GB2133631A

GB2133631A - Liquid level sensor switch

Info

Publication number: GB2133631A
Application number: GB08400487A
Authority: GB
Inventors: Edwin Albert Dvorak; George Nagy; Boris Puscasu
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1983-01-10
Filing date: 1984-01-10
Publication date: 1984-07-25
Also published as: DE3400312A1; GB2133631B; US4467156A; DE3400312C2; CA1213652A; GB8400487D0

Description

1 GB 2 133 631 A 1

SPECIFICATION

Liquid level sensor switch BACKGROUND OF THE INVENTION

Field of the Invention.

The present invention is directed to the field of liquid level sensors and more specificallyto the area of sensors that detect changes of liquid level about a 75 predetermined level.

Description of the Prior Art.

Liquid level sensors containing switches to indicate whether a sensed liquid is above or below a pre determined level are numerous in the prior art.

A liquid level system for detecting the level of vehi cle engine oil is disclosed in U.S. Patent 3,939,470, wherein thermistors are located at opposite sides of an oil reservoir exposed to the oil therein. The system 85 detects variations in thermal dissipation at the ther mistors when they are immersed in oil or exposed to the air above the oil. While the sensors themselves appear to be simple in construction, the system itself requires a rather complex circuit to monitor the sen- 90 sors and makethe determination asto whetherthe oil level has dropped below the predetermined level.

Another type of liquid level sensor is disclosed in U.S. Patent 3,750,124 which utilizes a more complex sensor than that described in the above-noted patent 95 and a relatively simple circuit to determine when the liquid level has dropped below a predetermined level.

The system is shown incorporated in a vehicle brake master cylinder reservoir and utilizes an electrical reed switch sensor mounted horizontally in the verti- 100 cal wall of the reservoir. The sensor incorporates a permanent magnet encapsulated in a float surround ing the reed switch. Whenever the liquid level is above the predetermined level, the float is buoyantly supported to its uppermost position and, depending 105 upon the orientation of the sensor, placesthe magnet adjacent the bottom of the reed switch or floats the magnet above the reed switch. When the liquid level drops below the predetermined value. the float is lowered and causes the opposite effect on the reed 110 switch due to the repositioning of the magnet with respect thereto. The associated circuit monitors the opening and closing of the reed switch to control the illumination of a warning lamp if the level has drop ped below the predetermined level. The primary dis- 115 advantage of employing the reed switch sensor of the 124 patent is due to the requirement that the entire sensor be mounted in a particular orientation, with respect to the vertical, in order that the float contain ing the magnet be properly aligned for responding to 120 buoyant forces or the lack thereof.

According to the present invention, there is pro vided a self-orienting liquid level sensor switch as hereinafter set forth in claim 1.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is an elevational cross-section of the pre ferred embodiment of the present invention.

Figure 2 is an end view of the weighted float ele- 130 ment as shown in Figure 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodimentof the present invention is shown as a float sensor 10 in Figure 1, horizontally mounted through an aperture 3 in a substantially vertical wall 2 of a liquid container, such as an oil reservoir of an automotive engine. Internally threaded nut 4 is welded internally to the wall 2, coaxial with the aperture 3, to provide a mountingfor the sensor 10.

This embodiment of the sensor 10 includes a metal housing 26 having external threads 31 cut along its length so as to be threadable into the support nut 4. When mounted, the housing 26 defines an atmospheric end that is external to the container and a liquid contacting end internal to the container. The atmospheric end has a hex-head 36 with a central aperture to allow insertion and extraction of an electrical connector (not shown). The atmospheric end of the housing 26 also includes a slot38that will accept a locking spring (not shown) to hold the electrical connector in place. A flange 40 (in the alternative, a metal washer) is configured to extend from the body 28 and functions with an associated phenolic washer 42 to provide a seal with respectto the container wall 2 and the aperture 3. The internal portion of the housing 26 provides for an electrical terminal 32 that is embedded in a block of insulator material 29 and retained therein. An 0- ring 28 surrounds a portion of the-termina] 32 to provide a seal to pressurized liquids within the container. The electrical terminal 32 has a bayonet end which extends towards the atmospheric end opening of the housing 26 and a cup-shaped portion which opensto the liquid contacting end, and defines a cylindrical contact surface 30. The insulator block 29 and electrical terminal 32 are held in place within the housing 26 by a retainer spring clip 33. A rubber sleeve 34 is also provided within the housing 26 to provide hermetic sealing to a connector (not shown) when inserted.

The sensor 10 also includes an elongated hollow retainer cage 20 that defines an internal chamber is crimped at22 into a groove24formed nearthe liquid contacting end of the housing 26. The elongated retainer cage 20 is relatively cylindrical in shape and defines a plurality of apertures 21 and 23 which provide for relatively unrestricted flow of liquid therethrough.

A generally cylindrical float element 12 formed from a phenolic formed compound having a desntiy that is less than the liquid of which the level is to be sensed. The float element 12 is configured to float freelywithinthe internal chamberof the retainercage 20 and is of sufficient size so as to be generally aligned with the axis of the cage 20.

Thefloat 12is providedwith an electrical conductor 14 that is formed of a metal having a density that is greater than the liquid. The conductor 14 runs the length of the float element 12 and extends downward to an exposed point 18 opposite the inner chamber surface of the retainer cage 20. The opposite end of the conductor 14 extends to an exposed point 16 which is oppositethe inner surface 30 of the electrical 2 GB 2 133 631 A 2 terminal 32. In this embodiment, the electrical conductor 14 provides self-righting ballast to the float element 12 so that it will be pre- oriented with respect to a vertical reference no matter what the angular orientation of the sensor 10, assumes when the housing 26 is tightly threaded into the nut 4.

In operation, when the liquid level is above a level, which is sufficient to float the element 12 and electrical conductor 14, grounding of the terminal 32 through the retainer cage 20 and housing 26 will be interrupted. However, if the liquid level drops sufficiently so that electrical contact is made at both points 18 and 14 to cause grounding of the terminal 32, the appropriate circuitry can be used to indicate a low liquid level.

Claims

1. A self-orienting liquid level sensor switch corn- prising:

means defining a housing; means for attaching said housing to a substantially vertical wall of a liquid holding container; means mounted within said housing defining an electrically isolated terminal; means defining a float element; means attached to said housing for controlling the maximum movement of said float element; and electrically conductive means mounted on said float means to provide electrical grounding of said terminal means when said liquid level is below a predetermined level and for orienting said float element with respect to the vertical.

2. A sensor as in Claim 1, wherein said attaching means includes an externally cutthread on said housing for mating with an internally cut thread in an aperture of said substantially vertical wall and wherein said housing an retaining means are formed of electrically conductive material and are grounded to said liquid holding container.

3. A sensor as in Claim 1, wherein said float means is formed of a buoyant material, said electrically conducting means is formed of a non- buoyant material and said electrically conducting means is attached to said buoyant material so as to effectively weight one portion thereof and thereby cause the buoyant material to be predictably oriented by gravitational forces.

4. A sensor as in Claim 1, wherein said housing and said retainer means are generally cylindrical in shape and said float means comprises a generally cylindrical shaped element extending along the Iongitudinai dimension of and within said retainer means; and said electrically conductive means includes a metal conductor extending along the length of said flat means, having exposed ends at either end of said float means that are respectively held from contacting said retainer means and said terminal means when said float means is buoyant in a liquid having a level above a predetermined level with respect to said sensor and to respectively contact said retainer and said terminal when said float element is allowed to drop due to said liquid being below said predetermined level.

5. A sensor as in Claim 4, wherein said float ele- ment isformed of a material having a densitywhich is less than the liquid having the level to be sensed and said metal conductor has a density greater than said liquid, so asto orientsaid float means with respectto said vertical in reponse to gravitational forces.

6. In a liquid level sensing system, whereby a sen sor determines whether an associated non conducting liquid is above or below a predetermined level in a liquid holding container, a sensor suitable v for mounting through an aperture in a substantially vertical wall of said container comprising:

an elongated housing sealingly mounted within said aperture in any angular orientation and defining a liquid contacting end within said container and an atmospheric end that is external to said container; an electrical terminal within said housing, electri cally isolated from said container and said housing and extending between said liquid contacting end and said atmospheric end of said housing; a hollow retainer defining an internal chamber having one end connectedto the liquid contacting end of said elongated housing and having a plurality of apertures for allowing the liquid to enter and exit its internal chamber; afloat elementfreely contained within said internal chamber of said hollow retainer; and means having a density greater than that of said float element attached to one side of said element for orienting said float with respect to the vertical inde- pendent of the angular orientation of said housing as mounted in said vertical wall of said container and defining an electrical conductorfor providing an electrical switching connection between said electrical terminal and said retainer, responsive to said liquid falling below said predetermined level.

7. A sensor as in Claim 6, wherein said orienting and switching means comprises a single electrical conductor attached to said float element at a finite distance from the longitudinal axis of said float ele- ment so as to establish a predetermined orientation of said conductor and to allow performance of said switching function independent of the angular orientation of said housing.

8. A sensor as in Claim 7, wherein said float ele- ment is formed in a generally cylindrical shape to loosely fit within said internal chamber and to be freely rotatable about its own longitudinal axis.

W g Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon, Surrey, 1984. Published byThe Patent Office, 25 Southampton Buildings, London, WC2A lAYfrom which copies may be obtained.

z 1;