Diaphragm pump

Abstract

Provided is a diaphragm pump in which warpage is not likely to occur in a center plate. A diaphragm pump (1) is provided with a pump housing (10), a crank mechanism (20) attached to the pump housing (10), and a diaphragm constituting part (22) connected to the crank mechanism (20). The diaphragm constituting part (22) has a diaphragm (30) and a center plate (32) retaining an inner peripheral part (38) of the diaphragm (30). The center plate (32) has a first retaining member (34) having a fitting concave part (52) and a second retaining member (36) having a fitting convex part (58) press-fitted into the fitting concave part (52), and holds the inner peripheral part (38) of the diaphragm (30) between the first retaining member (34) and the second retaining member (36). A screw (48) for fixing the center plate (32) is attached via insertion holes (54) and (60) penetrating through the fitting concave part (52) and the fitting convex part (58). An inner diameter of the fitting concave part (52) and an outer diameter of the fitting convex part (58) are larger than the insertion holes (54) and (60).

Description

Technical Field:

[0001] The present invention relates to a diaphragm pump configured to perform suction and discharge of a fluid by reciprocatively oscillating a diaphragm. Background Art:

[0002] Patent Literature 1, for example, shows a diaphragm pump having a center plate attached to the center of a disk-shaped diaphragm formed from an elastic member, e.g. rubber. The center plate is reciprocated by a driving mechanism, e.g. a crank mechanism or an electromagnetic reciprocating mechanism, thereby sucking and discharging a fluid such as air or water. The center plate comprises an inner center plate and an outer center plate, which are secured to the driving mechanism by being pressed down to each other using a screw with the diaphragm clamped therebetween. It should be noted that the outer center plate has a recess formed in the center thereof, and the inner center plate has a projection formed in the center thereof. By inserting the projection into the recess, the center positions of the outer and inner center plates are aligned with each other. Citation List: Patent Literature:

[0003] Patent Literature 1: Japanese Patent Application Publication No. 2012-225190 Summary of Invention: Technical Problem:

[0004] There has been a growing demand for the above-described diaphragm pump to attain a higher output and a higher flow rate. One of schemes for attaining a higher output and a higher flow rate is to increase the diameter of the diaphragm. In such a case, it is desirable to increase the size of the center plate in proportion to the increase in the diaphragm diameter. However, if the center plate is increased in size, the distance from the center position, at which the center plate is retained by the screw, to the outer peripheral end of the center plate becomes correspondingly longer, so that the center plate becomes more likely to be warped by a force received from the diaphragm when the center plate reciprocates. The warpage of the center plate causes a gap to be generated between the inner center plate and the outer center plate, which may make it impossible to maintain the state of retaining the diaphragm, resulting in the diaphragm dislodging from the center plate.

[0005] Accordingly, it is an object of the present invention to provide a diaphragm pump configured so that the center plate is less likely to warp even if the center plate is increased in diameter. Solution to Problem:

[0006] That is, the present invention provides a diaphragm pump including: a pump casing; a driving mechanism section attached to the pump casing; a diaphragm having an outer peripheral portion and an inner peripheral portion, the outer peripheral portion being secured to the pump casing; a center plate connected to the driving mechanism section and retaining the inner peripheral portion of the diaphragm, the center plate having a first retaining member having a fitting recess, and a second retaining member having a fitting projection press-fitted into the fitting recess, the center plate being configured to clamp the inner peripheral portion of the diaphragm between the first retaining member and the second retaining member, and the center plate having an insertion hole extending through the fitting recess and the fitting projection; and a securing member installed through the insertion hole to secure the diaphragm to the driving mechanism section through the center plate; wherein the inner diameter of the fitting recess and the outer diameter of the fitting projection are larger than the insertion hole.

[0007] In the diaphragm pump, the first retaining member and second retaining member of the center plate are secured to each other by fitting of the fitting recess and the fitting projection, which are larger than the insertion hole through which the securing member is installed. Therefore, it is possible to shorten the distance from the position at which the first and second retaining members are secured to each other to the outer peripheral end of the center plate. Consequently, it is possible to make it less likely that the first retaining member and second retaining member of the center plate will be warped even if the first retaining member and the second retaining member receive a force from the diaphragm in a direction away from each other during pump operation. In particular, even when the center plate is increased in diameter, the occurrence of warpage during pump operation can be prevented by increasing the fitting recess and the fitting projection in diameter correspondingly.

[0008] In addition, the arrangement may be as follows. Not all of the outer peripheral surface of the fitting projection engages the inner peripheral surface of the fitting recess so that an accommodating space is formed between the inner peripheral surface of the fitting recess and the outer peripheral surface of the fitting projection. More specifically, the arrangement may be such that the fitting projection has a radially inwardly hollow portion, so that the accommodating space is formed by the hollow portion. Even more specifically, the arrangement may be such that the fitting projection has a plurality of the hollow portions equally spaced in a circumferential direction, whereby a plurality of radially outwardly projecting portions are formed, and only outer peripheral surfaces of the plurality of projecting portions engage the inner peripheral surface of the fitting recess.

[0009] By providing the accommodating spaces between the inner peripheral surface of the fitting recess and the outer peripheral surface of the fitting projection, deformed portions of the fitting recess and the fitting projection which are generated when the fitting projection is press-fitted into the fitting recess are allowed to enter the accommodating spaces. Consequently, it is possible to secure the first retaining member and the second retaining member to each other by firmly fitting together the fitting recess and the fitting projection and, at the same time, possible to prevent occurrence of warpage or other undesired deformation of the first and second retaining members when assembled together due to an excessive stress otherwise generated in other portions of the first and second retaining members.

[0010] Embodiments of a diaphragm pump according to the present invention will be explained below on the basis of the accompanying drawings. Brief Description of Drawings:

[0011] Fig. 1 is a perspective view of a diaphragm pump according to an embodiment of the present invention. Fig. 2 is a sectional view of the diaphragm pump in Fig. 1, taken at the center position of a diaphragm. Fig. 3 is a sectional view of a diaphragm assembly. Fig. 4 is a perspective view of an upper surface of a first retaining member of a center plate. Fig. 5 is a perspective view of a lower surface of a second retaining member of the center plate. Fig. 6 is a sectional view taken along the line A-A in Fig. 3. Description of Embodiments:

[0012] As shown in Fig. 1, a diaphragm pump 1 according to an embodiment of the present invention includes a pump casing 10 and a motor 12 attached to the pump casing 10. The pump casing 10 is provided with a suction port 14 and a discharge port 16. The diaphragm pump 1 is configured to suck in air from the suction port 14 and to discharge the air from the discharge port 16 by reciprocating a diaphragm assembly 22 (described later) built in the pump casing 10 by using the motor 12. The diaphragm pump 1 is configured to be installed at a predetermined position through rubber vibration isolators 18.

[0013] As shown in Fig. 2, the diaphragm pump 1 further includes a crank mechanism 20 coupled to the motor 12, and a diaphragm assembly 22 attached to the crank mechanism 20. A pump chamber 24 is formed between an inner peripheral surface 10a of the pump casing 10 and the diaphragm assembly 22. A one-way valve 26 is installed between the suction port 14 and the pump chamber 24. The one-way valve 26 allows air to flow only from the suction port 14 to the pump chamber 24. In addition, a one-way valve 28 is installed between the pump chamber 24 and the discharge port 16. The one-way valve28 allows air to flow only from the pump chamber 24 to the discharge port 16. The diaphragm assembly 22 is reciprocated mainly in an up-down direction by the crank mechanism 20, thereby causing the volumetric capacity of the pump chamber 24 to increase and decrease, and thus allowing air to be sucked into the pump chamber 24 from the suction port 14 and delivered from the pump chamber 24 to the discharge port 16.

[0014] The diaphragm assembly 22 includes a disk-shaped diaphragm 30 and a center plate 32 retaining the diaphragm 30. As shown in Fig. 3, the center plate 32 includes a first (lower) retaining member 34 and a second (upper) retaining member 36 and retains the diaphragm 30 by clamping an inner peripheral portion 38 of the diaphragm 30 between the first and second retaining members 34 and 36. The diaphragm 30 has an outer peripheral locking portion 42 projecting upwardly at an outer peripheral portion 40 thereof, an inner peripheral locking portion 44 projecting downwardly at an inner peripheral portion 38 thereof, and an intermediate curved portion 46 curved upwardly at an intermediate portion thereof. As shown in Fig. 2, the outer peripheral locking portion 42 of the diaphragm 30 is secured to the pump casing 10. In addition, the center plate 32 is secured to a connecting rod 50 of the crank mechanism 20 with a screw (securing member) 48.

[0015] As shown in Fig. 4, the first retaining member 34 of the center plate 32 has a circular fitting recess 52 in an upper surface 34a thereof and an insertion hole 54 extending through the center position of the fitting recess 52. The first retaining member 34 further has an annular locking groove 56 formed in the upper surface 34a at a position outward of the fitting recess 52. As shown in Fig. 5, the second retaining member 36 of the center plate 32 has a fitting projection 58 on a lower surface 36a thereof and an insertion hole 60 extending through the center position of the fitting projection 58. The second retaining member 36 further has two annular protrusions 62 formed on the lower surface 36a at respective positions outward of the fitting projection 58. The fitting projection 58 has six radially inwardly hollow portions 64 which are equally spaced circumferentially, whereby six projecting portions 66 are formed. The fitting projection 58 has the shape like a gear wheel.

[0016] As shown in Fig. 3, the diaphragm assembly 22 is assembled by fitting the inner peripheral locking portion 44 of the diaphragm 30 into the annular locking groove 56 of the first retaining member 34, and in this state, press-fitting the fitting projection 58 of the second retaining member 36 into the fitting recess 52 of the first retaining member 34. The inner peripheral portion 38 of the diaphragm 30 is clamped between the upper surface 34a of the first retaining member 34 and the lower surface 36a of the second retaining member 36 to be retained therebetween. In addition, the two annular protrusions 62 of the second retaining member 36 bite into the diaphragm 30, thereby enabling the diaphragm 30 to be retained even more firmly. As shown in Fig. 6, accommodating spaces 68 are formed in the hollow portions 64 of the fitting projection 58 between the fitting projection 58 and the fitting recess 52. The fitting projection 58 engages an inner peripheral surface 52a of the fitting recess 52 only at an outer peripheral surface 58a of each projecting portion 66. Before the diaphragm assembly 22 is assembled, the outer diameter of the fitting projection 58 is substantially the same as or slightly greater than the inner diameter of the fitting recess 52. Accordingly, when the fitting projection 58 is press-fitted into the fitting recess 52, the projecting portions 66 of the fitting projection 58 or the fitting recess 52 may be slightly deformed. However, the deformed portions may escape into the adjacent accommodating spaces 68; therefore, not much undue stress is applied to other portions. If the accommodating spaces 68 were not provided, there would be no way out for the deformed portions, so that a large stress might be applied to other portions, particularly to the base of the fitting projection 58 and the vicinity thereof. This could result in the second retaining member 36 warping as a whole. In contrast, the embodiment of the present invention can prevent the occurrence of warpage during the assembling process owing to the accommodating spaces 68 being provided. It should be noted that the shape and number of the projecting portions 66 and the accommodating spaces 68 can be changed as desired. In addition, accommodating spaces may be formed by forming radially outwardly hollow portions in the inner peripheral surface 52a of the fitting recess 52. Other various shapes are also conceivable for the accommodating spaces. That is, any shape is usable, provided that when the fitting projection 58 is press-fitted into the fitting recess 52, not all of, or only a part of, the outer peripheral surface 58a of the fitting projection 58 engages the inner peripheral surface 52a of the fitting recess 52 and accommodating spaces are formed in other portions.

[0017] The assembled diaphragm assembly 22 is secured to the connecting rod 50 of the crank mechanism 20 by using the screw 48, as described above. It should, however, be noted that the first retaining member 34 and the second retaining member 36 of the center plate 32 are practically secured to each other by fitting between the fitting recess 52 and the fitting projection 58.

[0018] In the diaphragm pump 1, the first retaining member 34 and the second retaining member 36 of the center plate 32 retaining the diaphragm 30 are integrally secured to each other not by the screw 48 but mainly by fitting between the fitting recess 52 and the fitting projection 58. The inner diameter of the fitting recess 52 and the outer diameter of the fitting projection 58 are larger than the insertion holes 54 and 60; therefore, the distance from the inner and outer peripheral surfaces 52a and 58a of the fitting recess 52 and the fitting projection 52, which are fitted to each other, to an outer peripheral end 32a of the center plate 32 is shorter than the distance from the screw 48 to the outer peripheral end 32a of the center plate 32. During pump operation, an outer peripheral portion 70 of the second retaining member 36 of the center plate 32 is subjected to a force from the diaphragm 30 in a direction away from the first retaining member 34. However, because the distance from the outer peripheral surface 58a of the fitting projection 58, at which the second retaining member 36 is secured to the first retaining member 34, to the outer peripheral end 32a thereof has been shortened, the second retaining member 36 is less likely to warp in comparison to a case where the first retaining member 34 and the second retaining member 36 are secured to each other only with the screw 48. In addition, because the fitting recess 52 and the fitting projection 58 are fitted to each other, the first retaining member 34 and the second retaining member 36 are prevented from rotating relative to each other. Thus, it is possible to prevent application of undesired force to the diaphragm 30, which would otherwise be caused by rotation of the second retaining member 36 when the screw 48 is tightened, and also possible to prevent the screw 48 from becoming loose during pump operation, which would otherwise be caused by rotation of the second retaining member 36.

[0019] Although some embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, the first retaining member of the center plate may be formed as a component integrated with the connecting rod of the crank mechanism. In addition, the second retaining member of the center plate may be secured to the crank mechanism, and the first retaining member may be secured to the second retaining member. In other words, the fitting projection may be formed on the connecting rod-side member, and the fitting recess may be formed in the other member. Although in the foregoing embodiment a structure comprising a motor and a crank mechanism is adopted as a driving mechanism section, other mechanisms, for example, an electromagnetic reciprocating mechanism, may also be usable. In addition, a fluid to be conveyed is not limited to air but may be a liquid, for example, water. List of Reference Signs:

[0020] 1: diaphragm pump 10: pump casing 10a: inner peripheral surface 12: motor 14: suction port 16: discharge port 18: rubber vibration isolators 20: crank mechanism 22: diaphragm assembly 24: pump chamber 26: one-way valve 28: one-way valve 30: diaphragm 32: center plate 32a: outer peripheral end 34: first retaining member 34a: upper surface 36: second retaining member 36a: lower surface 38: inner peripheral portion 40: outer peripheral portion 42: outer peripheral locking portion 44: inner peripheral locking portion 46: intermediate curved portion 48: screw (securing member) 50: connecting rod 52: fitting recess 52a: inner peripheral surface 54: insertion hole 56: annular locking groove 58: fitting projection 58a: outer peripheral surface 60: insertion hole 62: annular protrusions 64: hollow portions 66: projecting portions 68: accommodating spaces 70: outer peripheral portion

Claims

1. A diaphragm pump comprising:a pump casing;a driving mechanism section attached to the pump casing;a diaphragm having an outer peripheral portion and an inner peripheral portion, the outer peripheral portion being secured to the pump casing;a center plate connected to the driving mechanism section and retaining the inner peripheral portion of the diaphragm, the center plate having a first retaining member having a fitting recess, and a second retaining member having a fitting projection press-fitted into the fitting recess, the center plate being configured to clamp the inner peripheral portion of the diaphragm between the first retaining member and the second retaining member, and the center plate having an insertion hole extending through the fitting recess and the fitting projection; anda securing member installed through the insertion hole to secure the diaphragm to the driving mechanism section through the center plate;wherein an inner diameter of the fitting recess and an outer diameter of the fitting projection are larger than the insertion hole.

2. The diaphragm pump of claim 1, wherein not all of an outer peripheral surface of the fitting projection engages an inner peripheral surface of the fitting recess so that an accommodating space is formed between the inner peripheral surface of the fitting recess and the outer peripheral surface of the fitting projection.

3. The diaphragm pump of claim 2, wherein the fitting projection has a radially inwardly hollow portion, so that the accommodating space is formed by the hollow portion.

4. The diaphragm pump of claim 3, wherein the fitting projection has a plurality of the hollow portions equally spaced in a circumferential direction, whereby a plurality of radially outwardly projecting portions are formed, and only outer peripheral surfaces of the plurality of projecting portions engage the inner peripheral surface of thefitting recess.- 12 -

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