WO1987003958A1

WO1987003958A1 - Improvements in or relating to plummets

Info

Publication number: WO1987003958A1
Application number: PCT/GB1986/000793
Authority: WO
Inventors: Clifford Rayner
Original assignee: National Research Development Corporation
Priority date: 1985-12-24
Filing date: 1986-12-23
Publication date: 1987-07-02
Also published as: GB2185333A; GB8531787D0; GB8630826D0; GB2185333B

Abstract

The plummet operates by providing a vertical visible beam of light such as from a laser adjusted to the exact vertical by reflecting a beam of light from a bath of oil back to the light source. The oil may be any suitable industrial oil readily available on building sites and is therefore readily replaceable when lost or dirty. The plummet may be modified by the addition of an alignment gauge to enable it to be used to align two or more vertical members such as the guidance rails in a high speed lift shaft.

Description

IMPKOVEMENTS IN OK RELATING TO PLUMMETS The present invention relates to plummets and more particularly to plummets used for cnecKing the vertical alignment over a relatively long distance.

A traditional way of establishing a vertical is by means of a plu bline. This comprises a lengtn of normally thin string or wire witn a weight at one end. For establishing a vertical over a long distance a very heavy weight is used and for greater accuracy the weight is immersed in a water batn to damp its movement. There are many disadvantages of suc a system especially if used in open areas. Despite damping the weight tends to oscillate or swing. The weignt may be many pounds (e.g. 14 lbs - 6 Kg) ana tnerefore to stop it swinging is not easy. If a mark is required say at a half way point then unless someone is at the bottom to stop the weight swinging then this is not practical. Also any wind catches the string or wire causing it to bow and adding to the observed errors. In practise the string or wire is observed and a mid point of movement is estimated oy e surveyor. To acnieve nign accuracy over a long distance e.g. 50 metres is very difficult if not impossible with this method.

It is an object of tne present invention to proviαe a plummet capaole of operating over long vertical distances using an optical metnod and capable of achieving great accuracy over the wnole length of such vertical distance.

The present invention therefore provides a plummet for defining a vertical line over long distances including a lignt source means for mounting the lignt source at or above tne top of the vertical distance, an optical reflector, means for mounting the optical reflector at or below the Dottom of the vertical distance and means for adjusting the vertical alignment of the light source to provide a coincidence between the emitted and reflected light beam.

Preferably the light source is a laser, the beam of which is focussed to produce a pencil thin oeam of lignt. Preferably the laser is of tne continuously operating type and in the visible spectrum.

The optical reflector is preferably a bath of oil. More preferably the bath has no cover the oil being open to the atmosphere. In use, tne oil is preferably replaced when it becomes dirty. The oil may be a readily available industrial oil on a building site such as automobile engine oil.

The light source is preferably provided with means for moving it in tne X - Y direction to align it with a desired vertical line. An optical gauge may be provided for attachment to a first member, the vertical alignment of which is required such that the light beam may be positioned at a distance from the first member. The gauge may comprise means for aligning a second memoer accurately with respect to the first member.

Embodiments of the present invention will now be described, by way of example witn reference to the accompanying drawings, in which: -

Figures 1(a), Kb) and 1(c) snow the basic principle of the reflecting optical plummet according to the present invention;

Figure 2 shows an optical apparatus for use in the plummet of Figure 1 in greater detail;

Figure 3 shows diagrammatically an apparatus for suspending the optical apparatus in a lift shaft;

Figure 4 diagrammatically snows a lift shaft with the optical plummet of Figures 2 and 3 in position and illustrates an apparatus for aligning two or more members; Figures 5 and 6 snow an alternative optical/plummet design;

Figure 7 snows an alternative laser adjustment system;

Figures 8 and 9 snow an alternative lift rail alignment system to the arrangement of Figure 4;

Figures 10 to 13 snow a portion of the system of Figures 8 and 9 for positioning the laser;

Figures 14 to 16 show means for positioning the pentaprisms in the system of Figures 8 and 9; Figures 17 to 19 show an alternative X - Y adjustment system for the laser; and

Figures 20 to 23 snow a course levelling system for use with the system of Figures 17 to 19.

With reference now to Figures 1(a), (b) and (c) the principle of the optical plummet is shown. The apparatus comprises a light source 10 and a reflector 12. The beam of light 11 from the light source 10 is reflected back 13 from the reflector 12 to tne light source and impinges onto a target 14. Thus in Figure 1(a) tne beam 13 is reflected bac to a spot to tne right of the lignt source 10. In Figure l(o) tne oeam is reflected back to a spot to the left of lignt source 10. In both cases neither the beam 11 nor the reflected beam 13 is vertical. In Figure 1(c) nowever wnen the reflected beam 13 and the beam 11 form a coincident return image then the beam of light 11 is vertical. Once the beam of light 11 is established to be vertical tnen the reflector 12 can oe removed, it being only necessary to recheck the beam direction at intervals (say each nour) . The beam of light 11 therefore provides an optical "plumbline" which can be intercepted at any point along its patn to provide a vertical alignment. The lignt source is preferably a laser and tne light frequency is preferably chosen to be within the visible spectrum (a suitable laser being a HeNe which produces a reddisn beam. The reflector 12 may comprise a bath 18 of any suitable material e.g. plastics, metal into which preferably an oil 20 is poured. Since the top surface 22 will always be horizontal tne container shape and tne - surface 24 on which the container is placed is not of any consequence providing the surface is reasonably solid. The oil 20 may be any readily available industrial oil such as engine oil or gearbox oil but should preferably be as clean and dark as possible. No cover is required on the container but if the oil is spilt by, for example, kicking over the container, the oil may be readily replaced on most building sites. The reflector is therefore very inexpensive and not easily damaged, this being an important factor for any reflector which must be placed at the bottom of a tall structure where it is always liable to be damaged by, for example, falling objects.

The oil 20 is found to be not very susceptible to vibration and may be selected by its viscosity to damp out any vibrations. Thus the movement of vehicles on a site does not substantially extend the setting up period although obviously extremely strong viorations close to the reflector 12 may cause the return beam 13 to be dissipated. Such vibrations are also however likely to affect the mounting of the light source 10 and would also affect the previously known plumbline. The relative speed of setting up of the optical plummet however means that only a few seconds of relatively passive conditions are required to establish the vertical line. With reference now to Figure 2 the optical source 10 is drawn in greater detail. The source comprises a laser 30 of the continuous operating type tne light output 32 of which is directed towards a collimating beam arrangement shown simply by two lenses 34, 36. The target 14 is opaque and is mounted on the front of lens 36. The beam 11 passes therefore through a small hole 37 tne target 14.

The laser, lenses 34, 36 and target 14 are mounted in a cylindrical structure 38 whicn is provided with an annular flange 40. Three adjusting foot screws 42 (only two are snown for clarity) are mounted at 120° intervals around the structure 38 througn the flange 40 and serve to adjust tne vertical alignment of this structure and hence of beam 11 with respect to a plate 44. Plate 44 may be clamped by any suitaply designed clamp means and then to a structure of a building where a vertical alignment requires to be established.

In tne embodiment shown the plate 44 is removably clamped to further frame members 46, 48 by clamp, screws 50, 52. Frame members 46, 48 are in turn bolted onto a support frame 60 by bolts 56 (only one shown). Thus the plate 44 and optical apparatus 10 may be removed from the larger frame members 46, 48 to be stored in a carrying case. Frame members 46, 48 may be designed to suit a specific purpose and may contain adjustable screws or further clamps (not shown) to enable the optical apparatus to oe clamped in a desired position. Thus optical apparatus 10 , and plate 44 can be a standard item witn versatility being provided by individually designed frame member 46, 48.

In operation, beam 11 is generated Dy light source 10 and is reflected by reflector 12 positioned at the bottom of, for example, a lift shaft. The reflected beam 13 will normally initially strike part of the frame 44 or 46, 48 which may be coated with a suitable substance to provide a good target and is then adjusted by foot screws 42 until its image coincides with that of the beam 11. The beam 11 is then known to be vertical.

The beams 11 and 13 may be affected by a temperature αradient but are unaffected bv winds. Thus for outdoor work the apparatus will be accurate since no great temperature gradient should exist. For indoor work such as repair of lift shafts there may be temperature changes from the bottom to the top of the shaft which may cause the beam to fluctuate. Even so the accuracy of the beam over a length of 50 metres should be to within 1 mm.

Once the alignment adjustment has been made the reflector 12 can be removed and the coherent beam of light 11 will be vertical allowing alignment settings to be made at any point along its path.

A practical system for a lift shaft is shown in Figures 3 and 4. The apparatus 10, 44 may be attached to a suitable support system e.g. two expandable bars or pipes (ACROW bars) 60, 62 by a conventional arrangement 46, 48 providing X - Y movement of the apparatus 10. The bars 60, 62 may be expanded to be secured across the lift shaft 64 by pressure against opposing walls 66, 68. The optical apparatus 10 can then be positioned at a desired point anywhere across the lift shaft and beam 11 can be adjusted to provide the vertical alignment.

Referring now to Figure 4 the lift (not shown) runs on two guide rails 70, 72 on opposite sides of the shaft. A template 74 may be positioned between rails 70, 72 the template being exactly sized to a desired width. On the template 74 a first right angle reflector 76 is positioned at a first point close to rail 70 to deflect beam 11 onto a reflector 78 positioned close to rail 72. Since the template 74 is the correct width the alignment of beam 11 with reflector 76 will establish a correct vertical alignment of rails 70, 72 and by interposing a target 80 at 76 in the path of the beams from 76 and 78 the horizontal attitude of the guide rails 70 and 72 may be aligned to be parallel as well as vertical. Template 74 may be positioned at intervals of, for example, 1 metre along the whole height of the lift shaft to thereby allow adjustment and setting of the rails 70 , 72.

It may be seen that other optical apparatus may be used to check the accuracy of, for example, three rails by a suitable change in the optics 76, 78. 5 Thus the plummet can be used to align both in the vertical and horizontal planes.

With reference now to Figure 2 it may be seen that the target 14 is fairly small and that the alignment of the beam 13 onto the output beam 11 can be made fairly

10 exactly. This alignment can be improved by better optics to produce a thinner beam or by creating interference fringes in the output beam 11 which are replicated in the reflected beam 13 and which may therefore be used to provide more exact alignment.

15 The coincidence of the return beam 13 is easily to within 1 mm over a distance of 50 metres. This allows the apparatus to be used to monitor other effects. If the apparatus 10, 44, etc is clamped to the top of a dam structure inside a large hollow space present inside many

20. dams and then aligned accurately, for example, in winter then changes in movement of the structure of the dam as a result of seasonal changes in the water level may be observed. If the instrument is calibrated the exact movement can be measured and if automatic measurement is

25 required an array of photo cell detectors may be used.

If the apparatus 10, 44, etc is set up on a bridge when the bridge (or other similar structure) is unloaded then the effect of loading can be observed by observing and measuring the deviation in the returned light beam. ⁰ Adjustment of the optical alignment of the light source 30 to the telescope 34, 36 may be achieved optically by means of optical wedges or similar optical devices in area X. The alignment screws may be motor

5 operated such that the alignment may be carried out remotely, for example, from half way down the lift shaft. Similarly the X - Y movement described in relation to Figures 3 and 4 may be remotely controlled if desired. With reference now to Figures 5 and 6 a continuous operating laser 100 (class 2) is mounted vertically (see Figure 7) to provide a beam of light 110 in known manner. The beam enters a fibre optic ring device 102 whereby the beam is split into a plurality of beams 110' which emerge from individual fibres 111 on the edge of the ring as shown in Figure 6. The beams are focussed by a lens system 104 and emerges as a "cone" of light which is reflected as described hereinbefore by reflector 12 back to a detector 106 preferably of the quadrant sensing type. Typical diameters for the fibre optic ring, focussing lens and quadrant sensor are 50mm, 60mm, and 40mm respectively.

The system is particularly useful for monitoring the conditions in a structure such as a dam. The distance D will be fixed and therefore the focussing lens 104 can be adjusted to give a point of light on detector 106. Thus detector 106 can be adjusted to give under for example normal stress condition (e.g. dam half full) a zero output and the output can be automatically monitored to raise an alarm if the movement during for example spring flood conditions exceeds a danger level. Other uses may be for example in monitoring movement of tower blocks.

The laser in Figure 5 requires vertical alignment wnen fixed in a supporting form and a suitable arrangement is shown in Figure 7. The laser 100 is supported in a protective inner casing 120 by "0" rings 122. Casing 120 is movable by means of screw means 124 which acts against a compression spring 126 to adjust inner casing 122 with respect to an outer casing 128 which may be clamped in any suitable manner to a building or any other structure. Screw 124 gives movement in an X direction and a further screw (not shown) is included for movement in the Y direction. The bottom of inner casing 120 is held in a universal bearing 130 which may as shown be a rubber collar.

The X and Y screws 124 may be therefore adjusted such that the output beam 11 (Figure 1) is vertical thereby allowing the outer casing 128 to be clamped in a non-vertical position.

With reference now to Figures 8 and 9 an alternative vertical alignment system is illustrated for the alignment of for example lift guide rails 152, 154 in lift shaft 150. The laser source 100 which may be vertically alignable as shown with reference to Figure 7 is mounted on a platform 200 and the output beam 110 is made vertical as explained hereinbefore with reference to Figure 4 by the reflecting pool 12. A pentaprism and holder unit 300 is clamped to rail 152 to deflect beam 110 onto a pentaprism and holder unit 300' which in turn deflects the light beam 110' onto a target 400 held by a holder 402, and with the mirrored front surface 301 reflects light back to unit 300 for accurate setting as described with reference to Figure 4.

In Figure 9 the lift shaft is diagrammatically shown in partial plan with beam 110' being deflected by units

300, 300'. Units 300, 300' are shown in greater detail in Figures 14 to 16. The rails 152, 154 are adjustable by means of the fixing plates 156.

With reference now to Figures 10 to 13 the laser 100 is supported on platform 200 which requires to be adjustable in the X and Y directions to give correct alignment for the laser. The X adjustment is illustrated in Figure 10 and comprises a back plate 202 for fixing to the Y adjustment plates as shown in Figures 11 to 13 and an adjustment screw 204 for moving the plate 202 relative to a guide rail attachment block 206. (Guide rail attachment block 206 may be clamped to the guide rail by for example a wing nut and bolt as shown for units 300 (Figure 16)). Plate 202 is preferably mounted on ball bearings 208 onto a slide plate 210 attached to the block 206. Adjustment is preferably by means of a V block 212 and adjusting screws 214.

Adjustment in the Y direction is by means of the units shown in Figures 11, 12 and 13 in front elevation, side elevation and plan view respectively.

With reference to Figure 13, the laser 100 and associated casings is supported in a hole 220 in plates 222, 222'. Rubber "0" rings 224 provide a shockproof mounting. (The laser is adjustable as in Figure 7). Plates 222, 222' are linked together by further plates 226, 226' to form a rigid box which is slidable on four rods 228, 230, 232, 234 by means of a screw 236 acting against a front plate 240. The directions achieved by the X and Y adjustment are indicated by the arrows. Thus the laser is alignable vertically and is movable in the X and Y directions to shine a light beam down onto unit 300.

With reference now to Figures 14 to 16 the pentaprism holder 300 is shown in detail. The pentaprism - i_s of standard construction and therefore will • not be further described. Its purpose is to deflect light orthoganally as shown in Figure 9.

The pentaprism indicated generally at 302 receives light via a hole 304 and emits the output beam via hole 306. The holder comprises a plate 308 attached to a further plate which with a movable plate 312 forms a clamp adjustable in known manner by a wing nut and bolt arrangement 314 to clamp onto a rail 152 (shown dotted in Figure 16) . The pentaprism 302 is alignable by means of self aligning bearing 316 (indicated by holding nut 318 in Figure 15) and four adjusting screws 320, 322, 324, 326, by means of which the pentaprism can be aligned in X, Y and Z directions. With reference now to Figures 17 to 19 an alternative system for adjustment of the laser in the X-Y direction is shown. Figure 17 is a plan view, Figure 18 a section on line B-B and Figure 19 a section on line A-A. The laser 100 is mounted on a plate 400 which is adjustable against a further plate 402 to align the laser (not shown) mounted on the plate. The adjustment screws 404, 406, 408 are situated at the corners of an imaginary triangle and are therefore able to adjust the laser (or any other object) with respect to the vertical. For X-Y movement plate 402 is movable by further adjustment screws 410, 412 respectively. These screws cause plate 402 to slide on bearings 414 (X direction) and 416 (Y direction) respectively along rods 418, 420 and 422, 424. An outer frame member 426, 428, 430, 432 is provided to locate the rods 422 and 424 and may be then suitably mounted as shown with reference to Figures 20 to 23 on ACROW bars.

With reference now to Figures 20 to 23 to the frame are attached rollers 500, 502, 504, 506 (adjustment screws 410, 412 are shown for continuity but for simplicity the other fine levelling members and X-Y fine adjustment is omitted) .

The rollers 500, 502, 504, 506 are positioned on top of ACROW bars fixed into for example the lift shaft as in Figure 4. Rollers 500 and 502 are adjustable in height by means of lead screws 510, 512 acting on their support arms 514, 516 which pivot on a bearing 518. Rollers 504, 506 are adjustable in height by a knurled screw and bolt arrangement 520, 522. A pond bubble 524 is mounted on the frame so that the frame can be roughly (coarse) adjusted for level and then the arrangement of Figures 17 to 19 can be used for fine adjustment.

Locking screw 532 acting against the ACROW bars serves to lock the platform in the X direction.

Claims

1. A plummet for defining a vertical line over long distances including a light source, means for mounting the light source at or above the top of the vertical distance, an optical reflector, means for mounting the

5 optical reflector at or below the bottom of the vertical distance and means for adjusting the vertical alignment of the light source to provide a coincidence between the emitted and reflected light beam.

2. A plummet as claimed in Claim 1 in which the optical 0 reflector comprises a bath of oil the light being reflected from the surface of the oil.

3. A plummet as claimed in Claim 2 in which the bath of oil has no cover the oil surface being open to the atmosphere. 5

4. A plummet as claimed in Claim 3 in which the oil is an automobile grade engine oil.

5. A plummet as claimed in any one of Claims 1 to 4 in which the light source is a laser of the continuously operating type, emitting light in the visible spectrum. o

6. A plummet as claimed in Claim 5 in which the light source is collimated using a telescope to produce a pencil thin beam of light over a long distance.

7. A plummet as claimed in any one of Claims 1 to 6 in which the means for mounting the light source includes 5 means for moving the light source in an X - Y direction to align the light source with a desired vertical line.

8. A plummet as claimed in Claim 7 in which an optical pentaprism is provided for attachment to a first member, the vertical alignment of which is required, at a point _Q on the vertical optical path such that the light beam may be positioned at a distance from the first member.

9. A plummet as claimed in Claim 8 in which the optical gauge includes means for accurately aligning a second member with respect to the first member. 5

10. A plummet as claimed in Claim 9 in which the means includes one or more optical reflecting surfaces.

11. A plummet as claimed in Claim 1 in which the light source includes means for generating a hollow cone of light the cone tapering towards the optical reflector and being reflected back to the light source such that the cone is reduced to a point of light for the detection on a target positioned within the centre of the hollow cone.

12. A plummet as claimed in Claim 1 in which the light source includes a laser mounted in an inner casing the inner casing being adjustably mounted within an outer casing and including means for moving the inner casing relative to the outer casing to adjust the alignment of the output beam of the laser.

13. Apparatus for aligning lift guide rails including a plummet as claimed in Claim 1 in which the light source is mounted close to a first guide rail to provide a beam of light substantially parallel to the rail and including a first pentaprism contained within a first unit the unit being attachable by clamp means to the first guide rail at a desired position, a second pentaprism contained within a second unit said second unit- being attached to a second lift guide rail such that the plummet light beam is deflected by the first pentaprism to the second pentaprism and in which a target is clamped to the second lift guide rail to intercept light reflected by the second pentaprism for alighment of the second lift guide rail.

14. Apparatus for aligning lift guide rails including a plummet as claimed in Claim 1 in which the light source is mounted on an apparatus which apparatus includes means for mounting onto two support bars and includes means for adjusting the laser in X, Y and Z directions to align the laser.

15. Apparatus for monitoring the movement of a structure including a plummet as claimed in Claim 1 or Claim 11.

16. A plummet for defining a vertical line over long distances including a light source, means for mounting the light source at or above the top of the vertical distance, a self levelling optical reflector, means for mounting the optical reflector at or below the bottom of the vertical distance and means for adjusting the vertical alignment of the light source to provide a coincidence between the emitted and reflected light beam.

17. A plummet for defining a vertical line over long distances substantially as described with reference to the accompanying drawings.