AN APPARATUS FOR DETERMINING THE FLUID CONTENT OF A CONTAINER

Abstract: An apparatus (10) to establish when the quantity of fluid remaining on a container falls below an adjustable predetermined level has a base (11), which houses elements adapted to deflect proportionally to the weight applied to them. A lid (12), adapted to sit on the elements, receives or supports the container. The elements are arranged to operate a switch (62) when deflection of the elements reaches or falls below a predetermined value, thereby activating a warning or alarm system. The warning system can include one or more light-emitting diodes (15, 16) or an audio/visual alarm (20) and can be either integral with the apparatus or remote therefrom. The elements can comprise a number of levers (54) which are operatively linked together, which respond to the weight of the container on the lid (12).

Description: AN APPARATUS FOR DETERMINING THE FLUID CONTENT OF A CONTAINER Field of the Invention The present invention relates to an apparatus for use in determining the fluid contents of a container. It further relates to an apparatus which can trigger an alarm signal when the weight of a fluid container falls below a predetermined value. Background to the Invention Where a fluid is supplied in a non-transparent container, it is difficult to ascertain the volume of fluid remaining therein. Where the container is relatively light in weight or can be lifted easily, an approximate measure can be made by lifting and/or shaking the container. Certain containers, for example, some designs of kettle, have an indicator integral within a wall of the container and visible graduations to inform the user as to how much fluid is present. However, for containers such as gas cylinders, commonly used to supply gas to a central heating system or a cooker, the situation is not so simple. Although gas containers may be equipped with pressure gauges, such gauges give only an approximate guide and even with regular checking can run out at inconvenient times. A similar problem is encountered with other pressurised containers such as beer barrels, which are often difficult to monitor due to their location away from the point of sale, often in a cellar. Changeover valves can be used with such pressurised containers which supply from one cylinder to another when the pressure in the first cylinder becomes too low, this still leaves the problem of the user remembering to check the two cylinders to change the first cylinder, and being able to check the contents of the second cylinder before it also runs out. It is an object of the invention to provide an apparatus which allows easy monitoring of the fluid contents of a container. It is a further object to provide an apparatus which signals an alarm when the fluid content drops below a pre-set value. Summary of the Invention According to the present invention there is provided an apparatus for establishing when the quantity of fluid remaining in a container falls below an adjustable predetermined level, the apparatus comprising: a base, housing elements adapted to deflect proportionally to the weight applied to them, and a lid adapted to sit on the elements in the base and for receiving or otherwise supporting the container thereon in which the elements are arranged to operate a switch when deflection of the elements reaches or falls below a predetermined value, the switch enabling a circuit comprising a warning or alarm system. The elements preferably comprise one or more levers operatively linked together. Advantageously, the levers are operable by tabs extending downwardly from the lid. The switch is preferably mounted directly on the elements, the direct linkage reducing the chance and size of an error. The switch is preferably pivotally mounted on one of the elements. Advantageously, the switch is connected to the element by means of a tensioning member which biases the switch to return to its normal position. The pivotal mounting of the switch prevents damage when the force urging the switch into a closed position becomes too great. The tensioning member ensures that the switch returns to a rest position when the force is removed. The circuit is preferably enabled by contact of the switch with a switch receiver. The position of the switch receiver is preferably adjustable. Adjustment is advantageously by means of a screw-threaded adjustment means acting on the switch receiver, the screw-threaded adjustment providing small incremental changes to be made and consequentially, high sensitivity. A tensioning member advantageously links the adjustment means to the switch receiver to take out any play in the upward or downward motion of the switch receiver. The apparatus can additionally comprise a restraining member to prevent rotation of the switch receiver on turning of the adjustment means. The restraining member is preferably attached to the upper part of the apparatus to aid assembly of the apparatus and give increased repeatability of measurement. The warning system preferably comprises one or more visual displays, such as light emitting diodes located on the apparatus. Advantageously the warning system can also comprise an audio/visual alarm remote from the apparatus. The linkage between the remote alarm and the apparatus can be via a wire or alternatively electromagnetic radiation. Brief Description of the Drawings The present invention will now be described more particularly with reference to the accompanying drawings which show by way of example only an embodiment of mass determining apparatus according to the invention. In the drawings: Figure 1 is a perspective view of a platen; Figure 2 is a perspective view of an audio visual indicator; Figure 3 is a perspective view of a radio frequency (RF) receiver to receive a signal from the transmitter of Figure 4; Figure 4 is a perspective view of a radio frequency (RF) transmitter; Figure 5 is a perspective view of the platen of Figure 1 with the top press removed; Figure 6 is a detailed view of the switching system; Figure 7 is a perspective view of levers and a switch arm, with the other components removed; and Figures 8 to 10 are perspective views of the switch lever and switch arm with the other components removed. Description of the Preferred Embodiment Throughout this description, references to a fluid should be taken to include not simply liquids, but also particulate solids which can be caused to flow upon application of a force. Figure 1 shows a platen, generally referenced 10, comprising a base pressing 11 and a top pressing 12 both formed from steel and having a paint finish. A rubber mat 13 is bonded by means of an adhesive to the upper surface of the top pressing 12. The top pressing 12 and the base pressing 11 of the platen 10 are substantially circular, the platen 10 however comprising an extension 14 to house control and display features. The control and display features comprise two warning light emitting diodes (LED) 15 and 16 and an on/off switch 17. The display features further comprise an adjuster knob 18 for use in calibrating the apparatus. A remote audio/visual indicator 20 as illustrated in Figure 2 can be added in addition to the warning LED's 15, 16 to indicate when the pre-set level of liquid has been reached in the container resting on the platen 10. Figures 3 and 4 illustrate components of a remote audio visual indicator for use when the container is being stored in a position not normally accessed by people or personnel responsible for maintenance of the container. An audio/visual receiver 30 is contained within a housing and is powered from the standard mains supply via an A/C transformer adapter. The transmitter 40 is connected to the platen 10 by a short wire from which it receives both the signal and its power supply. On receipt of the signal from the transmitter 40 by the receiver 30, the receiver 30 emits an audible and visual warning of the content level in the container. Transmission from the transmitter 40 to the receiver 30 is achieved using an A/M radio frequency and has a maximum range of approximately 45 metres. The housing for the receiver 30 is typically 65mm wide, 145mm in length and 30mm in depth. A typical material from which the outer casing is formed is polyacrylonitrile butadiene styrene (ABS). A typical size for the transmitter 40 is 36mm in width, 63 mm in length and 15mm in depth. The housing for the transmitter 40 is typically also formed from ABS. Turning now to Figures 5 and 6, which show the internal details of the platen 10. Four legs 50 are attached and extend downwardly from the top pressing 12 (not illustrated). The base pressing 11 and the top pressing 12 are held together by an assembly spring 51. The assembly spring 51 acts to hold the base pressing 11 and the top pressing 12 together and maintains a pre-set tension between them. The base pressing 11 further houses a battery case 52 which itself houses the 9-volt batteries used to power the electronic circuitry of the platen 10. A circuit board 53 processes information received from the other components and, where necessary, sounds the alarms. A N-shaped primary lever 54 is supported at N-shaped slots 55A,B formed in the base pressing 11 and in use supports the top pressing 12. The top pressing 12 is further supported by two secondary levers 56A,B. These are themselves supported at a first end in N-shaped slots 57A,B made within the base pressing 11 and at a second end by slots within the primary lever 54. Each arm of the primary lever 54 and each of the secondary levers 56A,B is located within a N-shaped slot formed in the legs 50. The primary lever 54 further comprises a substantially triangular plate 58 at the apex formed by its two arms. The triangular plate 58 retains the main spring 59 which biases the primary lever 54 in an upward direction. As shown in detail in Figures 7 to 10, a switch lever 60 is pivoted about pivot point 61 and houses on its outer surface a switch 62. A switch lever spring 63 is attached at a first end to the triangular plate 58 and at a second end to a retaining tab 64 located on the underside of the switch lever 60 and which extends inwardly underneath the primary lever 54. The platen 10 further comprises an on/off switch 17. A switch arm 65 is screw threadedly connected to adjuster knob 18 and is held in spaced relationship from adjuster knob 18 by switch-arm tensioner 66. The switch-arm tensioner 66 consists of a spring which acts to maintain the separation between the adjuster knob 18 and the switch arm 65. A switch arm guide 67 which is welded to the top pressing 12 is located within a hole in the switch arm 65 and prevents the switch arm 65 from rotating when the adjuster knob 18 is actuated. A sigmoid metal strip 69 is located at a first end to switch 62. The second end of the strip 69 extends beneath the switch arm 65. In use, an empty bottle is placed on the rubber mat 13 on the top pressing 12 of the platen 10. The weight of the bottle is transferred through the four legs 50 extending from the top pressing 12 to the primary and secondary levers 54, 56A,B. A primary lever 54 and the two secondary levers 56A,B are deflected in a downward direction, the primary lever 54 acting against the main spring 59. When the bottle has reached an equilibrium position, the adjuster knob 18 is rotated and, acting through the switch arm tensioner 66 causes either upward or downward motion of the switch arm 65. Rotation of the adjuster knob 18 is continued until the switch arm 65 contacts the strip 69. The contact between the switch arm 65 and the strip 69 causes an electric circuit to be formed actuating the warning LED's 15,16. If desired, and to conserve energy the system may now be switched off by means of the on/off switch 17. The empty bottle is removed and replaced by a full bottle on the rubber mat 13 of the platen 10 and the on/off switch 17 again actuated. As the weight of the full gas bottle is greater than that of the empty gas bottle, the primary lever 54 is depressed further than previously by the empty bottle and the contact between the strip 69 and the switch arm 65 is broken, with the result that the warning LED's 15, 16 are not activated. As the contents of the bottle are removed, the bottle becomes lighter and the tension from the main spring 59 causes the primary lever 54 to rise until eventually contact between the strip 69 and the switch arm 65 is re-established, activating the LED's 15, 16. An operator is thus alerted to the fact that the bottle needs to be changed for a fresh bottle. Where bottles used for each fresh batch of fluid are identical, no further calibration of the apparatus is required and a new bottle may simply be inserted. As the relative weight between two conditions of the container are being measured, for example full and empty, any errors in measurement will tend to cancel each other out. The apparatus as described herein thus provides for an accurate and repeatable indication as to when a container is empty. It can also be used to indicate when a container is almost empty. In this usage, when the near empty condition is indicated, the container can be changed immediately which minimises the time when supply of fluid is not available. This mode of action can be set quite simply, wherein the above method is used to determine the contact point when an empty bottle is present. Once the empty bottle has been removed and a new one installed on the platen, the switch arm 65 can be depressed by means of the adjuster knob 18 to bring it into closer proximity with the strip 69. As the strip 69 rises as a result of the bottle being emptied, contact between the strip 69 and the switch arm 65 takes place before the bottle is empty. Although the apparatus as herein described comprises a number of levers to communicate the weight of the bottle and its contents to the electric circuitry, a number of modifications can be made without departing from the scope of the invention. For example the top pressing can rest on a disc or other member held in spaced relationship to the top pressing, the raising and lowering of which causes an electric circuit to be closed or opened to activate or deactivate a warning system. The disc or other member can be supported on a hydraulic system to cushion it and provide a measured and consistent response to pressure being applied to the top pressing. A hydraulic system may find particular use where the apparatus is to be used to weigh large containers such as road tankers or intermediate bulk containers. The apparatus can be used therefore to monitor delivery of a load, and is particularly useful where the load must be isolated from the environment, as monitoring of the removal of fluid from the container can be carried out without the fluid coming into contact with the surrounding atmosphere. Furthermore, the measurement of a mass is known to be more accurate and less prone to error than measurement of a volume. The apparatus can also find use, for example, in the healthcare industry in which the administration of a medicament, for example, via an aerosol can be closely monitored. The adjustment means for the switch receiver may be calibrated so that a given number of turns is known to correspond to a certain weight. This would, for example, obviate the need for re-calibration where a particular fluid is supplied in two different containers, for example, either plastic or glass having known weight difference. Such a facility would also allow a container to be removed when only a certain quantity of fluid is remaining therein where a known quantum of the fluid content needs to be removed. In this case, the circuit which normally actuates the warning or alarm system can also be used to switch off a pump removing fluid from the container. It will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention.

Claims: CLAIMS: 1. An apparatus (10) for establishing when the quantity of fluid remaining in a container falls below an adjustable predetermined level, the apparatus (10) comprising: a base (11), housing elements adapted to deflect proportionally to the weight applied to them, and a lid (12) adapted to sit on the elements in the base (11) and for receiving or otherwise supporting a container thereon; the elements being arranged to operate a switch (62), when deflection of the elements reaches or falls below a predetermined value, the switch (62) enabling a circuit comprising a warning or alarm system. 2. An apparatus according to claim 1, wherein the elements comprise one or more levers (54) operatively linked together. 3. An apparatus according to claim 2, wherein the levers (54) are operable by tabs (50) extending downwardly from the lid (12). 4. An apparatus according to any preceding claim wherein the switch (62) is mounted directly on the elements. 5. An apparatus according to claim 4, wherein the switch (62) is pivotally mounted on one of the elements. 6. An apparatus according to either of claims 4 or 5, wherein the switch (62) is connected to the element by means of a tensioning member which biases the switch (62) to return to its deactivated position. 7. An apparatus according to any preceding claim, wherein the circuit is enabled by contact of the switch (62) with a switch receiver (65). 8. An apparatus according to claim 7, wherein the position of the switch receiver (65) is adjustable. 9. An apparatus according to claim 8, wherein adjustment of the switch receiver (65) is by means of a screw-threaded adjustment means (18) acting on the switch receiver (65). 10. An apparatus according to claim 9, wherein a further tensioning member (66) links the adjustment means (18) to the switch receiver (65) to maintain a constant distance between the adjustment means (18) and the switch receiver (65). 11. An apparatus according to any of claims 8 to 10, wherein the apparatus (10) comprises a restraining member (67) to prevent rotation of the switch receiver (65) on turning of the adjustment means (18). 12. An apparatus according to claim 11, wherein the restraining member (67) is attached to the upper part of the apparatus (10) to aid assembly of the apparatus (10) and give increased repeatability of measurement. 13. An apparatus according to any preceding claim, wherein the warning system comprises one or more visual displays, such as light emitting diodes (15,16) located on the apparatus (10). 14. An apparatus according any preceding claim, wherein the warning system comprises an audio/visual alarm (20) remote from the apparatus (10). 15. An apparatus substantially as herein described with reference to and as illustrated by the accompanying drawings.

Inventors: ROWLINSON IAN, ROWLINSON, IAN
Applicants: GASMAT ESPANA SL, ROWLINSON IAN, ROWLINSON, IAN
Application year: 2001
Main classification: G01G17
IPC codes: F17C13, G01G17