Patent Description:
A coaxial cartridge comprising the features of the preamble of claim <NUM> is known from <CIT>.

Two component co-axial cartridges are used so that one and the same hand-held dispenser can be used to dispense both one component and multi-component material. Such multi-component material is used in a plethora of fields of application ranging from industrial applications, such as the use of adhesives to bond structural components one to another, or as protective coatings for buildings or vehicles, to medical and dental applications. The multi-component material is, for example, a two-component adhesive comprising a filler material and a hardener. Co-axial cartridges are available with various ratios of filling, also known as mixing ratios, for example at mixing ratios of <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM> etc..

Since the producer of the coaxial cartridge does not necessarily produce the multi-component material stored within the coaxial cartridge, empty coaxial cartridges are frequently supplied to the producer of the multi-component material. The producer of the multi-component material then fills the coaxial cartridges with the desired multi-component material.

On backfilling coaxial cartridges problems may arise with respect to venting residual air from the coaxial cartridge. These problems may lead to a reduced storage life of components stored in the co-axial cartridge. Furthermore, problems may arise with respect to inserting the piston into the cartridge correctly. This problem of the correct piston insertion can lead to leaks also leading to a reduction in storage life. For this reason many producers favor the option of front filling coaxial cartridges in order to avoid problems associated with both the venting of residual air from the coaxial cartridge and an incorrect placement of the piston.

A further drawback on the prior art designs of coaxial cartridges are the comparatively high extrusion force required to dispense the material making the dispensing thereof more difficult. Yet a further drawback is presented by the amount of volume of material which is left behind as waste in the cartridge once this is empty. The latter problem is particularly undesirable due to fact that the coaxial cartridge is dimensioned to fit into the commercially available hand-held dispensers so that its outer size, e.g. diameter and length, and hence the maximum filling volume is pre-defined and any extra amount of waste is thus highly undesirable.

By way of example, <CIT> discloses a coaxial cartridge that is configured to be used with commercially available hand-held dispensers. The cartridge shown in <CIT> has been designed to achieve a compromise between filing volume and waste volume left behind in the cartridge. In order to achieve this compromise a two part piston design is used and the chambers of the cartridge in the storage position are arranged one after one another along the longitudinal axis of the cartridge.

However, due to the comparatively complex design of the cartridge, i.e. the two-part piston where each of the two parts of the piston are spaced apart axially by the length of the first chamber of the cartridge, and the components cooperating therewith, the maximum filling volume is reduced and it is generally not possible to fill the different components at the same time, but rather these have to be filled one after another which leads to an increased filling time.

In view of the above it is an object of the present invention to further increase the available filling volume of a coaxial cartridge while at least maintaining preferably further reducing the waste volume remaining in the cartridge for front filled cartridges. It is a further object of the invention to reduce the extrusion force on a cartridge while dispensing in order to improve the handling of the coaxial cartridges. It is a further object of the present invention to make available a coaxial cartridge that can be assembled and produced in an as cost effective and facile manner as possible.

Further prior art coaxial cartridges are known from <CIT>; <CIT>; and <CIT>.

This object is satisfied by a discharger in accordance with claim <NUM>.

Such a coaxial cartridge for multi-component materials comprises:.

The counter plug element may be configured to receive said plug element, preferably with said plug element being press fit into said plug receiving element. The method of assembling the coaxial cartridge can be simplified by the use of a plug element and a counter plug element cooperating therewith.

In this connection it should be noted that the outlet is typically formed so that it can be coupled to existing mixers and dispensers.

By forming the inner storage compartment within the outer storage compartment no complex axially spaced apart two-part design of the piston is required. This makes available more storage space than is achievable in prior art coaxial cartridges. By way of example the filling volume is increased by <NUM>% from <NUM> achievable with the coaxial cartridge of <CIT> to <NUM> respectively <NUM> achievable with the design of the cartridge presented herein.

Moreover, by forming the first storage chamber within the second storage chamber at the same axial height a front filling of two components at the same time is made possible leading to a reduction in the time required to fill the cartridges.

Due to the fact that two points of connection are used it has furthermore been found that the connection between the inner tube and outer tube is more rigid, whereby the extrusion force on dispensing can be reduced due to the increased rigidity of the coaxial cartridge.

Moreover, an amount of dead space, i.e. volume in which waste material that is left behind can be collected, can be reduced and can lie in a region between <NUM> and <NUM> depending on the precise design of the cartridge. In comparison to this the coaxial cartridge of <CIT> has a volume of dead space of <NUM>. The reduced amount of dead space can be achieved due to the ability of using more filigree components in the coaxial cartridge as this is more rigid per se.

Thus, by designing the cartridge presented herein with the first storage chamber that is arranged at the same axial height as the second storage chamber and by providing two points of connection to connect the inner tube to the outer tube, a coaxial cartridge is made available that has an increased filing volume while at least substantially maintaining the waste volume. Since the design of the piston can be adapted, it is less complex and the pistons for each storage chamber can work independently from one another, such that the pressure on dispensing can be further reduced improving the handling of the coaxial cartridge in a hand-held dispenser.

The first and second points of connection may be formed by different types of connections. This means that the first and second points of connection are not only formable at different positions at the head part of the cartridge, but may also comprise different components, with each component being adapted to the position at which the connection is made available.

The outlet and the first point of connection may be provided at a further distance from the longitudinal axis than the second point of connection. Forming the outlet and the first point of connection in an eccentric, i.e. decentralized manner, leads to an advantageous design, as the dead space present within a cartridge and hence the waste volume can be reduced by arranging the outlet offset from the longitudinal axis rather than at the longitudinal axis.

The first point of connection may be formed by a radially outwardly projecting lip that is provided at a part of the inner tube that projects into a part of the outer tube, with the radially outwardly projecting lip then engaging a step-like portion formed at the part of the outer tube into which the inner tube projects. In this way a reliable connection can be formed between the inner and outer tube at the outlet.

The first point of connection may be formed by a snap fit connection present at the outlet between the inner tube and the outer tube. A snap fit connection is an advantageous type of connection between two components that can be produced in a cost effective and simple manner.

The second point of connection may be formed at a smaller distance from the longitudinal axis than the first point of connection. By forming the second point of connection in a more a centralized manner than the first point of connection means that the connection between the inner and outer tube can be improved. Moreover, an assembly of the coaxial cartridge can be simplified as it is simpler to position and seal the inner tube relative to the outer tube. Thus, due to the more centralized design of the second point of connection in contrast to the first point of connection, the three functions the connections between the inner tube and the outer tube have to satisfy, namely sealing, holding, and positioning, can be improved in comparison to prior art cartridges.

The second point of connection may be formed between an inner surface of the outer tube that abuts an outer surface of the inner tube at the head part. Such a point of connection can be used to further minimize any residual dead space within a cartridge and lead to an improved positioning and holding of the inner tube relative to the outer tube.

A seal may be formed between the inner tube and the outer tube at the head part, wherein the seal surrounds the second point of connection, optionally wherein the seal is formed between the inner surface of the outer tube that abuts the outer surface of the inner tube. The provision of a seal between the inner tube and the outer tube can prevent a cross-contamination from occurring between the first and second storage compartments.

The plug element may have a plug part having a collar, with the collar having a wider diameter than the plug part arranged at an end of the plug element.

The inner tube may comprise a cylindrical outlet portion as said part that forms part of the outlet that is inserted into a cylindrical outlet portion provided at the outer tube that forms said further part of the outlet, optionally wherein the part of the inner tube that projects into a part of the outer tube is formed by the cylindrical outlet portion and the part of the outer tube into which the inner tube projects is formed by the cylindrical outlet portion provided at the outer tube. The provision of cylindrically shaped parts that cooperate with one another, on the one hand, simplifies the assembly of the coaxial cartridge. On the other hand, a reliable connection can thereby be formed if the connection is formed e.g. as the aforementioned snap-fit connection.

One or more sealing means or sealing members may be provided between the cylindrical outlet portion of the inner tube and the cylindrical outlet portion of the outer tube. In this way a seal is present between the inner tube and the outer tube that, on the one hand, can prevent a cross-contamination from occurring and, on the other hand, increase the storage life of components stored in the coaxial cartridge.

The cylindrical outlet portion of the inner tube may comprise a first passage leading from the first storage compartment to a first outlet opening of the outlet and a second passage leading from the second storage compartment to a second outlet opening of the outlet. By forming the outlet passages from both storage compartments within one component can ensure that no cross-contamination between materials stored within the coaxial cartridge can take place prior to the materials exiting the coaxial cartridge via the outlet.

The outlet may be a side by side outlet comprising first and second outlets having first and second outlet openings. It has hitherto been found that side by side outlets can beneficially be used in front filling applications.

An area of the first outlet opening may differ from an area of the second outlet opening. This can be particularly advantageous if the contents of the cartridge is intended to be dispensed a multiple of times, as the respective outlets can then be sealed off with a cap which then has differently shaped or sized plungers engaging the respective outlets. Such differently shaped or sized components make available a type of alignment means at the outlet.

The first and second outlets may comprise inner sealing surfaces, optionally wherein a supporting rib is provided between the cylindrical outlet portion of the outer tube and the cylindrical outlet portion of the inner tube, with the supporting rib being provided at the same axial height as the inner sealing surfaces or between the axial height of the supporting rib and a respective inlet opening of a passage of the outlet, in particular wherein the supporting rib is arranged adjacent to the axial height of the inner sealing surface.

The inner sealing surfaces can be provided to seal with respect to parts of a cap that may be inserted into the outlet during a storage of the cartridge in order to positively influence the storage life of the components stored in the cartridge. The inner sealing surfaces can also be used on front filling the cartridge in order to seal between the filling nozzle and the outlet to prevent contaminants from being introduced into the coaxial cartridge. The supporting rib is preferably arranged in the region of the inner sealing surfaces as a support member that strengthens that part of the outlet to ensure the inner sealing surfaces engage the respective part with which they cooperate.

The inner tube and the outer tube may comprise projections that project from a respective end face formed at the head part into the first and second storage compartments. The projections can be formed to engage recesses present at the piston in order to further minimize any dead space within the cartridge so as to further reduce any waste of material stored in the cartridge. The projections may be seals that cooperate with part of the piston.

The coaxial cartridge presented herein may further comprise a respective piston arranged in each storage chamber at an end of the coaxial cartridge that is disposed opposite of the head part.

The first and second storage compartments of the coaxial cartridge may comprise respective two-component materials. Such two-component materials may be selected from the group of members consisting of construction material, sealants, bond material, adhesives, paints, coatings and protective coatings and as such the coaxial cartridge presented herein may be used in an industrial sector both for the production of products as well as for the repair and maintenance of existing products, e.g. in the building industry, the automotive industry, the aerospace industry, in the energy sector, e.g. for wind turbines, etc. The coaxial cartridge presented herein may also be used in the medical, dental field or veterinary field.

According to a further aspect the present invention relates to a method of assembling a coaxial cartridge as discussed in the foregoing, the method comprising the steps of:.

The advantages discussed in the foregoing in connection with the coaxial cartridge are achievable by means of the method of assembly and hence likewise hold true for the method presented herein.

Further embodiments of the invention are described in the following description of the Figures. The invention will be explained in the following in detail by means of embodiments and with reference to the drawing in which is shown:.

In the following the same reference numerals will be used for parts having the same or equivalent function. Any statements made having regard to the direction of a component are made relative to the position shown in the drawing and can naturally vary in the actual position of application.

<FIG> shows a side view of an open and empty coaxial cartridge <NUM>. The coaxial cartridge <NUM> comprises a head part <NUM> having an outlet <NUM>. The outlet <NUM> can be sealed off with a plunger <NUM> that is held in position by means of a cap <NUM> (see <FIG>) that can be attached to the outlet <NUM>.

In the example shown in <FIG> the cap <NUM> can be attached to the outlet <NUM> by means of a threaded connection <NUM> of which an external thread <NUM>' is shown in <FIG>. Other forms of connections such as a bayonet type of connection, a plug and rotate type of connection etc. may also be provided in order to attach the cap <NUM> to the outlet <NUM> of the coaxial cartridge <NUM>.

A dividing wall <NUM> of the outlet <NUM> projects from the outlet <NUM> generally in parallel to a longitudinal axis A of the coaxial cartridge <NUM>.

The longitudinal axis A of the coaxial cartridge <NUM> coincides with the common axis of the coaxial cartridge <NUM> and extends from the head part <NUM> to the piston end <NUM> disposed opposite of the outlet <NUM>. The outlet <NUM> is eccentrically arranged with respect to the longitudinal axis A.

The cartridge <NUM> further comprises a cartridge wall <NUM> that extends from the head part <NUM> to the piston end <NUM>. The cartridge wall <NUM> is formed by an outer tube <NUM>.

<FIG> shows a sectional view of the coaxial cartridge of <FIG> along the sectional line A-A. The coaxial cartridge <NUM> further comprises an inner tube <NUM> having an inner space <NUM> forming a first storage compartment configured to store a first component M (see <FIG>). The inner tube <NUM> is arranged within the outer tube <NUM> at the longitudinal axis A, with the longitudinal axis A being common to both the inner tube <NUM> and the outer tube <NUM>.

A space <NUM> formed between the outer tube <NUM> and the inner tube <NUM> forms a second storage compartment configured to store a second component M' (see <FIG>).

The inner tube <NUM> is connected to the outer tube <NUM> at first and second points of connection <NUM>, <NUM> respectively present at the head part <NUM>. The first and second points of connection <NUM>, <NUM> are arranged at different positions <NUM>', <NUM>' at the head part <NUM>. The different positions <NUM>', <NUM>' are arranged spaced apart at different distances from the longitudinal axis A. In the present example both the first and second points of connection <NUM>, <NUM> are eccentrically arranged with respect to the longitudinal axis A.

It should be noted that the first and second points of connection <NUM>, <NUM> are also formed by different types of connections in the present example. This means that at least the shape of the first type of connection <NUM> differs from that of the second type of connection <NUM>. In addition to having a different shape the way in which the components of the first and second types of connection <NUM>, <NUM> engage one another can also differ.

First and second pistons <NUM>, <NUM> are arranged in the spaces <NUM>, <NUM> at the piston end <NUM>. The first piston <NUM> is arranged within the inner tube <NUM> and is configured to dispense the material M from the coaxial cartridge <NUM>. The second piston <NUM> is arranged within the space <NUM> formed between the inner tube <NUM> and the outer tube <NUM> and is configured to dispense the material M' from the coaxial cartridge <NUM>. The second piston <NUM> is a ring shaped piston with an aperture <NUM>' at its center.

The first and second pistons <NUM>, <NUM> are arranged moveable along the longitudinal axis A between the piston end <NUM> and the outlet <NUM>. On front filling the coaxial cartridge <NUM> via the outlet <NUM>, the first and second pistons <NUM>, <NUM> are moved such that they are directly adjacent to the head part <NUM> and are then moved towards the piston end <NUM>, rather like the action of filling a syringe, along the longitudinal axis A.

On dispensing the materials M, M' the pistons are moved in the opposite direction along the longitudinal axis A from the piston end <NUM> towards the head part <NUM>. A plunger of a dispensing apparatus (not shown) that cooperates with the first and second pistons <NUM>, <NUM> via a shuttle (not shown) or the like (such as a peeler device <NUM> discussed in connection with <FIG>) is inserted into the coaxial cartridge <NUM> from the piston end <NUM> for this purpose.

<FIG> shows an enlarged sectional view of view C of <FIG>, more specifically of the head part <NUM>. The first point of connection <NUM> is formed at the outlet <NUM> and the outlet <NUM> and the first point of connection <NUM> are provided at a further distance D2 from the longitudinal axis A than the distance D1 between the second point of connection <NUM> and the longitudinal axis A.

It should be noted in this connection that the distance D2 is the shortest distance between any part of the second point of connection and the longitudinal axis A.

The distance D2 can for example be selected in the range of <NUM> to <NUM> %, preferably <NUM> to <NUM>% of the internal radius of the outer tube <NUM> and in the present example amounts to <NUM>% of the internal radius of the outer tube <NUM>.

In this connection it should be noted that the distance D2 can, for example, be selected between <NUM> % and <NUM>% larger than the distance D1.

The distance D1 can for example be selected in the range of <NUM> to <NUM> %, preferably <NUM> to <NUM>% of the internal radius of the outer tube <NUM> and in the present example amounts to <NUM>% of the internal radius of the outer tube <NUM>.

The first point of connection <NUM> comprises a radially outwardly projecting annular lip <NUM> that is provided at a part <NUM> of the inner tube <NUM> that projects into a part <NUM> of the outer tube <NUM>, with the radially outwardly projecting lip <NUM> engaging an annular step-like portion <NUM> formed at the part <NUM> of the outer tube <NUM> into which the inner tube <NUM> projects at the outlet <NUM>.

More specifically, the first point of connection <NUM> is formed by a snap fit connection <NUM> present at the outlet <NUM> between the inner tube <NUM> and the outer tube <NUM> that is formed by the radially outwardly projecting annular lip <NUM> that is configured to engage the annular step-like portion <NUM>.

The inner tube <NUM> comprises a cylindrical outlet portion <NUM>' as said part <NUM> that forms part of the outlet <NUM>. The cylindrical outlet portion <NUM>' is inserted into a cylindrical outlet portion <NUM>' provided at the outer tube <NUM>. The cylindrical outlet portion <NUM>' forms said further part <NUM> of the outlet <NUM>.

The cylindrical outlet portion <NUM>' comprises a convexly shaped outer surface <NUM>" that cooperates with a concavely shaped inner surface <NUM>" of the cylindrical outlet portion <NUM>'.

It should be noted in this connection that the concavely shaped inner surface <NUM>" and the convexly shaped outer surface <NUM>' may extend in parallel to or substantially in parallel to the longitudinal axis A.

The outlet <NUM> is a side by side outlet <NUM> and at its end <NUM> facing the spaces <NUM>, <NUM> has respective first and second inlet openings <NUM>, <NUM>'. At its end <NUM> opposite the end <NUM> the outlet <NUM> has first and second outlet openings <NUM>, <NUM>' of the first and second outlets <NUM>', <NUM>".

The inlet opening <NUM> is connected to the outlet opening <NUM> in a fluid conducting manner in order to transport only the material M from the space <NUM> out of the outlet <NUM> via a first passage <NUM>.

The inlet opening <NUM>' is connected to the outlet opening <NUM>' in a fluid conducting manner in order to transport only the material M' from the space <NUM> out of the outlet <NUM> via a second passage <NUM>'.

An area of the first outlet opening <NUM> differs from an area of the second outlet opening <NUM>'. In fact the area of the first outlet opening <NUM> can be selected in the range of <NUM> to <NUM>% of the area of the second outlet opening <NUM>'.

In this connection it should be noted that the cylindrical outlet portion <NUM>' of the inner tube <NUM> comprises both the first passage <NUM> leading from the first storage compartment formed by the space <NUM> to the first outlet opening <NUM> of the outlet <NUM> and the second passage <NUM>' leading from the second storage compartment formed by the space <NUM> to the second outlet opening <NUM>' of the outlet <NUM>, with the first and second passages <NUM>, <NUM>' being separated from one another by the dividing wall <NUM>. The dividing wall <NUM> extends from and is integrally formed with an outer wall <NUM>' of the inner tube <NUM> in such a way that the material M, M' stored in the respective space <NUM>, <NUM> can only come into contact with one another.

In this connection it should be noted that the outer wall <NUM>' of the inner tube <NUM> is a cylindrical outer wall <NUM>' that extends from the head part <NUM> to the piston end <NUM>.

The area of the respective outlet opening <NUM>, <NUM>' is larger than the area of the respective inlet opening <NUM>, <NUM>' associated therewith. In this connection it should be noted that an area of the respective outlet opening <NUM>, <NUM>' may be selected in the range of <NUM> to <NUM>%, in particular of <NUM> to <NUM>%, of the area of the respective inlet opening <NUM>, <NUM>'.

The first and second outlets <NUM>', <NUM>" comprise inner sealing surfaces <NUM>, <NUM>' that circumferentially extend around the first and second passages <NUM>, <NUM>'. The inner sealing surfaces <NUM>, <NUM>' may be arranged at a part <NUM>, <NUM>' of the respective first and second passages <NUM>, <NUM>' which is arranged between the respective inlet opening <NUM>, <NUM>' and the respective outlet opening <NUM>, <NUM>' and which has the shape of a truncated cone with a wide part of the truncated cone being disposed closer to the respective outlet opening <NUM>, <NUM>' than the narrower part of the truncated cone.

The inner sealing surfaces <NUM>, <NUM>', respectively the part <NUM>, <NUM>', is arranged to extend over an axial height A2 which is above an axial height A1 measured as a distance between an inner end face <NUM> of the inner tube <NUM> and the start of the inner sealing surfaces <NUM>, <NUM>'.

The end of the inner sealing surfaces <NUM>, <NUM>' respectively of the part <NUM>, <NUM>' is spaced apart from the outlet openings <NUM>, <NUM>' of the first and second outlets <NUM>', <NUM>" by an axial height A3, with a height of the cylindrical outlet portion <NUM>' of the inner tube <NUM> being the sum of the axial heights A1 + A2 + A3.

In this connection it should be noted that A1 is typically selected in the region of <NUM> to <NUM> %, in particular in the region of <NUM> to <NUM>% of the height of the cylindrical outlet portion <NUM>' measured between the inner end face <NUM> of the inner tube <NUM> and the outlet openings <NUM>, <NUM>'.

It should further be noted that A2 is typically selected in the region of <NUM> to <NUM> %, in particular in the region of <NUM> to <NUM>% of the height of the cylindrical outlet portion <NUM>' measured between the inner end face <NUM> of the inner tube <NUM> and the outlet openings <NUM>, <NUM>'.

It should further be noted that A3 is typically selected in the region of <NUM> to <NUM> %, in particular in the region of <NUM> to <NUM>% of the height of the cylindrical outlet portion <NUM>' measured between the inner end face <NUM> of the inner tube <NUM> and the outlet openings <NUM>, <NUM>'.

A supporting rib <NUM> is arranged between the cylindrical outlet portion <NUM>' of the outer tube <NUM> and the cylindrical outlet portion <NUM>' of the inner tube <NUM>. The supporting rib <NUM> shown in <FIG> is formed at the cylindrical outlet portion <NUM>' of the inner tube <NUM>, but could likewise be formed at the cylindrical outlet portion <NUM>' of the outer tube <NUM>.

In the drawing shown the supporting rib <NUM> is arranged at an axial height that is directly adjacent to an axial height of the inner sealing surfaces <NUM>, <NUM>' between the inner end face <NUM> of the inner tube <NUM> and the outlet openings <NUM>, <NUM>'.

It should be noted in this connection that the supporting rib <NUM> could also be arranged offset from or even spaced apart from the inner sealing surfaces <NUM>, <NUM>' between the inner end face <NUM> of the inner tube <NUM> and the outlet openings <NUM>, <NUM>'.

It should also be noted that a centering rib <NUM>' may additionally be arranged between the outlet openings <NUM>, <NUM>' and the inlet openings <NUM>, <NUM>', more specifically between the supporting rib <NUM> and the outlet openings <NUM>, <NUM>', optionally on the convexly shaped outer surface <NUM>" of the inner tube <NUM>.

The function of the centering rib <NUM>', if provided, is to axially align the cylindrical outlet portion <NUM>' of the inner tube <NUM> relative to the cylindrical outlet portion <NUM>' of the outer tube <NUM> in order to thereby further ensure the coaxial arrangement of the inner tube <NUM> and the outer tube <NUM> relative to the longitudinal axis A.

Two annular sealing lips <NUM>, <NUM>' are provided as sealing members <NUM>, <NUM>' between the cylindrical outlet portion <NUM>' of the inner tube <NUM> and the cylindrical outlet portion <NUM>' of the outer tube <NUM>. The sealing lips <NUM>, <NUM>' shown in <FIG> are formed at the cylindrical outlet portion <NUM>' of the outer tube <NUM>, but could likewise be formed at the cylindrical outlet portion <NUM>' of the inner tube <NUM>.

The sealing lips <NUM>, <NUM>' are arranged at an axial height between the inner end face <NUM> of the inner tube <NUM> and the supporting rib <NUM> in order to prevent material M, M' from leaking between the cylindrical outlet portion <NUM>' of the outer tube <NUM> and the cylindrical outlet portion <NUM>' of the inner tube <NUM>.

The sealing members <NUM>, <NUM>' are provided to prevent multi-component material M' stored in the space <NUM> forming the second storage compartment from exiting the coaxial cartridge <NUM> between the cylindrical outlet portion <NUM>' of the inner tube <NUM> and the cylindrical outlet portion <NUM>' of the outer tube <NUM>.

<FIG> further shows that the second point of connection <NUM> is formed between an inner surface <NUM> of the outer tube <NUM> that abuts an outer surface <NUM> of the inner tube <NUM> at the head part <NUM>. The outer surface <NUM> is oppositely disposed of the inner end face of the inner tube <NUM>.

A seal <NUM> is formed between the inner tube <NUM> and the outer tube <NUM> at the head part <NUM>. The seal <NUM> surrounds the second point of connection <NUM> and is formed between the inner surface <NUM> of the outer tube <NUM> and the outer surface <NUM> of the inner tube <NUM>.

The second point of connection <NUM> is formed by a plug element <NUM> provided at the inner tube <NUM> that cooperates with a plug receiving element <NUM> as a counter plug element which is provided at the outer tube <NUM>. The plug receiving element <NUM> is configured to receive said plug element <NUM>. In the example shown the plug receiving element <NUM> receives said plug element <NUM> by means of a press fit.

The plug element <NUM> has plug part <NUM> having a collar <NUM>, with the collar <NUM> having a wider diameter than the plug part <NUM> arranged at the end <NUM> of the plug element <NUM>. A space <NUM> may be present between a base <NUM>' of the plug receiving element <NUM> and end <NUM> of the plug element <NUM>.

On connecting the plug element <NUM> to the plug receiving element <NUM>, the collar <NUM> engages a ring-like recess <NUM> formed within the plug receiving element <NUM> and is thereby received by means of a press-fit in the plug receiving element <NUM>.

<FIG> shows a side view of a filed coaxial cartridge <NUM> with the cap <NUM> installed at the outlet <NUM>. The cap <NUM> is screwed onto the external thread <NUM>' present at a collar <NUM> of the outlet <NUM>. The collar <NUM> projects from the front end <NUM> of the outer tube <NUM>.

<FIG> shows a sectional view of the coaxial cartridge <NUM> of <FIG> along the sectional line B-B. The coaxial cartridge <NUM> is filed with the multi-component materials M, M'. In order to ensure that the multi-component materials M, M' can be stored for a desired and pre-defined duration, the plunger <NUM> is inserted into first and second passages <NUM>, <NUM>' of the outlet <NUM> and is retained at the outlet <NUM> by means of the cap <NUM>. The cap <NUM> is retained at the outlet <NUM> by means of screwing this to the external thread <NUM>' present at the collar <NUM> of the outlet <NUM>. For this purpose the cap <NUM> has an internal thread <NUM>".

The plunger <NUM> comprises first and second plungers <NUM>', <NUM>" that are respectively inserted into the first and second passages <NUM>, <NUM>' and that abut the inner sealing surfaces <NUM>, <NUM>' in order to ensure a seal is present therebetween such that the material M, M' can be stored for the desired and pre-defined duration.

The supporting rib <NUM> is provided to support the inner sealing surfaces <NUM>, <NUM>' such that they are held in position when the first and second plungers <NUM>', <NUM>" are inserted into the first and second passages <NUM>, <NUM>', thereby ensuring a sealing contact between the inner sealing surfaces <NUM>, <NUM>' and the first and second plungers <NUM>', <NUM>".

Other types of caps are well known to the person skilled in the art and can naturally also be used. Also a film seal could be present in the region of the outlet openings <NUM>, <NUM>' to further ensure the desired and pre-defined storage life of the multi-component material M, M' stored in the coaxial cartridge <NUM>.

As also indicated in <FIG> and <FIG>, the inner end face <NUM> of the inner tube <NUM> and the inner surface <NUM> of the outer tube <NUM> comprise projections <NUM>, <NUM>, <NUM>' that project into the spaces <NUM>, <NUM> forming the first and second storage compartments.

The projections <NUM>, <NUM>, <NUM>' cooperate with grooves <NUM>, <NUM>, <NUM>' present at the first and second pistons <NUM>, <NUM>. The first piston <NUM> has the groove <NUM> which cooperates with the projections <NUM> and the second piston <NUM> has the grooves <NUM>, <NUM>' which cooperate with the projections <NUM>, <NUM>'.

The projections <NUM>, <NUM>, <NUM>' are arranged in a circumferential manner and face away from the head part <NUM> along the longitudinal axis A of the coaxial cartridge <NUM>. The projections <NUM>, <NUM>, <NUM>' are configured to engage the grooves <NUM>, <NUM>, <NUM>' of the pistons <NUM>, <NUM> such that substantially no air is trapped between the inner end face <NUM> and a conveying side <NUM>' of the first piston <NUM> and between the <NUM> and a conveying side <NUM>" of the second piston <NUM>.

These projections <NUM>, <NUM>, <NUM>' are thus present, on the one hand, so that on front filling the cartridges no residual air is trapped in the cartridge that could diminish the desired and pre-defined storage life and that once the coaxial cartridge <NUM> has been emptied, i.e. the multi-component material M, M' has been dispensed therefrom, as little waste material as possible remains in the coaxial cartridge <NUM>.

In a manner known per se the first and second pistons <NUM>, <NUM> have sealing elements <NUM> arranged at inner and outer surfaces thereof that seal between the respective piston <NUM>, <NUM> and the inner and outer tubes <NUM>, <NUM>.

Also indicated in <FIG> is the peeler device <NUM> that is coupled to sides <NUM> of the first and second pistons <NUM>, <NUM> disposed opposite of the respective conveying sides <NUM>', <NUM>".

On using the coaxial cartridge <NUM> in a dispensing device (not shown), the cap <NUM> and the plunger <NUM> are typically removed and a mixing tip (not shown) is attached in their place at the outlet <NUM> via the external thread <NUM>'.

An outer surface <NUM>‴ of the outlet <NUM> present between the external thread <NUM>' and the outlet openings <NUM>, <NUM>' may be configured as a sealing surface that is adapted to seal between the outlet <NUM> and the mixing tip in order to form a barrier for the multi-component material M, M' and to ensure that this exits the mixing tip via an outlet of the mixing tip (not shown) and not via the external thread <NUM>'.

It should further be noted that one or more slits (not shown) may be provided in the outer surface <NUM>"', with the one or more slits extending through the part <NUM> of the outer tube <NUM>. If provided this slit enables a more facile method of introducing the part <NUM> of the inner tube <NUM> into the part <NUM>, as the annular lip <NUM> can pry apart the part <NUM> more easily if this comprises a slit than if no slit is provided.

On inserting a plunger of a single component dispensing device (both not shown) into the piston end <NUM> the plunger presses against the peeler device <NUM> which in turn presses against the sides <NUM> of the first and second pistons <NUM>, <NUM>. Since single component dispensing devices typically only have one plunger the second piston <NUM> would not normally be actuated, and the wall <NUM>' would also hinder the movement of the plunger along the longitudinal axis A towards the head part <NUM>.

In order to ensure the second piston <NUM> is actuated the peeler device <NUM> is configured to also engage the second piston <NUM>. Since the outer wall <NUM>' at some point will inevitably contact the peeler device <NUM>, the peeler device <NUM> has gaps present therein (not shown) and a plurality of cutting blades (also not shown).

The cutting blades are configured to cut the outer wall <NUM>' in the longitudinal direction into strips. The cut strips of outer wall <NUM>' are then guided via the gaps to an outwardly inclined wall <NUM> whereby the strips of outer wall <NUM>' are deflected radially outwardly. The function of the peeler device in cooperation with the first and second pistons <NUM>, <NUM> and the cutting and peeling of the outer wall <NUM>' is known per se to the person skilled in the art.

A method of assembling the coaxial cartridge will be discussed in the following. In a first step the outer tube <NUM> having the part <NUM> of the outlet <NUM> formed at the head part <NUM> of the outer tube <NUM> is provided. The outer tube <NUM> could e.g. be produced in an injection molding process.

In the next step the inner tube <NUM> is inserted into said outer tube <NUM>, with the inner tube <NUM> comprising the remaining part of said outlet <NUM>. The inner tube <NUM> could also e.g. be produced in an injection molding process. In this connection the inner and outer tubes <NUM>, <NUM> can be made from the same material or from different materials as the case may be. The materials of the inner and outer tubes <NUM>, <NUM> is generally selected in dependence on the materials M, M' to be stored therein.

Following this the inner tube <NUM> is connected to said outer tube <NUM> at the two points of connection <NUM>, <NUM> that are present at the head part <NUM> to form the coaxial cartridge <NUM> with two storage compartments. The first point of connection <NUM> is formed by the snap fit connection <NUM> present at the outlet <NUM> and the second point of connection <NUM> is present at abutting end surfaces of the inner and outer tubes <NUM>, <NUM>.

It should be noted that a wall thickness of the cartridge wall <NUM>, i.e. a wall thickness of the outer tube <NUM>, is generally selected in the range of <NUM> to <NUM>, in particular in the range of <NUM> to <NUM>.

Claim 1:
A coaxial cartridge (<NUM>) for multi-component materials (M, M'), the coaxial cartridge (<NUM>) comprising:
- a head part (<NUM>) having an outlet (<NUM>),
- an inner tube (<NUM>) having a space (<NUM>) present therein, the space (<NUM>) forming a first storage compartment configured to store a first component (M), wherein part (<NUM>) of the inner tube (<NUM>) forms part of the outlet (<NUM>), and
- an outer tube (<NUM>), wherein the inner tube (<NUM>) is arranged within the outer tube (<NUM>) at a longitudinal axis (A) of the coaxial cartridge (<NUM>), with the longitudinal axis (A) being common to both the inner tube (<NUM>) and the outer tube (<NUM>); and wherein a space (<NUM>) formed between the outer tube (<NUM>) and the inner tube (<NUM>) forms a second storage compartment configured to store a second component (M'), and wherein part (<NUM>) of the outer tube (<NUM>) forms a further part of the outlet (<NUM>), wherein the inner tube (<NUM>) is connected to the outer tube (<NUM>) at first and second points of connection (<NUM>, <NUM>) respectively present at the head part (<NUM>), with the first and second points of connection (<NUM>, <NUM>) being arranged at different positions (<NUM>', <NUM>') at the head part (<NUM>), with the different positions (<NUM>', <NUM>') being arranged spaced apart at different distances from the longitudinal axis (A), and wherein the first point of connection (<NUM>) is formed at the outlet (<NUM>),
characterized in that
the second point of connection (<NUM>) is formed by a plug element (<NUM>) provided at the inner tube (<NUM>) that cooperates with a plug receiving element (<NUM>), provided at the outer tube (<NUM>).