EP0927080A1

EP0927080A1 - Method and apparatus for laying a granular pattern

Info

Publication number: EP0927080A1
Application number: EP97942529A
Authority: EP
Inventors: Kenneth Bibby
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-09-18
Filing date: 1997-09-16
Publication date: 1999-07-07
Also published as: WO1998011996A1

Abstract

A method for laying down a continuous, predetermined pattern of granular material upon a substrate (12) includes providing at least one station (S1) including a rotating drum (18) with a drum wall (20) defining a limited retention region (34) under vacuum, and a plurality of through-apertures (36) arranged in an element of the desired pattern. Granular material (G) applied to the surface (22) of the drum is held by vacuum in the desired pattern. After removal of excess granular material, the vacuum is discontinued causing the granular material to disengage from the drum surface and pass, by force of gravity, onto the surface of the substrate moving relative to the station in the form of the predetermined element of the desired predetermined pattern. An apparatus (10) for laying down a continuous, predetermined pattern of granular material upon a substrate is also described.

Description

METHOD AND APPARATUS FOR LAYING A GRANULAR PATTERN Background of the Invention The invention relates to forming a predetermined pattern of granules on a substrate.

It has been known to place granules of different colors upon a substrate, e.g. where the granules are particles of colored polyvinyl chloride (PVC) plastic and the substrate is a base for flooring tile or sheet, where the substrate is advanced step-wise through a series of stations where granules are placed onto the base through a set of flat stencils. The base is stopped at each station while the colored granules are placed, which restricts the process to use with patterns having straight "grout" lines placed perpendicular to the direction of movement to conceal stop marks formed by the step-wise advance.

Summary of the Invention According to one aspect of the invention, an apparatus for laying down a continuous, predetermined pattern of granular material upon a substrate comprises at least a first station comprising: a drum having a generally cylindrical drum wall mounted for rotation above the substrate, the drum wall defining a drum outer surface and a drum inner surface; a motor for rotating the drum outer surface through a sequence of positions comprising: a granular-material-receiving position, an excess granular-material-separation position, an granular-material -pattern-laydown position, and a cleaning position; a volume defined by the drum wall and a baffle contained therewithin with free ends disposed in sliding engagement with the drum inner surface in a manner to define a retention region of the volume corresponding generally to a segment of the drum outer surface between the granular-material -receiving position and the granular-material -pattern-laydown position, the retention region disposed in communication with a source of vacuum; a plurality of apertures defined by the drum wall and in communication between the drum inner surface and the drum outer surface, the plurality of apertures arranged in an element of the predetermined pattern to be formed upon the substrate; a hopper positioned to receive a supply of granular material and to deliver the granular material onto the drum outer surface at the granular- material-receiving position; pre-laydown retriever means, disposed generally between the excess-granular-material - separation position of the drum outer surface and the substrate, for receiving excess granular material from the drum outer surface; a cleaning member disposed at the cleaning position for removing granular material from the drum surface; post-laydown retriever means, disposed generally between the substrate and the cleaning position of the drum outer surface, for receiving granular material from the drum outer surface; and conveying means for continuous relative "movement between the station and the substrate.

Preferred embodiments of the invention may include one or more of the following additional features. The apparatus further comprises at least a second station spaced from the first station. The apparatus further comprises a main conveyor mounted for continuous movement of the substrate therealong, relative to the first station. The hopper comprises a granular material metering dam disposed in adjustable, spaced relationship to the drum outer surface. The pre-laydown retriever means is disposed generally below the excess granular- material-separation position of the drum outer surface and above the substrate in a position for intercepting excess granular material released from the drum outer surface before the excess granular material contaminates the substrate. The pre-laydown retriever means comprises a conveyor disposed to move generally transversely to the direction of the main conveyor, for retrieving excess granular material from the drum outer surface. The post- laydown retriever means disposed generally below the cleaning position of the drum outer surface and above the substrate for receiving granular material dislodged from the drum outer surface in a position for intercepting excess granular material dislodged from the drum outer surface before the excess granular material contaminates the substrate. The post-laydown retriever means comprises a conveyor disposed to move generally transversely to the direction of the main conveyor, for retrieving granular material remaining upon the first drum surface after laydown. The cleaning element comprises a brush mounted for engagement with the drum outer surface . The brush is mounted for reverse rotation on engagement with the drum outer surface.

According to another aspect of the invention, a method for laying down a continuous, predetermined pattern of granular material upon a substrate comprises the steps of: providing at least one station comprising a drum having a generally cylindrical drum wall defining a drum outer surface and a drum inner surface, a volume defined by the drum wall, a plurality of apertures defined by the drum wall and in communication between the drum inner surface and the drum outer surface, the plurality of apertures arranged in an element of the predetermined pattern to be formed upon the substrate, and a hopper for receiving a supply of granular material; providing conveying means for relative movement between the substrate and the at least one station; rotating the drum wall above the substrate through a sequence of positions comprising: a granular-material -receiving position, an excess granular-material-separation position, an granular-material-pattern-laydown position, and a cleaning position; positioning the free ends of a set of baffles disposed within the volume defined by the drum wall in sliding engagement with the drum inner surface to define a retention region of the volume corresponding generally to a segment of the drum outer surface between the granular-material-receiving position and the granular-material- pattern-laydown position; connecting the retention region to a source of vacuum; delivering granular material supplied to the hopper onto the drum outer surface at the granular-material-receiving position; allowing vacuum from the retention region within the volume of the drum to act , through the plurality of apertures arranged in an element of the predetermined pattern to be formed upon the substrate, on granular material upon the drum outer surface in the vicinity of the plurality of apertures, thereby to retain granular material upon the drum outer surface; rotating the drum outer surface to the granular-material- separation position and allowing excess granular material, not subject to action by the vacuum from within the retention region, to separate from the drum outer surface; retrieving separated granular material on pre- laydown retriever means disposed generally between the excess granular-material-separation position of the drum outer surface and the substrate, thereby to intercept separated granular material before it contaminates the substrate; rotating the drum outer surface to the granular-material-pattern-laydown position at the termination of the retention region under vacuum, and positioning the granular material upon the substrate in the element of the desired predetermined pattern by allowing the granular material to disengage from the drum outer surface by removal of the vacuum; continuing rotation of the drum outer surface to a cleaning station and engaging the drum outer surface with a cleaning member to dislodge remaining granular material from the drum outer surface; retrieving granular material separated by cleaning on pos -laydown retriever means disposed generally between the substrate and the cleaning position of the drum outer surface, thereby to intercept dislodged granular material before it contaminates the substrate; and continuing rotation of the drum outer surface through a series of cycles to laydown a continuous pattern of granular material upon the substrate.

Preferred embodiments of this aspect of the invention may include one or more of the following additional features. The method of comprises the further step of mounting the substrate on a main conveyor and moving the conveyor with the substrate thereupon past at least one station. The method comprises the further step of providing a series of spaced apart stations to lay additional elements of the predetermined pattern of granular material upon the substrate. The method comprises the further step of treating the substrate to secure the position of the granular material laid upon the substrate. For forming floor covering, the method of comprises the further steps of disposing a pattern of granular material of suitable plastic upon the substrate and securing the granular material by curing.

Preferably, the method comprises the further step of disposing a pattern of contrasting granular material, e.g. metallic flake, upon the substrate. For forming wall covering, the method comprises the further steps of disposing a pattern of granular material of suitable plastic upon the substrate and securing the granular material by curing. For forming food products, the method comprises the further steps of disposing a pattern of granular decorative material of suitable edible material upon a food substrate. The method comprises the further step of severing the substrate into a plurality of discrete elements.

Objectives of the invention include to provide a method and apparatus for laying down sequentially a series of pattern elements of granular material upon a substrate to form a predetermined pattern. Products suitable for this process include floor and wall coverings, decorated food products, roof tiles and rolls, and concrete pavers and blocks . Other features and advantages of the invention will be seen from the following description of a presently preferred embodiment, and from the claims. Brief Description of the Drawing Fig. 1 is a perspective view of an apparatus of the invention;

Fig. 2 is a side sectional view of the apparatus of Fig. 1;

Fig. 3 is a top plan view of the apparatus of Fig.

1; Figs. 4 and 5 are front plan and side section views respectively of a segment of the drum wall in the region between positions B and C;

Fig. 6 is a side section view of the segment of the drum wall at the lay-down position C of a first station, and Fig. 7 is a similar view of the drum wall at the lay-down position C of a subsequent station; and

Figs. 8 and 9 are top plan and side section views, respectively, of a floor covering formed according to the method of the invention. Fig. 10 is a perspective view of an apparatus of the invention with food product formed according to another aspect of the invention;

Fig. 11 is a similar view of an apparatus of the invention with roofing shingles formed according to yet another aspect of the invention; and Fig. 12 is a similar view of an apparatus of the invention with paving blocks formed according to the invention; and

Fig. 13 is a similar view of an apparatus of the invention with a wall covering fabric formed according to another aspect of the invention, while Fig. 14 is a plan view of the wall covering fabric of Fig. 13.

Fig. 15 is a somewhat diagrammatic view of single screen station of the invention.

Fig. 16 is a similar view of a station with silk screen attached to a perforated screen.

Fig. 17 is a similar view of a station with a cutout pattern attached to a perforated screen.

Fig. 18 is a similar view of a station mounted to be advanced along a stationary substrate. Fig. 19 is a similar view of a station with a tamping bar.

Fig. 20 is a similar view of a station with a feeder in the hopper.

Figs. 21, 22 and ^"23 are a similar views of stations with static controlled by di-ionized air, tinsel and a radioactive rod, respectively.

Fig. 24 is a similar view of a mold with a printed release sheet.

Fig. 25 is a similar view of a cut-out patterned screen with an overall screen inside.

Fig. 26 is a similar view of a station used for dispensing formula.

Fig. 27 is a similar view of a station for applying granules to a wet or dry surface. Fig. 28 is a similar view of a station for applying frit to ceramic tiles before firing.

Fig. 29 is a similar view of a station for applying granules to melamine-type sheets.

Fig. 30 is a similar view of a station for applying rubber crumbs before vulcanizing. Fig. 31 is a similar view of a station for applying hard (non-die cuttable) granules to resilient floor tiles.

Fig. 32 is a similar view of a station for applying clear coat granules to printed sheet .

Fig. 33 is a similar view of a station for applying non-slip granules.

Fig. 34 is a similar view of a station with an air knife applied after laydown. Figs. 35-38 are similar views showing, in sequence, a station applying granules to the surface of adhesive-coated base sheet; a roll of adhesive-and- granule coated base sheet; a mold or form lined with the adhesive-and-granule coated base sheet stock; and a molded, granule-coated product after removal of the base shee .

Figs. 39A and 39B are end and side views, respectively, each partially in section, of a lighter weight internal center pipe of the invention; and Figs. 40A and 40B are end and side views, respectively of an end suspension assembly for the internal center pipe of the invention, as shown in Figs. 39A and 39B.

Fig. 41 is a side section view of a rotary patterned screen with a removable end ring of the invention;

Fig. 42 is a side section view of a rotary patterned screen with an alternative embodiment of a removable end ring of the invention; and Fig. 43 is side section view of an assembly stand for mounting a rotary patterned screen having a removable end ring of the invention upon an internal center pipe, also of the invention.

Description of the Preferred Embodiments Referring to Figs. 1-3, an apparatus 10 of the invention for laying down a continuous, predetermined pattern of granular material upon a moving substrate 12 includes a main conveyor 14 mounted for continuous movement of the substrate therealong and at least two stations, S^ S₂, disposed at spaced position along the conveyor .

Each station, S, includes a drum 18 having a generally cylindrical drum wall 20 defining a drum outer surface 22 and a drum inner surface 24. The drum wall 20 is mounted for rotation above the substrate 12 by motor 26, through a sequence of positions, including: granular- material -receiving position (A) , excess granular- material -separation position (B) , granular-material - pattern-laydown position (C) , and a cleaning position

(D) . In the embodiment shown, the drum outer surface 22 and the surface of the substrate 12 move in the same direction at the granular-material-pattern-laydown position (C) ; however, the opposed surface may also move in opposite directions.

The drum wall 20 defines a volume 21 with a baffle 28 contained therewithin and having free ends 30, 32 disposed in sliding engagement with the drum inner surface 24, thereby to define a retention region 34 of the volume 21. The retention region 34 is disposed in communication with an external source of vacuum (V) and corresponds generally to a segment (E) of the drum outer surface 22 between the granular-material-receiving position (A) and the granular-material -pattern-laydown position (C) .

The drum wall 20 defines a plurality of apertures 36 disposed in communication between the drum inner surface 24 and the drum outer surface 22, the plurality of apertures being arranged in an element of the predetermined pattern to be formed upon the substrate (Figs. 4 and 5) . The size and density of the apertures are determined by the size and nature of the granular material. In preferred embodiments, the drum wall has the form of a screen defining densely packed, small diameter holes .

A hopper 38, e.g. a dam 39, mounted at the granular-material-receiving position (A) in resilient engagement with the drum outer surface 22, holds a supply of granular material (G) for delivery onto the substrate, as described below.

A first cross-conveyor 40 is located generally below the excess granular-material -separation position (B) , beneath the downward-moving surface of the drum 18, at a position to retrieve excess granular material separated from the drum outer surface 22 before it reaches the surface of the substrate. A similar second cross-conveyor 42 is located generally below the cleaning position (D) , beneath the upward-moving surface of the drum 18, at a position to retrieve granular material dislodged from the drum outer surface 22 by a rotating cleaning brush 44.

The method of the invention for laying down a continuous, predetermined pattern of granular material upon a substrate includes disposing a substrate 12 upon a main conveyor 14 and moving the conveyor with the substrate thereupon past a series of at least two stations 16 as described above.

According to the method, granular material (G) supplied to a hopper 38 is delivered onto the drum outer surface 22 at the granular-material-receiving position

(A) by allowing a predetermined thickness of the granular material from the hopper to pass beneath the granular material metering dam 39 mounted in adjustable, spaced relationship to the drum outer surface 22. Vacuum from the retention region 34 within the volume 21 of the drum 20 acts, through the plurality of apertures 36, on granular material (G) upon the drum outer surface 22. The action of the vacuum is localized to the vicinity of the apertures, thereby to retain granular material upon the drum outer surface arranged in an element of the predetermined pattern to be formed upon the substrate.

Rotation of the drum outer surface 22 to the granular-material-separation position (B) allows excess granular material (H) , i.e. the granular material not subject to action by the vacuum from within the retention region 34, to separate from the drum outer surface. The excess granular material (H) falls upon the cross- conveyor 40 (before it can reach the surface of the substrate) and is retrieved, e.g. for recycling.

Referring to Figs. 4 and 5, a segment of the drum wall 20 in the region between positions B and C, i.e., after excess granular material has been removed, leaving only granular material, G, retained on the drum outer surface 22 by the vacuum of the retention region 34 acting through the apertures 36 in the predetermined pattern, e.g. a square is shown by way of example only, as the choice of patterns is essentially unlimited. Referring now to Figs. 6 and 7, further rotation of the drum moves the outer surface 22 to the granular- material-pattern-laydown position (C) , where the retention region 34 under vacuum terminates in the area of engagement of the baffle free end 32 with the drum inner surface 24. Loss of vacuum as the drum outer surface passes the baffle free end causes the granular material to disengage from the drum outer surface and pass, by force of gravity, onto the surface of the substrate in the form of the predetermined element of the desired predetermined pattern. In Fig. 6, the drum wall 20 delivers the granular material in a first element of the predetermined pattern, and in Fig. 7, the drum wall 20' delivers granular material in a second, different, i.e. intervening, element of the predetermined pattern. Sequential development of the final pattern is shown also in Figs. 8 and 9, where, in the side view, it is seen that the granular material of the second element complements the angle of repose of the granular material of the first element to define an sharp line of demarcation in the finished pattern. It will be recognized that it is important that precise registration is maintained between separate elements of the predetermined pattern, which typically requires use of a line shaft 27 with the single motor 26 for rotation of all of the drums 18 in unison, and requires also that each drum be mounted for axial and transverse adjustment relative to movement of the substrate.

Continuing rotation of the drum outer surface 22 to the cleaning station ^'(D) where the drum surface is engaged with a cleaning member, e.g. a rotating brush 44, which dislodges any remaining granular material (J) from the drum outer surface 22. The dislodged granular material (J) separated by cleaning on post-laydown retriever means disposed generally between the substrate and the cleaning position of the drum outer surface, and falls upon the cross-conveyor 42 (again, before it can reach the surface of the substrate) and is retrieved, e.g. for recycling.

The substrate 12 is advanced continuously through a series of stations where additional elements of the predetermined pattern of granular material are applied sequentially upon the substrate.

After the laydown of the entire predetermined pattern is completed, the substrate may be advanced, e.g. to an oven, for curing of the granular material (s) to form an integral layer upon the substrate.

Other embodiments are within the following claims. For example, particles of different material, e.g. powdered material or metallic flake, may be applied to the substrate at one or more stations. The cleaning brush may be mounted for rotation or fixed.

Also, referring to Fig. 10, an apparatus 50 of the invention may be employed to apply decorative patterns 52 of, e.g., colored granulated sugar or chocolate upon the surface of a moving substrate of food products 54.

An apparatus 60 of the invention may be employed to apply a pattern of colored particles, e.g. shadow lines 62, upon rolled roofing material and/or on roofing shingle roll-stock prior to die cutting (64, Fig. 11) . An apparatus 70 of the invention may also be employed to apply a granite facing on concrete pavers or shadow lines 72 on concrete blocks 74 moving on a conveyor (Fig. 12) .

Referring to Figs. 13 and 14, an apparatus 80 of the invention may also be employed to form a wall covering fabric 82 having solid raised areas 84 of plastic, e.g. of polyvinyl chloride or other suitable plastic material, to replace use of plastic foam, known to increase risks in a fire. Other embodiments are also within the invention and claims.

For example, referring to Fig. 15, for single color patterns, only one screen station 90 may be employed. Referring to Fig. 16, a pattern may be made on a piece of suitable mesh material 92 , as in the manner of making silk screens. The mesh material may then be attached to a perforated drum screen 94 by tape or other means to produce a patterned laydown as described above. Referring next to Fig. 17, a pattern may be cut through a piece of thin flexible material 96, such as paper or film. The flexible material may then be attached to a perforated drum screen 98, e.g. by tape or other means, and covered with a piece of silk 100, to produce a patterned laydown as described above.

Referring now to Fig. 18, a patterned screen 102 may be rolled over a stationary substrate 104, with the screen supported in side plates 106, with a shelf 108 arranged to catch excess granules before they land on the substrate. A hopper 110 may also be attached to the side plates. By having screens made from a color separated pattern, and arranging index marks to suit, an in- registered laydown can be produced. Referring next to Fig. 19, a bar 112 across the substrate 114 may be arranged to have a vertical oscillation, with the bottom of the stroke set to the required laydown thickness, thus to provide tapping or tamping of the granules into a more constant thickness, with less smearing of the pattern, e.g. as compared to use of a roller. A stepped bar provides a similar effect, but in two or more stages.

For difficult-to-feed granules, or to achieve a very light laydown, a rotary finger bar hopper 116, shown in Fig. 20, may be used to control the flow of granules onto the screen, with the laydown thus controlled by varying the speed of the finger bar.

Certain granular materials are often difficult to print with, due to static electricity. This effect may be minimized by gently blowing air from a de-ionizer 118 onto the granule stream when it first lands on the screen, e.g. as shown in Fig. 21.

The clinging effect of static electricity can also sometimes be lessened by trailing a length of well grounded aluminum tinsel 120 across the face of the granule stream when it first lands on the screen (Fig.

22) .

Referring to Fig. 23, the use of an approved, properly specified and shielded radio-active rod 122 located in the granule stream may also help minimize the effect of static electricity.

By printing a granular pattern onto a wet release sheet previously coated with a suitable adhesive, the sheet may be rolled up, or sheeted, and subsequently used as a mold liner 124 when casting such products as concrete panels, blocks or foundation walls (Fig. 24) , and as described more fully below.

Referring to Fig. 25, for heavy laydown or special effects, a pattern may be cut through the wall of a tube 126, and an overall perforated screen 128 of the same diameter as the inside of the tube may be fitted into the tube. Granules or other media can then be doctored into the ensuing cavity, and held therein by suction, as described above. Referring next to Fig. 26, by arranging the size of the open areas of a screen 130, and using separate hoppers 132, 133, 134 for each ingredient of a formula, each revolution of the screen may be employed to deposit on a conveyor belt a complete set of ingredients. A synchronized cross conveyor 136 may be used to deliver each complete set of materials to a packing station at high speed. A photocell (not shown) on each stream detects missing items.

Granules may be laid into a suitable wet coating, which can then be dried or cured, e.g. in oven 138, to form a homogeneous sheet (Fig. 27) .

Frit or other glass granules 140 may be applied to a ceramic tile 142 before final firing (Fig. 28) .

Referring to Fig. 29, granules may be applied directly to a base sheet 144, or may be reverse printed onto a melamine wear layer, and then fused in the usual manner. Laminated flooring may also be produced in this manner, and the fused to high density ("HD") particle board 148. Rubber crumbs or granules may be deposited onto a base sheet in register to form a pattern (Fig. 30) , and then vulcanized in the usual manner.

Referring to Fig. 31, hard and natural granules may be printed upon and pressed into the surface of tiles 150 to give a longer lasting surface on a flexible back.

The granules may be applied while the tiles are in sheet form, and subsequently die cut 152 in register to keep the cutters away from the hard surface, or may be applied to individual tiles after cutting. Clear coat wear layer granules 154 may be applied in register with a previously printed sheet 156 (Fig.

32) , giving a registered embossed look while providing superior wear characteristics . This could also provide a VOC reduction. Referring to Fig. 33, non-slip granular material

158, e.g. aluminum oxide, may be printed on tiles 160 meant for stairs and ramps.

Light air flow from an air knife 162 (Fig. 34) after the laydown tends to move misplaced granules back to the nearest pattern block.

Referring next to Figs. 35-38, according to a further embodiment of the invention, a method for applying decorative facing to cast products involves

"printing" a thin layer of granular material 170 onto a base sheet 172 previously coated with a temporary adhesive, then causing the adhesive to dry, e.g. in roll form 174, holding the granules in place.

The base sheet is then used to line a mold or form

176, so that, when the form is filled with a material 178 to be cast, the material adheres to the granules. After removal of the cast material, the granules, and the base sheet from the form, the adhesive is reactivated to permit removal of the base sheet 172, leaving a finished product 180 with the granules exposed. Referring to Figs. 39A and 39B, a relatively lighter weight internal center pipe assembly 181 is formed from sheet metal sections 182, 183 secured together with clamp/adjustment bolts 187. Positioned between extension of the sheet metal sections are strips 184, e.g. of rubber or similar suitable material. The bolts 187 can be loosened for adjustment of strips 184 relative to the sheet metal sections 182, 183, in such a manner that exposed outer edges 184a of the strips 184 can be set straight and parallel, e.g. to the correct effective diameter of the internal center pipe 181 regardless of any deflection of the sheet metal, thus eliminating the necessity of machining. End dams 185 are clamped between sheet metal flanges 186 welded to sheet metal section 182. Also^" welded to the sheet metal section 182 is an extension section 188 that carries the assembly to a suitable suspension point, e.g. as described below. Sheet metal section 182 also defines suction holes 189 for creating a lower pressure region within the rotary patterned screen 190 supported by the internal center pipe 181.

Referring to Figs. 40A and 40B, a suspension assembly 210, attached to the non-rotating portion 196 of the printing machine, supports an internal center pipe assembly 181 within the screen 190 in such a manner that the screen can move slightly to accommodate out of roundness of the screen 190 and end rings 212. The suspension assembly includes a mounting block 191, mounting ears 192, left and right hand screwed spherical ball end bearings 193a, 193b and an attachment pin 194 extending through ears 214 attached to the extension section 188 of internal center pipe assembly 181. Referring next to Figs. 41 and 42, rotary patterned metal screens are typically provided with end rings permanently fixed in place. Various styles of end rings are available to accommodate different models of printing machines. The purpose of the end rings is to connect the screen to the rotary drive, and also to allow tension to be applied in a longitudinal direction to help keep the screen straight. As shown in Fig. 41, to facilitate insertion and removal of the center pipe, rotary screens 197 of the invention are provided with a modified end ring 198, removably attached to the screen with screws 199, extending through suitable holes provided in the screen.

A further advantage of this aspect of the invention is that the number of expensive center pipes required is reduced from one center pipe per screen to two center pipes per printing head, to allow for pattern changes. For example, for a machine having five heads and twenty patterns, the number of center pipes required would be reduced according to the invention from 100 to 10.

Referring to Fig. 42, in an alternative embodiment, a removable end screen assembly 216 includes a thin metal external split end ring 201 attached, e.g. with adhesive, to the outer surface of a rotary patterned screen 200. The ring 201 defines holes 218 for receiving suitable screws 202 for attachment of the external ring 201 to an end ring 203. The ring 201 can be split to accommodate different screen metal thickness.

Referring to Fig. 43, an assembly stand 220 includes a cantilevered shaft 222 supported by a frame 205. First, a modified end ring 204 is placed onto shaft 222. A center pipe 206 is then slid onto the shaft. A screen 207 without an internal end ring is guided over the center pipe fins 224. and secured by screws to the modified end ring. An external hinged ring 208 may also be attached to the screen 207 to keep it round and to facilitate handling.

According to preferred embodiments of this method of the invention, the base sheet may be paper or cloth. The granules may be applied either overall, or in a pattern using one or more colors, using the granular printing machine of the invention. The granules may be spread by scattering or by use of a doctor blade. The releasable adhesive may be water soluble, heat sensitive, etc. The cast material may, e.g., be: concrete, e.g. as used for building panels, foundation walls, building blocks, or paving material, or plastic, e.g. as used for counter-tops (Corian^® type) , or wall panel facing ( asonite^®) ; fiberglass, e.g. as used for bath tubs & surrounds; or edible granules, e.g. as used for food products. The granules may be natural or synthetic materials. The surface finish (roughness) will typically depend upon the depth of immersion of the granules in the adhesive, i.e. a thick layer of adhesive would result in a textured surface, and a thin amount of adhesive would result in a smoother surface. Also, in other embodiments of the invention, the drive of the substrate conveyor may coupled to the rotation drives of each drum in a manner to cause each drum to rotate with a surface velocity matching the velocity of the substrate conveyor. A pattern may be inlaid upon a previously deposited field, or a clear coat/wear layer may be deposited over a previously printed or laid pattern.

A mottled pattern of granules may be deposited upon a base tile sheet or web before calendering, thereby ensuring side-to-side pattern match and allowing larger mottle areas.

A pattern of very hard granules may be deposited on a tile sheet, which is then die cut in register away from the granules .

Granules may be removed from an overall deposited pattern before consolidation, thereby leaving a depression or hole to be filled in a subsequent step.

A resilient sheet of material, e.g. 0.125 inch (about 3.2 mm) thick, may be cut with a pattern to form a cavity or groove when disposed upon a screen, for deposit or removal of granules .

Claims

1. An apparatus for laying down a continuous, predetermined pattern of granular material upon a substrate, said apparatus comprising: at least a first station comprising: a drum having a generally cylindrical drum wall mounted for rotation above the substrate, said drum wall defining a drum outer surface and a drum inner surface; a motor for rotating said drum outer surface through a sequence of positions comprising: a granular- material -receiving position, an excess granular-material - separation position, an granular-material-pattern-laydown position, and a cleaning position; a volume defined by said drum wall and a baffle contained therewithin with free ends disposed in sliding engagement with said drum inner surface in a manner to define a retention region of said volume corresponding generally to a segment of said drum outer surface between said granular-material -receiving position and said granular-material -pattern-laydown position, said retention region disposed in communication with a source of vacuum,- a plurality of apertures defined by said drum wall and in communication between said drum inner surface and said drum outer surface, said plurality of apertures arranged in an element of the predetermined pattern to be formed upon the substrate; a hopper positioned to receive a supply of granular material and to deliver the granular material onto the drum outer surface at said granular-material - receiving position; pre-laydown retriever means, disposed generally between said excess-granular-material - separation position of said drum outer surface and said substrate, for receiving excess granular material from said drum outer surface; a cleaning member disposed at said cleaning position for removing granular material from said drum surface; post-laydown retriever means, disposed generally between said substrate and said cleaning position of said drum outer surface, for receiving granular material dislodged from said drum outer surface; and conveying means for continuous relative movement between said station and the substrate.

2. The apparatus of claim 1, further comprising at least a second station spaced from said first station.

3. The apparatus of claim 1, further comprising a main conveyor mounted for continuous movement of the substrate therealong, relative to said first station.

4. The apparatus of claim 1 wherein said hopper comprises a granular material metering dam disposed in adjustable, spaced relationship to said drum outer surface .

5. The apparatus of claim 1 wherein said pre- laydown retriever means is disposed generally below said excess granular-material -separation position of said drum outer surface and above said substrate in a position for intercepting excess granular material released from said drum outer surface before the excess granular material contaminates said substrate.

6. The apparatus of claim 3 wherein said pre- laydown retriever means comprises a conveyor disposed to move generally transversely to the direction of said main conveyor, for retrieving excess granular material from said drum outer surface.

7. The apparatus of claim 1 wherein said post- laydown retriever means disposed generally below said cleaning position of said drum outer surface and above said substrate in a position for intercepting excess granular material dislodged from said drum outer surface before the excess granular material contaminates said substrate.

8. The apparatus of claim 7 wherein said post- laydown retriever means comprises a conveyor disposed to move generally transversely to the direction of said main conveyor, for retrieving granular material remaining upon said first drum surface after laydown.

9. The apparatus of claim 1 wherein said cleaning element comprises a brush mounted for engagement with said drum outer surface .

10. The apparatus of claim 9 wherein said brush is mounted for reverse rotation on engagement with said drum outer surface .

11. A method for laying down a continuous, predetermined pattern of granular material upon a substrate, said method comprising the steps of: providing at least one station comprising a drum having a generally cylindrical drum wall defining a drum outer surface and a drum inner surface, a volume defined by the drum wall, a plurality of apertures defined by the drum wall and in communication between the drum inner surface and the drum outer surface, the plurality of apertures arranged in an element of the predetermined pattern to be formed upon the substrate, and a hopper for receiving a supply of granular material ,- providing conveying means for relative movement between the substrate and the at least one station; rotating the drum wall above the substrate through a sequence of positions comprising: a granular-material- receiving position, an excess granular-material - separation position, an granular-material -pattern-laydown position, and a cleaning position; positioning the free ends of a set of baffles disposed within the volume defined by the drum wall in sliding engagement with the drum inner surface to define a retention region of the volume corresponding generally to a segment of the drum outer surface between the granular-material-receiving position and the granular- material- pattern-laydown position; connecting the retention region to a source of vacuum; delivering granular material supplied to the hopper onto the drum outer surface at the granular- material-receiving position; allowing vacuum from the retention region within the volume of the drum to act, through the plurality of apertures arranged in an element of the predetermined pattern to be formed upon the substrate, on granular material upon the drum outer surface in the vicinity of the plurality of apertures, thereby to retain granular material upon the drum outer surface; rotating the drum outer surface to the granular- material -separation position and allowing excess granular material, not subject to action by the vacuum from within the retention region, to separate from the drum outer surface; retrieving separated granular material on pre- laydown retriever means disposed generally between the excess granular-material-separation position of the drum outer surface and the substrate, thereby to intercept separated granular material before it contaminates the substrate; rotating the drum outer surface to the granular- material-pattern-laydown position at the termination of the retention region under vacuum, and positioning the granular material upon the substrate in the element of the desired predetermined pattern by allowing the granular material to disengage from the drum outer surface by removal of the vacuum; continuing rotation of the drum outer surface to a cleaning station and engaging the drum outer surface with a cleaning member to dislodge remaining granular material from the drum outer surface; retrieving granular material separated by cleaning on post-laydown retriever means disposed generally between the substrate and the cleaning position of the drum outer surface, thereby to intercept dislodged granular material before it contaminates the substrate; and continuing rotation of the drum outer surface through a series of cycles to laydown a continuous pattern of granular material upon the substrate.

12. The method of claim 11 comprising the further step of mounting the substrate on a main conveyor and moving the conveyor with the substrate thereupon past the at least one station.

13. The method of claim 11 comprising the further step of providing a series of spaced apart stations to lay additional elements of the predetermined pattern of granular material upon the substrate.

14. The method of claim 11 comprising the further step of treating the substrate to secure the position of the granular material laid upon the substrate.

15. The method of claim 11 for forming floor covering comprising the further steps of disposing a pattern of granular material of suitable plastic upon the substrate and securing the granular material by curing.

16. The method of claim 15 comprising the further step of disposing a pattern of contrasting granular material upon the substrate.

17. The method of claim 16 wherein the contrasting material comprises a metallic flake.

18. The method of claim 11 for forming wall covering comprising the further steps of disposing a pattern of granular material of suitable plastic upon the substrate and securing the granular material by curing.

19. The method of claim 11 for forming food products comprising the further steps of disposing a pattern of granular decorative material of suitable edible material upon a food substrate.

20. The method of claim 11 comprising the further step of severing the substrate into a plurality of discrete elements.