Abstract: A manufacturing method is provided from manufacturing a dipper stick having a box shaped structure including an outer casing member formed of a high strength polymeric composite materials, an inner filler comprising polyurethane foam and disposed inside the outer casing member in order to be integrated with the outer casing member, and a plurality of bushing holders made of polymeric composite material and disposed at respective connecting portions of the box shaped structure in order to be integrated with the box shaped structure. The dipper stick is configured to be connected at the respective connecting portions to a bucket, a boom, dipper and bucket cylinders and a link, respectively.

Abstract: A high strength polymeric composite material dipper stick which comprises a structure including an outer casing member formed of high strength polymeric composite materials, an inner filler comprising polyurethane foam disposed inside the outer casing member in order to be integrated with the outer casing member, and a plurality of bushing holders made of polymeric composite material and disposed at connecting portions of the structure in order to be integrated with said structure. The present invention provides weight reduction of about 50%-60% in comparison with a conventional structural steel dipper stick, and also about 6.8%-13.9% in comparison with the conventional structural steel dipper stick on the basis of weight ratio of excavated earth.

Abstract: A laser pick-up device for an optical disk receives three laser beams to irradiate the optical disk and uses a six-division optical detector to detect the laser beams reflected from the optical disk and to track exactly the optical disk. A reflection type diffraction grating is positioned at a front position in order to divide and reflect the laser beam generated by a laser diode. A holographic element having the function of a toric lens is used as a diffracting device for the reflected beams. The six-division optical detector is positioned to one side and/or behind the diffraction grating. The grid gaps of the holographic element can be larger using the present invention which simplifies the manufacturing the holographic element and thereby provides a laser pick-up device that is suitable for mass production.