US2421076A - Accumulator - Google Patents

Description

Ma 27, 1947. B, UNTON 2,421,076

ACCUMULATOR Filed Sept. 4, 1942 FIG. a

- INVENTOR. THOMAS B. LINTON AT ORNEY Patented May 27, 1947 ACCUMULATOR Thomas B. Linton, North Hollywood, Calif., assignor, by mesne assignments, to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application September 4, 1942, Serial No. 457,372

4 Claims.

l This invention relates to hydraulic-pneumatic accumulators of the bladder type for use in hydraulic systems, for example in the hydraulic systems of airplanes.

Accumulators are used for storing hydraulic fluid under pressure. In general, they comprise a shell having an air connection and an hydraulic connection with a flexible partition between the air and hydraulic fluid so that the hydraulic fluid may act against the air without possibility of contamination by the air. The hydraulic fluid acts against the compressed air so that pressure will be maintained in the stored hydraulic fluid. It has been found that accumulators of the bladder type can be made lighter than accumulators of the diaphragm type, and it is with bladder type accumulators that this invention is concerned.

One of the tests to which all accumulators must be subjected is the application of a hydraulic test pressure which is usually double or triple the system pressure, when all air is removed from the accumulator. In such tests the bladder completely collapses, folding back upon itself and being pressed against the air inlet. To prevent the bladder from being extruded into the air inlet, and thereby damaged, metal discs are inserted in the bladder to, bridge or cover the air inlet hole. Therefore, means must be provided to center the metal discs upon collapse of the bladder so that they will fit over the air inlet. Also, means should be provided to cause a radius of bend in the bladder at the point where it folds back upon itself, inasmuch as the synthetic rubber material of the bladder becomes extremely brittle at very low ,test temperatures and may crack if a sharp bend is imposed upon it.

The present invention satisfies both of these requirements, and in general comprises an internal bead Within a bladder which causes a thick localized section which retains its position during deflation of the bladder, causing the bladder to fold about the bead to provide a radius of bend, and at the same time centering the metal discs to cover the air inlet.

It is therefore an object of the invention to provide an accumulator with a bladder which will center metal discs over the air inlet of the accumulator.

It is another object of the invention to provide an accumulator bladder having means to create 2 a radius of bend at the point where the bladder is folded upon deflation.

Still another object is to provide an accumulator bladder which will simultaneously provide a radius of bend for the bladder material and also center metal discs with respect to an air inlet.

In the drawings forming a part of this specification:

Figure l is an elevation view, in full section, of an accumulator of the type embodying the present invention; and

Figure 2 is an elevation view, in full section, of a bladder of elongated shape embodying the invention.

Referring to Figure 1, a shell Ill has welded to the bottom thereof a threaded hydraulic fitting l2 through which hydraulic fluid enters and leaves the accumulator. Welded to the upper end of shell I0 is a collar M which is internally threaded at 16 and provided with a shoulder l8 and an inwardly projecting lip 20. Fitted within shell I0 is a bladder 22 having a preformed shape substantially like the interior of shell l0. Formed on the upper end of bladder 22 is an outwardly projecting lip 24 which hooks over the inwardly projecting lip 20 of collar 14. At about the midsection of bladder 22 there is provided an internal bead 26 which forms the subject matter of the invention. Secured to the bottom of bladder 22 is a lower disc 28 and an upper disc 30 held together by a screw 32. Lower disc 28 fits over hydraulic outlet I2 when the bladder is fully extended as shown in full lines, and upper disc 30 fits over the air inlet as shown in dotted lines.

Placed within collar I4 is a plug member 34 which fits snugly against the upper end of bladder 22 and holds bladder lip 24 in contact with collar lip 20. An annular nut 36 is threaded into collar M to hold plug 34 in place. A cotter pin 38 passes through collar l4 and fits in a slot ill in nut 36 to lock nut 36 in position. Plug 34 has a central hole 42 therethrough into which is threaded an air valve element 44.

In operation, air is inserted into the accumulator through valve element 44 and the bladder assumes the general shape as shown in full lines. There it will be noted that lower disc 28 bridges the opening of hydraulic outlet l2, so that the air pressure will not force the bladder into outlet I2 and damage the bladder by extrusion.

Outlet I2 is then connected to a hydraulic system including a pump, and hydraulic fluid under pressure enters the accumulator forcing the bladder 22 upwardly until the air is compressed to a pressure equal to the hydraulic pressure. Thereafter hydraulic fluid will be added to or subtracted from the accumulator according to the de mands of the hydraulic system and the pressure available from the pump of the hydraulic system.

When it is desired to test the accumulator, the air valve 44 is opened allowing all air to escape from the inside of the bladder 22. Hydraulic fluid under pressure is then pumped in through fitting l 2 and the bladder gradually collapses, the thin lower half of the bladder projecting upwardly into the thicker upper half of the bladder, which maintains its position against the shell l because of its thicker section. The bead 26 guides the lower half evenly into the upper half of the bladder because it is a thickened portion which will resist deformation to a relatively greater extent than the thinner wall of the lower half. Thefinal state is that shown in broken lines in Figure 1, wherein the lower half of the bladder is pressed tightly against the upper half,

and the disc 30 is centered over hole 42. It will be noted from an examination of these broken lines that'there is an appreciable radius to the bend about bead 26. This radius is very important in preserving the bladder because at a low temperature such as 50 R, which may be encountered in actual use, the bladder material becomes somewhat brittle and often cracks if folded fiat upon itself without a radius being provided for the bend.

Shown in Figure 2 is an application of the invention to an elongated bladder 60, which has an upper bead 62 at about the mid-point of the bladder 60 and a lower head 64 below head 62. As the bladder 60 collapses the lower bead 64 will center the lower part of the bladder in its deflation 50 that it will not strike against one wall of the other first and be deflated thereafter by a dragging or rubbing motion against the wall which it touches. Upon further deflation, the bead 64 will curl internally with the rest of the bladder and the bead 62 then tends to center the bladder upon complete deflation, providing a radius of bend as well as centering any disc which may be inserted in the bladder. Figure 2 therefore shows an application of the invention to provide for progressive collapse of the lower part of a bladder such as is accomplished in Figure 1 by thinning the lower wall.

Referring to Figure 1, the bead 26 should be placed midway in the bladder as determined by completely inverting the lower half of the bladder into the upper half as assembled. so that the head will always be at the radius of bend of the bladder. The shape of the bead is important and is preferably an abrupt projection on the lower side and a gentle projection on the upper side, so as to ease the radius of bend to the greatest extent. This desired shape is limited. however, by the complications of molding the bladder 22 and the theoretical shape may be impracticable from the manufacturing standpoint. The shape shown, however, is satisfactory.

The invention has been described with reference to particular embodiments thereof. but it is not intended, however, to limit the invention to these embodiments nor otherwise except by the terms of the following claims.

I claim:

1. An accumulator bladder comprising a bladder of flexible material, and a plurality of transverse annular thickened sections in said bladder to centralize said bladder as it collapses to prevent rubbing of the material and to provide a head of material about which the fold occurs with an appreciable radius of bend for folds in the material.

2. An accumulator comprising a shell having an air opening and a hydraulic opening, a flexible bladder secured therein and separating said air opening from said hydraulic opening, said bladder having a portion conforming to the shape of said shell and having another portion adapted to telescope into said conforming portion, and an inwardly projecting head on said bladder substantially at the line of junction of the two bladder portions, said head forming a pad of material about which the bladder folds with an appreciable radius of bend when the portions completely telescope.

3. An accumulator comprising a shell having an air opening and a hydraulic opening. a flexible bladder secured therein and separating said air opening from said hydraulic opening, said bladder having a thickened portion normally conforming to the shell, and a thinner portion adapted to telescope into said thickened portion. said thickened portion terminating abruptly forming a termination line which allows the thinner portion to fold with an appreciable radius of bend when the portions are telescoped.

4. An accumulator comprising a shell having an air opening and a hydraulic opening. a flexible bladder secured therein and separating said air opening from said hydrau ic opening. said bladder having a ortion conforming o the shape of said shell a d having another port n ada ted to telescope into said conformi g portion. and an inw rd y rojecting head on said b adder substantia lv at the l ne of junction of t e two b adder portions, said head being smoot ly curved and forming a pad of material about which t e b adder folds with an appreciable rad us of bend hen the portions completely telesco e and the bead being of such cross-sectional s ape that t e angle between said other nortion of said bladder and the side of said bead adjacent thereto is less t an the angle between the first-mentioned or on and the other s de of the bead when the bladder is fully distended.

THOMAS B. LINTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,256,835 Mercier Sept. 23. 1941 1,301.354 Baird Apr. 22. 1919 841.791 Lemp Jan. 22, 1907 2.105.160 Pequerez Jan. 11, 1938 2,299,611 Clark Oct. 20. 1942 Re. 20.887 Mercier Oct. 18. 1938 2,246,621 Davis June 24, 1941 FOREIGN PATENTS Number Country Date 5.796 Great Britain May 12, 1885 53,868 Denmark Apr. '17, 1934

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