FIELD OF INVENTION
The present invention relates to a trammel for marking and cutting metallic fittings by holding gas cutting torch. It has to do particularly, although not exclusively, with attachments for conventional acetylene cutting torches of various types and sizes and which serve to guide the torch during the cutting operation so as to make perfect, or substantially perfect, straight-line cuts in metal plates, and the like, as well as circular cuts in metal plates. The invention is also intended to be used in fabrication, machining, erection and gas cutting of the pipe fitments. One application of this invention can be for marking and gas cutting of holes for pipe fitments over a wide range of pipe sizes and thickness.
BACKGROUND OF THE INVENTION:
A trammel is an engineering object defined as an instrument for drawing ellipses, a compass for drawing large circles that consists of a beam with two sliding parts — usually used in plural, or any of various gauges used for aligning or adjusting machine parts.
Welding and gas cutting are processes that has increasingly become ubiquitous in all industries.
The oxyfuel (oxygen to produce exothermic reaction while reacting with a fuel such as acetylene gas) process is the most widely applied industrial thermal cutting process because it can be used to cut wide range of thicknesses, low operational cost and can be operated manually or mechanized. There are several fuel gas and nozzle design options that can significantly enhance performance in terms of cut

quality and cutting speed. The cutting process is illustrated in Fig. 3. Basically, a mixture of oxygen and the fuel gas is used to preheat the metal to its 'ignition' temperature which, for steel, is 700°C - 900°C (bright red heat) but well below its melting point. A jet of pure oxygen is then directed into the preheated area instigating a vigorous exothermic chemical reaction between the oxygen and the metal to form iron oxide or slag. The oxygen jet blows away the slag enabling the jet to pierce through the material and continue to cut through the material.
As stainless steel, cast iron and non-ferrous metals form refractory oxides i.e. the oxide melting point is higher than the material, powder must be injected into the flame to form a low melting point, fluid slag.
In Engineering field many a times marking and gas cutting of holes for cylindrical fittings (fitting axis at various angles) is to be carried out over different variety of surfaces (spherical, cylindrical, cuboid, dome etc.).For a large size of metallic fitting, for example cylindrical, the shape of the marking depends upon the surface over which the hole has to be made and the angle which the axis of the cylindrical fitting makes with respect to the surface.
These markings are being done as per the development drawings/calculations considering the surfaces to be true. From development drawings or the calculations some guidance points on the curved surface are provided to the operator and the remaining marking is to be done by free hand joining of these points.
It is common practice to hand-guide a cutting torch to produce a cut in a piece of metal and since the cutting torch must be held entirely by hand and maintained in a given position with relation to the work, the operator is subjected to considerable physical strain in an effort to follow a guide line arid thus produce an accurate, or nearly accurate, cut. It is essential for him to wear the usual dark glasses worn by

welders and because of this, it is necessary for him to crouch over the work, getting his eyes as close to it as possible while holding the cutting torch in a given position, in order that he may see and thus follow a chalk line which has been previously placed upon the work to guide him during the cutting operation. Such practice, which is generally the practice followed today, is very tiring to the operator and as the result, the amount of cutting which can be done by an operator in a given period of time is necessarily limited due, at least partly, to the fact that the operator must rest between cutting jobs to overcome fatigue.
As per prior art these fitting are gas cut with manual gas cutting torch. Particularly making true cylindrical holes through thick surfaces by the manual marking method and the manual gas cutting is very time consuming, require high skill, cumbersome, laborious and difficult to achieve desired clearance and fit.
While such processes may be automated in certain contexts, a large number of applications continue to exist for manual welding operations, the success of which relies heavily on the proper use of a welding gun or torch. For instance, an improper torch angle can lead to a spatter, improper penetration, and overall poor weldment. However, inexperienced welders often have difficulty establishing the proper torch angle and torch workpiece distance during welding, and such skills may be somewhat difficult to teach. Furthermore, even experienced welders may have difficulty maintaining these important parameters throughout welding processes.
Certain gas nozzles have been proposed that are used to establish the proper torch to workpiece distance during spot welding. However, these nozzles are less than satisfactory in addressing the overall problem, in particular because they do not establish the proper torch angle, are limited in scope to spot welding applications, and do not teach proper technique. Therefore, there exists a need for a device that will aid welders or welding trainees in establishing the proper torch angle and torch to workpiece distance.

While various types of guides/attachments/trammels and/or circle cutting devices have heretofore been proposed, most have involved relatively complex apparatus, have been difficult to use and/or have not adequately provided for supporting and guiding a cutting torch in the cutting of both circles and straight or other curved lines.
As per prior art, there is no compensation mechanism for deviation in the surface to be marked /cut. First cutting has to be done with 50 mm allowance (for Diameters above 2000mm) and the final cutting has to be done in steps of 10 mm or so.
Hence, despite numerous prior proposals, none of the prior art devices has completely solved the varying problems encountered in the practical use of cutting torches where rapid, accurate torch cutting of straight or curved lines and circles of different diameters is necessary.
OBJECTS OF THE INVENTION
Accordingly, a principal object of this invention of a trammel attachment for holding gas cutting torch for marking and gas cutting metallic fittings and a method thereof is to have provisions adapted to facilitate smooth and accurate gas cutting both of straight or irregular lines as well as circles of different radii without restricting arcuate movement of the torch even when cutting in a restricted area.
A further object of this invention of a trammel attachment for holding gas cutting torch for marking and gas cutting metallic fittings and a method thereof is to provide a simple, readily vertically and horizontally adjustable cutting torch trammel attachment adapted accurately to guide the torch in cutting without impairing its cutting action or movement.

A further object of this invention of a trammel attachment for holding gas cutting torch for marking and gas cutting metallic fittings and a method thereof is to ensure provision of an adjustable gas cutting torch attachment which permits accurate cutting of circles of different radii while easily maintaining a predetermined torch tip spacing from the surface to be cut at varying cutting torch angles.
A still further object of this invention of a trammel attachment for holding gas cutting torch for marking and gas cutting metallic fittings and a method thereof is to ensure provision of a cutting torch circle cutting guide facilitating preheating of the surface to be cut.
A still further object of this invention of a trammel attachment for holding gas cutting torch for marking and gas cutting metallic fittings and a method thereof that easily accommodate the changes in angle of fitment, pipe diameter and deviation in surface where hole is to be made.
A still further object of this invention of a trammel attachment for holding gas cutting torch for marking and gas cutting metallic fittings and a method thereof that minimizes/removes the manual errors and thereby reduce cost and substantially reduce cycle time of the job thereof during marking, cutting and beveling of the hole for pipe fitments.
DETAILED DESCRIPTION OF ACCOMPANIED DRAWINGS
Other objects and advantages of this invention reside in the details of construction and operation as more fully hereinafter described and claimed, reference now being had to the accompanying drawing forming a part hereof wherein
Figure 1 is a 2-dimensional view of the invention, illustrating a preferred embodiment of apparatus of this invention;
Figure 2 is a 3-dimensional view of the apparatus shown in figure-1.

DETAILED DESCRIPTION OF THE INVENTION
Pivot Support 11 fits at a desired location on or near the job on which marking is to
be done. It is obviously desirable that the Pivot Support 11 is fixed at the same
angle at which the cutting has to be done. The length of Pivot Support 11 is to be
decided in such a way that it supports the height at which gas cutting/marking is to
be performed. A small span cylindrical rod 1 circumscribes Pivot Support 11 and
therefore making a cylindrical kinematic pair with Pivot Support 11. A cylindrical
pair keeps two axes of two rigid bodies aligned. Cylindrical rod 1, a part of this
cylindrical pair system, will have an independent translational motion along the axis
and a relative rotary motion around the Pivot Support 11 axis. Again, the height at
which the cylindrical rod 1 is to be kept on Pivot Support 11 will depend on the job
height, operational requirements, type of job etc. At a suitable height, the
cylindrical rod 1 shall be fixed at its place on Pivot Support 11 using threaded connection.
Cantilever hollow rectangular bar 2 is welded at the center of cylindrical rod 1 in such a way that bar 2 is perpendicular to rod 1. The length of hollow rectangular bar 2 is to be decided on the basis of the dimensions of cut/marking, i.e., the bigger the dimension, the lengthier will be the rectangular bar. However, the length and span weight of the cantilever shall pose a bending moment on the welded joint with cylindrical rod 1 and therefore any movement at joint can lead to inaccuracy in cut/marking performed using this trammel. Therefore parallel support is provided to hollow rectangular bar 2 through a plurality of hollow rectangular support bar 3 placed above and below bar 2. Welded at one end to cylindrical rod 1, these support bar 3 can be of L-shape and can be welded directly to rectangular bar 2 or alternatively hollow rectangular bar 4 can be welded to the free end of support bar 3 and rectangular bar 2.

A cross slide with rectangular slots with a horizontal slide member 5 and vertical slide member 7 welded to each other at 90° angle is circumscribed on rectangular bar 2 towards its free end through its horizontal slide member 5. A hollow rectangular bar 12 forms sliding kinematic pair with vertical slide member 7. The gas cutting torch (or marking attachment) shall be fixed on this hollow rectangular bar 12 and the overall distance of the torch tip and the job surface shall be maintained through plurality of threaded connections 9,10 in vertical slide member 7.
Following procedure is followed for use of the Mechanism during Marking and Gas Cutting of the hole profile with the developed mechanism:
The center of the hole is marked on the surface from the assembly drawing. Mark the four quadrant-points on the job surface. Tack the Pivot Support 11at a desired angle at a position near or on the job and fit the marking attachment (or gas torch in case of cutting)to hollow rectangular bar 12. The radius of hole shall be taken care by sliding cross slide horizontal slide member 5 on bar 2. Match the four quadrant-points with the marking head of the mechanism.
It is further important to note that in addition to providing a trammel attachment for accurately describing curved lines on uneven job surfaces with ease, it is apparent that the embodiment of the invention, as described hereinabove, shall provide an extremely critical technique for a) a gas cutting arrangement when the marking attachment on hollow rectangular bar 12is replaced by a gas cutting torch b) machining attachment when marking attachment on hollow rectangular bar 12 is replaced by a cutting tool or c) a semi-automatic pipe welding attachment when the marking attachment on the slider is replaced by a welding torch, and thereby providing an even further versatile scope of use.

There are various working examples for using such a trammel device for example for assembly of Branch Pipe Assembly in Water Boxes (Part of Power Plant’s Condenser), Air Extraction & Stand Pipes of Condenser, or Pipe fitting of the Turbo generator and Turbine as well as many others.
Since, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur by those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

WE CLAIM
1. A trammel attachment unit for accurately describing curved lines with acetylene torches or marking attachments comprising:
- a rectangular bar 2, a cylindrical rod 1 and hollow rectangular support bar 3 placed below and above the said bar 2, and pivoted together at one end to pivot support 11 in a compass-like member;
- the said cylindrical rod 1 fixed at its place circumscribing pivot support 11 using threaded connection and forming cylindrical pair;
- the cantilever hollow rectangular bar 2 perpendicularly welded at the center of cylindrical rod 1;
- a plurality of hollow rectangular support bar 3 to support cantilever hollow rectangular bar 2;
- cross feed with horizontal slide member 5 and vertical slide member 7 welded to each other at 90° angle and circumscribed on rectangular bar 2 towards its free end through its horizontal slide member 5 and connected at the free end of rectangular bar 2;
- a hollow rectangular bar 12 forms sliding kinematic pair with vertical slide member 7;
- a socket in each of the holders, and the hollow rectangular bar 12 freely reciprocable and slidably adjustable in vertical slide member 7, means for securing the hollow rectangular bar 12 in adjusted position in vertical slide member 7, and clamp means on hollow rectangular bar 12 for attaching the same to an acetylene torch or marking attachment.
- threaded connections 9, 10 for securing cylindrical rod 1 and hollow rectangular bar 12 at adjusted positions on pivot support 11 and vertical slide member 7 respectively wherein the pivot support 11 is fitted at a desired location on or near the job on which marking is to be done.

2. A method for using trammel attachment unit for describing an orbicular path marking for acetylene torches comprising:
- marking center of the circle to be manually marked on the surface from the assembly drawing;
- manually marking the four quadrant-points on the job surface;
- tacking the Pivot Support 11 at a desired angle at a position near or on the
job and fit the marking attachment (or gas torch in case of cutting) to hollow
rectangular bar 12;
- adjusting the height of the cylindrical rod 1 on Pivot Support 11 as per requirement;
- sliding cross slide horizontal slide member 5 on bar 2 as per the marking requirement;
- matching the four quadrant-points with the marking head.