US3445592A - Start mechanism for telegraph selector - Google Patents

Description

y 1969 G. c. MEYERS ET AL 3,445,592

START MECHANISM FOR TELEGRAPH SELECTOR Filed Oct. 19, 1965 '0 'IIIIIIII- INVENTORS GORDON c. MEYERS RICHARD L. VESSEL AT TOR Y United States Patent U.S. Cl. 178-33 6 Claims ABSTRACT OF THE DISCLOSURE A mechanism for assuring that the start lever of a telegraph selector will not interfere with the operation of the selector magnet armature thereof including an open portion on the selector magnet armature and a cooperating abutment on the start lever for permitting the startlever to move to a position over the armature without interfering with the operation of the armature and a pair of levers pivotally mounted on a portion of the orientation mechanism of the selector and operated by the selector start cam for moving the start lever otf of its pivot perpendicularly of the armature to a displaced position during the receipt of the information bits of a character by the selector magnet, then for moving the start lever away from the armature along a path extending parallel to the armature, then for moving the start lever perpendicularly of the armature back onto its pivot and then for moving the armature into engagement with the armature during the receipt of the stop pulse of the character by the selector magnet.

In telegraphy, to which this invention is most applicable, intelligence is transmitted from one station to another by way of seriatim electrical impulses carried over a conductor usually called a telegraph line. Each impulse is a binary bit, and these binary bits are represented on the telegraph line by the presence or absence of electrical current flowing through the line. The presence of current is called a mark and the absence of current is called a space. These binary bits are combined into groups of bits with each different group forming a discrete alphanumeric character, and one cycle of operation of a teletypewriter receiver is used to receive each character. Each charac er is normally made up of five character-designating code bits and two synchronizing bits which function to distinguish one character from another as signals are received over the telegraph line. A spacing synchronizing bit (called a start pulse) precedes the first code bit each character to signify the start of that character, and 'a marking synchronizing bit (called a stop pulse) follows the last code bit of each character to signify the end of that character.

From time to time the telegraph line experiences periods of idleness when no characters are being transmitted. The telegraph line then remains in the marking (presence of current) condition that it assumed during the stop pulse from the last character transmitted. When transmission is resumed and receipt of the first character begins, the telegraph line assumes its spacing (start pulse) condition. Therefore, whenever the telegraph line is in its marking condition, during the stop pulse of the previous character or an idle period in the line, the teletypewriter receiver mus be prepared to begin receipt of a new character at any time that the telegraph line changes from its marking condition to its spacing condition. Occurrence of this spacing condition on the telegraph line indicates the start of receipt of the next character and causes the teletypewriter receiver to begin a new cycle of operation.

The portion of a teletypewriter receiver which receives electrical impulses over a telegraph line is called the "ice selector. A selector converts the seriatim code bits of each character into simultaneous longitudinal displacements of mechanical levers thereby converting the electrical representation of the character received over the line into a mechanical representation in the displacement of the levers.

In start-stop telegraph receiving selectors, the first bit of each character is a synchronizing bit which starts the receiving selector in operation for one machine cycle. The start lever that senses the presence of this start bit must, in the case of a magnetic receiving selector, sense a movement of an armature from the idle-line condition (marking) to the start bit condition (spacing) without unduly loading the armature. Excessive loading of the armature distorts the operation of the selector and results in a loss of accuracy or selector operating margin. To avoid this, the start lever can be lightly rested against an abutment on the armature and apply a light loading perpendicular to the path of armature movement as shown in Patent No. 2,595,745, granted to W. J. Zenner on May 6, 1952. When the armature moves from the marking-stop position to the spacing-start position, the start lever slips off of the armature abutment and moves perpendicularly to the path of armature travel so as to fall in over the armature. The start lever must then either be removed quickly from the path of movement of the armature before the first code bit is received by the magnet or the start lever and armature abutment may be so shaped that the start lever may permit armature movement without first being withdrawn as shown in FIG. 18 of Patent No. 2,192,351, granted to E. E. Kleinschmidt on Mar. 5, 1940. Even this latter alternative, however, necessitates that the start lever be withdrawn at some point in the machine cycle. If the start lever is not withdrawn at the beginning of the machine cycle as in the Zenner patent mentioned above, it can be withdrawn at the end of the cycle as in the above-mentioned patent to Kleinschmidt. Since withdrawing of the start lever in either of the cited alternatives necessitates immobilizing the armature for a substantial time, the start lever cannot be withdrawn during the receipt of the code bits after the start pulse and before the stop pulse.

Since telegraph signals are subject to distortion as they pass from a transmitting station to a receiving station over a transmission channel, the code bits within these telegraph signals are sampled at their midpoints. In order to adjust the sampling point of the code bits for different conditions of distortion, each telegraph receiver is equipped with a range adjustment that varies the timing relationship between the incoming telegraph signals and the mechanism that samples the armature position at predetermined instants in each machine cycle. This is accomplished by moving start and stop controls for the clutch that drives the armature sampling mechanism.

It is an object of the present invention to increase the speed of telegraph apparatus by resetting the adjustable start mechanism of a variable-start-position, start-stop telegraph selector during the code-receiving portion of the machine cycle.

It is another object of the invention to start a machine cycle of a magnet-operated telegraph selector at a variable start location without immobilizing the magnet armature for a substantial period of time during the machine cycle.

According to the preferred embodiment of the invention, a te egraph selector cam sleeve is selectively coupled to a rotating shaft by a two-cycle-revolution clutch. When the selector armature having an open framework goes from its marking-stop position to its spacing-start position, an undercut start lever rotates on its pivot into the area vacated by the now spacing armature. This trips the selector clutch for one cycle of operation as shown in Patent No. 3,033,926, granted to T. I. Przysiecki on May 8, 1962; but unlike the start lever of the Przysiecki patent, the start lever now remains in this position during the start of the selector cycle with the armature free to assume either one or the other of its two possible conditions due to the undercut in the start lever and the open framework of the armature. As the selector cam assembly rotates, it operates a follower that raises the start lever off of its pivot and completely clear of the armature. Later in the cycle, another cam follower moves the start lever out of the direction of the path of armature travel. The first cam follower then lowers the start lever back onto its pivot and into the level of the armature. During the stop pulse of the telegraph signal and toward the end of the selector cycle, the other cam follower permits the start lever to rest against the end of the marking armature awaiting the receipt of a new spacing start pulse.

A more complete understanding of the invention can be had by referring to the following detailed description when considered in conjunction with the accompanying drawing wherein:

FIG. 1 is a view of the start mechanism during the stop or idle condition of the telegraph line;

FIG. 2 is the same view as shown in FIG. 1 with the exception that the cam is rotated to a position corresponding to a later time in the cycle of the selector and during receipt of a character; and

FIG. 3 is a view in perspective of the selector armature and start lever and showing the selector magnet.

Referring now to the drawing wherein like reference numerals designate the same parts throughout the several views, and more particularly to FIG. 3, the two wires of a telegraph line are connected to two coils of a selector electromagnet 11. These two coils are interconnected by a stub wire 21 so that they are connected in series with the telegraph line 10. The U-shaped core 13 of the selector magnet 11 is arranged so that its two legs pass through the two coils of the selector magnet 11 in series magnetically and so that the open ends of the U-shaped core 13 form two magnetic poles 14 that are bridged by an armature 15. The armature 15 is firmly mounted on a lightweight, open framework armature extension 16 which is pivoted at its right end on a pin 17 mounted to the frame 18 of the teletypewriter receiver. Therefore, the armature is free to move toward the poles 14 whenever current flows through the telegraph line 10 thereby energizing the coils of selector magnet 11 and causing magnetic flux to flow through the magnetic circuit comprising core 13 and armature 15. A spring 19, attached to armature eX- tension 16, pulls armature 15 away from poles 14 whenever current does not flow through the coils of selector magnet 11.

With this arrangement, the leftmost end 20 of armature extension 16 assumes the position shown in FIG. 3 whenever the telegraph line is in its marking condition and assumes the position indicated by the dotted lines in FIG. 3 whenever the telegraph line is in its spacing condition. Thus, the position of the armature extension 16 is a mechanical representation of the electrical condition of the telegraph line.

In order that the selector of the teletypewriter may convert the seriatim electrical code bits into simultaneous mechanical displacements, a rotating, multiple-cam sleeve is started at the beginning of each character and stopped at the end of each character. This cam sleeve provides the timing by which the selector of Zenner Patent 2,595,745 converts these seriatim armature-extension positions into simultaneous mechanical displacements. The selector mechanism described herein is identical with the selector of the Zenner patent except for the start mechanism and for the use of a two-cycle selector wherein one character is received in each half revolution of the selector cam sleeve.

The start of the operation of the selector mechanism is controlled by a start lever which is urged to move 4 to the right and to rest an abutment surface 30 formed on its end against the leftmost end 20 of the armature extension 16 whenever the selector magnet 11 is idle awaiting the start of a character. When a spacing start pulse is received by the magnet 11 over the telegraph line 10, armature extension 16 is dropped by the magnet 11 to the spacing position shown by the dotted lines in FIG. 3. The abutment surface 30 on start lever 25 is no longer blocked by the leftmost end 20 of armature extension 16 and, therefore, start lever 25 moves rapidly to the right to the position shown in dotted lines in FIG. 3.

The start lever 25 has an undercut portion 31 adjacent the abutment 30 and the armature extension 16 has an open portion between the end 20 and the armature 15. Therefore, although the right end of the lever 25 is over the extension 16, the lever 25 permits the open-structured armature extension 16 to immediately assume its marking condition again in response to a marking condition of the first code bit of the character. Thus, although the start lever 25 stays in its right-hand position, as indicated by the dotted lines in FIG. 3, the start lever does not interfere with the movement of the armature extension 16 since its leftmost end 20 is free to move up or down in the undercut portion 31 and since the tip of the lever 25 is not aligned with any solid portion of the extension 16.

As most clearly shown in FIG. 1, the start lever 25 is pivoted at its lower extremity on a fixed post 35 that is mounted to the frame of the teletypewriter. The start lever 25 is urged to rotate clockwise about fixed post 35 by a spring 36 and, when the armature extension 16 moves to its spacing position, the spring 36 rotates the start lever 25 clockwise about the fixed post 35 thereby moving the surface 30 to the right into the position shown in dotted lines in FIG. 3. Start lever 25 has a lug 40 extending from its midsection which ex ends into a slot 41 formed in a start ball 42. Start bail 42 is pivotally mounted on a ranging pivot 45 so that when the start lever 25 moves to the right the lug 40 in the slot 41 moves the start bail 42 to the right thereby rotating the start bail 42 clockwise about the ranging pivot 45. Firmly fixed to the start bail 42 is a stop arm 46 that is also pivoted on ranging pivot 45 so that when start bail 42 rotates clockwise about ranging pivot 45, it carries stop arm 46 with it. A bent-over lip 47 on the end of stop arm 46 is used to control the starting and stopping of a selector clutch 49 of the type shown and described in Nelson Patent 2,566,031 granted Aug. 28, 1951.

The driven member of the selector clutch 49 carries a control tab 48 (FIG. 1) on its periphery. Whenever control tab 48 is blocked from movement, the driven member of the clutch abruptly disengages from the driving member and stops. Whenever control tab 48- is unblocked, the clutch 49 engages and the driven member rotates with the driving member. Whenever stop arm 46 is in its counterclockwise extreme as a result of surface 30 on start lever 25 being held to the left of leftmost end 20 of armature extension 16, lip 47 is maintained in interfering relation with tab 48 of the selector clutch and the driven member of the clutch 49 is maintained disengaged from the driving member thereof.

As is fully set forth in the above-identified Zenner 2,595,745 patent the driving member of the selector clutch 49 is connected to a continuously rotating drive shaft 50 which provides continuous input drive power to the selector mechanism. The driven member of the selector clutch 49 is attached to a selector cam sleeve 51 that is rotatably mounted on drive shaft 50 so that whenever the selector clutch is engaged, selector cam sleeve 51 is coupled through the selector clutch to drive shaft 50 and rotates with drive shaft 50 until the tab 48 on the selector clutch is again blocked by lip 47 on stop arm 46. Therefore, when the telegraph line changes from the marking condition to the spacing condition and armature extension 16 drops to the position shown by the dotted lines in FIG. 1, the start lever 25 moves to the right under the action of spring 36 thereby rotating start bail 42 and stop arm 46 about ranging pivot 45 to remove lip 47 from engagement with tab 48 on the selector clutch. This permits the selector clutch to engage and couple the selector cam sleeve 51 to the drive shaft 50 in order to convert the seriatim electrical code impulses into simultaneous mechanical displacements.

As soon as start lever 25 moves to the right as shown in dotted linesin FIG. 1, it is lifted olf of its pivot 35 permitting the start lever to be moved leftwardly without interfering in any way with the operation of the armature extension 16. When surface 30 on start lever 25 has been moved to the left of leftmost end of armature extension 16, start lever is then lowered onto its pivot 35 and permitted again to rest its surface against the leftmost end 20 of armature extension 16 during the stop pulse at the end of the character.

To control these timed movements of start lever 25, a start cam 56 is firmly mounted on selector cam sleeve 51 to rotate with the selector cam sleeve. As soon as start lever 25 falls in over armature extension 16 during the spacing start pulse of a character, the selector clutch begins rotating selector cam sleeve 51 and start cam 56 with it. The selector considered herein is a two-cycle selector in that the selector starts and finishes receipt of a character in 180 of rotation of the selector cam sleeve 51. Therefore, the start cam '56 contains two identical cam profiles around its periphery.

A lifting lever 57 is pivoted on ranging pivot 45 and is biased to rotate counterclockwise about ranging pivot 45 by a spring 58 that is attached to a spur 59 projecting downwardly and to the right from lifting lever 57. The upper end of lifting lever 57 is formed into a camfollower portion 61. Spring 58 serves to hold cam-follower portion 61 in engagement with the start cam 56.

When selector cam sleeve 51 and start cam 56 begin rotating with shaft 50 from the position shown in FIG. 1, a ramp 63 on start cam 56 drives cam follower 61 rightwardly rotating lifting lever 57 clockwise about pivot 45 against spring 58. When lifting lever 57 rotates clockwise a lifting arm 64 on lifting lever 57 rises and engages a spur 66 on the bottom of start lever 25.

As ramp 63 on start cam 56 rocks lifting lever 57 clockwise about ranging pivot 45, lifting arm '64 continues to rise and lifts start lever 25 off of its fixed pivot (FIG. 2) until abutting surface 30 is high enough to clear the leftmost end 20 of armature extension 16 even when the armature extension is in its marking condition. Cam-follower portion 61 on lifting lever 57 then rides on dwell portion 67 of start cam 56, holding start lever 25 off of fixed pivot 35.

In FIG. 2 start cam 56 is shown rotated to a position corresponding to a later time in the cycle of the selector after the lifting arm 64 has raised start lever 25 suificiently to clear armature extension 16. At this time a cam-follower 68 on start bail 42 is engaged by a ramp 69 on start cam 56 which is identical to ramp 63 but displaced from it about start cam 56 by 180. As start cam 56 continues to rotate, ramp 69 pushes start bail 42 to the left (FIG. 2) and as start bail 42 moves to the left, it rotates counterclockwise about ranging pivot 45 thereby driving the lip 47 on stop arm 46 into the path of a second control tab 48 on the selector clutch 49. Since the selector receives a character during each half-revolution of rotation, the selector clutch 49 is stoppable in either of two rotational positions, 180 apart. To stop in either of two rotational positions, the selector clutch has two control tabs 48 each identical to the tab shown in FIG. 1. As lip 47 on stop arm 46 is moved into a position to engage the next clutch control tab 48 the leftward movement of start bail 42 also moves start lever 25 to the left by means of the engagement of lug on start lever 25 with the slot 41 on start bail 42. The cooperation of ramp 69 and cam-follower 68 thus moves start lever 25 leftwardly until surface 30 on start lever 25 is to the left of leftmost end 20 of armature extension 16. At this time, cam-follower portion 61 on lifting lever 57 drops oif of an edge 71 on start cam 56 thereby permitting lifting lever 57 to rotate counterclockwise under the action of spring 58 about ranging pivot 45, lowering lifting arm 64 and lowering start lever 25 onto fixed pivot 35.

After ramp 69 and cam follower 68 have moved abutment surface 30 to the left of leftmost end 20 of extension 16, cam follower 68 rides a dwell portion 72 (identical to dwell portion 67 but displaced by on start cam 56. When all of the code bits of the character have been received by the selector, the telegraph line assumes its marking stop condition. During this marking stop pulse, an edge 74 on start cam 56 passes cam follower 68 permitting spring 36 to move start lever 25 and start bail 42 to the right. Cam follower 68 then begins to fall into a notch 76 on start cam 56, but abutment surface 30 on start lever 25 strikes leftmost end 20 of armature extension 16 preventing cam follower 68 from falling into notch 76. As cam follower 68 tries to fall into notch 76, the next control tab 48 on the selector clutch 49 strikes lip 47 on stop arm 46 thereby stopping the selector cam sleeve 51 to await the start of the next character. The start mechanism is then in the condition shown in FIG. 1 awaiting the receipt of the spacing start pulse of the next character.

In telegraphy, each code bit is subject to distortion as it travels over the telegraph line. The extent and type of distortion is dependent upon the particular telegraph line. Therefore, a modern telegraph selector is made capable of accurately receiving signals having a wide variety of types of distortion. Since all of the code bits are of the same finite chronological duration, it is usually best to sample each code bit, with a selector of the type shown in the Zenner patent, near its chronological center. Since telegraph lines vary, a given selector is usually adjusted in place after installation and periodically thereafter. The selector adjustment that moves the selector sampling point with respect to the center of each code bit is called the range adjustment. Since the center of each code bit is always measured from the beginning of the start pulse, the range adjustment can best be made in the start mechanism of the selector which actually determines the time at which the selector clutch engages and rotates the selector cam sleeve that in turn controls selector timing.

In FIG. 1 start bail 42, stop lever 46, and lifting lever 57 are all pivoted on ranging pivot 45. Ranging pivot 45 corresponds to stud 38 in the Przysiecki 3,033,926 patent mentioned above and is similarly mounted on the teletypewriter frame so that it can be moved in a fixed arc about the axis of drive shaft 50. The range adjustment of the selector is accomplished by moving the ranging pivot through its fixed arc. As the ranging pivot is moved through its fixed arc, poor reception will usually be noticed as the ranging pivot reaches either extreme position. The points on the fixed arc where poor reception begins are then noted and ranging pivot 45 is placed midway between these points.

In order to sample the code bits later than their chronological center, the ranging pivot 45 is moved clockwise (FIG. 1) about the center of drive shaft 50 moving lip 47 on stop arm 46 clockwise about the center of drive shaft 50. This causes the selector clutch to stop at a more clockwise position. Since selector cam sleeve 51 rotates counterclockwise, it takes the selector cam sleeve longer to arrive at the same angular position after starting from its new position, thus sampling each bit later. In order to sample the code bits earlier, the ranging pivot 45 is moved counterclockwise about the center of drive shaft 50, moving lip 47 to a position that is more angularly advanced in the direction of selector cam-sleeve rotation. Therefore, selector cam sleeve 51 still starts at the beginning of the start pulse but from an angularly advanced position and with this head start arrives at each sampling position earlier.

Lifting lever 57 is also mounted on ranging pivot 45 in order that the time relationship between the start of selector cam sleeve 51 and the raising of start lever 25 oif of fixed pivot 35 is held constant. The curved surface 77 on lifting arm 64 is provided to engage with spur 66 on start lever 25 no matter where ranging pivot 45 is placed.

Since armature extension 16 does not move with ranging pivot 45, start lever 25 is mounted on the fixed pivot 35. Slot 41 and lug 40 permit relative movement between start lever 25 and start bail 42 about the center of drive shaft 50.

OPERATION The spacing start pulse permits extension 16 to drop so that start lever 25 rocks to the right. Rightward movement of start lever 25 rotates start bail 42 clockwise about ranging pivot 45 carrying cam follower 68 into notch 76. Clockwise rotation of start bail 42 rotates stop arm 46 clockwise about ranging pivot 45, removing lip 47 from engagement with control tab 48 (FIG. 1) on the selector clutch. This permits the selector clutch to begin rotating selector cam sleeve 51. When start cam 56 begins rotating, ramp 63 starts to rotate lifting lever clockwise raising lifting arm 64. Lifting arm 64 raises start lever 25 clear of armature extension 16. Another ramp on start cam 56 moves start bail 42 and start lever 25 to the left until lip 47 on stop arm 46 is positioned to block the next control tab of the selector clutch and until start lever 25 has moved to the left of armature extension 16. A lip on start cam 56 then lets lifting lever 57 lower start lever 25 back down to its original position. The other lip on start cam 56 then lets abutting surface 30 of start lever 25 rest against leftmost end 20 of armature extension 16 during the marking stop pulse to await the next spacing start pulse.

What is claimed is:

1. In a start-stop telegraph signal receiver the combination of:

a signal controlled receiving magnet having an armature;

a cam;

a rotary driver for the cam;

a clutch for connecting the cam to the rotary driver;

a start lever for sensing a movement of the armature;

.a pivot for supporting said start lever for oscillation in a path extending parallel to the armature;

a clutch-trip lever operated by the start lever in response to a movement of the armature for tripping the clutch to establish a driving connection through said clutch from the driver to the cam;

means operated upon the sensing by the start lever of a movement of the armature for lifting the start lever off of the pivot and for moving the start lever in a path substantially parallel to the path of movement of the armature; and

means operated by the cam for moving the start lever in a path substantially perpendicular to the path of movement of the armature.

2. The combination according to claim 1 wherein the cam operated means for moving the start lever is a cam follower mounted on the clutch-trip lever.

3. A printing telegraph receiving selector including:

a pivot member;

a start lever mounted on the pivot member;

a start cam;

means responsive to movement of the start lever for operating the start cam;

means responsive to operation of the start cam for displacing the start lever with respect to the pivot member to a shifted position, and

means responsive to operation of the start cam for pivoting the start lever in the shifted position.

4. The selector according to claim 3 wherein the pivoting means is a lever mounted in engagement with the start lever for actuation thereby and positioned for engagement by the start cam for actuation thereby.

5. In a telegraph selector mechanism of the type including a selector magnet having an armature, a fixed pivot, a start lever normally mounted on the fixed pivot in engagement with the armature and monuted for movement from a first to a second position in response to movement of the armature, a clutch, a clutch trip lever connected to the start lever for tripping the clutch in response to movement of the start lever to the second position and an orientation mechanism including an adjusable pivot for supporting the clutch trip lever and for varying the position of the clutch trip lever with respect to the start lever to compensate for signal distortion, a device for moving the start lever out of the second position and thereby freeing the armature for response to incoming signals including a lever mounted on the adjustable pivot for moving the start lever off the fixed pivot and means responsive to movement of the start lever from the first to the second position for operating the lever.

6. The device accrding to claim 5 wherein the selector mechanism further includes a constantly rotating drive shaft and a cam sleeve mounted on the drive shaft, wherein the clutch operates to couple the sleeve to the shaft for rotation therewith and wherein means for operating the lever includes a cam mounted on the sleeve in engagement with the lever for rocking the lever about the adjustable pivot to lift the start lever off the fixed pivot.

References Cited UNITED STATES PATENTS 2,505,729 4/1950 Zenner 17s 25 2,595,745 5/1952 Zenner 178-33 5,033,927 5/1962 Moebius 17833 THOMAS A. ROBINSON, Primary Examiner.

U.S. Cl. X.R. 17827

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