US2221790A - Prime mover and controlling means therefor - Google Patents

Description

PRIME MOVER AND CONTROLLING MEANS THEREFOR NOV- 19, 1940 A. D. FERGUSON PRIME MOVER AND CCNTROLLING' MEANS THEREFOR 4 Sheets-Sheet 2 Filed April 14, 1956 21. S NN a ,www

A@ @Mm NMQNw o o .w @MNR Nov. 19, 1940. A. D, FERGUSON 2,221,790' PRIME MovER 'ANl CONTROLLING MEANS THEREFOR I Filed Ap1.-;- 1-14, 193e 1 4 sheds-sheet 5 lllllllll.......f..1 ....Vf

Nov. 19, 1940. A. yD. FERGUSONv 2.2215790 Y' PRIME MovER' AND CONTROLLING MEANS THEREFOR Filed April 14, 1956 4. sheeps-sheet 4 llllllh Patented Nov. 19, 1940 UNITED STATES PRIME MOVER AND CONTROLLIN G MEANS THEREFOR Alexander D'. Ferguson, Michigan City, Ind., as-

signor to Sullivan Machinery Company, a cor,- poration of Massachusetts Application 'April 14, 1936, Serial No. 74,289

23 Claims.

My invention relates to steam driven pumping apparatus and more particularly to the steam driving devices for such apparatus, whereby a controlled delivery of pumped uid may be effected.

VIt is an object o f my invention to provide an improved, steam-driven pumping apparatus. It is another object of my invention to provide an improved steam engine valve gear. It is a further object of my invention to p-rovide an improved governing device for a compressor or other pump driving engine. It is a still further object to provide an improved combined speed and deliverypressure control for a pump-driving engine. It

is yet another object of my invention to provide an improved exhaust valve gear for an engine which may have occasion to operate either condensing or non-condensing. Other objects and advantages of the invention will hereinafter appear from the specification and the claims.

In the accompanying drawings, in which one embodiment of my invention is shown for purposes of illustration:

Fig. 1 is a fragmentary side-elevational View of a steam-driven compressor in which my invention is embodied in its illustrative form;

Fig. 2 is a vertical longitudinal section through a portion of the valve-actuating and controlling mechanism;

'30 Fig. 3 is a horizontal section through a portion of the valve actuating mechanism, some parts being shown in elevation and some broken away, and the section being taken on the plane of the section line 3-3 of Fig. 1;

Fig. 4 is an enlarged fragmentary section on the plane of the line 4-4 of Fig. 1 showing the exhaust valve control devices;

Fig. 5 is a fragmentary section on the plane of line 5,-5 of Fig. 4;

Fig. 6 is va fragmentary section on the plane of the line 6-6 of Fig. 4;

Fig. 'l is a perspective view of a cam for controlling compression during condensing operation;

Fig. 8 is a perspective view of a cam for controlling compression during non-condensing operation;

Fig. 9 is a perspective view of a cam for controlling admission and cut-off;

Fig. 10 is a fragmentary vertical section on the plane of the line Ill-I0 of Fig. 4;

Fig. 11 is a central vertical section through the steam cylinder of the apparatus shown in Fig. 1;

Fig. 12 is a vertical transverse section on the plane of the line I2-l2 of Fig. 11 showing detailsof an admission valve;

Fig. 13 is a vertical transverse section through the steam cylindeigshowing an exhaust valve, the section being taken on the plane ofV line I3-I3 :5- of Fig. 1;

Fig. 14 is a fragmentary vertical sectional view through an exhaust valve actuating mechanism;

Fig. 15 is a view similar to Fig. 14 but showing relative `positions of the valve actuating mecha- 10 nism with the exhaust valve open;

Fig. 16 is a detail section on an enlarged scale showing the admission valve packing;

Referring to the drawings, it will' be noted that Fig. 1 shows portions of a so-called angle- 15 compound compressor in which the illustrative embodiment of my invention is incorporated. This compressor comprises a horizontal low-'pressure cylinder I and a vertical high-pressure cylinder, not shown, but supported upon a pedestal 2 which is mounted upon a crank case 3. A steam driving cylinder 4 is mounted betweenthe'low pressure cylinder-I and the crank case 3.` As shown in Fig. 11, the steam cylinder dv is provided with a bore 5 in which a piston 6 is reciprocable. 25 Piston 6 has a horizontal piston rod 1, whose left hand end is operatively connected to and drives the fly wheel 8 and whose right hand end extends, as indicated at 9, into the low pressure compressor cylinder I and moves the piston (not shown) in 30 the latter. The steam cylinder has heads II and I2, each of which has a live steam space I3 therein, and each of which has associated with it an admission valve mechanism I 4. The cylinder is suitably jacketed as at I5. Referring to the 35 crank end of the cylinder, a section through which is shown in Fig. 12, it may be noted that live steam is conducted from a supply line I'I, under control of a stop valve I8, through one of the branched supply connections I9 into the live 40 steam space I3. The cylinder head is provided with suitable portions 2D which form a cylindrical housing 2l grooved as at 22 between its ends, the groove 22 communicating through a suitable passage 23 with the bore of the cylinder. Within a bore in the housing 2l there is mounted a cage 25, providing coaxial, longitudinally-spaced seats 26 and 21 for a double-beat poppet valve 28 controlling the admission and cut-off of steam to the 50 crank end of the cylinder. The valve 28 is of built up construction, and has a generally annular body 29 having an integral seating portion 30 to cooperate with the seat 26, and an upper, flexibly-mounted seat portion 3I, in the form of a 55 thin annulus or flange held in position by a collar 32.

Fig. 13 illustrates the provision for the control of exhaust. The cylinder 4 is provided, at Zones each spaced materially from the ends thereof and also from the central zone thereof, with exhaust ports of which one is shown in Fig. 13 at 35. These exhaust ports, which may be suitably gridded, communicate with seats 31, upon which exhaust-port-controlling valves 38 are adap-ted to seat. Passages 39 through the valve seat 31 open into an exhaust steam chamber 49 comprising branches respectively serving to conduct the exhaust steam from the different exhaust ports to a central exhaust space 4|, which may be connected through a suitable connection 42 to a condenser, to an exhaust steam outlet, or other suitable points as desired.

The admission valves 28 and the exhaust valves 38 are respectively mounted upon valve stems 43 and 44. The valve stem 43 is provided with a longitudinally extending packing 45 in a sleeve portion 46 formed integral with the valve cage 25. The exhaust valve stern 44 passes through a suitable sealing plug 46.

The valve stems 43 and 44 are each camactuated, and it is unnecessary to go into detailed description of both an inlet and an exhaust valve stem housing structure, as these are generally similar. It will be noted that housings 48 are provided to inclose the valve stems as shown in Fig. 14; and these housings provide suitable cylindrical guide and spring housing portions 59 aligned with the valve stems. In the guide portion proper of these portions 50 is a guide member 5i.' directly connected as at 53'to one of the valve stems. A spring 54 housed in the spring housing portion 50 acts between a shoulder 55 on the latter and a shoulder 56 on the guide member 52, and normally maintains the valve elements closed by moving the valve stems to valveclosing position. The guide members 52 carry cam engaging rollers 51, which are engaged by different cam devices in the case of the different valves. Suitable lubrication means is indicated at 58 to permit the -supply of lubricant to the guides and rollers.

An appropriate housing 60 supporting a series vof ball thrust bearings 6| is mounted upon the valve stem housing 'members-48, and incloses a valve actuating cam shaft 62. The cam shaft, which is hollow, is connected by a suitable coupling device 53 to an aligned driving shaft 64, carrying one of a pair of helical gears 65 and 66, the other of which is supported and rotated by the compressor crank shaft. It will be observed that these gears are of the same size and as a result the cam shaft 62 makes a revolution for each revolution of the crank shaft. The cam shaft 62 supports a pair of admission valve operating cams 68. 68 respectively near the opposite ends of cylinder 4, and a pair of exhaust valve controlling cam mechanisms 69, 69 respectively relatively close to, but on opposite sides of the median transverse plane of the cylinder 4. All of the cams mentioned are movably mounted upon the cam shaft 62, the admission valve actuating cam devices 68, 68 being connected for movement together through mechanism housed within the shaft, and the exhaust valve controlling cam mechanisms 69, 69 being operatively connected together through devices also arranged inside the shaft but surrounding a portion of the adjusting means for cams 68, 68. The admission valve controlling cams are automatically controlled in accordance both with the speed of operation of the driving engine of which they form a part, and with the delivery pressure of the compressor which said driving engine actuates. The exhaust valve control cam devices 69, 69 are controlled by mechanism which is automatically responsive to the exhaust conditions of the driving engine, occupying one position when the engine is operating condensing and another when the engine is operating non-condensing, and automatically shifting to the last mentioned position in the event of loss of vacuum.

To describe further the structure of the admissic-n valve controlling cams and the automatic control dewces for said cams, before taking up the structure of the exhaust valve control cam devices and the control mechanism of the latter, it may be noted that each of the admission valve control cams 68 is formed upon a sleeve 1| slidably mounted upon the exterior of the cam shaft 62. These sleeves support cam projections 12 which have valve-opening-eiecting, leading surfaces 13, and surfaces 14 for holding the admission valve open, and surfaces 15 for permitting closure of the admission valve. The surfaces 13, 14 and 15 are provided so that opening of the admission valve commences at the same instant in the cycle of piston travel irrespective of the position of the cam' device 68 longitudinally with respect to admission valve actuating rollers 51. However, the height of the cam portion proper and its width are both different longitudinally of the sleeve 1|, with the result that when the right hand end of the sleeve is opposite the cam-actuated roller 51 of an admission valve, the valve is opened both less long and less widely, While when the left hand end of the cam is opposite the roller the valve is held open for a longer period and is opened wider.

It will be observed that each of the sleeves 1| has a pair of alined holes 11 through which there extend pin elements 18 which pass through slots 19 in the wall of the hollow shaft 6'! and through openings 89 in connected block elements 8| slidably mounted within the bore of the shaft. The blocks 8| are connected together by rod portions 92, and the left hand block 8| is connected to a further block 83 which likewise carries a transverse pin 84 extending through slots 85 in the hollow shaft 62. Between a collar 86 xed to the periphery of the shaft 62 and a sliding sleeve 81 slidably mounted upon the exterior of the shaft 62 and connected to the block 83 by the pin 84 is arranged a spring 88 of appropriate strength to provide necessary resistance to the action of the speed responsive device, and also to the action of the pressure device above referred to and hereafter more fully described. The pin 84 has a projecting portion 99 connected by a suitable link 9| to another link 92 adjustably fixed as at 93 to one of a pair of parallel arms 94 pivotally supported by pins 95 carried by a sleeve 96 xed to the shaft 62 and carrying weights 91 of appropriate mass. It will be noted that as the shaft 62 is rotated, the weights 91 and arms 94 will tend to move under the action of centrifugalforce towards a position in which the arms 94 will lie in planes perpendicular to the axis of rotation of the shaft 62. Such a movement of the weights and arms will cause the linkage 92-91 to move the pin 84 and the sleeve 81', against the resistance opposed by the spring 83, toward the left, and will thus tend to move the rod 82 toward the left, which will result in a movement of the cam member 68 in a direction to diminish the period of admission valve opening. As a result it will be noted that overspeeding of the compressor will cut down on the degree to which the admission valves open and also cause earlier cut-off, while any tendency to slow down on the part of the compressor will result in a reduction in the centrifugal force exerted against the spring 88, and accordingly the latter will move the rod 82 to increase the quantity of steam admitted to the compressor cylinder and make cut-off come later.

The block 8| at the right hand extremity of the rod 82 has a rod |00 connected to it and extending into a cylinder forming member '|0| mounted upon the right hand end of the housing 60. Within this member is a cylinder bore |02 in which a plunger v|03 is reciprocably mounted. A ball |04 permits rotation of the rod |00 relative to the piston |03 Without material friction. A laterally extending arm |05 is carried by the piston |03 and extends through an opening |06 and has secured thereto a rod-like member |01 carrying stop nuts |08 and |09 respectively, and these are adapted to engage the opposite sides of a lug. ||0 through an opening in which the rod-like member |01 extends. The nut |08 limits the extent to which the plunger |03 can move the rod |00 and the connected system leftvvards. Nut |09l limits the distance that rod |00 and the connected system can be moved tothe right by spring 88. Pressure is supplied through a connection ||2 to the cylinder bore |02, such pressure being delivered under the control of a pilot mechanism ||3 from a pipe ||4 connected to the compressor discharge line. The device H3, which is of a well kno-Wn commercial form, performs a dual function. It reduces the pressure transmitted through it to a relatively small fraction of compressor discharge pressure. It also amplifies the changes in compressor discharge pressure. For example when the compressor discharge pressure desired is pounds, this device will cut down the pressure transmitted say to 25 pounds, at the same time upon an increase of compressor discharge pressure to 126 pounds it Will result in the transmission of a pressure of 30 pounds to the piston |03; and upon a reduction of one pound in the compressor discharge pressure, to 124 pounds, the pressure transmitted to the plunger |03 will be reduced several pounds. Accordingly the pressure control is one of great sensitivity. One structure of the character described is sold under the name of Fisher Pilot Valve.

Now turning to the exhaust valve actuating devices, it will be noted that a pressureresponsive device ||5 provides a cylinder |I6 in which a plunger |1 is reciprocable. This plunger is normally pressed in one direction by a spring H8; and the end of the cylinder ||6 towards Which plunger I1 is moved by the spring |8 is vented to atmosphere as at H9. Connection |20 at the opposite end, is led to the condenser to which the exhaust steam passes from the engine. Now, as long as a substantially subatmospheric condition is maintained in the condenser, it willbe obvious that plunger ||1 will be moved to the right as in Fig. 4, but upon the occurrence of a failure in condenser vacuum, the spring IIS will move the plunger I|1 to the left in Fig. 4. Plunger ||1 is connected to an operating rod |2| pivotally connected as at |22 to an arm |23 of a yoke |24 which is pivotally mounted on a transverse pin |25, carried onthe housing 60. The yoke carries pins v|21 which extend into an arcuate member |28 -which is received in the groove |29 of a sleeve |30 slidablyV splined as at |3| to the exterior of the shaft 62. The sleeve |30 has a pin |32 extending through a slot |33 in the shaft 62 and engaging one end of a sleeve |34 slidably mounted inside the shaft 62 and surrounding and slidable relative to the rod 82. Another sleeve |36 is slidably splined as at |31 to the shaft 62 and has a pin and slot connection |38 With the sleeve |34. A spring |39 normally maintains the sleeves |36 and |30 as far apart as possible. y

Each of the sleeves |30 and |36 has connected to itthree cams. These cams include an exhaust valve opening cam |40, a left hand lcam |4| controlling closure of the exhaust valve during condensing operation, and a right hand cam |42 controlling exhaust valve closure during noncondensing operation. Studs |43 extending through the cams and into the sleeves |30 and |36 respectively, and cooperating nuts |44 permit relative adjustment of the cams |4| and |42, each of which is slotted as at |45, relative to the cams |40 which are keyed as at |46 tothe shaft 62.

Cams 40 are set substantially opposite each other with respect to the shaft 62, and their leading edges control the time when the exhaust valves are opened. The cams |4I and |42 control the time when the exhaust valves are permitted to close. Obviously cam |42 will keep the exhaust valves open longer than cam |4|. The rollers 51 are Wide enough to engage cam |40 and either cam |4| or cam |42 concurrently. Both cams 4| or both cams 42 are operative at the same time.

The mode of operation of this mechanism Will be clearly understood by referring to Figs. 4, 5, 6, 7 and 8. During normal engine operation the cams |40 Will effect release at the desired points in the cycle. During condensing operation, the exhaust valves may be allowed to close relativelyv promptly and start compression relatively early in.l the strokes. Accordingly cams |4| Will be employed to bring this result about and they will be adjusted into operative position by sliding of the sleeves |30 and |36 opposite the rollers 51. If the back pressure rises, due to loss of vacuum in the condenser, spring ||8 will move the lever |23 to shift cams |4| out of cooperavtive relation with the rollers 51 and Will bring the cams |42 into position to engage the rollers, and thereby there will be produced a longer period of exhaust. It will be appreciated that the cams |40-the cams which control releaseare continuously in operative relation With the rollers' 51, and that the cams |4| and |42, which respectively effect' different delays before reclosure of the exhaust valves, with compression therefore occurring at different points in the engine cycle, are alternatively effectively in engagement with the rollers 51. When the engine is exhausting to a relatively low vacuum, the cams |4| contact With the rollers 51, While the cams |42 are completely o-ut of contact with the rollers. When the engine is operating noncondensing, they two cams |42 are in cooperative relation with the rollers 51, While the cams |4| have been 'moved axially out of contact with the rollers 51.

. `From the foregoing description it Will be evident that I have provided an apparatus peculiarly adapted to the operation of compressors or other pumps. It will be obvious that this apparatus will automatically maintain a desired operating speed except as an excess of air or other pumped fluid (due to diminished demand) may necessitate slower operation of the pump or compressor. It will be noted that in the event of loss of vacuum the condenser device will automatically prevent injury by extending the periods of exhaust. It will be evident that the apparatus is compact, and simple, and eiective.

While there is in this application specifically described one form which the invention may assume in practice, it will be understood that this form ofthe same is shown for purposes of illustration and that the invention may be modified and embodied in various other forms without departing from its spirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In an engine, in combination, a cylinder having a bore, a piston reciprocable in said bore, means for controlling admission to and exhaust from said cylinder bore including cam-operated admission and exhaust valves, a cam-supporting shaft rotatable during operation of said engine, longitudinally reciprocable cams mounted on said shaft for rotation thereby and of the Variablethrow type for controlling admission and cut-off, longitudinally reciprocable cam means mounted on said shaft for rotation thereby and of varied dwell for controlling release and compression, means responsive to the load on said engine for automatically controlling the position of said cams longitudinally of said shaft, and means responsive to the back pressure in the engine eX- haust for automatically controlling the position of said cam means longitudinally of said shaft.

2. In an engine, in combination, a cylinder having a bore, a piston reciprocable in said bore, means for controlling admission to and exhaust from said cylinder bore including cam-operated admission land exhaust valves, a cam-supporting shaft rotatable during operation of said engine, longitudinally reciprocable cams mounted on said shaft for rotation thereby and of the variablethrow, variable-dwell type for controlling admission and cut-off, longitudinally reciprocable cam means mounted on said shaft for rotation thereby and of varied dwell for controlling release and compression, means responsive to the load on said engine for automatically controlling the position of said cams longitudinally of said shaft, and means responsive to the back pressure in the engine exhaust for automatically controlling `the position of said cam means longitudinally of said shaft.

3. In an engine, in combination, a cylinder having a bore, a piston reciprocab'le in said bore, means for controlling admission to and exhaust from said cylinder bore including cam-operated admission and exhaust valves, a cam-supporting shaft rotatable during operation of said engine, longitudinally reciprocable cams mounted on said shaft for rotation thereby and of the Variablethrow type for controlling admission and cut-oil', longitudinally reciprocable cam means mounted on said shaft for rotation thereby and of varied dwell for controlling release and compression, means responsive to the speed of said engine for automatically controlling the position of said cams longitudinally of said shaft, and means responsive to the back pressure in the engine eX- haust for automatically controlling the position of said cam means longitudinally of said shaft.

4. In an engine, in combination, a cylinder having a bore, a piston reciprocable in said bore, means for controlling admission to and exhaust from said cylinder bore including cam-operated admission and exhaust valves, a cam-supporting shaft rotatable during operation of said engine, longitudinally reciprocable cams mounted on said shaft forrotation thereby and of the variable-throw, Variable-dwell type for controlling admission and cut-off, longitudinally reciprocable cam means mounted on said shaft for rotation thereby and of varied dwell for controlling release and compression, means responsive to the speed of said engine for automatically controlling the position of said cams-longitudinally of said shaft, and means responsive to the back pressure in the engine exhaust for automatically controlling the position of said cam means longitudinally of said shaft.

l v5. In an engine, in combination, a cylinder having a bore, a piston reciprocable in said bore, means for controlling admission to and exhaust from said cylinder bore including cam-operated admission and exhaust valves, a cam-supporting shaft rotatable during operation of said engine, longitudinally reciprocable cams mounted on said .shaft for rotation thereby and of the variable-,throw type for controlling admission and cut-off, longitudinally reciprocable cam means mounted onr said shaft for rotation `thereby and of varied dwell for controlling release and compression, means responsive both to the speed of and load on said engine for automatically controlling the position of said cams longitudinally of said shaft, and means responsive to the back pressure in the engine exhaust for automatically controlling the position of said cam means longitudinally of said shaft.

6. In an engine, in combination, a cylinder having a bore, a piston reciprocable in said bore, means for ycontrolling admission to and exhaust from said cylinder bore including cam-operated admission and -exhaust valves, a cam-supporting shaft rotatable during operation of said engine, longitudinally reciprocable cams mounted on said sha-ft for rotation thereby and of Vthe variable-throw, variable dwell type for controlling admission 'and cut-off, longitudinally reciprocable rca-m means mounted on said shaft for rotation thereby and of vvaried dwell for controlling release land compression, means responsive both to the speed ofand load on said engine for automatically controlling the position of said cams longitudinally of said shaft, and means responsive to the back pressure in the engine exhaust for automatically controlling the position of said cam means longitudinally of said shaft.

7. In an engine, a valve, an actuating plunger therefor, and cam actuating means for said plunger including cam means for providing for uniform valve opening movements thereof and separate cam means arranged at opposite sides of said rst mentioned cam means respectively for proviidng for different valve closing movements thereof.

8. In an engine, a valve, an actuating plunger therefor, and cam actuating means for said plunger including cam means for providing for uniform valve opening movements thereof and separate cam means arranged at opposite sides of said irst mentioned cam means respectively for providing for different valve closing movements thereof, said cam means having fluid operated controlling means governed by a pressure associated with the operation of the engine.

' 9. Inan engine, a valve, an actuating plunger therefor, and cam actuating means for said plunger including cam means for providing for uniform valve opening movements thereof and separate cam meansarranged at` opposite sides of said first mentioned cam means respectively for providing for diiferent valve closing movements thereof, said cam means having fluid oper-ated controlling means governed by the exhaust pressure of the engine.

10. In an engine 'driven pump system, an engine having a cylinder, a piston reciprocable in said cylinder, means for controlling admission to said cylinder including admission valves and valve controlling means variably controlled in accordance with the pump discharge pressure, and means for controlling exhaust from said cylinder including exhaust valves, valve controlling means variably controlled by engine back pressure to effect closure of said exhaust valves at different points in the travel of the engine piston in accordance with engine back pressure changes and valve controlling means for opening said exhaust valves at substantially the same points in the travel of the engine piston irrespective of engine back pressure variations.

11. In an engine driven pump system, an engine having a cylinder, a piston reciprocable in said cylinder, means for controlling admission to said cylinder including admission valves and valve controlling means variably controlled in accordance with the pump discharge pressure and the speed of operation of the pump, and means for controlling exhaust from said cylinder including exhaust valves, valve controlling means variably controlled by engine back pressure to effect closure of said exhaust valves at different points in the travel of the engine piston in accordance with engine back pressure changes and valve controlling means for opening said exhaust valves at substantially the same points in the travel of the engine piston irrespective of the engine back pressure variations. 1

12. In an engine, a valve, an actuating plunger therefor, and rotating cam means for actuating and controlling said plunger including cam means for effecting valve opening at a predetermined point in the cycle of said engine, and separate cam means arranged at opposite sides of said first mentioned cam means respectively and respectively effective to provide for valve closure at different points in the engine cycle.

13. In an engine, a valve, an actuating plunger therefor, and rotating cam means for actuating and controlling said plunger including cam means for effecting valve opening at a predetermined point in the cycle of said engine, and separate cam means arranged at opposite sides of said rst mentioned cam means respectively and respectively effective to provide for valve closure at different points in the engine cycle, said cam means having fiuid operated controlling means governed by a pressure associated with the operation of the engine for regulating their axial position.

14. In an engine, a valve, an actuating plunger therefor, and rotating cam means for actuating and controlling said plunger including cam means for effecting valve opening at a predetermined point in the cycle of said engine, and separate cam means arranged at opposite sides of said first mentioned cam means Arespectively and respectively eiective to provide for valve closure at different points in the engine cycle, said cam means having fluid operated controlling means governed by the exhaust pressure of the engine for regulating their axial position.

` 15. 'In an engine, a valve, an actuating plunger therefor, and cam actuating means for said plunger including cam means for providing for uniform valve opening movements thereof,y and separate cam means for providing for different valve closing movements thereof, said cam means having uid operated controlling means governed by pressure associated with the operation of said engine.

16. In an engine, a valve, an actuating plunger therefor, and cam actuating means for said plunger including cam means for providing for uniform valve opening movements thereof and separate cam means for providing for different valve closing movements thereof, said cam means having fluid operated controlling means governed by the exhaust pressure of the engine.

17. In an engine, a valve, an actuating plunger therefor, and cam actuating means for said plunger including cam means for providing for uniform valve opening movements thereof, and separate cam means for providing for different valve closing movements thereof, said cam means rotatable to effect their controlling function and having fluid operated controlling means governed by a pressure associated with the operation of the engine.

18. In an engine, a valve, an actuating plunger therefor, and cam actuating means for said plunger including cam means for providing for uniform valve opening movements thereof, and separate cam means for providing for different valve closing movements thereof, said cam means rotatable to effect their controlling function and having fluid operated controlling means governed by the exhaust pressure of the engine.

19. In a valve operating mechanism, means for the operation of a single valve comprising a valve stem, a cam cooperating with said .stem to effect opening of said valve at a predetermined point in the engine cycle, and separate cam means arranged at opposite sides of said first mentioned cam means and each controlling valve closure but respectively arranged to eifect valve closure at different points in the engine cycle.

20. In an engine, a valve, a stem for said valve, and cam actuating and controlling means for said stem including rotating cam means providing for stem movement in one direction at a predetermined point in the engine cycle, and separate rotating cam means arranged at opposite sides of said rst mentioned cam means vrespectively determining the opposite movements of said stem at different points in the engine cycle.

21. In an engine, a valve, an actuating plunger therefor, cam actuating means for said plunger including cam means for providing for uniform valve-opening movements thereof, separate cam means rotatable on a. common axis with said first mentioned cam means for providing for different valve-closing movements of said plunger, and means automatically governed by predetermined changes in engine exhaust pressure for controlling said last-mentioned cam means.

22. In an engine, a valve, an actuating plunger therefor, cam actuating means for said plunger including cam means for providing for uniform valve-opening movements thereof, separate cam means for providing for different valve-closing movements of said plunger, said several cam means rotatable on a common axis and movable longitudinally of said axis, and means responsive to changesin back pressure on the engine for moving said cam means longitudinally of saidaxis to provide for different valve closing movements of said plunger.

23. In an engine, a valve, an actuating plunger therefor, and cam actuating means for said plunger including cam means for providing for uniform valve-opening movements thereof, a plurality of separate mutually coaxial cam means each providing for different valve closing movements of said plunger, said plunger atv all times subjected to control by said mst-mentioned cam means and to one of said last-mentioned cam means, and means governed by engine exhaust pressure for automatically determining which of said last; mentioned cam means governs valve closure.

ALEXANDER D. FERGUSON.

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