Patent GB-191369-A (GB)
Title: Improvements in method of operating the cores of reciprocating electrical tools and the like
IPC: H02K33/00
Filed: 1922-12-07
Abstract: 191,369. Central Electric Tool Co., (Assignees of Weyandt, C. S., and Missien, E. J.). Jan. 4, 1922, [Convention date]. Percussive tools.-The core of a solenoid, such as is used in a reciprocating tool, is actuated by supplying alternate half waves of a single phase alternating current to the solenoid through a thermionic valve, the mass of the core and its length of stroke being so proportioned with regard to the pull of the coil and the supply fre quency that the coil is energized at the times when the core is at the ends of its stroke. A numerical example of weights and dimensions of a solenoid and core is given in the Specification. Figs. 1 and 6 show the use of a diode on an alternating current supply 30, 30<1> for energizing the solenoid operating the core. The core 4, Fig. 1, which strikes the tool stem 18, reciprocates in a non-magnetic tube 3 within the solenoid 25, the magnetic circuit of which comprises L- shaped radial bundles of iron laminµ 11, 14. The laminµ are joined by longitudinal bundles 9 at their outer ends and at their inner ends have lugs 15, Fig. 4, which enter recesses in the tube 3. The solenoid fills the interpolar space of the bundles, as shown by its section in Fig. 1, and is connected to the mains 30. 30<1> through a switch 32 and the diode 27. The switch 32 is closed by means of a magnet coil 33 which is connected directly across the mains by means of a finger switch 21 in the handle 2 of the tool. The diode filament 28 is heated by a transformer 29. Closure of the switch 32 allows the diode to pass alternate half waves of current through the coil 25 while the core travels from the ends of its stroke to the central position within the coil, its travel being completed by momentum during the periods when the diode passes no current. In the form shown in Fig. 6, the diode 26<a> is surrounded by a coil 42 connected to a coil 41 within the operating solenoid 25a for controlling the movement of the core. When the core arrives at its mid-position the increase of flux of the coil 25<a> induces a current in the coils 41 and 42 and the flux of the coil 42 abruptly stops the current flowing from the tubular anode 27a to the filament 28<a>, as shown at n and o in Fig. 8. If the armature tends to lag behind the current pulses, the points n, o slide down the curve towards the zero lines and the length of the pull on the core is increased. If the core leads on its normal speed the points n, o move up the curve and shorten the time of pull. The thermionic rectifier may be replaced by a mechanical device, as shown in Fig. 7, comprising a magnet coil 33a and switch arm 32a which closes a contact 37a to energize an operating coil 25a during one alternation and opens it during the next alteration. The coil 33<a> is controlled by a finger switch 21 as in the other Figures. A coil 42<a>, energized by an induced current in a coil 41 when the core 4 is at its central position, neutralizes the flux of the coil 33a and keeps the switch 32<a> in synchronism and so controls the movements of the core. The Specification, as open to inspection under Sect. 91 (3) (a) comprises also claims for reciprocating a solenoid core by supplying the coil with alternate current alternations at the moments when the core is at the end of its stroke otherwise than by means of thermionic valves; also claims for a striking tool constructed and oporated as described above. This subject-matter does not appear in the Specification as accepted.