US2194970A - Expansion engine - Google Patents

Description

MarchZG, 1940. 4 M; CLARK Y 2,194,970

EXPANSION ENGINE Filed Aug. 24, 19:58 Sheets-Sheet 1 a INVENTOR Jd/m IVE/TIT) C/d/"K Y M AT I'ORNEYS March 26, 1940.

JQM. CLARK 2,194,970

EXPANSION ENGINE 4 Sheets-Sheet 2 Filed Aug. 24, 1938 B INVENTOR Jo/m Merrill C/ar/r ATTORNEYS March 26, 1940. K 2,194,970

EXPANSION ENGINE Filed Aug. 24, 1938 4 sheets-sheet 5 f N m m M Q I -Q' k g as .g Q INVENTOR 40/70 Herr/71 C/ar/r BY ATTORNEYS March 26, 1940. CLARK 2,194,970

I EXPANSION ENGINE Filedfiug. 24, 1938 4 Sheets-Sheet 4 l N VE N TO R Jo/m Mar/77f Clark ATTORNEYS Patented Mar. 1940 i I v I I UNITED STATES PATENT OFFICE EXPANSION ENGINE John Merritt Clark, Northfield, N. .1.

Application August 24, 1938, Serial No. 226,421

4Claims. (Cl. 121163) This invention relates to expansion engines, .companying drawings in which like reference I especially to engines having a fluid-pressure cylcharacters designate like parts throughout the inder with a piston working therein and admisseveral views, and in which:

sion and exhaust ports through which the en- Fig. 1 is a fragmentary view in elevation of trance and exhaust of the expansible fluid is an embodiment'of the invention as applied to a 5' I controlled by a valve. locomotive drive with the piston in substantially In such engines, as usually constructed, the its mid-position and with portions of theoylin closure of the exhaust port; commences while der and valve chest shown in section; the piston is still a considerable distance from Fig. 2 is a view similar to Fig; l showing'the the end of its stroke resulting in a back pressure parts in position just before closure of an ex- 10 being formed against the piston which reduces haust' port and with certain levers and links the power of the engine and considerably derepresenteddiagrammatically; creases its efficiency. Also the valve in such Fig. 3 is a view similar to Fig. 2 showingthe engines uncovers the admission port gradually positions of the parts when the piston is at the r so that a substantial time interval results beend of a stroke; 1'5

tween the time of opening the admission port Fig. 4 is a view similar to Fig. 2 showing the and the time when the full fluid pressure is appositions of the parts just before the travel of plied to thepiston to advance it along the cylthe valve is reversed; r I v inder. Fig. 5 is a view similar to Fig.2 but withthe It is an object of my invention to increase parts in position just before the closure of eX- .20

the efliciency and power of such engines by rehaust port when the piston is near the forward lieving the back pressure acting against the end of the cylinder; piston by causing the exhaust port to remain Fig. 6 is a vertical sectional view at lines-B open until the piston has more nearly completed of Fig. 1' showing the guideway,'slide anda its stroke, thereby providing a passage of large portion of the slide operating mechanism;

area for the spent fluid. In accordance with my Fig. 7 is a top plan View of one of the'valve' invention this object is secured by a novel form operating slides shown in Fig. 1; of valve gear operating to efiect closure of the Fig. 8 is a View showing the relative positions exhaust port while the piston is advancing only of the piston and valve if the valve rod and slide a short distance near the end of its stroke. were integral and with no relative motion be-- 3 In accordance with a further object of theintween them; g vention, a novel type of valve gear is provided Fig.9 is a view showing a modified form of the in which a valve moves rapidly across the 'adinvention and, Fig. 10 is a View of a further mission port while the piston is near the end of modified form of the invention. 1 the cylinder so as to provide alarge area for the Referring to Fig. 1, the invention is shown-as admission of steam or other eXpansib-le fluid in applied to a steam locomotive having a main order to quickly build up the full available fluid drive wheel l0 having a crank pin H which is pressure behind the piston. I connected to crosshead l2 by a main driving rod In pursuance of a further object of the inl3,,the crosshead being slidable in a guidewayl i vention, I provide in association with such a formed between the parallel guide rods I5 and Him valve gear means which may include a novel ecand being connected to a piston I! by a piston centric arrangement which is connected to the rod l8. A crank arm I9 is securedto crank pin valve rod and which serves to delay the time II, the end of which is pivotally co1'1nec'ted,"a'. s of commencementof closure of the exhaust port. by pin 20 t on d of r d 2| h g th 'r By a further prcvision 0f the inventwmthe Same end is pivotally connected to a main reverse link- 45 eccentric arrangement is designed to move the 31 A support pin 23 which is carried by I Valve p y across the admission P0149 While tionary frame member 24 serves as a pivotal supthe PiStOIl is near the n of the cylinder; theme portfor reverse link 22. A radius rod 25 carries by prov s fu11 pressure Of t e fluid for a block 26 which is slidable in a slot 21 formed advancement f t e plston. in reverse link 22, the position of the block 26 50 Other Objec s and advantages Will pp as being controlled by the engineer from the cab the description of the particular physical em-v (not shown) of the locomotive through a link bodiments selected to illustrate the invention 23, b 11 crank 1ever 29 having arms 30 a d 3],. progresses. For a better understanding of the and link 32 whose lower end is pivotally coninvention, howevenreference is madetov the-acnectedzto theend of radius rod 25, as by a pin 55' 83. As shown, the bell crank 29 is pivotally supported by a pin 34 carried by a bracket 35 secured to frame 24.

The front end of link 25 is pivotally connected by a pin 35 to the upper end of a floating lever 3'! whose lower end is connected to crosshead [2 by a link 38. A pin 39 on lever 31 has pivotally connected to it a slide 48 slidable in guideways 4| formed in the spaced parallel guide rods 42 and 48 (Fig. 6). A valve 44, preferably of the type having spaced apart cylindrical ends formed as pistons 45 and 48, is mounted for reciprocation within a steam chest 41 to which steam under high pressure is supplied by a pipe 48 through a main admission passage 48. Valve 44 is operated from slide 48 through a valve rod 55 whose end is secured to a slide 5| which is in turn pivotally connected by a pin 52 to an eccentric strap 53 encircling an eccentric 54. Eccentric 54 is preferably formed integral with a lever 55 which is pivotally supported on a pin 58 secured to the parallel depending extensions 58 formed on slide 48, (Fig. 6). As shown more clearly in Fig. 7 the slide 48 is preferably formed of two spaced parallel side members 58 and Bi which are integrally connected by a transverse portion 62.

In order to provide an additional control over the valve 44 in addition to its control by the slide 40, I provide means for oscillating eccentric 54 about its pivotal support 58 thereby causing the valve 44 to approach or recede from slide 40. This additional control means comprises a link 83 whose .forward end has spaced apart ears 54 between which the upper end of lever 55 is pivotaliy supported as by a bolt 55 having a retaining nut 55 (Fig. 6). The rear end of link 53 is pivotally connected by a pin 5'? to the upper end of a floating lever 88 whose lower end is pivotally supported on a pin 59 secured to a slide 78 reciprocable in a guideway ll formed in a guide member 78. A link l3 connects pin '69 to an intermediate point 74 on a rock lever 15 pivotally supported on a stud 18 the lower end of rock lever '55 being in turn connected to floating lever 31 by a link 75a as shown (Fig. 1). Floating lever 58 is also connected to slide 48 by a short link I! one end of which is pivotally mounted on pin 39 and its other end pivotally connected to lever 68 by a pin 18.

Steam is admitted to and exhausted from cylinder 79 through the admission and exhaust ports 88 and Si and a series of orifices 82 formed in the valve seat liners 83. Main exhaust passages 84 and 85 are provided near the ends of steam chest 41 through which the spent steam is exhausted under the control of valve 44.

It will be readily understood from the foregoing disclosure that when the parts are in the relative positions illustrated in Fig. 1, steam will be admitted to the front end 86 of cylinder 19, the main steam supply entering the chest 41 from supply pipe 48 through passage 49 and leaving the chest through the orifices 82 whic are at all times in communication with port 88, through which the live steam' enters the front end of the cylinder. Valve 44 is shown disposed with its front piston 45 in position to block exhaust to the exhaust passage 84 while its piston 48 is disposed so as to leave the exhaust passage 85 wide open for spent steam from the rear end 87 of the cylinder, which passes through exhaust port 8! and orifices 82. It will. also be noted that eccentric 54 has been advanced to a position at the left of its pivotal mounting pin 58 so as to position valve 44 farther to the left than it would otherwise be, thereby delaying the time of closure of exhaust port 8| by piston 46, the expansion of the steam in the cylinder 19 being subsequently efiective to move the piston I! to the end of its stroke. As the steam pressure advances the piston I! into the position shown in Fig. 2, the link 63 and its associated parts retains lever 55 and eccentric 54 in position at the left of pivot pin 58, in order to delay closure of the exhaust port 8! until piston I1 is near the end of its stroke. This delay in closure of the exhaust port reduces very considerably the back pressure built up in the rear end 9 of the cylinder and therefore increases the mean efiective pressure applied to the piston during the stroke. Also, as shown in Fig. 2, the piston 45 has closed the port and thereby shut ofi the supply of live steam to the latter and front end ID of the cylinder. As the slide 40 is being moved to the right from the position of Fig. 2 into that of Fig. 3, link 63 and its associated parts rock lever 55 and eccentric 54 towards the right about pivot pin 58 so as to advance valve 44 over a greater distance than that travelled over by slide 48. This action results in a rapid motion of valve 44 so that the exhaust port 80 is put into full communication with exhaust passage 84 by piston 45 to permit free exhaust of the steam in the front end 86 of the cylinder. Piston 46, as shown in Fig. 3, has been moved into position to prevent the passage of spent steam into exhaust passage and to uncover orifices 82 to admit live steam into port 8|.

As the parts move from the position of Fig. 3

into that of Fig. 4 reverse link 22 causes radius rod 25 to move lever 55 and eccentric 54 quickly to the right about pivot pin 58, through the links 83, 11 and floating lever 68. This rapid motion causes piston 45 to fully open port 8| to the admission of live steam from chest 41 so that a high steam pressure is quickly built up behind piston H in the rear end 81 of the cylinder, thereby increasing the power developed during each piston stroke. It willalso be observed from an inspection of Fig. 4 that with the eccentric 54 positioned to the right of its pivotal support 58, piston 45 fully uncovers the orifice 82 so as to provide a free passage for spent steam through exhaust port 88 and exhaust outlet 84. This free passage for the exhaust is maintained until just before the parts reach the position shown in Fig. 5, while live steam is entering the rear end 81 of the cylinder. In the position shown in Fig. 5, the valve gear shown is moving slide 40 to the left and also rotating eccentric '54 to the left about its pivotal support 58 so the. exhaus port 89 will be soon opened by piston 45 for the admission of live steam and port 8| soon opened by piston 46 for the passage of exhaust steam from rear end 81 of the cylinder. 7 Referring to Figs. 8 and 2, the valve 44 is in the same position in each and Fig. 8 shows the corresponding position piston I1 would have if valve rod 58 and slide 48 were made integral and hence with no relative .motion between them. The gain in the period of exhaust and in the expansion of the live steam by use of my invention is represented by the difference in the positions of the piston l! as shown in these two figures.

In the modified form of the invention shown in Fig. 9 and in which like numbered parts correspond to those shown in Fig. l, the eccentric 58 is replaced by a floating lever 88 mounted on 25 the exhaust ports 80 and 8| may be controlled to pivot pin 82 carried by slide 40, the upper end of lever 88 being connected to valve rod 50 by a short link BI] and the lever being rocked on its pivotal support 82 by the link 13 and rock lever 15. In this modification, the slide H! and its associated parts are not used but the same beneficial results are secured as in theform of my invention shown in Fig. 1, the oscillation of lever 88 serving to delay the time of closure of the exhaustports 80,8! and thereby achieve the object ofv the invention by providing a free passage of large area for the spent steam'or other L fluid. I

The modification shown in Fig. is in all respects similar to that shown in Fig. 9 except that the leverage of lever 88 is made adjustable. As shown, three holes 82b are arranged one above the other in the slidelfla and in lever 88a and the fulcrum pin 82a may be fitted in either of the registering holes to thereby provide a control means for increasing or decreasing the extent of travelof valve 44. It will thus'be apparent that by the provision ofthis adjustable fulcrum on slide 40a, the amount of retarding action given to the valve to delay the closing of any desired extent.

In both forms of the invention verse link '22 operates in the usual manner to cause an earlier cut-oil of steam to the admission ports 80, 8| as the block 26is adjusted toward the pivotal support 23 of'the link and to cause a' reversal in the direction of rotation of the engine when it is moved into a position, on the opposite side of support 23 from that shown inFigs. .1

and 9. v 1 p i I have described whatI believe to be the best embodiments .of my invention. I do not wish, however, to be confined to the embodiments shown, but what I desire ,to cover by Letters Patent is set forth in the appended claims.

Iclaim:

shown, the re- 1.. In an engine having a. valve adapted to open and close steam ports therein and a reciprocatory piston, a valve gear for maintaining the mean effective pressure at a high'value throughout the stroke by lengthening the time of motion of the valve at any cut-off point and comprising a sub I stantially straight guideway, a slidable member mounted for reciprocation in said guidewayand means connecting the valve and slidable member andadapted-to vary the distance therebetween,

saidconnecting means comprising a lever pivotedto the slidable member at a point intermediate the ends thereof, and a link having: one of its ends connected to one end of the lever and its other-end to the valve.

2. A valve'gear as set forth in claim "1 in which thelever isprovided with a plurality of apertures spaced apart in the direction of its length,

efiective pressure at a high value throughout. the stroke by lengtheningthe time of motion of the valve at'any cut-off point and comprising a substantially straight guideway, .a slidable member mounted. for reciprocation in said guideway, means connecting the valve and slidable member for varying the distance therebetween and comprising'a lever' pivoted to theslidable member, and means for oscillating said lever comprising a rock lever, a pivotalsupport for the rock lever disposedat a level above the piston and a link point connecting the lever and an intermediate of the rock lever. i

i JOHN MERRIT'I CLARK.

' piston, 'a valve gear for maintaining the mean 1

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