US3532205A

US3532205A - Printing-carriage back-spacing mechanism for teleprinters

Info

Publication number: US3532205A
Application number: US644387A
Authority: US
Inventors: Hideo Ozaki; Yoshinori Tanaka
Original assignee: Nippon Electric Co Ltd
Current assignee: NEC Corp
Priority date: 1966-06-10
Filing date: 1967-06-07
Publication date: 1970-10-06
Anticipated expiration: 1987-10-06
Also published as: GB1189677A; DE1287109B

Description

Patented Oct. 6, 1970 Sheet MVENTORS A0050 9241/ Patented Oct. 6, 1970 3,532,205

v Patented Oct. 6,1970 3,532,205

Sheet 3 of 3 .JICS: 5 .IIEJU.

INVENTORJ H/OEO 02/440 PRllNTlNG-CARRHAGE BACKSPACHNG MECHANISM FOR TELEPRKNTEEIS Conventional carriage mechanisms in teleprinter devices are normally comprised of a carriage pulley belt for transmitting rotation from a drive wheel to a freely rotatable driven wheel. The drive wheel has secured thereto a ratchet for stepping the pulley belt. The printing typewheel assembly is mechanically secured to the pulley belt for advancement therewith. A tension spring is coupled between the left-hand end of the carriage typewheel assembly and a stationary support to normally bias the carriage typewheel assembly toward the left. A shaft couples the drive pulley to a ratchet which is stepped in clockwise fashion in order to drive the pulley belt toward the right in stepwise fashion against the pulling force of the tension spring. A space-suppression assembly is provided to prevent advancement of the carriage typewheel assembly during a print operation.

The driving mechanism, commonly referred to as a carriage drive bail, is mounted for rocking rearwardly and forwardly to drive the carriage advancement assembly which is comprised of a first pawl and a toggle linkage carrying a second pawl which is driven by the carriage drive bail to break at the knee of the toggle assembly and to remove its associated pawl from the ratchet while the first pawl holds the ratchet against counterclockwise rotation under the force of the tension spring. The carriage drive bail rocks in the reverse direction to straighten the toggle assembly whose pawl engages the next notch in the ratchet, causing the ratchet to be driven stepwise by one incremental step to advance the carriage typewheel assembly.

Backspace operation is performed by a third pawl pivotally coupled to the connecting pin of the toggle assembly so as to be moved therewith.

All three pawls are provided with shoulders which confront a release plate which is operative to release the first and second pawls from engagement with a tooth of the ratchet. The depth of the shoulder provided on the third pawl is greater then the first two pawls so as to cause the third pawl to be maintained against the ratchet wheel. An assembly is provided to prevent the release plate from being moved by an amount sufficient to drive the third pawl out of engagement with the ratchet. When the release plate removes the first and second pawls from the ratchet, the tension spring through the carriage typewheel assembly and the pulley rapidly urges the ratchet counterclockwise through an incremental angle to perform the backspace operation. The third pawl confronts the shoulder positioned to the left of the third pawl to prevent the backspacing movement from stepping more than one space to the left. The return of the release plate to its rest posi tion returns the first and second pawls back into engagement with the ratchet in readiness for the performance of either a forward spacing or rearward spacing operation under control of the operator.

The instant invention relates to teleprinters and other like typing devices, and more particularly to a novel backspacing assembly which is characterized by its simplicity of design, and which may be readily and simply added to already existing conventional teleprinter assemblies to afford such assemblies with the additional feature of performing a backspacing operation. There exist a number of applications in which it is advantageous to have a backspacing capability. For example, one conventional teleprinter system is comprised of at least a pair of teleprinters provided at remote locations for two-way transmission. Whenever an operator mistakenly depresses a key on the keyboard of his teleprinter in transmitting a message to a distant station, and, automatically, the teleprinter at the distant station prints the mistaken character, numeral, or other symbol operated at the sending station, the necessity, therefore, arises for backspacing both the trans mitting and the receiving printing carriages to the first mistyped character position, and transmitting a delete code to the distant station to strike the erroneously printed character. To accomplish the backspacing operation, a variety of backspacing mechanism designs for incorporation into teleprinter systems have been proposed. The majority of conventional backspacing mechanisms; have been found to be extremely bulky, complex mechanisms and quite unreliable in operation. it, therefore, becomes arprinciple object of the instant invention to provide a simple, common new and improved printing carriage backspacing system that can be most easily and rapidly incorporated into conventional teleprinter systems without backspacing facilities, and being of the type that the printing carriage is continuously urged by a spring under tension toward the left margin. inclusion of a backspacing facility into teleprinters of this design can, therefore, be made with a minimum modification to existing parts, assemblies, and mechanisms incorporated therein.

One outstanding feature in the design of the instant invention which enables the attainment of the above mentioned object, is the incorporation of a backspacing pawl performing a function substantially similar to that performed by a check pawl, which is one element of a pawl assembly consisting of a check pawl and a spacing pawl, in. such a manner that there may be produced a slight linear displacement between the check pawl and the backspacing pawl with respect to the spacing ratchet teeth, and further that all pawls may be released from the ratchet upon reception of a carriage return code, whereas the check and spacing pawls will be released temporarily upon the reception of a backspace code so as to permit the ratchet to rotate in the backspacing direction.

The instant invention is comprised of a backspacing pawl which is pivotally mounted to a pivotal pin forming the knee of a toggle assembly for the spacing pawl. The carriage operating bail causes the spacing pawl toggle assembly to collapse during movement in a first direction, thereby releasing the spacing pawl from the ratchet. The check pawl, however, remains in engagement with one tooth of the ratchet, restraining it from rotating in the backspacing" direction as a result of release of the spacing pawl from the ratchet. The carriage bail assembly moves in the reverse direction, causing the spacing pawl toggle assembly to be extended, straightening the toggle assembly and advancing the ratchet. by one tooth.

The carriage return operation is performed by releasing both the checking and spacing pawls from the ratchet, placing the ratchet under control of the tension spring which auto matically drives the typewheel carriage to the extremely lefthand end of the teleprinter assembly. This function is obviously performed in conventional systems as one part of the carriage return line feed operation to cause printing to begin on the next line. Release of the check and spacing pawls is performed by a rockable release plate which, upon depression of the appropriate function key, drives the check and spacing pawls out of engagement with the ratchet.

The operation of the release plate can be advantageously employed for the backspacing operation by causing the release plate to drive the check and spacing pawls out of engagement with the ratchet, while failing to move through a sufficient angle to likewise drive the backspacing pawl out of engagement with the ratchet. Once this function is performed, the backspacing pawl abuts the next tooth of the ratchet as it attempts to move toward the left or toward the backspace direction under control of the tension spring.

The release plate has its motion restrained by a mechanical linkage coupled to the rockable release plate to restrain its movement as soon as the release plate has released both check and spacing pawls from the ratchet, but before the release plate may remove the backspacing pawl from the ratchet. This control assembly may be added to already existing teleprinter structures with an absolute minimum of design modification and primarily with simply the addition of the backspacing pawl and the release plate restraining assembly.

The release plate restraining assembly is further fully compatible with system operation during a carriage return function by allowing the backspacing pawl, as well as the check and spacing pawls, to be fully disengaged from the ratchet in order to perform the carriage return operation.

It is, therefore, a major object of the instant invention to provide a novel device for use in teleprinters, and the like, to provide the capability of a backspacing operation through the mechanics of a backspacing assembly which is simple and straightforward in design and which may be relatively easily and rapidly added to conventional devices.

Another object of the instant invention is to provide a novel backspacing device for use in teleprinters, and the like, wherein the backspacing pawl is added to an assembly comprised of a check pawl and a collapsible stepping pawl, and having a release plate capable of releasing all pawls from an associated ratchet to perform a carriage return operation, and for releasing only the check and spacing pawls to the exclusion of the backspacing pawl to perform a backspacing operation.

Yet a further object of the instant invention is to provide a novel backspacing device for use in teleprinters, and the like, wherein the backspacing pawl is added to an assembly comprised of a check pawl and a collapsible stepping pawl, and having a release plate capable of releasing all pawls from an associated ratchet to perform a carriage return operation, and for releasing only the check and spacing pawls to the exclusion of the backspacing pawl to perform a backspacing operation,

and further comprising a mechanism for controlling the movement of the release plate so as to enable release of the check and spacing pawls under control of the release plate and to restrain the movement of the release plate to prevent disengagement of the backspacing pawl from the ratchet during an operation calling for backspacing movement.

The above as well as other objects will become apparent upon a consideration of the accompanying description and drawing in which:

FIG. I is a perspective view of those portions of a teleprinter assembly which are significant from the viewpoint of understanding the backspacing assembly of the instant invention.

FIG. la is an end view showing the essential part of the backspacing mechanism of FIG. 1.

FIGS. 2 through 6 are top plan views showing an essential part of the backspacing mechanism in a predetermined format of operation so as to explain the sequence of operations in order to understand the manner in which a teleprinter printing carriage is caused to perform a spacing, carriage return and backspacing operation. Each plan view is accompanied by a simplified diagramatic representation, FIGS. 2a through 60 respectively, showing the mode of operation and position of a plurality of pawls relative to their associated ratchet wheel.

FIGS. 7 through 10 are side elevational views showing the portion of the function mechanism which are operative upon the reception of a backspace code with the views 7 through 10 showing the mechanism in various stages of operation in order to clarify the functional aspects of the instant invention.

The backspacing mechanism of the instant invention may be advantageously adapted for use in a printing carriage assembly which is continuously placed under spring tension toward the left margin of the device, and which is provided with a spacing mechanism functioning to space or advance one character space (or pitch) against spring tension each time a character or space code is received. The printing carriage returns to the left margin by spring tension upon receipt of a carriage return code in order to actuate the carriage return mechanism. In conventional teleprinters, upon receipt of a carriage return code, both the spacing and backspacing pawl assemblies are released from the feed-wheel (i.e., the spacing ratchet) through the aid of a carriage return mechanism. With the present backspacing mechanism, receipt of a backspace code functions to release only the spacing mechanism from the feed-wheel when a backspace code is received by incorporating a mechanism with the carriage return mechanism to permit only the spacing mechanism to be released from the feed-wheel.

The backspacing mechanism, which is capable of remaining engaged with the ratchet wheel, is installed with the conventional spacing mechanism as an integral part thereof while a simple mechanism for performing a partial operation of the carriage return mechanism when. a reception of a backspace code is incorporated into the carriage return mechanism, is designed to perform a full release operation so as to release all pawls from the feed or ratchet wheel upon the reception of a carriage return code.

Briefly speaking, the backspacing mechanism, in accordance with the instant invention, is an improved version of conventional backspacing mechanisms in that the printing carriage can be backspaced accurately by incorporating a simple mechanism into mechanisms already employed for existing carriage return operations. FIGS. 1 and 1a illustrate a preferred embodiment of a backspacing mechanism which is incorporated into a teleprinter assembly of the stationary platen type.

The assembly shown therein is comprised of a spacing ratchet 2 arranged in the lower left-hand corner. The shaft 5; on which ratchet 2 is mounted extends vertically upward to receive a driving sprocket or pulley SP rigidly secured to the upper end of the shaft 8,. A printing carriage spacing belt 29 is entrained about the sprocket SP and a driven pulley 50 which is rotatably mounted upon a shaft S installed on the righthand side of the teleprinter frame (only the topmost portion of the shaft S protruding through pulley 50 being shown in FIG. 1). The function of the spacing belt 29 is to displace the carriage 28 which is rigidly secured thereto by clamping means 28a, either to the left or to the right as required, and under control of the rotational movement of sprocket SP.

The carriage 28 is maintained under tension by means of a large spring 1 having a first end thereof secured to a righthand side frame member F by means of a screw or pin P, and which has its opposite end clamped at 280 to the left-hand side of carriage 28. Spring I is entrained about a pulley 44 positioned near ratchet wheel 2. Spring 1 is extended by an amount sufficient to cause it to place carriage 28 under tension and normally bias it toward movement in the left-hand direction, as shown by arrow A. This spring force is transmitted through carriage 28 and belt 29 to ratchet wheel 2, causing wheel 2 to have a normal tendency to rotate in a counterclockwise direction about the longitudinal axis of shaft 5,, as shown by arrow 60. The rotation of ratchet wheel 2, however, is blocked whenever any one of the pawls 4 through 6 engages a notch or tooth provided in ratchet 2.

The center portion of the illustration of FIG. 1 shows a code bar assembly 27 comprised of a plurality of code bars, for example code bars 26, 26a and 26b, equal in number to the number of code bits forming the teleprinter code. The code bars of group 27 are employed for the purpose of selecting the particular character to be typed or printed as set forth, for example, in copending, U.S. application Ser. No. 644,936 filed June 7, 1967 now U.S. Pat. No. 3,431,943, and assigned to the assignee of the instant invention. When a code is received from the sending side teleprinter, the code received selectively operates code bars in the code bar group 27 of the receiving teleprinter which are actuated by the received code in order to select the appropriate character or symbol to be typed.

Thus, code bars, for example code bars 26, 26a and 26b, which are equal in number to the Mark codes of a received signal contained in a code, move upwardly and to the left simultaneously in a manner suggested by the above mentioned copending patent application.

A driving cam (not shown) rocks a drive arm 13 upward and downward. causing a function drive bail I2 coupled thereto by spring means 49. to likewise experience a reciprocating or upward and downward movement.

The assembly of FIG. I is further provided with a carriage return function lever 21 and a carriage backspace function lever 25, each having their forward end supported by shaft 30. The levers 21 and 25 pass beneath bail I2 and code bar assembly 27 so as to extend rearwardly with their free ends being respectively aligned with a carriage return function bail l9 and a carriage backspace function bail 23, respectively, so as to be aligned substantially coplanar therewith.

Levers 21 and 25 are respectively biased to rock upwardly by

springs

31 and 32 which maintain the upper edges of these levers 21 and 25 in contact with the lower edge of bail 12.

A carriage drive bail 11 is positioned in front of the function drive bail 12, and is designed to be rocked back and forth by means of a cam (not shown). The function of carriage drive bail 11 is to operate the printing mechanism (not shown) supported by carriage 28 and to drive pawl 5 through the action of a roller 8 secured to carriage drive bail 11 by fastening means 8a so as to project downwardly in order to make selective engagement with drive pawl 5 for the purpose of advancing ratchet wheel 2 one tooth after another against the tension of spring 1, causing carriage 28 to be spaced in a step-by-step fashion toward the right, as shown by arrow B.

A print suppression code bar 26, shown mounted in spaced parallel fashion relative to the code bars of the bar group 27, is employed for the purpose of suppressing or preventing a printing operation, and, at the same time, for blocking carriage 28 from spacing (i.e. incrementally moving) toward the right. When a character code is received, the print supression code bar 26 moves upwardly and to the left, so as to unblock the printing mechanism supported in the carriage 28, allowing the printing mechanism to operate and thereby perform the printing function. As part of the printing operation and substantially immediately after completion thereof, the carriage 28 moves one character space toward the right before a subsequent printing operation occurs. FIG. 3 illustrates the manner in which the spacing mechanism operates to cause the carriage 28 to move one space to the right.

Referring initially to FIG. 2, let it be assumed that a character code has been received from the sending teleprinter. This causes the print suppression code bar 26 to move upwardly and to the left causing its left-hand most end to strike extension 33provided on a space suppression latch 14. This causes space suppression latch 14 to rotate counterclockwise about its pivot S and against the normal biasing force of tension spring 48 coupled between space suppression latch I4 and a suitable portion of the teleprinter frame. Rotation of space suppression latch 14 counterclockwise about pivot 8;, from the position shown in FIG. 2 toward the position shown in FIG. 3 causes a shoulder 37 provided along latch 14 to be rotated out of the path of movement of a projection 36 provided on one edge of the spacing pawl 5 which will thereby enable the toggle linkage comprised of feed pawl 5 and toggle link 9 to buckle or collapse at its knee in a manner to be more fully described.

During the moment at which the space suppression latch 14 unlatches the projection 36 on feed pawl 5, the carriage drive bail 11 (See FIG. I) is in the midst of the first half of its function cycle and is swinging rearwardly causing its associated roller 8 to likewise swing rearwardly. This enables toggle link 9, which is normally biased by spring means 9a, to rotate in a clockwise direction about pivot pin 35 so as to follow the rearward movement of roller 8. This causes the right-hand endsof feed pawl 5 and backspace pawl 4, which are both rotatably mounted to toggle link 9 through pivot pin P,, to rotate counterclockwise from the position shown in FIG. 2 toward the position shown in FIG. 3. In other words, the toggle linkage comprised of feed pawl 5 and toggle link 9 is caused to buckle or break at the knee, collapsing the toggle linkage and driving the

pawls

4 and 5 from a first tooth 2a, as shown in FIG 2, into a position of engagement with the next tooth 2c, as shown in FIG. 3, the said next tooth being to the right relative to the tooth 2a from which the

pawls

4 and 5 have been removed.

The check pawl 6, which is pivotally mounted upon pin 35 together with toggle link 9, remains in engagement with the preceding notch (i.e., tooth 2a) of ratchet wheel 2 in spite of the rearward movement of roller 8, since the check pawl 6 is a straight rigid member and is unaffected by the rearward movement of roller 8.

FIGS. 2a and 3a show the diagrammatic representations to indicate the stepping operation. Before movement of roller 8 in the rearward direction (and assuming movement of shoulder 37 out of the path of motion of projection 36) all three pawls 4-6 are contained within notch 20 with pawl 5 having its left-hand most edge abutting against the shoulder-2b (FIG 2a). With the rearward movement of roller 8,

pawls

4 and 5 are withdrawn from notch 2a and move into notch 20 while some minor movement is experienced by ratchet 2, check pawl 6 nevertheless restrains ratchet 2 from moving a full incremental angle toward the right (i.e., counter clockwise). The forward movement of roller 8 causes the toggle assembly to move from the collapsed position of FIG. 3-

toward the extended position of FIG. 2 which drives

pawls

4 and 5 toward the left relative to FIG. 3 and hence toward the position shown in FIG. 2. This drives the ratchet 2 toward the left (i.e., clockwise) to advance carriage assembly 28 one space toward the right. In actuality, in moving from the diagrammatic position of FIG. 3 to the position of FIG. 2, all three pawls 4-6 would actually rest within a notch 20.

Of the two

pawls

4 and 5, it can be seen that feed pawl 5 extends slightly more toward the left than pawl 4, causing feed.

pawl 5 to operate as the stepping pawl in the performance of a stepping or spacing operation. The check pawl 6, inbeing restored to the state illustrated in F IG. 2, in actuality, climbs over the tooth adjacent the notch 20 to which the feed pawl 5 has been engaged and urges the ratchet 2 toward the left (Le. clockwise) against the tension of spring 1. This motion causes the sprocket, SP mounted upon ratchet shaft 8, to move to an angle equivalent to one tooth pitch thereby causing carriage 28 to move one character or space toward the right.

When a function code is received, a corresponding function lever, for example, carriage return function lever 21, is selectively operated so that a projection (not shown) provided on the underside of print suppression code bar 26 strikes the side of the carriage return function lever 21 which causes the code bar 26 to be blocked from moving upward and to the left as previously described and hence causes the printing operation to be blocked. This results in the space suppression latch 14 remaining in the stationary or rest position of FIG. 2. Therefore, notwithstanding the fact that the carriage drive ball 1 1 is rocked rearwardly, the projection 36 on the feed pawl 5 is caused to remain engaged with the notch 37 provided on space suppression latch 14 so as to block the toggle link 9 from following the movement of roller 8 beyond some slight movement. This blocks the toggle link 9 from rotating clockwise about pivot pin 35, preventing the feed pawl 5 and backspace pawl 4 from falling into the next notch and hence preventing the printing carriage 28 from spacing one incremental step toward the right. The actual movement of the toggle link 9 before projection 36 strikes shoulder 37 is only a fraction of one tooth pitch D (See FIG. 4a) so that the movement of

pawls

4 and 5 is so slight as to prevent the ratchet 2 from advancing beyond the notch 2a, shown in FIG. 4. In other words, the carriage 28 is thereby placed in a space suppression state.

On receipt of a carriage return code, the carriage return function lever 21 is enabled to be raised so as to follow the upward movement of bail 12 by having its upper edge in contact with the lower edge of bail 12 due to the biasing force of spring 31 coupled between lever 21 and bail 12. The free forward most end of lever 21 falls into the notch provided in carriage return function bail 19. The upward movement of the carriage return function lever 21 blocks the print suppression code bar 26 from moving upward and to the left with the result that the spacing of the printing carriage 28 is blocked in a manner substantially identical to that previously described.

The downward movement of the function drive bail I2 urges the carriage return function lever 21 to be rocked downwardly which, in turn, drives the carriage return function bail l9 downwardly against the biasing force of tension spring 38 coupled between an upward projection of bail l9 and stationary portion of the teleprinter frame.

The vertically downward movement of bail 19 is imparted to the free end of lever 20 as a result of the flange 39 which engages and drives lever 20 downwardly. The opposite end of lever 20 is rotatably mounted on shaft 30. The downward rocking movement experienced by lever 20 is imparted to a bell crank 16 pivotally mounted upon a pin 40 by means of a downward projection 20a provided along the lower edge of lever 20 intermediate the ends thereof which abuts a projection 16b provided on the bell crank assembly 16. This causes the bell crank assembly 16 to rotate about its pivot pin 40 in a counterclockwise direction. The rotation of bell crank 16 is imparted to a connecting link pivotally coupled to bell crank 16 and the lever 41 by pins 16a and 41a respectively. The substantially rearward linear movement experienced by connecting link 15 causes lever 41 to turn counterclockwise about pivot pin 35. This results from the fact that the end of lever 41 is clamped (by fastening means 42a) to the free end 42 of lever 3, which is pivotally connected to pin 35 and has a release plate 43 at its opposite end. Thus, the rearward movement of link 15 causes lever 3 to turn counterclockwise about pivot 35 together with lever 41, as shown by arrow C.

The left-hand end of lever 3 forms a release plate 43 which is situated between the extension provided on pawls 46 and the spacing ratchet 2. Thus, as lever 3 is turned counterclockwise, as shown by arrow C, release plate 43 moves from its rest or dotted line position as shown in FIG. 5 toward the solid line position of FIG. 5, causing the feed pawl 5 and check pawl 6 (normally, biased toward ratchet wheel 2 by springs 5b and 6b, respectively) to be released from ratchet wheel 2 in succession, followed ultimately by the release of backspace pawl 4. Under such conditions, the ratchet wheel 2 is free from any restraint whatsoever, placing carriage 28 completely under the control of the spring tension of spring 1 thereby causing it to be rapidly returned to the left margin as a result of this spring force. Although not shown in the diagrammatic view of FIGS. 5 and 5a, it should be obvious that the release plate 43 moves an amount sufficient to release pawl 4 from the ratchet 2 as well as

pawls

5 and 6.

Lever 3 is further provided with a downwardly extending projection 47 which, when the carriage return function lever 21 rocks to its lowest position, is caused to drop into a notch 46 provided in latch 7 positioned beneath the release plate 43 so as to remain locked in this position until the printing carriage 28 is fully restored to the left-hand margin.

The backspacing mechanism of the instant invention is designed so that the carriage return operation may be performed by one character pitch or spacing each time a backspaced code is received. In order to attain this objective, a backspace pawl 4 is provided upon a pivot shaft P as shown in FIGS. 26 to cause feed pawl 5 to undergo slight linear displacement in a manner to be more fully described.

Referring to FIG. 1, when any code other than a backspace code is received, the lifting operation of the backspace function lever 25 is blocked by a downward projection provided on at least one code bar of the bar group 27 (Sec FIG. 7) whereas, when the backspace code is received all code bars of bar group 27 are lifted and the backspace function lever 25 is free to rise without being impeded by the downward projection of any of the code bars of bar group 27 and thereby is lifted together with the bail 12 so as to follow the lifting operation of bail 12 through the spring connecting means 32.

FIG. 7 shows the position of the code bars of bar group 27 when any code other than a backspace code is received. As can clearly be seen, one or more of the code bars of bar group 27 is in a downward position blocking any upward movement of backspace function lever 25 under control of the spring means 32 coupled between lever 25 and bail 12. When a backspace code is received, all of the code bars of bar group 27 are lifted permitting the lever 25 to lift under control of the rocking of bail I2, as shown best in FIG. 8. The left-hand end of lever 25 as shown in FIG. 8 falls into a notch 23a provided in the carriage backspace function bail 23. This lifting operation places lever 25 in the path of movement of the print suppression code bar 26, as can best be seen in FIG. 8, to prevent bar 26 from shifting upward and to the left (i.e., vertically upward and out of the plane of FIG. 8), which is the movement undertaken by bar 26 when a carriage return code is received. Thus, the spacing of carriage 28, as well as the carriage return operation is thereby suppressed.

After bail 12 rocks to its highest level, it then moves downwardly causing lever 25 to be urged downwardly as well. The left-hand end of lever 25, being positioned in notch 23a, urges the backspace function bail 23 downwardly against the tension of spring means 38a. The downward vertical movement of bail 23 is imparted to lever 24 by means of flange 45 provided on bail 23 which bears against the upper edge of the left-hand most end of lever 24. The forward end of lever 24 is rotatably mounted on shaft 30 causing lever 24 to pivot about shaft 30. Lever 24 is provided with a downwardly depending projection 24a intermediate the ends of the lever 24 which is caused to make engagement with a projection 18a on bell crank 18 (See also FIG. 1), driving bell crank 18 to turn counterclockwise about shaft 40. The rotation of bell crank 18 is imparted to plate 17 which is clamped to the left-hand side of the bell crank 18 and which is mounted to pivot about pin 40. Plate 17 is provided with a transversly extending elongated projection 51 which, upon rotation of plate 17, is urged against bell crank 16 to drive it into counterclockwise rotation about shaft 40.

The function performed by bell crank 16 is normally associated with the carriage return operation. Thus, the link 15 moves rearwardly and the lever 3 provided with the release plate 43 is caused to turn counterclockwise about the pivot pin 35 in the same manner as was previously described with respect to the carriage return operation so as to release both the feed pawl 5 and the check pawl 6 by means of the release plate 43. The ratchet wheel 2 which has been engaged by the feed pawl 5 and the check pawl 6 with the relative positions as shown in FIGS. 4 and 4a, is permitted to be reversibly rotated through a nominal angle until the backspace pawl 4 completely engages the ratchet notch 2a with which the check pawl 6 was previously engaged, in a manner as can best be seen in FIG. 5, as a result of the release plate 43 releasing the feed pawl 5 and the check pawl 6 from engagement with the ratchet 2. The motion of ratchet wheel 2 is converted into linear motion of the carriage 28 to retract at a small distance toward the left, i.e., a distance toward the left nearly equal to one space. If the backspace pawl 4 were desired to be released from the ratchet 2 by release plate 43, the carriage 28 would be immediately restored to the left margin. To prevent such undesired operation (when receiving a backspace code), the following mechanism has been incorporated as part of the backspacing operation:

Considering any of the FIGS. 26 and 2a6a, it can be seen that each of the pawls 46 are provided with extensions each having an engaging edge 4a--6a, respectively, which edges are designed to be selectively engaged by release plate 43. When the pawls 46 are in their rest position, as shown in FIGS. 2 and 2a, it can clearly be seen that the edge 4a is furthest removed from the edges 5a and 6a which are substantially coplanar when in the rest position. With this arrangement, movement of the release plate 43 from the dotted line position of FIG. 5 toward the solid line position of FIG. 5 will cause the release plate 43 to first engage the edges 5a and 6a to

first release pawls

5 and 6 from ratchet 2 and to finally release pawl 4 from ratchet 2 through the engagement of release plate 43 with the edge 4a. However, the release operation performed by release plate 43 must be such that movement of release plate 43 will be interrupted prior to the release of backspacing pawl 4 from ratchet 2 and subsequent to the release of

pawls

5 and 6 from ratchet 2.

The timing of this interruption is carried out by the backspace function bail 23 in the following manner:

The lowermost edge of the backspace function pawl 23 is formed to provide a slanted or diagonal surface 52 for cooperative engagement with roller 22. As the bail 23 is driven downwardly against the tension of spring 38a and under control of lever 25, the slant surface 52 slidingly engages roller 22 causing the bail 23 to be tilted rearwardly (i.e., toward the left, as is shown in FIG. 9) as it moves downwardly.

When a backspace code is received all of the code bars of bar group 27 are lifted upwardly to the position shown in FIG. 8. Lever 25 follows the lifting of bail 12 as a result of the spring 32 coupling the

elements

12 and 25. The lifting of lever 25 causes its free end (left-hand end relative to FIGS. 710) to enter the notch 230 provided in bail 23.

After bail 12 reaches its topmost position, it then rocks downwardly from the position shown in FIG. 8 toward the position shown in FIG. 9 so as to drive lever 25 downwardly carrying with it bail 23. The flange-45 provided on bail 23 drives the left-hand most end of lever 24 downwardly which, in turn, causes projection 24a to operate the bell crank projection 18a in the same manner as was previously described.

As the downward movement of bail 23 continues under control of lever 25, its slant surface 52 engages roller 22 caus' ing bail 23 to move toward the left as it moves downwardly. The leftward movement or tilting movement of bail 23 as its slant surface 52 slidingly engages roller 22 causes the forward edge of lever 25 to be lifted out of notch 23a, as shown in FIG. 9, so as to abruptly discontinue the lowering movement of bail 23 at a predetermined moment. The bail 23 immediately moves upwardly under control of the tension spring 38a from the' position shown in FIG. 9 toward the position shown in FIG. 8; This abruptly discontinues the lowering operation of lever 24 under control of the projection 45 of bail 23 so as to suspend the release operation of release plate 43 prior to the release of backspace pawl 4 from ratchet wheel 2. The exact moment of interruption of release plate 43 is controlled by the relative positions of bail 23 and roller 22 and by the slant angle of slant surface 52:

Interruption of the rotational movement of lever 3 which carries release plate 43, prior to the release of the backspace pawl 4 from the ratchet wheel 2, indicates that the interruption occurs prior to the'time at which the extension 47 also carried by lever 3 falls into the notch 46 provided in latch 7. Thus, the lever 3 initiates the return stroke which restores the lever 3 to its initial position as well as restoring the backspace function bail 23, the backspace function lever 25 and the backspace drive lever 24 to their original positions, as shown in FIG. 10. By restoring lever 3 with its release plate 43 to its initial position, both the feed pawl 5 and the check pawl 6 which have been previously released, fall into a notch adjacent the notch with which the backspace pawl 4 is engaged, as is il lustrated in FIGS. 6 and 6a.

The carriage drive bail II which is executing a returning stroke by this time, begins to rock frontwardly. Roller 8 coupled to bail II by shaft 8a urges the toggle link 9 counterclockwise from the position shown in FIG. 6 to restore it to its original position so as to move it from the position shown in FIG. 6 toward the position of FIG. I. At the completion of the return stroke of carriage bail II, the right-hand end 4b of backspacing pawl 4 strikes the forward edge of a recessed arm I fixed on the frame of the device which exerts pressure thereon so as to rotate pawl 4 slightly counterclockwise about its pivot I so as to release the backspacing pawl 4 from ratchet 2 while it is in the normal or rest position. As soon as the pawl 4 is released from engaging a notch in the ratchet 2, ratchet wheel 2 retrogresses until the feed pawl which has already come into contact with a tooth flank surface reaches the bottom ofa notch.

Thus, the carriage 28 is caused to backspace through one character space in a simple and yet very accurate manner. The backspacing occurs as many times as backspace codes are received.

Briefly summarizing a backspacing operation:

Rest position is shown in FIG. 2. The pawl 5 furthest removed from pivot pin 35 engages notch surface 2b. Roller 8 moves toward the rear. Notch 37 is in the path of projection 36 preventing

toggle links

5 and 9 from collapsing (See FIG. 4).

Toggle links

5 and 9 however, do break slightly to permit pawl 4 to enter into notch 2a. Release plate 43 moves from the position of FIG. 4 to the position of FIG. 5 to release

pawls

5 and 6 from ratchet 2. Pawl 4 then engages notch surface 2b (ratchet moves nearly through one space). Release plate 43 returns from the (solid line) position of FIG. 5 to the position of FIG. 6 causing

pawls

5 and 6 to enter notch 2d to the leftof notch 20. Roller 8 moves toward the front again lifting pawl 4 out ofengagement with the ratchet 2 (See FIG. 2) to complete backspacing operation. At this time pawl 5 restrains ratchet 2.

In accordance with the backspacing mechanism of the instant invention, only a backspacing pawl 4, which is extremely simple in construction, is incorporated into a conventional spacing mechanism in such a manner that rotational movement of the already existing release plate 43 may be utilized for the backspacing operation and further that the carriage return operation may not be blocked. In addition, a

mechanism substantially similar to the conventional carriagev return function mechanism may be employed as the mechanism for detecting the receive backspace code and driving the release plate 43 toward thebackspace pawl 4 by an amount sufficient to perform the backspacing operation and, yet insufficient to perform a carriage return operation.

In conclusion, the instant invention can be seen to provide a great deal of utility in providing a carriage backspacing,

mechanism featured by a reliability of operation and economy in number of components employed and the ease of manufacture, installation and operation.

We claim:

I.' In a teleprinter assembly comprising a printing carriage assembly including:

a rotatable member; spring means for normally biasing said carriage assembly in a reverse direction; a spacing mechanism selectively engaging said rotatable member for advancing said carriage assembly against said spring means one space in a forward direction responsive to a space or character code; a carriage return mechanism responsive to a carriage return code for releasing said spacing mechanism from said carriage assembly rotatable member to place said carriage assembly under control of said spring means; the improvement comprising:

backspacing means coupled to said spacing mechanism and selectively engaging said rotatable member for enabling backspacing of said carriage assembly in said reverse direction by only one space responsive to each backspace code;

said backspacing means further comprising means coupled to said carriage return mechanism to release only said spacing mechanism from said carriage assembly drive member during a backspacing operation and to release both said spacing mechanism and, said backspacing means during a carriage return operation;

said carriage assembly being comprised of a carriage;

a belt entrained about rotatably mounted driving and driven pulleys;

said carriage being secured to said belt at a point between said pulleys;

said rotatable member being a ratchet wheel, a shaft coupling said ratchet wheel to said driving pulley;

said spring means being coupled to said carriage for normally urging said carriage in a reverse direction;

said spacing mechanism comprising; a pivotally mounted check pawl and a feed pawl;

said feed pawl being provided at one end of a collapsible toggle assembly having a pivotally coupled knee portion;

bias means normally urging said pawls into engagement with said ratchet wheel;

first reciprocating drive means engaging said toggle assembly adjacent said knee portion to alternately collapse and extend said toggle assembly during a spacing operation to cause said feed pawl to advance said ratchet wheel by one tooth for each reciprocating cycle completed by said drive means; and

said backspacing means further including a backspacing pawl being pivotally coupled to said toggle assembly knee portion.

2. The device of claim 1 wherein said carriage return mechanism is comprised of a rockably mounted release plate;

each of said check, spacing and backspacing pawls having an extension projecting beyond said pawls;

said release plate being mounted to rock between said ratchet wheel and said extensions; and

the extension of said backspacing pawl being further removed from said release plate than said spacing and check pawl extensions to cause said backspacing pawl to be the last pawl to be disengaged from said ratchet by the rocking of said release plate.

3. The device of claim 2 further comprising means for normally maintaining said backspacing pawl from said ratchet wheel when said spacing mechanism is in its rest position.

4. The device of claim 2 further comprising means for preventing the collapse of said toggle assembly during either a carriage return or a backspacing operation.

5. The device of claim 4 wherein said backspacing means is further comprised of control means coupled to said rockable release plate; second reciprocating drive means for driving said control means for controlling the amount of travel of said release plate and thereby preventing said release plate from disengaging said backspacing pawl from said ratchet wheel during a backspacing operation.

6. The device of claim 5 wherein said release plate control means is comprised of a rockable backspacing function lever operative to be lifted and lowered upon the occurrence of a backspacing operation;

a backspacing function bail having a notch engageable with said function lever as said function lever is lifted;

said function bail being biased in a first direction to be normally lifted;

the lowering of said function lever urging said backspacing function bail in a second direction to lower said function bail; and

second lever means coupled to said release plate and engaged by said function bail as it lowers for rocking said release plate.

7. The device of claim 6 further comprising stationary means positioned in the path of lowering movement of said function bail; and said function bail having a slant surface confronting said stationary means to disengage said function bail from said function lever to interrupt the rocking motion of said release plate prior to striking said backspacing pawl extension during a backspacing operation.

8. The device of claim 6 further comprising spring means coupling said second reciprocating drive means to said function lever; and liftable character code bar means selectively lifted upon receipt of a character or spacing code and unanimously lifted upon receipt of a backspacing code to enable said function lever to follow the lifting and lowering movement of said second reciprocating drive means.

9. The device of claim 8 further comprising a carriage return code bar liftable upon receipt of a carriage return code;

and said function lever normally blocking the lifting movement of said carriage return code bar when prevented from following the movement of said second reciprocating drive means by at least one of said character code bar means.