Patent Publication Number: US-2022219193-A1

Title: An adhesive deposition tool for applying structural adhesive to a wind turbine blade component

Description:
TECHNICAL FIELD 
     The present disclosure relates a tool for applying adhesive to a component of a wind turbine blade. In particular, it relates to the deposition of a bead of a structural adhesive onto an application surface of the component. 
     BACKGROUND 
     Typically, wind turbine blades are manufactured in two halves, or shells, which are adhesively bonded together along the leading and trailing edges of the blade. A shear web structure is provided between the shell halves. 
     Structural adhesive is used to bond the inner surfaces of the shells to the shear web structure, and to bond the edges of the shells together. It will be appreciated that the adhesive bonds provide critical connections between the various components of the blade, and that the bonds must therefore have extremely high integrity to withstand the high forces and fatigue loads experienced in operation. To this end, the process of creating adhesive bonds during production of wind turbine blades must be highly repeatable and robust. 
     It is known to apply adhesive to a surface of a wind turbine blade component using an adhesive deposition tool. Adhesive is supplied to the adhesive deposition tool at a constant flow rate and an operator moves the tool along an application surface of a first component, for example the inner surface of a blade shell, to deposit a continuous elongate bead of adhesive onto the surface. A second component, for example a web foot, to be adhered to the first component, is then placed on top of the adhesive bead and the assembly is cured to form an adhesive bond. 
     It has been found in practice that known adhesive deposition tools can produce adhesive beads having inconsistent cross-sections and thicknesses. Such inconsistencies negatively affect the repeatability and consistency of the bonding process. 
     It is against this background that the present invention has been developed. 
     SUMMARY OF INVENTION 
     According to an aspect of the invention, there is provided an adhesive deposition tool for applying a bead of structural adhesive onto an application surface of a wind turbine blade component, the tool comprising a top portion defining an upper boundary of an open-ended chamber, the chamber comprising a front end and a rear end, the rear end being the end from which adhesive is deposited onto the surface when the tool is moved along the surface; two side portions defining side boundaries of the chamber; and, a supply channel for supplying adhesive to the chamber, wherein the top portion and/or at least one side portion is configured such that the height and/or the width of the chamber decreases towards the front end of the chamber. 
     Preferably, the top portion comprises a first baffle downwardly pitched towards the front of the tool. 
     In addition, or alternative to the first baffle of the top portion, at least one of the two side portions may comprise a baffle inwardly pitched towards the front of the tool. 
     Preferably, the side portions forwardly extend ahead of the front end of the chamber. 
     Preferably, the top portion further comprises a second baffle downwardly pitched towards the rear of the tool so as to decrease the height of the chamber towards the rear end of the chamber. 
     Preferably, the height of the chamber at the front and rear ends of the chamber is substantially equal. 
     Preferably, the cross-sectional areas of the front and rear ends of the chamber are substantially equal. 
     Alternatively, the cross-sectional area of the front end of the chamber is smaller than the cross-sectional area of the rear end of the chamber. 
     Alternatively, the cross-sectional area of the front end of the chamber is greater than the cross-sectional area of the rear end of the chamber. 
     Preferably, the second baffle is configured such that the height of the chamber continuously decreases towards the rear end of the chamber. 
     Preferably, the top portion and/or the at least one side portion is configured such that the height and/or the width of the chamber continuously decreases towards the front end of the chamber. 
     Preferably, the top portion and/or the at least one side portion is configured such that the height and/or the width of the chamber increases and subsequently decreases towards the front end of the chamber. 
     Preferably, the tool further comprises a profiler having a cut-out profile portion. 
     Preferably, the cut-out profile portion of the profiler defines the rear end of the chamber. 
     Preferably, the overall length of the tool is greater than 180 mm. 
     Preferably, the tool further comprises an elongate handle defining the supply channel, wherein the elongate handle is configured to rearwardly extend away from the front end of the chamber. 
     Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One or more examples of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  shows structural adhesive being deposited on an application surface of a wind turbine blade component using a known adhesive deposition tool; 
         FIG. 2 a    is a rear perspective view of the adhesive deposition tool of  FIG. 1 ; 
         FIG. 2 b    is a cross-sectional view of the adhesive deposition tool of  FIG. 1  along its longitudinal axis; 
         FIG. 3 a    is a cross-sectional view of the adhesive deposition tool of  FIG. 1  along its longitudinal axis including a general illustration of how the adhesive flows within the tool when the tool is stationary; 
         FIG. 3 b    is a cross-sectional view of the adhesive deposition tool of  FIG. 1  along its longitudinal axis including a general illustration of how the adhesive flows within the tool when the tool is moved along the application surface; 
         FIG. 3 c    is a plan view of a bead of structural adhesive deposited on the application surface by the tool of  FIG. 1 ; 
         FIG. 4 a    is a rear perspective view of an example of an adhesive deposition tool in accordance with the invention; 
         FIG. 4 b    is a cross-sectional view of the adhesive deposition tool of  FIG. 4 a    along its longitudinal axis; 
         FIG. 5 a    is a rear perspective view of a second example of an adhesive deposition tool in accordance with the invention; 
         FIG. 5 b    is a plan view of the adhesive deposition tool of  FIG. 5 a   ; and, 
         FIG. 5 c    is a cross-sectional view of the adhesive deposition tool of  FIG. 5 a    along its longitudinal axis. 
     
    
    
     In the drawings, like features are denoted by like reference signs. 
     DETAILED DESCRIPTION 
     The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and examples in which the invention may be practiced. These examples are described in sufficient detail to enable those skilled in the art to practice the invention. Other examples may be utilised, and structural changes may be made without departing from the scope of the invention as defined in the appended claims. Moreover, references in the following description to “upper”, “lower” and any other terms having an implied orientation are not intended to be limiting, and refer only to the orientation of the features as shown in the accompanying drawings. 
       FIG. 1  illustrates a component of a wind turbine blade, in the form of a wind turbine blade half shell  1  (hereinafter, “the half shell  1 ”), supported in a blade mould  2 . The half shell  1  may form a windward half or a leeward half of a wind turbine blade. An operator  3  is shown depositing a bead of structural adhesive  4  (hereinafter, “the bead of adhesive  4 ”) on an application surface  5  of the half shell  1  using a known adhesive deposition tool  10 . In this example, the application surface  5  forms part of an inner surface  6  of the half shell  1  and the bead of adhesive  4  is used to bond a shear web (not shown) to the inner surface  6 . 
     The adhesive deposition tool  10  comprises an elongate handle  7 , to which a supply hose  8  is connected for delivering a continuous supply of structural adhesive to the tool  10 . The elongate handle  7  is used by the operator  3  to push the tool  10  along the application surface  5  of the half shell  1  in a spanwise direction (indicated by arrow S). That is to say, the tool  10  is pushed along the length of the half shell  1 . As the tool  10  is moved, the bead of adhesive  4  is dispensed in its wake. 
     The tool  10  is moved over the application surface  5  along a predefined adhesive deposition path  12 , which is indicated on the inner surface  6  of the half shell  1 . The adhesive deposition path  12  indicates the precise location at which the structural adhesive should be deposited in accordance with the design specification of the wind turbine blade. The adhesive deposition path  12  may be indicated on the inner surface  6  of the half shell  1  by means of laser projection. Alternatively, or additionally, the adhesive deposition path  12  may be physically marked on the inner surface  6  of the half shell  1  using a pen or pencil, or the like. The adhesive deposition path  12  therefore indicates a predefined path along which the tool  10  must be moved. A physical guide (not shown), attached to the inner surface  6  of the half shell  1  adjacent the adhesive deposition path  12 , might also be used for guiding the tool  10  along the adhesive deposition path  12 . The physical guide is arranged parallel to the adhesive deposition path  12  and is spaced apart therefrom by a predetermined distance. The physical guide extends longitudinally in the spanwise direction along the whole or part of the length of the half shell  1 . 
     With reference to  FIG. 2 a   , the tool  10  comprises a top portion  14 , two parallel side portions  16 , the elongate handle  7 , located substantially on the longitudinal axis of the tool  10 , and an adhesive profiler  20 . The adhesive profiler  20  is located at the rear end  21  of the tool  10  and comprises a rectilinear cur-out profile  22 , generally in the shape of a house, for profiling the structural adhesive as it is deposited from the tool  10  onto the application surface  5 . The front end  23  of the tool  10  is open. That is, the tool  10  does not include a feature to restrict the flow of structural adhesive from its front end  23 . 
     Turning to  FIG. 2 b   , the handle  7  defines a supply channel  24  for supplying structural adhesive  27  (hereinafter, “the adhesive  27 ”) to a chamber  26  that is defined within the volume of the tool  10  by the interior surfaces of the top and side portions  14 ,  16 , and the adhesive profiler  20 . The top portion  14  is configured to slope upwardly from the rear to the front end  21 ,  23  of the tool  10 , progressively increasing the height, and so the cross-sectional area, of the chamber  26  towards the front end  23  of the tool  10 . In use, the adhesive  27  is supplied to the chamber  26  through the supply hose  8  and then the supply channel  24 . The adhesive  27  is allowed to largely fill the chamber  26  before the tool  10  is moved by the operator  3  along the adhesive deposition path  12  in the direction S. As the tool  10  is moved, the adhesive  27  exits the tool  10  through the cut-out profile  22  of the adhesive profiler  20  to form the bead of adhesive  4  on the application surface  5 . Due to the high viscosity of the adhesive  27  at typical application temperatures of around 15° C. to around 30° C., the bead of adhesive  4  generally retains the shape of the cut-out profile  22  of the adhesive profiler  20  after it has been deposited on the application surface  5 . 
     Due to profile of the top portion  14 , configured to slope upwardly from the rear to the front end  21 ,  23  of the tool  10 , a large proportion of the adhesive  27  entering the chamber  26  from the supply channel  24  tends firstly to flow towards the front end  23  of the tool  10 , following the path of least resistance. This flow pattern causes the adhesive  27  to form a rounded nose  28  at the front end  23  of tool  10 , flowing downwards from the top portion  14  of the tool  10  towards the application surface  5 . This establishes a number of drawbacks with using the known tool  10 . For example, during the application of the adhesive  27 , it is desirable that the operator  3  controls the movement of the tool  10  so as to apply the adhesive  27  to the application surface  5  at approximately the same rate as it is supplied to the tool  10 . If the application rate of the adhesive  27  is below the supply rate, the rounded nose  28  of the adhesive  27  extends further forward of the front end  23  of the tool  10 . This can cause some of the adhesive  27 , forming the rounded nose  28 , to work its way underneath the side portions  14 ,  16  as the tool  10  is moved along the adhesive deposition path  12 . That is, some of the adhesive  27  gets drawn in between the bottom surfaces of the side portions  14 ,  16  and the application surface  5  as the tool  10  is moved along the adhesive deposition path  12 . This creates strips of adhesive  27  either side of the bead of adhesive  4 , which need to be removed before the shear web can be bonded to the inner surface  6  of the half shell  1 , adding to the workload of the operator  3  and generating wasted adhesive  27 . 
     Another drawback with using the known tool  10  is the creation of an inconsistent connection between the bead of adhesive  4  and the application surface  5  as the tool  10  is moved along the adhesive deposition path  12 . With reference to  FIG. 3 a   , when the tool  10  is stationary or moved so as to apply the adhesive  27  at a low application rate, some of the adhesive  27  entering the chamber  26  is pushed downward, by the continuous flow of the adhesive  27 , onto an area of the application surface  5  approximately below the supply channel  24  and extending rearwardly therefrom. The rest of the adhesive  27  generally flows forward to create the rounded nose  28 , in which the adhesive  27  flows downward from the top portion  14  of the tool  10  to sit on the application surface  5 . That is, the adhesive  27  at the base of the rounded nose  28  is not positively forced into but rests on the application surface  5 , establishing a poorer connection therebetween when compared to the situation in which the adhesive  27  is pushed onto the application surface  5 . This can lead to “dead areas” within the chamber  26 , generally indicated by  29 , in which the adhesive  27  continuously circulates without ever being laid down on the application surface  5 . As the application rate increases, some of the adhesive  27  at the base of the rounded nose  28  is drawn under the tool  10 , as shown in  FIG. 3 b   , to form part of the bead of adhesive  4 . Nevertheless, the difference in the pressures under which the adhesive  27  is initially laid down on the application surface  5  between the front and rear sections of the tool  10  can lead to inconsistencies in the profile of the bead of adhesive  4 . In particular, with reference to  FIG. 3 c   , in sections where the connection between the adhesive  27  and the application surface  5  is poorer, the bead of adhesive  4  is pulled and stretched as it is dispensed from the tool  10 . This causes its width to narrow, as generally indicated by  30 , relative to those sections of the bead of adhesive  4  in which the connection between the adhesive  27  and the application surface  5  is comparatively better. The operator  3  is therefore required to correct these inconsistences in the profile once the bead of adhesive  4  has been laid down on the application surface  5  to ensure a reliable bonding of the shear web. 
     The invention seeks to overcome or substantially mitigate at least some of the drawbacks associated with the known tool  10 . 
     In general terms, the adhesive deposition tools of the present disclosure are configured such that the cross-sectional area of the chamber, defined by a substantially vertical plane extending between lower and upper boundaries of the chamber, decreases towards a front region of the chamber. This is advantageous as it increases the pressure exerted by the adhesive on the boundaries of the chamber in that region of the chamber, comparative with the known tool, and, in doing so, improves the initial contact established between the adhesive and the application surface. 
       FIG. 4 a    shows an example of an adhesive deposition tool  32  comprising a top portion  14 , two side portions  16  and a supply channel  24 . An inner surface  34  of the top portion  14  defines the upper boundary of an open-ended chamber  26  within the volume of the tool  32 , and inner surfaces  36  of the two side portions  16  respectively define side boundaries of the chamber  26 . The chamber  26  comprises a front end  38  and a rear end  40 , and, in use, the application surface  5 , onto which structural adhesive is deposited from the tool  32 , defines the lower boundary of the chamber  26 . 
     With reference to  FIG. 4 b   , the tool  32  is operated in substantially the same way as the known tool  10 . That is, adhesive  27  is supplied to the chamber  26  through the supply channel  24 . The adhesive may be allowed to largely fill the chamber  26  before the tool  32  is moved by the operator  3  along the adhesive deposition path  12  in the direction S. As the tool  32  is moved, the adhesive  27  exits the tool  32  from the rear end  40  of the chamber  26  to form a bead of adhesive  4  on the application surface  5 . The supply channel  24  may be defined by an elongate handle  7 . The elongate handle  7  may be configured to extend rearwardly away from a front end  23  of the tool  32 . The operator  3  may use the elongate handle  7  to move to tool  32  along the adhesive deposition path  12 . 
     The top portion  14  is configured such that the height of the chamber  26  decreases towards the front end  38  of the chamber  26 , resulting in a progressive decrease in the cross-sectional area of the chamber  26  towards its front end  38 . Specifically, the top portion  14  comprises a first baffle  42  downwardly pitched towards the front end  23  of the tool  32 . This arrangement reduces the volume of chamber  26  towards its front end  38  This may restrict the flow of the adhesive  27  towards the front end  38 , preventing the formation of a large rounded nose of adhesive. The arrangement of the first baffle  42  may increase the pressure exerted by the adhesive  27  on the boundaries of the chamber  26  in that region of the chamber  26  (when compared with the known tool  10 ). This pressure increase pushes the adhesive  27  onto the application surface  5  below the front end  38  of the chamber  26 , improving the connection that is initially established therebetween. The decrease in the cross-sectional area of the chamber  26  towards the front end  38  may also increase the uniformity of the pressure along the chamber  26  under which the adhesive  27  is initially laid down on the application surface  5  before it exits from the rear end  40  of the chamber  26  to form the bead of adhesive  4 . The improvement in the initial contact formed between the adhesive  27  and the application surface  5  eliminates inconsistences in the profile of the bead of adhesive  4  brought about by the pulling or stretching of the adhesive  27  as it exits the tool  32 . 
     The top portion  14  may further comprise a second baffle  46 . The second baffle  46  may be downwardly pitched towards a rear end  21  of the tool  32  so as to decrease the height of the chamber  26  towards its rear end  40 . Downwardly pitching the second baffle  46  towards the rear end  21  of the tool  32  may progressively decreases the cross-sectional area of the chamber  26  towards its rear end  40 . This arrangement reduces the volume of the chamber  26  towards its rear end  40  which may restrict the flow of adhesive  27  thereto. Reducing the volume of the chamber  26  towards its rear end  40  may cause a pressure in that region of the chamber  26  to be exerted on the adhesive, similar to the pressure applied at the front end  38 , thereby improving the uniformity of the pressure under which the adhesive  27  is initially laid down on the application surface  5 . 
     In this example, the height of the chamber  26  at its front and rear ends  38 ,  40  is substantially equal. This arrangement serves to promote the formation of a stratum or layer of adhesive  27 , the upper region of which is generally indicated by line  48 , immediately above the application surface  5 , which flows unimpeded from the front end  38  of the chamber  26  to the rear end  40 . The stratum of adhesive  27  is continuously resupplied with the entrainment of adhesive  27  entering the chamber  26  as the tool  32  is moved along the adhesive deposition path  12 . This helps to prevent the formation of dead areas of recirculating adhesive  27  within the chamber  26 , thereby minimising waste. 
     Such dead areas of adhesive  27  are also avoided by ensuring that the cross-sectional area of the chamber  26  continuously decreases towards the front and rear ends  38 ,  40  of the chamber  26 , as opposed to decreasing over a series of intermittent steps that could give rise to pockets of recirculating adhesive  27  within the chamber  26 . For example, in the present example, the second baffle  46  is configured such that the height of the chamber  26 , and so the cross-sectional area of the chamber  26 , continuously decreases towards the rear end  40  of the chamber  26 . The top portion  14  is also configured such that the height of the chamber  26  continuously decreases towards the front end  38  of the chamber  26  through the use of the first baffle  42 . 
     More specifically, the top portion  14 , through the combination of the first and second baffles  42 ,  46 , may be configured such that the height of the chamber  26  increases and subsequently decreases in the direction of the front end  38  of the chamber  26 . This initial increase in the height contributes to an overall increase in the volume of the chamber  26  in comparison to the known tool  10 . Moreover, the overall length of the tool  32  is at least 180 mm, which is more than the length of the known tool  10 . Specifically, the overall length of the tool  32  of this example is 280 mm. This too contributes to a comparative increase in the volume of the chamber  26 , providing the advantage of the tool  32  being able to accommodate an increased amount of adhesive  27  within the chamber  26  during use. A chamber which has a larger volume will hold an increased volume of adhesive, and this helps the operator provide a consistent bead of adhesive. 
     The side portions  16  may be substantially parallel and since the height of the chamber  26  at its front and rear ends  38 ,  40  may be substantially equal, the cross-sectional areas of the front and rear ends  38 ,  40  may also be substantially equal. Accordingly, the pressure exerted by the adhesive  27  on the boundaries of the front and rear regions of the chamber  26  is considerably equal, further improving the uniformity of the pressure under which the adhesive  27  is initially laid down on the application surface  5 . 
     The side portions  16  may forwardly extend ahead of the front end  38  of the chamber  26  defining a channel  44  located ahead of the chamber  26 . The channel  44  is used to collect any excess adhesive  27  that might spill from the front end  38  of the chamber  26  in the event the supply rate exceeds the application rate of the adhesive  27 . This arrangement prevents adhesive  27  from spilling around and being drawn in underneath the leading edges of the side portions  16 , between the bottom surfaces of the side portions  16  and the application surface  5 , as the tool  32  is moved along the adhesive deposition path  12 . 
     Moreover, the channel  44  also provides the operator  3  a visual indication, during use, on whether the application rate of adhesive  27  needs to be altered. Ideally, the operator  3  would be able to see adhesive  27  at the front end  38  of the chamber  26 , indicating that the chamber  26  is full of adhesive  27 , as the bead of the adhesive  4  is laid down, but the existence of excess adhesive  27  in the channel  44  could be an indication that the application rate of the adhesive  27  needs to be increased relative to the supply rate. 
       FIGS. 5 a  and 5 b    show another example of an adhesive deposition tool  32  comprising a top portion  14 , two side portions  16   a ,  16   b  and a supply channel  24 . An inner surface  34  of the top portion  14  defines the upper boundary of an open-ended chamber  26  within the volume of the tool  32 , and inner surfaces  36  of the two side portions  16   a ,  16   b  respectively define side boundaries of the chamber  26 . The chamber  26  comprises a front end  38  and a rear end  40 , and, in use, the application surface  5 , onto which structural adhesive is deposited from the tool  32 , defines the lower boundary of the chamber  26 . 
     This example differs from the previous example of the tool  32  in that one of the side portions  16   a ,  16   b  is configured such that the width of the chamber  26  decreases towards the front end  38  of the chamber  26 , which provides the progressive decrease in the cross-sectional area of the chamber  26  towards its front end  38 . Specifically, the side portion  16   a  comprises a baffle  50  inwardly pitched towards the front end  23  of the tool  32 . This arrangement reduces the volume of chamber  26  towards its front end  38 , which restricts the flow of adhesive  27  thereto and increases the pressure exerted by the adhesive  27  on the boundaries of the chamber  26  in that region of the chamber  26  relative to the known tool  10 . This increase in pressure pushes the adhesive  27  onto the application surface  5  below the front end  38  of the chamber  26 , improving the connection that is initially established therebetween and increasing the uniformity of the pressure under which the adhesive  27  is initially laid down on the application surface  5  before it exits from the rear end  40  of the chamber  26  to form the bead of adhesive  4 . 
     The other side portion  16   b  may be straight. This is particularly advantageous if, during use, the tool  32  is being guided along the adhesive deposition path  12  using a physical guide as it maximises the contact between the tool  32  and the physical guide, ensuring the stability of the tool  32  as it is moved along the adhesive deposition path  12  by the operator  3 . In an alternative example, the outer surface of the side portion  16   a  comprising the baffle  50  may also be straight, so it too can be used to achieve maximum contact between the tool  32  and a physical guide during use. 
     The side portions  16   a ,  16   b  may forwardly extend ahead of the front end  38  of the chamber  26  defining a channel  44  located ahead of the chamber  26 . As with the previous example, the channel  44  is used to collect any excess adhesive  27  that might spill from the front end  38  of the chamber  26  in the event the supply rate exceeds the application rate of the adhesive  27 . This arrangement prevents adhesive  27  from being drawn in underneath the side portions  16  as the tool  32  is moved along the adhesive deposition path  12  and also provides the operator  3  a visual indication, during use, on whether the application rate of adhesive  27  needs to be changed. 
     With reference to  FIG. 5 c   , the top portion  14  comprises a baffle  46  downwardly pitched towards the rear end  21  of the tool  32  so as to decrease the height of the chamber  26  towards its rear end  40 , resulting in a progressive decrease in the cross-sectional area of the chamber  26  towards its rear end  40 . This arrangement reduces the volume of chamber  26  towards its rear end  40 , restricting the flow of adhesive  27  thereto. 
     The height of the chamber  26  at its front end  38  is greater than at its rear end  40 . However, due to the inwardly pitched baffle  50  on the side portion  16   a , the cross-sectional areas of the front and rear end  38 ,  40  of the chamber  26  are substantially equal. This has the advantage that the pressure exerted by the adhesive  27  on the boundaries of the front and rear regions of the chamber  26  is considerably equal, improving the uniformity of the pressure under which the adhesive  27  is initially laid down on the application surface  5 . 
     It will be appreciated that various changes and modifications can be made to the tool  32  without departing from the scope of the invention as defined in the appended claims. 
     For example, one of the examples shown includes a top portion  14  configured such that the height of the chamber  26  decreases towards the front end  38  of the chamber  26 , and the other example shows a side portion  16   a  configured such that the width of the chamber  26  decreases towards its front end  38 . However, other examples/variants of the tool  32  are envisaged in which the top portion  14  and at least one of the side portions  16   a ,  16   b  are configured such that both the height and width of the chamber  26  concurrently decrease in order to reduce the cross-sectional area of the chamber  26  towards its front end  38 . 
     Similarly, it will be appreciated by the skilled reader that the cross-sectional area at the front and rear ends  38 ,  40  of the chamber  26  need not be substantially equal. The tool  32  may be configured such that the cross-sectional area at the front end  38  of the chamber  26  is smaller than the cross-sectional area at the rear end  40 . Such a configuration may be used, for example, when one wishes to increase the pressure applied by the adhesive  27  to the front region of the tool  32  relative to its rear region. Alternatively, the tool  32  may be configured such that the cross-sectional area at the front end  38  of the chamber  26  is greater than the cross-sectional area at the rear end  40 . This configuration may be used, for example, to prevent a situation in which the flow of adhesive  27  towards the front end  38  of the chamber  26  is overly restricted, preventing the chamber  26  from filling completely, as might occur when the adhesive  27  is supplied at a low temperature, and so an increased viscosity. In both situations, however, the uniformity of the pressure under which the adhesive  27  is applied to the application surface  5  along the length of the tool  32  is improved when compared with the known tool  10 . 
     It will also be appreciated by the skilled reader that the baffles  42 ,  46 ,  50 , used to restrict the flow of adhesive  27  within the chamber  26 , do not necessarily need to be straight, but could instead comprise a non-straight profile, provided that the height and/or width of the chamber  26  decreases towards the front end  38  or, in the case of the second baffle  26 , the rear end  40  of the chamber  26 . For example, one or more of the baffles  42 ,  26 ,  50  might have a convex profile tapering towards the front or rear end  38 ,  40 , which could aid the development of the stratum of adhesive  27  at the bottom of the chamber  26  and also help to prevent the formation of “dead areas” of adhesive  27  within the chamber  26 . 
     Moreover, the tool  32  may further comprise an adhesive profiler located at its rear end  21  having a cut-out profile portion, defining the rear end  40  of the chamber  26 , for profiling the bead of adhesive  4 . The adhesive profiler might form part of a suite of interchangeable adhesive profilers. In which case, the tool  32  comprises a means for receiving an interchangeable adhesive profiler for altering the profile of the bead of adhesive  4  as the adhesive  27  is deposited from the tool  32 .