FIELD OF THE INVENTION

This invention relates to reciprocating engines and to reciprocating compressors, and in particular, but not exclusively to a crankshaft-less reciprocating engine for use in vehicles and power generation, whether powered by steam or by the internal combustion of a fuel.

BACKGROUND

Many vehicles and other machines use reciprocating engines. A key feature of any reciprocating engine is its efficiency.

The use of a crankshaft limits the efficiency of many reciprocating engines. When the reciprocating piston is near top dead centre, or near bottom dead centre, the crank of the crankshaft is at an angle that limits the turning force or torque that can be applied by the piston to the crank shaft. This problem is experienced over at least a third, and up to a half, of each revolution of a crank being driven by a reciprocating piston.

Also, many internal combustion engines have complex arrangements of reciprocating pistons, connecting rods, crankshafts, timing belts, valve operating equipment, etc, and a complex block or body to house and support all of these components. These all add to the complexity, cost and weight of most engines.

The inventor of the present engine is also the inventor of the engines described in PCT/NZ2004/000306 and in PCT/NZ2015/000029. While each of the engine configurations in these earlier applications had merits, they tended to suffer from problems with balancing, large quantities of moving parts, with high reciprocating mass and/or with efficient breathing.

The present invention is the culmination of over twelve years of development and research, and combines the benefits of current motor vehicle engine technology with some of the features pioneered in the earlier engines, to produce the following engine configuration which has been significantly simplified and enjoys the benefits of an efficient breathing system or valve operating mechanism combined with an efficient method for translating reciprocating motion into rotating motion.

Compressors often have a similar architecture to that of a reciprocating engine, and therefore suffer from many of the same problems. What is needed is a simple and reliable compressor for many applications.

In this specification unless the contrary is expressly stated, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned.

OBJECT

It is therefore an object of the present invention to provide a reciprocating engine which will at least go some way towards overcoming one or more of the above mentioned problems, or at least provide the public with a useful choice.

STATEMENTS OF THE INVENTION

Accordingly, in a first aspect, the invention may broadly be said to consist in a reciprocating steam engine having at least one cylinder, a drive shaft that is coaxial with the cylinder, and at least one piston configured to reciprocate within the cylinder and to cause the drive shaft to rotate, the reciprocating motion of the or each piston being converted to rotary motion by an interaction between at least one end cam and at least one cam engagement roller, and the or each piston is connected to the driveshaft via a sliding joint that allows reciprocating motion of the piston in line with a longitudinal axis of the drive shaft whilst preventing rotational movement of the piston about or relative to the drive shaft.

Preferably either the or each end cam, or the or each cam engagement roller is connected to a fixed frame of the engine. Preferably the engine includes one or more expansion chambers, the or each expansion chamber being defined between the or each cylinder inside diameter, a crown of the or each piston and a cylinder head or cylinder bulkhead facing the or each piston.

Preferably the or each piston is a double ended piston having a crown at each end of the or each piston.

Preferably the or each double ended piston defines an expansion chamber at both ends of the or each double ended piston.

Preferably the engine includes at least two double ended pistons.

Preferably the engine has two double ended pistons and is configured such that the two double ended pistons always travel in opposite directions to one another.

Preferably there is at least one inlet passage and at least one outlet passage in communication with the or each expansion chamber.

Preferably there is at least one valve controlling the flow of gases through the or each inlet and outlet passage.

Preferably the or each valve is a rotary valve.

Preferably the or each rotary valve is driven directly by the driveshaft.

Preferably the or each rotary valve includes a rotor that is mounted on the driveshaft.

Preferably the valves associated with each expansion chamber of a four expansion chamber version of the engine are configured to provide sequenced power exhaust strokes to sequence the power from each pair of expansion chambers.

Preferably the or each cylinder head or end bulkhead includes an inlet passage and an outlet passage, the flow through each being controlled by a rotary valve associated with the or each cylinder head or end bulkhead.

Preferably the or each end cam has a cam profile having two troughs and two peaks. Preferably the or each end cam has a section which slopes at forty five degrees relative to a longitudinal axis of the driveshaft, between each peak and trough of the cam profile of the or each end cam.

Optionally the or each end cam has a sinusoidally curved profile.

Preferably the joint between the or each piston and the driveshaft is a splined joint, having clearance to facilitate reciprocating motion of the or each piston.

Preferably the or each end cam or the or each cam engagement roller is fixed to a stationary part or frame of the engine.

Accordingly, in a second aspect, the invention may broadly be said to consist in a reciprocating internal combustion engine having at least one cylinder, a drive shaft that is coaxial with the or each cylinder, and at least one piston configured to reciprocate within the or each cylinder and to cause the drive shaft to rotate, the reciprocating motion of the or each piston being converted to rotary motion by an interaction between at least one end cam and at least one cam engagement roller, and the or each piston is connected to the driveshaft via a sliding joint that allows reciprocating motion of the piston in line with a longitudinal axis of the drive shaft whilst preventing rotational movement of the piston relative to the drive shaft.

Preferably the driveshaft passes through the or each piston.

Preferably the flow of gases into and out of the reciprocating internal combustion engine is controlled by one or more valves that are situated about the drive shaft.

Preferably the flow of gases into and out of the reciprocating internal combustion engine is controlled by one or more valves that are situated within a cylindrical space aligned with and defined by the outside diameter of the or each cylinder.

Preferably the flow of gases into and out of the reciprocating internal combustion engine is controlled by one or more valves that are operated by the driveshaft.

Preferably the or each valve is a rotary valve. Preferably the or each rotary valve is driven directly by the driveshaft.

Preferably the or each rotary valve includes a rotor that is mounted on the driveshaft.

Preferably the engine includes one or more combustion chambers, the or each combustion chamber being defined between the or each cylinder inside diameter, a crown of the or each piston and a cylinder head or cylinder bulkhead facing the or each piston.

Preferably the driveshaft passes through the or each cylinder head or cylinder bulkhead.

Preferably the driveshaft passes through the or each cylinder head or cylinder bulkhead and the driveshaft passes through the or each piston, and valves to control the flow of gases into and out of the or each combustion chamber are situated adjacent to the or each associated cylinder head or cylinder bulkhead and the valves are operated by the driveshaft.

Preferably there is at least one inlet passage and at least one outlet passage in communication with the or each combustion chamber.

Preferably there is at least one valve controlling the flow of gases through the or each inlet and outlet passage.

Preferably the engine includes an inlet passage and an outlet passage situated in the or each cylinder head or end bulkhead, and each inlet passage and outlet passage is in communication with an associated combustion chamber, and the flow through each inlet passage and outlet passage being controlled by a valve associated with the or each cylinder head or end bulkhead.

Preferably the flow through each inlet passage and outlet passage is controlled by a rotor.

Preferably the or each rotary valve includes a housing having an inlet port and an outlet port, and flow from the inlet port to an associated inlet passage, and flow to the outlet port from an associated outlet passage, is controlled by the rotor.

Optionally the valves to control the flow of gases into and out of the or each combustion chamber are poppet valves.

Preferably the reciprocating internal combustion engine has at least one cylinder and an output portion of the driveshaft extends from at least one end of the cylinders.

Preferably either the or each end cam, or the or each cam engagement roller is connected to a fixed frame of the engine.

Preferably the or each piston is a double ended piston having a crown at each end of the or each piston.

Preferably the or each double ended piston defines a combustion chamber at both ends of the or each double ended piston.

Preferably the engine includes at least two double ended pistons.

Preferably the engine has two double ended pistons and is configured such that the two double ended pistons always travel in opposite directions to one another.

Preferably the engine operates on a four stroke cycle.

Preferably the valves associated with each combustion chamber of a four combustion chamber version of the engine are configured to sequence the firing of each combustion chamber.

Preferably the or each end cam has a cam profile having two troughs and two peaks.

Preferably the or each end cam has a section which slopes at forty five degrees relative to a longitudinal axis of the driveshaft, between each peak and trough of the cam profile of the or each end cam.

Optionally the or each end cam has a sinusoidally curved profile.

Preferably the joint between the or each piston and the driveshaft is a splined joint, having clearance to facilitate reciprocating motion of the or each piston. Preferably the or each end cam or the or each cam engagement roller is fixed to a stationary part or frame of the engine.

Preferably the engine includes at least one spark plug in communication with the or each combustion chamber.

Preferably the engine includes at least one fuel injector in communication with the or each combustion chamber.

Accordingly, in a third aspect, the invention may broadly be said to consist in a reciprocating internal combustion engine having;

• at least one cylinder, a driveshaft that is coaxial with the or each cylinder, and at least one piston configured to reciprocate within the or each cylinder and to cause the driveshaft to rotate,

• one or more combustion chambers, the or each combustion chamber being defined between an inside diameter of the or each cylinder, a crown of the or each piston and a cylinder head or cylinder bulkhead facing the or each piston, and the driveshaft passes through the or each cylinder head or cylinder bulkhead and the driveshaft passes through the or each piston, and one or more valves configured to control the flow of gases into and out of the or each combustion chamber are situated adjacent to the or each associated cylinder head or cylinder bulkhead and the or each valve is operated by the driveshaft.

Preferably the or each valve is situated about the drive shaft.

Preferably the or each valve is situated within a cylindrical space aligned with and defined by the outside diameter of the or each cylinder.

Preferably the or each valve is a rotary valve.

Preferably the or each rotary valve is driven directly by the driveshaft. Preferably the or each rotary valve includes a rotor that is mounted on the driveshaft.

Preferably there is at least one inlet passage and at least one outlet passage in communication with the or each combustion chamber.

Preferably there is at least one valve controlling the flow of gases through the or each inlet and outlet passage.

Preferably the engine includes an inlet passage and an outlet passage situated in the or each cylinder head or end bulkhead, and each inlet passage and outlet passage is in communication with an associated combustion chamber, and the flow through each inlet passage and outlet passage is controlled by at least one valve associated with the or each cylinder head or end bulkhead.

Preferably the flow through each inlet passage and outlet passage is controlled by a rotor.

Preferably the or each rotary valve includes a housing having an inlet port and an outlet port, and flow from the inlet port to an associated inlet passage, and flow to the outlet port from an associated outlet passage, is controlled by the rotor.

Preferably the or each piston is a double ended piston having a crown at each end of the or each piston.

Preferably the or each double ended piston defines a combustion chamber at both ends of the or each double ended piston.

Preferably the engine includes at least two double ended pistons.

Preferably the engine has two double ended pistons and is configured such that the two double ended pistons always travel in opposite directions to one another.

Preferably the engine operates on a four stroke cycle.

Preferably the valves associated with each combustion chamber of a four combustion chamber version of the engine are configured to sequence the firing of each combustion chamber.

Optionally the valves to control the flow of gases into and out of the or each combustion chamber are poppet valves.

Preferably the reciprocating motion of the or each piston being converted to rotary motion by an interaction between at least one end cam and at least one cam engagement roller, and the or each piston is connected to the driveshaft via a sliding joint that allows reciprocating motion of the piston in line with a longitudinal axis of the drive shaft whilst preventing rotational movement of the piston relative to the drive shaft.

Preferably either the or each end cam, or the or each cam engagement roller is connected to a fixed frame of the engine.

Preferably the or each end cam has a cam profile having two troughs and two peaks.

Preferably the or each end cam has a section which slopes at forty five degrees relative to a longitudinal axis of the driveshaft, between each peak and trough of the cam profile of the or each end cam.

Preferably the joint between the or each piston and the driveshaft is a splined joint, having clearance to facilitate reciprocating motion of the or each piston.

Preferably the or each end cam or the or each cam engagement roller is fixed to a stationary part or frame of the engine.

Accordingly, in a fourth aspect, the invention may broadly be said to consist in a compressor having at least one cylinder, a drive shaft that is coaxial with the cylinder, and at least one piston configured to reciprocate within the cylinder when driven by the drive shaft, the rotary motion of the drive shaft being converted into reciprocating motion of the or each piston by an interaction between at least one end cam and at least one cam engagement roller, and the or each piston is connected to the driveshaft via a sliding joint that allows reciprocating motion of the piston in line with a longitudinal axis of the drive shaft whilst preventing rotational movement of the piston about or relative to the drive shaft.

Preferably either the or each end cam, or the or each cam engagement roller is connected to a fixed frame of the compressor.

Preferably the compressor includes one or more pumping chambers, the or each pumping chamber being defined between the or each cylinder inside diameter, a crown of the or each piston and a cylinder head or cylinder bulkhead facing the or each piston.

Preferably the or each piston is a double ended piston having a crown at each end of the or each piston.

Preferably the or each double ended piston defines a pumping chamber at both ends of the or each double ended piston.

Preferably the compressor includes at least two double ended pistons.

Preferably the engine has two double ended pistons and is configured such that the two double ended pistons always travel in opposite directions to one another.

Preferably there is at least one inlet passage and at least one outlet passage in communication with the or each expansion chamber.

Preferably there is at least one valve controlling the flow of gases through the or each inlet and outlet passage.

Preferably the or each valve is a rotary valve.

Preferably the or each rotary valve is driven directly by the driveshaft.

Preferably the or each rotary valve includes a rotor that is mounted on the driveshaft.

Preferably the valves associated with each pumping chamber of a four pumping chamber version of the compressor are configured to sequence the compressed gas flow from each pumping chamber. Preferably the or each cylinder head or end bulkhead includes an inlet passage and an outlet passage, the flow through each being controlled by a rotary valve associated with the or each cylinder head or end bulkhead.

Preferably the or each end cam has a cam profile having two troughs and two peaks.

Preferably the or each end cam has a section which slopes at forty five degrees relative to a longitudinal axis of the driveshaft, between each peak and trough of the cam profile of the or each end cam.

Optionally the or each end cam has a sinusoidally curved profile.

Preferably the joint between the or each piston and the driveshaft is a splined joint, having clearance to facilitate reciprocating motion of the or each piston relative to the driveshaft.

Preferably the or each end cam or the or each cam engagement roller is fixed to a stationary part or frame of the compressor.

In a fourth aspect, the invention may broadly be said to consist in a power generation plant or vehicle incorporating at least one reciprocating engine substantially as specified herein.

The invention may also broadly be said to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of the parts, elements or features, and where specific integers are mentioned herein which have known equivalents, such equivalents are incorporated herein as if they were individually set forth.

DESCRIPTION

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which: FIGURE 1 is a perspective view of a reciprocating steam engine according to the present invention,

FIGURE 2 is a cross sectional view of the reciprocating steam engine,

FIGURE 3 is a perspective view of a double ended piston of the reciprocating steam engine,

FIGURE 4 is a cutaway perspective view of the double ended piston,

FIGURE 5 is a perspective view of a driveshaft of the reciprocating steam engine,

FIGURE 6 is a perspective view of the reciprocating steam engine without an outer cylinder or the double ended pistons,

FIGURE 7 is a partially cutaway perspective view of the reciprocating steam engine,

FIGURE 8 is a perspective view of a second example of a reciprocating engine according to the present invention, the reciprocating engine being an internal combustion engine,

FIGURE 9 is a partially cutaway perspective view of the reciprocating internal combustion engine,

FIGURE 10 is a perspective view of a double ended piston of the reciprocating internal combustion engine,

FIGURE 11 is a cutaway perspective view of the double ended piston,

FIGURE 12 is a perspective view of a driveshaft of the reciprocating internal combustion engine,

FIGURE 13 is a partially cutaway perspective view of the reciprocating internal combustion engine without an outer cylinder or the double ended pistons, and FIGURE 14 is a perspective close up view of one end of the reciprocating internal combustion engine.

FIGURE 15 is a partially cutaway perspective view of a third example of a reciprocating internal combustion engine according to the present invention,

FIGURE 16 is a second perspective view of the third example of a reciprocating internal combustion engine, this time with a cylinder fully removed,

FIGURE 17 is a second perspective view of the third example of a reciprocating internal combustion engine with the cylinder and two reciprocating pistons removed,

FIGURE 18 is a perspective view of a driveshaft of the third example of a reciprocating internal combustion engine,

FIGURE 19 is a perspective view of one of the reciprocating pistons of the third example of a reciprocating engine,

FIGURE 20 is a partially cutaway perspective view of a cylinder support fitting and cam engagement rollers of the third example of a reciprocating internal combustion engine,

FIGURE 21 is a cutaway perspective view of one of the pistons of the third example of a reciprocating internal combustion engine.

FIGURE 22 is a perspective view of a part of a sliding joint of the reciprocating internal combustion engine,

FIGURE 23 is a perspective view of one end of the third example of a reciprocating internal combustion engine with the cylinder and a rotor of a rotary valve removed, and FIGURE 24 is a perspective view of a rotor of a rotary valve of the third example of a reciprocating internal combustion engine.

First Example

With reference to Figures 1 to 7, a first example of a reciprocating engine (11) according to the present invention will now be described. The reciprocating engine (11) is configured for use as a steam engine of the type suitable for use in vehicles or power stations.

In this example, the reciprocating steam engine (11) has a single cylinder (13) which defines four expansion chambers (15). The engine (11) also has a drive shaft (17) which is coaxial with the cylinder (13).

The engine (11) has two double ended pistons (19) configured to reciprocate within the cylinder (13) and to cause the drive shaft (17) to rotate. The reciprocating motion of each piston (19) is converted into rotary motion by an interaction between two facing end cams (21) associated with each piston (19) and two cam engagement rollers (23) associated with each piston (19). In this example, the end cams (21) are a part of the pistons (19) and the cam engagement rollers (23) are connected to a fixed frame (25) or body of the engine (11).

When steam acts to push against the pistons (19) to produce a reciprocating motion, this reciprocating motion is converted into rotary motion as the end cams (21) bear against the cam engagement rollers (23). In this way the pistons (19) both reciprocate and rotate during operation of the engine (11).

Each of the pistons (19) is connected to the driveshaft (17) via a sliding joint (27). The sliding joints (27) allow reciprocating motion of the pistons (19) in line with a longitudinal axis (29) of the drive shaft (17), while at the same time the sliding joints (27) prevent rotational movement of the pistons (19) about or relative to the drive shaft (17). The joints (27) between the pistons (19) and the driveshaft (17) are splined joints, or are like splined joints. The joints (27) have clearance to facilitate reciprocating motion of the pistons. ln this example, the joints (27) include a pair of splined sleeves (30) on the driveshaft (17) which each include eight radially extending and longitudinally aligned ridges (31) that are configured to engage with eight complimentary radially extending and longitudinally aligned valleys (33) on an internal bore (35) of each piston (19). The joint (27), or engagement between the pistons (19) and the drive shaft (17), allows the pistons (19) to reciprocate in line with the longitudinal axis (29) of the drive shaft (17) while at the same time driving the drive shaft (17) as the pistons (19) rotate.

In this example, the engine (11) has four expansion chambers (15). Each expansion chamber (15) is defined between the inside diameter of the cylinder (13), a crown (37) of an associated piston (19) and a cylinder head (39) or cylinder bulkhead facing the piston crown (37).

As noted above, the engine has two double ended pistons (19), and it can be seen that each piston (19) has a crown (37) at each end. Each piston (19) defines an expansion chamber (15) at both ends of each the piston (19). The engine (11) is configured such that the two double ended pistons (19) always travel in opposite directions to one another.

With reference to Figure 7 it can be seen that the lobes (41) of the end cams (21) of the adjacent pistons (19) are arranged to be 90 degrees out of phase relative to one another, while the cam engagement rollers (23) are all in line. This means that when one piston (19) is moving toward one end of the engine (11), the other piston (19) is moving toward the other end of the engine (11), and vica-versa.

Each end cam (21) has a cam profile having two troughs and two peaks, the shape of the curved profile being similar to a sinusoidal curve. Ideally the curved profile is a modified sinusoidal curve with the curve having sloping sections between each peak and trough that are aligned at an angle of substantially forty five degrees relative to a longitudinal axis of the driveshaft. The extended region in which the slope is at forty five degrees creates a situation in which the torque from the engine (11) is maximised for as much of the stroke of each piston (19) as possible. The reason for this is that while the force from each piston (19) is pushing against the forty five degree slope, the force being exerted by the piston (19) in a longitudinal direction is translated into an equal force in a circumferential direction.

The engine (11) also includes two inlet passages (43) and two outlet passages (45) in communication with each expansion chamber (15). There is also a rotary valve (47) controlling the flow of gases through each inlet and outlet passage (43) and (45). It can be seen in Figures 6 and 7 that in the example shown, there are two inlet passages (43) and two outlet passages (51) in each cylinder head (39). The flow through each inlet passage (43) and each outlet passage (45) is controlled by the rotary valve (47) associated with each cylinder head (39).

Each rotary valve (47) is mounted on the driveshaft (17) and is driven directly by the driveshaft (17). Each rotary valve (47) has two inlet ports (49) and two outlet ports (51) in a stationary housing (52) surrounding a rotor (53), each port being spaced 90 degrees from each adjacent port. Each rotor (53) has two rotor passages (55), and the rotor (53) is driven by the drive shaft (17).

The driveshaft (17) of the engine (11) rotates in an anti-clockwise direction when viewed from the left hand end as indicated by an arrow (57) in Figure 1. As the rotor (53) rotates, the rotor passages (55) move sequentially past then inlet ports (49) and then the outlet ports (51). Each time the rotor passages (55) align with the inlet ports (49), the rotor passages (55) also aligns with the inlet passages (43) in the cylinder head (39). And similarly, each time the rotor passages (55) align with the outlet ports (51), the rotor passages (55) also align with the outlet passages (45) in the cylinder head (39).

During the time that the rotor passage (55) is aligned with both an inlet port (49) and with an inlet passage (43), fresh steam can flow from an inlet manifold (not shown) and into the associated expansion chamber (15). Similarly, during the time that the rotor passage (55) is aligned with both an outlet port (51) and with an outlet passage (45), spent steam can flow from the associated expansion chamber and into an exhaust manifold (not shown). The rotary valves (47) are configured to provide sequenced inlet and exhaust strokes to sequence the power from each pair of expansion chambers. For example, if the expansion chambers are numbered 1 to 4 along the length of the engine, steam is introduced to expansion chambers 1 and 4 during a first stroke of the double ended pistons (19), and the steam is introduced to expansion chambers 2 and 3 during a second stroke of the pistons (19).

Second Example

With reference to Figures 8 to 14, a second example of a reciprocating engine (111) according to the present invention will now be described. The reciprocating engine (111) is configured for use as an internal combustion engine of the type suitable for use in vehicles or power stations.

In this example, the reciprocating internal combustion engine (111) has a single cylinder (113) which defines four combustion chambers (115). The engine (111) also has a drive shaft (117) which is coaxial with the cylinder (113).

The engine (111) has two double ended pistons (119) configured to reciprocate and rotate within the cylinder (113) and to cause the drive shaft (117) to rotate. The reciprocating motion of each piston (119) is converted into rotary motion by an interaction between two facing end cams (121) associated with each piston (119) and two cam engagement rollers (123) associated with each piston (119). In this example, the end cams (121) are a part of the pistons (119) and the cam engagement rollers (123) are connected to a fixed frame (125) or body of the engine (111).

When fuel is burned to create heat and the resulting pressurised gases, the gases push against the pistons (119) to produce a reciprocating motion. This reciprocating motion is converted into rotary motion as the end cams (121) bear against the cam engagement rollers (123). In this way the pistons (119) both reciprocate and rotate during operation of the engine (111). Each of the pistons (119) is connected to the driveshaft (117) via a sliding joint (127). The sliding joints (127) allow reciprocating motion of the pistons (119) in line with a longitudinal axis (129) of the drive shaft (117), while at the same time the sliding joints (127) prevent rotational movement of the pistons (119) about or relative to the drive shaft (117). The joints (127) between the pistons (119) and the driveshaft (117) are splined joints, or are like splined joints. The joints (127) have clearance to facilitate reciprocating motion of the pistons.

In this example, the joints (127) include a pair of splined sleeves (130) on the driveshaft (117) which each include eight radially extending and longitudinally aligned ridges (131) that are configured to engage with eight complimentary radially extending and longitudinally aligned valleys (133) on an internal bore (135) of each piston (119). The joint (127), or engagement between the pistons (119) and the drive shaft (117), allows the pistons (119) to reciprocate in line with the longitudinal axis (129) of the drive shaft (117) while at the same time driving the drive shaft (117) as the pistons (119) rotate.

In this example, the engine (111) has four combustion chambers (115). Each combustion chamber (115) is defined between the inside diameter of the cylinder (113), a crown (137) of an associated piston (119) and a cylinder head (139) or cylinder bulkhead facing the piston crown (137).

As noted above, the engine has two double ended pistons (119), and it can be seen that each piston (119) has a crown (137) at each end. Each piston (119) defines a combustion chamber (115) at both ends of each piston (119). The engine (111) is configured such that the two double ended pistons (119) always travel in opposite directions to one another.

With reference to Figure 9 it can be seen that the lobes (141) of the end cams (121) of the adjacent pistons (119) are arranged to be 90 degrees out of phase relative to one another, while the cam engagement rollers (123) are all in line. This means that when one piston (119) is moving toward one end of the engine (111), the other piston (119) is moving toward the other end of the engine (111), and vica-versa. Each end cam (121) has a cam profile having two troughs and two peaks, the shape of the curved profile being similar to a sinusoidal curve. Ideally the curved profile is a modified sinusoidal curve with the curve having sloping sections between each peak and trough that are aligned at an angle of substantially forty five degrees relative to a longitudinal axis of the driveshaft. The extended region in which the slope is at forty five degrees creates a situation in which the torque from the engine (111) is maximised for as much of the stroke of each piston (119) as possible. The reason for this is that while the force from each piston (119) is pushing against the forty five degree slope, the force being exerted by the piston (119) in a longitudinal direction is translated into an equal force in a circumferential direction.

With reference to Figure 13 it can be seen that the engine (111) includes an inlet passage (143) and an outlet passage (145) in each cylinder head (139). The inlet passages (143) and outlet passages (145) in each cylinder head (139) communicate directly with the adjacent combustion chamber (115). For each combustion chamber (115), the flow through its associated inlet passage (143) and outlet passage (145) is controlled by a rotary valve (147) associated with that combustion chamber (115).

Each rotary valve (147) is mounted on the driveshaft (117) and is driven directly by the driveshaft (117). Each rotary valve (147) has one inlet port (149) and one outlet port (151) situated in a stationary housing (152) surrounding a rotor (153). The inlet port (149) is spaced ninety degrees from the outlet port (151). The rotor (153) has a single rotor passage (155), and it is the rotor (153) or each rotary valve (147) that is driven directly by the drive shaft (117).

The internal combustion engine (111) operates on a four stroke cycle. For each three hundred and sixty degrees of rotation of the drive shaft, each piston reciprocates twice, having completed an induction stroke, a compression stroke, a power stroke and an exhaust stroke.

As each rotor (153) rotates through three hundred and sixty degrees, the rotor passage (155) moves once past its associated inlet port (149) and once past its associated outlet port (151). Each time the rotor passage (155) aligns with an inlet port (149), the rotor passage (155) also aligns with an inlet passage (143) in the adjacent cylinder head (139). And similarly, each time the rotor passage (155) aligns with an outlet port (151), the rotor passage (155) also aligns with an outlet passage (145) in the adjacent cylinder head (139).

During the time that the rotor passage (155) is aligned with both an inlet port (149) and with an inlet passage (143), a fresh charge of air flows from an inlet system or manifold (not shown) and into the associated combustion chamber (115). Similarly, during the time that the rotor passage (155) is aligned with both an outlet port (151) and with an outlet passage (145), exhaust gases flow from the associated combustion chamber (115) and into an exhaust system or manifold (not shown).

The driveshaft (117) of the engine (111) rotates in an anti-clockwise direction when viewed from the left hand end of the engine (111) as indicated by an arrow (157) in Figure 8. It can be seen that the rotor passage (155) must travel through approximately two hundred and seventy degrees as it travels from the inlet port (149) and around to the outlet port (151).

The rotary valves (147) are configured to provide sequenced power strokes from the four combustion chambers (115). For example, if the combustion chambers are numbered 1 to 4 along the length of the engine, from left to right, the sequence of the power strokes, or the firing order, in the example shown can be 1, 2, 4, 3.

The engine (111) also includes a spark plug (171) associated with each combustion chamber (115). In this example the spark plugs (171) are situated in an unswept portion of the cylinder (113) wall defining each combustion chamber (115). Alternatively the spark plugs could be mounted in the cylinder heads (139). A conventional ignition system can be used to provide power and control ignition timing for each spark plug (171). Alternatively the engine (111) could be configured for diesel fuel and may not require electronic ignition.

The engine (111) can also use conventional fuel systems, for example the fuel system can be a carburetted system, a metered LPG system, or a direct fuel injection system. The fuel injectors could be mounted in the cylinder (113) wall or in the cylinder heads (139). A variety of fuels could be used for example LPG, petrol or diesel.

Third Example

With reference to Figures 15 to 24, a third example of a reciprocating engine (211) according to the present invention will now be described. As with the second example (111), the reciprocating engine (211) is also configured for use as an internal combustion engine of the type suitable for use in vehicles or power stations. The engine (211) is the result of twelve months further development from the configuration of engine (111).

As previously, the reciprocating internal combustion engine (211) has a single cylinder (213) which defines four combustion chambers (215). The engine (211) also has a drive shaft (217) which is coaxial with the cylinder (213). In comparison to engine (111), the engine (211) has a shorter stroke and overall length, a modified cam follower roller arrangement, larger inlet and exhaust ports, and a modified sliding joint between the reciprocating and rotating pistons (219) and the driveshaft (217).

Again, the engine (211) has two double ended pistons (219) configured to reciprocate and rotate within the cylinder (213) and to cause the driveshaft (217) to rotate. The driveshaft (217) passes through each piston (219). As with conventional crankshaft engines, combusting fuel produces reciprocating motion in the pistons (219). But unlike conventional crankshaft engines, the reciprocating motion of each piston (219) is converted into rotary motion by an interaction between two facing end cams (221) associated with each piston (219) and two cam engagement rollers (223) associated with each piston (219). The reciprocating engines according to the present invention do not use crankshafts or connecting rods and for this reason are much simpler, lighter and have a potential to be much more efficient.

In these examples, the end cams (221) are a part of the pistons (219). The end cams (221) interact with cam engagement rollers (223) to cause the reciprocating pistons (219) to rotate. The cam engagement rollers (223) remain fixed relative to the structure of the engine (211) and are connected via cam engagement roller bearings (224) and cylinder support fittings (225) to a fixed frame (226) or body of the engine (211).

As noted above, when fuel is burned to create heat and the resulting pressurised gases, the gases push against the pistons (219) to produce a reciprocating motion. This reciprocating motion is converted into rotary motion as the end cams (221) bear against the cam engagement rollers (223). In this way the pistons (219) both reciprocate and rotate during operation of the engine (211).

Each of the pistons (219) is connected to the driveshaft (217) via a sliding joint (227). The sliding joints (227) allow reciprocating motion of the pistons (219) in line with a longitudinal axis (229) of the drive shaft (217), while at the same time the sliding joints (227) prevent rotational movement of the pistons (219) about or relative to the drive shaft (217). That is, the pistons (219) are fixed to the driveshaft (217) in such a manner that the driveshaft (217) will always rotate at the same speed that the pistons (219) are rotating at, that is the pistons (219) and the driveshaft (217) are rotationally coupled together. The sliding joints (227) between the pistons (219) and the driveshaft (217) are like splined joints.

In this third example, the engine (211) includes two sliding joints (227), and each sliding joint (227) includes four axial slots (229) in an internal axial bore (231) of each piston (219) and four complimentary shaped drive blocks (233).

As can be seen in Figure 22, the four drive blocks (233) are each rectangular in shape when viewed looking in a radial direction with respect to the driveshaft (217), and the four drive blocks (233) are each pivotally attached to a collar (235) on the driveshaft (217). Each collar (235) is keyed to the driveshaft (217) and is fixed relative to the driveshaft (217).

At each sliding joint (227) the drive blocks (233) each extend radially from the collar (235) and the principal axis of the rectangular shape of each drive block (233) is aligned longitudinally with the longitudinal axis (228) of the drive shaft (217). In this way, the four drive blocks (233) of each sliding joint (227) form a cross shaped drive fitting (236) on the driveshaft (217) when viewed from either end of the drive shaft (217). The sliding joint (227), or engagement between the pistons (219) and the drive shaft (217), allows the pistons (219) to reciprocate in line with the longitudinal axis (228) of the drive shaft (217) while at the same time imparting a driving force to rotate the drive shaft (217) as the pistons (219) rotate.

As noted above, the drive blocks (233) are pivotally attached to the collar (235). The drive blocks (233) are pivotally attached using shouldered machine screws (237) that are each fitted tightly into the collar (235) but do not hold the drive blocks (233) firmly against the collar (235). As an alternative, the collars (235) could be eliminated, and the drive blocks (233) could be pivotally attached directly to the driveshaft (217).

The sliding joints (227) include tilting pad bearings and have clearance to facilitate reciprocating motion of the pistons (219). The corners of the drive blocks (233) are chamfered to help lead oil into the gap between the drive blocks (233) and the axial slots (229). The clearance between driven faces (233a) of the drive blocks (233) and driving faces (229a) of the slots (229) allows the drive blocks (233) to pivot or tilt very slightly about the machine screws (237) as a film of oil accumulates between the driving faces (229a) of the slots (229) and the driven faces (233a) of the drive blocks (233). This forces a leading edge of the driven faces (233a) of the drive blocks (233) to tilt very slightly away from the driving faces (229a) of the slots (229) as the pressure of the accumulated oil increases. This helps to reduce wear between these two faces during operation of the engine (211).

In this example, the engine (211) has four combustion chambers (215). Each combustion chamber (215) is defined between the inside diameter of the cylinder (213), a crown (238) of an associated piston (219) and a cylinder head (239) or cylinder bulkhead facing the piston crown (238). The driveshaft (217) passes through the centre of the crowns (238) each double ended piston (219) and through the centre of each cylinder head (239) or cylinder bulkhead.

As noted above, the engine has two double ended pistons (219), and it can be seen that each piston (219) has a crown (238) at each end. Each piston (219) defines a combustion chamber (215) at both ends of each piston (219). The crown (238) at each end of each piston (219) has a series of radial vanes (240) that are configured to swirl or mix a fuel/air charge that enters the combustion chambers (215).

The engine (211) is configured such that the two double ended pistons (219) always travel in opposite directions to one another to allow the engine (211) to operate in a balanced fashion.

With reference to Figure 16 it can be seen that the lobes (241) of the end cams (221) of the adjacent pistons (219) are arranged to be 90 degrees out of phase relative to one another, while the cam engagement rollers (223) are all in line. This means that when one piston (219) is moving toward one end of the engine (211), the other piston (219) is moving toward the other end of the engine (211), and vice-versa.

Each end cam (221) has a cam profile having two troughs and two peaks, the shape of the curved profile being similar to a sinusoidal curve. Ideally the curved profile is a modified sinusoidal curve with the curve having sloping sections between each peak and trough that are aligned at an angle of substantially forty five degrees relative to the longitudinal axis (228) of the driveshaft (217). The extended region in which the slope is at forty five degrees creates a situation in which the torque from the engine (211) is maximised for as much of the stroke of each piston (219) as possible. The reason for this is that while the force from each piston (219) is pushing against the forty five degree slope, the force being exerted by the piston (219) in a longitudinal direction is translated into an equal force in a circumferential direction.

As with the second example of a reciprocating engine (111) each cylinder head (239) includes an inlet passage (243) and an outlet passage (245). The inlet passages (243) and outlet passages (245) in each cylinder head (239) communicate directly with the adjacent combustion chamber (215). For each combustion chamber (215), the flow through its associated inlet passage (243) and outlet passage (245) is controlled by a rotary valve (247) associated with that combustion chamber (215). The rotary valves (247) are situated about the driveshaft (217) and are situated within a cylindrical space aligned with and defined by the outside diameter of the cylinder (213).

As noted above, the driveshaft (217) passes through each cylinder head or cylinder bulkhead and the driveshaft passes through each piston. With reference to Figure 16 it can be seen that the valves that control the flow of gases into and out of each combustion chamber, in this example the rotary valves (247), are each situated adjacent to their associated cylinder head (239), and the valves are operated by the driveshaft (217).

Each rotary valve (247) includes a rotor (253) that is mounted on the driveshaft (217) and is driven directly by the driveshaft (217). With reference to Figures 23 and 24 it can be seen that each rotary valve (247) has one inlet port (249) and one outlet port (251) situated in a stationary housing (252). Note: in Figure 23 the rotor (253) has been removed from the driveshaft (217) to allow the interior of the forward end rotary valve (247) to be seen. When the rotor (253) is fitted onto the driveshaft (217) the rotor (253) is surrounded by the stationary housing (252).

The inlet port (249) is spaced approximately ninety degrees from the outlet port (251). The rotor (253) has a single rotor passage (255) that communicates for a short time with the inlet passage (243) during each revolution of the engine (211), and which similarly communicates for a short time with the outlet passage (245) during each revolution of the engine (211). The rotor passage (255) provides a flow path between the inlet port (249) and the inlet passage (243) during an induction stroke of its associated piston crown (238), and provides a flow path between the outlet passage (245) and the outlet port (251) during an exhaust stroke of its associated piston crown (238).

One of the key features of this invention is the fact that the rotor (253), and in effect the operation of each rotary valve (247), is driven directly by the drive shaft (217), giving a very simple and effective valve operating mechanism.

The internal combustion engine (211) operates on a four stroke cycle. For each three hundred and sixty degrees of rotation of the drive shaft, each piston reciprocates twice, having completed an induction stroke, a compression stroke, a power stroke and an exhaust stroke.

As each rotor (253) rotates through three hundred and sixty degrees, the rotor passage (255) moves once past its associated inlet port (249) and once past its associated outlet port (251). Each time the rotor passage (255) aligns with an inlet port (249), the rotor passage (255) also aligns with an inlet passage (243) in the adjacent cylinder head (239). And similarly, each time the rotor passage (255) aligns with an outlet port (251), the rotor passage (255) also aligns with an outlet passage (245) in the adjacent cylinder head (239).

During the time that the rotor passage (255) is aligned with both an inlet port (249) and with an inlet passage (243), a fresh charge of air flows from an inlet system or manifold (257) and into the associated combustion chamber (215). Similarly, during the time that the rotor passage (255) is aligned with both an outlet port (251) and with an outlet passage (245), exhaust gases flow from the associated combustion chamber (215) and into an exhaust system or manifold (259).

In this example the driveshaft (217) of the engine (211) rotates in an anti-clockwise direction when viewed from the left hand end of the engine (211) as indicated by an arrow (261) in Figure 17. With reference to Figure 23 it can be seen that the rotor passage (255) must travel through approximately two hundred and seventy degrees as it travels from the inlet port (249) and around to the outlet port (251).

The four rotary valves (247) situated along the driveshaft (217) are configured to provide sequenced power strokes from the four combustion chambers (215). For example, if the combustion chambers are numbered 1 to 4 along the length of the engine, from left to right, the sequence of the power strokes, or the firing order, in the example shown can be 1, 2, 4, 3.

Each rotor (253) is provided with a rotary valve seal (263) to prevent leakage of gases between the rotor passage (255) and the surrounding atmosphere. In this example, the rotary seal (263) is in the form of a series of segmented carbon seals which bear against a surface on an inside diameter of the stationary housing (252). Similarly, each piston (219) is provided with a compression ring in the form of a rotary piston seal (265). As with the rotary valve seal (263), each rotary piston seal (265) is also in the form of a series of segmented carbon seals, and in this case the carbon seals bear against the inside diameter of the cylinder (213).

With reference to Figure 16 it can be seen that the engine (211) also includes two spark plugs (271) associated with each combustion chamber (215). The spark plugs (271) are situated in an un-swept portion of the cylinder (213) wall defining each combustion chamber (215). Alternatively the spark plugs could be mounted in the cylinder heads (239). A conventional ignition system can be used to provide power and control ignition timing for each spark plug (271). Alternatively the engine (211) could be configured for diesel fuel and may not require electronic ignition.

As with the engine (111), the engine (211) can also use conventional fuel systems, for example the fuel system can be a carburetted system, a metered LPG system, or a direct fuel injection system. The fuel injectors could be mounted in the cylinder (213) wall or in the cylinder heads (239) or in the inlet manifold (257). A variety of fuels could be used for example LPG, petrol or diesel.

VARIATIONS

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting.

The examples described above both have a single cylinder which defines four expansion or combustion chambers. It is envisaged that alternative embodiments could have any number of cylinders, and the cylinders could in turn define any number of expansion or combustion chambers, for example an engine could have a single cylinder and define a single combustion chamber. However it is considered advantageous to have four combustion chambers provided within a single cylinder since that configuration provides a compact and balanced engine assembly.

In the examples described above, the engines have two 'double ended' pistons. It is envisaged however, that alternative embodiments could use more conventional 'single ended' pistons, and could have any number of pistons, even a single piston.

The engines described above both have two end cams and four cam engagement rollers per reciprocating piston. It is envisaged that alternative embodiments could use more or less of each.

In the examples described above, the end cams are part of the pistons, and the cam engagement rollers are supported on the fixed structure. It is envisaged that in an alternative embodiment, the end cams could be supported by the fixed structure and the cam engagement rollers could be supported by the pistons.

The examples described above use rotary valves. It is envisaged that in an alternative embodiment other types of valve systems could be used, for example poppet style valves that are operated by a cam or cams mounted on the drive shaft. The stems of the poppet valves could be moved directly by the cam or cams mounted on the drive shaft or could be moved by rocker arms that are themselves operated by the cam or cams. As a further alternative, electronically operated valves or poppet valves could be used.

The examples above describe engines. However, it is envisaged that at least the steam engine (11) version could operate as a compressor. The configuration could be identical except that the expansion chambers are reconfigured as pumping chambers, the drive shaft is driven by an external source, the pistons are used to compress gas instead of being driven by expanding gases, the exhaust ports becomes an inlets, and the inlet ports become compressed gas outlet ports.

Optionally the engines or compressors are air cooled or liquid cooled. DEFINITIONS

Throughout this specification the word "comprise" and variations of that word, such as "comprises" and "comprising", are not intended to exclude other additives, components, integers or steps.

The term 'double ended' piston is intended to describe a piston having two crowns, that is a piston configured to face a combustion chamber at each end of the piston.

ADVANTAGES

Thus it can be seen that at least the preferred form of the invention provides a reciprocating engine which has very few moving parts when compared to conventional engines. This is most clearly evident in the valve operating mechanism which includes rotary valves that are driven directly by the drive shaft, eliminating the need for complex valve operating mechanisms as used on four stroke crankshaft engines.

The engine design, with the crankshaft passing through each piston crown, lends itself to multi-cylinder versions, with no limit to the number of cylinders situated along a single rotating output shaft.

In addition the supporting structure or frame is relatively simple and compact, with the cylinder forming a significant part of the engine structure, providing significant weight savings.

The crankshaft-less operation provides an opportunity to improve engine efficiency by reducing losses caused when forces act on a crankshaft at an inefficient crank angle.