WO1999016071A1

WO1999016071A1 - Pickup base transferring device for disc player

Info

Publication number: WO1999016071A1
Application number: PCT/KR1998/000282
Authority: WO
Inventors: Beoung-Chel Park
Original assignee: Daewoo Electronics Co., Ltd.
Priority date: 1997-09-20
Filing date: 1998-09-16
Publication date: 1999-04-01
Also published as: CN1276084A

Abstract

A pickup base transferring device for a disc player has a driving motor installed on a deck for providing driving force to move a pickup base; a gear group for being driven by the driving motor; and a transferring part for transferring a pickup base in a radial direction of a disc by changing a rotational movement of the gear group into a linear movement of the pickup base. The transferring part has a base member of which one side part is fixed at the pickup base, a floating frame member for being connected with a driven gear of the gear group to be transferred along a transfer direction of the pickup base, the floating frame member having a rack gear extended along the transfer direction of the pickup base, the rack gear being engaged with the driven gear of the gear group, so that the floating frame member transfers along the transfer direction of the pickup base by an engagement of gears, and the floating frame member transfers along the transfer direction of the pickup base while sliding by a predetermined width on the base member, and an elastic member for connecting the floating frame member with the base member under an elastically slidable condition to absorb an impact applied to the base member when a moving state of the floating frame member is changed.

Description

PICKUP BASE TRANSFERRING DEVICE FOR DISC PLAYER

TECHNICAL FIELD

The present invention relates to a pickup base transferring device for a disc player, more particularly to a pickup base transferring device for a disc player for absorbing shock applied to a pickup base when the pickup base is transferred.

BACKGROUND ART

Recently, there has been developed a data recording and/or reproducing system using an optical disc such as a laser disc or compact disc.

Such system has an optical pickup actuator for reproducing data by irradiating laser beam along the data-recorded tracks of the discs and then detecting the beam reflected from the track for converting it to electrical signals.

The optical pickup actuator reproduces data recorded along the spiral track of a disc while moving in a radial direction of the disc. The optical pickup actuator is mounted on the pickup base and moves m the radial direction of the disc by a driving motor and a gear group m a desired speed.

A disc player being provided with the above- mentioned optical pickup transferring device is disclosed in U.S. P. 5,029,157 (issued at July 11, 1991) and 5,119,362 (issued at June 2, 1992).

Fig. 1 is a front cross-sectional view schematically illustrating a state of a conventional pickup base transferring device applied m a disc player. As shown m Fig. 1, an optical pickup actuator 12 is mounted at a pickup base 10. The pickup base 10 moves toward the center of the disc player from the outer circumference of a disc 40 in a horizontal direction to reproduce information recorded on spiral tracks of disc 40.

A transferring part for transferring the pickup base 10 has the following construction.

Two guide shafts 20 are installed parallel with each other for guiding the pickup base 10 with precision, disposed beneath the radial direction of disc 40, and thus, enabling the pickup base 10 to be moved toward the center from the outside of disc 40 in the radial direction of disc 40. The pickup base 10 is provided with a rack gear 14 which is formed parallel with guide shaft 20 at a side surface of the pickup base 10.

The driving motor 30, rotatable in high speed, is installed at a side part of the guide shaft 20. A speed reduction gear group 50 has a plurality of reduction gear interlocked to the driving motor 30 to reduce the rotational speed and increase power. A pinion gear 54 as a driven gear of the speed reduction gear group 50 engages with the rack gear 14 formed at the pickup base 10.

Thus, the pickup base 10, which the pinion gear 54 is engaged with, the rack gear 14 is movable with low speed along the guide shaft by speed-reducing operation of the speed reduction gear group 50 and the driving motor 30.

Accordingly, when the pickup base 10 moves under the disc 40 toward the center from the outside of disc 40 in the radial direction of disc 40 along the guide shaft 20 by the operation of the driving motor 30, the optical pickup actuator 12 mounted on the pickup base 10 is operated to reproduce the signal recorded in the disc 40. The pickup base 10 returns under the disc 40 toward the outside of disc 40 from the center in the radial direction of disc 40 along the guide shaft 20 by the reverse rotation of the driving motor 30. According to the above-mentioned pickup base transferring device, the rack gear 14, the speed reduction gear group 50 connected with the rack gear 14, and the driving motor 30 connected with the speed reduction gear group 50 are tightly interlocked, and the driving force of the motor 30 is transmitted to the pickup base 10 with minimal loss of energy.

When the pickup base 10 with the tightly interlocked construction is mounted on the CD ROMs or DVD ROMs to be driven by the driving motor 40, the pickup base 10 with the pickup actuator 12 moves at high speed for searching information recorded in the disc 40. At this time, the driving motor 40 may be start the rotational movement in the clockwise or counterclockwise direction, or may be stop the rotational movement in high speed. The sudden change of moving state of the driving motor 40 is transmitted to the speed reduction gear group 50 and the pickup base 10, and thereby, overloading the speed reduction gear group 50 and the pickup base 10, damaging gearing elements such as gear teeth, thus, decreasing the expected life of the gearing elements.

Furthermore, the sudden changes m the speed reduction gear group 50 and the pickup base 10 generates an excessive vibration to the actuator 12, thus causing the laser beam for reproducing the signal to be out of focus on the pit of the disc 40. Hense, reproduction sensitivity is deteriorated.

DISCLOSURE OF INVENTION Therefore, the present invention has been proposed to overcome the above described problems m the prior art, and accordingly it is an object of the present invention to provide a pickup base transferring device for a disc player for absorbing shock applied to a pickup base when the pickup base is transferred.

To achieve the above objects, the pickup base transferring device for the disc player comprises a driving motor installed on a deck for providing driving force to move a pickup base; a gear group for being driven by the driving motor; and a transferring part for transferring a pickup base in a radial direction of a disc by changing a rotational movement of the gear group into a linear movement of the pickup base, wherein the transferring part has a base member of which one side part is fixed at the pickup base; a floating frame member for being connected with a driven gear of the gear group to be transferred along a transfer direction of the pickup base, the floating frame member having a rack gear extended along the transfer direction of the pickup base, the rack gear being engaged with the driven gear of the gear group, so that the floating frame member transfers along the transfer direction of the pickup base by an engagement of gears, and the floating frame member transfers along the transfer direction of the pickup base while sliding by a predetermined width on the base member; and an elastic member for connecting the floating frame member with the base member under an elastically slidable condition to absorb an impact applied the base member when a moving state of the floating frame member is changed.

The elastic member comprises a pair of elastic pieces which are respectively formed at both sides of the floating frame member corresponding to the transfer direction of the pickup base. Stops are respectively formed at both sides of the base member corresponding to the elastic member of the floating frame member. Thus, when the floating frame member is moved by driving of the driving motor, the base member is elastically slidable against the floating frame member along the transfer direction of the pickup base, and therefore when the moving state of the floating frame member is changed, the impact applied to the base member can be absorbed by the elastic pieces.

The elastic member comprises a pair of springs. The floating frame member has a guide hole portion having a hole extended along the transfer direction of the pickup base at the central part thereof. The base member has a supporting part projected on the central part of the base member to be inserted into the hole. First and second projectors are projected along the transfer direction of the pickup base from both side part of the supporting part. Third and fourth projectors are respectively projected from inner side surfaces of the guide hole portion along the transfer direction of the pickup base. First and second springs are respectively displaced between the first and third projectors and between the second and fourth projectors. Thus, the base member is elastically slidable against the floating frame member along the transfer direction of the pickup base by the first and the second springs, and therefore when the moving state of the floating frame member is changed, the impact applied to the base member can be absorbed by the first and the second springs.

BRIEF DESCRIPTION OF THE DRAWINGS The above objects and other advantages of the present invention will become more apparent by describing m detail preferred embodiment thereof with reference to the attached drawings in which: Fig. 1 is a front cross-sectional view for schematically illustrating a state of a conventional pickup base transferring device applied in a disc player, Fig. 2 is an exploded perspective view for showing a transferring part of a pickup base transferring device for a disc player according to a first embodiment of the present invention,

Fig. 3 is a schematic plan sectional view for showing the pickup base transferring device for the disc player of Fig. 2, Fig. 4 is a front cross-sectional view for schematically showing a state of the pickup base transferring device for the disc player of Fig. 2 applied m a disc player,

Fig. 5 is an exploded perspective view for showing a transferring part of a pickup base transferring device for a disc player according to a second embodiment of the present invention, and

Fig. 6 is a schematic plan sectional view for showing the pickup base transferring device for the disc player of Fig. 5.

BEST MODE FOR CARRYING OUT OF THE INVENTION

The preferred embodiments of the present invention will now be described m detail with reference to the accompanying drawings .

Embodiment 1

Hereinafter, the pickup base transferring device for the disc player according to the embodiment 1 will be described m detail with reference to the drawings.

Fig. 2 is an exploded perspective view for showing a transferring part of a pickup base transferring device for a disc player according to a first embodiment of the present invention. Fig. 3 is a schematic plan sectional view for showing the pickup base transferring device for the disc player of Fig. 2. Fig. 4 is a front cross- sectional view for schematically showing a state of the pickup base transferring device for the disc player of Fig. 2, applied in the disc player.

A pair of guide shaft 114 are installed along a radial direction of a disc 120 of the disc player to precisely guide a pickup base 110 mounting an optical pickup actuator 112. The pickup base 110 is slidable along the guide shafts 114.

A driving motor 130 is installed on a deck for providing driving force to move the pickup base 110. A gear group 150 makes contact with the driving motor 130 to be driven by the driving motor 130. The gear group 150 is a speed reduction gear group which has a plurality of reduction gear interlocked to the driving motor 130 to reduce the rotational speed and increase power.

A transferring part 100 transfers the pickup base 110 in the radial direction of the disc 120 by changing a rotational movement of the gear group 150 into a linear movement of the pickup base 110.

The transferring part 100, as shown in Fig. 2, has a floating frame member 140, elastic pieces 144 and 144', and a base member 160.

The base member 160 has one side edge parallel with the transfer direction which is fixed to the pickup base 110. The side edge of the base member 160 is provided with a plurality of side holes 167, and a plurality of oin protrusions formed at a side edge of the pickup base 110 are inserted into the side holes 167 formed at the side edge of the base member 160, and thereby the base member 160 is fixed to the pickup base 110. The floating frame member 140 is connected with a driven gear 154 of the gear group 150 to be transferred along a transfer direction of the pickup base 110. The floating frame member 140 has a rack gear 142 extended along the transfer direction of the pickup base 110. The rack gear 142 is engaged with the driven gear 154 of the gear group 150. Thus, the floating frame member 140 transfers along the transfer direction of the pickup base by an engagement of gears .

The floating frame member 140 has a guide hole portion 148 having a hole extended along the transfer direction of the pickup base 110 at the central part thereof. A pair of bosses 162 are installed on the base member 160 so as to be inserted into the guide hole portion 148 of the floating frame member 140. Thus, the floating frame member 140 and the base member 160 is slidably connected to each other along the transfer direction of the pickup base 110 in a state that the bosses 162 of the base member 160 are inserted into the hole of the guide hole portion 148 of the floating frame member 140. Caps 168 are respectively put on the bosses 162 of the base member 160 to prevent the floating frame member 140 from being separated upwardly.

A pair of elastic pieces 144, 144' are respectively formed at both sides of the floating frame member 140 corresponding to the transfer direction of the pickup base 110. Stops 164, 164' are respectively formed at both sides of the base member 160 corresponding to the elastic pieces 144, 144' of the floating frame member 140. Thus, when the floating frame member 140 is moved by the driving motor 110, the base member 160 is elastically slidable against the floating frame member 140 by the elastic pieces 144, 144' along the transfer direction of the pickup base. Therefore, when the moving state of the floating frame member 140 abruptly changes, the impact applied to the base member 160 can be absorbed by the elastic pieces 144, 144'.

Hereinafter, the operation of the above-mentioned pickup base transferring device will be described in detail.

When the pickup base transferring device according to the embodiment 1 is applied m CD ROMs or DVD ROMs, the pickup actuator 112 mounted on the pickup base 110 is moved at high speed in the radial direction of the disc 120 for searching information recorded in the disc 120. As shown m Figs. 3 and 4, when the driving motor 130 starts its rotational movement at high speed in the clockwise direction, the rotational force is transmitted through the speed reduction gear group 150 interlocked to the driving motor 130 to the driven gear, i.e., pinion gear 154. Thus, the rotational force of the pinion gear 154 is delivered to the rack gear 142 of the floating frame member 140. Since the speed reduction gear group 150 is composed of even gears, the pinion gear 154 is counterclockwise rotated.

Thus, the floating frame member 140 starts to move toward the center of the disc 120, i.e., to the left m Fig. 3 or 4. Though the floating frame member 140 starts to suddenly move to the left by gear engagement, the base member 160 connected to the floating frame member 140 does not move suddenly while the left elastic piece 144 of the floating frame member 140 touches the stop 164 so that the base member 160 can be elastically moved by the elastic piece 144. Accordingly, though the sudden change of moving state of the speed reduction gear group 150 generated by the sudden change of moving state of the driving motor 140 is transmitted to the floating frame member 140, the base member 160, elastically slidable against the floating frame member 140 by the elastic pieces 144, 144' along the transfer direction of the pickup base, starts to move gradually since the impact applied to the base member 160 is absorbed by the elastic pieces 144, 144 * . Therefore, the pickup base 110 fixed to the base member 160 can start to move gently and slowly without excessive impact.

Meanwhile, when the pickup actuator 112 mounted on the pickup base 110 has found the information on the disc 120, the driving motor 130 stops suddenly to stop the pickup base 110. At the same time, the right elastic piece 144' of the floating frame member 140 engaged with the pinion gear 154 touches the stop 164 ' so that the base member 160 can be elastically moved by the elastic piece 144'. Accordingly, though the sudden stop of the speed reduction gear group 150 generated by the sudden stop of the driving motor 140 abruptly stops the floating frame member 140, the base member 160 slides elastically against the floating frame member 140 by the elastic pieces 144, 144' along the transfer direction of the pickup base. That is, the impact applied to the base member 160 can be absorbed by the elastic pieces 144, 144', and thus the base member 160 stops gently and slowly . Therefore, the pickup base 110 fixed to the base member 160 can stop gently and slowly without excessive impact .

Accordingly, though the sudden change of moving state of the speed reduction gear group 150 and the driving motor 140 is transmitted to the floating frame member 140, the elastic pieces 144, 144' of the floating frame member 140 of the transferring part 100 absorb the impact. Thereby, the excessive impact is not transmitted to the base member 160 and pickup base 110, so that the optical pickup actuator 112 mounted on the pickup base 110 is prevented from unnecessary vibration, whereby information in the disc can be recorded or reproduced with precision. Furthermore, due to the impact absorption of the elastic pieces 144, 144' of the transferring part 100, the constituent elements such as the driving motor 130, gears of the gear group 150, and the pickup base 110 are not overloaded, whereby they can be prevented from being damaged.

Meanwhile, the similar operational effect can be achieved in the case when the pickup base 110 suddenly starts or stops to move toward the outside of the disc 120, i.e., to the right m Fig. 3 and 4.

Embodiment 2

Hereinafter, the pickup base transferring device for the disc player according to the embodiment 2 will be described m detail with reference to the drawings.

Fig. 5 is an exploded perspective view for showing a transferring part of a pickup base transferring device for a disc player according to a second embodiment of the present invention. Fig. 6 is a schematic plan sectional view for showing the pickup base transferring device for the disc player of Fig. 5. A pair of guide shaft 214 are installed along a radial direction of a disc 220 of the disc player to precisely guide a pickup base 210 mounting an optical pickup actuator 212. The pickup base 210 is slidable along the guide shafts 214.

A driving motor 230 is installed on a deck for providing driving force to move the pickup base 210. A gear group 250 makes contact with the driving motor 230 to be driven by the driving motor 230. The gear group 250 is a speed reduction gear group which comprises a plurality of reduction gear interlocked to the driving motor 230 to reduce the rotational speed and increase power . A transferring part 200 transfers the pickup base

210 in the radial direction of the disc 220 by changing a rotational movement of the gear group 250 into a linear movement of the pickup base 210.

The transferring part 200, as shown in Fig. 2, has a floating frame member 240, elastic pieces 244 and 244', and a base member 260.

The base member 260 has one side edge parallel with the transfer direction which is fixed to the pickup base 210. The side edge of the base member 260 is provided with a plurality of side holes 267, and a plurality of join protrusions formed at a side edge of the pickup base 210 are inserted into the side holes 267 formed at the side edge of the base member 260, and thereby the base member 260 is fixed to the pickup base 210. A floating frame member 240 is connected with a driven gear 254 of the gear group 250 to be transferred along a transfer direction of the pickup base 210. The floating frame member 240 has a rack gear 242 extended along the transfer direction of the pickup base 210. The rack gear 242 is engaged with the driven gear 254 of the gear group 250. Thus, the floating frame member 240 transfers along the transfer direction of the pickup base by an engagement of gears.

The floating frame member 240 has a guide hole portion 248 having a hole extended along the transfer direction of the pickup base 210 at the central part thereof. A supporting part 268 is projected on the central part of the base member 260 to be inserted into the hole of guide hole portion 248. Thus, the floating frame member 240 and the base member 260 is slidably connected to each other along the transfer direction of the pickup base 210 in a state that the supporting part 268 of the base member 260 are inserted into the hole of the guide hole portion 248 of the floating frame member 240. First and second projectors 266, 266' are projected along the transfer direction of the pickup base from both side parts of the supporting part 268. Third and fourth projectors 246, 246' are respectively projected from inner side surfaces of the guide hole portion 248 along the transfer direction of the pickup base. First and second springs 270, 270' are respectively displaced between the first and third projectors 266, 246 and between the second and fourth projectors 266', 246'. Thus, the base member 260 is elastically slidable against the floating frame member 240 along the transfer direction of the pickup base by the elastic movement of the first and the second springs 270, 270'.

Stops 262, 262' are respectively formed at both sides of the base member 260 crossing the transfer direction of the pickup base so as to stop the floating frame member 240. The Stops 262, 262' are respectively provided with guide grooves 264, 264' formed along the transfer direction of the pickup base so as to guide the floating frame member 240. The floating frame member 240 has guide pieces 244, 244' formed corresponding to guide grooves 264, 264' to move the guide pieces 244, 244' along the guide grooves 264, 264'.

A pair of bosses 272 are installed on the base member 260. The floating frame member 240 has a pair of contact hole portions 246 corresponding to the bosses 272. The contact hole portions 246, 246' have respectively holes extended along the transfer direction of the pickup base 110. Thus, the bosses 272 are respectively inserted into the guide hole portions 246 of the floating frame member 140 and also slidable in the guide hole portions 246. Caps 252 are respectively put on the bosses 272 of the base member 260 to prevent the floating frame member 240 from being separated upwardly.

Thus, the floating frame member 240 and the base member 260 are slidably connected to each other along the transfer direction of the pickup base by the first and the second springs 270, 270'. Therefore, when the moving state of the floating frame member 240 is changed, the impact applied to the base member 260 can be absorbed by the first and the second springs 270, 270'.

Hereinafter, the operation of the above-mentioned pickup base transferring device will be described in detail .

When the pickup base transferring device according to the embodiment 2 is applied in CD ROMs or DVD ROMs, the pickup actuator 212 mounted on the pickup base 210 is moved at high speed in the radial direction of the disc 220 for searching information recorded in the disc 220. As shown in Figs. 5 and 6, when the driving motor 230 starts its rotational movement at high speed in the clockwise direction, the rotational force is transmitted through the speed reduction gear group 250 interlocked to the driving motor 230 to the driven gear, i.e., pinion gear 254. Thus, the rotational force of the pinion gear 254 is delivered to the rack gear 242 of the floating frame member 240. Since the speed reduction gear group 250 is composed of even gears, the pinion gear 254 is counterclockwise rotated.

Thus, the floating frame member 240 starts to move toward the center of the disc 220, i.e., to the left in Figs. 3 and 4. Though the floating frame member 240 starts to suddenly move to the left by gear engagement, the base member 260 connected to the floating frame member 240 does not move suddenly while the right spring 270' positioned m the hole of floating frame member 240 touches the supporting part 268 of base member 260 so that the base member 260 can be elastically moved by the spring 270'. Accordingly, though the sudden change of moving state of the speed reduction gear group 250 generated by the sudden change of moving state of the driving motor 230 is transmitted to the floating frame member 240, the base member 260, elastically slidable against the floating frame member 240 by the springs 270, 270' along the transfer direction of the pickup base, starts moves gradually since the impact applied to the base member 260 is absorbed by the springs 270, 270'. Therefore, the pickup base 210 fixed to the base member 260 can start to move gently and slowly without excessive impact.

Meanwhile, when the pickup actuator 212 mounted on the pickup base 210 has found the information situation under the disc 220, the driving motor 230 stops suddenly to stop the pickup base 210. At the same time, the left spring 270 of the floating frame member 240 engaged with the pinion gear 254 touches the supporting part 268 of base memoer 260 so that the base member 260 can be elastically moved by the spring 270. Accordingly, though the sudden change of moving state of the speed reduction gear group 250 generated by the sudden change of moving state of the driving motor 230 is transmitted to the floating frame member 240, the base member 260 slides elastically against the floating frame member 240 by the springs 270, 270' along the transfer direction of the pickup base; that is, the impact applied to the base member 260 can be absorbed by the springs 270, 270'. Therefore, the pickup base 210 fixed to the base member 260 can stop gently and slowly without excessive impact .

Accordingly, though the sudden change of moving state of the speed reduction gear group 250 and the driving motor 240 is transmitted to the floating frame member 240, the first and second springs 270, 270' of the floating frame member 240 of the transferring part 200 absorb the impact. Thereby, the excessive impact is not transmitted to the base member 260 and pickup base 210, so the optical pickup actuator 212 mounted on the pickup base 210 is prevented from unnecessary vibration, whereby information in the disc can be recorded or reproduced with precision. Furthermore, due to the impact absorption of the elastic pieces 270, 270' of the transferring part 200, the constituent elements such as the driving motor 230, gears of the gear group 250, and the pickup base 210 are not overloaded, whereby they can be prevented from being damaged.

Meanwhile, the similar operational effect can be achieved in the case when the pickup base 210 suddenly starts or stops to move toward the outside of the disc 220, i.e., to the right in Figs. 5 and 6.

In the above, the present invention is described in detail by using the preferred embodiment, but the invention is not limited to the above embodiment. It should be obvious to people skilled in the conventional art that modifications can be made to the invention as described above without departing from the spirit or the scope of the invention. However the invention is limited by the accompanying claims as below.

Claims

CLAIMS :

1. A pickup base transferring device for a disc player comprising: driving means for providing a driving force to move a pickup base; a gear group for being driven by the driving means; and a transferring part for transferring a pickup base m a radial direction of a disc by changing a rotational movement of the gear group into a linear movement of the pickup base, wherein the transferring part has a base member of which one side part is fixed at the pickup base; a floating frame member for being connected with a driven gear of the gear group to be transferred along a transfer direction of the pickup base, the floating frame member having a rack gear extended along the transfer direction of the pickup base, the rack gear being engaged with the driven gear of the gear group; and an elastic member for elastically connecting the floating frame member with the base member to absorb an impact applied the base member when a moving state of the floating frame member is changed.

2. A pickup base transferring device for a disc player according to claim 1, wherein the elastic member comprises a pair of elastic pieces which are respectively formed at both sides of the floating frame member corresponding to the transfer direction of the pickup base, the base member has stops respectively formed at both sides of the base member corresponding to the elastic pieces of the floating frame member, whereby when the floating frame member is moved by driving of the driving means, the base member is elastically slidable against the floating frame member along the transfer direction of the pickup base.

3. A pickup base transferring device for a disc player according to claim 2, wherein the floating frame member has a guide hole portion having a hole extended along the transfer direction of the pickup base at the central part thereof, and the base member has a pair of bosses installed thereon so as to be inserted into the guide hole portion of the floating frame member.

4. A pickup base transferring device for a disc player according to claim 1, wherein the elastic member comprises a pair of springs, the floating frame member has a guide hole portion having a hole extended along the transfer direction of the pickup base at the central part thereof, and the base member has a supporting part projected on the central part thereof to be inserted into the hole, first and second projectors are projected along the transfer direction of the pickup base from both side part of the supporting part, third and fourth projectors are respectively projected from inner side surfaces of the guide hole portion along the transfer direction of the pickup base, and first and second springs are respectively displaced between the first and third projectors and between the second and fourth projectors, whereby the base member is elastically slidable against the floating frame member along the transfer direction of the pickup base by the first and the second springs.

5. A pickup base transferring device for a disc player according to claim 4, wherein the base member has stops respectively formed at both sides thereof crossing the transfer direction of the pickup base so as to stop the floating frame member, the stops respectively has guide grooves formed along the transfer direction of the pickup base so as to guide the floating frame member, the floating frame member has guide pieces formed corresponding to guide grooves to move the guide pieces along the guide grooves.