Technical field of the invention

This invention relates to a level comprising a suitably tubular conduit which is at least partly filled with liquid and which, at least at a first end thereof, is transparent for making visible a first liquid surface for reading, which is located in said conduit and corresponds to a second liquid surface located at the other end of said conduit and serving as reference level, both ends of said conduit being sealed by means of yieldingly movable means, whereby the enclosed liquid mass is allowed to move within certain limits while being at the same time prevented from escaping from the conduit. State of the art A level which is sealed at both ends in the manner stated above is previously known from US patent 762072. One drawback of this known level is however that the conduit contains but a single liquid mass which is defined or terminated by two air-filled spaces, namely one space at each end of the liquid mass. This means that air bubbles can migrate from one end to the other, for instance if the conduit is placed on a floor with all parts on substantially the same level. This means that the bubble level will give incorrect indications when levelling.

Summary of the invention

The present invention aims at overcoming the above-mentioned drawback by providing a level obviating the risk of any occurrence of migrating air bubbles in the conduit. According to the invention, this is achieved in that the liquid is divided into two liquid masses which are separated by means of a flexible membrane and one of which is accommodated in that part of the conduit which is transparent and which, in

addition to the liquid mass, contains a certain amount of air or gas above said liquid surface, and the other of which completely fills the conduit. Brief description of the drawing In the drawing, ^*

FIG 1 is a perspective view of a preferred embodiment of the level, and FIG 2 is a perspective section of the level. Detailed description of a preferred embodiment of the invention

The preferred embodiment of the level according to the invention essentially comprises three main parts, namely a reference part 1, a tube 2 and a levelling part 3. The reference part 1 and the levelling part 3 have the form of cylindrical containers connected with the tube at its respective ends.

Fig. 2 shows in more detail the design of the level. Through an inlet opening 4 provided in the bottom 5 of the reference part 1 and connected to the tube, liquid can flow into the container defined by the wall 6 and the top 7. The top 7 is provided with an air hole 8 screened from the rest of the container by means of a yielding bladder-shaped membrane 9 of plastic or rubber. The container also has a recess 10 which can be used for hanging the reference part 1 on a suitable level on a nail, hook or the like.

The levelling part 3 has a design similar to that of the reference part 1 , thus comprising a bottom 5' with an inlet opening 4' , and a top 7' with an air hole 8' . The levelling part 3 however differs from the reference part 1 by having a transparent glass tube 11 provided between two boundary walls 12,12' and extending through holes in the respective boundary walls. Together with the bottom 5' and the top 7', the walls 12,12' define a lower chamber 13 and an upper chamber 14, the chamber 13 communicating with the tube 2 via the inlet opening 4' and the chamber 14 communicating with the

ambient atmosphere via the air hole 8'. The ends of the glass tube 11 are sealed by means of bladder-shaped rubber membranes 15,15' which are housed in the lower chamber 13 and the upper chamber 14, respectively. The closed space defined by the glass tube 11 and the rubber bladders 15 and 15' is filled about half with liquid and half with gas. The liquid may suitably be coloured in order to make the liquid column 16 show more clearly in the glass tube. The glass tube is provided with a level marking 19 corresponding to a level marking 20 on the reference part.

As will have been appreciated from the foregoing,' the level according to the preferred embodiment thus has two separate liquid systems, namely a first system comprising the reference part 1 , the tube 2 and the lower chamber 13 in the levelling part 3, and a second system comprising the rubber bladders 15 and 15' and the glass tube 11 in the levelling part. The first liquid system should be completely filled with liquid to avoid the occurrence of air bubbles sticking in the flexible tube and giving rise to functional dis¬ turbance, while the other liquid system, as previously mentioned, is only partly filled with liquid, suitably about half of it. This is necessary in order to provide a free liquid surface 17 in the glass tube 11.

When using the level, the reference part 1 is thus placed at the starting point or reference point with the level marking 20 on the level to be trans¬ ferred to the other end of the tube. If the levelling operation should be performed by a single person, the reference part can be hung in the recess 10. The levelling part 3 is then vertically adjusted so that the liquid surface in the glass tube 11 coincides with the level marking 19. In this position, the level markings 19 and 20 are in exactly the same horizontal plane, and the position of the level marking 19 can be transferred wherever desired. To ensure that the

level markings 19 and 20 are actually located in the same horizontal plane when the liquid surface is opposite the -level marking 19, the device must be correctly calibrated. There are basically two methods for cali- brating the level. In both cases, the reference part and the levelling part should be held close together. According to the first method, the level marking 20 has not been provided originally, but the two parts are displaced relative to each other until the liquid surface coincides with the level marking 19, whereupon this level marking is transferred from the levelling part 3 to the reference part 1. According to the other ^* method, both level markings 19 and 20 have originally been provided and are placed adjacent each other on the same level, whereupon liquid is drawn from or supplied to one of the two liquid systems until the liquid surface 17 in the glass tube coincides with the level marking 19.

The level according to the present invention has a number of advantages over prior art tube-type levels. For instance, the device is completely closed, i.e. there is no risk of liquid escaping from the system unintentionally. Also, there are no valves which must be opened or closed, i.e. the risk of incorrect levelling has been eliminated. These two features further contribute to making the device easy to use by a single person. The arrangement with two separate liquid systems, the larger of which is completely filled with liquid, obviates the risk of incorrect levelling caused by the existence of air bubbles in the tube, and makes it possible to supply a colouring agent to only one of the liquid systems in case it is desirable to have a differently coloured liquid column.

The term "level" as used herein should be understood in its broadest sense, that is includes not only levelling devices using water or water-base liquids, but also devices using many other types of liquids.

Conceivable modifications of the invention

In the preferred embodiment, the conduit 2 is a flexible rubber or plastic tube. This is so because the level is primarily intended to be used for free levelling, for instance on a building site. It may however also be desirable to mount a levelling system according to the invention in a more stationary fashion, in which case the conduits may instead consist of rigid pipes. One possible such application is in caravans where there is a need of levelling when parking the caravan. In e.g. the building trade, use is made of straightedges of light metal. These may have a length " of 6-8 and are used, for example, for making cast surfaces level. To further increase the usefulness of such straightedges, they may be provided with a levelling system according to the present invention. Instead of filling the levelling part with half liquid, half gas as in the embodiment here described, it may be filled with two immiscible liquids, for instance oil and water.

To permit a distinct reading of the level in the glass tube, a floating body may be disposed therein, and the reading is made on the top surface of the floating body or on a scale provided on the circum- ferential surface thereof. Finally, it should be pointed out that the glass tube 11 need not consist of glass, but any other transparent material is possible to use, for instance plastic.