FIELD OF THE INVENTION

[001] The present invention generally relates to an inspection device for a machining tool used in the manufacturing process and, particularly, related to a fixture for inspecting a welding tool that is associated with a heat staking machine.

BACKGROUND OF THE INVENTION

[002] It is a paramount factor in any machining process to set a machining tool in accordance with the desired work to be carried out and the dimensional accuracy thereof. Be it a drilling operation or boring operation or milling operation, the depth of cut and the dimensional accuracy of the work to be performed should be set before start of the operation. In modern computerized and automatic machining operation, unless the machining tools are pre-set with reference to the work piece as per the the dimensional accuracy of the work to be performed, it may cause poor quality part, work failure, wastage of time due to rework and thereby the ultimate loss of cost for production. This may go even worse in operations like welding where a series of operations to be performed in a sequence in a single part like armature conductor welding with commutator in armature assembly for automotive starting motor.

For explaining the purpose for which the present invention is intended, a welding operation, generally termed as xheat staking', in an armature assembly is described herein below, however, it should be understood that the intention of the present invention should not be restricted with the application described herein below; rather it should be considered within the scope of the appended claim. Referring to FIG.l, position of armature assembly (10) with reference to the welding tool is shown. The armature assembly (10) comprises an armature core (11) and a commutator (12) which are shown in relation with the welding tool, which otherwise referred as electrode (13). The electrode (13) is fixed with a tool holding device (not shown) after adjusting desired depth of weld using a gauging instrument. The armature core (11) is a laminated iron core wherein plurality of slots (14) is provided on the peripheral surface of the armature core (11) longitudinally. Said plurality of slots (14) is being adapted to receive armature conductors (15), which are made of copper wire. The armature core (11) has a shaft (16) centrally disposed, and one end thereof is mounted with the commutator (12). The commutator (12) has plurality of copper segments (17) corresponding to equal number of the armature slots (14).

Referring to FIG.2, a partial cross sectional view of the commutator (12) in relation with the electrode position during the welding operation is shown here. The copper segment (17) has base portion (18) provided with a slot (19) adapted to receive free end of the armature conductor (15). An insulator (20) is disposed between two copper segments in order to separate each copper segment (17) from conducting electricity with each other. A pair of armature conductor is placed in the slot (19) one above another. In the ideal situation, tip surface (21) of the electrode (13) is made to be positioned exactly above the periphery of the slot (19) or the armature conductor (15) at a distance (Dl), which is predetermined as per the depth of effective welding requirement using the gauging instrument, for efficiently welding the armature conductor (15) with the commutator (12). In radial direction, central axis of the electrode (13) is made to locate coaxial with the slot (19) at a djstance (D2) from the periphery of the slot (19) as shown in FIG.2, and in axial direction, central axis of the electrode (13) is made to locate at a distance (D3) from face (22) of the base portion (18) of the commutator (12).

Locating central axis of the electrode (13) in these three directions at desired distance for effective welding is a critical task as far as the welding or, precisely, heat staking process is concerned. Any misalignment in the location of the electrode with reference to the welding position in any of these directions will cause failure of the part.

A typical welding tool arrangement consists of the electrode (13) and the holding device (not shown) for holding said electrode. The electrode (13) is of cylindrical body in nature and has tapered welding end (23) at one end which is having a cross section diametrical in nature. The diameter at the tip of welding end (23) is determined in such a manner to effectively weld free end of the armature conductor (15) with the slot (19). A proper trade off between the size of the slot (19) and the diameter of the welding end (23) has to be maintained for quality welding. The holding device is provided with a hole adapted to receive the electrode and provision is given in the holding device to adjust the axial position of the electrode within the holding device. A stopping means is provided in the holding device to arrest the axial and rotational movement of the electrode within the holding device.

In a practical situation, there are chances that the alignment between the electrode and the holding device may not be proper, and the dimensional accuracy of the electrode and the hole provided to receive the electrode in the holding device may not be accurate. This poor quality dimensional accuracy may result in fault tool position in comparison with the required dimensional accuracy of the welding tool arrangement. Ultimately, the position of the electrode in the radial direction (D2) and axial direction (D3) may vary and create welding at a position that is not intended. This poor quality tool position ultimately affect the welding quality in the armature assembly, thereby rejection of the part without any scope of further rework. The worst scenario due to the fault tool position is that variation in the radial direction cause contact of two adjacent copper segments (17), which in turn create short circuit in the armature electrical system thereby rejection of the part.

[003] Hence there was a very much need for a fixture to inspect the welding tool arrangement in terms of the position of the electrode with reference to the holding device. As the holding device is rigidly fixed on machine tool, adjustment in the holding device will not be done, rather the electrode need to be aligned as per the intended position. According to the preferred embodiment of the present invention, the fixture is initially preset by a master welding tool and then used to perform inspection of the welding tool that is to be fitted onto the machine tool for welding operation. Any misalignment in the electrode position will be identified with the help of dial indicator associated with the fixture according to the present invention.

OBJECT OF THE INVENTION

[004] The present invention overcomes the shortcomings associated with the background art and achieves other advantages not realized by the background art.

[005] The principal object of the present invention is to provide a fixture for inspecting desired position of welding tool such as electrode with reference to holding device thereof.

[006] Another object of the present invention is to provide a fixture which is less complex in construction, design and assembly.

[007] Yet another object of the present invention is to provide a fixture that is very much flexible to adapt for such tool inspection in varied applications with bare minimum modifications.

SUMMARY OF THE INVENTION

In broad aspect of the present invention, a fixture for inspecting a welding tool associated with a heat staking machine is disclosed herein below. The fixture comprises a base that does removably and slidably carry a tool fixing means for fixing the welding tool as it is fixed in heat staking machine. Further includes a tool alignment measuring means that is removably supported on the base, wherein the tool fixing means and the tool alignment measuring means are disposed in an operating relationship with each other in the base. The tool alignment measuring means comprises at least a leg which is having one end removably mounted on the base and another end is adapted to removably receive a first guiding rod, wherein the first guiding rod is horizontally disposed with the leg. Further includes a first guiding block that is slidably disposed on the first guiding rod and is adapted to removably and vertically receive a second guiding rod. A second guiding block is slidably disposed on the second guiding rod and provided with a slot adapted to receive tapered welding end of the welding tool. The welding tool has an electrode that is removably and adjustably fixed on to an electrode holder.

In another aspect of the present invention, the leg includes a first metallic plate and a second metallic plate, which are identical in design and, vertically mounted on top surface of the base at a spaced apart relationship with each other. The one end of the metallic plates has at least a first hole adapted to receive a pin for positioning the metallic plates on top surface of the base and at least a second hole for rigidly mounting with the base. The another end is provided with a first through hole perpendicular to planar surface of the metallic plate for receiving ends of the first guiding rod. A second through hole is made radially from longitudinal edge of the metallic plate up to the first through hole for arresting axial and rotational movement of the first guiding rod using fastening means. The first guiding rod includes two cylindrical rods which are identical in design and disposed between the first and the second metallic plates one above another in a same plane vertically by inserting through the first through hole.

In yet another aspect of the present invention, the first guiding block has a first through hole adapted to slidably receive the first guiding rod, a second through hole adapted to receive a first dial indicator, a third through hole perpendicular to the second through hole form front surface of the first guiding block up to the second through hole for arresting axial movement and rotational movement of the first dial indicator, at least a bore at bottom surface adapted to receive top end of the second guiding rod and a fourth through hole perpendicular to the bore from lateral surface of the first guiding block for removably fixing the second guiding rod and for arresting rotational movement thereof. The second guiding block comprises at least a first through hole adapted to slidably receive the second guiding rod, wherein bottom end of the second guiding rod is provided with an elastic member to suspend the second guiding block so as to reduce the impact of gravitational load of the second guiding block and to facilitate manual uplifting of the second guiding block easy during the inspection time. The slot provided in front surface of the second guiding block is extended along central axis thereof backwardly thereby to receive and align with the tapered welding end of the welding tool. The first guiding block and the second guiding block are disposed in the tool alignment measuring means in an operating relationship with each other. The second guiding block is disposed in the tool alignment measuring means in an abutment relationship with the first dial indicator and a second dial indicator, wherein the second dial indicator is mounted on a mounting means fixed with the first metallic plate.

In yet another aspect of the present invention, the tool fixing means comprises a tool aligning block for removably fixing the welding tool. The tool aligning block is made identical to a tool holding means provided in the heat staking machine and removably mounted on a tool guiding block. The tool guiding block is horizontally guided over a rail that is removably and longitudinally disposed on top surface of the base and a stopper is provided at outer end of the rail to restrict axial movement of the tool guiding block from moving beyond outer periphery of the base.

In another broad aspect of the present invention, a method of inspecting a welding tool associated with a heat staking machine comprises the steps of removably fixing a master welding tool on the tool aligning block using fastening means, engaging welding end of the master welding tool with the slot provided in front surface of the second guiding block such that tapered profiled of the welding end of the master welding tool exactly engage with corresponding tapered profile of the slot, adjusting the first dial indicator and the second dial indicator to bring 'zero' position of the dial scale reading to match with needle position of the dial indicator, removing the master welding tool from the tool aligning block and removably fixing the welding tool that is to be mounted on the heat staking machine on the tool aligning block using fastening means.

[008] Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[009] The present invention will be better understood fully from the detailed description that is given herein below with reference to the accompanying drawings of the present invention, which, however, should not be deemed to be a limitation to the present invention to the specific embodiments, but, are for the purpose of explanation and understanding only.

In the drawings:

[010] FIG.1 is a perspective view of an armature assembly that is positioned with reference to a welding tool of a heat staking machine during the welding process as per the known art.

[011] FIG.2 is an enlarged partial elevation of commutator of the armature assembly of FIG.1 in relation with position of the welding tool.

[012] FIG.3 is a perspective view of a fixture according to one embodiment of the present invention for inspecting the welding tool associated with the heat staking machine.

[013] FIG.4 is an enlarged cut sectional view taken along line A- A of one end of a first metallic plate of the fixture of FIG.3 according to one embodiment of the present invention.

[014] FIG.5 is an enlarged cut sectional view taken along line A- A of another end of the first metallic plate of the fixture of FIG.3 according to one embodiment of the present invention.

[015] FIG.6 is a cut sectional view taken along line B-B of the fixture of FIG.3 illustrating operational relationship between a tool fixing means and a tool alignment measuring means.

[016] FIG.7 is an enlarged view of circular portion of the tool fixing means of FIG.6 showing engagement relationship between the welding tool and the tool alignment measuring means according to preferred embodiment of the present invention.

[017] FIG.8 is a perspective view of the fixture of FIG.3 fixed with a master welding tool to preset first and second dial indicators in 'zero' reading according to preferred embodiment of the present invention.

[018] FIG.9 is a perspective view of the fixture of FIG.3 replaced with the welding tool that is to be inspected; therein the deviation of dial indicators needle from the zero reading shows variation in the alignment of the welding tool according to preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[019] While this invention is susceptible of embodiments in many different forms, the detailed description of the preferred embodiments with reference to the corresponding drawings shown herein below are to be understood that the present disclosure shall be deemed as an example of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described. In the description below, like reference numerals are used to describe the same, similar or corresponding parts in the several views of FIG 1- 9

[020] Referring to FIG.3, a fixture (100) according to one embodiment of the present invention comprises a tool alignment measuring means (101) and a tool fixing means (102) which are relatively disposed in an operating relationship with each other in a base (103). The base (103) is a metal plate having a rectangular shape adapted to accommodate the tool fixing means (102) at forward end (104) and the tool alignment measuring means (101) at backward end (105) thereof. According to one embodiment of the present invention, the tool alignment measuring means (101) has at least a leg (106) adapted to be removably mounted on top surface of the base (103) at one end (107) thereof and removably and horizontally receive a first guiding rod (108) at another end (109). According to another embodiment of the present invention, the leg (106) includes a first metallic plate (110) and a second metallic plate (111) which are identical in design and construction. Referring to FIG.4, according to one embodiment of the invention, the one end (107) of the metallic plates (110, 111) has at least a first hole (112) adapted to receive a pin (113) for positioning the metallic plates (110 & 111) on top surface of the base (103) and at least a second hole (114) for rigidly mounting with the base (103) via fastening means (115) such as bolts. Optionally, the one end shall be provided with a plurality of first holes for receiving a plurality of pin and a plurality of second hole for mounting the metallic plates with the base. Equal number of a first hole and a second hole is provided in the base (103) at the backward end (105) and along longitudinal edge thereof to removably support both the first and second metallic plates (110 & 111), Referring to FIG.5, according to one embodiment of the invention, the another end (109) is provided with a first through hole (116) perpendicular to planar surface of the metallic plates (110 & 111) for receiving ends of the first guiding rod (108). A second through hole (117) is made radially from longitudinal edge of the metallic plates (110 & 111) up to the first through hole (116) for arresting axial and rotational movement of the first guiding rod (108) using fastening means (118) such as bolts. Optionally, the first guiding rod includes two cylindrical rods which are identical in design and construction and horizontally disposed between the first and the second metallic plates one above another in a same plane vertically by inserting through the first through hole. Correspondingly, a plurality of first through hole and second through hole is provided in another end of the metallic plates.

[021] Referring to FIG.6, according to preferred embodiment of the present invention, the tool alignment measuring means (101) of the fixture (100) further comprises a first guiding block (119) that is inserted over the first guiding rod (108). The first guiding block (119), for demonstration purpose of the principles of working of the present invention, is made as a rectangular metal body and is disposed between the first and the second metallic plates (110 & 111) longitudinally. In one embodiment, the first guiding block (119) has a first through hole (120) provided longitudinally adapted to slidably receive the first guiding rod (108), wherein in another embodiment, a plurality of first through holes are provided corresponding to the number of the first guiding rod so as to slide along the first guiding rod between the first metallic plate and the second metallic plate. A second through hole (121) is provided in the first guiding block vertically adapted to receive a first dial indicator (122). A third through hole (123) is made perpendicular to the second through hole (121) from front surface of the first guiding block (119) up to the second through hole (121) adapted to receive a first fastening means (124) such as bolt thereby to arrest axial and rotational movement of the first dial indicator (122). At least a bore (125) is provided at bottom surface of the first guiding block (119) adapted to vertically receive first end of a second guiding rod (126), wherein the second guiding rod (126) is removably fixed via a second fastening means (127) such as bolt through a fourth through hole (128) that is provided perpendicular to the bore (125) from lateral surface of the first guiding block (119) up to the bore (125), which in turn arrest rotational movement of the second guiding rod (126).

[022] According to preferred embodiment of the present invention, the tool alignment measuring means (101) of the fixture (100) further comprises a second guiding block (129) that is vertically and slidably disposed along the second guiding rod (126). The second guiding block (129), for illustration purpose of the principles of working of the present invention, is made as a T' shape metal body and slidably disposed in the second guiding block as inverted T' profile. In one embodiment of the present invention, the second guiding block (129) comprises at least a first through hole (130) adapted to slidably receive the second guiding rod (126). In another embodiment, both left and right hand of the T' shape is provided with the first through hole adapted to slidably receive the second guiding rod. Second end of the second guiding rod (126) is provided with a washer (131), which is removably fixed by fastening means (132) such as bolts for holding an elastic member (133) such as compression spring to suspend the second guiding block (129) so as to reduce the impact of gravitational load of the second guiding block (129) and to facilitate manual uplifting of the second guiding block (129) easy during the inspection time. In preferred embodiment, the first guiding block (119) and the second guiding block (129) are disposed in the tool alignment measuring means (101) in an operating relationship with each other. In another embodiment, middle leg of the T' shape is projected vertically upward to maintain an abutment relationship with the first dial indicator (122) mounted in the first guiding block (119). According to one embodiment of the present invention, front surface of the second guiding block (129) has a slot (134) that is tapered along central axis thereof backwardly adapted to receive and align with welding end (135) of a welding tool (136) that is to be inspected, wherein the welding tool (136) is removably fixed on the tool fixing means (102). For explanation purpose of the present invention, welding end (135) of the welding tool (136) is considered as taper, hence the slot (134) provided in the second guiding block (129) is tapered backwardly in order to receive and mate with the tapered welding end (135). As such the tool fixing means (102) and the tool alignment measuring means (101) are relatively and operatively disposed in an engagement relationship with each other.

[023] According to preferred embodiment of the present invention, the welding tool (136) comprises an electrode (137) and an electrode holder (138). Referring to FIG.6 & FIG.7, the electrode (137) is an individual cylindrical body having the welding end (135) tapered to desired diametrical area so as to weld an armature conductor with the corresponding copper segment of the commutator without touching nearby copper segment. Another end (139) is flattened surface. The electrode holder (138) is rectangular metal body having provided with plurality of threaded holes (140) to removably mount on the tool fixing means (102) via fastening means such as bolts. In one embodiment, the electrode holder (138) is provided with a stepped diameter through hole (141) having a larger diametric portion (142) at forward end of the electrode holder (138) adapted to adjustably receive the electrode (137) and a smaller diametric portion (143) at backward end of the electrode holder (138) adapted to threadingly receive an adjustable rod (144). The adjustable rod (144) does abut with another end (139) of the electrode (137) and thereby adjust depth of weld as desired using a known gauge. After finishing the setting of desired depth of weld, the electrode (137) is rigidly mounted with the electrode holder (138) via a fastening means (145) such as bolt through a through hole (146) which is provided on top surface of the electrode holder (138) at forward end.

[024] According to one embodiment of the present invention, the tool fixing means (102) comprises a tool aligning block (147) for removably fixing the welding tool (136). The tool aligning block (147) is rectangular body having a centrally projected area (148) extended longitudinally on top surface thereof adapted to configure with a groove (149) extended longitudinally on bottom surface of the welding tool (136), hence to guide the welding tool (136) on top of the tool aligning block (147). The tool aligning block (147) is made identical to a tool holding means provided in the heat staking machine and removably mounted on a tool guiding block (150) via fastening means such as bolts. The tool guiding block (150) is a rectangular body horizontally and longitudinally guided over a rail (151) which is removably and longitudinally disposed on top surface of the base (103) at backward end (104) thereof via fastening means such as bolts and a stopper (152) is provided at extreme backward end of the rail (151) to restrict the tool guiding block (150) from moving beyond outer periphery of the base (103).

[025] According to preferred embodiment of the present invention, a mounting means (153) is fitted on to the first metallic plate (110) via fastening means (154) such as bolts. This mounting means (153) has a hole (155) which coaxially aligned with a hole (156) provided on the first metallic plate, as shown in FIG.4, adapted to receive a second dial indicator (157). The second dial indicator (157) is rigidly mounted with the mounting means (153) via a fastening means (158) through a threaded hole provided on the mounting means (153). The second dial indicator (157) is positioned in the first metallic plate (110) to maintain an abutment relationship with the second guiding block (129).

[026] According to preferred embodiment of the present invention, the method of working of the present invention is described herein below in detail with reference to FIG.8 and FIG.9. The FIG.8 shows a master welding tool (158) fixed on the tool fixing means (102) of the fixture (100) of the present invention. A master welding tool, generally referred as reference welding tool, is defined as a welding tool which is predefined as per the dimensional accuracy of the welding process with respect to the position of the electrode in the electrode holder in terms of depth of weld and position of the electrode in X direction and Y direction as shown in FIG. 9. Also, orientation of the master welding tool (158) in its entirety is defined with respect to the actual mounting position of the welding tool (136) in the heat staking machine during the welding process. As a first step in the inspection process, according to the present invention, the master welding tool (158) is located on to the tool aligning block (147) with the help of the centrally projected area (148) and removably fixed via fastening means such as bolts. Once the master welding tool (158) is rigidly fixed on the tool fixing means (102) as a welding tool is mounted on the tool holding means of the heat staking machine, the tool fixing means (102) is manually pushed towards the tool alignment measuring means (101), thereby to mate the tapered welding end of the master welding tool (158) with the slot (134) provided on the front surface of the second guiding block (129). To mate the slot (134) with the tapered welding end of the master welding tool (158), the second guiding block (129) is adjusted in the vertical direction along the second guiding rod (126) and in the horizontal direction along the first guiding rod (108) via the first guiding block (119). As the first dial indicator (122) and the second dial indicator (157) is in abutment relationship with the second guiding block (129), any deviation in the movement of the second guiding block (129) will be reflected in the reading scale (159) of the first dial indicator (122) and the second dial indicator (157). After engaging the tapered welding end of the master welding tool (158) with the slot (134) in the second guiding block (129), reading in both the dial indicators (122 & 157) shall be noted and then by rotatably adjusting dial (160) of the dial indicators 'zero' reading (161) in the scale of the dial indicators shall be matched with needle (162) position in both the first and the second dial indicators (122 & 157). Once the needle (162) is adjusted to 'zero' reading (161), then the master welding tool (158) shall be removed from the tool fixing means (102) of the fixture (100).

[027] Referring to FIG.9, the welding tool (136) that is to be inspected is fixed on the tool aligning block (147) and the tapered welding end (135) of the welding tool (136) is made engaged with the slot (134) provided on the second guiding block (129). During the engaged condition, if the needle (162) in the first dial indicator (122) does not coincide with the 'zero' reading (161), then it is understood that position of the electrode (137) with reference to the electrode holder (138) is not as per the requirement of welding operation and the electrode (137) is shifted in Y direction (163). And, if the needle (162) in the second dial indicator (157) does not coincide with the 'zero' reading (161), then it is understood that position of the electrode (137) with reference to the electrode holder (138) is not as per the requirement of welding operation and the electrode (137) is shifted in X direction (164). Any variation from 'zero' reading (161) in either of these first and the second dial indicators (122 & 157) shows that the welding tool (138) is not properly aligned and need correction in either

the electrode holder (138) or the electrode (137) or both. The cause for these variations could be any or combinations of dimensional inaccuracy in the groove (149) provided at bottom of the electrode holder (138), through hole (141) provided in the electrode holder (138) and the electrode outer diameter.

[028] It will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts disclosed in the foregoing description. Accordingly, the preferred embodiments described in detail herein are illustrative only and are not limiting to the scope of the invention, which is to be given the full extent of the appended.

We Claim:

1. A fixture (100) for inspecting a welding tool (136) associated with a heat staking machine, comprising:

a base (103) removably and slidably carry a tool fixing means (102) for fixing the welding tool as it is fixed in the heat staking machine;

a tool alignment measuring means (101) removably supported on the base (103), the tool fixing means (102) and the tool alignment measuring means (101) are disposed in an operating relationship with each other in the base (103), wherein

the tool alignment measuring means (101), comprising: at least a leg (106) having one end (107) removably mounted on the base (103) and another end (109) adapted to removably receive a first guiding rod (108);

a first guiding block (119) slidably disposed on the first guiding rod (108) and adapted to removably receive a second guiding rod (126); and

a second guiding block (129) slidably disposed on the second guiding rod (126) and provided with a slot (134) adapted to receive welding end (135) of the welding tool (136).

2. The fixture (100) for inspecting the welding tool (136) according to claim 1, wherein the welding tool (136) comprises an electrode (137) and an electrode holder (138).

3. The fixture (100) for inspecting the welding tool (136) according to claim 1, wherein the first guiding rod (108) is horizontally disposed on another end (109) of the leg (106) and the second guiding rod (126) is vertically disposed with the first guiding block (119).

4. The fixture (100) for inspecting the welding tool (136) according to claim 1, wherein the tool fixing means (102) comprises a tool aligning block (147) for removably fixing the welding tool (136), wherein

said tool aligning block (147) is made identical to a tool holding means provided in the heat staking machine and removably mounted on a tool guiding block (150), wherein

said tool guiding block (150) is horizontally guided over a rail (151) that is removably and longitudinally disposed on top surface of the base (103) and a stopper (152) is provided at outer end of the rail (151) to restrict axial movement of the tool guiding block (150) from moving beyond outer periphery of the base (103).

5. The fixture (100) for inspecting the welding tool (136) according to claim 1, wherein the leg (106) includes a first metallic plate (110) and a second metallic plate (111) which are identical in design.

6. The fixture (100) for inspecting the welding tool (136) according to claim 5, wherein said first and second metallic plates (110, 111) are vertically mounted on top surface of the base (103) at a spaced apart relationship, and comprises:

the one end (107) having at least a first hole (112) adapted to receive a pin (113) for positioning the metallic plates on top surface of the base (103) and at least a second hole (114) for rigidly mounting with the base (103) via fastening means;

the another end (109) provided with a first through hole (116) perpendicular to planar surface of the metallic plates (110, 111) for receiving ends of the first guiding rod (108); and

a second through hole made radially from longitudinal edge of the metallic plate up to the first through hole (116) for arresting axial and rotational movement of the first guiding rod (108) using fastening means.

7. The fixture for inspecting the welding tool according to claim 1, wherein the first guiding rod (108) includes two cylindrical rods which are identical in design and disposed between the first and the second metallic plates (110, 111) one above another in a same plane vertically by inserting through the first through hole (116).

8. The fixture (100) for inspecting the welding tool (136) according to claim 1, wherein the first guiding block comprises:

a first through hole (134) adapted to slidably receive the first guiding rod (108);

a second through hole (121) adapted to receive a first dial indicator (122);

a third through hole (123) perpendicular to the second through hole (121) form front surface of the first guiding block (129) up to the second through hole for arresting axial movement and rotational movement of the first dial indicator (122); and

at least a bore (125) at bottom surface adapted to receive top end of the second guiding rod (126); and

a fourth through hole (128) perpendicular to the bore (125) from lateral surface of the first guiding block (129) for removably fixing the second guiding rod (126) and for arresting rotational movement thereof.

9. The fixture (100) for inspecting the welding tool (136) according to claim 1, wherein the second guiding block (129) comprises at least

a first through hole (130) adapted to slidably receive the second guiding rod (126), wherein

bottom end of the second guiding rod (126) is provided with an elastic member (133) to suspend the second guiding block (129) so as to reduce impact of gravitational load of the second guiding block (129) and to facilitate manual uplifting of the second guiding block (129) easy during the inspection time.

10. The fixture (100) for inspecting the welding tool (136) according to claim 1, wherein the slot (134) provided in front surface of the second guiding block (129) is extended along central axis thereof backwardly thereby to receive and align with the welding end (135) of the welding tool (136).

11. The fixture (100) for inspecting the welding tool (136) according to claim 10, wherein the slot (134) is tapered backwardly.

12. The fixture (100) for inspecting the welding tool (136) according to claim 1, wherein the first guiding block (119) and the second guiding block (129) are disposed in the tool alignment measuring means (101) in an operating relationship with each other.

13. The fixture (100) for inspecting the welding tool (136) according to claim 1, wherein the second guiding block (129) and the first dial indicator (122) are disposed in the tool alignment measuring means (101) in an abutment relationship with each other.

14. The fixture (100) for inspecting the welding tool (136) according to claim 6, wherein the first metallic plate (110) is provided with a mounting means (153) adapted to mount a second dial indicator (157).

15. The fixture (100) for inspecting the welding tool (136) according to claim 1 and the preceding claim, wherein the second guiding block (129) and the second dial indicator (157) are disposed in the tool alignment measuring means (101) in an abutment relationship with each other.

16. A method of inspecting a welding tool (136) associated with a heat staking machine, the method comprising:

removably fixing a master welding tool (158) on a tool aligning block (147) of a tool fixing means (102) using fastening means;

engaging welding end of the master welding tool (158) with a slot (134) provided in front surface of a second guiding block (129) of a tool alignment measuring means (101) such that tapered profile of the welding end of the master welding tool (158) exactly engage with corresponding tapered profile of the slot (134);

adjusting dial (160) of a first dial indicator and a second dial indicator to bring 'zero' reading (161) of the dial scale reading to match with position of a needle (162) of the dial indicators;

removing the master welding tool (158) from the tool aligning block (147);

removably fixing the welding tool (136) that is to be mounted on the heat staking machine on the tool aligning block (147) using fastening means;

engaging welding end (135) of the welding tool (136) with the slot (134) provided in front surface of the second guiding block (129) such that tapered profile of the welding end (135) of the welding tool (136) exactly engage with corresponding tapered profile of the slot (134); and recording dial scale reading (159) in the first dial indicator (122) and the second dial indicator (157).

17. The method of inspecting the welding tool (136) according to claim 16, wherein the welding tool (136) has an electrode holder (138) provided with a through hole (141) longitudinally adapted to receive an electrode (137).

18. The method of inspecting the welding tool (136) according to claim 16, wherein the second guiding block (129) is disposed in the tool alignment measuring means (101) in an abutment relationship with the first dial indicator (122) and the second dial indicator (157).

19. The method of inspecting the welding tool (136) according to claim 16, wherein position of the electrode (137) with reference to the electrode holder (138) for welding armature conductor with commutator in axial direction of armature is recorded in the first dial indicator (122) and position of the electrode (137) with reference to the electrode holder (138) in radial direction of armature is recorded in the second dial indicator (157).

20. The method of inspecting the welding tool (136) according to claim 19, wherein axial variation in the position of electrode (137) with reference to the electrode holder (138) causes the second sliding block (129) to slide along a second guiding rod (126) up or down, which further actuate the first dial indicator (122).

21. The method of inspecting the welding tool (136) according to claim 18, wherein radial variation in the position of electrode (137) with reference to the electrode holder (138) causes the second sliding block (129) to slide along a first guiding rod (108) left or right through a first guiding block (19), which further actuate the second dial indicator (157).