GB2144958A - Arc welding electrode hand holders - Google Patents

Abstract

A welding handpiece as conventionally used for manual metal arc welding but including a make- break contact means 9, 12. This contact means is operable in sequence of rotations of a head portion 4 including electrode jaws 7 within a body portion housing the contact means. With the jaws in the open position the jaws are isolated from the supply current. As the head is rotated and after the jaws grip the electrode (not shown) the contact means provides a path for the current from the source to the electrode. Upon reverse rotation the contact means once again isolates the jaws. The jaws then release the electrode. <IMAGE>

Description

SPECIFICATION Welding handpiece This invention relates to welding handpieces, that is to say the hand held implements by which a welder moves an electrode relative to the work when performing a manual electric welding operation. Such handpieces conventionally comprise an insulated tubular handle and a head at one end of the handle. The head is rotatable between two positions and its movement causes jaws within the head to open and close, thereby enabling the welder to discard the butt end of a used electrode and replace it with a fresh electrode. One of the jaws is connected to a source of welding current by way of a flexible or pliable insulated conductor extending axially through the handle.

Such handpieces are well known and a more detailed description is not required herein.

In conventional handpieces one of the jaws is electrically connected to the supply conductor at all times and to avoid the inconvenience of switching off the welding current at its source, welders remove the electrode butt and insert a fresh electrode while the jaw is alive.

This can result in an electric shock being sustained by the operator when working in moist conditions. An object of the present invention is to overcome that disability by isolating the welding supply from the electrode within the handpiece.

The invention consists in an electric welding handpiece of the kind comprising a handle, a rotatable head defining an electrode clearance opening, a jaw within said head adapted to grip an electrode inserted through said opening, operating means adapted to move said jaw from its electrode gripping position when said head is rotated in one direction and return said jaw to that position when said head is rotated in the opposite direction and conductor means extending through said handle for the supply of current to an electrode when gripped by said jaw, said handpiece being characterized in that make and break contact means are incorporated in said conductor means operable in consequence of rotation of said head to make the current supply to the jaw after an electrode has been gripped and break the current supply to the jaw before the electrode has been subsequently released.

A preferred embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of a welding handpiece according to the invention in an isolated position.

Figure 2 is a sectional plan view of the handpiece shown in Fig. 1 but in the welding position.

Figure 3 is a plan view of the handpiece shown in Fig. 2.

Referring to the drawings, the handle of the handpiece 1 is in two parts, namely, a cylindrical main portion 2 adapted to be gripped by a welder and a generally tubular slide 3 telescopically and rotatably mounted in the main part at the front or head end thereof.

The slide 3 is adapted to receive a conventional handpiece head 4 in the same manner as is the head end of a conventional handle.

The slide 3 also houses a metal stem 5 terminating at one end in a semi-spherical projection 6 adapted to bear against the moving jaw 7 within the head 4 for the operation thereof when the head is rotated; that stem 5 (and its function) is similar to the stem conventionally found within the handle of prior known handpieces. In short, as described so far, the slide 3 and stem 5 support the head 4 and operate the jaws 7 thereof exactly as if the slide 3 were the head end portion of a conventional handpiece. In such a conventional handpiece the end 8 of the stem 5 remote from the head 4 is adapted for the connection thereto of a welding current supply lead but in the present embodiment of the invention that end 8 of the stem 5 is enlarged and formed with a flat contact face 9 and is so adapted to function as one of a pair of make and break contacts.

The other contact of the pair is a metal component in the nature of an unthreaded bolt 10. It is housed within the main portion of the handle 2 with its unheaded end 11 projecting towards the contact face 9 of the stem 5 within the slide portion 3 of the handle. It also terminates at that end in a flat second contact surface 12. At its other end 13 it is adapted to receive, and by means of a transversely extending socket set screw 14 or the like, make mechanical and electrical connection to an end of the supply lead 15.

The unthreaded bolt 10 is retained within the main portion 2 of the handle 1 by means of a radially, inwardly projecting, circumferential flange 16 therein against the rear face 17 of which the head of the unthreaded bolt 10 is lodged. A helical compression spring 18 sleeved upon the stem of the unthreaded bolt 10 and compressed between the front face 19 of the flange 16 and an abutment washer 20 fastened on the shank of the unthreaded bolt by a circlip 21 or the like serves to hold the unthreaded bolt resiliently in position with its shank extending towards the contact face 9 of the aforesaid stem 5 in the slide 3.

A second compression spring 22 is compressed between the front face 19 of the flange 16 and the inner annular end face 23 of the slide 3. The slide 3 is thus urged outwardly of the main portion 2 of the handle 1 but its movement is controlled and limited by a plurality of guide studs 24, preferably made of nylon, projecting from it into part helical slots 25 including 3 detent portion 26 formed in the main portion 2 of the handle 1.

In operation and assuming the head is in the non-gripping position, a welder may insert an electrode into the head 4 and rotate the head to cause it to advance into the slide portion 3 so as to cause the electrode to be gripped by the jaw 7. During that action the guide studs 24 are engaged with the detent portion 26 so as to ensure that the slide 3 remains stationary and at one end of its limit of travel; once the electrode is gripped by the jaws 7 the head 4 can no longer advance into the slide.

The head 4 is then urged, by the welder, into the main portion 2 of the handpiece 1 thus dislocating the studs 24 from the detent portions 26. Further rotation 4 of the head 4 causes a corresponding rotation of the slide 3.

This, simultaneously causes axial movement of the slide 3 and head 4 (as a result of the interaction of the guide studs 24 and the helical slots 25) so bringing the two contact surfaces 9 and 12 together. Similarly, a subsequent electrode release operation initially causes the contacts 9 and 12 to separate but when the slide studs 24 reach the ends of the slots 25 in which they move, the head 4 then rotates relative to the slide 3 and the electrode butt (not shown) is released.

Claims (8)

1. An electric welding handpiece of the kind comprising a handle, a rotatable head defining an electrode clearance opening, a jaw within said head adapted to grip an electrode inserted through said opening, operating means adapted to move said jaw from its electrode gripping position when said head is rotated in one direction and return said jaw to that position when said head is rotated in the opposite direction and conductor means extending through said handle for the supply of current to an electrode when gripped by said jaw, said handpiece being characterized in that make and break contact means are incorporated in said conductor means operable in consequence of rotation of said head to make the current supply to the jaw after an electrode has been gripped and break the current supply to the jaw before the electrode has been subsequently released.

2. An electric welding handpiece according to claim 1 wherein said make-break means includes a slide, telescopically and rotatably mounted within said handpiece with a front end able to receive a conventional handpiece head, a stem resiliently mounted within said slide, having one end threadedly engaged with said head and bearing against said jaws and another end constituting a first contact of said contact means, guide means for axially displacing said slide upon rotation of said handpiece head to bring said first contact into or out of contact with a second contact of said contact means.

3. An electric welding handpiece according to claim 2 wherein said guide means comprises a guide stud projecting radial and outwardly from said slide and slidably engaging a substantially helical slot in the handpiece.

4. An electric welding handpiece according to claim 3 wherein said guide means comprises at least one further stud and a respective slot.

5. An electric welding handpiece according to claim 3 or claim 4 wherein said slot, or each of them, including a detent portion. and a helical compression spring coaxially mounted about said stem acting between said handpiece and said slide for holding said guide stud. or studs, in said detent portion or portions, with said contacts separated.

6. An electric welding handpiece according to any one of claims 2 to 5 wherein said handpiece includes an unthreaded bolt the shank of which constitutes said second contact and the head of which is connected to a supply lead.

7. An electric welding handpiece according to Claim 6 wherein said unthreaded bolt is resiliently urged towards said handpiece head by a second helical spring coaxially mounted about said bolt, the head of said bolt being retained behind a radially and inwardly projecting flange on said handpiece and said second spring acting against the front of said flange and an abutment washer fastened on the shank of said bolt, in order that upon rotation of said handpiece head said contact faces are held in spring loaded engagement.

8. An electric welding handpiece substan tiaily as herein described with reference to the accompanying drawings.