US2905302A

US2905302A - Selection mechanism for typewriter

Info

Publication number: US2905302A
Application number: US606600A
Authority: US
Inventors: John E Hickerson
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1956-08-28
Filing date: 1956-08-28
Publication date: 1959-09-22
Anticipated expiration: 1976-09-22
Also published as: GB855127A; BE587441Q

Description

Sept. 22, 1959 J E. HICKERSON 2,905,302

SELECTION MECHANISM FOR TYPEWRITER Filed Aug. 28, 1956 2 Sheets-Sheet 1 INKENTOR JOHN E. HICKERSON ATTORNEY Sept. 22, 1 5 J. E. HICKERSON SELECTION MECHANISM FOR TYPEWRITER Filed Aug 28, 1956 2 Sheets-Sheet 2 SELECTION MECHANISM FOR TYPEWRITER John E. Hickerson, Wappingers Falls, N.Y., assignor to International Business Machines Corporation, New York, N.Y., a corporation of New York Application August 28, 1956, Serial No. 606,600

7 Claims. (Cl. 197-52) This invention relates to typewriters, and more particularly to a mechanism for selectively positioning a single element printing head with respect to the platen of a typewriter.

The principal object of the present invention is to provide a low cost improved selecting mechanism for positioning a single element printing head which is capable of rapid and reliable operation over long periods of time.

When using purely mechanical means, the maximum speed of selecting the character may be limited by the time taken by the machine to complete the manipulation of the printing head to move the character to a reference position, and not by the speed of the operator. It is an object of the present invention to provide an improved form of electromechanical device for positioning the printing head, in which the operating speed is considerably increased, so that the machine speed is not the limiting factor.

It is possible that the operator may depress a second key lever before the character selected by the first key lever has printed; accordingly, it is another object to provide a means to prevent the manipulation of the printing head by operation of a second key lever during the selecting and printing time resulting from the depression of the first key lever.

Another object of the invention is to provide for only one displacement of the single element printing head for each operation of a key lever.

Further, an object is to provide for storage of a subsequent character during the time taken to manuipulate the printing head and print a character.

It is a still further object of this invention to provide a selecting mechanism wherein a uniform key lever force triggers a power-operated device which completes the manipulation of the selecting process without further manual force.

In the preferred form of the invention, the single element printing head is tilted and rotated in response to depression of key levers, each key lever being assigned to a character on the printing head. Depression of a selected key lever causes an interposer to engage a power bail and close an electrical circuit. The electrical circuit supplies power to the bail which drives the interposer against angular recesses in a pair of bars with the result that the bars are displaced laterally by the amount of movement required to both tilt and rotate the printing head to position the character that corresponds to the actuated key lever. One bar controls a tilt system comprising pulleys and a tape to tilt the printing head; another bar controls a rotation system comprising pulleys and a tape to rotate the printing head. After the selected character is positioned with respect to a platen, a bail drives the printing head to engagement with the paper and platen, and the printing head is moved to the next letter space by an electromechanical device.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

2,905,32 Patented Sept. 22, 1959 Fig. 1 is a perspective drawing of the selecting mechanism including the single element printing head and the tapes and pulleys for its control.

Fig. 2 is a top plan view of the tape control system for positioning the character on the single element printing head.

Fig. 3 is a section of the single element printing head through the plane 33 of Fig. 1.

Fig. 4 is an elevation showing the selecting mechanism actuating elements.

Fig. 5 is an elevation showing a return mechanism for the tape control system.

In Fig. 1, there is shown a key lever 10, which is only one of a plurality of key levers, each having a key button. The key levers extend over a plurality of interposers 11, each key lever extending over its respective interposer. The key lever 10 is pivotably mounted on a fixed rod 12 common to all key levers 10. Coupled to the key lever 10 in any suitable manner, such as by a stud 13, is a bell crank 14 with a lip upon which the key lever 10 rests. By means of a spring 15, the bell crank 14 is normally held in resilient engagement with the key lever 10, and the key lever 10 is held in its uppermost and rest position against a stop not shown. The bell crank 14 impinges upon the lip of an interposer 11 when the key lever 10 is depressed. The interposer 11 is slidably mounted and loosely pivoted on a fixed rod 16, which is common to all interposers, and is biased upwardly against a stop not shown and forwardly by a spring 17. Mounted directly beneath the interposer 11 and the remainder of the interposers and at right angles to them is a rod 18 which is forced down vertically when the interposer 11 is pivoted by the bell crank 14.

The rod 18 is connected to a bell crank 19, which pivots about a fixed rod 20 and both

rods

18 and 20 extend the width of the mechanism and are connected to another bell crank at the opposite end of the mechanism not shown. When the rod 18 is moved down by the interposer 11, the bell crank 19 is caused to pivot counterclockwise about the axis of the rod 20. Pivotably connected to the bell crank 19 by a stud 21 is an arm 22, which has a shoulder suitably constructed to operate against an actuating member of a contact assembly 23, which is normally open. A spring 24 couples the bell crank 19 and the arm 22 together and normally holds the arm 22 against the actuating member of the contact assembly 23 without closing said contacts.

When the arm 22 is swung counterclockwise by the bell crank 19, the contact assembly 23 closes thereby actuating a solenoid 25 by application of a DC. voltage 26 to its coil terminals. The solenoid 25 attracts an armature 27 and pivots a bell crank 23 about a stud 29. Coupled to the bell crank 23 is a rod 30, the other end of which is connected to an activating bail 31. The activating bail 31 is pivotally connected at its ends and extends beneath the interposer 11 and all other interposers. The energization and subsequent de-energization of the solenoid 25 will impart reciprocating motion to the activating bail 31 via the bell crank 23 and the rod 30. On its initial stroke the activating bail 31 engages the shoulder of the interposer 11 when said interposer is pivoted. A differential bar 32 has angular recessescut along its length with each recess of different degree of inclination opposite one of the interposers 11. The interposer 11 is engaged perpendicularly with the bar 32 by the activating bail 31 which causes the bar 32 to move laterally to the right by camming action at its engaging surface. Since the angle of the recess in the bar 32 determines the amount of lateral movement imparted to said bar for each particular character to be printed, the angle of cut must necessarily differ according to the desired movement of the printing head to position a particular 3 character with respect to the reference point. It follows that the differential bar 32, as well as a similarly constructed differential bar 33 may move laterally to the right or left by a predetermined amount depending upon ,the engageable cam surface opposite the particular interposer 11. The bar 32 is pivotally coupled to an arm 34 and an arm 35 at its ends by studs 36 and 37 respectively. Further, thearm 34 is pivotally connected to a fixed stud 38, and the arm 35 is pivotally connected to a fixed stud 39. At the same time that the interposer 11 en gages the bar 32, the interposer 11 engages the bar 33,

which is located directly beneath bar 32. Interposer 11 causes the bar 33 to move to the right laterally by camming action at the angular engaging surface of the bar 33. The bar 33 is pivotally coupled at its ends to an v arm 41 and an arm 42 by

studs

43 and 44 respectively.

With this arrangement of parts, lateral movement of the bars, 32 and 33 causes the arms 34 and 35 and the

arms

41 and 42 to pivot about the fixed pins 38 and 39 respectively. A pulley 50 is rotatably coupled by a pin 51 to the arm 34 at the arms end toward the printing head; likewise, a pulley 52 is coupled to the ann 35 by a pin 53. The tilt control system is composed of the pulleys 50 and 52, a double-track pulley 54, a tape 56, and a slidable member 58. As shown in Fig. 2,

the tape is strung in the following manner: From the notch in the upper track of the pulley 4, around the track in the pulley 54 on the side nearest pulley 52, around the pulley 50, through and fixed to the slidable memher 58, around the pulley 52, around the lower track of the pulley 54 on the side nearest pulley 50, and to the notch in the lower track of pulley 54. The slidable member 58 remains fixed with respect to a rod 59 during the selecting motion of the tape 56 and is moved in the letter space operation to be described later. With this arrangement of parts, the lateral movement of the centers of the pulleys 50 and 52 is translated to the circular movement of the pulley 54 through the tape 56. Movement of the pulley 54 tilts the printing head (in a manner to be described later) from its vertical axis by a predetermined amount to select the proper line of type about the surface of the printing head.

In Figure l, a rotation pulley 60 is rotatably coupled by a pin to the arm 41; likewise, the pulley 62 is coupled to the arm 35 by a pin. The rotation system is identical in construction and operation to the tilt control system and is composed of the

pulleys

60 and 62, a double track pulley 64, a tape 66, and the slidable member 58. The tape cooperates with these parts in the same way that the tape 56 acts in the tilt control system so that the lateral movement of the centers of the

pulleys

60 and 62 is translated to circular movement of the pulley 64. Thus, the printing head is caused to rotate about its vertical axis by a predetermined amount related to the particular key lever depressed.

The printing head, although forming no part of the invention, will be explained for the purpose of clarity. With reference to copending application Serial Number 547,481 filed November 17, 1955, which application is assigned to a common assignee, the single element printing head is in the form of a truncated sphere or ball with characters arranged on the face of the printing element (in rows and columns) with only one character in printing position at a time. One character at a time is moved to a single printing position by rotating and tilting the printing element.

In Fig. 3, a supporting tube 70 carries an integral base member yoke 71 having arms 72 and 73. A pivot pin 74 is supported in the upper end of the arms 72 and 73. A hollow tilt shaft 75 which carries a tilt gear 76 is passed axially through post 70. The tilt gear 76 is engageable with a complementary tilt gear sector 77 which is an integral portion of a tilt member or supporting frame 78 that is supported for tilting movement about the tilt pin 74. With this arrangement of parts the turning of the tilt shaft 75 causes pivoting of the tilt gear sector 77 to rock the supporting frame 78 about the tilt pin 74 and tilts a truncated shell 80 on which the characters are arranged.

A turn shaft 81 is supported coaxially of supporting tube 70 and lies within the tilt shaft 75. A turn gear 82 is mounted on the upper end of turn shaft 81 to mesh with an idler 83 supported for free rotation about the pivot pin 74. The idler 83 in turn is meshed with a turn pinion 84. The truncated spherical shell 80 having print characters arranged on the peripheral surface thereof is slid over cylinder 86 which has a bottom flange 87. With this arrangement of parts, the turning of the shaft 81 causes turning of gear 82, the idler 83, and the consequential rotation of the bevel gear 84. This action causes rotation of the truncated spherical shell 80.

In Fig. 1, it can now be seen that bar 32 causes movement of pulleys 50 and 52 which in turn move the tape 56 to rotate the pulley 54 which tilts the printing head 80 and that bar 33 causes movement of

pulleys

60 and 62 causing tape 66 to rotate pulley 64 which rotates the printing head 80. Therefore, the independent and cooperative movement of the pair of bars 32 and 33 manipulate the proper character on the spherical shell 80 to place the character at the single printing position with respect to a platen 89.

Near the limit of counter-clockwise travel of the activating bail 31, said bail 31 engages a normally open contact assembly 90 at an insulated portion thereon and closes said contact, completing a circuit composed of a DC. voltage source 91 and a solenoid 92 in series connection with electric wire. An armature 94 is disposed within the solenoid coil 92 and is pivotably connected to an arm 96 by a rivet 97. The arm 96 is fixed to a power bar 99 adapted for rotational movement. The power bar 99 has a lip extending beneath a pivotably mounted bracket 100 within a frame 102, and said bracket 100 has an arm above the power bar 99. A spring 103 normally holds the bracket 100 in a substantially horizontal position against a stop 104. When the solenoid 92 is energized, the armature 94 is attracted coaxially with said solenoid coil 92, the arm 96 is pivoted clockwise, and the lip on the power bar 99 is moved upward causing the bracket 100 to pivot within the frame 102. The supporting tube 70 of the printing head assembly is contained within the collar portion of the bracket 100. When the bracket 100 is pivoted by the power bar 99, the printing shell 80 is driven into engagement with the platen 89. When the contact 23 is opened as particularly described-hereafter and the activating bail 31 pivots clockwise, the contact 90 opens and de-energizes the solenoid 92. The spring 103 acting upon the bracket 100 restores the printing head, and the bracket 100 causes the solenoid armature 94 to return from its attracted position.

At the limit of counter-clockwise travel of the activating bail 31, a stud on the activating bail 31 engages the lever arm 22 pressing it downward and causing the shoulder of the arm 22 to become disengaged from the acti vating member of the contact assembly 23 opening said contact 23 and removing the voltage from the solenoid 27. The activating bail 31 is returned clockwise to its normal and disengaged position by the return stroke of hell crank 28 urged by a spring 49, and the interposer 11 is returned by the spring 17. If. the key lever 10 has remained depressed, the lip of the interposer 11 engages the bell crank 14 and pivots the bell crank 14 counter-clockwise about the stud 13 causing the lip of the bell crank 14 to move down and away from the key lever 10. The printing cycle cannot be repeated until the key lever 10 is returned to normal since the bell crank 14 is held in front of the lip on the interposer 11. Thus, the bell crank 14 is prevented from acting upon the top of the lip on the interposer 11 and causing it to engage the rod 18, which normally would close the contact 23. When the key lever has been released, the bell crank 14 is restored to rest position by the urging of the spring 15.

To effect leter spacing, the frame 102 carrying the printing head is caused to move laterally adjacent the fixed platen 89. The frame 102 is slidably supported by a rod 105 and a rod 106, both suitably fixed at their ends. The

rods

105 and 106 permit lateral movement of the frame 102 in response to movement of a tape 111. A pulley 112 is rotatably coupled to the base of the machine by a fixed pin 113, and the following pulleys are connected to the base in the same manner; pulley 114 and pin 115, pulley 116 and pin 117, pulley 118 and pin 119, pulley 121 and pin 122, pulley i124 and pin 12. 5, and pulley 126 and pin 127. The tape 111 is fixed to the printing head frame 102, engages the tracks of the

pulleys

112, 114, 124 and 126, is fixed to a notch in a rotatable pulley 126, engages

pulleys

121, 118 and 116, and is fixed to the frame 102. With this arrangement of parts, movement of pulley 126 will cause corresponding movement of the frame 102. Integrally attached to the pulley 126 is a gear 128, which accommodates a spring 129 within a recessed portion of the gear 128. The spring 129 couples the gear 128 to the fixed pin 127 in such a way that manual movement of the frame 102 from right to left compresses the spring 129, which stores energy for subsequent letter spacing. An idler gear 130 is mounted for rotation about a pin 131 and engages the gear 128 and a gear 132. A toothed,

circular member 133 is integrally connected to and coaxial with gear 132. Normally engaged with the circular, toothed member 133 is a dog 135, which restrains the member 133 from clockwise motion due to the urging of the spring 129. The dog is slotted, and a fixed pin 136 passes therethrough. A spring 137 couples the dog 135 to a fixed pin 138 with the tension of the spring 129 normally holding the lift side of the slot in the dog 135 against the pin 136. An L-shaped escapement member 139 is pivotably and slidably mounted on a fixed pin 141, and a slot in the escapement member 139 contains the pin 136. The width of the slot is greater than the diameter of the pin 136 to permit the escapement member 139 to pivot about the pin 141. The escapement member 139 is coupled to the pin 138 by a spring 142, and the right side of the slot in member 139 normally bears upon the pin 136- due to the tension of the spring 142.

As previously described, the printing shell 80 is made to strike the platen 89 by movement of the power bar 99 against the car on the bracket 100. After printing the character, the frame must be moved to the next letter space. Integrally connected to the power bar 99 is an arm 150 which actuates the spacing mechanism in response to movement of the power bar 99. A normally open contact assembly 152 is disposed above the arm 150 in a position where the contacts of the assembly 152 are closed near the limit of travel of the power bar 99 in its upwardly direction. The contacts of the assembly 152 machine by a spring 163 connected to the post 164. It --follows that when the printing shell 80 approaches the platen 89 the arm 150 attached to the power bar 99 closes the contacts of the assembly 152 which applies voltage to the solenoid 154. The armature 156 is attracted pivoting the bell crank 158 clockwise about the pin 159 causing the rod 162 and the lower part of escapement member 139 to move toward the rear of the machine. The escapevment member139 bears upon the dog 135 normally, and

when pivoted, disengages the dog 135 from the teeth in the circular member 133; and at the same time, the escapement member 139 engages the teeth of the circular member 133. Since the circular member 133 is free of the dog 135, it moves clockwise about the pin 142 moving the escapement member 139 to the right until the pin 136 rests against the left side of the slot in the escapement member 139. Movement of the circular, toothed member 133 causes the pulley 126 to turn advancing the tape 111 and the frame 102. For so long as the voltage is applied to the solenoid 154, the escapement member 139 prevents the reentry of the dog into the teeth of the circular member 133 and restrains the toothed member 133 from further motion. As the power bar 99 is. returning to its rest and lower position, the contacts of the contact assembly 152 are opened de-energizing the solenoid 154. By urging of the spring 163, the bell crank 158 pivots counter-clockwise withdrawing the armature 156 from the coil 154 and moving the rod 162 toward the front of the machine. The rod 162 pivots the escapement member 139 and moves the upper portion of the escapement member 139 out of engagement with the teeth on the circular member 133 and allows the dog 135 to become seated in the next tooth of member 133. The dog 135 is urged to the right until the left side of the slot in the dog 135 comes to bear against the pin 136 due to the clockwise motion of the toothed member 133; thereafter, the toothed member 133 is prevented from moving by the dog 135. The escapement member 139 moves to the left by urging of the spring until returned to rest position. This completes one cycle of the spacing operation to move the frame 102 one unit to the right.

Since the frame 102 carrying the printing head 80 moves longitudinally along the platen 89, it becomes necessary to adjust the tape control system for this movement in order that there be no spurious motion of the

pulleys

54 and 64. This is accomplished by sliding the member 58 along the bar 59 as the frame 102 moves laterally, said sliding member 58 moving in the direction opposite the travel of the frame 102. A tape connects to the sliding member 58, passes around a pulley 172 rotatable about the fixed pin 173, passes around a pulley 174 rotatable about a pin 175, connects to the frame 102, passes around a pulley 176 rotatable about a pin 177, passes about a pulley 1'78 rotatable about a pin 179, and connects to the slidable member 58. Thus, movement of the frame 102 to the right causes the same magnitude of movement of the sliding member 58 in the opposite direction causing the

tapes

56 and 66 to have no effect on the tilt pulley 54 and the rotation pulley 64 during spacing operations.

Should a second key lever 10 be depressed before the completion of the printing cycle begun by the operation of the first key lever 10, the earlier printing cycle will not be interrupted. In Fig. 4, first interposer 11 has been engaged by the activating bail 31 and operation of the second key lever 10 causes its respective bell crank 14 to engage its respective interposer 11, but the movement of the activating bail 31 past the shoulder of the second interposer 11 prevents said second interposer 11 from engaging normally. The second interposer 11 merely rides on the top of the activating bail 31. The loosely pivoted end of second interposer 11 is free to move downward and relieve the stress caused by said second interposer 11 when it rides upon the activating bail 31. A short time before the activating bail 31 returns to its extreme clockwise position on the return stroke, the second interposer 11 drops, operates the rod 18 which closes contact 23, and assumes a position whereby it may engage with the activating bail 31. Closing the contact 23 starts the reciprocating motion of the activating bail 31, second interposer 11 engages the activating bail 31, and the second printing cycle begins. This, in effect, stores the second key depression until recovery of the selecting mechanism from the first key depression.

It will be noted that there is shown in Fig. 5 a mechanism for returning the arm 34 to its home position. A like mechanism (not shown) is provided for the arm '41. An arm 180 is mounted for rotation about a fixed pin 181; likewise, an arm 182 is mounted for rotation about a fixed pin 183. Both of the arms 1%, 182 bear upon a fixed stud 184, which is connected to the arm 34. A spring 186 is attached to each

arm

180 and 182 and resiliently holds the arms against the fixed

pins

187 and 188 respectively. With this arrangement of parts, swinging of the arm 34 clockwise causes the stud 184 to pivot the arm 182 clockwise about the pin 183. The arm 180 is prevented from clockwise movement by the fixed pin 187, and the spring 186 is extended according to the movement of the arm 182. When the interposer has been withdrawn from the bar 32, the spring 186 causes the arm 182 to pivot counter-clockwise acting upon the stud 184 to return the arm 34 to the rest position for proper alignment of the printing shell 80.

While there has been shown and described and pointed out the fundamental novel features of the invention as applied to the preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the apparatus illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. Therefore, it is the intention to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. In a typewriter having a single element printing head with a plurality of characters thereon, a selecting mechanism for locating one character at a time at a reference position comprising, in combination, positioning means for tilting and rotating the printing head, a pair of members having cam portions constructed and arranged to displace said positioning means by predetermined increments, a plurality of actuating elements pivotally and slidably mounted each assigned to one of the characters on the printing head and each actuable to position said cam members according to the character selected, a bail mounted to reciprocate and slide said actuating elements when pivoted, power means operable to drive said bail, and key lever means adapted to pivot said actuating elements and activate said power means.

2. In a typewriter having a single element printing head with a plurality of characters thereon, a selecting mechanism for locating one character at a time at a reference position comprising, in combination, control means for tilting and rotating said printing head, positionable selection bars having recesses therein operable to actuate said control means, a plurality of actuating elements pivotally and slidably mounted each related to a character on the printing head and each actuable when pivoted to engage the selection bars at said recesses therein to position said bars, a bail operable to reciprocate and slide said actuating elements, power means activated when the selected interposer is pivoted to drive said bail, a plurality of operable key levers, and means responsive to the operation of said key levers for pivoting said actuating elements.

3. In a typewriter having an single element printing head with a plurality of characters thereon, a selecting mechanism for locating one character at a time at a reference position comprising, in combination, positioning means including a flexible strand and a plurality of pulleys arranged to tilt and rotate the printing head, a pair of selecting bars having a plurality of operating surfaces thereon mounted for lateral movement to actuate said positioning means, said operating surfaces being inclined with respect to the direction of lateral movement of said selecting bars, a plurality of interposers pivotally and slidably mounted each related to a character on the printing head and each engageable with the selecting bars at particular inclined surfaces thereon to position said bars laterally according to the character selected, a bail mounted to reciprocate effective to slide said interposers when said interposers are pivoted, power means for driving said bail responsive when one of said interposers is pivoted, a plurality of bell cranks engageable with the actuating elements each operable to pivot its respective interposer and actuate the power means, and a plurality of pivotable key levers coupled to the bell cranks to operate said bell cranks when one of said key levers is pivoted.

4. A claim in accordance with claim 3 wherein a bell crank pivotally mounted on one of said key levers is engageable with one of said interposers to pivot the latter when said key lever is pivoted, said bell crank being engageable with said interposer to pivot said bell crank when said interposer has been released from the bail thereby preventing repeated cycles from a single operation of said key lever.

5. In a typewriter including a printing member having a plurality of characters thereon, a selecting mechanism for locating one character at a time at a reference posi tion comprising, in combination, positioning means for manipulating said printing member, selecting means including cam elements adapted to operate said positioning means according to the character selected, a plurality of actuating elements operable to engage the cam elements of said selecting means, a bail mounted to reciprocate for driving said actuating elements, power means for operating said bail, and means including a plurality of key levers adapted to move from a rest position to an actuating position and return, to operate respective actuating elements and to activate said power means, and upon movement of respective actuating elements to be ineffective until returned to the rest position.

6. In a typewriter having a single element printing head with a plurality of characters thereon, a selecting mechanism for locating one character at a time at a reference position comprising, in combination, positioning means including a flexible strand and at least one pulley constructed and arranged to tilt and rotate said printing head, a pair of differential bars adapted for lateral movement having inclined portions at angles related to lateral distances for operating said positioning means by predetermined increments, a plurality of interposers pivotally and slidably mounted, each engageable with the ditferential bars at particular inclined portions thereon to position said differential bars according to the character selected, a pivotally mounted bail effective to slide said interposers when said interposers are pivoted, power means operable to drive said bail, a plurality of manipulatable key levers each associated with one of said interposers, and means coupled to said key levers for pivoting said interposers when said key levers are manipulated and activating said power means.

7. In a typewriter including a printing member having a plurality of characters thereon, a selecting mechanism for locating one character at a time at a reference position comprising, in combination, positioning means for manipulating said printing member, selecting means including cam elements adapted to operate said positioning means according to the character selected, a plurality of actuating elements operable to engage the cam elements of said selecting means, a bail mounted to reciprocate for driving said actuating elements, power means for operating said bail, and means including a plurality of key levers adapted to operate said actuating elements and to activate said power means, said bail operating when reciprocated to block all of the other interposers against being driven until completion of the selection cycle and thereafter permit a different and previously selected actuating element to be driven by said bail.

References Cited inthe file of this patent UNITED STATES PATENTS