GB2111678A

GB2111678A - Inclination indicator

Info

Publication number: GB2111678A
Application number: GB08137641A
Authority: GB
Inventors: Francis Gerald Darwen
Original assignee: Merryweather & Sons
Current assignee: Merryweather & Sons
Priority date: 1981-12-14
Filing date: 1981-12-14
Publication date: 1983-07-06

Abstract

An inclination indicator suitable for mounting on a fire-escape vehicle includes one or more mercury switches arranged to change conductive state when the inclination of the vehicle to the upright exceeds a threshold value, typically 7 DEG , in any direction. The change of conductive state is connected to operate a warning device, such as a lamp, if the inclination is too great. Radial (fig. 1) and ring (fig. 5) arrangements of 8 switches are described with both parallel and series connection. A circularly symmetrical switch (Fig. 3) is also described. The threshold value may be arranged to be different for different orientations of inclination. <IMAGE>

Description

SPECIFICATION Inclination indicator This invention relates to an inclination indicator, and in particular to an indicator suitable for mounting on a fire engine or other vehicle to indicate whether the attitude of the vehicle on the site on which it stands is sufficiently level for the safe operation of the fire-escape ladder. The indicator may also be used on mobile hoists and cranes.

Fire-escape ladders are capable of extension up to a hundred feet, or possibly more, and at such extensions the weight of a fireman or a person being rescued on the ladder may be sufficient to topple the vehicle on which the ladder is mounted. In order to avoid accidents resulting from the vehicle overturning in this way, it is necessary to specify limits on the operation of the fire-escape ladder. Such limits are frequently built into the mounting of the ladder on the vehicle, but on the assumption that the vehicle is standing on a substantially level site. If the inclination of the site departs from level by a considerable extent, it may become difficult to operate the ladder safely. The operation of a fire-escape ladder inevitably takes place under conditions of stress and errors of judgment are liable to occur.In practice, it has been found that a site inclination of up to 7" from the horizontal will allow safe operation of the ladder within the tolerances built into the limits of its operation.

The use of complex inclinometers has been proposed for levelling mobile cranes, but such inclinometers are scarcely suitable for use on fire-escapes because they are not robust and can take substantial time to settle. It is an object of the present invention to provide a simple robust inclination indicating device which is suitable for use on a fire-escape vehicle.

According to the present invention there is provided a machine inclination indicator including a body attachable at a surface thereof to a machine, one or more conductive liquid switches so mounted on the body relative to the surface thereof that when the inclination relative to the upright of a machine to which the body is attached exceeds a threshold value in any direction the switch or at least one of the switches changes conductive state, indicating means, and means for connecting the switch or switches to the indicating means to cause it to produce an indication whenever the switch or at least one of the switches changes conductive state.

In one embodiment of the invention, there are provided a plurality of switches each comprising a section of tube containing liquid and the longitudinal axis of each of which is disposed at a different orientation and at such an angle to the horizontal that the switch changes conductive state when the inclination to the horizontal of the longitudinal axis of the switch exceeds the threshold value. Clearly, the greater the number of switches at different orientations the more nearly can the threshold value be maintained constant for all possible orientations.

In the application of the invention to a fireescape vehicle with a turntable ladder, the threshold value is typically 7 , because the ladder can be plumed (rotated about its longitudinal axis) through this angle, and it is essential that the rungs of the ladder should be substantially horizontal whatever the slope of the site on which the vehicle is standing.

In another embodiment of the invention, there is a single switch which has a circular symmetry with the liquid content in a saucerlike receptacle having annular contacts. With such a switch there is no inherent variation in the threshold value with change of orientation, although there will be some change due to imprecision of manufacture and mounting, but this can be kept within acceptable tolerances without difficulty.

The switch or switches may be arranged to open or close an electrical connection. Where a plurality of switches is provided and the switches are closed when the threshold value is exceeded, then the switches will be connected in parallel with one another. If there are a plurality of switches and they are opencircuited when the threshold value is exceeded, then the switches would be connected in series.

In order that the invention may be fully understood and readily carried into effect it will now be described with reference to the accompanying drawings, of which: Figure 1 shows one example of the invention and the plan view of the plurality of switches included in it; Figure 2 shows a side view of the switches of Fig. 1; Figures 3 and 4 show plan and side views of a single switch having circular symmetry suitable for use in the invention; and Figure 5 shows a second embodiment of the invention with a plurality of switches connected in series.

In the embodiment of the invention shown in Figs 1 and 2, there are eight switches 1 connected in parallel between conductors 2 and 3. The switches consist of curved sections of tubing containing a portion 4 of mercury and having two contacts 5 and 6. The switches 1 are mounted in a body 7 in such a way that when the body 7 is attached to a suitable surface of a vehicle, then the portion 4 of mercury will connect together the contacts 5 and 6 in one of the switches if the inclination of the vehicle to the horizontal exceeds a threshold value, typically of 7 . The switches 1 are mounted in the body 7 so that they are substantially equally inclined to the horizontal.

The conductors 2 and 3 are connected in a circuit from a power supply connected to terminals 8 to an indicator 9 which may be a simple warning lamp. A switch 10 is provided for switching the device on and off. If desired, a test switch may be connected between the conductors 2 and 3, so that the operation of the indicator can be tested.

With eight switches set in a radial pattern as shown in Fig. 1, the variation in threshold value with the axis of the tilt of the device is about + < , assuming that the switches are set at about + 6+ to the horizontal. The device may have fewer than eight switches and there will be a corresponding increase in the variation of the threshold value with the reduction in the number of switches.On the basis of an inclination to the horizontal of 7" for each of the switches,an arrangement with four switches have a variation of about 2.9 overall and six switches will have a variation of 1.1'. Whereas a variation in threshold value of more than 1" would be unacceptable for a fire-escape vehicle, there may be applications for a device according to the invention in which a larger tolerance is acceptable.

The variation in the threshold value can be substantially eliminated by the use of a special form of mercury switch shown in Figs. 3 and 4. This form of switch has a saucer-like receptacle 11 containing a single portion 1 2 of mercury. On the receptacle 11 are mounted two circular wires 1 3 and 14 in such a position that the portion 1 2 of mercury will connect the wires 13, 14 together when the inclination of the switch to the horizontal reaches the threshold value. Clearly, the manufacture of such a switch is more difficult than that of the form of switch shown in Figs. 1 and 2, but it would have substantially no variation in the threshold values with different orientation of the angle of tilt.

In the examples of the invention described above it is assumed that the switches make a connection when the inclination of the switch or one of the switches reaches the threshold value. It would be equally possible for the switches to be arranged to be open-circuited when their inclination reaches the threshold value. Such a modification would require a different arrangement of conductors within the switch, particularly in the case of the switch shown in Figs. 3 and 4. Where switches of this latter kind are employed in the device, they would need to be connected in series as shown in the circuit of Fig. 5 and, since it is required that the indicator 9 produces a positive result when the inclination of the device reaches the threshold value, an additional connection 20 is provided from the terminals 8 to the indicator 9 to provide the necessary power for the display.

It may be required to have a different threshold value for different orientations of tilt of a vehicle, for example, because a vehicle is longer than it is wide, and the arrangement of switches in the indication device may be such as to incorporate such a variation in the threshold value. Alternatively, the arrangement of the conductors in a single switch of the type shown in Figs. 3 and 4 could be such that the variation in the threshold value was built into the switch.

Claims

1. A machine inclination indicator including a body attachable at a surface thereof to a machine, one or more conductive liquid switches so mounted on the body relative to the surface thereof that when the inclination relative to the upright of a machine to which the body is attached exceeds a threshold value in any direction the switch or at least one of the switches changes conductive state, indicating means, and means for connecting the switch or switches to the indicating means to cause it to produce an indication whenever the switch or at least one of the switches changes conductive state.

2. An indicator according to claim 1 including a plurality of switches each comprising a section of tube provided with contacts and containing liquid, and the longitudinal axis of each of which is disposed at a different orientation, and when installed on a machine, at such an angle to the horizontal that the switch changes conductive state when the inclination of the machine to the upright reaches the threshold value in a vertical plane parallel to the axis of the switch.

3. An indicator according to claim 2 including 4, 6 or 8 switches at equally spaced different orientations.

4. An indicator according to claim 2 or 3 wherein the change of conductive state of the switches on exceeding the threshold value is a change from non-conducting to conducting and the switches are connected in parallel.

5. A indicator according to claim 2 or 3 wherein the change of conductive state of the switches on exceeding the threshold value is a change from conducting to non-conducting and the switches are connected in series.

6. An indiator according to claim 1 including a single switch having a saucer-like receptacle for the liquid with one or more contacts surrounding the lowest point on the receptacle, so that when installed on a machine the state of the electrical connection between the contacts is changed when the inclination of the machine to the vertical exceeds the threshold value in any direction.

7. An indicator according to claim 6 wherein the switch is circularly symmetrical.

8. An indicator according to any of claims 1 to 7 wherein the threshold value is substantially the same for all orientations of the inclination.

9. An indicator according to any of claims 1 to 6 wherein the threshold value is different for different orientations of the inclination.

1 0. A machine inclination indicator substantially as described herein with reference to Figs. 1 and 2, Figs, 3 and 4 or Fig. 5 of the accompanying drawings or modified as herein described.