EP3928984A1

EP3928984A1 - Printing device

Info

Publication number: EP3928984A1
Application number: EP20760268.1A
Authority: EP
Inventors: Koichi Ichinose; Katsumi Dohi; Shinichiro NISHIGUCHI; Kazutoshi YAMASHIRO
Original assignee: Toshin Kogyo Co Ltd
Current assignee: Toshin Kogyo Co Ltd
Priority date: 2019-02-19
Filing date: 2020-02-07
Publication date: 2021-12-29
Also published as: EP3928984A4; JP7345900B2; CN113396061A; CN113396061B; WO2020170868A1; JPWO2020170868A1

Abstract

Provided is a printing apparatus having a function to suppress expansion and contraction of a conveyor belt during intermittent feeding movement of the conveyor belt.

A printing apparatus 10 includes a conveyor belt 11 for supporting a printing object from below and conveying the object in the horizontal direction; a belt drive mechanism 12 that causes the conveyor belt 11 to perform an intermittent feeding movement; a printing mechanism 13 that is disposed in the travel path of the conveyor belt 11, and performs printing on the object; a support base 14 for supporting the conveyor belt 11 from below during printing by the printing mechanism 13; and a belt feed assisting mechanism that assists intermittent feeding movement of the conveyor belt 11 by the belt drive mechanism 12.

Description

Technical Field

The present invention relates to a printing apparatus. More specifically, the present invention relates to a printing apparatus having a function to assist the intermittent feeding movement of a conveyor belt for conveying a printing object.

Background Art

Conventionally, a printing apparatus using a screen plate as shown in, for example, Patent Literature 1 has been provided. The printing apparatus disclosed in Patent Literature 1 includes a conveyor belt for conveying a fabric, with the fabric attached to the surface thereof; drive rollers for driving the conveyor belt; a screen plate that is to be positioned on the surface of the fabric, and on which a pattern to be printed is formed; a printing unit having a squeegee; and a support base for supporting the conveyor belt from the lower surface during printing on the fabric by the printing unit. A plate-making area is formed on the screen plate. The plate-making area has an area where ink is shielded, and holes through which ink passes. By placing ink on the screen plate and moving the squeegee on the surface of the screen plate with the screen plate pressed against the fabric, the ink passes through the holes in the screen plate, thereby performing printing on the fabric under the screen plate. When the movement of the squeegee is completed, the fabric is intermittently conveyed by the drive rollers and the conveyor belt, a surface area of the fabric on which printing is to be performed next is positioned under the screen plate, and printing is performed on the surface of the fabric sequentially.
Further, a printing apparatus using an inkjet mechanism as shown in, for example, Patent Literature 2 is also known. The printing apparatus includes a plurality of nozzles housed in a printhead, and the nozzles eject ink of multiple colors. The conveyor belt conveys a fabric intermittently at the printing pitch of the printhead. Each time the fabric is intermittently conveyed, the printhead is moved along the direction (the width direction of the fabric) perpendicular to the fabric conveyance direction to eject ink from the nozzles, thus performing printing of a pattern on the surface of the fabric.

Citation List

Patent Literature

PTL 1: JP2015-044330A
PTL 2: JP5116542B

Summary of Invention

Technical Problem

In printing apparatuses using a screen plate or an inkjet mechanism, conveyance errors may occur because of rough accuracy of intermittent feeding of a fabric. If the fabric is conveyed a distance shorter than the length of the printing pitch, the previously printed portion and the portion printed afterward may greatly overlap, causing color unevenness. If the fabric is conveyed a distance longer than the length of the printing pitch, a gap may be left between the previously printed portion and the portion printed afterward. Thus, if there are conveyance errors, printing cannot be performed on a fabric with high accuracy. Accordingly, there is demand for minimizing conveyance errors, and improving conveyance accuracy.
One of the causes of conveyance errors is the expansion and contraction of a conveyance belt itself. The conveyor belt of a printing apparatus is generally an endless belt, and is looped between a drive roller and a driven roller disposed on the upstream side and the downstream side in the fabric conveyance direction. A drive source such as a servomotor is connected to the drive roller. By causing the drive source to intermittently operate, the drive roller is rotated to intermittently convey the conveyor belt. Even in the case in which there are no errors when driving the drive roller, if the conveyor belt itself expands and contracts, the fabric conveyance position deviates from a desired position, resulting in a conveyance error. In particular, the central portion of the conveyor belt in the conveyance direction is not supported by the drive roller or the driven roller unlike both ends on the upstream side and the downstream side, and is thus likely to expand and contract. Moreover, when the conveyor belt is moved intermittently while the lower surface of the central portion of the conveyor belt is in contact with the support base and supported by the support base, a frictional force between the lower surface of the conveyor belt and the upper surface of the support base causes elongation in the central portion of the conveyor belt. Depending on the material of the conveyor belt, an error of about ±0.3 mm may occur.
The present invention has been accomplished in view of the problems described above. An object of the present invention is to provide a printing apparatus having a function to suppress expansion and contraction of a conveyor belt during the intermittent feeding movement of the conveyor belt.

Solution to Problem

The printing apparatus according to the present invention includes a conveyor belt for supporting a printing object from below and conveying the object in a horizontal direction; a belt drive mechanism that causes the conveyor belt to perform an intermittent feeding movement; a printing mechanism that is disposed in a travel path of the conveyor belt, and performs printing on the object; a support base for supporting the conveyor belt from below during printing by the printing mechanism; and a belt feed assisting mechanism that assists the intermittent feeding movement of the conveyor belt by the belt drive mechanism.
According to the above configuration, since the intermittent feeding movement of the conveyor belt is assisted by the belt feed assisting mechanism, expansion and contraction of the conveyor belt is suppressed, and printing on a fabric can be performed with high accuracy.
In an embodiment, the belt feed assisting mechanism assists the intermittent feeding movement of the conveyor belt each time the belt drive mechanism causes the conveyor belt to perform the intermittent feeding movement.
The belt feed assisting mechanism may be a gap-forming mechanism that forms a gap between the lower surface of the conveyor belt and the support base.
The belt feed assisting mechanism may include air holes formed in the support base, and an air supply mechanism that supplies air to be fed from the air holes toward the lower surface of the conveyor belt.
In another embodiment, the belt feed assisting mechanism is a push-up mechanism that pushes up the conveyor belt to separate the conveyor belt from the support base.
In this other embodiment, the push-up mechanism may include a push-up member that comes into contact with the lower surface of the conveyor belt, and pushes up the conveyor belt; and an elevating mechanism that raises and lowers the push-up member so that the top of the push-up member protrudes from and retracts into the upper surface of the support base.
The push-up member may be a push-up roller that rotates with movement of the conveyor belt.

Advantageous Effects of Invention

According to the present invention, since the intermittent feeding movement of the conveyor belt is assisted by the belt feed assisting mechanism, the expansion and contraction of the conveyor belt can be suppressed, and fabric conveyance errors can be reduced, thereby performing printing with high accuracy.

Brief Description of Drawings

Fig. 1 is a side view showing the entire schematic structure of a printing apparatus according to a first embodiment of the present invention.
Fig. 2 is a partially cut-away plan view showing the schematic structure of a main portion of a conveyor belt and a support base.
Fig. 3 is a partially cut-away enlarged perspective view of the main portion of the conveyor belt and the support base.
Fig. 4 is an enlarged cross-sectional view of a main portion of the printing apparatus.
Fig. 5 is a side view showing the entire schematic structure of a printing apparatus according to a second embodiment.
Fig. 6 is a plan view showing the schematic structure of the printing apparatus.
Fig. 7 is a perspective view of a push-up mechanism.
Fig. 8 is a side view showing another example of the push-up mechanism.
Fig. 9 is a side view showing another example of the push-up mechanism.
Fig. 10 is a plan view showing another example of the entire schematic structure of the printing apparatus.

Description of Embodiments

Embodiments of the present invention are described below with reference to drawings.
Figs. 1 to 4 show a printing apparatus 10 according to a first embodiment of the present invention. The printing apparatus 10 includes a conveyor belt 11 for supporting a printing object from below and conveying the object in a horizontal direction; a belt drive mechanism 12 that causes the conveyor belt 11 to perform an intermittent feeding movement; a printing mechanism 13 that is disposed in the travel path of the conveyor belt 11, and performs printing on the object; a support base 14 for supporting the conveyor belt 11 from below during printing by the printing mechanism 13; and a belt feed assisting mechanism 20 that assists the intermittent feeding movement of the conveyor belt 11 each time the belt drive mechanism 12 causes the conveyor belt 11 to perform the intermittent feeding movement. The intermittent feeding movement includes conveying the conveyor belt 11 a predetermined distance and stopping the conveyor belt 11, and refers to a movement of repeating the conveying and the stopping.
The printing object is, for example, a fabric C. The material of the fabric C is not particularly limited; and various materials made of natural fibers such as cotton and silk, and artificial fibers such as polyester, rayon, and acetate, may be used. The fabric is conveyed from the left side to the right side in Fig. 1. The direction in which the fabric is conveyed is referred to as the conveyance direction, and the direction perpendicular to the conveyance direction is referred to as the width direction of the fabric.
The belt drive mechanism 12 includes drive rollers 12a, 12a that are disposed on the upstream side and the downstream side in the conveyance direction, and that are rotationally driven; and a drive source (not shown), such as a servomotor, connected to the rotation shafts of the drive rollers 12a, 12a. The endless conveyor belt 11 is looped between the drive rollers 12a, 12a; and the drive rollers 12a, 12a are rotated by the drive source to causes the conveyor belt 11 to perform an intermittent feeding movement. A driven roller may be used instead of one drive roller 12a.
The conveyor belt 11 is formed from an elastic body such as urethane rubber, has an adhesive layer (not shown) on the upper surface thereof, and supports the fabric C. The long fabric C wound in a roll shape is disposed on the upstream side of the conveyor belt 11, unwound by an unwinding roller 15a, and attached onto the conveyor belt 11 by an attaching roller 15b. After printing is performed on the surface of the fabric C conveyed by the conveyor belt 11, the fabric C is wound by a winding roller 15c at the downstream side. Further, the surface of the conveyor belt 11 is washed with a washing device (not shown) disposed in the return path from the drive roller 12a on the downstream side to the drive roller 12a on the upstream side, and an adhesive layer is formed on the surface with a gluing device (not shown).
The printing mechanism 13 is for performing, for example, screen printing, and is attached to a frame 16 (Fig. 2) of the printing apparatus 10 so that the printing mechanism 13 is above the fabric C attached to the conveyor belt 11 and so that the printing mechanism 13 vertically faces the support base 14. The printing mechanism 13 includes a plate 13a, a printing unit 13b, and a movement mechanism (not shown) for moving the plate 13a and the printing unit 13b. The plate 13a has a screen (not shown) attached to the inside of a rectangular frame. The screen is perforated with minute holes according to a pattern to be printed. In the printing unit 13b, a pair of squeegee carriers reciprocate in the width direction along two guide frames between which the plate 13a is located and that extend along the width direction of the fabric C. A squeegee supported by the squeegee carriers applies squeegee pressure to the screen of the plate 13a during forward and backward movements. In printing by the printing mechanism 13, the screen of the plate 13a is first pressed against the surface of the fabric C, and then the squeegee moves on the screen. Accordingly, ink on the screen passes through the minute holes of the screen and reaches the fabric C, thereby printing a desired pattern on the fabric C. One or more printing mechanisms 13 are provided according to the number of ink colors used. For example, when ten ink colors are used, ten printing mechanisms 13 are arranged in the conveyance direction. Fig. 1 shows only one printing mechanism 13, for convenience of explanation. The printing mechanism 13 is not limited to the configuration of this embodiment, and may be, for example, an inkjet printing mechanism.
The support base 14 is provided under the conveyor belt 11 in the forward path, and supported by the frame 16 of the printing apparatus 10. As shown in Figs. 2 to 4, the support base 14 has a plurality of air holes 21 penetrating in the vertical direction. Ducts 22 that are opened on the upper side and communicate with the air holes 21 are attached to the lower surface of the support base 14. The ducts 22 are connected to air supply mechanisms 23 each including, for example, a blower fan, via air pipes 24. Air supplied from the air supply mechanisms 23 blows out of the air holes 21 through the ducts 22, and is fed toward the lower surface of the conveyor belt 11. The load of the conveyor belt 11 located above the support base 14 is supported by this air. The amount of air blowing per predetermined period of time and the speed of air blowing from each air hole 21 can be adjusted. By adjusting these, the conveyor belt 11 is floated upward from the support base 14 to form a gap between the lower surface of the conveyor belt 11 and the support base 14; accordingly, the upper surface of the support base 14 is released from contact with the lower surface of the conveyor belt 11. In Figs. 2 and 3, the printing mechanism, the fabric, and the belt drive mechanism are not shown.
The air holes 21, the air pipes 24, and the air supply mechanisms 23 provided in the support base 14 constitute belt feed assisting mechanisms 20. In this embodiment, each belt feed assisting mechanism 20 is a gap-forming mechanism for forming a gap between the lower surface of the conveyor belt 11 and the support base 14. However, the belt feed assisting mechanism 20 is not limited to one for forming a gap. Depending on the amount of air supplied per predetermined period of time and the speed of air blowing from each air hole 21, the conveyor belt 11 may be in contact with the support base 14, without floating upward from the support base 14.
In this embodiment, the support base 14 includes nine support plates 14A to 141 arranged continuously in the conveyance direction, each support plate having a length of 1200 mm in the conveyance direction, a length of 2400 mm in the direction (the width direction of the fabric C) perpendicular to the conveyance direction, and a thickness of 3 mm. However, the support base 14 is not limited to this configuration, and may be formed from a single flat plate. The number and size of the support plates may be freely set. In this embodiment, the diameter of each air hole 21 is set to be about 2 mm.
In this embodiment, as shown in Figs. 1 to 3, four ducts 22 are attached, in the width direction of the fabric C, to each of the second, fifth, and eighth support plates 14B, 14E, 14H. The four ducts 22 are connected to an air supply mechanism 23 via an air pipe 24. That is, in this embodiment, a total of three sets of one air supply mechanism 23 and four ducts 22, each set consisting of one air supply mechanism 23 and four ducts 22, are provided in the support base 14. In each of the support plates 14B, 14E, 14H, seven air holes 21 in the conveyance direction multiplied by four air holes 21 in the width direction of the fabric C are provided in an area that corresponds to each duct 22. That is, 48 air holes 21 are provided in each of the support plates 14B, 14E, and 14H.
The support plates in which the air holes 21 are formed, the number of air holes 21, and the area in which the air holes 21 are provided are not limited to this embodiment, and may be suitably selected as long as the load of the conveyor belt 11 located over the support base 14 can be supported to reduce the frictional force between the conveyor belt 11 and the support base 14. The air holes 21 may be formed in any area of the support base 14. The size and number of ducts 22, the number of air pipes 24, and the number of air supply mechanisms 23 are not limited as long as air can be supplied to the air holes 21. For example, a duct 22 may be provided for each of the support plates 14B, 14E, and 14H. Further, an air supply mechanism 23 may be provided for each of multiple ducts 22. In this case, the amount of air supplied from the air holes 22 communicating with the ducts 22 can be adjusted for each supply mechanism 23.
In this embodiment, the printing mechanisms 13 are provided directly above the first, third, fourth, sixth, seventh, and ninth support plates 14A, 14C, 14D, 14F, 14G, and 141, in which no air holes 21 are provided. However, if the air holes 21 have a diameter that does not affect printing on the fabric C by the printing mechanisms 13, the printing mechanisms 13 may be provided directly above the support plates 14B, 14E, 14H. In Fig. 1, only the printing mechanism 13 directly above the support plate 14A is shown.
The drive source for driving the drive rollers 12a, 12a, the printing mechanisms 13, and the air supply mechanisms 23 are connected to a control device (not shown), and their operations are controlled by the control device.
The printing operation of the printing apparatus 10 according to the first embodiment is as follows. First, the fabric C is conveyed under the printing mechanism 13 by the intermittent feeding movement of the conveyor belt 11, and stopped. Then, the plate 13a of the printing mechanism 13 is pressed against the fabric C from above, and ink is transferred to the fabric C through the minute holes provided in the plate 13a by movement of a squeegee, thereby performing printing on the fabric C. At this time, the surface of the support plate 14A of the support base 14 is in contact with the lower surface of the conveyor belt 11, and supports the fabric C. Next, the fabric C is conveyed and stopped by the intermittent feeding movement of the conveyor belt 11 so that an area of the fabric C on which printing is to be performed next is positioned under the printing mechanism 13. Printing is then performed on the area conveyed under the printing mechanism 13. Printing is performed on the fabric C by repeating these operations.
In the above printing operation, the air supply mechanisms 23 supply air to the air holes 21 in the support base 14 each time the belt drive mechanism 12 causes the conveyor belt 11 to perform the intermittent feeding movement. Specifically, during stopping immediately before the conveying movement of the conveyor belt 11, air is supplied to the ducts 22 via the air pipes 24 by the air supply mechanisms 23, as shown by arrow A1 in Fig. 4; and supplied to the air holes 21 of the support base 14 (support plate 14E in the example of the drawing), as shown by arrows A2. Thereby, the air is fed from the air holes 21 toward the lower surface of the conveyor belt 11, as shown by arrows A3, and the conveyor belt 11 is lifted from the support base 14 to form a gap between the conveyor belt 11 and the support base 14; accordingly, the conveyor belt 11 is released from contact with the support base 14. In this state, the conveyor belt 11 is conveyed by the belt drive mechanism 12. After the conveyor belt 11 is moved a predetermined distance and stopped, the air supply by the air supply mechanisms 23 is stopped. Thereby, the conveyor belt 11 is lowered onto the support base 14; accordingly, the conveyor belt 11 is brought into contact with the support base 14. Thereafter, printing is performed on the fabric C by the printing mechanisms 13. As described above, during the conveying movement of the conveyor belt 11, air is fed from the air holes 21 toward the lower surface of the conveyor belt 11, and the conveyor belt 11 is lifted from the support base 14 to form a gap between the conveyor belt 11 and the support base 14; accordingly, the conveyor belt 11 is released from contact with the support base 14.
According to the above configuration, since the air supply mechanisms 23 supply air to the air holes 21 of the support base 14, the conveyor belt 11 is supported from below by the air while floating upward from the support base 14, thereby reducing the frictional force generated between the lower surface of the conveyor belt 11 and the upper surface of the support base 14 during movement of the conveyor belt 11. This prevents elongation from occurring in the central portion of the conveyor belt 11, reducing conveyance errors. Thus, according to the printing apparatus 10 of this embodiment, the intermittent feeding movement of the conveyor belt 11 can be assisted.
The intermittent feeding movement of the conveyor belt 11 by the belt drive mechanism 12 may be performed while the conveyor belt 11 is in contact with the support base 14 without forming a gap between the conveyor belt 11 and the support base 14. Even in this case, the conveyor belt 11 is supported from below by air, and the frictional force generated between the lower surface of the conveyor belt 11 and the upper surface of the support base 14 during movement of the conveyor belt 11 is reduced, thus preventing elongation from occurring in the central portion of the conveyor belt 11 and thereby reducing conveyance errors.
In this embodiment, the air supply mechanisms 23 operate in synchronization with the intermittent feeding movement of the conveyor belt 11. During the conveying movement of the conveyor belt 11, air is supplied toward the lower surface of the conveyor belt 11 by the belt feed assisting mechanisms 20. While the conveyor belt 11 is stopped, and printing is performed by the printing mechanisms 13, air is not supplied. However, if supplied air does not affect printing on the fabric C by the printing mechanisms 13, the air may continue to be supplied toward the lower surface of the conveyor belt 11 by the belt feed assisting mechanisms 20, even during the printing operation of the printing apparatus 10. That is, during the intermittent feeding movement in which the conveyor belt 11 conveys the fabric C and the printing operation in which printing on a roll of the fabric C by the fabric printing apparatus 10 starts and ends, air may be continuously supplied toward the lower surface of the conveyor belt 11 by the belt feed assisting mechanisms 20. In this case, it is not necessary to control the air supply mechanisms 23 during the operation of the printing apparatus 10.
The belt feed assisting mechanism 20 is not limited to the configuration described above, and may have any configuration as long as the load of the conveyor belt 11 can be supported to reduce the frictional force between the lower surface of the conveyor belt 11 and the support base 14. For example, the belt feed assisting mechanism 20 may be a gap-forming mechanism in which an air injection device is disposed on both sides of the support base 14 in the width direction at a height position that is aligned with the upper surface of the support base 14, and air is injected by the air injection devices during the conveying movement of the conveyor belt to lift the conveyor belt 11, thereby forming a gap.
Figs. 5 to 7 show a printing apparatus 10 according to a second embodiment of the present invention. In the printing apparatus 10 according to this embodiment, the same reference numerals as used in the first embodiment are used for elements that are the same as those in the first embodiment; a detailed description thereof is omitted.
In this embodiment, a support base 14 includes a set 14a of support plates 14A to 14C and a set 14b of support plates 14D to 14F, the set 14a and the set 14b being spaced apart in the conveyance direction. The set 14a and the set 14b are configured by arranging the support plates 14A to 14F that are similar to those in the first embodiment; i.e., three plates are arranged continuously in the conveyance direction in each set. However, the support base 14 is not limited to this configuration. Each set may be formed from a single flat plate or from an arbitrary number of flat plates, instead of the support plates 14A to 14F. The size of the support plates 14A to 14F may also be arbitrary.
A push-up mechanism 30 constituting a belt feed assisting mechanism is disposed between the sets 14a and 14b of the support plates. The push-up mechanism 30 pushes up a conveyor belt 11 to separate the conveyor belt 11 from the support base 14. As shown in Fig. 7, the push-up mechanism 30 includes a push-up member 31 that comes into contact with the lower surface of the conveyor belt 11 and pushes up the conveyor belt 11, and elevating mechanisms 32 that raise and lower the push-up member 31 so that the top of the push-up member 31 protrudes from and retracts into the upper surface of the support base 14.
The push-up member 31 includes two push-up rollers 31A, 31A having substantially the same length as the length of the support base 14 in the width direction. The push-up rollers 31A, 31A are placed along the direction perpendicular to the conveyance direction, i.e., the width direction of a fabric C, and spaced apart in the conveyance direction. Each of the push-up rollers 31A, 31A has a bearing or the like inside, is rotatably supported by a rotation shaft 31a, and comes into contact with the lower surface of the conveyor belt 11 to rotate by movement of the conveyor belt 11. The number of push-up rollers 31A, 31A may be one or three or more. In order to reduce the frictional force between the conveyor belt 11 and the push-up rollers 31A, 31A during movement of the conveyor belt 11, it is preferable that the number of push-up rollers is smaller; whereas in order to stably lift the conveyor belt 11, it is preferable that the number of push-up rollers is larger. In this embodiment, the number of push-up rollers is two.
The elevating mechanisms 32 are provided on both longitudinal direction (fabric width direction) end sides of the push-up rollers 31A, 31A, one on each side. As shown in Fig. 7, each elevating mechanism 32 includes a movable plate 33; a pair of guide frames 34, 34 fixed to, for example, a frame 16 or a base (not shown) of the printing apparatus 10; and an actuator including, for example, a hydraulic cylinder 35. The movable plate 33 has shaft support grooves 33a on its inner surface. Both ends of the rotation shaft 31a of each of the push-up rollers 31A and 31A are supported in the corresponding shaft support grooves 33a. The longitudinal direction (conveyance direction) ends of the movable plate 33 are slidably supported in guide grooves 34a provided in the guide frames 34, 34. The hydraulic cylinder 35 includes a cylinder body 35a and a rod 35b that protrudes from and retracts into the cylinder body 35a, and the tip of the rod 35b is connected to the lower surface of the movable plate 33. The push-up rollers 31A, 31A attached to the movable plate 33 are raised and lowered along the guide frames 34, 34 by the protruding and retracting movements of the rod 35b. In a state where the rod 35b retracts into the cylinder body 35a, the top of each of the push-up rollers 31A, 31A is located below the upper surface of the support base 14. In a state where the rod 35b is extended from the cylinder body 35a, the top of each of the push-up rollers 31A, 31A is located above the upper surface of the support base 14. In a state where the push-up rollers 31A, 31A come into contact with the lower surface of the conveyor belt 11 and push up the conveyor belt 11, the height from the upper surface of the support base 14 to the top of each of the push-up rollers 31A, 31A is set to about 5 to 10 mm; however, the height is not limited thereto.
A drive source for driving drive rollers 12a, 12a, one or more printing mechanisms 13, and the actuators (hydraulic cylinders 35) of the elevating mechanisms 32 are connected to a control device (not shown); and their operations are controlled by the control device.
The printing operation of the printing apparatus 10 according to the second embodiment is described below in terms of differences from the printing apparatus 10 according to the first embodiment.
In the printing operation, during stopping immediately before the conveying movement of the conveyor belt 11, the rod 35b of the hydraulic cylinder 35 of each elevating mechanism 32 is extended to raise the movable plate 33, and the top of each of the push-up rollers 31A, 31A is thus lifted above the upper surface of the support base 14 to thereby separate the conveyor belt 11 from the support base 14. By raising the push-up rollers 31A, 31A, the conveyor belt 11 is lifted from the support base 14 to release the conveyor belt 11 from contact with the support base 14. In this state, the conveyor belt 11 is conveyed by a belt drive mechanism 12 to move a predetermined distance. At this time, the push-up rollers 31A, 31A rotate with the movement of the conveyor belt 11. This rotation reduces the frictional force between the push-up rollers 31A, 31A and the conveyor belt 11, and prevents the conveyor belt 11 from expanding and contracting under the influence of the push-up rollers 31A, 31A. When the conveyor belt 11 stops after moving a predetermined distance, the rod 35b of the hydraulic cylinder 35 retracts into the cylinder body 35a to lower the movable plate 33, and the push-up rollers 31A, 31A are thus located below the upper surface of the support base 14. As a result, the conveyor belt 11 is lowered onto the support base 14 to be brought into contact with the support base 14. Thereafter, printing on the fabric C is performed by the one or more printing mechanisms 13. As described above, during the conveying movement of the conveyor belt 11, the conveyor belt 11 is lifted from the support base 14 by the elevating mechanisms 32; accordingly, the conveyor belt 11 is released from contact with the support base 14.
According to the above configuration, since the push-up rollers 31A, 31A lift the conveyor belt 11 to separate the conveyor belt 11 from the support base 14 each time the intermittent feeding movement of the conveyor belt 11 is performed, no frictional force is generated between the lower surface of the conveyor belt 11 and the upper surface of the support base 14 when the conveyor belt 11 moves. This prevents elongation from occurring in the central portion of the conveyor belt 11, and thus reduces conveyance errors. Thus, according to the printing apparatus 10 of this embodiment, the intermittent feeding movement of the conveyor belt 11 can be assisted.
The push-up rollers 31A, 31A may not rotate with movement of the conveyor belt 11, and may be rod-shaped members. In this case, when the conveyor belt 11 is conveyed by the belt drive mechanism 12 to move a predetermined distance, the push-up rollers 31A, 31A come into contact with the lower surface of the conveyor belt 11, but do not rotate. Even in this case, the frictional force between the push-up rollers 31A, 31A and the conveyor belt 11 is smaller than that in conventional techniques.
The configuration of the elevating mechanisms 32 is not limited to this embodiment, and the elevating mechanisms 32 may have any configuration as long as the push-up rollers 31A, 31A can be lifted. For example, as shown in Fig. 8, the elevating mechanisms 32 may be rodless cylinders 40. In each rodless cylinder 40, for example, a cylinder tube 40b is disposed between upper and lower base portions 40a, 40a fixed to, for example, the frame 16 or the base (not shown) of the printing apparatus 10, a piston (not shown) is housed in the cylinder tube 40b, and a slide body 40c is provided on the outer peripheral surface of the cylinder tube 40b, so as to be slidable along the cylinder tube 40b. The piston and the slide body 40c move integrally by a magnetic coupling force. For example, by moving the piston by air, the slide body 40c follows the movement of the piston.
A pair of rodless cylinders 40 are provided per one push-up roller 31A. The pair of rodless cylinders 40 are disposed on both end sides (in the width direction of the fabric C) of each push-up roller 31A, and the tips at both ends of the rotation shaft 31a of each of the push-up rollers 31A, 31A are each fixed to the corresponding slide body 40c. By raising and lowering the slide bodies 40c, the push-up rollers 31A, 31A are raised and lowered so that the top of each push-up roller 31A is between a position above the upper surface of the support base 14 and a position below the upper surface of the support base 14. Moreover, a movable plate may be attached to each of the slide bodies 40c of a pair of rodless cylinders 40, the tips at both ends of the rotation shaft 31a of each of two push-up rollers 31A, 31A may be fixed to the corresponding movable plates, and the two push-up rollers 31A, 31A may be moved simultaneously by the pair of rodless cylinders 40.
The elevating mechanisms 32 may be cam mechanisms 50 shown in Fig. 9. Each cam mechanism 50 includes a rotating body 51 as a driver cam that rotates by rotation of a motor (not shown), and a rod-shaped member 52 as a follower cam disposed on the upper side of the rotating body 51. The rotating body 51 includes a circular disk portion 51a whose central portion is attached to an output shaft 51c of the motor, and a protrusion 51b that protrudes outward from the disk portion 51a. At the lower end of the rod-shaped member 52, a roller 52a that is rotatable by rotation of the rotating body 51 is provided in order to reduce the frictional force between the rod-shaped member 52 and the rotating body 51; and to the upper end of the rod-shaped member 52, a tip of the rotation shaft 31a of a push-up roller 31A is fixed. When the protrusion 51b faces upward by rotation of the output shaft 51c of the motor, the rod-shaped member 52 is lifted, and the push-up rollers 31A, 31A fixed to the corresponding rod-shaped members 52 are raised. When the protrusion 51b faces in a direction other than the upward direction (for example, laterally or downward), the push-up rollers 31A, 31A fixed to the corresponding rod-shaped members 52 are lowered.
The push-up member 31 is not limited to the push-up rollers 31A, 31A, and may have any configuration as long as it can come into contact with the lower surface of the conveyor belt 11 and push up the conveyor belt 11 to release the conveyor belt 11 from contact with the upper surface of the support base 14. For example, the push-up member 31 may be a spherical body rotatably supported by a base portion. The push-up member 31 may include a plurality of spherical bodies.
Further, in the embodiment shown in Fig. 5, the push-up mechanism 30 is disposed between the two sets 14a, 14b of support plates; however, the position of the push-up mechanism 30 is not limited thereto. For example, as shown in Fig. 10, the support base 14 may include three sets 14a to 14c of support plates, and a push-up mechanism 30 may be disposed between each of the sets 14a to 14c of support plates. In Fig. 10, a push-up mechanism 30 is disposed between the set 14a of support plates 14A, 14B and the set 14b of support plates 14C, 14D, 14E; and a push-up mechanism 30 is disposed between the set 14b of support plates 14C, 14D, 14E and the set 14c of support plates 14F, 14G. Moreover, a push-up mechanism 30 may be disposed on both conveyance direction end sides of the support base 14.
Embodiments of the present invention are described above; however, the present invention is not limited to these embodiments, and may be carried out with various modifications within a scope in which the gist of the present invention is maintained.

Reference Numerals

10:: Printing apparatus
11:: Conveyor belt
12:: Belt drive mechanism
13:: Printing mechanism
14:: Support base
20:: Belt feed assisting mechanism
21:: Air hole
22:: Duct
23:: Air supply mechanism
30:: Push-up mechanism
31:: Push-up member
31A, 31A:: Push-up rollers
32:: Elevating mechanism
33:: Movable plate
35:: Hydraulic cylinder
C:: Fabric (printing object)

Claims

A printing apparatus comprising:
a conveyor belt for supporting a printing object from below and conveying the object in a horizontal direction;

a belt drive mechanism that causes the conveyor belt to perform an intermittent feeding movement;

a printing mechanism that is disposed in a travel path of the conveyor belt, and performs printing on the object;

a support base for supporting the conveyor belt from below during printing by the printing mechanism; and

a belt feed assisting mechanism that assists the intermittent feeding movement of the conveyor belt by the belt drive mechanism.
The printing apparatus according to claim 1, wherein the belt feed assisting mechanism assists the intermittent feeding movement each time the belt drive mechanism causes the conveyor belt to perform the intermittent feeding movement.
The printing apparatus according to claim 1 or 2, wherein the belt feed assisting mechanism is a gap-forming mechanism that forms a gap between the lower surface of the conveyor belt and the support base.
The printing apparatus according to any one of claims 1 to 3, wherein the belt feed assisting mechanism comprises air holes formed in the support base, and an air supply mechanism that supplies air to be fed from the air holes toward the lower surface of the conveyor belt.
The printing apparatus according to claim 1 or 2, wherein the belt feed assisting mechanism is a push-up mechanism that pushes up the conveyor belt to separate the conveyor belt from the support base.
The printing apparatus according to claim 5, wherein the push-up mechanism comprises a push-up member that comes into contact with the lower surface of the conveyor belt and pushes up the conveyor belt, and an elevating mechanism that raises and lowers the push-up member so that the top of the push-up member protrudes from and retracts into the upper surface of the support base.
The printing apparatus according to claim 6, wherein the push-up member is a push-up roller that rotates with movement of the conveyor belt.