GB2203633A - Container with liquid level sensor - Google Patents

Abstract

A liquid-containing assembly e.g. a coffee making machine for an aircraft galley comprises a container having an open top, a closure adapted to abut against the open top of the container and including a block 28 of electrically insulating material, and a pair of elongate electric current conductors 50, mounted on the block 28 so as to project into the container 16. Each conductor 50, is pivotally mounted on the block 28, about a pivot axis 54, and moves between a position in which one end projects downwardly into the container 16 and a position in which said one end lies closely adjacent to the closure 20. Tension springs 64, urge the conductors into the vertical position. The container is filled via the closure and the conductor forms a level sensor which prevents over filling. <IMAGE>

Description

CONTAINER WITH LIQUID LEVEL SENSOR This invention relates to a container having a liquid level sensor and is particularly applicable to an aircraft galley coffee making machine.

In coffee making machines for aircraft galleys, a coffee pot is positioned under a closure member through which the pot is automatically filled with percolated coffee. It is necessary to sense the level of liquid in the pot in order to prevent it from being overfilled.

Conventionally, this is done by providing a pair of electrically conductive probes which project downwardly into the pot to the desired liquid level, the change in electrical resistance between the probes as they become immersed in the liquid being used to produce a control signal to interrupt the liquid supply. Prior to removal of the coffee pot from the machine, either the closure is raised or the support for the coffee pot lowered by a limited amount so as to disengage the closure from the rim of the coffee pot. The extent of this vertical movement is substantially less than the distance between the required liquid level and the top of the pot.

Consequently, it is necessary for the probes to be displaceable laterally to permit removal and replacement of the pot.

Patent specification US-A-3519769 discloses an aircraft galley coffee making machine having a liquid level sensor of this type. The contact probes are formed of stainless steel spring strip which are rigidly mounted on a block of insulating material secured to the closure. The two strips bend as the coffee pot is removed and replaced. In order to distribute the resulting bending along the length thereof, each strip is enclosed in a tapering elastomeric sheath, with the aim of reducing the possibility of either strip breaking due to metal fatigue caused by the repeated flexing movements which take place as the coffee pot is inserted and removed. The present invention aims to provide a sensing arrangement in which the contact strips are not subject to bending.

According to the invention, a liquid containing assembly comprises: a container having an open top; a closure adapted to abut against the open top of the container and including a block of electrically insulating material; a pair of elongate electric current conductors, each of which is pivotally mounted on the block for angular movement, about an axis located at an intermediate position along its length, between a position in which one end projects downwardly into the container and a position in which said one end lies closely adjacent to the closure;and a respective tension spring for each strip extending between a location on the strip on the other side of its pivot axis from said one end of the strip and a location on the closure above said pivot axis.

Each strip may be formed with a projection on one side thereof coincident with said pivot axis, the projection being received in a horizontally extending opening in the insulating block. Preferably the upper face of said opening has a flat surface which engages with a corresponding flat surface on the upper edge of the projection so that the tension spring tends to bias the strip into a predetermined position.

Preferably the two strips are coupled to one another by an electrically insulating sleeve member so that both probes pivot simultaneously, the pivot axes of the two strips being coincident. With this arrangement, a single tension spring may be connected to the sleeve, in which case the holes in which the projections on the strips are received are formed in electrically conductive metal inserts in the insulating block so as to provide an electrical connection to each strip. If a separate spring is provided for each strip, the springs themselves may serve to establish the required electrical connection.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a fragmentary side elevational view showing the top part of a coffee pot in position in an aircraft galley coffee-making machine; Figure 2 is a vertical sectional view of the level sensing probes of the coffee-making machine shown in Figure 1; Figure 3 is a cross-sectional view taken on the line 3 - 3 in Figure 2; Figure 4 is a cross-sectional view, similar to Figure 3, but with the probes in the position they would occupy when displaced during removal of the coffee pot from the coffee-making machine; Figure 5 is a fragmentary cross-sectional view taken on the line 5 - 5 in Figure 2; Figure 6 is a fragmentary cross-sectional view taken on the line 6 - 6 in Figure 2;; Figure 7 is a fragmentary cross-sectional view taken on the line 7 - 7 in Figure 2.

Referring to Figure 1, an aircraft galley coffeemaking machine comprises a housing including side walls 10 and 12 and a rear wall 14. A coffee pot 16 rests on a platform (not shown) secured to the bottom edges of the walls 10, 12 and 14. A bridge member 18 extends between the side walls 10 and 12 above the coffee pot 16 and carries a closure member 20. In Figure 1 the bridge member 18 is shown in a position permitting removal of the coffee pot 16. It can be lowered to a position in which the tapering side walls of the closure member 20 engage with the top of the coffee pot, thus securing it in position. Means (not shown) are mounted on the bridge member 18 for discharging percolated coffee into the coffee pot 16.

Turning to Figures 2 and 3, the bottom of the closure member 20 contains a cylindrical recess 22. A hole 24 extends through the top of the closure member 20 and is aligned with a larger diameter hole 26 extending through the support member 18. A base member 28 for a liquid level sensor in accordance with the invention is mounted in the hole 24 and secured in position by screws 30 and 32. As can best be seen from Figure 2, the base member 28 has a central recessed region projecting up through the hole 24 with two downwardly extending inner side limbs 34 and 36 inside the screws 30 and 32 and two downwardly extending outer side limbs 38 and 40 outside the screws 30 and 32.As can be seen from Figures 4 and 5, the outer side limbs 38 and 40 have bevelled edges which serve as ramps to engage with the rim of the coffee pot 16 if the latter is lifted too close to the closure 20 during insertion and removal. The bottom edges of the inner limbs 34 and 36 are of semi-circular crosssection for a reason which will be explained hereinafter.

A pair of static contact carriers 40 and 42 are secured to the inner side faces of respective inner limbs 34 and 36 and project through openings in the top of the carrier 28 so that electrical connection can be made thereto through the hole 26 in the bridge member 18.

The bottom end of each of the contact carriers 40 and 42 is semi-circular and each contains a respective hole 44, 46. As can be seen from Figure 6, the hole 44 in the contact carrier 40 is basically circular but its upper edge takes the form of a flat 48 positioned to be a tangent to its otherwise circular periphery. The hole 46 in the other contact carrier 42 is similarly shaped.

Each of the contact carriers 40 and 42 supports a respective pivoting contact probe 50, 52. The probes 50 and 52 have respective holes 54 and 56 near their upper ends and respective lateral projections 58 and 60 located below the holes 54 and 56 and extending into the holes 44 and 46 in the contact carriers 40 and 42 respectively.

Below the holes 54 and 56, the probes 50 and 52 are both embedded in a common probe sleeve 62 of synthetic plastics material. The sleeve 62 has a generally Vshaped cut-away portion in its lower edges which exposes part of the lower side faces of the probes 50 and 52.

Respective tension springs 64 and 66 extend between the holes 54 and 56 at the tops of the probes 50 and 52 and respective metal pegs 68 and 70 which are secured to the contact carriers 40 and 42. The effect of the flat 48 forming the upper surface of each of the holes 44 and 46 is that the springs 64 and 66 reliably bias the two contact probes 50 and 52 to the vertical position illustrated in Figure 3.

When the coffee pot 16 is in position in the coffee-making machine and the carrier 18 is lowered to bring the closure 20 into engagement with the top rim of the coffee pot, the probes 50 and 52 project downwardly, as illustrated in Figure 3. When the level of liquid in the coffee pot 16 reaches the lower ends of the probes 50 and 52, electrical connection is established therebetween and detection of this connection is used to cut off the supply of further coffee. The user then raises the carrier 18 to the position shown in Figure 1 so as to be able to remove the coffee pot 16 sideways, displacing the probes 50 and 52 to the position illustrated in Figure 7, against the action of the springs 64 and 66. The semicircular cross-section of the bottom edges of the inner limbs 34 and 36 ensures that they are not fouled by the probes 50 and 52 during this movement.

As soon as the coffee pot 16 is clear of the probes 50 and 52, they spring back to the position illustrated in Figure 3. They are displaced in the opposite direction when the coffee pot 16 is replaced.

One of the problems with liquid level sensors of this type is that condensation on the electrically insulating surfaces could lower the electrical resistance between the two contact carriers 40 and 42 sufficiently to give a false signal. In order to guard against this, two ribs 72 and 74 are formed on the underside of the base 28 between the two pegs 68 and 70. These ribs serve both to increase the surface length between the two contact carriers 40 and 42 and to provide vertical surfaces down which condensation can flow prior to dropping back into the coffee pot. Similarly, in order to prevent a build-up of condensation on the contact probe sleeve 62, a series of oblique grooves 72 are formed in the surface thereof. Surface tension causes any condensation to collect in the bottoms of the grooves from which it tends to flow downwardly. In practice, a larger number of grooves would be provided than the three illustrated in Figures 2 and 8.

Claims (8)

1. A liquid-containing assembly comprising: a container having an open top; a closure adapted to abut against the open top of the container and including a block of electrically insulating material; a pair of elongate electric current conductors, each of which is pivotally mounted on the block for angular movement, about an axis located at an intermediate position along its length, between a position in which one end projects downwardly into the container and a position in which said one end lies closely adjacent to the cIosure;and a respective tension spring for each strip extending between a location on the strip on the other side of its pivot axis from said one end of the strip and a location on the closure above said pivot axis.

2. A liquid-containing assembly according to claim 1, wherein each strip is formed with a projection on one side thereof coincident with said pivot axis, the projection being received in a horizontally extending opening in the insulating block.

3. A liquid-containing assembly according to claim 2, wherein the upper face of said opening has a flat surface which engages with a corresponding flat surface on the upper edge of the projection so that the tension spring tends to bias the strip into a predetermined position.

4. A liquid-containing assembly according to claim 1, 2 or 3, wherein the pivot axes of the two strips are coincident and the.two strips are coupled to one another by an electrically insulating sleeve member so that both probes pivot simultaneously.

5. A liquid-containing assembly according to claim 4, wherein the holes in which the projections on the strips are received are formed in electrically conductive metal inserts in the insulating block so as to provide an electrical connection to each strip.

6. A liquid-containing assembly according to claim 5, wherein a single tension spring is connected to the sleeve.

7. A liquid-containing assembly according to any of claims 1 to 4, wherein a separate tension spring is provided for each strip, each spring serving to establish electrical connection with the corresponding strip.

8. A liquid-containing assembly comprising, substantially as hereinbefore described with reference to the accompanying drawings.