GB1574181A

GB1574181A - Highspeed rotary branding process having increased die life and product produced therefrom

Info

Publication number: GB1574181A
Application number: GB559377A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-02-10
Filing date: 1977-02-10
Publication date: 1980-09-03

Description

(54) HIGHSPEED ROTARY BRANDING PROCESS HAVING INCREASED DIE LIFE AND PRODUCT PRODUCED THEREFROM (71) I, GARY CLIFFORD COLLEDGEJ a citizen of the United States of America, of 1810 South Santa Fe Avenue, Compton, State of California, United States of America, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: Highspeed embossing apparatus are known which are particularly well suited for use in the embossing of relatively deep decorative patterns in molding for furniture, picture frames and the like.Such apparatus employ a very hot die (1,000 to 1,2000F. or more) under a substantial pressure to emboss patterns which may have a depth of i inch or greater into lumber that is usually relatively soft at high speeds (for example, 200 feet per minute). Most prior art devices, however, typically ran at a temperature of about 500"F. and a speed of about 40 feet per minute.

In addition to embossing molding, it has long been desirable to be able to emboss a wood grain pattern on articles and particularly sheets or panels. The desirability of embossing such a pattern has increased in recent years since the supply of woods having desirable grain properties has dwindled substantially. The supply of many types of wood which have little or no grain pattern is relatively plentiful, but the use of such wood in furniture, decorative panels, cabinetry, etc., has been limited to situations in which the article would be finished by painting, a plastic laminate, etc.

In order to attempt to utilize woods having poor grain quality, a number of different approaches have been employed.

The most widespread process Ipresently in use is a printing process in which ink is imprinted onto the article in a wood grain pattern. In this process, the finish of the panel is controlled by the grain printer, and the manufacturer of the article must attempt to match other wood to the finish of the printed wood.

United States Patent No. 3,294,014 dis doses a process in which a die having a pattern of protrusions of substantial height simulating wormhoies is heated to a high temperature and urged against the wood product at a very high pressure. A similar process is shown in United States Patent No. 3,393,294 in which wormholes are formed by contacting the wood over a substantial period of time by using an endlesstract mounting of the heated protruding elements.

In addition, cold dies have been employed with very substantial pressures to attempt to crush or impress a wood grain pattern into a wooden article. This approach results in chipping and fracturing of the wood fiber, poor grain definition, slow speed and an inability of the impressed grain to visually stand out from the remainder of the wood with a corresponding need to use inks or color fillers to bring out the grain.

United States Patent Nos. 2,703,463 and 2,695,857 disclose low temperature, low speed processes which depend upon high pressure and even support of the panels to effect embossing. A high temperature, highspeed embossing apparatus and method similar to that disclosed in my United States Patent No. 3,730,081 is shown in United States Patent No 3,764,767. In this apparatus and method very high die temperatures on the order of about 1,000 F. are achieved by induction heating and enable embossing of molding at a rate of 200 feet per minute.

As was the case with my embossing aploara- tus, the device of U.S. Patent No. 3,764,767 is entirely adequate for embossing relatively soft lumbers with a pattern that is relatively gross or course in nature.

While attempts have been made to brand or emboss panels with fine or intricate wood grain patterns, two serious limitations have been encountered. First, branding an intricate pattern into an extremely hard material is very difficult It was found that not only is it desirable to be able to brand lumber having poor grain dharacteristics, but it is also highly desirable to be able to brand particle board and hard board, both of which have no grain characteristics and exhibit extreme surface hardness as compared to most commonly available lumbers.

Secondly, it was found that when an intricate and delicate die pattern was employed and heated to extremely high temperatures (1,000 to 1,2O()fl), oxidation and wear on the pattern caused rapid degradation of the same with attendant loss of definition in the pattern branded into the lumber. Thus, the operation of dies having delicate patterns at extremely high temperatures was found to cause the die patterns to have an unacceptably short life. This problem was increased when attempting to brand particle board or hard board, which presents an extremely hard surface. Oxidation and wear on the dies under the extremely high temperatures soon caused a degradation of the delicate patterns to a level prohibiting their further use.The cost of etching a steel die 18 inches in diameter and 4 feet in length with an intricate wood grain pattern is substantial ($400WS5000) and requires that the die be able to be used to brand a very substantial number of panels before it must be replaced.

It is believed that the oxidation and wear phenomena on the prior art dies at extremely high temperatures was not observed before because the patterns employed for embossing molding are inherently rather coarse or gross in nature. Accordingly, there normally are not thin crosssection die protrusions, and oxidation of several thousandths of an inch does not have any appreciable effect on the coarse pattern which is normally used to emboss moldings. Since most moldings are made with soft lumbers, the wear factor was also less than when attempting to brand particle board or hard board. When a die is formed with an intricate wood grain pattern, however, oxidation or wear of a few thousandths of an inch will completely eliminate many of the pattern protrusions creating discontinuities or bald spots in the pattern which are unacceptable.Additionally, carbon build-up ca the dies can fill the interstices between protrusions and similarly degrade the die pa(tern.

According to the invention we provide an improvnent in a process for rotary branding of a pattern into a material for example hardboard, particle board, plasterboard or lumber including the step of branding said material by passing the same under a heated rotary die at a speed effecting discoloration of the material in recessed areas impressed with said die but not intermediate said recesses, the improvement comprising the steps of:- selecting a rotary die having a pattern thereon comprising a plurality of protrusions formed and dimensioned to brand a wood grain Ipattern into said material; and maintaining the temperature of said die in the range of 8000F to 900"F during said branding step.

The temperature of said pattern on said die may be maintained in the range of 8250F to 8750F.

The invention also includes an article having an embossed charred wood grain pattern and other features as hereinafter claimed.

Figure 1 is a front elevational view, partially broken away, of a rotary branding machine suitable for use in practicing the process of the present invention.

Figure 2 is a side elevational view of the machine in Figure 1.

Figure 3 is a greatly enlarged, fragmentary view, in cross-section of the branding die and a sheet of material being branded.

Figure 4 is a greafly enlarged, fragmentary, cross-sectional view of a piece of plasterboard branded in accordance with the present process.

Apparatus suitable for practicing the method of the present invention may be seen in Figures 1 and 2. An embossing or branding machine, generally designated 21, having a rotary drum-like element 22 on which a branding or embossing die 23 is removably mounted. Mounted to base 24 is a drum support assembly, generally designated 26, to which drum shaft 27 is rotatably mounted, In order to accommodate the branding or embossing of materials of various thicknesses and in order to enable an adjustment of the branding pressure, support assembly 26 is preferably formed for selective vertical adjustment of the height of die 23 above work supporting table 28 and work engaging and advancing drum 29. Drum 29 can be used to advance the article or work piece 31 under die 23 and is operatively connected to a motor (not shown) which is usually mounted in base 24. The work advancing drum may be the sole source of power for advancement of member 31 beneath the die, or shaft 27 can be driven, either instead of drum 29, or in synchronism with drum 29.

Die 23 is formed with a grain defining pattern 32, and a plurality of resistance heating elements 33 are preferably carried by drum 22 in thermal and electrically insulated cavities in the drum immediately subjacent to die 23. Resistance heating elements 33 are electrically connected by conductors 34 to brush assembly 36, which is in turn connected to conductor 37 to control panel 38.

The positioning of resistance heating elements 33 subjacent to die 23 enables the die to be maintained at a uniform and relatively high temperature.

In order to prevent the transfer of heat along the shaft 27 to bearings 41 and 42, the bearings are formed for flow of coolant fluid therethrough and connected by means of fluid conduits 42 to fluid pumping means and a fluid reservoir (not shown). Rheostat 44 on the control panel is used to control the temperature of die 23 while knob 46 controls the coolant flow through bearings 41 and 42.

The contact pressure between the rolling of rotary die 23 and article 31 being branded is varied by means of drum supporting means 26. This can advantageously be accomplished by mounting hydraulic cylinders 51 to support arms 52 secured to base 24 of the embossing machine. Extending upwardly from cylinders 51 and reciprocally mounted therein are a pair of pistons 53, which are secured by their upper ends, by welding or the like, to water cooled bearings 41 and 42. Hydraulic conduits 54 are connected to cylinders 51 and control panel 38 for control of the shaft height above table 28 and the contact pressure between the die and the article being branded. Adjustment of the same is effected by hydraulic controls 58.

Finally, the rate of advancement of the material beneath the rotary die is controlled by knob 59, which controls the driving drum 29 and/or embossing drum 22.

Having described rotary branding appara tus suitable for use in the process of the present invention, the improved process of the invention which enables a substantial increase in the life of the branding die without losing the advantages of high speed production may be set forth in detail. Contrary to my initial efforts which indicated that higher temperatures enabled higher speeds and higher production, I have discovered that for rotary branding of patterns having intricate or delicate designs thereon, there is an optimum temperature range in which high production can be maintained without accelerated deterioration of the branding die.

Initially, it should be noted that the preferred manner of forming a branding or embossing die is to acid etch a low carbon steel plate or cylinder. The die material is preferably formed from 4135 Modified or 4140 Carbon Steel. These carbon steel alloys contain chromium and nickel, which it is believed enhance high temperature performance by slowing oxidation. First, the die material has an acid resist material deposited thereon, such as Kodak photoresist, and the acid resist material is then removed in all areas except the areas in which die pro trusions are to occur. The die blank is-then placed in an acid bath to form the die pattern. Many of the resulting grain defining protrusions in a wood grain pattern have a cross-sectional thickness in the range of 0.005 to 0.010 inches.

With a die formed as above described, it has been discovered that the life of the die can be greatly extended by operating the branding process at a die temperature in the range of 800 oF. to 9000F. Operating such a die at a temperature of 1 1000F., for example, allows branding of various types of plywood to proceed at a very high pro due tion rate. For 4-foot by 8-foot plywood panels of poor grain Luan mahogany, a production rate of 900 panels per hour can be achieved at die temperatures of 11000F.

The pattern definition branded into the panels, however, reaches unacceptable levels after a total of only 50,000 panels (7 shifts of 8 hours duration).

The same panels when branded at .8500F.

can be branded at a rate of 600 panels per hour, but the dies will produce high pattern definition in the branded product for more than 300,000 panels with no visible wear.

Below 8000 F. the production rate drops to 300 panels per hour. Additionally, below 8000F. more pressure is required which is particularly undesirable when branding hard board or particle board, which require more pressure than lumber as a result of their high surface hardness. As the temperature drops 800 F., there is also some tendency to fracture fibers (particularly when the branding speed exceeds 30 feet per minute) rather than heat shrink and burn away fibers in a branding process.

Since increased pressure can also accelerate die wear, a drop of in the life of the die is also observed when hard surfaced materials such as particle board are embossed at temperatures below 8000F. Thus, 4' x 8' particle board panels embossed with a die at 7000F. must be run at about a speed of 200 to 250 panels per hour, and the died is not hot enough to char the impressions left in the panel. By contrast, when operated at 8500F. to 875 F. panels of particle board can be branded at a rate of 450 panels per hour with the pattern impressions being charred or discolored. So significant die oxidation or wear occurs under these conditions.

When hard board panels are run at 1 1000F., a production rate of 360 panels per hour can be achieved, but the die has a life of only 20,000 panels. By contrast, at 9000F.

hard board panels can be branded at 200 per hour with no significant wear.

It should be noted that lowering the temperature and branding of hard surface materials does require substantially higher die contact pressures than when 1100 to 1200"F is employed. The possibility of attempting to use dies formed from less corrosive or higher strength materials has been considered. Stainless steel dies might be operable at higher temperatures without excessive oxidation or wear. Stainless steel, however, is extremely difficult to etch with a fine or intricate pattern. The cost of the etching process for an 18 inch diameter drum 4 feet in length using currently known technology increases from $4000 to $5000 for 4135 modified carbon steel to $25,000 for stainless steel. Whether such a stainless steel die would be satisfactory for high production runs is only speculative, and the cost is, in any event, prohibitive.

Typically, wood panels which are to be branded with a grain pattern are manufactured to a thickness tolerance of about 0.010 inches. Thus, over the width or length of the board a variation in thickness of 10 mils (0.010 inches) may be experienced. In order to insure branding of the complete grain pattern and further to reduce the incidence of charring intermediate of the pattern defining protrusions, it has been found preferable to form the die with a pattern depth of at least about 0.040 inches.

As may be seen in Figure 3, the nominal outside diameter 71 of the die protrusions 73 is etched to a depth d of at least 0.040 inches from the nominal inside diameter 75 of the die. It is further preferable that the depth d be about 0.060 inches. During the branding step, die 23 is urged to a depth less than the full depth of the die and preferably to about one-half of the depth of the pattern defining protrusions in the die.

For a die having a depth d of about 0.060 inches, the die will be set to have an interference or depth of penetration of about 0.025 inches. Since the panel may vary plus or minus 5 mils, the depth of penetration may range between about 0.020 and about 0.030 inches. This depth of penetration insures branding of the protrusion pattern into the panel without charring the wood intermediate the pattern. In other embossing processes the dies are urged to their full depth into the product being embossed.

The process of the present invention provides not only a grain pattern impression in the material, but also simultaneously brands, discolors or chars the pattern in a manner closely simulating the color of wood grain. This coloring is effected without the use of inks or flooding of cold impressions with paint and reversing the excess paint off the areas intermediate the grain pattern.

Thus, high speed grain pattern branding of panels can be accomplished in a single process without undue die wear and without special support for the panels.

In addition to branding lumber and composite wood based panels such as particle board and hard board, the process of the present invention can be used to Iproduce another new material, namely, branded plasterboard. Plasterboard (also known as dry wall and sheet rock) is formed with at least one paper layer and preferably as a sandwich (shown in Figure 4) of two paper or felt layers 81 and 83 which are bonded to a central hardened gypsum plaster core 85. As used herein, the expression "paper" shall include felt which is usually formed as a heavy paper made of organic or may include asbestos fibers. Plasterboard or sheet rock generally comes in large sheets, for example, 4' x 8', and is used as a backing or a substitute for plaster in the construction of residences, offices and other buildings.While plasterboard does afford many advantages in building construction, one of the disadvantages is that the plasterboard is almost always covered with another material such as paneling, paint, plaster, etc. The outside paper surfaces 81 and 83 of the plasterboard are usually unacceptable as a final structure surface.

The process of the present invention is comprised of rotary branding the outside paper layer on the blasterboard using the above described apparatus. The branding process is run at a die temperature preferably between 8500 and 9000 F. with a lineal speed of 50 feet per minute. Notwithstanding the fact that the plasterboard has a paper outer layer, the speed of embossing is slower than would be employed to brand ordinary lumber or hardboard or particle board. The slower speed enables a branding or discoloration of the paper by charring as well as a permanent deformation, all without charring the paper intermediate the line grain pattern.

Paper 83 is shown as being actually compressed into the plaster core and permanently deformed by embossed recesses 87 which have a depth which can be greater than the thickness of paper 83. Such branding and deformation can be accomplished without breaking through or piercing paper layer 83, and thus, the plasterboard does not crumble or sift out through the branded paper.

Once the outside layer 83 for the plasterboard is branded with a wood grain pattern, the paper layer 83 can be stained with a wood stain with the result that through this relatively inexpensive surface treatment, plasterboard can be used as a final or finished surface. If desired, the plasterboard can be nailed or otherwise secured in place and stained over the fastening nails or screws.

In order to further facilitate use of the plasterboard as a final finished surface, a side marginal groove may be formed simultaneously with the branding process at the other edge of the plasterboard panel. Thus, while the wood grain pattern is being branded in the panel, a portion of a Vshaped groove can be formed in the outer edge of the panel which will be constructed to mate with a complementary-shaped groove formed in the edge of another panel.

It is hypothesized that the slower operating speeds required for branding plaster board may in part be due to the inherent qualities of the plasterboard paper or possibly in part due to the plaster core 85 acting as a heat sink. The slower branding speed may also have a beneficial effect of reducing the likelihood of piercing the paper layer during branding. In any event, the portions of the pattern which are branded or embossed are permanently discolored, and the stain is employed merely to impart the desired wood color to the remainder of the surface.

WHAT I CLAIM IS: 1. In a process for rotary branding of a pattern into a material for example hardboard, particle board, plasterboard, lumber including the step of branding said material by passing the same under a heated rotary die at a speed effecting discoloration of the material in recessed areas impressed with said die but not intermediate said recesses, the improvement comprising the steps of: selecting a rotary die having a pattern thereon comprising a plurality of protrusions formed and dimensioned to brand a wood grain pattern into said material; and maintaining the temperature of said die in the range of 800"F to 9000F during said branding step.

2. A process for branding a pattern as defined in claim 1 wherein the temperature of said pattern on said die is maintained in the range of 8250F to 8750F.

3. A process for branding a pattern as defined in claims 1 or 2, wherein said rotary die is formed of low carbon steel, and said die is maintained at a temperature of 8500F to 8750F.

4. A process for branding a pattern as defined in claims 1, 2 or 3 wherein said rotary die is formed of 4135 modified carbon steel (AS.T.M.).

5. A process for branding a pattern as defined in claims 1, 2 or 3 wherein said rotary die is formed of 4.140 carbon steel (A.S.T.M.).

6. A process for branding a pattern as defined in claim 1 comprising the steps of: selecting a rotary die having a wood grain pattern formed thereon, said pattern being formed with pattern defining protrusions having a depth of at least 0.040 inches, and passing said material under said die during said branding at a speed producing discoloration of areas impressed by said protrusions but not discoloration of areas intermediate thereto and said die being urged into said material to a depth of one-half of the depth of said pattern defining protrusions.

7. A process for branding a pattern as defined in claim 6 wherein, said rotary die is selected to have pattern defining protrusions formed thereon having a depth of about 0.060 inches, and during said passing step said die is urged into said material to a depth of about 0.025 inches.

8. A decoratively branded wood based article for use in the fabrIcation of other products comprising: a solid composite material formed of bonded together wood based components and having an outer surface said outer surface being formed with a wood grain pattern comprising a plurality of fine recesses there in, and said recesses each being discolored by dharring of said wood based components.

The branded article as defined in claim 8 wherein, said composite material is formed as a sheet of particle board.

10. The branded article as defined in claim 8 wherein, said composite material is formed as a sheet of hardboard.

11. A decoratively branded article com prising: a sheet of plasterboard having at least one outwardly facing paper layer or felt bonded to a plaster based layer, and a plurality of recesses formed in said paper layer to produce a wood grain pattern, said recesses each being discolored by charring of said paper layer, and said paper layer being a normal color intermediate said recesses and being unbroken at said recesses.

12. An article as claimed in claim 9 or 12, substantially as hereinbefore described.

13. A process as claimed in claim 1, substantially as hereinbefore described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. side marginal groove may be formed simultaneously with the branding process at the other edge of the plasterboard panel. Thus, while the wood grain pattern is being branded in the panel, a portion of a Vshaped groove can be formed in the outer edge of the panel which will be constructed to mate with a complementary-shaped groove formed in the edge of another panel. It is hypothesized that the slower operating speeds required for branding plaster board may in part be due to the inherent qualities of the plasterboard paper or possibly in part due to the plaster core 85 acting as a heat sink. The slower branding speed may also have a beneficial effect of reducing the likelihood of piercing the paper layer during branding. In any event, the portions of the pattern which are branded or embossed are permanently discolored, and the stain is employed merely to impart the desired wood color to the remainder of the surface. WHAT I CLAIM IS:

1. In a process for rotary branding of a pattern into a material for example hardboard, particle board, plasterboard, lumber including the step of branding said material by passing the same under a heated rotary die at a speed effecting discoloration of the material in recessed areas impressed with said die but not intermediate said recesses, the improvement comprising the steps of: selecting a rotary die having a pattern thereon comprising a plurality of protrusions formed and dimensioned to brand a wood grain pattern into said material; and maintaining the temperature of said die in the range of 800"F to 9000F during said branding step.

13. A process as claimed in claim 1, substantially as hereinbefore described.