Abstract:
An improved modular trigger assembly for an arc welding gun includes a trigger housing pivotably mounted to a welding gun. A switch is mounted inside the trigger housing and is actuated by movement of the trigger housing. The trigger housing also includes a slideable locking crescent having a first end near a finger surface of the trigger housing. This locking crescent is so arranged that pressure on the first end surface serves both to depress the trigger and to lock the trigger in the depressed position.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an improved arc welding gun and particularly to an improved trigger assembly for such welding guns. 
     The various features of this invention are well suited for arc welding guns employing continuous feed, consumable electrodes. Although originally developed for welding guns which use a shielding gas from a separate source, the improvements of this invention are equally valuable when used in other types of welding guns, such as guns used in welding operations in which the electrode conveys material to the welding arc which generates a shielding medium at the arc or in submerged arc welding operations. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an improved trigger assembly for use in arc welding guns. According to this invention, an arc welding gun is provided with a modular trigger assembly which is pivotably mounted on the gun. A switch is mounted inside the trigger such that the trigger and the switch can be replaced as a unit. Because welding gun operators are usually gloved, a large trigger is generally required. By placing the switch inside the trigger, the volume of the trigger is utilized to reduce the volume of components which extend into the handle of the welding gun. 
     Preferably, the trigger assembly also includes a leaf spring which bears against the gun to bias the trigger away from the gun and also bears on and actuates the switch when the trigger is depressed. The preferred embodiment of the trigger assembly also includes a locking member slideably mounted in the trigger. This locking member is arranged such that the trigger can simultaneously be depressed and locked in the depressed position by depressing only the locking member. This arrangement is simple to use, for an operator is not required to depress two separate elements to lock the trigger, as with some welding guns of the prior art. Instead, the single motion of pressing the locking member performs both functions. Furthermore, the locking member can be released simply by momentarily depressing the trigger after the locking member has been set. Thus, no pulling motions and no coordinated manipulation of two or more elements are needed to either set or release the trigger. 
     The invention, together with further objects and attendant advantages, will be best understood by reference to the following description taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view in partial cutaway of an arc welding gun including a preferred embodiment of the trigger assembly of this invention. 
     FIG. 1a is a cross-sectional view taken along line 1a--1a of FIG. 1. 
     FIG. 2 is a detail view of the trigger assembly of FIG. 1. 
     FIG. 3 is a sectional view taken along line 2--2 of FIG. 2. 
     FIG. 4 is a detailed view of the trigger assembly of FIG. 2 showing the trigger locked in the down position. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings, FIG. 1 represents an arc welding gun 10 which incorporates a presently preferred embodiment of the trigger assembly of this invention. This welding gun is coupled to a quick connect connector 140 by means of a cable 70. In general terms the cable 70 serves to pass continuous lengths of consumable electrode 20, shielding gas, and welding current from the quick connect connector 140 to the welding gun 10. The quick connect connector 140 comprises a connector body 142 and a connector socket 144, and in use the socket 144 is coupled to a conventional source of continuous lengths of electrode, such as a wire feeder unit (not shown) and to conventional sources of shielding gas and welding current. Also, a pair of control leads 146,148 for controlling the wire feeder unit (not shown) is coupled to the socket 144. These control leads 146,148 are connected by the connector 140 to a pair of control conductors 14,16 in the cable 70. The conductors 14,16 are switched at the switch assembly 12 by the gun operator to control feeding of the electrode 20 to the gun 10. 
     The welding gun 10 in FIG. 1 includes an insulating handle 24, a cable clamp 30, a gooseneck 50, and a head assembly 56, in addition to the trigger assembly 12. As shown in FIG. 1, one half of the handle 24 has been removed to show the internal components of the gun 10. In use, the handle 24 would be assembled to completely enclose the internal parts of the gun 10 to protect the operator from exposure to welding current and associated heat. Preferably, the handle 24 is formed from a rugged insulating plastic in two halves which are reversably fastened together. The cable clamp 30 serves to secure the cable 70 in the gun 10 by firmly gripping the power conductors of the cable 70. The clamp 30 is securely connected to the gooseneck 50, by means of silver solder, for example, and serves to conduct welding current from the power conductors to the gooseneck 50. 
     The gooseneck 50 is a curved sleeve connected at one end to the clamp 30 and at the other end to the head assembly 56. The gooseneck 50, which is insulated by a silicone sleeve 52, is surrounded by an armor sleeve 54 which is held in place by insulating rings 58,60. The head assembly 56 conducts the welding current to a replaceable contact tip 62, which is preferably a locking contact tip as disclosed in U.S. Pat. No. 3,514,570. The contact tip 62 conducts welding current to the electrode 20 in the conventional manner. A gas nozzle 64 surrounds the contact tip 62 and conducts shielding gas to the welding arc. 
     Thus, the welding gun 10 conducts both shielding gas and welding current from the cable 70 through the clamp 30, the gooseneck 50, and the head assembly 56 to the region of the arc. 
     The trigger assembly 12 is shown generally in FIG. 1 and in greater detail in FIGS. 2-4. The trigger assembly 12 includes a trigger housing 90 molded from a heat resistant, insulating plastic material. The housing 90 defines two trigger pivots 92,94 which are sized to fit within matching trigger sockets formed in the welding gun handle 24. The trigger pivots 92,94 pivotably mount the trigger assembly 12 to the handle 24. 
     Mounted in the trigger housing 90 are a leaf spring 96 and a sealed two position switch 98 having a pair of terminals 100,102 and an actuating button 104. The switch 98 operates to connect and disconnect the terminals 100,102 depending on the position of the actuating button 104. As installed in the welding gun 10, the switch terminals 100,102 are connected to the control leads 12,14, and the switch operates to control the feeding of the electrodes 20 to the gun 10. 
     The leaf spring 96 bears on a contact surface 106 formed in the handle 24 and simultaneously acts to bias the trigger assembly 12 away from the handle 24 and to contact the actuating button 104. One advantage of this arrangement is an economy of parts. A second advantage is that the switch 98 is protected from excessive switching forces; the housing 90 defines a surface 108 which limits the range of travel of the spring 96 to protect the switch 98 from over travel of the trigger assembly. 
     The elements described above provide a self-contained, modular switching assembly which is well suited for use in welding guns where momentary trigger actuation is required. Some applications, however, require a trigger which can be locked in position, and for these applications, a spring loaded locking crescent 110 is provided. 
     This locking crescent 110 is slideably mounted in a curved groove 112 formed in the trigger housing 90 and is spring biased by a coil spring 114 into the position shown in FIG. 2. The locking crescent 110 defines a first end section 116 adjacent the finger surface 118 of the housing 90. This end section 116 is preferably serrated to provide a slip free surface. The other end section 120 is provided with a lip 122 sized to engage a mating lip 124 formed in the housing 24. 
     In operation the locking crescent 110 allows an operator to either lock the trigger down or release the trigger from its locked position with a single squeeze of the trigger assembly 12. When pressure is applied to the serrated end section 116 of the locking crescent 110, the pressure pivots the trigger housing 90 and actuates the switch 98. Simultaneously, this pressure slides the locking crescent 110 from the position shown in FIG. 2 to that shown in FIG. 4, where the lip 122 on the locking crescent 110 engages the lip 124 on the handle 24 to lock the trigger housing 90 in the down position. Once the trigger housing 90 is locked down, momentary pressure on the finger surface 118 disengages the locking crescent 110 from the lip 124, and the spring 114 then returns the locking crescent 110 to the position shown in FIG. 2. This unlocks the trigger housing 90. 
     Thus, it can be seen that the trigger assembly 12 can be locked or unlocked by momentary pressure. The operator is not required to manipulate more than one element to lock the trigger, nor is any pulling action required. This trigger assembly 12 can be conveinently locked and unlocked by a gloved operator and it is, therefore, well suited for use in welding guns. 
     Of course, it should be understood that various changes and modifications to the preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. It is, therefore, intended that such changes and modifications be covered by the following claims.