Patent GB-757510-A (GB)
Title: Improvements in or relating to level indicating devices
Inventor: PRYKE FORDHAM
IPC: G01C9/20
Filed: 1953-08-31
Abstract: 757,510. Level indicating devices. PYNFORD, Ltd. Aug. 31, 1954 [Aug. 31, 1953; Feb. 26, 1954], Nos. 24022/53 and 5747/54. Class 97 (2). [Also in Group X] A level indicating device for controlling the levelling of a structure comprises a number of gauge tubes which in use are fixed in an upright position to the structure with their reference marks at a given vertical distance from a reference line which it is required to make horizontal, the gauges being connected by flexible tubes to a container or containers for liquid, the container(s) being provided with an overflow device to maintain a desired liquid level therein. The overflow device may comprise a hole or weir in the container wall or a vertical tube passing through the bottom of the container which tube may be adjustable in height. The device is particularly useful in connection with the jacking up of buildings damaged by subsidence, in which case a gauge tube is fixed at each jacking position. Each jack is operated until the mark on its associated gauge tube coincides with the liquid level in the gauge tube. When a single container is used, the liquid level in the container is preferably below the final level set by the overflow, and further liquid is slowly introduced. Each jack then commences to operate when the liquid in the gauge reaches the mark and is operated to keep the mark up to the liquid level. Thus, the jacks come into operation at different times, but all work at the same rate. The preferred method of working, however, is for all the jacks to commence operating simultaneously but at different rates depending on the amount of lift required at the particular jacking point. This is accomplished by using a number of control containers to which the gauge tubes are selectively connected and providing means for effecting inter-related variations in the liquid levels in the various containers. Thus the containers may be of different sizes, so chosen that, if liquid is introduced into each at the same rate, the levels in the gauges rise at the required jacking rates and each jack is operated to keep the mark up to the liquid level in the gauge tube. However, it is preferred to adjust the effective heights of the overflow devices in the various containers, suitable arrangements being shown in the drawings. In Fig. 3, separate tanks C<SP>3</SP> are connected with the gauge tubes by flexible tubes T. Each tank has an overflow tube C<SP>1</SP> which slides through the hole C<SP>2</SP> and has an overflow inlet hole C<SP>4</SP>. The ends of the tubes C<SP>1</SP> are attached to a bar B<SP>2</SP>, pivoted at B<SP>3</SP>, and by raising the bar, for instance by a float Z which is raised by admitting liquid to the compartment Z<SP>4</SP>, the overflow tubes are raised by amounts proportional to their distances from the',post B<SP>1</SP>, which amounts are arranged to be equal to the lifts required at the corresponding jacking points. Liquid is constantly supplied to all the tanks to keep the levels up to the overflows. In Fig. 4, the containers are attached to a bar F and the overflow tubes R<SP>3</SP> are raised by turning the screw-thread N which works in a nut N<SP>5</SP>. The containers can be raised by fixing one end of the bar F in any one of the holes D<SP>7</SP>, thus enabling jacking lifts greater than the lengths of the containers to be made. Specifications 599,317, 629,355, 665,280, 671,312 and 672,269, [all in Group X], are referred to.