US2265297A - Contact device - Google Patents

Description

Patented Dec. 9, 1941 CONTACT DEVICE Donald G. Little, Baltimore County, Md., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application May a, 1940, Serial No. 334,029 4 Claims. 01. 200-166) This invention relates to electrical contact devices and more particularly to electromagnetic relays employing resilient contact members.

In devices of the above type, operation is often required in quick succession, for example, in keying radio transmitters, and' it is extremely important that the moving contact member, once actuated, shall remain in electrical contact with the contactor no matter how rapidly closing and successive opening of the relay contacts must be effected. Otherwise, the least unintentional operation of the contacts would interfere with the correct interpretation of the code characters to be transmitted. However, the sudden actuation of the moving contact stores up considerable kinetic energy and the sudden stopping caused by the stationary member results in a rebound of the moving contact. The resultant oscillatory action of the moving member will continue until the energy is dissipated. The rapid bouncing of the contact creates at each time an unwanted signal when the relay is employed for keying a transmitter.

The primary object of this invention is to prevent rebound of the moving contact from the stationary contactor upon impact therewith, and to this end means are provided for imparting the kinetic energy acquired by the main contact to an auxiliary member having freedom of motion, whereby to dissipate such energy.

Another object of this invention is to attain non-chattering operation of contact elements by a simple mechanical structure which can easily be adapted to various types of relay devices.

A particular feature of this invention is that the movable element of the relay contact carries an auxiliary member having substantially equal mass and equal velocity of travel as the movable member which by impact with the latter receives the kinetic energy and dissipates this energy by its resilient freedom of motion.

Other objects and advantages will be apparent from the following description of the invention,

pointed out in particularity by the appended claim-s, and taken in connection with the accompanying drawing, in which:

Figure 1 is a schematic, side elevational view of the principal elements of a relay constructed in accordance with this invention; and

Fig. 2 is a curve showing the operation of a conventional relay without contact -rebound prevention, whereas,

Fig. 3 shows a curve depicting the operation of the relay as illustrated in Fig. 1.

consists of a magnetizable core I having a magnetizing winding 2. The terminals thereof may be connected to any suitable source for energization, herein illustrated, as an example, by the battery 3 and the switch 4 which closes the circuit to the winding 2. The stationary contact member 5 is so positioned that its contact point 6 is in alignment with the contact point I of the movable member 8, the latter comprising a spring material which is held in a suitable manner by the support 9. The movable contact member 8 carries also a magnetizable portion I0 in alignment with the core I. Afiixed to the movable member 8 is an auxiliary member ll of elastic material similar to the former, the free end of which carries a mass l2 in the form of a contact point similar to 'l. The length of the auxiliary member I I, its shape, and distance from the movable member 8 are variable factors which depend upon the natural frequency of the movable member, its elasticity, and its mass. In a practical embodiment, it is to be so proportioned that the period of its oscillation should coincide approximately with that of the movable member and its effective mass shall be also approximately identical with the one of the movable contacts.

The operation of the relay in accordance with this invention can best be seenby comparing the curves of Fig. 2 and Fig. 3. In Fig. 2 the operation of a conventional type of relay is shown which does not have the auxiliary member H and only the simple contact member 8'and other associated elements. With respect to time as one coordinate, the velocity fluctuations of con-' tact I are shown in curve A, whereas curve B depicts its movement. From a to b, contact 1 is moving with increasing velocity from its position of rest into contact with 6. Between b and c the energy of motion of 1 MV) is imparted to 6 and compresses this contact and its support. From a to d, contact 6 is returning this energy to 1 minus the energy lost in heat and in the imperfect elasticity of. 6. At d it is seen that I bounces off of 6 and moves upward until the energy stored in the spring member 8 promptly forces contact I down again into contact with 8 at f. 'The whole process is then repeated until the energy originally acquired by contact I by the pull of the magnet 2 is dissipated as heat in the elastic material. the relay it is necessary that upon closure of the switch 4 a firm contact be maintained between contactors I and 6 from the time of their physical engagement at b in Fig. 2 until and beyond Referring to the drawing, the relay of Fig. 1 h as long as the switch 4 remainsclosed, as seen For correct operation of describing an oscillation.

. from the shaded projections of curve B on the bottom line of Fig. 2. Actually, contact is made only intermittently as between b and d, j and g, etc., thus transmitting false signals besides causing unnecessary sparking and wear of the contacts. In comparison it is seen in Fig. 3, which shows the operation of the relay in accordance with Fig. 1, that the movement of contact I, once it strikes contact 6, is immediately stopped and the accumulated energy is imparted to contact member l2, which continues to oscillate from the position of impact d. The movement of the auxiliary contact member I2 is seen then to be downward and at the point dimpacting with the moving contact 1. Likewise, the kinetic energy of I! due to its own movement, plus the energy imparted to it by 1 causes l2 to move up again, Contact 1 on the other hand, having given up its energy to 6 and I2, remains in firm contact with 6, as shown by the heavy line. It is essential if contact member 1 is to remain in contact with contact member 6 from time b onward, either that contact! make contact with 6 at zero velocity MV =O) or that the energy MW) be otherwise dissipated. The auxiliary member I2 performs this function and enables thereby the continued contacting of member 1 immediately after its impact with member 6. The kinetic energy of I and I2 is thus finally dissipated as heat from the internal losses of the spring of l2, except for the rebound of said movable element comprising a mass carried by said movable member and movable withequal velocity therewith, said mass being so arranged as to take over by impact with said movable element the kinetic energy thereof and dissipate said energy by vibratory motion.

2. In an electrical contacting device having contact members, one of which is movable with respect to the other and of a resilient character, means for moving said last mentioned member, and means for preventing rebound thereof upon impact with the other of said contact members part dissipated in the internal losses of contact 6 immediately after the initial impact of I and 6.

From a practical standpoint the oscillatory motion of l2 should be damned by high loss material in the spring of l2, by coating this spring with rubber or varnish-or by other well known means. Thus I 2 will be motionless soon after the point d of Fig. 3 and also soon after magnet I is deenergized so that a new-signal, dot, or dash may be sent. Thus the maximumspeed of keying is increased.

I claim as my invention:

1. In an electrical contacting device having relatively movable contact elements of a resilient character, means for moving one of said elements to contact the other, and means for preventing comprising a resiliently mounted mass carried by said movable member and of approximately equal physical properties, said mass being so arranged as to follow said movable member and upon impact therewith receive the'kinetic energy thereof and dissipate the same by continued vibratory motion.

3. In an electrical contacting device, a fixed contact member, an elastic contact member, means for moving the last-mentioned member to contact said fixed contact member, said elastic contact member terminating in a fork having a pair of arms, rigid contact points on each of said arms, one of which engages said fixed contact upon movement, and the other adapted to impact said engaging contact point, both said contacts being approximately equal as to their efiective mass.

4. In an electrical contacting device, a stationary contact member, an elastic contact member, means for moving the last-mentioned member to contact said fixed contact member, a rigid contact point at the free end of said elastic member for engaging said stationary contact upon movement, an auxiliary spring member affixed at one end to said elastic contact member, a

weight at the other endthereof approximately equal to the effective mass of said movable contact point and so coordinated with respect thereto as to physically engagesaid movable contact immediately upon impact of the latter with said fixed contact whereby the accumulated energy thereof is transferred to said auxiliary member to be dissipated in the spring support thereof.

DONALD G. LITTLE.

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