FIELD OF INVENTION
The present invention relates to a device and method for marking radius on pipes or an uneven surface. More particularly, the invention relates to a device and method for marking radius on pipes or an uneven surface especially the surface which is further gas-cutted along the marking line for a pipe to pipe weld in forming a Tee Joint in Power Plant piping.
BACKGROUND OF THE INVENTION AND PRIOR ART
In fabricating a Tee joint it is required to weld a pipe perpendicular to another pipe. This is done after gas cutting or drilling the intersecting portion. It is essential to have correct radius gas-cutted so that there is no mismatch during weld fit up. Manual gas cutting on pipe requires marking before going for cutting. Marking radius on the pipe using a string and pointer method, always results in an ellipse even though the radius is constant from a particular point or centre. This is because the plane of marking changes continuously. The same is the case by using a compass.
Using a computer Numerical control machine the torch travel has to be suitably adjusted based on the pipe radius and may not result in uniform flame length and is also costlier.

Hence a device is required which changes its orientation as per pipe to mark uniform radius on the pipe. Device should be handy enough to use and at the same time should be sturdy enough to give better accuracy. Piping of various diameters ranging from Dia.100mm to Dia.500mm can be marked using this device. To make the markings legible surface is to be coated with chalk or similar coloring medium..
A typical marking method for pipes or uneven surfaces by using the invention is as shown in Fig.1.
PRIOR ART:
On line Patent search was carried on the subject but patents could not be found having direct reference to this invention. However, in few patents where some reference could be made for ‘marking’ and could little contribute on the subject are referred in the subsequent paragraphs.
Patent Application number IN1207CHE1996 invention relates to devices for marking straight lines on flat surfaces and relates more particularly to improvements in so-called chalk line marking devices. For marking of a line on a receiving surface, the rear surface of the main body is seated against the receiving surface and a force is applied to the shuttle to tilt same forward and by so doing the marking string is drawn

forward. Upon release of the shuttle it is snapped rearward by the spring and at the same time substantially the entire length of the string snaps rearward into engagement with the receiving surface to mark same with a line indicated by chalk that is deposited on the receiving surface. During the line marking operation, the operator holds the marking device by a handle that is positioned in the vicinity of the biasing spring. The force for tilting the shuttle forward is applied to the latter by a finger of the operator's hand that is grasping the handle. The above mentioned patent is completely different from this patent and can be used for drawing lines on vertical walls only.
Patent Application number IN614KOL2015A Patent relates to “Jig/device for marking pitch circle diameter on any disc type object with known outer diameter and a method for the same. The above invention is for marking pitch circle diameter on disc type objects only and does not contribute for the present invention.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose a device and method for marking radius on pipes or an uneven surface, which can provide a centering mechanism to achieve zero shift in radius.

Another object of the invention is to propose a device and method for marking radius on pipes or an uneven surface, which is able to provide a device with simple scale and linear movement guide.
A still another object of the invention is to propose a device and method for marking radius on pipes or an uneven surface, which is capable of arresting the device with magnetic means on the pipe for a smooth working during marking radius on pipes or uneven surfaces.
A further object of the invention is to propose a device and method for marking radius on pipes or an uneven surface, which is able to provide a device which is easily mountable on the pipe, sufficiently rigid and stable in carrying out marking.
SUMMARY OF THE INVENTION
Accordingly, a device for marking of radius on the pipe surface comprising a V-block, sleeve, stem, scriber, and sliding scale assembly is designed. It is designed in a typical way to facilitate sliding of bars thereby the change in radius of marking scriber. Stem guides insides the sleeve for locating the centre of the radius to be marked on the circular pipe or workpiece.

As the device scriber is easily moved inside a guided hole marking can be done on uneven surface like pipe without change in radius.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: schematically shows the invented device assembly for marking radius. Figure 2: shows the detail of component V-block of the device. Figure 3: shows the detail of component guide block of the device. Figure 4: shows the detail of component support block of the device. Figure 5: Shows the detail of component Sliding scale Assembly.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
Fig. 1 shows the Invented Device. The device comprises of V-block (01), sleeve (02), Guide block (03), support block (04), sliding scale Assembly (05), scriber (06), stem (07) and magnet (08). The pipe surface to be marked is deeply punched or drilled with centre drill to locate the centre for drawing radius. Wet chalk powder paste is applied on the surface to make marked lines highly legible.
Sleeve (02) is screwed on to the V-block (01) and the stem (07) is placed to slide inside the sleeve (02).

This assembly is adjusted on the pipe or surface to be marked to locate the punched hole with the pointed end of stem (07). This is done by sliding V-block (01) upside on the stem for better visibility in positioning pointed end of stem (07). After location V-block (01) is released slowly for holding on to the pipe using magnet (08).
Sliding scale assembly (05) is manufacuted by welding slider scale with support block (04) as indicated in Fig.5.
Sliding scale assembly (05) is mounted with scriber (6) and assembled with the V-block assembly. Radius need to be marked is adjusted by sliding the bar in the guide block (03). Further sliding while marking has to be avoided by using locknuts (10). Graduations on the sliding scale assembly (05) has to be made accurately meeting the national or international standards.
Scriber is guided in the support block to move to and fro enabling to draw radius on pipe or an uneven surface. After marking, the V-block is removed manually if permanent magnet is used. If electromagnet is used, magnet is turned off and V-block is removed. The accuracy of marking depends on locating stem (07) in the centre and hence care is exercised in matching the stem (07) with centre punched on the pipe surface or workpiece (09). For ease of marking and handling, sliding scale assemblies (05) variants are manufactured to suit particular range of diameters.

WE CLAIM
1. A device for marking radius on pipes or an uneven surface, the said device
comprising;
a V-block (01) having a provision of being locked by a magnetic means (08);
a sleeve (02) screwed on to the V-block;
a stem (07) guided in the sleeve (02);
a guide block (03) for guiding the stem (07) at the top;
a sliding scale assembly (05) for adjusting the radius to be marked;
a scriber (06) for marking various radius;
a support block (04) for guiding the scriber (06);
Characterised in that,
sliding scale assembly (05) having accurate graduation is mounted with scriber (06) and assembled with V-block assembly (01) when the slider scale is welded with support block (4) wherein the sliding scale assembly is disposed for adjusting the scriber to different lengths for marking various radius on the surface wherein a lock nut (10) is disposed to arrest the sliding of stem (07) in the guide block (03) during marking.
2. A method for the device claimed in claim 1, the said method comprising;
punching deeply or drilling the pipe surface to be marked to create a center for
drawing radius;

applying wet chalk powder paste on the surface to make marked lines highly legible;
assembling the V-block (01) with the sleeve (02) screwed on to it and placing the stem (07) inside the sleeve;
adjusting the assembly on to pipe or surface, to be marked to located the punched hole with the pointed end of stem (07) by sliding V-block upside on the stem (07);
locating the punched hole with the pointed end of stem (07);
releasing slowly V-block and held on the pipe (09) using magnet (08);
avoiding further sliding by arresting the stem with lock nut (10);
wherein,
the scriber (06) is guided in the support block (04) to move to and fro to draw radius on pipe when the stem (07) is matched accurately with centre punched on the pipe surface to achieve accurate marking.