WO2006016382A1 - Process and apparatus for the production of double lens articles and resulting articles - Google Patents

Abstract

In the manufacture of double-lens articles, in which two lens are mounted parallel and kept joined together by an adhesive layer, a layer or bead of adhesive in dense, preferably paste-like form is deposited along a predetermined programmable path by means of a first robot associated with a device for dispensing and applying said adhesive, following which, by means of a second robot, the second lens is removed from a store and transferred to a position situated above said first lens, following which, again by means of said second robot, it is lowered so as to come into contact via its bottom or internal surface with the layer of adhesive arranged on the upper or external surface of said first lens.The application of said second lens is performed while exerting a certain pressure for a period of time sufficient to complete the adhesive union between said adhesive layer and the bottom or internal surface of said second lens.

Description

Process and apparatus for the production of double lens articles and resulting articles

The present invention relates to the production of double-lens articles, in particular double-lens face- masks used for example as skiing or motorcycling goggles and visors for protective helmets used when driving motor vehicles or worn for protection at work.

More specifically the present invention relates to a method for manufacturing double-lens articles and to the associated apparatus.

The invention likewise relates to the double-lens articles thus produced.

In the remainder of this description reference will be made, for the sake of convenience of the description, to double-lens masks, it being understood that this expression is not limiting in any way. Likewise the term "lens" will be used to indicate a shaped element made of transparent plastic, without this necessarily meaning a graduated lens (typical of sight glasses) .

As is known, double-lens masks made of transparent plastic are widely used since, as well as protecting the skier's or motorcyclist's eyes, they prevent problems of visibility which inevitably arise in the case of misting-up of single-lens masks.

This result, however, is dependent upon the two superimposed and spaced lens which form the mask being arranged at a distance from each other and the cavity thus formed being hermetically sealed with respect to the external environment, preventing the penetration of water and the formation of condensation inside it. At present the manufacture of these masks envisages the following steps:

1) a bi-adhesive seal consisting of elastically yielding material, for example closed-cell expanded polyurethane, is applied by means of gluing onto the external surface of the first lens, namely that which is intended to form the inner layer of the mask, or that which during use is directly adjacent to the user's eyes and face, ensuring that it follows the contour of this lens;

2) when the glue has set, the second lens, i.e. the lens intended to form the outer side of the mask, is applied on top of the said first lens, so as to glue the second lens along the peak or crest of the seal;

3) again when the glue has set, the mask finishing operations are performed.

It is obvious that all these operations must be performed manually, so that the production cost is very high.

Secondly it is difficult to ensure in a constant and repetitive manner that the seal arranged between the two lens provides an effective sealing action against possible infiltration of external air into the aforementioned cavity and that either one of the lens does not become unglued from the seal.

It- is obvious that the provision of a method which is able to avoid these problems and drawbacks would undoubtedly result in major advantages for industrial production.

The main object of the present invention is precisely that of providing a method for the production of double-lens articles in which the manual operations are eliminated and it is possible to obtain articles which are able to guarantee, on the one hand, a sealing action and resistance to ungluing and, on the other hand, precision and constancy in terms of quality.

These objects are achieved with the method according to the invention which envisages the following operations: a) positioning the internal lens or first lens on a support so as to leave its external surface totally free and accessible; b) applying onto the said external surface a layer - in particular in the form of a bead - of adhesive compatible with the material forming the two lens to be joined together, in a dense preferably paste-like condition, by means of first applicator means which can be guided along a predetermined programmable path so as to delimit a space on the said external surface of said internal lens; c) applying by means of second manipulator and applicator means the external lens or second lens so that its internal surface is positioned on top of the said external surface of said internal lens and makes contact pressure with the crest or peak of said layer of adhesive paste so that said space delimited by said bead on the external surface of said internal lens forms a cavity separating the mutually facing surfaces of said internal and external lens.

In the preferred embodiment of the present invention said adhesive is of the silicone type and said application of said external lens against said internal lens with said bead of adhesive silicone paste is performed while keeping the whole assembly under a controlled atmosphere so that the optimum conditions for preventing the formation of condensation or misting-up are established within said cavity.

Moreover, still in connection with the preferred embodiment of the present invention, said application of said bead of adhesive paste is performed by means of a first applicator robot, of the type known per se, which is programmed so that it can be made to move and supply said adhesive paste along a predetermined path, preferably parallel to the perimetral edge of said internal lens and at a predefined distance from the said edge. In particular, said first robot is equipped with an automatic dispenser connected to a tank storing said adhesive so that the movement of said robot along said predetermined path results in application, by said dispenser, of a quantity of adhesive sufficient to form said adhesive bead.

Said second manipulator means also consist of a robot designed to remove said external lens, bring it into position and apply it with a predetermined pressure against the external surface of said internal lens, after application of said bead of adhesive paste, which pressure is calibrated, however, so as to keep the aforementioned cavity between the two lenses at the desired value.

Said second robot may also perform unloading of the finished part, freeing the support for repetition of the production cycle.

As can be appreciated already from the description provided above, the method according to the present invention is able to eliminate substantially any manual operations and ensure a constant and repetitive quality as regards the sealing effect and resistance to separation.

In particular, precise application of the adhesive bead as well as precise mounting in position of said lens or external lens are ensured.

As regards the apparatus according to the present invention, it consists of at least one station provided with a temporary support for resting said first lens in position such that its external surface is free and accessible, a first robot having means for dispensing and applying adhesive in a dense in particular paste- like form, said first robot being programmable so as to move said dispensing and applicator means along a predetermined path, a second robot having means for removing and transferring into position a lens from a store to said temporary support.

In the preferred embodiment of the apparatus of the present invention, said apparatus comprises a rotating-table support having at least three working positions or stations, the said first lens being loaded in the first station or position, while in the second station said first robot operates so as to apply the dispensed amount of said adhesive along a predetermined path. In the third and last position or station, said second robot removes said second lens from a special store and applies it on top of the surface of said first lens, preferably exerting a controlled pressure so as to favour the adhesion of the internal surface of the second lens to the layer of adhesive projecting from the underlying surface of said first lens without, however, diminishing the predetermined thickness of the cavity which ultimately must remain between the two lenses .

In the preferred embodiment, said third station also has means, for example of the bell type, which can be connected to a controlled atmosphere source in order to establish a predetermined environmental condition, in particular having a controlled humidity, around said temporary support, said controlled atmosphere being activated during step (c) of said method.

These and ^uother aspects and advantages of the present invention will emerge more clearly from the following description of a preferred embodiment, provided with reference to the accompanying drawings in which:

Fig. 1 is partially sectioned view of a face-mask provided in accordance with the present invention;

Fig. 2 is a cross-section along the plane indicated by II-II in Fig. 1;

Figs . 3 and 4 are views which schematically illustrate two steps during implementation of the method according to the present invention; and

Fig. 5 is a schematic view of the apparatus according to the invention.

With reference first of all to Figures 1 and 2, these figures show a face-mask comprising an internal lens or first lens 10 (intended to be positioned close to the user's eyes and face) and a second lens or external lens 12 between which a cavity 14 delimited by a perimetral gluing bead 16 is formed.

Ventilation slits 18 are formed in the lenses 10 and 12.

Figures 3 and 4 illustrate the main steps of the method for manufacturing the mask shown in Figures 1 and 2 .

Fig. 3 illustrates the step involving application of the gluing bead 16, in the form of a adhesive silicone paste, to the external surface of the lens 10, said application being performed by means of a first robot 20 with which a device 22 for dispensing and applying the adhesive paste is associated.

The arm of the robot 20 is made to move so as to follow a predetermined path, ensuring formation of the bead 16 of adhesive silicone paste, the thickness of which is adjusted by controlling on the one hand the speed of displacement of the end of the robot arm and ^• on the other hand the amount of adhesive paste which is dispensed and supplied per unit of time.

The robot 20 is an apparatus of the type per se well known in the art and is programmable so as to impart to the end of its operating arm a movement such as to follow a predetermined path (which in this case coincides with the perimetral contour of the lens 10) so as to create the aforementioned adhesive bead at a programmed and controlled distance with respect to the perimetral edge of the lens 10.

Obviously, during this step, the internal lens or first lens 10 is supported on a temporary support (not shown) with which it is kept in contact for example by means of a vacuum action.

When the robot arm has completed the entire programmed path, a second robot removes a second lens which is transferred until it is positioned exactly above the first lens and then pressed against the free crest or peak of the gluing bead 16, the deposition of which has just been completed. After lapsing of a predefined amount of time, necessary for gluing the second lens, the arm of the second robot is disengaged from the second lens, namely it effects transfer of the rough-finished mask thus formed to an unloading station where it is conveyed away for further finishing.

As already mentioned, the method according to the present invention may also be implemented so that at least the step involving gluing of the second lens or external lens takes place in a predetermined environmental condition, in particular under controlled humidity conditions, so that the formation of condensation is prevented inside the cavity 14 which is thus formed between the mutually facing surfaces of the two lenses 10 and 12, improving the performance of the mask in terms of misting-up.

With reference now to Fig. 5, this shows schematically an embodiment of the apparatus according to the present invention, therefore being purely illustrative and in no way limiting.

In fact, the form which the apparatus assumes is dependent upon the type of robot which is used.

In Fig. 5 the reference number 22 denotes a rotating-table support (revolving in the direction indicated by the arrow 23) , having four stations A, B, C and D.

A first lens 10, removed from the store 24, is loaded in the station A, for example by the operator 0.

The station B in this case is not operative, so that the lens then passes to the station C where the robot 20 operates, the hinged operating arm of which, indicated by the reference number 21, has a dispenser/applicator 26 which is connected by a flexible pipe 27 to a pump supply source 28. The internal lens or first lens 10 is preferably rested on mushroom-type supports (not shown) which may also be in the form of suction cups inside which a vacuum is formed and which therefore effectively retain the lens 10 which is temporarily held in position.

The upper surface of the support is shaped so as to match the usual form of the lenses of masks which generally have a curvature suitable for embracing the top part of the user's face at the height of the eyes.

In Fig. 5 the robot 20 is shown in the condition where in the station C the bead of adhesive 16 is being applied onto the external surface of the first lens or internal lens 10 resting and retained on the temporary support.

It is obvious that the housing 42 is connected in a manner known per se to a vacuum source, such as for example a pump able to generate a vacuum of the desired intensity, which source may also be used to generate the vacuum required by the suction cups 24 retaining the first lens 10 on the temporary support 22 as well as by the suction cup associated with the manipulator of the arm 28 of the robot 20.

When formation of the bead of adhesive 16 on the upper or external surface of the first lens 16 has been completed, the rotation of the rotating table 22 from the station C to the station D brings the lens 10, with the associated temporary support if used, into the radius of action of a second robot 30 which, by means of its articulated arm 32, removes a second lens 14 from the store 34. The lens 14 is then transferred by the arm 32 into a position situated exactly above that of the lens 10 already positioned. Lowering of the arm 32 is then performed so as to bring the internal or bottom surface of the lens 14 into contact with the crest or peak of the bead of adhesive 16, applying also a predetermined pressure for a given period of time. As already mentioned, the pressure with which the second lens 14 is applied against the peak or crest of the adhesive layer 16 is adjusted so as to prevent this layer from being crushed, therefore maintaining the thickness of the cavity 14.

By keeping the arm 32 in said position for the predetermined amount of time (in the region of a few seconds) the adhesive union between adhesive 16 and internal surface of the lens is completed, obtaining the desired result, namely the formation of the double- lens mask shown in Fig. 1, albeit in the rough-finished state.

At this point the same arm 32 of the second robot 30 transfers the rough-finished mask to an unloading store 36, for example in the form of a conveyor belt which removes the rough-finished part or mask in the direction of the arrow. It is obvious that, if the first mask 10 is supported and retained by suction-type supports, before unloading the rough-finished mask from the station D, the action of the vacuum must be interrupted.

Some further explanations are required in connection with the method and the apparatus according to the present invention.

Firstly, as regards the lenses, they are normally made of polycarbonate, cellulose propinate or polyurethane derivatives. In connection with these materials, the adhesives most suitable from among those which are commercially available have proved to be those of the silicone type owing to the fact that, unlike acrylic or polyurethane adhesives, they do not colour nor are subject to yellowing.

Moreover, silicone adhesives, in addition to providing an adequate mechanical strength, also have a high environmental and thermal stability and low water absorption.

Preferable silicone sealants are those of the one- component type which polymerize by means of alcohol, such as for example those marketed by Dow Corning Inc. under the trade name DOW 7091.

As regards the apparatus on the other hand, and in particular as regards the robots and the dispenser and applicator equipment, good results have been obtained with the devices produced and marketed by Iscra Dielectrics in Conegliano (Treviso) , in particular with the extrusion pump and valve dispensing system, Model 231-111, and with the robot TMBlOO SCARA (as first robot) .

As second robot, instead, it is possible to use any instrument capable of removing the second lens (for example by means of suction cups) and transferring it into the position for joining to the said first lens, resting it on top of the latter with a predetermined pressure.

The invention has been described in relation to a preferred embodiment, but it is understood that modifications and variants which are conceptually and mechanically equivalent are possible and may be envisaged while remaining within its scope.

For example, instead of starting with the internal lens 10, depositing on its external surface the bead 16 of adhesive paste, it is possible to start with the external lens 12, depositing this time the bead of adhesive paste on the internal surface of the lens. In this case the shape of the temporary support 22 must be suitably modified, becoming concave instead of convex.

Finally the present invention includes the solution in which a thin layer of adhesive is applied onto the surface of the first lens and, again by means of the robot, a pre-formed seal is arranged on this layer of adhesive. Subsequently, after gluing of the seal has been completed, a new layer of adhesive is applied on top of the seal by means of the robot and the second lens is then applied.

In all cases, the robot is also used to apply a light pressure which favours gluing.

As a further alternative it is possible and feasible to use a seal which is pre-lined with an adhesive which can be activated for example by means of irradiation so that, after application of the seal and before application of the second lens, activation of the adhesive is performed.

Claims

1. Method for manufacturing a double-lens face- mask, characterized in that it envisages the following operations: a) positioning the internal lens or first lens on a support so as to leave its external surface totally free and accessible; b) applying onto the said external surface a layer - in particular in the form of a bead - of adhesive compatible with the material forming the two lens to be joined together, in a dense preferably paste-like condition, by means of first applicator means which can be guided along a predetermined programmable path so as to delimit a space on the said external surface of said internal lens; c) applying by means of second manipulator and applicator means the external lens or second lens so that its internal surface is positioned on top of the said external surface of said internal lens and makes contact pressure with the crest or peak of said layer of adhesive paste so that said space delimited by said bead on the external surface of said internal lens forms a cavity separating the mutually facing surfaces of said internal and external lens .

2. Method according to Claim 1, characterized in that said adhesive is of the silicone type and said application of said external lens against said internal lens with said bead of adhesive silicone paste is performed while keeping the whole assembly under a controlled atmosphere so that the optimum conditions for preventing the formation of condensation or misting-up are established within said cavity.

3. Method according to Claim 1, characterized in that said application of said bead of adhesive paste is performed by means of a first robot associated with a dispensing and applicator apparatus, of the type known per se, which is programmed so as to be made to move and supply said adhesive paste along a predetermined path.

4. Method according to Claim 3, characterized in that said predetermined path is parallel to the perimetral edge of said internal lens and at a predefined distance from the said edge.

5. Method according to Claim 1, characterized in that said application performed by second means for manipulating and applying the external lens or second lens onto the external surface of said first lens or internal lens is performed under a predefined pressure and for a predetermined period of time sufficient for ensuring completion of the adhesive union between the internal surface of said external lens and said adhesive bead, said pressure being calibrated so as to keep the thickness of the cavity between the two lens at a predetermined value.

6. Apparatus for the production of double-lens articles, characterized in that it comprises at least one station provided with a temporary support for resting said first lens in position such that its external surface is free and accessible, a first robot having means for dispensing and applying adhesive in a dense in particular paste-like form, said first robot being programmable so as to move said dispensing and applicator means along a predetermined path, a second robot having means for removing and transferring into position a lens from a store to said temporary support.

7. Apparatus for the production of double-lens articles according to Claim 6, characterized in that said adhesive is a silicone adhesive in paste form.

8. Apparatus for the production of double-lens articles according to Claim 6, characterized in that it comprises a rotating-table support having at least three working positions or stations, the said first lens being loaded in the first station or position, while in the second station said first robot operates so as to apply the dispensed amount of said adhesive along a predetermined path, in said third and last position or station said second robot removing said second lens from a special store and applying it on top of the surface of said first lens in contact with the peak or crest part of said adhesive applied to said surface.

9. Apparatus for the production of double-lens articles according to Claim 8, characterized in that said second robot exerts a controlled pressure so as to favour adhesion of the internal surface of the second lens to the layer of adhesive projecting from the underlying surface of said first lens, said pressure being calibrated so as to avoid crushing said adhesive layer.

10. Apparatus for the production of double-lens articles according^' to Claim 8, characterized in that said second robot unloads the double-lens article from said last station.