US 3847513 A
An air pump capable of delivering air under pressure completely devoid of entrained oil particles. The pump employs diaphragms and flexible reeds to avoid the necessity for lubricated sliding surfaces.
Description (OCR text may contain errors)
Unite States Patent 11 1 Foster Nov. 12, 1974 15 1 AIR PUMP 2,550,392 4 1951 Venning 74/55 75 Inventor: 0311161 5. 265m, Grosse Pointe 3211- Woods Mlch- 3,156,405 10/1964 CUI'Werl.... 417/416 3,162,324 12/1964 Houser 417/395  Ass'gnee Gale 3,166,239 1/1965 Greenhal gh 1 92/100  Filed: Dec. 15, 1971 3,514,231 5 1970 Belden 417/566 1211 Appl. No.: 132,554 FOREIGN PATENTS OR APPLICATIONS RelatedllLs Application Data 1,013,298 8/1963 Czechoslovakia 417/413 63 Sb.'t f S.N.797,761,Fb.1,1969, g gg f z er e 0 Pr1maryExammerW1ll1am L. Freeh Attorney, Agent, or FirmWhittemore, Hulbert & 1521 u.s.c1. 417/571, 92/98 RD Belknap  Int. Cl. ..f F04b 21/62  Field of Search 92/137, 100; 417/569, 565,  ABSTRACT 417/566 An air pump capable of delivering air under pressure completely devoid of entrained oil particles. The  References C'ted pump employs diaphragms and flexible reeds to avoid UNITED STATES PATENTS the necessity for lubricated sliding surfaces. 2,118,492 5/1938 Clark 92/137 2,483,218 9/1949 Meath 417/568 7 3 Drawmg m a 3 72 N, 7 9o l 1' R 1 30- 56 J 9 1 34 Efi 40 4e o I o 12 2o 16 AIR PUMP C ROSS-REFERENC E TO RELATED APPLICATION The present application is a substitute for abandoned application in the name of Daniel S. Foster, Ser. No. 797,761, filed Feb. 10, 1969, now abandoned.
BRIEF SUMMARY OF THE INVENTION Pumps for the purpose of delivering compressed air or oxygen or other gases, particularly in therapeutic use, should be capable of delivering the gas under pressure substantially completely devoid of entrained particles of oil or other lubricating material, which have pronounced harmful effects if taken into the lungs of a patient.
The present invention avoids the possibility of entrained particles of the character described by eliminating the necessity for conventional lubrication, particularly in the areas contacted by air or other vapor to be compressed and delivered by the pump.
This is accomplished primarily by providing a diaphragm type pump or a modified diaphragm pump employing generally a piston movable in a cylinder in which space is provided surrounding the piston, which space is enclosed by a flexible diaphragm. The piston is guided for its reciprocating movement by a pair of parallel flexible reeds which maintain orientation of the piston element while at the same time guiding it in a curved path approximating a straight line parallel to the axis of the cylinder.
The means for driving the piston element is a crank employing a flexible reed as a connecting rod and thus avoiding the necessity for lubricated bearings between the connecting rod and piston.
A special feature of the invention is in the location of the crank such that the tendency for the flexible reed to assume an S-shape under compression is substantially eliminated.
It is accordingly an object of the present invention to provide an air pump primarily for therapeutic use employing diaphragm means to eliminate the necessity for lubrication of the pumping elements and employing flexible reeds as guides and a flexible reed as a connecting rod to effect reciprocation of the pumping element.
Other objects and features of the invention will become more apparent as the description proceeds, especially when taken in conjunction with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION The pump comprises a mounting bracket having i an opening 12 through which extends a rotary shaft 14 having a counterbalance 16 attached to one side thereof and having a crank pin 18. Secured t0 the crank pin 18 is a bearing 20 by which a short connecting rod 22 is connected to the crank pin 18.
Carried at the upper end of the bracket 10 is a plate 24 to which is secured a-generally annular cylinder body 26. Extending laterally from one side of the cylinder body 26 is a projection 28 to which are secured reed spacer members 30, 32 and 34, the reed spacers being assembled in the relationship shown in FIG. 1 by an assembly screw 36. Parallel flexible reeds 38 and 40 are provided, the ends of which are clamped by the upper and lower reed spacers 30 and 34 to the center reed spacer 32.
Movable vertically within the cylinder body 26 is a piston 42 to the underside of which are fixedly secured an upper piston spacer 44, an intermediate piston spacer 46, and a lower piston spacer 48 clamping the other ends of reeds 38, 40 as shown.
Interconnecting the rigid connecting rod 22 and the piston 42 is a flexible reed 50 the upper end of which is clamped to the intermediate piston spacer 46 by a reed clamp 52 and clamping screw 54. The lower end of the flexible reed 50 is clamped in a slot provided in the upper end of the connecting rod 22 by a rigid reed clamp 55.
The piston reed spacers 44, 46 and 48 and the reed spacers 30, 32 and 34 are dimensioned to provide parallelism between the flexible reeds 38 and 40 so that there is constituted a parallel linkage which causes the piston 42 to move bodily without change in orientation in a substantially vertical but slightly curved path. However, the clearance between the piston 42 and the inner walls 56 of the cylinder are such as to permit this arcuate or curved linear movement of the piston without engagement between the piston and the cylinder.
In order to provide an effective dry seal between the piston 42 and the cylinder 26 there is provided a flexible diaphragm 58 the intermediate portion of which is clamped to the top surface of the piston by a circular piston cap 60 clamped to the piston 42 by clamping screws 62. The peripheral outer edge of the diaphragm 58 is in the form of an enlarged bead 64 which is received in an annular groove 66 formed in the upper surface of the cylinder, the bead being retained in sealing position by means of a valve plate 68. The valve plate 68 is provided with an inlet port 69 and an outlet port 70.
Mounted on the valve plate 68 is an air filter body 71 having a cavity 72 and an upwardly projecting post 74 provided with a through opening 76 for the passage of air being discharged from the pump. Located within the cavity 72 is a filter 78 which may be formed of any suitable material such for example as a synthetic felt or wool. An air filter cap 80 having an air inlet port 81 closes the open top of the cavity 72 and is retained in place by screws 82.
The bottom wall of the filter body 71 is provided with an inlet aperture 84 substantially smaller than the inlet 69 provided in the valve plate 68. The outlet passage 76 extending through the filter body 71 includes an enlarged chamber 86 which is substantially larger than the outlet port 70 provided in the valve plate 68. A flexible inlet valve 88 is provided between the inlet aperture 84 and the inlet port 69, the valve having a small air passage 90 extending therethrough. Similarly, a flexible valve 92 is provided between the chamber 86 and the smaller outlet passage 70, the valve being provided with a small outlet passage 94.
It will be observed that when the piston is moving downwardly the flexible valve 88 is drawn away from the bottom surface of the filter body by pressure difference above and below the valve so that air may drawn through the filter 78 and port 90 into the cylinder. However, as the piston moves upwardly the flexible valve 88 moves to the position shown, thus closing the port or passage 90 against the shoulder formed between the port 69 and aperture 84. Similarly, when the piston is moving upwardly the flexible valve 92 is flexed upwardly by air pressure away from the upper surface of the valve plate 68 within the chamber 86, thus providing a passage for the escape of compressed air or gas through the outlet 76. When the piston moves downwardly the flexible valve 92 is drawn against the upper surface of the valve plate 68 as shown, thus closing the outlet passage 94. The peripheries of valves 88 and 92 are gripped between valve plate 68 and the bottom wall of the filter body 71.
From the foregoing it will be observed that air drawn into the port 81 passes through the air filter 78 and through the passage 90 in the flexible valve 88 into the cylinder. This air or gas is compressed on upward movement of the piston and is forced out through the passage 94 provided in the flexible valve 92 and thence through the outlet passage 76. This air or gas during its passage through the pump is prevented from coming in contact with any lubricated surfaces and accordingly, perfectly dry air or gas may be compressed without the entrainment of any particles of oil or other lubricant.
It will be observed that the portion of the flexible connecting rod or reed 50 which interconnects the rigid connecting rod 22 to the piston has an intermediate portion below the reed clamp 52 and above the upper end of the lower reed clamp 55 which is capable of flexing when subjected to longitudinal compression.
A stroboscopic examination of the reed 50 while the pump is operating establishes that a reed of the desired flexibility assumes an S-shaped configuration as the reed is subjected to maximum endwise compression adjacent the end of the upward compression stroke of the pump. This condition exists when the center of rotation of the shaft 14 carrying the crank pin 18 is located directly beneath and on the axis of the cylinder 26. This deformation of the flexible reed 50 represents a loss in efficiency and it has been found that the S-shaped deformation is largely avoided if the center of rotation of the shaft, which is designated C in FIG. 1, is moved from the position in alignment with an undeflected reed 50 by a small amount in a direction to eliminate the curvature of the lower portion of the S-shaped distorted reed 50. This condition is illustrated in FIG. 2 where a vertical centerline CL is shown, connecting the axis of rotation C with the upper portion of the reed 50 which is clampd to extend in a vertical direction by the clamps 52. In this Figure the S-shaped deformation of the reed 50 is indicated in dotted lines at 50a. In the present case the loss of efficiency attributable to the distortion of the reed 50 to the shape illustrated at 50a is avoided by shifting the center of rotation of the crank shaft 14 to the position Cb which will cause the lower portion of the reed to assume the condition illustrated by the solid line 50b. The elimination of the upper portion of the S-shaped distortion is accomplished by positioning the lower piston spacer 48 in position to engage the left hand side of the reed as illustrated in the Figure, With this arrangement the reed is effectively retained in approximately straight line relationship when subjected to maximum load.
The amount of lateral displacement of the axis of rotation of the flexible reed in a pump having the dimensions exemplified in FIG. 1 is approximately 0.15 inches. While the dimensional shifting of the axis of rotation is relatively small, the improvement in efficiency of the pump is very substantial.
Referring now to FIG. 3 there is shown a vacuum pump produced from precisely the same components as the pressure pump illustrated in FIG. 1, but produced by inversion of some of the parts.
Identical parts are identified by the same reference characters in this Figure as in FIG. 1. The pump illustrated in FIG. 3 is a vacuum pump adapted to draw air through the port 81 in the cap or cover and to exhaust the evacuated air through port 96. In the case of the vacuum pump shown in FIG. 3, there is no necessity for providing the air filter 78 and instead, within the chamber 72 provided in the body 71 there is provided a tubular insert 98 which may be internally threaded for connection to suitable conduit means leading to the space to be evacuated. The tubular member 98 seats upon annular flange 99 and is of course retained in assembly by the cap or cover 80. The cylinder body 26 is inverted from the position shown in FIG. 1 so that the groove 66 which receives the bead 64 is located at the bottom of the cylinder. The flexible diaphragm 58 is in this instance, connected to the underside of the piston 42 and is clamped thereagainst by the piston cap 60 which is now secured to the underside of the piston 42 by the screws 62. Accordingly, with this arrangement the fold of the flexible diaphragm indicated at 100 which extends downwardly as seen in FIG. 1, now extends upwardly. With this arrangement the vacuum existing in the space above the piston 62 retains the fold of the flexible diaphragm in the correct direction and thus, avoids the tendency to draw the edge portion of the flexible diaphragm into the cylinder, which would exist if a relatively high vacuum existed in the space above the piston with the parts arranged as in FIG. 1.
The drawing and the foregoing specification constitute a description of the improved air pump in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.
What we claim is:
1. An air pump comprising a chamber, a piston movable in said chamber, inlet and outlet valved passages connecting to said chamber, flexible sealing means connecting the periphery of said piston to said chamber, guide means independent of said chamber for said piston, means for reciprocating said piston in the path determined by said guide means, in which said member is formed by a body having a cylindrical opening therethrough and an annular sealing surface at one end, said flexible sealing means is circular and has a peripheral portion in registration with said sealing surface, said chamber having an end wall in the form of a valve plate, said plate overlying said sealing surface and serving to clamp the peripheral portion of said sealing means against said surface, said body being reversible with respect to the remaining structure, the piston being movable with substantial clearance in the cylindrical opening, and a circular cap selectively attachable to opposite sides of the piston to convert the pump from a pump adapted to deliver air under substantial pressure to a pump adapted to produce a relatively high vacuum.
2. A pump as defined in claim 1 in which the portion of the flexible sealing means intermediate the annular sealing surface and the intermediate portion thereof which is clamped to the piston by the circular cap is folded outwardly within the space between the cylindrical opening and the piston for pumping air under pressure, and is folded inwardly in this space when operating as a vacuum pump.
3. An air pump comprising a chamber, a piston movable in said chamber, inlet and outlet valved passages connecting to said chamber, flexible sealing means connecting the periphery of said piston to said chamber, guide means independent of said chamber for said piston, means for reciprocating said piston in the path determined by said guide means, a crank, and a conmecting rod structure including a flexible reed portion connecting said crank to said piston, said reed being sufficiently stiff to operate said piston in compression strokes while said reed is subjected to compressive forces, said reed being secured directly to said crank and constituting the sole driving means between said crank and said piston.
4. A pump as defined in claim 3 in which said guide means comprises a parallel linkage comprising a pair of flexible reeds. Y
5. An air pump comprising a chamber, a piston movable in said chamber, inlet and outlet valved passages connecting to said chamber, flexible sealing means connecting the periphery of said piston to said chamber, guide means independent of said chamber for said piston, and means for reciprocating said piston in the path determined by said guide means, in which said valved passages each comprise a passage portion having a shoulder surface surrounding the passage and transverse to the length of the passage, a flexible valve member spanning the passage and having its edge sealed to said shoulder completely around the passage in a zone spaced radially outwardly from the passage and normally abutting the said surface, said valve member having a passage therethrough near .one edge thereof overlying said shoulder and in position to be closed by said shoulder surface when fluid pressure acting in one direction urges the valve member against said surface but in communication with the passage portion of larger diameter when the valve member is displaced from said shoulder surface by a fluid pressure acting in the opposite direction, in which said guide means comprises parallel linkage comprising a pair of flexible reeds, and in which the means for reciprocating said piston comprises a crank and a connecting rod structure including a flexible reed portion connecting said crank to said piston.
6. An air pump comprising a chamber, a piston movable in said chamber, inlet and outlet valved passages connecting to said chamber, flexible sealing means connecting the periphery of said piston to said chamber, guide means independent of said chamber for said piston, and means for reciprocating said piston in the path determined by said guide means, said chamber comprising a valve plate closing one end of said chamber, a filter body mounted on said valve plate, said filter body having a filter receiving chamber therein, an end wall, an inlet passage in said end wall and a post having an outlet passage therethrough extending from said end wall through the said filter receiving chamber, said end wall having an inlet passage, said valve plate having an inlet passage larger than and in registration with the inlet passage in said end wall, a flexible inlet valve clamped between said inlet passages and across the inlet passages and having a passage normally closed by engagement with the surface of said end wall within the inlet passage in said valve plate, the outlet passage in said post terminating at said valve plate in an enlarged portion larger than and in registration with the outlet passage in said valve plate, a flexible outlet valve clamped between the end wall and valve plate across said outlet passages, said flexible valve having a normally closed outlet passage communicating with the enlarged portion of the outlet passage through said post and normally closed by the surface of said valve plate at the side of the outlet passage therethrough.
7. An air pump comprising a chamber, a piston movable in said chamber, inlet and outlet valved passages connecting to said chamber, flexible sealing means connecting the periphery of said piston to said chamber, guide means independent of said chamber for said piston comprising parallel linkage comprising a pair of flexible reeds fixedly mounted at one end and conected to said piston at the other end, and means for reciprocating said piston in the path determined by said guide means comprising a crank and connecting rod structure including a flexible reed portion connecting said crank to said piston, in which said valved passages each comprises passage portions of different diameters having a shoulder surface transverse to the length of the passage, a flexible valve member spanning the passage and having its edge sealed completely around the valve member to the larger portion of said passage at the juncture between the larger and smaller portions thereof and normally abutting the said surface, said valve member having a passage therethrough near one edge thereof overlying said shoulder and in position to be closed by said shoulder surface when fluid pressure 1 ber is displaced from said shoulder surface.