The present invention is concerned with a device for leveling-in or similar purposes, comprising a cabinet fitted with a mirror on which sights are taken with the aid of a target or similar.

In civil engineering operations, such as water-supply works, sewerage works, road-building and other works involving the digging of trenches, as for the laying of pipes or similar, it is often necessary for the trench to have a certain constant gradient. The setting-out of such trenches with the aid of sighting instruments and lines of pegs is a time-consuming business involving many repeated operations and adjustments. The equipment used, such as ranging rods, sight rails etc., is often bulky and obstructs other work on the site.

The main purpose of the present invention, therefore, is to provide a device or instrument for leveling-in and similar operations whereby the above drawbacks are avoided and which is simple and convenient to use yet permits leveling-in to be done with high precision. This purpose is achieved by providing the device of the invention with the features specified in the Claims hereafter. >

The invention will be further described in the following paragraphs with reference to the drawings. Fig. 1 is a side view of the instrument mounted on a pipeline for leveling-in for the purpose of pipelaying. Fig. 2 is a view of the instrument seen from the direction II-II in Fig. 1. Fig. 3 shows a section through the mirror cabinet of the instrument in Fig. 1. Fig. 4 is a view of the mirror cabinet in Fig. 3 seen from the direction IV-IV in Fig. 3. Figs 5a - 5c show different views of the base of the in¬ strument's stand. Fig. 6a is a side view and Fig. 6b an end view of a target rod used in conjunction with the instrument of the invention. Fig. 7 shows a modified form of the invention.

The form of the instrument shown in Fig. 1 is illustrated and described in connection with the laying of pipes in a pipe trench. It is to be clearly understood, however, that the instrument of the invention can be used for other leveling-in purposes without thereby departing from the purpose of the

invention. The device or instrument of the invention incorporates a stand with a base 12 which is mounted on the first pipe 14 of a series, from whi pipelaying is to be continued as indicated by an additional pipe 16, the i strument being used for lining up and leveling in the pipes with the desir gradient between two points. When setting up the instrument it is positio with the aid of the stand 10 and the base 12 vertically above the center!i of the pipe. The stand may also be designed so that its length can be ad¬ justed to a convenient working height depending on the diameter of the pip 14, 16. Apart from the stand 10 and the base 12, the instrument of the invention includes a cabinet 18 which will be described more particularly below but whose essential feature is that a mirror mounted therein can be manually to the desired angle of inclination. The instrument 18 is used i conjunction with a target rod 20 consisting of a straight staff with a bas 22 intended to be inserted into and rest on the invert of the pipe being laid - pipe 16 in the example illustrated. The target rod 20 is further fitted with a marker or target 24 which is movable on the rod, and with a sight 26 at the top of the rod. It is further apparent from Figs 6a and that the marker or target 24 can be moved up and down the length of the rod 20, e.g. by sliding in a slot 28 in the said rod or staff 20. The device described in the foregoing is employed in the following manner: The instru ment 18 is set up as stated with the aid of the stand 10 and the base 12 on top of the first pipe 14, from which pipelaying is to be continued. The gradient is set, as will be described below, inside the mirror cabinet 18 b means of a knob or similar control. The staff 20 is set up with its base 2 on the invert of the first pipe, whereafter the operator looks through the hole 30 (Fig. 6b) in the sight 26 towards the mirror inside the instrument 18, and adjusts the position of the target 24 on the staff 20 until its reflected image coincides with a matching mark on the mirror inside the instrument 18. The target may, for example, as illustrated in Figs 6a and 6b, have a mono-colored top half, its lower half being marked 32, as with a pattern or similar, to permit easy identification of the center of the target in the reflected image. The mark on the mirror of the instrument 18 may be an ordinary cross as described further below. As laying proceeds, t position of each pipe, as pipe 16, is checked by inserting the staff 20 int the pipe with its base 22 resting on the invert, in the same manner as for the initial adjustment of the target, after which it is verified by looking through the sight 26 that the reflection of the target 24 coincides with th

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mark, such as a cross, on the mirror, as illustrated for example in Fig. 2; if so, the pipe is correctly lined up and leveled in. The lines of sight between the target 24, the instrument 18 and the sight 26 are marked "S" in Fig. 1.

The instrument 18, shown in section in Fig. 3, contains a mirror 34 which is suspended by means of pins 36 permitting it to tilt in a carrier 38, which is itself suspended at its top via e.g. a ballbearing 40 in the cabinet 42 of the instrument 18, so that the carrier 38 always assumes a vertical position. Also mounted on the carrier 38 at the upper end thereof is an adjusting mechanism 44 with a knob 46 which, via e.g. a bracket 48, bears on the mirror 34 in such a manner that by turning the knob 46, through the agency of screw threads or similar (not shown), the operator can adjust the inclination of the mirror 34 in relation to the carrier 38, as indicated by dashed lines, in opposition to the force of a return spring 50 fixed to the carrier 38 behind the mirror. The adjusting mechanism 44 may, as illustrated in Fig. 4, be provided with .a scale 52 round the knob 46, to indicate the gradient in, for example, parts per thousand in relation to the vertical. It further appears from Fig. 4 that the mirror 34 is provided with the above- mentioned cross mark 54 for the purpose of identifying in the mirror 34 the position of the target 24 mounted on the target rod 20 as described above. The casing 42 of the instrument 18 is provided with mountings 56, 58 for attachment to the stand 10 illustrated in Figs. 1 and 2, and the front of the instrument 18 may consist of a removable glass cover 60 which serves to protect the mirror and the adjusting mechanism. To ensure the rapid retarda¬ tion of the carrier 38 suspended in the instrument cabinet 42 the said car¬ rier 38 and the cabinet 42 are made with a snug fit along their sides and at the lower edge, as indicated by 62 in Fig. 3, whereby the carrier is retarded by the air which has to be displaced. To this end, also, sealing strips may be applied in the clearance space 62. The instrument 18 is preferably mount¬ ed in the stand 10 so as to be rotatable in an upper and a lower fixture, 64 and 66 respectively, for which purpose a knob 74 may be provided to permit the instrument 18 to be rotated in the stand and to facilitate ranging with the aid of a scale (not shown) below the knob on the fixture 66. This per¬ mits the fine adjustment of the instrument for the purpose of lining-up (Fig. 1).

The base 12 of the stand, shown in Figs. 5a - 5c, incorporates a central part consisting of two lengthwise supports 64 and two transverse supports 66. Hinged to this central part are two U-bars 68 which can be folded inwards

over the central part, as illustrated in Fig. 5b, and outwards away from t central part, as illustrated in Figs 5c and 2. By this means the base 12 be adjusted to fit pipes of varying diameters. To make the instrument ste ier and to further conform the base to different surfaces, sheets 70 of a flexible material, such as rubber of similar, are fastened between the central part 64, 66 and the outsides of the U-bars 68, and the said sheets may be weighted with sand or similar to stabilize the base and cause it to conform to the surface on which it is placed. The central part 64, 66 may also be fitted with feet 72 as shown in Figs 5b - 5c.

Fig 7 shows a modified form of the invention. In this embodiment the instrument 18' is mounted on a tripod 76 with three adjustable legs restin on the ground. The instrument 18' may have a bubble tube or similar (not indicated) to permit approximate horizontal setting. As shown in Fig. 7, target rod 20' may, as an alternative to the arrangement of Fig. 1, be set on top ^' of the pipe 16' during positioning, and the sight 26' may be movabl on the target rod 20' instead of being fixed at the top thereof. In certai applications the target rod 20' may have a movable sight 26' only and lack a target 24'. In this case observations are made by looking through the sight 26' straight into the mirror, when the sight 26' is to coincide with the mark, such as a cross or similar, on the mirror. In the case where a target 24' is used, it may consist of a light source to facilitate readin in conditions of poor visibility. The target 24' shown in Fig. 7 may consi of a lamp with a bi-colored glass, e.g. with the upper half red and the low half white, thus providing a distinct light indication in the mirror withou any need for the latter to incorporate a light source of its own.

When the target mirror is used for lining-up only, i.e. as an aid in pegging out, it is an advantage if the instrument can be used in very rough ground, as for example on road embankments and similar.

In the form of the invention shown in Fig. 8, a convex mirror 134, curved with respect to the vertical plane, enables the operator to see the reflection of the target rod 135 even from a position above or below the horizontal planes passing through the top or bottom edge respectively of th mirror.

It will be evident that the illustrated embodiments are merely example of the invention, which can be modified within the terms of the following Claims.

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