GB2157234A

GB2157234A - Reciprocating carrier, for example, in a printer

Info

Publication number: GB2157234A
Application number: GB08508073A
Authority: GB
Inventors: Bjorn Lorentz Wijkstrom; Gerth Erik Berton Fohlin; Rolf Sture Knut Johansson
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 1984-04-12
Filing date: 1985-03-28
Publication date: 1985-10-23
Also published as: SE8402057D0; GB8508073D0; SE8402057L

Abstract

In a positional sensing device for a motor driven reciprocating carrier (1) eg, for a printer. The motor, a sensing disc (8) rotatable in response to the linear displacement of the carrier, and control means actuable by the sensing disc are mounted on the carrier and form a compact unit together with the carrier. The carrier is moved by a motor driven helically around drum 7 and a line 10. The line 10 and a support rail 2 form an angle corresponding to the helix angle of the drum 7. The line 10 can be attached to the drum. <IMAGE>

Description

SPECIFICATION Positional sensing device for a motor-driven reciprocating means The present invention relates to a positional sensing device for a motor-driven reciprocating means arranged on a substrate, e.g. the carriage or carrier of a printer. More, specifically, there is intended a positional sensing device having a rotatable sensing member, the angular movement of which is proportional to the linear displacement of the reciprocating means.

It is known from the IBM Technical Disclosure Bulletin, Vol. 23, No. 6, Nov. 1980, pages 2358-2359 to drive a carrier for a printer with the aid of lines runing between a motor and the carrier. A first line driven by a motor drives a rotatable sensing disc, the angular movement of which is proportional to the motor's rotational angle. The carrier is connected to a second line running over a shaft through the sensing disc.

French Patent 20 85 581 teaches a similar sensing disc mounted directly on the motor shaft, the carrier then being driven by a single line.

A disadvantage with these known apparatus is that there is a large risk for errors in the positional determination of the carrier. Stretching in the lines namely results in that the carrier position does not necessarily coicide with that indicated by the sensing disc.

According to the present invention, there is provided a positional sensing device for a reciprocating means driven by a motor and arranged on a sub-structure and between two end walls, the device including a sensing member rotatably mounted on said reciprocating means, the member being provided with a rotating drive means and having its angular movement proportional to the linear displacement of the reciprocating means, in which device: the motor and a control means actuable by the sensing means are arranged on the reciprocating means, and together with the sensing means form a compact unit; the drive means comprises a rotatable drum provided with a helical groove; and first and second lines are each attached at one of their respective ends to a respective one of opposite end portion of the drum, and are wound towards its central portion, the other ends of the lines being attached to respective ones of said end walls such that the drum is urged to rotate when the lines are wound on and off as as result of the linear movement of the reciprocating means.

The invention will now be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a plan view of an example of a device according to the invention; and Figure 2 illustrates an improved implementation of a rotating drive means included in the device.

A carrier 1 for a printer is illustrated in Figure 1, conventionally equipped with a linear motor. The carrier is mounted on a support rail 2, fixed to a frame 3 between two end walls 4a, 4b. On the carrier, a shaft 5 is mounted in a bearing 6 at right angles to the direction of movement of the carrier. At one end of the shaft there is attached a drum 7 with a helical groove, and at its other end a sensing disc 8, e.g. an optically readable code disc.

Adjacent the code disc there is also an optical sensing means, 9,, e.g. in the form of a calliper extending round the code disc and mounted on the carrier 1. A line 10 stretched between the end walls 4a, 4b of the frame 3 is wound a few turns round the drum. The lines and support rail 2 form an angle corresponding to the helix angle of the helical groove, so that the line on each side of the drum runs parallel to the shaft 5 of the code disc as well as the centre of the support rail 2. This achieves that variations in the line tension due to the position of the carrier are substantially avoided.

The device functions in the following manner.

When the carrier 1 is moved sideways with the aid of its motor, the drum 7 is rotated and thereby the code disc 8 as well. The angular movement of the latter is detected by the optical sensing means 9, an unillustrated control means then ensuring that the carrier will be stopped in a desired position, corresponding to a given angular position of the code disc.

With the device, the indication given by the positional indicator has considerably better conformity with the exact position of the carrier than is the case in known devices. By the drum and code disc being comparatively light with reference to the carrier, the tension in the line will namely be relatively low and thereby the stretch will be minimal.

In the improved embodiment of the rotating drive means as seen in Figure 2, the line 10 comprises two parts 10a and 10b. Each part is attached at one end of one of the frame end walls 4a, 4b, and at its other end to a respective one of corresponding end portions 7a, 7b of the drum. The line parts are wound round the drum towards the middle of it, so that they are accomodated in adjacent grooves.

Since the lines are attached to the drum, the risk of slip between line and drum is substantially avoided. Furthermore it is achieved that the points of attack of the lines in respect of the drum come closer to each other, the torque striving to bend the drum thus being reduced.

1. A positional sensing device for a reciprocating means driven by a motor and arranged on a sub-structure and between the end walls, the device including a sensing member rotatably mounted on said reciprocating means, the member being provided with a rotating drive means and having its angular movement proportional to the linear displacement of the reciprocating means, in which device: the motor and a control means actuable by the sensing means are arranged on the reciprocating means, and together with the sensing means for a compact unit; the drive means comprises a rotatable drum provided with a helical groove; and first and second lines are each at

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Positional sensing device for a motor-driven reciprocating means The present invention relates to a positional sensing device for a motor-driven reciprocating means arranged on a substrate, e.g. the carriage or carrier of a printer. More, specifically, there is intended a positional sensing device having a rotatable sensing member, the angular movement of which is proportional to the linear displacement of the reciprocating means. It is known from the IBM Technical Disclosure Bulletin, Vol. 23, No. 6, Nov. 1980, pages 2358-2359 to drive a carrier for a printer with the aid of lines runing between a motor and the carrier. A first line driven by a motor drives a rotatable sensing disc, the angular movement of which is proportional to the motor's rotational angle. The carrier is connected to a second line running over a shaft through the sensing disc. French Patent 20 85 581 teaches a similar sensing disc mounted directly on the motor shaft, the carrier then being driven by a single line. A disadvantage with these known apparatus is that there is a large risk for errors in the positional determination of the carrier. Stretching in the lines namely results in that the carrier position does not necessarily coicide with that indicated by the sensing disc. According to the present invention, there is provided a positional sensing device for a reciprocating means driven by a motor and arranged on a sub-structure and between two end walls, the device including a sensing member rotatably mounted on said reciprocating means, the member being provided with a rotating drive means and having its angular movement proportional to the linear displacement of the reciprocating means, in which device: the motor and a control means actuable by the sensing means are arranged on the reciprocating means, and together with the sensing means form a compact unit; the drive means comprises a rotatable drum provided with a helical groove; and first and second lines are each attached at one of their respective ends to a respective one of opposite end portion of the drum, and are wound towards its central portion, the other ends of the lines being attached to respective ones of said end walls such that the drum is urged to rotate when the lines are wound on and off as as result of the linear movement of the reciprocating means. The invention will now be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a plan view of an example of a device according to the invention; and Figure 2 illustrates an improved implementation of a rotating drive means included in the device. A carrier 1 for a printer is illustrated in Figure 1, conventionally equipped with a linear motor. The carrier is mounted on a support rail 2, fixed to a frame 3 between two end walls 4a, 4b. On the carrier, a shaft 5 is mounted in a bearing 6 at right angles to the direction of movement of the carrier. At one end of the shaft there is attached a drum 7 with a helical groove, and at its other end a sensing disc 8, e.g. an optically readable code disc. Adjacent the code disc there is also an optical sensing means, 9,, e.g. in the form of a calliper extending round the code disc and mounted on the carrier 1. A line 10 stretched between the end walls 4a, 4b of the frame 3 is wound a few turns round the drum. The lines and support rail 2 form an angle corresponding to the helix angle of the helical groove, so that the line on each side of the drum runs parallel to the shaft 5 of the code disc as well as the centre of the support rail 2. This achieves that variations in the line tension due to the position of the carrier are substantially avoided. The device functions in the following manner. When the carrier 1 is moved sideways with the aid of its motor, the drum 7 is rotated and thereby the code disc 8 as well. The angular movement of the latter is detected by the optical sensing means 9, an unillustrated control means then ensuring that the carrier will be stopped in a desired position, corresponding to a given angular position of the code disc. With the device, the indication given by the positional indicator has considerably better conformity with the exact position of the carrier than is the case in known devices. By the drum and code disc being comparatively light with reference to the carrier, the tension in the line will namely be relatively low and thereby the stretch will be minimal. In the improved embodiment of the rotating drive means as seen in Figure 2, the line 10 comprises two parts 10a and 10b. Each part is attached at one end of one of the frame end walls 4a, 4b, and at its other end to a respective one of corresponding end portions 7a, 7b of the drum. The line parts are wound round the drum towards the middle of it, so that they are accomodated in adjacent grooves. Since the lines are attached to the drum, the risk of slip between line and drum is substantially avoided. Furthermore it is achieved that the points of attack of the lines in respect of the drum come closer to each other, the torque striving to bend the drum thus being reduced. CLAIMS

1. A positional sensing device for a reciprocating means driven by a motor and arranged on a sub-structure and between the end walls, the device including a sensing member rotatably mounted on said reciprocating means, the member being provided with a rotating drive means and having its angular movement proportional to the linear displacement of the reciprocating means, in which device: the motor and a control means actuable by the sensing means are arranged on the reciprocating means, and together with the sensing means for a compact unit; the drive means comprises a rotatable drum provided with a helical groove; and first and second lines are each at tached at one of their respective ends to a respective one of opposite end portion of the drum, and are wound towards its central portion, the other ends of the lines being attached to respective ones of said end walls such that the drum is urged to rotate when the lines are wound on and off as a result of the linear movement of the reciprocating means.

2. A device as claimed in claim 1, wherein said reciprocating means comprises a carriage or carrier for a printer.

3. A device as claimed in claim 1 or 2, wherein said sensing member comprises a sensing disc.

4. A device as claimed in any preceding claim, wherein the lines and the direction of movement of the reciprocating means form an angle corresponding to the helix angle of the helical groove.

5. A positional sensing device, substantially as herein described with reference to the accompanying drawing.