Abstract: A method and apparatus for metering and mixing multi-component plastics, in particular polyurethane, in which two or more hydraulic piston and cylinder units (A.sub.1 and A.sub.2) for each component, operate periodically by a balanced procedure. The pressure for the second piston and cylinder unit which takes over metering is equilibrated, before the beginning of the metering procedure, with the pressure of the first piston and cylinder unit which is in the process of metering. Switching from one piston and cylinder unit to the other (e.g. from A.sub.1 to A.sub.2) takes place in such a way that metering is taken over by the second piston and cylinder units at the same time as the first piston and cylinder unit is switched off. This is achieved by providing a pilot valve which has zero overlap and inevitably releases the component stream from the first piston and cylinder unit at the same time as the other piston and cylinder unit is switched off.

Abstract: The apparatus for mixing multicomponent plastics, in particular polyurethane, has a steadying attachment 1 which is arranged at the outlet orifice 12 of a mixing head 10. The steadying attachment is equipped with a plurality of lamellae 3 which are movable in the region of the emerging mixture of components and run in the direction of flow of the said mixture. Advantageously, the lamellae can be moved forward and back in a guide housing which has webs 2 which occupy the space between the lamellae and thus ensure cleaning. Steadying is achieved by greater friction with the wall and an increase in the outflow cross-section.

Abstract: The test apparatus is equipped with two valves, of which the valve arranged in the test line 3 which branches off from the return line 1 is a seat valve 7 whose outlet aperture 13 forms the end of the test line, so that the amount of component emerging through the outlet aperture passes directly into the test beaker 6. The other valve, which is preferably a sliding valve 9, is designed and arranged so that one valve opens only when the other valve is closed, so that undefined flow through both lines 1 and 3 is avoided. The test apparatus permits error-free determination of the test amount per unit time. No residues remain in the apparatus, and the individual parameters which are important for the test result can be determined exactly and simply.

Abstract: A mixing head essentially comprises a housing with a mixing chamber which has inlet orifices for the individual plastics components and an outlet orifice for the plastics component mixture. In the mixing chamber is located an expulsion plunger of identical cross-section, which plunger is connected to a working piston which can be actuated by a pressure medium, the plunger being movable to and fro between a mixing position, which leaves the inlet orifices open, and a position in the region of the front outlet orifice, in which it seals the inlet orifices from the mixing chamber. The mixing head moreover has a restrictor which can be pushed into and out of the mixing chamber by a pressure medium.

Abstract: When producing molded foam parts from liquid reaction components, the charge of gas in the initial components has a significant effect on the foam structure and quality of the molded part. This invention provides a process and apparatus for introducing a gas into at least one of the liquid reaction components prior to mixing said components for reaction. The component which is to be charged with gas is circulated from a feed tank through a recycle circuit to a compression zone which is maintained at a higher pressure than that of the feed tank. Said gas is admixed with said component at the point of initiation of the compression zone and the higher pressure is relieved through a throttle element prior to returning the gas-charged component to the feed tank. A finely divided stable gas dispersion which can be mixed with other components for reaction is obtained.

Abstract: A mixing apparatus for multi-component plastics, in particular polyurethane, possesses a mixing chamber (2) with inlet apertures (3) and (4) for the individual plastic components and an outlet aperture (8) for the mixture. In the mixing chamber, a control element (5), which has the same cross-section as the chamber and possesses overflow channels (6) and (7), can be moved to and fro for controlling the component streams. In order to avoid pressure peaks or pressure surges in the transport of the components when the control element passes from the closed position to the mixing position and vice versa, and to provide improved accuracy of metering, the inlet apertures in the inner wall of the mixing chamber, and the corresponding areas of the shell of the control element between its end face (13) and the overflow channels, are matched with one another with regard to their size.

Abstract: A mixing head for mutually reactive components, e.g. of a synthetic resin to be injected into a mold cavity, comprisess a control member which is shiftable in a mixing chamber opening into the mold cavity between a position in which mixing of the components can occur in this chamber and a position in which the member expels the mixture from the chamber and provides recirculating passages for the two components. A displacement body can be inserted into the chamber to control the mixing action by a fluid-operated actuator hydraulically coupled to a fluid displacement member shifted by the control member.

Abstract: A mold-handling apparatus in which a pair of mold carriers can be locked together for the molding process but, upon separation, each tilts through 45.degree. to afford improved access to the mold halves following a molding operation or before a molding operation. According to the invention, the upper mold carrier is swung about a fixed axis by a fluid-operated cylinder while another fluid-operated cylinder shifts a slider vertically to lower the pivot of the lower mold carrier and enable the latter to engage abutments which tilt the lower carrier.

Abstract: A packing for a piston-and-cylinder arrangement, especially for a dosing or metering unit for highly-filled reactive synthetic resin components such as a polyol or isocyanate, e.g. for producing polyurethanes, comprises a stack of yieldable rings of V-section with one member at an end of the stack bearing with a planar surface against a planar shoulder of the piston and the ring at the opposite end of the stack engaging a spring ring of V-section which confronts an abutment of the piston. According to the invention, the angle .alpha. between the two shanks of the V of the spring ring, in its unstressed state, is greater than the angle .gamma. between the flanks of the packing ring at this end of the stack which define the V of this packing ring. The arrangement is such that under stress the angle .alpha. can be reduced to a value less than the angle .gamma..

Abstract: A dosing unit for highly filled synthetic-resin components, usually a polyol and an isocyanate mixed with glass fiber, barite or chalk, comprises a piston which displaces the components or one of them, especially the filled component under the control of fluid pressure. The change in the feed rate of the fluid-controlled unit is varied by varying the speed of the displacing member of the fluid-controlled unit which is preferably a piston-and-cylinder arrangement. The piston-and-cylinder arrangement has its drive piston formed with a normal seal and its dosing or metering piston formed with an adjustable seal such that a tool can be inserted through the cylinder wall to rotate a toothed member of this latter piston to adjust for wear of its seal.

Abstract: A dosing unit for highly filled synthetic-resin components, usually a polyol and an isocyanate mixed with glass fiber, barite or chalk, comprises a piston which displaces the components or one of them, especially the filled component, under the control of fluid pressure. The change in the feed rate of the fluid-controlled unit is varied by varying the speed of the displacing member of the fluid-controlled unit which is preferably a piston-and-cylinder arrangement or a membrane or diaphragm-type displacement device.