JP2002365932A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify handling, to make an overall device small in size and light in weight, and to reduce manufacture cost by making a unit having a belt body light in weight and small in size. SOLUTION: This imaging device is equipped with a plurality of image carriers and a transfer means having the belt body, and forms an image by directly transferring images on a plurality of image carriers to sheet material carried on the belt body or secondarily transferring the image to the sheet material, after primarily transferring it to the belt body. The transfer means has one part or all of a support mechanism for supporting the belt body and is detachable from a device body, and a guiding member for guiding the supporting mechanism and a fixing means for positioning the support mechanism are provided in the device body. When the transfer means is attached to the device body, the support mechanism is guided by the guiding member and fixed by the fixing means, whereby the belt body is stretched and laid; and when the transfer means is detached from he device body, the tensile force of the belt body is released.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus such as a printer, a copying machine, a printing machine, and the like. In addition, the production cost can be reduced by improving the assembly accuracy and the assembly accuracy, and the size of the entire apparatus can be reduced.

[0002]

2. Description of the Related Art Conventionally, there has been provided an in-line type color image forming apparatus for obtaining a color image by arranging a plurality of image carriers in a line and superimposing toner images of respective colors. It transports an intermediate transfer belt (belt body) stretched by a plurality of rollers, and transfers yellow, magenta, cyan, and black toner images to the intermediate transfer belt by four image carriers arranged along a transport path. A color image is formed by sequentially performing primary transfer on the top and collectively performing secondary transfer on a sheet material. A configuration is also known in which a color image is similarly obtained by transferring toner images from a plurality of image carriers in a superimposed manner to a conveyed sheet material while conveying the sheet material by a suction conveyance belt (belt body). ing.

In an image forming apparatus using such a belt member as a transfer means, it is essential to stabilize the belt running property in order to prevent color misregistration at the time of transferring each color toner image, and to maintain the tension of the belt member. And guaranteeing mechanism is a very important design factor.

[0004]

In the case where the above-mentioned belt body is constituted as an intermediate transfer belt unit (hereinafter referred to as an ITB unit) detachable from the apparatus body for the purpose of replacing the belt body or maintaining the apparatus. There is. However, since the belt body needs to be stretched,
It is necessary to provide a tension control mechanism in the ITB unit,
It is necessary to design the ITB unit housing with sufficient strength and rigidity to withstand the tension. In addition, it is necessary to provide a drive roller, a transfer backup roller, a tension roller, etc. for stretching the belt inside the ITB unit, and to guarantee the distance between these axes and the axial position. It is necessary to make sure.

[0005] As a result, as a practical problem on the user side, the completed ITB unit is large and heavy without any change in the shape and size inside and outside the image forming apparatus. A great deal of labor is required when inserting and removing. Also, in order to avoid interference with other functional parts of the image forming apparatus main body,
It is necessary to make the opening of the apparatus body larger than expected.
In severe cases, the ITB unit weight may reach as much as about 78.4 N (8 kgf), assuming all the conditions of the image forming process. In addition, a large work space is required for temporarily placing the removed unit temporarily.

This is unsuitable for a general user to perform maintenance on a daily basis, so that maintenance costs are required in addition to the purchase cost and running cost of the image forming apparatus in order to inevitably receive periodic maintenance services and the like. It will be.

As a problem on the producer side, if the ITB unit has such a weight, the casing itself becomes large and heavy in order to maintain the strength and rigidity of the casing of the image forming apparatus main body. . For this reason, production costs are inevitable,
The product price of the image forming apparatus also becomes extremely high.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the weight and size of a unit having a belt body, thereby simplifying handling, reducing the size and weight of the entire apparatus, and reducing the production cost. .

[0009]

In order to solve the above problems, a typical configuration of an image forming apparatus according to the present invention comprises a plurality of image carriers and a transfer unit having a belt, An image forming apparatus for forming an image by directly transferring an image on an image carrier to a sheet material carried on the belt body, or by secondary-transferring to a sheet material after primary transfer on the belt body , The transfer means has a part or all of a support mechanism for supporting the belt body, is detachable from the apparatus main body, and has a guide means for guiding the support mechanism on the apparatus main body; And fixing means for positioning, when the transfer means is mounted on the apparatus body, the support mechanism is guided by the guide means,
The belt is stretched by being fixed by the fixing means, and the tension of the belt is released when the transfer means is detached from the apparatus main body.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A first embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a view for explaining the configuration of the transfer means according to the present embodiment, FIG. 2 is a view for explaining the operation of the transfer means, FIGS. 3 and 4 are views for explaining guide means of the apparatus main body, and FIG. 6 and 7 are diagrams for explaining the attaching / detaching operation of the transfer unit, and FIG. 8 is an overall configuration diagram of the image forming apparatus according to the present embodiment.

(Overall Configuration) First, the overall configuration of the image forming apparatus will be described with reference to FIG. FIG. 1 shows a color image forming apparatus to which the electrophotographic process technology is applied, and has a process cartridge 10 as an image forming unit for forming an image. Process cartridge 10Y, 10
M, 10C, and 10K form yellow, magenta, cyan, and black toner images, respectively.

Photosensitive drums 1Y to 1K as image carriers are provided in the process cartridges 10Y to 10K, and light sources 2Y to 2K for forming latent images are provided for the photosensitive drums 1Y to 1K. By irradiating light rays from the light sources 2Y to 2K, electrostatic latent images corresponding to the respective colors are formed on the photosensitive drums 1Y to 1K, and toner images of the respective colors are formed by a known electrophotographic process.

An intermediate transfer belt unit (hereinafter referred to as an ITB unit 100) as a transfer means is provided in the apparatus main body, and is configured to be detachable from the apparatus main body in a sheet conveying direction (the direction of arrow A in FIG. 1). are doing. ITB
Intermediate transfer belt 102 which is a belt body included in unit 100
Are arranged so as to be in contact with the respective photosensitive drums 1 and are rotated and conveyed in a direction indicated by an arrow B in the figure. Intermediate transfer belt
Reference numeral 102 denotes a resin or rubber belt having an electrostatic resistance value suitable for image transfer by an electrophotographic process.

Inside the intermediate transfer belt 102, primary transfer rollers 106Y to 106K are arranged.
The toner images formed on the photosensitive drums 1Y to 1K are superimposed and primary-transferred onto the intermediate transfer belt 102 at 0. When a monochrome image is formed, transfer is performed only from the photosensitive drum 1K, and transfer of other colors is not performed. The primary-transferred toner image is transferred to the secondary transfer roller 6 by driving the intermediate transfer belt 102.

In the lower part of the apparatus, there are provided a feeding section 3 for separating and feeding the sheet material S one by one and a conveying means 11, and a manual feeding section 4 is provided on the side of the apparatus. Sheet material S fed
Is transported to the pair of registration rollers 5 until the primary-transferred toner image reaches the secondary transfer roller, where the skew is corrected and the image forming apparatus stands by. And the intermediate transfer belt 102
The conveyance resumes in synchronization with the toner image above, and the intermediate transfer belt
The toner image on the intermediate transfer belt 102 is collectively and secondarily transferred to the nip between the secondary transfer roller 102 and the secondary transfer roller 6.
The sheet material S to which the toner image has been transferred is fixed by applying heat and pressure by a fixing device 8, discharged and stacked outside the device via a discharge unit 9.

(Transfer Unit) The ITB unit 100 as a transfer unit will be described with reference to FIG. I shown in FIG.
The TB unit 100 shows the top and side surfaces of the external appearance in a state outside the image apparatus. The ITB unit 100 has an intermediate transfer belt 102 which is a belt body.
Is a drive roller 103 as a support mechanism, a tension roller 1
05, is annularly supported by the secondary transfer backup roller 104.

The drive roller shaft 103a is connected to the unit frame 101.
The drive is transmitted from the apparatus main body via the coupling 109. The tension roller shaft 105a is configured to be able to reciprocate along a guide hole 110 provided in the unit frame 101, and is urged by a restoring spring 108 in a direction in which tension is applied to the intermediate transfer belt 102. One end of a link arm 107 is rotatably supported on the tension roller shaft 105a, and a backup roller shaft 104a is rotatably supported on the other end of the link arm 107. That is, the backup roller 104 is connected to the tension roller 105, and the tension roller 105
Is configured to be rotatable around the center.

Therefore, when the ITB unit 100 is detached from the apparatus, the backup roller 104 is pulled up by the intermediate transfer belt 102 when the restoration spring 108 urges the tension roller 105, and the backup roller shaft 104a is connected to the unit frame. It is stored in a storage position 114 which is a recess provided in 101. At this time, no prescribed tension for transfer is applied to the intermediate transfer belt 102, and the intermediate transfer belt 102 is
Completely stored within.

FIG. 2 is a block diagram of the ITB unit in FIG.
The C section is shown. FIG. 2A illustrates a state in which the intermediate transfer belt 102 is completely stored, and FIG. 2B illustrates an operation state. The position (two-dot chain line) in FIG. 2B is outside the apparatus, and the position (two-dot chain line) is locked and fixed with a specified belt tension in the apparatus.
Is rotated around the tension roller shaft 105a by the link arm 107. (Solid line) shows an intermediate state when the belt unit is attached and detached. FIG. 2 (c) shows a state where the apparatus is locked and fixed with a specified belt tension in the apparatus.
The tension roller shaft 105a reciprocates along the guide holes 110 provided in the unit frame 101 as shown in FIGS. This series of movable deformations are all performed by the guide means provided in the image forming apparatus main body. The ITB unit 100 alone does not have a positioning mechanism for each roller shaft, and the belt tension is released.

FIGS. 3 and 4 show guide means necessary for attaching and detaching the ITB unit 100. FIG. The guide means of the ITB unit 100 is provided facing the inner surface of the housing of the apparatus main body.
FIG. 3 shows guide means provided on one side of the inner surface of the housing, and includes a guide mechanism 301 having guide rails 302 and 303, a guide mechanism 304 having guide rails 305, and a driving roller shaft 10.
The lock mechanism 306 includes a lock mechanism 306 as a fixing means of 3a, a lock mechanism 307 as a means for fixing the backup roller shaft 104a, and a lock mechanism 308 as a means for fixing the tension roller shaft 105a. The guide means includes an ITB unit (not shown).
A mechanism for separating and contacting 100 photoconductor drums 1 is also provided.
FIG. 4 shows the guide means provided on the other side, and is in a mirror image-reversed positional relationship with the mechanism shown in FIG. Therefore, IT
The roller shaft positions of the B unit 100 are guaranteed by the lock mechanisms 306, 307, and 308 facing each other.

FIG. 5 shows the operation of the lock mechanism shown in FIG. Each roller shaft 103a, 104 of the ITB unit 100
a and 105a are inserted along the guide rails 302, 303 and 305, the locking mechanism 30 is pressed by the contact pushing force of the shaft.
6, 307 and 308 are rotated, and the position 306 shown by the two-dot chain line in the figure
a, 307a and 308a lock and fix each shaft. Lock mechanism 30
6, 307, and 308 are provided with an urging mechanism (not shown) that applies a force in the locking and fixing direction when locked and applies a force in the opening direction when released. Note that these lock mechanisms 306, 307, 308 do not necessarily need to have a function of interlocking with each other.

FIGS. 6 and 7 show the operation of inserting the ITB unit 100 having the above configuration into the guide means of the apparatus main body. First, as shown in FIG. 6A, the backup roller shaft 104a of the ITB unit 100 is connected to the guide mechanism 301.
Into the guide rail 303. Next, as shown in FIG. 6B, the drive roller shaft 103a is inserted in alignment with the guide rail 303. Next, as shown in FIG. 6C, the drive roller shaft 103a is inserted into the predetermined positioning and locking position 501, and the backup roller 104 is inserted into the predetermined positioning and locking position 502, and locked. At this time, the tension roller shaft 105a is inserted into the guide rail 305 of the guide mechanism 304. This state corresponds to the photosensitive drums 1Y to 1Y in the normal operation state of the image forming apparatus.
This is a state in which the intermediate transfer belt 102 is separated from K, and is also a state in which the image forming unit including the photosensitive drums 1Y to 1K is to be detached.

Then, as shown in FIG. 6 (d), the tension roller shaft 105a is locked at a predetermined positioning / locking position 503 by an unillustrated separation / contact mechanism provided in the apparatus main body with the ITB unit 100. At this time, the intermediate transfer belt 102 is guaranteed for the first time between the drive roller shaft 103a, the backup roller shaft 104a, and the tension roller shaft 105a and the axial position, and a predetermined belt tension is generated.

These series of operations are performed at the same time on the inner surface of the opposing housing shown in FIGS. 7 (a) to 7 (d). When removing the ITB unit 100 from the image forming apparatus main body, the operation is performed in the reverse order.

With the above configuration, the ITB unit 100 does not need a tension control mechanism for the intermediate transfer belt at all, so that the mechanism of the ITB unit 100 can be simplified and its weight can be reduced. Especially ITB
The weight of the unit 100 is about 3 from 78.4 N described in the conventional example.
It is possible to reduce the weight to 9.2N (4kgf). Also ITB
When the unit 100 is attached and detached and when it is detached, the intermediate transfer belt 102 is flat,
The TB unit 100 is reduced in size. By reducing the weight and size of the ITB unit 100, it is possible to improve the attachment / detachment operability and reduce the space required for the work. Further, the intermediate transfer belt 102 is the unit frame 1
01, the interference with other functional parts of the apparatus main body is reduced, and the handling in the work can be facilitated.

In addition to the simplification of the above mechanism, the distance between the axes of the rollers as the supporting mechanism and the axial position are guaranteed by the guide means provided in the apparatus main body, so that the dimensional accuracy control of the unit housing is eased. The production cost of the ITB unit 100 can be reduced.

Further, by reducing the size of the ITB unit 100 when the ITB unit 100 is attached and detached and in a detached state, the opening area for attachment and detachment in the apparatus main body can be reduced by up to about 40% (60% of the conventional size). It becomes possible to configure. Therefore, the overall height of the apparatus main body can be reduced, and the production cost of the apparatus main body can be reduced.

[Second Embodiment] A second embodiment of the image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 9 is an overall configuration diagram of the image forming apparatus according to the present embodiment.
FIG. 10 is a diagram illustrating the configuration of a transfer unit of the image forming apparatus, and FIG.
FIG. 12 is an enlarged view of a main part, illustrating the attaching / detaching operation of the transfer means. Parts that are the same as those in the first embodiment will be denoted by the same reference numerals, and description thereof will be omitted.

In the first embodiment, an intermediate transfer belt unit for forming an image by firstly transferring a toner image onto an intermediate transfer belt 102 as a belt body and then secondary transferring it onto a sheet material is used as the transfer means. Explained. On the other hand, in the present embodiment, the transfer unit will be described using a transfer / conveyance belt unit 200 that forms an image by directly transferring a toner image to a sheet material carried on a transfer / conveyance belt as a belt body.

In the image forming apparatus shown in FIG. 9, the transfer / conveying belt unit 200 has a transfer / conveying belt 202 as a belt, and the transfer / conveying belt 202 includes a driving roller 203, a tension roller 204, and an idler as a support mechanism. It is annularly supported by rollers 205 and 206. Further, transfer rollers 207Y to 207K are disposed inside the transfer / conveying belt 202 at positions facing the photosensitive drums 1Y to 1K of the respective colors, and the sheet material S is brought into contact with the photosensitive drum 1 by the transfer / conveying belt 202. The toner image is conveyed while being transferred, and the toner images of the respective colors are superimposedly transferred onto the sheet material S.

As shown in FIG. 10A, the drive roller 203 and the tension roller 204 are rotatably supported on the unit frame 201 in a fixed position, and the drive roller 203 is connected to the apparatus main body via a coupling 209. The drive is transmitted from. Also, as shown in FIG.
205a is the tension roller 204 by the link arm 210.
, The idle roller 206
The shaft 206a is configured to be rotatable with respect to the drive roller 203 by a link arm 211. Therefore, as shown in FIG. 10 (c), when the idle rollers 205 and 206 rotate,
The circumferential length of the transfer / conveyance belt 202 can be changed, so that a predetermined tension can be applied to the transfer / conveyance belt 202. Also, idle roller shafts 205a, 206a
When the transfer / conveyance belt unit 200 is removed, the transfer / conveyance belt 202 is urged by the tension of the transfer / conveyance belt 202 to rotate into the unit frame 201, and the storage positions 201a and 201b
Is stored in

The transfer / conveyance belt unit 200 is configured to be detachable from the apparatus main body in the sheet conveyance direction (the direction of arrow A in FIG. 9). This attachment / detachment operation is described in FIG.
This will be described with reference to FIG.

First, as shown in FIG. 11A, the idle roller shafts 205a and 206a of the transfer / conveyance belt unit 200 are inserted along the guide rail 310 of the guide means provided on the apparatus main body. Then, as shown in FIG.
05a and 206a are predetermined positioning and locking positions 504,
Locked at 505. In this state, the transfer conveyance belt 202 is separated from the photosensitive drums 1Y to 1K in a normal operation state of the image forming apparatus, and the photosensitive drums 1Y to 1K are separated.
At the time of attachment / detachment / replacement replacement of the image forming unit and work for removing jam of the sheet material S.

As shown in FIG. 11 (c), when the transfer / conveyance belt unit 200 is further pushed in, the drive roller shaft 203a and the tension roller shaft 204a move along the guide rails 311 and 312, respectively, to form the link arms 210 and 211. To ascend. The drive roller shaft 203a and the tension roller shaft 204a
At 6 and 507, that is, at the position where the transfer / conveying belt 202 comes into contact with the photoconductor drums 1Y to 1K, a locking mechanism (not shown) locks and fixes the belt.

Here, the tension roller shaft 204a is
As shown in (a) (part F in FIG. 10), it is attached to a long hole 211 a provided in the link arm 211,
The link arm 211 is configured to be movable in parallel in the longitudinal direction by a predetermined distance δ. On the other hand, as shown in FIG. 12B (part G in FIG. 11), the vicinity of the corresponding guide rail 312 is set at a locking position 507 where a predetermined belt tension is generated on the transfer / transport belt 202, by the tension roller shaft. It is configured to guide 204a.

As in the first embodiment, the guide rails 310, 311 and 312, which are guide means provided in the apparatus main body, are provided on both inner surfaces of the image forming apparatus main body in a mirror image inverted positional relationship. .

With the above configuration, even in an image forming apparatus using a transfer / transport belt unit that carries and conveys a sheet material and transfers a toner image to the sheet material,
The same effect as in the first embodiment can be obtained. Also,
Since the transfer conveyance belt 202 is configured to generate tension by the guide means, there is no need to provide a separation mechanism for separating the transfer conveyance belt 202 from the photosensitive drums 1Y to 1K. It can be.

[0038]

As described above, in the image forming apparatus according to the present invention, the transfer mechanism is provided with the support mechanism for supporting the belt member, and the apparatus main body is provided with the guide means for guiding the support mechanism, and the support mechanism. And a belt unit is stretched by the guide unit and the fixing unit when the transfer unit is attached to the apparatus main body, and when the transfer unit is removed from the apparatus main body, the tension of the belt body is set. , The tension control mechanism for the belt body is not required at all in the transfer means, so that the mechanism of the transfer means can be simplified and the weight can be reduced.

Further, when the transfer means is attached and detached and when the transfer means is detached, the belt body becomes flat, and the size of the transfer means as a whole is smaller than when the transfer means is attached. By reducing the weight and size of these transfer means, the operability of attaching and detaching can be improved, and the space required for the operation can be reduced. Further, since the belt body can be accommodated in the frame of the transfer means, interference with other functional parts of the apparatus main body is reduced, and handling in operation can be facilitated.

In addition to the simplification of the above mechanism, the distance between the axes of the rollers as the support mechanism and the axial position are guaranteed by the guide means provided in the apparatus main body, so that the dimensional accuracy control of the unit housing is eased. And the production cost of the transfer unit can be reduced.

In addition, since the belt member becomes flat or small when the transfer means is attached and detached and in a detached state,
It is possible to reduce the opening area for attachment and detachment in the apparatus main body. Therefore, the overall height of the apparatus main body can be reduced, and the production cost of the apparatus main body can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a transfer unit.

FIG. 2 is a diagram illustrating the operation of a transfer unit.

FIG. 3 is a view for explaining a guide means of the apparatus main body.

FIG. 4 is a view for explaining a guide means of the apparatus main body.

FIG. 5 is a diagram illustrating fixing means of the apparatus main body.

FIG. 6 is a diagram for explaining an attaching / detaching operation of a transfer unit.

FIG. 7 is a view for explaining an attaching / detaching operation of a transfer unit.

FIG. 8 is an overall configuration diagram of the image forming apparatus according to the first embodiment.

FIG. 9 is an overall configuration diagram of an image forming apparatus according to a second embodiment.

FIG. 10 is a diagram illustrating a configuration of a transfer unit of the image forming apparatus.

FIG. 11 is a diagram for explaining an attaching / detaching operation of a transfer unit.

FIG. 12 is an enlarged view of a main part of a transfer unit.

[Explanation of symbols]

 S ... sheet material 1 ... photosensitive drum 2 ... light source 3 ... feeding section 4 ... manual feeding section 5 ... registration roller pair 6 ... secondary transfer roller 8 ... fixing device 9 ... discharge section 10 ... process cartridge 11 ... conveyance means 100 ITB unit 101 Unit frame 102 Intermediate transfer belt 103 Drive roller 103a Drive roller shaft 104 Backup roller 104a Backup roller shaft 105 Tension roller 105a Tension roller shaft 106 Primary transfer roller 107 Link arm 108 … Recovery spring 109… Coupling 110… Guide hole 114… Storage position 200… Transfer / convey belt unit 201… Unit frames 201a, 201b… Storage position 202… Transfer / convey belt 203… Drive roller 203a… Drive roller shaft 204… Tension roller 204a … Tension roller shaft 205… idle roller 205 a… idle roller 206 ... idle roller 206a ... idle roller shaft 207 ... transfer roller 209 ... coupling 210-211 ... link arm 301, 304 ... guide mechanism 302-303, 305, 310-312 ... guide rail 306-308 ... lock mechanism 501-507 … Locking position

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H030 AA05 AA06 AA07 AB02 BB42 BB46 2H200 FA12 FA17 GA12 GA23 GA47 JA01 JB06 JB31 JB47 JC03 JC07 JC17 LA01 LA17 LA29 MC01

Claims (5)

[Claims] A transfer unit having a plurality of image carriers and a belt member, wherein images on the plurality of image carriers are directly transferred to a sheet material carried on the belt member, or In an image forming apparatus for forming an image by performing a secondary transfer to a sheet material after a primary transfer on a belt body, the transfer unit has a part or the whole of a support mechanism for supporting the belt body, and is provided on an apparatus body. The apparatus main body is provided with guide means for guiding the support mechanism, and fixing means for positioning the support mechanism. The support mechanism is provided when the transfer means is mounted on the apparatus main body. Is guided by the guide means, and the belt body is stretched by being fixed by the fixing means. When the transfer means is removed from the apparatus main body, the tension of the belt body is released. When Claim 1
The image forming apparatus as described in the above. 2. The image forming apparatus according to claim 1, wherein the support mechanism includes a plurality of rollers, and at least one of the rollers has a variable axial position. A contact mechanism, wherein the separating mechanism moves a shaft of a part of the plurality of rollers, and when the shaft of the moved roller is fixed by the fixing means, the belt body 2. The image forming apparatus according to claim 1, wherein a tension is applied to the belt body while being in contact with the image carrier. 3. The support mechanism comprises a plurality of rollers, wherein at least one roller has a variable axial position, and a guide means provided on the apparatus main body extends a distance between the plurality of rollers. 2. The image forming apparatus according to claim 1, wherein a tension is applied to the belt body at the same time when the transfer unit is mounted. 4. The belt body of the transfer means is made of an elastic material having elasticity as a base material.
The image forming apparatus as described in the above. 5. A plurality of rollers having a variable axial position among the plurality of rollers constituting the support mechanism, when the transfer unit is removed from the apparatus main body, the transfer unit becomes flat due to the elastic force of the belt body. The image forming apparatus according to claim 4, wherein the image forming apparatus is configured to be movable in a direction in which the image forming apparatus becomes smaller.