WO1991016139A1

WO1991016139A1 - Spray gun for applying foam, especially for filling hollow spaces in the automobile industry

Info

Publication number: WO1991016139A1
Application number: PCT/EP1991/000765
Authority: WO
Inventors: Mathias Pauls
Original assignee: Rathor Ag
Priority date: 1990-04-21
Filing date: 1991-04-20
Publication date: 1991-10-31
Also published as: ZA912934B; ATE118377T1; EP0478758A1; ES2068582T3; EP0478758B1; DE59104588D1

Abstract

The invention concerns a spray gun for the metered application of foam, especially for filling hollow spaces in the automobile industry, with an adapter component (2) connectable to a pressure vessel (3) for propellants and foaming agents and an operating lever (4) for releasing the foam, which has a metering chamber (8) to take a determined quantity of not yet fully expanded foam, a sealing component (12) which closes off the metering chamber (8) on the adapter side and is connected to an operating lever (4) via a control component (13), and a closing device (14) which closes off the spray gun on the nozzle side when the sealing component (12) is open and is connected via the control device (13) to the operating lever (4) so as to be operable in synchronism with the sealing component (12).

Description

Spray gun for applying foam, in particular for foaming cavities in the automotive industry

description

The invention relates to a spray gun for the metered application of foam, in particular for foaming cavities in the automotive industry, with an adapter part for a pressure vessel for blowing agents and foaming agents and an actuating lever for releasing the foam.

The invention relates in particular to a spray gun with which plastic foams, in particular one-component and two-component polyurethane foams, are brought out of a pressure container at their place of use with the aid of a blowing agent. The pressure vessel contains the foam components and the blowing agent, which is generally liquefied and correspondingly gasifies when there is a sufficient pressure drop, as a result of which the foam-forming component is foamed. The foam hardens more or less quickly when it comes into contact with a crosslinking agent, which in the case of one-component foams is air-neutral and is added in the form of a second component in the form of a second component, more or less quickly. The pressure vessels are subject to safety standards, which on the one hand ensure the safe containment of the foam components and the blowing agent and on the other hand the safe connection via suitable adapters to commercially available foaming devices.

The foams produced in this way are used as construction materials. They serve different purposes. When building, for example, frames can be sealed or cavities be sealed moisture-proof. Most foams of this type are therefore adjusted in such a way that they finally cure using the atmospheric humidity and only require little time for this process.

Plastic foams, especially polyurethane foams, are increasingly used in automotive engineering. Special attention should be paid to the foaming of hollow parts to prevent corrosion. Other areas of application are noise and thermal insulation and the protection of sensitive parts against mechanical injury. In the area of noise protection measures, there has recently been an increasing tendency to foam or foam into hollow profiles in order to dampen air vibrations. Such hollow profiles are contained in many places in self-supporting vehicle bodies, as are used in modern automobile construction. They are created by folding and rolling the sheet metal parts where the body is to be given additional stiffening. The design of the roof, which is said to have roll resistance, is particularly problematic. It has been shown that the rear roof rail is particularly susceptible to air vibrations, the damping of which is desirable.

The simplest way to dampen air vibrations in hollow profiles is to either completely foam these hollow profiles or to foam them at their ends with a sufficient amount of foam for this purpose. Already by foaming the ends, the exchange of air with the environment is effectively prevented - which at the same time leads to effective corrosion protection - and air vibrations are largely eliminated. Since the foaming at the ends of a material and weight brings moderate savings, it is preferred over the full foaming.

The problem here is the exact dosage of the foaming agent. While an overdosing has no negative consequences in addition to the waste of material, an underdosing leads to insufficient vibration damping and thus to a failure to achieve the intended effect. Underdosing, however, can hardly be avoided with conventional foaming processes, since the metering mechanisms do not work with the necessary reliability. Two effects play a role here.

On the one hand, the foaming agent is supplied in the form of a prepolymer provided with a blowing agent, which is under pressure. In the event of irregularities in the pressure or a decrease in the propellant gas pressure in the storage container, the amount of foam applied in the unit of time changes, which brings about a breakdown of the insulation effect when the critical amount is undershot. On the other hand, all foaming agents used in conventional automotive technology have a tendency to premature polymerization even in the spraying or dosing device. As a result, the time switching and switching mechanisms are changed to such an extent that the result is a slow decrease in the amount of foam over the operating life of the device. Cleaning these mechanisms is time-consuming and costly.

The object of the invention is therefore to provide a spraying device with which a reliable metering of foam for the foaming and foaming of cavities is possible. This device should in particular be insensitive to premature polymerization of the foaming agent or one largely preclude such premature polymerization.

This object is achieved with a spray gun of the type described at the outset, which has a metering chamber for receiving a defined amount of foam-forming agent or foam which has not yet fully expanded, a sealing element which closes the metering chamber on the adapter side and is connected to the actuating lever via a control element , and a closure element, which closes the spray gun when the sealing element is open on the mouthpiece side and is connected via the control element to the actuating lever which can be actuated synchronously with the sealing element.

The invention also relates to the use of this spray gun for foaming or foaming hollow profiles.

The invention furthermore relates to a method for metering foam, in particular for dispensing metered amounts of foam for closing the ends of hollow profiles in automobile construction, in which a defined amount of a mixture of blowing agent and foaming agent is introduced into a metering chamber of predetermined volume and if necessary, pre-expanded and the amount of foam that is introduced and optionally pre-expanded is then released using the remaining driving force of the blowing agent and complete expansion.

Preferred embodiments and modes of operation are the subject of the dependent claims.

The foaming agents used according to the invention are generally customary polyurethane prepolymers for one-component foams, which with the help a propellant can be applied from a pressure can. These prepolymers cure in a short time in the presence of water, which is generally provided by the moisture contained in the air. However, conventional two-component polyurethane foams can also be used, in which the polyurethane prepolymer is brought together with a compound containing hardener, as a rule a polyol, amino alcohol or polyamine, immediately before use, and thus after a short time hardens. Transitional forms from one-component to two-component foams are furthermore suitable, in which an amount of hardener which is not sufficient for complete curing is used and the complete curing takes place via air humidity.

Conventional fully and partially halogenated hydrocarbons, such as those used in foam technology, are suitable as blowing agents for the two-component and one-component foams mentioned above. Low-boiling hydrocarbons or hydrocarbon mixtures, for example propane and / or butane, can also be used. These hydrocarbon-containing blowing agents are also known to the person skilled in the art.

According to the invention, it is possible to introduce reliably metered amounts into cavities and in this way, for example, to foam or to foam hollow beams in automobile construction. The spray guns can be handled on the one hand as homogeneous units that are used in different locations, but they can also be installed as automatic machines and can thus be used on production lines in series production. Although they are particularly suitable for the automotive industry, their application is not restricted to this area of application. limits; They can be used in all areas in which cavities or hollow profiles have to be filled with a precisely metered amount of foam. B. in mechanical engineering, and in construction as well as in refrigeration and air conditioning.

According to the invention, the mixture of foaming agent and blowing agent is first led out of the pressure bottle via an adapter into a dosing chamber of a defined volume. This metering chamber is sealed off from the outside, so it fills up to the pressure equalization with the mixture of blowing agent and foaming agent, so that a pre-expansion may occur. After completion of the filling process, the opening through which the mixture is supplied is blocked and the metering chamber is opened to the outside, so that the possibly pre-expanded mixture can escape from the metering chamber into the object to be foamed or foamed under the residual pressure of the propellant contained therein. The driving pressure in the pre-expanded mixture is so high that the practically complete emptying of the metering chamber is ensured. After their emptying, the outlet opening is closed again and the feed opening for a new mixture of propellant gas and foaming agent is opened synchronously with it. In this way, a precisely defined amount of the mixture is pre-expanded in each cycle and taken to the location to be provided with foam.

The closure of the outlet opening largely prevents the entry of air humidity and thus the premature polymerization. The pressure built up internally and the expulsion of the pre-expanded mixture also have a corresponding effect. By suitable selection of the metering chamber volume, it is possible to meter the amount of foam released in such a way that it corresponds to the requirements.

The spray gun according to the invention which is suitable for carrying out this method is explained in more detail below with reference to the attached figures, which represent preferred embodiments. From these pictures show:

Figure 1 Fig.l a conventional spray gun for dispensing polyurethane foam with a pressure vessel attached.

2 shows a spray gun according to the invention with an attached metering chamber;

3 shows a section through the discharge tube and metering chamber of the spray gun according to the invention as shown in FIG. 2 with the metering chamber open;

4 shows a section through the discharge pipe and metering chamber of the spray gun according to the invention as shown in FIG. 2 with the metering chamber closed and the discharge pipe open;

5 shows a section through the discharge tube and metering chamber of a further embodiment of the spray gun according to the invention; and

6 shows a third embodiment of the spray gun according to the invention.

Fig. 1 shows a conventional spray gun, such as for applying polyurethane foam from a Pressure bottle is used and the starting point for the invention. An adapter (2) is located on a spray gun body (1), via which the pressure vessel (3) for the mixture of prepolymer and propellant gas is connected to the spray gun. A trigger (4) serves to actuate the spray gun and an adjusting screw (5) regulates the amount of foam or secures the gun when not in use. The foam produced is brought to the place of use via a spacer or discharge pipe (6) through an opening (7). Such a spray gun is described, for example, in German utility model G 83 04 005.6.

FIG. 2 shows the spray gun from FIG. 1 in a form modified according to the invention. The metering chamber (8) is screwed to the spray gun body (1) with the adapter part (2), the pressure vessel (3), the trigger (4) and the adjusting screw (5), on which the spacer tube is in turn attached (6) with the mouth (7). The dosing chamber (8) has a cylindrical shape and a defined volume; it is sealed both to the spray gun body and to the outside by sealing elements which can be actuated synchronously. The sealing elements are actuated synchronously by the trigger lever (4) via a control element, in the rest position the spray gun is closed to the outside and the metering chamber is open on the adapter side and when the lever (4) is actuated the metering chamber is closed and the outlet opening (7 ) is released synchronously.

Fig. 3 shows a section through the metering chamber and discharge tube of a spray gun according to the invention. The spray gun body (1) is followed by the metering chamber (8) in which the mixture of foam pre-expanded formers and blowing agents. The dosing chamber (8) merges into the discharge or spacer tube (6), which ends in the mouthpiece (7) with the discharge nozzle (9).

The metering chamber (8) is connected to the spray gun body (1) by a screw connection (16). The tightness is ensured by a seal (18), for example an O-ring. The metering chamber (8) can be detached from the spray gun body (1) via the screw connection (16), for example for cleaning or maintenance or to replace it with a metering chamber of a different volume. Like the dosing chamber (8) in the gun body (1), the mouthpiece (7) is screwed into the discharge tube (6) so that it can be replaced.

A feed channel (11) for the blowing agent / prepolymer mixture runs inside the spray gun body (1) and opens into the metering chamber (8), which in turn merges into the outflow channel (10) to the outlet opening. Inside the channels (10) and (11) and the chamber (8) there is a control element in the form of a control rod (13) which is connected in a conventional manner to the actuating or trigger lever (4). The control element (13) is arranged concentrically in the chamber and in the channels. It ends in a closure element (14) which is seated in the nozzle cone (15) of the nozzle element (9).

At the end of the metering chamber (8) on the adapter or valve side, a sealing element (12) is arranged concentrically around the control rod (13), which seals the feed channel (11) against the metering chamber (8) when the trigger valve (4) is actuated and which Blocking of blowing agent / prepolymer mixture. This sealing element preferably consists of a piston or cone, which is seated at the mouth edges of the channel (11). Further measures for sealing can be taken on the sealing element or its seat on the gun body (1), for example the arrangement of elastic sealing elements, etc. To improve the sealing effect, spring elements can be present which seal the sealing element (12) press against its seat.

Fig. 3 shows the closure body (14) and the sealing element (12) with the trigger cock (4) relaxed. In this case, the conical end of the closure element (14) seals the discharge channel (10) and the metering chamber (8) from the outside against the nozzle cone (15). In this state, the sealing element (12) releases the metering chamber (8) against the feed channel (11).

If the trigger lever (4) is now actuated, the sealing element (12) closes the trigger chamber (8) against the feed channel (11), while the closure element (14) releases the opening of the nozzle (9), so that pre-expanded mixture located in the chamber (8) can escape.

Of course, it is also possible to arrange the closure element (14) at the outlet opening of the chamber (8), so that the discharge or spacer tube is open to the outside. However, since this enables the unhindered entry of air and air humidity into the outlet channel (10), which in turn leads to its slow polymerization, such an arrangement is not preferred.

FIG. 4 shows the section according to FIG. 3 in a state in which the mouthpiece (7) is removed from the closure element (14) is released and at the same time the feed channel (11) is separated from the chamber (8) by the sealing element (12). This is the case when the trigger (4) is actuated. In the state shown, the blowing agent / prepolymer mixture flowing in from the pressure container (3) accumulates in the channel (11) in front of the sealing element (12), while at the same time the pre-expanded mixture located in the chamber under its residual pressure through the outlet channel (10) and the mouthpiece (7) flows out.

5 shows a section through the metering chamber and the outlet pipe of a further embodiment of the invention. In this embodiment, the dosing chamber (8) is partially integrated in the gun body (1); the screw connection (16) and the seal (18) connect a rear chamber part (19) to a front chamber part (20), which together form the dosing chamber (8). The volume of the metering chamber (8) can be varied by appropriately enlarging or reducing the size of the front chamber part (20); in extreme cases, the volume of the metering chamber (8) can be drastically reduced by omitting the front chamber part (20) and forming a direct transition to the spacer tube (6).

Fig. 6 shows a third embodiment in which the discharge or spacer tube (6) is connected to the metering chamber (8) via a screw connection (17). In this way, the discharge tube can be easily replaced.

The control element (13) with the closure element (14) and the sealing element (12) can be regarded as a normal extension of the usual closure control of a spray gun. Accordingly, it is possible by constructive familiar to the expert Measures to modify a conventional spray gun, as shown in FIG. 1, by switching on a metering chamber (8) and correspondingly extending and equipping the control rod according to the invention.

As already shown, the spray gun according to the invention can be used with particular advantage for foaming the ends of hollow profiles in automobile construction. The process according to the invention for foaming hollow profiles has proven to be particularly suitable for reliably foaming hollow profiles at the ends, so that effective damping of air vibrations is possible.

Claims

1. Spray gun for the metered application of foam, in particular for foaming cavities in the automotive industry, with an adapter part (2) for connecting a pressure vessel (3) for blowing agent and foaming agent and an actuating lever (4) for releasing the foam, characterized by a metering chamber (8) for receiving a defined amount of foam-forming agent or foam that has not yet been fully expanded, a sealing element (12) which closes the metering chamber (8) on the adapter side and is connected to the actuating lever (4) via a control element (13) and a closure element (14) which closes the spray gun on the mouthpiece side when the sealing element (12) is open and is operably connected via the control element (13) to the actuating lever (4) in synchronism with the sealing element (12).

2. Spray gun according to claim 1, characterized gekennzeich¬ net that the metering chamber (8) is arranged in the region of the transition from the gun body (1) to the spacer tube (6).

3. Spray gun according to claim 1 or 2, characterized in that the control element (13) is an axially in the tube (6) of the spray gun and in the metering chamber (8) extending control rod.

4. Spray gun according to claim 3, characterized gekennzeich¬ net that the sealing element (12) in the metering chamber

(8) at the valve-side opening is arranged concentrically around the control rod (13).

5. Spray gun according to claim 4, characterized gekennzeich¬ net that the sealing element (12) is a piston with a conical end or a cone, seated on the tube (6) of the spray gun.

6. Spray gun according to claim 5, characterized gekennzeich¬ net that the sealing element (12) is a cone with an O-ring.

7. Spray gun according to one of claims 3 to 6, da¬ characterized in that the end of the control rod (13) also forms the closure element (14) for the mouthpiece (7), the nozzle cone (15) of the mouthpiece (7) as Seat serves.

8. Spray gun according to one of claims 2 to 7, characterized in that the metering chamber (8) and / or the spacer tube (6) via a connection (16, 17) is detachably connected to the spray gun body (1).

9. Spray gun according to claim 8, characterized gekennzeich¬ net that the connection is a screw or

Bayonet connection is.

10. Spray gun according to one of claims 1 to 9, characterized in that the metering chamber (8) is variable in volume.

11. A method for dosing foam, in particular for dispensing metered amounts of foam for closing the ends of hollow profiles in automobile construction, characterized in that a defined amount of a mixture of blowing agent and foaming agent is introduced into a metering chamber of predetermined volume and, if necessary, pre-expanded and the introduced or pre-expanded The amount of foaming agent then using the remaining driving force of the Propellant and full expansion is released.

12. The method according to claim 11, characterized in that the delivery of blowing agent and foaming agent is blocked in the metering chamber when the introduced and optionally pre-expanded foam is released.

13. The method according to claim 11 or 12, characterized gekenn¬ characterized in that the dosing chamber is closed to the outside in the introductory and pre-expansion phase.

14. Use of the spray gun according to one of claims 1 to 13 for foaming or foaming hollow profiles.

15. Use according to claim 14 for foaming hollow profiles in automobile construction, in particular for damping air vibrations.