Previously, such U-shaped trough sections were formed either by rolling a plate back-and-forth between three rollers, or breaking it successively to form a bend. Troughs with long sides or deep troughs could not be formed in this manner because the sides became so unwieldy in the multi-operations of increment bends until a U-shape was obtained. If shallow U-bends were first formed and then angular sides were welded thereon to provide for the pitch of the resulting trough, this took time, and was expensive and did not produce smooth and uniform troughs.
It is known, however, that machines combining a precutting of a sheet or web at an angle and then wrapping it around a mandrel by a roller to form a curved piece are known as shown in:
Hale U.S. Pat. No. 2,156,337 issued May 2, 1939 in Class 153-66 Rutten U.S. Pat. No. 2,339,355 issued Jan. 18, 1944 in Class 153-2. PA1 Stubbings U.S. Pat. No. 4,070,890 issued Jan. 31, 1978 in Class 72-129. PA1 Crowell U.S. Pat. No. 478,090 issued July 5, 1892 PA1 Swoboda et al U.S. Pat. No. 691,205 issued Jan. 14, 1902 PA1 Blackley U.S. Pat. No. 2,276,012 issued Mar. 10, 1942 in Class 153-46 PA1 Weightman U.S. Pat. No. 2,350,379 issued June 6, 1944 in Class 153-46. PA1 Green U.S. Pat. No. 2,596,848 issued May 13, 1952 in Cl. 153-46 PA1 Bock U.S. Pat. No. 3,867,829 issued Feb. 25, 1975 in Cl. 72-321. PA1 Gail U.S. Pat. No. 957,200 issued May 10, 1910 PA1 Shaw Jr. U.S. Pat. No. 2,782,832 issued Feb. 26, 1957 in Cl. 152-46. PA1 Gier U.S. Pat. No. 1,129,663 issued Feb. 23, 1915. PA1 Wolfram U.S. Pat. No. 2,962,910 issued Dec. 6, 1960 in Cl. 74-230.17. PA1 Drachman U.S. Pat. No. 2,571,427 issued Oct. 16, 1951 in Cl. 254-167.
Also it is known to cut sheets into trapezoidal shapes by means of cutting torches as shown in:
The roll-bending of clamped sheets by a freely movable roller mounted on a lever arm is also known as shown in the following U.S. patents:
There are also hydraulic means for bending plates as disclosed in U.S. patents to:
The roll-bending of tubes around mandrels is known as disclosed in U.S. patents to:
Vertically adjustable movable rollers for aligning articles for a machine is known in
A common central drive for two parallel shafts is known from:
No combination of these patents, however, discloses applicants' steps of cutting and successively joining equal length sides of isosceles trapezoidal sheets to form a smooth trough sub-assembly, nor do they disclose some of the detailed features of applicants' bending machine, such as the specific means for adjusting a sheet with respect to a mandrel, the hydraulically clamping of the sheet by oscillation of the mandrel, and the balanced single-motor drive for two spaced arms that support the wrapping roller around the mandrel.