Patent Publication Number: US-6904888-B1

Title: Reciprocating piston device

Description:
Disclosure documents 507456 and 523965 respectively preceded Applicant&#39;s patent application as follows: 
     FIELD OF THE INVENTION 
     This invention relates to reciprocating piston motors, e.g., internal combustion engines, steam engines and fluid motors (air or hydraulic). A principal use of the invention is in internal combustion engines. 
     BACKGROUND OF THE INVENTION 
     In many conventional four cycle engines each piston is individually connected to the drive shaft by means of a connecting rod and crank arm. The drive shaft comprises a crankshaft having one crank pin and counterweight for each piston. 
     The conventional crankshaft is relatively long and heavy, especially in the case of eight cylinder in-line engines. In order to balance the internal engine forces, several relatively heavy counterweights are required (one for each piston). The crankshaft cost becomes a major factor. Also, the crankshaft bearings have to be relatively heavy and numerous to absorb momentary unbalanced forces. 
     Another problem with conventional piston engines is that each piston lacks lateral support. The conventional connecting rod obliquely transmits the axial force component of the piston without restraining the piston against lateral movement, such that the piston exerts a considerable lateral force on the cylinder wall. The piston has to be relatively long to distribute the lateral forces and prevent excessive wear on the piston or cylinder wall. 
     The long piston requirement and crankshaft design requirements tend to unduly increase the overall size and weight of the engine, especially with engines having a large number of cylinders. 
     Some engine designs have been proposed to overcome problems associated with conventional piston engines. In one such engine design the pistons are aligned in pairs. Two opposed in-line pistons are rigidly connected together for conjoint movement by a toothed rack, so that one piston moves toward the top dead center position while the other piston moves away from the dead center position and vice versa. The pistons can be relatively short because the forces are largely axial (not lateral). 
     A toothed gear in mesh with the tooth rack oscillates rotationally to provide the engine output force. Special clutches and counter shafts are required to translate gear oscillational motion into one way rotation of the output shaft. 
     The described engine designs overcome some problems associated with conventional engines. However, such designs have their own problems, associated with the require-ment for an increased number of shafts, and gears. In most cases slip clutches are required to translate gear oscillation into one way rotation of the output shaft. Slip clutch arrangements are shown in U.S. Pat. No. 5,673,665 (Kim), and U.S. Pat. No. 5,562,075 (Walsh) 
     U.S. Pat. No. 5,673,665, issued to Min-Tac-Kim on Oct. 7, 1997 shows an engine that includes two opposed in-line piston-cylinder assemblies having a piston rod rigidly connecting the two pistons, whereby one piston moves toward the top dead center position while the other piston moves away from the top dead center position, and vice versa Rack gear teeth on the piston rod are in mesh with gear teeth on two counter shafts extending transverse to the motion path of the piston rod. One way clutches on the counter shafts intermittently transmit drive forces to aligned shafts that have geared connections to an output shaft located midway between the aligned shafts. 
     As the piston rod moves back and forth the one-way clutches are alternately in the drive mode and slip mode, so that the output shaft is driven in one direction. 
     The drive system described in U.S. Pat. No. 5,673,665 is relatively complex. Five separate shafts are required to produce rotary movement of the output shaft. 
     U.S. Pat. No. 5,562,075, issued to N. Walsh on Oct. 8, 1996, shows an engine whereon two oppositely-moving pistons are linked to a rotary shaft that rocks back and forth in synchronism with the pistons. The shaft has ratchet connections with two separate bevel gears that are in mesh with a third output gear. The bevel gears are alternately in the drive mode and slip mode, so that the output gear is driven in one direction. In many respects, the engine of U.S. Pat. No. 5,562,075 is similar to the engines of U.S. Pat. No. 5,673,665. In both cases the drive force is directed through slip clutches. 
     U.S. Pat. No. 5,934,243, issued to G. Kopystanski on Aug. 10, 1999, shows an engine wherein each piston has a piston rod that has one toothed rack in mesh with a power drive gear and a second toothed rack in mesh with an idler gear. Apparently each piston drives the associated power drive gear on the downstroke and the idler gear on the upstroke. A system of timing gears is apparently used to provide power to an output shaft  78  when the piston is on the upstroke. Slip clutches are used to achieve uni-directional movement of the output shaft. The drive system is quite complex. Several shafts  38 ,  42 ,  14 , and  78  are required. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention relates to a reciprocating piston motor (engine) that inherently has a decreased volume and weight for a given power output. A resultant advantage is a lower cost and greater usefulness (due to the ability to fit into smaller size engine compartments). 
     The motor (engine) of the present engine uses shorter pistons and less complicated crankshafts, while having a desirable self-balancing character that minimize internal loads. 
     In illustrative embodiment of the invention comprises an engine wherein the pistons are arranged in pairs, so that two pistons are aligned on a common axis for conjoint reciprocating movement. All pistons are kinematically connected to a single intermediate shaft, which oscillates rotationally in response to back and forth movement of the pistons. 
     The intermediate shaft is kinematically connected to a crankshaft, that has a single crankshaft, that has a single crank pin offset from the crankshaft axis. Crank pin offset distance is designed to be equal to the piston stroke travel distance, so that the crankshaft experiences precisely one revolution for each complete reciprocation of the piston. The entire piston force is directed through the single crank pin, so that the crankshaft can be relatively short. Crankshaft bearings can be relatively light and low cost. 
     The engine (motor) of the present invention is advantageous in that forces on the pistons are primarily axial (not lateral), such that each piston can be relatively short. Also, the crankshaft design is greatly simplified, in that the crankshaft has only a single crank pin, irrespective of the number of pistons in the engine. The crankshaft can be relatively short and light weight, with consequent reduction in overall cost of the engine. Due to a combination of advantageous factors the engine can have a reduced size for a given power output. Overall cost of the engine can be relatively low. 
     Further features of the invention will be apparent from the attached drawings and description of illustrative embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view taken through an engine (or motor) embodiment of the Invention. 
         FIG. 2  is a sectional view taken on line A—A in FIG.  1 . 
         FIG. 3  is a sectional view taken on line B—B in FIG.  2 . 
         FIG. 4  is a fragmentary sectional view taken on line C—C in  FIG. 3   
         FIG. 5  is a fragmentary sectional view taken on line D—D in  FIG. 3   
         FIG. 6  is a sectional view taken through another engine (or motor) embodying the Invention.  FIG. 6  is taken in the same direction as  FIG. 2   
         FIG. 7  is a sectional view taken through a third embodiment of the invention. 
         FIG. 8  is a transverse sectional view taken on line E—E in  FIG. 7   
         FIG. 9  is a sectional view taken through another engine embodying the invention. 
         FIG. 10  is a transverse sectional view taken on line F—F in FIG.  9 . 
         FIG. 11  is a transverse sectional view taken on line G—G in FIG.  9 . 
         FIG. 12  is a transverse sectional view taken on line H—H in  FIG. 9   
         FIG. 13  is a transverse sectional view taken through a further engine embodying the invention. 
         FIG. 14  shows in section a further embodiment of the invention. 
         FIG. 15  is a sectional view taken on line I—I in FIG.  14 . 
         FIG. 16  is a sectional view taken on line J—J in FIG.  15 . 
         FIG. 17  is a sectional view taken through another engine embodying the Invention. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
     Referring to  FIGS. 1 through 5 , there is shown a four stroke cycle engine having four pistons, and constructed according to the present invention. The engine (or motor) includes a case  55  that supports two cylinder heads  57  containing the usual intake and exhaust valves, together with the associated cam shafts and timing gear employed in four stroke cycle engines. 
     This particular engine has four cylinders and associated pistons  31 A and  31 B that are grouped in two in-line pairs. The two aligned pistons  31 A are rigidly connected together by a bar (or rod)  39 A and the two aligned pistons  31 B are rigidly connected together by a bar (or rod)  39 B. Each bar  39 A or  39 B has teeth  41 A or  41 B extending therealong, whereby the respective bar constitutes a toothed rack. 
     A single pinion gear  43 A is in simultaneous mesh with both toothed racks  41 A and  41 B, so that each rack can serve as a driver for the pinion gear at different times in the engine cycle. Pinion gear  43 A is carried on an intermediate shaft  37  that extends rightwardly into a case section  63 , as shown in  FIG. 2  shaft  37  carries a sector gear  45  that is in mesh with teeth  49  formed on an elongated slide block  47 . Block  47  forms a second toothed rack. A suitable housing structure within case section  63  guides rack  47  for slidable up or down movement. As shown in  FIG. 3 , rack  47  is at the downward limit of its stroke. The dashed lines in  FIG. 3  indicate the upward limiting position for rack  47 . 
     A crankshaft  33  is rotatably supported in case  55  for continuous one-way rotation around a shaft axis  34 . At the right end, the crankshaft carries a flywheel  65 . At its left end, the crankshaft carries a gear  67  that can be used to drive the usual cam shafts or similar valve timing gear, and other accessories. A pulley  69  on the extreme left end of the crankshaft can be used to start the engine (using a starter motor). Crank-shaft  33  constitutes the output drive shaft for the engine. The engine load is connected to shaft  33 , e.g., through flywheel  65 . 
     Crankshaft  33  is provided with a single crank pin  35  whose axis is offset from shaft axis  34  by a predetermined distance, such that crankshaft  33  experiences one complete revolution for each complete reciprocation of the pistons  31 A and  31 B. The predetermined pin offset distance is designed to be approximately equal to the stroke travel distance of each piston, so that during piston motion in one direction shaft  33  rotates one half revolution; during return movement of the piston, crankshaft  33  rotates another half revolution. In  FIG. 1 , numeral  38  denotes the stroke travel distance of each piston, i.e., the distance from the top dead center position to the bottom dead center position. 
     The mechanism for driving crankshaft  37  consists of a single connecting rod  51 A trained between rack  47  and crank pin  35  on shaft  33 . Rack  47  carries a transverse pin  53 A that serves as a pivotal connection between the rack and connecting rod  51   
     During operation of the engine the four pistons  31 A and  31 B reciprocate through stroke distance  38 , such that gear  43  has a rotary oscillatory movement in the clockwise and counterclockwise directions. Intermediate shaft  37  oscillates back and forth under the impetus of gear  43 , a primary transmission mechanism. Shaft  37  imparts an oscillational rotation to sector gear  45 , a secondary transmission mechanism, that drives rack  47  up and down between the full line position and the dash line position (FIG.  3 ). Rack  47  acts on connecting rod  51 A to produce continuous one way rotation of crankshaft  33 . 
     As previously noted, crankshaft  33  experiences one complete revolution for each cyclic travel of the pistons (i.e., movement from the top dead center position to the bottom dead center position and back to the top dead center position). The desired relationship is achieved by making the offset distance of crack pin  35  approximately equal to the piston travel distance  38 . If the diameter of gear  45  is slightly less than the gear  43 A, then the crank pin offset distance is increased slightly. If the gear  43 A diameter is slightly greater than the gear  43 A diameter then the crank pin offset distance is decreased accordingly. The dimensional relationships are incorporated in the engine design. 
     In order to provide a desirable momentum for crankshaft rotation at the twelve o&#39;clock and six o&#39;clock positions, the crankshaft is provided with a counterweight  36  spaced diametrically away from crank pin  35  (i.e., on a diametrical line passing through the crank pin axis. 
     As shown in  FIG. 1 , the pistons  31 A and  31 B are adequately guided so that lateral loads between the cylinder walls and piston side surfaces are greatly minimized. This is due to the way that piston movement is transferred to pinion gear  43 A, and also to the fact that each piston acts as a guide for the other piston. Minimized loadings on the piston side surfaces enables the pistons to be shorter than pistons used in conventional engines. As a result, the size of the engine in the direction of piston motor can be somewhat reduced. 
     The engine (motor) shown in  FIGS. 1 through 5  has four pistons, but only one-crank-connecting rod assembly. This is due to the fact that the entire piston force is directed through a single intermediate shaft  37 . Oscillatory motion of shaft  37  is converted to continuous one way rotation of crankshaft  33  by means of a single sector gear  45 , toothed rack  47  and connecting rod  51 A. The crankshaft design is greatly simplified, due to the fact that only one crank pin  35  is required, irrespective of the number of pistons used in the engine. 
       FIG. 6  shows an engine (motor) that is basically the same as the engine shown in  FIG. 2 , except that the  FIG. 6  engine has eight pistons instead of four pistons. In the  FIG. 6  engine there are four pairs of in-line pistons arranged in a square pattern. Power is transferred to intermediate shaft  37  by two separate pinion gears  43 A,  43 A . 
     Even though the  FIG. 6  engine has eight pistons (rather than four), only one connecting rod  51  A crank pin  35  assembly is required for converting the oscillatory motion of shaft  37  into continuous one way rotation of crankshaft  33 . A relatively low cost crankshaft can be used in the  FIG. 6  engine. In  FIG. 6 , line B—B indicates a cross sectional view sight line that would produce a sectional view similar to that depicted in FIG.  3 . 
     The  FIG. 6  engine is in major respects similar to the  FIG. 1  engine except for the piston complement (eight pistons versus four pistons). 
       FIGS. 7 and 8  show an engine (motor) that is basically the same as the  FIG. 1  engine, except that the  FIG. 7  engine has six pistons, rather than four. The six pistons, rather than four. The six pistons are arranged in three pairs, each pair comprising two in-line pistons. As shown in  FIG. 8 , all six pistons are located in a common vertical plane designated by numeral  61  A. 
     In the  FIG. 7  engine, an auxiliary shaft  37 A is used to transfer oscillatory motion from the two lowermost pistons to intermediate shaft  37 . Shaft  37 A carries a pinion gear  43 B that is in simultaneous mesh with toothed rack  39 C and toothed racked  39 B. Pinion gear serves at times as a drive gear for toothed rack  39 C and at other times as a drive gear for toothed rack  39 B. Net power output is directed into the single oscillating shaft  37 . 
     Shaft  37  is kinematically connected to crankshaft  33  by the same connecting means  45 ,  47 ,  51 A that is used in the  FIG. 1  engine. In  FIG. 8 , line B—B is a sight line that would produce a sectional view generally similar to the sectional view depicted in FIG.  3 . The  FIG. 8  engine is in most respects similar to the engines depicted in  FIGS. 1 and 6 , except for the piston complement. 
       FIGS. 9 through 12  illustrate an in-line engine wherein the pistons are arranged in a single row. The  FIG. 9  engine would typically be more powerful engine useful as a stationary or marine engine, e.g., in diesel submarines, diesel locomotives or buses. The  FIG. 9  engine has a relatively low width, low volume and low weight, with a small engine compartment requirement. All pistons are arranged vertically, with the piston axes located in one common vertical plane parallel to the axis of intermediate shaft  37 . 
     Shaft  37  is not visible in FIG.  9 . However, the shaft is shown in phantom in  FIG. 9  to clarify the fact that shaft  37  spans the entire compliment of pistons. 
     Essentially, the entire piston power output is directed through shaft  37 . A pinion gear  43  is located on shaft  37  in registry with each toothed rack  41 A. Additionally, pinion gear  45  is located on shaft  37  in registry with toothed rack  41  that connects with piston  31  E. Consequently, all of the power pistons in the engine are kinematically connected to shaft  37 . Essentially, he entire piston power output is directed into shaft  37 . 
       FIG. 12  shows the connecting means for kinematically connecting the oscillating shaft  37  to the engine output crankshaft  33 . Rack  47  is formed, in part, by the toothed rod  41 E, such that oscillatory motion of shaft  45  is transferred to connecting rod  51 A via pivot pin  53 A. Connecting rod  51  has a swivel connection with crank pin  53 , whereby the entire power output of the engine is delivered to crankshaft  33 . As with the other embodiments of the invention, a low cost crankshaft, having only one crank-arm (pin) can be used. The pistons can be relatively short pistons, i.e., shorter than the pistons used in conventional engines wherein the pistons have pivotal connections with individual connecting rods. 
     The engine housing can be constructed in various ways. As shown in  FIGS. 9 through 12 , the engine housing includes a casing  55  containing six of the eight pistons, and a second casing  73  containing the remaining two pistons. A cover  71  provides access to casing  71  provides access to casing  73  (for assembly purposes). Valve housings  57 ,  57 ,  57  are provided for the necessary intake valves, exhaust valves and cam shafts. 
       FIG. 9  shows a mechanism for powering the various valve-operating camshafts. Gear  67  on crankshaft  33  is in mesh with a larger gear  84  carried on a first camshaft  83 . The camshaft is preferably sectionalized for assembly purposes. Camshaft  83  has a bevel gear connection  88  with a vertical shaft  86  that has a second (upper) crankshaft  83 . The camshafts are driven synchronously to operate the engine intake and exhaust valves in conventional fashion. 
     The engine depicted in  FIGS. 9 through 12  operates in a generally similar fashion to the earlier-described engines. Each piston is connected to a single oscillating shaft  37  via a first connecting means that includes individual toothed racks for the individual pistons and individual pinion gears carried by shaft  37  in mesh with the respective toothed racks. Shaft  37  is kinematically connected to crankshaft  33  by a single connection means that includes a single gear  45 , toothed rack  47  and connecting rod  51 A. 
       FIGS. 14 through 16  illustrate another form that the invention can take. As shown in  FIG. 14 , the engine has four pistons arranged in two piston pairs. The pistons in each pair are in axial alignment, as in the arrangement depicted in  FIG. 1. A  rigid bar (or rod)  39 A or  39 B rigidly connects the aligned pistons for conjoint movement between the top dead center position and bottom dead center position. 
     Intermediate oscillating shaft  37  is connected to rigid bars  39 A and  39 B by means of two swingable links  95 ,  95 , and a double-armed lever  93 . Each link  95  has one end thereof pivotally connected to an associated bar ( 39 A or  39 B) and a second end thereof pivotally connected to lever  93 . Lever  93  is affixed to shaft  37  so that linear reciprocation of pistons  31 A and  31 B produces a back and forth oscillation of shaft  37 . 
     The link-lever connecting mechanism depicted in  FIGS. 14 and 15  is an operable alternative to the rack-gear connection mechanism depicted in  FIGS. 1 ,  6 ,  7 , and  9 . In each case, the connection mechanism translates linear reciprocation of the associated pistons into rotary oscillation of the intermediate shaft  37 . 
       FIGS. 15 and 16  show a connection means for kinematically connecting shaft  97  to crankshaft  33 . The connection mechanism comprises a single lever  37  carried by shaft  97  and a connecting rod  51 B having a swivel connection on pin  53 A that is carried by the lever. The lower end of connecting rod  51 B has a swivel fit on crank pin  35 . As in the previously described embodiments of the invention, crank pin  35  is offset from the crankshaft rotational axis by a distance that approximately equals the stroke travel distance of the associated pistons ( 31  A or  31  B), whereby the crankshaft moves one complete revolution for each reciprocation of the pistons (from top dead center to bottom dead center and back to top dead center). 
     The  FIG. 14  engine is similar to the  FIG. 1  engine, in that four pistons are used. However, the number of pistons could be increased (or doubled), as will be apparent from  FIG. 6  (comparing  FIG. 6  with FIG.  1 ). The process would involve lengthening shaft  37  and adding another bank of pistons, to achieve a square piston pattern (similar to that depicted in FIG.  6 ). 
       FIG. 17  shows a further form that the invention can take. As shown, the engine has two pistons  31 D and  31 E movable linearly on two parallel axes. Piston  31 D is shown in the bottom dead center position, and piston  31 E is shown in the top dead center position. The positional difference represents the piston stroke travel distance. 
     A link  51 C extends downwardly from each piston to a three armed lever  99  that is affixed to the oscillating shaft  37 . The upper end of each link  51 C has a pivotal connection  98  with an associated piston. The lower end of each link  51 C has a pivotal connection  96  with lever  99 , whereby linear reciprocal movements of the pistons translate into rotary oscillation of shaft  37 . 
     Lever  99  is dimensioned so that pivotal connections  96  are located approximately on the centerlines of pistons  51 C during the entire piston travel, so that the load forces on the pistons are essentially axial during the entire piston travel. 
     The pistons exert relatively small lateral loadings on the cylinder walls, so that the pistons can be relatively short, as in the previously described embodiments of the invention. 
     Oscillatory shaft  37  is connected to crank pin  35  crankshaft  33  by a single connecting rod  51 B. One end of the connecting rod has a pivotal connection  53 A with lever  99 . The other end of connecting rod  51 B has a swivel fit on crank pin  35 , whereby oscillatory motion of shaft  37  is translated into continuous one way rotation of crankshaft  33  around shaft axis  34 . 
     The components are dimensioned so that pivot connections  96 ,  96  are a common distance from the axis of shaft  37 . Also, the crank pin axis is offset from crankshaft axis  34  by approximately the same distance as the piston stroke distance, as in the previously described embodiments. 
       FIG. 17  shows an engine (motor) having two pistons. However, the number of pistons could be increased, as by lengthening shaft  37  and adding one or more additional pairs of pistons. An additional lever would be required on shaft  37  for each pair of additional pistons. The  FIG. 17  engine design can be employed in engines having different numbers of pistons, e.g., two pistons, four pistons, six pistons or eight pistons. 
     It will be seen that all of the described embodiments have the common feature relating to the employment of a single intermediate oscillating shaft  37  located in the drive train so that the entire piston power output is directed through the oscillating shaft. In  FIGS. 1 ,  6 ,  7 ,  9  and  13 , the connecting means between the pistons and oscillating shaft.  37  comprises a toothed rack connected to one or more pistons, and a pinion gear carried by shaft  37 . In  FIGS. 14 and 17 , the connecting means between the pistons and the oscillating shaft comprises a set of links connected to the pistons and a lever carried by the oscillating shaft. 
     Another feature common to all of described embodiments of the feature is the employment of a crankshaft having a single crank pin  35  operatively connected to to oscillating shaft  37 . In  FIGS. 1 ,  6 ,  7  and  9 , the connecting means comprises a single sector gear  45 , toothed rack  47 , and connecting rod  51 A. In  FIGS. 16 and 17 , the connecting means comprises a lever  97  and  99 , and a connecting rod  51 B. 
     A principal advantage of the invention is that the crankshaft can ba relatively low cost item, whatever the number of pistons employed in the engine. Another advantage of the invention is that the pistons experience minimal side loads, such that relatively short pistons can be employed. Engines constructed according to the invention can be relatively small and light for a given power output.