Patent GB-481165-A (GB)
Title: Method and means for spot-welding aluminium and aluminium alloys
IPC: B23K11/18
Filed: 1936-09-04
Abstract: 481,165. Electric welding aluminium or alloys thereof. ALUMINUM ALLOYS WELDING CORPORATION. Sept. 4, 1936, No. 24260. Convention date, Sept. 10, 1935. [Class 83 (iv)] [Also in Group XXXV] In spot-welding aluminium or aluminium alloy plates, particularly of #" or more in thickness, the electrodes are first pressed against the overlapping plates and a stabilized current of substantially constant ainperage is then applied only while said pressure remains substantially constant. When the current is cut off the pressure is then diminished until a predetermined lower pressure is attained which is maintained for a time before releasing entirely. The pressure may, if desired be increased while the material is hot after the lower pressure has been maintained for some time. Aluminium alloys containing manganese, magnesium, copper, or the alloy sold under the Registered Trade Mark "Duralumin" may thus be welded. Heating is effected in the body of the plates instead of at the exterior so as to prevent the formation of holes at the welding point. The electrodes 44, 45 have conical ends terminating in a surface 64. A steel plate 53 may be placed between the work and the electrode 45 to prevent penetration of the work thereby and the electrode 44 sinks into the part 50 without breaking the crust 62. In a modification slugs 70, 71 of the same material as the work mav be inserted as shown in Fig. 7 to increase the thickness of the welded spot. The pressure and current vary according to the nature and thickness of the material. The current mav vary from 35,000-150,000 amps at a voltage of 4-8. For Duralumin " plates “" thick a pressure of 80 to 100 lb. may be used, but for softer materials it may be as low as 60. The predetermined lower pressure for an original pressure of 100 or 60 pounds should not be below 80 or 451b. respectively. For welding plates of 51S material 3/16" thick, an amperage of 40,000 may be used, the time being ¥ of a second. Welding may be effected by electrodes 44, 45 inclined to form an acute angle with each other and carried by arms 20, 27 connected to the terminals of the secondary of a transformer. A water cooled steel block 39 is inserted between the portions 37, 38 of the arm 27 to serve as a high resistance to stabilize the current. The electrodes may each be grounded through resistances 80, 81 to dissipate parasitic voltages. The electrode 44 is forced down by toggle levers 17, 21 and adjustable spring 24 provided with a pressure gauge 26, the toggles being operated through a link 16 engaging a cam 12 on a shaft rotated by reduction gear from a motor. The cam has a substantially flat portion 13 and a cylindrical portion 14 so that the pressure may rise gradually as shown at 55, Fig. 8, to a maximum, whereupon between points 59 and 66 current is applied while maintaining the pressure constant. After the current is cut off the pressure decreases due to penetration of the work by the electrode as shown at 65 and remains for an interval at such pressure, which is finally gradually reduced to zero, as shown at 68. The current is controlled by a contact 56 on the cam shaft and a switch 58. In order to effect a rise of pressure at the end of the period 67 the cam may be formed with a projection. The increased pressure is maintained for a time and then gradually reduced to zero. After welding the first spot the current may be increased in order to weld the second spot. The process may be combined with a hardening or tempering process. The Specification as open to inspection under Sect. 91 states that the steel block 39 may be replaced by a variable resistance and that the machine may be employed for welding other materials than aluminium. This subject-matter does not appear in the Specification as accepted.