JPS585794B2 - Print ribbon drive mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION The present invention involves winding a print ribbon across the printhead of a printing machine onto a spool on one side of the printing machine and onto an opposing spool on the other side of the printing machine. This invention relates to a mechanism for driving a printing ribbon for a printing machine.

A print ribbon drive mechanism for alternately winding print ribbon onto opposing spools further rotates the spools based on tension or resistance during winding, and a swing lever loads the ribbon onto the empty ribbon spool. So far, devices have been proposed that have the function of being wrapped around the top.

An example of such a ribbon drive structure is U.S. Pat. It is described in No. 4046246.

This patent describes a swingable drive arm that serves to alternately wrap print ribbon around one or the other of a pair of ribbon spools.

Another example of this type of ribbon drive structure is described in US Pat. No. 3,880,271.

The ribbon drive structure includes a swingable feed beam having two detent positions for this purpose, the two grooves of which alternately fit into the drive stud.

The beam thus has two principal positions, each with one
One of the pair of ribbon spools is driven.

IBM Technical Disclosure Paper No. 21
Volume No. 9, February 1979, p. Another example of this type of structure is described in 3687-3688.

In this construction, a longitudinally movable moving pawl acts to alternately drive one or the other of two ribbon spool ratchets, with a shifter control sensing the amount of ribbon on one of the spools. , the mechanism can be changed from driving one ratchet to driving the other ratchet.

The shifter control is in operation when the spool is emptied of ribbon and drives the detent bar from one position to the other to drive the shifting pawl from one of the ratchet wheels to the other. Falling when switching.

SUMMARY OF THE INVENTION It is an object of the present invention to alternating the actuation of two opposed ribbon spools solely in response to nearly empty ribbon in one of the two opposed ribbon spools without being affected by ribbon tension. , an improved ribbon that avoids certain operational problems associated with using ribbon tension to reverse the ribbon by driving a freshly emptied ribbon spool in the ribbon winding direction. It is also necessary to improve the drive mechanism.

A more specific object of the invention is that the switching crosspiece swings from one main position to the other by reciprocation of the support under the control of a device sensitive to the absence of ribbon on the ribbon spool, and then empties. Such an improved ribbon drive includes a swingable switching crosspiece supported by a reciprocating support that also supports a printhead and is configured to drive a spindle supporting a ribbon spool in the ribbon winding direction. It is to bring about a mechanism.

The invention advantageously includes such a reciprocating support for supporting a printhead, with the switching crosspiece mounted on the support so as to be swingable.

The two spindles, each supporting one of the two print ribbon spools, are equipped with ratchet teeth, and the swingable switching rung moves the support and print head towards the spindles given the ribbon winding rotation. It has a pawl surface that engages with the ratchet teeth to rotate the spindle and rotate the associated ribbon spool in the ribbon winding direction.

Each spindle supports a trigger lever,
This is in response to the ribbon being wound on the interlocking ribbon spool, and when the ribbon is almost empty from the spool, the trigger lever drops and engages the fixed abutment, causing the spindle and its interlocking spool to wind the ribbon. Avoid further rotation in the direction of removal.

This is the operating position of the trigger lever; the swinging crosspiece has opposed cam surfaces which, when in its operating position for swinging the crosspiece, actuate the trigger levers of the two spindles. in contact with the ribbon to enable the interlocking pawl surface to engage the ratchet teeth on the spindle of the empty ribbon spool;
Next, the ribbon spool is rotated in the ribbon winding direction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The print ribbon drive mechanism includes a switching crosspiece 20 that is oscillatably mounted on a carrier 22 of a printhead 24 of a printing machine.

The print head 24 has a leading end piece 24a, through which the printing ribbon 26 passes.

Ribbon 26 is attached to ribbon feed spools 28 and 30, and its ends are secured to the spools.

The spools 28 and 30 each have a toothed spindle 3
2 and 34.

The teeth of the spindle 32 have tooth flanks 32a extending in the radial direction and tooth flanks 32b connecting the tooth flanks 32a and extending at an angle to the radius.

The teeth of spindle 34 have a radially extending surface 34a and a tooth surface 34b connecting tooth surface 34a and extending at an angle to the radius.

Since the teeth are as seen in plan view in FIG. 1, it will be noticed that the tooth flanks 32b and 34b are sloped inwardly toward the center of the spindle in opposite directions, which will be explained below. As can be seen, this is so that the crosspieces 20 approaching the spindles 32 and 34 from opposite directions can engage the radially extending tooth surfaces 32a and 34a.

Carrier 22 is slidably mounted on stationary guide rod 36 to permit reciprocal movement of carrier 22, and thus printhead 24, in directions 37 and 38.

In this way, the print head 24 has 37 print lines.
The print line extends in the direction of the print medium 4 and 38.
0.

To this end, printhead 24 may be of wire type, including wire 24b.

The wire selectively passes through tip piece 24a to move ribbon 26 away from tip 24a and into contact with media 40;
Reactive dots are printed on the medium 40.

Carrier 22 is driven reciprocally in directions 37 and 38 by suitable motive means (not shown).

Spool brackets 42 and 44 are attached to printhead 24
Brackets 42 and 44 support spindle studs 48 and 50, respectively.

Spool bracket 42 with attached spindle stud 48 is shown in detail in FIG. 2, as is the assembly of spindle stud 50 on spool bracket 44.

The top surface of the bracket 42 has a recess 5 with a vertical shoulder 52.
1, and the bracket 44 also has a similar shoulder 53.

Reversible trigger levers 54 and 55 are swingably mounted on the spindles 32 and 34.

Levers 54 and 55 and their toothed spindles 32 and 3
The lever 54 and its installation are shown in detail in FIGS. 2, 3, and 4, as the installation is similar.

The lever 54 is attached to the bracket 5 fitted on the stud 48.
6 is swingably mounted on the upright portion 56a of the spindle 32 through the hole 32c upwardly.
It's growing inside.

The lever 54 has a toe portion 54a, and a tongue 57a of a leaf spring 57 fitted on the bracket 56 extends beyond the toe portion 54a, applying a swing force to the lever 54 to move the lever 54 to the center of the spindle 32 and the stud 48. Swing the lever away from the line and push the lever downward until it engages with the top surface of the bracket 42.

A drag spring 58 is attached to the bracket 42 and engages the teeth of the associated spindle 32, and a similar drag spring (not shown) is used for the spindle 34.

Each spindle 32 and 34 has a non-circular outer surface that extends through the non-circular hole 28 in the spool 28.
a or a hole 30a in the spool 30, and is adapted to mesh with it.

The crosspiece 20 has pawl surfaces 60 and 62 at each end and cam surfaces 64 and 66 at each end.

The rungs are swingably mounted on the carrier 22 by pins 68 that extend through holes 72 in the rungs 20 to limit the swinging movement of the rungs 20.

Overcenter spring 74 connects crosspiece 20 and carrier 22
between the pins 70 to hold the crosspiece in either of its distal positions limited by the pins 70.

In operation, carrier 22 and print head 24 reciprocate in opposite directions 37 and 38 so that head 24 prints a print line onto print media 40 .

Initially, the crosspiece 20 is in the position shown in FIG.
Assume that it swings in a clockwise direction around to the limit determined by pin TO.

When the head 24 moves with the carrier 22 in the direction 38 to achieve a print line on the media 40 in this direction, the pawl surface 62 moves and engages one of the tooth surfaces 34a of the spindle 34, thus causing the spindle 34 to As shown in FIG. 1, the spindle 34 is rotated by a certain arc degree in a clockwise direction around the spindle axis, for example, by X of the teeth of the spindle 34.

Spool 30 is non-rotatably coupled to spindle 34 so that spool 30 also rotates by the same arc.

Ribbon 26 is secured at each end to spools 28 and 30, and as spool 30 is rotated in this manner, the ribbon is wound around spool 30 in a corresponding clockwise direction about the axis of spindle 32 (FIG. 1). (see) is wound from a freely rotating spool 28.

Carrier 22 and print head 24 are then moved in the opposite direction to print a print line in this direction.

However, when the crosspiece 20 is in the position shown in FIG. 1 with respect to the carrier 22, the pawls 60 are not in line with the teeth of the spindle 32, but pass over and do not contact them.

Thus, spindle 32 and spool 28 do not rotate with printhead 24 and carrier 22 as they reciprocate in direction 37 in this manner.

Each subsequent movement of print head 24 and crosspiece 2-0 in the direction 38 winds a corresponding length of ribbon 26 onto spool 30, while each movement in direction 37 winds the ribbon 26 around spindle 32 and spool 30. 28 is not affected in any way.

When the ribbon is emptied on the spool 28 and there is virtually no ribbon left on the spool 28, the trigger lever 5
4 is connected to the lever 54 by the ribbon 26 on the spool 28.
The lower end 54a of the bracket 42 is no longer held in a position where it does not come into contact with the upper surface of the bracket 42.

Thus, since the lever 54 is not held by the ribbon 26, it swings downward under the action of the spring tongue 57a, and the lower end 54a of the lever 54 contacts and rests on the upper surface of the bracket 42.

During the final arc of rotation of spindle 32 and spool 28 (in the clockwise ribbon winding direction as shown in FIG. 1), lever end 54a moves downwardly into recess 51 and against shoulder 52. , spindle 32 and spool 2
8 prevents further rotation in the direction of the axis of the spindle 32 in the clockwise direction shown in FIG.

The carrier 22 and crosspiece 20 are then moved in the direction 37 so that the camming surface 64 abuts the lower end of the trigger lever 54 and brings it into contact with the shoulder 52 , thus causing the crosspiece 20 to move this Swing to the limit of movement in the direction.

Next, when the carrier 22 and the head 24 move in the direction 37, the pawl 60 hits the tooth surface 32a of the spindle 32, thus causing the spindle 32 and the spool 38 to rotate in the counterclockwise direction shown in FIG. The ribbon 26 is wound on the spool 30 at the same time as the ribbon 26 is wound on the spool 30.

When crosspiece 20 is at the limit of rotation in the counterclockwise direction shown in FIG. It works to wind up.

The lever 54 is swung upwardly by the ribbon 26 as it wraps around the spool 28, and the lever 54 swings upwardly from the bracket 42.
The mesh with the top surface of the is disengaged.

Finally, the ribbon is emptied from the spool 30 and the trigger lever 55 swings downward into engagement with the abutment surface 53 to prevent further winding of the ribbon 26 from the spool 30 and spindle 34.

Also, the cam surface 66 hits the trigger lever 55 and the shoulder 53
, and the crosspiece is again swung back to the position shown, where the pawl surfaces 62 act on the teeth of the spindle 34 as described above.

When ribbon 26 is emptied from either spool 28 and 30, crosspiece 20 is released by the action of camming surfaces 64 and 66 on trigger levers 54 and 55, respectively.
The ribbon 26 is thus reciprocated to the limit of its swinging motion, and the ribbon 26 is sequentially and alternately wound onto the spools 30 and 28 from the other spool.

The ribbon drive mechanism of the present invention has numerous advantages.

That is, the ribbon drive mechanism according to the present invention
8 and 30, the ribbon 26
Since it does not utilize the tension of the ribbon 26, there is no risk of reversing the movement of the ribbon before either spool is empty, and the printing wire 4b is
It is not prevented from being moved to 0, nor is the ribbon and wire jamming prevented from completely reversing the ribbon.

The ribbon drive mechanism of the present invention does not require a spool to be placed on the spool to change the winding direction, which can create undesirable ribbon tension and requires manual rotation when installing a new ribbon into the machine. ribbon 26
There is no need to use a trailing sensing arm.

The loading path for the ribbon is simple, especially since it does not pass around such tension arms.

The ribbon drive has a small number of parts, so the cost of the mechanism is very low.

This does not apply any drag to the carrier 22 of the print head 24 during printing.

The tension in ribbon 26 does not increase during reversal.

Also, as an assembly, the swingable crosspiece 20 as well as the carrier 22 and printhead 24 have a desirably low inertia.

[Brief explanation of drawings]

Figure 1 shows spindles supporting a pair of ribbon spools, a trigger lever swingably mounted on each spindle, and a switching crosspiece swingably mounted on a reciprocating support supporting a printhead. 1 is a plan view of a print ribbon drive mechanism incorporating principles of the present invention, including; FIG. FIG. 2 is an exploded view of one of the spindles and a trigger lever swingably mounted thereto. Figure 3 shows 1 of the spindle as seen from line 3-3 in Figure 1.
FIG. FIG. 4 is a partial view of one of the trigger levers and its support. 20...Switching crosspiece, 28 and 30...
・Spool, 32 and 34...Spindle, 5
4 and 55... Tricker lever.

Claims (1)

[Scope of Claims] 1. First and second toothed spindles rotatably arranged to support first and second printing ribbon spools, respectively, which are spaced apart from each other by a predetermined distance; and a carrier capable of linearly reciprocating between the first spindle and the second spindle; a first pawl portion formed on the first spindle side and a second pawl portion formed on the second spindle side; The pawl can be engaged with the teeth of the first spindle, but the second pawl is in a first position where it cannot be engaged with the teeth of the second spindle, and the first pawl is in the first position of the first spindle. a crosspiece attached to the carrier such that the second pawl cannot engage with the teeth but is swingable between a second position in which the second pawl can engage with the teeth of the second spindle; When the printing ribbons are respectively wound up from the first and second spools and the remaining amount of the printing ribbons on the first and second spools respectively becomes substantially zero, the printing ribbons are wound from the axes of the first and second spools respectively first and second trigger levers that are swingably attached to the first and second spindles, respectively, so as to protrude outward and are held at predetermined operating positions on the side of the crosspiece; said first and second spindles to swing said crosspieces to said first and second positions, respectively, when said carrier moves toward said first and second spindles, respectively, with said trigger levers in said actuated positions; first and second cam surfaces formed on first and second spool sides of the rung, respectively, for engaging first and second trigger levers, respectively.