GB2185333A - Checking vertical alignment - Google Patents

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

SPECIFICATION Improvements in or relating to plummets The present invention relates to plummets and more particularlyto plummets used for checking the vertical alignment over a relatively long distance.

Atraditional way of establishing a vertical is by means of a plumbline. This comprises a length of normally thin string orwirewith aweightatoneend.

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 bath to damp its movement. There are many disadvantages of such a system especially if used in open areas. Despite dampingtheweighttendstooscillateorswing.The weight may be many pounds (e.g. 14 Ibs- 6 Kg) and thereforetostop it swinging is noteasy. If a markis required say art 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 itto bow and adding to the observed errors. In practise the string or wire is observed and a mid point of movement is estimated by the surveyor.

To achieve high accuracy over a long distance e.g. 50 metres is very difficult if not impossible with this method.

It is an object ofthe present invention to provide a plummet capable of operating over long vertical distances using an optical method and capable of achieving great accuracy over the whole length of such vertical distance.

The present invention therefore provides a plummetfordefining 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 optical reflector at or below the bottom ofthe vertical distance and means for adjusting the vertical alignment of the light sourceto provide a coincid- ence 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 beam of light. Preferably the laser is ofthe continuouslyoper- ating type and in the visible spectrum.

The optical reflector is preferably a bath of oil.

More preferablythe bath has no coverthe oil being open to the atmosphere. In use, the 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 theX-Y direction to align it with a desired vertical line.

An optical gauge may be providedforattachment to a first member, the vertical alignmentofwhich is required such that the light beam may be positioned at a distance from the first member. The gauge may comprise meansforaligning a second memberac curatelywith respect to the first member.

Embodiments of the present invention will now be described, by way of example with reference to the accompanying drawings, in which: Figures 1(a), 1(b) and 1(c) show the basic principle ofthe reflecting optical plummet according to the present invention; Figure2 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 4diagrammatically shows 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 5and 6show an alternative optical plummet design; Figure 7shows an alternative laser adjustment system;; Figures8and9showan alternative lift rail alignment system to the arrangement of Figure4; Figures lOto 13 show a portion of the system of Figures 8 and 9 for positioning the laser; Figures 14to 16show means for positioning the pentaprisms in the system of Figures 8 and 9; Figures 17to 19 show an alternative X- Y adjust- ment system for the laser; and Figures 20to 23 show 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 10is reflected back 13from the reflector 12 to the light source and impinges onto a target 14. Thus in Figure 1(a) the beam 13 is reflected backto a spot to the right of the light source 10. In Figure 1 (b)the beam is reflected backto a spottothe left of light source 10. In both cases neitherthe beam 11 nor the reflected beam 13 is vertical. In Figure 1(c) however when 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 then the reflector 12 can be removed, it being only necessary to recheck the beam direction at intervals (say each hour). The beam of light 11 therefore provides an optical "plumbline" which can be intercepted at any point along its path to provide avertical alignment. The light source is preferably a laser and the light frequency is preferably chosen to be within the visible spectrum (a suitable laser being a HeNe which produces a reddish 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 the container shape and the 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 overthe container, the oil may be readily replaced on most building sites.

The reflector is therefore very inexpensive and not easily damaged, this being an importantfactorfor any reflector which must be placed atthe 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 viscosityto damp out any vibrations. Thus the movement of vehicles on a site does not substantially extend the setting up period although obviously extremely strong vibrations close to the reflector 12 may cause the return beam 13 to be dissipated. Such vibrations are also howeverlikelyto affectthe mounting ofthe 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 nowto Figure 2 the optical source 10 is drawn in greater detail. The source comprises a laser 30 ofthe continuous operating type the light output 32 of which is directed towards a collimating beam arrangement shown simply bytwo lenses 34, 36.Thetarget 14 is opaque and is mounted on the front of lens 36. The beam 11 passes therefore through asmall hole37thetarget14.

The laser, lenses 34,36 and target 14 are mounted in a cylindrical structure 38 which is provided with an annular flange 40. Three adjusting foot screws 42 (only two are shown for clarity) are mounted at 120 intervals around the structure 38 through the flange 40 and serveto adjustthe vertical alignment ofthis structure and hence the beam 11 with respect to a plate44. Plate 44 maybe clamped by any suitably designed clamp means and then to a structure of a building where a vertical alignmentrequiresto bees- tablished.

In the embodiment shown the plate 44 is remov ably clamped tofurtherframe members 46,48 by clamp screws 50,52. Frame members 46,48 are in turn bolted onto a supportframe 60 by bolts 56 (only one shown). Thusthe plate44and optical apparatus 10 may be removed from the largerframe members 46,48 to be stored in a carrying case. Frame mem bers 46,48 may be designed to suit a specific pur pose and may contain adjustable screws orfurther clamps (not shown) to enable the optical apparatus to be clamped in a desired position. Thus optical apparatus 10,and plate44can be a standard item with versatility being provided by individually des ignedframe member46,48.

In opsration, beam 11 is generated by light source 10 and is reflected by reflector 12 positioned atthe bottom of, for example, a lift shaft. The reflected beam 13will normally initially strike partoftheframe 44 or46, 48 which may be coated with a suitablesub stance to provide a good target and is then adjusted byfoot screws 42 until its image coincides with that ofthe beam 11. The beam 11 is then known to be vertical.

The beams 1 and 13 may be affected byatem- Erature gradient but are unaffected by winds. Thus for outdoorworkthe apparatus will be accurate since no great temperature gradient should exist. For in door 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 ofthe beam over a length of 50 metres should beto 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 set- tingsto be made at any point along its path.

A practical system for a lift shaft is shown in Fig urns 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 ofthe 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 nowto Fig ure 4 the lift (not shown) runs on two guide rails 70,72 on opposite sides ofthe shaft. Atemplate 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 inter valsof,forexample, 1 metrelongthewholeheightof the lift shaft to thereby allow adjustment and setting oftherails70,72.

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.

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 thetarget 14is fairly small and thatthe alignmentof the beam 13 onto the output beam 11 can be made fairly exactly. This alignment can be improved by better optics to produce a thinner beam or by creat ing 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 align ment.

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 pre sent inside many 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. Ifthe instrument is calibrated the exact movement can be measured and if automatic measurement is required an array of photocell detectors may be used.

If the apparatus 10,44, etc is set up on a bridge when the bridge (or other similar structure) is unloa ded then the effect of loading can be observed by observing and measuring the deviation in the re turned light beam.

Adjustment of the optical alignment ofthe light source 30 to the telescope 34,36 may be achieved optically by means of optical wedges or similar opti cal devices in area X. The alignment screws may be motor operated such that the alignment may be car ried out remotely, for example, from halfway 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 ofthe 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 diametersforthe fibre optic ring, focussing lens and quadrantsensorare50mm,60mm,and40mm 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 beadjustedto give a point of light on detector 106. Thus detector 106 can be adjusted to give underforexample normal stress condition (e.g. dam halffull) a zero output and the output can be auto matically 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 when fixed in a supporting form and a suitable arrangement is shown in Figure 7. The laser 100 is support ted 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 1 26to adjust inner casing 122 with respect to an outer cas- ing 128which may be clamped in any suitable mannerto a building or any other structure. Screw 124 gives movement in a X direction and a further screw (not shown) is included for movement in theY direction. The bottom of inner casing 120 is held in a universal bearing 130which may as shown bea rubber collar.

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

With reference nowto Figures 8 and 9 an alternative vertical alignment system is illustrated for the alignment offor example lift guide rails 152,154 in liftshaft 150.

The laser source 100 which maybeverticallyalign- able as shown with reference to Figure 7 is mounted on a platform 200 and the output beam 110 is made vertical as explained herein before with reference to Figure 4 bythe 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 backto unit 300 for accurate setting as described with reference to Figure 4.

In Figure 9the 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 14to 16. The rails 152, 154 are adju- stable by means of the fixing plates 156.

With reference nowto Figures 10to 13the laser 100 is supported on platform 200 which requires to be adjustable in the X and Y directions to give correct alignmentforthe laser. The X adjustment is illustrated in Figure 10 and comprises a back plate 202 for fixing to theY 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 ofthe units shown in Figures 11,12 and 13 infronteleva- tion, side elevation and plan view respectively.

With reference to Figure 13, the laser 100 and associated casings is supported in a hoie 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 byfurther 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 Ydirectionsto shine a light beam down onto unit 300.

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

Thepentaprism indicated generallyat302 receives light via a hole304and emits the outputbeamvia 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 nutand bolt arrangement314to 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 nut318 in Figure 15) and four adjusting screws 320,322,324, 326, by means of which the pentaprism can be aligned in X,YandZdirections.

With reference now to Figures 17to 19 an alternative system for adjustment of the laser in the X-Y direction is shown. Figure 17 is a plan view, Figure 18a 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 alignthe laser (not shown) mounted on the plate. The adjustment screws 404,406,408 are situated at the corners of an imaginarytriangleandarethereforeableto adjustthe laser (or any other object) with respectto the vertical.

ForX-Ymovement plate 402 is movable byfurther 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 outerframe 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 butfor simplicitythe otherfine levelling members and X-Yfine 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 screws 510,512 acting on their support arms 514,516 which pivot on a bearing 518. Rollers 504,506 are adjustable in height bya 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 forfine adjustment.

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

Claims (17)

1. A pl ummet for defining avertical line over long distances including a light source, meansformount- ing the light source atorabovethetop ofthevertical distance, an optical reflector, means for mounting the optical reflector at or below the bottom ofthever- tical distance and means for adjusting the vertical alignment ofthe 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 reflector comprises a bath of oil the light being reflected from the surface ofthe oil.

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

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 ofthe continuously operating type, emitting light in the visible spectrum.

6. A plummet as claimed in Claim Sinwhichthe light source is collimated using a telescope to pro- dunce a pencil thin beam of light over a long distance.

7. A plum met as claimed in any one of Claims 1 to 6inwhichthemeansformountingthe lightsource includes 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 ofwhich is required, at a point 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.

10. Aplummetasclaimed 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 lightfor 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 innercasing the inner casing being adjustably mounted within an outercasingand including meansformoving the inner casing relative to the outer casing to adjust the alignment of the output beam of the laser.

13. Apparatusforaligning liftguide railsinclud- ing a plummet as claimed in Claim 1 in which the light source is mounted close to a first guide rail to providea beamoflightsubstantiallyparalleltothe rail and including a first pentaprism contained within afirst unitthe unit being attachable by clamp means to the first guide rail ata desired position, asecond 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 foralignmentofthesecond lift guide rail.

14. Apparatusforaligning lift guide railsincluding 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 directionsto align the laser.

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

16. Aplummetfordefining avertical 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 ofthe vertical distance and means for adjustingtheverticalalignmentofthelightsourceto provide a coincidence between the emitted and reflected light beam.

17. Aplummetfordefining avertical line over long distances substantially as described with reference to the accompanying drawings.