Abstract: A hydraulic spool valve 40 (FIG. 2(a)) of the edge control type in which the peripheral ends 31, 33 of a spool land 47 cooperate with a radial service port 41 to define by axial spool position the the closure of the port 41 and degree of opening to supply or return port 18, 19. The spool 25 is located in a sleeve 14 itself located in a housing 11 and O-ring seals 22', 22" inhibit leakage between sleeve and housing beyond the seals. Leakage fluid up to the seals exerts a contracting force onto the sleeve and when the spool is in a neutral position closing the service port stiction occurs between the sleeve and the end 36 of the spool land closest to the return port.

Abstract: A valve which allows the rapid discharge of a fluid from a reservoir (13) to a working volume (12) includes a housing (10) and a cylindrical sleeve (14) movable axially within the housing between a closed position in which it separates the reservoir (13) from the working volume (12) and an open position in which the reservoir (13) communicates with the working volume (12). Sealing means (20, 21) are provided to prevent leakgage of the fluid when the sleeve is in the closed position. Actuating means are provided for moving the sleeve (14) between its two positions. The sealing means comprises seals (20, 21) located to engage one end (19) of the sleeve around the outer and inner peripheries respectively when the sleeve (14) is in the closed position.

Abstract: A potentiometric circuit arrangement 30 is based on a resistive potentiometer tarck 11 with a capacitively coupled `wiper` 14', the resistive track being driven by switched alternating voltages of +/- V at 12 and -/+(X-V) at 13, where X is a reference voltage and V is the output of an integrator 15 to which the voltage sensed by the elecrode 37, and rectified at 36, is applied. A null voltage point establishes itself at the position of the electrode and stabilizes the integrator output at a d.c. voltage proportional to the distance of the `wiper` from the track end 12. Any `wiper` displacement taps a non-null signal which integrated applies new voltages to the track until the null point is re-established at the `wiper` position. The capacitive pick-up enables a potentiometer-type voltage output with less wear of the track, less drag against motion and less electrical noise, and electronic differentiation (27) of the position signal to give a rate signal.

Abstract: This invention relates to a system including an autopilot, with a simulator, for a fluid borne vehicle, and, in particular, to such a system including novel means to compute, in real time, and for depth keeping, and pitch keeping, purposes, any change of, or `out-of-trim`, heave force, and any change of, or `out-of-trim`, pitching moment, acting on the vehicle. For simplicity the general term out-of-trim forces is used when both are referred to.

Abstract: Apparatus with a multi-axis mechanism to perform, say, measurements or tests, has at least one pair of temperature detectors individually for each of selected members of the mechanism, each pair of temperature detectors being arranged to sense temperature differences transversely across the associated member. The required positions of the temperature detectors are predetermined from a preliminary examination of the mechanism, so that the extent and direction of each predetermined aspect of thermal distortion within the mechanism, can be computed from simultaneously detected transverse temperature differences, employing algorithms devised as a result of the preliminary examination of the mechanism. Compensation for corresponding selected errors in the measurements or tests can be calculated from the computed extent and direction of each of the predetermined aspects of thermal distortion within the mechanism.

Abstract: An assembly is provided including two members capable of relative rotation about a common axis, and with electrical interconnections extending between the two members, the assembly, being for example, part of a gimbal system, wherein the electrical interconnections may be divided into two groups, selected such that, because of the voltages, and/or currents, carried by the electrical interconnections, it is desired that the electrical interconnections of one group are screened electrically from the electrical interconnections of the other group, by a screen which does not extend along the whole length of either group.

Abstract: A method of providing a joint between articles of materials of different coefficients of thermal expansion comprises providing a preform of Indium between the articles, and, at ambient temperature, applying pressure to the articles to compress the Indium therebetween, the pressure being applied in a cyclical manner. A satisfactory joint is provided without employing complex cleaning of the co-operating surfaces of the constituent parts of the joint.

Abstract: In a fluid control valve, a force acting on the spool is produced by the inevitable inclination of the fluid flow into the spool chamber, and the force tends to be balanced by the fluid flowing over first and second surfaces of the spool, the inclination of the fluid flow as it leaves the spool chamber to a return port being less than, and of opposite sense to, the inclination of its entry. The fluid is received from the spool chamber by a chamber associated with the return port, the return port chamber being shaped to divert a portion of the fluid. In a known valve construction, the portion of the fluid is diverted to re-enter the spool chamber, to enhance the balancing force.