US2658111A - Switching apparatus - Google Patents

Description

Nov. 3, 1953 K. w. GRAYBILL ET AL 2,658,111

SWITCHING APPARATUS 2 Sheets-Sheet 1 Filed May 16, 1950 FIG. 2

IN VEN TOR. KENNETH W. GRAYBILL BY HANS SENGEBUSCH ATTORNEY Nov. 3, 1953 K. w. GRAYBILL ET AL 2,658,111

SWITCHING APPARATUS Filed May 16, 1950 2 Sheets-Sheet 2 5041) 27 I III 42 L lll l l l l |||||u o L H t INVENTOR. KENNETH W. GRAYBILL Y HANSSENGEBUSCH ATTORNEY Patented Nov. 3, 1953 SWITCHING APPARATUS Kenneth W. Graybill, Elmhurst, and Hans Sengebusch, Villa Park, Ill., assignorsa to Automatic. Electric Laboratories, Inc.,, Chicago, 111., a, corporatio-n. of Delaware Application May- 16, 1950, Serial No. 162,334

16' Claims. 1

Thisinvention relates to. improvements in automatic telephone exchange systems. and more particularly to. switching apparatus for such systems.

In such systems. it is. desirable to obtain a switching apparatus. which while attending to a large number of lines will not become too bulky, complicated or expensive. Such a switching apparatus is of great importance as it will enable a considerable reduction in the. amount of exchange space necessary to house such switching equipment as well as reducing costs. in manufacturing and maintaining such switching apparatus as compared with systems using switching. apparatus of the existing types.

An object of the invention therefore. is te provide an improved switching apparatus characterized in that the apparatus is constructed and arranged to perform both a rotational and a radial movement with respect. to its axis of rotation.

, Another object of the invention is th provision in this type of switching appartaus of an clectromagnet having a curved pole-piece and curved armature considerably simplifying the linkage which was formerly necessary to accomplish radial movement from different rotative positions.

A further object of the invention in keeping with the last mentioned object is the provision of means in the form of the curved pole-piece magnet to directly drive the switch in its radial movement regardless of its rotative position.

Still another object of the invention is the provision of an improved radial stepping mechanism.

A feature of the invention resides in the provision of a plunger at the axis of rotation of the switch for operating off normal and predetermined step contact springs.

' Another feature of the invention resides in the novel arrangement of a plunger operated release mechanism for the switch.

- And still another feature in keeping with the last named feature is the provision of a particular release mechanism for the switch.

.These and other object and features will be more particularly pointed out in the ensuing specification and appended claims taken in con junction with the accompanying drawings in which:

Fig. 1 is a plan view of the switch.

Fig. 2 is a side elevation of the switching mechanism partially broken about its axial hub to more clearly show the axial plunger arrangement referred to above.

Fig. 3 is a schematic sketch showing the operational relationship of the axial plunger with 2. the wiper shaft. and the off normal and particue. lar step springs.

Fig. 4. is an enlarged portional plan view of the release mechanism. for the switch.

Fig. 5 is an enlarged portional side elevation taken from the lower side of Fig. l, also showing particularly the release mechanism and especially the. release plunger arrangement.

Fig. 6 is an enlarged portional side elevation showing theparticular release mechanism taken from the left side of Fig. 4.

The apparatus; illustrated in the drawings, Iv through. 5' involves a base I and a shouldered post in thereon onto which is rotat-ively mounted a wiper carriage 2 having a hub 3, and along one end of the base a radially disposed contact. bank of bare wire contacts 4. In this bank there are ten groups of contacts, each group comprising a pair of dual rows of bare wire contacts, the rows being ten wire contacts. deep. These Wire contacts 4. are particularly shown in Figs. 1 and 2 and are held in position by insulator elements 5 and 6, the lower insulator element: 6 being secured to the base I. Tag ends 4aof the bare wire contacts extend below insulator 6 for the purpose of connection t leads soldered thereto in well-known manner. Centrally" disposed along the opposite edge of base I from the. radial contact bank is a curved pole piece radial stepping magnet l. Magnet 1 has a curved polepiece 8 attached to the end of the core adjacent post 3a, and in spaced relation thereto and above. it, a curved end 9 of a heelpiece 10. The other end of the heelpiece is joined with the other end of the core and fixed by means of a bolt II and spacer [2 to the base I; Radial stepping magnet l is relatively flat, the core being substantially rectangular in cross section. Pivotally mounted to the hub 3 and positioned between the hub and the curved polepiece and heelpiece of magnet l is a correspondingly curved radial stepping armature 13. Its pivotal mounting It lies in a plane very near to that of the curved heelpiece Ill. Armatur I3 extends upwardly from its pivotal mounting l4 and is bifurcated thereabove. A retractile spring I5 is secured at one end to armature l3 and at the other to an extension below wiper carriage 2. Slideably mounted on carriage 2 is wiper shaft IE. Wiper shaft i5 is tubular and has a spring 16a running from its wiper end !1 through its entire length and is secured at its other end to a rearward extension l8 of the wiper carriage 2. Running longitudinally a predetermined distance in the under side of shaft I6 is a slot 19, the

purpose of which will be more particularly detailed hereinafter. Along the upper central por tion of shaft it are 13 notch-like recesses. Piv otally mounted to the bifurcated extension of armature l3 above shaft I6 is a pawl 20. Pawl is normally positioned in the foremost notch with relation to the contact bank of shaft 16 and is urged downwardly thereinto by spring 2| attached to pawl 20 and the bifurcated extension of armature It. Just forward. of the pawl tip the distance of its stroke is positioned a pawl stop 22. Rotatively mounted to the side of the carriage 2 is a radial detent 23. This detent 23 is normally seated in the notch immediately rearward to that seating pawl 20 and therebeneath. Detent 23 also has a retractile spring 24 to urge it normally downward into the notches. Secured to the wiper end I? of wiper shaft 16 are a pair of dual armed wipers 25, which are aligned by means of pegs 26 with respective dual rows and bare wire contacts 4. In normal position wipers 2Z5 lie just out of contact with the bank wires so that the first radial step of the wiper shaft [6 will. carry them into contact with the first group of contacts in the particular radial row with which the wiper carriage is aligned.

The rotational stepping mechanism will now be described. Extending in a plane parallel to the base I and secured to the hub 3 is a ratchet disk 21 containing eleven notches along on side of the hub, and associated therewith and affixed to the base is a rotary stepping magnet 28 having an armature 29 and a rotary stepping pawl 30 pivotally attached to the end thereof. Rotary pawl 30 has a small spring 3| urging it always into the ratchet teeth of disk 21, Armature 29 also has a retractal spring 32 to hold it normally out of its operated, driving position. Rotary pawl 38 is provided with a front stop 30a attached to base i at a point equal to the full stroke of pawl 30. Likewise, backstop 36b is provided in a well-known manner. On either side of radial stepping magnet l are positioned sets of contact springs 33 and 34 and also another set of contact springs 35 is positioned between the hub and the radial contact bank. These springs are insulatively secured to the base I in well-known manner. Each of these three sets of Contact p gs is operated by an operating arm, pivotally mounted to the base I. These are respectively 36, 37 and 38. The springs are operated at various rotary positions of wiper carriag 2 when their contact arms engage studs such as studs 39 and 40 on disk 21.

Mounted on hub 3 and extending from either side thereof is a rotary stop plate Illa (Fig. 1). he stop plate I90. determines the rotary sweep of carriage 2 mounted on hub 3 by being positioned to engage either extremity of the curved end of heelpiece ill.

The releas mechanism will now be detailed with particular attention being had to the enlarged views particularly specific to releas depicted in Figs. 4, 5 and 6. Along the side of base I opposite from the rotary stepping magnet 28 are mounted two magnets, the release magnet 4| and the partial release magnet 42. The release magnet 4! is equipped with an armature 43 which lies in a plane substantially parallel to that of base I. At the end 44, of the armature 43, in a plane normal thereto, a release link 45 is rotatably mounted. Release link 45 extending downward from its rotatable mounting on arma ture 43 is bifurcated, the extremities being designated at 46 and 47 (Fig. 6). A spring 48 connected to bifurcation 4i and the extreme end 44 of armature 43 tensions the release link 45 normally against the partial release armature Between hub 3 and armature 43 rotatably mounted to base i are two release lever mountings. One of these rotatably mounted release mountings 50 is for radial release. A rotary detent 52 is mounted on one side of the rotary release mounting 5! and is positioned beneath the rotary pawl 30 and in the next adjacent ratchet tooth thereto. A. rotary detent spring 52a is mounted on the base I and adapted to bias the rotary detent 52 into engagement with the ratchet teeth of disk 21. Another arm 53 of the rotary release mounting extends on the other side of the rotatable mounting 5| and is normally positioned under tip 45 of the bifurcated release link 45. The radial releas mounting 50 has a similar arm 54 extending therefrom on one side of its rotatable mounting and normally positioned immediately beneath the other tip 41 of the bifurcated release link 45. Extending from the other side of the radial release mounting 50 is an arm 55. At the extrem end of arm 55 is an arcuate member 56, its arcuate degree corresponding to the curvature of the hub 3. This member 56 is in a plane parallel to base I and may be particularly seen in Figs. 4 and 5. Slideably mounted adjacent hub 3 through a hole provided therefor in disk 21 is a release plunger 51. Release plunger 51 extends between arcuate member 55 and the rotatable radial detent 23. Member 56 is arcuately arranged so that the lower end of release plunger 5! will always rest thereon regardless of the rotary positio of the wiper carriage. Partial release magnet 42 is positioned adjacent release magnet 4| so that its armature 49 engages the side of bifurcated tip 41 of release link 45. As release link 45 is rotatably mounted, movement of armature 49 will cause the release link to rotate sufiiciently to remove tip 46 from alignment with rotary release lever 53 while tip 41 which is somewhat wider than tip 46 remains aligned with radial release lever 54. The consequence of this disengagement will be more particularly pointed out in the release operation of the switch.

The sets of radial off-normal and particular step springs 58 and 58a respectively are mounted along the edge of the base adjacent rotary stepping magnet 28. A rod 59 having a buffer 60 at one end and engaging the oil-normal springs 58 which are tensioned thereagainst is pivotally mounted and connected at its other end attached to the lower end of a plunger 6| as shown diagrammatically in Fig. 3. Plunger 5| shown in Fig. '2 is mounted inside of hub 3 and along the axis of rotation thereof. The upper end of plunger 6| is attached to a bell crank 62 which is rotatably mounted at pin 63 to the side of wiper carriage 2. The other arm 64 of the bell crank extends upwardly into slot 59 in the wiper shaft I6, and at normal rests against end 65 of slot I9 under tension transmitted thereto from the oilnormal spring set 58 over the linkage described and shown in Fig. 3. Und r the off-normal spring set tension, bell crank arm 64 rotates counterclockwise on the first radial step of wiper shaft IE and springs 58 break contact. When the radial movement reaches its last step, the other end of slot l9 designated at 86 engages and further rotates bell crank arm 64 to operate particular step springs 580., thru buffer 50 and the intermediate linkage. As it was stated that plunger 6! is positioned within hub 3 and on its axis, it will be undcrstood that the hub is supplied with necessary apertures through which the connecting rod 59 and the bell crank 62 may extend.

sets of interrupter springs 61 and 68 may be provided respectively for the rotary and radial stepping movements For example springs 61 are shown positioned so that they will break contact when the rotary stepping armature 29 pulls up. Likewise a bllfil 69 extending SidWiS flOI'n the upper extremity of the bifurcated radial armature l3 may be engaged to break the contacts 6f springs BB when armature l3 pulls up.

o eration The operation of the switch from the normal position of the mechanism as described herein before now follows:

When rotary stepping magnet 28 is alternately energized and deenergized as by dial pulsing in well-known manner, armature 29 is alternately attracted and released. by the magnet and retractile spring 32 respectively. Each time armature 29 is attracted pawl 30 drives the ratchet toothed disk 21 one step in a clockwise direction. As pawl 30 reaches its full stroke, rotary detent 5! falls into place in the next adjacent rachet tooth from its former position. Steppin ina net '28 in deenergi'zin'g permits reti-actile spring 32 to pull pawl 30 backward and under the urging of spring 30, it falls intothe next tooth. This operation may be repeated to -step the disk to an of its ten positions. As the disk 2? is ri idly connected to hub 3 and thereby to the wiper carriage and wiper assembly thereof, the wiper carflags 2 and Wiper assembly thereon moves to the rotary position corresponding to the number of times the "rotary step ing magnet is pulsed or stopped. This then places the dual wiper pairs 25 at the mouth of the corresponding group of bare wire contacts in the bank. The radial stepping magnet 1 is now similarly energized and deenergized, as by dial pulses in equally well=known manner. Each time magnet i energizes, curved armature I3 is attracted to the correspondingly curved p'o1e--piece 8 of the radial step ing mag= net regardless of the rotary position to which the carria e has previously been directed. As armature i3 is attracted to pole-piece 8, pawl is urged forward. and as it is within one of the notches on shaft 15, it slides the shaft forward to the limit of its stroke where it is stoppedb stop 22. Meanwhile detent 23 rides up the radial surface in the notch in which it is resting and when the pawl 20 reaches its full stroke falls down into the next adjacent notch under tension of spring 24. This movement of shaft [6 in turn steps the wipers 25 into Contact with the first pairs of wire contacts in the particular group to which the carriage had previously been rotated. Detent 23 then holds the shaft in this position while magnet deenergizes, and retractal spring I5 thereu on pulls armature I 3 back. and away from the pole-piece. In so doing, pawl 25 drops into the next adjacent notch under tension of spring 2|. Meanwhile, as the pawl 29 had been moved forwardand returned, the interrupter springs 68 were alternately broken and made by buffer 69. Also as pawl 29 drove the shaft i6 forward in its first step, the tension in radial offnormal springs 58 rotates arm 54 of hell crank 52 counterclockwise so that the axial plunger 5! raises, buffer 60 being moved by springs 53. In this manner the radial oil-normal springs 58 opcrate. This radial stepping may then be reheated a number of times corresponding to the impulses operating magnet 1.

Returning for a moment to the rotary move= merit of carriage '2, it will be understood that arms 36, 31 and 38 will operate springs 33. 34 and 35 depending upon the position of studs such as 39 and 40 in disk 2! with which they engage In order to release the switch, release magnet M is energized. As armature 43 is attracted, m lease link 45 and its bifurcated ends 48 and 41 are pressed downward engaging arms 53 and 54 of the rotary and vertical release mountings respeu' tively. As it was previously stated that these release mountings were rotatable, it will be seen that depressing of arms 53 and 54 respectively raises rotary detent 52 and arm 55. Arm 55 cor responding'ly, through its arcuate end 56, raises plunger 51 which in turn rotates the radial ue= tent 23 clockwise out of its notch and raising pawl 20 above it likewise out of its notch. shaft [6 and attached wipers 25 return rearwardly to normal under the tension or retractile spring lea, As soon as the wipers 25 have left the contact bank, the rotary detent 52 in being rotated clock= wise and urging rotary pawl 30 alone with itself out of the ratchet teeth or disk 2i, the entire carriage rotates counterclockwise back to the norm'al position with stop plate 8a against the left extremity of pole=piece 8, shown in Fig. 1, under the spring tension of a helical spring or in the hub or a spring such as 10 (Fig. 1 In case ch15 partial release is desired, the partial release mas net 42 is energized first, to prepare the switch for partial release only. when armature 49 is attracted in this manner, the bifurcated till 51 of release link 45, being pivotally mounted, ro tates until tip 46 is free of arm 53, but tip 41 being wider, is still in alignment with arm 54. Subsequently, upon operation of magnet 41-, re lease will occur as before except that only arm 54 will be depressed therefore permitting only radial release by plunger 51. In this manner partial radial release only is effected.

Having described our invention in detail what we desire to be protected by Letters Patent of the United states is:

1. In an electromagnet, a magnetic structure comprising a heelpiece and pole-piece with curved ends spaced apart and in registry one above the other, a correspondingly curved. arri'la-- ture, means pivotally mounting said armature for rotation about one axis. and means rotatably mounting the same for movement about a second axis perpendicular to said first axis, both mount ings independent of said heelpiece and pole piece, said pivotal mounting means arranged. in sub stantially the same plane as said heelpiece.

2. In an electromaenet, a coil having a rectum gula'r shaped core, a pole-piece connected to one end of said core and. having a curved pole surface, a heelp'iece having curved end spaced apart from and in. registry with said curved pole surrace, said heelpieeg connected at its other end to the opposite pole ei'ld of said core, and a cori-e spondingly curved, armature, rotational mounting means independent of said pole and heel pieces for mounting said armature to rotate about one axis, ivotal mounting independent of said pole and heel pieces tor mounting said arma ture to pivot about a second axis, said second perpendicular to the iiitasis, the ivotal mounting of said armature being in substantially the same plane with the curved end of the heelpiece.

3.- In an automatic switch; a base, a plurality of sets of contacts arranged in groups on said base, a set of wipers movably mounted with relation to said base, means for moving said wipers in one direction to a position for selecting a particular set of said contacts and for holding it in said position, an electromagnet on said base, a curved pole-piece on said magnet, a correspondingly curved armature for said magnet mounted to move with said wipers, and means controlled by said armature when said magnet is operated for directly moving said wipers in another direction regardless of the position resulting from the movement in said one direction while the wipers are held in said one position.

4. In an automatic switch, a rotatably mounted carriage, wipers slideably mounted thereon, means for rotating said carriage to any one of a plurality of predetermined positions, an electromagnet positioned adjacent said carriage mounted independently thereof, a curved pole-piece on said magnet, and a curved armature for said magnet pivotally mounted on said carriage, means on said carriage for moving said wipers along said carriage in any of said carriages predetermined positions, said armature pivoted in response to the operation of said electromagnet to control the operation of said second means.

5. In an automatic switch as claimed in claim 4, a stop plate on said carriage, one end of said plate making contact with one end of said polepiece in one rotary position of said carriage and the other end of said plat making contact with the other end of said pole-piece in another rotary position of said carriage, the rotary sweep of said carriage thereby determined by the engagement of the extremities of said curved pole-piece with said plate.

6. In an automatic switch, a rotatably mounted carriage, a shaft slideably mounted thereon and having stepping notches, means for rotating said carriage to any one of a plurality of predetermined positions, an electromagnet positioned adjacent said carriage and mounted independently thereof, a curved pole-piece on said magnet, a correspondingly curved armature for said magnet pivotally mounted on said carriage, said armature pivoting in one direction responsive. to the energization of said magnet, a bifurcated extension on said armature, said shaft being. in the cleft of said bifurcation, a retractile spring connected to said armature causing said armature to pivot in the opposite direction upon deenergization of said magnet, and a pawl pivotally connected to said bifurcated extension engaging the notches on said shaft so that when said armature is pivoted in the first direction said pawl steps said shaft radially in any of said carriages predetermined positions, and detent means for maintaining said shaft in any radial position when said magnet is deenergized.

7. In an automatic switch as claimed in claim 6, a plurality of radially disposed banks of bare wire contacts, and wipers extending from said shaft engaging said contact banks when said shaft is radially stepped.

8. In an automatic switch, a rotatably mounted carriage, a wiper shaft slideably mounted thereon having an elongated slot therein, means for sliding said shaft in steps along said carriage, a bell-crank rotatably mounted to said carriage and one end thereof within said slot, said crank engagable with one end of said slot, 9. plunger mounted along the axis of said carriage and connected at one end to the other end of said bell-crank, a set of contact springs, a buffer for said springs connected to the other end of said plunger, and a projection within said slot engaging and rotating said crank to operate said springs when said shaft is stepped one step in one direction, said springs again operated when the end of said slot, corresponding to the last step of said shaft in said one direction, engages and again rotates said crank.

9. In an automatic switch, a rotatably mounted carriage, a notched wiper shaft slideably mounted thereon, means for rotating said carriage to any one of a plurality of predetermined positions, a radial stepping magnet adjacent said carriage and mounted independently thereof, a curved pole-piece on said magnet, a curved armature for said magnet pivotally mounted on said carriage so that said armature is pivoted by the energization of said radial stepping magnet in any rotary position of said carriage, means on said carriage for restoring said armature upon the deenergization of said radial stepping magnet, a pawl pivotally connected to said armature and engaging said notches so that as said armature is pivoted said shaft is projected in the radial direction, a radial detent rotatably mounted to said carriage and normally positioned beneath said pawl in the next adjacent notch so that as said pawl projects said shaft one step said detent maintains said shaft in the stepped position, a plunger slideably mounted on said carriage engaging said radial detent, a rotary detent maintaining said carriage in the rotated position, a release magnet, an armature therefor, a centrally pivoted radial release lever, one end engaging said release armature, the other end being arcuate and engaging said plunger regardless of the rotary position of said carriage so that the energization of said release magnet operates said release magnet armature which in turn pivots said radial release lever which in turn slides said plunger to disengage said radial detent from said notches, a centrally pivoted rotary release lever, one end engaging said release armature, the other end engaging said rotary detent, said rotary detent disengaged when said release armature pivots said rotary release lever responsive to operation of said release magnet.

10. In an automatic switch as claimed in claim 9, a partial release magnet and an armature therefor, and means operable responsive to the operation of said partial release magnet for disengaging said rotary release lever from said release armature so that only said radial release lever is pivoted upon the subsequent operation of said release magnet.

11. In an electromagnet, a magnetic structure having a curved pole-piece, and a curved armature, means pivotally mounting said armature for rotation about one axis, and means for rotatably mounting the same for movement about a second axis perpendicular to said first axis, both mountings independent of said curved polepiece the curvature of said curved armature being equal to the curvature of a circle having its center at the axis of rotation of said armature and having a radius equal to the distance between said armature and its axis of rotation, the curvature of said curved pole-piece being equal to the curvature of a circle juxtaposed and concentric with said other circle.

12. In an electromagnet, a magnetic structure having a curved pole-piece and a curved armature having a surface concentric with a surface of said pole-piece, means for rotating said armature about an axis in a circle concentric to a circle including the curve of said pole-piece, and means for moving said armature about another axis perpendicular to the first axis thereby changing its concentric relationship with said polepiece means for mounting said armature independently of said pole-piece.

13. In an automatic switch, a rotatably mounted carriage, a shaft having stepping notches slidably mounted thereon, means for rotating said carriage to any one of a plurality of predetermined positions, an electromagnet positioned adjacent said carriage and mounted independently thereof, a curved pole-piece for said magnet, a correspondingly curved armature for said magnet pivotally mounted on said carriage, a bifurcated extension on said armature, said shaft being in the cleft of said bifurcation, a retractal spring for said armature and a pawl pivotally connected to said bifurcated extension for engaging the notches on said shaft to step said shaft radially in any of said carriages predetermined positions responsive to operation of said magnet, a retractal spring for said shaft connected to said carriage, a detent rotatably mounted on said carriage extending beneath said pawl and normally in the next notch from that occupied by said pawl, a release magnet and armature, a plunger slidably mounted adjacent said carriage engaging said detent, and linkage connecting connecting said release armature and said plunger for causing said plunger to rotate said detent and the pawl thereabove free of said notched shaft so that said shaft may restore under tension of its retractile spring responsive to operation of said release magnet.

14. An electric switch mechanism including a carriage having an axis of rotation, a magnet having a curved pole-piece mounted adjacent said carriage, an armature for said magnet, means for movably mounting said armature on said carriage for allowing movement of said armature about another axis, said armature having a curved surface opposite said curved surface of said pole-piece and concentric therewith, means for rotating said carriage to move the armature relative the magnet about said first axis while maintaining said surfaces in concentric relation, whereby energizations of said magnet may operate said armature about said other axis regardless of the rotary position of the car riage.

15. In an electric switch having an element, means for operating said element in a radial motion comprising a pawl contacting said element, an electromagnet with a curved heelpiece, and a curved armature connected to said pawl, rotatable means carrying said armature and said element mounted independently of said electromagnet, a pivotal connection between said armature and said rotatable means with an axis of pivot perpendicular to the axis of rotation of said rotatable means, and means for rotating said rotatable means to rotate said armature about a circle concentric to a circle including the curve of said heelpiece.

16. In an electromagnet, a magnetic structure comprising a heelpiece and pole-piece with curved ends spaced apart and in registry one above the other, a correspondingly curved armature, rotatable means mounting said armature, said armature arranged to pivot about an axis perpendicular to the axis of rotation of said means, said first axis arranged in substantially the same plane as said heelpiece and means for rotating said rotatable means independently of said heelpiece and pole-piece.

KENNETH W. GRAYBILL. HANS SENGEBUSCH.

References Cited in the file Of this patent UNITED STATES PATENTS Number Name Date ,269,278 Henderson June 11, 1918 1,504,227 Gent Aug. 12, 1924 2,419,301 Tragesser Apr. 22, 1947 2,460,921 Candy Feb. 8, 1949 2,481,276 Andersson Sept. 6, 1949 2,499,632 Coake Mar. 7, 1952 FOREIGN PATENTS Number Country Date 85,768 Sweden Mar. 10, 1936 292,261 Germany May 28, 1914

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