Abstract
An air-operated double diaphragm pump, wherein the pump (40) is disposed with a shaft (30) and a bushing (28). The shaft (30) includes a plurality of indentations which allow passage of air and the bushing (28) is adapted to receive the shaft (30) and be in sliding engagement with the shaft (30). The bushing (28) includes vents (22) formed on the bushing and a hole (24) formed at each respective terminal portion of the bushing (28) to allow passage of air. The bushing (28) also includes ribs (26) protruding radially outwards from inner surface of the bushing (28) toward the shaft (30). The indentations (34) disposed along the shaft (30) and hole (24) formed at each terminal portion of the bushing (28) are alignable to create a path for air to travel.
Claims
1. An air-operated double diaphragm pump, characterized in that the pump (40) is disposed with: a shaft (30) in mechanical connection with a first and a second diaphragm (44a & 44b) of the pump (40), the shaft (30) includes a plurality of indentations (34) disposed radially lengthwise along length of the shaft (30), wherein the indentations (34) allow passage of air; and a bushing (28) adapted to receive the shaft (30), the bushing (28) and shaft (30) being in sliding engagement with each other, the bushing (28) includes at least two vents (22) formed on the bushing and a hole (24) formed at each respective terminal portion of the bushing (28) to allow passage of air, the bushing (28) further includes ribs (26) protruding radially outwards from inner surface of the bushing (28) toward the shaft (30) and disposed along length of the bushing (28); wherein the indentations (34) disposed along the shaft (30) and hole (24) formed at each terminal portion of the bushing (28) are alignable to create a path for air to travel.
2. The pump (40) as claimed in claim 1, wherein the shaft (30) is fastened to the first and second diaphragm (44a & 44b).
3. The pump (40) as claimed in claim 2, wherein the shaft (30) further includes a threaded hole (32) formed at each terminal ends of the shaft (30) respectively, the threaded holes (32) are adapted to receive threaded members for mechanical connection with first and second diaphragms (44a & 44b) in order to fasten the shaft (30) to the first and second diaphragm (44a & 44b).
4. The pump (40) as claimed in claim 1, wherein the indentations (34) are disposed at middle portion of the shaft (30).
5. A shaft (30) as claimed in claim 1, wherein the shaft (30) comprises of a plurality of indentations (34) disposed lengthwise along length of the shaft (30), wherein the indentations (34) allow passage of air.
6. A bushing (28) as claimed in claim 1, wherein the bushing (28) comprises of at least two vents (22) formed on the bushing (28) and a hole (24) formed at each respective terminal portion of the bushing (28) to allow passage of air, the bushing (28) further includes ribs (26) disposed along length of the bushing (28) protruding radially from inner surface of the bushing (28) towards shaft (30).
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The drawings constitute a part of this specification and include an exemplary or preferred embodiment of the invention, which may be embodied in various forms. It should be understood, however, the disclosed preferred embodiment is merely exemplary of the invention. Therefore, the figures disclosed herein are not to be interpreted as limiting, but merely as the basis for the claims and for teaching one skilled in the art of the invention.
[0012] FIG. 1a shows a front diagrammatic cross-sectional view of a prior art air-operated double diaphragm pump having a chamber filled with compressed air to pump fluid.
[0013] FIG. 1b shows a front diagrammatic cross-sectional view of the prior art air-operated double diaphragm pump shown in FIG. 1a with a chamber completely filled with compressed air and another chamber filled with fluid.
[0014] FIG. 1c shows a front diagrammatic cross-sectional view of the prior art air-operated double diaphragm pump shown in FIG. 1a having a chamber filled with compressed air and pushing fluid out while in another chamber, air present at air side of the chamber is allowed to escape while drawing fluid in.
[0015] FIG. 1d shows a front diagrammatic cross-sectional view of the prior art air-operated double diaphragm pump shown in FIG. 1a with one chamber completely pushing fluid out while being completely filled with compressed air and another chamber completely pushing air out while being completely filled with fluid.
[0016] FIG. 2a shows an isometric view of a bushing used in a preferred embodiment of the present invention.
[0017] FIG. 2b shows a top cross-sectional view of the bushing shown in FIG. 2a, taken from section B-B of FIG. 2d
[0018] FIG. 2c shows a front cross-sectional view of the bushing shown in FIG. 2a, taken from section C-C of FIG. 2d
[0019] FIG. 2d shows a front view of the bushing shown in FIG. 2a
[0020] FIG. 3a shows an isometric view of a shaft used in a preferred embodiment of the present invention.
[0021] FIG. 3b shows a top view of the bushing shown in FIG. 3a
[0022] FIG. 3c shows a front cross-sectional view of the bushing shown in FIG. 3a, taken from section A-A of FIG. 3b
[0023] FIG. 3d shows a side cross-sectional view of the bushing shown in FIG. 3a, taken from section B-B of FIG. 3c
[0024] FIG. 4a shows a front cross-sectional view of a shaft being in sliding engagement with a bushing.
[0025] FIG. 4b shows the same shaft and bushing shown in FIG. 4a with the shaft having moved to a terminal point.
[0026] FIG. 5a shows a front cross-sectional view of an air-operated double diaphragm pump being the preferred embodiment of the present invention having a chamber being filled with compressed air to pump fluid.
[0027] FIG. 5b shows a front cross sectional view of the air-operated double diaphragm pump shown in FIG. 5a having a chamber filled with compressed air and another chamber filled with fluid.
[0028] FIG. 5c shows a front cross-sectional view of the air-operated double diaphragm pump shown in FIG. 5a having a chamber filled with compressed air and pushing fluid out, while in another chamber, air present at fluid side of the chamber is allowed to escape while drawing fluid in.
[0029] FIG. 5d shows a front cross-sectional view of the air-operated double diaphragm pump shown in FIG. 5a having one chamber completely pushing fluid out while being completely filled with compressed air and another chamber completely pushing air out while being completely filled with fluid.
DETAILED DESCRIPTION OF THE INVENTION
[0030] Detailed description of preferred embodiment of the present invention is disclosed herein. It should be understood, however, that the embodiment is merely exemplary of the present invention, which may be embodied in various forms. Therefore, the details disclosed herein are not to be interpreted as limiting, but merely as the basis for the claim and for teaching one skilled in the art of the invention. The numerical data or ranges used in the specification are not to be construed as limiting.
[0031] Positions of components such as left chamber and right chamber are located as such to aid understanding of the invention and it would be appreciated by a person skilled in the art that positions of such components are not necessarily restricted as how they are described in this description and may vary based on a manufacturer's configuration.
[0032] In a preferred embodiment of the present invention, changes are made to configuration of parts of an AODD pump, in particular, a bushing and a shaft in engagement with the bushing. Such changes enable an increased flow rate of an AODD pump while reducing consumption rate of compressed air which is achieved by reducing obstacles for air to travel from compressed air inlet to compressed air outlet and also mechanical friction between shaft and bushing.
[0033] FIG. 2a shows an isometric view of a bushing (28) while FIG. 2b shows a top cross-sectional view of the same bushing (28), FIG. 2c shows a side cross-sectional view of the bushing (28), and FIG. 2d shows a front view of the bushing (28). Openings (21) at side of the bushing (28) allow a shaft to be passed through and correspond to diameter of shaft to which the bushing (28) is to be fitted such that a sliding fit is achieved. Vents (22) function to allow compressed air to pass through during operation of the AODD pump. Holes (24) receive compressed air from a compressed air inlet which is then directed into a chamber in order to move a diaphragm. As it can be seen in FIG. 2b which shows a cross sectional view from above and FIG. 2c which shows a side cross sectional view from a longitudinal side of the bushing (28), inner diameter of the bushing (28) is not constant, but varies at different sections of the bushing (28) by means of ribs (26) disposed along length of inner surface of the bushing (28) to increase the bushing relief area which improves airflow between bushing (28) and shaft by providing gaps for air to travel and allowing shaft to slide smoothly through bushing (28) as there is less surface area to cause friction between bushing (28) and shaft. These ribs (26) protrude radially from inner surface of the bushing (28) towards shaft and make sliding contact with the shaft. The bushing (28) is preferably made of plastics material such as ABS, DERLIN HDPE, LDPE, PE, however any rigid material with low friction are equally suitable.
[0034] FIG. 3a shows an isometric view of a shaft (30) while FIG. 3b shows a top view of the same shaft (30), FIG. 3c shows a front cross-sectional view of the shaft (30) and FIG. 3d shows a side cross-sectional view of the shaft (30). The shaft is provided with indentations (34) disposed lengthwise at middle portion of the shaft (34). These indentations (34) function to allow air to pass freely through them. The shaft (30) is fastened to left and right diaphragms of an AODD pump at terminal ends of the shaft (30) where threaded holes (32) allow mechanical connection between the shaft (30) and the diaphragms of the AODD pump. The threaded holes (32) are adapted to receive screws, nuts or any elongate member configured for threaded connection. Alternatively, the terminal ends of the shaft (32) may not include threaded holes (32) but other means to allow for mechanical connection to diaphragm such as threaded ends, mating connections, or permanent connections such as welding or adhesives. Similar to the bushing (28), the shaft (30) is preferably made of plastics material such as ABS, HDPE, LDPE, PE, or any rigid material with low friction.
[0035] FIG. 4a shows a cross-sectional view of the shaft (30) which is held by the bushing (28). Compressed air is allowed to pass through vents (22) and holes (24) of the bushing (28). Due to indentations (34) present on shaft (30), compressed air is allowed to pass through freely without blockage when the indentations (34) are aligned with the holes (24) and vents (22). A slide valve (not illustrated) directs compressed air to one side of the bushing (28) which goes into a first chamber and also initiates a first stroke, whereby the shaft (30) is moved to a first terminal point, wherein the terminal point is an end point which the shaft (30) does not travel past and instead changes direction. When the shaft (30) has travelled from one terminal point to another terminal point, a stroke is completed.
[0036] As shown in FIG. 4b when the shaft (30) is moved to a first terminal point, which ends a first stroke, the indentations (34) on the shaft (30) are aligned with holes (24) and vents (22) of the bushing (28) such that a path is created which allows air from a slide valve directed to holes (24) to bleed through the path created by the alignment of the indentations (34) with the holes (24) and vents (22) and exhausted out. This creates a differential pressure which causes the slide valve to change direction and direct air to other side of the shaft (30) and bushing (28). When the slide valve changes direction, it will divert compressed air to the other side of the bushing (28) to a second chamber which initiates a next stroke. Due to quick change of direction in which the slide valve supplies air, a volume of air remains in a chamber rather being exhausted out completely during the next stroke. This causes the pump to use lesser air for the next stroke. Also, inertial losses are minimized when the shaft changes direction as it does not come to a halt and stop at a terminal point while air in a chamber is being vacated but immediately changes direction and moves to another point. As such, shifting rate of the pump is improved. This in effect increases flow rate of the pump to allow increased output when compared to a prior art AODD pump having same air consumption rate. Comparatively, a pump producing the same output as a prior art AODD pump consumes 30-40% less air than the prior art AODD pump.
[0037] FIG. 5a shows a preferred embodiment of the present invention in which an AODD pump (40) is disposed with a shaft (30) and bushing (28) as shown in FIGS. 2a to 2d and 3a to 3d. In place of a conventional pilot valve is a slide valve (42) which directs compressed air from a compressed air inlet (41) to one of two chambers (43a/43b) based on position of the slide valve (42). Inner volumetric area of the chambers (43a/43b) are separated by a diaphragm (44a/44b) and allow air and fluid to be pumped into and out of these chambers (43a/43b). It would be understood by a person skilled in the art that the diaphragms (44a/44b) separate air and fluid sides of the chambers (43a/43b) and do not allow air/fluid to mix. As with conventional prior art AODD pumps, compressed air is first directed into a chamber, which, as shown in this figure is right chamber (43b) of the AODD pump (40). Due to pressure of compressed air in chamber at compressed air side of right chamber (43b) being greater than pressure of air occupying fluid side of right chamber (43b), right diaphragm (44b) is moved rightwards which also causes left diaphragm (44a) connected to the right diaphragm (44b) via shaft (30) to be moved rightwards. Rightward movement of the left diaphragm (44a) causes fluid to be drawn into fluid side of the left chamber (43a). As there is no exhaust valve at either chambers (43a/43b), air is allowed to bleed and exit through compressed air outlet (45) while right chamber (43b) is being pressurized. Further, the pump (40) is configured such that air resistance in path of compressed air between compressed air inlet (41) and compressed air outlet (45) is minimized. This is achieved by providing paths between compressed air inlet (41) and compressed air outlet (45) for compressed air to travel, such as vents (22) formed on bushing (28) and indentations (34) on shaft (30). By reducing air resistance, less air is trapped between left and right chambers (43a & 43b) which in effect reduces mechanical resistance of the shaft (30).
[0038] In FIG. 5b, shaft (30), left diaphragm (44a), and right diaphragm (44b) have moved to right terminal point. This causes indentations (34) to be in line with the holes (24) at right side of the bushing (28). Compressed air now does not fill the right chamber (43b) but is directed towards the compressed air outlet (45). This also causes the shaft (30), along with left diaphragm (44a) and right diaphragm (44b) to shift in direction. Differential pressure causes slide valve (42) to be moved to another position which allows compressed air to be directed to left chamber (43a).
[0039] Now as shown in FIG. 5c, build-up of pressure of compressed air at air side of left chamber (43a) causes pressure of compressed air to be greater than pressure of fluid drawn into fluid side of the left chamber (43a) and fluid is pumped outwards while fluid is drawn into fluid side of the right chamber (43b). As with prior art AODD pumps, check valves (not illustrated) ensure that there is no backflow of fluid into fluid inlet and fluid travels in only one direction, which is towards the fluid outlet.
[0040] In FIG. 5d, shaft (30), left diaphragm (44a), and right diaphragm (44b) has reached left terminal point and changes direction. Due to increased shift rate of the shaft (30), compressed air is not fully vacated from right chamber (43b) by the time the shaft (30), left diaphragm (44a) and right diaphragm (44b) shift direction and some amount of compressed air remains in compressed air side of the right chamber (43b). As such, amount of compressed air needed to pressurize right chamber (43b) is less and this translates into less compressed air required to operate the AODD pump. Fluid can now be drawn again into fluid side of left chamber (43a) while fluid drawn into fluid side of right chamber (43b) is now pumped outwards. Indentations (34) are in line with holes (24) at left side of the bushing (28) and air is allowed to escape to compressed air outlet (45). Shaft (30), left diaphragm (44a), and right diaphragm (44b) move rightwards and the cycle begins anew.
