GB2199085A

GB2199085A - Glue melting and dispensing apparatus

Info

Publication number: GB2199085A
Application number: GB08630439A
Authority: GB
Inventors: Anthony Edward Lyons
Original assignee: POWER ADHESIVES Ltd
Current assignee: POWER ADHESIVES Ltd
Priority date: 1986-12-19
Filing date: 1986-12-19
Publication date: 1988-06-29
Anticipated expiration: 2006-12-19
Also published as: GB2199085B; GB8630439D0

Abstract

Glue melting and dispensing apparatus (2) comprising heater means (34) for melting an adhesive stick (20), first passage means (22) through which the adhesive stick is fed having a blocked downstream end (64) apertures (48) which extend outwardly from the first passage means and through which melted adhesive from the surface of the adhesive stick passes, second passage means (50) for receiving melted adhesive from the apertures and for causing the received melted adhesive to pass in a direction opposite to the direction of movement of the adhesive stick in the first passage means, third passage means (52) for receiving the meted adhesive from the second passage means and for causing the received melted adhesive to pass in a direction opposite to the direction in which the melted adhesive moves in the second passage means, and an adhesive dispensing device (14) which is in communication with the third passage means. An alternative embodiment is also disclosed (Figs 7 and 8). <IMAGE>

Description

GLUE MELTING AND DISPENSING APPARATUS This invention relates to glue melting and dispensing apparatus.

Glue melting and dispensing apparatus is known.

The apparatus is usually in the form of a pistol and such pistols are known as hot melt glue guns. The known hot melt glue guns are fed with an adhesive stick which is known as a glue stick. The glue guns all have heater means for melting the glue sticks and the guns work on a straight through melt principle in which the glue stick entry point and the melt adhesive exit point are on the same axis. The known guns basically all employ a tube with either a parallel or a tapered bore with various arrangements of internal fins or protrusions being employed in order to get heat to the centre of the adhesive stick and to thereby break up the adhesive stick and to obtain and maintain maximum melting of the adhesive stick. The adhesive enters one end of the tube and exits at the other end of the tube.

With the known glue guns, the extrusion rate of molten adhesive is limited when the unmelted core of the adhesive stick blocks the exit from the tube. Although molten adhesive is present in the tube, it cannot escape.

It is an aim of the present invention to obviate or reduce this problem.

Accordingly, this invention provides glue melting and dispensing apparatus comprising heater means for melting an adhesive stick, first passage means through which the adhesive stick is fed for being melted by the heater means, a plurality of apertures which extend outwardly from the first passage means and through which melted adhesive from the surface of the adhesive stick passes, second passage means for receiving melted adhesive from at least some of the apertures and for causing the received melted adhesive to pass in a direction opposite to the direction of movement of the adhesive stick in the first passage means, third passage means for receiving the melted adhesive from the second passage means and for causing the received melted adhesive to pass in a direction opposite to the direction in which the melted adhesive moves in the second passage means, and an adhesive dispensing device which is in communication with the third passage means and which is for dispensing the melted adhesive from the third passage means, the first passage means having a blocked downstream end which is such as to cause melted and unmelted adhesive reaching the blocked downstream.

end to pass into the second passage means whereby any unmelted adhesive is then melted by the heater means during use of the apparatus as it passes back along the second passage means and then along the third passage means.

It will thus be apparent that the apparatus of the invention allows unrestricted exit of any molten adhesive from the first passage means and from the adhesive dispensing device directly the molten adhesive becomes available, irrespective of whether there is an unmelted core of an adhesive stick still in the first passage means.

Preferably, the first passage means is such that it tapers towards its blocked downstream end.

Usually, the first passage means will be of circular cross section for receiving an adhesive stick of similar circular cross section. However, if desired, the first passage means could be of another type of cross section for example square, for receiving an adhesive stick of a similar cross sectional shape.

Preferably, the first passage means is for receiving adhesive sticks of from 6 - 25mm diameter.

The apertures in the first passage meansvcan be of any desired and appropriate size, shape and number.

Preferably, the second passage means is shorter than the length of the first passage means that is provided with the apertures.

The second passage means is conveniently arranged to run parallel with and alongside the first passage means.

The third passage means is conveniently arranged to run parallel with and underneath the second passage means.

The adhesive dispensing device will usually be a nozzle.

The heater means may be a known type of heater means so that, for example, it may be a cylindrical heater, a rope heater or a cast in heater. If a cylindrical heater is employed, then one, two or three of the cylindrical heaters may be employed and they may be located in lobes or side extensions to the apparatus. If a rope heater is employed, it may be wrapped around the exterior of the apparatus. Such known arrangements in which the heater or heaters are basically arranged around the outside of the apparatus means that substantial heat loss can take place into ambient air and this lost heat is then not available to melt the adhesive stick or to maintain the temperature of the melted adhesive. Accordingly, in a preferred embodiment of the invention, the heater means is enclosed in a body part of the apparatus, which body part also contains the first, second and third passage means.By enclosing the heater within the body part of the apparatus, heat loss into the ambient air is reduced and a higher proportion of the heat from the heater means is available for melting the adhesive stick and maintaining the temperature of the melted adhesive.

Preferably, the apparatus of the invention is in the form of a pistol so that it forms a glue gun. The glue gun has a hand grip and the glue gun forms a convenient design for easily dispensing the melted glue.

The apparatus of the invention may however be in other shapes if desired.

Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 is a side view of a known gun and shows in cross hatched lines the part of the gun where an adhesive stick is melted; Figures 2 and 3 are side and cross sectional views of the part of a known glue gun where the adhesive stick is melted; Figure 4 is a longitudinal cross section through the part of a glue gun in accordance with the present invention in which an adhesive stick is melted; Figure 5 is a section on the line AA shown in Figure 4; Figure 6 is a longitudinal section like that of Figure 4 but taken in a different plane; Figure 7 is a longitudinal section which is comparable to the longitudinal section shown in Figure 4 but which shows alternative apparatus in accordance with the invention; and Figure 8 is a section on the line BB shown in Figure 7.

Referring to Figure 1, there is shown glue melting and dispensing apparatus in the form of a known hot melt glue gun 2. The gun 2 has a handle 4 and a body 6. An adhesive stick (not shown) is loaded into the body 6 via an adhesive stick loading flange 8 and an adhesive stick inlet tube 10. The gun 2 has a trigger 12 for advancing the adhesive stick through the gun 2 to an adhesive dispensing device in the form of a nozzle 14. The advancing mechanism for advancing the adhesive stick is well known and it will not be described herein in detail. The shaded part 16 of the gun 2 is where the adhesive stick is melted. A heater (not shown) in Figure 1 is provided in this shaded part 16 to melt the adhesive stick. The heater is electrically heated via a power cable 18 which connects to the heater through the handle 4 as shown.

Referring now to Figures 2 and 3, the shaded part 16 shown in Figure 1 is shown in more detail and this shaded part 16 shown in Figures 2 and 3 represents a known construction from a known gun 2. It will be seen that an adhesive stick 20 is fed along a tapering passage 22 in a housing 24. The passage 22 tapers towards the nozzle 14.

The end of the passage terminates in a hole 26 which is normally blocked by a ball valve obturator 28. The obturator 28 is spring biased by a spring 30 to a position in which it seats against a valve seat 32 surrounding the hole 26 and thus closes the hole 26.

A heater 34 is provided in a side extension part 36 of the housing 24. The heater 34 is shown fed with electrical current via a pair of wires 38,40. The wires 38,40 are inside the power cable 18 shown in Figure 1.

Figure 3 illustrates how the heater 34 is able to melt the surface part 42 of the adhesive stick 20, whilst the centre core 44 of the adhesive stick 20 remains unmelted. The centre core 44 thus progresses along the passage 22 until it arrives at the position shown in Figure 3 where it blocks the hole 26. Thus the melted adhesive from the surface part 42 of the adhesive stick 20 cannot escape through the hole 26 for delivery through an aperture 46 in the nozzle 14. Thus the extrusion rate of molten adhesive from the nozzle 14 becomes limited or non-existent when the unmelted centre core 44 reaches the hole 26 and, at best, more time must be allowed for the heater 34 to melt sufficient of the centre core 44 to at least partially unblock the hole 26.

Referring now to Figures 4,5 and 6, there is shown the shaded part 16 in Figure l but in a new form which is in accordance with the present invention.

In Figures 4,5 and 6 similar parts as in Figures 1,2 and 3 have been given the same reference numerals for ease of understanding. In Figures 4,5 and 6 the housing 24 is provided with the tapering passage 22 for receiving the adhesive stick 20. The tapering passage 22 constitutes first passage means 22 through which the adhesive stick 20 is fed for being melted by heater means in the form of the heater 34. A plurality of apertures in te form of slots 48 extend outwardly from the first passage means 22. Melted adhesive from the adhesive stick 20 passes radially outwardly through the slots 48.

The housing 24 also has second passage means 50 for receiving melted adhesive from the first six slots 48 extending from the nozzle 14 end of the housing 24. As the melted adhesive passes through the slots 48 nearer and nearer to the nozzle 14 end of the housing 24, then this melted adhesive forces the melted adhesive in the second passage means 50 in a direction opposite to the direction of movement of the adhesive stick 20 in the first passage means 22.

The melted adhesive in the second passage means 50 is received by third passage means 52. As can be seen from Figures 5 and 6, the first passage means 50 and the second passage means 52 are separated from each other by a pair of webs 54,56.

The nozzle 14 is in communication with the third passage means 52 via an outlet hole 58 which leads to the obturator 28, the spring 30 and the aperture 46.

As explained above, the spring 30 is effective to seat the obturator 28 against the valve seat 30 to normally close the exit from the third passage means 52 until melted adhesive being pushed along the third passage means 52 passes through the hole 26 and presses the obturator 28 off its valve seat 32. The nozzle 14 is provided with a screw threaded reduced diameter portion 60 which screws into a complementary screw threaded hole in a boss 62 on the housing 24.

It will be seen that the first passage means 22 has a blocked downstream end 64 which is such as to cause all melted and unmelted adhesive reaching the blocked downstream end 64 to pass into the second passage means 50 through the slot or slots 48 adjacent the blocked downstream end 64. Any unmelted adhesive passing into the second passage means 50 then has plenty of time to be melted by the heater 34 as the unmelted adhesive passes back along the second passage means and then along the third passage means as mentioned above.

It can be seen most clearly from Figure 5 that the second passage means 50 is formed by two separate passages which run parallel to and alongside the first passage means 22. The third passage means 52 is formed by two separate passages which run parallel with but underneath the passages forming the second passage means 50.

It will be seen from Figure 4 that the heater 34 is positioned inside the housing 24. This is in contrast to existing systems having either one, two or three cylindrical heaters located in lobes or side extensions to the housing 24 (see Figure 3), or alternatively having a rope heater wrapped around the exterior of the housing 24. The arrangement shown in Figure 4 in which the heater 34 is inside the main part of the housing 24 reduces heat loss into ambient air. Thus, a higher proportion of heat from the heater 34 is available to melt the adhesive stick 20 and to maintain the temperature of the melted adhesive.

During use of the gun 2, the combination of the taper in the tapered first passage means 22 and the slots 48 present to the advancing adhesive stick 20 a series of scraping edges which direct the molten adhesive out of the first passage means 22 and through the slots 48. Due to the presence of the second passage means 50 and the third passage means 52, the molten adhesive is kept appropriately molten and at a substantially even temperature.

Referring now to Figures 7 and 8, there is shown an alternative design to that shown Figures 4,5 and 6.

Similar parts as in Figures 4,5 and 6 have been given the same reference numerals.

In Figures 7 and 8, the slots 48 have been replaced by holes 66. The second passage means 50 is formed as can best be seen in Figure 8 between the outside of a member 68 containing the holes 66 and a half shell member 70. The third passage means 52 is formed by the pair of longitudinally extending slots which are best seen in Figure 8.

In Figures 7 and 8, the heater 34 is mounted in an outer sleeve or casing part instead of in the main housing 24 as can be seen. Such a position of the heater 34 may not be as efficient as the position of the heater 34 shown in Figures 4,5 and 6.

It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of example only and that modifications may be effected. Thus, for example, the housing 24 may be of another shape. Various types of feed mechanisms may be employed for feeding the adhesive stick 70 through the gun 2. Furthermore, the gun 2 could be of an entirely different. shape, and apertures other than the slots 48 or the holes 66 may be employed.

Claims

1. Glue melting and dispensing apparatus comprising heater means for melting an adhesive stick, first passage means through which the adhesive stick is fed for being melted by the heater means, a plurality of apertures which extend outwardly from the first passage means and through which melted adhesive from the surface of the adhesive stick passes, second passage means for receiving melted adhesive from at least some of the apertures and for causing the received melted adhesive to pass in a direction opposite to the direction of movement of the adhesive stick in the first passage means, third passage means for receiving the melted adhesive from the second passage means and for causing the received melted adhesive to pass in a direction opposite to the direction in which the melted adhesive moves in the second passage means, and an adhesive dispensing device which is in communication with the third passage means and which is for dispensing the melted adhesive from the third passage means, the first passage means having a blocked downstream end which is such as to cause melted and unmelted adhesive reaching the blocked downstream end to pass into the second passage means whereby any unmelted adhesive is then melted by the heater means during use of the apparatus as it passes back along the second passage means and then along the third passage means.

2. Glue melting and dispensing apparatus according to claim 1 in which the first passage means is such that it tapers towards its blocked downstream end.

3. Glue melting and dispensing apparatus according to claim 1 or claim 2 in which the first passage means is of circular cross section for receiving an adhesive stick of similar circular cross section.

4. Glue melting and dispensing apparatus according to claim 3 in which the first passage means is for receiving adhesive sticks of from 6 - 25 mm diameter.

5. Glue melting and dispensing apparatus according to any one of the preceding claims in which the second passage means is shorter than the length of the first passage means that is provided with the apertures.

6. Glue melting and dispensing- apparatus according to any one of the preceding claims in which the second passage means is arranged to run parallel with and alongside the first passage means.

70 Glue melting and dispensing apparatus according to any one of the preceding claims in which the third passage means is arranged to run parallel with and underneath the second passage means.

8. Glue melting and dispensing apparatus according to any one of the preceding claims in which the adhesive dispensing device is a nozzle.

9. Glue melting and dispensing apparatus according to any one of the preceding claims in which the heater means is a cylindrical heater, a rope heater, or a cast in heater.

10. Glue melting and dispensing apparatus according to any one of the preceding claims in which the heater means is enclosed in a body part of the apparatus, which body part also contains the first, second and third passage means.

11. Glue melting and dispensing apparatus according to any one of the preceding claims and which is in the form of a pistol.

12. Glue melting and dispensing apparatus substantially as herein described with reference to Figures 4 to 8 of the accompanying drawings.