The object of the invention is an apparatus for spraying biodegradable straws and a method for spraying biodegradable straws.

The solution belongs to the area of the food industry related to the production of biodegradable straws for the consumption of beverages.

The food industry uses drinking straws, which are usually made of plastic, for a variety of beverages. Most plastics have a long decomposition period of up to 200 years, so these types of drinking straws pose a serious threat to ecosystems. Nowadays, biodegradable straws are an increasingly popular alternative to standard plastic straws. Biodegradable straws can be made from a variety of materials that break down naturally, for example: from paper, straw, pasta, apple pomace, polyactide PLA. A growing trend to replace plastics with environmentally friendly biodegradable materials leads to a continuous development of these materials in order to improve their properties and parameters, and thus to increase their range of application and dissemination. In order to improve the properties or to give specific parameters, biodegradable drinking straws can be coated with various types of coatings, for example: providing water resistance, increased rigidity of the straw and hardness of its surface, increased resistance to hot drinks, or giving specific taste qualities.

From the document US2014/0084077 A1, an apparatus and a method for coating straws with water-soluble vitamins are known. In the solution disclosed in the US application, the inner or outer surface of the straw is sprayed with an aqueous solution containing vitamins B12 and C, using a nozzle connected to an airbrush spraying the aqueous solution with vitamins in the form of a fine mist. After spraying, the straw is left to dry, allowing a dried coating of vitamins to form on its surface.

From the document US 2021/0059447 A1, an apparatus and a method for coating pasta straws with flavour enhancing substances are known. Pasta, as a material for drinking straws, has certain disadvantages: firstly it has an aroma affecting the taste of the consumed product, secondly the pasta straw immersed in water for a longer period of time softens and loses its properties. In order to improve the properties of the pasta straw, the US document introduces the coating of the straw with beeswax. In the solution disclosed in the application US 2021/0059447 A1, the pasta straws are immersed by means of a movable rod in beeswax, and then emerged and inflated with air from nozzles designed to remove excess wax, cool and harden the wax. From the document US3109590A, an apparatus and a method for reinforcing the ends of paper straws susceptible to deformation, distortion and softening in water are known. The method comprises coating or dipping the paper straw in a moisture resistant reinforcing material, for example solidifying wax.

A problem to be solved by the present invention is to provide a complex apparatus for coating biodegradable straws by spraying them whilst conveying on a conveying unit and irrespective of the type of coating agent.

The object of the invention is an apparatus for spraying biodegradable straws, comprising a conveying unit for guiding the biodegradable straws, at least one nozzle positioned above the conveying unit for spraying a coating agent solution onto the biodegradable straws, a drying unit positioned downstream of the at least one nozzle, in the direction of conveyance of the biodegradable straws, for drying the biodegradable straws coated with the aqueous solution of the coating agent by draining water from the coating agent solution. The conveying unit is adapted to guide the biodegradable straws transversely to the conveying direction, in a single layer.

The apparatus according to the invention is characterized in that the conveying unit is further adapted to rotate the biodegradable straws around their longitudinal axis when spraying the biodegradable straws or when drying the biodegradable straws.

The apparatus according to the invention is characterized by further comprising a cutting head adapted to cut the biodegradable straws at an angle, situated upstream of at least one nozzle, in the direction of conveyance of the biodegradable straws.

The apparatus according to the invention is characterized in that at least one nozzle is adapted to spray the coating agent solution onto the ends of the biodegradable straws.

The apparatus according to the invention is characterized in that at least one nozzle for spraying the coating agent solution is situated in a partially closed chamber.

The apparatus according to the invention is characterized in that the partially closed chamber with at least one nozzle is further provided with an aerosol extraction unit for aerosol containing sprayed droplets of the coating agent which have not settled on the surface of the biodegradable straws.

The apparatus according to the invention is characterized in that at least one nozzle is in the form of a spray gun with a controlled flow of air and coating agent solution.

The apparatus according to the invention is characterized in that the coating agent solution is a curing agent, a flavour enhancer, a medicinal agent, in particular selected from the group consisting of: water glass, vitamin C, vitamin B, sugar, and food colouring agents.

The apparatus according to the invention is characterized in that the drying unit is provided with at least one heat source of the group: infrared, warm air blowing, gas burners.

The object of the invention is also a method for spraying biodegradable straws, comprising the following steps wherein: the biodegradable straws are guided transversely to the conveying direction, in a single layer, on the conveying unit, the biodegradable straws are sprayed with a coating agent solution by means of at least one nozzle, arranged above the conveying unit, the solution-coated biodegradable straws are dried by draining water from the coating agent solution by means of a drying unit arranged downstream of at least one nozzle. The method according to the invention is characterized in that when spraying the biodegradable straws with the coating agent solution or when drying on a conveying unit in the form of a rotary conveyor, the biodegradable straws are rotated around the longitudinal axis.

The method according to the invention is characterized in that before spraying the biodegradable straws are cut at an angle with a cutting head.

The method according to the invention is characterized in that during cutting the biodegradable straws are held on the conveying unit so that they do not rotate about their own axis.

The method according to the invention is characterized in that the coating agent solution is sprayed onto the ends of the biodegradable straws.

The method according to the invention is characterized in that during spraying at least one full rotation of the biodegradable straws around their longitudinal axis is performed.

The method according to the invention is characterized by comprising an additional step wherein, during spraying, the excess coating agent solution is drawn off by an aerosol extraction unit.

The method according to the invention is characterized in that the spraying comprises feeding, in the form of a conical jet, the coating agent solution onto the ends of the biodegradable straws.

The method according to the invention is characterized in that the biodegradable straws are sprayed with a solution of a coating agent: a curing agent, a flavour enhancer, a medicinal agent, in particular selected from the group comprising: water glass, vitamin C, vitamin B, sugar, and food colouring agents.

An advantage of the solution according to the invention is that the surface of the biodegradable straws can be evenly coated with a coating agent. The apparatus and the method according to the invention are not limited to the use of one type of coating agent and can be used with identical results to coat biodegradable straws with curing agents as well as with taste enhancers and medicinal agents, for example vitamins. An additional advantage of the solution according to the invention is the acceleration of the coating formation process by using a drying unit downstream of the nozzle, which significantly shortens the drying process of the coating formed from the coating agent.

The object of the invention is shown in more detail in a preferred embodiment in a drawing in which:

Fig.1 shows an apparatus for spraying biodegradable straws in the first embodiment in an axonometric view;

Fig. T shows the apparatus for spraying biodegradable straws in the second embodiment in an axonometric view;

Fig.2 shows a nozzle unit having nozzles arranged at every 90°

Fig. 2' shows a nozzle unit having nozzles arranged at every 120°

Fig.3 shows a nozzle unit having nozzles arranged in a line alternately

Fig.4 shows the apparatus for spraying biodegradable straws in a side view

Fig.5 shows a cross-section A-A through a conveying unit upstream of a cutting head;

Fig.6 shows a cross-section B-B through the conveying unit downstream the cutting head; Fig.7 shows a cross-section C-C through the conveying unit upstream of at least one nozzle;

Fig. 7' shows a cross-section C-C through the conveying unit upstream of at least one nozzle in the second embodiment of the conveying unit;

Fig.8 shows a cross-section D-D through the conveying unit between the drying units; Fig. 8' shows the cross-section D-D through the conveying unit between drying units in the second embodiment of the conveying unit;

Fig. 1 shows an apparatus 1 for spraying biodegradable straws 2 in the first embodiment in an axonometric view. The apparatus 1 for spraying the biodegradable straws 2 comprises a conveying unit 3, for example in the form of a conveyor belt for guiding the biodegradable straws 2, at least one nozzle unit 4 situated above the conveying unit 3, for spraying the coating agent solution 10 onto the biodegradable straws 2, and a drying unit 5. The nozzle unit 4 may comprise one or more nozzles 4'. The conveying unit 3 shown in Fig.1 guides the biodegradable straws 3 transversely to the conveying direction, in a single layer, one after another, preferably placed in the flute 12 of the conveyor 3. Preferably, the biodegradable straws 2 are spaced apart on the conveying unit 3. In this embodiment, during the spraying of the coating agent solution 10, the straws 2 are put into rotation around their longitudinal axis X by means of a stationary raceway 3C.

Such a solution allows the nozzle unit 4 to be situated only on one side of the conveying unit 3 on its upper or lower side, because the straw 2, while moving in the spraying area, performs at least one complete rotation around its longitudinal axis X so that it is coated around its entire circumference with the coating agent 10. It is possible to have an embodiment wherein the unit of nozzles 4 arranged at a certain distance from one another above and below the conveying unit 3 is used, as shown in Fig. T. In such an embodiment, the straws 2 are transported lying still in the flutes 12 of the conveying unit 3, preferably so that the distances among the individual nozzles 4' enable the surfaces of the biodegradable straws 2 to be coated by an even layer of the coating agent solution 10, first on their upper circumferential surface and then on their lower circumferential surface without the need to rotate them during spraying. The following figures show a fragment of the apparatus 1 in subsequent embodiments in a side view wherein the unit of nozzles 4 arranged both above and below the conveying unit 3 is used, with a fixed linear or angular distribution. In the case of angular distribution shown in Fig.2-2', the nozzles 4' may be arranged every certain angle, for example four nozzles every 90° (Fig. 2) or three nozzles every 120° (Fig. 2'), on a circle whose centre is in line with the theoretical longitudinal axis X running through one of the straws 2 located on the conveying unit 3 in the spraying area. Other angular distributions are also possible, depending on the number of the nozzles 4' and the manner of their arrangement. In Fig. 2, the straws 2 are conveyed in the flutes 12 by means of the conveying unit 3 in the form of a belt 11 with the flutes 12. During the conveyance, the straws 2 remain lying still in the flutes 12 transversely to the conveying direction. In the embodiment shown in Fig. 2', the straws 2 are transported during spraying by means of the conveying unit 3 in the form of belts. The straws 2 placed on the bottom belt are transported in the direction according to the conveying direction of the bottom belt indicated by the arrow T. When straws 2 are conveyed on the bottom belt, the upper belt holds the straws on their upper side and can also move in the direction T at a speed being the same as or different from the speed of the bottom belt. It is also possible to build an embodiment wherein the upper belt is stationary or wherein the upper belt moves in the direction opposite to the direction T at a speed lower than that of the lower belt. The solution wherein the lower belt has a different speed than the upper belt will cause the straws 2 to be put into rotation about their longitudinal axis X and to roll on the lower belt in the direction T. An advantage of such a solution is that the entire circumferential surface of the straws 2 conveyed under the nozzle unit 4 is thoroughly coated with the coating agent 10. Fig. 3 shows a fragment of the apparatus 1 with the unit of nozzles 4 arranged in a predetermined linear distribution alternately above and below the conveying unit 3. The straws 2 transported on the conveyor 3 will be coated twice with the coating agent 10, first on their upper circumferential surface at least 180° of the circumference, then with the unit of nozzles 4 situated below the conveyor 3 on their underside circumferential surface, at least 180° of the circumference. Then again on their upper circumferential surface and again on their underside circumferential surface.

Regardless of how the nozzle unit 4 is arranged, it is most important to coat the straws 2 evenly with the coating agent 10 over the entire circumferential surface of the straws 2.

It is also possible to build an embodiment wherein the straws 2 will be coated with a first coating agent by means of the first nozzle unit 4, followed by a second coating agent by means of the second nozzle unit 4.

The spray nozzles 4' in the nozzle unit 4 may take various forms, for example a spray gun with an adjustable flow of coating agent and with an adjustable flow of air. The spray gun allows the coating agent solution 10 to be dispensed in the form of a conical jet. The conical jet is optimal in terms of spraying efficiency since only minimum amounts of the sprayed coating agent solution 10 are deposited on the parts of the apparatus rather than on the biodegradable straws 2. The use of double adjustment also allows avoiding air turbulence in the spray zone. The spray nozzles 4 are preferably placed in a partially closed chamber. In the embodiment shown in Fig.1, the drying unit 5 is situated downstream of at least one nozzle unit 4. The purpose of the drying unit 5 is to dry the biodegradable straws 2 coated with the coating agent solution by draining water from the coating agent solution. Moreover, the drying unit 5 is provided with at least one heat source selected from the group consisting of: an infrared lamp, a warm air blower, gas burners. The choice of type of the drying unit 5 is largely determined by the type of coating agent solution used. The drying process time can be adjusted by varying the distance of the drying unit 5 from the biodegradable straws 2 transported on the conveying unit 3, the heating power of the drying unit 5 or the length of the drying unit 5 under which the straws 2 are transported. In the process of spraying the biodegradable straws 2 on the apparatus 1 for spraying the biodegradable straws 2 shown in Fig.1 , firstly, the biodegradable straws 2 are guided transversely to the conveying direction, in a single layer, on the conveying unit 3. Subsequently, the biodegradable straws 2 are sprayed with at least one nozzle unit 4 situated above the conveying unit 3. The spraying is carried out with the coating agent solution 10. The last step of the process comprises drying the solution-coated biodegradable straws 2 by draining water from the coating agent solution 10 by means of the drying unit 5 arranged downstream of the at least one nozzle unit 4.

Fig. 4 shows the apparatus 1 for spraying the biodegradable straws 2 in a side view. This embodiment additionally comprises a hopper 9 of biodegradable straws 2 from which biodegradable straws of double length are fed to the conveyor belt 3 by means of a drum conveyor 8. The apparatus 1 for spraying the biodegradable straws 2 is additionally provided with a cutting head 6 adapted to cut the biodegradable straws of double length at an angle substantially in the middle of their length, the cutting head 6 being situated upstream of at least one nozzle unit 4, with reference to the straw conveying direction. As a result of cutting the straws 2 at an angle, the straws will have a sharp end, making it easier to pierce the beverage packaging. During cutting, the biodegradable straws are held so that they do not rotate about their axis and remain relatively stationary. Due to the provision of the cutting head 6, it is possible to simultaneously coat two streams of the biodegradable straws 2 conveyed in parallel by two conveying units 3, using a single nozzle unit 4 situated above the ends of the sharp-ended straws and a single drying unit 5. The cutting head 6 is optional and is only present in the solution in which the double-length straws are fed from the hopper 9. The apparatus according to the invention is also used in coating processes for straws without a sharp end. The conveying unit 3 shown in Fig. 4 is in the form of a rotating conveyor provided with two conveyor belts, which will be described in detail with reference to Fig. 5. In the embodiment of the apparatus 1 for spraying the biodegradable straws 2 shown in Fig. 4, the straws 2, after being cut by means of the cutting head 6, are conveyed towards the nozzle unit 4. Fig. 4 also shows an aerosol extraction unit 7 for aerosol containing sprayed droplets of the coating agent 10 which have not settled on the surface of the biodegradable straws 2. The aerosol residue may interfere with the spraying process by settling on parts of the apparatus 1. Depending on the type of coating agent used, it may also pose a potential hazard to the operator of the spraying apparatus 1 as there is a risk of aerosol residue entering the lungs. The aerosol extraction unit 7 is arranged under the nozzle unit 4 and is positioned in a partially closed chamber 13. The use of the aerosol extraction unit 7 is optional and depends on the properties of the coating agent solution 10 used, while the choice of coating agent 10 depends on the desired properties of the final product. For example, the coating agent solution 10 may be: a curing agent e.g. water glass, agents to increase the strength of the straw for hot beverages, an agent to improve the taste e.g. sugar, an agent to change the visual qualities of the straw e.g. food colouring agents, a medicinal agent e.g. vitamins C, B. Moreover, the invention is not limited to the mentioned embodiments. The use of the aerosol extraction unit 7 is particularly advantageous when curing agents in the form of water glass are used.

As shown in Fig. 4, after spraying by means of the nozzle unit 4, the biodegradable straws 2 are transported on the conveying unit 3, towards the drying unit 5. In the embodiment shown in Fig. 4, the drying unit 5 in the form of four radiant heaters emitting infrared radiation is used. In this embodiment, the radiant heaters are situated at the same distance from the straws 2, respectively above and below the conveying unit 3. The drying time of the coated biodegradable straws 2 can be adjusted by varying the distance of the radiant heaters from the surface of the dried biodegradable straws 2. In order to obtain an optimal drying time, the radiant heaters are preferably arranged at a distance that ensures an effective heat transfer to the outer surface of the straws 2, without destroying the conveyed straws. Embodiments using more/less radiant heaters are also possible.

The distances among the biodegradable straws 2 on the conveying unit 3 are preferably adjusted by varying the operating speed of the conveying unit 3 and/or by varying the operating speed of the drum conveyor 8 or another type of unit supplying the conveying unit 3 with the biodegradable straws 2. Fig. 5 shows a cross-section A-A through the conveying unit 3 upstream of the cutting head 6. The shown cutting head 6 cuts the double-length biodegradable straw 2 at an angle a, for example at an angle of 45°, as a result of which sharp straws 2B and 2A, as shown in Fig. 6, are obtained.

Fig. 6, on the other hand, shows a cross-section B-B through the conveying unit 3 downstream of the cutting head 6. After the straw 2 has been cut by the cutting head 6 into two parts 2A and 2B, they are spaced apart, for example by means of a spacing element 15 or by means of rotating rollers (not shown in Fig. 6) arranged over the straws 2B, 2A tangentially to their circumferential surfaces. The straws 2A and 2B are spaced in the flutes 12 of the conveying unit 3 along their axis X.

Fig. 7 shows a cross-section C-C through the chamber 13 with the conveying unit 3 arranged inside upstream of at least one spray nozzle 4'. In this embodiment, the conveying unit 3 is in the form of a rotating conveyor, for example provided with two conveyor belts, respectively a first conveyor belt 3A and a second conveyor belt 3B, running at different speeds so that the sharp biodegradable straws 2A, 2B conveyed between the belts 3A, 3B are put into rotation around their own axis X. The conveyor belts 3A, 3B in this embodiment need not have any transporting flutes. The straws 2A, 2B can be transported by means of the conveyors in the direction of the outlet of the apparatus 1 on their smooth working surface without flutes. The surface of the conveyors without transporting flutes has an advantageous effect on the rotation and the rolling of the straws 2A, 2B on the lower belt 3B. To increase the friction between the surface of the conveyed sharp biodegradable straws 2 and the conveyor belt 3A, 3B, the conveyor belt may be made of rubber. In the embodiment shown in Fig. 7, the coating agent solution 10 is sprayed by means of the nozzle 4', only on the cut ends of the biodegradable straws 2A, 2B.

Fig. 7' shows a cross-section C-C through the chamber 13 with the conveying unit 3 arranged inside, situated upstream of at least one nozzle 4' for spraying, in the second embodiment of the conveying unit 3. As shown in Fig. 7', stationary raceways 3C are arranged in the conveying unit 3. In this embodiment, the rotational movement of the sharp biodegradable straws 2A, 2B about their axis X is a result of the action of the stationary raceways 3C arranged in the conveyor run 3, causing the conveyed straws to rotate. The straws 2A, 2B are conveyed in the flutes 12 of the conveyor 3B transversely to the conveying direction. In the spraying area in the flutes 16 of the conveyor 3B, there are arranged stationary raceways 3C projecting with their upper surface above the bottom of the flute 12 so that the conveyed straws 2A, 2B are rolled on the upper surface of the stationary raceway 3C while remaining in the flute 12 of the conveyor 3B. Such rolling of the straws 2A, 2B may take place in the conveying section where the coating agent 10 is sprayed, as well as in the chamber 14 where the drying unit 5 is situated. The embodiments of the conveying unit 3 described above with reference to Fig. 7 and Fig. 7' make it possible to rotate the biodegradable straws 2A, 2B around their longitudinal axis X during spraying or during drying so that an effect of uniform coating of the straws 2A, 2B around the entire circumference of the straws can be achieved using a minimum number of the nozzles 4' and as short section of the drying unit 5 as possible. Preferably, during spraying, at least one full rotation of the biodegradable straws 2A, 2B around their longitudinal axis X is performed.

Fig. 8 and Fig. 8' show respectively the drying process using the drying unit 5 in the form of radiant heaters arranged in the chamber 14, with the use of two different conveying units 3. The drying unit 5 shown in this embodiment is arranged both above and below the conveying unit 3. It is also possible to position the drying unit at an angle to the straws 2A, 2B. The angle value should be in the range of 0-180°. It is important that the heat energy transferred from the drying unit reaches directly the sharp ends of the straws with the coating agent 10 applied. Fig. 8 shows the conveying unit 3 in the form of two conveyor belts, respectively the first conveyor belt 3A and the second conveyor belt 3B, running at different speeds. Fig. 8' shows the conveying unit 3 comprising stationary raceways 3C. The principle of operation and the function of the stationary raceways 3C are explained in the description of Fig. 7'. By using the rotation of the biodegradable straws 2A, 2B during the drying process, the duration of the drying process can be further adjusted. Preferably, during drying, at least one full rotation of the biodegradable straws 2A, 2B around their longitudinal axis X is performed.

The above-described apparatuses for spraying the biodegradable straws 2, 2A, 2B, as well as the method for spraying the biodegradable straws 2, 2A, 2B may be used for spraying straws made of various types of materials, for example: paper, wood, pasta or other biodegradable materials.