Abstract: A leak detector has a gas probe 1 for sensing signal gas escaping from an enclosure containing that gas at a pressure slightly in excess of ambient surrounded by a curtain of barrier gas. The reading of a gas analyzer such as a mass spectrometer depends on the height of the probe from the surface. A height sensor is attached to the leak detector and a programmable amplifier 6 contains information on the characteristic curve of the gas sensor. An output signal from the programmable amplifier compensates for the height of the probe from the surface being detected. The speed of the leak detector can be corrected for in the same way.

Abstract: A leak detector comprises a detector head which is to be scanned across a surface to detect a signal gas eminating from the surface. The opposite side of the surface from the head is supplied with a signal gas under pressure so that signal gas passes through leaks in the surface. Detection of signal gas by the head should then constitute detection of a leak. A curtain 1 of barrier gas is provided around a sample inlet 2 to protect the inlet from spurious signal gas. Orifices 36 provide narrow high velocity jets 38 which impinge on the surface S within curtain 1 and break up jets such as 34 of signal gas which escape under the curtain 1 without allowing the signal gas to reach the sample inlet.

Abstract: The leak detector comprises an annular chamber 11 which leads to a circumferential orifice 14 which in turn leads to an annular duct 21 which is symmetrical about the axis of the detector. Barrier gas is fed to the annular chamber 11, for example from an annular chamber 18 and emerges from the opening 20 to form a substantially laminar flow. Leaks are detected by means of a signal gas within an enclosure at a pressure slightly in excess of ambient, and the signal gas is detected from leaks via a probe 2 which is connected for example to a mass spectrometer. The curtain 1 is stable and enables uneven surfaces to be tracked.

Abstract: A method of, and apparatus for, detecting leaks from a surface provides a sampling device (10) making use of an air curtain (C). The body (11) of the device (10), the curtain (C) and a surface (B) to be tested together define a sampler volume (S). Pressure in the sample volume (S) is regulated to draw signal gas from a source thereof to the volume (S) along leak path (L) which exists. Sampled gas is withdrawn from the volume for checking by means of a mass spectrometer (18) for the presence of signal gas.

Abstract: Apparatus for measuring the road wheel hub alignment of a vehicle on its production line includes a pair of electro-optical units for attachment to a pair of road wheel hubs and a master control and display unit. The electro-optical units each comprise an array of photo-sensitive devices which are illuminated by a directional beam of light from the other unit, and include a display for indicating to an operator the state of alignment of the hub to which the unit is attached. Alignment of both hubs can be monitored by a display on the master control unit, which includes an output to a data recording means so that the state of alignment of the hubs on each vehicle passing down the line can be automatically recorded. The photo-sensitive devices are arranged in a radial plane of the axis about which the hubs swivel for adjustment, and in a plane perpendicular to the axis of rotation of the road wheels to enable simultaneous independent adjustment of the hubs.