An investigation into miniature hydraulic actuation techniques for needle control on industrial knitting and sewing machines

The thesis is presented in four main parts: (1) the design and development of a hydraulic circular weft knitting machine; (2) the construction and testing of a hydraulic lockstitch sewing machine; (3) a detailed design study and analysis of pulse-generating rotary valves; (4) the design of a multi-feeder hydraulic circular weft knitting machine. Part 1 deals with the knitting machine aspect of the project consisting of verifying that a multi-actuator rotary valve system would operate with the desired time displacement profile, and in the correct sequence. This was then used as the basis for developing a ninety-six-needle, single feeder hydraulic circular weft knitting machine. This prototype machine was tested to obtain an assessment as to the advantages offered by hydraulic knitting techniques. Part 2 involved replacing the needle and thread take-up mechanisms of a lockstitch sewing machine, by two miniature hydraulic actuators, controlled by a rotary valve. The purpose of this machine was to prove that stitches could be formed successfully, thus demonstrating any beneficial features offered by hydraulic sewing devices. Part 3 deals with the detailed design study for pulse-generating rotary valves resulting from the previous applications. This valve was a new concept in valve technology and having established its definite potential, warranted the formation of a design procedure. The study outlines a method of optimising the torque required to rotate the bobbin by the construction of a mathematical model. Part 4 was concerned with designing a multi-feeder hydraulic circular weft knitting machine. This machine, controlled by an integrated actuator rotary collar valve to generate pulses, demonstrated how a series of twelve knitting time-displacement profiles could be created by ninety-six actuators positioned in a circular configuration. Thus, the research programme has been aimed at demonstrating how high speed motions, normally obtained by mechanical devices (cams, linkages) can be produced by miniature hydraulic actuation techniques. The feasibility of using these techniques has been verified by the building and testing of probably the first ever hydraulic knitting and sewing machines.