US2352041A - Piston structure - Google Patents

Description

June 20, 1944. v VAN DEN BERG 2,352,041

PISTON STRUCTURE Filed July 23, 1940 7 GAS CAB/.5 LIQUID Inventor: Walter" van den Berg, by 7 5 His Attorney Patented June 20, 1944 2,352,041 PISTON-STRUCTURE Walter van den Berg, Cologne-Mulhelm, Ger- Alien Property Custodian many; vested in the Application July 23, 1940, Serial In Germany January 31, 1940.

Claims.

In fluid filled electric cable installations, as the cable heats and cools with changes of load thereon, expansion and contraction of the impregnating medium-takes place. To avoid undue changes of pressure within the conductor enclosure, means are provided to receive the fluid medium from the cable as it expands and to feed it back to the cable as its temperature and that of the cable decreases. To accomplish this, variable capacity reservoirs are employed in which a gas under pressure is employed as a yieldable means to accommodate any increasein volume of the impregnating magages the under surface of the cover 3, the latter being clamped in place by an annular series of clamping bolts l3 which enter the ring. Gas under Positive predetermined pressure is admitted to the'plston chamber 1 by suitable means, such as the pipe it, having any usual form of shutoff means. The bottom wall 2 of the tank has a piston stop l5 of suitable construction, in this case a ring which is brazed or welded to the wall.

terial and to feed it back to the conductor enclosure as it contracts. Care must be exercised to prevent the gas from mixing with the impregnating material. iAS ordinarily constructed, these reservoirs are expensive and require the utmost care in their manufacture, and usually a considerable amount of special manufacturing apparatus.

The object of my invention is the provision of an improved piston structure for cylindrical reservoirs which is simple in construction, reliable in operation, and of relatively low initial cost.

For a consideration of what I believe to be novel and my invention, attention is directed to the accompanying description and the claims appended thereto.

In the attached drawing, which is illustrative of my invention, is shown a reservoir in vertical section.

The reservoir comprises a tank having a cylindrlcal wall I of relatively thin metal, a bottom wall 2 which is curved inwardly to give it the necessary strength to resist internal pressure which is above that of the atmosphere, and a cover 3. Inside of the casing so formed is a ring 4 which is brazed or otherwise secured thereto in a manner to provide a fiuidtight joint. Inside of the casing is a cylinder 5 of heavier metal which has a carefully smoothed inner surface as it is on that surface that the free piston 6 moves up and down. It is important to make the inner surface smooth for upon it in large measure depends the separation of the gas in the chamber 1 above the piston and the liquid or other fluid from the cable in the chamber 8 below the piston. This chamber is in free communication with the tank chamber 9, as for example through lateral openings l0,.the effect of which is to greatly enlarge the cubical contents of the retaining or storage space for cable liquid. The upper end of the cylinder is supported by the ring 4 and the two parts are united by a brazed or welded joint II. The upper end of the cylinder and the inner part of the top surface of the ring are chamfered to receive a compressible packing l2 which ennumber of floating rings ing rings Liquid or other fluid from the cable is admitted to the chambers 8 and 9 through the pipe IS. The stop prevents the piston when in its lowermost position from interfering with the admission of fluid to the chamber 8 from the cable.

The free piston 6 comprises top and bottom plates l1 and i8 between which are located a l9, two being shown in the present illustration. Each ring has a pair of oppositely inclined or beveled peripheral surfaces 20 for engagement with packing rings 2| which are made of material that is somewhat elastic. The top and bottom plates or heads are also provided with beveled faces or surfaces 22 which cooperate with the surfaces 20 to force the packing rings outwardly into contact with the wall of cylinder 5. The floating rings and the end plates have cooperating engaging shoulders 23 and 24 which prevent undue lateral displacement of one part with respect to another, especially when pressure is applied to the plates. Each floating ring has shoulders on opposite sides thereof, one shoulder suchas 24 engages a flange on a head while shoulder 25 engages a shoulder on the adjacent ring. The packing rings are of trapezoidal cross-section, are fitted into substantially conical recesses, and are pressed tightly against the wall of the cylinder by a wedging action due to the beveled or coned surfaces, for example when the upper plate I! is subjected to gas pressure and the lower plate I 8 to cable liquid pressure. The packing rings may be made of rubber where the fluids to which they are exposed do not adversely affect them, or they may be made of any other convenient artificial material which is resistive to the action of fluids.

The plates are loosely connected which permits of a limited freedom of movement of the floati9. This has the advantage of equalizing the pressures on the packing rings instead of causing a higher pressure at one region over that of another. To accomplish this, the upper plate I! has a hub-like socketed center which is screw threaded to receive and retain the threaded part of member 26. The member has a sleeve-like extension in which is located a cylindrical element 21 secured to the lower head l8, the two parts 26, 21 having an easy sliding flt, thus acting to allgnthe heads. The sleeve 28 has a slot 28 to receive an end of a pin 28 fastened to the element 21, the slot walls and the pin limiting the maximum separation of the end plates and preventing relative angular movement of the parts. The lower plate has a hub-like socketed center portion which has a screw threaded opening to receive the lower end of the cylindrical part 21. The screw threaded arrangement permits of a limited amount of vertical adjustment. As indicated, the arrangement above described permits of limited independent movements of the heads and rings. Because the heads and floating rings are not positively connected, the pressures on the several packing rings are equalized both vertically and laterally with the result of affording a complete separation of the gas and cable liquid. Stated another way, the floating rings have a limited amount of play. The top and bottom plates have smooth edges and make an easy fltwithin the cylinder so that, they will not injure the smooth surface of the cylinder wall as the piston moves up and down. As will be noted, the end plates are always under pressure when the reservoir is in use, the pressures acting in opposite directions. As the cable liquid or fluid expands, the free piston is pushed upwardly in opposition to the gas pressure in chamber 1. When the cable fluid contracts, the gas pressure forces the piston downward and thus the cable fluid is maintained under the predetermined positive pressure and the formation of voids or gas containing spaces in the cable prevented. I have described the chamber 1 fllled with gas and chambers and 9 with cable fluid but this arrangement can be reversed. The free piston being constantly under opposing fluid pressures, the packing will always be under pressure and in contact with the cylinder wall. As a result of this, there will be at'all times a complete separation of the fluids and there will be no opportunity for one fluid to leak into the other. There will be very little tendency in this respect for the pressures quickly become equal and opposite.

From another viewpoint, a piston structure according to my invention has two axially spaced end plates l1, I! with annular cylindrical projections facing each other and forming cylindrical surfaces or shoulders 23. The two end plates or heads are connected by a loose connection 21,

28, 29 permitting limited axial movement of each head independent of the other head. Ring means are interposed between the heads. These rin means have an outer diameter equal to that of the heads and form cylindrical projections telescoping with the'p'rojecti'ons of the heads and forming together with the latter annular grooves for receiving elastic packing rings.

My invention has been described in connection with a cable but it may be used with other types of electrical apparatus where separation of two fluids, both under pressure, is desirable.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A piston for use in a cylinder the opposite ends of which are subjected to fluid pressures comprising a member in the cylinder separating the two fluid pressures and movable in response to changes of pressure on opposite sides thereof, the member having end heads, each of which has an outwardly beveled surface, means connecting the heads permitting of a limited axial movement of one with respect to the other, floating rings located between the heads and capable of limited axial movements with respect to the heads, the ringshaving outwardly beveled surfaces, and packings between the beveled surfaces of the rings and between a ring and a head, said packings being forced outwardly against'the cylinder wall by the opposing fluid pressures on said end heads.

2. A piston for use in a cylinder the opposite ends of which are subjected to fluids under predetermined positive pressure, comprising a member having end heads, an annular flange on each head, a mechanical connection between the heads permitting a limited amount of independent axial movement thereof, a series of floating rings ach having annular shoulders on opposite sides thereof, certain of said shoulders cooperating with each other and others with the flanges on the heads to restrict sidewise movement while permitting of a greater axial movement, and compressible packings adjacent the shoulders which are forced outwardly by the pressures at opposite ends of the cylinder exerted on the heads.

3. A piston for use in a cylinder the opposite ends of which are subjected to fluids under predetermined-positive pressure, comprising a member having end heads, each of which has a conical peripheral surface, an annular flange on each head, a series of floating rings, each having outwardly extending conical surfaces and annular shoulders, one on each side thereof, one of the shoulders on each of the end rings engaging a flange on a head, the adjacent shoulders on the rings engaging each other, the shoulders and flanges permitting axial movement of one part with respect to another, packings located between the conical surfaces which are forced outwardly against the cylinder wall due to the opposing pressures at opposite ends of the cylinder exerted on the heads, and means for limiting the separation of the end heads.

4. Piston structure comprising axially spaced end heads of like diameter with annular projections facing each other, loose connecting means aligning the heads and permitting limited independent axial movement of each head, floating ring means having an outer diameter equal to the diameter of the heads being interposed between the heads and having annular projections telescoping the head projections and defining therewith annular grooves for accommodating packing ring means.

5. Piston structure comprising axially spaced heads of like diameter having annular projections facing each other, means loosely connecting theheads and permiting limited independent movement of each head, a plurality of floating rings each having a diameter equal to that of the heads and forming an annular axial projection on each side, the annular projections of adjacent rings telescoping each other and forming a groove for accommodating a packing and the ring projections adjacent the heads telescoping the respective projections of the heads and forming other annular grooves for accommodating packing rings.

' WALTER van m BERG.

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