Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B19/00—Single-purpose machines or devices for particular grinding operations not covered by any other main group
  • B24B19/08—Single-purpose machines or devices for particular grinding operations not covered by any other main group for grinding non-circular cross-sections, e.g. shafts of elliptical or polygonal cross-section
  • B24B19/11—Single-purpose machines or devices for particular grinding operations not covered by any other main group for grinding non-circular cross-sections, e.g. shafts of elliptical or polygonal cross-section for grinding the circumferential surface of rings, e.g. piston rings
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B11/00—Machines or devices designed for grinding spherical surfaces or parts of spherical surfaces on work; Accessories therefor

Definitions

• the invention broadly relates to a method and apparatus for manufacturing keystone type piston ring structures which are typically employed as compression rings in engines and utilized in a wide variety of engine applications.
• the objective of the ring structure is to effect a seal in the space between an associated piston and liner to prevent the high-pressure combustion gases or the ' air charge from escaping down the liner during the compression or power strokes; to transmit heat energy from the piston to the cooled cylinder liner; and to absorb a certain part of the fluctuations of the piston side thrust.
• Some internal combustion engines have compression rings with the bottom wall or both the bottom and top walls beveled, making the ring thinner at the inside than at the outside diameter.
• the associated groove in the piston for receiving the ring is machined to the same general shape.
• the gas pressure acting on the top wall of the ring owing to the beveled bottom surface produces an additional force pressing the ring outwardly against the cylinder wall and helping to adequately effect the desired seal.
• the ring slides slightly into the associated groove, is pressed against the upper groove wall, crushes the carbon which is deposited on it, and keeps the ring from sticking. It is an objective of the present invention to produce a piston ring structure for a fluid pressure system
• Another object of the invention is to produce a piston ring having at least one inwardly inclined wall of curved cross-section which may be readily and economically manufactured.
• a specific object of the invention is to provide method and apparatus for making a piston ring having at least one inwardly machined wall of a curved cross-section BRIEF DESCRIPTION OF THE DRAWINGS
• Figure 1 is a top plan view of a piston ring incorporating the salient features of the present inventio
• Figure 2 is a front view of the piston ring illustrated in Figure 1;
• Figure 3 is a sectional view of the piston ring illustrated in Figures 1 and 2 taken along line 3-3 of Figure 1;
• Figure 4 is an enlarged fragmentary sectional view of the piston ring illustrated in Figures 1 and 2 in use within a groove of an associated piston;
• Figure 5 is a schematic illustration of an apparatus for achieving the top or bottom wall configuration of the piston ring illustrated in Figures 1 through 4;
• Figure 6 is an enlarged fragmentary sectional view of a modified form of the piston and piston ring assembly illustrated in Figures 1, 2, 3 and 4.
• Figure 7 is a schematic perspective view of a modified form of grinding equipment for forming a piston ring in accordance with the method of this invention.
• Figure 8 is an enlarged scale, sectional view of the ring holding mechanism of Figure 7.
• the present invention relates to piston rings which are self-tensioned annular metal pieces installed in piston grooves to provide a moveable seal between the combustion chamber and the crankcase of an internal combustion engine, and the manufacture of such rings.
• the metal used for piston rings must meet a number of requirements.
• the metal must be a good bearing material and have a low rate of wear.
• the metal of the ring will be coated with a material having such properties.
• the metal additionally should be suitably hard and of high strength, yet readily machinable. It must be a good spring material and resistant to fatigue. Ring materials must be able to operate under conditions of boundary lubrication while carrying high loads.
• the metal must substantially retain its mechanical strength while working at elevated temperatures and pressures in the associated engine. Also, the hot corrosive products of combustion should not have an extremely adverse effect on the wearing qualities and properties of the metal of the r ings. To reduce the wear of piston rings and impart desirable characteristics thereto, a number of coatings an platings may be applied.
• Some types of special facings such as for exampl a thin bearing surface of antifriction metal or chemical treatment, facilitate the run-in or seating of new rings.
• Such facings may cause tiny rough spots on the surfaces of the rings and the associated cylinder liner to wear off gradually, so that good surface to surface contact is achieved without excess friction which might cause scuffin or scarring.
• rings of proper design are combined into sets t provide the best and optimum performance for each engine under all operating conditions.
• a piston ring 10 embodying the features of the present invention, having a gap 12.
• the ring 10 is typically referred to as a keystone-type piston ring having an outer peripheral wall 14 often referred to as the piston ring face; and inwardly converging top wall 16; and inwardly converging bottom wall 18, and an inner wall 20.
• the top wall 16 and the bottom wall 18 are formed to assume a slightly concave cross-sectional configuration, as is more clearly apparent in Figure 4 wherein the piston ring 10 is shown as being received in a groove 22 formed in the peripheral side wall of an associated piston 24.
• the groove 22 is defined by an inwardly converging top wall 26 an inwardly converging bottom wall 28, and a rear wall 30.
• the piston 24 is adapted to reciprocate within a cylinder defined by a cylinder wall 32.
• the diameter of the ring 10 when free, is typically slightly larger than the cylinder bore; consequently, when the ring is squeezed into the cylinder, it presses against the cylinder wall 32 of the engine and tends to effect a seal. This initial sealing action is greatly improved in operation by the pressure of the engine during the power stroke, as illustrated in Figure 4 (which exaggerates the clearances for the sake of clarity) .
• the ring When there is little or no gas pressure to be sealed, the ring is free in the groove 22 and its own tension creates only a light pressure against the cylinder wall 32, causing minimum friction and wear; but when the gas pressure increases, the ring is caused to press correspondingly tighter both against the cylinder wall 32 and against the piston groove 22, thus cooperating to improve the seal and reduce the leakage, resulting in a more efficient and pollution-free engine.
• Figure 4 shows the piston and piston 'ring assembly during the power stroke of the engine wherein the pressure of the combustion gases is instantaneously applie to the top wall 16 and the rear wall 20 of the ring providing an outward pressure component tending to hold th ring face 14 in sealing relation with respect to the cylinder wall 32.
• the lower wall 18 of the ring tends to be cammed outwardly along the inclined wall 28 of ' the groove 22. Manifestly, this action tends to create an maintain a sealing relation between the ring face 14 and the cylinder wall 32.
• the technique for finishing the top wall 16 and bottom wall 18 of the ring 10 is accomplished by the apparatus schematically illustrated in Figure 5.
• the apparatus consists basically of a rotating lapping sphere 40, the peripheral surface of which is coated with abrasiv particles.
• the piston ring 10 being finished is suitably contained within an annular confining fixture 42.
• a disc shaped hold down plate 44 having a diameter slightly less than the inside diameter of the confining fixture 42 is employed to apply substantially equal downward pressure to the top wall 16 of the ring 10 to thereby cause the bottom wall 18 of the ring to move into contact with the spherica peripheral surface of the lapping sphere 40 along a' path passing thru the cental 40a of lapping sphere 40.
• the abrasive particles carried thereby effectively form a concave surface concurrently on all areras of the bottom wall 18 of the contained ring 10.
• the ring 10 is turned over so that the opposite wall 16 is brought into contact with the spherical abrasive surface to achieve the desired concave surface.
• the lapping sphere 40 has been referred to as being a sphere, which means that it may rotate about an axis passing through its center and accomplish the desired grinding action on the top or bottom wall 16, 18 of the ring 10, an obvious modification of this invention (Fig. 7) would form the lapping surface as a spherical segment surface 45a on a member 45 rotating about the axis of a power shaft 456.
• the main requirements of such member 45 is that (1) the extent of its working surface must be in excess of the diameter of the constrained ring 10 in.
• FIGs 7 and 8 schematically illustrate an apparatus for the commercial production of piston rings 10 and permits a plurality of such rings to be concurrently ground on the rotating spherical segment surface 45a of a working member 45.
• the machine 46 is provided with a base housing 47 wherein are mounted an appropriate motor and drive mechanism for rotating the working member 45. Also, grinding slurry pumps and a reservoir (not shown) may be contained within the housing 47.
• a plurality of upstanding inverted L-shaped support brackets 50 each bracket functioning to support an axially moveable fixture 60 within which is constrained a piston ring 10 whose converging surface is to be ground to a spherical segment contour in the manner schematically illustrated in Figure 5.
• a conventional fluid actuated cylinder mechanism 55 is suspended from the end of each support post 50 which overlies the rotating spherical segment working surface 45a.
• Cylinder 55 has an output shaft 55a for supporting and axially shifting the constraining fixture 60 within which the piston ring 10 is secured with one of its converging sides exposed so as to be engaged by the rotating spherical segment surface 45a. Since the mechanism for supporting and axially shifting the fixture 60 is entirely conventional, the details thereof have not been shown but it should be understood that fixture 60, hence the ring 10, is moveable into engagement with the rotating spherical segment surface 45a along a path that i coincident with the axis of the constrained ring 10 and also constitutes a radius of the spherical segment working surface 45a.
• O .. WI particles may be supplied in the form of a water based or oil based slurry which is applied to the rotating spherical segment surface of the grinding member through a suitable pipe 70.
• Figure 6 shows an embodiment of the invention similar to that illustrated in the embodiment of Figures 1 through 5, inclusive, but the piston ring 10* includes only a single inwardly converging surface.
• the top wall 16' is flat and generally perpendicular to the ring face 14'.
• the ring 10 includes a rear wall 20' which is generally parallel to the ring face 14*, and an inwardly converging bottom wall 18'.
• the associated groove 22' of the piston 24' is formed with an interior configuration similar to the cross-sectional configuration of the ring 10'.
• the groove 22' includes a top wall 26' which is generally flat, an inwardly converging bottom wall 28', and a flat rear wall 30'.
• the sealing action of the piston ring 10' is improved, in operation, by the pressure of the engine gases.
• the pressure of the compression gases against the top wall 16' of the ring 10' forces the ring downwardly on the lower wall 28" of the groove 22' of the piston 24", tending to cam the ring 10* radially outward.
• This action leaves a clearance at the top side 16* of the ring 10', permitting the gas pressure to travel behind the rear wall 20' which acts to additionally urge the ring 10' to expand radially outwardly against the cylinder wall 32'.
• FIG. 6 A block diagram illustrating an exemplary embodiment of the invention.
• FIG. 6 A block diagram illustrating an exemplary embodiment of the invention.
• FIG. 6 A block diagram illustrating an exemplary embodiment of the invention.
• FIG. 6 A block diagram illustrating an exemplary embodiment of the invention.
• FIG. 6 A block diagram illustrating an exemplary embodiment of the invention.
• FIG. 6 A block diagram illustrating an exemplary embodiment of the invention.
• FIG. 6 A piston ring structure having at least one inwardly convering wall formed to have a slightly convex cross-section configuration.
• the associated groove of the piston adapted to receive the ring would be defined by an inwardly converging facing wall.
• the sealing action of the piston ring is improved by reason of the curved configuration of the ring surface as it contact the respective groove surface.
• the novel design of the piston ring results in line-to-line contact between the facing surfaces of the piston rings and the respective facing surface of the peripheral groove formed in the piston.
• These line-to-line contacts are preferably radially spaced from one another and typically are spaced apart over a substantial portion of the entire width of th upper and lower sealing surfaces-of the piston ring.
• the forces applied against the one ring surface by the combustion gases for example, will actually be concentrated at the opposite surface of the ring and are applied in the concentrated form to the adjacent groove surface along the two spaced apart line-to-line contacts as is clearly illustrated in Figures 4 and 6.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Pistons, Piston Rings, And Cylinders (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
• Grinding And Polishing Of Tertiary Curved Surfaces And Surfaces With Complex Shapes (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=25485721

Family Applications (1)

Country Status (11)

Cited By (1)

Families Citing this family (1)

Citations (8)

Family Cites Families (1)

• 1979
  • 1979-09-07 JP JP50174479A patent/JPS55500828A/ja active Pending
  • 1979-09-07 WO PCT/US1979/000716 patent/WO1980000671A1/en unknown
  • 1979-09-07 DE DE7979901360T patent/DE2963680D1/de not_active Expired
  • 1979-09-20 AU AU51018/79A patent/AU534639B2/en not_active Ceased
  • 1979-09-24 IN IN1001/CAL/79A patent/IN152905B/en unknown
  • 1979-09-27 MX MX179426A patent/MX151646A/es unknown
  • 1979-09-27 IT IT50382/79A patent/IT1193284B/it active
  • 1979-09-27 AR AR278217A patent/AR223849A1/es active
  • 1979-09-28 CA CA000336652A patent/CA1116863A/en not_active Expired
  • 1979-09-28 ES ES484548A patent/ES484548A1/es not_active Expired
• 1980
  • 1980-04-22 EP EP79901360A patent/EP0020502B1/en not_active Expired

Patent Citations (8)

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