Patent Grant
6867383
1. Field of Invention
The present invention relates to the field of fluid transport, and more particularly but not by way of limitation, to an improved liquid level assembly with a diaphragm sealed housing.
2. Discussion
Many functional components, such as electrical switches, must be packaged in various protective housing or containers as may be required to protect the switches from the environment in which the switch is used. Examples can be found in switches used to control the operation of sump, sewage and effluent pumps.
It is known that sealing such switches can suffer deterioration from fluid leakage, and seals for switch supporting housings have not been found adequate when the switches vary dimensionally over a relative wide range of tolerances. Heretofore, a proper seal has not been devised for the proper engagement of the switch and switch support container when a flexible membrane normally used in such switches must be exposed to hostile fluid environment while also accommodating manufacturing tolerances varying widely.
The present invention provides a liquid level assembly for use in controlling liquid levels between predetermined heights, the liquid level assembly having a switching assembly responsive to the liquid head for sending on and off signals to a pump. A housing has an internal cavity and the switching assembly is supported therein. The housing has an open end communicating with the housing cavity, the open end being sealed by a flexible membrane to transmit pressure of the liquid external to the housing to the switching assembly in the housing cavity.
The seal has a diaphragm with a center planar portion disposed to abut the switching assembly, a peripheral web portion and a flexible bellows portion connecting the planar portion and the peripheral web portion. A plurality of knob members extend from the peripheral web portion and are spatially disposed to press against the switching assembly and the housing to accommodate differences in manufacturing dimensions of the switching assembly.
The advantages and features of the present invention will be apparent from the following description when read in conjunction with the accompanying drawings and appended claims.
In many cases electrical components, such as switches, must be protected from the environment in which the components are used. For instance, in the case of liquid level controllers, the switches must be housed in a protective housing to avoid direct contact with the liquids in which the switches are immersed. For custom designed components, this may involve simply designing a housing with appropriate seals to protect an inner cavity in which the component is disposed. However, where components can vary widely dimensionally, sealing the housing has been problematic.
An example of such is presented with the instance of a liquid level switch that is commonly used to control the operation of various sump, sewage and effluent pumps. The switching mechanism has a pressure responsive, spring biased switching disk, and movement of the switching disk opens and closes contacts disposed in the body of the switching mechanism. The spring has an adjustment screw that permits the force of the switching disk to be preset within predetermined limits.
One such switching mechanism is generally cylindrical in shape, and the body of the switch and its switching disk are held together by a metal band that is swaged around the switch body and the perimeter of the switching disk. This swaging process results in wide dimensional variations of the assembled switch. That is, the final diameter and width of the swaged metal band vary over a wide dimensional range, resulting in a wide tolerance range for the total height of the assembled switching mechanism.
To make the switching mechanism water-tight for use in a target environment, the banded switching mechanism and switching disk are disposed in a plastic housing, and the housing is sealed with a diaphragm seal with a flexible bellows portion that abuts the switching disk. This arrangement causes external pressure that is exerted against the flexible bellows portion to be exerted against the switching disk.
The enclosure of the banded switching mechanism and switching disk in the sealed plastic housing allows the submersion of the switching mechanism in a liquid tank, while protecting the switching mechanism and assuring the integrity of the switching mechanism. Connected to an appropriate pump for the application, the switching mechanism senses the head of liquid above it, and the pump will be turned on or off as required to control the level of the liquid within a preset range.
Turning now to a description of the present invention, shown in
The body of the switching mechanism 102 is generally cylindrically shaped, and the switching disk 104 is secured to the body of the switching mechanism 102 by a metal support band 121 that is swaged around the perimeter of the body. This swaging process is not dimensionally consistent, resulting in wide dimensional variations in the height of the assembled switching mechanism 102. That is, the final diameter and width of the swaged metal band has been found to vary over a wide dimensional range, resulting in dimensional variation of the total height of the assembled switching mechanism 102.
To make the switching mechanism 102 water-tight for use in liquid level control in a target environment, the switching mechanism 102 is supported in a plastic housing assembly 108. The housing assembly 108 has an upper housing member 110 that forms an internal cavity 112 in which the switching mechanism 102 is disposed. A lower housing member 114 partially seals the internal cavity 112 at its bottom and is secured to the upper housing member 110 via screws 116. Several openings 118 are provided in the lower housing member 114, and the seal of the internal cavity 112 is completed by the provision of a diaphragm seal 120 secured between the upper housing member 110 and the lower housing member 114.
The diaphragm seal 120 is a flexible member having a flexible bellows portion 122 that abuts against the switching disk 104. The bottom surface of the diaphragm seal 120 is exposed directly to the liquid in the target environment via the openings 118, and the pressure of the liquid is exerted against the flexible bellows portion 122 so as to move the switching disk 104. The diaphragm seal 120 is preferably made of a flexible, compressible material, such as Nitrile, or other suitable elastomer, and preferably having a durometer range of about 40 to 60.
The enclosure of the banded switching mechanism and switching disk 104 in the sealed plastic housing assembly 108 allows submersion of the switching mechanism 102 in a liquid environment, such as in a tank (not shown), while protecting and ensuring the integrity of the switching mechanism 102. A wiring conduit (not shown) is extended through a threaded opening 124 in the upper housing member 110 to connect to the switching mechanism 102. The wiring conduit connects to an appropriate pump for a particular application, and the switching mechanism 102 senses the head of liquid on the diaphragm seal 120 so that the pump will be turned on or off as required to control the level of the liquid within a preset range.
Turning now to the drawings and more particularly to
A plurality of knob portions 130 are integrally formed with, and extend upwardly from, the peripheral web portion 126. The knob portions 130 are spatially and radially disposed on the web portion 126 to abut against the switching mechanism 102, in a manner made clear below.
Several of the knob portions 130 are disposed along an inner circular pattern 132, and the remaining knob portions 130 are disposed along an outer circular pattern 134, as shown. The number of knob portions 130 provided on the peripheral web portion 126 is not believed to be critical; rather, the number of such knob portions 130 will be empirically determined for each specific application. Also, while inner and outer circular patterns are depicted, it will be appreciated that in some cases a single circular pattern can be utilized, and in other applications it may be desirable to arrange the knob portions in other patterns.
Returning to
The diaphragm seal 120 is pressed against and across the open end of the upper housing member 110 by the lower housing member 114, which presses against the peripheral web portion 126. As best shown in
The openings 118 in the lower housing member 114 permit the liquid environment to apply head pressure against the flexible planar portion 125 of the diaphragm seal 120 to move the switching disk 104 to actuate the switching mechanism 102, which in turn signals a pump (not shown) to operate to remove liquid from the tank until the head pressure against the switching disk 104 is reduced, thereby adjusting the liquid level.
The bellows portion 122 of the diaphragm seal 120 extends downwardly and upwardly, as shown, to hold the flexible planar portion 125 of the diaphragm seal 120 against, or slightly separated from, the switching disk 104. The knob portions 130 extending from the peripheral web portion 126 are positioned to abut the under surface of the support band 121 and to press the support band 121 against the shoulder recess 138.
The diaphragm seal 120 as used in the liquid level assembly 100 serves three purposes: 1) the diaphragm seal 120 contains the built-in sealing bead 128 that, when compressed into sealing engagement with the groove 140 in the lower end of the upper housing member 110, prevents water (or other surrounding liquid) from entering the housing cavity 112, thereby protecting the switching mechanism 102; 2) the diaphragm seal 120 provides a built-in bellows portion 122 that allows the center flexible planar portion 125 to move up and down to actuate the switching mechanism 102; and 3) the diaphragm seal 120 provides a series of compressible knob portions 130 that are compressed against, and holds, the switching mechanism 102 in a set, firm position within the housing cavity 112 of the housing assembly 108.
Assembly of the liquid level assembly 100 proceeds as follows: the switching mechanism 102 is placed into the housing cavity 112 of the upper housing member 110. The diaphragm seal 120 is then placed over the switching mechanism 102 and against the bottom edge of the upper housing member 110, with the sealing bead 128 in the groove 140.
The lower housing member 114 is then placed against the bottom of the peripheral web portion 126 of the diaphragm seal 120 and mechanically fastened to the housing by the screws 116, compressing the sealing bead 128 into firm engagement with the groove 140. At the same time the sealing bead 128 is being compressed, the knob portions 130 are moved upward into engagement with the support band 121. The arrangement of the knob portions 130 in the two circular patterns 132, 134 assures that the support band 121 is always contacted by most, if not all, of the knob portions 130 to physically and firmly hold the switching mechanism 102 in place, thereby preventing potential movement of the switching mechanism 102 in the housing cavity 112.
For purposes of this description, it has been assumed that the liquid level assembly 100 is used in an application in which the liquid in a tank is periodically removed to maintain the liquid level between predetermined set point levels that are determined by adjustment of the screw 106. It will be appreciated that the liquid level assembly 100 could as well be utilized in an application in which liquid is pumped into a tank to maintain the liquid level between predetermined set point levels.
It is clear that the present invention is well adapted to carry out the objects and to attain the ends and advantages mentioned as well as those inherent therein. While presently preferred embodiments of the invention have been described in varying detail for purposes of the disclosure, it will be understood that numerous changes may be made which will readily suggest themselves to those skilled in the art and which are encompassed within the spirit of the invention disclosed and as defined in the above text and in the accompanying drawings.
This application claims priority to U.S. Provisional application No. 60/458,478 filed Mar. 28, 2003, entitled Liquid Level Assembly With Improved Diaphragm Seal.
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