US2416070A

US2416070A - Selective relay

Info

Publication number: US2416070A
Authority: US
Inventors: John J Shively
Original assignee: Individual
Current assignee: Individual
Priority date: 1942-08-26
Filing date: 1942-08-26
Publication date: 1947-02-18
Anticipated expiration: 1964-02-18

Description

Feb. 18, 1947.- .1.J. sHlvE-LY SELECTIVE RELAY Filed Aug. 26. .1942

5 Sheets-Shea?l l y .INVENTOR c/oH/v dcSH/vE/ Y waff/@.5

Feb.1s,1947. V .'J.J.SHNELY 2,416,070

SELECTIVE RELAY 3 Sheets-Sheet 2 Fledt Aug. 26, 1942 INVENTOR ATTORNEYS Feb. 18, 1947. J. J. sHlvELY SELECTIVE RELAY 3 Sheets-Sheet I5 Filed Aug. 26, 1942 95- v /as 9 Ffa /J 9# @im INVENTOR /oH/v d. cSH/ v51. y. BY Zbs, M Y Ml-Q ATroRNr-:Ys

Patented Feb. 18,l 1947 UNITED STATES PAT-ENT OFFICE 3 Claims.

The present invention pertains to improvements in selective relays and circuits therefor.

An object of the invention is to provide an improved relay adapted to control a circuit or circuits in response to a pre-determined number of electrical impulses.

Another object is to provide a device of the above nature including means to prevent actuation of the circuit controls when the number of impressed electrical impulses exceeds the said pre-determined number.

A further object is to provide apparatus of the above nature including means adapted to actuate switching contacts upon entering a given station from one direction but to avoid actuating said contacts upon entering said station from the opposite direction.

Another object is to provide a relay of the above nature including automatic means to reset the switching means to initial position.

Another object is to provide time-delay means to control the automatic resetting apparatus.

Another object is to provide suitable circuit arrangements by which the invention may heapplied to a variety of control purposes.

A further object is to provide apparatus of the above nature which is simple, compact, and which may be easily and cheaply manufactured.

Other cbjects and advantages of the invention will become evident in the course of the following description in connection with the accompanying drawings, in which- Figure 1 is a longitudinal view of a preferred form of the device in normal position, the view being taken in partial vertical central section;

Figure 2 is a similar view illustrating the position of the parts when the relay magnet is energiZed;

Figure 3 is a fragmental view showing an alternative detail form of the time delay mechanism;

Figure 4 is a rear elevation of the device, showing the selective switching means in normal lposition;

Figure 5 is a partial similar View showing the selective switching means in engaged position;

Figure 6 is a cross sectional view partially in the plane 5-6,`Figure 5;

Figure 7 is a diagrammatic sectional view of the selector contacts, referring to the plane '1 -1, Figure 5;

Figure 8 is a detail cross Asectional view of the switching head on the lines 8 8, Figure 9;

Figure 9 is a detail sectional View of the switching head on the lines 9 9, Figures 5 and 8;

vFigure 10 is a diagrammatic illustration of the switching relationship during operation of the relay magnet;

Figure 1'1 is a similar diagram illustrating the apparatus at .the instant of completing the selected circuit;

VFigure 12 is asimilar View showing the parts at the time Vof automatic reset;

Figure 13 is a diagram illustrating a typical application of the device to multiple circuit control;

Figure 14 illustrates alternative switching and circuit connections;

Figure 15 illustrates the provision of a plurality of selector switching stations to the device;

Figure :16 shows an alternative form of the selector switching parts; and

Figure 17 is a sectional view of the contact members in the plane |1-|1, Figure 16.

Referring to Figures l, 2, 4 and '6, the ,numeral 20 denotes a channel-shaped frame having upwardly extending Abearing portions 2| and 22 (Figure 6) in which is journalled a .cross-shaft 23. Airatchet 24 is 'secured centrally on the shaft 23. A pawl 25, pivoted on a cross rod 25, is adapted to engage the ratchet 24. An electro-magnet .21, mounted on an angular frame 28, is secured in the channel frame 29. An armature 29 is movably `held in knife-edge relationship in the magnet frame 28 and is normally held retracted from `the magnet 21 by a spring 30, as shown in Figure 1.

The karmature 29 has a .forked extension 3i into which is `secured in :snap relation a .spring clip or yoke 32. The upper or cross bar portion 33 of the yoke 32 overlies the ratchet 24, and in normal position ,asshown inFigures l1 and 6, the bar stands clear of the ratchet teeth. When the magnet 21 is energized, as in Figure 2, thereby drawing the armature .29and yoke 32 downward, the bar 33 engages the ratchet 24 and revolves the latter through substantially the arc of one tooth. During this action the spring construction of the yoke 32 permits the bar 33 to follow the circular motion of the ratchet.

A forked lever 34 is pivoted on a cross-rod 35 in the frame 20 below the armature 29, and is urged upward by diagonal springs 36. Due to the sectional showing in Figures 1 and 2, only one leg 31 of the forked lever 34 and one spring 33 appear therein, but it will be understood that the second yleg and spring are similar to those shown, the legs spanning the magnet 21 and magnet frame 28.

A light leaf-spring 38 is secured to the lever 34, and the free end of the spring 38 extends through a slot 3s in the downwardly bent rear end il of the pawl 25. When the lever is in upper or normal position, as shown in Figure 1, it presses the leaf spring 33 ilat against the bottom of the pawl t and' holds the latter clear of the ratchet 24. However, when the lever Sil is depressed as in Figure 2, the spring 3S is flexed and urges the pawl 25 resiliently into engagement with the ratchet 2t.` i

An adjustable screw lll in the armature 29 is adapted to engage the top of the forked lever 34 depress the latter, as shown in Fig. 2, when the armature is drawn down by the magnet 2l.

4 actuate the switch 62 in the usual manner during upward movement of the lever 34.

Referring to Figures ll, 5, and 6, it will be seen that the rear end 5l of the shaft 23 carries a disk e8 tightly secured thereon, as by pressing or the like.

The disk e3 has a radially extending lug 69 adapted to engage a stationary stop 1Q provided on the frame side member 22. A torsional reset spring 7l coiled around the shaft 23, Figures 2 and 6, normally holds the lug 69 retracted against the stop 'lll as shown in Figure 4.

After depression of the lever 3B and afterfthe armature 253 has been released by the magnet 2l', the upward return of the lever Sil is controlled by time delay means of any suitable type, herein illustrated as a pneumatic device constructed a follows:

A bottom cap (i2 secured to the frame 2li, has screwed therein a body member or casing 43, forming a lower chamber 44. Aexible diaphragm of a suitable air-tight material such as flexible fabric impregnated with synthetic rubber, is peripherally sealed to the top of the casing i3 by means of a screw ring 45. Pressure disks l? and i3 are pressed against the central portion of the diaphragm 45, a screw 4S securing the disks and diaphragm together and also to the bottom of the lever 34.

When the lever 34 is in normal position, Figure l, the elevation of the diaphragm i5 provides an upper chamber 5@ between the latter and the casing 53. A central passage 5l in the 'casing A3 terminates in a downwardly directed valve seat 52. A thin valve disk 53 is normally pressed upward against the seat 52 by a light spring 54, a stud 55 serving to guide the spring and also to act as a limit stop for the disk 53.

A small orifice 56, leading from the upper chamber 53 onto the lower chamber All, is cooperative with a cone-pointed screw 5l to form an adjustable needle-valve passage between the chambers.

The lower chamber lil may have a breather opening 53 provided with a screen 59 to prevent entry of dust. Where the device is to be used in locations involving very fine dust, undue moisture, fumes, or the like, breather 58 may be omitted, and if it is desired to minimize compression in the lower chamber, an alternative construction such as that shown in Figure 3 may be used. In the latter construction, the bottom cap 42a is deepened and is secured in a suitable opening in the main frame Ella by'any convenient means, such as a strap 6i). This structure provides large volume in the lower chamber 44a, preventingA undue rise in pressure during operation as hereafter set forth, but at the same time remaining sealed against the exterior atmosphere.

An offset bracket bl, Figures 1, 2, and 6, is secured to the side of the frame 20 and carries switching means 52 of any suitable type herein illustrated as a well-known commercial switch having an actuating leaf 63 and normally open contacts 6A and t5. As the internal structures of such switches are Well-known in the art and form per se no part of the present invention, no detailed description thereof isr required, the contacts fili and vand their operation-being Shown diagrammatically in Figures l0 to 16,

inclusive. f

An adjustable pin, securedin the forked lever 3lis adapted to engage the leaf 63 and The disk 63 has therein an even number of l.equally spaced tapped holes l2, the holes corresponding in number and angular spacing to the number vand spacing of the teeth of the ratchet 2d. A transverse block 'i3 is secured to the disk by means of two shoulder screws lll. An insulating disk 'l5 has two oppositely disposed holes le engaging the shanks l'l of the screws 14.

Light compression springs 'i8 on the Shanks 'Il normally hold the insulating disk 'l5 fiat against the block li'l, but the holes iii have sufcient clearance about the Shanks ll to allow the disk to be rocked inwardly and outwardly against the spring pressure as illustrated in Figures 6 and 9. An outwardly extending metallic switch arm I9 is secured to the insulating disk l5.

Two parallel contact leaves til and 8| are mounted on the frame member 22, being electrically insulated from the frame and from each other as shown in Figure 6, andv provided with

terminal lugs

32 and 83 respectively, Figures 4 and 5.

The leading edges 34 and 85 of the contact leaves and 8l are flared outwardly as shown sectionally in Figure 7, the flared opening between the leaves being in the normal path of circular travel of the switch arm 'F9 and normally adapted to receive the latter in the manner of a knife-switch. The outer leaf 8i? is resilient, while the inner leaf 8l is substantially rigid and has an outwardly inclined deflector tab 86 eX- tending from its rear edge.

When the arm l@ is swung in its forward direction by the ratchet mechanism, that is clockwise in Figures 4,: and 5, the arm enters the switching position from the right, it moves between the leaves 8i! and Si to engage both of them and establish a conducting bridge between them as shown in full lines in Figures 7 and 6. If the arm i3 receives further forward motion it moves out of contact position toward the left, the disk 'd5 rocking to vallow the arm i9 to over-ride the deflector tab 8G. Thereafter, upon return or reset motion of the arm lil toward the right (Figure 7) the arm engages the inner side of the deflector tab 86 and is rocked inwardly to ride behind the leaf 8l, thus avoiding contact with the outer leaf 3Q.

From the foregoing description, illustrated clearly by the arrow paths in Figure "i, it is evident that the arm lS can establish electrical connection between leaves 8i! and 8l only when it engages the switching station in a forward direction, such connection being prevented when the arm enters and passes the station in the reverse or reset direction.

y Referring again to Figures l, 2 and 3, the general operation of the device is as follows:

The device being initially in normal or re-set position, when the magnet 2l receives an energizing impulse, lthe Varmature 29 is drawn downward to revolve the ratchet 24 and to depress the'b lever 3d `as `previously described. As the lever 34 is depressed, the depression of the vattached diaphragm 45 suddenly forces air out of the chamber Sil past the check valve 53. When the magnet 2l is die-energized the armature 23 immediately snaps up to normal position, but rise of the lever 34 is restrained by the resistance to upward motion of the diaphragm i5 due to atmospheric pressure above it, the check valve 53 being closerL against reentry of air below the diaphragm. The pawl consequently remains in engagement with the ratchet 24, holding the latter against rearward rotation by the torsion spring 1l.

Under the upward urge of the diagonal springs 36, a partial Vacuum is created below the diaphragm 45, and air moves in through the re stricted needle valve orice 5t to gradually relieve the vacuum and allow the diaphragm to rise throughout a period of time dependent on the strength of springs and the adjustment of the needle screw 5l in the oriiice 55.

If the magnet 2'! receives n-o further impulse until the diaphragm has allowed the lever 3d to engage and rock the pawl 26 as shown in Figure 1, the pawl releases the ratchet 24 and the shaft 23 is rotated rearwardly by the springA li to reset position, the lug 59 encountering the stop l@ as shown in Figure 4. However, if a second impulse is received by the magnet 2l before the lever 34 has had time to release the pawl 25 as described, the lever 34 is again driven downward and the above action repeated, the ratchet being advanced a 'second step.

From the foregoing it is evident that a series of impulses to the magnet 2l causes the ratchet 24 and attached parts to be rotated by successive steps without reset until, following an impulse, a sufficient pause occurs to permit the lever 34 to rise without interruption. It is further evident that the duration oi the time required for reset to be effected may be set by adjustment of the needle valve screw 5l.

As the shaft 23 is advanced by rotative steps, the switch arm 'i9 (Figures #l and 5), is moved by corresponding steps, and when the requisite number of impulses has been applied, the arm closes the connection between. members lili and 8l as previously described. The shoulder screws 'll may be placed interchangeably in any selected pair of holes l2 in the disk (it, allowing the arm 'i9 to be set at various angular normal positions with respect to the contacts Sli and il! to cause closure of the latter after any desired number of impulses within the range of the device. Thus in Figure l the arm is set to close contact on the second impulse for purposes of illustration.

During upward movement of the forked lever 34, near the upp limit of its travel, the pin 6E, Figure engages the leaf 63 to actuate the switch 62.

When the device is to be applied to circuits such as those illustrated herein, the relationship between the actions ci the switch arm lli, lever 34, and switch are set sho .n in Figures io, ll and l2.

Figure lil illustrates that the switch i2 has been released by the pin G5 and thereby allowed to open early in the downward motion of the lever 34, that is, before the switch arm 'lli can have connected the contacts Sil and 8 l.

Figure ll illustrates the instant of closure of the switch 62, when the lever 34 is engaging the pawl 25 but before rocking the latter to disengage it from the ratchet.

. Figure 12illustrates the device during re-set lll - tions on the iirst and third impulses.

with the arm "I9 revolving rearwardly, the pawl 25 released and the switch d2 remaining closed.

In the diagrams, Figures lo, l1 and 12, wires 8l and 8S may represent leads forming part of a circuit to be closed by the device, wire 8l being connected to the vContact leaf member Sil and wire St .to one terminal 3Q of switch @2, while contact leaf and the second terminal Sill of switch 62 are connected by a short lead 9|.

Figure l0 shows that no circuit is established between leads t? and Sil during the motion of switch arm is, since switch @2 has opened before the arm 'i9 can bridge contacts il@ and 8i, as set forth above. In Figure lo, however, contacts 8l! and 8l are already bridged, so that closure of switch 52 completes the connection between leads 'l and E353, and this connection persists during the time required for the lever 34 to rock the pawl 25 to disengaged position, whereupon reset occurs and the circuit is broken by arm 'l as shown in Figure l2. However, it is evident also that if the selector arm i9 is in any other than contact position when the rise of arm is being completed as 'set forth, no circuit is closed.

To summarize the above described action brieiiy, it will be seen that if at the completion of a series of energizing impulses, the selector arm 'lo is on contact station, the device will first close a control circuit, then automatically re-set. If at the completion of the series the arm 'I9 is in any other than contact position, no control circuit is closed, and the device simplyy re-sets.

Figure 13 illustrates the application of the device to selective remote control of a plurality of devices by means of a single pair of wires. The magnets 2l, 2l@ and 2lb of three of the devices hereinafter generally designated as selective relays 94, 54a and 94h are connected in parallel across common wires E52 and 53 over which the selector impulses are to be sent. The selector arm 19 is arranged to engage contacts Sil and 8| on the second impulse, while arms lQa and 19h are respectively set to engage their contact sta- For purposes of clarity and to avoid undue structural showing and complication of the diagrams, the stops 7B, 'lila and lill are shown diagrammatically as engageable directly by the arms lll, '49a and 79h, it being understood that mechanically the various arm settings may be made as explained in connection with Figures e, 6, and 8.

As previously stated, the invention is adapted to selectively control the operationcf any desired types of electrical devices, and for purposes of illustration such devices are shown as power relays 55, a and S5". The magnet 9S of relay 95 is connected on one side to the wire 87 and on the other to a conductor al connected to one side of a suitable source oi local current. The wire 88, connected to the switch terminal 89 as described in connection with Figures l0, ll and 12, comprises the second side of the local current Supply.

The power relay 95 may have any desired secondary switching arrangement suitable for the particular circuit or circuits it is to control, such as normally open contacts et adapted to control a circuit through leads S9 and. lilll. Relay 555 may also include a pair of normally open contacts Ill! connected via leads |62 and ISS with conductors 8l and 88 respectively, and adapted to provide a holding circuitI for the relay 95 as hereinafter described.

The connections of power relays S5@ and 95h i and their relationships with their selective relays 'I9a and 19h are the same as those relating to relay $5, the corresponding parts throughout being designated by the same numerals with suffixes a and b respectively.

To operate .the system, a series of impulses is sent over the control conductors 9'2 and 93, the time intervals between impulses being less than that necessary to allow re-closure of the switches 62, $32ad and 62h in the manner previously set forth. For example, let it be assumed that it is desired to actuate power relay S by remote control over

wires

92 and 93, without closing either power relays 95a or 95h.

Since selective relay 94 is set to close contacts 80 and 8l in the second step position of arm 79, two impulses are sent over the

lines

92 and 93. These impulses are received by all three magnets 2l, :Ele and 2lb, causing the arms 19, 19e and lsb to be advanced two angular step ,g

positions as shown. Since the second impulse is the last of the series, as soon as the predetermined tinie-delay period of the selective relays permits, the

switches

62, 62a and 62h are closed as described in Figure 11.

Figure 13 shows the condition of the three sets of apparatus at the instant of these closures. Since arm 79 is bridging contacts 8) and 8l, a circuit is established from supply conductor 88 via switch t2, wire 9|, contact member Sl, arm 19, contact member 8l), and wire 8l to power relay magnet 96, thence to supply line ill. er relay 95 is thereby closed as shown. No such circuits are established through selective relays 94a or Sb, however, since arm 'lila has over-ridden its switching position and arm lh has not reached its switching position. As a consequence, only relay Q5 is actuated following the series of two impulses.

Subsequent to closure of switches 62, 622L and 62h, that is upon completion of the pre-determined time-delay-period of the three selective relays 9i, 9de and 9th, all three reset to Zero position by release of their pawls in the manner previously explained. Upon reset, arm i9 breaks its connection between contacts 3l] and 8l, and if power relay 95 is equipped with the holding contacts lili which close as it is energized, its magnet 96 continues to receive current via branch m3, contacts lill and branch E92 until its main current supply is subsequently broken either manually or automatically, depending on the type of apparatus controlled by it.

During resetthe arm ige of relay Qta, in passing through its switching station, is prevented from bridging its contacts 853a and 8la in the manner set forth in connection with Figures 6 and 7, so that no circuit can be established therethrough. Similarly, arm lh can establish no circuit, as it engages no contacts whatever.

While the operation has been illustrated by a' .relays connected to a common pair of control conductors, the only relay which will close its desired circuit in response to a series of im- Pow- " mined for equal duration, but any exact equality of time lag normally is not required, it only being essential .that none of the relays shall have a time-lag to switch-closing position shorter than the normal interval between impulses of a series.

The diaphragm delay means operates as a type of dash-pot, but lacks the disadvantages of the usual type of dash-pot such as close-fitting rubbing parts subject to sticking, requiring lubrication, liable to varied action due to temperature changes, etc. Lack of these inherent faults, plus the eiiective protection of the orice 56 against dust and the like, adapts the device to operation over long periods without substantial variation and to accuracy oi' setting without unduly precise and expensive manufacture.

As previously stated, the invention is adapted to incorporation in a wide variety of circuit arrangements and combinations, Figure 13 being one typical illustration.

Figure 14 illustrates several variations in circuit arrangement as follows, the relay @il being set to respond to three successive impulses from the lines S2 and 93. In this variation the second wire i523 from the movable holding contact member lll of power relay g5, instead of being connected directly to supply line 88, is normally connected thereto thro-ugh the switch 62. By this arrangement, supposing the relay to have been locked in upon actuation of the selective relay Sli, the rst subsequent impulse received by magnet 2l will cause the switch contacts Effi and 65 to open as in Figure l0, thereby breaking the described holding circuit of relay @5 and allowing the latter to open. In multiple station systems using this device, the setting of the various selective relays would preferably be 'made from the number two impulse stations upward, no relay being set to actuate its connected device (for instance relay 95) on one impulse, leaving the single impulse operation available for remotely controlled release. With such a systemy the operator, after throwing and locking in any desired connected device by the proper series of impulses, can then release the remote connection at any time by sending a single impulse over the

control lines

92 and 93.

Figure le also illustrates means by which' the relay 95 or similar device may be furnished with current over the

samecommon wires

92 and 93 which carry the selecting impulses. In this case wires BS and ii's" are connected to

lines

93 and 92, respectively, and a suitable condenser ls'i is connected between the magnet 2 and line 92. The condenser H65 is impervious to dir-ect current, but is adapted to pass alternating current for which the magnet 2l is wound, as for example telephone ringing current. A steady source of direct current is provided in

lines

92 and 93, which current has no effect on magnet 2l, due to the condenser.

When alternating current impulses are impressed on the

lines

92 and 93 they energize the magnet 2l, and if the series has the proper nurnber of impulses (three in Figure 14) the selective relay connects the power relay 95 to the direct current supply in

lines

92 and 93 in the manner previously pointed out.

Figure 14 further illustrates that the switch 22, Figures l, 2, and 4, may be provided with additional contacts for any desired purpose. For eX- ample, the movable contact 64 may be made to engage a lower contact |66 when the magnet 2l is energized, completing a circuit through a device such as a signal lamp |01.

Figures 16 and 17 show an alternative construction of the selective switching arm and contact mechanism. In this form the arm |08 comprises a resilient leaf provided with a conducting hub |09, both hub and arm being insulated from the rotary shaft end 67 by a bushing I I0 of iiber or the like.

A stationary brush II I is adapted to convey current to the hub |09 and arm |68. A stationary contact member |I2 is laterally inclined as shown on Figure 17, and has on its underside a iiat insulating member |I3. The end of the arm |08 is also laterally inclined. When the arm |08 is rotated in its forward directionthat is from the right in Figure 17-it encounters the outer face of the contact member ||2 to establish electrical contact therewith.

Further forward movement of arm |03 causes the latter to flex outward, over-ride the contact member II2, then snap inward again. Upon rel set, when the arm moves backward or toward the right in Figure 17, it engages the insulating member II3, flexes inwardly to under-ride the latter, and thus passes the switching station without having engaged the contact member I I2.

In the previously described examples the selective relays have been described as each having a single switching station, but it will be obvious that the device may be constructed to provide a plurality of switching stations on the same relay, as illustrated diagrammatically in Figure 15. In this example, in addition to contact mernbers 80 and 8|, adapted to be engaged by the arm 19 at the ninth impulse, a second pair of similar contacts |I4 and II5 may be provided for engagement in station I. An example of the use of such plural switching stations would be in the case of a multiple device system wherein it may be desired to control two or more devices individually or in combination. Thus one selective relay may be controllable either by seven or by nine impulses as shown, while another selective relay of the same system may be similarly arranged for response either to three or to nine impulses. By this arrangement, a series of three impulses `will actuate only one of the relays, a series of seven will actuate only the other, while a series of nine will actuate both at once.

While the invention has been set forth in preferred form, it is not limited to the precise structures illustrated, as various modifications may be made without departing from the scope of the appended claims.

What is claimed is:

1. In a device of the character described, in combination, a support, a shaft journalled in said support, a ratchet on said shaft, resilient means urging said shaft and ratchet in one rotary direction, a stop on said support, a member on said shaft adapted to engage said stop in said direction, means including an electro-magnet responsive to successive electrical impulses to revolve said ratchet step by step in the other direction, a pawl, means operable by said advancing means to move said pawl into holding engagement with said ratchet, means to release said pawl from said ratchet, and a time-delay device adapted to delay the operation of said releasing means.

2. In a device of the character described, in combination, a support, :an electro-magnet on said support, an armature cooperative with said magnet, said armature being normally retracted from said magnet, a ratchet mechanism on said support and operable by said armature, said mechanism including a holding pawl, a member movably attached to said support .adjacent said armature, resilient means normally urging said member against said pawl to hold said pawl out of holding engagement, said armature when attracted by said magnet being adapted to move said member out of engagement with said pawl, resilient means attached to said member and yadapted to move said pawl into engagement lwith said member when said pawl is disengaged by said member, and means connected between said member and said support and adapted to retard return movement of said member toward said pawl when said member has been released by said armature.

3. In a device of the character described including a ratchet and electromagnetic means to move said ratchet, a holding pawl adapted to engage said ratchet, a member normally engaging said pawl to hold the same out of engagement with said ratchet, said member being movable away from said pawl by said electromagnetic means, and means operable by said member upon withdrawal thereof from said pawl to press said pawl into engagement with said ratchet.

JOHN J. SHIVELY.

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

UNITED STATES PA ILNTS Number Name Date 2,235,038 Pearce Mar. 18, 1941 1,613,446 Dumont Jan. 4, 1927 2,245,862 Koenig June 17, 1941 1,795,149 Shivers Mar. 3, 1931 835,441 Laird Nov. 6, 1906 2,269,856 Nelsen Jan. 13, 1942 2,063,354 Thorp Dec. 8, 1936 2,263,298 Haimbaugh Nov. 13, 1941 2,327,429 Hull Aug. 24, 1943 2,103,373 Oestnaes Dec. 28, 1937 2,029,136 Stevens Jan. 28, 1936 2,296,760 Barry Sept. 22, 1942 2,274,564 Richardson Feb. 24, 1942 1,995,721 Sanford Mar. 26, 1935 FOREIGN PATENTS Number Country Date 189,222 Greek Aug. l2, 1907