US3014620A - Fluid dispensing device - Google Patents

Description

Dec. 26, 1961 A. H. MOORE FLUID DISPENSING DEVICE Filed April 20, 1959 [mm/m INVEN TOR. ARTHUR H. M m URE- United States Patent Office 3,914,620 Patented Dec. 26, 1961 3,014,620 FLUID DISPENSHNG DEVICE Arthur H. Moore, Dayton, N..'l., assignor to Radio Corporation of America, a corporation of Delaware Filed Apr. 20,,195d, Ser. No. 897,364 1 Claim. '(Cl. 222-70) This invention relates to improved dispensing devices for filling containers with fluid. More particularly it relates to improved devices for rapidly filling containers with precisely metered quantities of viscous fluids.

In attempting to fill containers with viscous fluids many problems are encountered. Such fluids, when poured into a container to be filled, are diflicult to control in that, when the container is full, it is difficult to shut off the stream of pouring fluid and this frequently results in spillage of the fluid over the sides of the container. In mechanized processes wherein it is desirable to rapidly fill one container after another, the difficulty in shutting off the flow of fluid results in excessive time elapsing between filling operations. Once a container has been filled, time is also lost in initiating a second fill cycle due to the difculty encountered in starting flow of a viscous fluid. Furthermore, in such processes, it is difficult to accurately meter the quantity of fluid pouring into a container since, because of the long drip time required for such viscous fluids, the flow must be cutoff suificiently before the container is full so that actual filling is completed during the drip time of the fluid.

This problem is particularly acute with respect to providing automatic equipment for filling small size transistor cans with encapsulant. Transistor cans are frequently filled with a viscous, electrically-insulating fluid in order to protect the semiconductor body and its electrodes. One type of material with which transistor cans are filled comprises a dispersion of heat conducting particles such as, for example, Alundum in a silicone liquid. A particular dispersion frequently employed comprises 4 parts by weight of Alundum in one part silicone oil and has a viscosity which varies from about 10,000 centipoises up to about 20,000 centipoises. The heat conducting particles dispersed in the silicone fluid (partially Alundum) are frequently a highly abrasive material. Because of this fact, it is generally necessary to provide a means for piping the dispersion from a source thereof to the cans, which piping cannot have included therein any mechanical valves for controlling flow of the dispersion. In one method for filling transistor cans, the dispersion is contained in a sealed reservoir having a pipe leading therefrom to a position convenient for emptying into a transistor can. Air pressure is applied to the sealed reservoir forcing the dispersion through the piping and into the transistor can. At a predetermined time before the transistor can is filled, the supply of compressed air to the reservoir is cut OE and the compressed air in the reservoir exhausted into the atmosphere. Filling of the transistor can is completed by allowing the viscous fluid-remaining near the outlet portion of the piping to drip into the transister can. When this is completed, the transistor can is removed, a new and emptyone positioned under the outet, and compressed air again forced into the sealed reservoir to once more initiate flow through the piping. This method is employed for metering the dispersion into transistor cans having a capacity as low as .012 cubic inch into which is poured .009 cubic inch of dispersion. Thus it can be seen that in the procedure as recited considerable time will be lost both in finishing the filling operation by the slow method of dripping and in initiatinga new 7 filling cycle.

It is a primary object of this invention to provide improved apparatus for automatically dispensing fluids into containers.

It is a further object of this invention to provide improved apparatus which accurately and rapidly meters predetermined quantities of a viscous fluid into containers.

It is another object of this invention to provide improved apparatus for filling containers with viscous fluid while at the same time preventing overflow and any dripping from the apparatus between filling operations.

It is yetanother object of this invention to provide improved apparatus for filling containers with a viscous dispersion of abrasive particles in a fluid, said apparatus requiring no mechanical valves to control the flow of said fluid.

These and other objects and advantages are met by providing auxiliary apparatus to be employed with a reservoir supply system for filling containers. The reservoir supply system includes a pressurized supply system having conduit means connected thereto and having an outlet for filling containers. The auxiliary apparatus comprises means for varying the pressure on fluid in said conduit means adjacent said outlet and means controlling said auxiliary apparatus to actuate the same to exert additional pressure on the fluid adjacent the outlet at the same time that fluid begins to flow toward said outlet from the reservoir and to create a back suction at the outlet at the instant fluid ceases to flow from the reservoir toward the outlet.

In a preferred embodiment the auxiliary apparatus comprises an-air cylinder having a cylinder head, and a piston slidably mounted within said cylinder. A pipe communicates between the interior of the cylinder adjacent the cylinder head and the conduit means near the outlet thereof. In operation, flow of viscous fluid is initiated from the reservoir while, at the same time, the piston in the air cylinder is moved toward the cylinder head. When a suflicient quantity of fluid has been emptied into a container, the flow of fluid from the reservoir is cut 0E and, simultaneously therewith, the piston in the air cylinder is retracted. This action of the piston creates a suction action in the cylinder adjacent thecylinder head and causes viscous fluid remaining in the conduit means near the outlet thereof to be sucked back to prevent afterdrip. When a new and empty can is positioned adjacent the outlet, flow of fluid from the reservoir is again ini tiated simultaneously with the movement of the piston toward the cylinder head. This movement of the piston causes fluid contained in the pipe to be forced to the outlet of the conduit means thus acting to speed up the start of a new filling cycle.

V The single figure of the drawing is a schematic, partially cross-sectional View of a preferred embodimentef the invention.

As was discussed heretofore, one prior art means for providing apparatus to fill transistor cans includes a pressurized're'servoir 1t} and conduit means 11 having .an outlet I12 for transporting fluid from pressurized resand to exhaust air from the reservoir 10 upon cornpletion of the filling cycle. The present invention comprises means in combination with the prior art dispensing apparatus for accurately and rapidly controlling quantities of fluid dispensed from the can-filling spout 12.

The embodiment of apparatus illustrated in the drawing includes an'air cylinder 16. Within the air cylinder 16 is a piston 17 controlled by a conventional drive means 18 operated by compressed air fed through a three-way valve 24. In operation, compressed air is fed into the drive means 18 through a pipe 24a to force the piston 17 forward and through another pipe 24b to cause re to initiate a new fill cycle.

traction of the piston 17. Forward of the piston within the air cylinder 16, the interior thereof is enlarged to provide two cavities therein 19 and separated by a flexible diaphragm 21. Such cavities may conveniently be provided by including as part of the air cylinder a cylinder head 22 which is joined to the main body of the air cylinder at a plane which includes the diaphragm 21. The cavity 19 nearest the cylinder head 22 has a feed pipe 23 leading therefrom and joining with the supply conduit 11 near the outlet 12 thereof.

Control of feed from the reservoir 10 and cooperating action of the air cylinder 16 is accomplished by an electrical circuit having a microswitch positioned near the outlet 12 of the supply conduit and triggered by the positioning of the transistor can 13 beneath the outlet 12. When the microswitch 25 is so triggered, current from a source 26 is caused to flow through a timer 27 and to simultaneously actuate two solenoids 28 and 29. The first of said solenoids being coupled to the threeway valve 14 controlling the supply of compressed air to the reservoir 10 and the second of said solenoids being coupled to the three-way valve 24 controlling the supply of compressed air for actuating the piston drive means 18.

Transistor cans 13 are indexed under the outlet 12 by such means as, for example, an indexed turntable B0. The drive means and indexing means for the turntable being well known in the art neither is shown in the figure. Once a transistor can is positioned under the outlet -12 it triggers the microswitch 25 starting the timer 27 and triggering each of the solenoids 2S and 29 to cause compressed air to flow into the reservoir 10 and to cause compressed air to flow into the drive means 18 forcing the piston 17 forward. The forward motion of the piston 17 forces the diaphragm 21 toward the cylinder head 22 and causes air to be forced out of the cylinder head cavity 19 into the pipe 23. At the same time, compressed air flowing into the reservoir 10 causes fluid to be forced through the supply conduit 11 and into the transistor can 13 located under the outlet 12. With the timer 27 set to allow for a predetermined quantity of fluid to flow into the transistor can 13, flow of fluid will continue until the can is full. At the end of the fill time, the timer 27 actuates both solenoids 28 and 29 simultaneously to turn the three-way valve 14 to a position to exhaust compressed air from the reservoir 10 into the atmosphere and at the same time to reverse the operation of the drive means 18 thereby causing piston 17 to move away from the diaphragm 21 thereby flexing the diaphragm 21 away from the cylinder head 22. This movement of the diaphragm creates a suction action in the cylinder head cavity 19 causing fluid to be drawn upward into the connecting pipe 23 and thereby sharply cutting off the flow of fluid in the transistor can 13.

When one transistor can on the turntable has been filled, the indexing means for the turntable 30 is actuated positioning a new and empty transistor can under the outlet 12, which again triggers the microswitch 25 At the beginning of the second and all subsequent fill cycles, deflection of the diaphragm 21 toward the cylinder head cavity 19 causes fluid previously withdrawn upward into the pipe 23 to be expelled therefrom and to flow into the transistor can 13. In this way the operation of the air cylinder appreciably speeds up the initiation of a fill cycle.

The invention as taught herein provides means for filling transistor cans at a great increased rate. For example, heretofore, using the prior art apparatus previously described, one type of transistor can could be filled at a rate of about 840 per hour. Using apparatus of the present invention, the rate is about 2400 per hour. This type of can has a capacity of about .026 cubic inch and is filled with about .018 cubic inch of dispersion.

While a specific embodiment of this invention has been described in connection with a procedure for filling transistor cans with a dispersion of abrasive particles in a viscous liquid, it is not intended that the improved apparatus be limited to this use. It is obvious that the device of this invention is applicable to the dispensing of any viscous liquids wherein it is desired to fill containers in rapid sequence with a minimum of delay between fill cycles.

What is claimed is:

A fluid dispensing device for filling containers with a viscous fluid comprising a closed reservoir for holding a supply of said fluid in surface contact with a volume of air; conduit means extending below the surface of said fluid in said reservoir and having an outlet adapted to empty fluid into said containers and having an opening therein adapted to expose a surface of fluid in said conduit means; first air pressure means associated with said reservoir for cyclically applying air pressure to the surface of said fluid in said reservoir, whereby successive predetermined quantities of said fluid are forced from said reservoir through said conduit means and out through said outlet; second air pressure means including a cylinder, a cylinder head, a piston mounted within said cylinder, and a flexible diaphragm mounted within said cylinder between and spaced from said cylinder head and said piston, whereby said cylinder, cylinder head, and diaphragm define a first closed air cavity and said cylinder, diaphragm, and piston define a second closed air cavity; a pipe communicating between said first closed air cavity and said opening in said conduit means; means actuating reciprocating movement of said piston in said cylinder; and control means including timing means associated with both said fluid forcing means and said piston actuating means such that said piston moves toward said cylinder head at the same time fluid begins to flow toward said outlet from said reservoir, thereby exerting additional pressure toward said outlet, and such that said piston retracts at the instant fluid ceases to flow from said reservoir toward said outlet, thereby creating a back suction adjacent said outlet.

References Cited in the file of this patent v UNITED STATES PATENTS 486,746 Wildi Nov. 22, 1892 1,078,028 Zeamans -3 Nov. 11, 1913 2,103,817 Johnson Dec. 28, 1937 2,150,760 Cozzoli Mar. 14, 1939 2,577,933 Triggs Dec. 11, 1951 2,650,003 Coleman Aug. 25, 1953

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