Method for coupling a protective net to flexible tube for a sprinkler
A structure and a method for coupling a protective net to a flexible tube, comprising shaping the flexible tube, wrapping the flexible tube with the meshed protective net made of stainless steel, and welding both ends of the flexible tube to both ends of the protective net. A solution heating process for the flexible tube and welding process for the flexible tube and the protective net are simultaneously carried out under the same condition in the same furnace. As a result, the protective net and the flexible tube are uniform in terms of physical properties. Furthermore, intergranular corrosion of stainless steel by inevitable stress generated upon welding a flexible tube and a protective net using any one of conventional methods, and crevice corrosion between a welding ring and a flexible tube, are prevented.
1. A method for coupling a protective net to a flexible tube for a sprinkler, comprising:
wrapping a flexible tube having crest and valley portions with a meshed cylindrical protective net made of stainless steel wire, in a manner such that inward parts of straight tube portions of both ends of the flexible tube are wrapped with both ends of the protective net;
winding both ends of the protective net with stainless steel wire of larger diameter than the wire of the protective net, so as to fix temporarily both ends of the protective net to the inward parts of the straight tube portions;
applying welding material to both ends of the protective net;
fusing the welding material so that the fused welding material is introduced between both ends of the protective net and the inward parts of the straight tube portions, thereby welding the flexible tube and the protective net, while solution heating the flexible tube so as to remove stress and work hardening; and
unwinding and removing the steel wire from both ends of the protective net.
2. The method as set forth in claim 1 , wherein the flexible tube is made of austenite stainless steel, and the welding material is Ag-Mn type, Ag-Cu type, or Ni-Cr type brazing material.
3. The method as set forth in claim 2 , wherein the brazing material is BNiCr type brazing material.
4. The method as set forth in claim 1 , wherein the temperature for heating and welding is 1,050° C. to 1,150° C.
5. A method for coupling a protective net to a flexible tube for a sprinkler, comprising:
wrapping a flexible tube having crest and valley portions with a meshed cylindrical protective net made of stainless steel wire, in a manner such that inward parts of straight tube portions of both ends of the flexible tube are wrapped with both ends of the protective net;
applying welding material to both ends of the protective net; and
fusing the welding material so that the fused welding material is introduced between both ends of the protective net and the inward parts of the straight tube portions, thereby welding the flexible tube and the protective net, while solution heating the flexible tube so as to remove stress and work hardening,
wherein the welding material is applied to both ends of the protective net and outward parts of the straight tube portions not wrapped with both ends of the protective net, and then an end of a reducer or a nipple is fitted in the straight tube portions, the reducer or the nipple is welded to the straight tube portions of the flexible tube while heating the flexible tube; and
wherein the reducer or the nipple is formed, at one end thereof, with a first large inner diameter portion and a second large inner diameter portion having the inner diameter larger than the inner diameter of the first large inner diameter portion, the end of the protective net is welded to the flexible tube while being fitted in the second large inner diameter portion, and the outward part of the straight tube portion not wrapped with the end of the protective net is fitted in the first large inner diameter portion.