1. Outline of HP bond
HP(Hot Press) type bond is shown as below Figure 1.
This is to make connection the conducting current wire to the bond terminal of almost flat plate with tightening tool.
It makes slits of grating pattern at reverse side of terminal and brazing to the rail as same manner as soldering works.
Fig.1 HP type rail bond
Fig2. Principle of HP bond brazing method
Up to today, low temperature soldering connection type bond is to cope with rail vibration by the strength of solder itself. Therefore, it’s durability seems to be unreliable because of proceeding destroy at the part of solder by rail vibration.
However, it can be solved this problem with our HP type bond on the quite new idea.
The remarkable characteristic of HP type bond is designed to be high durability with this serious vibration by the connection strength ( terminal surface and solder, solder and rail surface) of solder itself.
Principle of HP bond (to be brazed on the flat surface of rail) is to be excellent for holding high durability of vibration and included many ideas to cope with vibration for terminal type forming rail, etc. It shows superior durability compared with welding method.
This HP type bond is easy for removal and able to fix again (reuse) without metamorphic structure to the rail because of low temperature soldering connection style.
2. Background of the technology
It is very important for HP bond method to keep the quality of solder because this terminal is to be brazed on the rail.
It was targeting to realize connection strength of solder, PH free, CD free and melting point at low temperature. Finally it was successful to develop new solder material (Sn-Ag-Zn eutectic alloy) on the support and direction of Machinery Electronics Laboratory of Fukuoka Prefecture Industrial Technology Center. (Patent registered No.48 48331)
Further, HP type rail bond method targeting to both AC electrification section and Non electrification section has been also developed jointly collaboration with Railway General Technology Laboratory of Japanese government sector. (Patent registered No.4524324)
Afterward, we took care of another development for rail bond for DC current. The diameter of conducting current wire is to be different between DC electrification section and AC electrification/ non electrification section.
The voltage at DC electrification section is lower than AC electrification section.
(for example, 1500 volts at DC against 20,000 volts at AC) Therefore, DC electrification section needs bigger current. It means the bigger diameter of conducting current wire essentially needed to DC electrification section.
The weight of bond for DC section will be heavier than AC section due to the bigger diameter of conducting current wire at DC section which is to be affected badly to vibration stress to the terminal.
This is big question on the way of development which is subject of reducing this vibration stress to the terminal.
In this field, it was successful to make new better shape of terminal which is possible to reduce maximum 14 percent against the stress counted to the same bond for AC.
It was possible to absorb and spreading the stress after shifting stress point to inner terminal side.
This is joint collaboration with Machinery Electronics laboratory of Fukuoka Prefecture Industrial Technology Center. (Patent Application No. 20121-85354)
Fig.3 New type rail bond
It was realized superior durability against rail vibration compared with welding type bond.
3. Characteristics of HP type rail bond
a) High durability
- It was cleared 2 million times with hammering vibration test in the condition of vibrating acceleration 1.2 to 1.8 million G (this is equal to the vibration value at the severe vibrating section of Kagoshima main railway) and confirmed more than 60 percent remaining brazed area at terminal.
b) Pb free and Cd free solder is to be used
- Sn-Ag-Zn eutectic alloy is to be used.
c) Heat affection is to be minimized to rail
- Melting point of solder material is low at 216 degree C.
- It is nothing to have metamorphic structure to the rail and easy to remove and fix again (for reuse).
d) Simplify working
- It is possible to simplify working at site. (bond terminal is to be crimped by special tool and brazed with heat up above the terminal by burner)
- It can be worked in short time and finished conformity.
