Abstract: A method of detecting a coded magnetic thread is provided that includes sensing the response of a magnetic field detector as a thread passes the detector, the response varying from an initial magnitude in first and second senses to exhibit a first peak, and then in the first sense to exhibit a second peak; comparing the response with first and second thresholds disposed about the initial magnitude in the first and second senses respectively; and indicating the passage of a code element of the thread when the response passes the second threshold and then the first threshold in a predetermined manner characterized in that the first threshold is adjusted in accordance with a first predetermined algorithm based on the magnitude of the first peak. The first predetermined algorithm adjusts the first threshold so that the magnitude of the first threshold is the average of a predetermined number of preceding first peaks.

Abstract: Systems and methods for identifying a coded magnetic thread comprise generating a digital representation of the thread and comparing the digital representation with one or more known digital representations; scanning the digital representation to locate a predetermined code sequence; and rotating the digital representation to locate the predetermined code sequence in a predetermined position corresponding to the position of the predetermined code sequence in a stored version of the or each known digital representation prior to carrying out the comparison.

Abstract: A method of detecting a magnetic thread comprises causing relative movement between the thread and an array of magnetic heads, each head generates a signal upon detecting a portion of the thread. The arrival of a thread at one of the heads is detected, that head being denoted a primary head, and the head on each side a secondary head. Output signals from the primary and secondary heads are monitored to generate a representation of the thread, and the magnitude of the signals from the primary and secondary heads are compared such that if the magnitude of the output signal from a secondary head exceeds that from the primary head, the primary and secondary heads are reallocated accordingly.

Abstract: A sheet detecting assembly for use in detecting sheets passing along a transport path. The assembly comprises a linear array (15-17) of radiation emitters extending transverse to the transport path. At least one first radiation emitter (29A) at an end of the array is physically oriented so as to generate a radiation beam centred a line which crosses the transport path at a non-orthogonal angle, and at least one second emitter (29A) is physically oriented so as to generate a radiation beam centred on a respective line substantially orthogonal to the transport path; and a detector system for detecting the radiation after it has impinged on a sheet.

Abstract: A tool for reducing torque on work string, eg for gas or oil production, comprises an upper clamp (2), a lower clamp (3) and connection means (4), the three components formed as a unitary structure (1). The tool also comprises bearing means, preferably made from an elastomeric compound, and an annular body (7) (see FIG. 4) held in place over the connection means by the clamps. The clamps may comprise spigots (5) for retaining the connection means. In a preferred embodiment the annular body is in two semi-annular components connected at one end to allow them to pivot, and the other end comprises mating castellations for receiving a fastening pin. The annular body may comprise a number of replaceable wear pads (14) which may be made of bronze or an elastomer. The unitary structure of the tool enhances the integral strength and efficiency of the clamps.