Patent GB-725923-A (GB)
Title: Device for determining the inclination and direction of drill holes in the ground
IPC: E21B47/022
Filed: 1953-10-26
Abstract: 725,923. Cliriometers. SVENSKA DIAMANTBERGBORRNINGS AKTIEBOLAGET. Oct. 26, 1953 [Oct. 28, 1952], No. 29546/53. Class 97 (2). In a bore-hole clinometer comprising a cylindrical casing 1 of substantially the same diameter as the bore-hole and which is to be thrust into the bore-hole to the point whereat the inclination and direction of the bore-hole are to be determined, with a contact arm 9 mounted as a pendulum in the casing 1, an electromagnet 4 is mounted in the casing a magnet, fast with contact arm 9, is journalled in the casing about an axis 7 at right-angles to its magnetic axis and to the longitudinal axis of the casing, and a stationary contact 28 is mounted in the casing in the path of the contact arm 9 which can thus be moved towards or away from contact 28 by energization of electromagnet 4 in opposite directions, an electric circuit located above ground comprises a current source 38, switch 37, meter 35, means (e.g. a variable resistance 36) for varying the current in the circuit, and electric conductors 31, 33 connecting the electromagnet 4 to the circuit, a second electric circuit located above ground comprises a current source 43, indicating means 41, and electric conductors 31, 34 connecting the contact arm 9 and the contact 28 to the second circuit, and means are attached to the casing 1 to turn it about its longitudinal axis, and to determine the amount of such turn, from above the ground. The lower end of the casing is closed by a screwed plug 24, and the upper end is closed by a plug 19 of rubber or the like in which are embedded three contactpins 20 connected to conductors 31, 33, 34. A tube 2, having similar plugs 19 with contacts 20 at both ends, the contacts being connected by conductors, is fixed to the casing by a sleeve 23 surrounding casing 1 and screwed on to tube 2. A number of tubes 2 are connected end-to-end, the last being secured to a head 22, the joints being secured by sleeves 16 engaging fine threads 17 and quick pitch threads 18 to bring the ends with the contacts 20 together. Straight tongues 14 enter grooves 15 so that the head 22, tube 2 and casing 1 all turn together when head 22 is turned. The upper member 46 of head 22 has a scale 47 and sights 49, 50 which can be laid on a fixed mark. An index on the lower part of the head then indicates the angle from the fixed direction through which the head has been turned. The clinometer is first calibrated by placing it in a vertical position above ground. A variable resistance 39 is set to a chosen value, and by means of variable resistance 36, the .current supplied to electromagnet 4 from battery 38 is increased until arm 9 swings to the right and strikes contact 28, closing a circuit from battery 43 to galvanometer 41. If necessary the direction of the current in electromagnet 4 may be reversed by a reversing switch 40, but in this case the current in the galvanometer circuit must also be reversed by a reversing switch 42, since the circuits have a common conductor 31 earthed through casing 1 at 32. The current required to move arm 9 into contact with contact 28 is noted. The clinometer is then tilted in a plane perpendicular to axis 7 to a number of angles to the vertical, and the magnitude and direction of the current required to make or break the contact between arm 9 and contact 28 is noted for each angle and plotted on a graph. The clinometer is then lowered to the required depth by attaching tubes 2. The consequent increase of resistance in the meter circuit is compensated by an equal reduction in the setting of variable resistance 39. The current required to make or break contact between arm 9 and contact 28 is found. This value can be used to find the inclination of the casing to the vertical provided that the axis 7 is in a horizontal plane. The casing may be turned until the maximum current reading is found by trial and error, but it is preferred to take readings at various angles of rotation of the casing and to plot the current readings against the angle. The angle for maximum current then indicates the direction in which the bore-hole is inclined, and the mean between maximum and minimum currents on the plotted curve corresponds to its inclination from the vertical. When the clinometer is to be used in holes which are substantially horizontal, a pendulous mass is attached to arm 9, which may then be light, to keep it horizontal when no current passes through electromagnet 4.