US1568755A - Automatic telephone system - Google Patents

Description

2 Sheets-Sheet 1 Filed Dec. 5, 1921 F A LUNDQUIST El AL AUTOMATIC TELEPHONE SYSTEM 1 MNQQM Jan. 5 1926.

F A LUNDQUIST Er AL AUTOMATIC TELEPHONE SYSTEM Filed Dec. 5. 1921 I Patented Jan. 5, 1926.

FRANK A. LUNDQUIST AND JGI-IN A. KBOPIP, OF CHICAGO, ILLINOIS, ASSIGNORS TO HENRY S. CONRAD, TRUSTEE, OF KANSAS CITY, MISSOURI.

AUTOMATIC TELEPHONE SYSTEM.

Application filed December To all whom it may concern:

Be it known that we, FRANK A. LUND- gUIS'l and JOHN A. Kaorr, citizens of the United States, and residents of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

This invention relates to an automatic telephone system of the type in which the switches are pneumatically operated, but are controlled in part at least by electrical devices.

Qne of the objects of the invention is the provision of a system of the above character in which the use of electrically controlled devices and electric circuits are reducedto the minimum.

A further object of the invention is to provide a system of this character in which the various parts are simple in character and few in number.

One of the features of the invention is the provision of a system in which the release of a series of switches is controlled by a single electromagnet, each switch in the series exercising a pneumatic control over the adjacent switch to, upon its release, cause the release of the adjacent switch. In other words, the invention contemplates the provision of a pneumatic series release arrangement.

Another feature of the invention is the provision of means by which, when a switch is automatically selected, air under pressure is applied toa pneumatic motor to operate mechanism to place the selected switch in condition for. operation.

A still further feature of the invention is the provision of a simple and efficient device for controlling valves to shift from one thereof the automatically controlled valve associated with each of the crank shafts;

Figure 3 is a cross-sectional view of a check valve employed in association with certain of the pneumatic motors or sylphons of the present invention;

Figure 4 is a cross-sectional view on the line 4-4 of Figure 3;

Figure 5 shows the circuits and apparatus of a selector switch, the apparatus in gen eral being shown schematically, and

Figure 6 is a cross-sectional view on the line 66 of Figure 5.

In the drawings the various parts have, in the interests of simplicity and clearness, been shown largely schematically, and it is believed that the invention will be readily understood from the present drawings taken in connection with the following description.

It may be desirable, however, to refer to applicants prior filed application, Serial No. 406,145, filed August 26, 1920, Patent No. 1,514,625, Nov. 11, 1924, for a more detailed description of a line switch of a character similar to that herein disclosed, and to application of Frank A. Lundquist, Serial No. 412,915, filed September 27, 1920, Patent No. 1,516,539, Nov. 25, 1924, for a more detailed disclosure of the detailed arrangement of the parts of a selector switch of the general character of that shown in Figure 5.

Referring now to the drawings, the line terminal contacts at the line switch are indicated by reference characters 1 and 2. These contacts may be formed as integral projecting portions of the metallic strips 3 and 4. Associated with each pair of strips 3 and 4, and individual thereto, is a crank shaft 5. The arrangement of the contacts and crank shafts may be substantially the same as that shown in application Serial No. 4 above n e ed ta ount ,1?-

osite each vertical row of contacts 1 and 2 1s a line switch structure consisting of the parts schematically indicated in Figure 1. This structure consists primarily of a pneumatic motor 6, and a pair of brushes 7 and 8 which together form a brush set. The motor 6 consists of two cylinders, one being telescopically arranged about the other, the outer one being closed at its upper end and the inner one being provided with an air inlet orifice at its lower end. The brushes 7 and 8 may be mounted on any desirable form of a carriage and are arranged to wipe over the successive sets of contacts 1 and 2 in the vertical row of contacts to which each pair of brushes is individual.

The brushes 7 and 8 are provided with the wipers 9 and 10 respectively which are n constant engagement with the fixed vertical rods 11 and 12. These rods 11 and 12 form the electrical leads from the switch brushes and are arranged to be connected, through certain contact devices to be hereinafter described, to the subscribmrs line conductors to which the switch iS individual.

13 and 14 represent pneiunatic mot or sylphons of the multiple diaphragm type such as described in the applications above mentioned. 15 and 16, and 1'? and 18 represent air valves all of the same character. So far as the present invention is concerned, these valves may be of any desired form, it being essential only that the valve shall be open when the pins projecting from the ends of the valves are pushed inwardly. These valves, however, are preferably ol a 'i'orm such as shown and described in the prior filed applications above referredto.

Associated with the sylphons 15 and 1-l and schematically indicated in both cases directly below the sylphons, are the leaky check valves 19 and 20. These check valves in the present instant are so arranged as to permit the sylphons to be expanded slowly but to be retracted or emptied very quickly. A check valve of the character indicated at 19 and 20 is shown in Figures 3 and 4. It consists of a cylinder 21 having a .valve seat 22 at one end thereof. Slidable within the cylinder is a substantially triangular valve member 28, one end of which is shaped to co-operate with the valve seat 22 to produce a substantially air tight engagement. Extending longitudinally of the valve member 23 and centrally thereof is a small opening 24. Attached to one end of the valve member 21 by any desired manner as by the coupling 25 is a tube 26 and joined to the opposite end of the member 21 by the coupling 27 is the tube 28. A check valve such as shown in Figures 8 and st may be employed with a sylphon of the character shown at 13 and 14, to cause the sylphon to be slow to expand and quick to contract when joined to the sylphon with the tube 26 adjacent the sylphon. If, however, the check valve of Figure 3 is inserted in the inlet tube to the sylphon with the tube 28 adjacent the sylphon, the sylphon will be quick to expand. but slow to contract. In each case, the air passing through the check valve in one direction must leak through the hole 2-l, but when the greater pressure exists on the lower side of the valve member 23, as seen in Fig. 8, the valve member 23 is displaced and air may pass rapidly.

At 29 and are represented the line conductors extending from the substation to the line switch, and 31, 32, represent the normals of the subscriber's line which may terminate in contact terminals at a connector switch.

Assuming that the conductors 29 and 30 are electrically connected at the substation by reason of the subscriber removing his receiver from his hook, a circuit will be completed from ground, through electromagnet 3-1, contacts and 36, out over the line conductor 29, through the sub-station apparatus, back over conductor 30, through contacts 37 and 38, and electromagnet 39 to battery and ground. Magnets 34 and 39 will both be energized by the series circuit through their windings and will attract their armatures, thus opening the valves 16 and 18. The tubes extending from the top of each of these valves will lead to a source of compressed air. The pushing upwardly of the pin projecting from the lower end of valve 18 will cause air under lrl'QSSUlG to be admitted to the sylphon 14, but Ll is n'rade slow to expand by reason of the check valve 20. The pushing inwardly of the pin projecting from the lower end of valve 16 per mits air under pressure to be supplied to the tube 40 which is joined to the sylphon l3 and also to the valve 17 by suitable branches. The valve 17 is normally main tained open in a manner which will be sub sequently described, and air therefore is supplied through valve 17 and tube 41 to the pneumatic motor 6. The outer casing of the motor 6 moves upwardly carrying the brushes 7 and 8 with it. As soon as the brushes 7 and 8 reach the terminals 1 and 2 of a trunk which is idle, the lever 42 airried by the outer cylinder of the motor 6 will engage the crank bar 5 (.OYIGSPOIltllIlQ to the idle trunk, and will stop the upward movement of the motor 6, with the brushes 7 and 8 in contact with the terminals 1 and 2. Due to the pivotal arrangement of the lever 12 on the cylinder 6, the seized crank shaft 5 will be rotated so the cranks will occupy a substantially vertical position, and thus be placed out of the path of the lever 42 of any line switch to be subsequently operated. Although air was suppliwl to the any appreciable extent sylphon 13 at the same time it was supplied to the cylinder motor 6, on account of the check valve 19 being associated with the sylphon 13, sylphon 13 will not operate to until after the brushes 7 and 8 have reached and stopped on the contacts of the idle trunk. If desired, the sylphon 13 may be'so arranged that it will operate only at a higher pressure than the cylindrical motor 6, so no movement whatever of the sylphon 15% will occur until after the upward movement of the motor 6 has ceased.

The expansion of the sylphon 13 forces Lhe rod or bar 43 upwardly. When the bar 48 is in its normal position, the horizontal arm of the bell crank lever 44 rests upon the pin 45 projecting from the bar 43. Engaging one end of the horizontal arm of the bell crank 44 is a pin 46 the other end of which engages the spring 47 fixed to the horizontal arm of the bell crank lever 48. The lever 48 is pivoted at 49 and its downwardly projectingarm engages the valve pin of the valve 17, thus normally maintaining valve 17 open. As the bar 43 moves upwardly,the horizontal arm of the bell crank 44 is carried upwardly by the pin 45 until the point where pin 46 engages the bell crank 44 has passed beyond the line connecting the opposite end of the pin and the pivot 50 for the bell crank When this position has been reachechdue to the action of the spring 47, the pawl 51 at the upper end of the bell crank 44 is snapped into engagement with the rack 52 on the outer cylinder of the motor 6, and also the horizontal arm of the bell crank 48 is rotated downwardly. The rotation of the bell crank fever 415 permits the valve 17 to close, thus shutting off the air from the motor 6, and it also causes the closure of the pairs of contacts 53 and 54 immediately above the bell crank 48.

Pivotally secured to the upper end of the bar 43 is a lever which is pivotally mounted at 56. As the bar 43 moves upwardly, the free end of the lever 55 moves downwardly and engages the armature'of he electromagnet 39, thus forcing the armature downwardly and permitting valve 18 to close and shut off the air from the sylphon 14. As above explainedflthe sylphons 13 and 14 are made slow to expand by reason of the check valves 19 and 20, and it may be further explained that the sylphon 14 is arranged to be slower to expand than the sylphon 13 preferably by making the opening 24 in the check valve 20 smaller than the opening in the check valve 1.9. By this arrangement, the lever 55 will engage the armature of the magnet 39 and close the valve 18 before the sylphon 14 has expanded sufficiently to open the contacts 35, 36, and 37, 38, associated therewith, and thus prevent the connections between the line conductors 29 and 30 and the windings of the magnets 34 and 39 being interrupt-cc.

The normal conductor which it has been explained, terminates in a contact in the connector switch bank, is the third or test conductor. When the motor 6 moves from its normal position it opens the normal contacts 57 and thus isolates the test contact of the calling line.

The closure of the pairs of contacts 53 and extends the line conductors through to the rods 11 and 12, and thence through the wipers 9 and 10 to the switch brushes 7 and 8. The brushes 7 and 8 being in engagement with the contacts 1 and 2, the circuit is extended through conductors 58 and and the pairs of contacts 60 and 61, to the windings of the electromagnet (32 of the seized selector switch.

Carried by each of the crank shafts 5 at the end thereof is a lever 63. These levers arranged at successively increasing distances from the last vertical row of contacts 1 and 2. Associated with each of the levers 63 and in a position to be operated thereby when the cranks of a corresponding crank shaft occupy a substantially vertical position, is a valve 15. Thus, when a trunk is seized and the corresponding crank shaftis rotated to its busy or unselectable position, the corresponding valve 15 is opened and air under pressure passes through the tube 64 to the sylphon 65 which is associated with the seized selector switch.

Pivot-ally joined to a projection ('36 on the sylphon 55 one end of a lever 67 which is pivoted at 68. Pivotally secured to the opposite end of the lever 67 is one end of a crank (59, the opposite eno of which is pivotally connected to the bar 70. The bar 70 is provided with a pair of inclined slots 71 and '72 which receive the fixed pins 72) and 74 carried by the fran'ie members. As the sylphon 5 expands, the bar 70 is drawn to the left as viewed in Figure 5 and, due to the slot and pin arrangement described, the bar 70 is lowered and permits the pawl 7 5 to engage the upwardly extending ratchet teeth 75 on the bar 76. It is, of course, understood that the bar 70 normally retains the pawl 75 out of engi gement with the teeth on the bar 76.

The bar 76 is slidably mounted in the frame in any desired manner.

Slidably connected to the left end of the bar 76 as viewed in Figure 5 is a bar 77 which is carried by the outer or movable cylinder of the motor 78. The bar 77 is provided with a slot 79 through which projects a pin 80, carried by the bar 76. The bar 7 is provided with a notch 81 over which lies the actuating spring of the pairs of springs 60 and 61. When the bars 76 and '77 occupy the relative position shown.

in Figure 5, however, the left end of the bar 76 projects east the notch 81 and retains the pairs 0% springs 60 and 61 in their closed position.

\Vhen the bar was drawn downwardly by the action of the sylphon or motor 65, in addition to permitting the pawl to engage the teeth 7 5 as above stated, it also operated to release to operative position the pawls S1 and 82. Pawl 81 when released is arranged to operatively engage the ratchet teeth 83 on the bar 76. lVhen, however, the bar 70 is in its raised position, the oop 84 formed integral with the bar 70 engages a laterally projecting pin 85 on the end of the pawl lever 81 and holds the pawl 81 in its retracted position as indicated in Figure 5. The pawl 82 when reeased by the downward movement of the bar 70 is arranged to operatively engage the ratchet teeth 86 carried by the switch carriage 87. This carriage 87 may, it de sired, consist of an angle iron strip with the flanges at the ends inturned as at 88, and provided with openings, through which extend the fixed bar or rod 89. The carriage 87 is arranged to slide horizontally on the bar 89 as will be hereinafter described. The teeth 86 if desired may be formed in one flange of the angle strip indicated in Figure 6. The pawl 82 is provided at its rearwardly extending end with a laterally projecting pin 90 which s arranged to be engaged by the hook 91 carried by the bar 70. The pawls 81 and 82 are pivotally mounted on the fixed pins 92 and 93, respectively, and are urged toward their operative positions by the springs 94 and 95.

Carried by the carriage 87 and extending at right angles to the guide rod 89' is a guide bar 96 on which is slidably mounted the carriage 97. The carriage 97 may be provided with right angularly extending end portions 98 having openings therein which receive the guide bar 96. Pivotally secured to the lug 99 projecting from the carriage 97 is a link 100, the opposite end of which s pivotally connected to one end of the bell crank lever 101. The bell crank 101 is pivotally mounted at 102 011 the upwardly projecting arm 103, fixed to the carriage 87. The pawl 75 is pivotally secured to the left end of the bell crank 101, as viewed in Figure 5.

Supported on the carriage 97 is a brush set arrangement schematically indicated. in the present drawings by the brushes 104 and 105, and the trip or trunk selecting arm 106. This brush set arrangement may be of substantially the same character as that shown in the previously filed application 412,915, above referred to.

Returning now to the operation which follows the seizure of the contacts 1 and 2,

(Figure 1) upon the operation of the line switch it will be remembered that upon the selection of the trunk, a circuit was completed for the windings of the magnet 62 in parallel with the windings of the magnets 34 and 39. Upon completion of this circuit, the magnet 62 attracted its armature 107. This attraction of the armature 107 by the magnet 62 operated to open the valve 108, and to close the valve 109, as will be apparent from an inspection of Figure 5 of the drawing. The opening of valve 108 permits air under pressure to be supplied to the sylphon or motor 110 which expands.

Pivotally connected to the movable side of the sylphon 110 is one end of a lever 111 which is pivotally supported at 112. As the sylphon 110 expands, the upper end of the lever 11.1 is moved to the right, and engages the valve pin 113 of the valve 114, to open the valve. This permits air to be supplied through the inlet tube 115 to the pneumatic system. The only thing which is operated on, however, at this time is the switching or operation changing motor 116 which is of the type consisting of two telescopically arranged cylinders such as are now well understood.

Projecting from the lower surface of the outer cylinder of the motor 116 is a lug 117 to which is pivotally secured one end of? a link 1.18. The opposite end of the link 118 is pivotally connected to the upwardly extending arm of the bell crank lever 119. This lever 119 is pivotally supported at 120 on a guide bracket 121 slidably mounted on the framework of the switch. The bell crank 119 is provided at the free end of its horizontal arm with a pawl 122 which is adapted to engage the escapement teeth 123 which are arranged in staggered relation on opposite flanges of the channel shaped escapement 124. This escapement member 124 is pivotally supported at its ends as by the pivot pins 125 being received by bearings carried by the frame. This escapement member 124 may be of substantially the same character as described in the prior filed applications above noted. Pivotally connected to one flange of the escapement member 124- is a link 126, the opposite end of which is secured to the sylphon or motor 127. It may be here noted that the sylphons 110 and 127 are made quick to expand and slow to release by means of the check valves 128 and 129 respectively, which are associated therewith. These check valves as above explained may be of the character shown in Figure 3, but arranged with the tube 28 adjacent to the sylphon, air under pressure being supplied to the tube 26. It will thus be seen that as long as the pressure existing in the tube 26 is greater than that in tube 28, the m vabl lve mem r 2 Will 116 is stopped right at the start.

be forced upwardly and permit the free ingross of air into the sylphon. When, however, the pressure is removed from the tube 26, the movable element 23 drops onto the valve seat 22, thus closing it and permitting the escape of the air only by way of the relatively minute opening 2 1 through the center of the member The various valves shown at 108, 109, 114-, 130, 131 and-182 in Figure 5 may be of the same character as that shown at 15 in Figure 1, and described in application 412,915.

Upon the opening of valve 11s the motor 116 starts to expand, but by its first movement it causes the downward rotation of the pawl 122 which engages the first one of the teeth 123 on the escapement bar 124 and thus the forward movement of the motor No other operation than this preliminary movement of the motor 116 follows from the initial energization of the magnet 62.

As will be well understood, the contacts of the selector switch are arranged in rows or groups in the usual manner, each or" which rows represents a certain division of the exchange. The calling subscriber now will operate his sending device to send a series of pulses to set his selector switch opposite the desired row of contacts. These impulses will pass from ground through the upper winding of magnet 62, aair of contacts 60, conductor 59, contact 1, and brush 7, wiper 9, rod 11, contacts 53, contacts 35, conductor 29, through the sub-station apparatus back through conductor 30, contacts 37, 38, pair of contacts 51-, rod 12, wiper 10, brush 8, contact 2, conductor 58,

- pair of contacts 61 and the other winding of magnet 62 to battery.

Due to the pulses passing over this circuit, the armature 107 will be rapidly vi rated causing the alternate opening and closing of the valves 1'08 and 109'.

Due to the check valve 128 associated with the sylphon 110, the sylphon 110 will maintain its expanded position and air under pressure will be continuously supplied through the valve 114, to the pipe or tube 134. li itlr the first retraction of the armature 107, the valve 109' is opened, thus admitting air under pressure to'the tube 135. This tube 135 is connected to the sylp-hon 127 which expands with the first impulse of air, and due to the check valve 129 remains expanded throughout the series of pulses. The expansion of the sylphon 127 rocks the eseapeinent member 1251-, and permits the pawl 122 to slide off from the first tooth at the left and engage the second tooth on the escapement rack.

Valve 131 being held open at this time in manner which will be subsequently explained, the pulses of air under pressure are supplied through the tube 136 to the cylindrical motor 137.2Then1otor 137 is provided its free or movable end with a pivoted link 138 which is guided in the frame in any desired manner. To the outer end of the link 158 is pivot-ally joined the pawl 139, which is urged to engagement with the teeth 86 carried by the carriage 87 by means of the spring 140. Vv hen, however, the motor 137 is fully retracted by means of the spring 141, the upwardly extending arm 1 12 carried by the pawl 139 engages a fixed pin 14-3 and the free end of the pawl is rotated downwardly so as not to engage the teeth 86. The pulses of air passing into the motor 137 cause it to be alternately expanded and contracted, causing the pawl 139 to oscillate back and forth, and thus move the rack consisting of'the teeth 86 to the right, step by step, the dis tance of one tooth for each expansion and contraction of the motor 137. As above explained, the pawl 82 isarranged to engage the teeth 86 and the carriage 87 is thus held in its advanced or adjusted position;

During this forward movement of the carriage 87, the pawl 75 secured to one end of the bell crank 101 rides loosely over the ratchet teeth 75' in the rack or ratchet bar 76;

At the termination of the series of impulses, the magnet 62 will remain energized, thus permitting the valve 109 to remain closed. Sylphon 127 new contracts and ro tates the escapement bar 124 so as to permit the pawl 122 to become disengaged from the second tooth in the escapement, and move a relatively long step to the third tooth. This movement of the cylinder 116- brings the cam 144- into engagement with the cam surface 145 of the valve controlling member 146. This valve contrlling member ispivotally supported on a fixed pin 147, and has a vertically extending portion, the lower end of which is normally held in engagement with the valve operating pin of the valve 131 by means of the spring 148, thus normally maintaining the valve 131 open. hen, however, the cam 1 14 engages the cam surface 145 on the valve opera-ting memher, the member 146- is rotated on the pin 147 and the upwardly projecting portion is brought into engagement with the valve operating pin of the valve 130. In this position, the valve 131 is closed and the valve 130' is open. Air under pressure is now definitely shut off from the motor 137 by valve 131, but the opening of valve 130 supplies air through tube 1 -9 to the motor 78. Motor 78 expands and forces the rackbar 7 6' to the right asviewed in Figure 5. The pawl 75 is now inengagement with one of the teeth 7 5 and the forward movement of the rack 7 6 causesthe rotation of the bell crank 101 about its pivot 102, thus forcing t carria 97 upwardly. During the up- Ward movement of the carriage 97, the carriage 87 may be locked in a fixed position by means such as shown in an application of Frank A. Lundquist, Serial No. 418,714, filed October 22, 1920. As this part of the structure forms no part of the present invention, the disclosure has not been confused by inserting this detail. The carriage 97 continues to move upwardly until the arm 106 engages the crank arm of a crank shaft 150, which is associated with an idle trunk. The arm 106 upon engaging a crank of crank shaft 150 will rotate the shaft to its busy or unseleetable position in a manner which is well understood.

The crank shaft 150 will be provided at one end with a valve operating member 151 which is arranged to engage the valve actuating pin of the valve 132 in the same manner that the arm 63 (Figure 1) engages the valve operating pin of the valve 15. The member 151 engaging the pin of the valve 132 will cause air under pressure to be supplied to the succeeding selector or connector switch in. the same manner that the operation of valve 15 by the arm 63 causes air to be supplied to the selector switch shown in Figure 5. The parts 64;, 65, and 67 of Figure 5 may correspond in every way with the parts 64-, 65 and 67, and the succeeding selector may be the same as that shown in Figure 5.

As long as the electromagnet 62 remains energized, valve 109 remains closed, and the sylphon 127 remains contracted.

When, however, the subscriber sends the next series of impulses to the switch beyond, that is, the next switch in the series, the first break of the line circuit will cause the armature of magnet 62 to fall ofland open valve 109. This will again expand the sylphon 127, which will rotate the escapement 124 and permit the motor 116 to move pawl 122 into engagement with the last tooth on rack 1241-. The valve actuating member 145 will now drop onto the depressed end of cam 144-, and valves 130 and 131 will both be maintained closed. Cam 1414 is shaped on its depressed end so that the valve actuating member 145 will drop just far enough to allow both the valves 130 and 131 to close. The valve 130 being closed motor 78 will retract. Upon reaching its retracted position, the cam portion of the lower spring of the pair 61 will drop into the notch 81 in the bar 77, and the pair of contacts 60 and 61 will open, thus cutting off the windings of the magnet 62. At this time, the left end of the bar 7 6 is no longer opposite the notch 81 so that the spring is permitted to drop freely into the notch.

As the magnet 62 now remains de-enew gized, valve 108 is closed and sylphon 110 is permitted to contract and thus permit valve 11 1 to close. Thus, air at this time is taken off from all the motors of the selector in Figure 5, except from the sylphon 65 which, it will be understood, is so constituted as to be nonleaking, and thus the waste of the air under pressure is reduced to a minimum.

The pulses being sent out by the sub scriber to the succeeding switches will operate these switches in the same manner as the 7 switch in Figure 5 was operated, the selector of Figure 5 being entirely uninfluenced by the pulses sent to the succeeding switches, due to the fact that its controlling relay 62 is entirely removed from the impulse circuit upon the retraction of the motor 78. It will also be understood that as the succeeding switches are actuated, their controlling magnets may be cut off or removed from the circuit in a manner similar to the way in which magnet 62 was isolated.

It will be noted that the retaining means for the line switch of Figure 1 is held in its operative position by means of the expanded condition of the sylphon 13, the air to which is supplied by the valve 16 controlled by the winding of the electromagnet 8- 1 in series with the subscribers line conductors. that the pawls 81 and 82 which retain the movable parts of the selector switch in Figure 5 in their advanced or set position are controlled solely by the sylphon 65 which is supplied with air under pressure through the valve 15 which is held open by means of the arm 63 on the crank shaft 5 engaging its valve operating pin. In the same manner, the opening of the valve 132, (Figure 5) will cause air under pressure to be supplied to a sylphon 65 at the succeeding switch, and this sylphon in turn will operate mechanism similar to that shown in Figure 5 for permitting the retaining mechanism of this succeeding switch to assume its operative position.

It will now be understood that the retaining means for each of the switches following the line switch is under the sole control of a pneumatically operated device which is supplied with air under pressure due to the sole fact that the trunk terminating in this switch has been seized and is held by the preceding switch in the series, that is, by maintaining open a valve such as 15 in Figure 1 or 132 of Figure 5. By this arrangement, a series of pneumatic re lease is provided.

Assuming that the switches are all in their set positions upon the calling subscriber replacing his receiver upon its hook, the circuit through the magnet 34 will be interrupted and its armature will fall off and permit valve 16 to close. This will cut off the air pressure from the sylphon 13 It will further be noted which will contract, and in contracting the pin 45 carried by the arm 43 will engage the horizontal arm of the bell crank This will so lower the free end of the horizontal arm of the bell crank 44 that the point where the pin 46 engages this arm will pass below the line connecting the opposite end of the pin 46 and the pivot 50. The spring 47 will thereupon act to rotate the bell crank levers L and 48 both in a clockwise direction. The rotation of the lever L8 will cause its downwardly projectlng arm to engage the valve operating pin of the valve 17 to open the valve which is the normal condition of this valve. The retraction of the pawl 51 will permit the cylinder 6 carrying the brush carriage to drop down. This will permit the seized crank shaft 5 to rotate to its normal position, and thus remove the arm from engagement with the valve pin ot the valve 15. Valve 15 will then close and will cut off away from the sylphon of Figure 5.

Sylphon 65 at the selector switch will now contract and in contracting will cause the sliding bar 7 0 to move to the right and upwardly by reason of its pin and slot mounting. As the bar moves upwardly, it will raise the pawl from engagement with the teeth 75 and the carriage 97 will be restored to its lowermost position by gravity, or if desired a spring may be pro; vided to assist this return motion. The upward movement of the bar 70 will also cause the loop 84: to engage the pin 85 on the pawl 81 to move it to an operative position, and similarly the hook 91 carried by the bar 70 will engage the pin on the pawl 82 to remove it from engagement with the ratchet teeth 86. Thus, the bar '76 and the carriage 87 ,will be free, and will be returned to their normal positions as shown in Figure 5 under the influence of appropriate springs.

It is to be understood that applicants 1nvention is not to be limited to the present disclosure, which in the interest of simplicity and clearness is largely schematic, but our invention is to be limited merely by the scope of the appended claims.

hat we claim is:

1. In an automatic telephone system, a switch, a pneumatic motor associated with said switch, switch retaining mechanism governed by said motor, means for automatically seizing said switch and a valve operated incident to seizing said switch for causing compressed air to be supplied to said motor.

2. In an automatic telephone system, a switch, a pneumatic motor associated with said switch, switch retaining mechanism associated with said motor and arranged to be actuated thereby, a second switch, means for causing said second switch to seize said first mentioned switch, a valve for control ling the supply of compressed air to said motor and means actuated incident to said second switch seizing said first switch for opening said valve.

3. In an automatic telephone system, a switch, a retaining device for holding said switch in operated position, a pneumatic motor for controlling said retaining device, a valve controlling the operation of said motor, means for seizing said switch and means actuated incident to seizing said switch for opening said valve.

4. In an automatic telephone system, a series of switches, a retaining device for one of said switches, a pneumatic motor for c'on trolling the operative condition of said retaining device and a valve for controlling said motor associated with another of said switches.

5. In an automatic telephone system, a series of switches, a retaining device for one of said switches, a pneumatic motor for controlling the operative condition of said retaining device, a valve for controlling said motor and means at an adjacent one of said switches for actuating said valve.

6. In an automatic telephone system, a series of switches, a retaining device for one of said switches, a pneumatic motor for con-- trolling the operative condition of said retaining device, a valve for controlling said mot-or and means at a preceding one of said switches for actuating said valve.

7. In an automatic telephone system, a series of switches, retaining devices, one for each of a plurality of said switches, pneumatic motors, one for each of said retaining devices for controlling the operation thereof, valves for each of said motors for governimii the supply of compressed air thereto, each of said valves being at a switch diiierent from the switch with which the motor it governs is associated.

8. In an automatic telephone system, a series of switches, retaining devices, one for each of a plurality of said switches, pneumatic motors, one for each of said retaining devices for cont-rolling the operative condition thereof, valves, one for each of said motors for governing the supply of compressed air thereto, each ot said valves being at a switch preceding the switch with which the motor it governs is associater 9. In an automatic telephone system, a plurality of switches forming part of a series, a pneumatic motor actuated retain ing device for each of said switches and tubes for supplying compressed air to said motors, respectively, each extending from its motor to a preceding switch of the series.

10. In a trunk selecting switch, a mechanical stopping device representing an idle trunk. a movable switch carriage, an arm on said carriage for engaging said stopping device, a valve and. means carried by said device for actuating said valve upon said arm engaging said device.

11. In a trunk selecting switch a mechanical stopping device representing an idle trunk, a movable carriage, an arm on said carriage for engaging and displacing said stopping device, a valve and means carried by said device for actuating said valve upon the displacement of said device.

12. In a trunk selecting switch a mechanical stopping device representing an idle trunk, a movable switch carriage, an arm on said carriage for engagin and displacing said stopping device, a vaive and a lever carried by said device for actuating said valve upon the displacement of said device.

13. In a trunk selecting switch, a crank shaft representing an idle trunk, a movable switch carriage, an arm on said carriage for engaging and rotating said crank shaft, a valve and an arm projecting from said crank shaft for actuating said valve upon rotation of said shaft.

14. In a trunk selecting switch, a crank shaft representing an idle trunk, a movable switch carriage, an arm on said carriage for engaging and rotating said crank shaft, a valve and an arm projecting from said crank shaft for opening said valve upon rotation of said shaft.

15. In a trunk selecting switch, a mechanical stopping device representing an idle trunk, a movable switch carriage, an arm on said carriage for engaging said step ping device, a valve, means carried by said device for actuating said valve upon said arm engaging said device, a second switch, a retaining device for said second switch and a pneumatic motor for actuating said retaining device, said valve being arranged to control the supply of air to said motor.

16. In a trunk selecting switch, a me chanical stopping device representing an idle trunk, a movable switch carriage, an arm on said carriage for engaging said stopping device, a valve, means carried by said device for actuating said valve upon said arm engaging said device, a second switch, a retaining device for said second switch, a pneumatic motor for controlling said retaining device, and a tube extending from said valve to said motor.

17. In a trunk selecting switch, a crank shaft representing an idle trunk, a movable switch carriage, an arm on said carriage for engaging and rotating said crank shaft, a valve, an arm projecting from said crank shaft for opening said valve upon rotation of said shaft, a second switch, a retaining device for said second switch, and a pneumatic motor for controlling said retaining device, said valve being arranged to control the supply of air to said motor.

18. In a trunk selecting switch, a crank shaft representing an idle trunk, a m0vable switch carriage, an arm on said carriage for engaging and rotating said crank shaft, a valve, a motor, an arm projecting from said crank shaft for opening said valve upon rotation of said shaft and a tube extending from said valve to said motor.

19. In an automatic telephone system, a switch having primary and secondary motions, pneumatic motors, one for producing each of said motions, valves, one for controlling each of said motors, a change over device for simultaneously closing one of said valves and opening the other and subsequently maintaining both said valves closed and an escapement mechanism for controlling said change-over.

20. In an automatic telephone system, a switch having primary and secondary motions, pneumatic motors, one for producing each of said motions, valves, one for con trolling each of said motors, a change-over device for simultaneously closing one of said valves and opening the other and subse .quently maintaining both said valves closed,

an escapement mechanism for controlling said change-over and a slow acting pneumatic motor for controlling said escapement mechanism.

21. In an automatic telephone system, a

switch, a relay for controlling the operation of said switch, a pneumatic motor for operating said switch, a plunger carried by said motor, a trunk extending to said switch, contacts at said switch through which said relay is normally operatively connected to said trunk and a cam on said plunger for controlling said contacts.

22. In an automatic telephone system, a switch, a relay for controlling the operation of said switch, a pneumatic motor for operating said switch, a. plunger carried by said motor, a trunk extending to said switch, contacts at said switch through which said relay is normally operatively connected to said trunk, a contact operating member, a depression in said plunger over which said contact operating member normally rests, a switch actuating device slidably connected to said plunger, said actuating device being arranged to normally overlie said depression and retain said contacts in their actuated position, means for moving said plunger to actuate said switch, means for returning said plunger to its normal position to cause said contacts to open.

23. In an automatic telephone system, a switch, a pneumatic motor associated with said switch, a source of power, means for automatically seizing said switch and a device mechanically operated incident to seizing said switch for supplying power from said source to operate said motor.

24. In an automatic telephone system, a switch, a source of power, a retaining de vice for holding said switch in operated position, a motor for controlling said retaining device, another device for controlling the operation of said motor, means for seizing said switch, and means mechanically actuated incident to seizing said switch for operating said other device to cause the to be actuated thereby, a second switch,

means for causing said second switch to seize said first mentioned switch, a device for controlling the source of power to said motor, and means mechanically actuated incident to said second switch seizing said first switch for actuating said device to cause the operation of said motor.

27. In an automatic telephone system, a switch having primary and secondary motions, motors, one for producing each of said motions, devices, one tor controlling each of said motors, a change-over device for simultaneously closing one of said devices and opening the other and subsequently maintaining both said devices closed and an escapement mechanism for controlling said change-over device.

netic device, said magnetic device for controlling the pneumatic devices, and means for disconnecting the magnetic device when the mechanism completes an operation.

29, In a telephone system, a switching mechanism having lines leading thereto, pneumatic motors and a single electro-magnet in said mechanism, a circuit for said magnet, means for operating said magnet over said circuit to cause said pneumatic motors to operate said mechanism to connect said lines to other lines, means for opening said circuit when the mechanism completes connection to said other lines, and means consisting of a pneumatic device for releasing said mechanism.

30. In a telephone system, a selector switch having lines leading thereto, said switch having a plurality of motors and only one relay, acircuit for said relay, means for operating said relay over said circuit to cause said motors to operate said switch to connect said lines to other lines, means for opening said circuit when the switch complete-s connection to said other lines, a device in said switch for controlling the release of the same, and means for controlling said device from a preceding switch to cause the release of said first switch.

Signed at Chicago, Illinois, this 21st day of November, 1921.

FRANK A. LUNDQUIST.

Signed at Chicago, Illinois, this 21st day of November, 1921.

JOHN A. KROPP.

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