US2916584A - Electrically-operated latching relays - Google Patents

Description

Dec. 8, 1959 c. P. MOLYNEUX 2,916,584

ELECTRICALLY-OPERATED LATCHING RELAYS Filed May 24, 1957 2 Sheets-Sheet. 1

FIG. I

12 Permanent Magnet INVENTOR Cecil F. Molyneux ATTO R N Dec. 8, 1959 c. P. MOLYNEUX ELECTRICALLY-OPERATED LATCHING RELAYS 2 Sheets-Sheet 2 Filed May 24, 1957 EY S fi F I G. 4

INVENTOR Cecil F? Molyneux BY Miami ATTORN United States PatentO ELECTRICALLY-OPERATED LATCHING RELAYS Cecil Patrick Molyneux, Southampton, N.Y., assignor to Filtors, Inc., Port Washington, N.Y., a corporation of New York Application May 24, 1957, Serial No. 661,407

14 Claims. (Cl. 200-104) My invention relates to improvements in latching relays of'the type including an electromagnetic unit adapted to rotate an armature which in turn operates an electric switch or switches.

The relay of the'present invention is of a sub-miniature type particularly useful as a component of airborne electrical equipment, for example, in the firing control systems of aircraft guns.

One of the objects of the invention is to provide a relay which is adapted to remain in energized position indefinitely without the consumption of power and without the use of mechanical devices such as ratchets, clutches, etc.

A further object of the invention is to provide a latching relay which is not affected by vibration and shock and which can be used over wide temperature ranges and the environment encountered at extremely high altitudes, even with continuous duty.

Another object of the invention is to provide a hermetically sealed relay adapted to actuate in an extremely short period of time even at nominal voltage.

A further object of the invention is to provide a latching relay in which the switch elements are actuated with a minimum of bounce between contacts.

According to my invention the improved latching relay comprises a support, a latch-in coil carried by the support, an armature associated with the coil for movement to an energized position when this coil is energized in response to the passage of an electric current therethrough, switch means acutated by the movement of the armature, and a permanent magnet arranged to hold the armature and the switch means in actuated position after the coil has been de-energized. The relay construction also preferably includes a reset coil for returning the armature and switch means to unenergized position. This: is accomplished by energizing the reset coil whose magnetic field counteracts the field of the magnet and moves the armature and switch means to a reset position.

The permanent magnet is selected or arranged with respect to the armature to provide a magnetic field tending to bias the armature to energized position but which does not apply a sufficient force to move the armature and switch means to that position. On the other hand, the magnetic field provided by the permanent magnet is sufficient to hold the armature and switch means in energized position. The construction, including the permanent magnet, has the advantage that the switch means may be held in energized position indefinitely without the consumption of power. The circuits controlled by the switch means are, therefore, maintained intact, even though the supply of electricity to the latch-in coil should fail.

Conventional electromagnetic relays have the disadvantage that the electric switch means, such as the contacts when actuated, will bounce and cause sparking and sometimes welding of the contacts. It has been noted that as many as eight bounces occur when a conventional type relay closes. Accordingly, the improved relay of the present invention includes means for reducing the bounce, this means comprising a momentum means adapted to apply a continuing force on the actuated switch means after actuation, thereby counteracting any tendency to bounce in the reverse direction. This increases the dependability and life of the relay and insures a dependable operation.

The dependability of the relay is further insured by providing a hermetically sealed construction. This is extremely important where the relays are used as aircraft components or as components of fire control systems of aircraft and other guns.

The improved latching relay of the present invention includes other features and advantages described more in detail hereinafter with the accompanying drawings forming a part of this application.

In the drawings:

Fig. 1 is a vertical broken sectional view through a latching relay constructed in accordance with the invention;

Fig. 2 is a horizontal sectional view of the latching relay taken on the line 2-2 of Fig. 1;

Fig. 3 is a horizontal sectional view taken on the line 33 of Fig. 1;

Fig. 4 is an exploded view in perspective of certain elements of the latching relay shown in Figs. 1 and 3;

Fig. 5 is a circuit diagram of the relay illustrated in Figs. 1 to 4; and

. cludes an armature arrangement which, in certain respects is similar to that disclosed in commonly owned Patent No. 2,767,357, granted October 16, 1956.

Referring to the drawings, the latching relay comprises a cylindrical case or shell 10 having an integral top wall 12. The case is of magnetic material, preferably steel, so as to provide a magnetic path for upper and lower pole pieces 14 and 16, these pole pieces being spaced apart and having slotted cylindrical end portions extending into the ends of a bobbin 18 fitted within the cylindrical case 10, as shown in Fig. l. The bobbin is made of insulating material, such as nylon, and is provided with an axial opening into which the pole pieces extend. The bobbin 18 carries a latch-in coil 20 and a reset coil 22, both of fine copper wire and spaced with respect to each other by a cylindrical annular spacer 24 of insulating material.

The circular-shaped flange 26 of the upper pole piece 14 rests on the upper part of the bobbin 18 and has a diameter considerably smaller than the interior diameter of the case 10 and carries a permanent magnet 28, preferably an alnico magnet in the form of a cylindrical block mounted between and in contact with the head of the pole piece 14 and the steel wall 12. The magnet 28 and the flange 26 of the pole piece 14 are surrounded by a solid metal frame ring 30 of non-magnetic material such, for example, as aluminum. This ring is mounted between the upper end of the bobbin 1.8 and the top wall 12 of the case.

At the lower end of the bobbin 18, the lower pole piece 16 includes an integral circular shaped flange 32, the edge of which extends to the inner surface of the steel casing 10 along the lower portion of the bobbin 18.

The slotted cylindrical portions of the pole pieces extend axially into the opening in the bobbin and have ends.

spaced apart in the central section of the opening bya space 34. The pole piece 14 comprises facing elements 36 and 38 separated by the slot in the pole piece, while ranged in alignment with the respective elements 36 and 38. Each of these elements has the same cross-sectional shape, that is, that shown for the elements 40 and 42 in Fig. 2, so as to provide two straight flat plane surfaces of unequal width extending at an obtuse angle with respect to each other, the narrower surface 43 of each pole piece element being. employed as an engagement surface for an armature block 44. This armature block is arranged in the slots of the pole pieces and in vertically overlapping relationship with the pole pieces 14 and 16.

The armature 44 is a substantially rectangular-shaped blockof magnetic material with flat parallel sides and edges, having a width corresponding approximately to the diameter of the cylindrical-shaped portions of the pole pieces extending into the axial opening through the bobbin 18. The armature 44 is mounted in fixed position on a shaft 46 of non-magnetic material having a small end at the top fitting in a bore 48 in the pole piece 14. At the lower end the shaft 46 is of relatively large diameter and extends through a bore 50 in the lower pole piece 16. Upper and lower spacer washers 52 and 54 are carried on the shaft 46 within the slotted portions of the pole pieces to center the armature, since the armature 44 is somewhat shorter than the space provided.

In assembling the pole pieces, they are accurately spaced a definite distance apart and, accordingly, their inwardly-extending cylindrical portions are advantageously surrounded by a spacer sleeve 56 of nonmagnetic material, such as brass, cut to a definite length. This sleeve accurately fits over the cylindrically-shaped inwardly-projecting elements of the pole pieces and against the inner surfaces of the end flanges of the pole pieces as shown in Fig. 1. This sleeve, therefore, accurately spaces the pole pieces with respect to each other and they must be accurately located so that the engagement surfaces 43 of the elements 36 and 38 on the opposite sides of the armature are in vertical alignment with the corresponding engagement surfaces 43 of the respective elements 48 and 42. This is accomplished by securing the pole pieces together with two brass screws 58 in the manner shown in Fig. 4. These screws extend through and are counterswung in the top pole piece and respectively pass along adjacent to the longer inside faces of the elements 36 and 40 and 38 and 42. The screws are threaded into tapped holes in the lower pole piece, as indicated in Figs. 2 and 4. The pole pieces are aligned with the armature in engagement with the engagement faces 43, after which the screws 58 are tightened so that the pole pieces are drawn firmly against the ends of the spacer sleeve 56.

The flange 32 of the lower pole piece is provided with marginal notches, not shown, for respectively accommo- F dating the current leads for the coils 20 and 22. The flange of the bobbin is provided with corresponding notches, one of which is shown at 60 provided on the outside with a projection 62 so that the lead is insulated from the flange 32. The current leads from the coils 20 and 22 extend into a housing 64 in the lower part of the casing 10, which is closed off by a terminal header 66 comprising a pair of metal plates 68 and 70 carrying a desired number of contact pins or terminals. The plates 68 and 70 are brazed or welded together and the terminal header assembly 66 is brazed or soldered to the lower end of the casing by a soldering compound 72. Prior to securing the terminal header to the casing, a bridge 74 is soldered or brazed to the plate 70, the bridge including legs 76 having lugs 78 which are soldered or welded to the plate 70. The upper part of the bridge 74 is spot welded or otherwise secured to the lower portion of the pole piece 16, so that the complete assembly may be held together and inserted in-the casing at one time, whereupon the periphery of the terminal header 66 is soldered or brazed to the lower end of the casing 10 to provide a hermetically sealed unit.

The terminal header 66 is illustrated as carrying three terminal pins connected to the leads for the coils and 22. These include a terminal pin 77 for the plus lead of the latch-in coil, aterminal pin 78 as a common minus lead for the coils 20 and 22 and a terminal pin 79 as a plus terminal for the reset coil 22. These terminals are identified in the circuit diagram shown in Fig. 5.

The terminal header 66 also carries terminal pins 80, 81 and 82 for a switch means or unit actuated by the movement of the armature 44. All of the terminal pins which extend through the terminal header 66 are rigidly secured thereto and insulated therefrom in a hermetically sealed manner by providing respective holes through the metal plates 68 and 70 substantially larger in diameter than that of the pins, and each pin is secured and sealed in these holes by means of fused glass beads 82, as shown in Fig. 1. It will be understood, therefore, that the terminal header with its pins is constructed in advance and processed under conditions adapted to fuse the glass beads and provide a rigid sealed construction.

The contact pins 81 and 82 respectively carry fixed contact arms 83 and 84, the contacts of which are respectively engageable by the contacts on the opposite faces of a movable control arm 85 made of spring material and secured to the terminal pin inside the housing 64. The contact arm 85, as shown in Figs. 1 and 4, extends laterally and upwardly between the contact arms 83 and 84 and includes an inwardly-extending portion 86 at the top which projects into a slot or notch 87 in the marginal edge of an actuator disc 88 of insulating material, such as nylon. This disc, as shown in Figs. 1 and 3, includes an embedded metal plate 89 which gives strength to the actuator and which is made use of in securing the actuator 88 to the portion of the shaft 46 Which extends into the housing 64. The actuator may be fixed to the shaft by spinning the marginal edge of the shaft under the plate 89 as at 90. The shape of the movable contact arm provides a structure suitably adapted to the relatively small space and at the same time gives the effect of a relatively long spring arm.

The movable control arm is a spring biased to engage contact arm 84 and hold the armature 44 against the screws 58 as a back stop. When the latch-in coil 20 is energized, the armature 44 is rotated through a small angle and the actuator 88 moves through the same angle to shift the movable switch arm 85 against its spring bias, in the direction of the arrows in Figs. 3 and 5, to close a circuit from the contact pin 80 through the fixed contact arm 83 and its terminal pin 81. This is the latch-in position of the armature and switch elements shown in Figs. 2 to 5. When the actuator 88 is operated in the opposite direction, it moves the movable contact arm 85 to its normal position in engagement with the contact of the contact arm 84, thereby closing a circuit involving the terminal pins 80 and 82. The switch, therefore, as illustrated in Figs. 1 to 5, is a single pole, double throw switch adapted to control two circuits.

When one of the coils 20 and 22 is energized, the actuator 88 is moved instantly and rapidly, so that normally some bounce would be expected between the engaged contacts. This adverse effect is greatly reduced or entirely eliminated by the inclusion of a fly wheel 92 of heavy metal in the form of a disc axially arranged with respect to the shaft 46 and the actuator 88 and mounted in frictional engagement with the lower portion of the actuator 88. The fly wheel or weight 92 is held in the position shown in Fig. 1 by a pin 94 pressed into an axial bore in the shaft 46 and having an enlarged head 96 recessed in the weight 92 in an enlarged bore provided with a spring 98 which biases the weight into frictional engagement with the lower portion of the actuator 88. The weight or fly wheel 92 is preferably made of a very heavy metal, in order to absorb the kinetic energy of the contact springs and the moving parts of the relay.

When one of the coils is actuated, for example, the latch-in coil, and the actuator is being rotated on its axis, the fly wheel 92 is also rotated, but when the actuator 88 is stopped, as for example when the switch contacts engage, and the sides of the armature hit the engagement surfaces 43 of the, pole pieces, the fly wheel weight 92 continues to rotate on the pin 94, and because of its frictional engagement with the actuator 88, it applies an anti-bounce force to the actuator. In other words, it applies a more or less steady pressure rotational force in the direction of rotation after the switch contacts have engaged and the actuator 88 has stopped. Bounce is, therefore, substantially eliminated.

Figs. 1 to 5 of the drawings illustrate the described relay with the switch arm 85in latched position, the latch-in coil 20 energized and the armature moved into engagement with the narrow engagement surfaces 43 of the pole pieces. Even if the coil 20 is de-energized, the magnet 28 will hold the armature in latched position. When the current is discontinued to the latch-in coil 20 and a current is applied to the reset coil 22, the holding power of the permanent magnet 28 is overcome and the armature and actuator are rotated in the opposite direction to their normal positions thereby opening the circuit through the contact arm 83 and closing a circuit through the contact arm 84.' The permanent magnet is selected so that it has insufficient strength to rotate the armature, actuator and switch or switches to the latch-in 'position.

As shown in Figs. 2 and 4, the latch-in coil 20 actuates the armature 44 to bring diagonally opposite portions of its side surfaces into engagement respectively with the aligned engagement surfaces 43 of the two pole pieces. However, when the reset coil 22 is energized, and the armature rotated in the opposite direction, its sides do not eng -.ge the other wider, flat surfaces of the pole piece elements 36 to 42, but instead, these side faces of the armature respectively engage the brass screws 58 so that the armature is readily movable by the latch-in coil.

While a single switching means is illustrated in connection with the relay of Figs. 1 to 5, it is to be understood that, as'is usually the case, this relay includes a plurality of switches located symmetrically around the periphery of the actuator 88, this actuator having a corresponding number of notches 87 for the reception of the movable control arms. Such a multiple switch arrangement for the relay is illustrated in the circuit diagram of Fig. 6. This diagram depicts the configuration of a six-pole, double-throw relay in which the elements of one switch are utilized to transfer electrical energy to the latch-in and reset coils. In order to reduce the complexity of relay switching and control circuitry, it is often desirable to have the latching relay pull-in or latch, on receipt of an electrical impulse of known polarity, and conversely, to reset or unlatch on receipt of a second electrical impulse of the same polarity. This result is accomplished by the arrangement shown in Fig. 6, which is a modification in this respect of the circuit diagram shown in Fig. 5.

Referring to Fig. 6, six switches are shown, each of which has the same construction as that illustrated in Figs. 1, 3, 4 and 5 of the drawings. As shown in Fig. 6, the latch-in coil 20 and the reset coil 22 are each connected to a common terminal 78. In this instance, however, the other lead of the latch-in coil 20 is connected by a lead wire 100 to a fixed contact terminal 101 of one of the six switches, while the other lead of the reset coil 22' is connected by a lead wire 102 to the other fixed contact terminal 103 of the switch. The terminals 77 and 79 are, therefore, not used in this arrangement. A spring switch arm 105, connected to a terminal 106 and biased against the contact of fixed terminal 101 is movable between the fixed contact terminals 101 and 103 in the same manner as the switch arm 85 in Figs. 3, 4 and 5.

Fig. 6 depicts theposition of the six relay control arms, such as 105 in the unlatched position. However, when an electrical impulse of proper polarity is applied'tothe terminals 78' and 106, the current flows through the arm 105, the fixed contact 101 and the lead to the latch-in coil 20'. This causes the armature to move to the latch-in position and, therefore, to transfer all of the control arm contacts to the latch-in position. At the same time, of course, the control arm 105 is moved into engagement with the contact of terminal 103 and thereby transfers the terminal 106 from the latch-in coil 20' to the reset coil by way of fixed contact terminal 103 and lead wire 102. When a second electrical impulse of like polarity is now applied to the terminals 78 and 106, the reset coil is energized, which sets up a magnetic field, the vector of which is opposite to that of the permanent magnet 28 causing the armature and the control arms of the six switches to return to the reset position. The direction in which the relay coils are wound or connected will decide the electrical polarity to which the relay will respondto the foregoing sequence of operation.

The frame piece 30 of non-magnetic material between the case 10 and the periphery of the flange 26 of the pole piece 14 and the permanent magnet 28 provides a high reluctance between these elements and the side wall of the case 10, so that the steel case forms a return magnetic path from the upper end of the permanent magnet to the pole piece 16. The arrangement of the coils and the permanent magnet is such that the results described above are accomplished. For example, the top of the permanent magnet 28 may be regarded as a north pole with the bottom as a south pole. The pole piece 14 will, therefore, be a north pole and the pole piece 16 will be a south pole.

While the latch-in and reset coils are shown in a particular relationship in the drawings, it is to be understood that the location of the coils with respect to each other is immaterial so long as they are arranged to apply their forces to the pole pieces in the manner described above. Itis to be furthermore understood that the switches actuated by the actuator 88 may be arranged differently than that described above. For example, the arrangement may be such that the latch-in coil closes a circuit or circuits, whereas the reset coil merely opens these circuits without closing others. Various arrangements in this respect may be provided without departing from the spirit and scope of the invention.

What I claim is:

1. A latching relay comprising a case of magnetic material having a closed end, an electromagnetic coil located in said case intermediate its ends and having an axial opening, pole pieces respectively extending into said opening and in spaced relation therein, an armature located in said opening in overlapping relation with the pole pieces, journals extending from each end of the armature for mounting the armature for angular movement, a permanent magnet located in the closed end of the case with one pole adjacent to the closed end and the other pole adjacent one of said pole pieces, said permanent magnet and said one pole piece being spaced from the side wall of the case, one of said journals projecting through the other pole piece, an actuator fixed to said projecting journal, and a control operable by the actuator when the coil is energized, said permanent magnet being adapted to hold the armature, actuator and control in latched position when the coil is de-energized.

2. A latching relay as claimed in claim 1, including a metal closure for the opposite end of the case hermetically sealed thereto and providing a housing in which the actuator and control are mounted, said control comprising electric switch means including terminal pins sealed with respect to and extending through the closure means.

3. A latching relay as claimed in claim 2, in which each terminal pin is sealed and insulated with respect to the metal closure by a glass sealing means mounting the terminal pin in fixed relation with respect to the closure.

4; A latching relay as claimed in claim 1, including a reset coil associated withsaid pole pieces for moving said armature and actuator in a direction to unlatch the control.

5. A relay as claimed in claim 1, including a reset coil associated with said pole pieces for moving said actuator and control in a direction to unlatch the control, said control comprising a double-throw electric switch means having a movable contact arm, and a momentum means movable with the actuator when either of the said coils are energized and adapted to continue the application of force to the movable contact arm after the actuator'has stopped, whereby contact bounce is reduced.

6. A'relay as claimed in claim 1, including a body of non m'agnetic material surrounding the permanent magnet and the-portion of said one pole piece adjacent thereto and locatedin-the space'between the permanent magnet and-the side wall of the case.

7. A latching relay as claimed in claim 1, including a resetcoil associated with said pole pieces for moving said armature and actuator in a direction to unlatch the relay, said control including a double-throw electric switch having latch-in and reset positions for respectively supplyingelectric current to said coils.

8. A latching relay comprising a case of magnetic material having a closed end, an electromagnetic coil located in 'said case intermediate its ends and having an axial opening, pole pieces respectively having portions extending into said opening and in spaced relation therein, an armature located in said opening in overlapping relationwith the pole pieces therein, each pole piece including an annular flange projecting toward the side wall of the case at its end of the coil, journals extending from each end of the armature for mounting the armature for angular movement, a permanent magnet located in the closed end of the case with one pole engaging the closed end of the case and the other pole engaging the flange of the adjacent one of said pole pieces, said permanent magnet and the flange of said adjacent pole piece being spaced from the side wall of the case, a body of non-magnetic material located between the side wall of the case and the permanent magnet and the flange of said adjacent pole piece, the flange of the other pole piece extending to the side wall of the case, one of said journals projecting through the other pole piece, an actuator fixed to said projecting journal, and a control operable by the actuator when the coil is energized, said permanent magnet being adapted to hold the armature, actuator and control in latched position when the coil is deenergized', whereby contact bounce is reduced.

9. A relay as claimed in claim 8 including a reset coil associated with said pole pieces for moving said actuator and control in'a direction to unlatch the control, said control comprising a double-throw electric switch means having a movable contact arm, and a momentum means movable with the actuator when either of the said coils are energized and adapted to continue the application of force' to the movable contact arm after the actuator has stopped.

10. A latching relay comprising a case of magnetic material, a support in the case, a latch-in coil carried by the support, an armature associated with the coil, an actuating means movable by the armature to a latch-in position when the coil is energized, a switch means actuated by the movement of the actuating means when the latch-in coil is energized, a permanent magnet mounted inthe case in a'position to act on the armature in the same direction as the coil and adapted to hold the armature, actuatingmeans and switch means in actuated latchin position when the coil is de-energized, and a momentum rheans carried by and frictionally engaging the actuating means-for reducing bounce in the switch means.

11-. A latching relay as claimed in claim 10, in which the actuating means is rotatable and the momentum means comprises a weight of high specific gravity axially arranged with respect to the actuating means.

12. A latching relay comprising a case, an electromagnetic actuator including a coil located in said case intermediate its ends and having an axial opening, two pole pieces respectively extending into said opening from its opposite ends and located in spaced relation therein, a rotatable armature located in said opening in overlapping relation with the pole pieces, journals extending from each end of the rotatable armature for mounting the armature for angular rotary movement, means forming a closed magnetic circuit connecting the outer ends of said pole pieces including a permanent magnet located in a position with one of its poles in contact with the outer end of one of said pole pieces, an actuating means fixed to one of said extending journals for movement by the armature, and a control operable by the actuating means when the actuator coil is energized and the armature rotated to latching position, said permanent magnet being adapted to hold the armature, actuating means and control in latched position when the actuator coil is deenergized but having insufiicient power to actuate the control to the latching position.

13. A latching relay as claimed in claim 1, in which the control comprises an electric switch means having a movable contact arm, and a momentum means movable with the actuator when said coil is energized and adapted to continue the application of force to the movable contact arm after the actuator has stopped, whereby contact bounce in the switch means is reduced.

14. In a latching relay including an electromagnetic actuator provided with latch-in and reset coil windings and a pair of spaced pole pieces of magnetic material associated with the coil windings, a movable armature mounted in operative position with respect to said pole pieces for actuation in opposite directions respectively by the coil windings and for movement to latch-in and reset positions when said respective coil windings are energized, an electric contact switch means for controlling an electric circuit, and an actuating means connecting the switch means with the movable armature, the improvement including means forming a closed magnetic circuit outside said coil windings connecting said pole pieces of the electromagnetic actuator, a permanent magnet located in a fixed location with respect to said pole pieces and included in series in said closed magnetic circuit, said permanent magnet acting in the closed magnetic circuit in the same direction as the latch-in coil winding and being adapted to hold the armature and control device in latched position when the latch-in coil winding is deenergized but having insufficient power to actuate the control device to the latching position, said reset coil winding having sufiicient power to overcome the power of the permanent magnet and move the control device to the reset position when the latch-in coil winding is deenergized, and a bounce-reducing momentum means movable with the actuating means for the switch means when either of said coils are energized and adapted to continue the application of force to the actuating means after it has been stopped, whereby bounce in the switch means is reduced.

References Cited in the file of this patent UNITED STATES PATENTS 2,301,992 Agnew Nov. 17, 1942 2,539,547 Mossman et al. Ian. 30, 1951 2,544,719 OBrien et al. Mar. 13, 1951 2,731,527 Marsh Jan. 17, 1956 2,767,357 Naylor Oct. 16, 1956 2,790,876 Wagner Apr. 30, 1957 2,832,867 Luhn Apr. 29, 1958 2,856,483 Farmer Oct. 14, 1958 UNITED STATES PATENT {)FFEQE CERTIFICATE GF CORRECTiGN Patent No, 2,916,584 a December 8, 1959 Cecil Patrick Molyneux It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column '7, line 50, claim 8, strike out whereby contact bounce is reduced" and insert the same after "stopped" and before the period in line" 59, claim 9,

Signed and sealed this 14th day of June 1960.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Oflicer- Commissioner of Patents UNITED STATES PATENT @FFKCE CERTIFICATE or coEc'ri Patent No, 2,916,584 December 8, 1959 Cecil Patrick Molyneux It is hereby certified that error appears in the printed specification of the above numbered patent requiring correct-ion and that the said Lettere Patent should readas corrected below.

Column 7, line 50, claim 8, strike out whereby contact bounce is reduced" and insert the same after "stopped" and before the period in line 59, claim 9,

Signed and sealed this 14th, day of June 1960.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Oflicer' Commissioner of Patents

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