Two cycle engine scavenge ports

Claim 2

In a two cycle internal combustion engine having a piston with a head, a skirt portion, and an underside opposite the head end, said engine being of a type which has a chamber open to the underside of the piston comprising a scavenge pump system, a power cylinder defined by a wall and having a first end and a distal end, said piston being slidably mounted in said cylinder for reciprocation in said cylinder through power and compression piston strokes between a bottom dead center position adjacent said first end and a distal position, said piston having a piston head timing edge, exhaust means opening to relieve combustion pressure in said cylinder during part of each power stroke of said piston, scavenge port means opening through the wall of said cylinder, transfer passageway means connected to said scavenge port means and communicating with said scavenge pump system, said scavenge port means in said cylinder being positioned to have the major portion thereof positioned closer to the first end of said cylinder than to said distal end of said cylinder, said scavenge port means having distal portions positioned remote from said first end, said distal portions being covered and uncovered by said piston timing edge as said piston reciprocates in said cylinder, separate valving means timed by piston position to control communication between said transfer passageway means and said scavenge pump system to prevent such communication until the exhaust means has opened during each power stroke and until the piston head timing edge is closer to its bottom dead center position than the distal edges of said scavenge port means by a distance which uncovers an area of said scavenge port means effective to increase power output of said engine by increasing mass flow rate from said scavenge pump system, said separate valving means comprising a scavenge pump system outlet port opening to said transfer passageway means and to said scavenge pump system, said piston skirt blocking said outlet port during portions of the piston stroke, and a control port defined in said piston skirt positioned to align with said outlet port to control communication between said transfer passageway means for said scavenge port means and said scavenge pump system throuGh said outlet port.

Claim 3

The combination as specified in claim 1 wherein said scavenge port means extends from the distal edge thereof toward the first end of said cylinder substantially to a level corresponding to the bottom dead center position of the timing edge of said piston.

Claim 4

The combination as specified in claim 1 wherein said scavenge port means includes first scavenge port means no greater than normal height and second extra height scavenge port means, said first scavenge port means opening to separate transfer passageway means from the transfer passageway means for second scavenge port means, said first scavenge port means being positioned between said second scavenge port means and said first end of the cylinder, communication between the scavenge pump and the cylinder through said first scavenge port means being controlled by the piston and the piston head timing edge, and said separate valving means being associated with the second scavenge port means.

Claim 5

The combination as specified in claim 1 wherein said scavenge port means comprises a continuous scavenge port extending from substantially adjacent a reference line defined by the piston timing edge in the piston bottom dead center position, to the distal edge of said continuous scavenge port, and said distal edge being positioned more than 30 percent of the piston stroke from said reference line.

Claim 6

A two cycle engine having a cylinder and a power piston with a piston skirt, a piston head timing edge and an underside, and which utilizes the underside of the piston as a piston of a scavenge pump system and which has scavenge ports located in a first end portion of the cylinder, said cylinder having said first end adjacent a line along the piston timing edge with the piston in a bottom dead center position, and said cylinder having a distal end, said cylinder having exhaust means which opens to discharge exhaust gases, transfer passageway means leading from said scavenge pump system to the scavenge ports, said scavenge ports in said cylinder being covered and uncovered by said piston timing edge as the piston reciprocates in the cylinder, said scavenge ports in said cylinder having distal edges spaced from the first end of said cylinder, said scavenge ports extending toward the first end from the distal edges, the major portion of said scavenge ports being closer to said first end than to said second end, at least one of said scavenge ports having portions of significant flow area adjacent said distal edges which are uncovered by said piston when the piston timing edge is closer to the first end of the cylinder than substantially 20 percent of the piston stroke, separate valving means to control flow from said scavenge pump system into said transfer passageway means and then to said at least one scavenge port independent of said piston head timing edge to prevent communication from said scavenge pump system to said at least one scavenge port until the piston has reached a preselected position wherein a portion of said at least one scavenge port having an area for flow from said scavenge pump system which is effective to increase power output of said engine is uncovered and said exhaust means is open, said separate valving means comprising a scavenge pump system outlet port opening to said transfer passageway means and to said scavenge pump system, said piston skirt blocking said outlet port during portions of the piston stroke, and a control port defined in said piston skirt positioned to align with said outlet port at said preselected position to control communication between said transfer passageway means and its associated scavenge port and said scavenge pump system.

Claim 7

A two cycle engine having a cylinder and a power piston with a piston skirt, a piston head timing edge and an underside, and which utilizes the underside of the piston as a piston of a scavenge pump system and which has scavenge ports located in a first end portion of the cylinder, said cylinder having said first end adjacent a line along the piston timing edge with the piston in a bottom dead center position, and said cylinder having a distal end, said cylinder having exhaust means which opens to discharge exhaust gases, transfer passageway means leading from said scavenge pump system to the scavenge ports, said scavenge ports in said cylinder being covered and uncovered by said piston timing edge as the piston reciprocates in the cylinder, said scavenge ports in said cylinder having distal edges spaced from the first end of said cylinder, said scavenge ports extending toward the first end from the distal edges, the major portion of said scavenge ports being closer to said first end than to said second end, at least one of said scavenge ports having portions of significant flow area adjacent said distal edges which are uncovered by said piston when the piston timing edge is closer to the first end of the cylinder than substantially 20 percent of the piston stroke, separate valving means to control flow from said scavenge pump system into said transfer passageway means and then to said at least one scavenge port independent of said piston head timing edge to prevent communication from said scavenge pump system to said at least one scavenge port until the piston has reached a preselected position wherein a portion of said at least one scavenge port having an area for flow from said scavenge pump system which is effective to increase power output of said engine is uncovered and said exhaust means is open, said separate valving means comprising a scavenge pump system outlet port opening to said transfer passageway means and to said scavenge pump system, said piston skirt blocking said outlet port during portions of the piston stroke, and a control port defined in said piston skirt positioned to align with said outlet port at said preselected position to control communication between said transfer passageway means and its associated scavenge port and said scavenge pump system.

Claim 8

In a two cycle engine having a cylinder and a power piston which has a skirt and a piston head timing edge, and which utilizes the power piston as a piston of a scavenge pump, said cylinder being defined by a cylindrical wall having an inner surface, scavenge port means defined through said wall and open to said cylinder, The cylinder having a support wall portion and a power chamber portion, said scavenge port means opening to said power chamber portion, said scavenge port means opening to said power chamber portion, exhaust port means opening to said power chamber portion, said power chamber portion having a first end portion adjacent a reference line along the piston timing edge with the piston in a piston bottom dead center position, and a distal end, at least a major portion of said scavenge port means being located in the first end portion of said power chamber portion of said cylinder and occupying a major portion of the cylinder wall circumference not occupied by said exhaust port means, transfer passageway means leading from said scavenge pump to the scavenge port means, said scavenge port means being covered and uncovered by said piston as the piston reciprocates in the cylinder, said scavenge port means having a distal edge spaced from said reference line, at least some of said scavenge port means being uncovered a substantial amount when the piston timing edge is closer to the first end of said power chamber portion of said cylinder than substantially 20 percent of its stroke, said transfer passageway means opening to a scavenge pump outlet control port defined in the support portion of said cylinder wall, said outlet control port aligning with the skirt of said piston when said piston first uncovers said some scavenge port means when the piston is moving toward its bottom dead center position from the distal end, and a piston skirt control port defined in said piston skirt and positioned in alignment with said outlet port only when said piston is closer to its bottom dead center position than a preselected position wherein a substantial portion of said some scavenge port means and a portion of said exhaust port means is uncovered.

Claim 9

In a two cycle engine having a cylinder and a power piston which has a skirt and a piston head timing edge, and which utilizes the power piston as a piston of a scavenge pump, said cylinder being defined by a cylindrical wall having an inner surface, scavenge port means defined through said wall and open to said cylinder, The cylinder having a support wall portion and a power chamber portion, said scavenge port means opening to said power chamber portion, said scavenge port means opening to said power chamber portion, exhaust port means opening to said power chamber portion, said power chamber portion having a first end portion adjacent a reference line along the piston timing edge with the piston in a piston bottom dead center position, and a distal end, at least a major portion of said scavenge port means being located in the first end portion of said power chamber portion of said cylinder and occupying a major portion of the cylinder wall circumference not occupied by said exhaust port means, transfer passageway means leading from said scavenge pump to the scavenge port means, said scavenge port means being covered and uncovered by said piston as the piston reciprocates in the cylinder, said scavenge port means having a distal edge spaced from said reference line, at least some of said scavenge port means being uncovered a substantial amount when the piston timing edge is closer to the first end of said power chamber portion of said cylinder than substantially 20 percent of its stroke, said transfer passageway means opening to a scavenge pump outlet control port defined in the support portion of said cylinder wall, said outlet control port aligning with the skirt of said piston when said piston first uncovers said some scavenge port means when the piston is moving toward its bottom dead center position from the distal end, and a piston skirt control port defined in said piston skirt and positioned in alignment with said outlet port only when said piston is closer to its bottom dead center position than a preselected position wherein a substantial portion of said some scavenge port means and a portion of said exhaust port means is uncovered.

Claim 10

The two cycle engine of claim 6 wherein said some scavenge port means terminates at a position spaced toward the distal end of said power chamber portion from said reference line, and a second scavenge port is positioned between said some scavenge port means and the reference line, said second scavenge port opening to a separate transfer passageway communicating with said scavenge pump whenever the piston uncovers said second scavenge port.

Claim 11

In a two cycle engine having a piston with a piston skirt and a head and a rear side and being of the type which has a chamber comprising a scavenge pump system open to the rear side of the piston, a power cylinder having a bore defined by a cylinder wall and having a first end and a second distal end, said cylinder wall having a lower support portion, a piston slidably mounted in said cylinder for reciprocation through a piston stroke in said cylinder, said piston having a piston head timing edge movable through said piston stroke from a bottom dead center position adjacent a first end of said cylinder toward the second distal end of said cylinder, said cylinder having a diameter that is greater than 1.25 times the piston stroke, scavenge port means defined through the wall of said cylinder and communicating with said bore, exhaust port means defined through a wall of said cylinder and positioned adjacent the first end of said cylinder and extending toward the distal end a preselected amount, transfer passageway means connected to said scavenge port means and communicating with said scavenge pump system, said scavenge port means being positioned around the periphery of said cylinder wall to occupy a substantial portion of the cylinder wall, said scavenge port means in said cylinder positioned to have major portions thereof positioned closer to the first end of said cylinder than to said distal end of said cylinder, at least one of said scavenge port means having a distal portion, said distal portion being covered and uncovered by said piston as it reciprocates in said cylinder, valving means remote from said one scavenge port means to control communication between a transfer passageway connecTed to said one scavenge port means and said scavenge pump system to prevent communication between the scavenge port system and the cylinder through said one scavenge port means until the piston timing edge is substantially closer to its bottom dead center position than the distal edge of said one scavenge port means, and at least a portion of said exhaust port means is uncovered to permit pressure in said cylinder to reduce toward atmospheric pressure, said valving means comprising a scavenge pump system outlet port defined in the lower support portion of said cylinder wall and opening to said transfer passageway means and to said scavenge pump system, said piston skirt blocking said outlet port during portions of the piston stroke, and a control port defined in said piston skirt open to the rear side of the piston and positioned to align with said outlet port during portions of the piston stroke.

Claim 12

In a two cycle engine having a piston with a piston skirt and a head and a rear side and being of the type which has a chamber comprising a scavenge pump system open to the rear side of the piston, a power cylinder having a bore defined by a cylinder wall and having a first end and a second distal end, said cylinder wall having a lower support portion, a piston slidably mounted in said cylinder for reciprocation through a piston stroke in said cylinder, said piston having a piston head timing edge movable through said piston stroke from a bottom dead center position adjacent a first end of said cylinder toward the second distal end of said cylinder, said cylinder having a diameter that is greater than 1.25 times the piston stroke, scavenge port means defined through the wall of said cylinder and communicating with said bore, exhaust port means defined through a wall of said cylinder and positioned adjacent the first end of said cylinder and extending toward the distal end a preselected amount, transfer passageway means connected to said scavenge port means and communicating with said scavenge pump system, said scavenge port means being positioned around the periphery of said cylinder wall to occupy a substantial portion of the cylinder wall, said scavenge port means in said cylinder positioned to have major portions thereof positioned closer to the first end of said cylinder than to said distal end of said cylinder, at least one of said scavenge port means having a distal portion, said distal portion being covered and uncovered by said piston as it reciprocates in said cylinder, valving means remote from said one scavenge port means to control communication between a transfer passageway connecTed to said one scavenge port means and said scavenge pump system to prevent communication between the scavenge port system and the cylinder through said one scavenge port means until the piston timing edge is substantially closer to its bottom dead center position than the distal edge of said one scavenge port means, and at least a portion of said exhaust port means is uncovered to permit pressure in said cylinder to reduce toward atmospheric pressure, said valving means comprising a scavenge pump system outlet port defined in the lower support portion of said cylinder wall and opening to said transfer passageway means and to said scavenge pump system, said piston skirt blocking said outlet port during portions of the piston stroke, and a control port defined in said piston skirt open to the rear side of the piston and positioned to align with said outlet port during portions of the piston stroke.

Claim 13

The combination as specified in claim 8 wherein said cylinder has a lower support portion, and said piston has a piston skirt supported by said lower portion during portions of the piston stroke and wherein said valving means comprises a scavenge pump system outlet port defined in the lower support portion and opening to said transfer passageway means and to said scavenge pump system, said piston skirt blocking said outlet port during portions of the piston stroke, and a control port defined in said piston skirt open to the rear side of the piston and positioned to align with said outlet port during portions of the piston stroke.

Claim 14

The combination as specified in claim 8 wherein said distal edge of said scavenge port means extends at least 30 percent of the piston stroke from a reference line defined by the piston timing edge in bottom dead center position.

Claim 15

The combination as specified in claim 8 wherein said one scavenge port means extends continuously from the distal edge thereof toward the first end of said cylinder substantially to a level corresponding to the bottom dead center position of the timing edge of said piston.

Claim 16

The combination as specified in claim 8 wherein said scavenge port means includes first scavenge port means no greater than normal height and second extra height scavenge port means, said first scavenge port means opening to transfer passageways separate from the transfer passageway means for second extra height scavenge port means, said first scavenge port means being positioned between said second scavenge port means and said first end of the cylinder, and said valving means opening the transfer passageway means associated with the second scavenge port means to communication with the scavenge pump system during substantially the same portion of piston stroke as when the piston timing edge uncovers said first scavenge port means.

Claim 17

In a two cycle engine having a cylinder and a power piston which has a skirt and a piston head timing edge, and which utilizes the underside of the power piston as a piston of a scavenge pump, said cylinder being defined by a cylindrical wall having an inner surface, scavenge port means defined through said wall and open to said cylinder, the cylinder having a lower wall portion and an upper portion, said scavenge port means opening to said upper portion, said upper portion having a first end adjacent a reference line along the piston timing edge with the piston in bottom dead center position and having a distal end, at least the major portion of said scavenge port means being located adjacent the first end of said upper portion of said cylinder, transfer passageway means leading from said scavenge pump to the scavenge port means, said scavenge port means being covered and uncovered by said piston as the piston reciprocates in the cylinder, said scavenge port means having a distal edge spaced from said reference line by a distance such that portions of said scavenge port means are uncovered by the piston timing edge prior to the time the pressure of combustion gases in the upper portion of the cYlinder has reduced to nearly rear compression pressure, said transfer passageway means opening to a scavenge pump outlet control port defined in the lower portion of said cylinder wall, said outlet control port aligning with and being blocked by the skirt of said piston when the piston is moving toward its bottom dead center position from the distal end to prevent amounts of said combustion gases harmful to engine performance from flowing back into the scavenge pump system, and a piston skirt control defined in said piston skirt and positioned in alignment with said outlet port only when the pressure of combustion gases has reduced to a desired level.

Claim 18

In a two cycle engine having a cylinder and a power piston which has a skirt and a piston head timing edge, and which utilizes the underside of the power piston as a piston of a scavenge pump, said cylinder being defined by a cylindrical wall having an inner surface, scavenge port means defined through said wall and open to said cylinder, the cylinder having a lower wall portion and an upper portion, said scavenge port means opening to said upper portion, said upper portion having a first end adjacent a reference line along the piston timing edge with the piston in bottom dead center position and having a distal end, at least the major portion of said scavenge port means being located adjacent the first end of said upper portion of said cylinder, transfer passageway means leading from said scavenge pump to the scavenge port means, said scavenge port means being covered and uncovered by said piston as the piston reciprocates in the cylinder, said scavenge port means having a distal edge spaced from said reference line by a distance such that portions of said scavenge port means are uncovered by the piston timing edge prior to the time the pressure of combustion gases in the upper portion of the cYlinder has reduced to nearly rear compression pressure, said transfer passageway means opening to a scavenge pump outlet control port defined in the lower portion of said cylinder wall, said outlet control port aligning with and being blocked by the skirt of said piston when the piston is moving toward its bottom dead center position from the distal end to prevent amounts of said combustion gases harmful to engine performance from flowing back into the scavenge pump system, and a piston skirt control defined in said piston skirt and positioned in alignment with said outlet port only when the pressure of combustion gases has reduced to a desired level.

Claim 19

In a two cycle engine having a piston with a piston skirt, a head end and an underside opposite the head end, said engine being of a type which has a chamber open to the underside of the piston comprising a scavenge pump system, a power cylinder defined by a wall and having a first end and a distal end, said piston being slidably mounted in said cylinder for reciprocation in said cylinder during a piston stroke from a bottom dead center position adjacent said first end to a distal position, said piston having a piston timing edge, an exhaust port defined in said cylinder on one side thereof, an opposite scavenge port means extending from a line generally along the piston head timing edge in bottom dead center position to a distal end at a level more than 30 percent of the piston stroke toward the distal end of the cylinder, with the major portion of said opposite scavenge port means being closer to the first end of said cylinder than the distal end, said opposite scavenge port means being positioned generally diametrically opposite the center of said exhaust port, a first transfer passageway connected to said opposite scavenge port means, side scavenge port means in the cylinder wall located circumferentially between the opposite scavenge port means and the exhaust port and being positioned closely adjacent the sides of the opposite scavenge port means and occupying a substantial portion of the cylinder wall circumference between the side edges of the opposite scavenge port means and the side edges of the exhaust port, second transfer passageway means opening to the scavenge pump system from said side scavenge port means, said scavenge port means being covered and uncovered by said piston timing edge as said piston reciprocates in said cylinder, and separate valving means timed by piston position to control communication between said first transfer passageway and said scavenge pump system to prevent such communication until the piston timing edge is closer to its bottom dead center position than the distal edge of said opposite scavenge port means, said separate valving means comprising a separate scavenge pump system outlet port opening to said first transfer passageway and to said scavenge pump system, said piston skirt blocking said outlet port during portions of the piston stroke when portions of the opposite scavenge port means of significant flow area and at least a portion of said exhaust port are uncovered by the piston, and a separate control port, corresponding to the outlet port, defined in said piston skirt and positioned to align with said outlet port to control communication between said first transfer passageway and said scavenge pump system through said outlet port.

Claim 20

In a two cycle engine having a piston with a piston skirt, a head end and an underside opposite the head end, said engine being of a type which has a chamber open to the underside of the piston comprising a scavenge pump system, a power cylinder defined by a wall and having a first end and a distal end, said piston being slidably mounted in said cylinder for reciprocation in said cylinder during a piston stroke from a bottom dead center position adjacent said first end to a distal position, said piston having a piston timing edge, an exhaust port defined in said cylinder on one side thereof, an opposite scavenge port means extending from a line generally along the piston head timing edge in bottom dead center position to a distal end at a level more than 30 percent of the piston stroke toward the distal end of the cylinder, with the major portion of said opposite scavenge port means being closer to the first end of said cylinder than the distal end, said opposite scavenge port means being positioned generally diametrically opposite the center of said exhaust port, a first transfer passageway connected to said opposite scavenge port means, side scavenge port means in the cylinder wall located circumferentially between the opposite scavenge port means and the exhaust port and being positioned closely adjacent the sides of the opposite scavenge port means and occupying a substantial portion of the cylinder wall circumference between the side edges of the opposite scavenge port means and the side edges of the exhaust port, second transfer passageway means opening to the scavenge pump system from said side scavenge port means, said scavenge port means being covered and uncovered by said piston timing edge as said piston reciprocates in said cylinder, and separate valving means timed by piston position to control communication between said first transfer passageway and said scavenge pump system to prevent such communication until the piston timing edge is closer to its bottom dead center position than the distal edge of said opposite scavenge port means, said separate valving means comprising a separate scavenge pump system outlet port opening to said first transfer passageway and to said scavenge pump system, said piston skirt blocking said outlet port during portions of the piston stroke when portions of the opposite scavenge port means of significant flow area and at least a portion of said exhaust port are uncovered by the piston, and a separate control port, corresponding to the outlet port, defined in said piston skirt and positioned to align with said outlet port to control communication between said first transfer passageway and said scavenge pump system through said outlet port.

Claim 21

The combination as specified in claim 14 wherein said side scavenge port means includes at least two normal height scavenge port means, one on each side of said opposite scavenge port, at least two separate extra height scavenge port means, one on each side of said opposite scavenge port, said extra height scavenge port means being positioned toward the distal end of the cylinder from the normal height scavenge port means, said extra height scavenge port means having separate transfer passageways connected thereto, and piston skirt port valving means associated with the transfer passageways for the extra height port means to control comMunication between said scavenge pump system and the extra height scavenge port means, portions of said extra height scavenge port means being uncovered before the valving means associated therewith opens the extra height port means to the scavenge pump system.