GB1594347A - Steam operable piston engines - Google Patents

Description

(54) STEAM-OPERABLE PISTON ENGINES (71) I, EDWARD ATHELSTAN HALFORD, of Flat 14, Marryat Court, New Milton, Hampshire, England, a British Subject, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to piston engines operable by steam pressure.

The invention has for its principal object the provision of an improved engine of this type which has a number of cylinders and which is designed particularly for the operation of road vehicles, although its use is not limited to these.

The invention provides improvements both in the engine itself and also in a number of its parts and associated equipment.

According to the present invention, there is provided a piston engine operable by steam pressure, comprising a main shaft journalled in bearings, a driving plate mounted on the shaft, wherein the driving plate has an annular working surface lying in a plane which is at an angle to a plane perpendicular to the shaft axis, a plurality of cylinders spaced around the main shaft, each cylinder having a working piston located therein by piston rings with a piston rod extending from it, the piston rods engaging the driving plate by means of thrust pads so that reciprocation of the pistons rotates the main shaft, the pads, piston rings and bearings being of a bearing composition consisting essentially of carbon and the engine being arranged to be lubricated by water and/or by steam.

Further features and aspects of the invention will become clear from the following description.

The invention will be more fully described, by way of example, with reference to the single Figure of the accompanying drawing, which is a sectional view, partly diagrammatic showing the main parts of an engine exemplifying the invention.

Referring to the drawing, the engine shown comprises a casing formed of a number of sections, including a central section 1, a front end section 2 and a rear end section 3, which sections are secured together in a fluid-tight manner using suitable bolts and seals (not shown).

Extending longitudinally along the casing is a main shaft 4 which is rotatably carried in carbon bearings 5, 6, 7 and 8.

Water seals 9 and 10 are provided at the ends of the casing.

The shaft 4 is surrounded within the central casing 1 by a suitable number (preferably an odd number) of cylinders 11, in this case five. A double-acting piston 12 having a piston rod 13 operates in each cylinder. Each piston 12 is provided with a number of carbon piston rings 14.

Each piston rod 13 passes through a seal 15 and projects into the end section 2 of the casing, where it operates on a swash plate 16 which is secured to and drives the main shaft 4. As shown the plate 16 has parallel opposed faces 17 and 18 which are parallel to each other and oblique with respect to the shaft 4.

The reciprocating motion of the piston 12 is converted into a rotary motion of the shaft 4 by the force of the pistons 13 engaging the faces 17 and 18 of the plate 16. This engagement is through anti-friction pads 19 and 20 which are hemispherical in shape and are made of carbon. These fit in sockets 21 and 22 carried by a caliper cross head 23 fixed to the end of the piston rod 13. In order to facilitate assembly the caliper 23 is split centrally and the two sections are bolted together by longitudinal bolts (not shown).

In order to allow wear of the pads 19 and 20 to be taken up the socket 22 is screwed into a threaded hole in the caliper 23, so that it can be adjusted to leave a running clearance between the pads and the swash plate, after which the socket 22 is locked in position by a suitable locking nut.

As will be understood, owing to the oblique angle between the swash plate 16 and the axis of the shaft 4 reciprocation of the pistons 12 will rotate the shaft.

Distribution of the working fluid (steam) to the various cylinders 11 may be contolled by slide valves, preferably ones of the balanced piston valve type. A specially designed cam, co-axial with the main shaft may, operate such valves via a roller and bellcrank, as will now be described.

The cam, shown generally at 25. is constructed in the following manner. A solid cam member incorporating a grooved collar 26 is straight splined to the main shaft 4 so that it can be moved longitudinally thereto by a forked lever 27 which is engaged with the collar 26. Portioned parts of the member 25, of such widths as to acccpt a roller 28 on a bell-crank 29 are so constructed that the leading flank of each portion is cut co-axial to the axis of the shaft 4 so that lift and lead are constant, but the trailing flank of each portion is cut so that the trailing flank.

though still co-axial to the shaft. varies as to the length of its lift dwell. Thus. the roller 28 may engage any selected one of the cam portions 30 to control valve lift dwell. steam cut-off to the cylinders 11 being simiiarly affected since the period of opening of the steam ports depends on the lift dwell. For normal use, three varying periods of liftdwell should be adequate but more may be provided in the case of heavy load applications.

Reverse is obtained by machining a portion 31 of the member 25 so that the flank is at an angle of 180 to the other leading flanks. By arranging this next to that giving maximum cut-off position the control actuating the lever 27 may be moved straight from a forward to a reverse rotation of the engine, this acting, in an emergency, as a very powerful brake without mechanical damage.

In the case of heavy load applications, two reverse cams, with differing lift-dwells may be incorporated. In both forward and reverse action any predetermined cut-off positions may be selected. Further, to save machining, the whole cut-off assembly may be cast by either die-casting or the lost wax technique.

Very preferably, the axes of the slide valves are parallel to those of the cylinders and the valves are operated from the cam(s) through a knuckle joint.

The engine which has been described is connected to and operates with associated equipment various parts of which will be more fully described. This equipment includes a feed water pump, a feed water heater, a steam generator, a flow meter and control mechanism which may include a combined thermostat and steam pressure control unit.

Fuel combustion. feed water flow and pressure and temperature of the working fluid are automatic and will now be described as applied preferably to monotube type steam generators but thy are equally applicable to other types of vapour pressure generators.

A low pressure carburettor type of apparatus feeds fuel from a float chamber to ajet situated in the throat of a Venturi tube through which combustion air is blown by an electrically driven fan. causing a partial vacuum therein which draws fuel, which may be kerosene or alcohol, in the form of a spray, from the jet. A suitably positioned sparking plug, sparking continuously under the action of an electronic-inductive ignition system. which needs no mechanically operated make and break, ignites the combustible gases which are then blown tangentially into a combustion chamber at the top of a steam generator. whence they are lead into a central combustion tube, which may be made from heat-resistant metallic gauze or a porous refractory material and in which there is fitted a conical flame or gas deflector.This arrangement prevents combustion gases from depositing soot on a series of verticallydisposed spiral pancake coils of water tubing surrounding the tube, which tubing, in turn, is surrounded by a circular heat-resistant metal container.

The combustion gases cause the combustion tube to glow, thus heating the inner coil of the spiral pancakes by radiation. These gases and gases which have passed through the central tube strike a refractory surface forming the bottom of the generator, causing them to spread outwards and upwards through the outer coils of the spiral pancakes. heating them by convection. Finally the gases exhaust to atmosphere via a suitable vent below the bottom of the combustion chamber.

Disposed around and above the combustion chamber are a number of tubes which form a super-heater. The whole generator, including its cover, is thermally insulated to minimise radiation, by suitable heat insulating cladding which may be contained by an outer shell, preferably of aluminium.

The intensity of the combustion flame is varied by increasing or decreasing the amount of air drawn into the inlet of the electrically driven blower fan and thus varies the amount of fuel drawn from the jet. This is achieved by a slide provided across the fan air intake or by a butterfly valve, as in the case of an I.C. engine throttle which operates in a tube leading to the air intake. The slide or butterfly valve may be operated by two devices, a flowmeter and a temperature control which will hereinafter be described.

The intensity of the flame may be controlled by an electric device varying the current and therefore the speed of the motor driving the blower fan.

Thus, the intensity of the burner flame is always proportional to the load on the generator, i.e. to the needs of the engine.

The flowmeter is operated by a fluid supply from an engine-driven fluid feed pump. The fluid, after passing through the flowmeter is supplied to the steam generator via a feed water heater and a non-return valve. The construction and operation are as follows: Fluid from the feed-water pump enters one end of a cylinder in the flowmeter, which is provided with a longitudinal slot the width of which increases gradually. A loosely fitted piston is normally pressed to the one end of the cylinder bore by means of a heavy spring located between the piston and the end of the cylinder bore.Any increase in engine speed forces more fluid into the flow meter, thus causing the spring-loaded piston to move longitudinally, thus to allow more fluid to pass into the steam generator via the feedwater heater until balance is needed between the fluid pressure and the force of the spring, the position of the spring being always proportional to the engine speed. When balance is obtained, any further movement of the piston would result in excess water imposing an undue load on the steam generator. Consequently an extension rod provided at the end of the piston which normally seals a relief valve will open the relief valve so as to allow the excess water to return to the main water supply through an outlet connection. This constitutes a safety precaution.

Means are provided for varying the blower-fan speed, but if for any reason, this control should malfunction a fail-safe microswitch may be provided which may cut the current to either the fuel pump or the blowerfan motor or both at once until conditions return to normal. In the meantime, lack of combustion flame will result in loss of latent heat from the Venturi casing. To minimise this loss, the Venturi casing may be clad with suitable thermal insulating material.

If the aforementioned control cuts the fuel supply and leaves the blower-fan motor running, the air intake to the fan still be heated by suitable sheet-metal ducting draining warm air from the top tank of the condenser which will stay hot for sufficient time to produce a warm flow of air through the Venturi, further minimising loss of thermal efficiency.

The vapour temperature in the steam generator is controlled by a combined thermostat and steam pressure-control unit placed in the supply line between the generator and the engine. A casing tube of suitable length and diameter is provided with a vapour connection to each end. One of these is connected to an extension of the superheater coils in the generator. A safety valve which is mandatory, is connected to this tube as near the generator as possible and is set to blow-off at a pressure beyond the designed normal steam maximum pressure, but so that it still, before blow-off, leaves a more than adequate margin of safety. Blow-off steam is led direct to the main water tank so that no danger is caused when the system is switched on and the combustion gases will heat the super-heater coils.

Heat will flow, by convection and conduction along the casing tube which, preferably is lagged along its length by thermal insulating cladding. The end remote from the generator is connected direct by a pipe connection to a balanced type steam throttle, the steam outlet of which is connected directly to the steam inlet to the engine.

Thus, vapour led to the engine is travelling an already heated path, resulting in a minimum of condensation in the cylinders of the engine.

A rod or tube with a high co-efficient of expansion, such as brass, is affixed to one end cover of the aforementioned casing tube with its other end bearing against a metal diaphragm. Differential expansion relative to the casing tube will cause this rod or tube, bathed in vapour, to transmit movement to the diaphragm the edges of which are sealed.

A "fail-safe" snap switch, in case of malfunction of the mechanism, is incorporated to cut the current either to the fuel pump or the blower-fan motor separately or together.

The speed of the blower-fan electric motor may be varied by electronic means.

Fluid from the flowmeter, before entering the generator, passes through the feed water heater the fluid flowing through coiled tubing contained in a sealed metal casing which accepts exhaust steam direct from the engine.

The coiled tubing, being bathed in steam therefore heats up the fluid prior to entering the generator via a non-return valve.

Exhaust steam leaves the casing at the end remote from its entry thereto and may be led direct to the top of a condenser from the bottom tank of which condensed steam may be extracted by a pump which returns it to the main water supply. Alternatively, exhaust steam may be led to reaction or impulse type turbine driving a cooling fan and, by a suitable coupling at the rear thereof an alternator for battery charging. This further lowers the steam pressure and temperature assisting complete condensation.

Exhaust steam may, on its way to the condenser or turbine pass, as a loop through the hotwell feeding the feed water pumps, to further thermal efficiency.

Exhaust steam, on its way to the above mentioned turbine, may pass, via a valve under the control of the operator, through a shunt system consisting, in the case of vehicles, of underfloor ribbon tube radiators for vehicle heating. In the case of boats, a similar shunt system with suitably disposed ribbon radiators, may be used for cabin heating. Further, via suitable manually controlled valves the exhaust steam may be led to a suitably designed cooking apparatus.

Both heating and cooking may be operated separately or in combination, the engine speed and therefore the respective temperature to either the cooking or heating apparatus being manually adjusted to requirements. This obviates the carrying of butane containers the cause of many fires.

With water producing the vapour pressure.

the engine and its ancilliary equipment will have to be protected from frost. The temperatures involved preclude the use of any antifreeze solution and lagging will only protect the system for limited periods. Therefore. in the case of vehicles or boats a thermostat, located in an exposed position. sensing the ambient temperature and, when this falls to near freezing, with a safety margin. operates a snap-switch so wired that the burner fan motor starts simultaneously opening an electro-magnetic pilot valve allowing sufficient steam to pass to the engine causing it to run until the whole system warms up to a predetermined temperature when the thermostat switches off.

To prevent vehicle or boat movement with the engine running some form ofclutch must be incorporated in the final drive. This may be of simple in or out dog clutch, or one of friction type but preferably of an electromagnetic type normally permanently engaged by switching on the main dashboard key, switching off of which breaks all battery and component electrical connection. If, however. it is desired to run the engine, for any adjustments necessary, with the vehicle or boat stationary a subsidiary switch under operator control may cut the current to the electro-magnetic clutch only. Automatic drain valves are fitted to the ends of all cylinders so spring loaded that they will only open under the pressure of any incompressible condensate but remain closed under any pre-determined steam pressure.Unlike most conventional relief valves which exhaust to atmosphere, the drain valves lead any condensate to the exhaust steam manifold. Thus no loss of fluid or steam is possible resulting in minimal feed-water addition in the case, as here of a fully condensing system.

Lubrication of all moving parts of the engine is carried out as follows-ngidly affixed to the mainshaft, located near the end cover of the valve operating housing, is a double lobed cam operating, vertically, a piston pump the plunger of which is suitably spring-loaded for return. The pump takes water from within the casing 1, 2, 3 and pumps it to friction surfaces of the engine for lubrication thereof.

Since there is no metal to metal contact in any moving parts no lubication oil is necessary therefore this pump forces distilled water throughout the system. The outlet of the pump, provided with a conventional nonreturn valve, is connected by suitably drilling to the hollow main shaft and feeds, by radial drillings the self-aligning carbon main bearings, the carbon pads mating with the swash plate surfaces and the caliper cross-head carbon-lined drillings in the swash-plate housing. The Allen type main piston rings and the piston rings of the balanced inlet valves, all composed of a suitable carbon composition are adequately lubricated by super-heated steam the carbon being capable of operating. without friction, at much higher temperatures than any steam temperature ever likely to be employed.A thwartwise extension of the valve housing constitutes a sump. generously provided with cooling fins as may be the swash plate housing. The feedwater opposed-piston type pump is operated by a scotch-crank mechanism driven by the main shaft direct.

In a static application, such as a generator set one inlet valve cam is still necessary to operate the valves by the aforementioned roller and bell-crank assembly but no reverse is necessary nor, except in the case of such a unit being subjected to ambient temperatures, is any clutch device necessary to prevent vehicle or boat movement as already described. To satisfy variable loads on the engine some preferred type of throttle governor must be incorporated. This may be driven by gears of belts or chain.

Condensing arrangements will vary according to the size of and power of the generating set. In the case of small factories or private dwellings the above described system will be adequate. In the case of large buildings when high volume cooling water may be available exhaust steam may be condensed thereby obviating the need for an exhaust steam turbine and cooling fan driven thereby. However, since a small storage battery is still necessary to supply current to the induction coil operating the sparking plug, already described, to keep this battery charged an alternator, driven in tandem or by means of triangular gearing or belting from the output shaft of the engine must be incorporated.

Where applicable, exhaust steam, before being condensed may be utilised for heating or process work.

The following are features of the present invention, some of which appear in the drawing The engine may operate as simple, doubleacting or double-setting opposed piston types and the steam cycle may be one of the following:-- simple expansion, multiple expansion or the uniflow principle for which it is particularly suitable.

Tangential side thrust of the swash plate on the piston rods is obviated since the aforementioned cross-head calipers carry a "T" shaped extension sliding in broached "T" slots on the swash plate housing.

Correct running clearance between the bearing cage and the swash plate assembly is obtained by screwing into the swash plate housing a member with a fine thread provided with, at the end remote from the swash plate, a locking ring.

As has been said, distribution of the working fluid to the various cylinders can be controlled by slide valves, preferably of the balanced piston valve type, but rotary valves or poppet valves may also be used. A specially designed cam which may engage a roller tappet direct working at 90 to the cylinders or co-axial with the cylinders through a bell-crank may be mounted at the end of the main shaft. A second cam may be mounted on the opposite end of the main shaft enabling inlet and exhaust valves to be operated independently.

The design of the engine may incorporate full condensing and, in the case of a surface condenser of limited capacity, caused by restricted space, it is possible, in order further to enhance the condensing effect, to take a bleed from the feed-water system at reduced pressure, the water being sprayed into the condenser tubes against the flow of the exhaust steam which it will condense. The condensate is then returned to the water-tank for reuse.

This jet condenser would be used preferably only when the engine is operating on late cut-off and would be brought into operation by the opening of a combined reducing and control valve operated either mechanically or electrically when the valve gear is in a late cut-off position.

This arrangement will enable the size of the surface condenser and feed-water heater to be reduced.

When, for any reason, the controls reduce the volume of air passing through the Venturi tube below that necessary for proper combustion, such as when stopping or starting or when the gases are not ignited, small amounts of fuel may still be drawn from the jet causing local wetness which, on reignition, might cause a flame-out. To prevent this a small diameter bleed pipe may be connected between the throat of the Venturi and a spring loaded diaphragm chamber.

The diaphragm carries a taper needle which enters the base of the jet normally closed by the spring when the depression in the throat of the Venturi is at atmospheric pressure or insufficient air is passing to support combustion but opens progressively as the depression in the Venturi throat increases due to a greater volume of air being drawn into the burner as the speed of the blower fan motor is increased by the aforementioned generator controls.

WHAT 1 CLAIM IS: 1. A piston engine operable by steam pressure, comprising a main shaft journalled in bearings, a driving plate mounted on the shaft, wherein the driving plate has an annular working surface lying in a plane which is at an angle to a plane perpendicular to the shaft axis, a plurality of cylinders spaced around the main shaft, each cylinder having a working piston located therein by piston rings with a piston rod extending from it, the piston rods engaging the driving plate by means of thrust pads so that reciprocation of the piston rotates the main shaft, the pads, piston rings and bearings being of a bearing composition consisting essentially of carbon and the engine being arranged to be lubricated by water and/or steam.

2. An engine according to claim I, wherein the axes of the cylinders are parallel to that of the main shaft.

3. An engine as claimed in Claim 1 or Claim 2, wherein the pistons are doubleacting and engage annular working surfaces which are parallel to each other on opposite sides of the driving plate.

4. An engine as claimed in any of the preceding Claims, wherein the driving plate is a swash plate fixedly mounted on the main shaft.

5. An engine as claimed in any of the preceding Claims, wherein the driving plate has annular working surfaces on both of its sides which are engaged by the faces of pads having part-spherical surfaces where they engage in cup-shaped recesses, in members connected with the piston rods, such that each rod carries a pair of said pads which slidably engage opposite sides of the driving plate and are angularly movable relatively to the plate during running of the engine.

6. An engine as claimed in any of the preceding Claims, wherein the supply of steam to the cylinders is controlled by slide valves of the piston type.

7. An engine as claim in any of the preceding Claims, wherein the supply of steam to the cylinders is controlled by a cam mounted on the main shaft.

8. An engine as claimed in Claim 7, wherein the axes on the slide valves are parallel to those of the cylinders and the valves are operated from the cam through a knuckle joint.

9. An engine as claimed in any of Claims 6 to 8, wherein the valves are adapted to be operated by any of a selected one of a number of cam surfaces of a cam or cams mounted on the shaft to give forward and reverse drives.

10. An engine as claimed in Claim 9, wherein the surfaces are so shaped that the valves can be operated to give different times for valve opening and closing which can be selected in accordance with the speed or power required.

11. An engine as claimed in Claim 9 or Claim 10, wherein the cam or cams are

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (17)

**WARNING** start of CLMS field may overlap end of DESC **. bearing cage and the swash plate assembly is obtained by screwing into the swash plate housing a member with a fine thread provided with, at the end remote from the swash plate, a locking ring. As has been said, distribution of the working fluid to the various cylinders can be controlled by slide valves, preferably of the balanced piston valve type, but rotary valves or poppet valves may also be used. A specially designed cam which may engage a roller tappet direct working at 90 to the cylinders or co-axial with the cylinders through a bell-crank may be mounted at the end of the main shaft. A second cam may be mounted on the opposite end of the main shaft enabling inlet and exhaust valves to be operated independently. The design of the engine may incorporate full condensing and, in the case of a surface condenser of limited capacity, caused by restricted space, it is possible, in order further to enhance the condensing effect, to take a bleed from the feed-water system at reduced pressure, the water being sprayed into the condenser tubes against the flow of the exhaust steam which it will condense. The condensate is then returned to the water-tank for reuse. This jet condenser would be used preferably only when the engine is operating on late cut-off and would be brought into operation by the opening of a combined reducing and control valve operated either mechanically or electrically when the valve gear is in a late cut-off position. This arrangement will enable the size of the surface condenser and feed-water heater to be reduced. When, for any reason, the controls reduce the volume of air passing through the Venturi tube below that necessary for proper combustion, such as when stopping or starting or when the gases are not ignited, small amounts of fuel may still be drawn from the jet causing local wetness which, on reignition, might cause a flame-out. To prevent this a small diameter bleed pipe may be connected between the throat of the Venturi and a spring loaded diaphragm chamber. The diaphragm carries a taper needle which enters the base of the jet normally closed by the spring when the depression in the throat of the Venturi is at atmospheric pressure or insufficient air is passing to support combustion but opens progressively as the depression in the Venturi throat increases due to a greater volume of air being drawn into the burner as the speed of the blower fan motor is increased by the aforementioned generator controls. WHAT 1 CLAIM IS:

1. A piston engine operable by steam pressure, comprising a main shaft journalled in bearings, a driving plate mounted on the shaft, wherein the driving plate has an annular working surface lying in a plane which is at an angle to a plane perpendicular to the shaft axis, a plurality of cylinders spaced around the main shaft, each cylinder having a working piston located therein by piston rings with a piston rod extending from it, the piston rods engaging the driving plate by means of thrust pads so that reciprocation of the piston rotates the main shaft, the pads, piston rings and bearings being of a bearing composition consisting essentially of carbon and the engine being arranged to be lubricated by water and/or steam.

2. An engine according to claim I, wherein the axes of the cylinders are parallel to that of the main shaft.

3. An engine as claimed in Claim 1 or Claim 2, wherein the pistons are doubleacting and engage annular working surfaces which are parallel to each other on opposite sides of the driving plate.

4. An engine as claimed in any of the preceding Claims, wherein the driving plate is a swash plate fixedly mounted on the main shaft.

5. An engine as claimed in any of the preceding Claims, wherein the driving plate has annular working surfaces on both of its sides which are engaged by the faces of pads having part-spherical surfaces where they engage in cup-shaped recesses, in members connected with the piston rods, such that each rod carries a pair of said pads which slidably engage opposite sides of the driving plate and are angularly movable relatively to the plate during running of the engine.

6. An engine as claimed in any of the preceding Claims, wherein the supply of steam to the cylinders is controlled by slide valves of the piston type.

7. An engine as claim in any of the preceding Claims, wherein the supply of steam to the cylinders is controlled by a cam mounted on the main shaft.

8. An engine as claimed in Claim 7, wherein the axes on the slide valves are parallel to those of the cylinders and the valves are operated from the cam through a knuckle joint.

9. An engine as claimed in any of Claims 6 to 8, wherein the valves are adapted to be operated by any of a selected one of a number of cam surfaces of a cam or cams mounted on the shaft to give forward and reverse drives.

10. An engine as claimed in Claim 9, wherein the surfaces are so shaped that the valves can be operated to give different times for valve opening and closing which can be selected in accordance with the speed or power required.

11. An engine as claimed in Claim 9 or Claim 10, wherein the cam or cams are

longitudinally adjustable on the main shaft to control the operation of the valves.

12. An engine as claimed in any of the preceding Claims wherein the cylinders, valves and valve operating mechanism are housed in a casing adapted to contain water, water being pumped in use from the casing to carbon to metal friction surfaces for lubrication of these surfaces.

13. A piston engine according to Claim 1, including a carburettor type liquid fuel burner substantially as hereinbefore described.

14. A piston engine according to Claim 1, including a thermostat and pressure control mechanism substantially as hereinbefore described.

15. A piston engine according to Claim 1, including a steam generator substantially as hereinbefore described.

16. A piston engine. substantially as hereinbefore described or shown in the accompanying drawing.

17. A road vehicle incorporating a piston engine as claimed in any preceding Claim.