US3346087A

US3346087A - Pitch changing apparatus for proportional escapement typewriter

Info

Publication number: US3346087A
Application number: US311377A
Authority: US
Inventors: Colombo Giannino; George A Holt
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1963-09-25
Filing date: 1963-09-25
Publication date: 1967-10-10
Anticipated expiration: 1984-10-10
Also published as: AT276444B; BE653390A; NL136051C; US3346086A; DK119464B; NL134493C; FR1417229A; FI43602B; FI43738B; DK116518B; CH427861A; DE1761559B1; NL6410570A; NL6410572A; GB1053186A; SE314388B; FR1417231A; SE307591B; NO117541B; BE653527A

Description

Y G. COLOMBO ET AL PITCH CHANGING APPARATUS FOR PROPORTIONAL Oct. 1o, 1967 ESCAPEMENT. TYPEWRITER v Filed Sept. 25, 1963 s sheets-Sheet 1 INVENTORS. GIANNINO COLOMBO Y GEORGE A. HOLT ATTORNEY.

Oct. 10, 1967 G. coLoMBo ETAL 3,346,087

v FITCH4 CHANGING APPARATUS FOR PROPQRTIONAL ESCAPEME'NT TYPEWRITER 'Filed sept. 25, 195s Oct-10,1967 AL 3,346,087

FITCH CHANGING APPARATUS FOR P ROPORTIONAL ESCAPEMENT TYPEWRI Filed Sept. 25, 1965 G. COLOMBO ET TER 5 Sheets-Sheet 5 FIG. 5

FIGB

m|rx1|||||||||1|5 100 United States Patent O 3,346,087 PITCH CHANGING APPARATUS FOR PROPOR- TIONAL ESCAPEMENT TYPEWRITER Giannino Colombo, Milan, Italy, and George A. Holt,

Lexington, Ky., assignors to International Business Machines Corporation, New York, NX., a corporation of New York Filed Sept. 25, 1963, Ser. No. 311,377 Claims priority, application Italy, Oct. 1, 1962,

27,656/ 62 13 Claims. (Cl. 197-34) The present invention relates generally to the typewriter and printing arts and more particularly to the provision of improved pitch changing apparatus for use with a proportional escapement typewriter. The pitch changing apparatus comprises not only typist controlled means for changing the pitch or the distance moved by a carrier for each basic escapement unit but also scale means and a character storage indicator means which are automatically changed when the pitch changing means is actuated.

A single element typewriter provided with proporti-onal escapement apparatus offers a significant advantage when compared with more conventional proportional escapement typewriters. The print element is easily removed and replaced whereby the type style or font is readily changed. In order to allow such a proportional escapement typewriter to accommodate a large number of print elements having an almost unlimited number of various size type styles formed thereon and/or to vary the appearance of material printed with a single size type style, it is desirable to provide typist controlled pitch changing means capable of selectively varying the distance moved by the print element for each basic escapement unit. In this manner, the pitch or average number of characters prin-ted in a predetermined distance can be selectively varied while still preserving and maintaining the basic proportional escapement scheme employed in the typewriter. For example, relatively small size characters forming a particular type style will usually be printed with a different pitch (more characters printed in a predetermined distance) than the relatively large size characters of a diiferent type style.

Briefly, the present invention is concerned with the provision of pitch changing apparatus for a proportional escapement typewriter which permits the typist to selectively vary the pit-ch of the printing as well as automatically change the scale means and the character storage indicator means displaying the amount of usable character escapement information in storage. A number of gear means are disposed between the proportional escapement apparatus and the movable carrier of the typewriter. The

ICC

typist the amount of information in storage and the position of the movable carrier with respect to the stored escapement information. The pitch selection lever is connected to the scale means and the character storage indicator means so that these latter means are automatically changed when the typist actuates the pitch selection lever.

lt is the primary or ultimate object of the invention to provide highly improved typist actuated pitch changing apparatus for a proportional escapement typewriter. The pitch changing apparatus comprises a plurality of gear sets which are selectively coupled under typist control in driving relation Ibetween proportional escapement apparatus and the movable carrier of the typewriter. The selected gear set determines the distance moved by the carrier for each basic escapement movement of the proportional escapement apparatus.

Another object of the invention is the provision of pitch changing apparatus for a proportional escapement typewriter having improved selecting apparatus for engaging and connecting the selected gear set in driving relation between the carrier and the proportional escapement apparatus. Detent means are provided and the construction of theselecting apparatus is such that only one of the gear sets can be engaged at any one time. Further, the driving forces transmitted through to the gear sets in combination with the detent means insure that one of the gear sets is positively engaged aft-er a pitch changing operation.

Yet another object of the invention is to provide pitch changing apparatus for a proportional escapement typewriter wherein a scale member on the typewriter is autotypist is provided with a pitch selection lever whose position determines which of the gear means operatively and drivingly couples the proportional escapement apparatus and the movable carrier. Each of the gear means is adapted to move the carrier through a different distance for the same movement of the proportional escapement means.

The invention also is -concerned with the provision of scale means and a character storage indicator means for use with a proportional escapement typewriter having a limited storage capability for escapement information. The character storage indicator means clearly shows the matically changed when the typist operates the pitch selection lever to select the desired pitch for printing. The arrangement is such that the correct scale is always exposed to the typist in accordance with the selected pitch.

A further object of the invention is the provision of a character storage indicator for a proportional escapement typewriter having limited memory capability for storing escapement information. The character storage indicator shows the typist the amount of usable escapement information stored in the memory. As will be hereinafter more fully explained, the character storage indicator is an open-ended and generally tubular member which is slidable on the scale member in accordance with movements of the typewriter carrier. This indicator shows the exact position of the carrier with respect to the escapement information stored in memory whereby the typist is clearly shown the limits in which forwardspacing and backspacing operations on a character-by-character basis can be performed.

A still further object of the invention is the provision of pitch changing apparatus for a proportional escapement typewriter wherein a character storage indicator showing the amount of usable escapement information in storage is automatically changed when the typist selects a diiferent pitch. The indicator is slidable on and rotatable with the scale member whereby the typist is always presented with the correct scale and the correct portion of the visual indicator.

A still further object of the invention is the provision of pitch changing apparatus having the characteristics set forth above which is extremely simple in construction and operation but yet highly reliable. Further, the pitch changing apparatus can be manufactured at a minimum of cost.

The foregoing and other objects and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings.

FIGURE 1 is a front perspective view of a single element proportional escapement typewriter embodying pit-ch changing apparatus constructed in accordance with the teachings of the present invention;

FIGURE 2 is a front perspective view of the pitch changing apparatus employed in the typewriter of FIG- URE l;

FIGURE 3 is a sectional view taken generally along the lines 3-3 of FIGURE 2;

FIGURE 4 is an end sectional view as seen from the section line 4 4 of FIGURE 3;

FIGURE 5 is an enlarged plan view showing in greater detail the character storage indicator employed in the typewriter -of FIGURE l;

FIGURE 6 is an end sectional View taken along the section line 6-6 of FIGURE 5 FIGURE 7 is an enlarged plan view of a sheet member which is formed to provide the character storage indicator; and

FIGURE 8 is a fragmentary flattened plan view of a portion of the scale member showing particularly the scales formed thereon.

Referring now to the drawings, and initially to FIG- URE 1 thereof, the reference numeral 10 designates generally a single element typewriter of the proportional escapement type embodying pitch changing apparatus constructed in accordance with the teachings of this invention. The typewriter 10 comprises an interchangeable print element 11 detachably secured to a mounting post 12. The print element 11 is carried on a rocker plate 13 which in turn is pivoted by pins 14 to a carrier 15. The carrier 15 is mounted for longitudinal silding movement on guide shaft 16 in front of a stationary printing platen 17. The carrier 15 has a connection, not particularly shown, with a lead screw 18 extending in generally parallel relation with respect to and below the printing platen 17. The distance and direction of the angular rotations imparted to the lead screw 18 determine the direction and extent of the escapement and backspace movements of the print element 11.

The interchangeable print element 11 has the general shape of a truncated spheroid and a plurality of different size characters 20 formed thereon are arranged in generally aligned horizontal and vertical rows. The typewriter is provided with a plurality of character keylevers, such as keylever 21, and a number of function keylevers, including a case shift keylever, not shown. Each of the character keylevers is associated with two of the characters formed on the print element with the state of the case shift keylever determining which of the two characters is selected. For example, if only the keylever 21 is depressed, the lower case h is selected; while if both the keylever 21 and the case shift keylever are actuated, the upper case or capital H is selected. The print element 11 is mounted for rotational and tilting movements on the rocker plate 13 and these movements are controlled by character selection apparatus, not shown, in response to keylever actuation to bring a selected character into printing position.

After the print element has been rotated and tilted as required to bring a selected character into printing position, the rocker plate 13 mounting the print element is pivoted upwardly about pins 14 by the action of print cam 23 which is slidably mounted on guide shaft 16 for longitudinal movement with carrier 15. The guide shaft 16 is rotated during each print cycle by an electric motor operating through suitable clutch and driving apparatus, not shown, to cause the print element 11 to be rocked forward toward the printing platen 17 and eect printing of the selected character. The print element falls back from the printing platen and is returned to its original or home position. The lead screw 18 is then rotated to control the advancement of the print element by an escapement distance corresponding to size or width of the previously selected and printed character.

In general, a character printing operation is characterized by three major steps. The first step is the selection of a character and the rotation and tilting of the print element as required to bring the selected character into printing position; the second step comprises rocking the print element toward the printing platen to effect printing of the character; and the third step includes advancing the print element by a distance proportional to the size or width of the printed character.

The escapement apparatus for the typewriter comprises the lead screw 18 and means for rotating the lead screw in the proper direction and through a preselected angular distance corresponding to the escapement distance associated with a selected character. During forward escapement operations, the carrier 15 and print element 11 are moved on a character-by-character basis from left to right in front of the printing platen 17 when looking at FIG- URE 1 of the drawings. When backspacing is accomplished, the print element moves in the opposite direction on a character-by-character basis. In general, the escapement apparatus comprises a constant torque device 25 and associated driving means which tend to rotate the lead screw 18 and control movement of the carrier 15 and print element 11 with respect to the printing platen 17; escapement control apparatus 26 having a plurality of settable elements defining a limited memory; character escapement selection apparatus 27 for controlling the `state of the settable elements in response to the characters selected; and pitch changing apparatus 28 providing a variable drive connection between the escapement control apparatus 26 and the lead screw 18 for changing the escapement pitch. The escapement control apparatus 26 is actuated by the character escapement `selection apparatus 27 in response to character or function selection by the typist to control, in combination with the pitch changing apparatus 28, the amount of angular movement imparted to the lead screw 18 by the constant torque device 25. During backspacing operations, the escapement control apparatus 26 is itself driven to drive the lead screw in tlt opposite direction via the pitch changing apparatus The escapement contr-ol apparatus 26 comprises a pin wheel 30 which is keyed to a shaft 31. The shaft is journaled for rotation in a generally U-shaped mounting bracket 32 (see FIGURE 2) which is located in the right rear portion of the typewriter. Slideably mounted in slots about the circumference of the pin wheel 30 are a plurality of pins 35 whose lengths are greater than the thickness of the pin wheel. Each of the -pins defines a memory element which is settable in either of two states. The first or set state is when the end portion of a pin projects to one side of the pin wheel and the second or reset state is when an end portion of the pin projects outwardly on the other side of the pin wheel. The pin Wheel 30 and its associated pins 35 define a memory having a plurality of memory elements each capable of assuming either of two states. The distance between any two of the pins defines a standa-rd or basic single escapement unit.

In addition to the pin wheel 30 itself, the escapement control apparatus 26 comprises a pin setting assembly 36 and an escapement pawl assembly 37. In general, the pin setting assembly and the escapement pawl assembly are responsive to the actuation of character escapement selection apparatus 27 when the typist selects a character or another machine function. The pin setting assembly 36 is operative to position the pins 35 to define the angular distance through which the pin wheel is allowed to rotate during an escapement operation. The escapement assembly 37 comprises an escapement pawl, not shown, which is adapted to engage only the pins on the pin wheel that are in the set state. After the pin setting assembly has determined the state of the pins, the escapement pawl is released and the pin wheel rotates in the direction indicated by arrow 39 under the action of constant torque device 25 through a predetermined angular distance until the next adjacent set pin engages and returns the escapement pawl.

The number of reset pins between adjacent set pins on the pin wheel 30 is determined by the pin setting assemblyl 36 in response to character selection by the typist. As mentioned above, the distance between two of the pins defines a single basic escapement unit and the pin wheel 30 may rotate through an angular distance corresponding to any of a number of the basic escapement units depending on the proportional escapement scheme employed in the typewriter. For example, when the characters i or l are selected, the pin wheel may rotate through an angular distance corresponding to two basic escapement units while if the characters a and c are selected the rotation ofthe pin wheel may correspond to three escapement units. However, the distance moved by the carrier for each basic escapement unit is regulated by the pitch changing apparatus 28Vas will be hereinafter more fully explained.

The pins 35 on the pin wheel 30 are not reset after a proportional escapement operation but rather maintain their states until they again pass through the pin setting assembly 36. The pin wheel and the pins thus define a limited memory for storing information corresponding to past'escapement operations. Use is -made of the limited memory capability of the escapement control apparatus by providingbackspacing apparatus, not shown, which permits backspacing of the carrier and print element on a character-by-character basis to a previous printing position. Further, forwardspacing apparatus, also not shown, allows forwardspacing of the carrier and print element from a previous printing position to the last or furthest printing position. Since the amount of escapement information which can be stored in the memory is usually limited by size and cost considerations to something less than a line of typing, it is necessary to provide a character storage indicator showing lthe typist the amount of usable escapement information in the memory.

The above description is intended to serve as a background for consideration of the pitch changing apparatus 28 of the present invention. The proportional escapement typewriter, and particularly the backspacing mechanism, is completely described in a copending patent application entitled Proportional Escapement Apparatus for a Single Element Typewriter, application Ser. No. 311,373, led Sept. 25, 1963, concurrently with the present application and assigned to the assignee of the present invention to which reference should be made.

The pitch changing apparatus 28 is disposed between the lead screw 18 and the escapement control apparatus 26 and provides an adjustable gearing lmeans for regulating the distance travelled by carrier 15 and interchangeable print element 11 for each basic escapement unit. While the escapement control apparatus 26 defines the absolute number of basic escapement units associated with an escapement operation, the pitch changing apparatus 28, under typist control, determines the actual distance moved by the carrier 15 and print element 11. This apparatus provides the typist with a means for changing the pitch or the average number of characters printed in a predetermined length to vary the appearance of material printed with the same print element or to allow the printing of material with various size type styles formed on different print elements.

As shown in FIGURES 2-4 of the drawings, the shaft 31 mounting the pin wheel 30 extends through a side plate of the mounting bracket 32. Keyed or otherwise rigidly attached to the projecting end of the shaft 31 in aligned side-by-side relation are three pinion gears 40-42 each having the same number of teeth and, as a consequence different pitches (the number of teeth per unit distance of pitch circumference). Meshing with the pinion gears 40-42 are pitch gears 43-45 each having the same pitch as the corresponding one of the pinion gears 40-42. The pitch gears 43-45 are mounted for interpendent rotary movement on and with respect to the shouldered end portion 46 of shaft 47. The shaft is disposed in parallel relation with respect to shaft 31 and extends between the side plate of bracket 32 and a spaced frame 48. Means, to be later described, are provided for detachably securing any selected one of the pitch gears 43-45 in driving engagement with the shaft 47. The pitch gears 43-45 in combination with the pinion gears 40-42 define three selectable gear sets each capable of drivingly interconnecting the

shafts

31 and 47. The shaft 31 mounts the pin wheel 30 while t-he shaft 47 is connected by a gear train comprising idler gears 49-51 to lead screw 18. It should be understood that other gearing arrangements can be employed depending on the ratios required. For example, the gears 40-43 may have the same pitch (the number of teeth per unit distance of pitch circumference) with the total number of teeth for each gear depending on its diameter.

The selected one of the gear sets 40, 43; 41, 44 or 42, 45 which drivingly interconnects the

shafts

31 and 47 determines the extent of actual movement of the carrier and print element for each basic escapement unit. For example, when the gear

set comprising gears

42 and 45 is selected, the lead screw 18 will rotate through a greater angular distance for a predetermined angular movement of the pin wheel 30 than if either of the other gear sets had been selected under the same condition. Similarly, if the gear

set comprising gears

41 and 44 is selected, the carrier and print element move through a greater distance for the predetermined angular movement of pin wheel 30 than when the gear

set including gears

40 and 43 operatively interconnect the

shafts

31 and 47.

The shouldered end portion 46 of shaft 47 has an elongated slot 52 therein extending beneath the axially aligned and independently rotatable pitch gears 43-45. Received within the slot 52 is a key 53 having a rounded end portion 54 which is pivoted to an annnular operating member 55 by pivot pin 56. A leaf spring 57 is received in the slot 52 and exerts a biasing force on the key 53 tending to move the end portion 54 thereof radially outward fr-om the slot. As most clearly shown in FIG- URES 3 and 4 of the drawings, each of the pitch gears has a center opening 58 of a size sufficient to permit rotation between the gear and the shaft 47. An axially extending flange 59 is provided adjacent the opening S8 which serves as a spacer. A plurality of circumferentially spaced and radially extending slots 60 are formed in the inner periphery of the gear for receiving the rounded end portion 54 Aof the slidable key 53. Also, the inner peripheral edges of each pitch gear are beveled at 62 to facilitate movement of the key 53 and selective engagement of the gear sets as will be later explained.

Extending into a circular slot 63 in the annular operating member 55 are a pair of vertically spaced arms 64 of U-shaped actuator 65. The actuator 65 is mounted for pivotal movement on a stud 66 whose axis extends transversely with respect to the axis of the shaft 47. An extension 67 of the actuator projects transversely into the space between the arms 68 of a U-shaped pivoted member 69. One arm 68 of the member 69 is operatively connected to a typist controlled pitch selection lever 70 via link 71, fitting 72 and shaft 73. The arrangement is such that when the typist moves the pitch selection lever 70, the annular operating member 55 is moved axially on the shaft 47 to disengage the key 53 from one of the pitch gears and move this key to a position where another ofthe pitch gears is drivingly connected to shaft 47.

Detent means for holding the apparatus in a selected pitch position is provided. This detent means comprises three axially aligned semi-circular recesses 74 in the shouldered portion 46 of shaft 47. Cooperating With the recesses 74 are a pair of balls 75 received in a radial aperture in the annular operating member 55. The balls 75 are forced into locking engagement with the recesses 74 by the action of a band 76 of elastic and resilient material encircling the annular operating member 52.

It may happen that, after rotation of pitch selection lever 70 and movement of the key 53 to select a different gear set, a slot 60 in the selected one of the pitch gears 43-45 will not be aligned with the rounded end portion 54 of the key 53. In this case, the end portion of the key 53 is cammed downwardly by the adjacent beveled edge 62 of the selected pitch gear against the action of leaf spring 57. The slot 52 is deep enough to allow the end portion 54 of the key 53 to be moved to a position directly below the selected pitch gear. At this time, none of the pitch gears 43-45 will be drivingly connected to shaft 47. Since the pin wheel 30 is eifectively disconnected from the escapement system, the constant torque device 25 will rotate shaft 47 through lead screw 18 until a slot 60 in the selected pitch gear passes over the end portion of the key. The leaf spring 57 immediately forces the end portion 54 of the key 53 into the aligned slot 60 and the selected pitch gear is drivingly connected to shaft 47. The arrangement is such that one of the pitch gears is always drivingly connected to the shaft 47. It is also important to note that the shape of the end portion 54 of the key 53 and the size of beveled edges 62 of the pitch gears in combination with the detent means makes it impossible to connect more than one of the pitch gears to the shaft.

Since the pitch changing apparatus provides a means for selectively varying the distance moved by the carrier and the print element for each basic escapement unit, it is necessary to provide a means for changing the scale presented to the typist. Also, as explained above, the pin wheel 30 provides a memory for only a limited number of past escapement operations. If full and effective use is to be made of the memory capability of the pin wheel and the apparatus permitting backspacing and forward spacing on a character-by-character basis, a visual indicator must be provided which shows the typist the amount of usable character information stored in the memory at any particular instant in time. The number of pins carried by the pin wheel is predetermined and this defines the number of basic escapement units available in storage. However, the indicator must be capable of being changed to indicate the extent of stored character information depending on the pitch selected by the typist.

As is shown in FIGURE 1 of the drawings, a connect ing link 78 extends from the arm 68 of the U-shaped pivoted member `69 to a bellcrank 791 pivotally mounted adjacent the right hand side of the typewriter. A pin 80 engages a slotted lever 81 carried on one end of scale member 82. The scale member extends across the front of the typewriter in generally aligned parallel relation with respect to printing platen 17 and is positioned in cooperating relation with a pointer 83 mounted from and movable with the carrier 15. The scale member 82 has a generally semi-circular cross section (see FIGURE 6) and printed, etched or otherwise formed on the periphery of the scale member at three cir-cumferentially spaced points 85-87 are reference indicia defining pitch scales. These pitch scales are shown in the flattened plan view of the scale member which forms FIGURE 8 of the drawings. Each of the pitch scales extends the length of the scale member 82 and corresponds to one of the pitches which can be selected by the typist upon actuation of the pitch selection lever 70. A cover member or frame 88 of the typewriter has an elongated opening 89 therein which nestingly receives scale member 82 and the pointer 83. The arrangement is such that the lower end of the pointer 83 and a limited circumferential area of the scale ymember 82 on which is formed one of the pitch scales CAD is exposed to the typist. When the typist moves the pitch selection lever 70, the scale member 82 is rotated via the link 78 and bellcrank 79 to present a different scale to the typist corresponding to the selected escapement pitch. The detent means comprising the recesses 74 in the shaft 47 and the balls 75 is operative to insure that the scale member 82 is always positioned so that one and only one of the pitch scales is presented to the typist.

A character storage indicator 90 is provided by a generally cylindrical and slit tube 91 which is open at each end. The longitudinal side edges 92 of the tube are bent inwardly and are received in an elongated slot 93 in the back of the scale member 82. The arrangement is such that the character storage indicator 90* is mounted on the scale member 82 for independent sliding movement but is rotatable with this member.

As is most clearly shown in FIGURE 7 of the drawings, the character storage indicator 90 has a pair of

windowlike openings

94 and 95 on the opposite sides thereof. The front window-like opening 94 has a pair of

steps

96 and 97 in each side edge thereof so that this window-like opening comprises three portions 98-100 of different lengths. The side edges of the

steps

96 and 97 and the portion 100 define three pairs of reference marks. The lengths of the portions 98-100 or the distances between the reference marks are selected in accordance with the storage capability of the pin wheel 30 and the various ratios of the gear sets comprising the gears 40-45. The number of pins carried by the pin wheel is the same regardless of the pitch selected by the typist but the actual distance in a line of printing represented by these pins is dependent on which gear set drivingly interconnects the pin wheel 30 and the lead screw 1S. For example, when the gear

set comprising gears

40 and 43 is selected, the print element 11 and carrier 15 will move through a shorter distance for one complete revolution of the pin wheel than if either of the other gear sets had been engaged. This distance is represented by the portion 98 of the window-like opening 94. The

portions

99 and 100 have lengths corresponding to other pitches which can be selected by the typistjThe side edges of the rear window-like opening are tapered at 101 for reasons 'to be later explained.

As mentioned above, the character storage indicator 90 is mounted for sliding movement on the scale member 82. The pointer 83 overlies the front window-like opening 94 while a fixed projection 102 extends into the rear window-like opening 95. The projection 102 is rigidly mounted from a bracket 103 attached to the carrier 15. The arrangement is such that only one of the length portions 98-100 of the front window-like opening 94 is exposed to the typist through the opening 89 in the cover frame 88 in accordance with the selected escapement pitch while the projection 102 cooperates with the tapered side edges 101 of the rear window-like opening 95. The tapered side edges of the rear opening define abutment surfaces which, yas will be explained later, cooperated with the projection 102 that is movable with carrier 13. A different length portion in the front windowlike opening 94 is presented to the typist and a correspondingly different length portion of the rear window-like opening 95 is aligned with the projection 102 each time the escapement pitch is changed by actuation of pitch selection lever 70.

The character storage indicator 90 in cooperation with the pointer 83 always shows the typist at a glance the position of the print element 11 with respect to escapement information stored in the pin wheel. The character storage indicator 90 moves with the carrier 15 due to the projection 102 engaging the tapered sides edges 101 of the rear window-like opening 95. For example, during a carriage return operation, the projection 102 will engage one side of the rear window-like opening 95 in the indicator and move the indicator to the extreme left hand margin position. Then, as typing proceeds, the indicator 90 will remain stationary until the pin wheel 30 has been filled with usable escapement information. The projection 102 will eventually engage the other side of the rear window-like opening 95 and thereafter the carrier and the indicator will move as a unit in front of the printing platen 17 during normal typing operations.

If it is desired to backspace, backspacing apparatus is actuated to backspace the print element on a character-bycharacter basis and the carrier moves to the left independently of the indicator. The indicator 90 and the pointer 83 show the typist how far the carrier may be backspaced on a character-by-character basis using the escapement information stored in the pin wheel. After backspacing to the desired previous printing position, the pointer and indicator show the typist how far to forward space to arrive at the furthest printing position. The projection 102 engages and moves the indicator 90 except when the carrier is positioned within the memory range of the pin wheel.

It is possible that projection 102 will be located adjacent one of the edges of the rear window-like opening 95 when the typist moves the pitch selection lever 70 to change the escapement pitch. If the pitch is decreased, the cooperation between the projection 102 and the tapered edge 101 when the indicator is r-otated will slidably move the indicator on the scale member 82 to its correct position. The arrangement is such that the projection 102 cannot be removed from the rear windowlike opening under any normal operating condition.

It should now be lapparent that the objects initially set forth have been accomplished. An improved pitch changing apparatus for proportional escapement typewriters has been provided which is extremely simple in construction but highly reliable in operation. The character indicator allows the typist to make full use of the inherent capabilities of a proportional escapement typewriter having a limited memory for past escapement information. More or less than three escapement pitches can be provided by increasing or decreasing the number of pitch gears and making corresponding changes in the scale member and character indicator. Although the teachings of this invention have been shown applied to a single element typewriter, they are also applicable to other typewriters.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and other change-s in form and details 'may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. Pitch changing apparatus for changing the printing pitch of a typewriter having escapement control apparatus and a movable carrier comprising:

a plurality of selectively engageable drive means for drivingly interconnecting said escapement control apparatus and 4said movable carrier;

each of said drive means corresponding to a printing pitch;

a scale means comprising an elongated scale member having a plurality of reference scales formed on and extending axially of said member at spaced points about the periphery thereof;

a pointer mounted from and movable with said carrier disposed in cooperating relation with said scale member; Y

an indicator having longitudinally spaced pairs of reference marks thereon defining areas of various lengths disposed about the periphery of said indicator;

means' mounting said indicator for independent longitudinal movement with respect to and rotary movement with said scale member;

a projection mounted from and movable with said carrier adapted to engage said indicator for movement with said carrier;

a typist controlled pitch selection means; and

means interconnecting said pitch selection means, said drive means and said scale member for engaging a selected one of said drive means and rotating said scale member to present a selected one of said scales and a selected one of said spaced pairs of reference marks to the typist when said pitch selection means is actuated.

2. Apparatus according to claim 1 further characterized by:

said indicator comprises an open-ended generally tubular member slidably received over said scale member;

a first window-like opening in said tubular member having stepped side edges defining said longitudinally spaced pairs of reference marks and providing openings of various lengths;

a second window-like opening in said tubular member opposite to said first window-like opening; and

said projection mounted from and movable with said carrier extending into said second window-like opening.

3. Apparatus according to claim 2 further characterized by:

a cover member for said typewriter having a slot therein;

said scale member and said indicator being visible to the typist through said slot; and

said slot being of a size to permit viewing of only the scale on said scale member and the opening in said indicator corresponding to the selected pitch.

4. Pitch changing apparatus for changing the printing pitch of a typewriter having proportional escapement control apparatus capable of storing a limited amount of escapement information and a movable carrier capable of being backspaced on a character-by-character basis comprising:

a plurality of selectively engageable drive means for drivingly interconnecting said escapement control apparatus and said movable carrier with each of said drive means corresponding to a different printing pitch;

means mounting said indicator for longitudinal sliding movement across the typewriter;

said indicator having spaced abutment surfaces thereon corresponding to said areas of various lengths;

a projection mounted for movement with said movable carrier positioned to engage said abutment surfaces; and

typist controlled pitch selection means for selecting one of said drive means and for rotating said indicator to present to the typist the length area corresponding to the selected pitch.

5. Apparatus according to claim 4 further characterized by:

said indicator having a window-like opening therein whose side edges are tapered to define said abutment surfaces;

said projection extending into said window-like opening; and

the lengths of said areas corresponding to the amount of escapement information capable of being stored by said proportional escapement control apparatus in accordance with the printing pitches selectable by the typist.

6. A scale means for a typewriter having a carrier movable longitudinally to effect printing and backspacing comprising:

an indicator having at least one pair of longitudinally spaced reference marks thereon defining an area of predetermined length;

means mounting said indicator for longitudinal movement along a path generally parallel to the path of movement of said carrier; and

said indicator having at least one pair of spaced abutment surfaces thereon corresponding to said area of predetermined length; and

projection means mounted for movement with said movable carrier positioned to engage either of said abutment surfaces of said indicator to move the same in a direction depending upon the direction of longitudinal movement of said carrier.

7. Apparatus according to claim 6 further characterized by: v

said means mounting said indicator comprises an elongated scale member having reference indicia formed thereon;

said indicator having a generally tubular shape and being slidably received over said scale member; and

said indicator having a window-like opening therein providing said area of predetermined length through which a portion of said reference indicia can be seen.

8. Apparatus according to claim 6 further characterized by:

said typewriter having proportional escapement apparatus capable of storing a limited amount of past escapement information; and

said area of predetermined length corresponding to the storage capability of said proportional escapement apparatus.

9. Pitch changing apparatus for changing the printing pitch of a typewriter having escapement control apparatus and a movable carrier wherein said pitch changing apparatus drivingly interconnects said escapement control apparatus and said carrier comprising:

a rotatable shaft having an axially extending slot therein;

a plurality of annular gears each having a number of radially extending and circumferentially spaced key slots disposed about the periphery thereof and adapted to communicate with said slot in said shaft;

a key received in said slot in said shaft and having a keying projection for positioning within the key slots of said gears;

resilient means biasing said keying projection in a direction toward engagement with said key slots',

typist controlled gear selecting means for effecting relative movement between said key and said gears to permit selective coupling of said gears in driving relation with respect to said shaft to change the printing pitch of said typewriter;

the opposite side edges of each of said gears being beveled adjacent the inner edges thereof;

said beveled edges defining camming surfaces for moving said keying projection radially inwardly in said slot in said shaft upon actuation of said typist controlled gear selecting means when" one of said key slots in a selected gear is not aligned with said keying projection;

a scale member having a plurality of pitch scales thereon corresponding to printing pitches represented by said plurality of gears;

a pointer mounted for movement with said movable carrier and cooperating with said scale member; and

means interconnecting said typist 4controlled gear selecting means and said scale member to change the pitch scale when said typist controlled gear selecting means is actuated to drivingly connect a different one of said plurality of gears to said shaft.

10. Pitch changing apparatus for changing the printing pitch of a typewriter having escapement control apparatus and a movable carrier comprising:

a plurality of selectively engageable gearing means each corresponding to a printing pitch for drivingly interconnecting said escapement control apparatus and said rnovable carrier;

a scale means comprising a number of scales corresponding to the printing pitches represented by said gearing means;

a typist controlled pitch selection lever;

means interconnecting said pitch selection lever, said gearing means and'said scale means for engaging a selected one of said gearing means and for changing the scale in accordance with the printing pitch selected when said pitch selection lever is actuated;

said scale means comprises an elongated member;

said scales comprising markings extending axially of said member at spaced points about the periphery thereof; and

said meansv interconnecting comprising means to rotate said member in response to actuation of said pitch selection lever.

1l. Apparatus according to claim 10 further characterized by:

a cover member for said typewriter having a slot therein;

said elongated member being visible to a typist through said slot; and

said slot being of a size to permit exposure of only the markings corresponding to the selected printing pitch.

12. Pitch changing apparatus for changing the printing pitch of a typewriter having escapement control apparatus and a movable carrier comprising:

a plurality of selectively engageable drive means for drivingly interconnecting said escapement control apparatus and said movable carrier;

each of said drive means corresponding to a printing pitch;

a movable scale means corresponding to the printing pitches represented by said drive means comprising an elongated scale member having a pl-urality of reference scales formed on and extending axially of said member at spaced points about the periphery thereof;

a pointer mounted for movement with said carrier disposed in cooperating relation with said scale means;

a typist controlled pitch selection means; and

means interconnecting said pitch selection means, said drive means and said scale means for engaging one of said drive means and moving the scale means to change the scale in accordance with the printing pitch selected when said pitch selection means is actuated.

13. Pitch changing apparatus for changing the printing pitch of a typewriter having escapement control apparatus and a movable carrier comprising:

each of said drive means corresponding to a printing pitch;

a movable scale means comprising a plurality of scales corresponding to the printing pitches represented by said drive means;

a typist controlled pitch selection means;

means interconnecting said pitch selection means, said drive means and said scale means for engaging one of said drive means and moving the scale means to change the scale in accordance with the printing pitch selected when said pitch selection means is actuated;

said scale means comprising an indicator;

said indicato-r having longitudinally spaced pairs of reference marks thereon defining areas of various lengths disposed about the periphery of said indicator; and

said means interconnecting said pitch selection means, said drive means and said scale means comprising means to -rotate said indicator in response to actuation of said pitch selection means to present a dif- 13 14 ferent one of said pairs of reference marks to the 2,205,289 6/ 1940 Ha-usman 197-187 X typist. 2,395,763 2/1946 Sagner 197-120 X References Cited 2,397,578 4/ 1946 Turquand 197-63 2,421,119 5/1947 Grief 197-194 UNITED STATES' PATENTS 5 2,580,211 12/ 1951 Aebi 1974-63 ganpbell 3,225,886 12/1965 Cetran et a1. 197-s4 ay or 1,451,722 4/1923 Valentine 74-371 FOREIGN PATENTS 1,518,089 12/1924 Manquen 74.-:571 531,983 1/ 1941 Great Brltam- 1,564,767 12/1925 Egfart 74-371 Brwn E. Pllmy Examiner.

2,165,223 7/1939 Chisholm 197--84.1 E. T. WRIGHT, Assistant Examiner.

Claims

1. PITCH CHANGING APPARATUS FOR CHANGING THE PRINTING PITCH OF A TYPEWRITER HAVING ESCAPEMENT CONTROL APPARATUS AND A MOVABLE CARRIER COMPRISING: A PLURALITY OF SELECTIVELY ENGAGEABLE DRIVE MEANS FOR DRIVINGLY INTERCONNECTING SAID ESCAPEMENT CONTROL APPARATUS AND SAID MOVABLE CARRIER; EACH OF SAID DRIVE MEANS CORRESPONDING TO A PRINTING PITCH; A SCALE MEANS COMPRISING AN ELONGATED SCALE MEMBER HAVING A PLURALITY OF REFERENCE SCALES FORMED ON AND EXTENDING AXIALLY OF SAID MEMBER AT SPACED POINTS ABOUT THE PERIPHERY THEREOF; A POINTER MOUNTED FROM AND MOVABLE WITH SAID CARRIER DISPOSED IN COOPERATING RELATION WITH SAID SCALE MEMBER; AN INDICATOR HAVING LONGITUDINALLY SPACED PAIRS OF REFERENCE MARKS THEREON DEFINING AREAS OF VARIOUS LENGTHS DISPOSED ABOUT THE PERIPHERY OF SAID INDICATORS; MEANS MOUNTING SAID INDICATOR FOR INDEPENDENT LONGITUDINAL MOVEMENT WITH RESPECT TO AND ROTARY MOVEMENT WITH SAID SCALE MEMBER;