GB2195446A - A liquid level indicator - Google Patents
A liquid level indicator Download PDFInfo
- Publication number
- GB2195446A GB2195446A GB08623170A GB8623170A GB2195446A GB 2195446 A GB2195446 A GB 2195446A GB 08623170 A GB08623170 A GB 08623170A GB 8623170 A GB8623170 A GB 8623170A GB 2195446 A GB2195446 A GB 2195446A
- Authority
- GB
- United Kingdom
- Prior art keywords
- face
- liquid
- liquid level
- light
- level indicator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000007788 liquid Substances 0.000 title claims abstract description 86
- 238000010438 heat treatment Methods 0.000 claims description 21
- 239000000463 material Substances 0.000 claims description 16
- 229920003023 plastic Polymers 0.000 claims description 10
- 230000002093 peripheral effect Effects 0.000 claims description 9
- 239000004033 plastic Substances 0.000 claims description 8
- 230000003287 optical effect Effects 0.000 claims description 6
- 239000004417 polycarbonate Substances 0.000 claims description 4
- 229920000515 polycarbonate Polymers 0.000 claims description 4
- 230000003247 decreasing effect Effects 0.000 claims description 2
- 230000004044 response Effects 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 239000002184 metal Substances 0.000 description 3
- 230000008093 supporting effect Effects 0.000 description 3
- DHKHKXVYLBGOIT-UHFFFAOYSA-N acetaldehyde Diethyl Acetal Natural products CCOC(C)OCC DHKHKXVYLBGOIT-UHFFFAOYSA-N 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
- G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
- G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
- G01F23/284—Electromagnetic waves
- G01F23/292—Light, e.g. infrared or ultraviolet
- G01F23/2921—Light, e.g. infrared or ultraviolet for discrete levels
- G01F23/2922—Light, e.g. infrared or ultraviolet for discrete levels with light-conducting sensing elements, e.g. prisms
- G01F23/2924—Light, e.g. infrared or ultraviolet for discrete levels with light-conducting sensing elements, e.g. prisms for several discrete levels, e.g. with more than one light-conducting sensing element
-
- A—HUMAN NECESSITIES
- A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
- A47J—KITCHEN EQUIPMENT; COFFEE MILLS; SPICE MILLS; APPARATUS FOR MAKING BEVERAGES
- A47J27/00—Cooking-vessels
- A47J27/21—Water-boiling vessels, e.g. kettles
- A47J27/212—Water-boiling vessels, e.g. kettles with signaling means, e.g. whistling kettles
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Thermal Sciences (AREA)
- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Cookers (AREA)
Abstract
A liquid level indicator comprises a body (18) for mounting within or above a liquid container (1) e.g. an electric kettle, the body comprises a plurality of elongate rods (19) with ends (21) which internally reflect light when in air but not when in liquid. To increase the angle from which the indicator can be viewed the top faces (20) of the rods are shaped to cause light travelling up a rod to be refracted at the face and to diverge on emerging. The indicator is mounted in the lid of the kettle. <IMAGE>
Description
SPECIFICATION
A liquid level indicator
This invention relates to a liquid level indicator.
As disclosed in, for example, US-A2,368,705, US-A-3,535,933, EP-A-6317 and
GB-A-412,803, liquid level indicators have been proposed which comprise a body to be mounted within or above a vessel containing a liquid. Such a body which may be mounted to a lid of the vessel defines a plurality of nonintersecting light paths which may be formed by respective elongate rods. Each light path extends between a respective first face at one end of the body and a second face, adjacent second faces being disposed at different levels and each second face being shaped so as to cause light travelling along the respective light path to be totally internally reflected back to the respective first face if the second end face is in air but not if the second end face is immersed in liquid.When such a body is mounted to a vessel containing liquid with the first faces of the rods uppermost and so that the rods depend toward the liquid, the number of second faces immersed in the liquid will depend on the liquid level within the vessel and accordingly a indication of the liquid level can be obtained by viewing the first faces and determining which ones appear illuminated (not immersed in the liquid) and which appear dark (immersed in the liquid).
Unfortunately, it can be very difficult to determine whether a particular first face is illuminated or not unless the first face is viewed from directly above which, of course, may restrict the amount of light which can enter the rods and so cause the first faces of the rods whose associated second faces are not immersed to appear to be almost indistinguishable in brightness from the first faces of the rods whose associated second ends are immersed in the liquid, making an accurate determination of the liquid level within the vessel difficult.
It is an object of the present invention to overcome or at least mitigate the above-mentioned problems.
According to one aspect of the present invention, there is provided a liquid level indicator comprising a body for mounting within or above a vessel containing a liquid, the body defining a plurality of non-intersecting light
paths, each light path extending between a
respective first face at one end of the body and a respective second face at another end of the body opposite the said one end, adjacent second faces being disposed at different levels and each second face being shaped to cause light travelling along the respective light
path to be incident on the second face at an
angle equal to or greater than the critical angle for an interface between the second face and air but less than the critical angle for an interface between the second face and liquid characterised in that each first face is shaped to cause light travelling along the respective light path to be refracted at the first face and to diverge from the light path on emerging from the first face so as to spread out transversely of the light path.
Each first face may be recessed and may be symmetrical about an axis extending parallel to the associated light path so that a peripheral portion of the first face projects beyond a central portion of the first face to cause light travelling along the light path from the associated second face to be incident on the first face at such an angle greater than zero that the light is refracted, and not totally internally reflected, at the first face; for example if the first face interfaces with air then the angle will be greater than zero but less than the critical angle for an interface between air and the first face, the critical angle for the boundary or interface between two optical media being defined, as is well known, as the smallest angle at which light travelling in the medium having the greater refractive index can be incident on the interface and be totally reflected at the interface. Each first face may, for example, be prismatic being defined by two or more intersecting planar surfaces. Alternatively, each first face may define a conical surface or may define a continuously curved surface.In any case, the first faces will be shaped such that light travelling along the light path from the associated second face is incident on the first face at such an angle greater than zero that the light is refracted, and not totally internally reflected, at the first face; for example if the first face interfaces with air then the angle will be greater than zero but less than the critical angle for an interface between air and the first face.
Generally, each second face is symmetrical about an axis extending parallel to the associated light path and is in relief so that a central portion thereof projects beyond a peripheral portion thereof. Each second face may, for example, be prismatic being defined by two or more planar intersecting surfaces, may define a conical surface or may define a continously curved surface.
A series of light paths may be provided, the second faces being arranged to provide a row of different length light paths, the length of the light paths decreasing in a step-wise manner from one end of the row to the other.
Each light path may be defined by a respective rod of a light transmissible material, for example a plastics material such as a polycarbonate.
In another aspect, the present invention provides a liquid level indicator, comprising a
body for mounting within or above a vessel
containing a liquid, the body comprising a
series of elongate rods each having first and second end faces defining therebetween a respective light path, each first end face being recessed so that a peripheral portion of the first face projects beyond a central portion thereof and being shaped to cause light travelling along the respective rod to be incident on the first face at such an angle greater than zero that the light is refracted at the first face and diverges from the light path on emerging from the first face so as to spread out transversely of the light path, the rods being of different lengths so that each second face is disposed at a different level, each second face being defined by one or more surfaces extending at an angle to the longitudinal axis of the associated rod, which angle is greater than or equal to the critical angle for an interface between air and the second end face but less than the critical angle for an interface between liquid and the second end face so that light travelling along a rod is totally internally reflected back toward the associated first end.
face when the second end face is immersed in air but is refracted when the second end face is immersed in liquid. Each elongate rod may be formed from a plastics material such a polycarbonate.
The present invention also provides an electrical kettle comprising: a vessel having a plastics material body defining a base wall and a side wall together forming a receptacle for liquid, a channel member mounted to the vessel body so as to define with a closure member closing the channel a hollow handle for the kettle and a plastics material lid closing the receptacle, an upper portion of the receptacle opposite the handle being shaped to provide a spout defining with the lid a passageway for permitting liquid to be poured from the receptacle; an electrical heating element disposed within the receptacle adjacent the base wall; an electrical control unit electrically connected to the heating element and disposed within a chamber formed in the body between the side wall of the receptacle and the closure member so as to provide for connection of the heating element to an electrical supply; a mechanical linkage extending through the handle and movable between a first position in which the heating element is electrically connectable to an electrical supply via the electrical control unit and a second position in which the mechanical linkage causes a movable rod of the electrical control unit to move to break electrical contact of the heating element via the control unit to the electrical supply; a manually operable switch mounted partially within or adjacent the handle, which switch is connected to the mechanical linkage to move the linkage between the first and second positions so that the linkage is in the first position when the switch is in an ON position and the linkage is in the second position when the switch is in an OFF position; a steam responsive device disposed within an upper part of the handle for receiving steam emanating from liquid in the receptacle via an aperture formed in the inner side wall adjacent the steam responsive device and for moving the ON/OFF switch to the OFF position in response to steam contacting the steam responsive member to cause the mechanical linkage to move the movable rod to disconnect the heating element; spring biassing means for biassing the ON/OFF switch toward the ON or the OFF position when the switch moves toward the ON or the OFF position, respectively; and an optical liquid indicator which liquid level indicator comprises a body mounted to the lid, the body comprising a series of elongate rods depending from the lid, each rod having a first end face forming part of an outer surface of the lid and a second end face within the receptable and each first end face being recessed so that a peripheral portion of the first face projects beyond a central portion thereof such that light travelling along the respective rod is incident on the first face at an angle greater than zero but less than the critical angle for an interface between air and the first face so that the light is refracted by the first face and diverges from the light path on entering the air so as to spread out transversely of the light path, the rods being of different lengths so that each second face is disposed at a different level, each second face being defined by one or more surfaces extending at an angle to the longitudinal axis of the associated rod which angle is greater than or equal to the critical angle for an interface between air and the second end face but less than the critical angle for an interface between liquid and the second end face so that light travelling along a rod is totally internally reflected back toward the associated first end face when the second end face is immersed in air but is refracted when the second end face is immersed in liquid.
A liquid level indicator in accordance with the present invention enables the indicator to be viewed within a wider field of view so that it is not necessary to view the indicator from directly above so avoiding any possibility of the viewing action preventing light entering the light paths and enabling a quick and easy determination of the liquid level within a vessel incorporating the indicator. Where the vessel comprises an electrical kettle, the water level indicator facilitates filling of the kettle through the spout obviating the need to remove the lid to check how full the kettle is and moreover enabling the indicator to be read clearly without the necessity for the person reading the indicator to view the indicator from directly overhead which is particularly difficult when filling a kettle.
In order that the invention may be more readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a schematic longitudinal crosssectional view of an electrical kettle embodying the invention;
Figure 2 is a side -view, partly in section, of a liquid level indicator embodying the invention for the electrical kettle shown in Figure 1;
Figure 3 is a top plan view of the liquid level indicator shown in Figure 2; and
Figures 4 to 6 are top plan views of different lids for electrical kettles showing alternative arrangements for liquid level indicators embodying the invention.
Referring now to the drawings. Figure 1 illustrates an electrical kettle embodying the invention.
As shown in Figure 1, the electrical kettle comprises a body in the form of a vessel 1 defining a receptable 2 for receiving a liquid.
The vessel 1 is taller than it is wide and may have any desired shape, for example, the vessel may be of rectangular or circular crosssection and may be approximately cylindrical.
The vessel 1 is formed of a suitable heat resistant plastics material, for example an acetal copolymer, and has a base 3 for supporting the kettle on a work surface (not shown).
The base 3 is integrally formed with a side wall 4 to define the receptacle.
A handle 5 for the kettle is provided by an open channel-cross-section member 6 attached to the side wall, the channel-cross-section member 6 being closed by a closure member 7 so as to define with the closure member 7 a hollow handle for the kettle communicating with a chamber for receiving electrical and mechanical control circuitry for the kettle as will be described below. Although the channel member 6 may be separately formed and then attached to the side wall 4, in the arrangement shown in Figure 1 the channel member 6 is formed integrally with the side wall 4 and bows outwardly from the side wall 4 so as to define between the channel member 5 and the side wall 4 an aperture 8 for facilitating gripping of the handle.
An upper end of the channel member 6 has a lip 9 which engages over an upstanding projection 10 of a flange 11 of an upper edge 4a of the side wall. The lip 9 is secured to the projection 10 by a screw (not shown). A lower end of the channel member is connected by means of screws (not shown) to the base 3.
An upper portion of the side wall 4 opposite the handle 5 is shaped so as to extend outwardly to form a spout 12 for the kettle.
The receptacle 2 is closed by a lid 13 which fits within an opening defined by the edge 4a of the side wall 4 so that a downwardly extending lip 14 of the lid 13 rests on the flange 11. A depending wall 15 of the lid defines with the spout 12 a passageway .16 for permitting liquid to be poured from the receptacle 2.
An optical water level indicator 16 is mounted within an aperture 17 formed in the lid 13. In the arrangement shown in Figures 1 to 3, the optical water level indicator 16 comprises a body 18 moulded from an optically transparent plastics material such as a polycarbonate so as to define a series or row of graduated length rods 19 integrally connected at their upper ends. The rod 19 may also be connected together by ribs 18a and 1 8b (Figure 2) spaced along their length to -strengthen the body 18. Each rod 19 defines a light path between an upper or first end face 20 of the rod 19 and a lower or second end face 21 of the rod 19.
With the lid 13 in place to ciose the receptacle 2, the rods 19 depend from the lid 13 and, because of their graduated lengths, each rod 19 extends a different distance into the receptacle 2 so that the second end faces 21 of the rods 19 are disposed at different levels within the receptacle 2.
Each second end face 21 is shaped so as to cause light travelling longitudinally or axially along the respective rod 19 to be incident on the second end face 21 at an angle greater than or equal to the critical angle for an interface between the second end face and air but less than the critical angle for an interface between the second end face and liquid so that light travelling along the respective rod 19 will be totally internally reflected from the second end face 21 back towards the respective first face 20 when the second end face is immersed in- air but will be refracted into the liquid when the second end face is immersed in liquid in the receptacle 2. As will be appreciated when light is totally internally reflected at a second end face 21 the corresponding first end face 20 which would otherwise appear dark, seems to be illuminated and appears bright.As mentioned above, the rods are of graduated lengths so that the second end faces 21 are disposed at different levels in the receptacle 2. Thus, whether or not the second end faces 21 are immersed in liquid will depend on the level of the liquid within the receptacle and so that number of first end faces 20 which appear bright or illuminated provides an indication of the liquid level within the receptacle. To take a particular example, for the liquid level 22 shown in Figure 1, only the second end faces 21a and 21b of the rods 19a and 19b will not be immersed in the liquid and accordingly only the first end faces 20a and 20b of these two rods will appear illuminated, the other first end faces appearing dark as indicated by the cross-hatching in Figure 3.
The series or row of first end faces thus provides a scale which may be calibrated by the association of indicia with one or more of the end faces to indicate the amount of liquid such as water within the receptacle in pints or litres or merely to indicate whether the kettle is full or empty. Of course, the accuracy of the level indication will depend on the number of rods 19 provided, ten are shown, and the minimum difference in level between the second end faces. The longest of the rods 19 may be used to mark a minimum level of liquid which can be used in the kettle while the shortest of the rods may be used to mark a maximum level.The rods 19 adjacent the minimum and maximum level markers may be only slightly different in length so as to provide a warning that the maximum or minimum level is approaching, appropriate visual indications identifying the rods being provided on the lid 13 adjacent the rods 19.
In the arrangement shown in Figures 2 and 3, each second end face 21 is a relief surface with a centremost portion 21' of the end face 21 -extending axially of the rod beyond a peripheral portion 21" of the second end face 21. Each second end face 21 may be a conical surface or may be a prismatic surface, formed by a number, for example two or four, planar surfaces which extend from the periphery 21" of toward the centremost portion 21' of the second end face so as to meet at the centremost portion 21'. Alternatively, the second end faces may be defined by a smoothly curved surface.If the rods 19 are of circular or round cross-section, then the second end faces 21 will be conical or smoothly curved surfaces whereas if the rods 19 are of rectangular cross-section, then the second end faces 21 will be prismatic surfaces. it will, of course, be appreciated that the shape of the second end faces is not important, it merely being necessary that the second end faces are shaped such that light travelling along a rod
19 is incident on the second end face 21 of the rod at an angle which is greater than or equal to the critical angle for an interface between air and the second end face but less than the critical angle for an interface between liquid such as water and the second end face so that, when the second end face 21 is immersed in air, light travelling axially along the -rod 19 is totally internally reflected back up the rod to the first end face 20 but, when the second end face 21 is immersed in water,
light travelling axially along the rod is refracted into the water.
In order to increase the angle at which the first end faces 20 can be viewed to enable the liquid level within the receptacle to be determined, the first end faces are shaped so as to cause light travelling along a rod 19 toward the respective first face to be refracted at the first end face and to diverge from the light
path, that is the longitudinal axis of the rod,
on emerging from the first end face so as to
spread out transversely of the light path.
In the arrangement shown in Figures 1 to 3, the first end faces 20 are recessed, that is the periphery 20' of each first end face 20
extends beyond the axially centremost portion of the first end face 20". As shown in Figures 1 to 3, the first end faces are complementary in shape to the second end faces although this need not necessarily be the case.
The first end faces 20 may be, for example, conical, prismatic or smoothly curved surfaces provided that the first end faces 20 are shaped so that light travelling along the rods 19 is incident on the first end faces at such an angle as to cause the light to be refracted and to diverge outwardly in a direction transverse to the axes of the rods on emerging from the first end faces. If the rods are of circular or round cross-section then the first end faces 20 will be conical or smoothly curved surfaces whereas if the rods are of rectangular cross-section the first end faces 20 will be prismatic surfaces.The angle at which light travelling along a rod is incident on the associated first end face 20 should, of course, be less than the critical angle for the interface between the first end face 20 and the material into which light emerges from the first end face 20, the material normally being air.
The first end faces 20 may be covered with a planar transparent plastics material cover to prevent dirt accumulating in the recessed first end faces 20. Alternatively, the first end faces 20 may be filled with a relatively low refractive index material so as to provide a flat surface, it merely being necessary to ensure that light will still be refracted at the first end face so as to diverge on emerging from the first end face and spread out transversely of the light path.
For the sake of completeness, the electrical heating and the control components of a kettle incorporating the optical level indicator discussed above will now be briefly described.
As shown in Figure 1, an electrical immersion heating element 24 is disposed within the receptacle 2 above a metal base plate 25 provided on the inner surface of the base wall 3 of the kettle.
The heating element 24 is mounted so as to be electrically connected to an electrical control unit 26 via an opening in the side wall 4. The electrical control unit 26 is secured to the outer surface of the side wall 4 adjacent the opening. The control unit 26 has an inter
nally threaded locking ring member 28 which
engages an externally threaded portion on a
head part 27 of the heating element 24. The
control unit has terminal pins 29 connectable via an aperture in the closure member 7 to an
appropriate mains suply connector and lead
(not shown).
The electrical control unit 26 incorporates
sets of contact members for enabling the
mains supply to be connected and discon
nected from the heating element. The control
unit includes thermal cut-out or 'boil-dry' cut
out means, usually a bimetallic member in
contact with the hot spot of the heating ele
ment (not shown), for opening a pair of contacts to disconnect the heating element from the mains supply when no liquid is present in the receptacle. The control unit also includes an automatic cut-out mechanism for switching the kettle off when liquid within the kettle boils. This cut-out mechanism comprises a mechanically movable switching. member in the form of a spring biassed pin 32 and a me
chanical lever assembly or linkage 30 which extends through the hollow handle to connect with a manually movable ON/OFF rocker switch 31 mounted within the top of the
handle 5.Although the use of a rocker control switch is preferred, it should of course be appreciated that alternative control switches could be used, for example a slidable control
switch could be used. Both the mechanical
lever assembly 30 and the switch 31 are
pivotally mounted to the body of the vessel
on respective pivot memebers 30a and 31a.
In the arrangement shown, the lever assembly
30 is mounted to a lever pivot member in the form of a bracket 30a. The lever pivot mem
ber may be replaced by a lever pivot mount
ing element formed by two opposed support
ing members projecting from the integrally formed with respective opposite internal surfaces of the channel cross-section extension.
In particular, although not shown, each sup
porting member may provide a U-shaped recess within which is pivotally supported a respective pivot pin provided on the lever assembly. Each U-shaped recess may be closed by a respective web projecting from an inside surface of the cover member so as to retain the respective pivot pin in the recess and complete the pivotal mounting.
The connection -between the switch 31 and the lever assembly 30 is such that, when the switch 31 is in the ON position, the lever assembly 30 is in a first position as shown in
Figure 1 and when the switch 3 1 is moved from the ON to the OFF position the lever assembly is pivoted to a second position in which the lever assembly pushes on the pin 32 to cause a set of contacts within the control unit to be opened to disconnect the heat
ing element 26 of the kettle from a mains supply.
A steam responsive member 33 in the form of a coil of a material available commercially and known-as memory metal is provided on a stem 34 of the rocker switch 31. The stem 34 of the rocker switch is disposed within a steam chamber 35 provided within the hollow
handle into which steam may pass via an aperture 35a formed in the side wall 4. The
memory metal steam responsive member 33
is arranged to expand when steam enters the steam chamber due to boiling of liquid within the receptacle to move the rocker switch 31 to the OFF position so causing the lever assembly 30 to push on the movable pin 32 to disconnect the power supply from the heating element. An overcentre spring 36 is provided to bias the rocker switch 31 toward the ON or OFF position when the rocker switch begins to move toward the ON or the OFF position, respectively.Although not shown, the spring 36 may alternatively be located within a recess or hollow in the rocker switch 31. In such an arrangement one end of the coil spring 36 would be located on an interior surface of the rocker switch 31 while the other end would be located on the rocker switch pivot member 31a. In one particular example, a spring-biassed cam follower arrangement may be used. Thus, the rocker switch pivot member 31a may provide an upwardly extending passage within which passage is received a spring carrying at its free end a ball on which a cam or shaped surface of part of the rocker switch rides so that as the- rocker switch is moved toward the ON or OFF position, the combination of the spring biassing and cam surface biasses the rocker switch into the ON or OFF position respectively.Of course, it should be appreciated that any appropriate spring biassing means connectable between the rocker switch and the lever assembly or the rocker switch pivot member 31a could be used.
An electrical kettle as described may be filled via the spout and the liquid level within the kettle clearly determined by viewing the first end faces 20 of the liquid level indicator, without need to peer downwardly from directly above the indicator to be able to see which of the first end faces appear bright or illuminated.
In the arrangement shown in Figure 1 to 3, the rods 19 are arranged in a straight line extending across the lid from the spout 12 to the handle 5. However, various arrangements of the series of rods 19 are possible. Thus, for example, as shown in Figure 4, the rods may be disposed in a straight line as in Figure 1 but extending along a gripping rib 37 defined between two recesses 38 formed in a modified lid 13' for an electrical kettle. Alternatively, with a lid 13' similar to that shown in Figure 4, the rods 19 may be arranged in a straight line which extends transversely of the rib 37. Of course, in the latter case the transverse dimensions and/or the number of rods provided will be reduced compared to the arrangement shown in Figure 1.In a further alternative where the lid is provided with a central knob, the rods 19 may be disposed in the lid in a line extending parallel to the periphery of the lid and/or the periphery of the knob. Thus, where a lid 13" is provided for a circular cross-section vessel as shown in
Figure 6, the rods 19 may be disposed along an arc of a circle concentric with the periphery of a knob 38 and surrounding recess 39. Any desired configuration for the line on which the rods are disposed may be used, for example the rods could be arranged along a spiral.
The rods 19 are normally, but not necessarily, of constant transverse or lateral crosssection and may have any desired cross-section, for example rectangular, square or oval (Figure 5) but are preferably of circular crosssection (Figures 1 to 3, 4 and 6). Furthermore, although as described above, the rods
19 are arranged to decrease or increase in length from one end of the row to the other, this need not necessarily be the case. Thus, the different length rods 19 may be arranged in any desired order and the change in length could vary so that, for example, the difference in length between the longer rods was less than that between the shorter rods, depending on where most accuracy in indicating liquid level is required. Also, more than one rod of a given length may be provided.
As discussed above, the rods 19 are effectively independent bodies, being joined only at their upper or first end faces and by the ribs
18a. However, the body 18 may be a single solid body provided at one end with a series of first end faces and at another end of the body opposite the one end with a series of second end faces so that a respective light path is provided between opposed first and second end faces.
Claims (20)
1. A liquid level indicator comprising a body for mounting within or above a vessel containing a liquid, the body defining a plurality of non-intersecting light paths, each light path extending between a respective first face at one end of the body and a respective second face at another end of the body opposite the said one end, adjacent second faces being disposed at different levels and each second face being shaped to cause light travelling along the respective light path to be incident on the second face at an angle equal to or greater than the critical angle for an interface between the second face and air but less than the critical angle for an interface between the second face and liquid, characterised in that each first face is shaped to cause light travelling along the respective light path to be refracted at the first face and to diverge from the light path on emerging from the first face so as to spread out transversely of the light path.
2. A liquid level indicator according to Claim 1, wherein each first face is recessed and is symmetrical about an axis extending parallel to the associated light path so that a peripheral portion of the first face projects beyond a central portion of the first face to cause light travelling along the light path from the associated second face to be incident on the first face at an angle greater than zero such that the light is refracted at the first face and diverges on emerging from the first face.
3. A liquid level indicator according to Claim 1 or 2, wherein each first face is prismatic being defined by two or more intersecting planar surfaces such that light travelling along the light path from the associated second face is incident on the first face at an angle greater than zero such that the light is refracted at the first face and diverges on emerging from the first face.
4. A liquid level indicator according to Claim 1 or 2, wherein each first face defines a conical surface.
5. A liquid level indicator according to Claim 1 or 2, wherein each first face defines a continously curved surface.
6. A liquid level indicator according to any preceding claim, wherein each second face is symmetrical about an axis extending parallel to the associated light path and is in relief so that a central portion thereof projects beyond a peripheral portion thereof.
7. A liquid level indicator according to any one of Claims 1 to 6, wherein each second face is prismatic being defined by two or more planar intersecting surfaces.
8. A liquid level indicator according to any one of Claims 1 to 6, wherein each second face is a conical surface.
9. A liquid level indicator according to any one of Claims 1 to 6, wherein each second face is a continously curved surface.
10. A liquid level indicator according to any preceding claim, wherein a series of light paths are provided, the second faces being arranged to provide a row of different length light paths, the length of the light paths decreasing in a step-wise manner from one end of the row to the other.
11. A liquid level indicator according to any preceding claim, wherein each light path is defined by a respective rod of a light transmissible material.
12. A liquid level indicator, comprising a body for mounting within or above a vessel containing a liquid, the body comprising a series of elongate rods each having first and second end faces defining therebetween a respective light path, each first end face being recessed so that a peripheral portion of the first face projects beyond a central portion thereof and being shaped to cause light travelling along the respective rod to be incident on the first face at such an angle greater than zero that the light is refracted at the first face and diverges from the light path on emerging from the first face so as to spread out transversely of the light path, the rods being of different lengths so that each second face is disposed at a different level, each second face being defined by one or more surfaces extending at an angle to the longitudinal axis of the associated rod, which angle is greater than or equal to the critical angle for an interface between air and the second end face but less than the critical angle for an interface between liquid and the second end face so that light travelling along a rod is totally internally reflected back toward the associated first end face when the second end face is immersed in air but is refracted when the second end face is immersed in liquid.
13. A liquid level indicator according to
Claim 11 or 12, wherein each rod is moulded from a plastics material such as polycarbonate.
14. A liquid level indicator substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.
15. A lid for a vessel adapted to contain a liquid, the lid having a liquid level indicator in accordance with any one of the preceding claims depending therefrom.
16. A lid for a vessel substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.
17. An electrical kettle wherever incorporating a liquid level indicator in accordance with any one of Claims 1 to 14 or wherever having a lid in accordance with Claim 15 or 16.
18. An electrical kettle comprising: a vessel having a plastics material body defining a base wall and a- side wall together forming a receptacle for liquid, a channel member mounted to the vessel body so as to define with a closure member closing the channel a hollow handle for the kettle and a plastics material lid closing the receptacle, an upper portion of the receptacle opposite the handle being shaped to provide a spout defining with the lid a passageway for permitting liquid to be poured from the receptacle; an electrical heating element disposed within the receptacle adjacent the base wall; an electrical control unit electrically connected to the heating element and disposed within a chamber formed in the body between the side wall of the receptacle and the closure member so as to provide for connection of the heating element to an electrical supply; a mechanical linkage extending through the handle and movable between a first position in which the heating element is electrically connectable to an electrical supply via the electrical control unit and a second position in which the mechanical linkage causes a movable rod of the electrical control unit to move to break electrical contact of the heating element via the control unit to the electrical supply; a manually operable switch mounted partially within or adjacent the handle, which switch is connected to the mechanical linkage to move the linkage between the first and second positions so that the linkage is in the first position when the switch is in an ON position and the linkage is in the second position when the switch is in an OFF position; a steam responsive device disposed within an upper part of the handle for receiving steam emanating from liquid in the receptacle via an aperture formed in the inner side wall adjacent the steam responsive device and for moving the ON/OFF switch to the OFF position in response to steam contacting the steam responsive member to cause the mechanical linkage to move the movable rod to disconnect the heating element; spring biassing means for biassing the ON/OFF switch toward the ON or the OFF position when the switch moves toward the ON or the OFF position, respectively; and an optical liquid indicator, which liquid level indicator comprises a body mounted to the lid, the body comprising a series of elongate rods depending from the lid, each rod having a first end face forming part of an outer surface of the lid and a second end face within the receptable and each first end face being recessed so that a peripheral portion of the first face projects beyond a central portion thereof to cause light travelling along the respective rod to be incident on the first face at an angle greater than zero but less than the critical angle for an interface between air and the first face so that the light is refracted by the first face and diverges from the light path on entering the air so as to spread out transversely of the- light path, the rods being of different lengths so that each second face is disposed at a different level, each second face being defined by one or more surfaces extending at an angle to the longitudinal axis of the associated rod, which angle is greater than or equal to the critical angle for an interface between air and the second end face but less than the critical angle for an interface between liquid and the second end face so that light travelling along a rod is totally internally reflected back toward the associated first end face when the second end face is immersed in air but is refracted when the second end face is immersed in liquid.
19. An electrical kettle substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.
20. Any novel feature or combination of features desribed herein.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8623170A GB2195446B (en) | 1986-09-26 | 1986-09-26 | A liquid level indicator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8623170A GB2195446B (en) | 1986-09-26 | 1986-09-26 | A liquid level indicator |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8623170D0 GB8623170D0 (en) | 1986-10-29 |
| GB2195446A true GB2195446A (en) | 1988-04-07 |
| GB2195446B GB2195446B (en) | 1990-02-28 |
Family
ID=10604829
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8623170A Expired - Lifetime GB2195446B (en) | 1986-09-26 | 1986-09-26 | A liquid level indicator |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2195446B (en) |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2234426A (en) * | 1989-08-03 | 1991-02-06 | Haden D H Ltd | Improvements in or relating to heating vessels |
| FR2690740A1 (en) * | 1992-05-04 | 1993-11-05 | Spmp Sa | Liquid level indicating appts. e.g. for culture container - has transparent rods with conical lower ends at different heights above floor of container, which reflect light back towards source when not immersed in liq. to appear bright, and which appear dark when light is refracted into liq.. |
| WO2001089357A1 (en) * | 2000-05-22 | 2001-11-29 | Eltek S.P.A. | Washing agent dispenser for a household a dishwasher |
| WO2002000072A1 (en) * | 2000-06-27 | 2002-01-03 | Pulse Home Products Limited | Illuminated jug kettle |
| GB2454005A (en) * | 2007-10-26 | 2009-04-29 | Jenny Maxwell | A liquid detecting apparatus for detecting a level of a liquid in addition to the presence of a liquid |
| WO2010071953A3 (en) * | 2008-12-22 | 2010-10-21 | Whirlpool S.A. | An ice mold filling device |
| WO2010109375A3 (en) * | 2009-03-23 | 2011-05-05 | Koninklijke Philips Electronics N.V. | Fluid level indicator |
| CN104948261A (en) * | 2015-04-29 | 2015-09-30 | 宁波大叶园林设备有限公司 | Lubricating oil dipstick displaying lubricating oil level with light guide and engine ignition and lubrication method |
| CN104938299A (en) * | 2015-04-30 | 2015-09-30 | 宁波大叶园林科技有限公司 | Garden irrigator with liquid-level light-guide display and involute curve nozzle |
| CN104948299A (en) * | 2015-04-29 | 2015-09-30 | 宁波大叶园林设备有限公司 | Liquid level and fuel oil level light guide display and engine ignition and lubrication method |
| CN104989489A (en) * | 2015-06-02 | 2015-10-21 | 宁波大叶园林设备有限公司 | Engine of lawn mower, with fuel gas mixer integrating gas mixing flues and three-level decompressing chamber |
| CN105179045A (en) * | 2015-06-02 | 2015-12-23 | 宁波大叶园林设备有限公司 | Two-stroke engine with logarithmic spiral and sine gas port decompression integrated mixer |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7706671B2 (en) | 2005-03-16 | 2010-04-27 | B2M Asset Management, Llc | Multi-function liquid container |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1087760A (en) * | 1965-09-29 | 1967-10-18 | Gen Motors Corp | Tank closure caps |
| GB1130224A (en) * | 1964-12-28 | 1968-10-09 | Illinois Tool Works | Liquid level indicators |
| US3535933A (en) * | 1969-02-17 | 1970-10-27 | Illinois Tool Works | Liquid level indicator |
| EP0039187A1 (en) * | 1980-04-28 | 1981-11-04 | Economics Laboratory, Inc. | Liquid level indicator |
-
1986
- 1986-09-26 GB GB8623170A patent/GB2195446B/en not_active Expired - Lifetime
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1130224A (en) * | 1964-12-28 | 1968-10-09 | Illinois Tool Works | Liquid level indicators |
| GB1087760A (en) * | 1965-09-29 | 1967-10-18 | Gen Motors Corp | Tank closure caps |
| US3535933A (en) * | 1969-02-17 | 1970-10-27 | Illinois Tool Works | Liquid level indicator |
| EP0039187A1 (en) * | 1980-04-28 | 1981-11-04 | Economics Laboratory, Inc. | Liquid level indicator |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2234426A (en) * | 1989-08-03 | 1991-02-06 | Haden D H Ltd | Improvements in or relating to heating vessels |
| FR2690740A1 (en) * | 1992-05-04 | 1993-11-05 | Spmp Sa | Liquid level indicating appts. e.g. for culture container - has transparent rods with conical lower ends at different heights above floor of container, which reflect light back towards source when not immersed in liq. to appear bright, and which appear dark when light is refracted into liq.. |
| WO2001089357A1 (en) * | 2000-05-22 | 2001-11-29 | Eltek S.P.A. | Washing agent dispenser for a household a dishwasher |
| US6851581B2 (en) * | 2000-05-22 | 2005-02-08 | Eltek S.P.A. | Washing agent dispenser for a household a dishwasher |
| WO2002000072A1 (en) * | 2000-06-27 | 2002-01-03 | Pulse Home Products Limited | Illuminated jug kettle |
| GB2454005A (en) * | 2007-10-26 | 2009-04-29 | Jenny Maxwell | A liquid detecting apparatus for detecting a level of a liquid in addition to the presence of a liquid |
| WO2010071953A3 (en) * | 2008-12-22 | 2010-10-21 | Whirlpool S.A. | An ice mold filling device |
| WO2010109375A3 (en) * | 2009-03-23 | 2011-05-05 | Koninklijke Philips Electronics N.V. | Fluid level indicator |
| CN104948261A (en) * | 2015-04-29 | 2015-09-30 | 宁波大叶园林设备有限公司 | Lubricating oil dipstick displaying lubricating oil level with light guide and engine ignition and lubrication method |
| CN104948299A (en) * | 2015-04-29 | 2015-09-30 | 宁波大叶园林设备有限公司 | Liquid level and fuel oil level light guide display and engine ignition and lubrication method |
| CN104938299A (en) * | 2015-04-30 | 2015-09-30 | 宁波大叶园林科技有限公司 | Garden irrigator with liquid-level light-guide display and involute curve nozzle |
| CN104989489A (en) * | 2015-06-02 | 2015-10-21 | 宁波大叶园林设备有限公司 | Engine of lawn mower, with fuel gas mixer integrating gas mixing flues and three-level decompressing chamber |
| CN105179045A (en) * | 2015-06-02 | 2015-12-23 | 宁波大叶园林设备有限公司 | Two-stroke engine with logarithmic spiral and sine gas port decompression integrated mixer |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8623170D0 (en) | 1986-10-29 |
| GB2195446B (en) | 1990-02-28 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| GB2195446A (en) | A liquid level indicator | |
| US4840137A (en) | Liquid level gauging apparatus | |
| DE3835386C2 (en) | Device for displaying an operating state of a cooking vessel | |
| CA2353056C (en) | Vessel with measuring capability | |
| EP1294260B1 (en) | Illuminated jug kettle | |
| MXPA06000982A (en) | Portable refractometer. | |
| US2468833A (en) | Container liquid level indicator | |
| WO1998027851A1 (en) | Liquid heating vessels | |
| CA1043584A (en) | Appliance for making coffee and the like | |
| US5021933A (en) | Illuminated magnifying glass | |
| US3773425A (en) | Visual comparator system | |
| US4164145A (en) | Self-powered electrical meter for display of a liquid-level or the like measurement | |
| US2432875A (en) | Level indicating device | |
| US2472665A (en) | Liquid level signal device for tanks | |
| US3961676A (en) | Weighing scales | |
| US2289374A (en) | Illuminating means for water gauges | |
| US4539270A (en) | Battery cap indicator with levered float | |
| EP0039187B1 (en) | Liquid level indicator | |
| USRE39827E1 (en) | Vessel with measuring capability | |
| US3279254A (en) | Liquid level gauge | |
| US2487664A (en) | Step action buoyancy scale | |
| JPS6171020A (en) | Electric pot | |
| GB2198533A (en) | Liquid level monitor | |
| CN221431055U (en) | Pelvis measuring meter | |
| ATE111219T1 (en) | LEAKAGE PROBE FOR LIQUIDS. |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19960926 |