US2859701A - Diaphragm pump - Google Patents

Description

' Nov. 11, 1958 H. A. WILLIAMS 2,859,701

. DIAPHRAGM PUMP Filed NOV. 25, 1955 IN VEN TOR.

F v HERSCHELAWILLIAMS BY M.

An rn s United States Patent burg Electib-(Zoatirig: Corpg llidianapolis, Ind., a: corporationof Indiana Application November 25, 1955, SeiiaTNii; $985 4' Claims; (e1. roa -1'50 The invention here relates to a pump of the diaphragm type and in particular to a pump for use with porcelain enamel slips and other liquid suspensions of abrasive material. a

In the electrostatic spray coating of articles of manufacture such as automatic home laundry equipment it is necessary to quite accurately meter the flow of porcelain enamel slip or other liquid coating material to the atomizing device. Dilhculties arise when ceramic materials are to be'fed to the atomizing device. Because of the extreme abrasivequalities of ceramic materials, it is desirable to use a diaphragm pump but no known diaphragm pump would accurately deliver over long periods of time the precise volumes of liquidcoating material required for high quality electrostatic spray coating. i

The invention provides a diaphragm pump highly resist: ant to abrasive materials which will deliver extremely constant flows of liquidsubstantially entirely free from the influence of variations in pump chamber pressures and liquid viscosities and which will deliver such flows for lengthy periods of time. The pump includes novel diaphragm control members which materially reduce the unit bending stresses in the diaphragm and thereby increase thelife of the diaphragm as well as insure uniform deformation of the diaphragm for each cycle of the pump and thereby insure a consistent flow of liquid. Preferably the pump chamber is essentially a small vertical cylinder which minimizes undesirable settling within the chamber of solids from the liquid being pumped.

An object of this invention is to provide a simple pump which will resist wear, closely meter the flow of liquid, andoperate over longperiods of time with a minimum of attention. Means for accomplishing the foregoing and related objects of the invention will now be described in detail with reference to the accompanying drawings in whichi v V Fig. 1 is a partially broken away elevational view of an embodiment of the invention;

, Fig. 2 is a plan view of the pump shown in Fig. l' with its cover plate removed;

, Fig. 3 is a partial cross-sectional view of one of the diaphragm control members in Fig. 1 showing its construction; and i Fig. 4 is a further view of the diaphragm control memher.

The invention is particularly adapted for pumps for liquids containing abrasive material. However, the in vention is not so limited, may be used for any liquid, and

may assume many different forms. The following description is illustrative of the principles of the invention whose scope is not to be restricted by such description.

1- and 2 show two similar pump units embodying the invention and operated from a single source of power. The apparatus includes amain pump casing 10, which is bored to receive an eccentrically driven plunger 11', and a lower casing 12 adapted to receive a drive shaft for the plunger. Mounted on opposite sides of main cas- Patented Nov. 11;,- 1958 ing are a pair of similar pump heads 13 and 14, only the latter of which will be described in detail.

, Plunger 11 is adapted to be moved: onbearings 15 (only one being shown) back and forth along its. axis by means of an eccentric motion transmitted by adrive shaft 16 which is rotatably mounted on a pair of antifriction bearings 17 and 18 which in turn are mounted within lower casing 12. Drive shaft 16is rotated by a suitable source of power 19, the details of which form nopart of the invention. I

v The upper end16a of drive shaft 16 is cylindricalwith its axis set eccent'rically in relation to the major axis'of rotation of shaft 16. An anti-friction bearing 20' surrounds upper end-16a of the drive shaft and bearing 20 is seated within thecenter portion of plunger 11, which center portion isin the form of a yoke 11a" with. the outer surface. of bearing 20 resting snugly against opposing interior surfacesof yoke-11a as shown. Accordingly; rotationpf drive shaft 16- will be transmitted as a-bac'l: and forth movement of plunger 11 along its major axis;

I A cover plate 21 mounted on top of main casing. 10 is designedto protect the'plunger 11', shaft 16 and bearing 20 from dust and other foreign matter.

Eachend of plunger 11 is adapted to receive in the following order a disc-like first diaphragm control mem her, a flexible diaphragm, a second diaphragm control member, a retaining washer and a bolt. Near each end of: theplunger there is a shoulder portion 11b against which the rear face of a first diaphragmcontrol member 22 is secured. A- diaphragm 24' is confined or secured be-- tweenthe adjacent interior faces of first diaphragm. controlmember 22 and asecond diaphragm control member 26. Awasher 30; anda bolt'32, the latter being screweii tightly into the threadediend of plunger 1=1=,senve to hold the diaphr-agm and itstwo control members lirinlyi'together on the-plunger.

Diaphragm 24' ismade of a suitable 'llexibl'eg. liquid proof material such as reinforced: rubber. The diaphragm is genera-lly' disc-shaped and its outer: edges" are confined between the opposing faces of main'acasilig 11] and purnp head 14- by -a. series of belts or othermeans not shown. Pump headj14 is bored vertically to provide a generally vertical cylindrical pump chamber 34 and: is also bored horizontally to provide'a'cylindr ical recess ad joining chamber 34 t'oreceive the end of: plunger 11 and diaphragm control member 26: Chamber 34' is relat tively small and has almost no'corners' into which solids containedin the liquid being, pumped might 'settle'to? cause clogging or other undesirable effects. A one-way check valve 36,;designed to prevent the flow of liquid from chamber 34, is mounted in the entrance passageway to the chamber and a similar one-way check valve 37 is mounted in the exit passageway to prevent the flow :of:- liquid back into the chamber. Check valves-'36 and 37' maybe connected to suitable hoses or other liquid"sup"-- ply means".

Figs. 3 and 4 are more detailed views of diaphragmcontrol member 26; it being understood that member 22 is ofsimilar construction and operates in 'a substan tially similar manner. The use of members to control v the movement of the diaphragms in pumps isknown. Such members generally have been used to prevent buckling of the diaphragm about the plungera's in the case where excessive fbacl; pressures might be builtup within the pump chamber. Diaphragm control mam bers 22 and 26 achieve this result but have the further novel features of keeping the unit bendings t'res'ses wit in signed so that its inner face, that is, the face or surface lying next to the diaphragm, will be in contact with substantlally the entire free, unconfined portion of the diaphragm when the plunger is at one end of its stroke. For this reason the diameter of the disc-shaped member is preferably only slightly less than the diameter of the cyllndrical recess in pump head 14 within which member 26 is reciprocated. In one pump constructed and successfully operated embodying the invention here, the clearance between the outer edges of the control members and the adjacent surfaces of the casing and pump head was only 4 of an inch. 7

To prevent entrapment of air between the diaphragm and the inner face of member 22, which might prevent the diaphragm from hearing properly against control member 22 and result in a non-uniform liquid flow durmg operation of the pump, a series of holes may be provlded in the control member. Similar holes such as 26a shown in Fig. 4 perform an even more important function in diaphragm control member 26 in that they prevent the entrapment of liquid between diaphragm 24 and the inner face of member 26 during the pumping cycle. The holes in the diaphragm control members are particularly important where the clearance between the moving member and its stationary chamber is small and also where the liquid contains a suspension of solids, because without the holes fluid tends to be restricted in its movement forth and back between the diaphragm and its control member.

Further to insure that the free portion of the diaphragm will rest against the inner face of the diaphragm control member without unnecessary strain on the diaphragm, this face of the control member is given a unique curvature corresponding substantially to the position of the diaphragm at the end of the plunger stroke in which the unconfined diaphragm will have minimum stresses throughout its extent. It is apparent that if diaphragm control members were not used the diaphragm would most likely be subject to maximum deformation, and hence maximum bending stresses and wear, at those points where the diaphragm emerges from confinement between the stationary casing and pump head and where the free portion of the diaphragm is attached to the moving plunger. In order to reduce wear at these points and to equalize the wear over the entire free, unconfined portion of the diaphragm, the inner face of each diaphragm control member is designed to include surface portions which lie preferably substantially tangent or parallel to the position of the confined portions of the diaphragm both where the diaphragm is attached to the casing and to the plunger, thereby avoiding sharp deformation and excessive wearing of the unconfined diaphragm normally caused by the back-and-forth movement of the plunger. The interior face of member 26 is preferably curved gradually and smoothly between its two tangent or parallel portions, that is, between its outer surface portion and its inner surface portion I as shown in Fig. 3. Thereby the deformation of the diaphragm is made approximately equal throughout its extent and the bending stresses at any one point will be at a minimum.

As a specific example of a pump embodying the invention, a pump substantially as shown in Figs. 1 and 2 was constructed with a plunger stroke of A6 of an inch. All of the pumps diaphragm control members were made similar to member 26 whose inner face had a curved outer surface portion 0 which was tangent to the adjacent diaphragm-confining surface of pump head 14, and also substantially normal to the axis of plunger 11. At the same time, surface portion I was tangent to the center diaphragm-confining surface of the control member itself. The normal distance between the two tangent surface portions 0 and I (distance X as shown in Fig. 3) was one half of the stroke of plunger 11 or ,6 of an inch.

. Thus with the plunger at one end of its pumping stroke, the outer surface portion 0 of the inner face of member 26 rests against and holds the adjacent free, unconfined diaphragm surface substantially parallel to the diaphragm portion confined by pump head 14 and thereby prevents sharp deformation and wear of this free portion of the diaphragm. The similar construction of diaphragm control member 22 prevents sharp deformation and wear of the free diaphragm at the opposite end of the pumping stroke. And while plunger 11 moves through its stroke, that portion of the free diaphragm nearest to interior surface portion I of the control member will be guided by surface portion I so as to prevent excessive deformation and wear of that free diaphragm portion.

In order to achieve a simple curved surface for the inner face of member 26 which is free of discontinuities and at the same time containing portions 0 and I each tangent to its nearest confined diaphragm portion, that surface of the inner face including and between portions 0 and I may be developed by two arcs of equal radii R, each tangent to its nearest diaphragm portion as shown in Fig. 3 and which arcs meet tangent to each other at a mid-point between surface portions 0 and I. v I claim:

1. A diaphragm pump comprising a casing, a plunger movably mounted within said casing, a pump head affixed to said casing, a flexible diaphragm having its outer edge confined between said casing and said pump head, and a pair of disc-like diaphragm control members mounted on said plunger with the center portion of said diaphragm confined between opposing inner faces of said members, the diameters of said members being only slightly less than the diameters of the respective cylindrical recesses in said casing and said pump head within which said members are contained whereby substantially the entire free, unconfined portion of the diaphragm may be supported by an inner face of one of said members, the outer portion of the inner face of each diaphragm control mem her being smoothly curved, and that portion of said inner face which lies most closely adjacent to the confined center portion of the diaphragm being tangent to said center portion, and the portion of said inner face which lies most closely adjacent to the confined outer edge of the diaphragm being tangent to said outer edge when the plunger is at one end of its pumping stroke.

2. A diaphragm pump as set forth in claim 1 in which the diaphragm control members contain a plurality of holes therethrough to prevent the entrapment of fluid between said diaphragm and said control members during the operation of said pump.

3. A diaphragm pump comprising a casing, a plunger movably mounted within said casing, a pump head affixed to said casing and containing a generally vertical cylindrical pump chamber with vertically extending fluid inlet and exit passages therefrom, a diaphragm of flexible, liquid-resistant material whose outer edge is confined between opposing surfaces of said casing and said pump head, said casing and said pump head each providing a generally cylindrical recess on either side of the free, unconfined portion of said diaphragm, and a pair of generally disc-shaped diaphragm control members mounted on said plunger with the center portion of said diaphragm confined between the center portions of the opposing inner faces of said members, the diameters of said members being only slightly less than the diameters of the respective cylindrical recesses in said casing and said pump head within which said members are contained whereby substantially the entire free, unconfined portion of the diaphragm may be supported by an inner face of one of said members, the outer portion of the inner face of each diaphragm control member being smoothly curved, and that portion of said inner face which lies most closely adjacent to the confined center portion of the diaphragm being tangent to said center portion, and the portion of said inner face which lies most closely adjacent to the confined outer edge of the diaphragm being tangent to said outer edge when the plunger is at one end of its pumping stroke.

4. A diaphragm pump as set forth in claim 3 in which the diaphragm control members contain a plurality of holes therethrough to prevent the entrapment of fluid between said diaphragm and said control members during the operation of said pump.

References Cited in the file of this patent UNITED STATES PATENTS Russell July 2, 1901 Harper Jan. 19, 1943 Theis Dec. 13, 1949 Colbert Apr. 13, 1954

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