GB2156440A

GB2156440A - Dispenser for meltable materials

Info

Publication number: GB2156440A
Application number: GB08405211A
Authority: GB
Inventors: David Martin Evans; Adrian Douglas Stokes
Original assignee: Henkel Loctite Ireland Ltd
Current assignee: Henkel Loctite Ireland Ltd
Priority date: 1984-02-29
Filing date: 1984-02-29
Publication date: 1985-10-09
Also published as: GB8405211D0

Abstract

The invention relates to a dispenser, particularly for hot melt adhesive, which is heated by catalytic combustion of a fuel. In one embodiment the dispenser comprises a barrel (1) accommodating the adhesive and provided with a nozzle (2). A combustion chamber (8) in heat exchange relationship with the barrel is supplied with fuel, e.g. isobutane, from a fuel chamber (5). A catalyst (11) is provided in the combustion chamber. Ignition means (14, 15, 16) are provided and the supply of fuel is controlled by a thermostat linked to a valve (10). In an alternative embodiment the combustion chamber (8) surrounds the barrel (1). <IMAGE>

Description

SPECIFICATION Dispenser This invention relates to a dispenser for meltable materials.

Many materials which are present initially in a solid form need to be heated, for example to above their melting point, prior to being dispensed. The most commonly used such materials are hot melt adhesives, sealants and fillers. At present such materials are generally dispensed by means of a dispenser which includes electric heating means. However, electric heating has the disadvantage that the dispenser cannot be used other than in close proximity to a supply of electricity. In addition, electric heating is relatively slow and electrically heated dispensers for hot melt adhesives may require several minutes to heat up before the adhesive can be used.

It is an object of the present invention to provide a dispenser for materials which need to be heated prior to being dispensed, in particular meltable materials, which does not require a source of electricity.

The present invention provides a dispenser for materials which need to be heated prior to being dispensed which includes heating means for the material to be dispensed wherein the heat is provided by the catalytic combustion of a fuel.

The dispenser according to the present invention will generally comprise a barrel for accommodating the material to be dispensed, which barrel is provided with a nozzle. A combustion chamber is provided in heat exchange relationship with the barrel, for example, adjacent to or surrounding the barrel. The combustion chamber is provided with a supply of fuel controlled by a valve and a catalyst for the combustion reaction of the fuel is located in the combustion chamber. The dispenser will generally also include a thermostat which is linked to the valve so that the supply of fuel to the combustion chamber is dependent on the temperature. An ignition device will generally also be required to initiate the combustion reaction.

The fuel is preferably a hydrocarbon which is gaseous under normal conditions but which can be readily liquified under pressure. Most preferably the fuel is isobutane. Any suitable catalyst for the combustion reaction of the fuel with oxygen may be used. The catalyst is preferably applied to a support such as mineral wool, e.g. silica wool. In the case where the fuel is isobutane, the catalyst is preferably a noble metal, more preferably a platinum group metal, most preferably platinum.

The material to be dispensed is accommodated in the barrel which is provided with a nozzle to assist dispensing. Preferably, the barrel and the nozzle are replaceable to enable the same dispenser to be used for dispensing different materials without risk of contamination of one material by another.

The nozzle will be of conventional design for most applications but for special applications, e.g.

where a particular profile is required for the material to be extruded, an appropriately shaped nozzle can be used. Use of a replaceable barrel and nozzle also allows the same dispenser to be used for extruding materials with different shaped profiles of the extrudate.

The combustion chamber is positioned so that heat generated therein is transferred to the material to be dispensed located in the barrel. Generally, the combustion chamber will either be positioned adjacent to or surrounding the barrel.

The dispenser according to the invention also includes a reservoir for fuel which will generally be refillable in the manner of a cigarette lighter. The temperature which is obtained in the combustion chamber depends on the amount of fuel supplied to the combustion chamber. The supply of fuel is controlled by a valve which is, in turn, controlled by a thermostat. Initially the valve will be fully open to allow rapid heating, however, as the material to be dispensed heats up to the desired temperature, the thermostat will close the valve to restrict the supply of fuel to the combustion chamber and thus merely maintain the required temperature. If the dispenser is intended to be used to dispense materials with different melting points, then a variable thermostat can be used and means can be provided for adjusting the temperature to be maintained.

Although the catalyst is capable of maintaining the combustion reaction once it is initiated, it will usually be necessary to provide ignition means in the combustion chamber to initiate the combustion reaction. For example, the ignition means can be a heating element, e.g. a platinum wire, connected to a battery and actuated by suitable means, e.g. a button on the outside of the dispenser. A small amount of catalyst may be provided adjacent tothe heating element to assist in initiating the reaction.

Oxygen is required for the combustion reaction and the combustion chamber must be provided with adequate access to the atmosphere to allow sufficient oxygen to be drawn in. initially, flow of the fuel from the reservoir to the combustion chamber will in turn draw oxygen into the combustion chamber from the atmosphere. Small amounts of exhaust gases need to be vented to the atmosphere but the amounts are minimal and only small vents are required. It is important that the fuel used be pure and, in particular, that it does not include any impurities which will reduce the life of the catalyst or lead to odorous combustion products.

The amount of heat produced in the combustion chamber depends on the amount of fuel supplied and the nature of the catalyst, in particular, the density of packing, the density of impregnation and the amount of catalyst. These features are adjusted in any particular case to ensure that the required temperature can easily be attained.

The dispenser according to the present invention has the advantage that it can be used at any desired location independent of a power source. In addition, catalytic heating is much faster than electrical heating. With electrical heating it is generally necessary for the dispenser to have a heavy body to retain heat. Since catalytic heating is so much faster than electrical heating the required amount of heat can be generated as and when required and, accordingly, the dispenser can be of simpler construction with the result that it is lighter and easier to use.

The invention will now be described in more detail with reference to the accompanying drawings in which: Figure 1 is a cross-section of a dispenser according to the invention in which the combustion chamber is adjacent to the barrel; and Figure 2 is a cross-section of an alternative embodiment of a dispenser according to the invention in which the combustion chamber surrounds the barrel.

As shown in Figure 1 the dispenser comprises a barrel 1 provided with a nozzle 2 and an end piug 4. The barrel is accommodated in a moulded body 3 which is attached to a fuel chamber 5 by means of screws 6. The fuel chamber is in the form of a moulding which also serves as a handle for the dispenser and is provided with a valve 7 for re-filling with fuel. The body also includes a combustion chamber 8 which is supplied with fuel by a fuel supply pipe 9. Supply of fuel from the fuel chamber 5 to the fuel supply pipe 9 is regulated by a valve 10.

The catalyst chamber is provided with a catalyst 11 retained in position by a fine mesh 18. The valve 10 is controlled by a thermostat (not shown) which is connected to the valve by a thermostat tube 12.

The supply of fuel is also controlled by an on/off switch in the form of a ring 13. When the switch is in the off position no fuel passes to the combustion chamber. When the switch is moved to the on position, fuel flows to the combustion chamber subject to the control by the thermostat by means of valve 10. Combustion is initiated by a heating element 14 in the form of a platinum wire. The platinum wire is heated by a battery 15 when actuated by a button 16.

Vents 17 are provided in the body of the dispenser to allow air to reach the combustion chamber and to allow venting of combustion products.

In Figure 2 the components are represented by like reference numerals except that the ignition device (14, 15. 16) and the vents (17) are not shown.

In Figure 2 the combustion chamber 8 surrounds the barrel. In addition, the on/off control 13 is in the form of a simple switch rather than a ring.

In both embodiments of the invention, the catalyst type and density, barrel wall thickness, thermostat characteristics and design of the vents are chosen to provide a temperature adapted to the melting point of the material to be dispensed. The temperature will generally be in the range of 180 to 9000C depending upon the material to be dispensed.

Claims

1. A dispenser for materials which need to be heated prior to being dispensed which includes heating means for the material to be dispensed characterised in that the heat is provided by the catalytic combustion of a fuel.

2. A dispenser as claimed in claim 1 which comprises a barrel for accommodating the material to be dispensed, the barrel being provided with a nozzle, a combustion chamber in heat exchange relationship with the barrel, a supply of fuel to the combustion chamber, and a catalyst for the combustion reaction of the fuel located in the combustion chamber.

3. A dispenser as claimed in claim 2, further comprising a thermostat which controls the supply of fuel to the combustion chamber by means of a valve.

4. A dispenser as claimed in claims 2 or 3, further comprising an ignition device in the combustion chamber, to initiate the combustion reaction.

5. A dispenser as claimed in any of claims 2 to 4, in which the catalyst is a platimum group metal applied to a support.

6. A dispenser as claimed in any of claims 2 to 5 which is adapted to use isobutane as the fuel.

7. A dispenser as claimed in any of claims 1 to 6 adapted to dispense a hot melt adhesive.

8. A dispenser substantially as herein described with particular reference to the accompanying drawings.