US3514113A - Sealing mechanism for high pressure piston pumps - Google Patents

Description

y 6, 1970 K. WEISWURM 3,514,113

SEALING MECHANISM FOR HIGH PRESSURE PISTON PUMPS Filed July 26, 1967 IN VEN TOR. 04 640 wf/a' woe/v m m M United States Patent Ofiice 3,514,113 Patented May 26, 1970 US. Cl. 277-3 5 Claims ABSTRACT OF THE DISCLOSURE A pressure-actuated, resilient seal is mounted in close tolerance, sliding fit relation on the piston of a high pressure piston pump, and is pulley-shaped to form an inner, pressure chamber that surrounds the seal. An outer pressure vessel, mounted on top of the pump housing, communicates with the inner pressure chamber by means of a pair of fluid passages connected therebetween, and contains a non-compressible fluid that fills both the inner chamber and connecting fluid passages.

A connecting line extends between the compression chamber of the pump and the top surface of the noncompressible fluid in the outer pressure vessel, and is used to transmit pressure in the pump compression chamber by way of the non-compressible fluid to the inner, pressure chamber and thus apply a sealing force to the resilient piston seal.

Background of the invention This invention relates to the field of pressure-actuated resilient piston seals particularly as they apply to high pressure piston pumps.

In the previous development of resilient seals per se, conventional methods have included use of a mechanically applied force with or without pressure actuated means combined therewith to apply a sealing force to the seal. The advantages offered by the use of pressure'actuation in either applying, or assisting in the maintenance of the seal in its sealed position are obvious. Not only is the pressure actuated seal relatively independent of any inherent loss of resiliency normally occurring as a result of its prolonged, or frequent use, but it also tends to compensate for any uncertainty in what degree of mechanically applied force is adequate to deflect the seal to an eflective sealed condition.

The present piston sealing mechanism was specifically developed for use on a high pressure piston pump designed to maintain a uniform gas pressure level in the main storage tank involved in the refilling or recharging of the divers supply tanks used with Scuba equipment. In this regard, in order to increase the duration of underwater time available to such divers, it has been proposed to pressurize their supply tanks with gas at relatively high pressure, thus increasing the amount of gas available in each tank. Since the use of a pressurized storage tank without a pump would mean that, after each refill or recharge of a divers supply tank, the pressure therein would decrease a significant amount, it is self-evident that a high pressure pumping system was required to maintain the gas pressure in the main storage tank at its initial level in order that the entire gas supply stored therein would be available for recharging purposes at maximum efficiency. For example, if the initial pressure were 2200 psi, one recharge would reduce the pressure to about 1800 p.s.i., a second refill to about 1400 p.s.i., and so on. Perhaps only about one half of the gas stored in the storage tank would be used and therefore, the cost of a diving operation would become excessive.

In considering the use of a high pressure piston pumping system to maintain a uniform gas pressure in the main storage tank used in connection with Scuba operations, an improved high pressure piston sealing mechanism of the type developed in the present invention was found necessary for maximum efficiency of operation of the pumping system. In particular, the present sealing mechanism constitutes an improvement in both sealing the piston and, in addition, in reducing excessive friction Wear between the seal and piston normally inherent in other sealing means used with similar pumping systems, as will be explained hereinafter in detail.

Summary of the invention The principal object of the present invention, therefore, is in the provision of a new high pressure piston pumpsealing mechanism having unique and improved means adaptable to automatically create, apply and control the required sealing force at the piston seal.

A further object of the invention resides in the use of a high pressure piston pumping system having an improved piston sealing mechanism incorporating fluidpressure means adapted to transmit and apply the relatively high pressure developed by the pumping system itself to the piston seal, combined with novel gas pressure-transmitting means adapted to automatically compensate for the relatively high pressures tending to unseat the piston seal.

A still further object of the invention is in the use of a high pressure piston pump sealing mechanism utilizing new and novel pressure means adapted to transmit and apply a positive sealing pressure on the piston seal, coupled with unique fluid pressure means constituting a part of said pressure-transmitting and applying means and automatically periodically applying the full sealing pressure developed in the pump in a direction tending to activate the seal to its fully sealed position just before the same internal pump pressure becomes fully effective to act against and thereby prevent the seal from being activated to its fully sealed position is just equivalent to a slight overpressure sufficient to overcome the internal pump pressure and activate the seal to its piston-sealed position with minimum friction between the piston and seal.

Other objects and advantages of the invention will become apparent from the following detailed description, taken in connection with the simple figure of the drawing, which represents a partly schematic and broken-away, sectional view of the preferred embodiment.

Description of the preferred embodiment Referring to the single figure of the drawing, the improved seal of the present invention, which may be formed of any suitable resilient material, is indicated at 1 and includes a straight bore center opening that is dimensioned to provide a close tolerance, sliding fit on the piston 2 with a smooth finish. Seal 1 is unique in that it is made pulley-shaped as shown to form an inner, pressure chamber illustrated at 6 that is an integral part of the seal 1 and is disposed in circumferential or surrounding relation to the seal and therefore provides a positive means for applying any pressure transmitted thereto as a sealing force directly against the active sealing portion of the seal 1 that is disposed or arranged adjacent to the piston 2. Both the seal 1 and the piston 2 are enclosed within a pump housing assembly that in cludes the front, center and rear housing parts indicated at 3, 4 and 5, respectively. Center part 4 which is shown bolted to and disposed between front and rear parts 3 and 5, incorporates a straight bore center opening somewhat similar to that of seal 1 but considerably enlarged over that of either front or rear part 3, 5. in this manner, center part 4 incorporates a substantially reduced inside diameter portion that is arranged in a position to ensure the completion of the previously noted inner pressure chamber 6, initially formed by the shape of the seal 1. Center part 4 also incorporates a fluid passage at 4a, which passage 4a connects to and is continuous with a similar fluid passage 7 formed in an upper pressure vessel 8 that is mounted by suitable hardware (not shown) on the top of pump housing parts 3, 4, 5. Fluid passage 7 extends from its connection with passage 4a in an upward direction, as viewed in the single figure of the drawing, to form a continuous fluid passageway that is in communication with the interior of the pressure vessel 8. A non-compressible fluid with its top surface shown at 11 as filling only part of the said pressure vessel 8 is used to fill both the connecting fluid passages 4a and also 7, and the previously-noted pressure chamber 6. Thus, any pressure applied to the said top surface 11 of the fluid is directly transmitted thereby undiminished to the aforesaid inner pressure chamber 6 which, in turn, applies a sealing pressure to the seal 1.

A principal feature of the present arrangement is in the provision of a connecting line as at 9, between the pump compression chamber at 10 and the aforesaid outer pressure vessel 8 to thereby apply pressure formed within said compression chamber 10 directly to the top surface 11 of the noncompressible fluid which is utilized to further transmit the pressure applied thereto by connecting line 9 to the inner pressure chamber 6, as noted hereinabove. Thus, the pressure formed within the pump compression chamber, and against which the seal 1 is used to seal the piston, is utilized in the unique manner of the present invention to actually apply the required sealing force against the seal. Additional O-ring seals may also be provided, as at 12 in the pump housing, should the resilient material used in seal 1 be of the so-called cold molding type.

In its use as an integral part of the means for transmitting and applying a sealing force on the seal 1, the outer pressure vessel 8, in effect constitutes a reservoir for the fluid through which the requisite sealing pressure is applied. As such, it is useful both for facilitating the admission of the fluid to the inventive sealing system, as well as in minimizing the effect of any movement imparted to the fluid column in the said vessel 8 and the interconnecting fluid passages 4a and 7, and the inner pressure vessel 6 during the flexure of the seal 1 between its fully sealed and unsealed positions. In addition, since the outer pressure vessel 8, together with the aforesaid interconnecting fluid passages 4a and 7, and inner chamber 6, forms a significant part of the total pressure-transmitting and applying means of the present invention, the total volume of gas which might otherwise be utilized during the operation of other types of sealing mechanisms is thereby reduced to a considerable extent. This reduction in the total required gas volume in the present arrangement has the most advantageous effect of ensuring a corresponding improvement in the overall piston pump efficiency by causing a considerable increase in the pump compression ratio at the end of the piston pumping stroke.

With the use of the combined gas and fluid pressuretransmitting sealing means hereinbefore explained, the gas pressure formed within the compression chamber 10 is practically immediately transmitted through gas that has previously expanded through the interconnecting gas passage 9 and applied thereby to the top surface 11 of the fluid partially filling the outer pressure vessel 8. This gas pressure is thereafter immediately transmitted undiminished through the fluid in interconnecting fluid passages 4a and 7 to the inner seal pressure chamber 6, which thereafter simultaneously applies the same pressure to activate the seal 1 by flexing the latter-to its fully sealed position around the piston 2. Although the gas pressure formed within the compression chamber 10 also tends to act against the forward or upstream surface of the seal 1 and might be considered to thereby apply the same pressure in an opposite direction against the seal and thus exactly balance or counteract the pressure acting thereagainst in the chamber 6, this opposing action of said gas pressure is, in practice, somewhat delayed in its action. This delay is caused, in effect, by the close tolerance, sliding fit relation normally occurring between the inside surface of the seal 1 and the piston 2. Thus, while the gas pressure exerted from within the compression chamber 10 during each compression stroke of the piston 2 is relatively freely transmitted to the sealing side of the seal 1 by virtue of the pressure-transmitting and applying means 9, 8, 7, 4a and 6, which elements greatly facilitate such sealing action, application of the same gas pressure to the inside surface of the said seal is not facilitated. In other words, gas pressure developed within the chamber 10 must inherently act against the upstream edge surface of the seal 1 and initially counteract the close tolerance sliding fit thereof to the piston 2 before it can enter any space thereby formed between the inside neal surface and piston 2. This initial requirement therefore automatically imposes a measurable delay before the full gas pressure may act in a direction from within the compression chamber 10 tending to unseat the seal 1. In the meantime, the entire pressure developed within said compression chamber 10 is all but immediately transmitted to the inner pressure chamber 6 and thereby to the seal 1 in a direction actually deflecting the said seal to its fully sealed position before the same gas pressure has become fully operative in the opposite direction due to the previously noted delay imposed thereon. Therefore, what is in effect an overpressure is automatically initially formed in the said inner pressure chamber 6 to thereby assure the full deflection of the seal 1 during each compression stroke of the piston 2 to thereby completely seal the latter during the pumping operation of the present assembly.

Thus, a new and improved high pressure piston pump sealing mechanism has been developed by the present invention that includes the unique feature of automatically utilizing the interior pump pressure to apply an over compensating sealing pressure against the piston seal. Moreover, with the further adaptability of the invention both to automatically and periodically limit the maximum sealing pressure applied to the piston seal to that developed during the piston compression stroke, coupled with the application of a lesser but substantial counteracting pressure opposing said sealing pressure, excessive wear of the seal due to friction between the seal and piston is also reduced to a relative minimum.

I claim:

1. An improved sealing mechanism for a high pressure piston pump comprising a pump housing, a compression chamber formed in said housing, a piston slidably positioned in said compression chamber, a resilient seal mounted in substantially fixed relation within said housing and having an inner surface formed from a straight bore center opening and initially circumferentially disposed in close tolerance sliding fit relation on said piston and subsequently adapted to be deflected to a fully sealed position on said piston, and a combined pressure-transmitting and applying means interconnected between said compression chamber and said resilient seal at a position remote from its close tolerance sliding fit relation with said piston and adapted both to automatically transmit the pressure formed within said compression chamber to a sealing pressure suflicient to deflect the seal to its fully sealed position on said piston against the opposing pressure acting to unseat the seal, said pressure-transmitting and applying means further including a gas pressure-transmitting passage means in direct and open communication with and adapted to initially transmit gas pressure equal to the pressure formed within said compression chamber, and a fluid-pressure-transmitting means containing a non-compressible fluid and interconnected between said gas pressure transmitting means and said resilient seal and adapted to automatically apply a sealing force to said seal suflicient to fully seal the piston.

2. An improved sealing mechanism as in claim 1, wherein said fluid pressure transmitting means includes at least one pressure chamber containing a non-compressible fluid and comprising an integral portion of said resilient seal, the fluid in said chamber being acted on by the pressure transmitted thereto by said gas pressure-transmitting passage means to immediately thereafter further transmit the same pressure undiminished to said seal to thereby deflect the latter to its fully sealed position.

3. An improved sealing mechanism for a high pressure piston pump comprising a pump housing, a compression chamber formed in said housing, a piston slidably positioned in said compression chamber, a resilient seal mounted in substantially fixed relation within said housing and having an inner surface formed from a straight bore center opening and initially circumferentially disposed in close tolerance sliding fit relation on said piston and subsequently adapted to be deflected to a fully sealed position on said piston, and a combined pressure-transmitting and applying means interconnected between said compression chamber and said resilient seal at a position remote from its close tolerance sliding fit relation with said piston and adapted both to automatically transmit the pressure formed within said compression chamber to a sealing pressure suflicient to deflect the seal to its fully sealed position on said piston against the opposing pressure acting to unseat the seal, said pressure-transmitting and applying means further comprising an inner pressure chamber formed from, and integral with, said resilient seal, at least one fluid passage connected in communication With the interior of said inner chamber, and gas pressure-transferring means directly interconnected with said compression chamher and further being in communication with said fluid passage and thereby adapted to transmit the pressure applied thereto from said compression chamber as a sealing pressure within said inner chamber and on said resilient seal, the pressure so applied being at least equivalent to that required to seal the piston and which is consistent with the minimum friction between the seal and piston.

4. An improved sealing mechanism as in claim 3, where in said gas pressure transferring means includes an outer pressure vessel adapted to be mounted exteriorly of said pump housing and incorporating a second fluid passage in continuous communication with said first-named fluid passage and containing a non-compressible fluid filling said fluid passage and said inner chamber and utilizable to transmit a sealing pressure.

5. An improved sealing mechanism as in claim 4, said outer pressure vessel being partially filled With fluid and incorporating an upper air space in direct communication with said gas pressure-transferring means to thereby transmit the gas pressure received therefrom undiminished throughout said non-compressible fluid to said seal; said outer pressure vessel further constituting a reservoir of fluid minimizing any changes in the overall fluid level resulting from the deflection of said seal, and still further ensuring a reduction in the total gas volume required in the sealing of said piston to thereby increase the resulting compression ratio in said compression chamber at the end of the piston pumping stroke.

References Cited UNITED STATES PATENTS 1,709,949 4/1929 Rasmussen et al 277-34 2,085,777 7/1937 Williams 277-3 2,193,587 3/1940 Fortune et al. 277-34 2,307,575 1/1943 Davis 277-34 X 2,446,620 8/1948 Swallow et a1. 2773 X 3,337,222 8/1967 Smith et al 277-343 3,352,563 11/1967 Flair 277-27 FOREIGN PATENTS 704,032 2/ 1954 Great Britain.

SAMUEL ROTHBERG, Primary Examiner US. Cl. X.R.

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