GB138090A - Improvements in speedometers for vehicles and the like - Google Patents

Abstract

138,090. Dayton Engineering Laboratories Co., (Assignees of Kettering, C. F.). Aug. 28, 1918, [Convention date]. Speed-indicator transmission mechanism; magnetic speed indicators.-In speed-indicating apparatus, means are provided whereby the movement of a vehicle is communicated indirectly to a speed indicator of the magnetic-drag type through an electric motor, the speed of which is governed by the speed of the vehicle by means of a rheostat driven by the motor and a contact carried by an escapement device controlled by a magnet energized intermittently from the vehicle wheel, this mechanism operating as a hunting switch. In the form shown in Figs. 1, 2, and 3, a motor 50 receiving current from a battery 110 serves to drive the shaft 42 of the speed indicator 40, the current being controlled by the frequency with which spring contacts 119, 120 are closed by a pin 122 on the vehicle wheel. Driven from the shaft 42 by reducing-gearing is a wheel 65 carried by a stub-shaft 66, on which is mounted a collecting-ring 72 in circuit with the commutator brushes 59, 60 and a rheostat 76 carried by an insulating-ring 75. Also mounted on the shaft 66 is an escapement device comprising two wheels 81, 85 connected by a spiral spring 88 and a pin 83 on the lower wheel engaging a slot 86 in the upper wheel. A wiper contact 78 adapted to move over the rheostat is carried by the underside of the wheel 81, connexion between which and the disk 72 is effected by a spiral spring 91. Pallets 102, 103, pivoted on a post 100 on the base-plate 47, are provided to engage the wheels 81, 85, a spring 106 serving normally to hold the pallet 102 in engagement. Formed in one with the pallets is the armature 101 of an electro-magnet 104 which is in circuit with the battery and the contacts 119, 120. In operation, when the vehicle is at rest, the contact 78 is out of engagement with the rheostat 76 and situated at the right hand thereof as viewed in Fig. 1, the spring 91 being tensioned. As the vehicle wheel re volves, the contacts 119, 120 are closed, and the magnet energised to rock the pallets to lock the wheel 85 and free the wheel 81, which is moved by its spring 91 to bring the pin 83 to the lefthand end of the slot 86, thus causing the contact 78 to move over the rheostat and close the motor circuit. De-energization of the magnet causes the position of the pallets to be reversed by the spring 88 through the length of the slot 86. Simultaneously, the rheostat is rotated away from the contact 78 in a clock-wise direction, this sequence of events continuing until the motor shaft is revolving in consonance with the vehicle wheel. In a modified form of the apparatus, the escapement wheels are mounted concentrically with the motor shaft and the reducing-gearing between the motor shaft and the collecting-ring comprises internal epicyclic gearing operated by an eccentric on the motor shaft.