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  Diaphragm pumpUSPTO Application #: 20070258835Title: Diaphragm pump Abstract: A diaphragm pump comprising a pressure chamber arranged such that the volume of the pressure chamber is expanded and contracted by oscillation of a diaphragm (5), a suction-side check valve (7) for sucking air into the pressure chamber and a discharge-side check valve (8) for discharging air from the pressure chamber. The suction-side check valve is arranged to close by a valve body (17) being elastically deformed and brought into close contact with a valve seat, and open by the valve body elastically returning to the normal shape and coming out of contact with the valve seat. The discharge-side check valve is arranged to open by a valve body (18) being elastically deformed and producing a space relative to a valve seat, and close by the valve body elastically returning to the normal shape and coming into close contact with the valve seat. (end of abstract)
Agent: Frishauf, Holtz, Goodman & Chick, PC - New York, NY, US Inventors: Isao Ichiyanagi, Kazuhiko Maegawa USPTO Applicaton #: 20070258835 - Class: 417413100 (USPTO) Related Patent Categories: Pumps, Motor Driven, Electric Or Magnetic Motor, Collapsible Wall Pump, Diaphragm Type The Patent Description & Claims data below is from USPTO Patent Application 20070258835. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates to a diaphragm pump having a pressure chamber arranged such that the volume of the pressure chamber is expanded and contracted by oscillation of a diaphragm. [0003] 2. Description of the Related Art [0004] A diaphragm pump comprises, as a wall of a pressure chamber, a diaphragm which is driven, for example, by an electromagnet to oscillate so that the oscillation of the diaphragm expands and contracts the volume of the pressure chamber alternately. The diaphragm pump sucks a fluid (air, for example) into the pressure chamber through a suction-side check valve when the volume of the pressure chamber is expanded, and pressurizes and discharges the air from the pressure chamber through a discharge-side check valve when the volume of the pressure chamber is contracted. [0005] Generally, when the discharge pressure of the diaphragm pump is raised, the discharge quantity thereof tends to decrease. When the operating pressure of the diaphragm pump is raised to obtain a high discharge pressure, however, a high pressure in the pressure chamber makes it difficult for the diaphragm to oscillate. This easily causes variation in the time for which the suction-side check valve is open, and thereby makes the amount of a fluid sucked into the pressure chamber unstable. Thus, as characteristic curve A in FIG. 6 shows, a phenomenon that the discharge quantity of the diaphragm pump becomes unstable at operating pressures of 40 kPa and higher is produced. [0006] In order to remove such instability phenomenon, Japanese Unexamined Patent Publication No. 2003-269339 has proposed providing a hole that connects a pressure chamber and a sealed space (casing) which is located behind a diaphragm and contains an electromagnet for driving the diaphragm to oscillate, so that the pressure in the pressure chamber is applied to the diaphragm as a back pressure. The adoption of such arrangement, however, causes a problem that the casing (sealed space) containing the electromagnet requires a complicated structure. [0007] For an alternate diaphragm pump which has diaphragms provided at the opposite ends of a rod-like shaft driven by an electromagnet to move back and forth so that the volumes of paired pressure chambers are expanded and contracted in a complementary manner by means of the diaphragms, a particularly complicated structure is required, since a device for preventing the paired pumping chambers from becoming connected through the casing (sealed space) containing the electromagnet is required. SUMMARY OF THE INVENTION [0008] The primary object of this invention is to provide a diaphragm pump that can remove operational instability at high operating pressures, without requiring a complicated structure. [0009] In order to achieve this object, a diaphragm pump according to this invention comprises a diaphragm driven to move back and forth, a pressure chamber arranged such that the volume of the pressure chamber is expanded and contracted by the oscillation of the diaphragm, a suction-side check valve fitted to a suction port for the suction chamber and arranged to open and suck a fluid from the suction port into the pressure chamber when the volume of the pressure chamber is expanded, and a discharge-side check valve fitted to a discharge port for the suction chamber and arranged to open and discharge the fluid from the pressure chamber to the discharge port when the volume of the pressure chamber is contracted, and is characterized in that [0010] the suction-side check valve includes a valve body of an elastic material fitted to a valve seat provided near the suction port, with a space between, and is arranged to close by the valve body being elastically deformed and brought into close contact with the valve seat, and open by the valve body elastically returning to the normal shape and coming out of contact with the valve seat, and [0011] the discharge-side check valve includes a valve body of an elastic material fitted to a valve seat provided near the discharge port, in close contact with the valve seat, and is arranged to open by the valve body being elastically deformed and producing a space relative to the valve seat, and close by the valve body elastically returning to the normal shape and coming into close contact with the valve seat. [0012] Desirably, the diaphragm is connected to an oscillator driven by an electromagnet to move back and forth so that the diaphragm is driven by the electromagnet to oscillate. [0013] In a preferred aspect of this invention, the diaphragm pump comprises a rod-like oscillator driven by an electromagnet to move back and forth in the axial direction, diaphragms provided at the opposite ends of the oscillator, respectively, and paired pressure chambers each including one of the diaphragms and arranged such that the volumes of the paired pressure chambers are expanded and contracted in a complementary manner. [0014] In the diaphragm pump having the above structure, the suction-side check valve is arranged to have a space between the valve body and the valve seat, and hence functions as a normally-open check valve. By using this suction-side check valve in combination with the discharge-side check valve which functions as a normally-closed check valve, the time for which the suction-side check valve is open in the process of expanding the volume of the pressure chamber for sucking air from the suction port into the pressure chamber can be made longer, so that a load on the diaphragm can be reduced. [0015] Since the load on the diaphragm is reduced, it is not necessary to apply part of the pressure in the pressure chamber to the diaphragm as a back pressure as in the conventional case, and hence, a complicated structure is not required. Further, even when the diaphragm pump is operated at a high operating pressure, the diaphragm can be caused to oscillate with certainty, since the load on the diaphragm is reduced as mentioned above. Thus, also when the diaphragm pump is operated at a high operating pressure, stable operational characteristics can be guaranteed. [0016] Also in the alternate diaphragm pump having paired pressure chambers arranged such that their volumes are expanded and contracted in a complementary manner, it can be ensured that a sufficient amount of air is sucked into the paired pressure chambers, alternately. Consequently, mutual interference of the paired pressure chambers, or in other words, unstable operation of one pressure chamber affecting the operation of the other pressure chamber can be prevented. Thus, the operational balance between the paired pressure chambers can be prevented from becoming unstable, and the pressure difference liable to be produced between the paired pressure chambers can be removed. Since it can be ensured that a stable amount of air is sucked into the paired pressure chambers even when the diaphragm pump is operated at a high operating pressure, the discharge pressure of the diaphragm pump can be easily kept constant and the above-mentioned instability phenomenon can be prevented effectively. BRIEF DESCRIPTION OF THE DRAWINGS [0017] FIG. 1 is a cross-sectional view schematically showing the structure of an electromagnetic diaphragm pump in an embodiment of this invention, [0018] FIG. 2 is an enlarged view of a suction-side check valve shown in FIG. 1; [0019] FIG. 3 is an enlarged view of a discharge-side check valve shown in FIG. 1; [0020] FIG. 4 is a characteristic diagram showing an example of change of pressure in a pressure chamber of a conventional electromagnetic diaphragm pump, over time; [0021] FIG. 5 is a characteristic diagram showing an example of change of pressure in a pressure chamber of an electromagnetic diaphragm pump according to this invention, over time; and Continue reading... Full patent description for Diaphragm pump Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Diaphragm pump patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. 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