with reference to the drawings wherein like reference numerals designate corresponding parts in the several views , a welding device 10 having a electrode driving system according to the present invention is best shown in fig1 . the welding electrode 11 is a continuous welding electrode having a welding flux coating formed on the outer surface of a metal core 12 . the flux coating has short flux sections 13 evenly spaced from neighboring sections by gaps 14 of an equal distance . such continuous welding electrode 11 enables the welding operation to be carried out in a continuous manner to provide a high quality weld having a smooth surface . two slidable carriages , namely a left slidable carriage 15 and a right slidable carriage 16 are slidably mounted to the enclosure 17 by two upper mounting bolts 18 and 19 , and two lower mounting bolts 20 and 21 respectively as best shown in fig1 , 2 , 3 and 6 . the left slidable carriage 15 and the right slidable carriage 16 are identical in construction but having different lengths ; namely , in the example shown , the left slidable carriage 15 is longer than the right slidable carriage 16 by one flux section 13 plus one gap 14 . the construction of the left slidable carriage 15 is shown in fig4 , 5 , 7 and 8 and described herein in detail . the slidable carriage has a main body portion 22 having an upper ball bearing sleeve 23 and a lower ball bearing sleeve 24 located on the outer left side of the main body portion 22 and extending horizontally and parallel to one another . the mounting bolts 18 and 21 are inserted through the upper ball bearing sleeve 23 and lower ball bearing sleeve 24 for slidably mounting the slidable carriage to the enclosure 17 of the welding device 10 . an elongated casing 25 extends outwardly and forwardly from the middle of the front edge of the main body portion 22 . the elongated casing 25 has a generally c - shaped cross sectional shape as best shown in fig6 . the main body portion 22 has two parallel rearwardly extending side walls 26 and 27 with a rotatable crank shaft 28 rotatably mounted thereto . the rotatable crank shaft 28 has a drive shaft 29 and an offset rotary shaft 30 . the mounting between the offset rotary shaft 30 and the side wall 27 is such that the rotational movement of the offset rotary shaft 30 will transform into a linear reciprocating movement of the main body portion 22 relative to the mounting bolts 18 and 21 . a drive housing 31 is located at the rear of the enclosure 17 a drive crank shaft 32 is rotatably mounted in the drive housing 31 and it is coupled to a speed controlling gear box 33 which is , in turn , coupled to the driving gear 34 rotatable by an electric motor ( not shown ). coupling rods 35 and 36 are linked between the rotatable crank shaft 28 and the drive crank shaft 32 , so that rotation of the drive crank shaft 32 by the stepping motor will cause the offset crank shaft 30 to rotate accordingly for imparting the reciprocating motion of the main body portion 22 . in the meantime , the stepping motor will also initiate a drive wheel 37 mounted horizontally on the opposite side of the main body portion 22 as shown in fig4 . the rotation of the drive wheel 37 will cause two cam wheels 38 and 39 to rotate in the same direction . two pivotal arms 40 and 41 are pivotally mounted in a cantilever manner on the main body portion 22 . these pivotal arms 40 and 41 are pivotable relative to the mounting pins 42 and 43 respectively and they are normally maintained in a horizontal position parallel to one another by two tension springs 44 and 45 respectively mounted between the pivotal arms 40 and 41 and the main body portion 22 . at the normal position , abutment pins 46 and 47 provided on the pivotal arms 40 and 41 are in contact engagement with the periphery edge of the cam wheels 38 and 39 and the free end portion of the pivotal arms 40 and 41 abut two slider pins 48 and 49 slidably mounted on the main body portion 22 . two elongated rotatable bars 50 and 51 are rotatably mounted in the elongated casing 25 in a mutually parallel manner by support bearings 52 , 53 , 54 and 55 . three gripping plates 56 , 57 and 58 , and 59 , 60 and 61 are mounted on the rotatable bars 50 and 51 respectively as shown in fig4 , 5 and 7 adjacent to the support bearings 52 , 53 , 54 and 55 . the gripping plates 56 , 57 and 58 are reinforced by support blocks 62 , 63 and 64 , the gripping plates 59 , 60 , and 61 are reinforced by support blocks 65 , 66 and 67 respectively . two pivotal rods 68 and 69 are respectively mounted on the rotatable bars 50 and 51 adjacent to the end support bearing 52 , and torsion springs 70 and 71 are mounted between the pivotal rods 68 and 69 and the rotatable bars 50 and 51 respectively . the pivotal rods 68 and 69 abut the slider pins 48 and 49 . when the slider pins 48 and 49 are pushed inwards by the pivotal arms 40 and 41 , the slider pins 48 and 49 will push the pivotal rods 68 and 69 respectively to turn the rotatable bars 50 and 51 accordingly . the turning of the rotatable bars 50 and 51 will , in turn , turn the gripping plates 56 and 59 , 57 and 60 , and 58 and 61 away from one another to an open position . continue rotation of the cam wheels 38 and 39 will subsequently return the pivotal arms 40 and 41 to the parallel horizontal positions to release the pushing force on the slider pins 48 and 49 , therefore the tension springs 44 and 45 and the torsion springs 70 and 71 will turn the rotatable bars 50 and 51 back to the original position . the gripping plates 56 and 59 , 57 and 60 , and 58 and 61 will accordingly return to a closed position adjacent to one another as shown in fig7 . at the closed position , the gripping plates will grip the metal core of the welding electrode through its gaps 14 , while at the open position , the gripping plates will release its grip on the welding electrode to allow it to advance forward . the gripping plates will be at the closed position when the left slidable carriage 15 is in the forward moving stage in its reciprocating motion so that the welding electrode 11 is advanced forward by the left slidable carriage 15 . as shown in fig1 the right slidable carriage 16 is identical in construction and operation to the left slidable carriage 15 but are 180 degrees out of phase with one another ; namely the left slidable carriage 15 is one flux section 13 plus one gap 14 longer than the right slidable carriage 16 such that gripping plates of the left slidable carriage 15 and right slidable carriage 16 are located at alternate gaps 14 of the welding electrode 11 . thus , the gripping plates on the right slidable carriage 16 are at the open position when the right slidable carriage 16 is in the return moving stage while the left slidable carriage 15 is at the forward moving stage with the gripping plates in the closed position , so that the welding electrode 11 is advanced forward by the left slidable carriage 15 ; and when the right slidable carriage 16 is in the forward moving stage with its gripping plates located in the closed position , the left slidable carriage 15 will be in the rearward moving stage with its gripping plates at the open position , so that the welding electrode is advanced forward by the right slidable carriage 16 . in this manner , the welding electrode 11 is continuously advanced alternately by the left slidable carriage 15 and the right slidable carriage 16 by their reciprocating movement . while this invention is susceptible of embodiment in different forms , the drawings and the specification illustrate preferred embodiments of the invention , with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention , and the disclosure is not intended to limit the invention to the particular embodiments described .