US4535682A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Pistons
Assignee: AE PLC
•
Filing: 1982-08-06
•
Granted: 1985-08-20
•
Expires: 2002-08-06
Abstract
Abstract A piston for an engine or motor has a skirt which includes two portions which are urged towards an associated cylinder during the various strokes of the working cycle. Each portion is provided with a bearing surface or surfaces for sliding engagement with the associated cylinder during reciprocation. The piston is provided with formations which pass lubricant to and over the bearing surfaces.
Inventors
- 👤 John G. Collyear
- 👤 David A. Parker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 12:18
CPC Classifications
F; F16; F16J; F16J1/00; F16J1/08; F16J1/02; F01; F01M; F01M1/00; F01M1/08; F01M2001/083; F02; F02F; F02F3/00
Claims Analysis
Total Claims: 53
Claim 1
Independent Claim
297 words
A piston for reciprocation in a cylinder of an internal combustion engine wherein lubrication with an associated cylinder is provided by an oil film, comprising a crown, a gudgeon pin bore, a ring belt, a first generally cylindrical skirt portion to one side of a plane including the piston axis and the gudgeon pin bore axis, a second generally cylindrical skirt portion to the other side of said plane, said skirt portions being attached to the ring belt, a small number of discrete bearing surfaces formed on the first and second skirt portions, each of said skirt portions having an associated one of said skirt portions therearound and being spaced radially outwardly of the associated one of said skirt portions by a small distance, a circumferentially extending front edge to each bearing surface, a circumferentially extending rear edge to each bearing surface, generally axially extending side edges interconnecting the front and rear edges of each bearing surface, a shallow hydrodynamic ramp connecting each said circumferential front edge to the surrounding skirt portion, the end of said ramp remote from the associated bearing surface being spaced from the surface in a radial direction by less than 125 microns. a shallow hydrodynamic ramp connecting each said circumferential rear edge to the surrounding skirt portion, the end of said ramp remote from the associated bearing surface being spaced from the surface in a radial direction by less than 125 microns, the surrounding skirt portions providing retained oil said small distance from said bearing surfaces and said ramps co-operating with the cylinder to force a thin oil film over the bearing surfaces during motion of the piston relative to the cylinder to hydrodynamically lubricate said bearing surfaces as the bearing surfaces transmit lateral thrust from the piston to the co-operating cylinder.
Claim 2
Dependent Claim
297 words
A piston for reciprocation in a cylinder of an internal combustion engine wherein lubrication with an associated cylinder is provided by an oil film, comprising a crown, a gudgeon pin bore, a ring belt, a first generally cylindrical skirt portion to one side of a plane including the piston axis and the gudgeon pin bore axis, a second generally cylindrical skirt portion to the other side of said plane, said skirt portions being attached to the ring belt, a small number of discrete bearing surfaces formed on the first and second skirt portions, each of said skirt portions having an associated one of said skirt portions therearound and being spaced radially outwardly of the associated one of said skirt portions by a small distance, a circumferentially extending front edge to each bearing surface, a circumferentially extending rear edge to each bearing surface, generally axially extending side edges interconnecting the front and rear edges of each bearing surface, a shallow hydrodynamic ramp connecting each said circumferential front edge to the surrounding skirt portion, the end of said ramp remote from the associated bearing surface being spaced from the surface in a radial direction by less than 125 microns. a shallow hydrodynamic ramp connecting each said circumferential rear edge to the surrounding skirt portion, the end of said ramp remote from the associated bearing surface being spaced from the surface in a radial direction by less than 125 microns, the surrounding skirt portions providing retained oil said small distance from said bearing surfaces and said ramps co-operating with the cylinder to force a thin oil film over the bearing surfaces during motion of the piston relative to the cylinder to hydrodynamically lubricate said bearing surfaces as the bearing surfaces transmit lateral thrust from the piston to the co-operating cylinder.
Claim 3
Dependent Claim
25 words
A piston according to claim 1, wherein the lines of intersection between the surface of each ramp and planes including the piston axis are straight.
Claim 4
Dependent Claim
25 words
A piston according to claim 1 wherein the lines of intersection between the surface of each ramp and planes including the piston axis are curved.
Claim 5
Dependent Claim
28 words
A piston according to claim 1, wherein the angle of each ramp relative to a notional cylindrical surface coaxial with the piston axis is less than 1.5 degrees.
Claim 6
Dependent Claim
24 words
A piston according to claim 1, wherein generally cylindrical skirt portion is spaced radially inwardly of said bearing surfaces by less than 125 microns.
Claim 7
Dependent Claim
16 words
A piston according to claim 1, wherein each said bearing surface is generally rectangular in shape.
Claim 8
Dependent Claim
59 words
A piston according to claim 6 wherein the relation of the axial extent of said rectangular bearing surface to the circumferential length of said bearing surface is such as to ensure that at least some of the lubricant leaves said bearing surface over the edge thereof which is the trailing edge during reciprocation of the piston in one direction.
Claim 9
Dependent Claim
29 words
A piston according to claim 7 wherein the length of the bearing surface in an axial direction is less than the width of the surface in a circumferential direction.
Claim 10
Dependent Claim
59 words
A piston according to claim 1, wherein there are, on each generally cylindrical skirt portion at least three bearing surfaces for transmitting lateral thrust during reciprocation of the piston in one direction, two of said bearing surfaces being towards the crown end of the piston and the remaining surface or surfaces being towards the lower end of the piston.
Claim 11
Dependent Claim
26 words
A piston according to claim 9 wherein the two crown end bearing surfaces have a greater surface area than the remaining bearing surface or bearing surfaces.
Claim 12
Dependent Claim
45 words
A piston according to claim 9 wherein the crown end bearing surfaces are equidistantly spaced on either side of a plane including the piston axis and normal to the gudgeon pin bore axis and wherein a reemaining bearing surface is symmetrically disposed about said plane.
Claim 13
Dependent Claim
36 words
A piston according to claim 11, wherein the spacing between the crown end bearing surfaces is at least as great as the circumferential length of that remaining bearing surface which is symmetrically disposed about said plane.
Claim 14
Dependent Claim
22 words
A piston according to claim 1, wherein each rectangular bearing surface has a ramp extending up to each axially extending edge thereof.
Claim 15
Dependent Claim
26 words
A piston according to claim 13 wherein each of said ramps to the axial edges of each rectangular bearing surface has an angular extent of 10°.
Claim 16
Dependent Claim
30 words
A piston according to claim 1, and including a ring band extending around the crown, the ring band being formed with at least one bearing surface spaced radially outwardly thereof.
Claim 17
Dependent Claim
44 words
A piston according to claim 1, wherein the piston has a nominal diameter D and wherein the total bearing surface area to one side of a plane including the gudgeon pin axis and the piston axis is between 0.05 and 0.95 πD 2 /9.
Claim 18
Dependent Claim
49 words
A piston according to claim 1, wherein all the bearing surfaces to one side of the plane including the piston axis and the gudgeon pin bore axis extend no more than 30° to either side of a plane including the piston axis and normal to the gudgeon pin axis.
Claim 19
Dependent Claim
27 words
A piston according to claim 1, wherein the lines of intersection of the surface of each said bearing surface and planes including the piston axis are straight.
Claim 20
Dependent Claim
27 words
A piston according to claim 1, wherein the lines of intersection between the surface of each said bearing surface and planes including the piston axis are curved.
Claim 21
Dependent Claim
274 words
A piston for reciprocation in a cylinder of an internal combustion engine wherein lubrication with an associated cylinder is provided by an oil film, comprising a crown, a gudgeon pin bore, a ring belt, a first generally cylindrical skirt portion to one side of a plane including the piston axis and the gudgeon pin bore axis, a second generally cylindrical skirt portion to the other side of said plane, said skirt portions being attached to said ring belt, at least three discrete bearing surfaces formed on each of the first and second skirt portions, each of said at least three bearing surfaces having an associated skirt portion therearound and being spaced radially outwardly of the associated skirt portion by a distance of less than 125 microns, shallow hydrodynamic ramps extending from the associated skirt portion to each bearing surface, two of said at least three bearing surfaces and associated ramps forming a row and being aligned and being spaced or opposite sides of a plane including the piston axis and normal to the gudgeon pin bore axis, the at least one remaining bearing surface and associated ramps being spaced axially from said two of said at least three bearing surfaces and associated ramps, the at least three bearing surfaces on each skirt portion transmitting lateral thrust from the piston to the co-operating cylinder with the surrounding skirt portions providing retained oil said distance from said bearing surfaces and said shallow hydrodynamic ramps co-operating with the cylinder to force a thin oil film over the bearing surfaces during motion of the piston relative to the cylinder to hydrodynamically lubricate said at least three bearing surfaces.
Claim 22
Dependent Claim
274 words
A piston for reciprocation in a cylinder of an internal combustion engine wherein lubrication with an associated cylinder is provided by an oil film, comprising a crown, a gudgeon pin bore, a ring belt, a first generally cylindrical skirt portion to one side of a plane including the piston axis and the gudgeon pin bore axis, a second generally cylindrical skirt portion to the other side of said plane, said skirt portions being attached to said ring belt, at least three discrete bearing surfaces formed on each of the first and second skirt portions, each of said at least three bearing surfaces having an associated skirt portion therearound and being spaced radially outwardly of the associated skirt portion by a distance of less than 125 microns, shallow hydrodynamic ramps extending from the associated skirt portion to each bearing surface, two of said at least three bearing surfaces and associated ramps forming a row and being aligned and being spaced or opposite sides of a plane including the piston axis and normal to the gudgeon pin bore axis, the at least one remaining bearing surface and associated ramps being spaced axially from said two of said at least three bearing surfaces and associated ramps, the at least three bearing surfaces on each skirt portion transmitting lateral thrust from the piston to the co-operating cylinder with the surrounding skirt portions providing retained oil said distance from said bearing surfaces and said shallow hydrodynamic ramps co-operating with the cylinder to force a thin oil film over the bearing surfaces during motion of the piston relative to the cylinder to hydrodynamically lubricate said at least three bearing surfaces.
Claim 23
Dependent Claim
222 words
A piston for reciprocation in a cylinder of an internal combustion engine wherein lubrication withan associated cylinder is provided by an oil film, comprising a crown, a gudgeon pin bore, a ring belt, a first generally cylindrical skirt portion to one side of a plane including the piston axis and the gudgeon pin bore axis, a second generally cylindrical skirt portion to the other side of said plane, said skirt portions being attached to said ring belt, a small number of discrete bearing surfaces formed on the first and second skirt portions, each said bearing surface having generally circumferentially extending front and rear edges and generally axially extending side edges extending between said front and rear edges, shallow hydrodynamic ramps connecting each said front and rear generally circumferential edge to the surrounding skirt portion, each said discrete bearing surface being surrounded by an associated one of said skirt portions and being spaced radially outwardly of said associated skirt portion by less than 125 microns, the surrounding skirt portions providing retained oil closely adjacent the bearing surfaces and said ramps co-operating with the cylinder to force a thin oil film over the bearing surfaces during motion of the piston relative to the cylinder to hydrodynamically lubricate said bearing surfaces as the bearing surfaces transmit lateral thrust from the piston to the co-operating cylinder.
Claim 24
Dependent Claim
222 words
A piston for reciprocation in a cylinder of an internal combustion engine wherein lubrication withan associated cylinder is provided by an oil film, comprising a crown, a gudgeon pin bore, a ring belt, a first generally cylindrical skirt portion to one side of a plane including the piston axis and the gudgeon pin bore axis, a second generally cylindrical skirt portion to the other side of said plane, said skirt portions being attached to said ring belt, a small number of discrete bearing surfaces formed on the first and second skirt portions, each said bearing surface having generally circumferentially extending front and rear edges and generally axially extending side edges extending between said front and rear edges, shallow hydrodynamic ramps connecting each said front and rear generally circumferential edge to the surrounding skirt portion, each said discrete bearing surface being surrounded by an associated one of said skirt portions and being spaced radially outwardly of said associated skirt portion by less than 125 microns, the surrounding skirt portions providing retained oil closely adjacent the bearing surfaces and said ramps co-operating with the cylinder to force a thin oil film over the bearing surfaces during motion of the piston relative to the cylinder to hydrodynamically lubricate said bearing surfaces as the bearing surfaces transmit lateral thrust from the piston to the co-operating cylinder.
Claim 25
Dependent Claim
19 words
A piston according to claim 21 wherein each said shallow hydrodynamic ramp has an angle of less than 1.5°.
Claim 26
Dependent Claim
264 words
A piston for reciprocation in a cylinder of an internal combustion engine wherein lubrication with an associated cylinder is provided by an oil film, comprising a crown, a gudgeon pin bore, a ring belt, a first generally cylindrical skirt portion to one side of a plane including the piston axis and the gudgeon pin bore axis, a second generally cylindrical skirt portion to the other side of said plane, said skirt portions being attached to said ring belt, a small number of discrete bearing surfaces formed on the first and second skirt portions, each said discrete bearing surface being surrounded by an associated one of said skirt portions and being spaced radially outwardly of the associated one of said skirt portions by a small distance, a circumferentially extending front edge to each bearing surface, a circumferentially extending rear edge to each bearing surface, generally axially extending side edges interconnecting the front and rear edges of each bearing surface, a shallow hydrodynamic ramp having an angle of less that 1.5° and connecting each said circumferential front edge to the surrounding skirt portion, a shallow hydrodynamic ramp having an angle of less than 1.5° and connecting each said circumferential rear edge to the surrounding skirt portion, said ramps co-operating with the cylinder to force a thin oil film over the bearing surfaces during motion of the piston relative to the cylinder to hydrodynamically lubricate said bearing surfaces as the bearing surfaces transmit lateral thrust from the piston to the co-operating cylinder and the surrounding skirt portions providing retained oil said small distance from said bearing surfaces.
Claim 27
Dependent Claim
264 words
A piston for reciprocation in a cylinder of an internal combustion engine wherein lubrication with an associated cylinder is provided by an oil film, comprising a crown, a gudgeon pin bore, a ring belt, a first generally cylindrical skirt portion to one side of a plane including the piston axis and the gudgeon pin bore axis, a second generally cylindrical skirt portion to the other side of said plane, said skirt portions being attached to said ring belt, a small number of discrete bearing surfaces formed on the first and second skirt portions, each said discrete bearing surface being surrounded by an associated one of said skirt portions and being spaced radially outwardly of the associated one of said skirt portions by a small distance, a circumferentially extending front edge to each bearing surface, a circumferentially extending rear edge to each bearing surface, generally axially extending side edges interconnecting the front and rear edges of each bearing surface, a shallow hydrodynamic ramp having an angle of less that 1.5° and connecting each said circumferential front edge to the surrounding skirt portion, a shallow hydrodynamic ramp having an angle of less than 1.5° and connecting each said circumferential rear edge to the surrounding skirt portion, said ramps co-operating with the cylinder to force a thin oil film over the bearing surfaces during motion of the piston relative to the cylinder to hydrodynamically lubricate said bearing surfaces as the bearing surfaces transmit lateral thrust from the piston to the co-operating cylinder and the surrounding skirt portions providing retained oil said small distance from said bearing surfaces.
Claim 28
Dependent Claim
22 words
A piston according to claim 23 wherein each bearing surface is spaced from the surrounding skirt portion by less than 125 microns.
Claim 29
Dependent Claim
276 words
A piston for reciprocation in a cylinder of an internal combustion engine wherein lubrication with an associated cylinder is provided by an oil film, comprising a crown, a gudgeon pin bore, a ring belt, a first generally cylindrical skirt portion to one side of a plane including the piston axis and the gudgeon pin bore axis, a second generally cylindrical skirt portion to the other side of said plane, said skirt portions being attached to said ring belt, at least three discrete bearing surfaces formed on each of the first and secnd skirt portions, each of said at least three bearing surfaces having an associated skirt portion therearound and being spaced radially outwardly of the associated skirt portion by a small distance, hydrodynamic ramps having an angle of less than 1.5° extending from the associated skirt portion to each bearing surface, two of said at least three bearing surfaces and associated ramps forming a row and being aligned and being spaced on opposite sides of a plane including the piston axis and normal to the gudgeon pin bore axis, the at least one remaining bearing surface and associated ramps being space axially from said two of said at least three bearing surfaces and associated ramps, the at least three bearing surfaces on each skirt portion transmitting lateral thrust from the piston to the co-operating cylinder with the surrounding skirt portions providing retained oil said small distance from said bearing surfaces and said hydrodynamic ramps co-operating with the cylinder to force a thin oil film over the bearing surfaces during motion of the piston relative to the cylinder to hydrodynamically lubricate said at least three bearing surfaces.
Claim 30
Dependent Claim
276 words
A piston for reciprocation in a cylinder of an internal combustion engine wherein lubrication with an associated cylinder is provided by an oil film, comprising a crown, a gudgeon pin bore, a ring belt, a first generally cylindrical skirt portion to one side of a plane including the piston axis and the gudgeon pin bore axis, a second generally cylindrical skirt portion to the other side of said plane, said skirt portions being attached to said ring belt, at least three discrete bearing surfaces formed on each of the first and secnd skirt portions, each of said at least three bearing surfaces having an associated skirt portion therearound and being spaced radially outwardly of the associated skirt portion by a small distance, hydrodynamic ramps having an angle of less than 1.5° extending from the associated skirt portion to each bearing surface, two of said at least three bearing surfaces and associated ramps forming a row and being aligned and being spaced on opposite sides of a plane including the piston axis and normal to the gudgeon pin bore axis, the at least one remaining bearing surface and associated ramps being space axially from said two of said at least three bearing surfaces and associated ramps, the at least three bearing surfaces on each skirt portion transmitting lateral thrust from the piston to the co-operating cylinder with the surrounding skirt portions providing retained oil said small distance from said bearing surfaces and said hydrodynamic ramps co-operating with the cylinder to force a thin oil film over the bearing surfaces during motion of the piston relative to the cylinder to hydrodynamically lubricate said at least three bearing surfaces.
Claim 31
Dependent Claim
297 words
A piston for reciprocation in a cylinder of an internal combustion engine wherein lubrication with an associated cylinder is provided by an oil film, comprising a crown, a gudgeon pin bore, a ring belt, a first generally cylindrical skirt portion to one side of a plane including the piston axis and the gudgeon pin bore axis, a second generally cylindrical skirt portion to the other side of said plane, said skirt portions being attached to said ring belt, at least three discrete bearing surfaces formed on each of the first and second skirt portions, each of said at least three bearing surfaces having an associated skirt portion therearound and being spaced radially outwardly of the associated skirt portion by a small distance, shallow hydrodynamic rmps extending from the associated skirt portion to each bearing surface, the ends of said ramps remote from the associated bearing surfaces being spaced from the associated surface in a radial direction by less than 125 microns, two of said at least three bearing surfaces and associated ramps forming a row and being aligned and being spaced on opposite sides of a plane including the piston axis and normal to the gudgeon pin bore axis, the at least one remaining bearing surface and associated ramps being spaced axially from said two of said at least three bearing surfaces and associated ramps, the at least three bearing surfaces on each skirt portion transmitting lateral thrust from the piston to the co-operating cylinder with the surrounding skirt portions providing retained oil said small distance from said bearing surfaces and said shallow hydrodynamic ramps co-operating with the cylinder to force a thin oil film over the bearing surfaces during motion of the piston relative to the cylinder to hydrodynamically lubricate said at least three bearing surfaces.
Claim 32
Dependent Claim
297 words
A piston for reciprocation in a cylinder of an internal combustion engine wherein lubrication with an associated cylinder is provided by an oil film, comprising a crown, a gudgeon pin bore, a ring belt, a first generally cylindrical skirt portion to one side of a plane including the piston axis and the gudgeon pin bore axis, a second generally cylindrical skirt portion to the other side of said plane, said skirt portions being attached to said ring belt, at least three discrete bearing surfaces formed on each of the first and second skirt portions, each of said at least three bearing surfaces having an associated skirt portion therearound and being spaced radially outwardly of the associated skirt portion by a small distance, shallow hydrodynamic rmps extending from the associated skirt portion to each bearing surface, the ends of said ramps remote from the associated bearing surfaces being spaced from the associated surface in a radial direction by less than 125 microns, two of said at least three bearing surfaces and associated ramps forming a row and being aligned and being spaced on opposite sides of a plane including the piston axis and normal to the gudgeon pin bore axis, the at least one remaining bearing surface and associated ramps being spaced axially from said two of said at least three bearing surfaces and associated ramps, the at least three bearing surfaces on each skirt portion transmitting lateral thrust from the piston to the co-operating cylinder with the surrounding skirt portions providing retained oil said small distance from said bearing surfaces and said shallow hydrodynamic ramps co-operating with the cylinder to force a thin oil film over the bearing surfaces during motion of the piston relative to the cylinder to hydrodynamically lubricate said at least three bearing surfaces.
Claim 33
Dependent Claim
30 words
A piston according to claim 20 or 26 wherein the angles of the ramps relative to a notional cylindrical surface coaxial with the piston axis are less than 1.5 degrees.
Claim 34
Dependent Claim
35 words
A piston according to claims 20, 21 or 23 wherein said skirt portions are spaced radially inwardly of the said at least one bearing surface by less than 125 microns and more than 25 microns.
Claim 35
Dependent Claim
20 words
A piston according to claim 20, 21, 23, 36 or 37 wherein said bearing surfaces are generally rectangular in shape.
Claim 36
Dependent Claim
59 words
A piston according to claim 29 wherein the relation of the axial extents of said rectangular bearing surfaces to the circumferential lengths of said bearing surfaces is such as to ensure that at least some of the lubricant leaves said bearing surface over the edge thereof which is the trailing edge during reciprocation of the piston in one direction.
Claim 37
Dependent Claim
29 words
A piston according to claim 30 wherein the lengths of the bearing surfaces in an axial direction are less than the widths of the surfaces in a circumferential direction.
Claim 38
Dependent Claim
55 words
A piston according to claim 20, 21 or 23 wherein there are at least three bearing surfaces for transmitting lateral thrust during reciprocation of the piston in one direction, two of said bearing surfaces being towards said crown of the piston and the remaining surface or surfaces being towards the lower end of the piston.
Claim 39
Dependent Claim
26 words
A piston according to claim 32 wherein the two crown end bearing surfaces have a greater surface area than the remaining bearing surface or bearing surfaces.
Claim 40
Dependent Claim
52 words
A piston according to claim 32 wherein the crown end bearing surfaces are equidistantly spaced on either side of said plane including the piston axis and normal to the gudgeon pin bore axis and wherein the remaining bearing surface, or one of the remaining bearing surfaces, is symmetrically disposed about said plane.
Claim 41
Dependent Claim
43 words
A piston according to claim 34 wherein the spacing between the crown end bearing surfaces is at least as great as the circumferential length of the remaining bearing surface, or that one of the remaining surfaces, which is symmetrically disposed about said plane.
Claim 42
Dependent Claim
22 words
A piston according to claim 29 wherein each rectangular bearing surface has a ramp extending up to each axially extending edge thereof.
Claim 43
Dependent Claim
26 words
A piston according to claim 36 wherein each of said ramps to the axial edges of each rectangular bearing surface has an angular extent of 10°.
Claim 44
Dependent Claim
30 words
A piston according to claim 29 wherein said ring belt extends around the crown and said ring belt being formed with one or more bearing surfaces spaced radially outwardly thereof.
Claim 45
Dependent Claim
49 words
A piston according to claim 20, 21, 23, 25 or 26 wherein the piston has a nominal diameter D and wherein the total baring surface area to one side of said plane including the gudgeon pin axis and the piston axis is between 0.05 and 0.95 πD 2 /9.
Claim 46
Dependent Claim
42 words
A piston according to claim 20, 21, 23, 25 or 26 wherein the bearing surfaces to one side of said plane including the piston axis and the gudgeon pin bore axis extends no more than 30° to either side of said plane.
Claim 47
Dependent Claim
31 words
A piston according to claim 20, 21, 23, 25 or 26 wherein the lines of intersection of the surfaces of said bearing surfaces and planes including the piston axis are straight.
Claim 48
Dependent Claim
31 words
A piston according to claim 20, 21, 23, 25, or 26 wherein the lines of intersection between the surfaces of said bearing surfaces and planes including the piston axis are curved.
Claim 49
Dependent Claim
49 words
A piston according to claim 25 wherein bearing surfaces are equidistantly spaced on either side of said plane including the piston axis and normal to the gudgeon pin bore axis and wherein the remaining bearing surface, or one of the remaining bearing surfaces, is symmetrically disposed about said plane.
Claim 50
Dependent Claim
38 words
A piston according to claim 43 wherein the spacing between said two bearing surfaces is at least as great as the circumferential length of said at least one remaining bearing surface which is symmetrically disposed about said plane.
Claim 51
Dependent Claim
24 words
A piston according to claim 26 wherein said two bearing surfaces have a greater surface area than the remaining bearing surface or bearing surfaces.
Claim 52
Dependent Claim
51 words
A piston according to claim 26 wherein said two bearing surfaces are equidistantly spaced on either side of said plane including the piston axis and normal to the gudgeon pin bore axis and wherein the remaining bearing surface, or one of the remaining bearing surfaces, is symmetrically disposed about said plane.
Claim 53
Dependent Claim
42 words
A piston according to claim 46 wherein the spacing between said two bearing surfaces is at least as great as the circumferential length of the remaining bearing surface, or that one of the remaining surfaces, which is symmetrically disposed about said plane.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-08-19 | 1989-02-18 | 1989-08-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-08-19 | 1993-02-18 | 1993-08-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-08-19 | 1997-02-18 | 1997-08-20 | $7700.00 | Window Closed / Lapsed |