Abstract: The invention refers to the construction and the procedure for injection molding multi-layer plastic products. The procedure is to first injection mold the first layer (1) with ribbed protrusions (12). In the closed product structure, the segments (1?, 1?) of the first layer (1), with an opening (11) shaped with a solid core or in any other known way, are joined into a skeleton via inlets (13), with coupling or in any other known way. First formed layer (1) is then precisely positioned into the next mold, and over the whole, or a part of the outer surface another layer (2) is injection molded, whose opposite ribs (21) fill in the cavities between the ribs (12), and the ribs (22) now protrude out of the surface of layer (2).

Abstract: A noiseless valve includes a leading spiral spindle (4) having a thread (8) at one end by which it is screwed into a spiral (8') of a piston holder (10). The piston holder (10) has a cylindrical shape and is placed into a valve body (1). The leading spiral spindle is secured by the key (13) in axial direction. A piston (12) is attached to an upper part (12) of the holder (10). The piston (16) has an edge rim with two teeth (18) cooperating with grooves (22) furnished on posts (21) of a rubber seal holder (19). The rubber seal holder (19) is attached to the valve body (1) at an end where the piston (16) stands out. The piston (16) is pressed against a rubber seal (23) placed in the rubber seal holder when the valve is closed. Two spiral teeth (6', 10'), disposed diametrically opposed and mutually shifted by 90.degree., are provided on a bottom head surface of the piston holder (10) and on a rim (6) of the leading spiral spindle (4).

Abstract: This invention relates to a silent valve, consisting of a body 9 in which a shaft 10 having thread 8 is rotatably positioned for helical engagement with a piston carrier 7. Piston carrier 7 has an opening 24 on its head, in which a boss 25 of the piston 1 is positioned. The piston 1 is removably secured to piston carrier 7 by teeth 22 which grasp a circumferential flange 18 of the piston 1. A ring-like seal 15 is positioned on the piston 1 for selective opening of slots 4 on the hollow portion of head 3 for allowing fluid to flow through the valve. Piston carrier 7 also has a flange 38 with notches 39, 40 receiving cogs 35, 36 of securing element 20, positioned on the neck 30 of the shaft 10.