IE41995B1 - Spraying method and apparatus - Google Patents

Abstract

The coating is applied with a spray pistol. A jet of bitumastic is sprayed in solution without air, and simultaneously a jet of air projects short fibres into the bitumastic jet. The two jets are moved together over the area to be coated, thus producing fibre-reinforced bitumastic cladding in a single pass. The portable pistol can have a front spray head, with jets for bitumastic and fibre, to the rear of which is a chopper mechanism for the fibre, which is delivered to it in a continuous strip, air being delivered to the mechanism to transport the chopped fibres to the nozzle. A trigger at the rear controls the supply of bitumastic material.

Description

This invention concerns method and apparatus for applying a coating of bitumastic material» Such coatings may be useful as roof coverings but have a variety of other purposes.

The method according to the invention is characterised by simultaneously spraying bitumastic material in solution (as defined below) without air and spraying short fibres by air entrainment, in overlapping patterns, and moving the sprays together over the area to be coated, so as to produce a coating of fibre-reinforced bitumastic material in a single pass.

It has been found that bitumen may be dissolved in a solvent such as naphtha to form a liquid of relatively low viscosity (say 6 centipoise) at ordinary temperatures, the liquid nevertheless carrying any desired filler (such as finely ground asbestos, bentonite or mica) in a stable suspension. This liquid can fairly easily be pumped and sprayed. Liquid of this viscosity would, however, be useless as a surface coating as it would simply run off. The liquid, surprisingly, has been found to have thixotropic properties. After being sprayed at relatively high pressure, e.g. of the order of 300 pounds per square inch,, through one or more orifices of relatively small mean diameter, e.g. .020 to ,040 inch, the droplets of liquid coalesce on the surface to be coated at a much higher viscosity, say of the order of 100 centipoises.

The term bitumastic material in solution as used herein means bitumen dissolved in solvent and carrying filler material in suspension. This is to be contrasted with bituminous emulsion. According to the invention bitumastic material is sprayed as a liquid under pressure. It is not sprayed by air-atomization.

The invention provides also a portable spray gun comprising: a spray head having at least one nozzle for bitumastic material in solution and an outlet for air-entrained short fibres, the nozzle having a mean orifice diameter of the order of .020 to .040 inch, a high pressure connection for supply of bitumastic material in solution to said nozzle at a pressure of the order of several thousand p.s.i., a connection for supplying air to said outlet, means to supply short lengths of fibre into the air stream passing to said outlet, said means including a chopper for chopping fibres supplied in a continuous rope, and a hand grip rigid with said spray head and remote therefrom. - 3 41995 Two embodiments of the invention will now be described by way of example, in which: Figures 1 and 2 are respectively a plan view and an elevation of a spray gun according to the inven5 tion.

Figure 3 is a section on a vertical longitudinal plane of a spray head forming part of the gun, with nozzles removed.

Figure 4A and 4B are diagrams showing in front and side elevation a typical spray pattern of the gun, and Figures 5’and 6 are views similar to Figures 1 and but showing a modified form of gun.

Referring to the drawings, and in particular Figures and 2, the spray gun there shown comprises a spray head designated generally 2 at the front. Bitumastic material in solution (as above defined) is fed to the spray head through a straight pipe 3 from a connection 4 at the rear of the gun, and fibres entrained in an air stream are fed to the spray head from a chopper 5 through a large-diameter straight pipe 6 running in Spaced parallel relation to the pipe 3. The pipe 3 is connected to the chopper 5 by a weld 6a, and extends above and to the rear of the chopper to a hand grip assembly designated generally 7. An air manifold 8 extending rearwardly from the chopper 5 parallel to the pipe 3 forms part of this assembly. The assembly 7 further includes a hand grip 10 surrounding the rear end of the pipe 3 and a pair of members 11, 12 of strip material joining the hand grip 10 to the manifold 8 and, with it, forming a guard for a trigger 13 controlling the supply of material from the connection 4, Trigger adjustment is provided by screw 14 on the hand grip 10. - 4 41995 The chopper designated generally 5 comprises an air motor 20 supplied through a pipe 20a with air from a first chamber in the manifold 8 having a nipple 21 at the rear for connection to an air hose. The motor 20 drives cutters (not shown) which continuously advance and chop into short lengths a fibreglass roving 22, which is in the form of a rope and is led through guides from a cheese in a back-pack worn by the operator of the gun. Chopped roving is delivered to a chamber 23 at the front of the chopper 5; this chamber is fed with air through a pipe 24 from a second chamber in the manifold 8 having a nipple 25 for connection to an air hose. Air supplied to the chamber 23 has an ejector action on roving out by the chopper blades and entrains the fibres in the air streams.

An air pressure regulator is provided on the backpack for air supplied to nipple 25. The air supply to the cutter motor 20 is controlled by a needle valve which is unseated as required by a finger-operated lever 27.

The fibreglass supply through pipe 6 is adjusted by (a) increasing the air pressure in the chamber 23, to eject the cut fibres quicker, (b) by increasing the air pressure on the chopper motor 20 which draws through the glass fibre string quicker therefore chopping more fibreglass per minute and (c) removing or inserting cutters from the chopper 5 to lengthen or shorten the cut fibres as required (e.g. to give lengths in the range from 3/8 to 1¾11). Pressures of 20 lbs/sq.ins. on the blower and 30 lbs per sq. ins. on the chopper may be used.

The spray head designated generally 2 and shown also in Figure 3 has an inlet connection 30 on the rear for 419 9 5 supply of bitumastic material in solution through the pipe 3. From the connection 30 two passages are formed in the head leading to bores 32, one at either side of the front end 35 of the head. Each of the bores 32 mounts a nozzle 36. The direction of spray from each nozzle can be set by means of a lever 38. The nozzles illustrated are commercially available from Graco Spray Equipment Ltd., of Slough, Bucks., England.

The head 2 is formed at its rear with an inlet opening 40; the pipe 6 leads into this opening, which connects with a large-diameter passage terminating at 41 centrally at the front 35 of the head.

The bitumastic material in solution is supplied to the connection 4 on the gun through a flexible conduit from a heavy duty pump (not shown) at a pressure Of 3000-3300 lbs. per sq. inch. Such pumps are available commercially but may require modification to increase the volume or pressure delivered having regard to the very long runs of flexible hose (say of the order of 600 feet) often needed. Pressures are controlled by a needle valve not shown but located where the pipe 3 enters the head 2.

The trigger 13 provides an on-off control by means of a rod (not shown) running within the pipe 3. Instead of the valve described, valves may be provided at the nozzles 36 pilot-operated by air pressure under control of the trigger.

The orifice diameter in the nozzles 36 governs the quantity of bitumastic material in solution supplied per minute and therefore the thickness of coating applied to a given surface with the spray gun moving at a given speed.

A range of mean orifice diameters between .020 inch and .040 inch may be used. A mean orifice diameter of .033 inch has been found suitable for a standard re-coat roofing application.

The formation of the nozzle orifice governs the shape of spray pattern and therefore the area covered by one passage of the spray gun, and also determines where, within the spray pattern, the main concentration of material is supplied. For a standard re-coat roofing operation an oval shaped nozzle orifice producing a spray pattern in the form illustrated has been found suitable, the oval shape providing the greater quantity of material at the centre, it has been found advantageous to adjust the nozzles 36 so that the major axes of the ovals are at 15° on opposite sides of the centre line.

The nozzles are adjusted to produce overlapping spray patterns.

Figures 4A and 4B show typical spray patterns. At the area A, which may be some 12 from the nozzles, the bitumastio material and glass fibre patterns approximately coincide. At this distance the bitumastic material and glass fibres are deposited simultaneously. At any other distance some bitumastic material will be deposited before and after the glass fibres, though to some extent the fibres are entrained with the bitumastic material spray once they encounter it. The head should not be held too close to the surface to be coated, because in this case too much bitumastic material may reach the surface before the glass fibres.

The spray gun illustrated in Figures 1 and 2 has been designed for spraying horizontal or gently sloping surfaces. The operator may hold the hand grip 10 in his right hand and place his left hand under the chopper 5 with a finger ready to actuate the motor control 27 . In this way the gun can be held generally horizontal or sloping slightly downward.

The spray gun shown in Figures 5 and 6 is generally ' similar to that of Figures 1 and 2 but is adapted for spraying vertical surfaces. Similar parts are given the same reference numbers aid will need no further description.

In the spray gun of Figures 5 and 6, the nozzles 36^ are directed forwardly, as is also the nozzle 41^ for 1 the air-entrained fibres. The hand grip 10 is here placed transverse to the pipes 3,6 in the manner of a pistol grip and the trigger guard suitably modified.

The nozzles 36^ are of a slightly different construction from that shown in the previous application.

The nozzle 41^ is formed as an extension of the pipe 6 through a block 50 carrying the passages for bitumastic material in solution, and terminates with a V-grooVe 51 (in plan) which helps to confine the fibres laterally.

Apart from the attitude of its operation, the method of use of the gun of Figures 5 and 6 is identical with that of the gun of Figures 1 to 3 and produces the same sort of spray pattern as in Figures 4A and 4B.

Various modifications can be made. An important feature of the spray guns illustrated is the open frame structure of the gun formed by the pipes 3,6 interconnected by spray head 2 and chopper 5 with the hand grip assembly spaced rearwardly of the latter. The air manifold for example may be replaced by a simple structural assembly holding the air pipes to the chopper. A single connecting member between the pipes 3,6 is shown as 53 in Figures 1 and 2; more can be provided depending on the length of the pipes.

Claims (13)

1. CLAIMS:1. A method of applying a surface coating of bitumastic material and fibres by means of a spray gun, characterised by simultaneously spraying bitumastic material in solution (as hereinbefore defined) without air and spraying short fibres by air entrainment, in overlapping patterns, and moving the spray patterns together over the area to be coated, so as to produce a coating of fibre reinforced bitumastic material in a single pass.

2. A method of applying a surface coating of bitumastic material and fibres by means of a spray gun, characterised by spraying bitumastic material in solution (as hereinbefore defined) without air at a pressure of the order of several thousand p.s.i. through one or more orifices each of which has a mean diameter of the order of .020 to .040 inch, spraying short fibres by air entrainment and moving the spray patterns together, in overlapping relation, over the area to be coated, so as to produce a coating of fibre-reinforced bitumastic material in a single pass.

3. For spraying bitumastic material in solution (as hereinbefore defined) to form a surface coating by the method of Claim 2, a portable spray gun comprising: a spray head having at least one nozzle for bitumastic material in solution and an outlet for air-entrained short fibres, the nozzle having a mean orifice diameter of the order of .020 to .040 inch, a high pressure connection for supply of bitumastic material in solution to said nozzle at a pressure of the order of several thousand p.s.i., a connection for supplying air to said outlet, means to supply short lengths of fibre into the air stream passing to said outlet, said means including a chopper for chopping fibres supplied in a continuous rope, and a hand grip rigid with said spray head and remote therefrom.

4. A spray gun as claimed in Claim 3, wherein the means to supply fibres Includes an air motor driving the chopper and connected to the air supply connection.

5. A spray gun as claimed in Claim 4, further including a pipe leading from the chopper to the spray head to convey air-entrained fibres to said outlet, wherein the connection for bitumastic material in solution includes a pipe leading from a connector for said material adjacent the hand grip to the spray head to convey said material to the nozzle or nozzles, the spray head, chopper, hand grip and said pipes forming aft open frame.

6. A spray gun as claimed in Claim 5, wherein the pipes are straight and in spaced -parallel relation, with the chopper being situated between the spray head and the hand grip.

7. A spray gun as claimed in Claim 5 or Claim 6, wherein 419 9 5 said air supply connection includes an air manifold extending between the chopper and the hand grip and supplying air to the chopper.

8. A spray gun as claimed in Claim 7, wherein the pipe for bitumastic material in solution is, intermediate in its length, connected to the chopper to rigidify the frame.

9. A spray gun as claimed in Claim 7, wherein the hand grip extends between the pipe for bitumastic material in solution and the manifold.

10. A spray gun as claimed in any of Claims 7 to 9, wherein a trigger is provided to control supply of bitumastic material in solution to the nozzle or nozzles and the hand grip includes a trigger guard which extends between the pipe for bitumastic material in solution and the air manifold.

11. A spray gun as claimed in any of Claims 3 to 10, wherein the spray head comprises a central opening forming said outlet for the air-entrained fibres, and two nozzles for bitumastic material in solution located one on either side of it.

12. A method as claimed in Claim 1 or Claim 2 of applying a surface coating of bitumastic material by means of a spray gun, substantially as hereinbefore described with reference to Figures 4A and 4B of the accompanying drawings. 11 41995

13. A portable spray gun substantially as hereinbefore described, with reference to Figures 1 to 4 or Figures 5 and 6 of the accompanying drawings.