GB2066940A - Hot-air gun - Google Patents

Abstract

A hot-air gun for use in the shrink- wrapping of plastics material comprises a burner portion having a cowl (11) and a handle portion (12), the handle portion carrying all of the remaining working parts of the gun. Such arrangement provides balance and safety and allows the use of two hands should the operator so desire. <IMAGE>

Description

SPECIFICATION Hot-air gun The present invention relates to a hot-air gun for use in connection with the shrink-wrapping of plastics material, preferably polythene. More particularly, the present invention relates to a hand-held, gasfired hot-air gun, capable of projecting hot-air in large enough volume to bring polythene sheet material to a sufficiently high temperature to cause the polythene to shrink and thereby seal any goods over which it is placed, into a tight and secure package.

In general, hot-air guns comprise a burner portion including a cowl, means for supplying fuel gas to the gun, means for mixing the fuel gas with air, means for feeding the gas-air mixture to the burner portion, means for igniting the gas-air mixture and handle means for holding the gun.

Many prior art hot-air guns hve primarily been concerned with the burner portion of the gun. In many instances, the construction of such burners is extremely complicated and same are difficult to maintain and require the use of specialised tools.

Furthermore, the majority of hot-air guns at present in use are of a substantial weight thereby making it difficult for an operator to use same over long periods without fatigue.

It is an object of the present invention to provide an improved hot-air gun, for use in the shrinkwrapping of plastics material, which at least minimises the disadvantages of prior art guns mentioned above.

We have unexpectedly discovered that an improved hot-air gun can be provided whereby the handle portion, contrary to previous ideas of a unit which just fits the hand of the operator, is constructed to house all of the working parts of the gun, with the exception of the burners and the cowl therefor, in such a way as to give balance, safety and to allow the use of two hands should the operator so desire.

According to the present invention there is provided a hot-air gun for use in the shrink-wrapping of plastics material, said gun comprising a burner portion and a handle portion, the handle portion extending from the burner portion and the handle portion carrying all of the remaining working parts of the gun.

In accordance with an embodiment of the invention, the handle portion comprises an elongate rectilinear member carrying a trigger member and housing a gas control valve and an ignition device. In order to provide balancing of the weight of the cowl and burners, the handle portion is much longer than that previously used thereby enabling the gas control valve and the ignition device to be fitted in the end region remote from the end connected to the burner portion. The operating hand grip is located between the control valve and ignition device and the end of the handle connected to the burner portion. Such arrangement brings the centre of gravity of the gun into the region of the hand grip and thereby removes the unstable effect experienced in prior art hot-air guns due to the top-heavy nature thereof.Furthermore, utilising an elongate handle in accordance with the invention allows the operator to utilise two hands for holding the gun.

In a further embodiment of the present invention, the handle portion is removably connected to the burner portion which thereby enables simple interchange of handles if necessary. Moreover, the working parts located in the handle can be removed therefrom, thereby enabling the handle portion and working parts carried therein to be easily maintained. The gas control valve and the ignition device can be of any desired form known in the art. For safety reasons, the operating hand-grip is in the form of a "deadmans handle" whereby removal of pressure from such grip automatically causes the gas supply to be stopped. Thus, it is not possible for the gun to operate when the operating grip is not actuated.

The burner portion of the gun preferably comprises one or more gas jets and an associated number of burners. The burner portion, in order to comply with British Standards, is provided with a cowl therefor.

Each burner is preferably formed from a tube, into which another tube having expanded ends has been forced, so that it fits tightly and will not easily fall out, but at the same time it being possible to move such other tube along the inside of the burner tube in order to give a restricted area at different distances along the inside of the burner tube. This restricted area causes the gas, which is injected into the burner from the jet, to speed up, thereby reducing the pressure and thereby causes a pulling-in of air at the base of the burner tube through holes or slots provided therein. Such holes or slots can be restricted by varying amounts, by utilising a sleeve arrangement which may be slid up and down the outside of the burner tube and tightened in position.

Any number of these burners can be screwed on to a gas duct containing removable jets, thereby making easy change of jets and burners possible particularly when using different thicknesses of plastics material, thereby saving energy.

The igniter is generally located at the end of the tube and the volume of the gas-air mixture passing through each burner tube is controlled to ensure ignition will take place.

It is also within the scope of the present invention to provide a hot-air gun of the type referred to above wherein the handle portion is extendible for utilising same when applying heat to plastics material located at a distance above which the operator can reach.

In one embodiment of the invention, the elongate handle has a linkage which is connected at one end to the operating handle portion and at the other end to the igniter device and the gas-control valve. In a further embodiment, such linkage can be dispensed with and instead the operating grip will act directly on the ignition device and the gas control valve.

The handle portion is made as light as possible and is generally formed of stainless steel. One or more vents may be provided in the handle in order to improve the lightweight nature thereof.

The present invention will be further illustrated by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a hot-air gun in accordance with the invention; Figure 2 is a schematic view on an enlarged scale of the handle portion of the device of the invention.

Figure 3 illustrates the operation of the igniter and the gas control devices; Figure 4 illustrates an exploded view of the burner portion of the device, and showing various types of burner arrangements which may be used, and Figures 5, 6 and 7 illustrate modified arrangements for the safe operation of the gas control valve.

Like reference numerals have been utilised to denote identical parts in the Figures.

As illustrated, the gun in accordance with the invention comprises a burner portion having a cowl 11 and a handle portion 12 extending from the burner portion and being connected thereto via bracket 13. Such arrangement enables the handle portion 12 to be detachably connected to the burner portion 11. All working parts may be maintained by unskilled people, no special tools are required, few parts are necessary and maintenance is simple. The handle 12 carries an operating hand grip 14, which operates on the deadmans handle principle. Gas is supplied to the gun from a suitable pressurised source via pipe 15 and the ignition device and the gas control valve are located in the region 16 of the handle portion 12.Vents 17 are provided in the handle portion to reduce the weight thereof. Twill be noted from Figure 1, that the handle can easily be gripped with one or two hands by the operator.

In Figure 2, the handle portion 12 is shown having the operating hand grip 14 removed therefrom.

Again, the ignition device and the gas control valve would be located in the region 16 of the handle portion 12. The location of the vents 17 is shown more clearly in this Figure.

Figure 3 shows the arrangement regarding operation of the ignition device and the gas control valve.

The operating grip handle will be connected to linkage 31 which, in turn, is connected to bell crank lever 35. Operation of the hand grip causes the linkage 31 to act on the lever 35 thereby causing depression of members 36 and 37 to cause operation of the ignition device 32 and to actuate the control valve 33 to permit flow of gas from supply pipe 15 to pipe 34 to transmit the gas to the burner portion.

Figure 4 illustrates a suitable burner arrangement comprising a main gas duct 41 for supplying gas to a plurality of jets 42, 42', 42".... Screwed onto each gas jet is a burner in the form of a tube 43. Various types of burners are illustrated, referenced 43', 43"... Into each tube is fitted an insert in the form of another tube 45 having expanded ends 46. Such arrangement means that the insert 45 can be located in the burner tube 43 and can be drifted each way to give a resistricted area, at different distances along the inside of the burner tube.This restricted area causes the gas which is projected into the burner tube from a jet to speed up thereby reducing the pressure and thus pulling in air at the base ofthe burnertube through holes or slots 44,44', 44"... These slots or holes can be restricted by varying amounts by the provision of a sleeve 47 which is slid up and down the outside of the burner tube and tightened in position. Any number of the burner tubes 43,43', 43"... can be screwed onto gas duct 41 containing removal jets 42,42', 42", making easy change of jets and burners possible, for example when required using different thicknesses of polythene, thereby saving energy.

The cowl is of any conventional shape to prevent accidental passage of the operator's hand into the burner region. In order to cool down the gun in the region of the burners, the cowl is preferably provided with a plurality of perforations.

As illustrated in Figures 5, 6 and 7 three different gas control valve arrangements are shown wherein gas enters through the supply pipe and upon compression of the spring, by actuation of the hand grip, gas is allowed to pass into the outlet tube.

Due to the preferred arrangement of the gun having a plurality of burners which are easily changed or adjusted, the correct amount of hot air is supplied which is needed to shrink, melt or soften plastics materials or for the burning off of paint etc., using the minimum amount of energy.

The ignition device will preferably comprise a conventional and simple operating piezo crystal.

It will thus be seen that the gun in accordance with the present invention provides many significant advantages over the prior art guns and complies with all safety requirements.

It will thus be seen that the hot-air gun in accordance with the invention possesses the following important features: 1. Safety - the use of a deadmans handle, selfignition caused by actuation of the handle and the provision of a large cowl covering the burners together with the utilisation of a specially constructed gas valve as illustrated in Figure 5, ensures that there is no chance of gas unintentionally reaching the burner.

2. Lightweight-the handle portion is preferably formed of stainless steel to give light strength and the gas-control valve and piezo crystal are mounted into the rear end of the handle to give the necessary balance.

3. Ease of use - the gun of the invention is the only hot-air gun on the market which can be used with one or two hands and thereby prevent the operator suffering fatigue when using the gun for long periods.

4. Easy maintenance - by removal of appropriate screws and nuts, the handle can be disconnected from the burner portion by an unskilled operator.

Moreover, simple change of the crystal will rectify the ignition device and the remaining parts, which are few in number, require no special tools for their operation.

5. Low cost- due to the location of the working parts in the handle portion, together with the handle portion being formed of lightweight material, the gun can be produced at low cost and thereby be within the financial reach of small businesses.

6. Energysaving - the exchange of jets and burners allows the correct amount of hot air to be utilised for shrinking different thicknesses of polythene, thus saving energy and avoiding burning of holes through the polythene film.

It will thus be seen that the hot-air gun in accordance with the present invention has many advantages over the prior art guns and due to the centre of gravity being moved to be in the region of the grip portion, the gun is much easier to hold and can be operated utilising two hands if desired.

Claims (15)

1. A hot-air gun for use in the shrink-wrapping of plastics material, said gun comprising a burner portion and a handle portion, the handle portion extending from the burner portion and the handle portion carrying all of the remaining working parts of the gun.

2. A hot-air gun as claimed in claim 1, in which the handle portion comprises an elongate rectilinear member carrying an operating hand-grip in the form of a trigger member and housing a gas control valve and an ignition device.

3. A hot-air gun as claimed in claim 2, in which the gas control valve and the ignition device are fitted in the end region remote from the end connected to the burner portion.

4. A hot-air gun as claimed in claim 3, in which the operating hand-grip is located between the control valve and ignition device and the end of the handle connected to the burner portion.

5. A hot-air gun as claimed in any one of claims 2,3 and 4, in which the operating hand-grip is in the form of a "deadmans handle".

6. A hot-air gun as claimed in any preceding claim, in which the handle portion is removably connected to the burner portion.

7. A hot-air gun as claimed in any preceding claim, in which the burner portion is provided with a protective cowl and comprises one or more gas jets and an associated number of burners.

8. A hot-air gun as claimed in claim 7, in which each burner if formed from a tube into which another tube having expanded ends has been forced, so that it fits tightly into the burner tube but at the same time it being possible to move such tube along the inside of the burner tube.

9 A hot-air gun as claimed in claim 9, in which each burner tube has one or more holes or slots provided in the base region thereof.

1Q A hot-air gun as claimed in claim 9, in which the opening provided by such holes or slots is restricted by utilising a sleeve arrangement which may be slid up and down the outside of each burner tube and tightened in position.

11. A hot-air gun as claimed in any preceding claim, in which the handle portion is extendable.

12. A hot-air gun as claimed in any one of claims 2,3 or 4, in which the elongate handle has a linkage which is connected at one end to the operating handle portion and at the other end to the igniter device and a gas control valve.

13. A hot-air gun as claimed in any preceding claim, in which the handle portion is formed of stainless steel.

14. A hot-air gun as claimed in any preceding claim, in which one or more vents are provided in the handle portion, to reduce the weight thereof.

15. A hot-air gun substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.