ACTUA TING THIS PROCESS

DESCRIPTION

The present patent concerns paint rollers and in particular it concerns a new process for producing paint rollers and a system actuating this process.

Paint rollers are known that comprise a cylindrical element, generally made of plastic, coated with a material suited to he dipped in the colour or paint in general to be transferred on a surface to he painted, and a handle comprising a substantially L-shaped structure with a small arm suited to be inserted in the cylindrical element for the axial rotation of the cylindrical element itself, and a small arm suited to be used as a grip.

Said cylindrical element has its external cylindrical wall coated with said material generally consisting of sponge, spongy material, bristles, fringes, polyethylene fibres, nylon, wool - mohair or another type of wool, depending on the intended use of the roller.

Said cylindrical element also comprises closing plugs positioned at its ends to constrain said plug.

Paint rollers of various sizes are known, meaning rollers whose cylindrical element has varying diameter and length. For example, there are known paint rollers for w ^r alls, rollers for corners, much smaller in size, and rollers for precision works, having intermediate sizes.

Paint rollers are generally produced using rods with defined length, which are first covered with a coating material suitable for the intended use and then cut to size.

Each rod segment, whieh constitutes the coated cylindrical element, is then conveyed to the following stage for assembly of the handle and the closing plugs at the ends. This process involves the production of large amounts of scrap, considering that there are various standard sizes for the length of the cylindrical elements, depending on the paint roller to be obtained.

Furthermore, this process requires the intervention of operators who from time to time have to position each rod on the production line and therefore follow the production process constantly.

In the systems and according to the processes presently known, the rod coating material is attached to the cylindrical wall of the tube, using glue that is applied to the cylindrical wall itself. It has been observed that this adhesion effect isn't stable and long-lasting and that the coating material can be easily detached from the tube, even manually.

Document CA 2178360 concerns a system according to which the cylindrical wall of the rods is pre-heated before applying an adhesive strip to the wall itself, in order to heat the adhesive substance and facilitate the adhesion of the coating material that is applied thereon.

The application of an adhesive substance or glue and its adhesion time considerably limit the advance speed of the system and thus also its hourly production.

Systems and processes are known in which the rods are heated using gas or fuel, which involves risks and limitations of use in relation to the safety of the system.

The subject of the present patent is a new type of process for the production of paint rollers and a system actuating said process.

It is the main object of the present patent to allow paint rollers to be produced in a continuous process, thus optimising hourly production.

It is another object of the present invention to provide a process that is completely automated and requires the minimum intervention by the operators.

it is another object of the invention to reduce the production of scrap to a minimum.

It is another object of the invention to guarantee the permanent adhesion of the coating material to the rod.

These and other direct and complimentary objects are achieved by the new process for producing paint rollers and a system actuating said process. The new process comprises, in its main parts, the following steps: loading of cylindrical tubular rods made of a plastic material and having a given length; handling the rods, which are placed and maintained in a continuous motion resulting from the combination of axial rotation and translation in the axial direction according to an advance direction; application of the coating material of said rods after pre-heating of the external cylindrical surface of the rods to a degree sufficient to cause the softening or surface melting of the cylindrical wall, and thus allow the successive application and direct thermal bonding between the cylindrical surface and the coating material.

In order to carry out said pre-heating of the cylindrical surface, the system actuating said process comprises one or more heating elements consisting of one or more electrical resistances positioned upstream of a station for tire application of the coating material.

Said heating elements are in a such a position that the rod, maintained in said rototranslation motion, comes to be at a distance sufficiently close to the heating elements, so that they can progressively heat the entire cylindrical surface of the rod during its advance and rotation movement, and cause its surface to melt.

According to the invention, in order to guarantee the permanent adhesion of the coating material to the rod, the latter, made in a plastic material that is preferably polypropylene or a compatible material, is heated to the surface melting temperature of the material, meaning approximately 500-650 °C. According to the invention, furthermore, also the underside of the coating material is heated, meaning the surface intended to adhere to the external wall of the rod, also said underside being completely or partially coated with or made of polypropylene or a compatible material, useful to fix the fibres of the material.

Said underside of the coating material is heated with air up to 100-150 °C, in order to slightly soften the material so as to facilitate and improve the successive adhesion of the same to the surface of the rod.

In this way, the two materials are substantially welded together through melting, so that they permanently adhere to each other, differently from that which happens using glue or interposed adhesive substances.

The system actuating said process comprises a loading station in which the rods are superimposed and parallel to one another, for example constrained between vertical C-shaped guides, and arranged in said advance direction, and wherein at least one pusher element consecutively thrusts the rod towards a lower position on a loading rail arranged according to said advance direction, while the successive rod occupies, due to gravity, the lowest position in the loading station.

The pusher element thrusts the rod until it reaches a rototranslation unit that grasps the rod and transmits the rototranslation advancing movement to it. The process preferably includes also the step of joining each loaded rod to the rod loaded successively, by heating the opposing adjacent ends of the two rods in such a way as to obtain a single continuous rod.

The union of two consecutive rods is performed by means of said pusher element that presses the last rod loaded against a heating device and then against the opposite end of the rod already grasped by said rototranslation unit.

In order to proceed to the application of the coating material, which is provided in the form of a continuous strip wound in a coil and arranged so that it is inclined with respect to the axis of the rod, the coating material itself is unwound and then wound around the rod, thus adhering to the softened cylindrical surface of the rod itself.

Said strip unwinding and winding operation is carried out automatically due to the rototranslation motion of the rod.

For the rototranslation of the continuous rod, the system actuating the process comprises said rototranslation unit, in turn comprising a device suited to rotate the rod around its axis and at least one pair of jaws operating alternately and suited to cause the continuous axial translation of the rod in said advance direction.

The process preferably includes also the step of cutting the coated rod to size so as to obtain coated cylindrical elements, with or without a further step of applying the closing plugs to the ends of each cylindrical element. The system actuating said process thus preferably comprises also at least one cutting station, comprising cuttmg tools, like tor example a cutter or a blade in general, suited to cut the cylindrical surface of the rod with the coating applied thereon. Said cutting station preferably translates in said advance direction of the rod, when it moves forwards in the advance direction, so as to follow the rod during the cutting step, and when it moves backwards in the opposite direction, so as to return to the starting position. The rotary motion of the rod guarantees that the cut is performed on the entire cylindrical surface. The characteristics of the new system actuating the process for producing paint rollers are highlighted in greater detail in the following description with reference to the drawings that are attached by way of examples without limitation.

Figure 1 shows a diagram of the system, while Figures 2, 3 and 4 show the following in detail: loading station ( 1) and joining station (2) for the rods (A) (Figure 2), rototranslation unit (3) for handling the rods (A) and preheating station (4) for heating the cylindrical wall (Ac) of the rods (A) (Figure 3), the application station (5) for applying the strip (51) of coating material used to coat the rods (A), the cutting station (6) and the unloading station (7) (Figure 4).

The new system comprises a first loading station (1) suitable for loading rods (A) having a cylindrical tubular shape and a given length.

Said loading station (1 ) comprises a repository (1 1) for said rods (A), positioned so that they are superimposed and parallel to one another, and oriented in a given direction (X).

Said repository in turn preferably comprises one pair of vertical and opposing C-shaped guides (12), arranged specularly and suited to house the opposing ends (Al , A2) of the rods (A) in the repository, having the purpose of guiding the fall by gravity of the rods (A) during the loading step.

The loading station (1) comprises at least one pusher element (13) suited to act from time to time on the rod (A) that is in the lowest position in said repository (11), pushing it on a loading rail (14) oriented according to an advance direction (X).

Said pusher element (13), translating in the advance direction during its forward movement, pushes the single rod (A) until it reaches a rototranslation unit (3) for handling the rods (A), which comprises at least one pair of jaws (31 , 32) suited to alternately grasp the rod (A) and transmit to it a rototranslation advancing movement resulting from the combination of an axial rotary motion of the rod (A) and an axial translation motion in said advance direction (X) away from said loading station (I).

Said pusher element (13), in addition to translating said rod (A) towards said rototranslation unit (3). allows it to be rotated when it is grasped by said jaws (31 , 32).

Said rototranslation unit (3) comprises in particular a device (33) suited to rotate the rod (A) around its axis (Ax) and said at least one pair of jaws (31, 32) operating in an alternating manner, suited to cause the continuous translation of the rod (A) in said advance direction (X).

Said jaws (31, 32) rotate with said rotation device (33) and in turn translate with respect to said rotation device (33), being connected to suitable translation means (36), such as gears and racks.

In detail, said rod rotation device (33) comprises a motor (34) and transmission belts (35) suited to transmit the rotary motion to said rod (A). Therefore, with reference to Figure 2, when the rod (At) grasped by the jaw (31) of the rototranslation unit (3) exits from the loading station (1), the successive rod (As) coming from the repository (11) occupies, due to gravity, the lowest position in said loading station ( 1 ), where said pusher element (13) thrusts it towards said rototranslation unit (3).

In the preferred solution and with reference to Figure 2, the system also comprises a joining station (2) for the rods (A), where each rod (As) coming from the repository (1 1 ) is joined to the rod (At) just grasped by the rototranslation unit (3) that has left the loading station (1 ).

Said joining operation is performed by heating the opposing adjacent ends (Al, A2) of the two rods (As, At) to be joined. Said joining station (2) thus comprises at least one moving heating element (21 ). suited to be alternately interposed between said opposing ends (Al , A2) of two rods (At, As) to be joined, in order to heat them and soften the material of which they are made.

Said pusher element (13) thus applies an axial pressure on the last rod loaded (As), first against said heating element (21 ), then, once said heating element (21) has returned to its rest position, against the opposing end (A2) of the rod (At) already grasped by said rotoiransiation unit (3), and thus according to a rototranslation motion, so as to obtain a single continuous rod.

Said pusher element (13) allows the idle rotation of the rod (As), so that said moving rod (At) involves in its motion also said successive rod (As), thus maintaining the movement of the continuous rod (A) uninterrupted.

Said heating element (21) is, for example, a heating disc, also suited to translate idly following the thrusting action of said rod (As) translated by said pusher element (13).

The continuous rod (A) obtained is thus kept in a continuous motion resulting from the combination of axial rotation and translation in the axial direction and in the advance direction through said rototranslation unit (3). Downstream of said rototranslation unit (3). the system preferably comprises at least one pre-heating station (4) suited to heat the external cylindrical surface (Ac) of the rod (A), which is necessary for the successive application of the strip (51) of coating material to be used to coat the rod (A).

The strip (51) of coating material is in fact fixed to the external cylindrical surface (Ac) of the rod (A) through thermal bonding.

Said thermal bonding is obtained by applying the strip (51) to the rod (A) once the cylindrical surface (Ac) of the latter has been heated to a degree sufficient to soften the plastic material of which the rod (A) is made.

Said pre-heating station (4) preferably comprises one or more heating elements (41 ), such as one or more electrical resistances, in such a position that said rod (A), maintained in said rototranslation motion, comes to be at a distance sufficiently close to the heating elements (41 ) so that the latter can progressively heat the entire cylindrical surface (Ac) of the rod (A) during its advance movement.

Immediately downstream of said pre-heating station (4) there is an application station (5) for the application of the coating material in the form of a continuous strip (51) wound in one or more coils, with one or more tensioning elements (52), if any, and arranged in a preferably inclined position with respect to the axis (Ax) of the rod (A).

For example, said strip (51) is inclined by approximately 45° with respect to the axis (Ax) of the rod (A).

Said application station (5) comprises a device suited to eliminate, for example by burning, any imperfections, bristles or threads projecting beyond the lateral edges of the strip (51).

Once one end of the strip (51) has been applied to the cylindrical surface

(Ac) of the rod (A), the strip (51) adheres to it and, due to the rototranslation motion of the rod (A), said strip (51) unwinds and winds around the rod (A), adhering to its cylindrical surface (Ac) as the rod (A) advances.

The new system comprises also a cutting station (6) suited to cut said coated rod (A) to size so as to obtain coated cylindrical elements (C).

Said cutting station (6) comprises one or more cutting tools (61), such as a cutter or a blade in general, suited to cut the cylindrical surface (Ac) of the rod (A) with said coating strip (51) applied thereto. Said cutting station (6), meaning at least said one or more cutting tools (61) _* preferably translate in said advance direction (X) of the rod (A), in order to follow the rod itself during the cutting operation, while the rotary motion of the rod (A) guarantees that the cut is performed on the entire cylindrical surface (Ac).

According to the invention, said cutting station (6) comprises a translating element (62) or spindle suited to be inserted axially in the rod (A) to be cut, in order to stabilize the rod (A) during cutting and to hold and unload said coated cylindrical elements (C), which are unloaded and collected in an area, hopper or unloading station (7).

Said cutting station (6) comprises also jaws (63) suited to support the rod (A) during the cutting operation.

Said cutting tools (61), said translating element (62) and said jaws (63) of the cutting station can move with their own motion or can be idle, being pushed and/or driven by the movement of the rod (A).

In the preferred solution, said translating element or spindle (62) is suited to be inserted in the rod (A) and to expand in order to grasp the rod (A), in such a way as to serve also as an internal support during the cutting operation, avoiding any bending and twisting effect on the rod (A).

According to the invention, said spindle (62) rotates with independent motion with the same number of revolutions as said motor (34) of the rototranslation unit (3), being mechanically connected to it.

Once the rod (A) has been cut completely, said spindle (62) moves backwards, said jaws (63) open and the cylindrical element (C) obtained from the cutting operation falls into said unloading station (7).

These are the schematic outlines that are sufficient to implement the invention for a person skilled in the art, consequently, in the construction step, changes may be made that do not affect the substance of the innovative concept.

Therefore, with reference to the above description and the attached drawings, the following claims are expressed.