US2961493A

US2961493A - Tau-type cross-bar switch

Info

Publication number: US2961493A
Application number: US464153A
Authority: US
Inventors: Torisu Ryokichi
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-10-22
Filing date: 1954-10-22
Publication date: 1960-11-22
Anticipated expiration: 1977-11-22

Description

Nov. 22, 1960 RYOKICHI TORISU 61,

T-TYPE CROSS-BAR SWITCH Filed Oct. 22, 1954 8 Sheets-Sheet 1 INVENTOR R YOK ICH l TOR BY 7M ATTORNEY 8 Sheets-Sheet 2 Filed Oct. 22, 1954 INVENTOR Jon su RYo K I cm ATTORNE Nov. 22, 1960 RYOKICHI TORISU 2,961,493

T-TYPE CROSS-BAR SWITCH Filed Oct. 22, 1954 8 Sheets-Sheet 3 FIG. 3

INVENTOR RYOK IQH! BY w ATTORNEY T-TYPE CROSS-BAR SWITCH Filed 001:. 22, 1954 8 Sheets-Sheet 4 FIG. 9a F|e.9b FIG. IOa F|G.|Ob 32 I l- I] DDQCIDUUD J INVENTOR RYOK C 012 a 5L),

BY r ATTORNEY Nov. 22, 1960 RYOKICHI TORISU 2,961,493

T-TYPE CROSS-BAR SWITCH Filed Oct. 22, 1954 8 Sheets-Sheet 5 PIC-3.70

Flal7c 53 FIGWb INVENTOR RYomcm ATTORNEY Nov. 22, 1960 RYOKICHI TORISU 2,961,493

T-TYPE CROSS-BAR SWITCH Filed Oct. 22, 1954 8 Sheets-Sheet 6 FIG. l2b

INVENTOR ATTORNEY Nov. 22, 1960 RYOKICHI TORISU 2,961,493

'r-TYPE CROSS-BAR SWITCH Filed Oct. 22, 1954 8 Sheets-Sheet 7 FIG. I40 FIG. |4b

E E E L L L INVENTGR RYO K 6 HI To By M /62 ATTORNEY NOV- 22, 1960 RYOKICHI TORISU 2,961,493

T-TYFE CROSS-BAR SWITCH Filed Oct. 22, 1954 8 Sheets-Sheet 8 INVENTOR BY 745W/4%%\ ATTORNEY United States Patent T-TYPE CROSS-BAR SWITCH Ryokichi Torisu, 1054 Kamitakaido 4 chome, Suginami-ku, Tokyo, Japan Filed Oct. 22, 1954, Ser. No. 464,153

11 Claims. (Cl. 179-2754) This invention relates to improvements in switching mechanisms and particularly to switches of the cross-bar type for use in establishing connections.

It is an object of the invention to provide an improved and simplified switch structure of this type, inexpensive to manufacture, and having low maintenance costs.

Cross-bar switches consist essentially of a number of contact sets arranged in vertical and horizontal rows, with the set of contacts at the intersection of any two rows operated by conjoint motion of vertical and horizontal cross-bar members associated with said rows.

Switches of this type have also been provided where the number of intersecting members or bars of one group, for example, the horizontally located bars, sometimes referred to as selecting bars, is one half that number of the intersecting members or bars of the other group or veritcally located bars, sometimes called holding bars. In this case the longitudinal motion of a bar of the smaller group in either of two directions controls the selection of one or the other vertical row of contact sets for operation by a single movement of a bar in the larger group.

It is in connection with this type of switch that the present invention has been disclosed, although it should be understood that many of the improvements forming the subject matter of the present invention may be applied to other types of cross-bar switches Without departing from the spirit of the invention.

One of the features of the switch structure embodying the applicants invention is that longitudinal motion has replaced cross-bar rolling motion which has heretofore been employed in practice; another feature is a frame which is die-cast or punched out and press-worked, with switch-in plugs, and on which selecting magnets and holding magnets are fixed. The selecting magnets with common yoke are all concentrated at the left, two rows of five cores arranged one below another. Each selecting magnet has an armature, whose vibration, when released, is snubbed by a common rubber or spring carrying bar fixed on the common yoke. The holding magnets are also arranged likewise having a common yoke on which the cores and the armatures of the magnets are carried in horizontal position in a horizontal row.

Further novel features of the switch structure reside in the construction and mounting of the contacts and their assembly. In this arrangement a horizontal row of contact sets constitutes a single sub-assembly. This subassembly comprises a bottom member extending across a plurality of contact sets, upon which are superposed horizontal strips of contact springs, horizontal strips of insulation material, a horizontal strip of members having U-shaped bends at their forward ends, and a horizontal strip carrying obstruction fingers, in pairs in the illustrative embodiment, and in some instances further comprises supporting springs rand/or auxiliary springs, that may also be formed in strips. Such horizontal sub-assembly is secured together, by eyelets in the illustrative embodiment herein, so that it is very convenient to handle. The strips that horizontally interconnect the contact elements, etc. in the illustrative form are at the rear of the assembly. Thus, the unnecessary connecting strips at the rear ends of the springs that are punched out in continuous rows can be cut with a cutting device to form the necessary terminals for common vertical wiring, leaving the remaining or necessary connecting strips to serve as common horizontal wiring. A stack of a number of the subassemblies just described are preferably secured together in superposed relation, in the form shown by bolts passing through the eyelets, in assembling the complete switch contact group.

Another feature of the switch structure of the invention is in the construction and mounting of all the selecting mechanism of contact group at the front part of the contact group, by which the space factor has been greatly improved. One end of the selecting bar is attached by means of a hearing or pivot to the arm protruding from the armature of the selecting magnet, and the other end is secured by means of a screw to a supporting spring held neutral by a snubbing spring having normally open contacts. Also, on the selecting bar are protruding claws each of which is placed in between a pair of obstruction fingers and moves to left or right in accordance with the motion of the selecting magnet. The upper end of the holding bar is similarly attached as by means of a bearing, to the arm extending from the armature of the holding magnet and the lower end is secured as by means of a screw, to a supporting spring which is held at a definite position by pressing against a slightly bent supplemental spring with a definite pressure to give snubbing effect to the holding bar. The holding bar has punched out claws, on each of which is welded an arm having a U-shaped configuration as shown in Fig. 19a, so that when the selecting bar moves one of the obstruction fingers and brings it on the bottom of the U-shape portion of the U-shaped spring and the holding magnet operates, this U-shaped arm presses the finger to operate one set of contacts. These selecting bars and holding bars with their arms can be die-cast.

An additional feature which has been incorporated in this invention is in the special construction of the contact group in the switch structure. Bringing the stationary contacts to the front, a contact strip serving as stationary contact is provided to make contact with every other movable contact arranged in the horizontal row. Each of the protruding contact parts of this contact strip is bent at its root along a thin insulating strip, bringing the continuous part in the back of the insulating strip. Another like contact strip, turned around with respect to the first contact strip, is placed on the other side of the insulating strip and each of its protruding contact parts is bent along the insulating strip in opposite directions, bringing the continuous part of the contact strip into the back of the insulating strip, which therefore is held in between the two contact strips. Moreover, these contact strips have terminals at both ends, which being unbent protrude at each end opposite to each other. On the side of continuous parts of the contact strip is provided another thin insulating strip which when inserted in a saw-tooth shaped strip serves as a contact stopping bar. The movable contact springs alone are fixed in a usual manner and hold the ladder with a force exerted by their being slightly bent, and are stopped in place by the U- shaped springs, and at the same time the free ends of movable contact springs are made to rest lightly on the above mentioned insulating strip. With the structure thus described, by providing a switching selecting bar, further simplification and reduction of size of the switch can'be realized. Especially, the number of contact groups belonging to this switching selecting bar is one-half as many (as the number of the contact groups, and the contact strip located at the bottom, is placed in between the insulating strips as other contact strips, but the contacts belonging to one holding bar and regarded as a single continuous one having the terminal in front, is independent of contacts belonging to other holding bars.

The invention has been illustrated in the accompanying drawings in which:

Fig. 1 is a front elevation view;

Fig. 2 is a side elevation section taken on the line 1-1 of Fig. 1 looking in the direction of the arrows;

Fig. 3 is a portion of a top plan view showing a portion of the interior in detail;

Fig. 4 is a common yoke located between the two rows of selecting magnets;

Fig. 5 shows detail of cross-section taken on line 2--2 of Fig. 4;

Figs. 6a and 6b show details of the selecting magnet armature;

Figs. 7a and 7b show details of continuous movable springs which may be formed by punching out of a metal s eet;

Fig. 8 shows a detail of portion 40 of Fig. 7;

Figs. 9a and 9b show details of continuous stationary springs which may be formed by being punched out;

Figs. 10a and 10b show details of a continuous U- shaped spring;

Figs. 11a and 11b show details of continuous supplemental springs which may be formed by being punched out;

Figs. 12a and 12b show details of the obstruction fingers in pairs welded onto the grooves of an iron plate;

Figs. 13a and 13b show an assembly unit;

Figs. 14a and 14b show an assembly unit with supportmg springs;

Figs. 15a, 15b and 15c show a common rubber which fixes the selecting armatures with a common strip shown in Figs. 16a and 16b which are fixed by screws onto the common yoke while the rubber snubs the vibration of the armatures;

Figs. 17a, 17b and 17c show details of a selecting bar; b Figs. 18a, 18b, 18c and 18d show details of a holding Figs. 19a and 19b show details of a holding finger for the holding bar;

Fig. 20 shows the detail of a holding bar on whose claws are welded the holding arm;

Figs. 21a and 21b show details of a cover guide which serves as a handle for the switch;

Fig. 22 shows another type of stationary contact strip;

Fig. 23 shows a punched-out stationary contact strip;

Fig. 24 shows a punched out insulator for the stationary contact strip;

Fig. 25 shows details of a cross-sectional view taken on line 33 of Fig. 22;

Fig. 26 shows another type of stationary contact strip for switching upper contact group or lower contact p;

Fig. 27 shows a punched-out stationary contact strip for switching;

Fig. 28 shows a punched-out insulator for the switching stationary contact strip;

Fig. 29 shows details of a cross-sectional view taken on line 4-4 of Fig. 26;

Fig. 30 shows a saw-toothed strip which is mounted by the stationary contact strips shown in Fig. 22 and Fig. 26;

Referring now to the drawings and primarily to Figs. 1, 2 and 3, the structure comprises a frame 6 that is diecast or punched-out and press worked only.

Assembly units

65, 67 and 68 are assembled on the frame 6 by nut and bolt means 66' passed through the eyelets 46 (Figs. 13a and 13b) of each assembly unit; the L-shaped top iron plate 26 of assembly unit 68 is secured tightly onto the frame by a screw. Selecting magnets 7 are concentrated at the left hand side of the frame and a pair of said magnets are placed side by side horizontally and ordinarily five pairs of said magnets are arranged in vertical rows, one pair below another. As best shown in Fig. 3, a common yoke 10 is located between the two vertical rows of the selecting magnets. The surface of said common yoke has small projections 5 and large projections as shown in Fig. 4. The small projections 5 are fitted in the hole 64 of a selecting armature 9 shown in Figs. 6a and 6b. Consequently, the projections 5 are formed as shown in Fig. 5 in order that when the armature 9 is attracted by either of the two magnets, the movement of the armature may be made smoothly. The common rubber 11, shown in Figs. 3 and 15a and 15b is placed on the armature 9. On the top of common rubber 11 is placed a common strip 12, all of which are secured tightly by a screw on each of the large projections of said common yoke 10. Since the part secured by the screw does not have the rubber 11, it can be tightened rigidly, but the part where there is rubber will be given a suitable pressure by the compressed rubber. Hence, when an armature operates, other armatures are not affected, and the rubber prevents vibration of the armature at the time of release and at the same time keeps the armature at the neutral position. This rubber may be replaced by a common spring of, for example, a spiral shape for the same purpose.

As is also well shown in Fig. 3, one end of a selecting bar 50 is pivoted to the end of an arm 13 extending from armature 9, and the other end of the selecting bar 50 is fixed by means of screw 52 to the supporting spring 87.

I This spring with the help of supplemental springs 62,

holds the selecting bar 50 in a definite position and at the same time prevents the selecting bar from vibrating. That is, together with the above mentioned common rubber 11, this spring enables the armature 9 to operate and release surely and quickly. Besides, the supplemental springs 62, accompanying the motion of the supporting spring 87, operates the normally open contacts 60 and 61.

In the form shown in Figs. 2 and 3, the selecting bar 50 has claws 53 punched out of the bar strip, but it may be more easily formed by die-casting. Each of these claws 53 is inserted in between the corresponding pair of obstruction fingers 23 extending out from each of the assembly units and spaced at a definite distance from the adjacent pair. When the left selecting magnet 7 or right selecting magnet 7 operates, this selecting bar 50 moves to the left or right longitudinally, respectively, moving the left obstruction finger 23 or right obstruction finger 23 respectively to the left or to the right, and bringing the ob struction finger over and to substantially the center of the U-shaped part '37 of U-shaped spring 22, and is released as soon as the obstruction finger is held by the holding bar as explained hereafter. Consequently, it is substantially difierent from the existing types of cross-bar switches in which the finger thereof, after being held at an operating position, exerts on the bar a reaction pressure that is twice as much as the pressure required for supporting it in a neutral position when the bar moves in opposite directions. This is because the obstruction finger of the present type travels a very small distance and does not exert any action on the bar at all when it is held by the holding bar. That is, when the switch load becomes heavier, the load on thefselecti'ng bar becomes lighter, and even for the heaviest 'of loads at initial operations of the switch, the load is less than half of the maximum load for the existing types of cross-bar switches.

As shown further on Figs. 1 and 2, holding magnets 14 are lined up horizontally at the top of the frame and their yoke 15 is common to all of the holding magnets. Armature 17 is of a simple construction suitable for resting on a knife edge, and operates normally open contacts 63 located on top of the holding magnets. The contacts 63 are a make-contact as shown in Fig. 2, but switching contacts or other contacts may be mounted in its place as required.

Holding bars 55 (Figs. 1 and 2) are pivoted at 18 to the arm 54 extended out from armature 17 and mounted at the other end by means of a supporting spring 28 (Figs. 14a and 14b). Supporting spring 28 is slightly bent upward, so that if it is brought to a horizontal level by a supplemental spring 29, it presses the supplemental spring 29 upwardly with a definite pressure. In other words, by the supplemental spring 29 the holding bar 55 is held at a definite position and quickly stops the bar when it is released. The holding bar has, as shown in Figs. 18a, 18b and 180, claws 56 punched out of the bar and the claws are welded or otherwise secured onto the side wall of the bar 55. On these claws are welded or otherwise secured the arm 57 shown in Figs. 19a and 19b, making the shape of the whole holding bar 55 as :shown in Fig. 20. This whole holding bar may be produced by die-casting in the shape shown in Fig. 20. The part 58 of arm 57 presses down the obstruction finger .23 brought over on the U-shape portion 37 of the U-shaped spring 22 by the selecting bar as described previously, and closes the contacts associated with the U-shaped spring which is reinforced by a flanged edge 56 All of the cross-bar and armature mechanism is located, as shown Fig. 2, in front of the contact groups, making good use of the space. The switch as a whole is 'very compact.

The cross-bar switch, being very small in size and light 1' in weight, is readily constructed as a plug-in type device; on the frame 6 are provided plugs 49 shown at the -right hand side of Fig. 2 to make the switch a complete plug-in type device for convenience of installation and maintenance. For the further benefit of easy handling the handles 48 (Fig. 3) are provided on the frame. The handles 48 also serve as a cover guide for the switch cover which snaps on firmly to the frame by the spring '71, shown in Figs. 21a and 21!) together with holding portion 70 whereupon it may be grasped.

The assembly unit is made, as shown in Figs. 13a and 13b, by securing the contact springs, U-shaped springs 22 and obstruction fingers 23 by means of eyelet 46. These individual springs such as movable springs 21, stationary springs, U-shaped springs, and supplemental springs 62 are fabricated, as shown in Figs. 7a, 7b, 9a, 9b, a, 10b, 11a and 11b, respectively, in continuous forms, and the obstruction fingers also are welded, as shown in Figs. 12a and 12b on the grooves of

iron plates

24, 25, having each pair of fingers slightly bent at the center toward each other with their points touching lightly.

The holes into which the flanges of eyelets 46 as well as the fastened ends of the eyelets of the next unit fit snugly, are indented on the bottom of the iron plane 25. The eyelets 46 are passed through the iron plate 25, insulator 31, stationary spring 19, supplemental spring 29, insulator 31, movable spring 21, in this order, as many contacts as required are assembled or piled up and then finally the last insulator 31, U-shaped spring 22, supplemental spring 20, and iron plate 24 having obstruction fingers 23 are piled on, and secured tightly by bending with a definite pressure the upper end of the eyelets to assemble all these parts into an assembly unit. After the assembly unit is adjusted and inspected, the

unnecessary parts

32, 34 and 38 shown in Figs. 7a, 9a and 11a, respectively, are cut away by placing the assembly unit in a specially designed cutter to form the terminals as shown in Figs. 13:: and 1312. Then for the sake of safety the insulators 47, Fig. 13b, are inserted in place. In Figs. 14a and 14b are shown the assembly unit having supporting spring 28 and supplemental spring 29 added to the assembly unit shown in Figs. 13a and 13b.

The contact group of the cross-bar switch is constructed as shown in Fig. 2, by piling on assembly unit 67, as many of the assembly units 65 as are required, and assembly unit 68 which is different from assembly unit 65 in the upper iron plate 26. Vertical common wiring is obtained by passing a bar wire 30 vertically straight through the terminals 69' of Fig. 13a, formed by cutting the portion 40 shown in Figs. 7a and 13b, as shown in more detail in Fig. 8, by the specially designed cutter mentioned above, and soldering. In this case the movable spring 21 and its adjacent spring are continuous at point 39 in one piece (see Fig. 7a), the soldering is only half as much, and there is more space available to make the work easy. In Fig. 2 is shown the switch with three contact points for each spring pile, but if a switch with siX contact points is required, the addition of three contact points can be obtained by piling up three additional movable springs formed by turning over the movable spring 21 shown in Fig. 7a; and the common vertical wiring for these group of three additional movable springs can be obtained by soldering a wire vertically in the other side of the vertical common wire for the other group of movable springs, thus requiring no additional pieces or parts.

If the stationary contact springs are replaced by a contact strip as shown in Fig. 22, the above described assembly unit will consist of movable springs, U-shaped springs and the iron plate for the only obstruction fingers, requiring no supplemental spring as well. With contact strip 73, the portion 78, is bent in right angle at the point 79, and leaving a space for the thickness of insulator 74, it is again bent slightly more than right angle, so that the portion 78 thus bent fits into the cutout portion of the insulator 74. Another contact strip 73 formed in the same manner is fitted on to the other side of the same insulator 74 by revolving the contact strip around longitudinally, so that the portion 78, properly bent, fits into the cut out portion on the other side of the insulator 74. By placing an insulator 75 underneath the above formed strip, the contact strip shown in Fig. 22 is obtained. The cross-section view of the contact strip in Fig. 22 taken on the line 33 in the direction of the arrows is shown in enlarged view in Fig. 25. That is, in this case also, the stationary con tacts are continuous for every other contact so that no common Wire is required and both ends are made terminals, enabling either terminal to be used for Wiring. The assembly unit for switching purposes requires only half as many stationary contact strips as existing types of cross-bar switches. In this case, however, the stationary contact 76 is independent for each vertical bar, and two contacts are continuous as shown in Fig. 27, and the portion 39 of movable contact spring 21 is cut out to make each contact an independent contact. The stationary contact strip 76 is also formed like 73 and is fitted into the cut-out portion of the insulation 77. Since these contact strips 73 and 76 are slightly over bent, as described previously, they are closely fitted with the insulators. The cut-out portion 84) of the stationary contact strip 76 is not really needed but is provided to make the bending process easy and accurate. In Fig. 30 is shown the saw-toothed strip which holds these stationary contact strips 81 and 82. The contact strips 81 and 82 are fitted in the cut-out

portions

84 and 85, respectively. The portions 86 are provided for the purpose of holding in a definite posit-ion the U-shaped springs, which receive slight pressure from the slightly bent movable contact springs, as described previously, through the ladders 2.7, by means of iron strips passing through the portions 37 of the U-shaped springs and the portions 36 of strip 83. The saw-toothed strip 83 is secured onto a smooth iron plate which is screwed on the extended portion in any well known manner and not shown in the figures, of the part 66 of the frame 6, and can be removed from the frame together with the stationary contact strips. The upper part of the saw-toothed strip is also secured on an iron plate which is held by the supporting rod extending from the frame 6.

While this invention has been disclosed in connection with but a single form of switch, it should be understood that the various features thereof could readily be applied to other forms of switch structures without departing from the spirit thereof and that the present disclosure should only be considered as illustrative of one embodiment of the invention.

What is claimed is:

1. In a cross-bar switch structure in sub-combination, a frame, a common yoke extending forwardly along one side of the frame, two rows of selecting magnets arranged on opposite sides of said common yoke, each magnet of each row being paired with a magnet of the adjacent row, a selecting armature for each pair of selecting magnets, said selecting armatures being supported on said common yoke and movable thereon toward the respective selecting magnets of said pairs, a second common yoke extending forwardly along an end of the frame and substantially perpendicular to the first yoke, a row of holding magnets along said second yoke, and a holding armature for each of said holding magnets, said holding armatures being supported on said second common yoke and tiltable toward said holding magnets.

2. In a cross-bar switch structure in sub-combination, a frame, a common yoke extending forwardly along one side of the frame, two rows of selecting magnets arranged on opposite sides of said common yoke, each magnet of each row being paired with a magnet of the adjacent row, a selecting armature for each pair of selecting magnets, said selecting armatures being supported on said common yoke and movable thereon toward the respective selecting magnets of said pairs, a second common yoke extending forwardly along an end of the frame, a row of holding magnets adjacent said second yoke, and a holding armature for each of said holding magnets, said holding armatures being supported on said second common yoke and tiltable toward said holding magnets, said selecting armatures each having a forwardly extending arm and having a selecting bar attached to said arm, the opposite end of each selecting bar being supported by spring means, said spring means comprising a central spring pressed from both sides by a snubbing spring with contact springs associated with said snubbing springs, said holding armatures each having a forwardly extending arm and having a holding bar attached to said arm, the opposite end of each holding bar being supported by holding bar spring means assembled, with holding bar snubbing spring means, in a contact spring group.

3. In a cross bar switch, a sub-combination according to claim 2, combined with groups of contact springs assembled in horizontally extending units, each unit extending throughout a horizontal row of contact groups and comprising in superposed relation, an elongated base plate, mutually insulated paired stationary and movable contact springs, a relatively stiff operating spring having a U- shaped end projecting beyond the ends of the contact springs, and a second elongated plate having pairs of obstruction fingers located midway between adjacent groups of contact springs, a plurality of said horizontally extending units being assembled one beneath the other and being attached to said frame.

4. In a cross-bar switch, a sub-combination according to claim 3, the lowermost of said horizontally extending units comprising said holding bar springs and holding bar snubbing springs.

5. In a cross-bar switch, a sub-combination according. to claim 4, said horizontally extending units being attached to said frame at their rear portions and having the free ends of their spring assemblies forwardly extending, said selecting bars carrying claw means interposed between the paired obstruction fingers, respectively, and said holding bars carrying bifurcated claws in straddling relation to said paired obstruction fingers, and placed to engage with that obstruction finger displaced by movement of a selecting bar.

6. In a cross-bar switch, a sub-combination according to claim 3, the stationary contact springs being formed in horizontal strips inter-connected at every other point at the rear, the supplemental springs also being formed in horizontal strips inter-connected at the rear to constitute common connections for the remaining every other stationary contact springs, and the movable contact springs being formed in strips inter-connected in pairs of springs at the clamped point.

7. In a cross-bar switch of the type comprising a number of sets of contacts arranged in a horizontal row and selectively actuable by cross-bar means, in sub-combination, a contact strip comprising a contact spring for each set, said springs'being arranged generally parallel and in the same plane, said springs having severable integral interconnections adjacent the ends thereof remote from their contact ends, said interconnections being optionally severable and retainable to constitute terminals for vertical wiring and horizontal inter-set connections, respectively, the contact springs having offset integral extensions connecting them to said interconnections, so that two identical contact strips, relatively inverted in a pileup, may provide two relatively olfset terminals for vertical intra-switch wiring.

8. In a cross-bar switch structure in sub-combination, a frame, a common yoke extend-ing forwardly along one side of the frame, two rows of selecting magnets arranged on opposite sides of said common yoke, each magnet of each row being paired with a magnet of the adjacent row, a selecting armature for each pair of selecting magnets, said selecting armatures being supported on said common yoke and movable thereon toward the respective selecting magnets of said pairs, a second common yoke extending forwardly along an end of the frame, a row of nolding magnets adjacent said second yoke, and a holding armature for each of said holding magnets, said holding armatures being supported on said second common yoke and tiltable toward said holding ma nets, said selector armatures being retained on said yoke by a retaining bar secured to the yoke, said retaining bar comprising resilient means for holding said armatures in non-tilted position and for snubbing their return thereto from either tilted position.

9. A cross-bar switch structure comprising a frame including means for providing stationary parallel contact strips serving as stationary contact springs, said means comprising an insulator strip having cut out portions along each side of the length thereof, a set of interconnected even numbered contact portions on said contact strips bent into the cut out portions on one side of the insulator strip and a set of interconnected odd numbered contact portions on said contact strips bent into the out out portions on the other side of the insulator strip, each set of interconnected contacts having terminals at opposite ends, plain insulating strips and parallel notched supporting strips arranged with their notches to receive said contact strips together with said plain insulating strips.

10. A sub-combination according to claim 1, further comprising selecting bars extending across the front of said frame and operably associated with said select-ing armatures, holding bars extending across the front of said frame transversely of said selecting bars and operably associated with said holding armatures, and groups of contacts projecting forwardly in said frame, said selecting and holding bars establishing connections at the front of said contact groups.

11. A sub-combination according to claim 10, said frame carrying plug means engageable with complementary plug means of a rack, all the magnets and all the contacts carried by said frame being Wired to said plug means, for enabling said frame and the structure carried thereby to be employed as a complete plug-in type crossbar switch.

References Cited in the file of this patent UNITED STATES PATENTS 2,399,962 Vincent May 7, 1946 2,516,745 Baker July 25, 1950 2,577,067 Arthur Dec. 4, 1951 2,636,398 Lehs Apr. 28, 1953 2,692,304 Eilertsen et a1. Oct. 9, 1952 2,731,516 Vincent Jan. 17, 1956