US591529A - Duplex engine - Google Patents

Description

(Nb Model.) 2 Sheets-Sheet 1. H. B. GALE.

DUPLEX ENGINE.

Patented Oct. 12, 1897.

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(No Model.) 2 Sheets-Sheet 2 H. B. GALE.

DUPLEX ENGINE.

No. 591,529. Patented Oct. 12,1897.

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HORACE B. GALE, OF SAN FRANCISCO, CALIFORNIA.

DUPLEX ENGINE.

SPECIFICATION forming part of Letters Patent No. 591,529, dated October 12,1897. Application filed September 18, 1894- Renewed March 18,1897. Serial No. 628,228. (Nomodelfi To aZZ whom it may concern.-

Be it known that I, HORACE B. GALE, a citizen of the United States, residing at San Francisco, in the county of San Francisco and State of California, have invented certain new and useful Improvements in Duplex Engines; and

I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertainsto make and use the same.

This invention relates to the class of steamengines commonly known as duplex, and

used for operating pumps. The distinguishing feature of the class is a pair of pumps operated by separate steam cylinders and pistons so arranged that the mechanism of each pump controls the valve-gear by which steam is admitted to operate the other pump, there being nocrank shaft or equivalent positive mechanical connection between the two pumps.

The object of myinvention is to provide means by which such an engine having only two steam-pistons coupled to each pump-rod can be operated with the degree of steamexpansion and economy obtained in a'threeone of the low-pressure cylinders being connected to work one of the pumps, while the intermediate cylinder and the other low-pressure cylinder are connected to work the other pump. I

In the accompanying drawings, which form a part ofthis specification, Figure 1 is a diagram representing the steam cylinders and receivers of a duplex engine with their pipe connections and pressure-regulating valves arranged according to my invention. Fig. 2 is avertical section of the automatic pressureregulating valve, illustrating the preferred construction thereof; and Fig. 3 is a diagram of the pumps.

In the diagram, 1 indicates the high-pressure cylinder; 2, the intermediate cylinder; 3 and 3, the two low-pressure cylinders, and 4 and 4 the two main pump-rods.

5 indicates the steam-supply pipe leading to the steam-chest of cylinder 1, and 6 the exhaust-pipe from that cylinder, which discharges into the first receiver 7.

8 indicates the supply-pipe leading from the first receiver into the steam-chest of cylinder 2, 9 the exhaust-pipe from that cylinder, and 10 the secondor low-pressure receiver, from which the pipes 11 and 12 lead to the steam-chests of cylinders 3 and 3, respectively.

13 and let indicate the exhaust-pipes from the two low-pressure cylinders, which may lead to a condenser or to the atmosphere if the engine is non-condensing.

In practice 'I prefer to place the receivers of horizontal engines transversely directly over the cylinders which take steam from them. Thediagram may be considered as a plan View of such an engine, with the receivers and piping revolved out of their usual position to show better the principle of the connections.

In Fig. 3,,A and B indicate in plan view the twomain pump-cylinders, the plungers O and D being shown by dotted lines.

F indicates the force-main, and S the suc--,

The detail of the construction and arrangement of the pumps is not essential to the invention, the only requisite being that there shall be two pumps, each adapted to be operated by one side of the engine, as already specified.

15 indicates the casing of the automatic pressure-regulating-valve, and'16,17,-and 18 small regulating-pipes connecting the latter respectively with thesteam-chest of cylinder 1 and with the two receivers 7 and lO. The main throttle-valve used in starting and stopping the engine is indicated by 19, while 20,

21, and 22 indicate auxiliary throttle-Valves which are supplied usually for purposes to be explained farther on.

23 indicates a by-pass valve used to charge the second receiver before the engine is started, and 2i and 3f safety-valves.

The engine alve-gear, which is not representcd in the diagram, may be any style of the smooth and uniform operation of the engine depends should not be disturbed by variations in the working pressure, such as are liable to occur in general service. Heretofore the only successful method of maintaining automatically this required equality between the forces applied to the two pumps under all conditions of service has been to make the two sides of the engine exact duplicates of each other in fact, two distinct enginesconnected only'through their valve- On the other hand, it has been well' known that, other eonditionsbeing thesame, a single large engine will accomplish a given work with greater economy than a pair of smaller engines of the same total capacity,

and numerous attempts have been made to reduce the number of cylinders required for a given ratio of expansion, and thus to diminish the cost and improve the efficiency of the engine by cross-compounding 'i. e., by connecting two or more cylinders upon opposite sides in series as regards the passage of steam through them; but in such attempts the arrangements and proportions of the steamcylinders heretofore used have always been such that changes in the working pressure have affected the two sides of the engine unequally, so that if the engine were adjusted towork correctly at any given pressure any material change therein would destroy the equilibrium of efforts on the two sides of the engine and interfere with the equable operation of the two pumps. Efforts have been made in certain constructions to correct this defect by means of hand throttlevalves adjusted differently on the two sides of the engine, but wide variations in the working pressure or in back pressure necessitate excessive throttling to maintain an equable relation between the action of the two pumps, which involves a considerable falling off in economy, besides some extra attention. The devices by which I have been able to remedy these defects are based upon certain principles of action of multicylinder compound en-' gines, which may be briefiystated'as follows: It is found in such engines whose valves have a fixed adjustment that the pressures in the intermediate receivers adjust themselves in a fixed ratio to the initial pressure and var Y together with it. The effect of this action is to maintain an approximately constant ratio between the efiective pressures on all the pistons except the last or low-pressure piston, but as the back pressure on this piston is determined by external conditions and has no fixed relation to the initial pressure the ratio of the effective pressure on this piston to that on the others changes with every variation in either the initial pressure or back pressure.

To produce a cross-compound duplex engine which shall maintain automatically a constant relation between the efforts applied to the two pump-rods under different working pressures, I have accordingly found it necessary, first, to provide means of balancing the variable effort on the low-pressure piston. This I do by providing a pair of equal low-pressure cylinders, located one on each side of the engine, so as to balance each other, the pair of cylinders being supplied with steam from a common receiver, as shown. In this arrangement all fluctuations in back pressure, as well as in boiler-pressure, must affect the two equal low pressure pistons alike, and by the principle previously stated variations in the boiler-pressure will affect the pressure on the high-pressu re and intermediate-pressure pistons in the same ratio. Consequently as variations in the final exhaust-pressure cannot affect the high-pressure and intermediate-pressure pistons, if the efforts exerted on the two latter pistons are once adjusted to equality that relation will be maintained automatically as long as the valve-adjustment of the engine is unchanged. Such an engine therefore when once adjusted to produce the required equable action of the two pumps will maintain that adjustment under all variations of boiler-pressure and Vacuum that may be required by the conditions of the work and needs no other regulation than to control the initial pressure to correspond with variations of head in the forcemain, so as to keep the pumps working at the desired speed-the same attention as is required with common duplex engines. The engine may be run, for example, either concondensing or non-condensing without any change in its adjustments.

In the arrangement of the cylinders it is immaterial whether the two low-pressure cylinders are placed next to the pumps or at the opposite end, the thing necessary being that one of them shall be coupled with one of the other cylinders on each side of the engine, so as to equalize the effect of the back pressure. WVithout this feature it is impossible by any proportions of parts to produce a cross-compound duplex engine that will maintain antomatically the required equilibrium of effort on the two pump-rods under all conditions of pressure.

The proportion of cylinders which I have found best suited to accomplish this result is that which makes the displacement of the intermediate piston a mean proportional between that of the high-pressure pistonwand the sum of the displacements of the two lowpressure pistons. Such a proportion is illustrated in the drawings, where the diameters of the high-pressure, intermediate, and lowratio of the numbers 8, 14, and 17, the length of stroke being the same in each. The volume of the displacement of eachpiston during one stroke will be in this case proportional to its area or to the square of its diameter, and the effective volumes of the cylinders therefore will be proportional to the squares of the numbers 8, 14, and 17, or to the numbers 64, 196, and 289, respectively. Accordingly, letting V V V and V represent the effective volumes-t'. 6., piston displacements-of the cylinders 1, 2, 3, .and 3, respectively, We may write the proportions V 7 :64.: 196: (approximately) 1 :3,

and V V +V -64: 2 289:64: 578

. (approximately) '1 9.

Therefore in this case we have by a close approximation This equation may be expressed in words by saying that the effective volume of the-inter-' mediate cylinder is a mean proportional between that of the high-pressure cylinder and the sum of the effective volumes of the two low-pressure cylinders, Hence the dimensionsgiven correspond within practical limits to the rule stated. To illustrate how this method of proportioning the cylinders serves to maintain the equable operation of the two sides of the engine, we may apply the principle that the absolute pressure of the steam in the different cylinders isinversely proportional, approximately, to the volume which it occupies. Hence in the example cited the absolute pressures in the high-pressure, intermediate, and low-pressure cylinders will stand nearly in the inverse ratio of the eifective volumes of these cylinders; or, if we let P P and P represent the absolute pressures of the steam admitted to these cylinders, respectively, we have P :P :P =9:3:1. I

As the back pressure on the highpressure piston corresponds to the admission-pressure for the intermediate piston and the back pressure on the latter corresponds to the admission-pressure for the two low-pressure pistons the efiective pressures on the high-pressure and intermediate pistons Will be in the ratio of the differences of these numbers; or

(P P (P P (93) (3-1) :6 2.

Moreover, as the Work done by each piston is the product of the effective pressure and the or the ratio of equality. In other words, the same'quantity of work will be done in each stroke by the high-pressure piston as is done :by the intermediate-pressure piston. pressure pistons are intended to be in the The displacements and effective pressures each being equal for the two low-pressure i pistons, it is apparent that the arrangement and proportions described are such as to produce equality of work on both sides of the engine, irrespective of the absolute values of the initial pressure and back pressure. These pressures therefore may be varied independently, as required by the conditions of the work, without any change in the adjustment of the engine.

It is assumed in the foregoing calculation either that there are no cut-off valves or that they are set to cut off the steam at the same point in the stroke in all the cylinders and that the capacity of the receivers is sufficient, so that the intermittent discharge of the exhaust into them will not produce extreme fluctuations of pressure. The rule of proportioning which has been given is the only one ical equality between the forces acting on the two sides of the engine being unnecessary in practice, and the definitions herein given of the correct cylinder proportions therefore are not to be interpreted as excluding such trifling variations on either side thereof as will not practically affect .the equilibrium of the forces applied to the pump-rods.

The auxiliary throttle- valves 20, 21, and 22 (shown in Fig. 1) are unnecessary for purposes of regulation and may be omitted; but the two valves 21 and 22 afford a convenient means of compensating for any small errors in the cylinder'proportions or in the setting of the cut-off valves. The amount of throttling required on one side or the other to effect such an equalization should be extremely slight, a variation of a fraction'of a pound pressure being usually sufficient, and this adjustment, once made,'does not need to be altered for variations in the the working pressures. Ifthe cut-off valves are set with perfect accuracy, no throttling on either side is required. When the cut-off valves are thrown out of action or set to cut off very late in the stroke, the valves 20, 21, and 22 serve an other useful purpose in diminishing the fluctuations of pressure in the steam-chests of I the intermediate and low-pressure cylinders, due to the intermittent discharge of steam into the receivers 7 and 10. By means of these valves each receiver is practically divided into two chambers, the first consisting of the receiver proper and the second of the steam-chests connected therewith, and the use of a partially-closed valve between these parts damps the fluctuations in the steamchests and permits the use of smaller receivers than otherwise would be needed to obtain smooth action of the pumps when run without cut-off valves. For these reasons I generally prefer to supply the valves 20, 21, and 22, although they may be dispensed with.

To facilitate charging the receivers at the proper relative pressures for starting the engine, and also to maintain automatically the correct relation between the receiver-pressures and the initial pressure under rapidlyvarying loads, I attach sometimes a special equilibrium-val\-'e 15, a good form of which is shown in Fig. 2, which acts to shunt a small portion of steam around the high-pressure cylinder, or the intermediate cylinder, as may be required, so as to maintain the correct ratio of pressures under all circumstances.

Fig. 2 shows a tubular piston-valve whose interior is constantly in communication, through the ports 25, with the lower chamber 26 of the casing 15, and which has a second set of ports 27, by which a communication may be opened between the interior of the valveand either of the chambers 28 or 29, according to the position of the valve. To the lower end of the valve is attached a dashpiston 30, which works in a cylindrical downward extension of the chamber 26, which is kept filled with water resulting from condensation of steam. The oflice of the dash-piston is to prevent too sudden movements of the valve, and a spring 35 is used to balance its weight. The upper piston of the valve 31, which separates the chambers 28 and 20, is turned to a slightly smaller diameter than the central piston 32, whiehseparates the chambers 26 and 28. The chamber 26 is connected with the intermediate-pressure receiver, the chamber 28 with the high-pressure steam-chest, and 29 with the low-pressure receiver. The intermediate pressure, therefore, acting upward on the piston 32, is opposed by the low pressure and the high pressure acting downward respectively on the piston 31 and the annulus representing the dilference between the areas of these two pistons.

I prefer to proportion the diameters so that the annular area exposed to high pressure bears the same ratio to the area exposed to low pressure as the displacement of the highpressure piston of the engine bears to that of the i ntermediate-pressure piston. With this proportion the valve will be in equilibrium when the difference between the high pressure and the intermediate pressure multiplied by the displacement of the high-pressure piston is equal to the difference between the intermediate pressure and the low pressure multiplied by the displacement of the intermediate piston. This is also the condition under which the same work will be done on both sides of the engine, assuming either that cut-01f valves are not used, or that they are adjusted symmetrically on the two sides.

Whenever the intermediate pressure exceeds its proper value, the piston-valve will be lifted and a little steam allowed to pass through the central tube from the lower to the upper chambert'. 6., from the intermediate to the low-pressure receiver-shunting the intermediate cylinder and restoring the equilibrium of work and pressures. If the intermediate pressure falls below its proper value, the valve is lowered, allowing a little steam to pass from the higlrpressure chamber 28 to the intermediate-pressure chamber 26-i. 0., from the high-pressure steam-chest to the first receiver-raising the pressure therein by the amount required to restore equilibrium. \Vhen correct proportions are used and the cut-off valves are accurately adjusted, the quantity of steam shunted by the equilibrium-valve is inappreciable, except during rapid changes in the working pressure. Other proportions for the valve-pistons than those described would necessitate either an unsymmetrical adjustment of the cut-off valves or the shunting of an excessive quantity of steam.

To start the engine, assuming that the valves 20, 21, 22, and are open, the main throttle-valve 19 is opened gradually, admitting steam directly into the highpressure steam-chest through the automatic valve 15 to the first receiver 7 and through the small by-pass valve 23 to the second receiver 10 until the pressures are sufficient to start the engine. After it has made a few strokes the valve 23 is closed. If there is then any difference in speed between the two piston-rods 4 and 4, it may be corrected by the equalizing- throttles 21 and 22, after which the equilibrium will be maintained automatically.

The automatic by-pass and pressure-regulating valve 15 is not a necessary adjunct of the engine, and with accurate proportions and adjustment of the cut-off valves the equilibrium of action between the two sides will be maintained, under ordinary conditions, without it, but it is useful for the purposes which have beendescribed. \Vhen it is omitted, a small by-pass pipe and a hand-valve 33, connecting the steam and exhaust spaces of the high-pressure steam-chest, are used for charging the first receiver in starting.

It is evidently possible to vary the details of the arrangement of the cylinders and re.- ceivers somewhat, while retaining all the essential features of the combination. Thus,

for instance, the engines steam-chests might be made of sufiicient capacity to serve instead of external receivers, which might then be omitted. It is obvious also that, with the means provided in the automatic and hand valves for rectifying slight faults in the equilibrium of work on the two sides of the engine, absolute accuracy in the proportions of the cylinders is not essential; but to secure the greatest economy in operation and to avoid waste of steam by throttling, by-passing, or unsymmetrical cut-off adjustment it is important that the proportions of the cylinders, as well as their arrangement, should conform substantially to the principles herein set forth.

I am aware that multiple-expansion rotative engines have been constructed heretofore in which arrangements of cylinders somewhat similar to that included in the present combination have been employed, including a pair of low-pressure cylinders placed side by side and coupled to a common crankshaft. I do not, therefore, claim this arrangement of cylinders broadly. The combination of this arrangement with the special proportions of cylinders herein set forth, however, has not been applied heretofore in direct-acting duplex pumping-engines, which, having no crank-shaft connection, depend upon the balance of forces between the two sides of the engine fortheir correct operation, and by the combination of this arrangement of cylinders and intermediate receivers, proportioned as described, in a four-cylinder triple-expansion engine of this class a new and useful result is accomplished-namely, the automatic adaptation of such an engine to any desired or accidental changes of working pressure and back pressure without impairing its efliciency or requiring hand adjustment to maintain the equable operation of the two pumps.

What I claim, therefore, as my invention, and desire to secure by Letters Patent, is

1. The combination, in a cross-compound triple-expansion duplex pump-engine, of a pair of pumps, a pair of equal low-pressure cylinders, one on each side of the engine, a high-pressure cylinder coupled with one of the said low-pressure cylinders to operate one of the pumps, an intermediate-pressure cylinder-whose effective volume is a mean proportional between that of the high-pres sure cylinder and the sum of the effective volumes of the two low-pressure cylinderscoupled with the other low-pressure cylinder to operate the other pump, and receivers interposed respectively between the high-pressure and the intermediate cylinder, and between the intermediate and the two low-pressure cylinders, whereby the required equable operation of the 4 two pumps is maintained automatically under different working pressures, substantially as set forth.

2. The combination, in a triple-expansion, duplex pumping-engine, of four engine-cylinders, comprising one high-pressure cylinder, one intermediate cylinder, and two lowpressure cylinders, one of the latter coupled with the high-pressure cylinder to operate one of the pumps, and the other coupled with the intermediate cylinder to operate the other pump, an intermediate pressure receiver which receives the exhaust of the high-pressure cylinder and delivers it to the intermediate cylinder, a low-pressure receiver which receives the exhaust of the intermediate ,cylinder and supplies each of the two low-pressure cylinders,and an automatic by-pass valve for regulating the pressures in the receivers, by which a quantity of steam is shunted by one or more of the cylinders, so as to maintain the receiver-pressures in such a relation as will produce an equable action of thetwo pumps, under variable working conditions.

The combination in a four cylinder, triple-expansion, duplex pumping-engine, of a pair of low-pressure steam-cylinders of approximately equal volume, one on each side of the engine, a high-pressure cylinder coupled with one of the said low-pressure cylinders, an intermediate pressure cylinder, whose effective volume is approximately a mean proportional between that of the highpressure cylinder and the sum of the effective volumes of the two low-pressure cylinders, coupled with the other low-pressure cylinder, an intermediate-pressure receiver between the high-pressure and the intermediatepressure cylinders, a low-pressure receiver between the intermediate-pressure cylinder and the two low-pressure cylinders, and an automatic pressure-regulating valve, by which steam is shunted by the high-pressure or intermediate-pressure cylinder, into or out of the intermediate-pressure receiver, as re quired to maintain equality of work between the two sides of the engine under varying working pressures, substantially as set forth.

4. In a cross-compound, duplex, steam pumping-engine, an automatic by-pass valve for regulating the pressure in the intermediate receiver, which consists of a casing having high-pressu re, intermediate-pressure, and low-pressure chambers, two connected pistons of different effective areas kept in equilibrium by the intermediate pressure acting on the larger piston, opposed by the high pressure and low pressure acting respectively on the smaller piston and on the annulus representing the difference in the areas of the two pistons, and a port whose opening is controlled by the movement of the pistons whereby steam is shunted into or out of the intermediate receiver as required to keep the pressures in equilibrium, substantially as set forth.

5. In a cross compound, duplex, steam pumping-engine, an automatic, two-way, bypass valve for regulating the pressure in the intermediate steam-receiver, which consists of a casing having chambers connected respectively with the high pressure steamchest, the intermediate receiver, and the lowpressure receiver, a piston-valve having two istons of different diameters, kept in equilibrium by the intermediate pressure acting piston by which too sudden movements of the 10 on the larger piston, opposed by the high Valve are prevented,substantiallyas set forth. pressure and low pressure acting respectively In testimony whereof I affix my signature on the smaller piston and the annulus reprein presence of two witnesses.

5 sentin the diiference in area of the two pis- 7 1 tons, p orts by which communication is opened HORACIL GALE between the intermediate-pressure chamber Witnesses: and either the high-pressure or low-pressure O. H. BURLEIGH, chamber, as may be required, and a dash- ISAAC GALE.

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