GB2281232A

GB2281232A - A process for polishing a panel

Info

Publication number: GB2281232A
Application number: GB9325203A
Authority: GB
Inventors: Anthony Coyle; James Stanley Carleton
Original assignee: COYLE JOHN E
Current assignee: COYLE JOHN E
Priority date: 1993-08-27
Filing date: 1993-12-09
Publication date: 1995-03-01
Anticipated expiration: 2013-12-09
Also published as: IE930629A1; GB2281232B; GB9325203D0; IE80402B1

Abstract

A process for polishing a timber surface of a panel using an inline apparatus comprises applying a first coat of lacquer to the surface by a lacquer applicator roller (13) in a lacquer applicator station (12). The first coat is cured to a relatively tacky state in an ultra-violet curing oven station (14). A second coat of lacquer is applied to the first coat while still in the tacky state by two lacquer applicator rollers (16) and (17) sequentially in a second lacquer applicator station (15). The second coat is cured in a UV light curing oven station (18). Prior to applying the first coat of lacquer the timber surface of the panel is sanded in a sanding station (3) and stained in a staining station (5). The stain is dried in a warm air drying oven (10) and in an infra-red drying oven (11). <IMAGE>

Description

"A process for polishing a panel The invention relates to a process for polishing a timber surface of a panel using an ultra-violet curable lacquer, and in particular, though not limited to a process for polishing a panel having a timber surface formed by a veneer sheet of timber laminated to a substrate. The invention also relates to a panel having a surface polished by the process according to the invention.

In the manufacture of furniture, in particular, tables, cabinets, book shelves and other articles of furniture in which panels of relatively large surface area are required, in general, it is desirable that the panels should be polished, either to a relatively high gloss finish or to a matt finish. In general, such polishing is carried out using ultra-violet curable lacquers, such as, for example, acrylic based lacquers. Such lacquers are relatively convenient to use in that they can be cured relatively easily by exposure to ultra-violet light. However, where it is desired to provide a polished surface with a relatively deep lacquer layer, for example, a layer of 40 gms/sqM, or greater, acrylic varnishes, if they are to be employed in a continuous inline polishing process are in general unsatisfactory.To achieve weights of finished depths of lacquer layer of the order of 40 gms/sqM and greater, in general, it is necessary to apply at least three, and in many cases more coats of lacquer, and in general, it has been found that each coat should be dry, in other words, fully cured before the next coat can be applied.

Indeed, to achieve a polished surface with a finished layer depth of 50 gms/sqM to 55 gms/sqM, it has been found that, in general, five coats of lacquer are required, with each coat being fully cured prior to the next being applied. This, it will be appreciated in an inline process is uneconomical. Firstly, a lacquer applicator station is required in the inline process for each coat applied. Additionally, in order to cure each coat of lacquer after it has been applied to the surface of the panel, W light curing oven stations are required after each lacquer applicator station. This, leads to relatively high expense in the provision of an inline apparatus.Furthermore, because of the number of stations which the panel must pass through, and the dwell time required in the W light curing oven stations to achieve full curing of each coat, the process time -for each panel is relatively long.

There is therefore a need for a polishing process for polishing a timber surface of a panel which overcomes these problems.

The present invention is directed towards providing such a polishing process.

The term "tacky state" as used throughout this specification and in the claims in relation to the partial curing of a coat of lacquer means a state where the lacquer is partly cured and is in the form of a relatively solid gel, but is not fully cured.

The coat feels relatively tacky or sticky to touch.

In general, this state is reached when the coat is approximately three quarters cured.

According to the invention there is provided a process for polishing a timber surface of a panel with an ultra-violet curable lacquer in an inline apparatus comprising a first lacquer applicator station having one lacquer roller applicator, a first UV light curing oven station, a second lacquer applicator station having an upstream lacquer roller applicator and a downstream lacquer roller applicator, and a second W light curing oven station, the stations being sequentially arranged in line, the process comprising the step of passing the panel through the stations sequentially so that on exiting from one station, the panel substantially immediately enters the next station, and the process further comprising the steps of applying a first coat of the ultra-violet curable lacquer to the timber surface of the panel in the first lacquer applicator station, the first coat being applied to the timber surface in a quantity in the range of 9 gms/sqM to 15 gms/sqM of timber surface to be polished, curing the first coat in the first W light curing oven station to a tacky state, applying a second coat of the ultra-violet curable lacquer over the first coat in the second lacquer applicator station, the second coat being applied in a quantity in the range of 15 gms/sqM to 30 gms/sqM of timber surface to be polished, and subjecting the lacquer coats to W light in the second W light curing oven stations until the lacquer coats are dry.Preferably, the power output of the second UV light curing oven station is in the range of 60 watts/sqM to 100 watts/sqM of timber surface to be polished, and the lacquer coats are subjected to the UV light in the second UV light curing oven station for a time period in the range of 20 seconds to 35 seconds.

In one embodiment of the invention the power output of the W light in the first W light curing oven station is in the range of 20 watts/sqM to 60 watts/sqM of timber surface to be polished, and the first coat of lacquer is subjected to the W light in the first W light curing oven station for a time period in the range of 10 seconds to 15 seconds.

Preferably, the power output of the W light in the first W light curing oven station is in the range of 30 watts/sqM to 50 watts/sqM of timber surface to be polished.

Preferably, the power output of the IN light in the first IN light curing oven station is approximately 40 watts/sqM of timber surface to be polished.

Preferably, the power output of the UV light in the second liv light curing oven station is in the range of 70 watts/sqM to 90 watts/sqM of timber surface to be polished.

Preferably, the power output of the liv light in the second IN light curing oven station is approximately 80 watts/sqM.

Advantageously, the first coat of lacquer is subjected to the W light in the first IN light curing oven station for a time period in the range of 11 seconds to 14 seconds.

Advantageously, the first coat of lacquer is subjected to the W light in the first W light curing oven station for a time period of approximately 12F seconds.

Advantageously, the lacquer coats are subjected to the W light in the second W light curing oven station for a time period in the range of 21 seconds to 24 seconds.

Advantageously, the lacquer coats are subjected to the W light in the second W light curing oven station for a time period of approximately 22d seconds.

In general, it is preferred that the first coat of lacquer is applied in a quantity in the range of 10 gms/sqM to 12 gms/sqM of timber surface to be polished, and preferably, the first coat of lacquer is applied in a quantity of 11F gms/sqM approximately of timber surface to be polished.

In general, it is preferred that the second coat of lacquer is applied in a quantity in the range of 20 gms/sqM to 23 gms/sqM of timber surface to be polished, and preferably, the second coat of lacquer is applied in a quantity of 22 gms/sqM approximately of timber surface to be polished.

In one embodiment of the invention the upstream roller in the second lacquer applicator station applies the lacquer in a quantity in the range of 9 gms/sqM to 12 gms/sqM of timber surface to be polished.

Advantageously, the upstream roller in the second lacquer applicator station applies the lacquer in a quantity of 10.75 gms/sqM approximately of timber surface to be polished.

In one embodiment of the invention the downstream roller in the second lacquer applicator station applies the lacquer in a quantity in the range of 9 gms/sqM to 12 gms/sqM of timber surface to be polished.

Advantageously, the downstream roller in the second lacquer applicator station applies the lacquer in a quantity of 10.75 gms/sqM approximately of timber surface to be polished.

In one embodiment of the invention the timber surface is stained prior to the application of the first coat of lacquer, a stain being applied to the timber surface by a stain applicator station upstream of the first lacquer applicator station. Preferably, the stain applicator station comprises an upstream stain roller applicator and a downstream stain roller applicator arranged sequentially upstream of the first lacquer applicator station. Advantageously, the stain is a water based stain.

Advantageously, the panel is passed through a drying tunnel arranged inline between the stain applicator station and the first lacquer applicator station.

Advantageously, the stain is dried in the drying oven at a temperature in the range of 450C to 500C for a time period in the range of 25 seconds to 35 seconds.

Preferably, the timber surface is brushed with a roller brush arranged inline between the downstream stain roller applicator and the drying oven.

In a further embodiment of the invention the timber surface is sanded to a relatively smooth finish prior to the application of the first coat of lacquer.

Advantageously, the surface is sanded prior to the application of the stain. Preferably, the sanding of the timber surface is carried out in a first sanding station provided upstream of the stain applicator station.

In another embodiment of the invention the cured lacquer coat on the panel is sanded to remove nibs of timber extending through the lacquer coat after passing through the second W light curing oven station. Advantageously, a second sanding station is provided downstream of the second W light curing oven station for sanding the lacquer coat.

Additionally, the invention provides a panel comprising a timber surface, the timber surface having been polished using the process according to the invention.

The invention will be more clearly understood from the following description of a preferred embodiment thereof given by way of example only, with reference to the accompanying drawing, which illustrates in block representation, apparatus for carrying out the process according to the invention.

Referring to the drawing there is illustrated a block representation of apparatus according to the invention indicated generally by the reference numeral 1 for carrying out a polishing process according to the invention for polishing a timber surface of a panel (not shown) with an ultra-violet curing lacquer, which in this case is an acrylic based lacquer. Typically, the process is for polishing the surface of a veneer sheet laminated to a substrate, of for example, fibreboard, blockboard, chipboard, high density particle board, medium density particle board, low density particle board or any other suitable substrate. The veneer sheet may be a sheet of mahogany, teak, oak, or indeed, any other suitable timber.The panel may be a panel which would be suitable for use as a panel for a tabletop, a leaf for a table, a shelve for a bookcase, a panel for the side of a bookcase, a cabinet, or a door for a cabinet or the like.

The apparatus 1 is an inline apparatus and comprises a plurality of stations arranged inline through which the panel to be polished is sequentially passed. The stations are arranged so that as the panel exits from one station it immediately enters the next downstream station. A conveyor 2 conveys the panels from one station to the next, and as discussed below conveys the panels through some of the stations. A first sanding station 3 is provided at the upstream end of the apparatus 1 and comprises three sanding belts (none of which are shown). A first of the sanding belts is arranged to sand the timber surface to be polished transversely relative to the grain of the timber surface, and the other two sanding belts are arranged downstream of the first sanding belt to sand the timber surface of the panel in the direction of the grain.Such a sanding station will be well known to those skilled in the art. A dust extractor station 4 mounted adjacent to and downstream of the sanding station 3 draws dust resulting from sanding of the panel away from the apparatus 1 and also removes any residual loose dust resulting from sanding lying on the timber surface to be polished. Such a dust extractor station will be well known to those skilled in the art.

A stain applicator station 5 applies a coat of water based stain to the timber surface of the panel prior to the application of the lacquer. The stain applicator station 5 is located immediately downstream of the dust extractor station 4. The stain applicator station 5 comprises a pair of elongated transversely extending stain roller applicators, namely, an upstream stain roller applicator 6 and a downstream stain roller applicator 7 which are arranged sequentially one after the other for applying the water based stain to the timber surface of the panel.

Pinch rollers (not shown) co-operate with the upstream and. downstream stain roller applicators 6 and 7 for transferring the panel through the stain applicator station 5. The stain is applied by the upstream and downstream roller applicators 6 and 7 to the timber surface in a quantity to provide the desired shade and a uniform finish over the timber surface. The stain roller applicators 6 and 7 are arranged so that the panel on exiting from the upstream stain roller applicator 6 immediately enters the downstream stain roller applicator 7. Such stain roller applicators will be well known to those skilled in the art.A brush station 8 which comprises an elongated transversely extending brush roller 9 is mounted immediately downstream of the stain applicator station 5 for brushing the timber surface for dispersing stain relatively evenly over the entire timber surface of the panel to be polished. Such roller brushes will be well known to those skilled in the art.

A drying tunnel station 10 is located immediately downstream of the brush station 8 for receiving the panel for drying the stain. The drying tunnel station 10 comprises a warm air drying tunnel and extends for a length of approximately 6 meters. The conveyor 2 extends through the drying tunnel station 10 for transferring the panel through the drying tunnel in a time period of approximately 30 seconds. The temperature of the air in the drying tunnel is maintained at approximately 450C to 500C. Thus, each panel is subjected to an air drying temperature of approximately 450C to 500C for approximately 30 seconds for drying the stain. An infra-red heated drying oven station 11 is located in the apparatus 1 immediately downstream of the drying tunnel station 10 so that panels exiting from the drying tunnel station 10 immediately pass into the drying oven station 11.

The conveyor 2 conveys the panels through the infrared drying oven station 11 in approximately 10 seconds. The temperature in the infra-red drying oven station 11 is in the order of 700C to 800C.

A first lacquer applicator station 12 is located in the apparatus 1 sequentially immediately downstream of the infra-red drying oven station 11 for receiving panels from the infra-red drying oven station 11. The first lacquer applicator station 12 comprises a single elongated transversely extending lacquer roller applicator 13 for applying a first coat of the ultraviolet curable lacquer to the timber surface of the panel in a quantity of approximately 11F gms/sqM of timber surface to be polished. A first W light curing oven station 14 is located in the apparatus immediately downstream of the first lacquer applicator station 12 for curing the first coat of lacquer on the timber surface of the panel to a relatively tacky state. The first W light curing oven station 14 comprises one single W lamp which directs W light onto the first coat of lacquer to be cured.The power output of the IN lamp in the first W light curing oven station 14 is approximately 40 watts/sqM of timber surface to be polished. The conveyor 2 conveys the panels through the first W light curing oven station 14, which is sized so that each panel takes approximately 12F seconds to pass through the oven station 14.

A second lacquer applicator station 15 is provided immediately downstream of the first W light curing oven station 14 so that the panel on exiting from the first W light curing oven station 14 passes immediately into the second lacquer applicator station 15. The second lacquer applicator station 15 applies a second coat of the ultra-violet curable lacquer over the first coat while the first coat is still in the relatively tacky state. The second lacquer applicator station 15 comprises a pair of elongated transversely extending lacquer roller applicators, namely, an upstream lacquer roller applicator 16 and a downstream lacquer roller applicator 17. The upstream and downstream lacquer roller applicators 16 and 17 are arranged so that the panel passes sequentially from the upstream lacquer roller applicator 16 to the downstream lacquer roller applicator 17.The upstream lacquer roller applicator 16 of the second lacquer applicator station 15 applies the ultra-violet curable lacquer to the timber surface of the panel in a quantity of approximately 10.75 gms/sqM of timber surface to be polished. The downstream lacquer roller applicator 17 applies the ultra-violet curable lacquer in a quantity of approximately 10.75 gms/sqM of timber surface to be polished, immediately on top of the lacquer applied by the upstream lacquer roller applicator 16.

Although the lacquer roller applicators of the first and second lacquer applicator stations 12 and 15 have not been described in detail, such lacquer roller applicators will be well known to those skilled in the art. Pinch rollers (not shown) co-operate with the lacquer roller applicators of the first and second lacquer applicator stations 12 and 15 for transferring the panel through the respective lacquer applicator stations 12 and 15.

A second liv light curing oven station 18 is provided in the apparatus 1 immediately downstream of the second lacquer applicator station 15 for curing the second coat of lacquer on the timber surface of the panel. The second liv light curing oven station 18 comprises a plurality of W lamps which direct W light at the second coat of lacquer to be cured. The total power output of the IN lamps in the second IN light curing oven station 18 is approximately 80 watts/sqM of timber surface to be polished. The conveyor 2 conveys the panels through the second IN light curing oven station 18 which is of length so that each panel takes approximately 22 seconds to pass through the oven station 18.Thus, the second coat of lacquer of each panel is cured at a IN light power output of approximately 80 watts/sqM of timber surface to be polished for a time period of approximately 22F seconds.

It has been found that by subjecting the panel in the second W light curing oven station 18 to IN lamps of combined power output of 80 watts/sqM of timber surface to be polished for 22F seconds is sufficient to fully cure both the first and second coats of lacquer provided the first coat as stated above is cured to a tacky state prior to the application of the second coat of lacquer.

A second sanding station 19 is provided in the apparatus 1 immediately downstream of the second W light curing oven station 18 for removing any nibs of timber extending through the lacquer on the timber surface of the panel. The second sanding station 19 is a two belt sander. One belt is arranged to sand the lacquer transversely of the grain of the timber surface, and the other belt is arranged to sand the lacquer parallel to the grain of the timber surface.

Such sanders will be well known to those skilled in the art.

While the drying tunnel, the infra-red oven and the IN light curing oven stations have not been described in detail, such tunnels, and ovens will be well known to those skilled in the art.

The conveyor 2 conveys the panels through the dust extractor station 4, the brush station 8 and the oven stations 10, 11, 14 and 18 as discussed above.

However, the conveyor 2 only conveys the panels to and from the sanding stations 3 and 19 and the applicator stations 5, 12 and 15. The sanding stations 3 and 19, and, as already briefly described, the applicator stations 5, 12 and 15 comprise their own conveying mechanism for conveying the panels through the respective stations.

The speed of the conveyor 2 and the speed of operation of the various stations is such that the time taken for a panel to pass through the apparatus 1 from the time it enters the first sanding station 3 until it exits through the second sanding station 19 is approximately 3 minutes.

In use, panels are sequentially fed into the first sanding station 3 and the panels are sequentially passed through the apparatus 1 from the first sanding station 3 through the stations of the line and exit through the second sanding station 19. The panels are conveyed through the apparatus 1 with the grain of the timber surface of the panel parallel to the direction of travel of the panel through the apparatus 1. The panel on exiting through the second station 19 is ready for assembly. After assembly a light coat of solvent pre-catalysed lacquer is applied to the timber surface of the panel by spraying.

While the apparatus 1 has been described as comprising first and second sanding stations, in certain cases, these may be omitted. However, in all cases, it will be appreciated by those skilled in the art that it is important that the timber surface of each panel should be prepared to a sufficiently smooth degree so that it is ready to receive the lacquer. It will be appreciated that where stain is not required on the panel, the stain roller applicators, the brush roller and the drying tunnel station and infra-red oven station may be omitted or by-passed.

The invention is not limited to the embodiment hereinbefore described which may be varied in construction and detail.

Claims

1. A process for polishing a timber surface of a panel with an ultra-violet curable lacquer in an inline apparatus comprising a first lacquer applicator station having one lacquer roller applicator, a first W light curing oven station, a second lacquer applicator station having an upstream lacquer roller applicator and a downstream lacquer roller applicator, and a second IN light curing oven station, the stations being sequentially arranged inline, the process comprising the step of passing the panel through the stations sequentially so that on exiting from one station, the panel substantially immediately enters the next station, and the process further comprising the steps of:: applying a first coat of the ultra-violet curable lacquer to the timber surface of the panel in the first lacquer applicator station, the first coat being applied in a quantity in the range of 9 gms/sqM to 15 gms/sqM of timber surface to be polished, curing the first coat in the first W light curing oven station to a tacky state, applying a second coat of the ultra-violet curable lacquer over the first coat in the second lacquer application station, the second coat being applied in a quantity in the range of 15 gms/sqM to 30 gms/sqM of timber surface to be polished, and subjecting the lacquer coats to IN light in the second W light curing oven station until the lacquer coats are dry.

2. A process as claimed in Claim 1 in which the power output of the IN light in the second W light curing oven station is in the range of 60 watts/sqM to 100 watts/sqM of timber surface to be polished, and the lacquer coats are subjected to the IN light in the second W light curing oven station for a time period in the range of 20 seconds to 35 seconds.

3. A process as claimed in Claim 1 or 2 in which the power output of the W light in the first W light curing oven station is in the range of 20 watts/sqM to 60 watts/sqM of timber surface to be polished, and the first coat of lacquer is subjected to the W light in the first W light curing oven station for a time period in the range of 10 seconds to 15 seconds.

4. A process as claimed in any preceding claim in which the power output of the W light in the first IN light curing oven station is in the range of 30 watts/sqM to 50 watts/sqM of timber surface to be polished.

5. A process as claimed in Claim 4 in which the power output of the IN light in the first IN light curing oven station is approximately 40 watts/sqM of timber surface to be polished.

6. A process as claimed in any preceding claim in which the power output of the W light in the second IN light curing oven station is in the range of 70 watts/sqM to 90 watts/sqM of timber surface to be polished.

7. A process as claimed in Claim 6 in which the power output of the W light in the second IN light curing oven station is approximately 80 watts/sqM.

8. A process as claimed in any preceding claim in which the first coat of lacquer is subjected to the W light in the first W light curing oven station for a time period in the range of 11 seconds to 14 seconds.

9. A process as claimed in Claim 8 in which the first coat of lacquer is subjected to the IN light in the first IN light curing oven station for a time period of approximately 12F seconds.

10. A process as claimed in any preceding claim in which the lacquer coats are subjected to the W light in the second W light curing oven station for a time period in the range of 21 seconds to 24 seconds.

11. A process as claimed in Claim 10 in which the lacquer coats are subjected to the IN light in the second W light curing oven station for a time period of approximately 22F seconds.

12. A process as claimed in any preceding claim in which the first coat of lacquer is applied in a quantity in the range of 10 gms/sqM to 12 gms/sqM of timber surface to be polished.

13. A process as claimed in Claim 12 in which the first coat of lacquer is applied in a quantity of 11F gms/sqM approximately of timber surface to be polished.

14. A process as claimed in any preceding claim in which the second coat of lacquer is applied in a quantity in the range of 20 gms/sqM to 23 gms/sqM of timber surface to be polished.

15. A process as claimed in Claim 14 in which the second coat of lacquer is applied in a quantity of 22F gms/sqM approximately of timber surface to be polished.

16. A process as claimed in any preceding claim in which the upstream roller in the second lacquer applicator station applies the lacquer in a quantity in the range of 9 gms/sqM to 12 gms/sqM of timber surface to be polished.

17. A process as claimed in Claim 16 in which the upstream roller in the second lacquer applicator station applies the lacquer in a quantity of 10.75 gms/sqM approximately of timber surface to be polished.

18. A process as claimed in any preceding claim in which the downstream roller in the second lacquer applicator station applies the lacquer in a quantity in the range of 9 gms/sqM to 12 gms/sqM of timber surface to be polished.

19. A process as claimed in Claim 18 in which the downstream roller in the second lacquer applicator station applies the lacquer in a quantity of 10.75 gms/sqM approximately of timber surface to be polished.

20. A process as claimed in any preceding claim in which the timber surface is stained prior to the application of the first coat of lacquer, a stain being applied to the timber surface by a stain applicator station upstream of the first lacquer applicator station.

21. A process as claimed in Claim 20 in which the stain applicator station comprises an upstream stain roller applicator and a downstream stain roller applicator arranged sequentially upstream of the first lacquer applicator station.

22. A process as claimed in Claim 20 or 21 in which the stain is a water based stain.

23. A process as claimed in any of Claims 20 to 22 in which the panel is passed through a drying tunnel arranged inline between the stain applicator station and the first lacquer applicator station.

24. A process as claimed in Claim 23 in which the stain is dried in the drying oven at a temperature in the range of 450C to 500C for a time period in the range of 25 seconds to 35 seconds.

25. A process as claimed in Claim 23 or 24 in which the timber surface is brushed with a roller brush arranged inline between the downstream stain roller applicator and the drying oven.

26. A process as claimed in any of Claims 20 to 25 in which the timber surface is sanded to a relatively smooth finish prior to the application of the first coat of lacquer.

27. A process as claimed in Claim 26 in which the surface is sanded prior to the application of the stain.

28. A process as claimed in Claim 26 or 27 in which the sanding of the timber surface is carried out in a first sanding station provided upstream of the stain applicator station.

29. A process as claimed in any preceding claim in which the cured lacquer coat on the panel is sanded to remove nibs of timber extending through the lacquer coat after passing through the second IN light curing oven station.

30. A process as claimed in Claim 29 in which a second sanding station is provided downstream of the second IN light curing oven station for sanding the lacquer coat.

31. A process for polishing a timber surface of a panel with an ultra-violet curable lacquer in an inline apparatus, the process being substantially as described herein with reference to and as illustrated in the accompanying drawing.

32. A panel having a polished timber surface, the timber surface having being polished with an ultraviolet curable lacquer by a process for polishing as claimed in any preceding claim.