US1851395A - Pump packing - Google Patents

Description

March 29, 1932. w, J, MacARTHUR 1,851,395

PUMP PACKING Filed May 29; 1930 FIG.I

WILLIAM J. MQSARTHUR p uron M60. I ATTO Er Patented ltlar. 1952 I UNlTED STATES PATENT IOFFICE 4 WILLIAM J. HAOARTHUB, LOS ANGELEB, CALIFORNIA, ASSIGNOB Q1 ONE-BALI '10 m .A. MAYNARD, 0] L08 ANGELES, CALIFORNIA rm racxme Application filed Kay 29, 1980. Serial No. 457,179.

My invention pertains to the art of packing the shafts of centrifugal pumps or the rods or plungers of reciprocating pumps to prevent the leakage of liquids therefrom. More 6 specifically it pertains to the type of packing in which asolid metallic ring is used to surround the rod or shaft and in which leakage is prevented by a close fitting of the ring around the moving part and an end engage- 1 ment of the ring with the inside end of the stufling boxinwhich the ring is placed.-

An object of my invention is to provide a packing suitable for either high or low.

pressures and of-such construction that it will be tight, durable and almost entirely free from frictiom- In a copending application, filed May 29, 1930 under Serial No. 457,178 I have described and claimeda packing element hav-' with a packer of my invention and with the said means for excluding grit, parts being broken away to show the internal construction of the device.

Referring to the figure, A is a pump rod which may be revolvable as in a centrifugal pump or reciprocating as in a plunger or piston pump, B is a broken portion of the ump end, C is the packing box and D a anged gland attached thereto.

The inner end 10 of the packing box is bored to a loose fit over the rod A and the outer end 11 is bored to a greater diameter to accommodate the packing ring 12 and other elements about to be described. The inner face of the gland D is provided with a projection 13 fitting within the bore 11 and with a shoulder 1 1 having its inner face parallel to the squared outer face of the packing box. A copper or other gasket placed between this The figure illustrates a pump end provided shoulder and the face of the box suflices to prevent leakage underneath the gland when the holding bolts 15 which pass through the flanges 1616 are drawn tight.

The packing ring '12 is a solid, rigid ring of steel or other hard metal with squared and faced ends; This ring is a snug sliding fit on the rod and if not so fitted will not function to produce the results which I obtain. The outer diameter of the ring must be materially less than the inner diameter of the bore 11 to allow for free lateral movement of the ring within the box. A radial clearance of should be allowed in any case and in large units the radial clearance may beas much as In the inner end of the packing ring 12 are formed a plurality of longitudinal sockets 17 within which are placed open coil springs 18. These springs are positioned on studs 19 which in turn project upwardly from a floating ring 20. This ring should have an outside diameter no greater than that of the packing ring 12, to permit it free lateral movement, and should fit quite loosely around the rod A. The springs should have only sufficient tension to hold the outer end of the packing ring in engagement with the socket ring later described. The floating ring may be abutted against the inner end of the enlarged bore 11 or it may be nonfrictionally supported on a ring of bearing balls as at 21.

The inner'end of the proj ection 13 from the gland D is formed to the curvature of a spherical are as at 23 and into this arcuate curvature is fitted a socket ring 24, having a correspondingly curved outer end and a flat faced inner end 25 engaging the outer end of the packing ring 12. The curved surfaces should be ground together to the best possible fit, as should also the flat faces. The inner diameter of thesocket ring should be substantially greater than the diameter of the rod and.

the outer diameter should be substantially less than the diameter of the bore, so that the ring will not bind or cramp either on the rod or in the bore in sliding on its arcuate bearing. It will be seen that in this combination the arcuate surfaces slide on each other with a ball and socket movement to per-.

2' mit distortion or whip of the rod while the faced outer end of the packing ring is free to move laterally over the faced inner end of the socket'ring to compensate side movement of the rod.

The packing ring 12 must be a close sliding fit on the rod, a clearance not greater than '2/ 1000 inch and preferably as little as 1/1000 inch radially being indicated. With such slight clearances the metal of the ring is materially compressed under the higher pressures, up to 1000# per square inch, often carried in hydraulic and oil pipe line pumps.

Because of this compression of the ring metal a relatively thin ring, of the order of. A to wall, will often bind on the rod during the discharge stroke even though it be perfectly free during the suction stroke or when the pressure is released. It is therefore desirable to make these rings of substantial thickness, as say to 1 wall or even heavier when the ring is of large diameter.

When rings of such thickness are used the end friction, on the surfaces 23 and 25, rises to a high value, the ring being urged toward these bearing surfaces by a weight which, at any given discharge pressure, is proportional to the cross sectional area of the ring. This end bearing friction may, and in experience often does, become so great as to lock the packing ring against the free lateral movement which is essential to maintaining its freedom on the rod, thus causing the rapid destruction of the ring or the rod or both.

To avoid this difficulty I have provided for relieving the bearing pressure by reducing the contacting area of the faces 23 and 25, as indicated at 26 and 27. The required cut may be taken from either of a pair of engaging faces, or from both, but to ensure freedom in both lateral and arcuate movement each pair of faces should be relieved substantially as shown.

The packing ring 12 and the socket ring 13 are both of materiallyless diameter than the bore 11 in which they are placed, the slots 26 and 27 being thusin free communication with the interior of the pump and being filled with liquid at the same pressure as that which urges the rings toward the bearing faces. The relieved area ofeach ring is thus in static balance as regards pressure and, while the pressure per square inch on the remaining engaging surface is not reduced, the area in frictional contact may be reduced to that of a ring say A,] thick. The pressure per square inch being unchanged by this reduction in area, the frictional resistance to lateral or swivelling movement is reduced in proportion to the reductlon 1n contact area andthe desired freedom-of movement thus permitted I to the rod.

When muddy or ing pumped, and particularly if the pump pressure is high, it is difficult to prevent finegritty water or oil are belydivided abrasive solids from entering the clearance between the rod and the packing ring and destroying the close fit on which leakage tightness depends. I have provided a means for overcoming this diificultyby forcing a suitable liquid into this clearance at a pressure higher than the maximum pump pressure, thus positively excluding abrasives from the sliding surfaces. This means may also be applied to the lubrication of the sliding surfaces if desired.

lVith the packing ring and preferably close to its inner end I form a groove 28. Into this groove at a convenient point a hole 29 is drilled through the wall of the ring and tapped at its outer end. Into this tapped hole I threada piece of small steel tubing 30, this tube passing through a larger diameter opening in the wall of the packing box 0. This opening is provided with a packing gland -31 retaining a suitable soft packing 32.

It will be understood that the packing ring 12 will have no end play in the packing box, even in a reciprocating pump, provided only that the springs 18 are of suflicient strength to prevent the packing ring from retracting during asuction stroke. The soft packing,

therefore, need not be adapted to permit side play to the tube 30, but it must be so inserted as to permit relatively free end play of the tube to an extent equal to the maximum lateral movement of the packing ring within the box. The outer surface of the tube 30 should be truly cylindrical and should be polished.

The outer end of the tube 30 is placed in communication with a source of supply, not shown, of a liquid under pressure. The available pressure must be in excess of the maximum pressure existing within the pump to e tank and discharging back into the tank though a relief valve. These pumps, which in'their action, may be driven from any convenlent source of power, and in these small are well known and understood, are positive sizes will discharge against heads of 1500.# per square inch, or more. The leakage past a properly fitted ring will be extremely small, say not to exceed a gallon in twenty four hours, and if preferred the fluid su ply may be drawn from a small pressure tan having a weighted piston or other suitable means for maintaining a constant pressure under a very slight discharge. v

The sealing fluid must obviously be clean and free from abrasive material. The leakage into the interior of the pump should be so slight that contamination of the pum discharge will be inappreciable, so that a 0st any liquid may be used for sealing. In a pump used for gasoline, such liquid as water or glycerine is to be recommended, the latter in particular as affording some lubrication of the ring, while in a water pump or a crude axis of said rod, and-an anti-friction thrust bearing for urging said packing ring toward said gland; means for preventing the intrusion of abrasive material into the space be-' tween said packing ring and said rod, comprising: a circumferential channel on the inner surface of said packing ring, means for maintaining a supply of nonabrasive liquid at a pressure not less than the maximum pressure within said pump, a metallic tube for said liquid between said circumferential channel and through the packing ring to said liquid supply means.

- 2. In a pump rod packing having a cylindrical box about said rod, a gland closing the outer end of said box, a socket ring engaging said gland upon a small part of its arcuately curved face, a packing ring engaging said socket ring on a plane perpendicular to the axis of said rod, and an anti-friction thrust bearing for urging said packing ring toward said gland; means for preventing the intrusion of abrasive material into the space between said packing ring and said rod, compnsmg: a circumferential channel on the inner surface of said packing ring, means for maintaining a supply of nonabrasive liquid at a pressure not less than the maximum pressure within said pump, and means of communication for said liquid between said circumferential channel and said liquid supply means,- said communieating means passing through the packing ring and through the wall of said box an being free to move therethrough.

In witness that I claim the foregoing'I have hereunto subscribed my name this 10th day of May, 1930.

WILLIAM J. MACARTHUR.

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