GB2076965A

GB2076965A - An adjustable base for topographical apparatus

Info

Publication number: GB2076965A
Application number: GB8017930A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-06-02
Filing date: 1980-06-02
Publication date: 1981-12-09

Abstract

An adjustable base (2) for topographical apparatus, comprises a first platform (4) for supporting a telescope (6), a second platform (18) which slidably supports the first platform via pads (20) and a lip (22) for rotation over the second platform whilst remaining in a fixed plane with respect to the second platform, adjuster screws (28, 30) and a bearing ball (32) for adjusting the second platform to a horizontal position, a third platform (42) supporting the adjuster screws and ball and attachment means (46) for attachment to a tripod (48). The ball (32) is located between the second and third platform orthogonally spaced from the adjuster screws (28, 30) which respectively engage a flat portion of the surface (36) of and a groove (44) in the surface (36) of the platform (18). <IMAGE>

Description

SPECIFICATION An adjustable base for topographical apparatus This invention relates to an adjustable base for topographical apparatus. This invention also relates to topographical apparatus when provided with the adjustable base. The topographical apparatus preferably takes the form of a level but the topographical apparatus may also be in the form of a theodolite or an alidade if desired.

There are three main types of level, namely true Dumpy levels, tilting levels and automatic levels.

The true Dumpy level has been largely superseded by tilting and automatic levels because it is slow to set up and it usually requires readjustment after each measurement. Tilting levels are well used and in these levels, setting up is effected by means of two bubbles, namely a coarse adjustment circular bubble and a fine adjustment elongate bubble. Once the coarse adjustment bubble has been centred, it will not usually need to be re-set However, the fine adjustment elongate bubble rarely remains centrally positioned if the telescope is rotated and the fine adjustment elongate bubble usually requires to be re-centred after each measurement has been taken.

Automatic levels only require centring of a coarse adjustment bubble and no further levelling is required since the automatic levels have a compensatorwhich attends to any necessary levelling during use of the level. The compensator is usually a wire suspended prism system or a liquid and in either case, the compensator is of a complicated construction which makes the level expensive and subject to malfunction.

It is an aim of the present invention to provide an adjustable base for topographical apparatus, the adjustable base enabling the topographical apparatus to be quickly used by inexperienced persons and without the possibility of inbuilt errors caused by defects in the adjustable base.

Accordingly, this invention provides an adjustable base for topographical apparatus, which base comprises a first platform member for supporting a telescope, a second platform member which supports the first platform member such that the first platform member is slidably rotatable over the second platform member whilst remaining in a fixed plane with respect to the second platform member, adjuster means for adjusting the second platform member to a horizontal position, athird platform member for supporting the adjuster means, and attachment means for enabling the adjustable base to be attached to a tripod, the adjuster means comprising first and second adjuster screws and a bearing member, the bearing member being located between the second and third platform members, the first adjuster screw locating against a substantially flat portion of the surface of the second platform member remote from the first platform member, and the second adjuster screw locating in a grooved portion in the surface of the second platform member remote from the first platform member.

The first platform member may have three pads which run on the second platform member. The second platform member preferably has a raised annular lip on which the three pads run. Advantageously, the first platform member is provided with a seal between the pads for preventing dirt from getting between the first and second platform members in use ofthe adjustable base. The seal may advantageously have a dampening effect on the rotating action of the adjustable base so that a heavy silky feel is obtained as the adjustable base is rotated.

Preferably, the first platform member is a disc.

Also preferably, the second platform member is a disc.

The first and second platform members are advantageously held together in a spring biased relationship. They may be held together by a bolt having a spring which forces the second platform member towards the first platform member. The spring biasing of the first and second platform members together causes them always to be in constant contact during the rotation of the first platform member about the second platform member and therefore ensures constant accuracy.

Preferably, the third platform member is a disc.

Since the function of the third platform member is merely to support the adjuster means, it should be appreciated thatthere is no need forthethird platform memberto be the same shape as the first and second platform members apart from aesthetic reasons.

Advantageously, the second and third platform members are held together in a spring biased relationship. They may be held together by a pair of springs. The spring biasing of the second and third platform members ensures that a constant pressure is applied on the adjuster means thereby taking up any back lash so that the adjustable base does not depend on high quality tolerance fits. Furthermore, any wear is automatically taken up so that the performance of the adjustable base is not adversely affected with use.

Usually, the bearing member will be a ball bearing member.

The attachment means for enabling the adjustable base to be attached to a tripod may comprise a screw threaded hole for receiving a bolt on the tripod.

The present invention also provides topographical apparatus comprising an adjustable base of the invention and a telescope.

The telescope may be mounted on a fourth platform member, the fourth platform member being secured to the first platform member, and the fourth platform member having a spirit bubble positioned alongside the telescope.

The topographical apparatus may also include a tripod.

An embodiment of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure lisa sectional view through an adjustable base in accordance with the invention; and Figure 2 is a diagrammatic plan view showing the operation of the adjustable base.

Referring to Figures 1 and 2, there is shown an adjustable base 2 comprising a first platform member 4 supporting a telescope 6. The telescope 6 is provided with a focusing wheel 8 and an eye piece 10. The telescope 6 is mounted on a fourth platform member 12 which is secured to the first platform member 4 and which is provided with a spirit level 14 alongside the telescope 6. The spirit level 14 has a spirit bubble 16 as shown. When the adjustable base 2 is provided with the telescope 6 as shown, it forms topographical apparatus in the form of a level.

The adjustable base 2 further comprises a second platform member 18 which supports the first platform member 4 such that the first platform member 4 is slidably rotatable over the second platform member 18 whilst remaining in a fixed plane with respect to the second platform member 18. The first platform member 4 is in the form of a disc and it is provided with three equally spaced pads 20 around its circumference. The second platform member 18 is also in the form of a disc and it is provided with an annular raised lip 22 on which the pads 20 run. As can be seen from Figure 1, the pads 20 running on the lip 22 leave a space 24 between the remainder of the platform members 4, 18. In order to prevent dirt getting into this space 24 during use of the adjustable base 2, the annular space between the pads 20 is closed by a seal 26.The seal 26 may also advantageously dampen the rotation of the platform member4 about the second platform member 18to give a desirable heavy silky feel as the first platform member4 is rotated.

The adjustable base 2 also comprises adjuster means for adjusting the second platform member 18 to a horizontal position. The adjuster means comprises a first adjuster screw 28, a second adjuster screw 30 and a ball bearing member 32. As shown in Figure 1,the ball bearing member32 is located in a recess 34 in the surface 36 of the second platform member 18 and in a recess 38 in the surface 40 of a third platform member 42. The third platform member42thus supports the ball bearing member 32 and also the first and second adjuster screws 28, 30.

The first adjuster screw 28 engages a substantially flat portion of the surface 36 of the second platform member 18, this surface 36 being the surface of the second platform member 18 remote from the first platform member 4. In contrast, the second adjuster screw 30 rotates in a V-shaped grooved portion 44 in the surface 36 of the second platform member 18.

Both of the adjuster screws 28,30 are screwed in and out of the third platform member 42 to tilt the second platform member 18 as will be described hereinbelow.

The adjustable base 2 further comprises attachmenu means in the form of an internally threaded aperture 46 for receiving a bolt (not shown) attached to a tripod. Only a head part 48 of the tripod is shown and the three legs of the tripod have not been shown.

It will be seen from Figure 1 that the first and second platform members 4, 18 are held together by a bolt 50 which screws into a screw threaded aperture 52 in the first platform member 4. The bolt 50 has a head 54 and a coil spring 56 is sandwiched between the head 54 and the surface 36 of the second platform member 18. The spring 56 ensures that the pads 20 always press on the lip 22 during rotation of the first platform member 4 about the second platform member 18 thereby giving constant accuracy of movement.

As shown in Figure 2, the second and third platform members 18,42 are spring biased together by a pair of springs 58,60. The springs 58, 60 ensure that a constant pressure is applied by the second platform member 18 onto the adjuster screws 28,30 to take up any backlash in the adjustable base 2 during its use and also to take up any wearthat occurs.

It can be seen from Figure 2 that the screws 28,30 and the ball bearing member 32 define between them a right angle. This means that the second platform member 18 can only be tilted in two mutually perpendicular planes, the tilting in one plane being effected by the adjuster screw 28 and the tilting in the other plane being effected by the adjuster screw 30. The grooved portion 44 ensures that movement in the non-desired plane does not occurwhen adjustment in the desired plane is being effected by adjustment of the adjuster screw 28.

The adjustable base 2 can thus be very quickly set merely by adjusting the two adjuster screws 28,30.

When the adjuster screws 28,30 have been correctly adjusted, the second platform member 18 will be perfectly horizontal. The first and second platform members 4, 18 are factory produced to an extremely high degree of accuracy. This means that when the second platform member 18 is horizontal, the first platform member 4 is also horizontal. The high degree of production accuracy will enable the first platform member4to be rotated around the second platform member 18 without affecting the horizontal relationship of the first platform member 4. No adjustment is required of the first and second platform members 4, 18 and therefore the first platform member4 will always remain in its desired relationship.The fact that the first platform member4 is always in the desired horizontal relationship can easily be checked by the spirit level 14 because the spirit bubble 16 will always be centrally positioned. If the adjustable base 2 should become damaged in any way during use, then this will easily be seen by virtue ofthefactthatthe spirit bubble 16 will be unable to remain centrally positioned during rotation of the first platform member 4. The spirit bubble 16 thus provides an extremely easy visual indication that the adjustable base 2 is or is not still working accurately.

If the spirit bubble 16 should move off its central position due to rotation of the first platform member 4, then this will be an indication that the adjustable base 2 has become damaged and that it should be returned to the factory for service.

The adjustment of the adjuster screws 28,30 is always effected when the telescope 6 is at right ang les to the plane of tilting. In orderto make this adjustment particularly easy, the first platform member 4 is provided with a mark (not shown). This mark is brought into alignment with a coloured mark, for example green, on the second platform member 18. One of the adjuster screws 28,30 will be similarly coloured and it will be this similarly coloured adjuster screw 28,30 that will then require adjusting. The second platform member 18 can then be rotated through 90 to bring a second and differently coloured mark, for example red, on the second platform member 18 into alignment with the mark on the first platform member 4. The other adjuster screw which will be of the same colour as the second mark can then be adjusted.When the two adjustments have been effected, the level will be fully set up for use and it will not require further setting during measurements and resightings.

The level can be used for setting out right angles and for this purpose an adjustable index bracket (not shown) will be provided on the first platform member 4.

The adjustable base 2 may be designed to fit on any standard tripod having a 5/8 inch Whitworth thread. Obviously, the adjustable base 2 can fit on any desired tripod. A plate may be attached to the adjustable base 2 to enable movement over a data mark. In addition to standard tripods, the tripod may be a light weight, simple and cheap tripod.

Various types of telescope 6 may be employed.

The telescopes will usually have a magnification of 15 to 20 and they may have stadia lines of 700:1. The level will enable reacing of a normal surveyor's staff and also a special staff where the operator lines up a target (ratherthan reading the staff) and allows a man holding the staff to read his position.

It is to be appreciated that the embodiment of the invention described above with reference to the accompanying drawings has been given by way of example only and that modifications may be effected. Thus, for example, the third platform member 42 need not be in the shape of a disc and it could merely have finger portions for supporting the adjuster screws 28,30 and the ball bearing member 32.

Claims

1. An adjustable basefortopographical apparatus, which base comprises a first platform memberforsupporting atelescope, a second platform member which supports the first platform member such that the first platform member is slidably rotatable over the second platform member whilst remaining in a fixed plane with respect to the second platform member, adjuster means for adjusting the second platform member to a horizon- tal position, a third platform member for supporting the adjuster means, and attachment means for enabling the adjustable base to be attached to a tripod, the adjuster means comprising first and second adjuster screws and a bearing member, the bearing member being located between the second and third platform members, the first adjuster screw locating against a substantially flat portion of the surface of the second platform member remote from the first platform member and the second adjuster screw locating in a grooved portion in the surface of the second platform member remote from the first platform member.

2. An adjustable base according to claim 1 in which the first platform member has three pads which run on the second platform member.

3. An adjustable base according to claim 2 in which the second platform member has a raised annular lip on which the three pads run.

4. An adjustable base according to claim 2 or claim 3 in which the first platform member is provided with a seal between the pads for preventing dirt from getting between the first and second platform members in use of the adjustable base.

5. An adjustable base according to any one of the preceding claims in which the first platform member is a disc.

6. An adjustable base according to any one of the preceding claims in which the second platform member is a disc.

7. An adjustable base according to any one of the preceding claims in which the first and second platform members are held together in a spring biassed relationship.

8. An adjustable base according to claim 7 in which the first and second platform members are held together by a bolt biassing a spring which forces the second platform membertowardsthe first platform member.

9. An adjustable base according to any one of the preceding claims in which the third platform member is a disc.

10. An adjustable base according to any one of the preceding claims in which the second and third platform members are held together in a spring biassed relationship.

11. An adjustable base according to claim 10 in which the second and third platform members are held together by a pair of springs.

12. An adjustable base according to any one of the preceding claims in which the bearing member is a ball bearing member.

13. An adjustable base according to any one of the preceding claims in which the attachment means for enabling the adjustable base to be attached to a tripod comprises a screw threaded hole for receiving a bolt on the tripod.

14. An adjustable base for topographical apparatus, substantially as herein described with reference to the accompanying drawings.

15. Topographical apparatus comprising an adjustable base as claimed in any one of the preceding claims and a telescope.

16. Topographical apparatus according to claim 15 in which the telescope is mounted on a fourth platform member, the fourth platform member being secured to the first platform member, and the fourth platform member having a spirit bubble positioned along side the telescope.

17. Topographical apparatus according to claim 15 or claim 16 and including a tripod.

18. Topographical apparatus according to claim 15 substantially as herein described with reference to the accompanying drawings.