RECIPROCATING PISTON MACHINE

Abstract: A reciprocating piston machine has pistons (5) arranged radially about a drive shaft (17) for reciprocation within chambers (3) formed circumferentially about a substantially cylindrical outer casing (1). Fixed to the drive shaft (17) is a rotor carrier (19). A number of lobed rotors (21) are mounted on the rotor carrier (19) for rotation about axle pins (25) which are parallel to and equidistant from the drive shaft (17). Upon rotation of the drive shaft (17) the lobed rotors (21) are carried with the rotor carrier (19) about the drive shaft axis and caused to rotate in a counter direction on the axle pins (25) by sequential interaction with the pistons (5). Positive connection between each piston (5) and the drive shaft (17) about the radially outer end portion of each stroke is achieved by piston pins (45) which engage with grooves (47) in the lobes (29) of the lobed rotors (21). Similarly, about the radially inner end portion of each stroke, positive connection is achieved by piston pins (51) which engage with grooves (53) in the rotor carrier (19).

Description: RECIPROCATING PISTON MACHINE FIELD OF INVENTION This invention relates to machines having reciprocating pistons such as internal combustion engines. BACKGROUND ART The present invention is a development of the rotary engine disclosed in Australian patent specification 473,864. DISCLOSURE OF THE INVENTION According to the invention there is provided a machine comprising an outer casing having chambers formed therein, a piston within each chamber, a central drive shaft, and transmission means for transmitting motion between the pistons and the drive shaft, said transmission means including a rotor carrier mounted on the drive shaft, a plurality of lobed rotors rotatably mounted on the rotor carrier for rotation about axes parallel to and equidistant from the drive shaft, the lobes of the rotors sequentially contacting the pistons during the radially outer portion of each stroke of the pistons, and means providing positive connection between each piston and the drive shaft at least at the radially outer end portion of each stroke of the piston and at least at the radially inner end portion of the stroke of the piston. Preferably, the positive connection means includes first connection means providing a detachable positive connection between each piston and the drive shaft at least at the radially outer end portion of each stroke of the piston, and second connection means providing a detachable positive connection between each piston and the drive shaft at least at the radially inner end portion of the stroke of the piston. A rotary machine according to the invention is particularly applicable as an engine in which case it further comprises means for causing reciprocation of the pistons in their respective chambers in a desired sequence thereby to cause the rotors to rotate about their axes and about the drive shaft axis to thereby impart rotation to the drive shaft. Preferably said means for causing reciprocation of the pistons includes means for causing internal combustion in said chambers in said desired sequence. In the preferred form of the invention, the first connection means serves to prevent radial separation between each piston and the particular rotor lobe with which it is in contact as the piston arrives at and leaves the radially outer end of its stroke in circumstances (such as cranking and the situation commonly termed over¬ run where a vacuum is induced in the combustion chamber following closure of the fuel/air throlling device) when there is either no effective load, or a negative load, on the piston. In addition, the first connection means co¬ operates with the second connection means to provide a connection between the piston and the drive shaft to effect movement of the piston in the radially inward direction in circumstances when there is either no effective load, or a negative load, on the piston. In a preferred form of the invention, the first connection means comprises at least one first projecting member mounted on each piston and adapted to locate in a groove formed in each particular rotor ' lobe with which the piston makes contact. It is preferred that the second connection means comprises a cam member carried on the central drive shaft, and at least one second projecting member mounted on each piston and adapted to locate in a respective groove formed in the cam, whereby location of said at least one second projecting member in the groove effects said position connection between the piston and the drive shaft. ■ Preferably the cam member is provided with a cam surface at its outer periphery, each of the pistons being adapted to frictionally engage the cam when the piston- is under positive load. The cam serves to limit the extent of radially inward movement of each piston when it is under positive load. This arrangement also ensures that the second connection means is only operative to apply a driving force to the piston when there is no effective load, or a negative load, on the piston. Preferably the cam is formed integrally with the rotor carrier, the outer periphery of the rotor carrier defining the cam surface. Preferably that portion of each piston which is contacted by the rotor lobes is concave. Preferably that portion of each piston which engages the cam is convex. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood by reference to the following description of one specific embodiment thereof as shown in the accompanying drawings in which:- Fig. 1 is a schematic front elevation of a reciprocating piston machine in the form of an internal combustion engine, with various parts of the engine cut away. Fig. 2 is a schematic part-sectional side elevation of the embodiment of Fig. 1, Fig. 3 is an exploded view of the rotor carrier, lobed rotors and one piston. Fig. 4 is a schematic diagram of the machine shown in Figs. 1, 2 and 3 indicating the general principles of operation of the machine. Fig. 5 is a schematic view of the machine showing the rotor carrier and the lobed rotors engaged against the radius at the bottom of some of the pistons-. Fig. 6 is a view similar to Fig. 5 showing the upper pins of the pistons engaged in the recessed contours of the lobed rotors; and. Fig. 7 is a view similar to Fig. 6 showing the lower pins of the pistons engaged in the recessed contours on the outer faces of the rotor carrier. DESCRIPTION OF PREFERRED EMBODIMENT The embodiment of the reciprocating piston machine shown in the drawings is in the form of an internal combustion engine employing a two-stroke cycle. The engine comprises a substantially cylindrical outer casing 1 within which is formed a plurality of chambers 3 each having a piston 5 therein. A working space 7 of variable volume is defined between each chamber 3 and the piston 5 therein. The volume of each working space 7 varies with reciprocatory movement of the respective piston. An inlet means 8 including an inlet port 9, is provided for admitting a combustible mixture into the working space. An exhaust means 11 including an exhaust port 12, is provided for exhausting spent products of combustion from the working space. A sparking means 15 is provided for igniting compressed combustible mixture in the working space 7. A transmission means is provided for transmitting motion between the pistons 5 and a central drive shaft 17 whereby on reciprocation of the pistons in their chambers in a desired sequence (according to the firing order of the engine) rotation is imparted to the drive shaft. The transmission means of tjiis embodiment of the invention includes a rotor carrier 19 mounted on the drive shaft 17 for rotation therewith. The rotor carrier supports a plurality of lobed rotors 21 for rotation about axes 23 parallel to and equidistant from the drive shaft 17. The rotors 21 are mounted on the rotor carrier 19 by means of respective shafts 25 supported between a pair of spaced plate members 27. In the illustrated arrangement, there are three lobed rotors 21, each rotor having three lobes 29 as shown in Fig. 1 of the drawings. With this arrangement, the number of chambers 3 and pistons 5 required is ten, although eight may also be employed. The outer periphery of the rotor carrier 19 defines a cam 31. The profile of the cam is in three sections 33 each of which extends between two adjacent rotors 21, as shown in Fig. 1. As shown in Fig. 2 of the drawings, the cam profile is defined by the outer periphery of the two spaced plate members 27 which together form the rotor carrier. Referring now to Fig. 3 of the drawings, each piston 5 has a body 35 and a pair of diametrically opposed leg portions 37 at the radially inner end of the body. The leg portions 37 are formed integrally with the body of the piston. Between the leg portions 37 and at the radially inner end of the body 35, the piston has a lobe engaging portion 39. The lobe engaging portion 39 is concave. On the inner side of the leg portions 37 of the piston there are provided shoulders 41 the faces 43 of which define a follower for the cam 31. The faces 43 of the shoulders 41 are of convex configuration and each is adapted to frictionally engage the outer periphery of one of the plate members 27. During operation of the engine (which will be described more fully hereinafter) the central drive shaft 17 rotates in one direction and the lobed rotors 21 rotate about their respective axes 23 in the opposite direction. Each lobe 29 of each rotor contacts the lobe engaging portion 39 of every third piston. The lobe exerts a radially outward force on the piston thereby to cause the piston to undergo a compression stroke. The subsequent power stroke of the piston applies a radially inward force on the rotor lobe. This radially inward force on the rotor lobe causes the rotor to rotate about its respective axis 23 and also about the drive shaft axis to thereby impart rotation to the drive shaft. The rotor lobe subsequently moves away from the piston and the rotor advances towards the next piston. As the rotor lobe moves away from the convex portion 39 of the piston, the particular cam section 33 trailing the rotor comes into contact with the convex cam follower defined by the two shoulder faces 43 formed on the piston. The piston rides along the moving cam section 33 until it is engaged by one of the lobes of the next rotor. In this embodiment of the invention, the engine is provided with a first connection means for preventing radial separation between each piston and the particular rotor lobe with which it is in contact as the piston arrives at and leaves the radially outer end of its stroke. In the absence of the first connection means, such separation may occur during cranking and over-running of the engine and could well be damaging to the engine. The engine is also provided with second connection means which in conjunction with the first connection means establishes a positive mechanical connection between the piston and the drive shaft in order to move the piston in the radially inward direction at required times as the drive shaft rotates, in circumstances where there is no effective load on the piston. The first connection means comprises first projecting members in the form of a pair of opposed pins 45, each pin being mounted on and projecting inwardly from a respective one of the piston leg portions 37. The first connection means further comprises a pair of grooves 47 formed one on each side face 49 of each rotor lobe. The grooves 47 on each rotor lobe are adapted to receive the pins 45 on each piston when the rotor lobe moves into contact with the piston. With the pins 45 of a piston received in the grooves 47 formed in a rotor lobe, there is a positive connection between the piston and the rotor lobe which prevents radial separation therebetween. The grooves 47 each have a lead-in section 47a, an intermediate section 47b and a lead-out section 47c, . as shown in Fig. 1. The second connection means comprises second projecting members in the form of a pair of opposed pins 51, each pin being mounted on and projecting inwardly from a respective one of the piston leg portions 37. The pins 51 are located radially inwardly of the pins 45 as shown in Fig. 1. The second connection means further comprises a pair of grooves 53 corresponding to each cam section 33, the grooves being located one on the outer side face of each plate member 27, inwardly of the cam section. The grooves 53 have a lead-in point and a lead-out point. The grooves 53 corresponding to each cam section 33 are adapted to receive the pins 51 on each piston before the cam section moves into contact with the piston. With the pins 51 of a piston received in a pair of grooves 53 formed in the plate members, there is a positive connection between the piston and the drive shaft via the side plates in order to effect movement of the piston in its radially inward direction in the required timing sequence in circumstances where there is no effective load on the piston. The general principle of the operation of the reciprocating piston engine shown in Figs. 1 and 2 will now be described in relation to Figs. 4 to 7. As will be apparent from Fig. 4, the outer casing 1 acts a stationery inner gear, the rotor carrier 19 acts a sun gear and the three lobed rotor 21 acts as a planet gear. Thus, the downward action of the piston (not shown) in the working space 7 on the lobe 29a of the rotor 21 will rotate the rotor 21 in the direction of arrow A and the rotor carrier 19 in the direction of arrow B. Fig. 5 shows the position of each piston 5 within its cylinder or chamber 3 and the engagement of lobes 29a, b, c, d and e against the concave lobe engaging portions 39 of the pistons 5a, d, e, g and h. In Fig. 6, the upper pins 45 (which, in the embodiment shown in Figs. 1 to 3, constitute the first connection means) projecting inwardly from the leg portions 37 of pistons 5 are engaged in the recessed grooves 47 formed on each side 49 of each rotor lobe 29. Fig. 7 shows the connection between the lower pins 51 which project inwardly from the leg portions 37 of the pistons 5 (the "second connection means" of the embodiment shown in Figs. 1 to 3) and the grooves 53 on the outer side faces of the plate members 27. Operation of the engine will now be described in relation to one piston, commencing with the piston at its radially innermost position (i.e. at the bottom-dead- centre position). When the piston is in that position, the shoulder faces 43 on the piston are in contact with one of the cam sections 33 on the rotor carrier and the pins 51 are received in the corresponding grooves 53 in the rotor carrier. As the central drive shaft 17 rotates, the pins 51 traverse the grooves 53 and the faces 43 on the piston ride along the cam section 33 which is profiled to commence movement of the piston in the radially outward direction (i.e. a compression stroke of the piston). On continued rotation of the drive shaft, one of the lobes of the rotor trailing the particular cam section 33 moves into contact with the piston, engaging the piston at its lobe engaging portion 39. The grooves 47 in the lobe then receive the pins 45 on the piston through their respective lead-in sections 47a. At this stage the piston is connected to both the rotor carrier (via the second connection means) and the lobed rotor (via the first connection means). On further rotation of the central drive shaft, the pins 51 on the piston continue to traverse the grooves 53 in the rotor carrier and subsequently leave the grooves. The lobed rotor continues to urge the piston towards the radially outermost position. During this compression stroke of the piston, a combustible fuel mixture is introduced into -working space. When the piston is at or near the radially outermost position (i.e. top-dead-σentre position) the compressed fuel mixture in the working space is ignited by the sparking means 15. During the subsequent expansion (power) stroke of the piston, the piston exerts a radially inward force on the rotor lobe which causes the rotor to rotate about its axis 23 and about the drive shaft axis to thereby impart rotation to the drive shaft. In the initial part of the expansion stroke of the piston, the pins 45 traverse the grooves 47 towards the lead-out section 47c. Before the pins 45 leave the grooves 47 (which in this embodiment takes effect at an angle of 36 degrees in advance of the rotor shaft referred to the radial centreline of the piston) the pins 51 commence engagement with the grooves 53 corresponding to the particular cam section 33 trailing at the end of the rotor (which engagement takes effect at an angle of advance of approximately 12 degrees). The piston then continues its movement towards the bottom- dead-centre position. The cycle is then repeated. During normal running of the engine, the first and second connection means have no influence on the movement of the piston with the exception that the first connection means prevents over-travel of the piston at its top-dead- centre position. The cam limits the radially inward extent of movement of the piston thereby to define its bottom-dead-centre position. However, in circumstances where there is no effective load on the piston, or a negative load, (such as during cranking and over-run of the engine) , the first and second connection means provide positive connection between the piston and the drive shaft in order to move the piston in the radially inward direction from its top-dead-centre position to its bottom- dead-centre position. It should be 'appreciated that the scope of the invention is not limited to the scope of the embodiment described. For instance, the first and second projecting members may be in the form of spindles instead of pins, if desired. In addition, a rotary machine according to the invention is not limited in application to internal combustion engines and may be applied to air compressors, hydraulic motors, steam engines, pumps and like devices.

Claims: CLAIMS 1. A reciprocating piston machine comprising an outer casing having chambers formed therein, a piston within each chamber, a central drive shaft, and transmission means for transmitting motion between the pistons and the drive shaft, said transmission means including a rotor carrier mounted on the drive shaft, a plurality of lobed rotors rotatably mounted on the rotor carrier for rotation about axes parallel to and equidistant from the drive shaft, the lobes of the rotors sequentially contacting the pistons during the radially outer portion of each stroke of the pistons, and means providing positive connection between each piston and the drive shaft at least at the radially outer end portion of each stroke and at least at the radially inner end portion of the stroke of the piston. 2. A machine according to claim ' 1 wherein said positive connection means includes first connection means providing said detachable positive connection between each piston and the drive shaft at least at the radially outer end portion of each stroke of the piston, and second connection means providing said detachable positive connection between each piston and the drive shaft at least at the radially inner end portion of the stroke of the piston. 3. A machine according to claim 1 and further including means for causing reciprocation of the pistons in their respective chambers in a desired sequence thereby to cause the rotors to rotate about their axes and about the drive shaft axis to thereby impart rotation to the drive shaft. 4. A machine according to claim 3 wherein the means for causing reciprocation includes means for causing internal combustion in said chambers in said desired sequence. 5. A machine according to claim 2 wherein the first connection means comprises at least one first projecting member mounted on each piston and adapted to locate in a groove formed in each particular rotor lobe with which the piston makes contact. 6. A machine according to claim 2 wherein the second ' connection means comprises a cam member carried on the central drive shaft, and at least one second projecting member mounted on each piston and adapted to locate in a respective groove formed in the cam, whereby location of said at least one second projecting member in the groove effects said position connection between the piston and the drive shaft. 7. A machine according to claim 6 wherein the cam member is provided with a cam surface at its outer periphery, each of the pistons being adapted to frictionally engage the cam when the piston is under positive load. The cam serves to limit the extent of radially inward movement of .each piston when it is under positive load. This arrangement also ensures that the second connection means is only operative to apply a driving force to the piston when there is no effective load, or a negative load, on the piston. 8. A machine according to claim 7 wherein the cam is formed integrally with the rotor carrier, the outer periphery of the rotor carrier defining the cam surface. 9. A machine according to claim 8 wherein that portion of each piston which is contacted by the rotor lobes is concave ' and that portion of each piston which engages the cam is convex.

Inventors: BURNS ALAN ROBERT, CHANDLER GRAEME ALFRED, BURNS, ALAN, ROBERT, CHANDLER, GRAEME, ALFRED
Applicants: TENNYSON HOLDINGS LTD, TENNYSON HOLDINGS LTD.
Application year: 1986
Main classification: F01B9
IPC codes: F01B9, F02B57, F02B75