DE3120974C2 - Device for filling cavities with aminoplast foam - Google Patents

Abstract

Method for filling cavities with aminoplast foam, in which a urea resin solution and a hardener solution are pumped through separate hose lines to the place where the foam is formed, and the foam is formed in a spray head by combining the urea resin solution and the hardener solution under the action of compressed air, in which the resin component solution and the hardener solution are pumped by metering pumps and the control of the liquid quantities transported in the transport hoses is carried out in such a way that if the pressure curve in just one line is uncontrolled, the pump motor is switched off by a relay until the pressure fluctuation has been eliminated. A device for carrying out the method is also shown.

Description

The invention relates to a device for filling cavities with aminoplast foam according to the preamble of the patent claim.

Such a device is known from DE-OS 29 36 223.

Aminoplast foams, especially urea-formaldehyde foams, are used to fill cavities, especially in construction. Urea solutions and hardener solutions are pumped in portable containers via hoses using displacement pumps to the location where the foam is to be produced, for example cavities such as shafts, pipelines, cable shafts, ventilation systems, heating ducts and the like, and are then foamed directly into the cavity to be filled using a foaming or spray nozzle and compressed air.

Urea-formaldehyde foams are described below as representative of all other aminoplast foams.

In the known method of filling cavities with aminoplast foam, the quality of the foam is checked, i.e. quality control, by adding a color concentrate to a component that gives the foam a certain color. If this component is dosed too heavily or too weakly, the foam will be dark or lighter in color. This can then be recognized by the worker operating the spray head and remedied if necessary, e.g. by cleaning the corresponding nozzle. However, this is only a purely visual quality control, which is particularly difficult to carry out or fails when cavities that are difficult to control are to be filled with foam. Although it is possible to determine by taking samples after hardening whether the urea-formaldehyde foam produced on site in the cavity meets the quality standard, the subsequent determination that this standard may not have been met means that the incorrect foaming must be removed, which is often difficult due to the poor accessibility of the cavities. In addition, this means a considerable additional expenditure on labour and materials and therefore ultimately an expense that the foam producer must factor in in advance when setting the price.

Another difficulty is calculating the foam volume, which serves as the basis for billing. The cavities to be foamed are often branched and their contents cannot be determined precisely. The calculations are therefore inaccurate. Billing that measures the consumption of urea resin and hardener solution also leads to inaccurate results because these solutions are in tanks where consumption can usually only be determined using a dipstick. The difference in the height of the liquid level is determined, and consumption can be calculated from this and from the area of the tank.

However, since the base area of the container is relatively large due to the required capacity, even a small difference in height means a relatively high consumption of components. An accurate measurement using the dipstick is not possible. In addition, an inclination of the containers, which are usually mounted on a small truck, can cause significant measurement errors.

Neither the foam volumes nor the material consumption measured by soundings therefore represent reliable data for costs and thus for invoicing.

When billing the customer, the foam producer must therefore rely on experience, which can be calculated from the average consumption for foaming cavities of a certain size. For normal foaming work, the measurement is usually the basis for billing. The theoretical cavity size is determined and the calculated foam volume can then be multiplied by a cubic meter price to determine the invoice amount.

However, the foam volume, which is decisive for billing, also depends to a large extent on the temperature at the foaming point. At different temperatures, this can result in different consumption of raw materials to produce the same volume of foam. This is because the foam volume is not proportional to the consumption of raw materials at fluctuating temperatures.

A more precise determination of consumption would of course be possible by installing flow meters downstream of the pump flow. However, problems exist not only with regard to the exact measurement of consumption, but also with regard to quality control, whereby this quality control should not be carried out on the finished foam, but rather during the foaming process.

From the aforementioned DE-OS 29 36 223, a device for producing a reaction mixture from flowable, foam- or solid-forming components is known. The known device has a storage container for each component, from which a supply line to a common mixing head A metering pump is arranged in the feed line. Furthermore, bypass lines branching off from the feed line and leading back to the respective container are provided, each of which has a throttle valve that can be operated via a pulse line. The known device for foaming cavities is intended in particular for the production of molded parts in molds, i.e. for the production of solid foam products with a specific shape. In order for such a foam product to have reproducible, uniform properties, it is important to ensure automatic regulation and monitoring of the throughput quantities during injection into the cavity at predetermined pressures.

Starting from the known device according to the preamble of the patent claim, the object of the invention is to provide a device for foaming cavities with aminoplast foam based on a urea resin solution and a hardener solution, which enables not only an exact consumption control of the raw materials used but also an exact quality control during foam formation.

This object is achieved according to the invention in that the two metering pumps can be driven by a single motor and a pulsation damper is connected downstream of each of them, that in addition to the throttle valve, a pressure relief valve and a contact manometer are installed in each of the bypass lines, and that the two throttle valves and the two contact manometers are connected to a delay relay which is connected to a time switch and to the motor of the metering pumps, whereby the delay relay can be actuated by the respective contact manometer to switch off the time switch and the motor when only one pressure relief valve is opened when the throttle valve is closed, and by both contact manometers to switch off the time switch and open both throttle valves when both pressure relief valves are opened.

The device according to the invention thus enables precise control of the materials used, regardless of the size of the cavities to be foamed. However, exact quality control is also possible because, in the event of an unplanned pressure curve, foam formation is interrupted by stopping the supply of the solution containing the reactants to the spray head, thus preventing the production of faulty or inferior foam.

The invention is explained by an embodiment with reference to the drawing, in which the electrical connections are shown in dashed lines.

The dosing pumps 2 and 3 , driven by the motor 1, are installed above the containers for the components (I) and (II) (component (I) resin component, component (II) hardener solution). The components (I) and (II) are sucked in. Pulsation dampers 4 and 5 are connected downstream of the pumps.

The hose lines to the spray head and a bypass line branch off from the pulsation dampers. The pressure relief valves 6 , which function as check valves, the contact pressure gauges 7 and the throttle valves 8 are installed in the bypass lines, which are returned to the respective component container.

For example, when the required working pressure is 9 bar, the pressure relief valves 6 are set to 10 bar and ensure that the entire delivery rate is fed to the spray head. If there is dirt in a nozzle, pressure builds up in the corresponding line, the pressure relief valve opens and, as a result of the downstream closed solenoid valve, pressure builds up in the bypass, which is registered by the contact manometer. The manometer sends an electrical pulse to the delay relay 9 , which waits to see whether the same pulse comes from the contact manometer in the second circuit. Since this pulse does not normally come when only one nozzle is blocked, the delay relay switches off the timer 10 and the pump motor 1. The error can now be rectified (in most cases this involves cleaning the nozzle) before foaming is resumed.

However, if both spray head valves are closed, meaning that foaming is intentionally interrupted, pressure builds up in both bypass lines and both contact pressure gauges send their pulses to the delay relay 9 . This switches off the timer 10 and opens the throttle valves 8 so that the components are now pumped around the circuit and circulated at the same time. When foaming is resumed by opening the valves on the spray head, the bypass lines are depressurized and the contact pressure gauges send a second pulse, which triggers the closing of the throttle valves 8 and the switching on of the timer 10 .

Since the dosing pumps deliver exactly the same amount of material per unit of time, the timer can be calibrated to measure quantities. To do this, simply multiply "time · delivery rate/time unit".

Claims (1)

Device for filling cavities with aminoplast foam, each with a container for a urea resin solution and a hardener solution, which is connected to a spray head via a feed line in which a metering pump is arranged, and each with a bypass line branching off from the feed line and leading back to the respective container, in which a throttle valve actuable via a pulse line is arranged, characterized in that the two metering pumps (2, 3) can be driven by a single motor ( 1 ) and a pulsation damper ( 4, 5 ) is connected downstream of each of them, that in addition to the throttle valve ( 8 ), a pressure relief valve ( 6 ) and a contact manometer ( 7 ) are each installed in the bypass lines, and that the two throttle valves ( 8 ) and the two contact manometers ( 7 ) are connected to a delay relay ( 9 ) which is connected to a time switch ( 10 ) and to the motor ( 1 ). the dosing pumps ( 2, 3 ) are connected, wherein the delay relay ( 9 ) can be actuated by the respective contact manometer ( 7 ) when only one pressure relief valve ( 6 ) is opened and the throttle valve ( 8 ) is closed, in order to switch off the timer ( 10 ) and the motor ( 1 ), and by both contact manometers ( 7 ) when both pressure relief valves ( 6 ) are opened, in order to switch off the timer ( 10 ) and open both throttle valves ( 8 ).