Adhesive-applying apparatus

Abstract

 A nozzle (14) having a flexible blade member (16) with a concave adhesive-receiving surface (48) in combination with a rotary transfer roll (12) having a convex portion (20A) and side wall elements (18) forms a reservoir for adhesive "upstream" (in the direction of roll rotation) of the line of contact of an applying edge (52) of said surface (48) with the surface of the convex portion of the roll, the arrangement being such that a layer of the adhesive, doctored by blade member (16) to control its thickness and with its width controlled by the wall elements (18), is applied to the roll surface and carried thereby to the operating locality (10). By selecting, for the convex portion of the roll, a material which is deformable, but in a readily controllable manner, by the operator pressing the surface of a workpiece to be coated against the surface of the convex portion, a desired degree of surface contact between the two surfaces, and thus a desired width of adhesive coating, can be readily achieved.

Description

[0001] This invention is concerned with improvements in or relating to adhesive-applying apparatus whereby a layer of moisture-curable adhesive in a molten state can be applied to a surface portion of a workpiece presented to an operating locality of the apparatus.

[0002] One such apparatus is described in EP-A 0347736 comprising a cylindrical transfer roll arranged at the operating locality, together with heating means for heating the transfer roll, and drive means for effecting rotation of the transfer roll, a flexible blade member terminating in a straight edge which is held in line contact engagement with the surface of the transfer roll, the "upstream" (in terms of the direction of rotation of the transfer roll) face of said member being inclined at an acute angle to a plane which lies tangential to the surface of the transfer roll and passes through the line of contact with the blade member, and two wall elements arranged one at either side of the blade member and extending "upstream" therefrom and sealingly engaging with the transfer roll, thus to form with the blade member and the surface of the transfer roll a reservoir to which molten adhesive can be supplied from a supply thereof and in which it can be contained, the arrangement being such that as the transfer roll is caused to rotate a layer of molten adhesive, the thickness of which is determined by the flexible blade member, is formed on the surface of the transfer roll and carried thereby to the operating locality.

[0003] By using a cylindrical transfer roll, then according to the hardness of the material from which the roll is formed, adhesive can be applied, where the surface to be coated has a degree of convexity e.g. the surface of the marginal portions of the bottom of a shoe, either up to and slightly over the edge where the roll is relatively soft, or, for a medium hardness of roll (which nevertheless allows some deformation) up to the edge, or, for a relatively hard roll, just short of the edge, the actual width of the applied adhesive depending upon the pressure applied by the operator in holding the surface against the roll.

[0004] In practice, however, it has been found that whereas in most cases a roll of suitable hardness can be selected to accommodate for particular application needs, in certain circumstances the particular needs cannot be met using a cylindrical roll. For example in the case of a shoe bottom to which an outsole is to be secured by adhesive, where the outsole periphery lies significantly within the shoe bottom outline, it is important, in order to avoid any trace of adhesive being visible in the finished shoe, that the edge of the adhesive coating lies short of the edge of the surface; using even the hard roll this has been difficult to achieve, especially where the surface is relatively flat and the edge sharply defined. Moreover, again in practice it has been found necessary to space the edge of the adhesive coating still further from the shoe bottom edge in the inside waist region than in, say, the forepart region and such flexibility in adhesive application is not provided where reliance is essentially placed upon roll hardness.

[0005] It is thus the object of the present invention to provide an improved adhesive applying apparatus in the operation of which the foregoing difficulties are substantially avoided.

[0006] The invention thus provides an adhesive-applying apparatus whereby a layer of moisture-curable adhesive in a molten state can be applied to a surface portion of a workpiece presented to an operating locality of the apparatus, said apparatus comprising an applicator block which is tapered and which provides a flexible blade member having an adhesive-guiding surface terminating at an applying edge, a transfer roll arranged at the operating locality, together with heating means for heating the transfer roll and drive means for effecting rotation thereof, said roll having a surface portion which the applying edge of the blade member forms a line contact engagement, and the adhesive supplying surface of the blade member constituting the "upstream" surface (in terms of the direction of rotation of the transfer roll), thereof, and two wall elements arranged one at either side of the blade member and extending "upstream" therefrom and sealingly engaging with the surface portion of the transfer roll, at opposite sides thereof, thus to form with the blade member and said surface portion a reservoir to which molten adhesive can be supplied from a supply thereof and in which it can be contained, wherein as the transfer roll is caused to rotate a layer of molten adhesive, the thickness of which is determined by the flexible blade member, is formed on the surface portion of the transfer roll and carried thereby to the operating locality, characterised in that portion of the transfer roll providing said surface portions is made of a material which is deformable under a pressure which affords the operator an adequate control of the amount of such deformation, in that the portion of the transfer roll providing the surface portion is convex, and in that the adhesive-applying surface of the flexible blade member is concave about an axis extending transversely of the applying edge.

[0007] By the definition of the deformability of the material of the convex portion of the transfer roll in terms of operator control is to be understood that the material will resist ready deformation under a light pressure such that the operator can readily control the deformation, but at the same time will not require excessive force to be applied by the operator such as again will lead to diminished control; rather the material is deformable under a range of pressures which lie within the competence of an operator throughout a working day and within his ready control. A material having a Shore A hardness in the region of 50° has been found to be suitable for this purpose.

[0008] It will be appreciated that, using the apparatus in accordance with the invention, in order to achieve a surface contact between the surface of the transfer roll and the workpiece surface, it will be necessary to deform the convex portion of the transfer roll, since otherwise effectively there will be only line contact therebetween. By being able readily to control the amount of such deformation, the operator can thus also control the width of the applied adhesive coating and indeed can vary it in accordance with the application needs.

[0009] It is of course desirable that the thickness of the adhesive-layer can be pre-set, e.g. according to the type of material to which it is applied, and to this end preferably blade member control means is provided whereby the force holding the flexible blade member in engagement with the transfer roll can be varied, thus to vary the thickness of the layer of molten adhesive formed on the surface of the transfer roll. Conveniently, therefore, the blade member control mean comprises a presser member which is engageable with the "downstream" (in terms of the direction of rotation of the transfer roll) face of the blade member adjacent the straight edge thereof and is movable in a direction towards or away from the transfer roll.

[0010] The molten adhesive may be supplied to the reservoir in any suitable manner but, as in the case of the apparatus described in EP-A 0347736, preferably the flexible blade member is formed with an internal passageway connected to an adhesive supply and opening into said "upstream" face of the blade member. In this way, it will be appreciated, the blade member itself forms part of the adhesive supply system, and in particular forms the final part of that system. This is of course advantageous in that when the apparatus is left for an extended period and the "exposed" adhesive, i.e. the adhesive in the final part of the supply path, cures by exposure to atmosphere, the flexibility of the blade member, in which the final part is provided, enables the cured adhesive readily to be removed. Such removal, moreover, is facilitated where the flexible blade member is made of a siicone rubber.

[0011] The convex portion of the transfer roll of the apparatus in accordance with the invention preferably has an outer surface of a material which is hard in relation to the deformable material of said portion and to which the adhesive exhibits low adhesion. Preferably the material forming said outer surface is polyethylene and the deformable material is silicone rubber. By the provision of the outer surface as referred it has been found that, when a build-up of cured adhesive forms on the surface, it is possible to strip the cured adhesive therefrom.

[0012] The wall elements by which the margins of the layer of adhesive transferred to the transfer roll are determined are preferably mounted in a carrier resiliently urged into engagement with the transfer roll, at opposite sides of the convex portion thereof;
conveniently the presser member is also mounted on said carrier, for movement in a direction towards or away from the transfer roll as aforesaid. Furthermore, for facilitating access to the flexible blade member, conveniently the carrier is mounted for movement between an operative position, in which the wall elements lie at either side of the flexible blade member, and an out-of-the-way position.

[0013] Any suitable means may be provided for heating the transfer roll, but one convenient form of such heating means comprises a pipe which is connected to a hot air source and by which hot air can be directed on to the surface of the transfer roll. For convenience of construction, furthermore, the pipe may be secured to the carrier, or indeed the carrier may be mounted on the pipe, the pipe itself being mounted for pivotal movement in a frame portion of the apparatus.

[0014] There now follows a detailed description, to be read with reference to the accompanying drawings, of one apparatus in accordance with the invention. It will of course be appreciated that this apparatus has been selected for description merely by way of exemplification of the invention and not by way of limitation thereof.

[0015] In the accompanying drawings:-

Figure 1 is a section view showing details of an applicator block, transfer roll and wall elements of the apparatus in accordance with the invention; and

Figure 2 is a detailed view, in front elevation, showing the mounting of the transfer roll.

[0016] The apparatus now to be described is generally similar, except as hereinafter described, to the apparatus described in EP-A 0347736. Said apparatus is thus suitable for use in the application of a layer of a moisture-curable adhesive in a molten state to a surface portion of a workpiece presented to an operating locality of the apparatus, and in particular, though not exclusively, for applying a layer of such adhesive to marginal portions of a lasted shoe bottom for the attachment of an outsole thereto. The apparatus thus comprises an operating locality at which is arranged a transfer roll 12 and an applicator block or nozzle 14 providing a flexible blade member 16 by which adhesive can be applied, in a layer of controlled thickness, to the surface of the transfer roll 12. In addition, the blade member 16 is flanked by two side wall elements 18, which operate to control the width of the layer of adhesive applied to the transfer roll 12. The blade member 16 and wall elements 18 are so arranged in relation to the transfer roll 12 as to form a reservoir into which molten adhesive can be supplied, as will be hereinafter described, and in which it can be contained, the arrangement being such that, as the roll 12 rotates, a layer of molten adhesive, doctored by the blade member 16, is carried on the surface of the roll to the operating locality.

[0017] The transfer roll 12 comprises a core 20 of deformable material which is shaped to provide a central convex portion 20A and two outside portions 20B which cooperate with the wall portions 18. Covering the core, further, is an outer, adhesive-receiving, layer or skin 22 which is hard in relation to the hardness of the core 20 and to which adhesive has low adhesion. Suitable materials for the core have been found to be silicone rubbers with a Shore A hardness in the region of 50°. A suitable material for the outer skin 22 has been found to be polyethylene, and in particular polyethylene tubing which can be shrunk onto the core 20. One such polyethylene is available from Hellermann Electric of Plymouth, Devon, England under the trade name "Helashrink".

[0018] The transfer roll 12 is constructed by mounting the core 20 on a tubular shaft 24 and securing washers 26 thereto, one at either side, whereafter the outer skin is shrunk over the core and washers. For mounting the transfer roll 12 in the apparatus, furthermore, a shaft 28 is provided, pivotally mounted on a frame portion 30 of the apparatus between an operative, horizontal, position and an out-of-the-way, loading, position, in which latter position the tubular shaft 24 of the roll 12 can be slid onto the shaft 28. Opposite the shaft 28, when in its operative position, is a drive shaft 32 which carries a sleeve 34 spring-urged towards the shaft 28 but retractable by hand. The drive shaft 32 has, at its end, a diagonal plate-like projection which can be received in a correspondingly slotted end of the tubular shaft 24, thus to create a driving engagement between the shafts 24, 32, whereby the roll is driven. The sleeve 34, which is retracted to allow the shaft 28 to reach its operative position, is released to hold the shaft in said position and thus hold the transfer roll 12 in operative position and in driving engagement with the drive shaft 32. The drive shaft 32 is driven by a belt-and-pulley arrangement, including a belt 36, by means of a motor (not shown).

[0019] The transfer roll 12 is driven such that its forward surface portion, i.e. the surface portion closest to the operator, moves in a downward direction so that, in presenting the bottom of a shoe S to the roll, the operator moves the shoe in a generally straight line away from himself.

[0020] For heating the roll, thus to retain the adhesive applied thereto in a molten condition, heating means is provided in the form of a pipe 42 through which hot air can be directed towards the surface of the roll. The temperature of the air must be sufficient to maintain the adhesive molten but without creating damage to the outer skin 22 of the transfer roll, and it has been found that a temperature in the range 85 to 145^oC gives adequate results, an optimum temperature being in the order of 120^oC.

[0021] For cooperating with the transfer roll 12 the nozzle 14 is disposed thereabove (see Fig. 2), and comprises a body 46 of silicone rubber having two faces 48, 50 inclined to one another with an apical angle of 70°, and forming therebetween an applying edge 52, which is held (as will be referred to hereinafter) against the surface of the convex portion of the transfer roll.

[0022] The "upstream" face 48 (in terms of the direction of the rotation of the roll 12) of the nozzle is concave about an axis which lies transversely of the applying edge 52. More particularly a notional line extending at the surface of the face 48 and parallel to said axis lies at an acute angle, to a plane extending tangentially to the surface of the transfer roll 12 at the point of contact between said surface and said notional line. Furthermore, the applying edge 52 is offset from the "top dead centre" of the transfer roll 12 by an angle of about 34° about the axis of rotation of the roll.

[0023] In the operation of the apparatus, adhesive is supplied between the concave face 48 of the body 46 and the surface of the transfer roll 12 and forms a pool or reservoir "upstream" of the applying edge, which latter edge acts as a doctor blade by which a layer of adhesive of controlled thickness is applied to the surface of the roll. For supplying adhesive to the reservoir the body 46 is formed with an internal passageway 54 which opens into the concave face 48 via a slot 56, through which adhesive can be supplied.

[0024] The hot air pipe 42 supports a carrier 82 for the two side wall elements 18, which are formed with arcuate engagement surfaces for sealingly engaging with the portions 20B of the surface of the transfer roll 12. The pipe 42, and thus the carrier 82, are pivotal about a horizontal axis, thus to move the side wall elements 18 to an out-of-the-way position, when it is desired to gain access to the nozzle body 46. In addition, it is desirable that the side wall elements 18 are spring-urged into engagement with the transfer roll surface. Thus, the carrier is urged downwardly by engagement with two spring plungers 84 carried by a housing for the nozzle 14, and the carriage, through the wall elements 18, is maintained in its operative position by engagement of the wall elements with the portions 20B of the transfer roll. The carrier 82 also supports a slide 88 on which in turn is supported a presser member 90 constituting blade control means of the apparatus. The presser member engages the "downstream" face 50 of the body 46, adjacent, but slightly spaced from, the applying edge and urges said edge into line contact engagement with the portion 20A of the transfer roll surface. It will be appreciated that the force exerted by the said edge against the transfer roll surface will be dependent upon the position of the presser member 90 and this is adjustable by moving the slide 88 lengthwise of the carrier 82. To this end, a rotary knob 92 is held captive in the slide and in threaded engagement with the carrier so that rotation of the rod moves the slide lengthwise relative to the carrier and thus serves to position the presser member 90 in a desired relationship with the body 46 of the nozzle.

[0025] It will thus be appreciated that the "upstream" face 48 of the body 46 terminating in the applying edge 52, together with the side wall elements 18 and the surface of the transfer roll 12 together form a container or reservoir for adhesive supplied through the slot 56, and thus, as the transfer roll 12 rotates, a band or layer of adhesive is applied to the surface of the roll, the thickness of the layer being controlled by the straight edge, and indeed by the force applied to it, and the width of the layer being controlled by the side wall elements 18. It will of course also be appreciated that the hardness of the nozzle also influences the thickness of the applied layer and a suitable hardness for the nozzle, in general use, has been found to be in the range 50 to 60 measured on the IRHD scale.

[0026] When the operator applies adhesive, it is desirable that the speed at which he moves the workpiece surface, e.g. shoe bottom, should be approximately the same as the peripheral speed of the transfer roll 12. It is envisaged that an operator, operating normally, will move the shoe bottom at a speed equivalent to approximately 90 rpm roll speed (although the application of a consistent layer of adhesive to the surface of the transfer roll can be achieve at much higher roll speeds). The speed of rotation of the roll should preferably therefore lie in the range 75 to 100 rpm; a speed of 80 rpm has been found acceptable in most cases. In using the apparatus in accordance with the invention described above, the surface of the transfer roll 12 will be maintained at the appropriate operating temperature by blowing hot air through the pipe 42 thereagainst and thus the adhesive layer on the roll will be maintained, albeit for a limited period, in its uncured state ready for application. A pool of adhesive will of course be contained within the reservoir formed by the surface of the roll, the concave face 48 of the flexible blade member 16 and the side wall elements 18, and this adhesive will be curing, albeit slowly. When the operator wishes to apply adhesive to a workpiece surface, e.g. a shoe bottom, by operation of a treadle (not shown) adhesive is supplied through the internal passageway 54 of the nozzle body 46 to said pool and at the same time the operator presses the workpiece surface against the convex portion of the surface of the transfer roll and applies the layer of adhesive by moving the workpiece surface relative to the roll. At, or shortly before, the end of the application the operator releases the treadle whereupon the valve 80 reverts to its closed position. Because of the convexity of said surface and also the deformability of the core 20 the operator is able, by applying the desired, but readily controllable, pressure to press the workpiece surface against said surface, to cause sufficient deformation of the core to take place such that the desired amount of surface contact is achieved between the transfer roll and the workpiece surface to give the desired width of applied adhesive coating to the latter.

Claims

1. Adhesive-applying apparatus whereby a layer of moisture-curable adhesive in a molten state can be applied to a surface portion of a workpiece presented to an operating locality of the apparatus, said apparatus comprising
   an applicator block (14) which is tapered and which provides a flexible blade member (16) having an adhesive-guiding surface (48) terminating at an applying edge (52),
   a transfer roll (12) arranged at the operating locality, together with heating means (42) for heating the transfer roll (12) and drive means (32, 36) for effecting rotation thereof, said roll (12) having a surface portion which the applying edge (52) of the blade member (16) forms a line contact engagement, and the adhesive supplying surface (48) of the blade member (16) constituting the "upstream" surface (in terms of the direction of rotation of the transfer roll (12)), thereof, and
   two wall elements (18) arranged one at either side of the blade member (16) and extending "upstream" therefrom and sealingly engaging with the surface portion of the transfer roll (12), at opposite sides thereof, thus to form with the blade member (16) and said surface portion a reservoir to which molten adhesive can be supplied from a supply thereof and in which it can be contained,
wherein as the transfer roll (12) is caused to rotate a layer of molten adhesive, the thickness of which is determined by the flexible blade member (16), is formed on the surface portion of the transfer roll (12) and carried thereby to the operating locality,
characterised in that portion (20A) of the transfer roll (12) providing said surface portions is made of a material which is deformable under a pressure which affords the operator an adequate control of the amount of such deformation,
in that the portion (20A) of the transfer roll (12) providing the surface portion is convex,
and in that the adhesive-applying surface (48) of the flexible blade member (16) is concave about an axis extending transversely of the applying edge (52).

2. Apparatus according to Claim 1
characterised in that the convex portion (20A) of the transfer roll has an outer surface (22) of a material which is hard in relation to the deformable material of said portion (20A) and to which the adhesive exhibits low adhesion.

3. Apparatus according to Claim 2
characterised in that the material forming said outer surface (22) is polyethylene.

4. Apparatus according to any one of the preceding Claims characterised in that the deformable material of which the convex portion (20A) of the transfer roll (12) is made has a Shore A hardness in the region of 50°.

5. Apparatus according to any one of the preceding Claims characterised in that the deformable material of which the convex portion (20A) of the transfer roll (12) is made is a silicone rubber.

Drawing