US1703274A - Steam engine - Google Patents

Description

Feb. 26, 1929. 1,703,274

J. KENNEDY STEAM ENGINE Filed Feb. 25, 1922 s Sheets-Sheet 2 ABSOLUTE VACUUM L/TVE INVENTOR Feb. 26, '1 929.

J. KENNEDY STEAM ENGINE Filed Feb. 23. 1922 5 Sheets-Sheet mum w 3 mm .ww; R a

S j MM. 0 N w n on. QM r ,mN wm WM 3 MN xN Feb 26, 19291 1,703,274

' J. KENNEDY STEAM ENGINE Filed Fb. 23, 1922 5 Sheets-Sheet 4 Feb. 26, 1929.

' 1,703,274 J. KENNEDY STEAM ENGINE Filed Feb. 23, 1922 5 Sheets-Sheet 5 ri -Z Patented Feb zfi, 192 9.

JULIAN KENNEDY, OF PITTSBURGH,PENNSYLVANIA.

STEAM I ENGINE.

, Application filed February 23, 1922. Serial No. 538,620.

Figure 1 is a longitudinal sectional view through an engine cylinder embodying the present invention, certain 01' the parts beingillustrated in section;

Figure 2 is a sectional enlarged scale;

Figure 3 is a diagrammaticview illustrat; ing an indicator card curve; 7

Figure 4 is a .view corresponding to 1 illustrating a slightly modified form of the present invention;

Figure 5 is an end elevation partly in section, of the construction illustrated in Figure 4:; i r 1 Figure 6 is a detail sectional view ofa portion of the valve" operating means;

Figure 7'is a diagrammatic view, 'corre sponding to igure 3, illustrating the relationship between the curvesfor opposite ends of the cylinder, and c Figure 8 is a diagrammatic View illustrating one form of valve gear for controlling the steam admission valves. r

The present invention relates broadly to steam engines and more particularly to steam detail view on an engines ofthe unifiow type.

Due to the economy of operation of uniflow engines, it 1S veryv des rable under a good many conditions to make use of such engines.

A serious objection, however, to such use has,

been the fact that it has heretofore not been possible to reverse the same at any desired point during the cycle of operation,

By the present invention, I have provided a construction by means of which it is possible to reverse a uniliow engine at any point in the rol re during the operation thereof, there by overcoming existing'objections to the use of such engines. 7 Referrin more particularly to Figures 1 to 8 of the drawings, there is illustrated a poi"- tion or a uniflow engine comprising a cylinder 2 having a piston 3 and piston rods 4, eperable through the stuflingboxcs 5 at each end of the cylinder. Intermediate the ends of the cylinder there are provided a series of exhaust openings 6 communicating with an exhaust port 7, by means of which the expanded steam is permitted to escape from the,

en ginecylinder as soon as the the exhaust openings. Y V

Cooperating with the cylinder 2 is a'steam admission chamber 8, havingan inlet port 9. Adjacent each end of the chamber 8 there is provided a steam inletiport 1O communicat piston uncovers ing withthe interior of the cylinder 2. I The Figure admission of steam from the chamber 8 to the cylinder 2,- through the ports 10, is controlled by means of piston valves 11 carried by a valve-operatlng rod 12 travelto the right-hand end of the cylinder,

. the expanded steam having been permitted to escape through the exhaust openings 6. Continned operation'of the engine will cause the valve-operatlng rod 12 to move. to the right,

thereby uncovering the port 10; and permitting the passage of steam into the right-hand it will be apparent that steam is admitted at approximately the point A and is cut ofi' at approximately the point 13'. During vthe travel of the pistonfiromthe point- B to the point C, thesteam willbeexpanding as is customary. At'the point C, the exhaust openings will be uncovered and the steam released, the exhaust openings remaining un-T covered from the point C to the point D; The return movement of the piston from the point 'D to the point A will resu'ltfirstin a gradual compression, and then a'rapid compression ito produce a compression in the cylinder substantially equal to the pressure of the entering steam. to thereby obviate any hammermg. These operations wiltbe repeated for pressed, and, if the engine were underany load, reversal would not be possible, "In the construction disclosed, however, I have provided means for relieving the pressure 1n one itch end of the cylinder during each c l f i 0170111131011. l r r end otthe cylinder when it is desired to reverse the direction of traveLofthepiston].

Referring more particularly to Figures 1 and 2 of the clawing's, it will be noted that there is provided, adjacent each end of the chamber 8 a port 13 leadinggto the space 14:

below the valve 15. The'valvel5 is preferably loaded to any desired degree by a spring 16, or equivalent means, whereby the valve will only openwhen it is subjected to the p're- I V 1 60 In Figure l of the'drawings the piston 3 1s 1llustrated as having ust completed its determined pressure. Adjusting means. 117' may be provided for varying the point at which the valve will open. Assume that the piston 3 is traveling toward the left as viewed in Fig. 1 and that it has passed the point of cut-oil, the valve 11 will be in such position that the port is isolated from the chamber 8 and, during the major portion of the stroke, the port 10 will be completely closed so as to permit expansion of the steam in the cylinder. If it is desired to reverse the engine the valve rod 12 will be moved to the left so as to bring the reduced portion 11 of the piston valve over the port 10 and thus establish coininunication between the port 10 and the port 13. This will immediately permit the steam in the right-hand end ofthe cylinder to eX- haust therefrom by lifting the valve and escape either to the atmosphere or to the condenser depending upon the connections to the valve. The movement of the valve-operating rod 12 to the left will be eli'ective for uncovering the port 10 at the lef -hand end of the cylinder and thereby admit steam for producing the travel of the piston in the opposite direction. The movement of the valve which is required for reversing the engine may be accomplished by any suitable reversing mechanism as, for example, the well known Stephenson reversing link gear.

Referring to Figure 3, it will be assumed that the piston has reached the point corresponding with the point E in the expansion curve, and that it is desired to reverse the direction of travel of the piston. The valveoperating rod will be moved as described, and immediately the pressure of the steam which was undergoing expansion will drop inc i cated by the chain'line F to the pressure represented by the chain line G. It will be obvious that the pressure indicated by the chain line G may vary in accordance with the load ing: of the particular valves, and that in the drawing the relation between this pressure line and the absolute vacuum line for purposes of illustration only. In this figure l have also illustrated the pressure drop which I will occur if the engine is reversed when the piston hasreached a point in its travel corresponding to the point H.

Referring to hi 1 which shows the piston as having just completed its stroke to the right, it will be seen that the valve rod 12 must/"be moved to the right so as to establish communication between the chamber 8 and the port 10 in order to allow admission of steam to the right hand end of the cylinder. It will be seen from Fig. 1 that this movement of the valve rod 12 necessarily results in the port 10 at the left hand end of the cylinder being placed in communication with the corresponding port 13 at the left hand end of the cylinder. As pointed out, however, the relief Valve is sprmg loaded and of course the pressure in-the left hand end of the cylinder i,ros,274

at this time is quite low. In consequence no steam escapes through the relief valve and before the cushioning pressure in the left hand end of the cylinder has been built up to a point corresponding to the blow off pressure of the relief valve, the valve rod at 10 will have again moved to the left in such amount as to isolate the relief valve from the cylinder. lt will be apparent, therefore, that my improved construction does not interfere with the normal operation of a unil'low enpansion has just been talrwith engines of the uni'llow type having poppet valves controlling the admission of steam in this form of my invention the cylinder has a series of cent-rally a: k

exhaust openings 21 communicating with the exhaust port 22, as before described. The piston 23 carried by the piston lfi'iQ is ad t to reciprocate in opposite direct-ions in accordance with the admission of steam to the cylinder. Such admission is controlled by a poppet valve 25 adjacent 1e left-hand end of the cylinder centre ling the passage of steam from the inlet port 26 to the'cylinder and by the poppet valve 2? adjacent to the righthand end of the cylinder controlling the admission of steam thereto from theinlet port 28.

In addition to the inlet valves 25 d 27, there is located adjacent each end of the cylinder an auxiliary valve mechanism ccmprising; a. poppet valve 2 adapted to open inw l and held normally in closed position by suitable compression spring 30 surroundi the valve stem ill. 'lhese valves are 1) adapted to be opened in timed relation with the operation of the engine the action of the splines 30 by cams 32 mounted on sleeves 33 into which pass the ends of theczun shafts 341:. At their outer ends the cam shafts 3 1 are each provided with a bevel gear 35 meshing with. a second bevel. 36 carried by the shaft 37. The shaft 87 is ofthe type ordinarily provided "ith unillow engines and carries the eccentrics 3f-lfor opening the poppet valves 25 and 27. The valve gear for acconiplishing this movementis duplicated for each vof'che valves 25 and 27, and com prises an arm 89 actuated by the eccentric 38 I nd pivotally secured to a rocker segment ill. The rocker segment in turn has a pivotal connection 41 carried by one arm of an adjusting' lever 42, whereby the position of the pivotal mounting for the rocker seg'n'ient may ated as described.

be varied to vary .the point of admission and I the point of cut-offbf the live steam. Mounted inthe slot 43" of therocker segmentis a slice 44' secured to the lowerend of the link 45, the upper end of which link is operatlvely secured to a cam 46 for actuating one of the which control the auxiliary poppet valves 29 by a lever 49 having a pivotal mounting .50 intermediate its ends. The upper end of the lever 49 is slotted as 'indicatedat 51, to provide a lost-motion connection with the pin 52 of the slide 44. The lower end of the lever 49 is similarly adapted through a lost motion.

connection 53, to reciprocate the rod 54. This rod 54 is provided ad1acent oneend with antifriction rolls 55 spaced to straddle the collar 56 on the sleeve 83. By reasonof this connection, it will be apparent that movement of the reversing lever 47 will be effective for reciprocating the rod 54 and consequently the sleeve33. The reciprocating movement of the sleeve 33 is convertedinto rotary motion for advancing the cam. 32 substantially 180 by providing a high pitch thread 57 on the end of the cam shaft 34 adapted to mesh with a similar thread 58011 the interior of the.

sleeve 33. This mechanism is also duplicated as having just completed its travel toward the right-hand end ofthe cylinder 20. Continued operationof the engine will result in opening the poppet valve 27 to admit live steamto the right-hand end of the cylinder 20 for moving the-piston to the left. During suchmovemenuiif it is desired to reverse the engine, the reversing lever 47 willbe oper This will result in closing the valve 27 and opening the valve 25. At the same time, it will result in openingthe auxiliary valve 29 at the right-hand end of the cylinder. Immediately upon the open- 1ng of the valve 29 trapped steam which was undergoing expansion in the right-handend of the cylinder will escape by the valve 29 7 into the chamberll and then past the valve 15 either to the condenser or to the atmosphere. It will be understood that the valve 15 may be constructed as described in detail in connection with Figures 1 and 2.

In vFigure 7 there isillustrated diagrammatically the indicator card having a'cu-rve thereon. for each end of the cylinder, the curves being arranged in comparative relationship. .For sake of brevity, I have illustrated the points on the curveswith the same reference letters used in describing Figure 3,

with a prime aflixed thereto. In this figure,

however, I have illustrated by the chain line K'the drop in'pres'sure which will occur if the'engine is reversed at the pointL.

.Now assume that it is desired to'reverse' the. engine at a time when the piston is movin toward the right hand end of the cylinder under the influence of'steain admitted by the valve 25. The pressure condit on in the right handend of thecyli'nder'will be represented by a point on the compression line of the indicator card, the particular location of this point depending upon the position of the piston at the time'the reversing is effected. Assume that it is' at the point M. The valve 29 at the left hand end of the cylinder will of course be open and the pressure in the left hand end. will drop. At the same time steam will be admitted to the right handend and the pressure curve would befrepresented by at least apart'of the chain line extendingfupwardly from the point M in Figure 7 I The maximum'prcssure which would be 'shown'on an indicator card for this particularstroke is immaterial to the operation of the engine,

but it' will be .understood' that the pressure will tend to'rise to'th'e maximum inlet pressure. It may not reach suchmaximum pressure due to closing of the inlet valve within a very short period of time but in any event the pressure will rise to such a point that the piston will bev stopped and will commence a thus reversing the engine.

It will beunderstood that knowing the conditions in one "end-of the'cylinder, thecondireturn travel withoutcompleting its stroke,

'tions in the opposite end ofthecylinder mayl be readily determined by drawing perpendicular lines from anypoint inthe upper'line of the power curvefor the right-hand end'of the cylinder to the lower line of the power curve for the left-handend of the cylinder, it being necessary to have a condition of compression on onc'side of the piston while expansion istaking place on the opposite side and vice versa. It will also be understood that during the normal operation of the engine, the opening of the auxiliary valves 29 will not permit any escape from the" cylinder as the cams 32 will be timed to produce such opening movement at a point in the power curves below the line G. During such time,

as the pressure in the cylinder will be less than the pressure at which the relief valves are set to open, pressure conditions within the cylinder willnot be affected by the relief valves.

While I have illustrated a preferred embodiment of my invention, both in connection with a piston valve uniflow. motor and a poppet valve unifiow motor, various changes may be made in'the construction and operation of the motor without departing from the spirit of my invention or scope of In broader claims. The invention may also e applied to other types of unifiow motors as desired.

The advantages. of the present invention arise from the n'ovisionot' means permitting the move ,al vof a unifloW engine at any time during ie :QPQlliltlOll thereof such mechanism including eneans for releasing the Y mall engine operation, hut movable upon reversal of the ellglhli) be lfore exhaust taxes place to Eopen the passage and permit o'l es cape of steam through said means when it is desired to reverse the engine.

'2. In a uniflow engine, mechanism for versing the same, said mechanism including a valve adapted to open when subjected to relatively low steam pressure, a steam passage from the cylinder to said valve, and .a controlling valve effective for closing/oft said passage so as to pre entescape oi steam during normal engine ope ion, ut movable upon reversal of the engine before exhaust takes place to open the passage and permit vof escape off steam through the first mentioned valve avl-ien it is desired to areverse the engine. a p

3. In a unifloW engine, mechanism for reversing the same, said mechanism including a spring loaded valve adapted to open the relatively low steam pressure, a steam pas sage from the cylinder to said spring loaded valve, and a controlling valve effective for closing off said so as to prevent escape of steam during normal engine opela tion, hut movable upon reversal of the engine before exhaust takes place to open the passage and permit of escape of steam thizough said spring loaded valve when it is .desired to re verse the engine.

4. In a unifiow engine, mechanism for e first mentioned valve when it is desired to reverse the engine.

'5. In a nniiloW engine, a cylinder, a pi "ton, means cont the admission of steam to each end or L-llG cylinder, and mechanism for reversing the en gine, said mechanism including means for rel ising trapped steam if m an end of the cylindei a steam passa e from the cylinder to said means, said means for controlling the admissionof steam being tur- V a they adapted for closing- Oil said passage so as to pirevent escape of steam through said releasing means during nonmal en-gineo tien, but movable upon reversal-lot: the engine before exhaust takes place to open the passage and permit of escape of. eam through said means when it is desired engine.

In testimony my hand.

whereof I have vhereunto set JULIAN KENNEDY.

to reverse the

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