Ribbon lift mechanism

Abstract

 An erase ribbon lift mechanism (1) for a typewriter. The print ribbon lift mechanism is driven by a motor and cam, and lifts the print ribbon on every print and erase cycle. In addition, a second cam (15) on the motor's shaft (21) drives the erase ribbon lift mechanism (1), which further comprises an electro-magnet driven latch (37,23). At the beginning of an erase cycle, a five millisecond pulse applied to the electromagnet (35) activates the latch (37,23) so that the erase ribbon will also be raised. The erase ribbon is on the platen side of the print ribbon so that when both ribbons are lifted, the printed character will be erased.

Description

[0001] The invention relates to a ribbon lift mechanism for an impact printer and specifically to an erase ribbon lift mechanism for a typewriter.

[0002] Modern electronic typewriters utilize a stationary platen, and the character print elements are carried by a scanning carriage that moves along the platen on a line of printing. Typical of such typewriters are the Xerox Memorywriter series of electronic typewriters.

[0003] In such typewriters, the print ribbon is normally positioned between the print characters and the platen. When it is desired to erase a character, the carriage is moved to the appropriate position, the ink ribbon dropped and the erase ribbon raised into position between the print characters and the platen.

[0004] One well known method of raising the erase ribbon is to use a separate stepping motor for that purpose. An alternative is the use of two solenoids, one for raising the print ribbon and one for raising the erase ribbon.

[0005] In order to lower the price of an electronic typewriter, it is necessary to accomplish this erase function using fewer parts or lower cost components.

[0006] The present invention as recited in the appended claims is intended for use in a typewriter having a rotating electric motor which drives a cam shaft and cam follower which, in turn, raises a lever attached to the print ribbon. In operation, each time a typewriter key is depressed, the print ribbon is raised, so that the hammer will impact the ribbon against the platen to produce a printed letter.

[0007] In this system, the cam shaft may be connected to a second cam which drives a second mechanism, similar to the first, for raising the erase ribbon. However, there are basic differences. The erase ribbon mechanism is controlled by a latching member which, in turn, is preferably driven by a low power electro-magnet. When the latch is set, the erase ribbon will be raised each time the erase key is depressed.

[0008] The character key corresponding to the letter being erased need not be depressed since the letter is stored in memory and the appropriate character on the print wheel will be struck automatically.

[0009] The print ribbon is raised for every key depression, print or erase, and, in addition, the erase ribbon is raised for erase key depressions. The result is that, for erasures, both ribbons will be raised. Therefore the erase ribbon is located between the print ribbon and the platen so that an erasure will result when both ribbons are up.

[0010] The use of this invention in the manner described above allows the print ribbon motor to be used to also drive the erase ribbon. The additional parts required for this invention are a second cam, some springs and levers, and a low power electro-magnet, which cost less than the prior art equivalent erase mechanisms.

[0011] One way of carrying out the invention is described in detail below with reference to the drawings, which illustrates the preferred embodiment and in which:

Figure 1 is a top view of the erase ribbon lift mechanism of this invention with the trip lever mechanism deleted for purposes of clarity.

Figure 2A-2C are side views of the erase ribbon lift mechanism of this invention showing the relative positions of the mechanism components during operation.

[0012] Referring now to the Figures, erase ribbon lift mechanism shown generally as 1 includes the cam driven lever 3 and ribbon lift arm 5. Cam driven lever 3 and ribbon lift arm 5 are mounted for rotation on pivot post 7, which pivot post 7 is supported on carriage frame 9 (see Figure 1). Cam driven lever 3 is provided at one end with a cam follower roller 11, which is mounted for rotation on cam driven lever 3 by means of post 4. Cam follower roller 11 is biased by ribbon lift arm spring 13 into contact with cam 15 (see Figures 2A-2C). Spring 13 is positioned to urge cam driven lever 3 in a clockwise direction (as seen in Figures 2A-2C). Spring 13 is connected to ear 19, which is formed as a part of ribbon lift arm 5, and to pivot member 17, which is formed as a part of cam driven lever 3. Cam 15 is rotated by cam drive shaft 21. Cam drive shaft 21 is connected to a motor (not shown) and to the ink ribbon lift cam (not shown), which is also mounted to rotation with cam drive shaft 21.

[0013] A trip lever 23 is mounted for rotation on ribbon lift arm 5 by trip lever pivot 25. Trip lever 23 is biased in a counterclockwise direction (as seen in Figures 2A-2C) by trip lever spring 27, which is connected to ribbon lift arm 5 and trip lever 23. Trip lever 23 includes an arm 29 having a projection 31. Trip lever 23 is provided with a slot 47. Cam driven lever projection 49 formed on cam driven lever 3 projects through slot 47 for interaction therewith as described below.

[0014] A trip lever release mechanism shown generally as 33 (see Figures 2A-2C) is provided to activate the ribbon lift mechanism 1 of this invention. Trip lever release mechanism 33 is not shown in Figure 1. Trip lever release mechanism 33 is mounted on carriage frame 9 and includes an electromagnet solenoid 35, trip lever release member 37, trip lever release member spring 39 and trip lever release member support 41. Trip lever release member 37 is fulcrumed about fulcrum point 43 which is part of electromagnet 35. Spring 39, which is connected to support 41 and release member 37, biases trip lever release member 37 in a counterclockwise direction (as seen in Figures 2A-2C). Spring 39 thus holds release member 37 against stop 45 formed on support 41.

[0015] A projection 51 is formed on release member 37 to contact projection 31 formed on trip lever 23 when release member 37 is held against stop 45 by release member spring 39. Trip lever arm projection 31 is held against release member projection 51 by trip spring lever 27. Slot 47 in trip lever 23 is designed to allow unobstructed movement of projection 49 on cam driven lever 3 as long as trip lever projection 31 is in contact with release member projection 51.

[0016] In operation, and as shown in Figure 2A, cam shaft 21 rotates as ink ribbon lift (not shown) is being operated. As cam 15 rotates with cam shaft 21, cam follower roller 11 causes cam driven lever 3 to pivot around pivot post 7. As long as release member projection 51 is in contact with trip lever projection 31, projection 49 on cam driven lever 3 does not contact any part of trip lever 23 as it traverses slot 47 in the directions shown by arrows 53.

[0017] Referring now to Figure 2B, when it is desired to activate erase ribbon lift mechanism 1, electromagnet 35 is activated, for example, by touching the erase key on the typewriter keyboard (not shown), causing the trip lever release member 37, which is made of a ferromagnetic material, to be drawn towards it as cam 15 starts to move the cam lever 3 counterclockwise to lift the erase and print ribbon. The pivoting of release member 37 clockwise around pivot 43 removes projection 51 on release member 37 from contact with projection 31 on trip lever 23. Since trip lever 23 is no longer impeded by release member 37, trip lever 23 is pivoted in a counterclockwise direction around trip lever pivot 25 by trip lever spring 27. Trip lever 23 continues moving counterclockwise until edge 55 comes into contact with projection 49 on cam driven lever 3. Trip lever spring 27 holds trip lever 23 firmly against cam driven lever 3.

[0018] Referring now to Figure 2C, as cam is rotated to the erase ribbon lift position shown in Figure 2C, cam driven lever 3 is rotated counterclockwise around pivot 7. As cam driven lever 3 rotates counterclockwise, projection 49 contacts abutment surface 57 formed in trip lever slot 47. As cam driven lever 3 pivots counterclockwise around pivot 7, projection 49 lifts trip lever 23 and, because trip lever 23 is connected to ribbon lift arm 5 by pivot 25, trip lever 23 also lifts ribbon lift arm 5. Each time a cam 15 turn of 180° is completed, the erase ribbon is lifted. Since the erase cycle is started by pulsing electromagnet 35, when the erase function is completed, electromagnet 35 is deenergized and point 57 will be disengaged automatically. Deactivation of electromagnet 35 allows release member spring 39 to pull release member 37 back into position against stop 45. As the erase ribbon lift arm 5 drops, projection 51 on release member 37 contacts projection 31 on trip lever 23 causing trip lever 23 to rotate clockwise around trip lever pivot 25, thus moving trip lever 23 out of contact with projection 49.

[0019] Referring back to Figure 2A, as cam 15 continues to rotate, cam driven lever 3 rotates counterclockwise, but since projection 49 is not in contact with trip lever 23, ribbon lift arm 5 is not raised.

[0020] Ribbon lift arm 5 is provided with an aperture 59 for attaching the ribbon and erase ribbon guide support (not shown). As can be seen from the above description, the erase ribbon lift mechanism 1 of this invention provides a trip lever 23 for connecting a cam driven lever 3 with an erase ribbon lift arm 5 only when electromagnet 35 is pulsed.

[0021] To summarise, Figure 2A shows the mechanism in its normal, or type, mode of operation, where, for each cycle of cam 15, projection 49 travels up slot 47 without contacting surface 57. The erase ribbon, attached to arm 5 is therefore not lifted.

[0022] Figure 2B shows the mechanism after the low power electromagnet 35 has received its five millisecond activating pulse, when the erase key has been depressed. The release member 37 has been retracted so that the trip lever 23 has rotated counterclockwise slightly, allowing the projection 49 to contact the surface 57. The erase ribbon lift process has thus been activated. In fact, after the five millisecond pulse ends, the mechanism will remain in this position because the release member 37 is prevented from returning to its former position by the projection 31.

[0023] Figure 2C shows the action of the mechanism after a key is depessed during an erase cycle. As the cam 15 rotates, the lever 3 drives the trip lever 23 upward, which in turn lifts the erase ribbon left arm. Finally, as the arm drops, the trip lever projecion 31 contacts the release member projection 51, reverting the mechanism back to the configuration of Figure 2A.

[0024] Although specific components have been disclosed herein, many modifications and variations will occur to those skilled in the art. Such modifications and variations are intended to be included within the scope of the appended claims.

Claims

1. An erase ribbon lift mechanism for a typewriter, comprising:
a pivot post,
a lever for pivoting about said pivot post at a point between the two ends of the lever,
means for lowering and then raising a first end of said lever for each character key depression, and
means for selectively coupling the second end of said lever to said erase ribbon during an erase cycle.

2. The mechanism of Claim 1 wherein said means for coupling comprises an electro­magnet which upon receipt of an electrical pulse, latches the coupling between said erase ribbon and said second lever end so that the erase ribbon will be raised during the erase cycle, and further comprises means for unlatching said coupling before the end of the erase cycle.

3. An erase ribbon lift mechanism which comprises:
a ribbon lift arm for lifting an erase ribbon;
a cam driven lever;
a trip lever for connecting and disconnecting said ribbon lift arm and said cam driven lever;
a release member movable between a first position where said release member disengages said trip lever from said cam driven lever and said ribbon lift arm, and a second position where said release member releases said trip lever so that said trip lever can connect said cam driven lever and said ribbon lift arm;
first bias means for causing said trip lever to connect said cam driven lever with said ribbon lift arm;
a release member actuator for moving said release member from said first position to said second position; and
second bias means for biasing said release member towards said first position.

4. The erase ribbon lift mechanism of claim 3 wherein said ribbon lift arm and said cam driven lever are mounted for rotation on a common pivot post.

5. The erase ribbon lift mechanism of claim 3 or claim 4 wherein said trip lever is mounted for rotation on said ribbon lift arm.

6. The mechanism of any of claims 3 to 5 wherein said release member is driven by an electromagnet towards said second position.

7. A typewriter having a print and an erase ribbon, including a ribbon lift mechanism comprising:
means for lifting the print ribbon to printing height for each print and erase cycle, and
means for mechanically coupling the erase ribbon to the print ribbon prior to an erase cycle to raise the erase ribbon with the print ribbon to print height for each erase cycle and for disengaging said coupling at the end of the erase cycle.

8. The mechanism of claim 7 wherein the erase ribbon is generally aligned with said print ribbon and positioned closer to the platen than said print ribbon so that the character will be erased when both ribbons are at printing height.

9. The mechanism of claim 7 or claim 8 wherein the means for coupling comprises a latch for coupling the print and erase ribbons prior to an erase cycle and means for automatically disengaging the latch at the end of an erase cycle.

10. The mechanism of claim 9 wherein said latch comprises an electromagnet for setting the latch prior to an erase cycle and a biasing means for resetting the latch at the end of the erase cycle.

Drawing