WO1991017410A1

WO1991017410A1 - Alignment device

Info

Publication number: WO1991017410A1
Application number: PCT/GB1991/000675
Authority: WO
Inventors: Michael John Smith
Original assignee: Michael John Smith
Priority date: 1990-04-28
Filing date: 1991-04-29
Publication date: 1991-11-14
Also published as: GB9009606D0

Abstract

An alignment device comprises a body (10) with two reference faces at right angles. A cord (15) has one end attached to the interior of the body (10) and extends out through an aperture (17) in the body. Position sensing means are mounted in the body for sensing and indicating any deviation of the angular position of the cord (15) from a reference position relative to the reference faces. The device also includes level sensing means for levelling the device, these level sensing means being mounted in a plate (11) which is rotatably mounted in the device. The position sensing means and the level sensing means may both be mechanical, electrical, or electronic. The cord may engage with a pulley coupled to a revolution counter.

Description

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The present invention relates to alignment devices of the type used in building, decorating, and like work, and more particularly (though not exclu¬ sively) to combined alignment and levelling devices.

One technique is to use a pair of vertical transparent tubes containing a suitable liquid and linked by a communicating tube. However, the general bulk, fragility, and inconvenience of this is obvious.

The standard levelling device is therefore a spirit level. This consists essentially of a long straight piece of wood or extruded metal, with a slightly curved tube or "glass" set in it filled with a coloured liquid ("spirit") apart from a small bubble. When the level is horizontal, the bubble is centred in the glass; if the level is tilted, then the bubble is shifted away from the centre of the glass. A second glass may be set transversely in the level so that it can also be set vertically.

The simplest spirit levels only permit the determination of horizontality. Many spirit levels, however, include two glasses, set at right angles, so that horizontality can be determined by observing one glass and verticality by observing the other. Greater generality can be achieved by mounting the glass in a disc which is rotatable and can be set at any desired angle. We will for convenience use terms such as "horizontal" and "levelling", but it will be under¬ stood that in general, we are actually concerned with setting to some given angle to the horizontal or vertical.

Such spirit levels are cheap and versatile. However, they suffer from a number of disadvantages. With a spirit level, for example, it must be possible to view the glass from above or the side; this makes it difficult to use much above eye level (say above 1.75 λ

If the direction of primary interest is the vertical rather than the hori¬ zontal, then a plumb line can of course be used instead. This is however not readily adapted for the determination of angles other than the true vertical; further, a plumb line must be free of obstructions, which makes it difficult to transfer its verticality to a fixed support.

SUBSTITUTE SHEET The principle of the basic spirit level and/or plumb line has therefore been developed in a variety of ways, most of which involve the provision of some form of electrical or electronic sensing of horizontality or verticality.

A spirit level is typically somewhat less than 1 m long. This length is chosen as a compromise between a reasonable accuracy and giving extended align¬ ment, on the one hand, and reasonable portability and the ability to be useable in small spaces, on the other. A level longer than 1 would be inconvenient to carry around and would frequently not be useable for levelling small items; a level shorter than say 0.1 m would be inaccurate.

A spirit level has been proposed having a pair of sliding arms which extend to effective double the length of the level, but this is clearly only a partial solution to the problem.

A problem therefore arises when an alignment has to be extended for some considerable distance, of say some meters. What is normally done is to mark, on a suitable vertical surface, the level obtained from the spirit level, and then to extend this level. This requires a suitable surface to be available. It may be possible to extend a level set in this way by using a straight edge, if the verti¬ cal surface on which the level is marked extends as far as required. Alterna¬ tively, the level can be extended by means of a thin cord which is aligned with the level marked on the surface.

The alignment can of course be extended by means of a cord which is aligned directly with the spirit level. However, it is difficult to check the horizontality of such a cord, because it does not afford a firm support against which the level can be placed. It has been proposed to include a small spirit level between two parts of a cord, but the weight of the spirit level means that it is liable to cause the cord to sag and so produce inaccuracy. To avoid the danger of the spirit level rotating around the axis of the cord, it needs to have its centre of gravity well away from that axis and to have a substantial weight.

One possible "high-tech" solution to these problems is to incorporate a laser in a spirit level. This effectively extends the length of the spirit level indefinitely. However, it has various disadvantages. It is costly; the visibi¬ lity of the laser beam along its length is low, and dependent on ambient condi-

SUBSTITUTE SHEET tions (so that it is less visible in bright light); and there are safety consider¬ ations associated with lasers.

One major object of the present invention is to provide a levelling device which, while being relatively cheap, provides substantial flexibility of use and which permits ready alignment of a cord.

Accordingly the present invention provides an alignment device comprising a body with at least one reference face, extension means in the form of a cord having one end attached to the interior of the body and extending out through an aperture in the body, and position sensing means mounted in the body for sensing and indicating any deviation of the angular position of the cord from a reference position relative to the reference face or faces. The position sensing means may be mechanical, electrical, or electronic.

It will be realized that although an alignment device having only the features just defined is useful for extending a given alignment, its utility is limited because it does not include means for determining a desired alignment (with reference to the horizontal or vertical). Preferably therefore the device also includes level sensing means for levelling the device. The level sensing means are preferably mounted in a plate which is rotatably mounted in the device. The level sensing means may be mechanical, electrical, or electronic.

Further significant features of the invention will become apparent from the following description of a levelling device in accordance therewith, given by way of example and with reference to the drawings, in which:

Fig. 1 is a side view of the device;

Fig. 2 is a diagrammatic view of the mechanism mounted in the rotatable disc of the device;

Fig. 2A is a diagrammatic view of a modification to the structure of Fig. 2;

Fig. 3 is a diagrammatic view of the line position sensing means;

Fig. 3A is a diagrammatic view of a modification to the structure of Fig. 3; and

SUBSTITUTE SHEET Figs. 4 and 5 show modified forms of the device.

Referring to Fig. 1, the device is in the form of a hollow 45°-45°-90° triangular plate 10. The shorter sides form reference faces and can conven¬ iently be between 100 and 200 mm long, and the thickness of the order of 10 mm. The plate has a large circular opening in which is mounted a hollow rotatable disc 11. The disc 11 has a pointer line 12 formed or marked on it, and there is a 360° scale 12 marked on the plate around the disc. The device 10 and the disc 11 present substantially the same appearance on both sides.

An electrical position sensor for sensing verticality is mounted in the disc 11. An indicator 14, comprising a. pair of lights spaced apart along the length of the long side of the plate 10, is mounted on the long edge of the device. The body of the device includes circuitry for driving the indicator and a battery (accessible through a conventional cover), not shown. The circuitry is connec¬ ted to the position sensor mounted in the disc 11 by means of a flexible cable: there are cooperating stop means (not shown) on the disc 11 and plate 10 which allow the disc to be rotated through an angle somewhat in excess of 360° but prevent continuous rotation.

In use, the disc 11 is rotated by the user to a desired angular position. The device is then tilted by the user to bring the pointer line 12 to an approx¬ imately vertical position. The indicator 14 is driven by the position sensor in the disc 11 so that one of the lights in lit when the sensor is tilted slightly to one side on the vertical and the other light is lit when the sensor is tilted to the other side of the vertical. When both lights are in the same state, the sensor is at true verticality. (That common state may be chosen to be either both lit or both off.)

It is thus evident that the device can be used to set the two short sides at any desired angle to the vertical and horizontal. The angle may of course be set to zero, so that the two short sides will be directly vertical and horizontal. The engagement of the disc 11 in the plate 10 may be provided with a click stop for the zero angle, to make that angle easier to select precisely. (This may make angles sufficiently close to zero unsettable, but that drawback can readily be overcome by turning the device over and selecting an angle close to 90°, or by setting the disc to 180°).

SUBSTITUTE SHEET It will be evident that the device can be used at any height. Since the indication is by means of a light-generating indicator, the indication can be seen from above or below. The indicator 14 is preferably set in the long edge of the plate 10 without protruding from that edge, and arranged so that the lights are visible from either side of the device. (Alternatively, the indicator can be located on the face of the plate 10, and protrude slightly from both sides of the plate.)

The device also includes a line or cord 15 mounted on a spring-return reel (not shown) included in the plate 10 and operable to rewind the cord by means of a button 16. The cord 15 emerges from a recess 17 in the long edge of the plate 10 which accommodates a hook 18 on the end of the cord 15 when it is rewound. The plate 10 carries a marker 19, on the short side opposite the recess 17, which is level with the cord 15. The device includes an electrical cord position sensor which drives a cord indicator 20 which is similar to the indicator 14 but indicates the position of the cord 15 relative to the adjacent reference face of the device.

The cord reel can of course be manually windable instead of spring-return.

The indicators 14 and 20 may of course each consist of say '4 indicator lights, with the outer ones lighting when the pointer line 12 is far from verti¬ cal and the inner one lighting when it is close to vertical. Alternatively, indicator means such as a bargraph device on an LCD can be used.

Fig. 2 shows a suitable form of the electrical position sensor mounted in the disc 11 for sensing verticality. The sensor comprises a pendulum arm 25 pivoted at 26 and with a weight 27 attached to its lower end. The arm 25 also has a plate 28 attached to it near the weight 27. A pair of optical light sources and sensors 29 are mounted on the disc 1 1 adjacent to the plate 28 as shown.

Each light source produces a beam which shines on its associated sensor, but the beams can be interrupted by the plate 28. The pointer line 12 is so aligned and the light sources and sensors so located that when the arm 25 is exactly aligned with the pointer line, both sensors are illuminated, but a slight rotation of the disc causes the plate 28 to interrupt one or other beam. As

SUBSTITUTE SHEET mentioned above, the plate 10 includes circuitry (not shown) for energizing the light sources, sensing the outputs of the sensors, and driving the indicator 14.

The plate 28 may be an integral portion of the arm 25 and/or also act as the weight 27. Obviously, the spacing of the light sources and sensors may be . made slightly less than the width of the plate 28, so that the alignment of the pointer line 12 and the arm 25 will be indicated by both light beams being interrupted. Each sensor may drive a trigger circuit so that it effectively pro¬ duces a digital output (ON or OFF). Alternatively, the sensors may drive a dif¬ ference circuit which produces a continuously variable output; if this is done, then a more elaborate form of indicator may be used.

Other means for sensing the alignment of the arm 25 may be used.

Further examples of optical techniques include the following. A segment encoding disc or a portion thereof may be used, either attached directly to the pendulum arm or geared to it for increased sensitivity. The sensitivity of the system may be also increased by using a prism, a diffraction grating, or a Moire interference effect, with a comb attached to the arm 25 and moving past a fixed comb of slightly different tooth spacing (somewhat like a Vernier scale). The position of maximum (or minimum) match can be detected by various means, e.g. optically or magnetically.

Examples of conductive techniques include the following. The arm may carry a contact which slides against a resistive track mounted on the inside of the disc 11 and across which a voltage is maintained; the voltage picked off by the sliding contact would then indicate the position of the arm. A bubble tube containing conductive liquid may be used, with electrical contacts suitably sealed in the tube. As very simple sensing means, one or more mercury switches could be used, though the accuracy obtainable with these may be limited.

Capacitive techniques include the following. The arm may consist of, or carry, a conductive plate which swings adjacent to a fixed conductive plate, with the capacitance between the moving and fixed plates being measured to determine the position of the arm. Each of the plates may consist of a fan of separate segments. Alternatively, a bubble tube may be used, containing a dielectric liquid and having capacitor plates formed on the tube.

SUBSTITUTE SHEET Magnetic techniques include attaching a magnet to the end of the arm and sensing its position by means of a pair of Hall effect devices, reed switches, or the like.

A mechanical coupling may be provided at the lower end of the arm 25 to magnify its movement and increase the sensitivity of the device. For example, as shown in Fig. 2A, a light thread 30 may be attached to the end of the arm, and wound round a small diameter spindle 31 with a disc 32 attached to it. The disc 32 will then rotate as the arm 25 swings, and its angular position can be sensed in various ways, e.g. by means of a pair of optical light sources and sensors mounted adjacent to the disc, with the disc having suitable holes therein, or by resistive, capacitive, or magnetic position sensing means.

In a low-cost version of the device, a purely mechanical position sensor, e.g. a bubble tube as in an ordinary spirit level and mounted in the disc 11, could be used instead of the electrical position sensor.

Fig. 3 shows a suitable form of the electrical cord position sensor which indicates the position of the cord 15 relative to the lower reference face of the device. The cord 15 passes through an aperture in the recess 17 and over a pulley 35 to the spring return reel mentioned above. The sensor comprises a lever arm 36 pivoted at 37 and with a spur 38 having a small hole through which the cord 15 passes. The arm 36 also has a plate 39 attached to its right-hand end. A pair of optical light sources and sensors 40 are mounted in the plate 10 adjacent to the plate 39 as shown.

The two light sources and sensors 40 sense the position of the arm 36 in the same way as the two light sources and sensors 29 sense the position of the arm 25. The aperture in the recess 17 through which the cord 15 passes is large enough to allow the cord 15 to move the arm 36 up and down enough to be so sensed. The sensors drive the indicator 20 in the same way as the sensors 29 drive the indicator 14.

It will be realized that the angular movement of the arm 35 is magnified relative to the angular movement of the line 15 by the ratio of the distances of the pulley 35 and the pivot 37 from the spur 38.

SUBSTITUTE SHEET The same modifications and variations can be applied to the electrical cord position sensor as were discussed above with regard to the electrical position sensor mounted in the disc 11. In a low-cost version of the device, a purely mechanical cord position sensor, e.g. a bubble tube as in an ordinary spirit level and mounted on the arm 36, could be used instead of the electrical cord position sensor. The casing of the device would obviously have suitable windows making the bubble tube visible.

Fig. 3A shows a modification of the line position sensing means and associ¬ ated components. The arm 35 carries a spirit level 45 which can be observed directly through windows (not shown) in the casing of the device. The arm also carries an extension 46 on the opposite side of the pivot 37, to counterbalance the weight of the bubble tube 45 and the right-hand part of the arm.

The pulley 35 is replaced by an eccentric 47 over which the line 15 slides. By turning this eccentric, the height of the line 15 can be adjusted. (As an alternative, the line can be passed through a small aperture the position of which can be adjusted vertically.)

The line 15 is wound on a line tensioning and rewind spool 48. A revo^¬ lution counter 49 may be coupled to this, or to a pulley 50 over which the line 15 runs (such as the pulley 35) to give an indication of the length of the line which has been drawn off the spool. If the counter is electrical or electronic, then the spool or pulley may for example have an encoding wheel attached. Other means of measuring the length of the line drawn off, such as electrical contacts, magnetic sensing, or optical sensing, may also be used. The counter is preferably resettable, to allow either absolute or incremental length measure¬ ment.

Fig. 4 shows an alternative form of device. This device 10' is square shaped, and has a disc 11' with a pointer 12' and scale 13'. Level sensing means 55 are mounted on the disc 11'. In addition, cord position sensing means 56 are mounted on the disc 11' rather than directly on the body of the device 10'. The cord 15' is carried on a spool 48', and taken onto the disc 11' for position sensing via pulleys 57 mounted on the disc.

Fig. 5 shows another alternative form of device. This device 10" is square shaped, and has a pair of bubble tubes 60 and 61 at right angles forming level

SUBSTITUTE SHEET sensing means. The cord 15" is carried on a spool 48", and passes over a pul¬ ley 47" and through an adjustment device 62. A slot 63 has position sensing means 64, consisting of a sliding block 65 mounted in the slot and carrying a pivoted bubble tube arm 66 with a spur 67 through which the cord 15" passes. A scale 67 allows setting of a desired angle.

SUBSTITUTE SHEET

Claims

1 An alignment device comprising a body (10) with at least one reference face, extension means in the form of a cord (15) having one end attached to the inter¬ ior of the body and extending out through an aperture (17) in the body, and pos^¬ ition sensing means (36-40) mounted in the body for sensing and indicating any deviation of the angular position of the cord from a reference position relative to the reference face or faces.

2 A device according to claim 1 including level sensing means (20, 25-29) for levelling the device.

3 A device according to either previous claim wherein the level sensing means are mounted in a disc (11) which is rotatably mounted in the device.

4 A device according to claim 3 wherein the position sensing means are also mounted in the disc (Fig. 4).

5 A device according to any previous claim wherein the angular position sensed by the position sensing means is adjustable (Fig. 5).

6 A device according to any previous claim wherein the cord is carried on a spool (48).

7 A device according to claim 6 wherein the cord is coupled to a rotation counter.

8 A device according to claim 7 wherein the revolution counter is resettable.

9 Any novel and inventive feature or combination of features specifically disclosed herein within the meaning of Article 4H of the International Conven¬ tion (Paris Convention).

SUBSTITUTE SHEET