GB1590935A

GB1590935A - Tangential expanders for oil-control piston rings and apparatus for use in making a plurality of said expanders

Info

Publication number: GB1590935A
Application number: GB721978A
Authority: GB
Original assignee: NII TEKHNOL TRAKTOR I SELSKOKH
Current assignee: NII TEKHNOL TRAKTOR I SELSKOKH
Priority date: 1978-02-23
Filing date: 1978-02-23
Publication date: 1981-06-10

Description

(54) TANGENTIAL EXPANDERS FOR OIL-CONTROL PISTON RINGS AND APPARATUS FOR USE IN MAKING A PLURALITY OF SAID EXPANDERS (71) We, NAUCHNo-IssLEDovATELsKy INSTITUT TEKHNOLOGII TRAKTORNOGO I SELSKOKHOZYAISTVENNOGO MASHINO STROENIA, of Marxistaskaya ulitsa 20, Moscow, Union of Soviet Socialist Republics (U.S.S.R., a State Enterprise organized under the laws of the U.S.S.R. do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement::- The present invention relates to the design of internal combustion piston engines, and more specifically it relates to tangential expanders for engagement with compound oil-control piston rings and to apparatus for making a plurality of such tangential expanders.

An object of the present invention is to provide a tangential expander for oil-control piston rings, comprising a joint designed to ensure easy fitting of the oil-control rings on the piston, and easy insertion of the piston, with the rings, into the cylinder.

Another object of the present invention is to provide a tangential expander with the simplest possible and reliable jointing device which does not call for the use of any additional structural elements.

Still another object of the present invention is to provide apparatus for cutting a length of spring material into tangential expanders and for forming the joints of said tangential expanders.

And, finally, still another object of the present invention is to provide such apparatus which is simple to manufacture and service and is reliable in operation.

To achieve these and other objects, according to the present invention we provide a tangential expander for engagement with oilcontrol piston rings in an annular groove in a piston, comprising a split annular compression spring formed from flat corrugated spring strip and having a pair of opposed peripheral series of lateral U-shaped flanges for engagement with faces and edges of the piston rings and a pair of lateral semi-U shaped end flanges at the ends of the respective series, said ring-engaging and end flanges being formed from the U-tips of the corrugations of the spring strip and said end flanges being insertible between the series of ring-engaging flanges to positions adjacent to the respective endmost ring-engaging flanges to form a joint capable of retaining the compression spring in the groove in the piston during insertion of the piston rings into the groove.

Preferably each end flange is formed from a lateral ring-engageable U-shaped flange by hingeing inwards and splitting said flange.

Each U-shaped flange includes a marginal thrust shoulder, and the end flanges are displaced inwards through a distance equal to not less than the thickness of the spring strip plus the height of the thrust shoulder so that each tooth-like end flange in jointing position is flexibly locked between opposed U-flanges.

Such a technical solution offers the simplest and most reliable joint which permits the tangential expander to be held locked during the installation of the flat rings into the piston groove and to be flexibly compressed.

together with the flat rings to a smaller diameter during insertion of the piston with its rings into the cylinder liner, thus facilitating this latter operation.

Further according to the present invention we provide apparatus for use in manufacturing a plurality of tangential expanders from a length of compression-spring material which is formed from flat corrugated spring strip and has a pair of opposed series of lateral U-shaped flanges formed from the U-tips of the corrugations of the spring strip and suitable for engagement with the faces and edges of the piston rings, said apparatus comprising a pair of devices each having opposed reciprocable workpiece-engaging means cooperable to bend and cut the workpiece, and feeding means for conveying said spring material lengthwise intermittently through said devices to a position in which the devices on operation simultaneously with each other effect hingeing inwardly and splitting of a pair of U-shaped flanges of the respective series and thereby form a pair of semi-Ushaped joint-forming end flanges respectively on successive lengths of the spring material.

Preferably the feeding means include a rotatable storage drum for the length of spring material, a toothed wheel having a radial slot therein and having teeth capable of meshing with the spring material so that the toothed wheel on rotation reels a predetermined length of the material from the storage drum to operative position and following said rotation the slot in the wheel registers with the opposed reciprocable workpieceengaging means of the devices to permit actuation of the devices. Such a layout of the apparatus permits accurate measurement of the required lengths of the spring material, and accurate cutting of the spring material to form the tangential expander.

Preferably also in the apparatus each workpiece-engaging device includes a pair of opposed reciprocable cutters and a bending tool reciprocably mounted in one of the cutters and spring-urged towards the other cutter. Such a layout permits the combined shaping of the joint elements, viz. the simultaneous cutting of the tooth-like end flanges and bending them inward for insertion to a locking position between opposed U-shaped flanges in forming the joint.

Preferably also the toothed wheel is such that a single revolution thereof effects the reeling-off of a length of spring material equal to the length required for the production of one tangential expander.

An embodiment of the invention will now be described in detail by way of example with reference to the accompanying drawings in which: Fig. 1 shows a compound oil-control piston-ring assembly with a tangential expander; Fig. 2 shows a portion of the tangential expander illustrated in Fig. 1 embodying a joint and engaging flat rings; Fig. 3 is a top plan view of the portion illustrated in Fig. 2; Fig. 4 is a section taken along the line IV-IV in Fig. 2; Fig. 5 is an isometric view of the tangentialexpander joint; Fig. 6 is a schematic diagram of apparatus for making tangential expanders; Fig. 7 is a view along the arrow VII in Fig. 6; and Fig. 8 is a diagram of a sectional detail view of Fig. 6 showing a pair of workpieceengaging devices for forming the ends of the tangential expander.

Referring to the drawings: The compound oil-control piston-ring assembly comprises two chrome-plated flat rings 1 (Fig. 1) intended to distribute uniformly an optimum layer of oil over the cylinder face and to scrape off the surplus oil into the engine oil sump. The flat rings 1 are made in the form of flat circular plates whose diameter is close to the cylinder bore diameter and which are made of high-carbon spring steel strip, flattened and hardened, and bent edgewise into regular circles with expansion clearances 2 at the ends which permit linear expansion of the rings 1 in the course of operation at temperatures up to 150"C. The working surface 3 of the rings is coated with chrome or molybdenum to promote wear resistance.

The rings 1 are flexible, and retain their initial shape during installation on the piston even when stretched by 8--10% across the diameter.

A tangential expander 4 is formed from a flat spring strip and is designed to ensure engagement of the chrome-plated flat rings 1 with the cylinder face and with the sides of the annular piston groove during reciprocation of the piston, so that surplus oil is discharged through holes in the piston into the engine oil sump.

The tangential expander 4 comprises a split circular compression spring of generally U-shaped cross section, and a joint at the ends of the spring. As mentioned above, the spring is formed by bending a high-carbon spring steel flattened strip, of rectangular section and with rounded edges, into a sinuously corrugated strip, bending the outer margins of the U-tips of the corrugations to form thrust shoulders 5, bending the U-tips to form opposed series of lateral U-shaped flanges 6, coiling the resulting generally Usectioned spring into a ring, and heattreating the ring to impart flexibility thereto.

The radial and axial forces transmitted by the compression spring to the flat rings 1 via the thrust shoulders 5 (Figs. 2 through 5) and the opposed faces of the U-shaped flanges 6 are created due to the compression of the spring which occurs when the oil-control rings are inserted with the piston into the cylinder.

The joint of the tangential expander is intended to ensure efficient installation of the oil-control ring assembly on the piston and efficient insertion of the piston, with rings, into the cylinder.

The joint is formed by bending inwards the endmost lateral U-flanges of the respective series, and splitting the resultant inwardly sloped U-flanges to leave a pair of semi-U shaped tooth-like end flanges which are insertible into the opposed ends of the U-section spring to lie adjacent to the endmost U-flanges of the spring to form a flexible joint which retains the spring in the piston groove against radial and axial displacement during insertion of the piston rings into the groove.

In the course of operation of the oilcontrol ring assembly, the flat rings are constantly pressed against the geometricallyvarying surface of the cylinder face and must move freely without jamming and scoring in a radial direction relative to the lateral Uflanges which, in contracting and expanding, move in a tangential direction.

The relative motion between the flat rings and the U-flanges in service of the expander are ensured by the structure of the rings which have rounded edges made in the flattened steel strip during manufacture of the strip.

Apparatus for making the joints on lengths of compression-spring material to form said expanders includes a bending-and-cutting mechanism 7 (Figs. 6, 7) in the form of two pairs of opposed bodies 8, 9 reciprocated by cams 10 on guide shafts 11 towards and from the spring material 12 (Fig. 8).

In this version of the apparatus each pair of opposed bodies 8, 9 (Figs. 6, 7) slides on two guide shafts 11, and the pairs are installed symmetrically relative to a central axis 13.

Secured on the bodies 8 are thrust cutters 14 (Fig. 8) provided with projections 14a which snap into spaces in the spring material 12 and thus set the degree of bending of the U-flanges of the spring material. The thrust cutters 14 also have surfaces 14b which form supports for the spring material 12 to keep it from bending in the course of the U-flange bending and cutting.

The bodies 9 carry cutters 15 which have therein slots 1 5a accommodating bending punches 16.

Each bending punch 16 has a head 1 6a for limiting its travel under the force of a spring 17, and has a surface 1 6b which stands out from the surface 15b of the cutter 15 thereby ensuring first bending and then cutting of the spring material 12. The bodies 8, 9 in each of the two pairs are arranged so that the thrust cutters 14 or the cutters 15 are located at the opposite sides of the spring material (as shown in Fig. 8). This arrangement of the bodies 8 and 9 ensures bendingand-cutting actions on the spring material 12 respectively at two spaced locations simultaneously to form the expander joint.

Mounted on a common shaft with the cams 10 is a pin wheel 18 (Fig. 6) of a Maltese cross mechanism, said wheel meshing with the Maltese cross 19 which in turn is drivingly connected to a toothed wheel 22 via spur gears 20 and 21. The toothed wheel 22 has therein a radially extending slot to permit passage through the wheel of thrust cutters 14 and the cutters 15 (Fig. 7).

The teeth of the wheel 22 which are intended to move the spring material 12 and hold it stationary during the bending-andcutting operation, are cut with a pitch equal to the pitch of the U-flanges, the number of teeth in the wheel 22 being equal to the number of corrugations required to form one expander which is thus formed during one revolution of the wheel 22.

This design of the toothed wheel 22 in combination with the flexibility of the spring material 12 ensures reliable meshing of the wheel 22 with the spring material in the course of the feeding movement, and the fixing of the spring material on the teeth of the wheel 22 in the course of the bendingand-cutting operation.

The toothed wheel 22 is connected by a gear wheel 23 (Fig. 6) and a wide-tooth gear wheel 24 with nut-gears 25 one of which carries a receiving drum 26 (Fig. 7) and the other of which carries a mandrel 27 with a spiral.

For conveying the cut-off expander into the receiving drum 26, the apparatus is provided with a guide 28 located between the toothed wheel 22 and the receiving drum 26. The guide 28 is in the form of a segment whose curvature ensures that the tangential expander moves over an arc without unbending which would cause permanent deformation thereof. Thus, the periphery of the segment 28 has therein an arcuate slot 28a. Connected to the segment 28 is a bail 29 closing the slot to form a guideway which keeps the spring material 12 from bulging in the course of its movement.

The bail 29 has therein slots through which project sprocket wheels 30, 31, the sprocket wheel 30 being connected by the gears 32 and 33 with the toothed wheel 22, while the sprocket wheel 31 is driven by a shaft of the cams 10 via bevel gears 34-37. The sprocket wheel 31 is drivingly connected via a spur wheel 38 with a toothed sleeve 39 which acts through a helical slot on a lever 40 which serves to throw the finished expander from the surface of the sleeve 39 into the receiving drum 26 which is provided with internal circular grooves to receive the finished expanders. The receiving drum 26 and the mandrel with the spiral 27 are withdrawn to their initial positions by a high-speed drive comprising an electric motor 41, a reduction unit 42 and spur gears 43, 44, 45.For automatic functioning of the device there is provided a working feed drive comprising an electric motor 46, a reduction unit 47 and a bevel gear 48.

The apparatus functions as follows The end of the stored strip of spring material is reeled off the mandrel 27 and hooked to the toothed wheel 22. Then the electric motor 46 is started, and its rotation is transmitted via the reduction unit 47 and bevel gears 48 and 34 to the shaft carrying the cams 10 and pin wheel 18. On rotation, -the pin wheel 18 turns the Maltese cross 19 through a preset angle, and as a result the toothed wheel 22, which is drivingly connected to the Maltese cross 19 through the gears 20 and 21, turns one revolution and stops, having moved the spring strip a certain distance.From the toothed wheel 22 rotation is transmitted through the gears 33 and 32 to a sprocket wheel 30 which moves the spring strip along the guideway, and through the gears 23 and 24 to the nutgears 25 which turn one revolution and move axially through a pitch of the driving screw, thus making ready the next vacant groove in the receiving drum 26 to receive the expander, and unreeling the spring strip from the mandrel 27. After the pin wheel leaves the slot in the Maltese cross 19, the cylindrical cams 10 act on the bodies 8 and 9 to move them towards the spring strip, one of the cams being provided on the shaft of the pin wheel 18, while the other is provided on a shaft 49 rotated by the pin wheel shaft through the agency of gears 50. Having approached the spring strip, the bodies 8.

with the thrust cutters 14 stop, whereas the bodies 9 with the cutters 15 continue moving and their bending punches 16 bend the spring -strip towards the thrust cutters 14. Then the bending punches 16 stop, but the cutters 15 continue moving relative to the bending punches 16 to compress the spring 17 and cut the spring. Then the bodies 8, 9 are withdrawn to their initial positions.

During the next revolution of the toothed wheel 22, the cut-off expander is moved through the guideway at 28 by the sprocket wheel 30 and by the continuously rotating sprocket wheel 31 which transfers the expander into the groove of the lever 40, and on to the external surface of the toothed sleeve 39. The slot in the turning sleeve 39 acts on the lever 40, and the latter throws the expander into the groove of the receiving drum 26.

As soon as the last expander snaps into the slot of the receiving drum 26, the electric motor 46 stops, and the madrel 27 and the receiving drum 26 are replaced and withdrawn by the high-speed drive to their initial positions.

The above-described apparatus ensures the cutting of the spring material into a series of tangential expanders with the requisite accuracy, and forms their joints.

After an appropriate heat treatment, the finished expanders are used in intenral combustion engines as expanders for the oilcontrol piston-rings which are made of steel strip.

The use in the engines of chrome-plated oil-control rings made of a steel strip and with tangential expanders, as proved by the stand and operation engine tests, cuts down the loss of sum oil to the upper part of the cylinder to an amount which is 15-2 times lower than the amount lost with the use of oil-control rings of other designs; the fuel consumption also decreases.

It should also be pointed out that the oilcontrol rings made of a steel strip are more technologically processable and can be manufactured by the advanced methods of cold working combined with heat treatment, the effective yield of metal being 93-95(, whereas in the manufacture of cast-iron rings made by casting and machining the effective yield of metal is not over 25% in the U.S.S.R. and 40% abroad.

Bearing in mind that the apparatus according to the present invention ensures cutting of a profiled spiral into expanders with the requisite accuracy and forms a high-quality expander joint which is indispensable for mechanized assembly of a piston with rings, involving wide application of the rings of the above-mentioned design, the efficiency of the apparatus is sufficiently high, as is proved by the results described above.

WHAT WE CLAIM IS: 1. A tangential expander for engagement with oil-control piston rings in an annular groove in a piston, comprising a split annular compression spring formed from flat corrugated spring strip and having a pair of opposed peripheral series of lateral U-shaped flanges for engagement with faces and edges of the piston rings and a pair of lateral semi U shaped end flanges at the ends of the respective series, said ring-engaging and end flanges being formed from the U-tips of the corrugations of the spring strip and said end flanges being insertible between the series of ring-engaging flanges to positions adjacent to the respective endmost ring-engaging flanges to form a joint capable of retaining the compresssion spring in the groove in the piston during insertion of the piston rings into the groove.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the surface of the sleeve 39 into the receiving drum 26 which is provided with internal circular grooves to receive the finished expanders. The receiving drum 26 and the mandrel with the spiral 27 are withdrawn to their initial positions by a high-speed drive comprising an electric motor 41, a reduction unit 42 and spur gears 43, 44, 45. For automatic functioning of the device there is provided a working feed drive comprising an electric motor 46, a reduction unit 47 and a bevel gear 48. The apparatus functions as follows The end of the stored strip of spring material is reeled off the mandrel 27 and hooked to the toothed wheel 22. Then the electric motor 46 is started, and its rotation is transmitted via the reduction unit 47 and bevel gears 48 and 34 to the shaft carrying the cams 10 and pin wheel 18. On rotation, -the pin wheel 18 turns the Maltese cross 19 through a preset angle, and as a result the toothed wheel 22, which is drivingly connected to the Maltese cross 19 through the gears 20 and 21, turns one revolution and stops, having moved the spring strip a certain distance.From the toothed wheel 22 rotation is transmitted through the gears 33 and 32 to a sprocket wheel 30 which moves the spring strip along the guideway, and through the gears 23 and 24 to the nutgears 25 which turn one revolution and move axially through a pitch of the driving screw, thus making ready the next vacant groove in the receiving drum 26 to receive the expander, and unreeling the spring strip from the mandrel 27. After the pin wheel leaves the slot in the Maltese cross 19, the cylindrical cams 10 act on the bodies 8 and 9 to move them towards the spring strip, one of the cams being provided on the shaft of the pin wheel 18, while the other is provided on a shaft 49 rotated by the pin wheel shaft through the agency of gears 50. Having approached the spring strip, the bodies 8. with the thrust cutters 14 stop, whereas the bodies 9 with the cutters 15 continue moving and their bending punches 16 bend the spring -strip towards the thrust cutters 14. Then the bending punches 16 stop, but the cutters 15 continue moving relative to the bending punches 16 to compress the spring 17 and cut the spring. Then the bodies 8, 9 are withdrawn to their initial positions. During the next revolution of the toothed wheel 22, the cut-off expander is moved through the guideway at 28 by the sprocket wheel 30 and by the continuously rotating sprocket wheel 31 which transfers the expander into the groove of the lever 40, and on to the external surface of the toothed sleeve 39. The slot in the turning sleeve 39 acts on the lever 40, and the latter throws the expander into the groove of the receiving drum 26. As soon as the last expander snaps into the slot of the receiving drum 26, the electric motor 46 stops, and the madrel 27 and the receiving drum 26 are replaced and withdrawn by the high-speed drive to their initial positions. The above-described apparatus ensures the cutting of the spring material into a series of tangential expanders with the requisite accuracy, and forms their joints. After an appropriate heat treatment, the finished expanders are used in intenral combustion engines as expanders for the oilcontrol piston-rings which are made of steel strip. The use in the engines of chrome-plated oil-control rings made of a steel strip and with tangential expanders, as proved by the stand and operation engine tests, cuts down the loss of sum oil to the upper part of the cylinder to an amount which is 15-2 times lower than the amount lost with the use of oil-control rings of other designs; the fuel consumption also decreases. It should also be pointed out that the oilcontrol rings made of a steel strip are more technologically processable and can be manufactured by the advanced methods of cold working combined with heat treatment, the effective yield of metal being 93-95(, whereas in the manufacture of cast-iron rings made by casting and machining the effective yield of metal is not over 25% in the U.S.S.R. and 40% abroad. Bearing in mind that the apparatus according to the present invention ensures cutting of a profiled spiral into expanders with the requisite accuracy and forms a high-quality expander joint which is indispensable for mechanized assembly of a piston with rings, involving wide application of the rings of the above-mentioned design, the efficiency of the apparatus is sufficiently high, as is proved by the results described above. WHAT WE CLAIM IS:

1. A tangential expander for engagement with oil-control piston rings in an annular groove in a piston, comprising a split annular compression spring formed from flat corrugated spring strip and having a pair of opposed peripheral series of lateral U-shaped flanges for engagement with faces and edges of the piston rings and a pair of lateral semi U shaped end flanges at the ends of the respective series, said ring-engaging and end flanges being formed from the U-tips of the corrugations of the spring strip and said end flanges being insertible between the series of ring-engaging flanges to positions adjacent to the respective endmost ring-engaging flanges to form a joint capable of retaining the compresssion spring in the groove in the piston during insertion of the piston rings into the groove.

2. A tangential expander according to

claim 1, wherein each end flange is formed from a lateral ring-engageable U-shaped flange by hinging inwards and splitting said flange.

3. Apparatus for use in manufacturing a plurality of tangential expanders according to claim 2 from a length of compression-spring material which is formed from flat corrugated spring strip and has a pair of opposed series of lateral U-shaped flanges formed from the U-tips of the corrugations of the spring strip and suitable for engagement with the faces and edges of the piston rings, said apparatus comprising a pair of devices each having opposed reciprocable workpiece-engaging means co-operable to bend and cut the workpiece, and feeding means for conveying said spring material lengthwise intermittently through said devices to a position in which the devices on operation simultaneously with each other effect hingeing inwardly and splitting of a pair of Ushaped flanges of the respective series and thereby form a pair of semi-U shaped jointforming end flanges respectively on successive lengths of the spring material.

4. Apparatus according to claim 3, wherein each workpiece-engaging device includes a pair of opposed reciprocable cutters and a bending tool reciprocably mounted in one of the cutters and spring-urged towards the other cutter.

5. Apparatus according to claim 3 or 4, wherein the feeding means include a rotatable storage drum for the length of spring material, a toothed wheel having a radial slot therein and having teeth capable of meshing with the spring material so that the toothed wheel on rotation reels a predetermined length of the material from the storage drum to operative position and following said rotation the slot in the wheel registers with the opposed reciprocable workpiece-engaging means of the devices to permit actuation of the devices.

6. Apparatus according to claim 5, wherein the toothed wheel is such that a single revolution thereof effects the reeling-off of a length of spring material equal to the length required for the production of one tangential expander.

7. A tangential expander for engagement with oil-control piston rings in an annular groove in a piston, substantially as hereinbefore described with reference to the accompanying drawings.

8. Apparatus for use in the manufacture of tangential expanders for engagement with oil-control piston rings in an annular groove in a piston, substantially as hereinbefore described with reference to the accompanying drawings.