'lieved to permit the rewinding operation, the relief valve will close, the flywheel still being in operation to take advantage of the increase in pressure consequent upon the closing of the valve.
In a third embodiment, a split ring is flexibly held to the surface of the starting pulley and connected with the valve. As the ring moves with the starting pulley in the initial actuation thereof, it will open the valve through I the action of acam ,With which it is provided. When the .tension on the starting cordis released and the rewindings operation commences, the ring will move reversely with the pulley to permit the valve to close while the fly- In the drawings: -Fig. l is. a-view partially in side elevation and par- :tially in section on the line 1- 1 of Fig.2.
Fig. 2 is a plan view of the engine shown in Fig. 1. Fig. 3 is a fragmentary detail view taken in section on 1' the line 33 of Fig. 2.
Fig. 4 is an enlarged detail view taken in section on the line 4-4 of Fig. 1.
Fig. 5 is a view taken in section on the line 5-5 of I Fig. 4.
Fig. 6 is a view taken in. section on line 6--6 of Fig. 4. Fig. 7 is a still further enlarged fragmentary detail view 'iin.perspective showing that portion of the cam track which is illustrated in section in Figs. 5 and 6. s Fig. 8 is aview in end elevation of the engine shown Fig. 13 is a view taken in section on the line 1313 of Fig. 12.
There are many ways in which compression in an in ternal combustion engine cylinder can be relieved. Broadly it is immaterial how this is accomplished as long as relief is controlled by a valve. In the preferred embodiments, the compressed gases are not released into the open air but are admitted into a chamber which, in etfect, so increases the capacity of the combustion chamber as to reduce the compression to any desired extent.
As illustrated, the engine 15 is a two-cylinder, twocycle engine in which the cylinders 16 and 17 are horizontal. The crankcase 18 to which mixture is admitted from carburetor 19 provides suitable bearing for a crankshaft 20 having the usual cranks to which pistons 21 and 22 are connected for reciprocation in cylinders 16 and 17.
As best shown in Figs. 1, 8 and 9, the block which provides the cylinders 16 and 17 has a terminal casting 25 which provides heads for both of the cylinders and into which the cylinder jackets 26 are extended as shown at 27 in Fig. 9. tlnto the cylinder head casting 25 extend the combustion chambers 28, 29 as shown in Figs. 1 and 9. It so happens that in the particular engine chosen to exemplify the invention, there is a supplemental head at 30 which happens to be cored in a manner not pertinent to the present invention to receive cooling water from duct 31 of cylinder head casting 25 and to return such water through duct 32 to the discharge pipe 33 (Fig. 1).
The present invention incorporates in this supplemental head casting 30 a pair of chambers 35, 36 to which ducts 37, 38 extend from the respective combustion chambers 28, 29 subject to the control of valves 40, one of which is illustrated in Fig. 9. It will be obvious from Fig. 9 that when valve 40 is seated, there is no communication between the combustion chamber 28 and the relief chamber =35. However, when the valve 40 is forced inwardly against the compression of its spring 41, communication will be established through duct 37 between the combustion chamber and the relief chamber, thereby in efiect increasing the capacity of the combustion chamher by the capacity of the relief chamber. In practice, the compression is reduced from about 5.7:1 to about 3.6:1 when the valve opens. However, these figures are given merely by way of example since the invention is not concerned with any particular ratio.
The dusts leading to the relief chambers should be so designed that flame will not be propagated from the respective combustionchamber into the respective relief chamber. Instead of screening the ports, this objective is desirably achieved by making the duct 37 of so small a diameter that flame will not be propagated through it. In practice, the duct is made with a No. 29 drill. It should not be much smaller than .136 inch because otherwise dirt might accumulate in it. It might be perhaps 5 of an inch larger in diameter, but this is unnecessary.
The two valves 40 are identical, each being provided with a stem 42 mounting a spring seat Washer 43 against which the compression spring 41 acts. The valves are displaced concurrently by the setscrews 44 mounted on the arms 45, 46 of rockshaft 50. While it is broadly immaterial how compression is relieved, the particular arrangement as herein described is believed to be novel and is claimed per se. The manner in which the rockshaft is actuated automatically to open the valves will now be described. At the upper end of crankshaft 7A is a flywheel 5. For starting purposes, this is actuated in a starting direction (clockwise as viewed in Figs. 2 and 4') by means of starting rope 56, rewind pulley 57 and a ratchet and pawl driving connection from the pulley to the flywheel (not shown because it is conventional). A spiral spring 58 having a fixed anchorage at 59 is connected at 60 with the starter pulley 57 to rotate the pulley counterclockwise as viewed in Fig. 4 to rewind the startingrope in the pulley groove 61 following a starting operation. The starting r01 has the usual handle 61% guided in a thimble 62 in housing 63, the handle being exposed to the grasp of the operator.
In accordance with the first embodiment of the present invention, the upper Surface of the starting pulley 57 is flanged to provide channels 65 and 66 which are generally concentric with crankshaft 20 at differing radii, there being one or more crossover connections 68, '69 from one channel to the other at the full depth of the respective channels as clearly appears in Fig. 7. Each crossover passes through the flange 70 between the channels 65 and 66 and each crossover is bounded in part by reduced-depth flanges 71, '72 which are so formed as to guide a cam follower from groove 65 to groove 66 when the pulley is rotated in starting direction and to guide the cam follower from groove 66 back into groove 65 when the pulley is being rotated in a rewinding direction. The crossovers are sufficient in number so that the outward displacement of the cam follower will occur very shortly following the initiation of pulley rotation in either direction. Each reduced-depth partition 71 and 72 is formed on the side opposite the crossover slot 68 with an inclined surface as shown at 73', 74- in Figs. 5, 6 and 7. These permit the cam follower hereinafter described to continue in the annular groove to which it has been actuated through the crossover, notwithstanding continued rotation of the pulley in the direction which brought about the crossover.
The cam follower '75 may comprise a stud of nylon or the like attached by screw 76 to the end of a lever 77 which comprises a spring strap fastened to rockshaft 50 as best shown in Figs. 1, 2 and 8. The pulley being rotated clockwise for starting, and the cam follower being in the inner groove 65 as shown in Fig. 4, it will be evident that continued movement will cause the reduced-depth partition 71 to deflect the follower 75 throught the crossover channel 69 into the outer groove 66, thereby oscillating rockshaft 50 in a direction to cause its arms 45, 46 to open the valves 40. During continued rotation of the pulley as the starting rope is unwound from its groove 61, the cam follower 75 will remain in the outer cam groove 66, riding over the inclined surface 74 of the reduced-depth partition 72, the flexibility of the lever 77 accommodating this movement, which is repeated at every crossover (two being illustrated in Fig. 4).
On the rewind rotation of the starting pulley 57, subject to the action of the rewind spring 58, the first crossover which encounters the cam follower 75 will deflect the cam follower back to the inner groove 65, thus allowing the valves 40 to seat subject to the bias of their own springs and subject to the compression within the combustion chambers. During the continued rewind rotation of the pulley, the cam follower 75 will remain in the inner groove 65, riding up the inclined plane 73 at the rear of each of the reduced-depth partitions 71, thus allowing the valves 40 to remain closed throughout the period of continued crankshaft rotation initiated by the starting pu y- Since the starting rope will ordinarily be released for a rewinding operation just as soon as the flywheel is brought up to speed, and since it will require no more than 180 of movement of the starting pulley to permit the closing of the valves 40, it will be evident that the valves will close while the flywheel is still in rotation at substantially the maximum speed to which it has been driven by the starting rope.
The flexible lever 77 which accommodates the vertical movement of the cam follower 75 is guided, and whipping is prevented, by the means separately illustrated in Fig. 3. The starter housing 80 is provided with a boss 81 from which projects a guide pin 82 disposed transversely above the flexible lever 77. A sliding guide member 85 having flanges 86 to engage the lever 77, and in which the lever is free for limited longitudinal reciprocation, is also guided for limited movement transversely of the lever upon the pin 82. Thus, the lever is free for controlled limited movement either laterally or longitudinally but is confined at a point such that vibration will be damped and the cam follower is restrained against such excessive movement as would dislodge it from the cam grooves in the pulley as above described.
It will be apparent that the device as above described exemplifies one arrangement whereby a sharp reduction in compression in the combustion chamber is achieved automatically as soon as the starting rope is pulled and full compression is restored automatically as soon as the starting rope is released, thereby enabling the starting operation to take place to the best possible advantage while the crankshaft is till rotating at maximum starting speed. Moreover, the gases withdrawn from the combustion chamber for the purpose of reducing compression are not exhausted into the atmosphere nor into the exhaust passages where, in either case, theymightcontribute to a fire hazard. On the contrary, the gases remain confined within the engine, flowing back and forth through the ducts 37, 38 responsive to movement of the pistons in the respective cylinders as long as the respective valves remain open.
In the embodiment shown in Fig. 11, the starting pulley 570 follows conventional practice, differing from the starting pulley 57 previously described in that it has no cam grooves. The starting cord 56 is trained about the starting pulley in the usual manner except that when it leaves the starting pulley it is entrained about a pulley 90 on bell crank 91 before passing about idler pulleys 92 and 93 to the handle 61. When the bell crank 91 yields in response to tension exerted by handle 610 on the starting cord 56, the pin 94 of the bell crank operates in the slotted end of lever 770 to displace valve 40 in a direction to open the valve as in the embodiment first described. Lever 770 performs the same function as lever 77 in the first described embodiment.
As soon as tension on the starting cord is relieved to permit the cord to rewind on the pulley 570 under the influence of the spring 58 shown in Fig. 4, the valve 40 will be seated by its own sp 'ng 41 (Fig. 9), causing lever 770 and bell crank 91 to oscillate back to their original position as illustrated in Fig. 11.
In the construction shown in Figil2 and Fig. 13, the pulley 571, is, like the other starting pulleys herein disclosed, provided with bearing support from the starter housing 80 and has a dog or dogs 95 arranged to drive flywheel 55. There are many available driving arrangements. The particular one illustrated in Fig. 13 is the one shown in 'Irgens application Ser. No. 600,103, filed July 25, 1956. The starting pulley has an upstanding flange 96 frictionally engaged by the split ring 100, the ends of which are drawn together upon the flange by a tension spring 101. The split ring 100 tends to move with the flange 96, but it is permitted only limited movement in either direction. The spring 101 is connected between lugs 103, 104 projecting radially from the ends of the split ring 100 and spaced to receive between them a stop member 105 which projects inwardly f om housing 80. The arrangement is such that whether the starting pulley is being propelled by the starting rope 5.6 or
by therecoil spring 58 which rewinds the rope, the lugwhich engages thestop will always be the lug which is trailing in the direction of starting pulley rotation. Accordingly, the trailing part of the split ring will be held while the friction on the leading part of the split ring will tend to open the ring against the bias of tension spring 101, thereby limiting the torque fnctionally transmitted to the ring. Accordingly, the ring will remain against the stop until the direction of the starting pulley is reversed. In the initial movement of the starting pulley in either direction, the ring will immediately move until the other lug engages the stop.
The split ring carries a cam 110 and the lever 771 carries the cam follower pulley 111 which, riding on the surface of the cam within the limited range of movement permitted the split ring, will oscillate lever 771 to open and close the pressure of these valves, the lever corresponding in its flux and operation to the lever 77 of the first described embodiment and the lever 770 of the second described embodiment. Thus, in the rotation of the starting pulley clockwise from the position of Fig. 12, the split ring will move from the position shown to the position in which lug 104 engages stop 105. This will cause cam 110 to ride beneath roller 111 to oscillate lever 771 to open the valve. In the initial rewinding motion of the pulley, regardless of the point from which it starts, the split ring will oscillate back to the position in which it is illustrated in Fig. 12, thereby permitting the valve to close.
The present application is a continuation in part of my application 652,510, filed April 12, 1957, and now abandoned.
1. The combination with an internal combustion engine including a cylinder having a combustion chamber portion and a piston reciprocable therein for the COIl'lPl'fiSr sion of a charge in said portion, of a starter for effecting piston reciprocation, means automatically effective during starter operation for relieving compression in said portion during a part of the period of starter operation, said means having starter controlled connections for terminating such compression relief automatically while the piston continues in movement consequent upon starter operation, the starter comprising a pulley having a starter rope and a rewind spring, the said means including a cam connected with the pulley, a cam follower With which the cam coacts and a compression relief valve mounted on the cylinder, the cylinder having a relief port controlled by said valve.
. 2. The combination with an internal combustion engine including a cylinder having a combustion chamber portion and a piston reciprocable therein for the compression of a charge in said portion, of a starter for effecting piston reciprocation, means automatically effective during starter operation for relieving compression in said portion during a part of the periodof starter operation, said means having starter controlled connections for terminating such compression relief automatically while the piston continues in movement consequent upon starter operation, said engine including a crankshaft having the crank connected with the piston and having a flywheel, the starter comprising a pulley in driving connection with the flywheel and provided with a starter 4. The device of claim 2 in which the member ac member.
5. The device of claim 4 in which the shoe is a split ring having means biasing its free end portions toward each other, and a stop in the path of-said portion to limit the movement of said ring and, by engagement with one of said portions, to reduce the friction between the spring and the pulley.
6. The device of claim 4 in which the shoe comprises a split ring, the pulley having an annular bearing portion engaged by the ring and the ring being provided with a cam, and a cam follower engaging said cam and connected with said member and constituting the actuating connection therefor.
7. The combination with an internal combustion engine including a cylinder having a combustion chamber portion and a piston reciprocable therein for the compres-' sion of a charge in said portion, of a starter for effecting piston reciprocation, means automatically effective dur-- ing starter operation for relieving compression in said portion during a part of the period of starter operation,
; said means having starter controlled connections for terminating such compression relief automatically while: the piston continues in movement consequent upon.
starter operation, the starter comprising a recoil starter including a pulley having a starter rope and a rewind spring and provided Withinner and outer cam grooves having crossover channels, a cam follower riding in the grooves, the crossover channels being adapted to direct the cam follower to the inner groove or the: outer groove according to. the direction of pulley rotation, the pulley being provided with inclined planes'for lifting the cam follower over the crossover channels to allow it to remain in a; given groove, the cylinder being. provided witha relief port, a valve controlling the port and valve operating motion transmitting connections from the cam follower to the valve.
8. The device ofclaim 7 in further combination with means providing a relief chamber having a duct communicating with said port and controlled by said valve whereby said chamber is adapted to receive and return mixture compressed in said combustion chamber portion rope and a rewind spring, means for relieving pressure comprising a valve movable to and from a seat about a port with which said cylinder is provided, a valve opening member in operative connection with the valve, and means whereby said member is actuated in a valve opening direction during initial movement of the pulley by the starter rope and in a direction permitting the valve to close in the initial movement of the pulley by the re- Wind spring.
3. The device of claim 2 in which the member actuating means comprises a yieldable pulley about which a portion of the starter rope is trained.
while the valve is open, for precluding flame propagation from the combustion chamber portion to the relief chamber.
9. The combination with an internal combustion engine having a crankshaft, cylinder, piston, and connecting rod, the cylinder having a combustion chamber portion outwardly of its piston and being provided with a relief port opening from said chamber, of a relief chamber communicating through said port with the combustion chamber, a valve mounted on the cylinder and controlling said communication, a starter for said engine, means for actuating the starter, and means controlled by the starter actuating means for opening said valve, the starter comprising a recoil starter including a pulley, a cord wound on the pulley and a rewinding spring, the valve opening means comprising an idler pulley having a yieldable mounting and about which a bight of the cord is trained, the yieldable mounting of the idler pulley ha ing a connection with said valve for the opening thereof when the connection yields in response to the tensioning of said cord in starting.
10. The combination with an internal combustion engine having a crankshaft, cylinder, piston, and connecting rod, the cylinder having a combustion chamber portion outwardly of its piston and being provided with a relief port opening from said chamber, of a relief chamber communicating through said port with the combustion chamber, a valve mounted on the cylinder and controlling said communication, a starter for said engine, means for actuating the starter, and means controlled by the starter actuating means for opening said valve,
the cylinder comprising means i g,947,3oo
the starter comprising a recoil starter including a pulley and a rewi'nding spring, the valve opening means comprising a drum Connected with the pulley, a brake shoe frictionally engaged with the drum, and a mechanical actuating connection from the brake shoeto the valve for moving the valve in an opening direction when the drum rotates the shoe in the course of use of the starter.
11. The combination with an internal combustion en-, gine having a crankshaft, cylinder, piston, and connecting rod, the cylinder having a combustion chamber portion outwardly of its piston and being provided with a relief port opening from said chamber, of a relief chamber communicating through said port with the combustion chamber, a valve mounted on the cylinder and controlling said communication, a starter for said engine, means for actuating the starter, and means controlled by the starter actuating means for opening said valve, the starter comprisinga recoil starter including a pulley and a rewinding spring the valve opening means comprising a drum connected with the pulley, a brake shoe frictionally engaged with the drum, and a mechanical actuating connection from the brake shoe to the valve for moving the valve in an opening direction when the drum rotates the shoe in the course of use of the starter, the shoe comprising a split ring having means biasing its parts into engagement with the drum, means limiting movement of the ring about the axis of the drum, and a cam connected with the ring and a cam follower actu-.
ated by the cam and connected with the valve, the ring being so controlled by the limiting means asto be movable only through a small angle within which the valve is actuated according to the direction of rotation of the drum.
12; The combination in an engine having a cylinder provided with a combustion chamber and a piston re:
ciprocable in thecylinder and a crankshaft having a crank" in operative connection with the piston, the cylinder having a relief port opening from the combustion chamber,
of a valve normally seated against'the cylinder in said port and movable inwardly toward the combustion chamber in an opening direction, the valve having an outwardly exposed stem, a rocker arm mounted for movement respective the cylinder, the stem being disposed in the path of rocker arm movement to be engaged thereby in a valve opening direction, a lever connected with the 8 rocker arm, a recoil starter comprising a pulley in driving connection with the crankshaft and having a rope wound thereon, a spring for rewinding the starting rope upon the pulley, cam means connected Withthe pulley and a cam follower operatively associated with the 'cam meansand connected with the lever, the said cam means constituting means for actuating the lever ,to oscillate the rocker arm in a direction to open the valve upon rope actuated movement of the pulley.
13. The device of claim 12 in which the cam means comprises pulley surfaces defining inner and outer cam grooves and a valve actuating crossover between said grooves for deflecting the follower from one groove to the other according to the direction of pulley rotation by the rope or the spring, the pulley having other surfaces for lifting the cam follower toclear the surfaces consti-' tuting the crossover while allowing it to remain in a given' is provided with guide means in which the lever is longitudinally slidable, the guide means being provided with means upon which it is transversely reciprocable, the
guide means confining the cam follower to the grooves while accommodating the flexing of said lever.
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