GB2032006A

GB2032006A - Dispensing liquiform materials

Info

Publication number: GB2032006A
Application number: GB7931211A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-09-07
Filing date: 1979-09-07
Publication date: 1980-04-30

Abstract

Air and moisture sensitive materials are charged into a two chamber dispenser (3) which is adapted to expel its contents under pressure, by first reducing to a minimum the volume of the product- holding chamber. The product is then charged into the dispenser via the outlet valve (7) of the dispenser, the valve having been fitted before or after reduction of the volume of the product chamber and being preferably of the tilt-valve type. Apparatus for filling through a tilt- valve (7) has a filling tube (32) which extends into the valve and forces valve apertures (25) past a resilient seal (22) thus enabling product to pass into the product chamber from opening (35) in the filling tube and apertures (25). The filling tube (32) has a sleeve (33) which seats on an end plate (34) of the filling tube (32). As tube (32) is withdrawn sleeve (33) reseats on the plate (34) to stop flow of product. Additional tubes (30) and (31) serve to guide the filling tube centrally into the valve. <IMAGE>

Description

SPECIFICATION Dispensing of liquiform materials This invention relates to a method and apparatus for filling containers adapted to dispense their contents under pressure. More specifically, but not exclusively, the invention relates to the charging of air-and moisturesensitive materials into such containers.

Special two-chamber pressurisable dispensers are known for use in the dispensing under pressure of materials incompatible with conventional fluorocarbon propellants. Two forms are known, the "piston pack". and "flexible bag" types. In the piston pack a piston of plastics material divides the dispenser into two chambers, one for product and one for propellant. The production chamber has a manually operable outlet valve and the propellant chamber has means for introducing propellant into the chamber and a seal for retaining the propellant therein. The flexible bag type of dispenser has a bag or bottle of deformable plastics material within a can and seaied to the neck thereof. Product is held inside the bag and propellant is introduced into the space between the bag and the wall of the can.Such containers are filled by introducing product into the product space followed by the introduction of propellant into the propellant space. The valve assembly is then crimped on to the can neck.

One particularly important problem to which this invention is addressed, is in the dispensing of moisture-curing room temperature vulcanisable silicones (RTVS) which are used as bonding or sealing agents. RTVS have hitherto been dispensed from a manually deformable flexible tube or, for larger scale use, from a manually operable dispensing gun which forces a piston axially through a cylindrical tube to extrude the RTVS from a nozzle at the opposite tube end.

A disadvantage of the previous dispensers is that it is difficult to dispense the contents of the tube at a uniform delivery rate thus leading to irregular rates of application of the material. Highly viscous materials such as RTVS require the application of a fairly high manual pressure and it is difficult for an operator to maintain a uniform pressure and simultaneously to guide the nozzle accurateiy over the locus of application.

Although the foregoing has been given mainly in relation to RTVS it will be obvious that many other materials behave in this way with similar results.

An object of this invention is to provide method and apparatus for charging product into pressurisable two chamber dispensers.

According to the present invention there is provided a method of filling a two chamber container comprising sealing to the container a dispensing valve communicating with the product chamber, reducing the product chamber to minimum volume, charging product to the product chamber by back-filling via the dispensing valve.

The volume of the product chamber may be reduced to minimum by the application of a suction to the product chamber or by the application of pressure to the propellant chamber, for example by introducing the propellant before filling the product.

The valve may be fitted before or after reduction of the product chamber volume.

The product chamber may additionally be purged with dry inert gas such as nitrogen prior to reducing the product chamber volume.

The method of this invention will now be described and for reasons of clarity a description will first be given of a particularly preferred dispenser shown in part-section in Fig. 1 of the accompanying drawings.

Referring to Fig. 1, a dispenser has a pressure vessel 1 provided by an extruded aluminium can with side wall 2, part conical top 3 and an inverted-domed base 4. The base 4 is attached to the side wall 2 by crimped joint 5. A manually operable release valve 6 having components 7 located inside the container is installed in the top 3 by means of a crimped joint 9.

A piston 10 is located inside the vessel and has wall portion 11 and a crown portion 12 which conforms generally in shape to the inside surface of top 3, a recess 1 3 in the piston 10 being provided to acommodate the valve components 7 when the piston is located close to the can top.

The piston 10 divides the vessel 1 into a product chamber 14 and a propellant chamber 1 5.

The domed base 4 has a central aperture for introduction of propellant into the chamber 1 5.

After filling the aperture is closed by a plug 16, conveniently of rubber.

To improve wall-to-wall contact between piston and vessel the piston may be provided with reinforcing rings, for example, or, as shown in Fig.

1, the hollow piston 10 may be filled with resilient plastics material 1 7, such as plastics foam.

Conveniently an oversize cylinder of foamed plastics material may be force fitted into the piston so that it urges the side wall 11 outward against the vessel wall.

The dispenser instead of having a piston which slides axialiy within the vessel may instead have a collapsible bag which is sealed to the neck of the vessel, the interior of the bag providing the product chamber and the space between bag and vessel wall being the propellant chamber.

The dispensing valve 6, as shown in Fig. 1, is of the "tilt-valve" type. It consists of a metal holder 20 for fixing the valve to the vessel 1 by means of a crimped joint 21, a plug 22 of resilient material held within the holder 20, and a centrally disposed tube 23 extending through the plug 22. The end of the tube 23 is closed by a closure plate 24 and a number of apertures 25 are provided in the tube adjacent the plate 24. The metal holder 20 does not engage the tube 23 around its upper portion but instead leaves a circumferential space 26 which allows the tube 23 to be tilted.

The tube 23 may be provided with a dispensing nozzle or spout and is preferably fitted with means for preventing unintentional operation of the valve.

Such matter is the subject of out copending patent application No.

When filling product by the method of the invention into the dispenser shown in Fig. 1 , the valve assembly 6 is first crimped to the vessel and the vessel is evacuated through the valve to draw the piston 10 towards the top 3 of the vessel. The product is then introduced into the product chamber 14 via the valve 6. The final stage of the filling operation is to charge the propellant into the propellant chamber 1 5 via the aperture in the base which is then plugged.

An alternative filling procedure using the dispenser of form shown in Fig. 1 , comprises first filling propellant into the chamber 1 5 and this forces the piston 10 to the top. The valve is then fitted and the product charged via the valve.

The process has a number of interesting advantages accruing from the fact that the propellant does not come into contact with the product. The main purpose of making this invention was to provide a means of dispensing material such as RTVS which cures in contact with moist air. Any attempt to dispense RTVS in a conventional "aerosol" container results in the RTVS soiidifying because of moisture in the propellant. However, even when the moisture was removed from the propellant a conventional "aerosol" is still unsatisfactory because the propellant produced bubbles in the product thus giving an aerated or foam-like appearance to the dispensed material. What is required, of course, is to be able to fill with product without contact with moisture and this is achieved by the method of this invention.

From an economic viewpoint, propellants used in conventional "aerosols", that is, chlorofluorohyd rocarbons, are expensive.

However, the dispenser used in this invention enables other materials to be used, for example, carbon dioxide, which are relatively cheaper.

Carbon dioxide has found limited applications in conventional aerosols but it is so incompatible with most products that such applications are very few indeed. Carbon dioxide is attractive as a propellant not merely because it is inexpensive but because it is considered to be rather less of an atmospheric pollutant than the conventional propellants. The possibility of using carbon dioxide as a propellant makes these two-chamber dispensers economically attractive for dispensing any liquid normally dispensed by conventional "aerosols" as the additional cost of the special dispenser is more than offset by the savings made by the use of carbon dioxide rather than the conventional propellants.

The present invention also provides apparatus for charging liquiform material to a dispenser through a tilt-valve as hereinbefore defined comprising a filling tube connectible to a reservoir of material to be charged and insertable into the outlet tube of the tilt-valve to abut the closure plate thereof and to open the tilt-valve and a centering tube enclosing and in sliding engagement with the filling tube for positioning the outlet tube of the tilt-valve for insertion of the filling tube.

More preferably the invention provides appartus for charging liquiform material to a dispenser through a tilt-valve (as hereinbefore defined) comprising a telescopically mounted assembly of coaxial tubes consisting of a filling tube connectible to a reservoir of material to be charged and insertable into the outlet tube of the tilt-valve to abut the closure plate of the said outlet tube, said filling tube having an end plate and an aperture at or near the end plate permitting passage of material from the filling tube, a tubular sleeve surrounding said filling tube and having a flange for seating on the outer end of the said outlet tube of the valve, a guide tube around said sleeve, spring bias means between the guide tube and the sleeve to urge the sleeve towards the valve outlet tube, and a centering tube for engaging the valve assembly and centering the outlet tube thereof for insertion of the filling tube.

The apparatus of the invention will now be described by way of example with reference to Figs. 2 and 3 of the drawings of which: Fig. 2 is a longitudinal section of apparatus of the invention; and Fig. 3 is the same apparatus during use in charging material via a tilt-valve.

Referring to Figs. 2 and 3, material charging apparatus consists of an assembly of four coaxial tubes which are capable of mutual relative axial movement.

The outermost tube 30, of the assembly is a centering tube. Within tube 30 is a slidable guide tube 31 through which extends a filling tube 32. A sleeve 33 encloses the lower end-portion of the filling tube 32.

The delivery end of the filling tube 32 is closed by an end plate 34 which also provides a seat for the end of the sleeve 33. One or more apertures 35 are provided in the filling tube 32 at the delivery end adjacent the end plate 34.

Sleeve 33 has a flanged end portion 36 against which a spring 37 acts. Sleeve 33 is slidable under the action of spring 37 in a recess in the next outermost tube, the guide tube 31.

Guide tube 31 is slidable within outermost tube, the centering tube 30. Co-operating notches 38 in tubes 30 and 31 serve to retain guide tube 31 within centering tube 30.

Centering tube 30 is spring loaded by means of spring 39 which acts also against an advancing arm 40 which is provided with means (not shown) for up and down movement of arm 40.

The lower end portion 41 of centering tube 30 is in the form of a collar for engaging a tilt-valve assembly and a ring 42 of resilient material is provided around the said end portion 41.

The various components of the charging apparatus are assembled as follows. Sleeve 33 is slipped over the filling tube 32 and seats on the end plate 34, spring 37 is placed on the flanged end 36 around the upper end of the filling tube 32, and filling tube 32 isthen screwed into a threaded portion 43 in guide tube 31. Centering tube 30 and spring 39 are slipped on to the guide tube 31 located therein by notches 38 and the guide tube is screwed into the advancing arm 40 by means of co-operating threads 44.

In use (Fig. 3) the apparatus is advanced towards a tilt-valve 7 until the centering tube 30 abuts the valve assembly 7 and this stops the advance of tube 30. Guide tube 31, sleeve 33 and filling tube 32 continue to adyance, both entering into the outlet tube 23 of the valve 7. Advance of the sleeve 33 is halted when flanged end 36 abuts the outer end of outlet tube 23. Guide tube 31 and filling tube 32 advance yet further, compressing spring 37. End plate 34 contacts closure plate 24 of the valve 7 and forces outlet tube 23 sufficiently far from the resilient seal 22 to expose the apertures 25.

Product is then forced under pressure through filling tube 32, and apertures 35 and 25 into the product chamber 14 of the dispenser (Fig. 1).

At the end of the charging sequence the apparatus is withdrawn and as the apparatus withdraws, sleeve 33 is pushed by spring 37 over the apertures 35 in filling tube 32 and seats on end plate 34 thus cutting off flow of product. As the apparatus is withdrawn further the various components retract back to the position shown in Fig. 2.

Claims

1. A method of filling a two chamber container comprising sealing to the container a dispensing valve communicating with the product chamber, reducing the product chamber to minimum volume, charging the product to the product chamber by back-filling via the dispensing valve.

2. A method according to claim 1, in which the volume of the product chamber is reduced by the application of suction to the chamber.

3. A method according to claim 1, in which the volume of the product chamber is reduced by charging propellant to the propellant chamber.

4. A method according to claim 1 or claim 2, in which the product chamber is purged with nitrogen.

5. Apparatus for charging liquiform material to a dispenser through a tilt-valve as hereinbefore defined comprising a filling tube connectible to a reservoir of material to be charged and insertable into the outlet tube of the tilt-valve to abut the closure plate thereof and to open the tilt-valve and a centering tube enclosing and in sliding engagement with the filling tube for positioning the outlet tube of the tilt-valve for insertion of the filling tube.

6. Apparatus according to claim 5, comprising a telescopically mounted assembly of coaxial tubes consisting of a filling tube connectible to a reservoir of material to be charged and insertable into the outlet tube of the tilt-valve to abut the closure plate of the said outlet tube, said filling tube having an end plate and an aperture at or near the end plate permitting passage of material from the filling tube, a tubular sleeve surrounding said filling tube and having a flange for seating on the outer end of the said outlet tube of the valve, a guide tube around said sleeve, spring bias means between the guide tube and the sleeve to urge the sleeve towards the valve outlet tube, and a centering tube for engaging the valve assembly and centering the outlet tube thereof for insertion of the filling tube.

7. A method of filling a two chamber container according to claim 1, substantially as hereinbefore described.

8. Apparatus for charging liquiform material to a dispenser through a tilt-valve, substantially as hereinbefore described with reference to and as illustrated by Figs. 2 and 3 of the drawings.