Patent GB-315783-A (GB)
Title: Improvements in or relating to electric motors
IPC: H02K33/12
Filed: 1929-02-04
Abstract: 315,783. Weyandt, C. S. July 18, 1928, [Convention date]. Reciprocating machines; motors, cooling; casings.-A portable electric motor unit comprises a motor of reciprocating or other type, a rectifying " valve" device through which power is supplied to the motor and a casing structure in which are housed both the rectifying device and the motor. The rectifier mav be carried by a part of the casing structure which is detachable from the part of the structure which houses the motor itself and the rectifier and motor may be cooled by an air current which may be produced by a fan forming a part of the portable unit or separate therefrom. The Figure shows applications to percussive tool motors embodying copper cuprous oxide rectifiers of the type described in Specification 314,939 [Class 38 (ii), Electric currents, converting, &c.]. Fig. 1 shows a tool in which the core 5 is reciprocated in a tubular guide 6 by field coils 3, 4 housed within groups of laminae 9, 10, 11 having rings 14 entering slots in the guide and secured by screwed rings 15. The motor is enclosed by a magnetic housing 2 and end members 16, 22 secured together by tie rods. The former supports the tool guide 17, which is restrained by a resilient transverse member 18, and the latter contains a snap-on switch 30 and a back buffer comprising a spring 25, spring case 29 and transverse leaf spring 24. It also forms a housing for the rectifier which may consist of a number of dry unit cells mounted between brackets 33 and separated by insulating washers 39. These units are connected between the alternating supply cable 37 and the coils 3, 4 and if the time constant of the circuit be high the number of units required may be kept small as described in Specification 314,939 [Class 38 (ii), Electric currents, Converting &c.]. The rectifier is cooled by air holes 23<a> in the housing and in an alternative form the rectifier is mounted in an offset duct on the tool handle to which is connected an air supply pipe which also contains the electric leads. The air passes over the rectifier and through air passages in the motor to exhaust holes in the front cover 16. For this, an independent blower 96, Fig. 4, is used, mounted in a portable housing 88 and driven by a motor 93 fed by a generator 82 which also supplies current through the rectifier 40 to the reciprocating motor field coils 3, 4. The housing has two plug connectors 91, 97 for the blower and tool motors respectively and the plug 97 also serves to transmit air to the pipe 66 which is plug-connected to the tool handle offset duct. When the switch 99 is on contact 100 the blower supplies air to the tool motor whether the tool is running or idle and when it is on contact 102 the blower motor is controlled by the tool motor switch 63. The motor-driven blower plant and the coupling pipe form no part of the present invention. The rectifier may occupy positions in the unit other than in or adjacent to the handle member. It may, for instance, be mounted in an annular casing either within or without the motor housing. Figs. 5 and 6 show a tool upon which the rectifier 157 and blower 149 are directly mounted and in which a low frequency supply 160 is used for the field coils 162, 163 and a threephase high frequency supply 161 for the blower motor coils 164. The rectifier units are mounted radially around the blower motor in a casing 156 perforated at 159 for entry of the cooling air which passes over the rectifier, through passages 151 to the impeller chamber 152, through a duct 154 and openings 136 to longitudinal passages in the tool motor and exhaust ports 155. A lead 171 common to the two supplies contains the tool switch 138 which breaks the circuit of the rectifier and both field coils 162, 163, and a second switch 177 breaks two phases of the high frequency motor. The Specification as open to inspection under Sect. 91 (3) (a) comprises also the following:- The use of rectifying means, not necessarily of the valve type and not necessarily included in the same housing as the motor which it supplies is described. The rectifying means may form a portable unit as shown in Fig. 5 (Cancelled) containing a motor-driven blower 92, 96 and a rectifier 120 so mounted as to be cooled by air which is drawn in through holes 125 in the housing and ejected through an air pipe coupled to the housing at 122. A form is also described in which the tool contains a cooling motor for its reciprocating motor as in Figs. 5 and 6 and in which the rectifier is mounted as a portable unit with a separate motor-driven blower for cooling it, this unit being connected to the tool by an air pipe and electric leads and to the two electric supplies by a plug connector. An independent rectifier is shown in Fig. 10 (Cancelled) comprising two sets of dry disc rectifier units 208 in a perforated housing the end walls of which have members 209, 213 for receiving the cables 211, 214 which are respectively connected to the alternating-current supply and the operated motor. A perforated plate secured to the housing enables the rectifier to be hung on a hook or the like. This subjectmatter does not appear in the Specification as accepted.