US1149589A - Air-cushioning mechanism. - Google Patents

Description

L. D. LOVEKiN.

AIR CUSHIONING MECHANISM.

APPLICATION FILED DEC.7, 1912.

1,149,589. Patented A11 10, 1915.

3 SHEETS-SHEET 3.

2 INVENTOR WITNESSES z 001/ 1 a I r 4 ATTORNEY tantra seine r TE opinion LUTHER D. LOVEKIN, 0F PHILADELPHIA, PENNSYLVANIA AIR-CUSHIONING MECHANISM.

Specification of Letters Patent. Patented Aug; 10 1915.

Application filed December 7, 1912. Serial No. 735,412.

To all whom it may concern I Be it known that'I, LUTHER D. LovnKIN, a citizen of the United States of America, residing in the city and county of Philadelphia,- in the State of Pennsylvania, have invented a certain new and useful Improvement in Air-Cushioning Mechanism, of which the following is a true and exact de scription, reference being had to the accompanying drawings, which form a part thereof. 1

My present invention consists in improved apparatus for cushioning the movements of steam engine valves and like reciprocating parts, to thereby reduce the shock, wear, and loss of power, otherwise resulting from the inertia or inertia and weight of the reciprocating parts, and also to make it easier to shift the valves or valve gear by the reversing lever or other adjusting device when the engine is running at highpistonspeed.

With a railwaylocomotive equipped with my improved inertia cushioning mechanism, it is both safe and comparatively easy to shift the reversing lever while the engine is running at high piston speed, whereas without the use of such cushioning mechanism the operation of shifting the reversing lever is so diiiicult and dangerous that it is the usual practice not to shift the reversing lever under conditions in which it is highly desirable that it should be shifted.

One specific object of my invention is to provide a cushioning mechanism comprising a cushioning cylinder and a piston working therein, with simple and effective provisions for equalizing the pressures in the opposite ends of the cushioning cylinder when the cushioning piston is'at the middle of its stroke.

Another specific object of my invention is to provide simple and effective means for equalizing the pressures in the opposite ends of the cushioning cylinder when the engine is at rest regardless of the position of the cushioning piston. Y

Another specific object of my invention 18 to provide simple and effective means for varying the maximum pressures obtained in the ends of the cushioning cylinder as the speed of the engine varies, so that the inertia forces which increase with the square of the speed, may be effectually neutralized at all speeds.

My invention comprises various features of construction, which are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, and of the advantages possessed by it, reference should be had to the accompanymg drawings and descriptive matter, in which I have illustrated and described va- 'ious forms in which my invention 'may be embodied. i

Of the drawings: Figure 1 is a sectional elevation of one form of my improved cushionlng mechanism, and a portion of the steam chest and valve with which it'may be employed. Fig. 2 is a section taken on the line -2 of Fig. 1. Fig. 3 is a sectional elevation of another form of my improved mechanism. Fig. 4 is a sectionalelevation of still another modification. Fig. 5 is a diagrammatic representation of a locomotive equipped with a form of my improved valve cushioning mechanism, meansfor automatically varying the pressure of the pressure fluid supplied to the cushioning cylinders. Fig. 6 is a sectional elevation of a pressure controlling valve employed in Fig. 5. Fig. 7 is a view taken similarly to Fig. 1, illustrating a slightly including p modified construction; and Fig. 8 is an end elevation of the piston shown in Fig. 7.

In the drawings,Figs. 1 and 2 represent my invention in a form especially adapted for use onasteam railway locomotive, of which A represents the steam chest, and B a main distributing valve. The stem B of the valve B is shown as passing through a stufling box C of a kind commonly employed in locomotives, formed in the head G which closes one end of the steam chest A. D represents the cylinder member proper of my improved valve cushioning mechanism. As shown, the cylinder D is secured at one end to the head C, which closes the otherwise adjacent open end of the cylinder D. At its opposite end the cylinder D is closed by the integral end wall D and the plug D which closes a central aperture in the wall D Midway between its ends the cylinder D is enlarged to provide a chamber D which is open at its ends to the interior of the cylinder through the annular ports D and D Radially disposed strengthening ribs D connect the inner and outer walls of the chamber D Plugs D close core apertures formed in the outer wall of the chamber D The piston E working in the cylinder D comprises a cylindrical sleeve-like body portion connected to a hub portion E by a web E and ribs E The hub E of the piston is secured to the valve stem B. Circumferential grooves E and E formed in the piston one at each side of the web E and extending through the sleevelike body of the piston form annular ports which register with the corresponding ports D and D of the cylinder when the piston E is at the center of its'movemen't and thereby connect the opposite ends of the cylinder to the chamber D at that instant. E represent piston packing rings of usual construction. Pressure fluid, which may be steam or air, and in the case of a locomotive is preferably the latter, is supplied to the chamber D from a suitable source of supply by the pipe F. G represents a suitable oil cup for supplying lubricating material to the contacting piston and cylinder walls. H and H are drain cock connections to the opposite ends of the cylinder space, and H a drain cock connection to the chamber D by which water of condensation, or water carried into the cylinder with the compressed air when the latter is the pressure fluid employed, may be drained out of the cylinder. As shown, the drain cock connection H is di rectly connected to the cylinder D, while the other connection H is connected to the member C. The opposite ends of the cushioning cylinder are connected by a by-pa ss I in which, in the form shown, is mounted a valve or cook J by which the flow through this by-pass may be regulated.

In, operationas the piston E moves into its central position the opposite ends of the cushioning cylinder are connected by the bypass formed by the chamber D the cylinder ports D and D and the piston ports E and E and this bypass should preferably be of suflicient cross sectional area to permit substantial equalization of the pressures to be obtained under all conditions of operation while the piston is traveling through the portion of its path in which this by-pass is open. While the chamber D is thus open to the two ends of the cushioning cylinder, pressure fluid is supplied by the pipe F to maintain the static pressure so to speak in the cushioning cylinder at the desired value. As there is no exhaust from the cylinder D, it will be apparent that the pressure fluid which needs to be supplied in regular operation when the ports E and E register with the ports D andD is only that which is requiredto make up for leakage, and, when steam is the pressure fluid employed,

- to compensate for the condensation which may occur in the cylinder. As the piston E moves away from its central position in either direction the steam or air in front of the piston is compressed while the steam or air at the rear of the piston expands and de creases in pressure. In consequence, the

body to be neutralized is in general Zero at mid-stroke, rises to a maximum as each end of the stroke is reached, and then falls to zero on the return to the mid-stroke position.

The inertia forces of the valve gear which are to be neutralized, increase with the square of the speed of the engine. To neutralize the inertia forces, therefore, it is necessary that the maximum differential of the pressures at the opposite ends of the cushioning piston E should vary with the square of the speed of the engine. If the by-pass 1, shown in Figs. 1 and 2, be entirely closed or be dispensed with, it will be apparent that the desired variation in the differential between the pressures at the op posite sides of the piston E, may be obtained by manually or automatically varying the pressure of the fluid supplied to the cushioning cylinder by the pipe F in proportion to the square of the engines speed. \Vith a constant pressure of the fluid supplied by the pipe F the desired variation in the differential of the pressures at the opposite sides of the piston E when the latter is tomatically to different positions for different speeds of the engine. Results sufliciently good from a practical standpoint may be obtained, however, without any change in the position of the valve J, or in the pressure of the fluid supplied by the pipe F, by setting the valve J so that the bypass will offer a substantial resistance to the rapid flow of air or steam from one end of the cylinder D into the other. With the by-pass thus restricted, the volume of air flowing through it on each stroke of the piston E will automatically decrease as the speed of reciprocation increases, and consequently the maximum pressures in the opposite ends of the cylinder will increase with the speed. Cushioning mechanism thus operating with a by pass of fixed but restricted capacity and adapted to entirely neutralize the inertia of p the locomotive will 'ive effective neutralization at all other speeds, except perhaps at very low speeds at which the neutralization of the valve gear inertia becomes a matter of small importance. The use of the constantly open by-pass permits the pressures in the opposite ends of the cushioning cylinder to be perfectly equalized in any position "of the cushioning piston when the engine is at rest, and this of course is desirable as it avoids any appreciable strain, due to the pressure conditions then existing 1n the cushioning cylinder, on the reversing lever or other valve gear adjusting device.

The equalization of the pressures in the opposite ends of the cushioning cylinder, and the admission of the makeup pressure fluid when the parts are in mid-stroke, are of advantage in other ways than those re ferred to above. For instance, this insures that the linking up the valve gear to any extent, does not interfere with the proper supply of the pressure fluid to the cushion ing cylinder. Furthermore, the substantial equalization of pressures at mid-stroke insures a desirable uniformity in operation of the two ends of the cushioning cylinder under all conditions. In particular, it eliminates the possibility of a dangerous over compression in the cushioning cylinder on a sudden increase in speed, such as may occur, for instance, when the locomotive drivers in starting or while running at moderate speed, suddenly begin to slip. Since the compression and expansion occurring in each end of the cushioning cylinder during each complete reciprocation of the piston are each divided into two stages separated by the period at mid-stroke during which pressure equalization occurs and the pressure fluid necessary to make up for leakage or condensation losses is supplied, it is possible to obtain in practice results more closely ap proximating the calculated theoretical re sults than can be obtained when the fluid in each end of the cylinder receives but one continuous compression and one continuous expansion during each to and fro move ment of the cushioning piston.

The pressure fluid supplied by the pipe F may be taken from any suitable source. In the case of a locomotive the pressure fluid should be taken from some other source than the steam chest of the locomotive, for the cushioning devices should work while the locomotive is drifting as well as when it is taking steam. Advantageously, the pressure fluid may be compressed air, furnished by the compressor for the air brake system, as in the arrangement shown in Fig. 5, wherein I have diagrammatically illustrated the application to a locomotive of valve cushioning mechanism and means for automatically varying the pressure of the cushioning fluid in response to variations in the engine speed. The valve cushioning cylinders D of Fig. 5 may be identical with the form shown in Figs. 1 and 2 except that the by-pass I may be and as shown is omitted. In Fig. 5 K represents the loco motive body and L the drivers, and M represents the main rod connecting the crank pin the outer end of the stem B of the distributmg valve is secured. One end of the lever P is connected by the link P to the crosshead N. The opposite end of the lever P is connected to one end to the radius rod Q. The latter is pivotally connected to the block sliding in the oscillating link S. The latter is fulcrumed at S and is connected at one end by the eccentric rod T to the crank pin T carried by the driver which also carries the crank pin M. The link R is adjusted in the slot of the link S by the reversing lever U and rock shaft U to one .arm U of which the reversing lever is connected by the rod U An arm U secured to the shaft U has pivotally connected to its free end a bearing sleeve U which slidingly receives the free end of the radius rod Q. It will be understood of course that while there will ordinarily be but one rock shaft U and a single connection therefrom to a single reversing lever U, the arms U and the remaining parts of the valve gear and cushioning mechanism will ordinarily be duplicated on the opposite sides of the locomotive.

V represents the usual compressor for the air brake system and V the usual air reservoir. As shown, the air for the cushioning cylinders D is directly supplied to the cushioning mechanism through an auxiliary reservoir IV connected to the reservoir V through a checkvalve W which prevents back flow from the reservoir W into the reservoir V and thus serves to prevent the reservoir W from emptying on a sudden reduction of pressure in the air brake reservoir V. The pipe WV runs from the reservoir W to the inlet port of a valve X. The supply pipe F for the front cushioning cylinder D leads from the delivery port of the valve X, and FA represents a branch pipe running to the cushioning cylinder (not I shown) at the back side of the locomotive.

The valve X shown in detail in Fig. 6, is a pressure reducing valve of well known type. The inlet and outlet chambers X and X of the valve X are connected by the port X controlled by a valve member X constantly urged toward itsclosed position by a spring X The stem of the valve member X is connected to a piston X working in the chamber X The latter is open at its lower end to the outlet chamber X through the ports X and the uppermost end of the chamber X is in communication with the inlet chamber X through a channel termito the valve member Z is engaged at its upper end by a diaphragm X which closes the upper end of a chamber X. The lat ter is in free communication with the outlet chamber X 'of the valve. The upper side of the diaphragm X is engaged by a spring X and the tension of the latter is adjusted by means of a cam X engaging the stem of a follower X bearing on the upper end of the spring. The cam X is connected by the lever arm X and connecting rod Y to a bell crank lever Y which is adjusted in accordance with the speed of the locomotive byza ball governor Y connected in the particular arrangement shown by shafts Y and bevel gears Y to a gear wheel Y carried by one of the locomotive drivers.

The operation: of the pressure controlling valve X will be readily apparent to those skilled in the art. So long as the supply pressure admitted to the inlet chamber X is appreciably greater than the pressure maintained in the outlet chamber X and this is the normal condition of operation,

the opening and closing of the port X will depend primarily on the pressure maintained in the upper end of the chamber X. This pressure will be regulated by the valve Z. The position of the valve Z depends upon the position of the diaphragm X which is acted on, on the one side by the delivery pressure in the chamber X and on the opposite side by the spring X The spring Z is preferably weak enough so that it has no other effect than to cause the valve member Z to seat when the diaphragm X rises and permits this seating. hen the delivery pressure in the chamber X rises to the value which the apparatus is adjusted to maintain, the pressure in the chamber X causes the diaphragm X to lift, thus permitting the valve Z to seat. WVhen the port X isthus closed by the valve member Z, the leakage out of the upper end of the chamber X past the piston X or through the restricted leakage orifice X in the piston which may be provided for that purpose, quickly reduces the pressure in the upper end of the cylinder X sufliciently to permit the valve member X to seat and close the port X When the delivery pressure falls below that which the apparatus is adjusted to maintain, the decreased pressure in the chamber X permits the spring X to depress the diaphragm X and move the valve Z to its open position. The pressure in the upper end of the chamber X then quickly builds up and forces the valve member X into its open position. To ention between the opposite ends of the cushioning cylinder such as is formed by the bypass I, and the characteristics of this by-pass connection if it be employed. If the bypass connection be omitted, the apparatus shown should be arranged to vary the pressure in the pipes F and FA in more or less exact accordance with the square of the speed of the locomotive. If the by-pass connection be employed the cam X should be arranged to vary the tension on the spring X so that the variation of the pressure in the pipes F and FA will, in conjunction with the regulating action of the restricted connection between the opposite ends of the cushioning cylinders, .give the desired cushioning effect at all speeds. To insure the desired reduction in pressure in the pipes F and FA on a fall in speed, I preferably provide the cushioning cylinders or the supply piping leading thereto with one or more restricted leakage outlets, through which pressure fluid may constantly escape. In Fig. 5 F represents a restricted leakage vent connected to the pipe F adjacent the cushioning cylinder for this purpose, and a similar vent from the pipe FA may be provided. These vent connections may well lead to the smoke box of the locomotive. The amount of pressure fluid which it is necessary to waste in this manner is comparatively small. With the automatic control of the pressure of the cushioning fluid supplied to the cushioning cylinders had with the arrangement shown in Fig. 5, it is possible to obtain results more closely approximating the theoretical results desired than are obtainable solely by the use of fixed but restricted connections between the opposite ends of the cushioning cylinders, but the advantages obtained will not always justify the use of the more complex apparatus.

As shown in Fig. 1 the effective areas of the opposite ends of the piston lb are not alike, inasmuch as the valve stem B passes through one end wall only of the cylinder 1). This may be more or less effectually compensated for, however, by making the clearance space at the right hand side of the piston E, when the latter is at the right hand end of its stroke, larger than the clearance space at the other side of the piston when the latter is at the left hand end of its stroke. Instead of thus compensating for differences in the effective areas of the opposite ends of the cushioning piston, the

areas may be made equal by providing the piston with a tail rod E passing through a stufiing box CC formedin the plug D which closes the aperture formed in the outer end wall D of the cushioning cylinder DC,

- as shown in Fig. 7. When it is desired to have the opposite ends of the cushioning cylinder connected at all times by a by-pass of fixed but restricted capacity, the external by-pass l of Figs. 1 and 2 may well be replaced by by-pass ports or channels formed in the cylinder or through the piston; and in Figs. 7 and 8 l have illustrated a piston EC having small ports E passing through it to provide this continuous but restricted communication between the opposite ends of the cushioning cylinder. By preference, as shown best in Fig. 8, I employ a plurality of small ports E rather than a single larger port of flow capacity equal to the aggregate capacity of the ports E since this minimizes the possibility of a serious clogging of the restricted by-pass by dirt particles. Aside from the features already referred to, the construction shown in Figs. 7 and 8 may be identical with that shown in Figs. 1 and 2, and corresponding parts are indicated by the same reference symbols.

In the modification shown in Fig. 3, B represents the stem of a vertically movable valve of an engine of the marine type. To the steinv B is secured a piston EA working in the cushioning cylinder DA which comprises two axially displaced portions of difi erent diameters. The lower and smaller portions D 01": the cylinder D extends into and is open at its lower end to the steam chest AA in which works the valve to which the stem B is connected. Annular ports D and D formed in the wall of the cylinder portion D and connected together by channels D form by-pass ports by which steam is admitted to the lower end of the upper and larger portion D of the cylinder DA when the piston EA is in or near its central position. At all othertimes the enlarged upper portion of the cylinder DA is cut off from communication with the steam chest by the piston portion E which fits the cylindrical portion D and is of an axial length substantially equal to the distance between the ports D and D. Annular ports D and D and connecting channels D formed in the wall of the cylinder chamber D serve to connect the op posite ends of the cylinder chamber D 5 when the piston EA is in its central position but at all other times the piston portion E which is of a length substantially equal to the distance between the ports D and D cuts off communication between the opposite ends of the larger piston chamber. D and D represent drain pipe connections to the cylinder chamber D at its upper and lower ends, respectively! With the arrangement shown in Fig. 3, the pressure fluid is steam, supplied to the cushioning chamber from the steam chest AA, but steam is admitted to the cylinder chamber D only when the piston EA is in its central position and in that position of the piston the opposite ends of the chamber D are in free communication. The clearance spaces at the opposite sides of the piston portion E should be proportioned to compensate not only for the difference in effective areas of the opposite ends of the piston but also to neutralize the weight as Well as the inertia of the valve stem B and parts connected to it.

In Fig. A. I have shown another form of apparatus adapted to be attached to the end of a locomotive steam chest to cushion the movement of the valve working therein. The cylinder chamber DB and piston member EB shown in Fig. A are in many respects similar to the members DA and EA of Fig. 3, and corresponding parts are given the same reference symbols in the draw ings. The cylinder DB is formed at the end adjacent the steam chest with a head D which is cored out to provide a pressure supply chamber D receiving steam or compressed air through a supply pipe FA. The chamber D is connected by the annular port D to the interior of the cylinder portion D at such a distance from the port D that the portion E of the piston EB does not close it at any point in the movement of the piston. The piston EB is extended at its end adjacent the steam chest and provided with an enlargement E at that end, which cuts oil communication between the steam chest and the port D.

In Fig. 22 represents a port for a drain pipe connection opening from the chamber D G represents an oil cup. In the arrangement shown in Fig. 4 the by-pass I and regulating valve J may be employed as in the construction shown in Fig. 1. Such a by-pass is generally not necessary, however, in the case of a marine engine and is not shown in Fig. 3.

It will be observed that with all forms of the cushioning mechanism shown the cushioning piston and the cylinder in which it works form effective crosshead guide provisions for the front end of the distributing valve to which the piston 15 connected, and the floating stufiing box packings shown in Figs. 1 and 7 give the valve stem freedom for small lateral achustment to compensate for any defect in alinement, such as is sometimes found in large slide valves.

While in accordance with the provisions of the statutes, I have illustrated and described the best forms of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed Without departing from the spirit of my invention, and that under some conditions certain features of my invention may be used Without a corresponding use of other features.

Having now described my invention, what I; claim as new and desire to secure by Letters Patent, is:

1. In a steam engine, the combination of a reciprocating valve, a cushioning piston attached thereto, a cylinder in which said piston works, a source of pressure fluid, and means for intermittently connecting the two ends of the cylinder to said source as said piston moves through its mid-stroke posi tion.

2. In a steam engine, the combination of a reciprocating valve, a cushioning piston attached thereto, a cylinder in which said piston works, a source of pressure fluid, means for intermittently connecting the two ends of the cylinder to a source of ressure fluid as said piston moves through 1ts midstroke position, and a bypass connection between the opposite ends 01": said cylinder.

In a steam engine, the combination of a reciprocating valve, a cushioning piston attached thereto, a cylinder in which said piston works, a source of pressure fluid, means for intermittently connecting the two ends of the cylinder to a source of pressure fluid as said piston moves through its midstroke position, and a restricted by-pass connection between the opposite ends of said cylinder.

4:. In a steam engine, the combination of a reciprocating valve, a cushioning piston member attached thereto, a cylinder member in which the said piston member Works, one of said members being formed with ports opened and closed by the relative movement of said members and adapted to place the two ends of the cylinder in free communication when said piston member is at mid stroke and to out off said communication in other positions of the piston member, and provisions for maintaining a substantially constant amount of an expansible cushioning fluid in said cylinder as the piston moves from one end to the other thereof.

5. In a steam engine, the combination of a reciprocating valve, a cushioning piston attached thereto, a cylinder in which said piston works, said cylinder being formed with by-pass ports adapted to establish free communication between the opposite ends of the cylinder when the piston is at mid-stroke, and being closed by said piston in other positions of the latter, and provisions for maintaining a substantially constant amount of an expansible cushioning fluid in said cylinder as the piston moves from one end to the other thereof.

6. In a steam engine, the combination of a reciprocating valve, a cushioning piston attached thereto, a closed cylinder in which said piston works, provisions dependent upon the relative movements of the piston and cylinder for establishing free communication between the opposite ends of said cylinder When the piston is at mid-stroke, and provisions for maintaining a substantially constant amount of an expansible cushioning fluid in said cylinder as the piston moves from one end to the other thereof.

' 7. In a steam engine, the combination of a reciprocating valve, a cushioning piston attached thereto, a closed cylinder in which said piston works, means for supplying pressure fluid thereto to maintain a predetermined average pressure therein, provisions dependent upon the relative movement of the piston and cylinder for establishing free communication between the opposite ends of said cylinder when the piston is at midstroke, and provisions establishing a restricted communication between the opposite ends of the cylinder in other positions of the piston.

8. In an engine, in combination with the valve gear, a valve actuated by the valve gear, a fixed dash pot cylinder, a piston arranged in said cylinder and connected with said valve, and means automatically responsive to the speed of the engine for varying the differential of the pressures acting on opposite sides of said piston when at the ends of its stroke as the speed of the engine varies.

9. In an engine, in combination with the valve gear, a valve actuated by the valve gear, a fixed dash pot cylinder, a piston arranged in said cylinder and connected with said valve, and means automatically responsive to the speed of the engine for varying the difl'erential of the pressures acting on opposite'sides of said piston when at the ends of its stroke as the speed of the engine varies, said means comprising a re stricted by-pass connection between the opposite ends of said cylinder.

10. In a locomotive, in combination with the valve gear and valve actuated by the valve gear, a fixed dash pot cylinder, a piston arranged in said cylinder and connected with said valve, and means adapted to establish communication between the opposite sides of the piston for all positions of the latter and arranged to offer comparatively slight resistance to the flow of fluid from one side of the piston to the other when the piston is moved at low speeds, and a resistance at high speeds causing the fluid on the opposite sides of the piston to be alternately compressed and expanded.

11. In a locomotive, in combination with the valve chest, the valve gear and valve actuated by the valve gear, a dash pot cylinder secured to the valve chest, a piston arranged in said cylinder and connected with said valve, and means adapted to establish communication between the opposite sides of said piston for all positions of the latter and arranged to offer comparatively slight resistance to the flow of fluid from one side of the piston to the other when the piston is moving at low speeds,

and a resistance at high speeds causing the dash pct.

13. In a locomotive, in combination with g the valve chest, the valve stem, the valve secured to said stem and arranged in the chest, said stem projecting through the forward head of the chest, a dash pot cylinder securedto the forward head of the chest substantially in axial alinement with said rod, a piston arranged in said cylinder and secured to said rod, a by-pass connecting the opposite sides of said piston, and a stuiiing boX for said rod in the forward head of said chest, said stufiingbox permitting lateral movement of said rod whereby said piston and said cylinder are adapted to support said valve.

LUTHER 1). LOVEKIN.

, Witnesses:

ARNOLD KA'rz, S. STEWART.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, I). C.

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