Patent GB-190505143-A (GB)
Title: Improvements in Electrically Driven Steering Gear for Ships and the like
Inventor: HARFIELD WILLIAM HORATIO
Filed: 1905-03-11
Granted: 1906-03-10
Abstract: 5143. Harfield, W. H., and Routledge, W. March 11. Switches; cut-outs.-In electrically - operated steering-gear, the rudder is. actuated by a motor, the current to which is controlled by switch gear not in direct mechanical connexion with the steering-wheel, but controlled by an auxiliary motor or electro - magnetic device introduced between the steering-wheel and switch gear. The switch gear is so arranged that the amount of starting-resistance cut-out is independent of the movement of the steering-wheel. In the arrangement shown in Figs. 1, 1<a>, and 2, the auxiliary motor d is controlled by the switch e, operated from the shaft a' through the bevel and epicyclic gearing shown. The rotation of the steering-wheel a rotates the disk i<4> and releases the lever h' from engagement with the cam i<5>, thus permitting the clutch h to engage. The switch e closing at the same time starts the auxiliary motor d, and, through the worm gearing, rotates the switch drum f, which controls the current to the main motor c by which the rudder is operated. The switch drum is made in two portions f<1>, f<2>, and is shown developed. The auxiliary motor d is arranged to run until a safe maximum current is passing through the main motor c. If this maximum is reached before the motor c starts, the auxiliary motor d stops until the motor c starts, when it completes the travel of the switch drum f until it is full on. For this purpose, two switches are provided in the auxiliary motor circuit, which are opened by one or other of the pins j<1>, j<2> on the drum f, according to the direction of rotation. When the switch drum has been rotated so that the step 3 is in circuit, one of the pins engages an arm, which impinges against one end of either of the levers j<4>, j<5>, which in turn engage teeth on the switch arms k<1>, k<2> and break the auxiliary-motor circuit. When the motor c starts, the arms k<1>, k<2> are released by the electromagnet. If the motor c has started when the step 3 is . in circuit, the electro-magnet moves the pivoted ends j<6>, j<7> of the levers j<4>, j<5> so that the circuit is not opened. A sudden overload on the motor c brings the solenoid n into operation and opens the clutch h, and the switch drum f is returned to its normal aud central position by the spring o<2>, connected to the levers o, o<1>. During rotation of the drum f, one of these levers engages the stop o<3> and puts the spring o<2> in tension. Emergency switches p<2> are arranged at the rudder to break the motor circuit when the rudder is hard over. The movement of the rudder rotates the shaft b<2> and returns the disk i<4> to its original position when the required movement is completed. In relay working, the premature stopping of the auxiliary motor is obviated and the drum f is allowed to complete its full travel, the number of relay switches operated being dependent upon the voltage across the main motor armature terminals. This arrangement is shown in Fig. 3. The switch drum in this case operates the five relay switches q . . . q<4>. A reversing-switch r, comprising two pairs of pivoted switch arms, is placed in the mainmotor circuit. The arms r . . . r<4> are designed to be operated by magnets r<5> ... r<8>, the first two of which are in circuit with the emergency switch p. When the drum f is rotated so that the contact is made by the contact-piece f<10>, the switch arms r', r<3> are operated to bridge the contacts r<8>, r<13> and also the contacts r<11>. The relay magnet q is energized and closes the relay circuit, thus permitting current to flow through the armature and the series coils of the motor c. The completion of the rotation of the drum f by the motor d opens the circuit of this motor by the switch j. A magnet t is connected across the brushes of the motor c and is energized only when the motor is running. If the motor c starts when the drum f operates the switch q, the magnet t closes the switch t<2>, so that the relay switches q<2>, q<3>, q' are closed. Dash-pots t<4>, t<6> are provided to delay the action slightly. An electro-magnetic brake is provided to stop the motor c upon the completion of the desired travel of the rudder, in addition to a short circuit across the armature terminals through the resistance r<15>. The auxiliary motor switch e comprises a pair of switch arms in connexion with contacts shown. One arm and the corresponding contacts are furnished with carbon blocks to render the switch more sensitive to the movement of the shaft a<1>. When working with heavy currents, the auxiliary motor drives a shaft upon which is mounted a number of cams engaging switch levers operated consecutively. This shaft takes the place of the starting-switch f, Fig. 1, and the auxiliary motor in this arrangement is similarly operated. In another modification, Fig. 13, applicable to relay working, the reverser magnets are operated by the switch e, in conjunction with the contacts C . . . C<3>. These contacts close the circuit of an electro-magnetic switch D, the arm of which contacts in succession with a set of contacts feeding current to a system of cutting-out switches similar to those shown in Fig. 3. The magnet is furnished with curved polar extensions D, D<2>. An electro-magnet E<1> is used to stop the switch e at its mid-travel if the main motor c is overloaded. The movement of this switch is damped by the dash-pot E<3>. Several methods of damping are described instead of the dash-pot, one utilizing an escapement mechanism, and another a centrifugal governor in conjunction with worm and ratchet gear. In order that the speed of the motor d may be independent of voltage or friction, a governor, Figs. 18 and 19, comprising centrifugal weighted arms J, is carried by the motor shaft and operates a brake J<1>. A cam on the switch drum f can be used to put the brake in or out of action. The time taken by the drum f in moving from its central position to the first contact is by this means reduced, and the movement of the remainder of the drum may be made slower. The invention, it is stated, may be employed in connexion with the Ward-Leonard system of controlling motors.