Disposable cartridges containing various products such as adhesives, sealants and the like are well known throughout many industries. The contents are usually expelled from the cartridges by means of a gun that acts against a piston contained within the cartridge to expel the contents from an aperture at the other end of the cartridge. The guns typically include a bed to retain the cartridge and a piston pusher mechanism, usually having a trigger to incrementally advance a piston pusher on the end of a rod that extends into the cartridge to bear against the piston. Standard single component cartridges typically have a diameter of around 46mm It is also known to use coaxial cartridges which dispense two components in a selected ratio. These cartridges are effectively formed by two coaxially arranged compartments each containing one of the two components and having a separate piston for discharge of the component. The two components are typically components of epoxy or polyester which when mixed in a selected ratio cure to form to form a hardened material. In this type of cartridge the two components are expelled from their respective separate compartments, passed through a static mixer and then some form of mixer nozzle for direct application. The cartridge dispensing guns used with these two component cartridges have a pair of coaxially arranged piston pushers that are simultaneously advanced by the same mechanism.

A difficulty arises because different types of materials require differing ratios between the two components contained within the cartridges. This is achieved by adjusting the diameter of the inner compartment so that the appropriate volumetric ratio between the components expelled by the same amount of linear movement of the corresponding pistons is achieved. Component ratios of 2: 1,8: 1, and 10: 1 are in common use. Another difficulty arises because coaxial cartridges have different capacities this changing the external diameter of the cartridge. These all require different cartridge dispensing guns.

It is an object of this invention to provide an improved cartridge dispensing guns for cartridges of the kind containing two components.

According to the present invention, there is provided a manually operable cartridge dispensing gun for cartridges of the kind containing two components, said gun including a bed to captively retain the cartridge, a manually operable drive assembly to advance inner and outer concentrically arranged piston pushers against corresponding pistons in the cartridge, the outer piston pusher being dimensioned to bear against a circumferentially outermost piston in the cartridge and including a central aperture to accommodate the inner piston pusher of a first dimension for use with an inner piston of a cartridge having a first component ratio, said inner piston pusher being selectively reconfigurable to a second, reduced, dimension for use with an inner piston of a cartridge having a second component ratio.

In a preferred embodiment the inner and outer piston pushers form a pusher assembly and the inner piston pusher is reconfigured by removing an element of the pusher assembly.

For example, the pusher assembly can include a rod that is advanced having a threaded end that receives a correspondingly threaded pusher. The end of the rod can be of a diameter selected to correspond to the second reduced dimension when the threaded pusher element is removed.

Preferably, the outer piston pusher takes the form of a circular ring.

In a preferred configuration the outer piston pusher is removable enabling the gun to also be used with standard single component cartridges.

In the preferred form of the invention a central rod aligned with the longitudinal axis of the cartridge is advanced by the drive assembly. The inner piston pusher is mounted to one end of the rod. The outer piston pusher is concentrically mounted with the inner pusher by means of two parallel extending rods that attach to the central rod adjacent the end remote from the cartridge. Preferably, guide slots are formed in an end plate on the bed of the gun to guide the parallel rods and maintain the position of the outer pusher with respect to the

inner pusher. The guide slots are preferably open so that the parallel rods can be resiliently displaced and disengaged from the guide slots in the end plate.

One embodiment of the invention will be now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a perspective view of a cartridge dispensing gun according to this invention; Figure 2 is an enlarged view of part of Figure 1 looking from the front of the gun; Figure 3 is an enlarged perspective view of part of the gun shown in Figure 1, looking from the rear of the gun; Figure 4 is an elevation of the gun shown in Figure 1; and Figure 5 is a rear end view of the gun shown in Figure 1.

Figures 1 to 5 show a cartridge dispensing gun 1 for cartridges of the kind containing two components. The cartridges are not illustrated but will be well known to those skilled in the art and are essentially formed by inner and outer concentrically arranged compartments containing separate components. Each compartment is associated with a respective piston for discharge of the component. So-called Jumbo cartridges are typically of an outer diameter of approximately 66mm, and standard cartridges are typically of an outer diameter of approximately 60mm. In the case of a 10: 1 two component cartridge the inner compartment typically is of the order of 19.5mm in diameter. In a 2: 1 component cartridge, the inner compartment diameter is approximately 37mm. In the case of 8: 1 cartridge, the outer diameter is typically 60mm and the inner compartment diameter is approximately 19mm The cartridge dispensing gun 1 is of the general type known to those skilled in the art.

It includes a bed 2 and a front plate 3. The cartridge (not shown) is positioned in the bed 2 and the front end of the cartridge bears against plate 3. Concentrically-arranged piston pushers 4 and 5 are advanced by an advancing mechanism 6 to expel the contents of the cartridge. The advancing mechanism 6 includes a central rod 7 aligned with the longitudinal axis of the cartridge and is advanced by repeated operation of a manual trigger 8 which displaces a reciprocable dog or clutch 8a which engages with, and releases from, the rod 7

in known manner. The trigger 8, clutch 8a and its co-operation with the rod 7 form a drive assembly of the advancing mechanism; such drive assemblies are well known per se for guns of this type and will not be described in greater detail. The rod 7 carries an inner piston pusher 4 that corresponds to the dimension of the inner piston of a two component cartridge, say of the 2: 1 type. That is, pusher 4 is slightly less than 37mm in diameter. Piston pusher 4 is threadedly engaged with rod 7 at its forward end 9 and can be manually removed. The threaded end 9 of rod 7 is dimensioned to correspond to the dimension of a second smaller piston of the two component cartridge say of the 10: 1 type. That is, the rod end 9 is slightly less than 19.5mm in diameter.

The outer piston pusher 5 is annular in form and is mounted by two rods 11,12 that extend parallel to rod 7. The rods 11,12 are threadedly engaged with the outer pusher 5.

The rear ends of rods 11 and 12 extend through a connecting plate 13, arranged transversely of rods 11,12 and 7. The rods 11,12 are secured to the connecting plate 13 by any suitable means. They can, for example, be threadedly engaged with the plate 13 or can be formed with a shoulder and an adjacent threaded portion that allows fastening nuts to secure the rod to the plate 13. Rod 7 is releasably secured to the connecting plate 13. This can be achieved by forming a shoulder 14 and an adjacent reduced diameter threaded end portion (not shown in detail) that receives a threaded knob 15. The plate 13 is clamped between the shoulder 14 and the threaded knob 15. The connecting plate 13 thus provides a fixed mechanical connection between rods 11,12 and 7. Consequently the advancement of the rod 7 by the advancing mechanism 6 simultaneously advances rods 11 and 12. In use this means that piston pushers 4 and 5 advance together.

Alignment of rods 11 and 12 is provided by means of an end plate 16 at the rear end of bed 2 adjacent the advancing mechanism 6. The end plate 16 is formed with two open slots 17,18 which include circular guide openings 19,20. The openings 19,20 are spaced to correspond to the spacing of rods 11 and 12 and open into slots 17,18. The rods 11,12 are releasably retained within the openings 19,20 by a resilient snap action and can be released therefrom. The snap-in retention of the rods 11,12 in the openings 19,20 can be achieved by lateral flexing of the rods 11,12 by passage along the opposed lateral edges of the end

plate 16, these edges being laterally divergent as illustrated; alternatively snap-in retention can be achieved by detents at the edge of the openings such that the rods 11,12 can be locked in the openings 19,20 by the detents. The assembly comprising outer pusher 5, rods 11 and 12 and connecting plate 13 to be removed from the gun by first removing knob 15, disengaging rod 7 from plate 13 and releasing rods 11,12 from the openings 19,20. With this assembly removed, the gun has a single pusher 4 and can be used with standard single component cartridges. It is to be noted that when the rods 11,12 are locked within the openings 19,20, they are able to freely move longitudinally within the openings.

In the normal configuration with both piston pushers 4 and 5 in place the gun provides for dispensing of two component cartridges in the substantially known manner. However the ability to remove or reconfigure piston pusher 4 allows for the gun to be readily adapted for use with two component cartridges of different component ratios, or in other words different inner compartment diameters. With the piston pusher 5 removed, the gun can be used with single component cartridges. This adaptability of the cartridge gun of the present invention provides a significant advantage of allowing a single cartridge gun to be used for a range of different cartridges.

The foregoing describes only one embodiment of this invention and modifications can be made without departing from the scope of the invention.

Throughout this specification and claims which follow, unless the context requires otherwise, the word"comprise", and variations such as"comprises"or"comprising", will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.