rod p 11 can also pivot on a fixed shaft p 16 connected to the top board 8 guiding board p 18 is fixed along top board 8 and has an extended rectangle guiding hole p 17 pin p 19 is located at the upper end of second rod p 12 and is inserted into guiding hole p 17 third rod p 13 is integrated with fourth rod p 14 by pin p 20 and they can also pivot about pin p 20 the upper end of third rod p 13 can pivot on the lower end of the first rod p 11 about pin p 21 the upper end of fourth rod p 14 can pivot on the lower end of the second rod p 12 about pin p 22 the lower end of third rod p 13 can pivot on pin p 24 of bracket p 23 which is fixed on the upper surface of pushing board p 30 guiding board p 26 is fixed on the upper surface of the pushing board p 30 and has an extended rectangular guiding hole p 25 pin p 27 is fixed at the lower end of fourth rod p 14 and can slide in guiding hole p 25 pushing board p 30 is pivoted in the counterclockwise direction by a spring p 28 as shown in fig3 the pushing board p 30 is located parallel to holding board h 11 next a first urging or biasing device d 1 of pushing board p 30 is explained spring d 12 is hooked between a projection d 11 which is fixed at the rear surface.