GB2243209A

GB2243209A - Moist air gun

Info

Publication number: GB2243209A
Application number: GB9001329A
Authority: GB
Inventors: Derrick Gilbert George Purser; Clifford Cothorp
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-01-19
Filing date: 1990-01-19
Publication date: 1991-10-23
Anticipated expiration: 2010-01-19
Also published as: GB9001329D0; GB2243209B

Abstract

Hand-held apparatus for the provision of a controlled supply of humidified air comprises a copper body (20) with a hollow, generally flat wedge-shaped shell upper portion (11) defining a chamber (11 a) and an extended handle portion (16) encased in a heat-resistant silicone rubber sleeve, the free end (17) of the handle having an inlet aperture (18) connected to a flexible hose which in turn is connected to an ultrasonic nebuliser for supplying humidified air. The chamber 11 houses a 50 W controllable cartridge-type heating element (7), aligned with an outlet jet (10) from the chamber. The element (7) lies within a cylindrical shroud (7a), to which it is secured by ceramic cement to ensure good thermal conduction from heater to shroud. The shroud extends beyond the end of the heating element so as to lie adjacent the outlet jet, which is removable for replacement by alternative jets to vary the shape of the emitted air stream and/or the extent over which it spreads. <IMAGE>

Description

MOIST AIR GUN This invention concerns a mcist air gun. and relates in particular to such a device for the provision of a carefully-controlled jet of warmed moist air, especially for use in the removal of glues and varnishes fro old or valuable documents and other artefacts In preservation and restoration work it is frequently desired to soften (in order subsequently to remove by peeling) certain types of animal glues which have been applied to repair ceramic and china goods, for example, or to bind books or adhere labels thereto.

This softening requires the controlled application of heat and humidity - if too high a temperature is used, the glue becomes liquid and may penetrate the surface to which it is applied, while if the humidity is too high then the substrate may be saturated, causing inks to run, and so on. Application of heat and moisture for this purpose has in the past been achieved by the use of steam raised from boiling water and applied via a suitable hose. Unfortunately, such a method permits no accurate temperature or humidity control. In addition, there may easily occur "spitting" of condensed steam from the hose onto the article being treated, which may in turn cause damage to, for example, unstable inks or to a valuable painting.

The present invention proposes a moist air gun specially designed in an attempt to attain safe and controlled application of a jet of moist air, and thus minimise at least some of the above-mentioned difficulties. More specifically, there is suggested a hand-held apparatus having a hollow body with inlet and outlet apertures, and a heating element located towards the outlet aperture by which a supplied stream of moist air is heated as it passes through the apparatus.

In one aspect, therefore, this invention provides hand-held apparatus for the provision of a controlled supply of humidified air, which apparatus comprises: a source of humidified air; a body connectable to the air source and having therewithin a chamber within which is contained a heating element, and through which is to pass the humidified air, the body having an inlet aperture to the chamber for receiving the humidified air, and an outlet aperture from the chamber, adjacent the heating element, through which aperture humidified a r may be emitted after warming by the heating element; and control means by which the operation of the heating element can be controlled and thus the temperature of the emitted air adjusted.

The apparatus of the invention permits the provision of a controlled supply of humidified (moist) air - the degree of humidity and temperature of the air stream may be determined by the operator within certain limits.

The body of the apparatus may be made of any suitable material, but it is conveniently made of a metal, and is preferably copper.

The body, which is conveniently in the form of a shell defining the chamber, might be of almost any shape - cylindrical, for example, and having the inlet aperture at one end and the outlet aperture at the other. It is preferred, however, that both body and chamber generally take the form of a right-angled triangle, with the outlet at one of the two acute angles and the inlet within an extended portion at the other, this extended portion constituting a handle by which tlie apparatus may readily be gripped. An embodiment with such a gun-like shape and disposition is illustrated in the accompanying drawings. As will be discussed in greater detail below, this arrangement may be explcited both to dictate the flow path of the air stream through the apparatus, and to help prevent spitting of water therefrom.The handle portion is advantageously encased in an insulating sleeve to protect the user when high temperatures are being employed - for the type of work described earlier, the required temperature is generally in the range from ambient temperature to 1000C.

The chamber-contained heating element may take any convenient form, but is preferably a 50W or 100W cartridge-type electric element encased within a sheath on which is located a built-in mounting thread. Such an element is supplied by W. J. Furze (reference HT/004821/001). In the preferred embodiment of the invention described earlier wherein the apparatus is generally triangular, the element is propitiously located within the chamber such that it lies adjacent and parallel to that edge of the chamber furthest from the handle portion and which in use is uppermost, and is aligned with the outlet aperture from the chamber.

The air supply which passes through the apparatus thus remains at ambient temperature until just before it leaves the apparatus, so heat losses are minimised (and the handle portion remains cool).

The heating element is preferably contained within a cylindrical sleeve, or shroud, which serves to enhance the surface area at which heat exchange may occur. In addition, the shroud may be chosen and arranged to provide a particular shape and size of cavity between itself and the chamber wall. In this way the shroud may, at least in part, dictate the flow of air therearound, and thus through the apparatus.

The shroud may be made of any material which is a good thermal conductor, for example a metal or an alloy such as brass. Its internal shape and dimensions must naturally fit the external form of the heating element which it encloses. However, a preferred embodiment of the invention utilises a shroud which extends beyond that end of the heating element lying nearest the outlet aperture of the chamber. The extended portion of the shroud thus terminates adjacent the outlet from the chamber, and since this part of the shroud becomes heated when the apparatus is in use, there is little or no chance for any cooling of the air stream to occur before it leaves the apparatus. Consequently, the problem of condensation, and so spitting, is very much reduced.

The chamber is intended to receive a supply of humidified air which enters via an inlet aperture from a suitable source (the humidifier), is heated to the desired temperature by the heating element, and then leaves via an outlet aperture. The humidified air supply may enter the chamber by way of the inlet aperture from a humidifier which is either directly attached thereto or is attached by a pipe, hose or other connection. A flexible (corrugated) hose of a rubber or plastics material is convenient for this purpose, permitting greater freedom of movement for the user to manipulate the apparatus.

The humidifier may be of any kind capable of providing humid air from a source of (dry) air - as ambient, atmospheric air - and water, and may employ zny suitable water vaporising device for this purpose (for example, a simple atomiser) coupled with means, such as a fan, for supplying the thus-humidified air to wherever it is required. The necessary degree of humidity of the air supply might vary depending upon the precise nature of the work being undertaken, and so the humidifier preferably allows at least some degree of adjustment of the humidity. Most conveniently, an ultrasonic nebuliser is used, such as is readily available commercially (for example from Salton [No.

1071)), and which typically comprises an ultrasonically-vibrated plate onto which droplets of water are fed at a controlled rate whilst a supply of air is blown thereacross.

The humidified air supply is passed into the chamber, where it flows around the heating element, thus acquiring the desired temperature, before being emitted from the apparatus through a suitable nozzle or jet aligned with the outlet aperture. The nozzle may simply be formed by appropriate shaping of the body of the apparatus in the region of the outlet aperture.

However, for greater versatility and control there is desirably provided a detachable jet which may, when required, be replaced by another aiternatively-shaped jet. In this way, by using suitably-shaped jets, the emitted humidified air stream may be applied either to a single area or in a more diffuse manner.

The temperature of the emitted air stream is adjusted by R temperature measurement and control system which governs the operation of the heating element. The system will typically be a closed loop control system - thus, having a suitable temperature detecting element (or probe) the output of which provides the input signal to a controller which determines the deviation of the actual temperature from the desired (set) value, and then adjusts the heater output accordingly. Provision may also be made for the detected temperature to be indicated to the user of the apparatus by means of an associated display.

The temperature detecting probe used may be any of those generally suitable for the purpose having regard to the anticipated temperature range. This range will vary depending upon the location of the probe, which might monitor either the temperature of the heating element itself, or that of the emitted heaed air (the temperature of which, as mentioned previously, will normally be from ambient to 1000C). Its exact location may be chosen at wll provided that acceptably accurate results are obtained - the position may depend upon the particular construction of the apparatus.A preferred embodiment of the invention employs two probes - a thermocouple located adjacent the heating element, which provides the input signal to the controller, and a thermistor which detects the temperature at a location adjacent the apparatus outlet aperture, and which is connected to a digital temperature display, thus providing means for checking that the desired air outlet temperature has been achieved by the action of the control system. It has been found that the best results are obtained by locating these two probes within a narrow tube externally mounted on the body of the apparatus parallel to the longitudinal axis of the heater, as illustrated in the accompanying drawings.

The controller may be a coiiventional device such as is available from suppliers like R.S. Components (temperature controller Type K, o. 344as74). A device having proportional control action (wherein the controller output signal is directly proportional to the deviation of the detected value from the desired value) may be acceptable, but for greater temperature stability it is preferred that the controller also permit derivative action (wherein the output signal is a function of the rate of change of the deviation with time), so that a sudden change is more quickly compensated.

An example of an apparatus according to the invention will now be described, though by way of illustration only, with reference to the accompanying drawings in which Figure 1 is a perspective view in part cut-away and part exploded form of an apparatus of the invention (the source of humidified air is not shown), Figure 2 is a simplified cross-sectional view of the apparatus of Figure 1, and Figure 3 is a schematic diagram of the apparatus of Figures 1 and 2 with associated humidifier and temperature display.

The apparatus of the Figures has a copper body (generally 20) comprising a hollow and generally flat wedge-shaped shell upper portion (11) defining a chamber (liy; best seen in Figure 2). The body 20 has an extended handle portion (16) encased in a heatresistant silicone rubber sleeve (15; not shown in Figure 2). At the free end (17) of the handle 16 is an inlet aperture (18) connected to a flexible hose (12; shown only in Figure 3). The hose 12 is in turn connected to an ultrasonic nebuliser (13; shown in Figure 7 in block form only).

The broadest part of the chamber 11 houses a 50 W cartridge-type heating element (7). This element is aligned with an outlet jet (10) from the chamber, and lies within a cylindrical shroud (7a), to which it is secured by ceramic cement (not shown) which ensures good thermal conduction from heater to shroud. The shroud extends beyond the end of the heating element 7 in one direction (to the left as shown) so as to lie adjacent the outlet jet 10. The jet 10 is removable, and may be replaced by either of the alternative jets (101 and 102; see Figure 1) to vary the shape of the emitted air stream and/or the extent over which it spreads.The extended end of the shroud 7a becomes warm during operation of the apparatus, thus helping to ensure that the moist air stream does not cool significantly before it is emitted, which in turn minimises the possibility of condensed water spitting onto the workpiece.

Along the external wall of the chamber 11 lies a narrow bore pipe (14; shown in Figure 3 only) which contains, at approximately its mid-point, a welded-tip PTFE-insulated tnermocouple (8; not shown in Figure 1).

Adjacent the end of the pipe is a 50-1500C thermistor (9; not shown in Figure 1). A cable (6) contains the wires connecting these components to a control box (1) which incorporates a variable temperature controller (4) having both proportional and derivative action, a liquid crystal temperature display panel (5) and a switch (3) for the overall power supply (not shown).

The box 1 also includes mounted thereon a hook (2) upon which the body of the apparatus may be rested when not in use.

In operation, the humidifier 13 is adjusted so as to produce a supply of air of the required humidity, which air supply enters the body of the apparatus through the inlet aperture 18 via the hose 12. The moist air then travels through the body and around the heating element 7, so attaining the required temperature. The air temperature is detected by the thermistor 9, and displayed at the control box 1. The warmed, moist air is then emitted from the apparatus through the jet 10, and may be directed at the glue deposit (for example) to be removed.

Should any condensation occur within the chamber, this may run down sloped walls of the upper portion 11 of the chamber, and is thus prevented from being ejected from the gun to damage the surface dyeing worked upon.

Claims

1. Hand-held apparatus for the provision of a controlled supply of humidified air, which apparatus camprises: a source of humidified air; a body connectcble to the air source and having therewithin a chamber in which there is contained a heating element, and through which is to pass the humidified air, the body having an inlet aperture to the chamber for receiving the humidified air, and an outlet aperture from the chamber, adjacent the heating element, through which aperture humidified air may be emitted after warming by the heating element; and control means by which the operation of the heating element can be controlled and thus the temperature of the emitted air thereby adjusted.

2. Apparatus as claimed in claim 1, in which said body is made of copper.

3. Apparatus as claimed in claim 1 or claim 2, in which both the body and the chamber take the general form of a rightangled triangle, with the outlet at one of the two acute angles and the inlet within an extended portion at the other, this extended portion constituting a handle by which the apparatus may readily be gripped.

4. Apparatus as claimed in claim 3, in which the handle portion is encased in an insulating sleeve to protect the user when high temperatures are being employed.

5. Apparatus as claimed in any of the preceding claims, in which the chamber-contained heating element is a 50W to 100W cartridge-type electric element encased within a sheath on which is located a built-in mounting thread.

6. Apparatus as claimed in claims 3 and 5, in which the heating element contained within the generally-triangular chamber is so located therein that it lies adjacent and parallel to that edge of the chamber furthest from the handle portion, and which in use is uppermost, and is aligned with the outlet aperture from the chamber, so that the air supply which passes through the apparatus thus remains at ambient temperature until just before it leaves the apparatus.

7. Apparatus as claimed in any of the preceding claims, in which the heating element is contained within a cylindrical, sleeve-shaped shroud, which serves to enhance the surface area at which heat exchange may occur, and the shape and dimensions of the shroud are chosen relative to the shape and size of the chamber so as to ensure optimum even heating of the humidified air which in operation is emitted from the apparatus.

8. Apparatus as claimed in claim 7, in which the shroud is formed of a good thermal conductor and extends beyond that end of the heating element lying nearest the outlet aperture of the chamber, and terminates adjacent the outlet from the chamber, so as thereby to ensure that there is little chance for any cooling of the air stream to occur before it leaves the apparatus.

9. Apparatus as claimed in any of the preceding claims, in which the source of humidified air includes a flexible hose interconnecting the inlet aperture to the heating chamber and an outlet aperture from a separate humidifier.

10. Apparatus as claimed in any of the preceding claims, in which the source of humidified air is or includes an ultrasonic nebuliser.

11. Apparatus as claimed in any of the preceding claims, in which during operation the humidified air supply is passed into the chamber, flows around the heating element thus acquiring the desired temperature, and is finally emitted from the apparatus through a nozzle aligned with the outlet aperture of the heating chamber.

12. Apparatus as claimed in claim 11, in which the nozzle takes the form of one of a number of alternatively-shaped, detachable and therefore replaceable jets, by choice of which the emitted humidified air stream may be applied in various manners.

13. Apparatus as claimed in any of the preceding claims which includes a temperature measurement and control system enabling the operation of the heating element and thus the temperature of the emitted air stream to be governed.

14. Apparatus as claimed in claim 13, in which the temperature-measurement and control system is one having a suitable temperature detecting probe the output of which provides the input signal to a controller which determines the deviation of the actual temperature from any desired pre-set value, and then adjusts the heater output accordingly.

15. Apparatus as claimed in claim 14, in which means are provided whereby the detected temperature is indicated to the user of the apparatus by rteans of an associated display.

16. Apparatus as claimed in any of claims 13 to 15, which includes two temperature detecting probes, one of them a thermocouple located adjacent the heating element which provides the input signal to the controller, and the other a thermistor which detects the temperature at a location adjacent the apparatus outlet aperature and which is connected to a digital temperature display.

17. Apparatus as claimed in claim 16, in which the two probes are both located within a narrow tube externally mounted on the body of the apparatus parallel to the longitudinal axis of the heater.

18. Apparatus as claimed in any of claims 13 to 17, in which the temperature controller is one wherein the output signal is a function of the rate of change of the deviation with time.

19. Apparatus as claimed in any of the preceding claims and substantially as herein disclosed.

20. HaLnd-held apparatus for the provision of a controlled supply of humidified air, substantially as herein described with reference to and as sown in the accanpanying drawings.