Abstract:
The invention relates to an adhesive gun which can be handled by individuals and can be used for applying in particular a two-component adhesive, which enables a large mixing ratio between a relatively viscous adhesive component and a relatively liquid adhesive component in an adhesive gun in a simple manner. In addition, the invention relates to a holder for a relatively liquid adhesive component, a mixing unit and a connecting piece for use in an adhesive gun of this type. The invention furthermore provides a method for applying a multi-component adhesive using an adhesive gun of this type.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims priority to NEDERLANDEN 1026872, filed Aug. 19, 2004. 
   FIELD OF THE INVENTION 
   The invention relates to an adhesive gun which can be handled by individuals and can be used for applying a multi-component adhesive, in particular a two-component adhesive, comprising a first cylindrical container provided with a first plunger for pressing a relatively viscous adhesive component out of the first cylindrical container, a second cylindrical container provided with a second plunger for pressing a relatively liquid adhesive component out of the second cylindrical container, a mixing unit into which the first cylindrical container and the second cylindrical container open, and drive means for moving the first and second plungers, the drive means being designed for a velocity of the first plunger which is greater than the velocity of the second plunger. 
   In addition, the invention also relates to a holder for a relatively liquid adhesive component, a mixing unit and a connecting piece for use in an adhesive gun of this type. The invention furthermore provides a method for applying a multi-component adhesive using an adhesive gun of this type. 
   BACKGROUND OF THE INVENTION 
   Multi-component adhesive, in particular two-component adhesive, is generally applied using an adhesive gun consisting of two parallel cylindrical compartments: a first container for a first adhesive component and a second container for a second adhesive component. Generally, the first adhesive component contains constituents which cure when mixed with the second adhesive component. In general, the second adhesive component comprises a catalyst for the curing reaction, the curing reaction comprising, for example, a (co)polymerisation, crosslinking or vulcanization reaction. The adhesive gun to be used is in this case designed such that the two components are pressed out of the containers by means of plungers, with the two plungers being moved simultaneously in order to achieve a constant and uniform flow of both components from their containers. The two components are brought together in order to then be applied to a surface to be treated via a mixing unit of the adhesive gun. In order to achieve an optimum adhesive result, the two components must be mixed homogeneously, in which case an accurate mixing ratio is important. 
   DESCRIPTION OF RELATED ART 
   EP 0 057 465 describes an adhesive gun in which both plungers are driven by a motor, using a mechanical distributor which is designed such that the plungers can be moved at different speeds. The mechanical distributor can be set such that the mixing ratio of the two components is set to between 1:1 and 10:1. With standard types of two-component adhesive, such mixing ratios result in a feasible curing time and an applied adhesive of sufficient quality. One drawback of this design is, however, that the mechanical distributor is relatively complicated and therefore susceptible to failure. Durability is very important with adhesive guns, since they often have to be used under circumstances which make them susceptible to failure. Furthermore, when large differences in the velocities of the plungers occur (for example, 10:1), it appears to be difficult with such adhesive guns to maintain the correct mixing ratio at a constant level and to achieve a good mixture. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is to enable a large mixing ratio between a relatively viscous adhesive component and a relatively liquid adhesive component in an adhesive gun in a simple manner. 
   To this end, the invention provides an adhesive gun of the type mentioned in the introduction, characterized in that the first cylindrical container has a larger inner diameter than the second cylindrical container. 
   Due to this simple adjustment, large mixing ratios appear to be possible. The flow rate from a cylindrical container is a function of, on the one hand, the velocity of the plunger pressing the adhesive component out of the container, and the inner diameter of the cylindrical container which, in combination with the axial cylinder length, determines the volume of the cylinder. By combining the ratio of the velocities of the plungers with a favourable ratio of the inner diameter of the cylinders, mixing ratios between the relatively viscous and the relatively liquid adhesive component of greater than 10:1, for example 20:1 or even 40:1, are conceivable without complicated technical measures being required in this case. Incidentally, it is conceivable for the composition of the adhesive components to be chosen such that, based on their viscosity, the adhesive components are effectively designated incorrectly: the designation merely serves to distinguish two different adhesive components. By combining a simple mechanical distributor for moving the plungers at different velocities with cylinders of different inner diameter, greater mixing ratios of adhesive components can be achieved than are known in the prior art, without this affecting the durability of the adhesive gun. In this case, the ratio between the velocities of the plungers may be fixed, but an adjustable mechanical distributor is also conceivable, such as is known, for example, from EP 0 057 465. The drive means may, for example, comprise an electric motor. 
   It is advantageous if the drive means are designed for a velocity of the first plunger which is at least 1.5 times greater than the velocity of the second plunger. As a result of the difference in velocities, the flow rate of the relatively viscous component which is pressed out of the first container by the first plunger is at least 1.5 times greater than the flow rate of the relatively liquid component which is pressed out of the second container by the second plunger. The eventual ratio of the flow rates of the relatively viscous and the relatively liquid component is obtained by multiplying the ratio of a cross sectional area of the cylindrical containers (at right angles to the longitudinal direction of the cylinder) by the ratio of the velocities of the plungers, which may thus be appreciably greater than 1.5, for example 10:1, 20:1 or 40:1. A flow rate ratio of 40:1 may, for example, be achieved by a velocity ratio of 2:1 of the plungers in combination with a ratio of 20:1 of the cross-sectional areas of the cylindrical containers. 
   In an advantageous embodiment, the drive means comprise a gear transmission. By means of gear transmissions, mechanical force can be converted to movement of the plungers, it being relatively easy to achieve a difference in the velocity between the plungers by using differently sized gears for transmission to the various plungers. It is preferable if the drive means comprise a planetary gear system. A planetary gear system provides a very reliable transmission, which can, moreover, be constructed in a very compact manner. 
   It is advantageous if the drive means comprise a toothed-belt transmission. A toothed-belt transmission provides some flexibility for the adhesive gun in order to be able to absorb peak loads which occur when the relatively viscous adhesive component is pressed out of the first container. Moreover, the toothed belt of the toothed-belt transmission will form the weakest link in the transmission. Thus, it is predictable which component will fail when overload occurs, which has the advantage that the toothed belt can easily be replaced. 
   It is advantageous if at least the first plunger is designed to be moved by means of a spindle. A spindle can move the plunger with a relatively large mechanical force which is required in order to press the relatively viscous adhesive component out of the first container. In addition, the movement can readily be controlled by means of a spindle, so that a constant flow rate and thus a constant mixing ratio of the adhesive components is possible. 
   In one preferred embodiment, the drive means comprise a pneumatic motor. A pneumatic drive is capable of generating sufficient power, while the adhesive gun can be designed to be relatively compact. Although it would also be possible to use a compact electric motor for the driving, a pneumatic motor is more advantageous than an electric motor because less heat is generated, which can have a detrimental effect on the quality of the adhesive components in the adhesive gun. As an alternative for the pneumatic motor, a hydraulic system could be used, but the pneumatic system is preferred as compressed air is usually available in circumstances where such adhesive guns are being used. 
   In one preferred embodiment, the inner diameter of the first cylindrical container is at least twice as large as the inner diameter of the second cylindrical container. This makes the flow rate of the relatively viscous component which is pressed out of the first container by the first plunger significantly greater than the flow rate of the relatively liquid component which is pressed out of the second container by the second plunger. With such a ratio between the inner diameters of the containers and in combination with the correct velocity ratio of the plungers, it is readily possible to achieve the desired mixing ratios, preferably greater than 10:1, between the relatively viscous and the relatively liquid component. 
   It is advantageous if at least the second cylindrical container is designed to be releasable. This results in an adhesive gun which is comfortable to use as the cylindrical container can easily be replaced by, for example, an identical container comprising the same adhesive component, or a similar container filled with an adhesive component with different physical or chemical properties. It is also possible to replace the cylindrical container with a cylindrical container of a different diameter, resulting in a simple way of achieving a different mixing ratio. In order to make this possible, the container may be provided with a displaceable adapter for interaction with the plunger in order to press the adhesive component out of the container. 
   Preferably, the mixing unit is provided with a static mixing element. The static mixing element results in a thorough mixing of the relatively viscous and the relatively liquid adhesive component while the adhesive components are being pressed out of the containers. The mixture of adhesive components can then be applied to a surface via the mixing unit, on which surface the mixed multi-component adhesive can cure. The mixing unit may comprise a number of mixing elements which project from the wall of a passage of the mixing unit. Various forms of static mixer are known, the mixing elements generally being fin-shaped. 
   In a preferred embodiment, the mixing unit comprises a supply pipe from the second container which opens inside a supply pipe from the first container. This results in improved mixing of the relatively viscous adhesive component from the first container and the relatively liquid adhesive component from the second container. An additional advantage when using the abovementioned static mixing element is that the static mixer does not have to be so large in order to achieve good mixing, which results in a reduction in the flow rate resistance through the mixing unit. Preferably, the ratio between the cross-sections of the supply pipe from the second container and the supply pipe from the first container is substantially identical to the flow rate ratio of the first and second containers which is determined by the diameters of the cylindrical containers and velocities of the plungers. This results in optimum mixing, while at the same time reducing the risk of the occurrence of resistance-increasing pressure variations within the mixing unit to a minimum. It is most preferable if the supply pipe from the second container ends at a central position within the supply pipe from the first container. This positioning results in optimum mixing. More preferably, the direction in which the supply pipe from the second container opens inside the supply pipe from the first container is substantially parallel to that of the supply pipe from the first container. This configuration brings about the best mixture. 
   It is advantageous if the mixing unit is designed to be releasably coupled, which makes the adhesive gun flexible for use with various applications. In addition, the mixing unit can be replaced in case the mixing unit is blocked. It is easy to choose another mixing unit, depending on the desired method of applying the multi-component adhesive (for example using a wider or narrower mixing unit) and the employed mixing ratio and flow rate of the adhesive components. 
   It is also advantageous if the mixing unit comprises a connecting piece which is releasably coupled to the mixing unit for connection to the second container. The releasably coupled connecting piece increases the flexibility of the adhesive gun. The releasable connecting piece can easily be replaced in case of a blockage and when a change is effected in the mixing ratio of the adhesive components where only the flow rate of the second container is changed and the flow rate of the first container remains the same. 
   In a preferred embodiment, the mixing unit is forced onto the first cylindrical container and the second cylindrical container by means of a closure element. This ensures that the connection between the containers is able to withstand the high pressure which may occur in the cylindrical containers. The closure element is preferably pivotable, so that the closure element can be displaced from a position in which it forces the containers and the mixing unit together to a release position in which it is possible to replace a mixing unit and/or at least one container. The closure element may be, for example, a closure fitting. 
   The invention also provides a releasable cylindrical container for use in an adhesive gun according to the invention. The releasable cylindrical container can be placed in the adhesive gun in a simple manner, so that a new container comprising the same adhesive component or a similar container filled with an adhesive component having different physical or chemical properties is quickly ready for use. By exactly determining the diameter of the cylindrical container, the mixing ratio with another adhesive component can be accurately determined. The releasable cylindrical container is preferably provided with a displaceable adapter which can interact with the plunger of the adhesive gun in order to press the adhesive component out of the container. This makes it possible to use containers of different diameter with the same plunger of the adhesive gun. 
   The invention also provides a mixing unit for use as a releasable mixing unit in an adhesive gun according to the invention. A mixing unit of this type may take various forms, depending on the desired use and mixing ratio to be employed. 
   The invention also provides a connecting piece for use as releasable connecting piece in an adhesive gun according to the invention. The diameter of the connecting piece depends on the desired flow rate relative to the flow rate which a mixing unit in the adhesive gun requires. 
   The invention furthermore provides a method for applying a multi-component adhesive using a manually operable adhesive gun. This method makes it possible to apply a multi-component adhesive comprising a relatively viscous adhesive component and a relatively liquid adhesive component in large mixing ratios, for example, 10:1, 20:1 or 40:1. Such large mixing ratios are not possible with the prior art without relatively complicated technical measures in the adhesive gun, making the adhesive gun relatively prone to failures. The adhesive gun according to the present invention makes it readily possible to apply multi-component adhesive with such large mixing ratios, enabling a method for applying multi-component adhesive which is relatively less prone to failures. 
   According to a preferred embodiment, the relatively viscous adhesive component implemented in the method according to the invention is a composition comprising a pre-polymer with end groups likely to react with water, for example the air moisture or the substrate moisture. The end groups are for example selected among alkoxysilanes, acetoxysilanes, isocyanates. The pre-polymers are preferably selected among polyethers (such as polypropyleneoxide), polyesters, polyether-urethanes, polyester-polyurethanes, silicones (such as polydimethylsiloxanes), polyurethanes or polyacrylates. This composition may comprise apart from the pre-polymer other customary additives such as one or more curing catalysts, fillers or plasticizers. 
   The relatively liquid adhesive component implemented in the method according to the invention is preferably a composition comprising a compound acting as a curing agent in the curing reaction of the pre-polymer contained in the relatively viscous adhesive component. Such compounds may be selected among for instance water, a glycol, a polyol or a polyamine. Water is a preferred compound. 
   Preferably the method according to the invention comprises applying a 2-component adhesive. 
   The method according to the invention enables the applicators of adhesives in the construction or transport industry to better control the quality and duration of the curing process of said adhesives, independently of the climatic conditions and of the season, and in particular independently of the relative humidity. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1   a  and  1   b  show different views of a preferred embodiment of an adhesive gun according to the invention. 
       FIG. 2  shows a diagrammatic overview of an adhesive gun according to the invention. 
       FIG. 3  shows a drive for use with an adhesive gun according to the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The invention will now be explained in more detail with reference to some examples.  FIG. 1   a  shows a preferred embodiment of an adhesive gun  1  according to the invention. In this illustration, moving parts, such as the drive and plungers, have not been shown because they are covered by a housing formed by three housing parts  2 ,  3 ,  4 . The housing  2 ,  3 ,  4  protects the moving parts from dirt and damage, so that the adhesive gun is more reliable. A first housing part  2  covers the plungers, a second housing part  3  protects the drive of the plungers, and the containers for the adhesive components are accommodated in a third housing part  4 . The division of the housing into various housing parts  2 ,  3 ,  4  enables part of the adhesive gun to be made accessible without subjecting other parts of the adhesive gun to dirt or damage. The figure further shows the releasable mixing unit  5  of the adhesive gun, provided with an internal static mixer (not shown). In addition, a connection  6  for compressed air is visible, which drives a pneumatic motor  9  via a handle  7  provided with a metering button  8 . The adhesive gun is furthermore provided with an additional handle  10  which enables increased stability when working with the adhesive gun. 
     FIG. 1   b  shows the adhesive gun  1 ′ from  FIG. 1   a  where the housing parts have been omitted in order to show the internal components of the adhesive gun. The toothed-belt drive  11  with which the pneumatic motor  9 ′ drives the two spindle transmissions  12 ,  13  which in turn drive the plungers  14 ,  15  can clearly be seen. Due to the difference in size of the spindle transmissions  12 ,  13 , the plungers  14 ,  15  move at different speeds. The plunger  14  of the first container  16 , which comprises the relatively viscous adhesive component, is moved at twice the speed of the plunger  15  for the second container  17 , which comprises the relatively liquid adhesive component. In order to ease the movement of the plungers  14 ,  15 , the end of each plunger remote from the container is provided with guide elements  18 ,  19  which rest on the housing (as shown in  FIG. 1   a ) in order to ensure a gradual displacement of the plungers  14 ,  15 . In addition, the guide elements  18 ,  19  are designed such that they block rotation of the plungers  14 ,  15  by the spindle transmissions  12 ,  13 , as a result of which the force of the pneumatic motor  9 ′ can be used in an optimum fashion for a translatory movement of the plungers  14 ,  15 . The guide elements  18 ,  19  are preferably made of a material having a low frictional resistance, such as Teflon. In this preferred embodiment, the guide elements  18 ,  19  are in the form of a rotatable guide wheel, which has the advantage that, compared to a non-rotatable guide element  18 ,  19 , the frictional resistance is minimized through rotation. The container  16  for the relatively viscous adhesive component has an inner diameter which is approximately six times larger than that of the container  17  for the relatively liquid adhesive component. The ratio of the inner diameters of the containers  16 ,  17  in combination with the ratio between the velocity of the plungers  14 ,  15 , makes it possible to achieve large mixing ratios between the relatively viscous and the relatively liquid adhesive component in a simple manner, for example a mixing ratio of 10:1, 20:1 or, in this case, 40:1 (relatively viscous component relative to relatively liquid component). The relatively viscous adhesive component is in this case a mass of curable material and the relatively liquid adhesive component is a mixture which contains a catalyst for the curing reaction. When the two components are combined, the mixture will cure by the effect of the catalyst. Only a very small amount of catalyst is required for curing. Compared to the known mixing ratios (10:1 or less), the larger mixing ratio thus leads to a saving in catalyst. This is advantageous from an economical point of view, as catalysts are generally relatively expensive. The container  16  for the relatively viscous adhesive component comprises a reinforced metal container, made for example of steel or aluminum, which is necessary in order to be able to withstand the great pressure which builds inside the container  16  as a result of the viscous mass being pressed out of the container  16 . For use, the container  16  is filled with a relatively viscous adhesive component, for example in the form of a sausage-shaped holder with a flexible, compressible casing. In use, the container  17  for the relatively liquid adhesive component is subjected to less force than the container  16  for the more viscous adhesive component. The container  17  for the relatively liquid adhesive component can therefore be designed as a releasable light plastic tube, which can easily be replaced after use by a new, filled tube. The two containers  16 ,  17  for the adhesive components open into the releasable mixing unit  20 , with the mixing unit  20  connecting directly to the container  16  for the relatively viscous adhesive component, and with the relatively liquid component being supplied by means of a releasable connecting piece  21  of the mixing unit  20 . The mixing unit  20  including the connecting piece  21  is secured on the containers  16 ,  17  by a closure fitting  22 . The closure fitting ensures that the connection between the cylindrical containers  16 ,  17  and the mixing unit  20  stays leak-tight, even with high pressure forces. The closure fitting  22  is a closure element which can be pivoted at right angles to the axial axes of the cylindrical containers  16 ,  17 , provided with two recesses for the two supply ducts of the mixing unit  20  from the containers  16 ,  17 . The figure shows how a thickening  23  of the connecting piece  21  engages with the closure fitting  22 , as a result of which the connection between the connecting piece  21  and the smaller cylindrical container  17  is ensured under compressive load. A similar connection to the mixing unit  20  by means of the closure fitting  22  has been realized for the larger cylindrical container  16 . By swinging the closure fitting  22 , the lock between a coupling element  24  of the closure fitting  22  and a mating coupling element  25  is opened, so that the mixing unit  20  can easily be removed. 
     FIG. 2  shows a diagrammatic overview of an adhesive gun according to the invention which shows a container  40  having a large diameter D 1 , filled with relatively viscous adhesive component A, a container  41  having a smaller diameter D 2 , filled with relatively liquid adhesive component B, plungers  42 ,  43  interacting with the respective containers  40 ,  41 , a releasable mixing unit  44  provided with internal static mixing elements  45 , and a releasable connecting piece  46  which connects the container  41  to the mixing unit  44 , the output  47  from the container  41  with adhesive component B opening centrally within the output  48  from the container  40  with adhesive component A. The plunger  42  for the adhesive component A is moved at a speed V 1 , which is at least twice the speed V 2  with which the plunger  43  for adhesive component B is moved. The ratio between the velocities of the plungers V 1  and V 2 , in combination with the ratio of the diameters of the containers D 1  and D 2  determines the ratio at which the two components are mixed further by the static mixing elements  45  and subsequently applied from the mixing unit  44 . The container  41  for adhesive component B is designed to be releasable and also comprises an internal adapter which is pushed by the plunger  43  inside the cylindrical container  41 . This enables the use of containers  41  having a larger diameter D 2 , by means of which the mixing ratio can be adjusted irrespective of the size of the plunger  43 . 
     FIG. 3  shows a drive  60  for use in an adhesive gun according to the invention, which illustrates how a shaft  61  which is driven by a motor transfers mechanical force via a toothed belt  62  to a first toothed wheel  63  and a second toothed wheel  64 . The first toothed wheel  63  and the second toothed wheel  64  have a different circumference, so that they reach different rotational speeds. Each of the toothed wheels  63 ,  64  separately drives a plunger  65 ,  66  by means of a spindle transmission, the two plungers  65 ,  66  moving at different velocities V 1 , V 2 . As the first toothed wheel  63  has a smaller circumference than the second toothed wheel  64 , the first toothed wheel  63  will rotate faster, as a result of which (using identical spindle transmissions, not shown) the plunger  65  of the first toothed wheel will move at a speed V 1  which is greater than the speed V 2  of the second plunger  66  of the second toothed wheel  64 . 
   Obviously, those skilled in the art will be able to conceive many other embodiments of an adhesive gun according to the invention in addition to the abovementioned non-limiting examples.