US2387598A - Oleopneumatic storage device - Google Patents

Description

Oct. 23, 1945. J, ME RCIER OLEOPNEUMATIC STORAGE DEVICE Filed March 17, 1942 3 Sheets-Sheet l INVENTOR H i ATTORNEY Oct. 23, 1945. J. MERCIER OLEOPNEUMATIC STORAGE DEVICE Filed March 1'7, 1942 3 Sheets-Sheet 2 INVENTOR ATTORNEY.

Oct. 23, 1945. J. MERCIER 2,387,598

OLEOPNEUMATI C STORAGE DEVICE Filed March 17, 1942 5 Shets-Sheet 3 INVENTOR BY zzo, 2414, M942;

A'ITORNEY Patented Oct. 23, 1945 UNITED STATES PATENT OFFICE omormmmnc STORAGE DEVICE Jean Merclcr, New York, N. Y. Application Marchl'l, 1942, Serial No. 435,111

4 Claims. (01. 222-389) This invention relates to an improvement in oleo-pneumatic storage devices consisting of a metallic container and a flexible and elastic bag inside said container. The bags are usually made of natural or synthetic rubber. Such devices are used on aircraft in order to provide a reservoir of oil or similar liquids under pressure. The container has one or more openings to admit and exhaust oil and the bag has an opening for the passage of a gas, in practice air. The bag is filled with air under pressure and closed or connected to a supplementary vessel also containing air under pressure. Oil is supplied under pressure to the container so as to compress the bag. It can then be withdrawn as required. Fresh oil is usually supplied as soon as the pressure falls below a desired value.

The operation of storage devices of this kind will produce frequent and alternating variations of the level of the liquid inside the casing and corresponding fluctuations of pressure.

My invention applies to devices of this kind in which the metallic container has a smooth inner surface and is of smoothly curved shape as, for instance, spherical or oval with or without a cylindrical portion extending between the spherical or oval ends. The bag is attached to one end portion of the container and the liquid is admitted and withdrawn at or near the opposite end of thecontainer.

For the use of such devices on aircraft the following requirements are important: the device must be adapted to hold as much oil as possible. If used together with a supplementary container for compressed air, it should be possible to fill the container with oil until the air is almost completely expelled from the bag. In the absence of a supplementary container the device will usually hold, at maximum pressure a quantity of oil exceeding one half and sometimes three quarters of its volume.

On the other hand, when oil is withdrawn and the bag expands it is equally important that by progressive expansion of said bag as much oil as possible and, in the case of an extreme expansion, practically all oil be expelled from the container.

In order to expel the oil as required it is necessary to avoid oil-pockets between the outer side of the bag and the wall of the container. Such oil pockets are harmful not only on account of the amount of oil lost for useful purposes but also because their presence may create a lack of uniformity in the stresses acting on the bag.

Storage devices of this kind, when used on aircraft, must usually work under high pressure.

When the bag is used alone, i. e. without an auxiliary container for air under pressure, it may be filled with air up to a. pressure of, for instance, 100-200 kg. per cm When the device is in operation and the bag is accordingly compressed, the pressure may rise to about 300-600 kg. per cm. or even more.

On account of the high pressure prevailing in the bag, even if no oil is present in the container, for instance, in a case in which, due to an emergency, the oil in the storage device has been completely utilized, the bag is subject to the risk of being forced into the oil-passage of the container and injured.

Attempts have been made to construct bags meeting these requirements. Similar bags have been proposed for use in shock absorbers or storage devices for other purposes. All these former proposals present shortcomings, either. because they do not meet all of the above described requirements or because the resistance of the bag to wear is not suflicient and consequently the device is not reliable.

According to the present invention, the bag is made in such dimensions with respect to those ofthe container that its operation therein 'will cause flexible and elastic but preponderantly flexible deformations of the bag. As a general rule, I have found that bags for the purpose described must be, when inflated up to the limit of their flexible deformability, of a shape substantially similar to that of the container, preferably contacting the container over approximately one half of its surface, and must have linear dimensions which are at least and preferably 05% or more of that of the container whereby the bag will occupy'in said condition at least 40% and preferably over 60% of the containers volume. By linear dimensions I mean the length of a sectional circumference, this section lying in a plane including a section of the oil passage member. The said condition of the bag must be reached at a pressure inside the bag of not more than a few hundredths, say l-5/100, of an atmosphere higher than the pressure prevailing outside. Upon further rise in internal pressure relative to the external pressure, the lower portion of the bag will elastically deform until it contacts the wall of the container completely. This elastic deformation of the bag must not expand its linear ings.

Fig. 1 shows a section of a spherical storage device.

Fig. 2 shows a longitudinal section of an elongated oval storage device.

Fig. 3 shows an enlarged section of the disc-like member in the oil-passage member.

Fig. 4 shows a section of an instrument adapted to pierce individual channels into saiddisc-like member.

Fig. 5 shows a partial section of a modification of the bag illustrated in Fig. 2.

Fig. 6 shows a partial longitudinal section of a modification of the device shown in Fig. 2.

Fig. '7 is a view of an outer face of the disc-like element in the oil-passage member.

Fig. 8is a partial view of a modified outer face of the disc-like element in the oil-passage member.

Fig. 9 is a view of another modification of the outer face of the disc-like element in the oil-passage member.

Fig. 10 is a diagrammatic perspective view illustrating the lines of intersection between conical outer portions of adjacent chanels in the disc-like element.

In Figs. 1 and 2, l and l", respectively, designate the container, 2 and 2', respectively, the bag, 3 and 3'. respectively, an air valve, 4 and 4, respectively, the oil-passage member.

The bag is shown in the position which it will.

occupy upon reaching its greatest flexible expansion. In the two examples, the liquid used was mineral oil, and the bag was filled with air. The bag was made of a synthetic rubber compound of the highest possible flexing life consistent with the necessity to preserve an elasticity of 200% at normal temperature.

The diameter of the container shown in Fig. 1 was 13". Consequently the inner circumference of the container was approximately 40" long and the outer circumference of the bag, when inflated up to the limit of its flexible deformability, was 34" long. Therefore the proportion between the linear dimensions of bag and container was approximately 85%, the proportion between their volumesapproximately 61%, and the proportion between their surfaces-i. e. the inner surface of the container and the outer surface of the bagapproximately 72%. The wall of the bag had a thickness of 6" over its upper portion, i. e. that extending between points 5 and 6, and including valve 3. The thickness then increased and reached 3 6" at points I and 8. Between these points, a special reinforcement bringing the thickness up to was provided at the area likely to contact the oil passage.

The longitudinal and transverse dimensions of the container shown in Fig. 2 were 13" and8", respectively. The thickness of the bag from airvalve 3 down to line 9-9 was 1 6"; it then increased gradually and reached 3%" in the area opposite to the oil-passage.

It is an important feature of my invention-to give the bag such dimensions and thickness that it will, when elastically inflated, not only contact the wall of the container progressively in the direction from the air valve to the oil passage but, moreover, do this without displacing at any time any of the parts which are already in contact with the container. In other words, as the inflation of the bag progresses and expands successive parts of it towards and into contact with the wall of the container none of the parts which previously have already reached the latter must be disturbed. For that purpose, the safest way is to test the bags in a container of identical shape with the real metallic container but made of glass or transparent plastic materials. The behavior of the bag can then be readily observed. When an irregular development of the bag is observed, this can be corrected by increasing the thickness of parts which are lagging or reducing that of parts which advance too fast. When it is seen that expansion beyond a certain point causes a disturbance of parts which were already in contact with the container this can be remedied by making the contacting portion of the bag thicker or the other portion thinner. However, when a bag is difllcult to adjust and fails to satisfy even after several corrections this is usually an indication that the bag is too small and should be made bigger. I It has already been proposed to make bags which will contact the container progressively but these bags were too small. During their expansion parts already in contact with the wall of the container are displaced whereby considerable Wear of the bag is caused.

It is of advantage to insert the plug-like passage member 4, 5, as shown so that it projects slightly into container I, l. Whenever bag 2, 2',

comes to rest on member 4, t, and the adjacent portion of container 8, l, the slightest irregularity or discontinuity of the surface supporting the same is liable to cause injury because of the high initial pressure to which bags are inflated according to the present invention. This condition exeludes a structure in which member t is slightly withdrawn in the port of container i into which it is inserted because an angular section would result which could not safely support the bag. It element 4 is flush with the adjacent wall portion of container 5 it must be fitted with the greatest accuracy so as to avoid the presence of any crevice into which the bag could be extruded.

On the contrary, the structure shown avoids any risk of injury to the bag in the simplest possible manner. Whenever the bag is applied against element 4 a part of the liquid present in container i will be trapped in the annular space a surrounding the projecting portion of element 4 and the surface of the trapped liquid will constitute a perfectly smooth bridge between the wall of container l and the inner end face or member 4.

Bags according to the invention may be provided with radial reinforcements tending to control their flexible deformation, 1. e.', to facilitate the folding of the bag in a predetermined manner when the fluid pressure in the container rises, and its unfolding when the latter again decreases The main purpose of controlling the flexible movements of the bag is normally to localize such movement in the zone where the bag can move freely and to avoid movement in the zone adjacent the point where said bag is The outer end portion lower portion of the bag a flat end-face as shown in Fig. l. The bag of Fig. 2 may be modified so as to give it a reinforced fiat .endi'ace as shown in Fig. 5.

It is of great advantage to give the oil-passage member the structure shown in Figs. 1,' 2, 3, 4, 7-10, comprising a plug-like member 32, the inner end portion-I call inner the side of the passage member directed toward the inside of the container and "outer the opposite end or sideof which is constituted by a disc-like element It pierced by a plurality of small channels it of particular shape. As the bag is required to expel the oil completel from the container, if needed, and as the bag will, in such a case, contact the oil-passage member under a pressure which may attain for example 150 kgJcmF, special precautions are necessary to prevent the bag from descending into the channels of the oil passage and from undergoing elastic stresses which it could not resist. It is not feasible to make the channels narrow enough to prevent the contemplated disturbance because this would impair the usefulness of the storage device. It would not be possible either to reinforce the lower end portion of the bag to such an extent that channels of sumcient size could be used because the reinforcement would impair the required elasticity and flexibility of the bag. The structure of'the channels according to my invention has been devised with the purpose of avoiding or at least reducing to a minimum any turbulence in the flowing liquid.

Channels l8 have three portions of different shape, to wit: A central cylindrical portion, an inner and an outer end portion. I call inner the portion directed towards the inside of the container and outer the opposite ortion.

In order to facilitate the clear understanding of the structure of the outer end portion of these channels, it will be helpful to assume that the channels are pierced into the disc-like element I! by an instrument H, a section of which is shown in Figure 4. Portion e of that instrument is to be cylindrical and portion I may be conical or pyramidal. This assumption is made merely to permit a clearer understanding of the structure of these channels, and the present application is not concerned with the actual process of making these channels. It is also clear that the inner end portion of these channels will be made in some other way.

By applying an instrument according to Figure 4 to the disc-like member, we will obtain holes the structure and arrangement of which will be explained in connection with Figure 3. Figure 3 shows an enlarged section of the disc-like element IS. The holes include the central cylindrical portion I 8 and the outer end portion 13. |9 will be conical or pyramidal according to the shape of portion of instrument IT. The walls 20 and 20 defining the outer end portion 9 taper off toward the outer end face 2| of disc-like member IS. The angle included between the tapered surfaces, as shown at 22 in Figure 3, should not be over 9.0 degrees. It is preferably smaller. The tapered portions of walls 20 of adjacent channels should meet along sharp edges. The angle above referred to must be big enough to make the formation of said sharp edges possible within the pracgoal limits for the length of the tapered porone.

If portion 1 of instrument i1 is pyramidal, we may apply it in such manner that adjacent P ramidal holes end in a common base line of the respective pyramids. Figure 3 shows in solid lines two adjacent channels made in this way. The common base line 23 of the two holes lies in the plane of end face 2 I. A view of this outer face 2|, in the case of an embodiment with four channels, is shown in Figure '7. 23 are the common base lines lying in the plane of the figure. Lines 24 indicate the edges of the pyramid and the small circles l8 indicate the central cylindrical portion of the channel. If more holes are required than can be arranged in the aforesaid manner within the periphery of the disclike element, then we would have to apply the instrument l1 so as to produce a hole in the manner shown in dash lines in Figure 3. In that case, the common base line of the two holes will be at 23' and the wall portion defining the first hole between 23 and 23' will be cut away. Figure 8 illustrates a partial view of the outer end face 2| in an embodiment with a plurality of triangular pyramidal holes, of which some extend down to the plane of the figure while others end in common base lines which lie in a plane parallel to that of the figure but located farther inside the disc-like element. Lines 25 indicate common base lines lying in the plane of outer face 2|. Lines 26 indicate common base lines lying in a plane inside the disc-like member. Lines 21 indicate the edges of the triangular pyramids. The small circles 28 indicate the beginning of the central cylindrical portion.

In the case of pyramidal holes, it is generally not necessary to resort to the complicated structure explained above. It is generally simpler to reduce the angle at the summit of the pyramid to obtain any necessary increase in the number of channels. However, if conical holes are desired, then the simplified structure, as illustrated for instance in Figure '7, becomes impossible because. if the cones are to end in the plane of end face 2|, islands will necessarily be left between the outer ends ;of adjacent cones. This would defeat the requirement that the walls of adjacent outer end portions shall meet along sharp edges,

and the absence of these sharp edges may lead to turbulent flow of liquid passing through said channels. Therefore, in the case of conical holes, the latter must be made in the manner illustrated in dash lines in Figure 3 except, of course, for the wall portions 20 nearest the periphery of element I5. Figure 9 illustrates a vie-w of the end face 2| in the case of an embodiment having three channels with conical outer end portions.

. Lines 29 are the lines of intersection between the three cones and lie in a plane perpendicular to that figure. Circles 30 indicate the beginning of the central cylindrical portion of the channels.

Figure 10 is a diagrammatic perspective view illustrating the lines of intersection 29.

In the preceding description of outer end portions of channels |8,'I have explained the structure of regular conical or pyramidal holes. In similar manner, these holes could also be made so as to have irregular pyramidal or conical shape. This would lead to a more complicated structure of the outer end of the disc-like memher 5, but without necessarily affecting the usefulness of channels IS.

The inner opening of the channels toward the bag must be completely rounded off. In practice, I have found it useful to join the cylindrical portion of the channels to the-fiat inner wall of the oil-passage member by a circularly curved flaring portion, the radius of the curvature (shown in Figure 3 at l) being approximately: equal to the radius of the cylindrical part of the channel.

The central cylindrical portion of channels l6 should be as short as possible. pends on the strength of the bag portion likely to come into contact with the oil-passage memher, the properties of the rubber compound employed and the pressure inside the bag when it is fully expanded. Under the usual conditions, I have obtained satisfactory results with diameters from four to ten hundredths of an inch.

The outer port 30 (Figs. 1, 2) of the plug-like passage member for a liquid will receive a pipe 3i (Figs. 1, 2) or the like for supply and discharge of liquid to and from the storage device. The inner endface of the plug-like member has preferably somewhat larger dimensions than the pipe. This wil permit piercing of a sumcient number of individual channels into the inner end of said plug-like member. The number of channels depends on the cross sectional area of the narrowest Its diameter deportion of each channel and the cross sectional area of pipe 3!. The sum of the cross sectional areas of all individual channels-taken at the narrowest point of each channel-shouldnot be less and preferabl more than 50% of the cross sectional area of pipe 3|. Otherwise the usefulness of the storage device will be impaired.

When storage devices of the type described above are used on aircraft, a drawback is sometimes observed when the storage device is brought out of the normal position and-especially when it is inverted-as may happen, for instance, when an airplane is flown upside down-so that the oilpassage member will be above the air-valve. In that case, the oil supplied to the container has the tendency to accumulate around that part of the bag which is attached to the container and the opposite end of the bag is forced by the hyginning at line I! and extending 2 /2" upward.

, The top portion of that bag, extending from the upper limit of the bonded area located at line IS in Fig. 6 up to air valve 3', was then omitted.

The bag must not be bonded too far downwards, i. e., in practice, not over the lower half of the bag or container, so that the portion of the bag which is required to move withrespect to the container when the device is in normal operation remains free to do so.

The point where bag and container are connected together does not need to be disposed at the apex of the container as shown in the drawings. Its place may be selected according to convenience over a relatively wide area reaching from said apex almost down to the line limiting the area where the bag may be bonded to the container. I

The bag is described and shown above in the shape and with the dimensions appropriate for operation. When new bags are made it is to be observed that their form may, in certain cases, change to a certain extent when they are for the first time operated in contact with mineral oil. Thus I have found that bags made of neoprene will frequently increase in size up to 20% during the first Weeks. I prefer to use other rubber compounds which will show no appreciable change, but compounds such as neoprene may also be employed providing that the bag is made correspondingly smaller and stronger.

Whenever I refer in the above specification or in the appended claims to the lower portion of the container, I mean that portion comprising the passage for a liquid, and I refer to the opposite portion as the upper portion. Accordingly I designate as upper and lower portions of the bag those portions thereof contacting the upper and the lower portions of said container when 40 the bag is flexibly or elastically expanded. The

drostatic pressure towards the oil-passage memher. This leads to undesired stresses onthe bag causing it frequently to be elongated to such an extent as to close the oil passage while a considerable amount of oil is retained in the container. To overcome this drawback, it is advantageous to attach the upper portion of the bag or parts thereof permanently to the wall of the container. This may be done by any of the known methods of bonding rubber compounds to metallic surfaces. The portion of the bag to be bonded may vary with different sizes and shapes of bag and container. In the two embodiments illustrated in the drawings, I have found it advantageous to bond the bag from the point where it is connected with the container 3 down to a line shown at I? in Fig. 1 and at 9 in Fig. 2.

Fig. 6 shows a section of the same container as in Fig. 2. The bag 2" is modified so as to contact the container by flexible expansion over a portion extending from the apex of the container down to a circumferential line located at l2. The same portion may be bonded to the container.

Fig. 6 also shows another possible modification. If the bag 2 is bonded to the container over a large area, portions of the bag between the bonded area and valve 3' may be omitted. Bags bonded over an area corresponding to $4; to A; of of the total surface (calculated from the complete bag) are fairly safe from being torn off.

A bag as described in connection with Fig. 2 was modified, in the manner shown in Fig. 6 and explained above, and bonded over an area beterms "upper and lower are used for convenience and not intended to limit the position of the storage device when installed and/or operated.

In the foregoing description, I have disclosed what I deem to be practical and eflicient embodiments of my present invention but I do not mean to be limited thereto. My invention comprises all changes in the arrangement, disposition or form of the parts which may be made without departing from its principal features as comprehended within the scope of the appended claims.

The storage device according to the invention, while devised with special regard to the requirements on aircraft, can with or without slight modifications be put to good use in a great number of other cases, as vehicles, ships or stationary machinery. It can be advantageously applied in connection with all machines or mechanical units wherever storage of an amount of fluid under pressure is desired. Moreover, there is, of course, no limitation as to the choice of fluids with which the device may be operated except for fluids which might corrode or otherwise damage tainer fastened to one of said portions, means to admit and exhaust a fluid to and from said bag,

' a passage for liquid in said container in the poring two smoothly curved portions opposite to each other, a rubber-compound bag in said container fastened to one of said portion-s, means to admit and to exhaust a fluid to and from said bag, a passage for liquid in said container in the portion opposite to that where the bag is fastened, said bag being adapted, when deflated, to contact the wall of said container over an area adjacent said means, and being further adapted,

dimensioned that, when inflated to the limit of its flexible expansion, it will be of smoothly curved and substantially similar shape to that of said container and contact a substantial portion of said wall of the same, and will, when further inflated contact the Wall of said container completely by elastic expansion.

3. Storage device according to claim 1 in which said bag, when inflated to the limit of its flexible expansion, contacts at least 50% of the wall of the container.

4. Storage device comprising a container having two smoothly. curved portions opposite to each other, a rubber-compound bag in said container fastened to one of said portions, means to admit and exhaust a fluid to and from said bag, a passage for liquid in said container in the portion opposite to that where the bag is fastened, said bag being so dimensioned that, when inflated to the limit of its flexible expansion, it will be of smoothly curved and substantially similar shape to that of a portion of the container, having a substantially fiat lower end-face of increased thickness, and will, when further inflated when being inflated, progressively to Contact 25 completely contact by elastic portion the remainfurther portions of said wall without causing a displacement of portions of said bag which are in contact with said wall, and said bag being so ing portion of the wall of said container.

JEAN MERCIE'R.

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