JPS6141317B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a print head for a dot printer.

First, a conventional example is shown in FIG. 1 is a support member, and a plurality of electromagnets 2 are attached to this support member 1. The electromagnet 2 includes a coil 4 attached to a yoke 3 and an armature 5 rotatably attached. A lid 7 on which a stopper 6 for determining the return position of the armature 5 is supported is attached to the support member 1.

Next, a guide holder 8 is attached to the support member 1 with screws 9. This guide holder 8
Needle guides 11 and 12 that align and slidably hold a plurality of needles 10 are fixed to the front and center of the needle. Furthermore, a plate-shaped spring support 14 is fixed to the rear portion of the guide holder 8, through which the needle 10 is inserted and which receives one end of a needle spring 13 formed of a coil spring. The other ends of these needle springs 13 are in contact with a cap 15 fixed to the rear end of the needle 10. Further, a platen 18 is provided on the front surface of the needle guide 11 and holds a paper 17 facing the printing ribbon 16. And armature 5
Printing is performed by sliding a specific needle 10 using the suction action of the needle.

However, before the armature 5 is attached during assembly, the needle 10 slides due to the force of the needle spring 13, as shown in FIG.
The leading end retreats from the position C of the needle guide 11, and the rear end projects further rearward from the suction position A of the armature 5. Therefore, it is impossible to insert all the needles 10 through the needle guide 11 and maintain all the armatures 5 in a pressed state and install the stopper 6 in this state, so the needles 10 are inserted through the needle guide 11. In this way, the armatures 5 must be temporarily fixed one by one, and after the stopper 6 is attached, each armature must be released from the temporarily fixed state, which is an extremely troublesome work.

In order to solve this drawback, if the return position of each armature 5 is determined by a corresponding stopper 6, the work of temporarily fixing the armature 5 can be omitted, but since a stopper 6 is required for each armature 5, The number of parts increases, and since a large number of stoppers 6 are attached, the number of assembly steps increases.

As another means, as shown in Figure 3,
By using the needle spring 19 with a large spring constant, the tip of the needle 10 will not come off from the needle guide 11, and even if the rear end exceeds the suction position A of the armature 5, it will be maintained in a very slight state.
Thereby, the armature 5 and the stopper 6 can be easily assembled. However, as the needle 10 approaches the platen 18 during printing, the load on the needle spring 19 increases rapidly. Therefore, it becomes impossible to print unless the distance between the needle guide 11 and the platen 18 is narrowed, and as a result, the printing ribbon 16 stains the paper 17, and the electromagnet 2 also needs to have a large capacity. , it has disadvantages such as increased power consumption.

The present invention has been made in view of these points, and an object of the present invention is to provide a print head for a dot printer that can be easily assembled.

In this invention, an elastic locking pawl is formed on a spring support that supports one end of a needle spring, and during assembly, this spring support is advanced toward the platen side and positioned, thereby inserting the needle into the needle guide at the tip. This makes assembly of the armature and stopper extremely easy, and after assembly the spring support is fixed in the retracted position and the needle is not inserted into the armature. The contact force is determined, and the position of the spring holder is determined by the locking claw of the spring holder engaging the locking recess on the side away from the platen, so the operation is easy, especially if other parts are It is configured so that it is not necessary.

An embodiment of the present invention will be described based on FIGS. 4 to 6. Components that are the same as those described in FIGS. 1 to 3 are designated by the same reference numerals, and description thereof will be omitted. The guide holder 8 is a spring support body 20 on a disc that slidably holds the needle 10 and supports one end of the needle spring 13.
It is held so that it can slide freely in the front and rear directions. An elastic locking pawl 21 is integrally formed on the spring support 20 with its tip expanded. Next, locking recesses 22 and 23 that engage with the locking claws 23 are formed in the guide holder 8 in two stages.

In such a configuration, during assembly, the spring support 20 is advanced toward the platen 18 so that the locking pawl 21 is elastically engaged with the locking recess 22. At this advanced position B', the tip of the needle 10 does not come off the needle guide 1, and the rear end is located in front of the suction position A of the armature 5.
Therefore, the armature 5 and the stopper 6 can be assembled very easily without inserting the needle 10 into the needle guide 11 and without being affected by the needle spring 13. At the final stage of assembly, the locking pawl 23 is engaged with the locking recess 23 on the side away from the platen 18 to determine the contact force of the needle 10 against the armature 5. This state is shown in FIGS. 4 and 6a. When a specific electromagnetic force 2 is applied, the armature 5 moves to the suction position A as shown in FIG. 6b, and the needle 10 is struck by the armature 5, causing the needle spring 13 to bend as shown in FIG. 6c. It flies and collides with the platen 18. Needle spring 13 is stopper 6
Since this does not affect the assembly of the spring, it is possible to use a spring with a small spring constant, and the distance between the platen 18 and the tip of the needle 10 can be widened. As a result, the printing ribbon 16
The needle 10 can be driven by the electromagnet 2 having a small capacity without contaminating the paper 17, and power can be saved.

Since this invention is configured as described above, the spring support can be moved forward and the armature and stopper can be assembled without being affected by the needle spring, and the spring support has two stages attached to the guide holder. Since an elastic locking pawl is formed that engages with the engagement recess formed in the holder, positioning after assembly is extremely easy, and no special positioning parts are required. A needle spring with a small spring constant is used to widen the space between the tip of the needle and the platen, which prevents the printing ribbon from staining the paper, and also has the effect of saving power by driving the needle with a small electromagnet. It is.

[Brief explanation of the drawing]

FIG. 1 is a horizontal sectional view showing a conventional example, FIGS. 2 and 3 are partial horizontal sectional views showing the support structure of the needle spring, and FIG. 4 is a horizontal sectional view showing an embodiment of the present invention. , FIG. 5 is a horizontal cross-sectional view of a portion of the spring support with the spring support extended, and FIG.
The figure is a partial horizontal sectional view showing the operation of the armature and needle. DESCRIPTION OF SYMBOLS 1... Support member, 2... Electromagnet, 5... Armature, 6... Stopper, 8... Guide holder, 10... Needle, 11... Needle guide, 13... Needle spring, 18... Platen, 20... Spring support, 21... Locking Claws, 22, 23...locking recesses.

Claims (1)

[Claims] 1 A support member is provided with a plurality of electromagnets each having an armature whose return position is determined by a stopper,
A needle guide is fixed to a guide holder connected to the support member, which is located in front and slidably holds a plurality of needles in alignment facing a platen, and two needle guides are fixed to the guide holder on the rear side of the needle guide. An elastic locking pawl that selectively engages with the locking recess is provided on a spring support that supports one end of a needle spring that forms a step locking recess and biases the needle in a direction away from the platen. A print head for a dot printer, characterized in that the spring support is moved from a position advanced toward the platen to a retreat position where the contact force of the needle to the armature is increased and fixed therein.