Technical Field

This invention relates to a device for indicating liquid levels, in particular a liquid level indicating device for indicating the level of oil or other liquid in containers such as tanks and the like. The invention is particularly concerned with oil storage tanks.

Background Art

A number of disadvantages are associated with existing liquid level indicating devices. For example, dip sticks and gauges cannot be seen from a distance and, frequently, containers such as tanks are located outdoors in inaccessible positions. Furthermore, monitoring of the contents can be necessary in inclement weather conditions. This is particularly true of tanks containing home heating oil, because consumption takes place during the winter, and thus monitoring must take place during winter weather. In addition, it is often necessary to remove the cap on a tank to monitor the contents while gauges can be easily broken and are expensive to replace. Another disadvantage associated with existing liquid level indicating devices is that the contents must be removed from tanks before fitting the devices. Clearly, this is inconvenient and can be very time consuming.

Ob.iect of the Invention

An object of the invention is to provide a liquid level indicating device mountable on a container to permanently monitor the depth of liquid within the container. A further object of the invention is to provide a liquid level indicating device having liquid level signalling means visible from a distance.

2037R

Summary of the Invention

According to the invention there is provided a liquid level indicating device for visually indicating the level of liquid in a tank comprising a level indicator which moves in response to a float characterised in that the indicator comprises an elongate indicator rod, a float connected to or incorporated in the rod, and a mounting means for mounting the rod retractably and vertically in an aperture in the tank, whereby the rod may float in liquid contained in the tank with an upper portion of the rod extending upwardly through the aperture in the tank to visually indicate a level of liquid in the tank the rod being progressively retractable through the aperture in response to a drop in the level of liquid in the tank below a predetermined level.

Preferably, the overall length of the rod is at least equal to the depth of the tank in which it is intended to be used, and may range in length from about 0.5m to 2.0m.

Preferably the rod is of telescopic construction, whereby the length of the rod may be adjusted.

Preferably the device comprises mounting means for mounting the rod retractably in the aperture, the mounting means including a seal for preventing rainwater which falls on the exposed surface of the rod from draining down the rod through the aperture into the tank. The seal permits the rod to move freely with the float while still maintaining a good seal against the ingress of water. The seal, preferably, comprises a body of foam impregnated with oil or another water repellant liquid surrounding the rod in the region of the aperture and retaining means for holding the seal in this location, enclosed and under compression.

Preferably the device is provided with a float at the lower end of the rod to provide the necessary buoyancy the float being pivotally mounted so as to be moveable between a first position generally parallel to the device to allow insertion through a hole in the roof of a tank and a second position generally at right angles to the device so as to keep the device afloat in relatively shallow liquid. The float is of elongate shape, for example of tubular shape.

Brief Description of the Drawings

Various embodiments of the invention will now be described having regard to the accompanying drawings in which:

Figure 1 is a front view of a first embodiment of a liquid level indicating device of the invention;

Figure 2 is an exploded, and partially sectional view of the liquid level indicating device of Figure 1 mounted on a tank;

Figure 3 shows a detail of a float of Figure 1;

Figure 4 shows the float of Figure 3 in a folded position for insertion in an aperture in the top wall of a tank;

Figure 4a, 4b and 4c show details of the float of Figure 3;

Figure 5 is a sectional elevation of an alternative embodiment of a float;

Figure 6 is a view, partly broken away, of the liquid level indicating device of Figure 1 inserted in a tank;

Figure 7 is a front elevation of a second embodiment of liquid level indicating device of the invention;

Figure 8 is a front elevation of a third embodiment of liquid level indicating device of the invention;

Figures 9a and 9b show details of a foldable flag for use with the device of the invention;

Figure 10 is an elevation of a fourth embodiment of liquid level indicating device, showing the lower part inserted into a tank; and

Figures 11 and 12 show elevations of a fifth embodiment of a liquid level indicating device of the invention;

Detailed Description of the Preferred Embodiment

Figure 1 is a front elevation of a preferred embodiment of a liquid level indicating device of the invention and Figure 2 is a similar view on a larger scale, shown exploded and partly in section. The liquid level indicating device is made up of a hollow tubular indicator rod 1 having equally spaced graduations 2 and numerals 3 marked thereon. The rod 1 is sealed at the upper end by means of a top seal 4. Preferably, the rod 1 is made from transparent plastics, and the graduations 2 and numerals 3 are contained on a coloured calibrated strip of paper or plastics inserted within the rod.

The rod 1 is slidably and vertically mounted in a mounting and sealing unit 28 for mounting the liquid level indicating device on a tank or other container. The unit 28 includes a seal for preventing the ingress of rain water into the oil tank along the surface of the rod 1.

The seal comprises a substantially T-shaped sleeve comprising a vertical tube 7 and an integral horizontal flange 16. An annular collar 29 surrounds the tube 7 at the top portion thereof. As described more fully below, the tube 7 is inserted downwardly into an oil-tank through a circular hole 13 cut in the top wall 8 of the tank. The annular flange 16 rests on the top wall 8 (see Fig. 2) of the tank surrounding the hole 13. The annular collar 29 fits into the hole 13 to retain the sealing unit 8 tightly in the hole.

As shown in Figure 2, a compressible gasket 5 is provided between the flange 16 and the top wall 8 of the tank to provide a good seal between the two surfaces. The gasket may be made from a closed-cell foamed plastics. Preferably the gasket 5 is of annular configuration having a central circular opening which fits over the collar 29.

A domed shaped cover or cap 23 co-operates with the flange 16 to form a housing containing a rod sealing element comprising a foamed plastics seal 14 of annular shape. Preferably; the seal 14 is oil-impregnated. The seal 14 contains a central circular aperture through which the rod 1 passes. More particularly, the seal 14 is

comprised of an oil-impregnated compressible foamed plastics. The foamed plastics may be an open cell polyether. The foamed plastics seal 14 may be impregnated with the same oil as that stored in the oil-tank, e.g. paraffin oil. When the domed shaped cover 23 is attached to the flange 16 it presses down on, and compresses, the foamed plastics seal 14, causing the foam to form a seal against the surface of the rod 1, and also causing oil contained in the foam to be squeezed from the foamed plastics and applied to the surface of the rod 1. This has the effect of forming a water-repellant oil film at the adjoining surfaces of the foamed plastics seal 14 and the rod 1. The oil also prevents the seal 14 from freezing in cold weather. Also the oil acts as a lubricant to permit free sliding movement of the rod 1 relative to the foamed plastics seal 14 while still having a good seal. In addition the ever present oil film serves as an inhibitor of fungal growth thereby protecting the rod 1 and prolonging its life.

The domed-shaped cover 23 is fixed to the flange 16 by self-tapping screws 25 and plastic cavity fasteners 26, which also serve to attach the flange 16 and seal assembly 28 to the roof 8 of the tank.

A float rod 9, is telescopically engaged within, and projects downwardly from the lower end of the tubular rod 1. The position of the float rod 9 relative to the tubular rod 1 is set by means of a retaining clamp 10, a brass adjustment screw 11, and a brass bushing 12. The float rod 9 may optionally be provided at its upper end with a cap (not shown). The float rod 9 is provided at its lower end with a float 15. The rod 9 may be made from plastics, such as polyvinyl chloride. If the rod 9 is too flexible there may be a tendency for it to bend under the force of the liquid acting on the float, particularly if the float is submerged in the liquid 27. In that case, the rod 9 may be made from a stiffer material such as aluminium. Alternatively, an aluminium insert rod may be inserted within the tubular float rod 9 to stiffen the rod 9.

Figure 3 shows an enlarged view of the float rod 9 and the float 15 immersed in liquid at the bottom of a tank 22. The float 15 consists of an elongate sealed blow moulded polyethylene tube which is

pivotally connected to the lower end of the float rod 9. It may have a length of about 220mm and a diameter of about 35mm.

As shown in Figure 4, in order to insert the float 15 into the tank, the float 15 is aligned vertically with the float rod 9 so as to pass vertically downwards through the circular hole 13 provided in the top wall 8 of the tank, and thereafter the float 15 pivots to its horizontal position. Use of a horizontal float instead of a vertical float (as shown in Fig. 5) allows shallower levels of liquid to be measured. The horizontal float 15 has a longitudinal groove 17 in the circumferential face thereof, extending from half way along the length of the float 15 as far as one end, to accommodate the float rod 9 when the float rod and float are in alignment, as shown in Figure 4, and as shown by broken lines in Figure 3. It will be understood that in use the float rod 15 does not actually adopt the horizontal orientation shown in broken lines in Figure 3. The float 15 is also provided with a circumferential groove 18 to accommodate a circumferential tie strap 19 used to pass through an eye 21 at the lower end of the float rod 9 so as to pivotally secure the float 15 to the float rod 9. The pivoted float 15 has the advantage that it prevents side-ways movement of the float rod 9. The pivotal float also has the advantage that it may be easily inserted into a tank. The pivotal float rod 15, by virtue of its horizontal orientation when in use so that all the buoyancy of the device is provided at the very bottom thereof, allows accurate measurement of the oil level when the tank 22 is almost empty. This may be contrasted with a vertical float which would strike the bottom of the tank when there is still liquid 27 remaining in the tank 22, but insufficient to keep the vertical float and rod afloat.

Although, not shown in the drawing, the axial length of that part of the float 15 containing the groove 17, may be greater than the length of that part of the float to the left (as shown in the drawing) of the circumferential groove 18. This is to provide additional buoyancy to compensate for the loss of buoyancy caused by the provision of groove 17. In other words the groove 18 is off-set from the centre line of the float 15.

In some situations a vertical float may be suitable, and Figure 5 shows a vertical float 20 attached to the lower end of the float rod 9

instead of the pivoting float 15. The float 20 is solid and is made from low density polystyrene covered in a plastics membrane.

Figure 6 shows the liquid level indicating device of the invention mounted in an oil storage tank 22.

The device of the invention may be supplied either as an integral part of an oil storage tank 22, or as a kit for fitting to an existing oil storage tank. The device is simple to fit and to operate, and the telescopic arrangement of the upper rod 1 and the float rod 9 enable the device to be adjustable to fit tanks of various sizes.

To install the liquid level indicating device in an existing tank or container 1, a circular hole 13 is first cut in a top wall of the tank. A template may be supplied with a fitting kit to facilitate the cutting of the hole 13, which typically has a diameter of about 38mm. Preferably, the device is mounted on the tank 22 at a location as far as possible away from the fill hole in order to avoid damage due to direct contact with flow turbulence encountered during the filling process. Also, the hole 13 to receive the device is preferably located at the highest centre-point location in the case of a round or curved surface tank, or on any convenient corner area in the case of a flat surface tank.

When the hole 13 has been cut, the set screw 11 is loosened (see Figure 2) and the telescopic float rod 9 is extended so that the total length of the device is slightly greater than the overall height of the tank 22. The adjustment set screw 11 is then lightly tightened. The float 15 is folded into the position shown in Figure 4, in which it is aligned with the rod 9, and the float 15 and rod 9 are inserted through the hole 13 in the tank. Once through the hole 13, the float 15 will fall into the horizontal position shown in Figure 3.

The device is pushed down until the float 15 touches the bottom of the tank 22. At this point the tubular rod 1 should protrude a short distance above the top wall 8 of the tank 22. This distance is measured and noted. The device is then raised to expose the adjustment screw 11, which is released. The overall length of the rods 1 and 9

are reduced by the distance noted above such that when the float 15 is in contact with the bottom of the tank, the rod 1 barely protrudes from the domed-shaped cover 23 of the mounting assembly 28. Thus, in this position the device would indicate that the tank is empty. The screw 11 is then fully tightened, and the device again inserted through the hole 13. At this stage the cover 23 is fixed to the roof 8 of the tank 22 by fasteners 26 as described above in relation to Figure 3.

In use of the device, when the tank 22 is full of oil the float 15 rises within the tank until the retaining clamp 10 abuts the lower end of the vertical tube 7. In this position the tubular indicator rod 1 is extended vertically above the tank 22 to its full length (approximately 60 cm), and the float 15 is immersed beneath the liquid 27. The indicator rod 1 remains fully extended until the level of oil or other liquid in the tank ,22 drops below approximately the half full level. As the liquid level drops further, the indicator rod 1 also drops proportionally to the remaining liquid content in the tank 22. Alternatively, the arrangement may be such that device at all times responds to the level of liquid in the tank. In that case the indicator rod 1 is longer than indicated above, and when the tank is full extends above the tank a distance approximately equal to the depth of the tank. Typically, the overall length of the rods 1 and 9, when fully extended is about 1.5m. When fully telescoped the overall length is about 0.85m. Generally, the overall length of the liquid level indicating device may vary from about 0.5m to 2.0m depending upon the size of the tank in which it is to be inserted.

The indicator rod 1 is suitably coloured so that it can be seen from a distance. For example, the top graduations 2 on the rod can be coloured a bright red colour to warn of low liquid levels in the tank

22. Instead or in addition, the indicator rod 1 may be fitted with a flashing light, or with a flag, as described hereinafter.

Suitably, the diameter of the indicator rod 1 is about 1cm, the float rod 9 has a diameter of about 0.8cm, such that it slides telescopically within the indicator rod 1.

Further embodiments of a liquid level indicating device of the

invention are hereinafter described with reference to Figures 7 to 12, where like reference numerals denote like parts.

Figure 7 shows a front view of a second embodiment of a liquid level indicating device of the invention. The liquid level indicating device is made up of a hollow tubular indicator rod 1 having equally spaced graduations 2 marked thereon. The graduations 2 are numbered consecutively from the top of the rod 1 to the bottom of the rod 1 by numerals 3. The graduations 2 are reference points only and do not measure volume. The rod 1 is sealed at both ends having a bottom seal 6 and a top seal 4. A weight 30 is mounted on the rod above the bottom seal 6. The weight 4 ensures that the rod 1 penetrates a liquid surface 27 in use and also stabilises the rod 1 to ensure a substantially vertical orientation of the rod in use.

At its upper end, the liquid level indicating device is provided with a cap 36 mounted over the top seal 4. The cap 36 is provided with a radially outwardly extending brim-like rain hood 31 to protect the rod 1 from rain. In particular, the hood 31 prevents rainwater from traveling down the surface of the rod into the tank. Optionally, a Light Emitting Diode 32 (hereinafter referred to as an LED) is mounted on the cap 36. The LED 32 is preferably a flashing LED which can be activated when the liquid level within a tank 22 is depleted. The LED 12 is powered by batteries 33 mounted in the rod 1 adjacent the top seal 4. The batteries 33 are connected to a micro-switch 34 mounted at the bottom end of the rod 1 adjacent the bottom seal 6 by micro-switch wires 35. When the liquid level within a tank reaches an undesirably low level, the micro-switch 34 is activated and a signal is transmitted along the micro-switch wires 35 to the batteries 33 and the LED 32 which then flashes.

The rod 1 is slidably and vertically mounted in a mounting unit 28 for mounting the liquid level indicating device on a tank 22 or other container. The mounting and sealing unit 28 is as described above in relation to Figure 2, and is inserted in an opening 13 provided in the tank 22. The rod 1 is slidable in the mounting unit 28 in the directions indicated by the arrow.

A slidable stop ring 37 is mounted on the outer surface of the rod 1. The stop ring 37 is mounted on the rod 1 between the mounting unit 28 and the cap 36. The stop ring 37 controls the depth to which the rod 1 may slide through the mounting unit 28 into the tank. Accordingly, when the stop ring 7 abuts the cover 23, the rod 1 will retract no further into the tank 22 regardless of the level of liquid within the tank.

In use, the rod 1 is of sufficient length and is fitted so that the bottom end of the rod 1 penetrates the liquid surface 27 to a depth of approximately 8 to 10cm. As the rod 1 is hollow and closed at both ends, the rod 1 is buoyant and floats on the liquid surface 27 without the need for a separate float as with the embodiment of Figure 1. For this reason, the diameter of the rod 1 in this embodiment is greater than that of the embodiment of Figure 1. If necessary the hollow rod 1 may be filled with a low-density foamed plastics. The weight 30 insures that the bottom of the rod 1 remains approximately 8 to 10cm below the surface 16 of the liquid. Therefore, as the liquid depletes, the rod 1 descends as shown by the arrow. When the liquid becomes excessively depleted the bottom of the rod 1 abuts the bottom of the tank 22 before the liquid is completely depleted. Accordingly, a liquid reserve remains. Abutment of the bottom of the rod 1 with the bottom of the tank 22 causes the micro-switch 34 to be activated and the LED 32 to flash to warn of the low level of liquid within the tank. In an alternative embodiment, the LED 12 could be made up of a series of LED's formed in the shape of letters to flash a message at liquid depletion such as "Out Of ". A similar flashing LED is optionally provided with the embodiment described in Figures 1 and 2.

Figure 8 shows a front view of a third embodiment of a liquid level indicating device of the invention. As shown in the drawing, the liquid level indicating device is made up of a hollow rod 1 having graduations 2 marked thereon together with a bottom seal 6 and a top seal 4. The rod 1 is also provided with a weight 30 adjacent the bottom seal 6. A slidable stop ring 37 is mounted on the rod 1 while the rod 1 is mounted in a mounting unit 28 as previously described. As shown in the drawing, the mounting unit 28 is mounted in the top wall 8 of a tank 22 with the rod 1 inserted through the mounting unit 28 into

the tank 22. The rod 1 is slidable in the directions indicated by the arrow.

The rod 1 shown in Figure 2 is also provided with a spherical float 38 to increase buoyancy. The float may be of a different shape than shown, and the relative dimensions of the float 18 and the hole 13 in the top wall 8 of the tank 22 should be such that the float may be passed through the hole 13 in fitting the device. The float 38 is located between the bottom seal 6 and the mounting unit 28. The float 38 is slidable on the rod 1 and is positioned according to the depth below the surface 16 the rod 1 is required to penetrate. In use, the float 38 floats on or in the liquid 27 in the tank 22. Therefore, as the level of liquid 27 within the tank fluctuates the float 38 is raised and lowered so that the rod 1 is moved upwards and downwards in the directions of the arrow between the inside and outside of the tank 22. When the level of liquid within the container is sufficiently depleted the stop ring 37 abuts the mounting unit 28 to prevent the liquid level indicating device from falling into the tank 22.

The rod 1 is also provided with a flag 39 mounted adjacent the top thereof. The flag 39, like the LED 12 of Figure 7 is easily visible from a distance. The flag 39 could also have printed matter marked thereon, e.g. a logo of an oil company. Therefore, the flag 39 is particularly adapted for use as an advertising device.

An alternative form of flag is shown in Figures 9a and 9b. In this arrangement the flag is a foldable flag 41. The foldable flag 41 is made up of a foldable material 26 supported between an outer spine 47 and the rod 1. The spine 47 is disposed adjacent the rod 1 when the flag 41 is in the folded position as shown in Figure 9a. The flag 41 is also provided with a lever 42, the lever 42 being a downwardly orientated extension of the spine 47. The lever 42 is arcuate in shape and extends downwards from the spine 47. A spring 45 is mounted on the rod 1 and is attached to the lever 42 at the spine-lever junction. The spring 45 urges the spine towards the rod 1. In use, as the rod 1 descends into the tank 22 with liquid depletion, the lever 22 abuts the top of the tank 22 so that the spring bias is overcome and the spine 27 is urged away from the rod 1 to unfold the flag. Movement of the lever 42 is indicated by an arrow.

The flag 41 is shown in the unfolded position in Figure 9b with the lever 42 abutting the top of the tank. The flag 41 is clearly visible from a distance in the unfolded position to warn of liquid depletion in the tank.

A flag 39, or a folding flag 41 may optionally be provided with the embodiment of Figure 1.

Figure 10 shows a front view of a fourth embodiment of a liquid level indicating device of the invention. As shown, the device is made up of an indicator rod 1 with graduations 2 marked thereon, a top seal 4, a flag 39, a bottom seal 6 together with a weight 30 and a float 48. The float 48 is made up of an expanded shaped portion of the hollow rod 1. The rod 1 is supported in a sealing and mounting unit 28 as previously described. The rod 1 is also provided with a bottom stop 43. The stop 43 is made up of a radially outwardly extending ring positioned below the mounting unit 28. The stop 43 is also formed from a shaped portion of the rod 1 and is located on the rod 1 so that it can abut the tube 7 of the mounting unit 28 when the liquid level 27 within the tank 22 is at half maximum. Therefore, the stop 43 prevents the rod 1 from being raised excessively above the surface of the tank 22 when the tank is full. Excessive projection of the rod 1 from the tank 22 could lead to instability of the liquid level indicating device and damage to the rod 1 particularly in high winds. Therefore, the unit 28 also provides support for the rod 1 to prevent flexing. Preferably, the indicator rod 1 is provided with a flag 39.

Figures 11 and 12 show front views of a further embodiment of a liquid level indicating device of the invention in relatively full and empty tanks respectively. As shown in Figure 11, the liquid level indicating device is made up of an indicator rod 1 mounted on a tank 22 with a mounting unit 28. The rod 1 has graduations 2, a weight 30 at its bottom end and a float 38 fitted over the rod 1 adjacent the weight 6. The float 38 is annular so that it can be fitted over the rod 1 and abuts a stop ring 43. The weight 30 is also annular to enable it to be fitted over the rod 1. An upper stop ring 10 is provided. The stop rings 10, 43 may be provided with set screws so that the stop rings can be tightened and loosened to enable the position of the stop rings on

the rod 1 to be adjusted.

The rod 1 is hollow and open at both ends. A secondary rod 49 coaxial with the rod 1 is mounted in the hollow rod 1. The secondary rod 49 is greater in length than the rod 1, is slidable in the rod 1 and provided with radially extending flanges 51 at each end to prevent the secondary rod 49 from passing through the rod 1.

In use, the liquid level indicating device is supported in the liquid 27 by the float 38. The liquid level indicating device is retractable through the mounting unit 28 as previously described and is raised and lowered according to the level of the liquid 27. As the level of liquid 27 is depleted, as shown in Figure 12, the rod 1 descends further into the tank 22 until the secondary rod 49 abuts the bottom of the tank 22. Therefore, when the secondary rod 49 abuts the bottom of the tank 22 the rod 1 continues to slide downwards over the secondary rod 49 also to abut the bottom of the tank 22. Accordingly, the top of the secondary rod 49 protrudes above the surface of the tank

22. The rod 49 is suitably coloured for example a bright red colour to warn of low liquid levels in the tank 22.

An advantage of this embodiment is that the rod 1 is open ended and does not have to be sealed while the float 38 can be fitted over the rod 1 and can be reused should the rod 1 be damaged.

The liquid level indicating device is suitable for use in for example heating oil, water and milk tanks and can be fitted to tanks without first removing their contents. The device dimensions can be altered so that the device is adaptable for use with various tank sizes.

The rod 1, the graduations 2, and the numerals 3 can be formed from bright colours to enhance the appearance of the liquid level indicating device.

From the foregoing, it will be apparent that numerous modifications and variations can be effected without departing from the true spirit and scope of the novel concept of the present invention. It will be appreciated that the present disclosure is intended to set

forth exemplifications of the invention which are not intended to limit the invention to the specific embodiments illustrated. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.

Where technical features mentioned in any claim are followed by reference signs, these reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.