US2720867A - Reciprocating fluid pressure engines - Google Patents

Description

Oct. 18, 1955 H, R. RICARDO 2,720,867

RECIPROCATING FLUID PRESSURE ENGINES Filed June 15, 1952 2 Sheets-Sheet l Inventor By 4 Mp W Attorneys ct. 18, 1955 H. RICARDO 2,720,867

RECIPROCATING FLUID PRESSURE ENGINES Filed June 13, 1952 2 Sheets-Sheet 2 A ttorney 5 United States Patent Office 2,720,867 RECIPROCATING FLUID PRESSURE ENGINES Harry Ralph Ricardo, London, England, assignor to National Research Development Corporation, London, England, a corporation Application June 13, 1952, Serial No. 293,237 Claims priority, application Great Britain June 14, 1951 8 Claims. (Cl. 121-166) This invention relates to reciprocating fluid pressure engines other than those of the uniflow type, and is particularly but not exclusively applicable to single acting steam engines or compressed air engines. An object of the invention is to provide a form of valve apparatus for such engines which will be simple, effective and easy to produce and which will avoid as far as possible the necessity for steam-tight glands.

In small reciprocating steam engines or compressed air engines, other than those of the uniflow type, the valve apparatus usually comprises either a flat slide valve or a circular piston valve working in a valve chest.

A flat slide valve requires a fluid-tight gland where the valve rod passes through the wall of the valve chest, while moreover the pressure on the outer face of the valve causes appreciable frictional losses.

If, on the other hand, a piston valve is employed, the leakage loss past the narrow lands of such a valve tends to be large and, unless the valve is given an abnormally long stroke, the length of seal provided by the lands of the piston valve between the ports they control is necessarily short, while moreover the valve is exposed to the full steam pressure throughout the whole of the cycle, including the exhaust stroke, and hence the time available for leakage of pressure fluid from the inlet port to the exhaust port is long. The leakage path in such a valve is moreover a linear function while the volume of the engine cylinder varies as the cube of its linear dimensions so that for an engine of given proportional dimensions leakage loss regarded as a proportion of swept cylinder volume increases rapidly as the size of engine becomes smaller and in very small engines tends to become a dominating factor. Further the conventional form of piston valve provides for no relief in the event of priming of the cylinder or in the event of the pressure in the cylinder exceeding that in the fluid supply passage of the valve chest for any other reason.

In a reciprocating fluid pressure engine according to the present invention comprising at least one working cylinder the working space of which communicates with a combined inlet and exhaust chamber through a combined inlet and exhaust passage or port the valve apparatus controlling the flow of working fluid to and from the combined inlet and exhaust chamber comprises an inlet valve of the seated type arranged to be opened by being lifted from its seat against the action of the working fluid in the working fluid supply passage and controlling an inlet port at one end of the combined inlet and exhaust chamber, an exhaust valve of the piston type operating within a bore opening out of the other end of the combined inlet and exhaust chamber so as to open an exhaust port when it moves in a direction away from the inlet valve, and an inlet-valve-operating member or part projecting from the end of the piston valve and serving to lift the inlet valve towards the end of the movement of the piston valve towards the inlet valve.

Preferably the inlet valve operating member is adjustable relatively to the piston valve towards and away from the 2,720,857 Patented Oct. 18, 11955 inlet valve so as to enable the period of opening of the inlet valve to be adjusted.

The form of the seated type inlet valve may vary. For example it may be in the form of a light disc seated upon an annular seating and suitably guided in its movement towards and away from that seating by parts, for example in the form of spaced ribs lying close to its circumferential wall. Alternatively the inlet valve may be in the form of a disc valve having a conical seating surface and arranged to be suitably guided during its movement towards and away from its seat for example by means of a guide portion formed integral with or secured to the valve and lying and moving within a cylindrical part of the inlet port on the side of the seating remote from the working fluid delivery passage, the guide portion being in the form of a spider or otherwise formed to permit free flow of working fluid past it.

Again in some cases the seated type inlet valve may be simply in the form of a ball member engaging a conical or like seating from which it is lifted by the inlet valve operating member.

In any case it will be seen that with an arrangement according to the invention the inlet valve is of a type which is simple and inexpensive to manufacture, does not rely upon a sliding flt and can maintain a fluid-tight seal when it is closed without attention and over long periods of use. Moreover the piston valve not only serves to lift the inlet valve during the desired periods but is itself subject to the full working fluid pressure only during the period of admission through the: inlet valve, that is to say during, for example, about 20% of the complete cycle, and thus at a time when the length of seal provided between the end of the piston valve and the exhaust port by the land of the piston valve is at or near the maximum. Thus throughout the expansion stroke, following the closing of the inlet valve, and throughout the whole of the exhaust stroke, the combined inlet and exhaust chamber is sealed off from the working fluid delivery passage by the closed admission valve and the piston valve is subject only to the pressure within the cylinder, which pressure for the whole of the exhaust stroke is either approximately atmospheric pressure, or, if a condenser is used is below atmospheric pressure.

The admission valve in constructions according to the invention may either be arranged to be maintained on its seating during its closed periods by the Working fluid pressure alone or by such fluid pressure with the aid of a light spring, and in any case it will be seen that it will act as an automatic relief valve should priming of the working cylinder occur or should the pressure in the working cylinder exceed that of the working fluid for any other reason.

The invention may he carried into practice in various ways but one construction of engine incorporating the invention is shown by way of example together with two modifications thereof in the accompanying drawings, in which Figure 1 is sectional elevation of the engine in a vertical plane containing the axis of its crankshaft, and

Figures 2 and 3 are cross sectional views taken in similar planes to that of Figure 1 showing modified forms of the valve gear according to the invention.

In the construction shown in the drawings, the engine comprises a crank case A on which is mounted a cylinder casting B in the form of a block containing a working cylinder bore B the outer end of which is closed except for a laterally extending combined inlet and exhaust passage B leading to a combined inlet and exhaust chamber B formed in the same casting as the cylinder. Supported in bearings in the crank case A is a crankshaft, of the kind comprising a shaft C supported at two points in its length in appropriate bearings C C and formed at one end with a single crank web C from the outer face of which projects a crank pin C surrounded by the big end bearing D of a connecting rod D by which it is coupled to a piston E reciprocating within the working cylinder bore B the end of the shaft C opposite to the crank pin projecting through a gland C in the crank case and carrying a flywheel C As will be seen the crankshaft C extends from the crank web C in the same direction as the combined inlet and exhaust passage B extends from the working chamber B of the cylinder so that a part of the crankshaft lies immediately below the combined inlet and exhaust chamber B Formed in the cylinder block immediately above the combined inlet and exhaust chamber B is an inlet chamber E into which leads a steam delivery passage E also formed in the cylinder block B, while formed in the cylinder block immediately below the combined inlet and exhaust chamber is an exhaust chamber F leading to an exhaust port F in the cylinder block. Extending vertically through the cylinder block B so as to traverse the inlet chamber E, the combined inlet and exhaust chamber B and the exhaust chamber F is a tubular sleeve G the upper end of which, which lies within the inlet chamber E, is conveniently enlarged in external and internal diameter and externally screwthreaded as shown at G to engage an enlarged screwthreaded bore in the cylinder block and thus hold the complete sleeve in position, this screwthreaded bore being closed at its outer end by a suitable end cap G Ports G are formed in the wall of the enlarged upper end G of the sleeve G permitting steam to flow from the inlet chamber E into the interior G of this enlarged upper end, and formed at the base of the bore of the enlarged upper end is an annular seating G on which normally rests a disc-like inlet valve H held in place by a light helical compression spring H extending between its upper face and the end cap G so that this disc Valve normally prevents entry of steam into the interior of the smaller daimeter part of the sleeve G.

Formed in the wall of the smaller diameter part of the sleeve are combined inlet and exhaust ports G communicating with the combined inlet and exhaust passage B and exhaust ports G communicating with the exhaust chamber F.

Mounted to reciprocate within the smaller diameter part of the sleeve is a piston valve I constituting an exhaust valve the upper face I of which, when the valve J is in its closed position, lies between the combined inlet and exhaust ports G and the exhaust ports G so as to cut off communication between the combined inlet and exhaust passage B and the exhaust chamber F whereas in its open position the piston valve I lies with its upper face 1 below the level of the upper edges of the exhaust ports 6' and thus permits free communication between the combined inlet and exhaust passage 13 and the exhaust chamber F through the part of the sleeve G between the combined inlet and exhaust ports G and the exhaust ports G Engaging and projecting upwardly from a screwthreaded bore in the upper end portion of the piston valve I is an inlet valve operating member or rod in the form of a screw K having a locknut thereon so that its extent of projection above the face I of the piston valve I can be adjusted, while the lower end of the piston valve is formed as a disc or foot I the lower face of which engages an eccentric L mounted upon the crankshaft, with a ball race L interposed between the eccentric and the face of the foot if desired. A helical compression spring M extends between the upper face of the foot I and an abutment surface on the cylinder .block B to maintain the foot always in contact with the eccentric ball race L The arrangement is such that at approximately the top of each stroke of the working piston E the inlet-valveoperating-member K engages and lifts the inlet valve H and maintains it lifted for, say, of crankshaft rotation and then permits it to close. The piston valve I then continues to move downwards and at about the end of the downward stroke of the working piston E uncovers the exhaust ports G in the sleeve G. The piston valve I then continues to move down for a further period during the beginning of the upward movement of the working piston for, say, 40 to 45 of crankshaft rotation, and then moves upwards with the working piston so as to close the exhaust ports G towards the end of the exhaust stroke. The piston valve I and the working piston E then rise together so that the residual steam in the working cylinder is compressed, the arrangement being such, for example, that this compression raises the pressure of steam in the working chamber B to a pressure approximately equal to the pressure in the steam delivery passage E thus causing an approximate balance of pressures on the inlet valve H at the moment when it is next opened.

It will thus be seen that the maximum lift of the inlet valve H will occur at a time when the working piston has descended upon its working stroke by an amount represented by a crank angle of about 40".

It will also be seen that for part of its downward movement the piston valve J is subject to working pressure so that it acts to some extent as a subsidiary piston.

It is desirable that the lift of the admission valve H shall be small since with the fairly early cut-off which is usually desired the lift of the inlet valve H represents only a very small proportion of the total stroke of the piston valve J and high lift would thus involve an abnormally long stroke for the valve I. Moreover the inlet valve H will return to its seating at a speed which is dependent upon its height of lift and it is desirable, for the purpose of minimising impact shock, to keep both the lift and the weight of the valve as small as possible therefore.

Nevertheless since, with reductions in the size of an engine of given relative proportions, the velocity of the inlet valve and its weight will both be reduced relatively to the area of its seating, the use of even a ball valve as the inlet valve can be tolerated in very small engines while in other cases a conical seated valve may be used.

Thus in the alternative arrangement according to the invention shown in Figure 2 in which the engine might otherwise be generally similar to that shown in Figure 1, a simple cylindrical bore N is formed in the cylinder block to accommodate the piston exhaust valve and extends from a coaxial inlet valve chamber N having a conical seat N into which the upper end of the bore opens, across the combined inlet and exhaust passage and across the end of an exhaust port F a ball valve 0 being arranged in the inlet valve chamber to engage the conical seat N while the piston exhaust valve I lies within the part of the bore below the combined inlet and exhaust passage B and carries the adjustable screw or like inlet r in which the piston valve J operates, instead of being enlarged extends into an inlet chamber P without any such enlargement and has a conical seating P at its upper end on which seats a conical seated disc type inlet valve P between the upper face of which and the end cap G closing the upper end of the inlet valve chamber lies a light helical compression spring H The conical seated valve P is formed or provided on its under surface with radial guide vanes P or the equivalent which form a stem to co-operate with the bore of the upper end of the sleeve J to guide the valve in its vertical movement.

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

1. A reciprocating fluid pressure engine including in combination at least one working cylinder into the Working chamber of which opens one end of a combined inlet and exhaust passage the other end of which communicates with a combined inlet and exhaust chamber, a cylindrical bore opening into the other end of the combined inlet and exhaust chamber, an inlet port situated at one end of said combined inlet and exhaust chamber and communicating with a working fluid supply passage, an inlet valve normally engaging a seating so as to close said inlet port, at least one exhaust port in the side wall of the bore, a piston exhaust valve disposed for reciprocation within the bore, means for imparting reciprocation to said piston valve to cause it to uncover the said exhaust port by movement in a direction away from the inlet valve and an inlet valve operating member in the form of an adjustable projection from the end of the exhaust valve adjacent the inlet valve which projection is adapted to engage with and open the inlet valve toward the end of the reciprocating movement of the exhaust valve toward the inlet valve.

2. A reciprocating fluid pressure engine as claimed in claim 1 wherein the inlet passage is coaxial with and of the same diameter as the cylindrical bore in which the exhaust valve reciprocates and thus forms in elfect a continuation of said bore at the end of the combined inlet and exhaust chamber opposite to the said bore.

3. A reciprocating fluid pressure engine as claimed in claim 2 in which the inlet valve comprises a disc seating on a substantially flat seating at the end of the inlet passage which opens into the working fluid supply passage.

4. A reciprocating fluid pressure engine as claimed in claim 1 in which the inlet valve comprises a disc seating on a substantially flat seating at the end of the inlet passage which opens into the working fluid supply passage.

5. A reciprocating fluid pressure engine as claimed in claim 1 in which the inlet valve is in the form of a ball engaging a conical seating at the end of the inlet passage which opens into the working fluid supply passage.

6. A reciprocating fluid pressure engine as claimed in claim 5 in which the inlet passage is coaxial with and of the same diameter as the bore in which the exhaust valve reciprocates and thus forms in efiect a continuation of said bore at the opposite end of the combined inlet and exhaust chamber from the said bore.

7. A reciprocating fluid pressure engine as claimed in claim 1 wherein the inlet valve comprises a head in the form of a disc having a frusto-conical seating surface and a stem rigid with the head and having at least one longitudinal groove therein, and wherein the head engages a seating at the end of the inlet passage which opens into the working fluid supply passage while the stem slides within the inlet passage with a close sliding fit.

8. A reciprocating fluid pressure engine as claimed in claim 7 in which the inlet passage is coaxial with and of the same diameter as the bore in which the exhaust valve reciprocates and thus forms in effect a continuation of the said bore at the end of the combined inlet and exhaust chamber opposite to the said bore.

References Cited in the file of this patent UNITED STATES PATENTS 1,502,244 Gore July 22, 1924 1,511,554 Woodring Oct. 14, 1924 1,633,357 Albertine June 21, 1927 2,171,316 Van Sittert Aug. 29, 1939 2,321,267 Van Der Werif June 8, 1943

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