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Publication numberUS3875835 A
Publication typeGrant
Publication dateApr 8, 1975
Filing dateApr 23, 1973
Priority dateApr 23, 1973
Also published asCA1000172A, CA1000172A1
Publication numberUS 3875835 A, US 3875835A, US-A-3875835, US3875835 A, US3875835A
InventorsEdwin E Roberts
Original AssigneeJohns Manville
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Duct board cutting apparatus and method
US 3875835 A
Abstract  available in
Images(4)
Previous page
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Claims  available in
Description  (OCR text may contain errors)

g i United States Patent 1 1 m1 Roberts Apr. 8, 1975 l l DUCT BOARD CUTTING APPARATUS AND METHOD Primary E.\-aminer-Donald R. Schran [75] Inventor; Edwin E. Roberts, Cypress. Tex. fizz Agent or firm-Robert Krone; John [73] Assignee: Johns-Manville Corporation,

Greenwood Village, Colo. [57] ABSTRACT [22] Filed: Apr. 23, 1973 Duct boards. from a stack of duct boards. are properly 2 App] 353 49 aligned for feed into a cutting station and are successively fed from the feed station to the cutting station. Once in the cutting station the duct board is fed and [52] US. Cl. 83/5; 144/136 R guided between knife blades and a backing ml] which [5|] Int. Cl. 826d 3/06; B27f 5/02 cut the duct a required for a particular appncatiom [58] F'eld Search-"r 83/5; 44/!36 l33 Drawing apparatus, rearward of the knife blades and 144/245 F the backing roll, draw the duct board through the knife blades and the backing roll while maintaining [56] Rderences cued the duct board in proper alignment for the cutting op- UNITED STATES PATENTS eration throughout a major portion of the cutting op- 2,987,088 6/l96l Dennison l44/245 F 3.605,534 9/l97l Barr 83/5 3.733975 5/1973 Terrasi 83/5 6 Clams 8 Draw MENTEUAPR ems SHEET UF 4 ONN @N DUCT BOARD CUTTING APPARATUS AND METHOD BACKGROUND OF THE INVENTION The present invention relates to a duct board cutting apparatus and method and in particular to an improved apparatus and method wherein the duct board is automatically fed into a cutting station of the apparatus and maintained in proper alignment for the cutting operation throughout the cutting operation.

In the past, when duct board has been cut to enable it to be formed into a conduit it has either been cut by hand or on a machine such as that disclosed in US. Pat. No. 3,605,534 issued to W. H. Barr on Sept. 20, 1971. Cutting duct board by hand is extremely time consuming and thus undesirable. While duct board cutting machines such as the one disclosed in the above mentioned patent, are much better than having to cut the duct board by hand, a need has remained for an automatic apparatus and improved method for cutting duct board.

BRIEF SUMMARY OF THE INVENTION It is an object of the present invention to provide a duct board cutting machine and method for cutting duct board wherein duct board is automatically fed to and through a cutting station of the apparatus with the duct board being maintained in proper alignment for the cutting operation throughout the entire cutting operation.

Accordingly, the apparatus of the present invention includes a feed station where the duct board is stacked for processing through the board cutting machine. After the board has been stacked and the cutting process has started the boards in the feed station are properly aligned for feed into the cutting station of the apparatus. The uppermost board is fed and guided into the cutting station where feed and guide means guide the duct board between knife blades and a backing roll to cut the board. Once the uppermost board has passed from the stack to the cutting station. the stack is ele vated to bring the next board into position for feed into the cutting station. Once the leading edge of a board passes through the knife blade means and the backing roll, it is gripped between two pair of drawing rolls which draw the board between the knife blades and the backing roll. The drawing rolls also maintain the board in proper alignment with the knife blades for the cut ting operation and during the latter part of the cutting operation, when the board is not in contact with the feed rolls which are forward of the knife blade means and the backing roll. the drawing rolls alone keep the duct board properly aligned. With this apparatus and method the board is automatically cut in a proper manner without fear ofthe board becoming jammed or misaligned while passing through the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of the apparatus of the present invention;

FIG. 2 is a plan view of the apparatus of the present invention;

FIG. 3 is a cross-sectional view taken substantially along lines 3-3 of FIG. 2;

FIG. 4 is a cross sectional view through the cutting station of the apparatus of the present invention;

FIG. 5 is a detail of a tool mounting assembly of the present invention taken substantially along lines 55 of FIG. 4;

FIG. 6 is a cross-sectional view of the feed station of the present invention taken substantially along lines 6-6 of FIG. 2;

FIG. 7 is a cross-sectional view of the feed station of the present invention, adjacent the cutting station, and taken substantially along lines 7-7 of FIG. 2;

FIG. 8 is a partial prospective view of a duct board cut on the apparatus of the present invention.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS The apparatus of the present invention generally indicated by reference 20 includes a cutting station 22 and a feed station 24. The apparatus is designed to automatically cut fiber glass duct board so that it can be folded to form a duct.

As shown in FIGS. 1-5 the cutting station includes a cutting assembly 26, a duct board feed and guide assembly 28, and a duct board drawing and aligning assembly 30. These three assemblies cooperate to effect an accurate cutting operation on the boards passed through the cutting station.

The board cutting assembly 26 includes a series of cutting tools 32 which are mounted on support brackets 34 that are affixed to a pair of support beams 36. These support beams 36 extend between and are bolted, welded or otherwise affixed to lateral frame assemblies 38. As best shown in FIGS. 4 and 5 each bracket 34 includes a rectangular tool support 40 made up of a pair of end plates 42 and side plates 44. The sides plates 44 are each provided with shoulders 46 which extend between the end plates 42 adjacent the lower portions of the side plates 44. The shoulders 46 provide support for the tools 32 which can be readily inserted into or removed from the tool support as will be explained hereinafter. The tool support 40 is welded or otherwise affixed to one leg of a channel-shaped member 48 which is slidably received on one of the support members 36. A conventional toggle clamp 50 is also welded to the same leg of the channel member 48. The toggle clamp is provided with a clamping element 52 which presses down on an upper surface of the tool 32 to clamp it in place when the toggle mechanism is in the position shown in FIG. 4. When the toggle lever 54 is moved to the position shown in phantom line in FIG. 4, an arm 55 of the toggle mechanism raises the clamping element 52 out of contact with the tool 32 to permit the tool to be removed from the tool support 40. The channel member 48 is provided with a stud 56 that is threaded through an aperture in its web or a clamping mechanism similar to 50. The stud is used to clamp the tool mounting bracket 34 in place at any desired location along one of the support beams 36. As shown in FIG. 4, the stud 56 cooperates with inturned flanges 58 of the channel member 48 to clamp the channel in place. By loosening the stud 56 the channel is unclamped from the support 36 and can be slid relative to the support to relocate the bracket when it is desired to cut a board in a different location.

All ofthe tool mounts are identical and as best shown in FIG. 2, adjacent support brackets 34 are mounted on opposite support beams 36. Due to the relative width of the channel members 48 and the tool supports 40, the mounting of adjacent support brackets on the opposing support beams 36 allow the tools 32 to be located close to each other if required.

Each tool 32 includes a mounting plate 60 and a knife blade 62 which are best illustrated in FIG. 5. As shown the mounting plate 60 is provided with a depending lateral flange 64 adjacent each side which rest on the shoulders 46 of the support bracket. Inward of these flanges is a second pair of depending flanges 66 through which screws or similar fastening means pass to mount the knife blade 62 on the mounting plate 60. The knife blade shown is one designed to cut the board to form a shiplap joint when the board is folded to form a duct. While this is one form of tool which can be used in the present apparatus, various types of cutting blades can be used depending on the type of cut desired. Consequently. this blade is merely illustrative ofthe type of blade which can be used with the apparatus of the pres ent invention. As shown the clamping element 52 ofthe toggle clamp mechanism presses down on the plate 62 to lock the tool 32 in place so that the knife blade 62 rides on a backing roll 70 or is spaced a short distance above the backing roll 70.

The backing roll 70 is a metallic roll which extends for the entire width of the cutting station. The roll is mounted in conventional bearing assemblies, adjacent each end and is driven by a DC motor and conventional drive train (not shown) housed within a housing 72. When the knife blade 62 is resting on the backing roll 70 the blade contacts the roll rearward of the cutting edges of the blade. With this relationship between the knife blade 62 and the backing roll 70, a duct board with a facing sheet on its lower surface can pass between the knife blade and the backing roll without the knife blade cutting into the facing.

The duct board feed and guide assembly 28 is located forward of the knife blade and backing roll and includes a pair of feed rolls 74 and 76 plus a guide roll 78. The feed rolls 74 and 76 are rotatably mounted at each end in conventional bearings and the longitudinal axis of these rolls extend parallel to the longitudinal axis ofthe backing roll 70. The rolls 74 and 76 are each covered with an abrasive material 82 to reduce slippage between the rolls and the duct board being fed. A lower surface of the upper roll 74 and an upper surface of the lower roll 76 are spaced apart a distance less than the thickness of the duct board to be fed through the appa ratus. With this spacing of the rolls, the rolls grip the duct board and as the rolls are rotated by the drive assembly in housing 72 the duct board is fed toward the knife blade and the backing roll.

The guide roll 78 is located between the backing roll 70 and the feed roll 76. The guide roll 78 is rotatably mounted at each end in a conventional bearing and rotates aobut an axis of backing roll 70. The upper sur face of the guide roll 78 is located in the same horizontal plane as the upper surfaces of the backing roll 70 and the feed roll 76. The guide roll 78 serves to support and guide the duct board as it travels from the feed rolls 74 and 76 to the backing roll 70 and the knife blade. The guide roll 78 is also rotated by means of the drive assembly housed within housing 72.

The drawing and aligning assembly 30 is located rearward of the knife blade and the backing roll. The drawing assembly is made up of two pairs of rolls 82, 84 and 86, 88. Each of these rolls is mounted in conventional bearings at each end and each roll rotates about an axis parallel with the axis of rotation of the backing roll 70.

The rolls are each covered with an abrasive material which is the same abrasive material utilized to cover feed rolls 74 and 76. The axis of rotation of the rolls 82 and 84 lie in a common vertical plane and the axis of rotation the rolls 86 and 88 lie in the same vertical plane.

Lower surfaces of the upper rolls 82 and 86, and upper surfaces of the lower rolls 84 and 88 are spaced from each other a distance less than the distance between the lower surface of roll 74 and the upper surface of roll 76. With this spacing there is less slippage between the drawing rolls 82, 84, 86 and 88 and the duct board than there is between the feed rolls 74 and 76 and the duct board. Consequently even though the feed rolls and the drawing rolls are driven at the same surface speed by the DC motor and drive assembly in housing 72, the drawing rolls maintain pull on the duct board to keep it from bunching up at the knife blade and backing roll.

The drawing rolls 82, 84 and 86, 88 serve a second function. Since the drawing rolls are pulling on the duct board, they guide the duct board. With the two pairs of rolls acting together to grip the duct board at spaced apart locations, the drawing rolls prevent the duct board from becoming misaligned even when the duct board is no longer gripped between the feed rolls 74 and 76.

The DC drive motor of the cutting station is provided with a control 90 that permits the speed of the motor to be adjusted. Thus the rate at which the duct boards pass through the cutting station can be adjusted to suit a particular cutting operation.

The feed station 24, includes an elevator assembly 92, a pair of duct board aligning assemblies 94, a duct board feed assembly 96, and a duct board guide assembly 98. These assemblies all cooperate to automatically feed duct board to the cutting station so that once duct board has been stacked in the feed station 24, the process of cutting the duct board is completely automatic.

The elevator assembly elevator platform which is secured to and raised and lowered by four endless drive chains 102. A stud or similar fastening means pro jecting from a link of each of these endless drive chains is bolted or otherwise secured to each corner of the platform 100. The endless drive chains are each trained about upper and lower sprockets with the upper sprockets 104 being drive sprockets and with the lower sprockets 106 being idler sprockets. The drive sprockets 104 are driven by means ofa reversible motor 108 through a conventional drive train. The motor 108 drives a shaft 110 through a drive chain and sprocket 112. The shaft 110 is rotatably mounted in conventional bearings and the drive sprockets for the chains 102 carrying one end of the platform 100 are affixed to the shaft. A fourth sprocket 114 is also affixed to this shaft. A drive chain 116 is trained about the sprocket and a sprocket 118 that is affixed to a shaft 120 that carries the other two drive sprockets 104 for the chains 102 carrying the other end of the platform 100. Thus, the drive sprockets 104 for drive chains 102 are all driven by the motor 108 through a conventional drive train to raise and lower the platform 100.

The duct board aligning assemblies 94 are located adjacent each side of feed station and are substantially identical in construction. Consequently, only the struc ture of the aligning assembly illustrated in FIG. 3 will be discussed in detail to avoid unnecessary repetition.

As shown each aligning assembly includes a elongate plate 132 which extends parallel to the direction of the duct boards as they pass through the cutting station. The plate 132 is mounted on a drive assembly 134 which includes a pair of drive arms 136. Pins 138 adjacent each end of the bar 132 are rotatably carried at the outer ends of the arms 136. The inner ends of the arms 136 are affixed to shafts 140 and 142. The shafts 140 and 142 are mounted in bearings 144 and 146 that are bolted or otherwise affixed to frame support brackets 148 and 150. The shafts 140 and 142 are each provided with a sprocket intermediate the bearings 144 and 146 which support the shafts. A drive chain 152 is trained about these sprockets so that the shafts 140 and 142 will be rotated in unison to effect an eccentric motion of the plate 132 to effect the alignment of the duct boards. The shaft 140 is provided with a second sprocket 154 through which the aligning assembly is driven by means ofa drive chain 156. As the shafts 140 and 142 are rotated, the bar 132 is moved inwardly and toward the cutting station and outwardly and away from the cutting station during each rotation of the shafts 140 and 142. The alignment of the duct boards is effected as the bar 132 is moving inwardly and toward the cutting station.

As best shown in FIG. 6, the drive chain 156 is also trained about a sprocket 158 mounted on a shaft 160. The shaft 160 is rotated by a drive chain 162 that is trained about a sprocket 164 mounted on the shaft 160 and another sprocket (not shown) that is mounted on a shaft 166. The shaft 166 is rotated through a drive chain 168 which is trained about a sprocket 170 mounted on the shaft 166 and a drive sprocket 172 of a motor 174.

As shown in FIG. 2 the other aligning assembly is driven off of the shaft 166 by a drive chain 176. The drive chain 176 passes around a portion of a sprocket 178 which drives the aligning mechanism, about an idler sprocket 180 and about a sprocket (not shown) on the shaft 166. This construction is necessary to assure that the aligning assembly on this side of the machine will have the same inward and forward movement toward the cutting station as the other aligning assembly.

The feed assembly 96 includes a bar 182 which extends perpendicular to the direction of travel of the duct board through the cutting station and which is reciprocated back and forth by an eccentric drive assemlby 184. The bar is provided with a pin 186 and 188 adjacent each end which projects upwardly from the bar and through an arm 190 and 192. The pins 186 and 188 are rotatably mounted in the arms 190 and 192. The arms 190 and 192 are in turn carried by arms 194 and 196. The arms 194 and 196 are welded or otherwise secured to the bottoms of shafts 160 and 166 and the arms 194 and 196 rotate with these shafts. The arms 190 and 192 are secured to the arms 194 and 196 by pins 198 and 200 which permit relative rotation between these members.

Plates 202 and 204 are welded or otherwise secured to the ends of the bar 182. The plates 202 and 204 project perpendicularly from the bar in a horizontal direction. Each plate carries a pair of rollers 206 and 208 respectively, which are received within channel members 210 and 212 extending in a direction parallel to the direction of movement of the duct board through the cutting station. With these guides to restrain lateral movement of the bar 182 the eccentric drive assembly 184 effects a reciprocating movement of the bar 182 when shafts 160 and 166 are rotated. In addition, since these shafts are the same shafts which are rotated to drive the aligning assemblies 94 the alignment of the boards is affected at the same time the boards are being fed into the cutting station 22.

The guide assembly 98 includes a grid work 214 against which the uppermost duct board is pressed when the duct board is in position to be fed into the cutting station 22. The guide assembly also includes a guide rail 216 which has an upper surface or edge 218 adjacent the feed roll 76 which lies in substantially the same plane as the upper surface of the feed roll 76. A portion 220 of the upper surface of the guide rail 216 adjacent a leading edge of the guide rail and adjacent each end of the rail is inclined downward from the trailing edge 218. The rail thereby presents a surface over which lateral portions of the duct board can slide so that they will be elevated to the proper elevation for feed between the feed rolls 74 and 76. The grid 214 in combination with the rail 216 combine to assure that any duct board being fed from the feed station 24 into the cutting station 22 is substantially flat so that the duct board will not become jammed in the apparatus.

The machine includes a control assembly, which comprises a control panel 222 plus limit switches 224. 226 and 228. The limit switch 224 is provided to actuate the control mechanism to halt the raising of the ele' vator when a duct board is in contact with the grid 200. The limit switch 226 is provided to actuate the control system to effect alignment of the duct board and the feed of the duct board into the cutting station 22. The limit switch 228 is provided to stop the feed mechanism once it has been reciprocated through a cycle to allow another duct board to be positioned for feed into the cutting station.

In operation. the duct boards are stacked on the platform while the platform is in its lowermost position. Once the desired number of boards have been stacked on the platform 100 a main switch 230 of the control panel is turned on and the motor 108 for aligning the elevator assembly is actuated to raise the platform 100 unit a duct board is in contact with the grid 200. As a duct board comes in contact with the grid 200, lever arms of the limit switches 224 and 226 are depressed and the switches are actuated. The limit switch 224 disengages the elevator motor 108 to stop the platform from rising any further. Simultaneously the limit switch 226 actuates the motor 174 for the aligning and feed assemblies 94 and 96 to effect the alignment and feed of the uppermost duct board into the cutting station 22. The plates 132 are wide enough that the uppermost duct board plus the two succeeding duct boards are all contacted by the plates. In this way the duct boards are contacted three times by the aligned assemblies 94 to assure that they are properly aligned before they are fed into the cutting station. Once the feed bar 182 has been reciprocated forward and back to its initial position, the limit switch 228 is contacted to stop the motor 174. As soon as the duct board passes from the feed station the lever arms of the limit switches 224 and 226 return to their original posi tion. Thus the limit switch 224 actuates the motor 108 for the elevator assembly to raise the elevator platform 100 to place the next duct board in position to be fed into the cutting station. The limit switch 226 actuates the aligning and feed assemblies and the cycle described above is repeated.

As the duct board is pushed from the feed station. it rides up over the guide rail 216 and between the feed rolls 74 and 76. The feed rolls 74 and 76 grip the leading edge of the duct and feed the duct over the guide roll 78 and between the knife blades 62 and the back ing roll 70. As the duct board passes between the knife blades 62 and the backing rolls 70 the duct board is cut. as shown in FIG. 8, to form a board 232 having cutout portions 234 which enable the board to be folded into a duct. While the cuts can have various cross-sectional configurations depending on the type of joint to be formed, the facing sheets 236 on the lower side of the board remain in one piece. After exiting from the knife blades and backing roll. the duct board passes between the drawing rolls 82. 84, and 86. 88. These rolls grip the duct board as it passes from the cutting blades and backing roll to maintain the duct board in proper alignment throughout the cutting operation and to keep the duct board under tension for proper cutting. Once the duct board has exited from the rolls 86 and 88 it is ready for packaging or for installation.

What is claimed is:

l. Duct board cutting apparatus comprising;

cutting station means for cutting a board composed of fibrous material, said cutting station means including a knife blade means affixed to a support of the apparatus and backing roll means rotatably mounted on said apparatus beneath said knife blade means. said knife blade means contacting said backing roll means rearward ofleading cutting edges of said knife blade means whereby a facing on a duct board can pass between said knife blade means and said backing roll without being severed. means for rotating said backing roll, means forward of said knife blade means and said backing roll for feeding and guiding board between said knife blade means and said backing roll means, feed station means for automatically feeding board to said feed and guide means of said cutting station said feed station means including means for aligning said board prior to the feed of said board to said cutting station. and means for guiding said board into said feed and guide means of said cutting station which elevates lateral portions of said board relative to a central portion of said board to flatten said board to prevent said board from becoming jammed during passage into the cutting station, and means rearward of said knife blade means and said backing roll means for drawing board between said knife blade means and said backing roll means and for keeping board in proper alignment for cutting as the board passes between said knife blade means and said backing roll means. said drawing roll means including a first pair and a second pair of rolls which are rotatably mounted on said apparatus on axes extending parallel to the axis of rotation of the backing roll with said first pair being mounted forward of said second pair, said first pair and said second pair of rolls each including an upper roll and a lower roll which lie in a common vertical plane with a lower surface of the upper roll being spaced from an upper suface of the lower roll a distance less than the thickness of the board being cut, and means for rotating said first pair and said second pair of rolls. 2. Duct board cutting apparatus as defined in claim 1 wherein:

said feed and guide means forward of said knife blade means and said backing roll includes a third pair of rolls which are rotatably mounted on said apparatus on axes extending parallel to the axis of rotation of the backing roll, said third pair of rolls including an upper roll and a lower roll which lie in a common vertical plane with a lower surface of the upper roll being spaced from an upper surface of the lower roll a distance less than the thickness of the board being cut and greater than the distances between the lower and upper surfaces of the first and second pair of rolls, and means for rotating said third set of rolls. 3. Duct board cutting apparatus as defined in claim 2 wherein:

said means for rotating said third pair of rolls rotates said third pair of rolls with a surface speed equal to the surface speeds of said first pair and said second pair of rolls. 4. Duct board cutting apparatus as claimed in claim 1 wherein:

said feed station means includes means for feeding an uppermost board from a stack of boards into said cutting station, and means for bringing a succeeding board into position to replace said uppermost board. 5. Duct board cutting apparatus as claimed in claim 4 and further comprising:

aligning means for aligning said uppermost board for feed into said cutting station. 6. Duct board cutting apparatus as claimed in claim 5 wherein:

said aligning means comprises a pair of elongate members extending generally parallel to the direction of travel of said board through said apparatus, said elongate members being mounted on said apparatus adjacent sides of said apparatus, and means for moving said elongate members toward each other and in the general direction of travel of said uppermost board as said uppermost board is being fed into said cutting station.

Patent Citations
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US3733975 *Jan 3, 1972May 22, 1973Stack Pac CorpCorner block forming apparatus
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3941018 *Dec 23, 1974Mar 2, 1976Glass Master CorporationBoard cutting machine
US4342349 *Feb 15, 1980Aug 3, 1982Daniel LipmanApparatus and method for grooving a board-like material, a grooving tool therefor and a structure made by the method
US4781510 *Oct 11, 1985Nov 1, 1988Manville Service CorporationInsulation board feeder
US4798118 *Feb 26, 1988Jan 17, 1989Carithers Jr Charles HApparatus for cutting V-grooves in mats
US4983081 *Jun 1, 1989Jan 8, 1991Glass Master CorporationApparatus and method for forming shiplap duct
US5024131 *Mar 20, 1989Jun 18, 1991Weidman Roger FDuct board cutter
US5077899 *Dec 6, 1990Jan 7, 1992Malco Products, Inc.Fiberglass panel cutter with interlocking blades
US5399049 *Jan 6, 1993Mar 21, 1995Amada Company, LimitedV-shaped groove forming machine and its control method
US5494385 *Mar 2, 1995Feb 27, 1996Amada Company LimitedV-shaped groove forming machine
US5567504 *May 31, 1994Oct 22, 1996Schuller International, Inc.Glass fiber duct board with coated grooves and the method of making the same
US5575598 *Mar 2, 1995Nov 19, 1996Amada Company, LimitedV-shaped groove forming machine and its control method
US5613417 *Apr 10, 1996Mar 25, 1997R. R. Donnelley & Sons CompanyApparatus and method for forming a groove in a board
US5697282 *Mar 15, 1994Dec 16, 1997Schuller International, Inc.Apparatus for and method of forming large diameter duct with liner and the product formed thereby
US5855154 *Apr 2, 1997Jan 5, 1999Johns Manville International, Inc.Method of forming large diameter duct with liner and the product formed thereby
US8186397May 11, 2009May 29, 2012Columbia Insurance CompanyHardwood texturing apparatus and methods for using same
US9352482Apr 12, 2012May 31, 2016Columbia Insurance CompanyHardwood texturing apparatus and methods for using same
US20110041659 *Aug 21, 2009Feb 24, 2011Dennis Clifford WilliamsPortable duct board cutting table
WO1990014914A1 *Apr 27, 1990Dec 13, 1990Glass Master CorporationApparatus and method for forming shiplap duct
WO1995024985A1 *Mar 14, 1995Sep 21, 1995Schuller International, Inc.Apparatus for and method of forming large diameter duct with liner and the product formed thereby
Classifications
U.S. Classification409/304, 409/317, 144/136.1, 83/875
International ClassificationB26D3/08, B23D3/06
Cooperative ClassificationB23D3/06, B26D3/08
European ClassificationB26D3/08, B23D3/06