GB2155691A - Indicating or measuring device - Google Patents

Abstract

An indicating or measuring device utilises a sensing element comprising a housing, preferably in the shape of a glass or plastics ring-like tube 1, which is arranged to be partially filled with a conductive fluid 2 such as mercury. The sensing element is provided with groups of electrical contacts 4-10, in the walls of the housing 1, which are engageable with the conductive fluid 2 to make or break electrical circuits. When the attitude of the sensing element is changed with respect to a reference direction e.g. horizontal the conductive fluid contained in the housing maintains the same attitude with respect to the horizontal. The electrical contacts are therefore arranged to provide information on the attitude of the sensing element with respect to the horizontal. Two specific embodiments of the indicating or measuring device are an aircraft instrument and an angle measuring device. <IMAGE>

Description

SPECIFICATION Indicating or measuring device This invention concerns an indicating or measuring device particularly but not exclusively for use as an aircraft instrument or instruments.

It has been proposed in aircraft to provide separate instruments to furnish information on turn and slip, climb and descend and artificial horizon. These instruments have previously relied on vacuum dependent means or gyroscopically dependent means to function correctly. Conditions can occur in which the vacuum pilot tube can become frozen and the gyroscope can be upset, causing the instruments to malfunction. In addition, the instruments tend to be rather bulky and expensive.

Furthermore, separate displays are usually provided for each instrument, with the result that they cannot be easily read at the same time.

The present invention provides a sensing element which utilises a conductive fluid to produce signals indicate of, for example, aircraft attitude, for display by a composite display device.

The sensing element is preferably constructed from a closed tube which is partially filled with conductive fluid. Electrical contacts are provided in the wall of the tube. Electrical circuits are completed or broken depending on the position of the surface or surfaces of the conductive fluid with regard to the various electrical contacts. In this way, signals indicative of the position of the surface of the conductive fluid can be obtained. If the sensing element is fixed in a known attitude in an aircraft, for example, these signals can provide an indication of the attitude of the aircraft due to the fact that in a closed tube the surface of the fluid will remain horizontal. By the use of more than one sensing element information can be provided regarding turn and slip, artificial horizon, and climb and descend.

Preferably, displays representing all three aspects of attitude are provided in one composite display.

From a further aspect the indicating or measuring device of the present invention can be used for the measurement of angles generally.

Devices, such as spirit levels, have been proposed which provide an indication of whether a surface, such as a table top or a brick wall, is horizontal or vertical. Such devices utilise the bubble which is formed in a generally straight closed tube partly full of liquid. The closed tube is housed in a member which can be layed flat on the surface to be measured. The closed tube is positioned such that, when the housing member is placed on a horizontal surface, for instance, the buble moves by gravity to the center of the tube, thus indicating that the surface is horizontal.

Markings are generally provided on the tube to indicate the correct positioning of the bubble for a horizontal surface. In general, two tubes are utilised in one elongate housing member, one tube being positioned at right angles to the other, so that one tube can be used to test vertical surfaces, and the other can be used to test horizontal surfaces.

The problem with these devices is that normally only horizontal and vertical can be measured. They can provide no measure of the angle of, for instance, a sloping roof.

The present invention further provides a device for measuring angles which utilises the sensing element housed within a housing member having a display element for displaying angles.

It has been found that the sensing element can be utilised with an appropriate display and housing to provide a device which is capable of measuring angles from 0 to 360 .

Features and advantages of the present invention will become apparent from the following description of embodiments thereof given by way of example with reference to the accompanying drawings, in which: Figure 1 shows a view along the central axis of a sensing element according to a first embodiment of the present invention; Figure 2 shows a front on view of a composite display provided according to a first embodiment of the present invention; Figure 3 shows a view along the central axis of a sensing element according to a second embodiment of the invention; Figure 4 shows a perspective view of a display provided according to a second embodiment of the invention; and Figure 5 shows a side view of a sensing element having a different contact arrangement.

Fig. 1 shows a sensing element 1 2 designed to provide information on turns and slip and artificial horizon, which comprises a container in the form of a tube 1 having a bore 11 of convenient diameter and formed into a convenient shape such as a annulus.

The tube 1 is partially filled with a conductive fluid 2, such as mercury, for example. The tube 1 is provided with a plurality of electrical contacts 4 to 10, preferably of copper, and an earth pin 3, also preferably of copper, which project through the wall of the circular tube 1 into the bore 11. The conductive fluid 2 provides a conductive path by which the electrical contacts 4 to 10 may be electrically connected to the earth pin 3. The electrical contacts are connected via conventional electrical circuitry means (not shown) to a display such as the one shown in Fig. 2.

Fig. 2 shows a composite display comprising a plurality of variously coloured light emitting devices such as Light Emitting Diodes (LED's) for use on any instrument panel to display information on turn and slip, climb and descend, and artificial horizon. A mounting plate 1 7 is provided to house the LED's 13 to 16. An array of LED's 1 3a to 1 3j of one colour are arranged in a vertical line on the mounting plate 1 7 to display information on climb and descend. An array of LED's 1 4a to 14h, which may be of another colour, are arranged in a line which bisects at a right angle LED's 1 3a to 13j, and display information on artificial horizon.LED's 1 6a to 16f, which may be of another colour, are situated at one end of the line of LED's 1 3a to 13j.

They are arranged such that 1 6a to 1 6c lie on one side of the line and 1 6d to 1 6e on the other LED's 1 6 display information on turn and slip. LED's 15, which may be of yet another colour, also display information on turn and slip. 15e to 15f are situated in pairs, each pair positioned adjacent the corresponding pair 14, 14b, or 149, 14h, of LED's 14.

LED's 15a to 15b are positioned immediately adjacent to the end of the line formed by the LED's 13.

The operation of the apparatus will now be described regarding the provision of information on artificial horizon and turn and slip in an aircraft.

The sensing element 1 2 is mounted in a fixed position such that its central axis is parallel to the longitudinal axis of the aircraft.

The electrical contacts 4a and 4b are diametrically opposite each other and the sensing element is mounted so that a line joining them is parallel to the horizontal. The earth pin 3 is separated from each of the contacts 4a and 4b by 90 . The angle formed between the earth pin 3 and any one of the contacts 5a to 1 0a is greater than 90 but less than 180 , on the same side of the sensing element 1 2 as the contact 4a. Similarly, the angle formed between the earth pin 3 and the contacts 5b to 1 0b is greater than 90' but less than 180 on the same side of the sensing element 1 2 as the contact 4b.

Electrical circuitry (not shown) is provided between contacts 4 and LED's 1 4 each contact 4a, 4b being connected to a bank of four LED's 1 4a to 1 4d or 14e to 1 4h respectively.

Electrical circuitry is provided between contacts 5 to 10 and LED's 15, 16. Contacts 8a, 9a, 10a and 8b, 9b and lOb are connected to the bank of LED's formed by 15a, 15b, 1 sic or 15e, 15f, 15b. Contacts 5a, 6a, 7a and 5b, 6b, 7b are connected to the banks of LED's formed by 16a, 16b, 1 6c or 16d, 16e, 16f.

The electrical circuitry is arranged such that when a conductive path is provided between the earth pin 3 and one of the contacts 14 to 1 6 via the conductive fluid 2, the corresponding LED or bank of LED's is lit.

When the aircraft is horizontal both contacts 4a and 4b will be provided with a conductive path to the earth pin 3 via the conductive fluid 2. LED's 14a to 14h will be alight due to the electrical circuit thus completed, indicating to the pilot of the aircraft that the wings of the aircraft are horizontal. If the aircraft rotates about its longitudinal axis such that the wings are no longer horizontal, the sensing element 1 2 will rotate to the same degree, but the conductive fluid will remain in substantially the same attitude as prior to the rotation of the aircraft. One of the electrical contacts 4 will no longer have a conductive path to the earth pin 3 and one of the banks of LED's 14a to 14d or 14e to 14h will no longer be alight. This indicates to the pilot that the aircraft is no longer horizontal.Which bank of LED's 14a to 14d or 14e to 14h is thus extinguished will indicate in which direction the aircraft has rotated. Information on artificial horizon is thus provided.

Continued rotation of the aircraft about its longitudinal axis will bring the conductive fluid 2 sequentially into contact with the electrical contacts 5 to 1 0a or 5 to lOb. The sensing element can be calibrated such that contacts 5, 6 and 7 indicate a degree of rotation of the aircraft corresponding to RATE ONE, RATE TWO and RATE THREE turn, respectively. The information being displayed on banks of LED's 16a, 16b, 1 6c and 1 6d, 16e, 16f. The sensing element can also be calibrated such that contacts 8, 9, 10 indicate a degree of rotation intermediate horizon and RATE ONE turn, RATE ONE and RATE TWO turn, and RATE TWO and RATE THREE turn respectively.The information being displayed on banks of LED's 15a, 15c, 15d and 15b, 1 Se, 1 Sf. Thus quantitive information regarding rate of turn and artificial horizon of the aircraft can be provided to the pilot.

By providing another sensing element similar to the element 1 but its central axis at right angles to the longitudinal axis of the aircraft, information regarding climb and descend can be provided in a similar way for display by the bank of LED's 1 3. Thus information regarding turn and slip, climb and descend, and artificial horizon can be conveniently provided to the pilot by the use of only two such sensing elements.

Preferably each sensing element is housed in a rigid disc-like plastics housing to provide protection. Both sensing elements in their separate housings are preferably housed in a larger cylindrical member together with the necessary electrical circuitry. The larger cylinder being provided at one end with a face to support the mounting plate 1 7 of the complex display. Each disc-like housing the individual sensing element is preferably provided with a serrated external periphery for engagement with corresponding serrations internal to the larger cylindrical member so as to support the cylinder housing therein. This arrangement permits accurate positioning and adjustment of the or each sensing element in the cylindri cal member.

Preferably, each sensing element is provided with damping means which acts on the conductive fluid to prevent undesirable oscillations or movement of the conductive fluid, thus preventing the production of output signals when proper rotation about the axis of the device is occurring. This damping means may be any means which exerts a damping force on the conductive fluid. Preferably a fluid, which may be alcohol for example, can be provided in the tube in addition to the conductive fluid. This fluid will act to provide damping of the conductive fluid. Advantageously, the bore of the tube of the sensing element is not completely filled with alcohol so as to produce a bubble in the manner of a spirit level, which can be used to provide a horizontal reference when adjusting the instrument.

The display need not be in the form of the composite display as herein described. It may be in the form of an analogue display, or any other type of suitable display.

The composite instrument or each individual instrument is preferably provided with its own stand-by power source, e.g. a NiCad.

battery, to permit continued operation of the instruments even in the presence of a general power failure of the aircraft electrical system.

In addition, the sensing element need not provide information only to a display device, but could additionally or alternatively provide information to some form of microprocessor controlled system, for example.

The tube 1 is preferably a plastics or glass tube of 1 /4" external diameter with a bore diameter of 3/16". This arrangement has the advantage that the sensing element is not affected by the changes in temperature. If it is found necessary in view of the use of different materials or different dimension, it is possible to provide a thermostatically controlled heater to maintain the sensing element at a constant temperature.

A second embodiment of the present invention relating to a device for use in measuring angles of surfaces, will now be described with reference to Figs. 3 and 4.

The sensing element 20 shown in Fig. 1 is similar to the sensing element described above in relation to the first embodiment of the invention, save that the contact arrangement is designed to make it suitable for use in measuring angles.

The sensing element 20 shown in Fig. 3 is in the form of a closed tube 21 having a bore 22 convenient diameter and being formed into a convenient shape such as an annulus.

The tube 21 is partially filled with a conductive fluid 23, such as mercury, for example.

The tube 21 is provided with electrical contacts 24 and 25 preferably of iron or tungsten and an earth pin 26, also preferably of iron or tungstent which project through the wall of the tube 21 into the bore 22. The conductive fluid 23 provides a conductive path by which the electrical contacts 24 and 25 may be electrically connected to the earth pin 26.

The sensing element 20 is rotatably mounted within the housing member 30 shown in Fig. 2. The sensing element 20 can be rotated through any angle by means of the handle 35.

The sensing element 20 is most conveniently rotatably mounted by fitting it into a cylinder (not shown), which in turn fits into another cylinder (not shown), thus allowing the sensing element 20 to be able to be rotated through 360 .

A face 40 of the housing member 30 is provided with a display section 37. The display section includes a graduated portion 32 which is graduated in terms of degrees of angle, light emitting diodes, 36 and 37, and pointers 33 and 34.

The contacts 24 and 25 of the sensing element are connected by electrical circuitry means (not shown) to LEDs 36 and 37 respectively. The contacts 24 and 25 are both situated at approximately 90 from the earth pin 26 respectively. When the respective contacts are electrically connected to the earth pin via the conductive fluid, the LEDs will light up.

The pointers 33 and 34 are mounted on a dial 38 which can be turned coincidently with the sensing element 20. Pointer 33 is coincident in position with contact 24, and pointer 34 is at a 90 angle to contact 24.

The operation of the device is as follows: The surface 31 is placed on an angled surface which is to be measured. The surfaces of the conductive fluid 23 in the tube 21 will remain horizontal. The dial 38 is turned, together with the sensing element 20, until LEDs 36 and 37 and the calibrated scale 32 to give the angle of the measured surface.

It will be appreciated that the device must be initially calibrated by placing it on a horizontal surface, and adjusting the position of the sensing element 20 and pointers 33 and 34 so that, when all LEDs are alight, an angle of 0 is read from the scale by the appropriate pointer.

It will also be appreciated that this device need not merely be limited to the type of display disclosed above. For instance, an all electronic display could be envisaged which incorporates a plurality of LEDs which light up to indicate the angle of the measured surface (i.e. the LEDs would be placed in a 360 circle, one for every 5 , for instance, and respective contacts would be provided in the wall of the tube). In this case there would be no need to mount the sensing element 20 so that it is capable of rotation. As a number of electrical contacts are provided in the wall of the tube one for every few degrees for example each contact being connected to a respective LED so that the LED lights up when the conductive fluid provides a connection between the contact in the earth pin.The number of LEDs alight would indicate the angle of the surface on which the device is placed.

It is also envisaged that suitable electronic interface means (known in the art) could be provided between the sensing element 10 and a suitable numeric display, LED for instance, so that a digital read out of angle could be obtained.

It will also be appreciated that the sensing element of this embodiment could be provided with damping means as described above in relation to the first embodiment.

A power source for the display, such as a rechargeable battery could be provided mounted within the housing 30.

A further embodiment of the sensing element is shown in Fig. 4, looking from the side, to illustrate a different contact arrangement to the one that has been so far described in relation to the above two embodiments.

The electrical contact 51 is in the form of a pin which enters through the front face of the sensing element 50, generally perpendicular to the face of the sensing element. At a point 52 pin is bent at an approximately 90 angle to its direction of entry to the sensing element, in a direction towards the surface of the mercury 53.

This contact arrangement enables the mounting of the contact within the tube to be performed more easiiy (by soldering for example) and also facilitates the mounting of the sensing element on any printed circuit board which is designed to incorporate circuitry for the operation of the sensing element (e.g. as all contacts are directed from the front of the sensing element, mounted on a printed circuit board would be simple).

It will be appreciated that any number of contacts can be mounted in this manner, and that such a contact arrangement would be utilised in any of the embodiments described above.

Claims (22)

1. A sensing element for use in an indicating or measuring device, the sensing element comprising a housing having walls defining a chamber arranged to be partially filled with a conductive fluid, and a plurality of electrical contacts engageable by said conductive fluid to make or break electrical circuits, whereby to provide information relating to the attitude of the sensing element with respect to a reference direction.

2. A sensing element in accordance with claim 1, wherein said housing is a closed tube.

3. A sensing element in accordance with claim 2, wherein the tube is in the form of a ring.

4. A sensing element in accordance with any preceding claim, wherein the electrical contacts are pins which project through the walls of the housing.

5. A sensing element in accordance with claim 4, wherein the pins are bent at a point along their length to form an angle of approximately 90 , the point at which the pins are bent within the chamber.

6. A sensing element in accordance with claim 5, wherein the pins are all arranged to point in the same direction.

7. A sensing element in accordance with any preceding claim, wherein there are a plurality of groups of contacts with a plurality of contacts in each group.

8. A sensing element in accordance with claim 7, wherein there is provided a further contact arranged to be connected to a source of reference potential.

9. A sensing element in accordance with any preceding claim and including conductive fluid, wherein damping means is provided to damp motion of the conductive fluid due to changes in attitude of the sensing element.

10. A sensing element in accordance with claim 9, wherein the damping means is a non-conductive fluid.

11. A sensing element in accordance with any preceding claim, wherein said conductive fluid is mercury.

1 2. A sensing element in accordance with any preceding claim, wherein the walls of said housing are of glass.

1 3. A sensing element in accordance with any preceding claim, wherein the walls of said housing are of plastics.

1 4. An indicating or measuring device, comprising at least one sensing element in accordance with any one of the preceding claims.

1 5. An indicating or measuring device in accordance with claim 14, wherein there are two sensing elements disposed at an angle to each other.

1 6. An indicating or measuring device in accordance with claims 1 4 or 15, and comprising a display connected to at least one sensing element.

1 7. An indicating or measuring device in accordance with claim 16, wherein said display comprises a plurality of display elements responsive to the making or breaking of electrical circuit by said conductive fluid.

18. An indicating or measuring device in accordance with any of claims 14 to 17, wherein the or each sensing element is housed in a relatively rigid casing.

1 9. An indicating or measuring device in accordance with claim 18, and comprising a further housing adapted to receive at least one sensing element and permit movement of the element with respect to the further housing.

20. An indicating or measuring device in accordance with any of claims 14 to 19, wherein the or each sensing element is maintained at a constant temperature by thermostatically controlled heating means.

21. An indicating or measuring device in accordance with any of claims 14 to 20, wherein the device is an aircraft instrument.

22. An indicating or measuring device in accordance with any of claims 14 to 20, wherein the device is an angle measuring device.