TECHNICAL FIELD

This invention is concerned with improvements in or relating to adhesive applicator devices and also to apparatus, comprising such devices, for applying adhesive progressively on the surface of a substrate along a selected path.

BACKGROUND ART

There is described in EP-A-0 351 993 an adhesive applicator device comprising a nozzle having a housing in which a ball is accommodated and through which adhesive supplied thereto under pressure can flow, wherein the housing has, at the nozzle outlet, an end face having an aperture through which the ball cannot pass but through which a portion of the ball projects, such projection being limited by engagement of a rearward surface of the ball with abutment means within the housing and being such as to provide a spacing, through which adhesive can flow, between the rim of the aperture and the surface of the projecting portion of the ball, whereby a layer of adhesive can be applied to a surface of a substrate into engagement with which the ball is brought and along which the ball is traversed when the device is in use.

This device, moreover, also comprises a brush assembly having a plurality of bristles which extend in a direction lengthwise of the nozzle housing and which are disposed about the whole of the periphery of the end face and project therebeyond by a distance which can be set so that the bristles deform when the device is pressed against a workpiece surface, together with drive means for effecting rotation of the brush assembly about an axis extending lengthwise of the nozzle, i.e. the longitudinal centre line of the device, whereby, when the

device is pressed against a workpiece surface the thus deformed bristles spread adhesive supplied from the nozzle over such surface.

In practice, this arrangement has proved to be highly successful in depositing a layer of adhesive on a substrate surface, e.g. along marginal portions of a shoe bottom, and in ensuring that the adhesive penetrates the surface by the brushing action, while at the same time the spread of the adhesive over the surface is closely controlled, essentially by controlling the deformation of the bristles.

The rate of flow of adhesive through the housing is a function of the viscosity of the adhesive, the pressure within the adhesive supply and the spacing between the rim of the aperture and the surface of the projecting portion of the ball. Moreover, the rate of flow of adhesive, together with the rate of traverse of the device along its selected path, determines the amount of adhesive which is applied to the substrate surface, so that there is little control over the thickness of the layer of adhesive applied to the substrate surface using this device. In some cases, it will be appreciated, thickness control is significant, e.g. in the case of an expensive adhesive or indeed where too thick a layer of adhesive would render the curing or setting time of the adhesive too long in terms of the particular application to which the adhesive is being put.

There is described in EP-A-0 102 765 an applicator nozzle, especially for a hand-held applicator device, having an end face which is concave and thus forms a depression into which an aperture opens through which adhesive can be supplied to the depression, the depression itself being bounded about the whole of its periphery by a doctor blade formed at the convergence of the surface of the depression and an outer surface of the

nozzle body. When this nozzle is in use, as relative movement takes place between it and the substrate surface and with the nozzle in contact with the workpiece surface, a band of adhesive is applied to the substrate surface, the width of the band being controlled by the width of the depression and the thickness of the band being controlled by the doctor blade, regardless of the direction of traversing movement of the nozzle in relation to the substrate. The nozzle in this case is made of a resiliently flexible material, e.g. silicone rubber, and consequently the thickness of the applied layer is determined essentially by the rheology of the material from which the nozzle body is made, rather than by any deformation thereof. In practical use, however, such a nozzle would be unsuitable in many applications because of wear, especially where there is any risk of the nozzle being moved across sharp metal surfaces, e.g. nail heads in the bottoms of shoes, which could tear the rubber. Consequently, for such applications a rubber nozzle would not generally be considered suitable.

OBJECTS OF THE INVENTION

It is thus one of the various objects of the present invention to provide an improved adhesive applicator device in the use of which the thickness of the applied layer can be accurately controlled, but the nozzle housing of which is of a durable material.

It is another of the various objects of the present invention, furthermore, to provide an improved apparatus for applying adhesive progressively on the surface of a substrate along a selected path, in the operation of which the applicator device is caused to follow the selected path automatically and also the thickness of the layer of adhesive applied by the applicator device is accurately controlled.

SUMMARY OF THE INVENTION The first of these objects is resolved, in accordance with the present invention, in an applicator device of the type set out in the second paragraph above, in that the end face constitutes a doctor member which, as the layer of adhesive is being applied, is held spaced from the substrate surface by a distance determined according to the amount of projection of the ball portion from the end face, and thus which determines the thickness of the applied layer, said doctor member being thus effective regardless of the direction of traversing movement.

It will be appreciated that by thus controlling the distance between the rigid end face of the nozzle housing and the substrate surface, the thickness of the applied layer can be closely controlled with at least the same degree of accuracy as in the case of use of the nozzle disclosed in EP-A-0 102 765, but without the risk of damage attendant upon the latter nozzle.

Again in the case of the nozzle of the applicator device in accordance with the present invention, preferably the end face is dished, thus to form a reservoir for adhesive which has flowed through said spacing.

In the applicator device disclosed in EP-A-0 276 944 the ball also acts in a ball valve capacity, being resiliently urged out of engagement with the abutment means and into sealing engagement with the rim of the recess, and being urged into a retracted position in engagement with the abutment means when the device is in use and the ball is pressed against the substrate surface. This ball valve function may also be used in the device of the present invention. It will of course be appreciated that such use of a ball would not

be readily feasible in the case of a nozzle of a flexibly resilient material, since in such a case it would be readily possible for the ball to be resiliently urged through the aperture rather than merely against the rim thereof, and consequently in the case of the nozzle of EP-A-0 102 765, a separate valve arrangement was provided.

In the device of the present invention preferably the nozzle housing providing the end face is mounted on a support providing the abutment means, said nozzle housing and support being positionally adjustable relative to one another along the direction of adhesive flow through the housing whereby to vary the amount of projection of the ball portion through the aperture, as determined by the abutment means, and thus the distance between the end face and the substrate surface, whereby to enable the thickness of the applied layer of adhesive to be varied. In this way, it will be appreciated, an additional advantage is thus created over and above the devices referred to above as forming part of the prior art. In practice, it is possible, using the device in accordance with the present invention, to put down a layer of adhesive of between 0.75 and 2.0mm by the simple adjustment of the relative positions of the two housing portions.

To facilitate this adjustment, moreover, preferably the nozzle housing and support are threadedly secured together. For ease of adjustment, furthermore, positioning means, e.g. a type of ball-and-detent arrangement, is preferably provided for determining the relative position of the nozzle housing and support along the direction of adhesive flow and for maintaining them in positionally adjusted condition.

It will thus be appreciated that, using the applicator device in accordance with the present

invention an accurately controlled layer of adhesive can be applied, selected for its thickness by the operator according to the needs of the particular case, using a doctor member which is held spaced from the substrate surface so that any risk of damage to the doctor member is minimised, if not indeed eliminated, and which in any event is made of a relatively durable material.

The second the various objects of the invention set out above is resolved in accordance with the present invention by the provision of an apparatus for applying adhesive progressively on the surface of a substrate along a selected path, comprising a support for the substrate, a support for supporting an adhesive applicator device in accordance with the present invention as set out in the preceding paragraphs, and drive means for effecting relative movement under programmed control along three coordinate axes between the substrate support and the applicator device support whereby to cause the applicator device to traverse the substrate surface lengthwise, widthwise and heightwise along the selected path, wherein the applicator device support comprises a holder for the device, said holder being supported for pivotal movement about a first axis extending transversely of the substrate surface and about a second axis extending lengthwise of the substrate surface, said first. and second axes intersecting at a point lying on a longitudinal centre line of the device passing through the centre of the ball, and wherein the position of the device about the first and second axes is varied under programmed control, when the apparatus is in use, thus to maintain the longitudinal centre line at a predetermined angle to the substrate surface in the direction of traverse as the device traverses along the selected path. it will of course be appreciated that the

applicator device in accordance with the present invention is particularly suited to automatic control in order to ensure that the doctoring of the thickness of the adhesive layer is closely controlled. In practice, moreover, it has been found advantageous to maintain the applicator device with its longitudinal centre line at an angle of between 5° and 15° to the normal to the substrate surface at the point of engagement of the ball therewith, such that the trailing portion of the doctor member, as viewed in the direction of traverse, lies more closely to the substrate than does the leading portion thereof.

The apparatus in accordance with the present invention, as in the case of the apparatus described in e.g. EP-A-0 351 993, has, in addition to an operating mode in which adhesive is applied by the applicator device to a substrate surface, also a path-determining mode of operation, in which a programmed instruction is created for the selected path under operator control by determining a succession of points along the path, each point being stored in the form of digitised coordinate axis values for the three coordinate axes, together with digitised values in respect of the angular disposition of the device about each of the first and second axes at each point. It would, however, be somewhat difficult for the operator when using the apparatus in its path- determining mode, to ensure that the angle of presentation of the nozzle housing to the substrate surface is accurately controlled; it would, it is considered, be far preferable for the operator to judge when the longitudinal centre line of the device extends normal, or substantially normal, to the substrate surface. To this end, therefore, and in accordance with the present invention, in the path-determining mode the angular disposition of the device is varied to ensure

that the longitudinal centre line of the device extends normal, or substantially normal, to the substrate surface at the point of engagement of the ball therewith and corresponding digitised values are stored, and in controlling the movement of the device in the operating mode the digitised values are modulated according to the desired angle of the longitudinal centre line of the device to said normal. Moreover, the angle at which the longitudinal centre line of the device is maintained to the normal to the substrate surface is preferably fixed. In another embodiment of the invention, on the other hand, it may be desirable that this angle be varied during the traversing of the device along the selected path, according to whether different bonding criteria are applicable at different sections of the substrate surface.

In the apparatus described in EP-A-0 351 993 the applicator device has a nozzle housing which can "float" relative to the tool holder, that is to say excessive pressure applied to the ball upon engagement with the substrate surface is accommodated by sliding movement of the nozzle housing bodily in relation to the tool holder, so that any irregularities in the substrate surface to be coated can be accommodated. In the case of the device in accordance with the present invention, on the other hand, such a ^' floating arrangement is not possible and consequently, in order to accommodate any irregularities in the substrate surface, conveniently the tool holder is itself supported for movement in a direction towards and away from the substrate support relative to its mounting; more particularly, the tool holder is supported on a four-bar linkage arrangement. In this way the amount of lateral displacement of the device in effecting such movement towards and away from the substrate support is minimised so as not to affect

detrimentally to any significant extent the following of the selected path, even where irregularities occur.

The above and other of the various objects and several aspects of the invention will become clearer from the following detailed description, to be read with reference to the accompanying drawings, of an applicator device and an apparatus comprising an applicator device in accordance with the invention. It will be appreciated that this device and this apparatus have been selected for description merely by way of exemplification of the invention and not by way of limitation thereof.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:- Fig. 1 is a fragmentary view in side elevation of a tool support arrangement forming part of the apparatus in accordance with the present invention and for supporting an adhesive applicator device in accordance with the invention; Fig. 2 is a section view showing details of the adhesive applicator device itself; and

Fig. 3 is a fragmentary view, in section, of a nozzle housing of the applicator device but with its position adjusted to increase the thickness of a layer of adhesive applied thereby.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The apparatus now to be described is generally similar, except as hereinafter described, to the machine described in EP-A-0 351 993, a modification of the machine described in EP-A-0 091 321, which is itself a modification of the apparatus described in EP-A-0 043 645

(which latter apparatus is for performing a roughing operation progressively along marginal portions of a shoe bottom, rather than an adhesive-applying operation) .

Reliance is placed upon the disclosure of the aforementioned EP specifications and in particular, where like parts are incorporated in the various machines/ apparatuses but are not shown in the drawings accompanying this specification, the reference numerals from the earlier specification are used but are placed in brackets to indicate that the parts are not shown in the present drawings.

The apparatus in accordance with the invention thus comprises a base (10) supporting by a bracket (12), a pivot shaft (14) about which a support (16) for a shoe support (18) can pivot. As can be seen from Fig. 1, the shoe support is arranged to support a shoe S, bottom uppermost, with the toe end thereof facing towards the front of the machine, i.e. towards the operator. At its rear, the base (10) supports a support column structure (22) carrying a casting (24) on which is supported, for pivotal movement about a vertical axis, a support casting 34 having two upstanding lugs 32 between which tool supporting means generally designated 26 is supported for pivotal movement about a horizontal axis 31.

The apparatus further comprises a first stepping motor (144) mounted on the base (10) and effective to take place about the horizontal axis provided by the shaft (14) (X-axis movement). Similarly, a second stepping motor (84) is provided, carried by the casting (24) and effective to cause pivotal movement of the support casting 34 about its vertical axis (Y-axis movement). In addition, a third stepping motor (122 described in EP-A-0 043 645) is supported by the support casting 34, rearwardly of its vertical pivot, to cause it, and thus the tool supporting means 26 supported thereby, to pivot about its horizontal axis 31 (X-axis movement) . It will be appreciated that the X-, Y- and Z- axes represent three coordinate axes along which a tool

supported by the tool supporting means 26 can be moved under the action of the three stepping motors (constituting drive means of the apparatus).

Further details of the construction by which movement along the three axes can take place can be found in EP-A-0 351 993, EP-A-0 091 321 and also in EP-A- 0 043 645.

The tool supporting means 26 comprises a housing (650) mounted for pivotal movement about said horizontal axis (31). From a forward face of the housing projects a hollow tubular arm 652 within which is accommodated, for rotational movement therein, a support rod 654. At the forward end of said rod is a plate 656 supporting two forwardly projecting arms 658, which are spaced apart widthwise of the apparatus and on each of which is mounted, for pivotal movement, a pair of parallel links 660, 662 which are connected, at their upper ends, by an angular support plate member 664'. The links 660, 662 together with the plate 664 and arms 658 thus comprise a first parallel linkage arrangement of the tool supporting means 26.

Mounted for pivotal movement about the axis at which the plate 664' is connected with the link 660 is a further support plate 666' the limit position for anti- clockwise (viewing Fig. 1) movement of which is determined by a plate 664έι formed as an extension on the support plate 664'. In addition, a further link 667 is pivotally connected to the link 660, at an intermediate position along the length thereof, and at their forward ends the plate 666' and link 667 are pivotally connected to a block 668 forming part of a tool holder generally designated 670. The support plate 666' and the link 667, together with the link 660 and the block 668 constitute a second parallel linkage arrangement of the tool supporting means 26.

The first and second parallel linkage arrangements are so arranged that, with the support plate 666' in contact with the plate 664a, the tool holder 670 is caused to pivot about a transverse axis which passes through a point P, through which point also passes the axis (shown in chain-dot line in Fig. 1) of the support rod 654. As will be described hereinafter, furthermore, when a tool is supported in the tool holder 670 a longitudinal centre line thereof (also shown in chain-dot line in Fig. 1) also passes through said point P. The point P represents a height datum of the apparatus in a desired relationship with which the bottom of a shoe S supported by the shoe support 18 can be positioned when supported in the shoe support by toe support means 470 and a heel support and heel end clamping arrangement 720. (The heel support and heel end clamping arrangement is shown in Fig. 1 with various details omitted; for further details reference should be made to GB-A-2 077 090.) In addition, the second parallel linkage arrangement of the tool supporting means 26 enables the tool holder 670 to move heightwise relative to the height datum represented by the point P, without varying the angular inclination of the tool supported thereby.

For effecting pivotal, or tilting, movement of the tool holder 670 about the transverse axis, the links 662 each have an extension 674' carrying a transverse rod 675 to which is pivotally connected a forward end of a push rod 676, the rearward end of which is connected to actuator means for effecting fore-and-aft movement thereof (as described in detail in EP-A-0 351 993). Similarly, for effecting pivotal movement of the tool holder about the axis of the support rod 654, further actuator means is a provided, again as described in EP-A-0 351 993. Turning to Fig. 2, the block 668 ^• of the tool

holder 670 comprises a base plate and side cheeks, and the tool itself is secured to the underside of the base plate. The tool thus comprises a mounting block 722 to which is secured a heated body 724 having at its lower end a projecting portion 726 which is of reduced diameter and is threaded to receive thereon a nozzle housing 728. The nozzle housing may be made of any suitable rigid, durable material, which also has good thermal conductivity e.g. stainless steel. Extending along a longitudinal centre line of the tool through the various integers thereof is a central passage 730 which terminates, at its lower end, in a central aperture 732 formed in an end face 734 of the nozzle housing 728, and the upper end of which accommodates a block 736 having a coaxial central passageway 738 which is open at its upper end. The end face 734 of the nozzle housing is dished so as to provide for a reservoir of adhesive supplied along the passageway 730. For controlling the flow of adhesive along said passageway, furthermore, as also in the case of the tool of EP-A-0 351 993, the tool comprises a ball 740 which is so dimensioned as to be captive within the nozzle housing but able to project from the central aperture 732 formed in the end face 734. Moreover, spring means 742 is provided for urging the ball 740 against the rim of the aperture 732 so as to form a seal therewith, thus preventing the flow of adhesive from the nozzle housing.

In operation, applying pressure to the projecting portion of the ball 740 causes it to retract, against the action of the spring 742, to a limit determined by abutment means 744 provided on the lower end of the projection 726 of the heated body 724. The abutment means 744 comprises a plurality of castellations which provide an abutment surface for the ball while

nevertheless allowing the passage of adhesive along the passageway 730.

The nozzle housing 728 is so arranged in relation to the abutment means 744 that a portion of the ball will always project from the central aperture 732 beyond the end face 734 when a rearward face of the ball is in engagement with the abutment means. In this way, when applying adhesive using this tool, the end face 734 acts as a doctor blade, regardless, by reason of its annular configuration, of the direction of movement between the end face and a substrate, e.g. a shoe bottom, to which adhesive is being applied. The thickness of the applied layer, moreover, will of course be determined by the relationship of the projecting portion of the ball 740 with the end face 734.

In order to control accurately the thickness of the applied layer, and in particular to ensure, where desired, that the thickness is uniform, it will of course be necessary to control the angle of disposition of the tool in relation to the substrate surface (or shoe bottom) , which control is of course provided for in the apparatus itself through the drive means and actuator means details of which are set out in the various EP specifications referred to above. Where it is desired to vary the thickness of the applied layer, the nozzle housing 728 is rotated, through its threaded engagement with the projecting portion 726 of the body 724 and as it so rotates the nozzle housing is wound up or down in relation to the abutment means 744, thereby varying the relationship between the end face and the abutment means and thus the amount by which the ball 740 will project beyond the end face 734 when in engagement with said means. In order to facilitate the positioning of the nozzle housing 728, moreover, suitable positioning means is provided; in the

case of the apparatus now being described said means comprises a leaf spring 746, having a semi-spherical end portion, and a plurality of detents 748 arranged around the periphery of the outer surface of the nozzle housing 728, is provided, said means thus serving to indicate the positions to which the nozzle housing can be moved and also to maintain it in its adjusted position.

For heating the body 724, a suitable heater is provided, e.g. in the form of an outer casing 750; other forms of heating, e.g. internal cartridge heaters, may also be contemplated within the scope of this invention.

In the apparatus now being described adhesive is provided in a canister 752 which is supported in the tool holder 670. To this end, side supports 754 (Fig. 1) are provided extending upwardly from the side cheeks of the block 668 and a top plate 756, which can be clamped onto an upper end of the canister 752 by means of spring clamps 758 is provided for holding the canister in position. At its lower end the canister is supported by a heated plate 760 (Fig. 2) carried by a block 762 threadedly secured to the block 722 and arranged within the passage 730 formed in the latter, the block 762 itself being provided with a central passage which accommodates the upper end of the block 736. An 0-ring 764 serves to seal the plate 760 and block 762.

The adhesive used is preferably moisture- curable, and consequently requires to be maintained in a sealed can which should only be opened when the can is placed in the tool holder. To this end, the upper end of the block 736 projects beyond the plate 760 and terminates in a piercing device 766 which can pierce the end plate of the canister 752 progressively as the latter is clamped firmly in position. By its configuration, moreover, the piercing device causes a flap 752a _^ to be created which is not severed from the end face of the

canister, but rather is folded back so as not to interfere with the flow of adhesive into the central aperture of the block 736.

For ensuring the flow of adhesive from a canister, moreover, pressure is applied to the adhesive at the upper end thereof, e.g. by a compressed air system.

Instead of an adhesive supply of this type, it is also contemplated within the scope of the present invention that a remote source of adhesive under pressure may be provided and connected to the upper end of the passageway 738 in the block 736 by a suitable hose; the hose would of course be heated.

As in the apparatuses described in the aforementioned EP specifications, the apparatus has both an operating mode and a path-determining mode. In the latter, moreover, the operator can, by e.g. a joystick control or cursor control (not shown), determine the path to be followed by the tool along the shoe bottom (or other substrate surface), at the same time determining the necessary angle of tilt both about the transverse axis and also the axis of the rod 654 and also the heightwise position of the tool support, thus to ensure that the tool is correctly positioned in relation to the shoe bottom (or substrate surface) at all times during the operating cycle.

It has been found desirable so to arrange the angular disposition of the tool during the operating cycle that the longitudinal centre line thereof is inclined to the normal to the shoe bottom (or substrate surface) by a small angle, e.g. up to 15°, such that the "trailing edge" of the end face 734 of the tool is closer to the shoe bottom (or substrate surface) than the leading edge in the direction of relative movement between the tool and the shoe (substrate). In the path-

determining mode it would be difficult for the operator accurately to assess such an angular disposition of the tool for each point to be digitised, and consequently it is proposed that the operator will locate the tool for each point with the longitudinal centre line of the tool normal to the shoe bottom (substrate surface) at the point of contact with the ball 740 of the tool. Thereafter, the adjustment of the angular disposition on the tool will be achieved by software. More particularly, in the path-determining mode the tool is moved progressively from selected point to selected point along the shoe bottom (substrate surface), in a manner generally as described in US-A-4 541 054, and the coordinate axis values and other values relating to the angular disposition of the tool are stored in digitised form for each point, these values constituting collectively a set of data which can then be filed and recalled for controlling the movement of the tool relative to the shoe bottom (substrate surface) in the operating mode of the apparatus.

It has been found that in this way a layer of adhesive can be applied to the shoe bottom (substrate surface) with an accurately controlled thickness, usually (but not necessarily) a uniform thickness along the length of the layer. Moreover, relatively thin layers, e.g. in the order of 0.75 to 2.00mm, can be applied in this way.