GB743520A - Improvements in means for forming syringe barrels - Google Patents

Abstract

743,520. Glass manufacture. BECTON DICKINSON & CO. Nov. 6, 1951, No. 1237/55. Divided out of 743,477. Class 56. A mandrel 15 on which glass tubular blanks are shrunk to acquire the accurately sized and finished bores. required for hypodermic syringes, has axial and radial passageways 16, 33, 35 so that vacuum may, be applied to the space between the blank and the mandrel to collapse the softened glass on to the mandrel. The mandrels 15 are spaced around a turntable 11 which is indexed from station to station, the bottom ends 17 of the mandrels being tapered to wedge in sockets at the upper ends of hollow shafts 19 which are rotated by radial shafts 30 and gear wheels 28, 29 and are connected to vacuum at 25. The blank 39 rests upon a collar 35 supported by a spring 37 from a shoulder 38 on the mandrel, the spring maintaining the top of the blank spaced from the top of the mandrel until the vacuum pulls it down. Heating is effected by burners 44 on a segment 12 which oscillates so that the burner follows the mandrel from one station to the next, and then returns to heat the next blank, the blank abandoned by this burner being heated by the next burner on the segment, and so on. The mandrel passes through several heating stations, and a station where the tip 42 is melted and sealed, before the vacuum is applied through the axial bore 16, radial passages 35 and top grooves 33. The burner at the vacuumapplication station is traversed upwardly along the blank to compel the blank to shrink on to the mandrel, first at the bottom and then progressively towards the top. The blank is then allowed to remain on the mandrel for a cooling period, the different coefficients of expansion freeing it from the mandrel for removal therefrom. In Fig. 6, the blank 93 rests upon a shoulder 99 of the mandrel 96, and has an open top which is plugged by a valve-like member 103 having a centering spill 105 which is received in the axial bore 97 of the manydrel. Heat is applied by burners 100. and the burner at the shrinking station heats the whole length of the blank without traversing. When vacuum is applied, the blank is shrunk on to the mandrel and the valve member 103 beds into the upper end of the blank. The zone 34 at the base of the mandrel may be very slightly flared, i.e., the zone may be about one-eighth to three-sixteenths of an inch long and the taper may be about one-thousandth of an inch.