EP1135259B1 - Thermal printing device with fast closure - Google Patents

Abstract

A thermal printing device is capable of being closed by clipping. The device according to the invention includes a printhead 2, a roller 4 integral with a gear assembly, whereon rests the printhead 2 when the device is in the printing position and two orifices 6, 7 on each lateral side of the frame, characterized in that the portion of the orifices 6 and 7 opposite the printhead is so configured as to present a position of unstable equilibrium of the roller when its axis is moving in said orifices 6, 7 when it is subjected to the pressure of the printhead. The invention is applicable to compact devices.

Description

The present invention relates to a printing device the type defined in the preamble of claim 1 wherein the loading and unloading of the paper is facilities and in particular the closure of its building.

Printing mechanisms usually consist of a print head attached to a frame. Thermal print head includes a ceramic support that carries the line of heating points and control chips of their power supply. The print head can pivot relative to the frame, most generally along an axis parallel to a longitudinal side of the frame. A roller is secured to the frame of way that its longitudinal axis is also parallel to one side longitudinal structure. The print head is held in abutment on the roller by a spring. The position of the roller must be perfectly controlled to obtain a good alignment with the thermal head, the printing medium is usually made of a roll of paper of which a face is sensitive to heat. This printing roll is driven in rotation by means of a training roller which itself is powered by a gear system and a small electric motor.

One of the main difficulties in using these mechanisms is to perform the introduction of the end of the thermal paper roll between the roll and the thermal print head. This maneuver loading is carried out to date in several ways.

A simplified system uses the print head as a cam so to lock the head in position.

Another system is to move the head away from the roller using a lever. Such a system is described for example in the document FR-A-2 737 · 152 and in document FR-A-2 737153. The mechanism thermal printing described in these documents comprises a frame, a roller, a print head, spring means for remember the print head against the roller and a cam mounted pivoting around an axis of the frame to move the print head by compared to the roll. These devices have the main disadvantages of complexity of the lifting mechanism (cam and lever), the need for a additional sensor, usually a switch, to detect the lifting and management of induced electronics.

There are also devices in which one proceeds to the separating the print head using a chassis element or a pivoting cover whose kinematics is relatively complex since it is necessary first to move the roller away, solidary of this element swivel, of the print head before you can rotate the entire when the roller is no longer in contact with the head, thus releasing the place for loading paper.

Other devices comprise locking means of the print head on the roll, which, when turned off, for example by pressing on a mechanical part, release the print head from the locking and allows the opening of the mechanism.

A device for thermal printing of a paper has been described having a thermal printing head cooperating by support with a roll of paper drive, wherein the print head is elastically supported by a fixed frame portion while the roller drive is carried by a movable frame part articulated on the fixed frame and forming access cover to the device compartment for the paper roll, the printing device being such that the contact area of the heated dot line of the print head on the paper drive roller is located behind the diameter of this roller passing through the hinge of the mobile frame on the fixed frame when the lid closes in the closing direction of the lid.

EP-0 765 761 also discloses a thermal printing device in which Side lights in the chassis receive the ends of the roll axis. of the claws allow the closure of the lid, to prevent the head from moving when closing the lid and return to its minimum pressure point, which is in no way a printing position.

Moreover, Patent Abstracts of Japan, vol. 098 No. 10 of August 31, 1998, JP-A-10,114,091, discloses A thermal printing device provided with side lights; the layout is such as closing the cover is necessary to allow the printer to operate by preventing bearings supporting the roller from rotating on themselves compared to the chassis.

This device has the major disadvantage of linking the closure of the mechanism at the position of the axis of rotation of the lid relative to the frame.

This device still has the disadvantage of being unable to allow the use of the mechanism in reverse and, in the case where the user would pull on the end of the paper roll or attempt to tearing with a manual paper cutter, this causes a loss meshing of the gables which results in an unpleasant noise and a opening the lid.

The known devices of the prior art, except the first mentioned above, are relatively complex with regard to their implementation, which raises problems of tolerances especially when looking for compact devices for reduce their size.

The invention therefore aims to overcome the disadvantages mentioned above.

An object of the invention is to allow locking and unlocking the roll against the print head, so that allow the easy introduction of the end of the paper roll between the roll and the print head.

Another object of the invention is to allow the locking and unlocking of the roller against the print head without complicating the device by cam or lever means.
To this end, the invention relates to a thermal printing device, having the characteristics of the characterizing part of claim 1. The lid consists of one or more articulated elements supports the roller and allows to bring it to the entrance of the upper part of the lights and allows its free movement inside said lights. The portions of the lights opposed to the print head are homothetic to each other with respect to the axis of rotation of the roller when it is engaged at the bottom of the lights.

A first advantage of the invention is that the mechanism can be extremely narrow with a simple clipping system.

The device is such that the parts of the lights opposite to the head printing have a shape guiding the roll of the input position on the chassis to the printing position so that during the moving the roller, it goes through a position of equilibrium unstable by means of a stop generating a hard point and of instability of the roller during the displacement of its axis in said lights, when it is under pressure from the print head.

The device is such that one light is wider than the other.

The device is such that the shape of the lower section of the light follows a spoke of the gear causing the gear integral with the roller.

The device further comprises a piece which is placed on the sprockets to protect them and serves the purpose of aligning the roll by compared to the gables.

The following description, with reference to the accompanying drawings, is This will make it possible to understand how the invention can be convenient.

Figure 1 is a schematic side view of the device thermal printing device according to the present invention, in the open position.

Figure 2 is a schematic side view of the device thermal printing device according to the present invention, at the beginning of closing.

Figure 3 is a schematic side view of the device of thermal printing according to the present invention, in passing on the stop forming an unstable equilibrium point.

Figure 4 is a schematic side view of the device thermal printing device according to the present invention, completely closed.

Figure 5 is a top view of the device according to the invention.

Figure 6 is a schematic side view of the device thermal printing device according to the present invention, completely closed, the opposite side to that of Figure 4.

Figure 7 is a view of the room that is placed on the sprockets.

In Figure 1, there is shown a printing device which comprises a chassis 1 supporting an engine, a head 2, a paper cutter having teeth 3, a roller 4 drive a thermal paper. Print head 2 is worn elastically by the part of the frame 1. The training roller 4 is carried by the cover 5. The device comprises a light 6 on a side side and a lumen 7 on the opposite lateral flank (see Figure 4). The light 6 is larger than light 7, but homothetic. The roller drive 4 has its axis 8 of rotation which is movable according to a axis 9 of displacement perpendicular to the axis 8 of rotation of the roller.

When closing, the cover 5 causes the movement of the axis of rotation 8 of the training roller 4 and advances it in lights 6 and 7 from the upper entrance of the lights and allowing its free movement inside lights 6 and 7.

We see in Figure 1 that the axis of rotation 8 has its initial position, in opening, that it moves to enter the upper section 10 of light 6 and 7, respectively (Figure 2), and that during the closing, the axis of rotation 8 moves towards the lower section 11 of the light 6 and 7 respectively passing over the equilibrium stop unstable 13.

The intersection of the two sections of the lights 6 and 7 form the stop unstable equilibrium 13.

As seen in Figure 4, a light 7 is larger as light 6, but homothetic.

In Figure 7, there is shown a part 12 which is placed on the gables to protect them and whose function is the alignment of the roller drive relative to the gears.

Thus the device according to the present invention is such that the roller drive is movable along an axis perpendicular to its axis of rotation and has two degrees of freedom from the lid.

The position of the drive roller in the closed position is given by its positioning at the bottom of the light. The lid has to function than to bring the axis of the drive roller into the chassis light and perform the movement of the roller axis of training according to a degree of freedom inside the light of the frame.

There is no condition between the axes passing on the one hand by the center of the training roller and the line of points of the head of printing and secondly between the axis of rotation of the roll drive and the axis of rotation of the lid. This is due to the fact that roller lock is not done relative to the lid but by compared to the bottom of the chassis light. In particular the lid has that a guide function of the drive roller in the light of the frame.

When closing, it is not the roll that rolls on the head but the print head pushes it away because the roll can go back into the light of the cover and so go under the top of the print head which is a sharp angle, to go straight lean on the flat surface of the print head. So we avoid that the teeth of the paper cutter attack the material of the drive roller. This movement towards the rear of the training roller can be carried out whatever the position of the device since it is not done by gravity, but by the pressure exerted by the print head.

The device is such that it can have a light arranged in the cover and a light in the frame, on each side of the device.

To improve the meshing, the lower section of the light of the frame contiguous and posterior to the abutment 13 can travel a portion of radius whose center is the center of the axis of the support of the pinion the pinion of the roller, and the radius must pass through the axis of rotation of the drive roller, in the closed position.

Thus, a first advantage of the device according to the invention is that when closing, the roller does not exert pressure on the print head, and therefore does not rub against the teeth of a manual paper cutter installed. This avoids the penetration of the teeth of the paper cutter in the soft material drive roller.

A second advantage of the device according to the invention is that the locking position of the drive roller when the lid is closed is carried out by a combination of the movements of the cover relative to the chassis, which uniquely determines the position relative to the chassis. The shape of the chassis light allows a firm positioning of the drive roller relative to the chassis and therefore to the print head, which is very important for the quality of printing.

The light of the chassis makes it possible to imply no constraint on the relative positions of the axis passing through the center of the roll of training (or axis of the training roller) and the line of points of the print head and the one passing through the axis of the drive roller and the axis of rotation of the lid since it is the position in the light which determines the closure.

The light, and more particularly the lower section located behind the stop 13 allows to fix the hardness of the lock, which is particularly important in the event that the paper is pulled by the user, when manually cutting. The device according to the invention not open at this time and do not lose its meshing.

Claims (6)

1. A thermal printing device including a lid (5), a chassis (1), a thermal printing head mounted elastically on the chassis (1), a driving roll (4) carried by the lid (5) and integral with a glar or pinion, whereas the printing head rests on the roll when the device is in printing position, ports (6, 7) being provided in each lateral side of the chassis, a port (6) on one lateral side of the chassis and a port (7) on the opposite lateral side of the chassis, in which ports (6, 7) are engaged the ends of a rotational axis (8) of the roll (4) in closing position of the lid (5), whereas the lid (5) includes a reception port of the roll, characterised:

   in that the driving roll (4) has the rotational axis (8) thereof which is mobile along the elongated port of the lid so that the roll has two degrees of freedom relative to the lid whereof one degree follows an axis of displacement (9) perpendicular to the rotational axis (8) of the roll (4) in order to, when closing the lid (5), cause the displacement of the rotational axis (8) of the driving roll (4) and make it progress through the ports (6, 7) of the chassis (1) while allowing the free displacement thereof inside the ports (6, 7), whereas the ports (6, 7) of the chassis (1) are shaped to guide the roll (4) from the inlet position onto the chassis (1) to the printing position, and delineating a balance position stop (13) of the axis (8) of the roll (4) as the latter is moved through the ports (6, 7), whereby this stop (13) is arranged between two positions of the axis (8) of the roll (4) respectively at the inlet of the upper section of the ports (6, 7) and at the bottom of the latter (6, 7) in closing position of the lid (5).
2. A thermal printing device according to claim 1, characterised:

   in that the lid (5) is made of one or several hinged elements.
3. A thermal printing device according to any one of the previous claims, characterised:

   in that the ports (6, 7) are homothetic with respect to one another, whereas one is greater than the other.
4. A thermal printing device according to any one of the previous claims, characterised:

   in that the ports (6, 7) include an upper section (10) for inserting the rotational axis (8) of the roll (4), and a lower section (11), the intersection between both sections (10, 11) forming the stop (13).
5. A thermal printing device according to claim 4, characterised:

   in that said lower section (10) includes a radius portion whereof the centre is the centre of an axis of a driving pinion of the roll (4), this radius going through the rotational axis (8) of the roll (4) at the bottom of the port (6, 7).
6. A thermal printing device according to claim 5, characterised:

   in that it includes a part (12) intended for the protection of the driving pinions of the roll (4) and for aligning the roll (4) relative to the pinions.

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