US3537619A - Dispensing apparatus - Google Patents

Description

United States Patent Inventors Appl. No.

Filed William K. Glesner Midland;

John K. Rexer, Essexville, Michigan 677,441

Oct. 23, 1967 Continuation-impart oi Ser. No. 525,665, Feb. 7, 1966, abandoned.

Patented Nov. 3, 1970 Assignee The Dow Chemical Company Midland, Michigan a corporation of Delaware DISPENSING APPARATUS 6 Claims, 3 Drawing Figs.

U.S. Cl 222/334, 92/253 Int. Cl .4 ..G0li' 11/30, F16j 9/00 Field of Search 222/334,

[56] References Cited UNITED STATES PATENTS 2,267,882 12/1941 Wilson 921253 2,321,160 6/1943 Schnitzer. 92/251X 3,165,032 1/1965 Konkle 92/252 3,216,627 11/1965 Best et a1. 222/334X OTHER REFERENCES Bulletin 34A of The Chicago Gasket Co. Received by the Patent office on June 10, 1952 3 pages. Pages 71 and 72 of Commissioner 5 Decisions of 1959.

Primary Examiner- Robert B. Reeves Assistant Examiner-H. S. Lane Attorneys-Griswold & Burdick, Richard G. Waterman and Robert B. Ingraham ABSTRACT: A pistontype dispensing apparatus is described suitable for polymerizable resins containing a particulate filler. A sealing and bearing ring of a deformable material such as polytetrafluoroethylene is protected by a metal retainer which serves to protect the sealing from hardened resin.

Patented Nov. 3, 1.970 3,537,619

INVEN'IORS. -W/'///am k. G/esn er BY John K. Rex er DISPENSING APPARATUS This application is a continuation-in-part of our copending U.S. Pat. application Ser. No. 525,665, filed Feb. 7, 1966 now abandoned.

This invention relates to an improved dispensing apparatus and more particularly relates to a positive displacement dispensing apparatus particularly suited and adapted for the dispensing of hardenable resinous materials containing therein a particulate solid filler.

in many operations, particularly in the matched die molding of filled synthetic resinous materials which may be hardened by heat or on standing, it is often desirable to accurately dispense a predetermined volume of resinous material, preferably by means of a positive displacement dispenser such as a piston within a cylinder coupled with appropriate flow control means, such as check valves or mechanically operated valves. Oftentimes, such positive displacement dispensers have the form of a cylinder having a tightly fitting piston disposed slidably therein, the liquid or fluid material to be dispensed is forced into the cylinder displacing the piston, the inlet valve closed, pressure applied to the piston, the outlet valve opened and the material dispensed through the outlet port. Oftcntimes, such hardenable resinous materials on standing tend to polymerize or harden on the walls of the cylinder in the area of the piston and frequently cause damage thereto. Usually, for most applications it is desirable to employ a synthetic resinous piston which resists the abrasive action of particulate fillers. However, such synthetic resinous material frequently will fracture when the piston is moved after standing for a period of time.

It is an object of this invention to provide an improved dispensing apparatus for synthetic resinous materials.

A further object of this invention is to provide an improved piston which does not crack or fracture and is not scored or damaged by exposure within the dispensing apparatus to a hardenable material containing particulate tiller. 7

A further object of this invention is to provide a positive displacement dispensing apparatus having an improved piston.

These benefits and other advantages in accordance with the present invention are achieved in a dispensing apparatus comprising a cylinder, a piston slida'bly disposed therein, a liquid inlet and a liquid outlet, means to reciprocally move the piston within the cylinder to thereby dispense liquid material therefrom in a predetermined quantity, the improvement which comprises the piston comprising a generally cylindrical rigid body having a first circular face and a second circular face, the first face being disposed adjacent liquid inlets and outlets, a synthetic resinous material having a generally cylindrical configuration and a diameter about equal to the diameter of the piston being disposed on at least the first face, a retainer plate having a diameter which is a sliding fit for the cylinder, the resinous material is disposed on the first face of the piston, the retainer plate being secured to the first end of the piston and adapted to compress the synthetic resinous material therebetween.

Further features and advantages of the present invention will become more apparent from the following specification when taken in connection with the drawing wherein:

FIG. 1 schematically represents a dispensing apparatus in accordance with the present invention.

FIG. 2 is a side view of a piston for the apparatus of the present invention.

FIG. 3 is an end view of the piston of FIG. 2.

In FIG. 1 there is schematically illustrated a dispensing apparatus in accordance with the invention generally designated by the reference numeral 10. The apparatus comprises in cooperative combination a cylinder 11 having defined therein a generally cylindrical cavity 12. The cylinder 11 has a first end 13 and a second end I4. In operative communication with the second end 14 is a fluid inlet 15 and a fluid outlet 16. The fluid inlet 15 has disposed therein a check valve 18, and the fluid outlet 16 has disposed therein a check valve 19 permitting flow in the direction indicated by the arrows. The check valve 18 is in communication with a molding material supply means 20 which contains and supplies a hardenable liquid resin containing a particulate filler. Within the cavity 12 of the cylinder 11 is disposed a piston 21 which seals to the inner cylindrical surface defining the cavity 12 and is in slideble contact therewith. The piston 21 is operatively supported by a piston rod or actuating means 22. The rod 22 extends through the first end 13 of the cylinder II. A second cylinder 24 is disposed in generally coaxial relationship with the first cylinder 11. The cylinder 24 has a cylindrical cavity 25 within which is disposed at second piston 26. The cylinder 24 has a first end 28 and a second end 29. A fluid conduit 30 is disposed at the first end 28 and a fluid conduit 31 at the second end 29. The cylinder 24, the piston 26 and the fluid conduits 30 and 31 in operative combination with a valve 30' and a pressurized fluid source 31' form an operating means generally designated by the reference numeral 32 adapted to reciprocally position the piston 21 within the cylinder I1.

in operation of the apparatus of FIG. I, optionally fluid to be dispensed is forced from the supply means 20 through the check valve 18, the conduit 15, into the cavity 11 or alternately is drawn into the cavity 11 by the application of fluid pressure through the fluid conduit 31, the check valve 19 remaining closed while the check valve 18 is open. When the piston 21 has been displaced toward the first end 13 to a desired degree, the flow of the fluid through the conduit 15 is stopped and beneficially, the fluid within the cavity 12 and the piston 11 is forced outwardly through the conduit I6 and check valve 19 by the application of fluid pressure by the fluid passageway 30 to force the piston 26 toward the second end 29 of the cylinder 24, thereby positively displacing a predetermined quantity of liquid from the cavity 12.

In FIG. 2 there is illustrated a piston in accordance with the present invention generally designated by the reference numeral 35. The piston 35 comprises a generally cylindrical body portion 36 having a diameter approximating the internal diameter of the cylinder within which it will fit but having a diameter sufficiently less to provide a free-sliding fit. The body 36 has a first end 37 and a second end 38. The first end 37 defines a first circular face 39lying in a plane generally normal to the axis of the cylindrical body 36. The second end 38 defines a second circular face 40 generally parallel to and disposed remote from the face 39. A synthetic resinous sealing material 43 is disposed adjacent the face 39. The material 43 has a generally cylindrical configuration and a diameter approximating that of the body 36. The material 43 is a resilient material or one that is subject to cold flow, such as polytetrafluoroethylenc and the like. A first retainer plate 45 is in engagement with the synthetic resinous material 43 and is of a rigid material, such as metal or the like. The retainer plate 45 has a diameter slightly less than the cylinder in which it is to operate. The retainer plate 45 defines a plurality of openings 46 through which pass bolts 47 which threadubly engage cavities within thebody portion 36-=and tension the retainer plate 45 in the direction of the face 39."Beneficially, the piston 35 has a generally cylindrical body of synthetic resinous material 48 similar to the material 43 and of generally like configuration disposed adjacent the face 40. A second retainer 49 defines a plurality of apertures 50 through which bolts 51 pass and threadably engage the body 36.

FIG. 3 depicts an end view of the piston 35 showing the retainer 45, the bolts 47, the face 39 and a piston rod engaging a cavity 52. The piston in accordance with the present invention, such as the piston 35 of FIG. 2, has disposed on one end thereof a cylindrical body of synthetic resinous thermoplastic material which is subject to cold flow, such as polytetrafluoroethylene, which beneficially may be applied in the form of an annulus or a plurality of rings to provide a desired thickness. A retainer plate of metal, such as the retainer plate 45, secures the annular resinous material to the body 36 and exerts a compressive force thereon. Advantageously, as depicted in FIG. 2, such an arrangement is beneficially employed on both ends of the piston in order to maintain it in coaxial alignment. Beneficially, the synthetic resinous material subject to cold flow is assembled to the piston body by means of the retainers, such as the retainers 45 and 49, the bolts loosely installed, that is, finger tight, the piston inserted into the cylinder, and the bolts tightened to provide the desired degree of compression on the synthetic resinous material to provide the desired seal. Beneficially, the retainer which is in contact with a hardenable material containing a particulate filler is machined to a dimension which is sufficiently large that the difference between the outside diameter of the retainer and the inside diameter of the cylinder is less than about two-particle diameters of a particulate filler employed in a hardenable material being dispensed such as about 0.001 inch. Thus, on standing after discharging hardenable material therefrom, a portion of the hardenable material may set up or harden within the cylinder, yet the piston may be moved by the application of a sharp blow or force above that normally required to move the cylinder without damage to the sealing elements such as the synthetic resinous body 43 or 48.

The apparatus in accordance with the present invention is readily prepared from a wide variety of materials. Beneficially, the piston body can be prepared from any metal which is nonreactive with the materials being handled or from rigid crosslinked synthetic resinous materials, such as glass reinforced polyesters, polyurethanes and the like. Beneficially, the synthetic resinous material employed in the piston is one subject to cold flow and does not swell in the presence of the material being handled. Particularly suitable are such materials as polytetrafluoroethylene, polypropylene, polyethylene, polyvinyl chloride, nylon, ethyl cellulose and the like. The selection of the particular material depends primarily upon the chemical characteristics of the system, but in a preferred embodiment of the invention, polytetrafluoroethylene is employed.

Pistons in accordance with the present invention have been successfully used for the'dispensing of polyestcr-styrenetype hardenable resin systems and are found to give exceptionally long life and exhibit minimal damage when the apparatus is improperly cleaned prior to standing idle.

As is apparent from the foregoing specification, thepresent invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. For this reason, it is to be fully understood that all of the foregoing is intended to be merely illustrative and is not to be construed or interpreted as being restrictive or otherwise limiting of the present invention, excepting as it is set forth and defined in the hereto appended claims.

We claim:

l. in a dispensing apparatus particularly suited and adapted for the dispensing of liquid hardenable resinous material containing a particulate filler, the apparatus comprising:

a cylinder, the cylinder having slidably disposed therein;

a piston, the cylinder having a liquid inlet and a liquid outlet;

means to reciprocally move the piston within the cylinder and thereby dispense liquid material therefrom in a predetermined quantity, the liquid inlet being in operable combination with;

a means to supply a hardenable liquid resin containing a particulate filler, the improvement which comprises the piston comprising a generally cylindrical rigid body having a first circular face and a second circular face;

at least one synthetic resinous body having a generally cylindrical configuration and a diameter about equal to the diameter of the piston, the synthetic resinous body being subject to cold flow and disposed on at least the first face of the piston; and

a retainer plate having a diameter which is a sliding fit for the cylinder, the retainer plate being disposed on an end of the resinous body, the resinous body being disposed on at least the first face of the piston, the retainer plate being secured to the first end of the piston and adapted to cornpress the synthetic resinous body therebetween and cause expansion thereof to substantially contact the cylinder walls and provide a sealing sliding fit, the retainer plate being adapted to be disposed adjacent the material to be dispensed.

2. The apparatus of claim 1 wherein the synthetic resinous body is polytetrafluoroethylene.

3. The apparatus ofclaim 1 wherein the retaining means are secured to the piston body by means of a plurality of bolts radially distributed about the longitudinal axis of the cylindrical piston body and generally parallel to the axis.

4. The apparatus of claim 1 wherein the retainer plates have a diameter of about 0.001 inch less than the internal diameter of the cylinder.

5. The apparatus of claim 1 wherein the inlet and outlet have disposed therein check valves oriented in such a manner to permit liquid to flow into the cylinder through the inlet and out of the cylinder through the outlet.

6. The apparatus of claim 1 wherein the second face of the piston has a plastic body thereon which is retained in the manner of the body disposed on the first face.

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