US2424130A - Magnetic device - Google Patents

Description

' m 15, 1947. T. L. WAKLEY MAGNETIC DEVICE Filed Feb. '7', 1945 F/GZ.

Inventor Thomas L.Waklgy 4W A Home y Patented July 15, 1947 r MAGNETIC DEVICE Thomas Leslie Wakley, Slough, England, assignor to Ronald Trist & Co. Limited, Slough, England,

a British company Application February 7, 1945, Serial No. 576,679 In Great Britain February 25, 1944 4 Claims.

This invention relates to energy-transmitting devices in which the energy is transmitted by magnets.

One eflective form of device of this kind is disclosed in British Patent No. 553,168. Broadly stated, in this device an actuating magnet having two poles separately by a short gap is arranged to act on and move an actuated magnet, also having two poles separated by a short gap, reversibly and with snap action between two mechanically limited positions, and in which the magnets are so mounted that one gap travels past the other on each reversal of the actuated magnet and that if the gaps were exactly opposite one another the like poles would be opposite one another. The advantage that is obtained by the use of such a device is that the actuated magnet is made to move with snap action purely by the interaction of the magnetic forces.

I have found that devices operating on the principle in question sometimes suffer from a minor drawback. The actuating magnet usually has two end positions between which it can be moved by an operating shaft or other device, and in moving from one of these the resultant of the interaction of the magnetic forces increases until it reaches a maximum, which does not occur immediately before that point where it changes direction; as the actuating magnet moves further, th'e resultant force (of the same sign) decreases very rapidly when compared with the previous rate of increase until it is zero. At some point during this decrease the value of the resultant force becomes such that the forc on the actuated magnet is too low to keep that magnet firmly in its end position, e. g. to keep an electrical contact directly operated by the actuated magnet in good electrical contact with a co-operating contact.

The principal object of this invention is to overcome the drawback just described.

Another object is to provide an improved form of energy-transmitting device incorporating a spring to ensure positive action.

Broadly stated, in my invention I interpose a spring or equivalent device (e. g. a rubber torsion bar) between the actuating magnet and th'e means by which that magnet is itself moved, so that the actuating magnet is moved through the spring or the like.

My invention will be more clearly understood from the following detailed description of the preferred embodiment of the invention when taken in conjunction with the annexed drawings,

inwhich:

Figure 1 is a perspective view of the device, which is shown somewhat diagrammatically for ease of illustration; and

Figures 2 to 5 are diagrams illustrating the operation.

In th device shown there are two annular magnets I and 2 each formed with a short gap between poles N1 and S1 and N2 and S2 respec tively. These magnets lie in the same planes and are mounted respectively on shafts 3 and I. The shafts 3 and 4 are parallel to one another and pass through a panel I5. Each magnet can thus rock about its own axis. It will be seen that the axes of the magnets are only so far apart that there is just enough clearance for the magnets to move about their axes without touching, or at any rate that; the distance between them is small. The gap of the magnet I, which is the actuated magnet, travels past. that of the magnet 2, which is the actuating magnet, in the course of the relative movements and the magnets are so arranged that if the gaps were opposite one another the like poles would be opposite one another. In fact, this exact relativ position is never attained, that is to say, the center lines of the two gaps never simultaneously lie in the line joining the centres of the magnets. It will also be seen that in the clockwise direction of rotation the north pole leads the south pole in the magnet I and the south pole leads the north pole in the magnet 2. The rocking mor ement of the actuated magnet I is mechanically limited in any convenient way and to illustrate the principle of operation an arm 5 rigid with the shaft 3 is shown as moving between fixed abutments or stops 6 and I.

In the arrangement described the magnet I will only remain at present in the two positions in which its arm 6 is in contact with one or other stop. Assuming that the magnet I has rocked anti-clockwise, so that the magnets are in the position shown in Figure 2, the pole S2 of the magnet 2 exercises repulsion on the pole S1 of the magnet I and attraction on the pole Ni. The pole N2 exercises repulsion of the same order of magnitude on the pole Ni. All these forces produce an anti-clockwise torque on the magnet I. Th pole N2 also attracts the pole S1, but the distance between these poles is relatively so large that the clockwise torque which it produces on the magnet I reduces the total anti-clockwise torque by only a small amount.

If the magnet 2 turns clockwise the position shown in Figure 2 is reached in which the forces between the poles S2 and S1 on the one hand and th poles N2 and N1 on the other hand, th'ough large, pass through and so close to the axis of the magnet I as to contribute no or substantially no torque holding the arm 'of the magnet l against the stop 6. In this position, the attractions between the poles N1 and S2 on the one hand and the poles s1 and N2 on the other hand substantially balance one another. In short, there is a position of unstable equilibrium. Directly this position is passed and the forces set up by the interaction of the fields are enough to overcome the friction of the axis, the magnet i will move in a clockwise direction. The attractive forces between the poles N2 and S1 and the repulsive forces between the poles N2 and N1 and S2 and S1 respectively rapidly exert a considerable torque, so that the magnet I, once it moves, snaps over to bring the arm 5 into contact with the stop I, and the position is then that shown in Figure 4.

The action just described is disclosed in the said British Patent No, 553,168. In my present invention, the device includes a driving or operating shaft 8 for moving the actuating magnet 2 and the shaft 4 i placed in alignment with this shaft 8 and connected to it by a blade spring 9 which passes through and is clamped in a slot in an enlarged end 10 of the shaft 8, the ends of this spring slidingly engaging in slots in pegs l l fixed to a bar 12 which is rigid with the shaft 4. A the actuating magnet 2 moves from its starting or end position (shown in Figure 2) the spring 9 absorbs energy until the position of maximum torque (shown in Figure 3) is reached. Then, without any further movement of the operating shaft 8 the actuatin magnet 2 continues to move under the action of the spring. The torque producing this movement is opposed by th magnetic torque but that is a smaller torque and rapidly diminishes, so that the change-over position is reached and the actuated magnet moves with snap action into the second position of rest in which the arm 5 is in contact with the stop 1, as shown in Figure 4. In effect, the position of unstable equilibrium ha been displaced to coincide with the position of maximum torque, that is to say, of maximum holding force on the actuated magnet i. The energy contained in the spring 9 carries the actuating magnet past the point of torque-reversal into the zone in which the reversed torque increases, so that the spring is flexed in the opposite direction, as also shown in Figure 4. The spring straightens itself out as the driving shaft turns further, until the position shown in Figure 5 is reached. By 1 reason of the provision of the spring 9 all risk of the actuated magnet I not being maintained firmly in its end position is eliminated.

I claim:

1. An energy-transmitting device comprising a movable actuating magnet having two poles separated by a short gap and an actuated magnet also having two poles separated by a short gap and mounted for reversible movement between two mechanically limited positions, said magnets being mounted so that one gap travels past the other on each reversal of the actuated magnet and so that when the gaps are exactly opposite one another the like poles of the two magnets are opposite one another, driving means for moving said actuating magnet and a resilient driving connection between said driving means and said actuating magnet and providing for yielding relative movement between said driving means and said actuating magnet.

2. An energy-transmitting device comprising a driving shaft, a shaft in alignment therewith, an annular actuating magnet mounted on said second shaft and having two poles separated by a short gap, a like actuated magnet mounted for reversible movement between two mechanically limited positions under the action of said actuating magnet about an axis parallel to that of said second shaft, said magnets being mounted so that one gap travels past the other on each reversal of the actuated magnet and so that when the gaps are exactly opposite one another the like poles of the two magnets are opposite one another, and a spring coupling said shafts together and providing for relative rotary movement between said shafts.

3. An energy-transmitting device comprising an actuated magnet mounted to oscillate about a given axis so that one of its poles traverses a given path of movement, a pair of stops for limiting the movement of said magnet in opposite directions, an actuating magnet arranged for movement so that one of its poles of the same polarity as said actuated magnet pole traverses a path adjacent the path of movement of said actuated magnet pole, the arrangement being such that when said actuating pole approaches said actuated pole, the actuated magnet is held against one of said stops by repulsion between said poles, and when said actuating pole passes said actuated pole, the repulsion force on said actuated magnet reverses and drives said actuated magnet against the opposite stop with snap action, a movable driving member for said actuating magnet, and a resilient element connecting said driving member and said actuating magnet and providing for yielding relative movement between said member and said actuating magnet.

4. An energy-transmitting device comprising a movable actuated magnet mounted so that one of its poles traverses a given path of movement, a pair of stops for limiting the movement of said actuated pole in opposite directions, an actuating magnet arranged for movement so that one of its poles of the same polarity as said actuated pole traverses a path adjacent the path of movement of said actuated pole, the arrangement being such that when said actuating pole approaches said actuated pole, the actuated magnet i held against one of said stops by a repulsion force between said poles which force reaches a maximum before said actuating pole reaches said actuated pole, and when said actuating pole passes said actuated pole, the repulsion force on said actuated pole reverses and drive said actuated magnet against the opposite stop with snap action, a movable drivin member for said actuating magnet, and a resilient element connecting said driving member and said actuating magnet and providing for yielding relative movement between said member and said actuating magnet, whereby when said actuating pole is approaching said actuated pole energy is stored in said resilient driving connection until the point of maximum repulsion is reached and thereafter said actuating pole i moved beyond said actuated pole by the stored energy in said resilient driving connection.

THOMAS LESLIE WAKLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,481,655 Thompson Jan. 22, 1924 2,091,841 Warren Aug. 31, 1937 2,201,836 McCune May 21, 1940 2,298,573 Little Oct. 13, 1942 FOREIGN PATENTS Number Country Date 553,168 Great Britain May 11, 1943

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