A polyimide copolymer containing a block polyimide polymer component composed of a rigid aromatic diamine compound and an aromatic tetracarboxylic acid compound and a random polyimide copolymer component composed of a flexible aromatic diamine compound and at least two types of aromatic tetracarboxylic acid compounds is prepared by a two-stage polymerization process. Resin molded products prepared from the polyimide copolymer have high modulus, low thermal expansion and low water absorption and can be used as TAB base films that require higher processability and precision.

A golf instruction device is disclosed which teaches golfers to learn and execute an inside-out swing. The device consists of a horizontal base that is placed on a supporting surface such as the ground or floor in a practice tee area. A guiding member that guides club head movement during the swing projects upwardly from the base and includes three guide sections. The first is a straight section that lies on the line of intended ball movement, the second extends rearwardly from the first section and curves inwardly relative to the golfer, and the third section is straight, extending forwardly from the first section but diverges outwardly or away from the golfer. By following the three guiding sections during the backswing and foreswing, the golfer learns to execute the inside-out swing properly.

A device for significantly enhancing the ability of ice hockey players of all experience levels for developing stick control and correct shooting movements while also increasing strength, balance and accuracy thereof which includes a framework defining a practice zone thereunder wherein a flexibly resilient member is secured to uniquely configured apertures defined in the blade of the training hockey stick to encourage correct stick movement and to discourage incorrect stick handling and shooting movements. The apertures are preferably located in the heel, the toe and/or the tip of the blade of the stick and are attached to the resilient member for building up strength and providing resistance thereto. The resilient member is knotted and positioned extending through one or more of the apertures in the stick blade and the apertures are shaped such as to retain the knot of the stick extending through the aperture responsive to correct stick movements and to release the knot responsive to incorrect stick movements. This teaching mechanism is achieved by forming apertures which includes a wider area on the tip side of the aperture and including narrow or more restricted areas on the heel part of the apertures.

A portable golf training apparatus and method of use for teaching golfers the consistent achievement of proper ball placement, correct alignment, proper foot placement and stance, and for providing a visual reference or target line in relation to alignment and foot position.

A golf alignment device that has a ground arm for placement parallel to a line directed at a target some distance away from a golfer and a ball placement line arm coupled to the grounded arm for indicating the ball placement with respect to the golfer and the target line, so that a golfer is aided in maintaining a perpendicular relationship between the two. Using such a device, a golfer is able to practice his swing for a variety of club faces.