US3838764A

US3838764A - Final positioning mechanism for single element type carrier

Info

Publication number: US3838764A
Application number: US00309062A
Authority: US
Inventors: H Decker
Original assignee: Triumph Werke Nuernberg AG
Current assignee: TA Triumph Adler AG
Priority date: 1970-12-14
Filing date: 1971-11-24
Publication date: 1974-10-01
Anticipated expiration: 1991-10-01

Abstract

A rotatably and tiltably positionable type carrier is mounted on a swingable support to move the type carrier from a normal to a printing position and is detentably finally accurately positioned for printing by detenting teeth which are rotatably mounted on the swingable support and resiliently biased to move into detenting engagement with complimentary rotate and tilt teeth on the type carrier but held out of engagement by a stationary member positioned to withdraw said teeth from engagement as the support moves from a printing to normal position and to allow movement of said detenting teeth toward engagement as the support moves from normal to printing position.

Description

United States Patent 1 1 Decker 1 Oct. 1, 1974 [5 FINAL POSITIONING MECHANISM FOR 3,343,642 9/1967 Weidanz et aL 197 55 x SINGLE ELEMENT TYPE CARRIER 3,353,648 11/l967 Amada et ul.

3,618,735 11/1971 Bleau 197/16 [75] Inventor: Herbert Decker, Lauf, Germany [73] Assignee: Triumph Werke Nuernberg A.G., Primary Examiner-Robert E. Pultrey Nuernberg, Germany Assistant Examiner-R. T. Rader [22] Filed: Nov. 24 1971 Attorney, Agent, or Firmloseph R. Spalla Related Apphcatlon Data A rotatably and tiltably positionable type carrier is 1 Continuation of 97,833, 1970, mounted on a swingable support to move the type carabandonedrier from a normal to a printing position and is detentably finally accurately positioned for printing by de- U-S u are on [51] Int. Cl B41] 1/60 swingable Support and resiliently biased to move into of

Search

18, 49, 52, 55, detenting engagement complimentary rotate and 197/48; 178/34 tilt teeth on the type carrier but held out of engagement by a stationary member positioned to withdraw [56] References C'ted said teeth from engagement as the support moves UNITED STATES PATENTS from a printing to normal position and to allow move- 2,902,132 9/1959 Walker 197/52 mentof Said detenting teeth toward engagememas the 2,926,768 3/1960 Becker et a1... 197 55 x support moves from normal to printing position. 3,233,715 2/1966 Fleig 197/16 X 3,330,398 7 1967 Hylan 197/55 x 17 Clam, 6 Drawmg Flg'lres PATENTED 3.838.764

summw I v 27 24 23 w 5 B 6 7 a Fiql INVENTOR HERBERT DECKER BYMR.

ATTORNEY MENIEU BU 1974 SHEET 2!]? 4 Fig-2 INVENTOR HERBERT DECKER BYM 2 3 ATTORNEY mma: Ham 3.838.764

SHEEI 30F 4 INVENTOR HERBERT DECKER ATTORNEY PATENIEU H974 3,838,764

SHEET "0f 4 INVENTOR HERBERT DECKER ATTORNEY FINAL POSITIONING MECHANISM FOR SINGLE ELEMENT TYPE CARRIER This is a continuation of copending US. application Ser. No. 97,833, filed Dec. 14, 1970, now abandoned.

BACKGROUND OF THE INVENTION The invention relates to structure for accurately detentably finally positioning single element type bodies which for type selective control are mounted to be rotated and also tilted and which to print are swingable against a printing surface.

In typewriters which have a type carrier or body which embodies on its exterior the various characters required for printing, it is necessary to accurately locate and detent the type carrier after it has been located approximately in any type selective position and shortly before the type positioned to print moves into printing contact. In connection with type carriers which are in the form of a rotatable body and of sphere or barrel shape, a dual detent system is required in order to accurately finally position or orient the desired character in the aspects of horizontal row and vertical column selection. For this purpose, devices are provided which are instrumental on one hand to accurately position the type carrier at the selected rotary position and on the other hand are instrumental to accurately position the type carrier at the selected tilt position. In order to bring the type carrier at a high rate of speed into any type-selective position, it is necessary to keep to a minimum those parts which selectively position the type carrier. The parts which are employed to orient and detent the type carrier should, as much as is feasible, be required to effect only minimal corrective rotative or tilting motion of the type carrier.

It is old and known to provide for these purposes a poweroperated cam drive which controls a spring loaded multi-armed lever pivoted below the type carrier which has a detent arm and which at the conclusion of tilting motion of the type carrier cooperates resiliently with teeth definitive of tilt positions, and which further controls a spring loaded detent lever which is cooperative with teeth definitive of different rotative positions. In order to effect corrective orientation of the type carrier it has been necessary to provide a power operated cam drive which acts by way of several intermediate members on a detent lever for correctively orienting the tilt of the type carrier, and which lever in turn acts on another detent lever to correctively orient the type carrier rotatively. In connection with each swinging motion of the type carrier therefore both detent levers are moved. Furthermore, in connection with each selective positioning operation of the type carrier the cam'drive has to act through a number of levers to orient the type carrier.

SUMMARY OF THE INVENTION A type carrier which has characters arranged in horizontal rows and vertical columns is accurately oriented and detented, without use of a power drive cam, just before the type carrier reaches the printing position with a minimum of elements by providing on the swingable type carrier support member a rod on which two spring loaded detenting levers are pivotally mounted. Each detent lever has an arm normally bearing, under spring influence, against a stationary stud, so that the detenting teeth of such levers are normally held 'released from detenting surfaces on the type carrier.

The detent arm is pivotally carried on said support rod between a shoulder and a collar, and axial adjustment of the detent arm is effected. by axial adjustment of its support rod.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional side elevation of a type carrier, a swingable support structure therefor, and orienting elements for the type carrier in normal released positions; v

FIG. 2 is a sectional side elevation similar to FIG. I, but with the type carrier actuated to printing position and the orienting elements in operated positions;

FIG. 3 is a plan view of the type carrier support structure and shows the orienting elements in their normal positions;

FIG. 4 is a fragmentary sectional side elevation of the type carrier moved to its print position and the element for rotative orientation in active position;

FIG. 5 is a fragmentary sectional side elevation showing a modified type carrier having curved rotative orientation defining formations; and

FIG. 6 is a view similar to FIG. 5 wherein an orientation element includes an active end of curved form.

DESCRIPTION OF EMBODIMENT OF THE INVENTION In front of a platen I for travel parallel thereto is mounted a carriage in the form of a housing 2 which bears a type carrier or head 3 having type characters 4 thereon. The housing 2 is mounted on a rail 5 and a shaft 6 for travel in the direction of the writing line. Turnable with the shaft 6 is a sleeve 7 which is slidable lengthwise thereon and has a cam 8 formed thereon. The sleeve 7 is in an axial direction confined by the housing 2 in conjunction with a bearing lug 9, see FIG. 3, so that it will move with the carriage 2 while the shaft 6 is lengthwise stationary.

A multi-armed cam follower 12 is pivotally mounted on a stud l0 and is retained thereon by a retainer washer 11. The middle arm of this follower 12 has a roll 13 which contacts the cam surface of the cam 8. Further contacting the cam surface is a rounded gliding surface 15 provided on a second arm 14. A third arm 16 of the cam follower lever 12 has a slot 17 in which is engaged a stud 19 carried on swingable support member 18 (FIG. 3) for the type carrier 3.

The support member 18 has extension, 20, 21 at two spaced locations provided with coaxial bearing holes by which it is mounted pivotally in the carriage or housing 2 through

studs

22 and 23 on the latter. The support member 18 serves to rotatably carry a rotate shaft 24 which at its lowerend carries a spring barrel 25, a guide pulley 26, and a collar 27 fastened by a set screw 28. On the upper end of the rotatable shaft 24 there is mounted a crown gear 29 which is in engagement with another crown gear 30. Coincidental with the engagement point of these

crown gears

29, 30 is a tilt axle 31 which is carried on the support 18 and serves to pivotally carry a tilt bridge 32. The type carrier 3 is mounted to an axle 34 extending from the crown gear 30 and turnably carried in the tilt bridge .32 by this axle is a knurled nut 33 which secures the type carrier to the axle.

The stated crown gear arrangement facilitates the tilting of the bridge 32 and is the subject of applicants copending U.S. application Serial No. 308,622. filed November 21. 1972. as a continuation of U.S. Serial No. 76,733 filed on Sept. 30, I970.

Orienting or detenting devices for the type carrier 3 consist of lever members generally designated by 35 and 36 which both are mounted on a rod 37. The rod 37 extends through bearing holes in spaced lugs 38, 39 (FIG. 3) and is held adjustably lengthwise thereon in position by a screw 40 in the lug 38, whereby the effective position of the lever member 35 is adjustable, it being noted that lever member 35 is situated on the rod 37 between a shoulder 49 on the rod and a collar 41 which is secured on the rod by a screw 42. In order to give the lever member 36 its appropriate axial position, a spacing washer 43 is provided between the lever member 36 and the lug 39. The lever member 35 terminates in an orienting tooth 44 which is constituted to cooperate with teeth 45 which on the inner side of the type carrier 2 afford locating teeth or formations. The lever member 35 includes a connecting bridge portion 46 intermediate two pivotal locations.

As can be seen in FIG. 1, there is on the lever member 35 at the end opposite to the orienting tooth 44 an engagement face 48. A torsion spring 50 is borne on the rod 37 and has two

opposite ends

51, 52 of which the end 51 bears against a surface 53 of the support member 18 and the end 52 bears against the edge of the said connecting bridge portion 46 of the lever member 35. As can also be seen in FIG. 1 the lever member 36 has an offset tooth 54 which through a bridge portion 55 is connected with a follower arm 56 which at its lower end has an engagement face 57. In association with the lever member 36 there is provided a torsion spring 58 on the rod 37 and such spring by one end 59 contacts the surface 53 of the support 18 and by its other end 60 bears resiliently against the edge of the bridge 55. As a counterpart to the offset tooth 54 there is provided on the tilt bridge 32 a toothed segment 61 providing four notches or formations 62 definitive of type selective positions of the four rows of types. In order to transmit tilting motions to the type carrier 3 the tilt bridge 32 has an ear 63 to which an operating link 65 is connected by a stud 64. A drive part (not shown) transmits tilting motion to the tilt bridge via a hole 66 in the link 65. In order to keep the

lever members

35 and 36 normally ineffectively located, a stud 67 is fast on the carriage housing 2 which carries a roller 68 retained thereon by a washer 69.

In order to effect a transitory printing operation of the type carrier 3 against the platen 1 in the direction A, see FIGS. 1 and 2, the shaft 6 is rotated one revolution by a clutch (not shown) in the direction of the arrow B. The cam follower 12 through the cam 8 acting on the follower arm 16 thereof, turns clockwise, caus ing the support 18 to be operated on the

studs

22, 23, counterclockwise by the slot 17 of the follower acting on the stud 19. The

lever members

35 and 36 being carried on the support 18 by the rod 37 move along with the support 18 in the direction of the arrow A. However, the stud 67 and the roller 68 remain stationarily located since they are on the carriage housing 2. A relative motion occurs thus between the rod 37 and the roller 68 in which the distance therebetween increases. As the rod 37 swings in a circle about said

studs

22, 23, there follow quickly after the start of the print motion, clockwise spring urged motions of both the

levers

35, 36 on the rod 37. These motions of the

levers

35, 36

take place because the pivotal rod 37 therefor moves with the support 18 during the printing movement of the latter toward the platen 1 away from the adjustable roller 68, and in view of which the

surfaces

48, 57 and said levers will be allowed to move clockwise by their

related springs

50 and 58. Furthermore, in view of this the detent tooth 44 of the lever 35 moves clockwise resiliently between the internal teeth 45 on the type carrier 3 and detent therewith with corrective final positio defining effect on the type carrier withthe detent tooth 44 engaging the internal teeth 45 at a location substantially aligned with the tilt axis 31 and the type character to be printed. Similarly, the detent arm 36 is moved resiliently clockwise so that its tooth 54 slides resiliently and correctively into one of the tilt position defining tooth gaps or formation 62 in the sector 61, the approximate tilt position having been established by the operation of thetilt bridge 32 through the link 65. In the printing position of the type carrier 3, the

arms

47 and 56 of the

levers

35 and 36 stand clear off the stationary roller 68, so that the

detent teeth

44 and 54 are exclusively under the influences of their

respective springs

50, 58 and have corrective final position defining effect.

The shapes of the

teeth

45 and 62 which define formations or indents, and the shapes of the

teeth

44 and 54 effect by their engagement exactly defined positions for the types 4 in reference to the platen l and the type carrier support 18.

As can be seen from FIG. 4, the distance-which the detent lever 35 is able to move varies somewhat for different tilt positions of the type carrier 3. Namely, it differs somewhat depending on the horizontal row to which the character to be printed belongs. However, in view of the location which the tilt axis 31 has, this difference of possible movement of the lever 35 is so minor that as a practical matter it can be ignored. The location of the pivot axis 37 of the detent lever 35 is on a line II-II, indicated in FIG. 4 which is substantially perpendicular to the alignment of the tilt axis 31, the type character to be printed, and the location of the detenting engagement of detent tooth 44 with the internal teeth 45. If it were substantially out of agreement with such line then the relative motion between the type carrier 3 and the lever 35 would be much greater for the differing row positioning movements, whereby in the extreme tilt positions the engagement area between the tooth notches 45 and the location defining teeth 44 would be smaller and would entail more localized operating pressures and wear.

In a modification illustrated in FIG. 5, any tooth notch 70 which is in active position conforms to the tilt path of the type carrier 3 at the location of the operated tooth 44. Any tooth notch 70 in its inactive position is thus curved in a radius which is centered in the tilt axis 31.

FIG. 6 illustrates another modification wherein an orienting tooth 71, for improved engaging conditions, is arcuate and is so formed that in each tilt position of the type body 3 a contact area of equal magnitude is in effect.

The invention achieves in an advantageous manner the detenting of a variously positionable type carrier in an exactly defined position as the type carrier nears the printing position, and does so in a most direct manner and without necessitating an extra power drive for the locating levers 35, 36. Advantage is taken of the printing motion which the support 18 of the type carrier has to execute toward the platen thereby to allow these 10- cating levers to become spring operated. Resultant to this, there is no necessity for a cam drive specifically to effect corrective type carrier locating operation, nor a train of motion transmitting means for operation thereby. The provision of the

location correcting levers

35, 36 of the invention are simple two-armed levers supported on a rod on the swinging support 18 and produce reliably the essential movement for correctively locating the type carrier. To give the lever member 35 a basically correct position to determine the correct type selective position for the type carrier 3, the rod 37 on which such lever is carried is axially adjustable on the support 18.

With the modified configurations of the locating member and the location defining teeth on the type carrier, shown in FIGS. 5 and 6, it is feasible to effect corrective tilt positioning always under equally advantageous conditions. The contact areas which come into effect are of the same magnitude for every tilt position.

The invention claimed is: 1. In a printing machine, the combination comprismg:

a type head having type characters formed thereon for impacting against a recording medium,

said type head being movable to position a selected type character for printing,

moving means for moving said type head to effect approximate positioning of the type character selected for printing,

a support member for supporting said type head and said moving means,

said support member being movably supported for moving said type head in a printing movement from a normal position to a printing position to impact the selected type character against a recording me dium,

drive means for driving said movable support member to effect the printing movement of said type head to impact a selected type character against a recording medium at a printing position,

detent formations associated with said type head for defining the correct impacting position of the semoving said detenting means into engagement with said detent formation to correctly position the selected type character for impacting against a recording medium at the printing poisition, and

disengaging means separate from said support member and stationary relative to the printing movement of said support member for acting on said detenting means independently of said drive means and in response to the movement of said support member to move said type head to the normal position for removing said detenting means from engagement with said detent formations.

2. In a printing machine according to claim 1, said acting means being in the form of a spring urging said detenting means into engagement with said detent formations.

3. In a printing machine according to claim 1, said disengaging means being in the form of a stationary member being engaged by said detenting means in response to the movement of said support member to move said type head to the normal position.

4. In a printing machine according to claim 1:

said type head being rotatable and tiltable for rotationally and elevationally positioning a selected type character for printing,

said detent formations associated with said type head serving to correctly define both the rotational and elevational position of a particular type character for impact, and

said detenting means being cooperable with said detent formations associated with said type head for correctly positioning said type head both rotationally and elevationally to impact a particular type character against a recording :medium.

5. In a printing machine, the combination comprising:

a support member for supporting said type head said moving means,

said support member being movably supported for moving said type head in a printing movement from a normal position to a printing position to impact the selected type character against a recording medium,

drive means for driving said movable support member to effect the printing movement of said type head to impact a selected type character against a recording medium at a printing position, detent formations associated with said type head for defining the correct impacting position of the selected type character on said type head,

detenting means for engagement with said detent formations to correctly position the selected type character prior to impacting against a recording medium,

said detenting means being carried by said support member for movement therewith, and

acting means acting on said detenting means independently of said drive means and in response to the printing movement of said support member to move said type head to the printing position for moving said detenting means into engagement with said detent formation to correctly position the selected type character for impacting against a recording medium at the printing position.

6. In a printing machine according to claim 5, said acting means being in the form of a spring carried by said support member and urging said detenting means into engagement with said detent formations associated with said type head.

7. In a printing machine according to claim 6, the combination further comprising a stationary member separate from said support member and stationary relative to the printing movement of said support member and acting on said detenting means independently of said drive means and in response to the movement of said support member to move said type head to the normal position for removing said detenting means from engagement with said detent formations.

8. In a printing machine according to claim 5:

and

said support member being pivotally supported for pivotally moving said type head between a normal position and a printing position,

said detenting means being pivotally supported on said support member for pivotal movement into engagement with said detent formations, and

said acting means being in the form of a spring carried by said support member for pivotally urging said detenting means into engagement with said detent formations.

9. In a printing machine according to claim 8, the combination further comprising disengaging means acting on said detenting means independently of said drive means and in response to the movement of said support member to move said type head to the normal position for removing said detenting means from engagement with said detent formations.

10. In a printing machine according to claim 9, said disengaging means being in the form of a member stationary relative to said support member and engaged by said detenting means in response to the movement of said support member to move said type head to the normal position.

11. In a printing machine, the combination comprismg:

a support member for supporting said type head and said moving means,

said type head having a cavity formed therein which opens towards the exterior surface,

one of said detent formations being located in said cavity for defining the correct rotational impacting position of the selected type character,

said detenting means including an arm extending into said cavity formed in said type head for engaging the detent formation located therein, and

acting means acting on said detenting means inde pendently of said drive means and in response to the printing movement of said support member to move said type head to the printing position for moving said detenting means into engagement with said detent formation to correctly position the selected type character for impacting against a recording medium at the printing position. 12. In a printing machine according to claim 11:

said type head being tiltable about an axis in said cavity formed insaid type head for elevationally positioning a selected type character for printing,

said rotational detent formation for correctly rotationally positioning the selected type character on said type head being in the form of teeth spaced circumferentially about said cavity,

said teeth having a configuration extending substantially parallel to the axis of rotation of said type head, and

said arm of said detenting means extending into said cavity of said type head having a tooth formed thereon for engaging said circumferentially spaced teeth at a location substantially aligned with the tilt axis and the type character selected for printing.

13. In a printing machine according to claim 11:

said type head being tiltable about an axis in said cavity formed in said type head for elevationally positioning the selected type character for printing,

said teeth having a configuration extending substantially parallel to the axis of rotation of said type head,

said arm of said detenting means extending into said cavity of said type head having a tooth formed thereon for engaging said circumferentially spaced teeth at a location substantially aligned with the tilt axis and the type character selected for printing, and

said tooth formed on said arm of said detenting means having an arcuately curved configuration conforming substantially with the radius of movement of said type head about the tilt axis at the location of engagement with said circumferentially spaced teeth.

14. In a printing machine according to claim 11:

said type head being tiltable about an axis in said cavity formed in said type head for elevationally positioning a selected type character for printing,

said rotational detent formation for correctly rotationally positioning a selected type character on said type head being in the form of teeth spaced circumferentially about said cavity,

said circumferentially spaced teeth having a curvature substantially conforming to the radius of movement of said type head about the tilt axis at the location of engagement with said tooth of said detenting means.

15. In a printing machine according to claim 11:

another of said detent formations associated with said type head being tiltable therewith for defining the correct elevational impacting position of the selected type character, and i said detenting means further including another arm for engaging said other detent formation defining the elevational positions of said type head.

16. In a printing machine according to claim 11:

said cavity formed in said type head opening exter nally toward said support member,

said type head being tiltable about an axis in said cavity for elevationally positioning a selected type character for printing,

said arm of said detenting means extending into said cavity of said type head and having a tooth formed thereon for engaging said circumferentially spaced teeth at a location substantially aligned with the tilt axis and the type character selected for printing, and

said arm of said detenting means being pivotally supported on said support member at a location substantially perpendicular to the alignment of the tilt axis and the location of engagement of said tooth with said circumferentially spaced teeth.

17. In a printing machine, the combination comprising:

moving means for rotating and tilting said type head to effect approximate positioning of the type character selected for printing,

a support member for supporting said type head and 3 5 said moving means and being pivotally movable in a printing movement between a normal position and a printing position to impact the selected type character against the recording medium,

detent formations associated with said type head for correctly defining the rotational and elevational position of the selected type character on said type head,

detenting means associated with said support member for engagement with said detent formations of said type head for correctly positioning said type head both rotationally and elevationally to impact the selected .type character against the recording medium,

said detenting means being in the form of levers pivotally supported on said support member for movement into engagement with said detent formations associated with said type head,

resilient biasing means for urging said detenting levers into engagement with said detent formations,

selected type character for printing.

v UNITED STATES PATENT OFFICE CERTIFICATE OF" CORRECTION PATENT NO. 3,838764 l I DATED I October '1, 1974 iNVENTOR(S) Herbert Decker I It is certified that error appears in the above-identified patent and that Said LettersPatent are hereby corrected as shown below:

In The Heading:

After item [21], insert --Foreign Application Priority Data December 23, 1969 Germany. 1964486.,1

Signed and sealed this 20th day of May 1975.

(SEAL) Attest:

i C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks

Claims

1. In a printing machine, the combination comprising: a type head having type characters formed thereon for impacting against a recording medium, said type head being movable to position a selected type character for printing, moving means for moving said type head to effect approximate positioning of the type character selected for printing, a support member for supporting said type head and said moving means, said support member being movably supported for moving said type head in a printing movement from a normal position to a printing position to impact the selected type character against a recording medium, drive means for driving said movable support member to effect the printing movement of said type head to impact a selected type character against a recording medium at a printing position, detent formations associated with said type head for defining the correct impacting position of the selected type character on said type head, detenting means for engagement with said detent formations to correctly position the selected type character prior to impacting against a recording medium, acting means acting on said detenting means independently of said drive means and in response to the printing movement of said support member to move said type head to the printing position for moving said detenting means into engagement with said detent formation to correctly position the selected type character for impacting against a recording medium at the printing poisition, and disengaging means separate from said support member and stationary relative to the printing movement of said support member for acting on said detenting means independently of said drive means and in response to the movement of said support member to move said type head to the normal position for removing said detenting means from engagement with said detent formations.

4. In a printing machine according to claim 1: said type head being rotatable and tiltable for rotationally and elevationally positioning a selected type character for printing, said detent formations associated with said type head serving to correctly define both the rotational and elevational position of a particular type character for impact, and said detenting means being cooperable with said detent formations associated with said type head for correctly positioning said type head both rotationally and elevationally to impact a particular type character against a recording medium.

5. In a printing machine, the combination comprising: a type head having type characters formed thereon for impacting against a recording medium, said type head being movable to position a selected type character for printing, moving means for moving said type head to effect approximate positioning of the type character selected for printing, a support member for supporting said type head and said moving means, said support member being movably supported for moving said type head in a printing movement from a normal position to a printing position to impact the selected type character against a recording medium, drive means for driving said movable support member to effect the printing movement of said type head to impact a selected type character against a recording medium at a printing position, detent formations associated with said type head for defining the correct impacting position of the seLected type character on said type head, detenting means for engagement with said detent formations to correctly position the selected type character prior to impacting against a recording medium, said detenting means being carried by said support member for movement therewith, and acting means acting on said detenting means independently of said drive means and in response to the printing movement of said support member to move said type head to the printing position for moving said detenting means into engagement with said detent formation to correctly position the selected type character for impacting against a recording medium at the printing position.

8. In a printing machine according to claim 5: said support member being pivotally supported for pivotally moving said type head between a normal position and a printing position, said detenting means being pivotally supported on said support member for pivotal movement into engagement with said detent formations, and said acting means being in the form of a spring carried by said support member for pivotally urging said detenting means into engagement with said detent formations.

11. In a printing machine, the combination comprising: a type head having type characters formed thereon for impacting against a recording medium, said type head being movable to position a selected type character for printing, moving means for moving said type head to effect approximate positioning of the type character selected for printing, a support member for supporting said type head and said moving means, said support member being movably supported for moving said type head in a printing movement from a normal position to a printing position to impact the selected type character against a recording medium, drive means for driving said movable support member to effect the printing movement of said type head to impact a selected type character against a recording medium at a printing position, detent formations associated with said type head for defining the correct impacting position of the selected type character on said type head, detenting means for engagement with said detent formations to correctly position the selected type character prior to impacting against a recording medium, said type head having a cavity formed therein which opens towards the exterior surface, one of said detent formations being located in said cavity for defining the correct rotational impacting position of the selected type character, said detenting means including an arm extending into said cavity formed in said type head for engaging the detent formation located thereiN, and acting means acting on said detenting means independently of said drive means and in response to the printing movement of said support member to move said type head to the printing position for moving said detenting means into engagement with said detent formation to correctly position the selected type character for impacting against a recording medium at the printing position.

12. In a printing machine according to claim 11: said type head being tiltable about an axis in said cavity formed in said type head for elevationally positioning a selected type character for printing, said rotational detent formation for correctly rotationally positioning the selected type character on said type head being in the form of teeth spaced circumferentially about said cavity, said teeth having a configuration extending substantially parallel to the axis of rotation of said type head, and said arm of said detenting means extending into said cavity of said type head having a tooth formed thereon for engaging said circumferentially spaced teeth at a location substantially aligned with the tilt axis and the type character selected for printing.

13. In a printing machine according to claim 11: said type head being tiltable about an axis in said cavity formed in said type head for elevationally positioning the selected type character for printing, said rotational detent formation for correctly rotationally positioning the selected type character on said type head being in the form of teeth spaced circumferentially about said cavity, said teeth having a configuration extending substantially parallel to the axis of rotation of said type head, said arm of said detenting means extending into said cavity of said type head having a tooth formed thereon for engaging said circumferentially spaced teeth at a location substantially aligned with the tilt axis and the type character selected for printing, and said tooth formed on said arm of said detenting means having an arcuately curved configuration conforming substantially with the radius of movement of said type head about the tilt axis at the location of engagement with said circumferentially spaced teeth.

14. In a printing machine according to claim 11: said type head being tiltable about an axis in said cavity formed in said type head for elevationally positioning a selected type character for printing, said rotational detent formation for correctly rotationally positioning a selected type character on said type head being in the form of teeth spaced circumferentially about said cavity, said teeth having a configuration extending substantially parallel to the axis of rotation of said type head, said arm of said detenting means extending into said cavity of said type head having a tooth formed thereon for engaging said circumferentially spaced teeth at a location substantially aligned with the tilt axis and the type character selected for printing, and said circumferentially spaced teeth having a curvature substantially conforming to the radius of movement of said type head about the tilt axis at the location of engagement with said tooth of said detenting means.

15. In a printing machine according to claim 11: another of said detent formations associated with said type head being tiltable therewith for defining the correct elevational impacting position of the selected type character, and said detenting means further including another arm for engaging said other detent formation defining the elevational positions of said type head.

16. In a printing machine according to claim 11: said cavity formed in said type head opening externally toward said support member, said type head being tiltable about an axis in said cavity for elevationally positioning a selected type character for printing, said rotational detent formation for correctly rotationally positioning the selected type character on said type head being in the form of teeth spaCed circumferentially about said cavity, said arm of said detenting means extending into said cavity of said type head and having a tooth formed thereon for engaging said circumferentially spaced teeth at a location substantially aligned with the tilt axis and the type character selected for printing, and said arm of said detenting means being pivotally supported on said support member at a location substantially perpendicular to the alignment of the tilt axis and the location of engagement of said tooth with said circumferentially spaced teeth.

17. In a printing machine, the combination comprising: a type head having type characters formed thereon for impacting against a recording medium, said type head being rotatable and tiltable for rotationally and elevationally positioning a selected type character for printing, moving means for rotating and tilting said type head to effect approximate positioning of the type character selected for printing, a support member for supporting said type head and said moving means and being pivotally movable in a printing movement between a normal position and a printing position to impact the selected type character against the recording medium, drive means for driving said movable support member to effect the printing movement of said type head to impact a selected type character against a recording medium at a printing position, detent formations associated with said type head for correctly defining the rotational and elevational position of the selected type character on said type head, detenting means associated with said support member for engagement with said detent formations of said type head for correctly positioning said type head both rotationally and elevationally to impact the selected type character against the recording medium, said detenting means being in the form of levers pivotally supported on said support member for movement into engagement with said detent formations associated with said type head, resilient biasing means for urging said detenting levers into engagement with said detent formations, stationary means for engaging said resiliently biased levers upon movement of said type head to the normal position for preventing said detenting levers from engaging said detent formations associated with said type head, and said detenting levers being operable independently of said drive means and movable under the urging of said resilient biasing means in response to the printing movement of said type head to the printing position for engaging said detenting formations associated with said type head to correctly position the selected type character for printing.