CN111908367B

CN111908367B - Big plate elevator

Info

Publication number: CN111908367B
Application number: CN202010622339.0A
Authority: CN
Inventors: 谢志军; 陈红德; 黄玲艳; 张�杰; 李哲豪
Original assignee: Monalisa Group Co Ltd
Current assignee: Monalisa Group Co Ltd
Priority date: 2020-07-01
Filing date: 2020-07-01
Publication date: 2021-11-16
Anticipated expiration: 2040-07-01
Also published as: CN111908367A

Abstract

A large plate elevator comprises an elevator frame, a carrying device which is arranged on the elevator frame in a lifting way and used for carrying a large plate, and a lifting device for lifting the carrying device; the carrying device comprises: a handling device frame; a first conveying part for conveying the large plate along a horizontal first conveying direction; a second conveying part for conveying the large plate along a second conveying direction which is horizontal and is orthogonal to the first conveying direction; and a lifting unit for lifting the first conveying unit relative to the second conveying unit.

Description

Big plate elevator

Technical Field

The invention relates to a green brick conveying technology, in particular to a large plate elevator.

Background

At present, ceramic large plates are more and more popular, and the ceramic large plates are ceramic plates with the area not less than two square meters and are made of various inorganic non-metallic materials such as pottery clay, ore and the like through production processes such as molding, high-temperature calcination and the like. Compared with other ceramic tile products, the ceramic large plate has the characteristics of large specification, strong decoration and the like. With the development of the technology, the thickness of the ceramic thin plate is thinner and thinner, and the area is larger and larger.

In the past, when green bricks stop, a section of belt moves upwards through a belt bracket, and different green bricks are supported and then transported away.

However, the lifting mode can enable the belt to generate elastic deformation when the belt bracket is lifted, so that the belt can be stretched and contracted for multiple times to generate larger deformation, and the service life of the belt is reduced. For multiple belts, if a single belt near the center portion is damaged, the time and difficulty of maintenance may be increased. Simultaneously, above-mentioned lift is after using a period, and a plurality of strong points of belt bracket receive the damage of different degree to the atress is inhomogeneous when going up and down, leads to the adobe to damage. And the pivot is staggered, so that the maintenance is complex, multiple leveling is needed, and the time and the labor are consumed.

Disclosure of Invention

The problems to be solved by the invention are as follows:

in view of the above problems, an object of the present invention is to provide a large plate elevator capable of transporting green bricks in two different horizontal directions, ensuring the stability of lifting and lowering of oversized green bricks, avoiding cracking of bricks, and facilitating maintenance.

The technical means for solving the problems are as follows:

in order to solve the problems, the invention provides a large plate elevator, which comprises an elevator frame, a carrying device which is arranged on the elevator frame in an elevating way and used for carrying a large plate, and an elevating device for elevating the carrying device; the carrying device includes: a handling device frame; a first conveying unit for conveying the large board along a horizontal first conveying direction; a second conveying unit for conveying the large board along a second conveying direction which is horizontal and orthogonal to the first conveying direction; and a lifting unit configured to lift and lower the first conveying unit with respect to the second conveying unit.

According to the invention, the carrying device and the lifting device of the large plate are independent from each other in function, so that the internal structure is simple and compact, and the hidden trouble that the large plate is damaged due to uneven stress during lifting is eliminated.

In the present invention, the first conveying unit may include a bracket and a plurality of sets of belt mechanisms provided in parallel to each other on the bracket; the second conveying part comprises a plurality of roller rods which are arranged on the conveying device rack in parallel; the belt mechanism and the roller rods are arranged in parallel and alternately. From this belt mechanism and roller stick staggered arrangement, a plurality of belt mechanisms wholly rise or descend when promoting or drawing down first transport portion, therefore the belt takes place tensile and shrink hardly, has reduced the deformation of belt, has guaranteed the atress stability of belt, has prolonged the life of belt. Meanwhile, the first carrying part is lifted as a whole, so that the green bricks are small in vibration and more uniform in stress and are not easy to damage.

In the present invention, the lifting unit may include a plurality of lifting mechanisms provided to the carrier frame, and a link rod connected to the plurality of lifting mechanisms to be driven by the plurality of lifting mechanisms; each of the plurality of lifting mechanisms includes a lifting mechanism support mounted to the carrier frame, a first rod member, and a second rod member; the first rod member is a bending rod having one end rotatably fixed to the link, and a bending portion thereof is rotatably fixed to the lifting mechanism support; one end of the second rod member is fixed to the bottom of the bracket, and the other end of the second rod member is rotatably connected to the other end of the first rod member. Therefore, the first carrying part can be lifted by a simple and reliable structure, a certain lifting mechanism is damaged, the lifting part can still continue to work, and the replacement and the maintenance are very convenient.

In the present invention, the first lever member may be bent at an angle of 90 degrees. The right angle structure is relatively balanced, laborsaving in rotatory in-process, and is less to the intensity of subassembly, rotation angle requirement, saves space.

In the present invention, the lifting device may include a lifting motor, a sprocket driven by the lifting motor to rotate, and a chain wound around the sprocket; one end of the chain is connected with the carrying device, and the other end of the chain is connected with a counterweight by bypassing the chain wheel. The weight makes the chain during operation atress evenly stable to make elevator motor's load reduce, the speed that the chain drove is more stable, and handling device's promotion process is also more steady, and the shake reduces by a wide margin, makes the adobe not fragile, also can reduce the loss of equipment simultaneously.

In the present invention, an auxiliary pulley having elasticity and pressed against the elevator frame may be provided below the conveying device. The auxiliary pulley is pressed against and rolled along the surface of the elevator frame, thereby allowing the horizontal position of the carrying device to be restricted while being lifted and lowered in the vertical direction by the lifting device. Because the auxiliary pulley is rich in elasticity, consequently can reduce handling device's rocking in handling device's promotion in-process to for it provides stable activity space, alleviateed the unstable action of whole equipment in service, make adobe operation process safer.

In the invention, the elevator frame is further provided with a plurality of detection electric eyes for detecting the position of the carrying device and a plurality of limit switches for limiting the movement of the carrying device; the carrying device is also provided with a plurality of large plate detection electric eyes for detecting the positions of the large plates. Therefore, the actions of the conveying parts can be controlled by monitoring the height of the conveying device and the position of the large plate, so that the lifting and conveying operations of the large plate can be smoothly and stably completed, the height and the lifting speed of the conveying device can be limited, the shock caused by sudden stop is prevented, and the production accidents caused by that the green bricks are damaged or the position of the conveying device is too high, too low or too high are avoided.

The invention has the following effects:

the large-sized green brick lifting device has the advantages that the large plate and the large-sized plate carrying device are lifted as a whole, green bricks can be carried by the carrying device along two different horizontal directions, the lifting stability of the oversized green bricks is ensured, the cracking of the bricks is avoided, and meanwhile, the structure is compact and the maintenance is easy.

Drawings

Fig. 1 is a schematic structural view of a large panel elevator according to an embodiment of the present invention, in which (a) is a front view of the large panel elevator and (b) is a side view of the large panel elevator;

fig. 2 is a schematic structural view of a carrying device of the large panel elevator shown in fig. 1, as viewed from above; (ii) a

Fig. 3 is a diagram showing relative positions of respective structures inside the conveying device 4 when a large board is conveyed by the roller bar 27;

description of the symbols:

1. a large plate elevator; 2. frame columns (elevator frame); 3. a weight iron block (weight); 4. a carrying device (carrying platform); 5. a chain; 6. a sprocket; 7. a sprocket drive shaft; 8. a transmission (transmission wave box); 9. a hoist drive shaft; 10. a lifting motor; 11. a guardrail; 12. a sprocket derailleur; 13. an auxiliary pulley; 14. detecting an electric eye; 15. a limit switch; 21. a pulley bracket; 22. a belt pulley; 23. a belt (first conveying unit); 24. a belt bracket; 25. a belt bracket; 26. a bracket; 27. a roller (second conveying part); 28. a roller rod transmission shaft; 29. a large panel detection electric eye; 291. an inner detection electric eye; 292. an outer detection electric eye; 30. a carrying device frame (carrying platform frame); 31. a lifting part bracket (positioning rotating component); 32. a first lever member; 33. a second lever member; 34. a movable joint; 35. a connecting rod; 36. the connecting rod drives the motor.

Detailed Description

The present invention is further described below in conjunction with the following embodiments and the accompanying drawings, it being understood that the drawings and the following embodiments are illustrative of the invention only and are not limiting thereof.

The large plate hoister can ensure the lifting stability of an oversized green brick, avoid brick cracking and is easy to maintain. The large plate hoister can be used for lifting and transporting large-size green bricks. Fig. 1 is a schematic structural view of a large board elevator 1 according to an embodiment of the present invention, in which (a) is a front view of the large board elevator 1 and (b) is a side view of the large board elevator 1. As shown in fig. 1 (a) and (b), the large plate elevator 1 of the present embodiment includes an elevator frame, a conveying device 4, and a lifting device.

The elevator frame is an integral support of a large plate elevator 1 and comprises frame columns 2, guardrails 11 and floors of each layer for arranging equipment such as a carrying device 4 and a lifting device.

The lifting device is a winding transmission mechanism arranged at the top layer of the elevator frame, and mainly plays a role of lifting the whole carrying device 4, so that the large plate is stably lifted to a specified height. The lifting device comprises a counterweight iron block 3, a chain 5, a chain wheel 6, a chain wheel transmission shaft 7, a transmission speed changer 8, a lifter transmission shaft 9, a lifting motor 10 and a chain wheel speed changer 12. The elevator motor 10 is a power source of the elevator apparatus, and transmits power to the elevator transmission shaft 9 through the transmission gear 8. Two ends of the transmission shaft 9 of the elevator are connected with two chain wheel transmission shafts 7 through chain wheel speed changers 12, and two chain wheels 6 are respectively arranged at two ends of the chain wheel transmission shafts 7. A chain 5 is wound on the chain wheel 6, one end of the chain 5 is connected with the carrying device 4, and a counterweight iron block 3 arranged in the stand column 2 of the frame is hung at the other end. An auxiliary pulley 13 for assisting the lifting of the conveying device 4 is provided below the conveying device 4 lifted by the plurality of chains 5. The auxiliary pulley 13 may be a rubber pulley having elasticity such as a rubber wheel, and is pressed against and rolled along the surface of the frame column 2, thereby allowing the horizontal position of the carrying device 4 to be vertically lifted by the lifting device.

If the large plate elevator only depends on the power of the lifting motor and the action of the chain to lift, the large plate elevator is easy to shake in the lifting process, and the motor load is large and the loss is high. After adding counter weight iron plate 3, because the gravity of iron plate makes 5 during operation atresss evenly stable of chain to make the load of motor reduce, the speed that chain 5 drove is more stable, and handling device 4's promotion process is also more steady, and the shake reduces by a wide margin, makes the adobe not fragile, also can reduce the loss of equipment simultaneously. And the auxiliary pulley 13 of colloid is rich in elasticity, so can reduce handling device 4's rocking thereby for it provides stable activity space in handling device 4's promotion in-process, has alleviateed the unstable action of whole equipment operation for adobe operation process is safer.

As shown in fig. 1 (a), four detection electric eyes 14 for detecting the height position of the conveying device 4 and four limit switches 15 for limiting the movement of the conveying device 4 are provided inside the rack column 2. The detection electric eye 14 may be, for example, a non-flush proximity switch. The detection electric eye 14 detects the horizontal position of the large plate, thereby determining how each of the below-described conveying units on the conveying device 4 operates. When the detection electric eye 14 detects that the conveying device 4 ascends or descends to a specified position, the whole conveying device 4 decelerates and stops rotating gradually by the lifting motor 10, so that the conveying device 4 is decelerated gradually to stop instead of stopping suddenly, vibration caused by stopping suddenly can be prevented, and green bricks can be prevented from being damaged. The limit switch 15 is used to limit the height of the carrying device 4 and prevent accidents, and may be installed at a position higher than the height of the operator on the frame column 2 and below the floor where the lifting device is installed. Meanwhile, the position of the carrying device 4 and the position of the large plate can be monitored by the detection electric eye 14 and the limit switch 15 to control the action of each carrying part, so that the lifting and carrying operation of the large plate can be smoothly and stably completed, and the specific content is described later.

Fig. 2 is a schematic structural view of the conveying device of the large panel elevator shown in fig. 1 as viewed from above, and fig. 3 is a view showing relative positions of respective internal structures of the conveying device 4 when a large panel is conveyed by the roller bar 27. The carrying device 4 mainly functions to carry a large board in a horizontal direction, and includes a first carrying section, a second carrying section, a lifting section, and a carrying device frame 30. In the present embodiment, the conveying device frame 30 is divided into an upper layer and a lower layer, the upper layer and the lower layer are fixedly connected by a plurality of support rods (only one of which is shown in fig. 3), the lower layer is provided with a first conveying portion that can be lifted relative to the conveying device frame 30 by a lifting portion to be described later, and the upper layer is fixedly provided with a second lifting portion.

The first conveying section is a so-called belt drive mechanism, and is composed of a bracket 26 and a plurality of sets of belt mechanisms provided in parallel to each other at the same height in the left-right direction on the bracket 26. As shown in fig. 3, in the belt mechanism, the pulley holder 21 is provided on the bracket 26, the pulley 22 is rotatably supported on the pulley holder 21, the belt brackets 24 are supported from below by the plurality of belt bracket holders 25 provided on the bracket 26, and the belt 23 is stretched by the pulley 22 in the belt brackets 24, whereby the outer surfaces of the belts of the plurality of sets of belt mechanisms collectively form a horizontal first conveying surface. When the first conveying section is operated, the belt 23 is driven by the belt driving motor shown in the figure by the pulley 22, and the large board positioned on the first conveying surface is conveyed in the left-right direction in fig. 2.

The second conveying unit is a so-called roll bar transmission mechanism, and is composed of a plurality of roll bars 27 arranged in parallel with each other at the same height in the left-right direction. The second conveying unit includes a roller 27, a roller support shaft provided below the roller 27 and on the conveying device frame 30, and a roller driving motor. In the present embodiment, the roller transmission shaft 28 may be a worm, and a worm wheel for transmitting power to the worm may be provided at one end of the roller 27, and the other end may be rotatably supported by the roller support shaft via a roller holder base or the like, so that the plurality of rollers 27 form a horizontal second conveying surface together. When the second conveying unit is operated, the roller drive shaft 28 is driven by the roller drive motor to rotate the plurality of rollers 27 together, thereby conveying the large board positioned on the second conveying surface in the vertical direction in fig. 2, i.e., in the conveying direction orthogonal to the first conveying unit.

The lifting unit is mainly used for lifting the first conveying unit relative to the second conveying unit. The lifting unit includes a plurality of lifting mechanisms provided in the conveyance device frame 30 and a link 35 connecting the plurality of lifting mechanisms. The lifting mechanism is constituted by a lifting part holder (positioning rotating unit) 31, a first lever member 32, and a second lever member 33. The lifting unit bracket 31 is attached to the conveyance device frame 30 by a fastener (e.g., a bolt). The first rod member 32 is a bending rod, and the bending angle thereof may be 90 degrees in the present embodiment. The first lever members 32 are pivotally connected at one end to the link 35 and are rotatably fixed to the lifting portion bracket 31 at the bent portions, so that the plurality of first lever members 32 are configured to be rotated together about the lifting portion bracket 31 as a fulcrum by the link 35. The second lever member 33 has one end fastened to the lower surface of the bracket 26 by a fastener and the other end connected to the other end of the first lever member 32 by a movable joint 34, thereby being formed in a structure that is raised or lowered in accordance with the rotation of the first lever member 32. In the present embodiment, the link 35 is also connected to a link driving motor 36 through a transmission mechanism. As described above, the lifting unit is configured to lift or lower the first carrying unit by driving the first and

second lever members

32 and 33 when the link 35 moves left and right by the link driving motor 36. The configuration of the lifting unit is not limited to this, and the first conveying unit may be lifted and lowered with respect to the second conveying unit.

In the present embodiment, as shown in fig. 2, the belt mechanism and the roller rods 27 are alternately arranged in parallel in the left-right direction in a plan view, that is, the plurality of belt mechanisms and the plurality of roller rods 27 are arranged in parallel and staggered with each other, so that the force applied to the large plate during the conveyance can be made uniform. When the first conveying part is lifted relative to the second conveying part through the supporting part, the relative height of the first conveying surface and the second conveying surface can be changed. Specifically, when the link driving motor 36 drives the link 35 to move to the right as shown in fig. 3, the first lever member 32 and the second lever member 33 lift the first conveying unit upward relative to the second conveying unit by the drive of the link 35 to raise the first conveying surface above the second conveying surface, so that the large plate can be conveyed in the first conveying direction (i.e., the left-right direction of the paper surface in fig. 3) by the belt transmission mechanism while being placed on the first conveying surface and separated from the second conveying surface. On the other hand, when the link driving motor 36 drives the link 35 to move leftward, the first lever member 32 and the second lever member 33 are driven by the link 35 to pull the first conveying portion downward relative to the second conveying portion, so that the first conveying surface is lowered to a position below the second conveying surface, and thus the large sheet can be conveyed in the second conveying direction (i.e., the direction of the inside and outside of the sheet in fig. 3) by the roller transmission mechanism while being placed on the second conveying surface and separated from the first conveying surface. In other words, the large plate can be selectively placed on one of the first conveying surface and the second conveying surface by the support portion, and thus can be conveyed in the conveying direction corresponding to the selected conveying surface. The belt mechanism and the rollers are not limited to the staggered arrangement shown in fig. 2, and two conveying surfaces capable of lifting and lowering relative to each other and stably carrying and conveying the large plate may be formed.

As shown in fig. 1 (b), the conveying device 4 is further provided with a large plate detection electric eye 29 for detecting the horizontal position of the large plate. To explain in more detail, the large plate inspection electric eye 29 shown in fig. 2 includes an inner inspection electric eye 291 and an outer inspection electric eye 292 provided on the carrier frame 30. Taking the example of the first conveying unit conveying a large plate from left to right, the inner detection electric eye 291 is provided at a position which is located inside the width direction of the conveying device frame 30 and is located more than one full length of the large plate from the left side of the conveying device 4 in the longitudinal direction in a plan view, and is mainly used for detecting whether the large plate completely enters the conveying device 4 by the first conveying unit. The outer detection electric eye 292 is provided on the outer side in the width direction of the conveyance device frame 30 in a plan view, and is mainly used for determining whether or not the large plate is completely separated from the conveyance device 4 by the second conveyance unit. Further, the positions of the inner detecting electric eye 291 and the outer detecting electric eye 292 are not limited to this, and a plurality of sets of electric eyes may be provided on the carrying device frame 30 to carry the large plate in four directions, i.e., up, down, left, and right.

When the large plate needs to be lifted, the lifting unit is first adjusted so that the first conveying surface is higher than the second conveying surface and is substantially flush with the brick discharging facility, not shown. The first conveying section is started, and the belt driving motor drives the belt pulley 22 to drive the belt 23 to convey the large board to the upper side of the roller rod 27 along the left-right direction, i.e., the first conveying direction. Specifically, the brick discharging facility discharges the large plate, the large plate continues to enter the conveying device 4 by the first conveying part until the large plate is detected by the inner side detection electric eye 291, at this time, it is determined that the large plate has completely reached the upper side of the roller rod 27, the first conveying part stops conveying, and the lifting part drives the first conveying part to appropriately descend until the first conveying surface is lower than the second conveying surface, so that the large plate brick blank is transferred to the roller rod 27.

Next, the elevator motor 10 is started to rotate the elevator transmission shaft 9, and the sprocket 6 is wound around the chain 5, whereby the large board and the carrying device 4 on which the large board is placed are lifted up as a whole to a predetermined height, which can be determined by the detection electric eye 14.

When the large plate reaches a predetermined height, the second conveying unit is started, the roller rod 27 is driven by the roller rod driving motor, and the large plate is conveyed in a second conveying direction (in the present embodiment, from the bottom to the top) orthogonal to the first conveying direction until the large plate is no longer detected by the outside detection electric eye 292, and at this time, it is determined that the large plate has completely left the conveying device 4, and the lifting unit drives the first conveying unit to lift and return to the original position. Thereafter, the conveying device 4 is lowered to the initial position, and the above-described flow is repeated.

The present invention may be used to convey a large plate from a high position to the conveying device 4, lower the whole conveying device 4, and then send the large plate in the other direction.

Therefore, the conveying device for conveying the large plate can be formed into a whole, the structure of the conveying device is simplified, and the conveying device is more reliable and is easy to maintain.

The belt is elastically deformed in the conventional large plate lifting mode when the belt bracket is lifted, so that the belt is stretched and contracted for multiple times to generate larger deformation, and the service life of the belt is shortened. Because the former lifting mode is not integral lifting, and a plurality of supporting points are arranged below each belt, when the supporting points are supported by the crank connecting rod below, certain precision requirements are required on the stability of the belt bracket, the strength requirements on processed parts are high, otherwise the belts in different areas swing back and forth to damage the belts. For multiple belts, if a single belt near the center portion is damaged, the time and difficulty of maintenance may be increased. Meanwhile, after the belt bracket is used for a period of time, a plurality of supporting points of the belt bracket are damaged in different degrees, and the green bricks are damaged due to uneven stress during lifting.

According to the present invention, the belt mechanisms and the roller rods 27 are arranged in a staggered manner, and the plurality of belt mechanisms are integrally raised or lowered when the first carrying section is lifted or lowered, so that the belt is hardly stretched or contracted, the deformation of the belt is reduced, the stable stress of the belt is ensured, and the service life of the belt is prolonged. Even if the lifting is unstable, the platform can only slightly incline, and the belt cannot be greatly stressed and changed, so that the problem of belt damage caused by the factors can be reduced or eliminated. The design of the first and second transport sections allows the transport device 4 to transport the green bricks in multiple directions, and the integrated design of the transport device 4 also makes it more convenient to adjust the height of the large panel. The belt bracket 24 does not need to be repeatedly separated from the belt 23 when the large board is lifted, and the belt bracket 24 and the bracket 25 are connected into a whole, so that accidents are less and safer. Even if a single supporting point is damaged, the conveying of the green bricks cannot be influenced, so that the influence on the green bricks is greatly reduced, and the breakage rate of the green bricks is reduced. Meanwhile, the lifting part consists of a plurality of lifting mechanisms and connecting rods, and the structure is simple and reliable. Even if a certain lifting mechanism is damaged, the lifting part can still continue to work, and the replacement and maintenance are also very convenient.

The above embodiments are intended to illustrate and not to limit the scope of the invention, which is defined by the claims, but rather by the claims, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A big plate elevator is characterized in that,

the lifting device is arranged on the lifting machine frame in a lifting manner and used for conveying large plates;

the carrying device includes:

a handling device frame;

a first conveying unit for conveying the large board along a horizontal first conveying direction;

a second conveying unit for conveying the large board along a second conveying direction which is horizontal and orthogonal to the first conveying direction; and

and a lifting unit configured to lift and lower the first conveying unit with respect to the second conveying unit.

2. Big board elevator according to claim 1,

the first conveying part comprises a bracket and a plurality of groups of belt mechanisms which are arranged on the bracket in parallel;

the second conveying part comprises a plurality of roller rods which are arranged on the conveying device rack in parallel;

the belt mechanism and the roller rods are arranged in parallel and alternately.

3. Big board elevator according to claim 2,

the lifting part comprises a plurality of lifting mechanisms arranged on the carrying device rack and a connecting rod connected with the plurality of lifting mechanisms to drive the lifting mechanisms;

each of the plurality of lifting mechanisms includes a lifting mechanism support mounted to the carrier frame, a first rod member, and a second rod member;

the first rod member is a bending rod having one end rotatably fixed to the link, and a bending portion thereof is rotatably fixed to the lifting mechanism support;

one end of the second rod member is fixed to the bottom of the bracket, and the other end of the second rod member is rotatably connected to the other end of the first rod member.

4. Big board elevator according to claim 3,

the bending angle of the first rod member is 90 degrees.

5. Big board elevator according to claim 1,

the lifting device comprises a lifting motor, a chain wheel driven by the lifting motor to rotate and a chain wound on the chain wheel;

one end of the chain is connected with the carrying device, and the other end of the chain is connected with a counterweight by bypassing the chain wheel.

6. Big board elevator according to claim 1,

and an elastic auxiliary pulley which is pressed on the elevator rack is arranged below the carrying device.

7. Big board elevator according to any of claims 1-6,

the elevator rack is also provided with a plurality of detection electric eyes for detecting the position of the carrying device and a plurality of limit switches for limiting the movement of the carrying device;

the carrying device is also provided with a plurality of large plate detection electric eyes for detecting the positions of the large plates.