GB2376048A

GB2376048A - An intermediate piston for dispensing sealant from a tube in sequence

Info

Publication number: GB2376048A
Application number: GB0207062A
Authority: GB
Inventors: David William Armfield; Andrew Robertson Drummond
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-03-31
Filing date: 2002-03-26
Publication date: 2002-12-04
Anticipated expiration: 2022-03-26
Also published as: GB2376048B; GB0207062D0

Abstract

An intermediate piston 11 suitable for use in a sealant tube 22 is positioned at an intermediate position between two consecutive batches of material A and B, keeping them separate, and has an openable means which when open permits material on the upstream side of the piston to pass through to the downstream side. The opening means may be a forward extending nipple which can be cut off to open the piston or a one way valve, such as a poppet valve, normally biassed closed. As piston 24 is advanced material B acts on the intermediate piston 11 which acts on material A causing it to be dispensed through nozzle 23, once all material A is dispensed the opening in the intermediate piston is opened allowing material B to be dispensed in sequence.

Description

Pistons This invention is concerned with pistons, and relates in particular to pistons for use in a tube of sealant, mastic, water-treatment chemicals, or the like.

Sealant tubes (also known as cartridges) are used to dispense mastics and sealant in conjunction with a "gun"into which the tube fits. The tube has a displaceable piston at the proximal end and a nozzle (or nozzle attachment means) at the distal end, and the action of the gun is to push along the piston at the proximal end of the tube so as to cause the tube contents to be extruded in a controlled fashion from a nozzle attached to the tube's distal end. An example of such a sealant gun is shown in the Specification of British Patent No: 1,555, 455). Typical uses for sealant tubes (and their contents) are for sealing baths and work surfaces against moisture, or for packing diverse materials-such as domestic central heating inhibitors - which are injected into the relevant receptacle with a special nozzle. The invention is particularly concerned with sealant tubes/contents intended for this latter use - injecting materials, such as corrosion-control and scale-inhibitor chemicals, into a receptacle such as a central heating system.

Whatever the product therewithin, most common known embodiments of sealant tube employ a tube full of product with a piston at one end which acts both as the means for pushing the contents along and as the closure at that one end (at the other, potential nozzle, end the tube is initially closed with a nipple end cap; when

appropriate the nipple is cut, to open that end, with a knife, scissors or the like). Once the contents are spent the tube is discarded, and a new one is needed.

One exception to this is the co-extruded tube, which contains two different products, and can dispense amounts of one with the other in a ratio corresponding to the co-extruded tube's cross-sectional areas.

Another exception is a tube containing a bag (sometimes called a sausage) which may have one chamber or two, to dispense one product against another (this particular form is used, for example, to dispense an epoxy adhesive and hardener in the correct ratio).

The present invention also concerns a design of the tube/piston combination to allow two products to be dispensed, but consecutively rather than together or in proportion. More specifically the invention relates to a tube with two (or more) batches of product separated by a special, additional, intermediate piston that, once in its fully-forward position, is"opened"to allow the product behind it (on its"upstream"side") to be channelled through (to its"downstream"side) and then out of the cartridge. Thus, as the tube is first used the main piston pushes the tube's contents out through the nozzle, and as it does so the remaining contents, including the intermediate piston, move slowly down the tube towards the nozzle end, the two products being all the while kept separate by the intermediate piston, one (the downstream product) in front and one (the upstream product) behind, and only the first of them-that in front (the downstream one)-being extruded. Then, when all the first, downstream, product has been pushed out, and the intermediate piston reaches the nozzle end of the tube, and there stops, the intermediate piston is opened, permitting passage therethrough of the second

batch of product (the upstream one) that is behind it, so that further use of the sealant gun pushes that second, upstream, product batch through the intermediate piston and thence out of the tube via the nozzle.

In one aspect, therefore, this invention provides a piston suitable for use in a sealant tube or the like as an intermediate piston, positioned in use between two consecutive batches of product and keeping them separate, one upstream, behind the piston, and one downstream, in front of the piston, which piston has within it openable means that when opened permits material on the upstream side of the piston to pass through to the downstream side.

In a second aspect the invention provides a sealant tube utilising an intermediate piston as just defined, and thus having the intermediate piston positioned between two consecutive batches of product and keeping them separate, one upstream, behind the piston, and one downstream, in front of the piston, which piston has within it openable means that when opened permits material on the upstream side of the piston to pass through to the downstream side.

The invention provides a piston suitable for use in a sealant tube or the like (and a tube using such a piston). The tube may be of any sort-that is, it may be for containing, and applying, almost any sort of material that can be so applied. Thus, the material can be, typically, a viscous, paste-like material such as is used for mastics, sealants, water-softener compositions,

and central-heating-system cleaning, de-scaling and protection compositions. Typical tube lengths are around 12 in (about 30 cm), with external diameters of about 2 in (about 5 cm).

The invention's piston is suitable for use in a sealant tube or the like as an intermediate pistonthat is, as a separator of two consecutive batches of product in the tube, one upstream, behind the piston, and one downstream, in front of the piston. As such it may be whatever size and shape is appropriate in the circumstances. Thus, for example, a preferred form of piston is a simple cup shape-tube-fitting, with parallel sides and a single bottom (or end) face in which is the opening means. This piston form is conveniently so orientated that the open end is on the upstream side-with the pressure applied to the product by the tube's main piston being directed into this cup, and tending to force the walls apart into sealing contact with the internal wall surface of the tube-and the closed end is on the downstream side. Typical internal tube diameters-and thus external piston diameters-are a little less than 2 in (about 5 cm); a typical piston length is 3/4 in (or about 2 cm).

The piston can be made of any appropriate material.

Most sealant tubes are made of a plastic, typically a polypropylene or high density polyethylene (HDPE), and the piston can with advantage be made of the same sort of substance, and typically low a density polyethylene (LDPE).

The piston of the invention has within it openable means that when opened permits material on the upstream

side of the piston to pass through to the downstream side. This opening means can be of any sort, but two are particularly convenient-one is a forwardlyextending nipple, that can be cut off to open up the piston to allow the upstream product to pass through, while the second is a one-way valve, that remains closed while there is both upstream and downstream product present in the tube (so that the pressure difference across the piston is generally zero) but opens automatically as soon as all the downstream product is dispensed. The one-way valve can take any convenient form. One such is like a poppet valve-a headed pin floating in a small hole through the piston with the head on the downstream side and biassed in the upstream direction to close the hole on the downstream side; while the tube still contains downstream product, and so the pressure across the piston is zero, the valve closes the hole, but as soon as the downstream product is exhausted the relative positive pressure on the piston's upstream side forces the valve open, so allowing the upstream product to pass.

Both of these types are described further hereinafter with reference to the accompanying Drawings.

The forwardly-extending nipple variety is the preferred of the two, the nipple being relatively elongate, so that as the piston reaches the end of its travel (where it makes sealing contact with the closed end of the tube) the nipple actually projects through the nozzle into the outside, and so can be cut off to allow the upstream product to be pushed out upon further action of the gun driving the system's main piston.

The openable means when opened should be of a sufficiently large aperture that the upstream product can pass therethrough without any significant hindrance.

An aperture of about 1/8 in (about 0.5 cm) is usually sufficient for this.

This principle of an intermediate piston can be applied to create more than two compartments, so that the cartridge/tube could hold more than two different products (or, of course, more than two different portions of the same product, or...).

The sealant tube-and any gun utilised with itmay, apart from the intermediate piston, be of any appropriate construction, and needs no further comment here. However, it may on occasion be desirable-or at least helpful-to be able to see how far along the tube the intermediate piston has been pushed, and so it may be advantageous to employ a tube made of some transparent material such as high clarity polypropylene.

To better understand the invention there are now described a number of specific applications.

Application One Across the country there are regions of hard water and regions of soft water. General-purpose corrosion inhibitors for metal central heating systems have been developed, but it is known that specific hard water or soft water inhibitors work better for their specific water type, and a general purpose inhibitor is a tradeoff (essentially hard water products should carry an appropriate level of scale inhibitor which can cause problems if added to soft water systems). The invention can provide both types of inhibitor in one package.

Application Two Consider a product in use in a central heating system (say, 300ml treats a 100 litre system). This may work fine in its diluted state, but components of the formula may not usefully mix together in concentrated form (problems might include solubility, pH, crystallisation, etc. ), so it might be wise to pack them separately, as Product A in front of the intermediate piston, and Product B behind it. It may not be important when dispensing to know whether Product A or B is dispensing (so a transparent tube is not important) but it is important that they are both dispensed. The invention will facilitate this, and the mixing of Products A & B can be left to the dynamics of the central heating system.

Application Three In the UK there are essentially two types of central heating system; one comprises copper and steel, while the other, known as"mixed metal", contains the aforementioned plus aluminium. Again, general purpose inhibitors have been developed that can be used in either, but there are trade-offs. Components to treat aluminium are not needed in systems that do not contain aluminium, and their presence can affect the performance of the steel inhibitor.

Current methods of packing such products (bottles, sealant tubes etc) do not allow for a variation in the product to be administered, whereas the system of the invention does. By packing Product A on one side of the intermediate piston, followed by product B (that's optionally required), at time of administration the Operative can decide whether to expel the whole tube

(A & B) or to stop after A. Note that the transparent tube plays its part here, in that the Operative can see when the invention's intermediate piston has advanced to its home position (though this can, of course, also be determined by the length of gun plunger remaining).

Consider a sealant tube that first contains soft water inhibitor (to perhaps half its volume) which is capped off with the intermediate piston of the invention. Hard water inhibitor can now be packed into the remaining volume of the tube (onto the back of the invention's piston) and capped off with a conventional piston.

In operation, the very first product to be dispensed will be the soft water product. Once all this is injected the intermediate piston will reach the end of the tube. If this piston is now opened-if of the nipple-using sort, the nipple is cut open-and the sealant gun is now operated, the hard water inhibitor will pass through the opening (cut nipple or one-way valve). Of course, if the hard water product is not needed then the operation is complete without doing this.

By knowing the hardness of the water (calcium carbonate temporary hardness indicator strips are available to aid this determination) the operative can make the appropriate decision.

Note that it is not possible to administer the hard water inhibitor unless the soft water inhibitor has first been expelled from the tube. That all of product A must be used before product B can follow (it is not possible only to dispense product B) should be noted in the design of the product to be administered.

The following Example is now given to illustrate the use of an intermediate piston of the invention, and a sealant tube utilising such a piston.

Example BS7593 is a procedure for commissioning central heating systems prior to operation. It states that a cleaner should be used, followed by the use of an inhibitor.

Consider a sealant tube which first contains cleaner product (to perhaps half its volume) which is capped off with an intermediate piston of the invention of the type having opening means in the form of an elongate nipple. Inhibitor is then packed into the remaining volume of the tube (onto the back of the invention's piston) and capped off with a conventional piston.

In operation, the very first product to be dispensed is the cleaner. Once all the cleaner is injected the invention's intermediate piston reaches, abuts and seals the tube's end, with the piston's elongate nipple projecting though and out of the tube's open end, and it is not possible to advance the second piston any further due to pressure build-up.

After completing the cleaning operation the engineer/plumber Operative cuts the nipple, which allows the flow of inhibitor product behind the piston.

It will be understood that is not possible to administer the inhibitor behind the intermediate piston unless all the cleaner in front of it has first been expelled from the tube.

Again, it will be seen that all of Product A (in front of the intermediate piston) must be used before Product B (behind it) can follow.

Embodiments of the invention are now described, though by way of illustration only, with reference to the accompanying diagrammatic Drawings in which: Figures 1A-C show respectively a valve-using piston of the invention in side (closed), end and side (open) view; Figures 2A, B show respectively a tube (cartridge) of the invention utilising a valve- using piston of the Figure 1 type, first before use and then after extrusion of all the downstream product; Figures 3A-C show respectively a nipple-using piston of the invention in section, side, and end view; and Figures 4A-C show respectively a tube (cartridge) of the invention utilising a nipple- using piston of the Figure 3 type, first before use and then after extrusion of all the downstream product and then after some extrusion of the upstream product.

Figures lA-C show respectively a valve-using piston of the invention in side (closed), end and side (open) view. The piston (11) is a stubby cylinder (12) having a low coaxial wall (13) around its edge on its downstream side. Axially of the piston is a valve, much

like a poppet valve-a pin-like rod (14) having a head (15) at one end and spring-like radial arms (16) at the other, and moving within a tubular opening (17) extending through the cylinder 12.

The arms 16 keep the valve head 15 drawn up (seated) against the downstream end of the tube 17, so keeping the valve closed. However, when upstream pressure significantly exceeds the downstream pressure the valve is forced open, as shown in Figure 1C. The wall 13 ensures that there is space on the downstream side for the valve head 15 to lift off its seating and so open the valve.

Figures 2A, B show respectively a tube (cartridge) of the invention utilising a valve-using piston of the Figure 1 type, first before use and then after extrusion of all the downstream product. The cartridge (generally 21) is an actual tube (22) with a nozzle mount (23) at one end (the distal end) and a piston (24) initially at the other (the proximal end). The piston 24 is driven by a piston rod (25) which is part of the"gun" (not shown) in which the tube 21 is utilised. As shown the tube 22 is filled with two different materials,"A"and"B", separated by a piston 11 of the invention (and as shown in Figure 1).

When the gun is actuated to force out the contents of the tube 22 the valve 14,15, 16,17 in the piston 11 is initially closed (by the spring arms 16), and so long as there is still material A downstream of the piston the pressure drop across the piston is very small. However, once the piston 11 reaches the nozzle end of the tube and stops, the pressure drop increases significantly, forcing open the valve (within the space created by the wall 13), and allowing the material B upstream of the

piston 11 to be forced through the piston and thence out through the nozzle mount 23.

Figures 3A-C show respectively a nipple-using piston of the invention in section, side, and end view.

This version of the piston (generally 31) is like a beaker (32), or a squat cup but without a handle, having an elongate nipple (33) protruding from its bottom (the in-use downstream end).

Figures 4A-C show respectively a tube (cartridge) of the invention utilising a nipple-using piston of the Figure 3 type, first before use and then after extrusion of all the downstream product and then after some extrusion of the upstream product.

The cartridge 21 is itself just like that shown in Figure 2, with a product-containing tube 22, a nozzle mount 23 and an end piston 24 driven by a piston rod 25 from the gun (not shown). As shown the tube 22 is again filled with two different materials,"A"and"B", this time separated by a piston 31 of the invention (and as shown in Figure 3).

When the gun is actuated to force out the contents of the tube 22 the nipple 33 in the piston 31 is initially whole/closed, and none of the material B behind/upstream of the piston 31 can pass that piston and leave the tube. However, once the piston 31 reaches the nozzle end of the tube it stops with the nipple 33 projecting through the nozzle mount 23. If the protruding nipple end is then cut off the material B upstream of the piston 31 can then be forced through the piston and thence out through the nozzle mount 23.

Claims

Claims 1. A piston suitable for use in a sealant tube or the like as an intermediate piston, positioned in use between two consecutive batches of product and keeping them separate, one upstream, behind the piston, and one downstream, in front of the piston, which piston has within it openable means that when opened permits material on the upstream side of the piston to pass through to the downstream side.
2. A piston as claimed in Claim 1, the piston having the form of a simple cup-tube-fitting, with parallel sides and a single bottom (or end) face in which is the opening means.
3. A piston as claimed in either of the preceding Claims, which is made of a low density polyethylene (LDPE).
4. A piston as claimed in any of the preceding Claims, wherein the openable means is either a forwardlyextending nipple, that can be cut off to open up the piston, or a one-way valve normally biassed closed.
5. A piston as claimed in Claim 4, wherein the openable means is a one-way valve like a poppet valve.
6. A piston as claimed in any of the preceding Claims and substantially as described hereinbefore.
7. A sealant tube utilising an intermediate piston as defined in any of the preceding Claims, and thus

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having the intermediate piston positioned between two consecutive batches of product and keeping them separate, one upstream, behind the piston, and one downstream, in front of the piston, which piston has within it openable means that when opened permits material on the upstream side of the piston to pass through to the downstream side.
8. A sealant tube as claimed in Claim 7, which is for containing, and applying, a mastic, sealant, or watersoftener composition, or a central-heating-system cleaning, de-scaling and protection composition.
9. A sealant tube as claimed in either of Claims 7 and 8, wherein the intermediate piston is in cup form, and so orientated that the open end is on the upstream side.
10. A sealant tube as claimed in any of Claims 7 to 9, which is made of a polypropylene or high density polyethylene (HDPE).
11. A sealant tube as claimed in any of Claims 7 to 10, which made of high clarity polypropylene.
12. A sealant tube as claimed in any of Claims 7 to 11 and substantially as described hereinbefore.