Patent GB-341534-A (GB)
Title: Improvements in and connected with magneto electric machines
IPC: H02K21/38
Filed: 1929-10-18
Abstract: 341,534. Dynamo-electric machines. NORTH & SONS, Ltd., Whippendell Road, and ALLEN, A. MASSEY-, 142, Queen's Avenue, both in Watford, Hertfordshire. Oct. 18, 1929, Nos. 31691/29 and 21746/30. [Class 35.] Magneto-electric and inductor machines.-In an ignition magneto particularly for use with aircraft engines, combined with automatic advance and retard mechanism comprising a centrifugal governor having bar-form weights disposed in longitudinal spaces in the rotor, the weights extend beyond the rotor at each end and are supported by levers mounted at the ends of the rotor. As shown applied to an inductor-magneto, the rotor comprises laminated iron segments c, c<1> clamped between end cheeks d, d<1> and having a central brass or other reinforcing ring f. The hubs g, g<1> of the end cheeks are fixed on a sleeve rotatably mounted on the spindle k. The sleeve carries also the distributer gearwheel o and the make-and-break cam p. Driving connection between the sleeve h and the spindle k is effected by a governor comprising bars q, q<1> located in the gaps between the inductor segments. At their ends the bars are supported by double-armed levers r, r<1>, Fig. 2, and s, s<1>, Fig. 4, pivoted at t on the end cheeks. The tails of the levers r, r<1> carry pins u, u<1> which engage faces on a cam l fixed on the driving spindle. The tails of the levers s, s<1> are formed with rounded edges and bear antifrictionally upon multiple leaf springs v, v<1> fixed to the hub g<1> of the end cheek d. When the spindle is driven in the anticlockwise direction as seen in Fig. 2, the tip portions of the lobes of the cam l press against the pins u, u<1> and the rotor is driven through the levers r, r<1> and pivots t. With increased speed, the governor weights q, q<1> move outwards and as the pins u, u<1> move inwards against the cam slopes, the rotor is advanced relatively to the driving shaft.. The degree of advance can be determined by appropriate design of the cam. Fig. 8 shows a modified arrangement for use in connection with engines, particularly certain types of aero engines in which a loss of advance is required at high speeds. The cam comprises two elements l<1>, l<2> of which the former is rotatable on the spindle and the latter is fixed to the spindle. Oppositely directed sockets v2, v<3> on the cams house compression springs w for pressing the two cams apart so that the declivities of the cam l<1> are kept against the pins u, u<1>. At the foot of each of these declivities, a reverse slope x is formed, which slope in the normal position shown is intersected by the acclivity y of the cam l<2>. Accordingly, the arrangement operates to advance the rotor relatively to the spindle until a speed is reached at which the pins u, u<1> arrive at the foot of the slopes of the cam l<1> and come in contact with the acclivities y of the cam l<2>. Further inward movement of the pins due to the governor action reduces the angle of advance of the rotor and this action takes place in opposition to the spring w. The outward movement of the governor weights is resisted by the leaf springs v, v<1> and in addition, a fusee spring z, Fig. 6, may be employed, one end being attached to a pillar 1 on the spindle, and the other end hooked in one of a number of holes 2 formed in a shell 3 attached to the rotor. Specification 235,274, [Class 35, Dynamo-electric generators &c.], is referred to. According to the first Provisional Specification, the weight supporting arms are in the nature of bell cranks, the secondary arms of which extend radially inwards and are formed with rounded ends engaging in notches formed on the spindle. If such arms are provided at both ends of the rotor, it is necessary to form a slot in the sleeve at one end in order to allow the secondary arm to pass through.