The invention relates to a pen with a barrel, a lead with a working end, a thrust device lying on the side of the lead opposite to the working end of the lead, and a force sensor, wherein the lead is adjustable between two operating positions responsive to an operation of the thrust device, i.e. a working position in which the working end of the lead protrudes from the barrel, and a rest position in which the working end of the lead is within the barrel, further wherein the force sensor is adapted to detect a force acting axially on the lead, and the lead, in the working position, is supported on the force sensor.

Pens of the above-mentioned type are known. If a user of the known pen moves the thumb with which they switch the pen laterally from the thrust device when switching to the rest position, the lead is accelerated in the direction of the pen end by a switch spring and slowed down abruptly upon reaching the end position (rest position). In doing so, high inertial forces occur, which can easily damage a sensitive force sensor as is integrated, for example, in electronic pens for measuring the contact pressure of the writing tip on the writing pad. This problem is worsened in case of a battery which is moved additionally and together with the lead. In order to keep the lead and, if applicable, the battery in the rest position in the barrel, even if the latter is moved, the switch spring must exert a minimum force on the lead and, if applicable, on the battery even in the rest position. This force is further increased through extension to the working position and the compression of the spring connected thereto, and acts on the lead and, if applicable, the battery, during retraction, so that it/they is/are accelerated with a multitude of the acceleration of gravity towards retraction.

Given the above problem, the invention is based on the object of further developing the pen of the above-mentioned type so that the force sensor is better protected from damage.

According to the invention, the given object with a pen of the above-mentioned type is achieved through decoupling the lead in the rest position from the force sensor.

In doing so, the invention is based on the finding that the decoupling of the lead from the force sensor in the rest position comes with the fact that the inertial forces occurring during slow down upon reaching the rest position cannot act on the force sensor. Thus, the force sensor is relieved from damaging forces when adjusting the lead from the working position to the rest position.

According to the invention, it is preferably provided that the force sensor is coupled with the thrust device with regard to axial movements regarding the barrel.

Thus, it can be achieved, for example, that the force sensor (together with the thrust device) is axially moved a longer distance than the lead when adjusting the lead from the working position to the rest position, so that a distance decoupling the lead from the force sensor can be established.

In doing so, according to the invention, preferably the force sensor abuts the end of the pressure facing the lead.

Further preferably, an optional elastic means is provided which pretensions the thrust device in the direction away from the lead.

This ensures that a distance decoupling the lead from the force sensor is automatically produced and maintained. However, even without this elastic element, protection of the force sensor is possible merely through the longer adjustment path, as will be explained in the following.

According to a further preferred embodiment of the invention, a stop is provided, on which the lead is indirectly or directly supported in the rest position.

This stop, on the other hand, serves to establish and to maintain a distance decoupling the lead or the lead/battery combination from the force sensor in the rest position. In the rest position, the lead or the lead/battery combination is not supported on the force sensor.

In order to protect the sensor, it is preferably provided that it has a larger axial displacement capability than the lead. In doing so, the lead strikes against the stop which is not supported on the sensor.

According to a further preferred embodiment of the invention, an electric or an electronic circuit coupled with the force sensor and a battery are provided, wherein the battery is connected to the electric or electronic circuit in the working position and is separated therefrom in the rest position. The battery can be any type of battery, e.g. a rechargeable battery (accumulator).

Thus, the electric or electronic circuit is switched on simultaneously with the adjustment of the lead from the rest position to the working position, or vice versa, switched off.

In doing so, it is preferably provided that the electric or electronic circuit is coupled with the thrust device with regard to axial movements regarding the barrel.

Thus, switching the electric or electronic circuit on or off by means of actuation of the thrust device can be realized in a particularly simple manner.

In this embodiment, a further spring which pretensions the thrust device in the rest position is to be provided, which actively lifts off the thrust device from the battery in the rest position, so that an electric contact via the contact springs is excluded.

Further preferred according to the invention, a circuit board is provided which carries the electric or electronic circuit and lies within the thrust device. Thus, the installation space inside the thrust device is used. Furthermore, the circuit board is protected with the circuit it carries.

Finally, according to the invention, preferably a slide is provided which holds the lead and the battery in a manner to be axially displaceable with regard to the barrel.

Such common slide for the lead and the battery is advantageous not only during assembly or replacement of the lead and/or the battery, but is also helpful when realizing common axial movements of the lead and the battery. The slide also enables the transfer of the axial force beyond the battery, irrespective of length tolerances of the battery. Thus, there is always the same pressure of the lead acting on the sensor, irrespective of the size and the embodiment of the battery.

In the following, the invention is further explained by means of a preferred example embodiment and with reference to the accompanying drawing with further details. Wherein:

Fig. 1 shows a longitudinal sectional view of a preferred example embodiment of the pen according to the invention in the rest position,

Fig. 2 shows the same view as Fig. 1 , but in the working position,

Fig. 3 shows the same view as Fig. 2, but rotated 90° about the longitudinal axis,

Fig. 4 shows a schematic explosion view of parts of the pen, and

Fig. 5 shows the same view as Fig. 4, but rotated 90° about the longitudinal axis and with additional axial views.

The following details of the shown pen can be taken from the drawing:

A front barrel 1 , which can also be referred to as gripping part, a barrel tube 2, a barrel end 3 with a switching mechanism and an optional clip, a thrust device 4 with electronic components therein, a slide 10 for receiving a lead 11 and a battery 12, an electronic circuit board 13, an abutment 22 which represents the rear stop for the slide 10, a front opening 101 for guiding through a writing tip 110, a front receptacle for receiving the lead 11 , a rear receptacle for receiving the battery 12, a rear opening 104 for a ground contact 122, a writing tip 110, ink 111 , an end portion 112, a plug 113 of the lead 11 , a spring 114 for compressing the lead 11 , a resilient metal contact 121 at the negative pole of the battery 12, a negative pole spring 130, a thrust device spring 131 and a positive pole spring contact 132 of the electronics on the circuit board 13.

Fig. 1 shows the pen in a switched-off condition (rest position). The spring 114 pushes the slide 10 which contains the lead 11 and the battery 12 backwards against the abutment 22 which is attached to the end of the barrel tube 2. At the same time, the spring 131 pushes the thrust device 4 backwards against the stop of the switching mechanism, thus lifting the spring contacts 132 from the ground contact 122 and the positive pole 123 of the battery 12 and thus galvanically separating the electronics on the circuit board 13 from its power supply. Thus, every switching off of the pen is at the same time connected to a reset of the programming which is re-read from the program memory of the pen during restart. At the same time, the power consumption in the switched-off condition (rest position) is restricted to the self-discharge of the battery 12 so that a switched-off pen remains usable for years.

When switching on, the thrust device 4 is slid onto the ground contact 122 and the positive pole 123 of the battery 12 and it pushes the slide 10 together with the lead 11 and the battery 12 forward until the switching mechanism snaps into its front switching position and the writing tip 110 comes out of the front end of the front barrel 1. Generally, the time which passes during switching is enough in order to activate the electronics so that the complete switching off is not disadvantageous to the functional efficiency of the pen.

Figs. 4 and 5 in particular show the following details: a switching ring 5, wherein the grooves on its circumferential face are not represented, a thrust device base 41 which consists of an injection molded part and has two cups which are held together by a film hinge, a thrust device cap 42 with a circumferential groove 43, a detent lug 44 at the end of the thrust device base 41 , a contact spring 132 for the ground contact 122, a contact spring 133 for the positive pole 123 of the battery 12 and a force sensor 134.

In the present example embodiment of the pen according to the invention, the thrust device 4 only consists of two parts by which the thrust device base 41 can be opened by means of a laterally attached film hinge in order to insert the circuit board 13. After closing, first the switching ring 5 which runs in a groove between the two thrust device parts can be slid onto the thrust device base 41. The assembly is completed when the thrust device cap 42 is put on and snapped in.

In Fig. 5, the view on the very right shows the thrust device 4 from the front. The view on the very left shows the thrust device 4 without a thrust device cap and a switching ring from behind.

The thrust device cap 42 is elliptical in order to prevent rotation in the end part of the barrel tube 2.

The two contact springs 132 and 133 are concentric to one another and protrude beyond the tip side end of the thrust device 4. When disengaging the thrust device 4, they are lifted off of the ground contact 122 and the positive pole 123 of the battery 12 because the thrust device 4 has more adjustment range during switching than the slide 10 which is prevented from further movement backwards by the abutment 22.

The function of the writing mechanism of a ball point pen represented in the drawing is known and is therefore not described in detail.

The force sensor 134 experiences the following stresses in the different operating positions:

1. In the switched-off condition, it is unstressed.

2. When switching on, the switching force is transferred from the thrust device 4 via the force sensor 134 to the spring 114 in order to indent the lead 11. Additionally, there are the inertial forces which are created through the acceleration of the lead/battery combination from the rest position. However, these are generally low because the sum of all these forces is equal to the force on the finger of the user with which the latter activates the pen.

3. In the working position, the force of the tensioned spring 114 for indenting the lead 11 acts on the force sensor 134 together with the longitudinal component of the writing force, i.e. the force with which the writing tip 110 is pressed onto the writing pad. In this operating position, the highest stress on the force sensor 134 is to be expected. In order to limit this force, the circuit board 13 can be elastically fixed in the interior of the thrust device

4. This solution is not shown in the drawing. 4. Then, apart from the inertial forces, if the user leaves their finger on the thrust device 4 and thus slows down the process, the forces during retraction are the same as the forces during expansion of the mechanism. However, if they let the mechanism snap back, first only the inertial force of the thrust device 4 itself minus the force of the thrust device spring 131 bears on the force sensor 134. However, when reaching the end position which is characterized by the abutment of the switching ring 5 on the stop at the barrel end 3, the lead/battery combination is abruptly slowed down in the slide 10 and the full force required for this would have to be guided via the force sensor 134 with a conventional construction of the pen.

The special feature of the pen according to the invention compared to the conventional pen is that the lead/battery combination reaches its stop in the form of the abutment 22 inside the barrel tube 2 in the slide 10 before the switching ring 5 drives to its stop. Thus, the full inertial force from slowing down the lead/battery combination is caught by the abutment 22 in the slide 10 and the force sensor 134 remains unaffected. Thus, in the example embodiment shown in the drawing, the diameter of the slide 10 at the location of the abutment 22 is larger than the diameter of the thrust device 4 which dives through the opening limited by the abutment 22.

The features of the invention disclosed in the above description, the claims and the drawing can be essential for the implementation of the invention in its different embodiments both individually and in any combination.