US2261265A - Flexible container - Google Patents

Description

Nov. 4, 1941. v H, MAASS 2,261,265

FLEXIBLE CONTAINER Filed Nov. 20, 1957 3 Sheets-Sheet l Nov. 4', 1941. H. MAAss 2,261,265

FLEXIBLE CONTAINER Filed Nov. 20, 1937 3 Sheets-Sheet 2- Patented Nov. 4, 1941 FLEXIBLE CONTAINER Herbert Maass, Berlin-Halensee, Germany, assignor to Siemens- Schuckertwerke Aktiengesellschaft, Berlin-Siemensstadt, Germany, a

corporation of Germany Application November 20, 1937, Serial No. 175,734 In Germany November 20, 1936 7 Claims.

The present invention relates to fluid systems and, more particularly, to containers of variable volume forming a member of such fluid systems for compressing, expanding, pumping or otherwise impelling a fluid medium.

In the construction of pumps, compressors or the like flexible containers areknown in which two opposite walls are firmly joined with each other along their periphery and the volume of the container is varied by moving the central portions of the wall relatively to the plane of the peripheral curve. If the elastic walls of such container are made of metal, very high stresses occur at relatively smallmovements so that obtainable variation of volume is rather small and the life of the container walls is very limited.

It is an object of the present invention to increase the flexibility of containers of the above type, in order to increase the variable capacity of the container and to reduce the stresses acting upon the material during the operation.

According to the invention a considerable increase in flexibility of the walls of an expansible container for fluid systems is attained by designing the wall shape according to certain novel points of view which will be understood from the following description of the embodiments shown in the drawings in which Figs. 1, 2 and 3 are of explanatory nature and serve to illustrate the considerations underlying the invention;

Fig. 4 exemplifies a shape of the container walls designed according to the invention;

Fig. 5 shows a modification of a portion of the shape shown in 4, and

Figs. 6 and 7 two other shapes of container walls also corresponding to the present invention; while Figs. 8, 9 and 10 explain three further ways of embodying the invention, and

Fig. 11 shows a refrigerator employing a con-' tainer made according to the invention as compressor for the refrigerant, this illustration representing a part-sectional view of the upper portion of the refrigerator.

In referring to Figs. 1, 2 and 3, the factors will at first be considered which, owing to the shape of the peripheral curve of a container of the type here concerned, infiuencethe flexibility of such container. In Fig. lis shown a plan view of a disk in general shape intended to form one of the flexible walls of such a container. In the present case it is assumed that the disk is to be raised at the point 0 out of the plane of illustration and that the periphery of the disk shall remain in this plane. In practice this is accomplished by the fact that the second disk which has the same shape and is joined with the illustrated disk along the common periphery, is correspondingly moved out of the plane of the periphery in the opposite direction.

In considering the two elemental areas OAB and ODE shown in Fig. 1 a ray from the point 0 which upon the movement of the disk is moved farthest from the plane of the peripheral curve, for instance, the straight line R1 or R2, is designated in the following as a radius vector, which straight line in the case of the elemental areas under consideration is the bisecting line of the angles 01 and d2 respectively. The radius vector R1 intersects the peripheral curve under the angle 0'1, the radius vector R2 under the angle c2. s1 and s2 denote the corresponding length of the arc of the elemental areas under consideration. The angle 0'1 amounts to about the angle :72 to about 30.

The elemental areas shown in Fig. 1 are separately considered in Figs. 2 and 3, and these elemental areas are drawn in these cases under the assumption that the pointO is raised out of the original plane through the height h. The perpendicular projection of the triangular elemental area OAB in Fig. 2 shows that the angle 11 1 of the elemental area is smaller than the angle 1 of the perpendicular projection.

Since in the case of flat disks a considerable change of the angle is actually not possible and must be taken up by the resiliency of the material, the change of angle is a measure for the tangential stresses occurring during the motion. Since those diaphragms which consist of two flat circular plates may be considered as composed of single elemental areas of the kind shown in Fig. 2 in which the radius vector intersects the peripheral curvealways under an angle of the reductions of the angles are summed. It

follows that the flexibility of such containers is very limited owing to the high tangential stresses. Since, however, as will be seen from Fig. 3, also an increase of the angle is possible, the stresses may be considerably reduced by a certain dimensioning of the angle of intersection.

A considerably greater flexibility of the container is attained according to the invention by the fact that the angle of intersection between the peripheral curve of the disk and the radius vector amounts in average to 45. When designing the disks, in such a manner, the individual elemental areas of the disks have such a shape that the changes of the angle at the point taken together are as small as possible.

In order to obtain a closed peripheral curve for the disk in which the angle of intersection between this curve and the radius vector amounts in average to 45, the periphery may be composed of different elements. For instance, the peripheral curve may be composed of the portions of a logarithmic spiral with an angle of intersection of 45. Such a case is shown in Fig. 4. Here the peripheral curve of the flat plate is composed of portions GH, HI etc. of a logarithmic spiral in which the angle of intersection 0' between this peripheral curve and any radius vector OK amounts to 45.

In such curve portions of logarithmic spirals the conditions for each elemental area considered corresponding to Fig. 1 are the saine. However, also other curves may be employed whose angle of intersection with the radius vector differs from 45 at certain points. In this case curve portions Whose angle of intersection is smaller than 45 must be allotted as compensation to such curve portions 'whose angle of intersection is greater than 45. This compensation must be eifected in such a manner that the angle of intersection amounts in average'to 45. It follows that in the case of rounded peripheral curves which in certain portions intersect the radius vector under,90, compensating curve portions are necessary in which the angle of intersection is smaller than 45.

In Fig. 5 is shown schematically the manner in which the peripheral curve according to .Fig. 4 may be rounded off. Sp denotes the'logarithmic spiral and Ah? the rounded off curve. 7

The general law according to which compensating curve portions whose angle of intersection in certain portions is smaller than 45 must be allotted to such marginal curves whose angle of intersection is greater than 45 reads as'follows:

sin n +cos n RY SlD'T 'FCOS T2 R2 The designations used in this equation are indicated in Fig. 1. The angle 1' denotes the departures of the angle of intersection between the marginal curve and the radius vector from 45 according to the formula =a-"-45. The elemental areas OAB and ODE in Fig. 1 are so (11- mensioned that the departures of the angle of intersection n from 45 are compensated for by the elemental area ODE with the intersecting angle 0'2. According to the 'above-mentioned'law,

therefore, the compensation is to be effected if, r

for instance, as shown in Fig. 5 the logarithmic spiral Sp is to be rounded off.

In forming the peripheral curve according to the invention also rectilinear portions may be employed. These portions may, for instance, be so arranged that the radius vector which bisects the angle 1 (Fig. 1) intersects the peripheral curve under 45. Such a peripheral curve with rectilinear portions is schematically shown in Fig. 6. A central or hub portion N is provided as is generally required in such flexible containers for supporting the container or for securing thereto a suction conduit and a pressure conduit. Such hub portions may, for instance, be designed with a polygonal cross-section. The plate then contains angular areas. In Fig.5 the hub portion N of the plate has the form of an hexagon from each side of which extend rectangular areas OADE, OCFG etc.

The average value of the angle of intersection in which the material is sharply bent.

case curve portions occur whose angle of intersection is greater than 45, the corresponding compensation must be effected by curve portions whose angle of intersection is smaller than 45 and which lie between two adjacent rectangular areas. Fig. 6 thus shows a rectilinearly limited peripheral curve which is so shaped that the bisecting line OH of the angle on and the bisecting line OK of the angle 9 intersect the peripheral portions AB and BC under an angle of 45.

If the periphery is composed of a plurality of spiral or rectilinear portions which abut each other so as to form a pointed angle, the surface,

as recognizable fromFigs. 2 and'6, when operating the containeryassurn'es 'the form of ridges Sucha ridge formation is not permissible in materials resistant to bending. Consequently, as shown in Fig. 5 such peripheral curves'are preferable in which the curve portions comprising theperiphery are correspondingly rounded off. 'However, the invention may also be carried into practice in such a manner that uniformly bent peripheral curves are employed. Since according to the invention the angle of intersection between the radius 'vector and the marginal curve should amount in average to 45, star-like figures St such'as shown in Fig. 7 are thus obtained.

The provision of a hub area in the case of unifolmly'bent peripheral curves may be effected by maintaining this uniform curvature in such a manner that 'all radii vectors are lengthenedby the radius of the hub area in the manner shown in Fig. 7 by a dotted line. The periphery Sin is then obtained.

In some practical cases a still greater flexibility of such containers maybe attained if the angle of intersection between the periphery and the radius vector is 'in average chosen somewhat greater than 45, for instance 46.

In'the case of'flexible'contai'ners thehub'p'ortions of the walls which in most cases have a'c'ircular. oval or the like shape may be replaced by a polygon, from each side of which extend rectangular areas whose outerside forms part of the periphery. This case is shown'in' Fig. 8 in which N denotes the circular hub of a flexible container wall which when dimensioning the marginal curve is replaced by a hexagon S. From the sides of the hexagon extend rectangular areas such as ABCD and AEFfGQand between the adjacent outer cornersBand E'of neighboring'rectangles is inserted a uniformly curved portion of the peripheral curve. This 'portion,"for instance, maycorrespo'nd to thecontourheveloped by correspondingly rounding ofi, frorn'the logarithmic spiral. In this-case in order to [prevent sharp points when rounding off' the peripheral curve also such portions are employed in which theradius from'the'point A intersects 'the periphery under According to Fig. 9 also -trapezoidal areas AIHD and AKLG'may be inserted, in which case a uniformly bent curve portion inserted between the angles I and K. In this case the average value .is formed along the contour BIKE so that also in this case the rectangular areas ABCD and AEFG are not considered whenforming the average value. If such rectangularly ortrapezoidally limited 7 intermediate areas are employed when designing the container, a continuously curved closed periphery cannot be attained, so that certain non-uniform changes in the bending stresses occur in the tangential direction.

The possibility shown in Fig. 7, taking into consideration the hub areawhen dimensioning the container wall, is insufficient if the hub is relatively large. If a uniformly bent periphery is to be obtained while providing a hub of relatively large diameter, the following way may be followed:

For this consideration it is assumed that the hub is replaced by a polygon, and rectangular and triangular areas .of equal height are drawn on the polygon sides, the vertexes of the triangular areas lying on the periphery of the wall plate, as Will be apparent from the discussion of Fig. 10 following later. The average value for each angle of the polygon is formed according to a contour line in which an angle of the rectangle on one of the polygon sides runs through the corresponding vertex of the triangle to the vertex of the adjacent triangle and then to the triangle of the rectangle relative to the other polygon side, in which case the valuesbelonging to the portions of contour line traversed in the opposite direction to that in which the periphery proper is'traversed-must be considered with opposite signs. In this case the polygon is so arranged that the vertexes of the two triangles belonging to a polygon angle lie at the points nearest and farthest from the center of the polygon and that the corresponding polygon sides are perpendicular to the line extending from the sides of the polygon to the respective vertexes of the triangles. The average value is formed according to the invention by considering the above-mentioned law for the equalization of the angles.

Fig. 10 shows an embodiment of foregoing type. N denotes the circular hub area of a plate. The hub is replaced by an equilateral hexagon S which is so arranged that the two vertexes M and O of the triangles DMA and AOG respectively belonging to the polygon angle A lie at points nearest and farthest from the center of the polygon and that the corresponding polygon sides AD and AG are perpendicular to the lines MP and OP. Between the points M and O is inserted a uniformly bent peripheral curve portion. This curve portion is shaped by considering the above-mentioned law for the formation of the average value which is formed along the trace B, M, O, E in the direction of the arrow. The values corresponding to the rectilinear curve portions B, M and 0, E are to be considered in this calculation with opposite sign as the values corresponding to the marginal curve portion Fig. 11 shows a practical embodiment of the invention in diagrammatic form in which is illustrated a domestic refrigerator equipped with a refrigerating apparatus of the compressor type.

A container consisting of two flexible walls I and firmly secured to the refrigerator cab-met, whereas the hub 4 is connected with a rod 6 movable in the upward and downward direction which is driven by a crank 1. The rod 6 is held by a guide 8 so that it carries out only an upward and downward movement upon the rotation of the crank I. The crank is driven by an electric motor 9 mounted on the top of the cabinet. A suction conduit H and a pressure conduit 12 extend through the lower hub 5. In the conduit II is arranged a suction valve l3 and in the conduit l2 a pressure valve l4. During the suction stroke of the compressor the refrigerant .is drawn into the working chamber of the compressor from the evaporator l5 shown schematically. through the suction conduit H and is forced into the condenser IB through the pressure conduit l2 during the compression stroke. The liquefied refrigerant collects in the container I! in which is arranged a float valve l 8 and passes into the evaporator l5 through the conduit I9. For a better dissipation of the heat of condensation and of the heat liberated in the compressor and the driving motor 9 a ventilator motor 20 is provided which supplies cooling air in the direction indicated by the arrows over the heat dissipating parts of the set. The cooling air enters the hood 2! at the side where the condenser is arranged and leaves. the hood through air outlet ports 22.

What is claimed is:

1. A member of a fluid system comprising a container of variable volume having two congruously shaped flexible walls connected with each I other along their periphery, said walls having a uniformly bent peripheral curve forming with the radius vector an angle of intersection averaging 45, said curve composed of individual portions of a logarithmic spiral forming with the radius vector an angle of intersection of approximately 45, and rounding-01f portions connecting said spiral portions, said rounding-off portions having parts forming with the radius vector an angle of intersection smaller than 45 allotted to parts forming an angle of intersection. greater than 45 so that the average angle of intersection of said rounding-off portions also amounts to approximately 45.

2. A member of a fluid system, comprising a container of variable volume having two opposite walls consisting of flexible plates of flat shape having a polygonal hub area, a plurality of rectangular areas extending radially from said hub area, and a quadrangular area located between each pair of neighboring rectangular areas and forming a tip projecting radially over said rectangular areas, said projecting rectangular area having its sides which form part of the periphery of said plates designed to intersect the radius vector with an angle amounting to 45 average.

3. As a member of a fluid system, a container of variable volume comprising two opposite flexible walls joined with each other along their periphery and having a substantially plane shape with their center areas substantially in contact with each other at the end of the pressure stroke of the container, said walls having a peripheral curve forming with the radius vector an angle of intersection averaging 45, a polygonal hub area, and equilateral triangular areas of two different heights radially extending from the sides of said polygonal area and having their vertexes lying alternately on the nearest and farthest points respectively of said peripheral curve as distanced from the center of said polygonal area, the portion of said peripheral curve connecting adjacent vertexes being uniformly bent so as to run outwardly from a rectangle: circumscribed to and having a common basis with each of said lower equilateral triangular areas and inwardly from the top side of a rectangle circumscribed to and having a common basis with each of said higher triangular areas, the curvature of said peripheral curve near the top sides of said rectangles compensating each other so that the greater angle of intersection with the radius vector near the lower rectangles compensates for the smaller angle of intersection near the higher rectangles so as'to result in said average angle of 45.

LAs a member of a fluid system, an expansible container composed of tWo congruous flexible wall plates arranged in face-to-face relationship and having a peripheral curve forming with the :radius vector an angle of intersection of 45 average, said flexible wall plates being tightly sealed to .each other along said peripheral curve andhaving a flat and plane shape when in relaxed position so as to have the tendency to have their central portions contact each other while permitting said central portions relative movements away from each other against said tendency.

5. As a member of a fluid system, an expansible container having two opposite congruous flexible walls sealed to each other along their periphery and having a fiat and plane shape when in relaxed positionso as to have the tendency to keep their central portions in contact with each other while permitting said central portions relative movements-away from each other against said tendency, said walls having a peripheral curve which comprises rectilinear portions forming outwardly pointing triangles, said rectilinear portions being-arranged to form with the radius vector bisecting the angle at the vertex of. said triangles an angle of intersection of average.

6. As amember of a fluid system, an expansible container having two opposite congruous flexible walls sealed to each other along their periphery andhaving a fiat and plane shape when in relaxed position so as to have the tendency to keep their central portionsvin contact with each other while permitting said'central portions relative movements away from each other against said tendency,lsaid walls having a uniformly bent peripheral curve presenting a plurality of rounded tips and forming with the radius vector an angle of intersection of 45 average.

7. A member of a fluid system comprising a container of variable volume having two congruously shaped flexible walls consisting of flat plates and connected with each other along their periphery so as to have their hub portions movablerelatively toeach other, said walls having a peripheral curve composed of portions forming with the radius vector an angle of intersection greater than 45 and portions forming an angle of intersection smaller than 45, said latter portions. being arranged as compensation with respect to said former portions so that the angle of intersection between said curve and the radius vector amounts to 45 average.

HERBERT MAASS.

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