US2518403A - Locomotive construction providing improved tractive effort characteristics - Google Patents

Description

Aug. 8, 1950 A. J. TOWNSEND ETAL 2,518,403

\ LOCOMOTIVE CONSTRUCTION PROVIDING IMPROVED TRACTIVE EFFORT CHARACTERISTICS Filed Sept. 15, 1947 SYSheetS-Sheet 1 Aug. 8, 1950 A. J. TOWNSEND ET AL LOCOMOTIVE CONSTRUCTION PROVIDING IMP VED TRACTIVE EFFORT CHARACTERISTICS Flled Sept. 15, 1947 6 Sheets-Sheet 2 Aug. 8, 1950 A. J. TOWNSEND ETAL 3 LOCOMOTIVE CONSTRUCTION PROVIDING IMPROVED TRACTIVE EFFORT CHARACTERISTICS Filed Sept. 15, 1947 6 Sheets-Sheet 3 g- 1950 A. J. TOWNSEND E'TAL 2,518,403

LOCOMOTIVE CONSTRUCTION PROVIDING IMPROVED TRACTIVE EFFORT CHARACTERISTICS Filed Sept. 13, 1947 6 Sheets-Sheet 4 INVENTQRJ Aug. 8, 1950 A. J. TOWNSEND ET AL 2,518,403

LOCOMOTIVE CONSTRUCTION PROVIDING IMPROVED TRACTIVE EFFORT CHARACTERISTICS Filed Sept. 13, 1947 V 6 Sheets-Sheet 5 XHAU5T CAM ASSEMBL Y IN TERMED/ATE MID 4 54/? MID 554/? FULL 6'54)? FULL 5m? ra/ew/wo RfI/ERSL' REVERSE FORWARD I 9 4', I fl :11.

MID-(2'- IQNVENTORS FORWiJ/FD 1+ MID 5c ffwjwszs l 3 I (67 65 BY b '1 ATTO R N EY5 Aug. 8, 1950 A. J. TOWNSEND ET AL 7 8, 03

LOCOMOTIVE CONSTRUCTION PROVIDING IMPROVED TRACTIVE EFFORT CHARACTERISTICS Filed Sept. 15, 194'! e Sheets-Sheet 6 FULL 6154/? m 654/? Mm 6541? FULL [4R- FORWARD F0/iW/1R0 5% PEI/575E [PEI/525E J7 F l Ji'qI ZZ- I XHAU5T og 10 v' I I Layman/W N r 1 a [I I I U I R 103 I020 F0/-?WARD (/NTER91E MT+*RVER$E FULL EAR (69) MID 6m 7 T M10 6154/? FULLGEAR FOR ARD ram/mp 5f REVERSE REVERSE EXHAUST ,/7.9 C REGULAR I COMPRESSION 1 !F0RwA/?0 -7*/NTERMDIATE+--RVER$E INVENTORS I Patented Aug. 8, 1950 UNITED STAT 02!? F [1 CE LOCOMOTIVE CONSTRUCTIQN. PROVIDING IMPRDVED TRACTIVE' EFFORT CHARACT- TERISTICS poraticn of Delaware Application September 13, 19A?l.:,.SeriaLND-.'Zi73.8-38;

(Cl. IM -I27) 15 Claims. 1

This invention relates to steam engines, espe-e cially locomotive steam. engines of the type having: double-acting cylinders and pistons, equipped with; valves; and control means providing. for reversal of. operation and: also for adjustment on? various valve events, such. as admission, cutofii", release and, compression, and in its preferred embodiment the invention involves? locomotive construction providing improved; tractive effort characteristics with normal manipulation of the reverse ear;

The invention is particularly directed to the provision of mechanism which will. secure automatically coordinated adjustments of certain. admission and exhaust valve events (notably cutoff and compression), so. as to obtain in practice the best possible results from the method here.- tofore disclosed by one of the present joint in- Ventors. (i. e. by Albert .1.. Townsend in his copending. application No 519,093., filed February 119.451) which method involves, among other things, the imposition of a braking force upon their locomotive engine means, at start. and: at low speeds, e. g. by subjecting the working steam, when the engine is operating. at late cut-oft, to the opposition of steam under compression in the opposite endof the cylinder, whereby the locomotive may be rendered less slippery at start and in the lower part of. the speed range, and/or theaverage tractive power may be increased in a practical manner.

Although the said copending application points out. how the said method may be practiced (to a limited degree) by manual manipulation of certain known equipment, for example, by suitable manipulations of independent reversing levers for separate admission and exhaust. valve gears of the prior art (an example of which art is illustrated in the Small and Freeman Patent No. 1,512,317), the present invention contemplates obtaining, to the maximum, all of the benefits of said method, in a very much easier way, by providing anextremely simple mecha.- nism, efiicient and reliable inoperation, which automatically coordinates, in any desired predetermined relationship, the admission and exhaust valverevents under the control of a, single control member, such as an ordinary power reverse lever in the cab, so that the desired exhaust valve events, both for starting, and slow running, and also for highrspeed operation, are always secured, with no special effort or attention on the part of the engineman.

More specifically, we contemplate the present invention the provision of such a mechanism which willsecure, the desir d extended compression- (at, start and low operating speeds) by. automatically advancing, the timin of the; ex: haust valve. closure, v relative to piston stroke, when. the mechanism. is set to provide late cutofi oi the admission valve; the mechanism, being designed to do this without any substantial OBI-.- responding alteration of. the release event or the. admission event, Furthermore, the mechanism of. the present invention effiects automati'a cally a pro ressive. reduction. of the period. of compression along; with a progressive reduction of the periDd; of admission until a predetermined cu,.t.--oif adjustment has; been. reached, whereupon,

, as the cutsofi adjustment. is progressively further advanced, the; period; of compression is again lengthened, by advancing the timing of the com.- pression event, progressively, preferably to. the point of minimum or earliest, cut-ofi adjustment (corresponding to the highest speed of operation of the locomotiveJ To bring out. more fully the nature and ade vantages. of the invention, it will be helpful to review briefly some. characteristic features. of

Y locomotive. practice, as follows:

In av typical engine, a; relatively late ClltrOfi, say at 7,5 or. 8101 of the piston strokev (or even more) utilized. at start and ll low running speeds; but the period" of admission may be shortened by advancing, the. point of cut-oil, either stepwise, or continuously, to aminimum of say 25%. (onwijth poppet valves, say 201% or even 15% or less) of the piston stroke, the cut-oil usually being progressively advanced as the. run.- ning. speed of the. locomotive increases. Beyond the point of. cut-off, the. steam admitted to the cylinder works expansively, and as the cut-n11 is advanced to provide progressively shorter periods of steam admission, the period during which the steam, works. expansively is progress sively increased,

The releaseeventmarks the. point in the stroke at which the exhaust. valve opens, and. the compression event takes. place at. the point in the piston stroke at which the exhaust valve closes. It has of course beenv customary to. progressively lengthen the period. of compression as the run-,- ning speed of the locomotive increases,

Attention now called to the knownfact that eftorts. to; increase the tractiive effort of locomotives as. by increasing the. locomotive boiler pres,- sure or the. cylinder diameter, tend. to. cause or atngravate slipping oi the driving. wheels. at start and at low runningspeeds of the. locomotive, be.- cause. of the resulting. reduction in] the. factor of adhesion. As above mentioned, at start and at low running speeds, a late cut-01f is utilized, and this results in admission of steam to the cylinder at full boiler pressure throughout most of the piston stroke, including those points at which the maximum peaks occur in the starting and slow-running tractive effort curves.

With the foregoing factors in mind the present invention further has as an object the provision of an improved locomotive steam engine, of simplified construction and operation, which combines the characteristics of relatively reduced slipperiness at start and low speeds, with relatively increased average tractive effort throughout the range of running speeds and especially in the mid-portion of the operating speed range in which relatively high tractive effort is of particular advantage in facilitating acceleration of 7 heavy trains.

Thus, the locomotivev with the improved valve gear of this invention may be constructed to have a given average tractive effort, but reduced slipperiness at start and low speeds; or may be constructed to have increased tractive effort throughout the speed range, without corresponding increase in slipperiness at start and at low speeds.

' To achieve this favorable combination of characteristics, the invention provides valve actuating and control means serving to extend the compression period at least under conditions of start, when the admission valve is adjusted for late cut-off, and preferably also during those adjustments of cut-off which are normally employed throughout about the lower one-half of the speed range of the locomotive, and to do this in a fully automatic manner, as least so far as coordination of the desired compression and cutoff. events is concerned. In effect, this extension of the compression period applies a braking force to the piston in predetermined coordination with the maximum admission, which acts to resist initiation of wheel slippage and also to stop slipping of the wheels. Thus, in one of its broader aspects, the invention contemplates the provision of 'means automaticallyv acting to apply a braking force to an operating part of the engine under conditions of starting and at lowrunning speeds of the locomotive.

Since, according to the invention, the braking force is derived from an extension of the period of compression, the braking force is applied by the pressure of (otherwise exhausted) steam acting directly on the piston, in opposition to the steam which is then performing the working stroke, and the braking force is therefore effective not only to stop slippage but also to resist initiation of slippage.

' In a typical locomotive steam engine according to the invention, the progressive adjustment of cut-ofi, say from 75% of the piston stroke (for starting) to of the piston stroke (for high speed running), is accompanied by a predeterminedly-coordinated progressive adjustment of the period of compression from a relatively long period (for starting) to a relatively short period (for about mid-running speed), the period of compression then being again progressively lengthened (for high speed running). Advantageously the period of compression utilized with late or starting cut-off is even longer than that utilized for high speed running of the locomotive.

tively coordinating the adjustments of the periods of admission and compression in the relationship above discussed, so that movement of the engineers control, e. g., the customary reverse lever, to the Full Gear position will concurrently provide both late cut-off and long compression for starting, and so that subsequent movement of the control progressively toward the Mid Gear or neutral position will progressively adjust the periods of admission and compression, this progressive adjustment of said periods being in like sense (both periods shortened) to about the middle of the range of adjustment, and then being in opposite senses (the period of admission shortened and the period of compression lengthened) as the mid gear or neutral position is approached.

The invention further contemplates operation of this novel mechanism not only in forward operation of a reversible locomotive steam engine, but also in reverse operation, at least to the extent of an automatically lengthened compression period at late cutoff; although in locomotives especially adapted to road service where there is little running in reverse, the compression period need not be lengthened at early cut-offs.

In accordance'with another aspect of the invention the foregoing features are incorporated in a locomotive engine equipped with poppet type steam distributing valves. Anengine so equipped is especially suited to the attainment of the operating characteristics above described, since separately movable poppet valves are utilized for admission and exhaust of steam, and such separately movable valves may readily be actuated in the required relation to the piston stroke providing the desired predetermined interrelation between the periods of admission and compression.

Still further the invention contemplates employment of cam mechanism for actuation of the steam distributing valves, this being particularly desirable when employing poppet type valves. Cam mechanism is especially suited to the attainment of the'operating characteristics described, since the desired variations of and coordinated interrelation between the periods of admission and compression may be achieved merely by utilizing appropriately shaped cams, driven in synchronism, and adjusted in common by a single manual control member. In a typical cam actuated poppet valve engine, the positive coordination of the admission and exhaust valve events in the interrelation described above is desirably accomplished by utilizing a camshaft which is 'rotatively driven in timed relation with the piston movements, the cam shaft carrying cams having differently configured cam surfaces for actuating the separately movable admission and exhaust valves; the coordination of progressive adjustment of the admission and exhaust events, especially the events of cut-off and compression, being preferably accomplished by employment of cams having surfaces of varying contour axially of the cam shaft and by arranging the cam shaft for axial shifting movement to bring differently shapedportions of the cam surfaces into effective cooperation with the admission and exhaust valves. 7

How the foregoing and other objects and advantages are attained will appear more fully from the following description referring to the accompanying drawings, in which Figure 1 is an outline side elevational view of portions of a two-cylinder steam locomotive, equipped according to the present invention;

anagram T E1gure=2 is: a Vertical sectional view through: a cam box for housing cam mechanism. foractuirating the valves of one of the cylinders. of the locomotive engine, the view being taken. in. a plane transverse the locomotive and containing the axis or the cam shaft mounted in the cant box above the right hand cylinder of the locomo tiive;

Figure 3 is a vertical sectional View: takers substantially in the plane indicated by line 3-3 on; Figure 2', to an enlarged. scale, and illustrating not only the cam mechanism but also: an as sociated: pair of poppet-type admission valves are arranged one toward each end ofthe cylinder, a portion of which latter also isshown (but withoutthe cylinder heads) Figure iis. a view similar to. Figure 31buttaken in the plane of a pair of poppet type. exhaust valves; as. indicated. by the section line 4-4. on Figured;

Figure. 5 is. a perspective View of an exhaust cam assembly according to the invention", the: View being. taken from adjacent the inner end of said assembly;

Figures. 6 to 1.0 inclusive are transverse sectional: views through the exhaust cam assembly;. the: sections being. taken as indicated by the sec tioni lines 6-6 to IBle on Figure 2,. but being enlarged;

Figure. 11 is a view somewhat diagrammatically representing. a development of an intake assent-- bly;. showing alsov the cam follower. for the crankend. intake valve, this view indicating the points: in the: cycle. of operation of the piston. in; the cylinder at which the crank-end admission valvez opens. and closes;

Figure 12 is a development. View similar to. Eigure 11, of an exhaust cam assembly according to Figures to inclusive and; showing: the cam follower for the crank-end exhaust. valve; and

Figure, 13.- is a development. view. similar to;- Eigure, 12. but based on; a. different form of exhaustcam assembly.

As; seen in Figure l the locomotivev comprises aboiler having asmokehox 21: toward its: for;- ward end with a discharge stack 22. The locomotivecab appears at 23- toward the left in Figure '1. Driving axles. such as indicated at: 274- are mounted in the mainframe members 2,5,. pairs of driving wheels 26 being. associated: with the driving; axles. For purposes of: illustration, itis assumed that the steam engine of the, locomotive; shown in Figure 1 incorporates a. pair of double-acting cylinders, one of which appears at. 2:1. A. piston 28 reciprocates: in each cylinder,v each piston. having a rod 29 extended. through theend. wall of the cylinder to the crosshead. 30. wl-iich is carried by crossheadguide 3!. Thecrosshead is adapted to be coupled by a connecting rod diagrammatically indicated at 32' with the; main crank pin 33 which. is associated with one of the driving axles 24. Side rods such as; diagrammatically indicatedat 32c! serve to interconnect driving wheels.

Steam, under the control or the main. throttle (not shown), is delivered through the supply pipe 34 and through branches 35-36 to the admission steam chests 31-48 at the head and: crank endsof the cylinder 2:1. Steam is exhausted, atv each end of cylinder 27 through chests. 39', and 4,0 and connected passages adapted to. carry the exhaust steam for ultimate discharge throughthe exhaust nozzle (not shown) in the; smokebox 24%. i

(iii.

Am described more: fully herebelow with. pare ticularreference. to Figures 2, 3' and a. the admission and exhaust. valves employed in the. chests ill-38; and 39 4fl are preferably of the. poppet-type, adapted to; be actuated. by cam. mechanism mounted and housed: in a cam. box generally indicated in. Figure lat M. The. cam mechanism is driven in. timed relation with. the

reciprocating motions of the piston, tor which.

purpose drive: shafting 42' is extended forwardly to: the cam box from. a: gear box. i t associated with a. return crank. 43 which. is carried by the: crank pin 33. The gear box Or drive unit M serves. tn-driyingly couple the; shafting 32. with; a pin on the return crank 43' in a manner which need not be considered in detail herein since it: forms: no.- part of the present invention per se,. such a. drive unit, however,. being: fully disclosed in the. copending application Serial No. 525,180,. filed March 6, 1944, of one of the present applis cents. and one. Raymond P. Delano, Jr:.,. WhlGhl applicationissued as Patent 2,441,199.. It is here noted,. however, that. the drive unit i l provides for rotation. of shafting 42 in timed relation to the driving wheels of the locomotive and. thus also in timed relation to: piston stroke. At the end of. the drive shaiting 3:2 associated with they cam; box: 4.5:, the shaft 62 is geared to. the cam shaft in the manner described shortly below.

As: further seen in Figure 1, an englneers reversal-ever 45 is arranged in the cab 23 and pro.- vides: for control of the cam mechanism. by rotaticnal adjustment of the interconnected shafts 4 6, Ail and 48, a power reverse gear is being employed for this purpose; A gear box 56 is associated. with shaft. 4'! to provide for the connection of a. transverse shaft which, in turn, is. associated with a shaft similar to that shown at 48 for control of the cam mechanism for the valves of the cylinder at the opposite side of the locomotive. The manner in which shaft 4:8 is associated: with the cam mechanism is described herebelow.

It is here.- noted that shaft-ing 3.2 (for driving the cam shaft) and shafting 4E4it8 (for reversal: and adjustment of valve events) are. provided with appropriate flexible and. slip joints which. need not be discussed herein.

Turning now to'Figures 2, 3, and 4, it will be seen that the cam box 4| serves to enclose and mount the camshaft 5i. The camshaft Si is supported for rotation and also for axial shi fting movement. For this purpose, toward its right hand end, as viewed in Figure 2, the camshaft is provided with a bearing 52 adapted to rotate and slide in a bearing sleeve 53. At the opposite: end of the camshaft (toward the left in Figure. 2)., the camshaft carries a member 54 provided with external splines adapted to co-- operate with complementary splines 55 formed internally on the rotative sleeve 56. The splined connection. between the parts 54 and 56 permits axial. shifting' movement of the camshaft but constrains the cam iaft torotate with the sleeve 56. Sleeve 56 is adapted to be driven by a worm wheel" 51 fixed thereto, which worm wheel meshes with. a worm 58- fixecl. on the shaft 42. above de-' scribed.

For the; purpose of shifting the camshaft axially, adepending fork 59straddles the camshaft and enga es a cooperating non-rotative mem bermfifl which. is fixed as against axial movement with'xrelationv to. the camshaft but within which the camshaft may freely rotate The fork 59 is. depends: from a support 64 which is connected with an internally threaded member '62 cooperating with a rotative screw threaded shaft 63. An extension 64 of this shaft has a spiral gear 65 fixed thereto, which gear meshes with a complementary gear 69 fixed on the control shaft 48 above described.

The camshaft BI is adapted to carry cams for actuation of the admission and exhaust valves at each end of the cylinder with which the cam mechanism is associated. Thus, as seen in Figure 2 the camshaft carries an :admissioncam 61 for forward operation and an admission cam 68 for reverse operation; and also an exhaust cam 69 for forward operation, an exhaust cam 10 for reverse operation, together with an intermediate cam member H having transition surfaces interconnecting those of the forward and reverse exhaust cams. The cams for admission and for exhaust are, for convenience in manufacture, made up of the several cam members above referred to, although it should be understood that this subdivision of the admission and exhaust cams has no bearing upon the sub ject-matter of the present invention. The cam members 61 and 6?; are desirably provided with keyways adapted to cooperate with a key 12 associated with the camshaft; and similarly the cam members 69, l9 and H are provided with keyways adapted to cooperate with key 13.

The cam box also serves to support intermediate or follower levers l4 and 15 carrying follower rollers 16 and 19' adapted to cooperate with the forward intake cam member 6'! and the reverse intake cam member 68, according to the axial adjustment of the camshaft. Similarly, intermediate or follower levers l8 and TI carrying follower rollers 19 and 19' are adapted to cooperate with exhaust cam members 69, i and H, according to the axial adjustment of the camshaft.

The admission valves at opposite ends of cylin-i der '2'! are shown in Figure 3, from which it will be seen that admission valve 80 controls the fiow of steam from the admission chest 31 to the cylinder port 8|, the admission valve 82 at the opposite end controlling admission of steam from the chest 38 to the port 83. Valve 89 has a stem 84 projecting inwardly to cooperate with the tappet 85 adapted to be actuated by the intermediate lever 14. At the other end of the cylinder, valve 82 has a stem 86 adapted to cooperate with tappet Bl which is actuable by the intermediate lever i5. Return springs 88 urge the valves 80 and 82 toward their closed positions, 7

The arrangement of the exhaust valves (Figure 4) is similar to that described above with reference to the intake valves. Exhaust valve 89 controls discharge of steam from the cylinder port 83 to the exhaust passage 40, the valve 9|] controlling exhaust from the port 8| to the exhaust passage 39. Valve 89 has a stem 9i ex tended for cooperation with tappet 92 which is actuable by the intermediate lever 11; and valve 90 has a stem 93 cooperating with a tappet 94 which is actuable by the intermediate lever I8. Return springs 95 normally urge the exhaust valves toward their seats.

With the arrangement of valves and cams above described, rotation of the camshaft and the cams carried thereby serves to open and close the valves, and axial shifting movement of thecamshaft serves to reverse the timing of the valve events and also to adjust the timing according to'the conditions of operation of the locomotive, for instance as between conditions of start and high running speed.

1 While the specific configuration of an assembly of exhaust cams according to the invention is illustrated in Figures -5 to 10 inclusive, it is. not thought necessary herein to illustrate the specific configuration of an assembly of intake cams. It is noted, however, that the development view of Figure 11 diagrammatically illustrates the reversal and adjustment of timing of the events of an admission valve obtainable with a cam assembly of the type illustrated at 61-68 in Figure 2. Figure 12 similarly diagrams the reversal and adjustment of timing obtainable with an exhaust cam assembly such as shown in Figures 5 to 10 inclusive.

Referring to Figure 11, the diagram there shown represents the admission cam assembly as though the cam surfaces thereof were slit axially of the camshaft and then flattened to the plane of thedrawing. The figure also shows an admission follower roller 16 superimposed upon the diagram of the cam assembly. Bearing in mind that the camshaft is axially shiftable in accordance with adjustment in position of the engineers reverse lever 45 (Figure 1), it will be understood that such axial shifting movement effects relative shift of the cam assembly and th follower roller 16', to provide for engagement of the follower roller with the cam members at various axial positions. The position marked Drift in Figure 11 corresponds to the mid or neutral setting of the engineers reverse lever. The operating range for forward operation of the locomotive extends between the Mid Gear Forward position and the Full Gear Forward position. A similar, though shorter, operating range is provided for reverse operation. The forward admission cam 6! is provided with a lobe the leading edge of which is indicated at 96 in the diagram of Figure 11, the trailing edge being indicated at 91. Lines 96 and 91 respectively illustrate the points, for any given axial adjustment of the camshaft, at which the admission valve opens and closes, the arrow F designating the direction of movement of the cam surfaces with respect to the follower roller 16'. Lines 98 and 99 applied to the reverse cam 68 correspond respectively to lines 96 and 91, for reverse operation, i. e., movement of the cam surfaces with respect to the follower roller 16 in the direction of the arrow R. From the diagram of Figure 11 it will be seen that when the engineers reverse lever is adjusted to the Full Gear Forward position the period of admission is relatively long, the cut-off (occurring along the line 91) taking place at about 75% of the stroke of the piston in one direction. As the engineers control is adjusted toward the mid gear range, the period of admission is progressively shortened, the point of out-off being progressively advanced to about 20% when the control is in the Mid Gear Forward position. Although the matter is not of direct concern with the present invention, it will also be seen from the diagram of Figure 11 that, as the engineers control is adjusted from the Full Gear Forward position to the Mid Gear Forward position, the point of admission (occurring along line 96) is progressively advanced, so as to provide a limited extent of pre-admission, for purposes well understood in this art.

Referring now to Figures 5 to 10 inclusive, it will be seen that the exhaust cam 69 for forward operation is provided with a lobe I 00 having a flank l0! at its leading side, and also having two relatively angled flanks 102 and 13 at its trailing side. Thus, upon rotation of the cam member 69 in the direction indicated by the arrow F in Figures to '17 .andl2 each-of the follower rollers 19, 19' of the intermediate levers l8 and 11 for the exhaust valves, rides up flank ID] to the cam lobe Hill then down one or the other of the flanks i532 and H13, depending upon the position of axial adjustment of the camshaft. The effect of this is described more, fully herebelow with reference to Figure 12. Here note, however, that the exhaust cam member for reverse operation similarly has a lobe [04 with a leading edge flankiQE and a trailing edge flank I06. The configuration of this reverse cam member will also be describedmore fully below with reference to Figure 12.

The inter-mediate cam member H of the exhaustcam assembly includesa central cylindrical surface ,3 9'! (see Figuresi; and 12) having a radius somewhat greater than thatof the base (circle of the cams, so as to provide for retaining the exhaust valves in partially open positions when the engineers reverse lever is adjusted to the neutra-l or- Drift position. The intermediate member ll also has transition surfaces extended from the cylindrical surface i 81 to the cam surfaces of the forward and reverse cam members 59 and 10.

Referring: now to the diagram of Figure 12, the line it In (applied "to the exhaust cam member 69 for forward operation) indicates the point in the cycle of operation at which the ,exhaustvalve follower roller 19' (or 19) commences to ride up upon the flank H! l of the lobe L00, thereby opening the exhaust valve. Lines [02a and [03a represent the points at which the follower roller 19' leaves the flank it or H113, depending upon the position of axial adjustment of the camshaft, it being understood that the associated exhaust valve closes at the time when the follower roller 79' crosses the line lllza or the line H1300.

Corresponding lines 585a and l llfia are applied to the exhaust cam member To for reverse operation. As will be seen from the diagram of Figure 12, the lobe m4 of the reverse cam member l0 trailing edge of the lobe which is angled with respect to line illiia and in which region axial shifting movement of the camshaft does not appreciably alter the point at which the exhaust valve.

tended or lengthened period of compression act- .4 also is configured to provide a line I861) at the ing as a brake upon movement of the piston in the cylinder under the influence of steam being admitted to the opposite end of the cylinder. A similar condition prevails for reverse operation of the engine, as will readily be apparent from the diagram of Figure 12.

The diagram of Figure 13. illustrates, by way of comparison, an exhaust cam configuration arranged to provide the more conventional progr 'veiy shortened. period of compression as the en neers reverse lever is moved. to the Full Gear position. Here it will be seen that the line :1: provides a progressively later exhaust valve closureas the engineers reverse lever is adjusted toward the Full Gear position.

.at start and at low runninng speeds.

Attention is now called to the fact that in Figures 11, 12 and 13, follower rollers 16', 18 and 19m, respectively, are illustrated in the positions they would occupy with the same adjustment of the engineers control (Full Gear Forward), and with the cams in-the same rotative position, i. e., a position corresponding to about 50% of the stroke of the, piston in one direction. With the parts in the positions just mentioned, it will be seen from Figure 11 that the admission valve associated with the follower roller 16 is open and will remain open to a cut-ofi point at about.75% of the piston stroke. With the conventional exhaust events diagrammed in Figure 1.3, and with the parts in the positions mentioned the exhaustvalve is open; whereas with the extended compression diagrammed in Figure 12 the exhaust valve is closed, with the parts in the positions mentioned (see valve 98 in Fig. 4)

The foregoing comparison of Figures 12 and .13 shows a marked contrast between the exhaust events conventionally .employecland the exhaust events provided by the arrangement .of the-present invention. Thus, whereas the conventionally employed exhaust events provide a progressive decrease in the period of compression as steam admission is lengthened, according to the present invention the compression point is progressively advanced in the range of cutoff adjustments provided for low running speeds and for starting, in automatic coordination with the adjustmentof the valve gear toward full-gear position.

The invention thus provides for predetermined coordination of the events of cut-off and compression in a manner utilizing compression of steam in the cylinder as a brake upon the operation of the piston at start and at low running speeds. In a locomotive of given overall tractive effort the automatic braking action effected by the mechanism of the present invention results in an increase of the factor of adhesion and thus a reduction in the slipperiness 0f the locomotive On the other hand, the benefit of the invention is exploited more fully if, at the same time, the overall tractive effort of the locomotive is increased, as by increasing the boiler pressure or the cylinder diameter. In this way, the overall tractive effort may be increased without reducing the factor of adhesion at start and .at low speeds, and, moreover, the increase in overall tractive effort may be concentrated in the intermediate range of running speeds, in which such increase is of espe- 1 cial advantage in facilitating the acceleration of great toa relatively lesser admission, and means for causing fluid pressure opposition to at least a portion ofa working stroke of the piston which opposition is substantially greater at startthan at running speeds of the locomotive. H

2". In .a fluid-pressure locomotive engine having .a doubleacting cylinder and piston, means for admitting. working fluid" alternately to the head and crank ends of. said cylinder in timed relation 2,51 s ns 11 to-theopposite' strokes of v the piston, means for altering the efiective admission of working fluid, during running of the engine, from a relatively great to a relatively lesser admission, means for causing fluid pressure opposition to at least a portion of a working stroke of the piston, means 'for altering the efiective opposition, during running of the engine, in like sense with the alteration of effective admission, and means positively efiecting a predetermined coordination of said alterations. V

3. In a fluid-pressure locomotive engine havinga double-acting cylinder and piston, means for admitting working fluid alternately to the head and crank ends of said cylinder in timed relation to the opposite strokes of the piston, adjustable means for altering the efiective admission of working fluid, during running of the engine, from a relatively great to a relatively lesser admission, means for causing fluid pressure opposition to at least a portion of a work- 'ing stroke of the piston, means for altering the effective opposition, during running of the engine, in like sense with the alteration of effective admission during a portion of the range of adjustment. and means for altering said effective opposition in a sense opposite to the alteration of effective admission during another portion of the range of adjustment, and means positi el effe ting a predetermined coordination of said alterations.

4. In a locomotive engine having a cylinder and piston. and valve means for eifecting admission, cut-off, release and compression of the steam with respect to both the head end and the crank end of said cylinder in timed relation to the p ston s roke, valve gear mechanism actuat n said valve means compr s n means for compression with said earl er cut-off. and a.

common control for all of said meansv .5. In a steam locomotive engine having a cylfinder and piston. and valve means for eflecting admission, cut-.oif, release and compression of the .steam with respect to both the head end and,

the crank end of said cylinder in timed relation to the piston stroke, valve gear mechanism actuating said valve means comprising means for altering the timing of the cut-off from a relatively late cut-oil to a relatively earlier cut-off with respect to each end of the cylinder, means for effecting a relatively long compression with said late cut-off and a relatively shorter compression with said earlier cut-off, andmeans for .eifectin substantiallv normal timing of release with both said late and-earlier cut-offs, and a common control for all of said means.

'6. In a locomotive engine having a cylinder and piston, and valve means for effecting distribution of the steamwith respect to both ends of said cylinder variably at least as to cut-oif and compression with relation to the piston stroke, valve gear mechanism actuating said valve means comprising means for altering the timing of the cut-01f from arelatively late cut-ofi to an intermediate cut-off and thence to a relatively early cut-off, and means for effecting a relatively short compression with said intermediate cutoff and a relatively long compression with each of said late and early cut-offs, and, for the last two mentioned means, adjusting mechanism 12 common to both whereby their operations are {automatically effected in positively predetermined relationship. 7

7.. In a locomotive engine having a cylinder, and valve means for effecting distribution of the steam with respect to both ends of said cylinder variably as to admission, cut-off, release and compression, valve gear mechanism actuating said valve means comprising means for effecting progressively longer compression with progressively earlier cut-off through a substantial portion of the range of cut-off adjustment and means positively coordinated therewith for ef- 'fecting progressively longer compression with progressively later cut-ofi through another portion of the range of cut-off adjustment.

8. In a locomotive engine having a cylinder,

and valves for efiecting distribution of the steam with respect to both ends of said cylinder variably as to admission, cut-01f, release and compression, valve gear mechanism actuating said valves comprising means for effecting progres- 'sively earlier timing of the admission, cut-on" and release throughout a predetermined range, means for efiecting progressively longer compression with progressively earliercut-ofi through a substantial portion of the range of cut-off adjustment, and means for effecting progressively longer compression with progressively later cutoflf through another portion of the range of cutoff adjustment, and a single control for adjusting all of said means together.

9. In a locomotive engine having a cylinder and piston, and valve means for efiecting admission, cut-on, release and compression of the steam with respect to both the head end and the crank end of said cylinder in timed relation to the piston stroke, valve gear mechanism actuating said valve means comprising means for altering the timing of the cut-off from a relatively late cut-off to a relatively earlier ciit-off with respect to each end of the cylinder, and cam means for controlling release and compression comprising a rotatable cam and a cam follower relatively shiftable with respect to each other axially of the cam, the cam having a lobe with a helical flank providing relatively long compression with said late cut-off and a relatively shorter compression with said earlier cut-oil.

10. A construction according to claim 9 and further including means positively coordinating relative shifting of the cam and cam follower with timing of cut-off.

11. In a locomotive engine having a cylinder and piston, and valve means for effecting admission, cut-oil, release and compression of the steam with respect to both the head end and the crank end of said cylinder in timed relation to the piston stroke, valve gear mechanism actuating said valve means comprising means for altering the timing of the cut-oil from a relatively late cut-off to'a relatively earlier cut-off with respect to each end of the cylinder, and cam means for controlling release and compression comprising a rotatable cam and a cam follower relatively shiftable with respect to each other axially of the cam, the cam having a lobe of greater circumferential dimension in an intermediate region lengthwise of the cam as compared with the circumferential dimension thereof in regions toward each end thereof.

12. A construction according to claim 11 and 7 further including means positively coordinating relative shifting movement of the cam and cam follower with timing of cut-ofif.

13. In a locomotive engine having a cylinder and piston, and valve means for effecting admission, cut-ofi, release and compression of the steam with respect to both the head end and the crank end of said cylinder in timed relation to the piston stroke, cam mechanism for actuating said valve means comprising a rotatable cam axially shiftable to alter the timing of the cut-01f from a relatively late cut-off to a relatively earlier cut-off with respect to a working stroke of the piston, and a rotatable cam axially shiitable to effect a relatively long compression with said late cut-off and a relatively shorter compression With said earlier cut-off.

14. A construction according to claim 13 and further including means positively coordinating axial shifting movements of said cams.

15. For a locomotive valve gear adapted to operate separate admission and exhaust valves, a cam assembly comprising an admission cam with a progressive surface adapted to effect a progressive change in admission valve closure from late closure to early closure, and. an exhaust cam with two oppositely progressing surfaces which are adapted sequentially to effect an early closure of exhaust valve means in conjunction with the aforesaid late closure of the admission valve means, a later closure of said exhaust valve means during an intermediate portion of the range of operation of said admission cam, and again a relatively early closure of said exhaust valve means in conjunction with said early closure of the admission valve means.

ALBERT J. TOWNSEND.

JULIUS J. KIRCHHOF.

REFERENCES CITED The following references are of record :in the file of this patent:

UNITED STATES PA'I'ENTS Number Name Date 2,138,053 Woodard Nov. 29, 1938 FOREIGN PATENTS Number Country Date 245,590 Great Britain Jan. 18, 1926

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