Sheet metal drafting device

This invention is a device which enables one to layout sheet metal elbows of many sizes, degree of angle, segments, and throat radiuses. Further this invention is a device for laying out round pipe sections to intersect another round pipe at a right angle either on or off center of the pipe being intersected to form a sheet metal T joint of many sizes and combination of sizes. Another advantage is the use of the transparent, rectangular, plastic elements, when one element is affixed upon the profile of an object to be intersected the lines required in this method of layout can be readily ascertained, thus eliminating the drafting of same. The gist of this invention is a layout device, and method which enables one to layout hundreds of sheet metal objects in much less time and without the preliminary procedures which are often used in this type of sheet metal fabrication.

An object of this invention is to provide an instrument for the purpose of 
expediting the layout time, and eliminating the preliminary procedure of 
laying out sheet metal elbow patterns of different sizes, angles, 
segments, and throat radiuses. 
Another object is to provide a layout method not unlike the present 
procedure of laying out T joint patterns, only that the end view elevation 
of the T joint can be easily ascertained by pivotally connecting the 
required rectangular, plastic element on the obverse or reverse side of 
the disk so the lines on the rectangular element intersects the proper 
concentric circular arc of the disk, thus eliminating the common procedure 
of drafting an end view elevation of a T joint for the purpose of 
obtaining lines with which to layout the end of a round pipe to intersect 
another round the same size or larger, either on or off center of the pipe 
being intersected. 
If the instrument is to be used for laying out templates for segments of an 
elbow, the required transparent, rectangular, plastic piece can be 
pivotally connected to the obverse side of the disk, together with the 
narrow plastic ruler, at a required degree on the protractor. This 
procedure is required, but it will eliminate the present method which 
necessitates the procedure of laying out a side profile of the elbow 
desired, scribing a concentric, circular arc, which is then divided into a 
number of equally spaced points, which are to be projected upward through 
the side profile of the elbow, which would produce the lines needed in the 
procedure of layout out an elbow template.

Referring to the drawing of FIG. 1, I have used the reference numeral 1 to 
designate the obverse side of the disk of metal and/or plastic. This side 
of the disk is divided in halves by a horizontal red line 5", two black 
lines 6" and 7" which run parallel with one each side of line 5", a black 
line 14" runs perpendicular to line 5", a series of holes spaced on 14" 
which I designate as 4', and a hole centered on the disk which is referred 
to as 1'. The upper half of 1 is imprinted with a plurality of concentric 
semi-circular arcuate lines 17" of even whole number sizes, each 
representing a diameter of round pipe, a protractor 5 is imprinted on this 
half of 1 with the base line upon the red line 5". The lower half of 1 has 
a plurality of concentric semi-circular arcuate lines 18" of uneven whole 
number sizes, each representing a diameter of round pipe. 
The reverse side of the disk FIG. 2 I have used the reference numeral 2, 
this side of the disk 2 is divided into halves horizontally by a black 
line 9", and vertically by a black line 21", both lines crossing at a 
common center 1". The upper half of 2 is imprinted with a plurality of 
concentric semi-circular arcuate lines 19" of uneven half sizes, each 
representing a diameter of round pipe. The lower half of 2 is imprinted 
with a plurality of concentric semi-circular arcuate lines 20" of even 
half sizes, each representing a diameter of round pipe. The spaced holes 
on the perpendicular line 21" are numbered 4'. 
The rectangular element of FIG. 3 is referred to as number 3 and is of a 
transparent, plastic material having a plurality of spaced parallel lines 
15" extending longitudinally representing equally spaced lines on a pipe 
surface curved transversely to said lines. Line 16" being the center line, 
with a series of spaced holes 2. Lines 12" near each end of element 3 are 
to provide a suitable means of picking up lines 15" and 16" to be 
transferred to layouts such as 6, 7, and 8. This procedure will be 
explained later in this article. Each element 3 is imprinted with the 
diameter 23", the circumference 25", and the graduating points to encircle 
a pipe of that diameter 24" which are 1 to 9 to 1. 
The element of FIG. 4 is numbered as 4, it is a clear plastic ruler with a 
red line 8" imprinted horizontally, a hole 3' two inches from one end to 
pivotally connect the ruler 4 to the obverse side of the disk 1, the hole 
5' is for the convenience of storing this instrument. 
FIG. 6 and FIG. 8 are detailed drawings of the layout device and the 
procedure used to layout an elbow pattern of a specific degree of bend, 
diameter, number of segments, and throat radius. For an example, FIG. 6 is 
how elements 3 and 4 are connected by a means to the obverse side of the 
disk 1 atop the protract 5 to aid in the process of laying out a 5 inch 
round elbow, having 90.degree. of curvature, four segments, and a 3 inch 
throat radius. Element 3 is set on 5 at 15.degree. from the vertical line 
14". 
Element 4 is then pivotally mounted atop the protractor 5 at 15.degree. 
above horizontal, which is also the red line 5" on the obverse side of the 
disk 1. 
The procedure of laying out templates for an elbow is shown in FIG. 8 
elements 6 and 7 are as follows, a length of material equal to the 
circumference of a 4 inch round pipe is inscribed on one end with a 
horizontal line 12" which represents the line 12" of element 3, from this 
line a number of equally spaced parallel lines 10" are extended 
longitudinally there of representing equally spaced lines on a pipe 
surface. For this layout the lines 10" are numbered 5 to 9 to 1 to 5. The 
total of these lines 10" are equal to the circumference of a 5 inch round 
pipe. With the use of drafting dividers the points 15" and 16" of element 
3 between the base line 12" and the black line 6" of the disk 1, may be 
transferred to the corresponding numbered line 10" of element 6, the 
points 6' on the lines 10" are now joined by a symmetrical curve 13". The 
shape of this template is referred to as a fish tail pattern, the seam is 
on the side of the finished segment, not at the throat or heel. To 
determine the layout procedure of the center section 7 of the elbow 
template, the points 22" at a right angle from the red line 8" of the 
plastic ruler 4 to the red line 5" of the disk 1 may be transferred to 
line 9 of the stretch out 6, then draw the horizontal line 11" and 
duplicate all points 6" below this line, and join by a symmetrical curve 
13". This procedure produces two segments of a five inch round elbow, 
having 90.degree.0 of curvature, four segments, and a 3 inch throat 
radius. 
When it is necessary to layout a template for a T joint, the end of a round 
pipe intersecting a round pipe at a right angle, the same size or larger, 
an element 3 piece is pivotally mounted on center of either the obverse 1 
or reverse side 2 of the disk. But for this example we are laying out a 5 
inch round pipe into a 71/2 inch round pipe. A stretch out 8 is drawn, 
which is equal in length to the circumference of a 5 inch round pipe. From 
the base line 12" a plurality of equally spaced lines 23" ae extanded 
longitudinally representing equally spaced lines on a pipe surface. For 
convenience these lines are numbered 5 to 9 to 1 to 5, with the use of 
drafting dividers or a compass the lines 15" and 16" from 12" of element 3 
to the 71/2 inch concentric, semi circular arc may be transferred to the 
corresponding numbered lines 23" of the template stretch out 8, then the 
points 7' on the lines 23" may be joined by a symmetrical curve 24. When 
the template material is cut along the curved line 24 and formed round, a 
template is formed for a round pipe intersecting another round pipe at a 
right angle. Different widths of element 3 may be used in a combination 
with a desired concentric, semi circular arc, on center or off center of 
the diameter pipe being intersected.