GB2287321A

GB2287321A - Fluid boiling-point measuring device

Info

Publication number: GB2287321A
Application number: GB9403896A
Authority: GB
Inventors: Nigel Alexander Buchanan
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-03-01
Filing date: 1994-03-01
Publication date: 1995-09-13
Anticipated expiration: 2014-03-01
Also published as: GB9403896D0; GB2287321B

Abstract

A portable fluid boiling point measuring device (1) includes a probe (2) for immersion in the fluid to be tested. The probe (2) comprises a casing (2a) and plug (9) defining chambers (3, 4) semi-encapsulating a sample of fluid (3a). The fluid (3a) is kept at an optimum level by a quantity of air being trapped in the upper chamber (4) above apertures (6a). The plug (9) separates chambers (3, 4) with a central fluid connection (9b 9c, 9d). A heater (8) around a central conduit (9a) heats the fluid (3a) causing fluid circulation upwards, cooler fluid being drawn down the conduit (9a) over a temperature measuring device (10). The test fluid (3a) ceases to circulate at boiling point when its temperature equalises. The device (1) shows this equalised temperature on the display (11). Fluid above boiling point vents through apertures (9c, 9d, 6a) and cooler fluid enters from base aperture (5) stabilising the boiling point. <IMAGE>

Description

"FLUID BOILING-POINT MEASURING DEVICE" The present invention relates to a device for measuring the boiling point of a fluid and, more especially, relates to a device for conveniently sensing the boiling point of hydraulic fluid, for example for testing the quality of brake fluid of a motor vehicle.

A hydraulic fluid such as motor vehicle brake fluid is hygroscopic, ie absorbs water (moisture). Water absorbtion has, of course, the effect of considerably reducing the boiling point of the fluid, with the result that in the case of motor vehicles, heavy vehicle braking may give rise to sufficient heat generation to boil the brake fluid thereby resulting in vapour entrapment in the fluid which could dangerously reduce braking performance.

Consequently, there is the need to test the quality of vehicle brake fluid by measuring the boiling point of the fluid, so that the measured value can be compared with an accepted standard to evaluate the fluid quality. Measuring devices are known for measuring the boiling point of fluid and especially the boiling point (and quality) of brake fluid. Basically, these devices include a heater to heat a quantity of the fluid to boiling point and a temperature sensor to sense the boiling temperature. Some of these devices, eg as shown in US Patent 4 958 937, require a sample of fluid to be removed from the vehicle reservoir for testing, and the subsequent testing procedure is of a somewhat delicate laboratory-like nature. This is inconvenient and is not readily acceptable for everyday garage operations.To meet this problem, other measuring devices have been provided capable of testing directly at the fluid reservoir, an example of such a device being shown in US Patent 4 484 823 (VJ090 12311), but the arrangement of the heating means in the device of US-A-4 484 823 precludes prompt temperature sensing. The device shown in International Application W090/123111 overcomes this problem by providing a hand-held sensor which, when inserted into the fluid to be tested, traps a small portion of the fluid in a semiencapsulated chamber in a probe part of the device for heating. This device, however, relies very much on correct depth immersion in the fluid.It is an object of the present invention to provide a fluid boiling-point sensing device which is capable of being hand-held and which can be used in a more convenient manner to sense the boiling points of fluids directly at a fluid reservoir, eg in a vehicle brake fluid reservoir.

Therefore, according to the present invention, a measuring device for measuring the boiling point of a fluid in a reservoir, in particular but not exclusively a vehicle brake fluid reservoir, includes a probe member for insertion into fluid to be tested in a reservoir, said probe member including a first lower part serving to retain a portion of the fluid to be tested. First aperture means being provided for the passage of fluid into and out from said first part from the reservoir. Fluid heating means in said first part located round a central conduit, said conduit having aperture means top and bottom. Located within said conduit a temperature sensor preferably of an electronic type.Said probe member further including a second part located above said first part and open at the bottom so as to be in fluid communication with said first part via centre apertures, allowing fluid communication with the fluid within said conduit. Said second part having second aperture means within the preferably cylindrical outer side wall for discharging of fluid air from the probe member to the reservoir and arranged so that when the said probe member is inserted into the reservoir fluid air is trapped in said closed topped second part to maintain a fluid boundary between said first and second parts. When the said probe is inserted into the fluid to be tested to a depth past said second aperture means and the said heating means operated, the fluid within the said first part is heated.Preferably the gap between the said cylindrical outer side wall and the said central conduit allows the said heated test fluid only to rise, pulling cooler fluid from the base of said probe. By restricting the size of the first aperture means, the said heated fluid is drawn down the said conduit means causing a convection flow of the said fluid being tested rising to the top of the said first part of the said probe and being drawn down the said central conduit past the said temperature sensor agitating the said test fluid within the said first part. The said fluid boundary between the said first and second parts restricting the said heated fluid connection to the said second part causing its temperature to stabilise within the said first part at boiling point.If the said temperature within the said first part was to rise to such a level that the boiling of the said test fluid caused excessive steam bubbles within the said first part, this said excessive steam bubbles would be vented via the said fluid boundary out the said second aperture means. Cooler fluid from the said reservoir is received into the said first part via the said first aperture means compensating for the evaporated said test fluid within the said first part and tending to stabilise the said test fluid temperature at its relevant boiling point. Preferably the probe member is of cylindrical form, said first and second parts defining cylindrical chambers, a plug being provided to close the top of the chamber of the second part and a second plug between the said first and second parts.Said second plug having a central aperture means facilitating fluid connection between the said first and second parts. The prooe member may comprise a single cylindrical casing, with said first aperture means located on a bottom wall of the casing.

Alternatively the probe member may be of radially spaced double-wall form with said second aperture means on the outer wall and additional fluid aperture means on the inner wall located above said second aperture means. Either of the first and second aperture means may comprise openings of a restricted form. The heating means preferably comprising an electrical heater supplied with power from an electrical battery while the temperature sensor which can comprise a thermocouple device is preferably linked to suitable monitoring and presentation means for registering the measured temperature value. The probe member is preferably part of a self-contained hand-held unit.

By means of the present invention, accurate testing of fluid in a reservoir is possible irrespective of the depth of immersion of the probe member in the fluid, provided that the second aperture means are below the level of the fluid in the reservoir and excessive probe depth in said reservoir does not incur fluid pressures within said probe to change the said fluid boundary level.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings wherein: Figs la and Ib shows a sectional elevation of a probe member of a brake fluid tester or analyser, in accordance with one embodiment of the present invention; Fig 2 A and 2B show pictorial views illustrating the use of the tester of Fig 1; Fig 3 shows a view similar to Fig 1 of a further embodiment of the present invention; and Fig 4 shows a graph of the temperature of fluid under test and heated in the tester against time.

Referring to Figs la and lb, a portable hand-held analyser or tester (generally indicated by ref 1) serves to sense the boiling temperature of a fluid, especially automotive brake fluid, so that the quality of the fluid can be established, the tester 1 including a probe member 2 for insertion into fluid to be tested. The probe member 2 comprises a lower part 3 and an upper part 4 there above, aperture means 5 permitting fluid flow into the part 3, and aperture means 6a for discharge of fluid from the probe member 2 within the upper part (4) level. The top of the aperture means 6 whereat a fluid level L1, L,a, is established in the member 2 generally defines the demarcation line between the lower and upper parts 3, 4, the upper part 4 being in fluid communication with the lower part 3 via aperture means (9d).The member 2 is of cylindrical form so that the parts 3, 4 comprise cylindrical chambers. The upper chamber (4) is closed at its top end by a plug (7). The lower chamber (3) houses an electrical heating element (8) and its leads (8a, 8b) which pass sealingly through the plug (7) and a second plug (9) serving to separate the upper chamber (4) and lower chamber (3).Extending from the base of the second plug (9) is a conduit (9a) with lower aperture (9b). Apertures (9c) level with the top of the lower chamber (3) and fluid connecting the upper chamber (4) and lower chamber (3) through aperture (9d). A temperature sensor (10) is located within the conduit (9a) and serves for measuring the boiling point of fluid heated in the lower chamber (3), as shown in Fig ib. The heated fluid (3a) rises and causes the same heated fluid to be drawn down the central conduit (9a) via apertures (9c, 9b). The temperature within this circulating fluid (3a) stabilises at boiling point. Excessive steam bubbles (3b) if created within the lower chamber (3) vent through the fluid boundary (L1, L,a) and aperture (6a). Cooler fluid from the reservoir being drawn in through aperture (5) helping to stabilise the fluid's (3a) temperature. The temperature sensor (10) passing sealingly through the plug (7). The boiling point temperature being shown on the temperature display (11). The electronic equipment required to change the temperature recorded by the sensor (10) into the temperature displayed (11) is not shown nor the power supply which would preferably be self contained rechargeable batteries.

Fig 3 shows a similar arrangement but with double cylindrical walls (2a, 2b) providing insulation for the part 3 and lower location of the fluid boundary (L1, L,a).

Claims

1. A Fluid Boiling Point Measuring Device for indicating the boiling point of fluid, especially a hygroscopic fluid such as hydraulic fluid, comprising a meter (1) preferably of the portable hand held type including a probe portion (2) for insertion into fluid in a fluid reservoir, heating means (8) being provided in the probe portion (2) for heating fluid semi-encapsulated within the probe portion (3) when the probe (2) is immersed, said meter additionally including monitoring means (10) for monitoring the temperature rise of fluid heated by said heating means (8) so as to indicate the boiling point temperature of the fluid (3a), characterised in that said probe includes a casing (2a) defining a housing (3) wherein a portion of fluid to be tested is semi-encapsulated.The temperature monitoring means (10) sensing the temperature of the circulating fluid (3a) in the housing (3) heated by the heating means (10) and in that fluid inlet means (5, 6a, 9c, 9d) are provided permitting fluid flows to and from the housing (3).

2. A Fluid Boiling Point Measuring Device, as claimed in Claim 1, comprising a probe (2) which can be advantageously arranged to enable the test fluid to flow into a chamber area (3) serving to semi-encapsulate a portion of the fluid requiring testing.

This test fluid can be advantageously kept at a set level by trapping a quantity of air within the area (4) above the aperture means (6a) such as to maintain a fluid/air boundary. At a level (Ll) below which the test fluid (3a) circulates within the lower portion (3) when heated by the heater (8). The fluid between the probe wall (2a) and the conduit (9a) rises drawing fluid from the base of the probe (2) and down the conduit (9a) via apertures (9c, 9b). A temperature monitoring device (10), preferably a thermocouple, measures the temperature within the test fluid (3a). As the temperature in the chamber (3) stabilises the temperature rise and circulating effect stops, the boiling point can then be ascertained.

3. A Fluid Boiling Point Measuring Device, as claimed in Claim 1 and proceeding claims, wherein there is provided a display means (11), preferably incorporating an electronic sensing means, wherein the temperature of the fluid on test (3a) as it reaches boiling point can be shown in degrees centigrade or fahrenheit.

4. A Fluid Boiling Point Measuring Device, as claimed in proceeding claims, wherein there is provided a latching device, preferably a known electronic latching device, which senses the rise in temperature of the fluid (3a) being tested as it is heated. As the temperature rise lessens, then levels as the test fluid boiling point occurs, this stabilised temperature is latched on within the electronics and the corresponding temperature is shown on the display (11) until the device is switched off or the next test sequence begun.

5. A Fluid Boiling Point Measuring Device, as claimed in proceeding claims, wherein there is provided a chamber (3) within the probe, preferably cylindrical, with aperture means in both the base (5) and the sidewall (6a, 6b). The apertures in the base (5) allow the fluid to be tested into the test chamber when the probe is emersed past the required fluid level (L,). They also allow the test fluid to flow easily from within the probe when the probe is withdrawn from the fluid. The apertures in the base (5) are advantageously kept to a size which allows the fluid to flow timeously into the test chamber (3) while restricting the flow of oxygen to the element (8) within in the probe (2) preventing any residue fluid within the probe being set alight if the device is inadvertently operated whilst in air, not in the test fluid.The apertures in the side of the probe (6a) are advantageously placed to trap a quantity of air in the upper part (4) within the probe (2) creating a thermal buffer (L,a) between the heated test fluid (3) and the control and display electronics (11).

6. A Fluid Boiling Point Measuring Device, as claimed in proceeding claims, wherein there is provided a probe portion (2) which when immersed in the test fluid past the probe apertures (6a) becomes largely insensitive to the depth of fluid being tested until immersed to such a level that the pressure within the fluid starts to compress the air pocket (4) altering the fluid air boundary (L,). This device can advantageously be used to test the boiling point of differing fluids which separate due to density, etc but are held in the same container. This device can advantageously be used to test vehicle brake fluids as it is not always possible to attain a correct probe depth due to reservoir location.

7. A Fluid Boiling Point Measuring Device, as claimed in proceeding claims, wherein there is provided a plug (9) between the lower chamber (3) and the upper chamber (4). The only fluid connection between the chambers (3, 4) is via the apertures (9d, c, b). The apertures (6a) in the upper chambers (4) are advantageously kept as low as possible, keeping the test fluid (3a), fluid air boundary (L,a) as near to the top of the aperture (9c) in the conduit (9a) as possible, preventing a hot spot of fluid forming next to the fluid air boundary (L,a) between the lower and upper chambers (3, 4).The heated test fluid (3a) being drawn down the conduit (9a) within the lower chamber (3) accentuating the circulating effect within the test fluid (3a) during the operation of the heater (8) and advantageously preventing undue loss of fluid vapour (3b) from apertures (9d, 6a) while mixing fluids (3a) of differing temperatures within the lower chamber (3) until the fluid temperature stabilises within the lower chamber (3) at or around boiling point.

8. Fluid Boiling Point Measuring Device as claimed in proceeding claims, wherein there is provided a lower chamber (3) within the probe portion (2).

During the operation of the device (1), the test fluid (3a) is heated by the heater (8), and circulates upwards between the outside wall (2a) of the probe (2) and downwards within the conduit (9a), the test fluid (3a) circulating till the test fluid (3a) temperature is uniform within the chamber. The fluid air pocket in the upper chamber (4) serving to create a thermal buffer (lea) at the level (L1). When the test fluid (3a) rises above the boiling point temperature within the lower chamber (3), excess vapour (3b) caused vents through the apertures (9d, 6a) and cooler fluid enters through aperture (5), tending to stabilise the test fluid (3a) at its boiling point temperature.

9. A Fluid Boiling Point Measuring Device, as claimed in proceeding claims, wherein there is provided a probe (2), the single cylindrical casing (2a) forming the outer wall of upper and lower chambers (3, 4) can be advantageously supplemented by a further radially spaced double wall form (2b) with the space between the casings (2a, 2b) being sealingly closed at their upper point by a plug (7). The aperture (6a) on the outer casing can be advantageously arranged to position the fluid boundary (Ll) at its optimum, regardless of the plug (9) configuration. A further advantage of the second casing is to provide insulation to the test fluid (3a) when heated by the heater (8) from the cooler fluid within the reservoir.