CN117360056A

CN117360056A - Scraping and sweeping assembly for stencil printer

Info

Publication number: CN117360056A
Application number: CN202210769243.6A
Authority: CN
Inventors: 张俭; 郭占青
Original assignee: Illinois Tool Works Inc
Current assignee: Illinois Tool Works Inc
Priority date: 2022-06-30
Filing date: 2022-06-30
Publication date: 2024-01-09
Also published as: TW202402551A; WO2024006031A1

Abstract

The present disclosure provides a squeegee assembly for a stencil printer that includes a squeegee mount, a squeegee blade holder, a pair of baffles, a pair of mounting blocks, and a pair of spring plates. The doctor blade has a travel path for scraping the material to be dispensed. The scraper frame comprises a connecting part and a supporting part which is positioned below the connecting part and supports the scraper. The pair of second end portions of the supporting portion are respectively retracted relative to the pair of first end portions of the connecting portion to form a pair of installation spaces below the connecting portion. The baffles are held on opposite sides of the travel path of the doctor blade. The pair of baffles are movable up and down relative to the support portion and are respectively at least partially located in the pair of installation spaces. A pair of mounting blocks are connected to the connection portion of the wiper blade holder. The elastic pieces are respectively connected to the mounting blocks and extend to the upper parts of the baffle plates. The pair of elastic pieces are pushed by the baffle plates to elastically deform when the pair of baffle plates move upwards, and enable the pair of baffle plates to move downwards through restoring force.

Description

Scraping and sweeping assembly for stencil printer

Technical Field

The present disclosure relates generally to a doctor blade assembly in a stencil printer for printing viscous substances, such as solder paste, onto a substrate, such as a printed circuit board.

Background

In a typical circuit board manufacturing process, stencil printers are used to print solder paste onto printed circuit boards. A circuit board, also referred to broadly as an electronic substrate, having a pattern of pads or some other conductive surface on which solder paste may be deposited, is automatically fed into a stencil printer. Some of the holes or marks on the circuit board, known as fiducial marks, are used to align the circuit board with the stencil or screen of the stencil printer prior to printing solder paste onto the circuit board. The datum point is used as a reference point when aligning the circuit board with the stencil. Once the circuit board is aligned with the stencil of the printer, the circuit board is raised to the stencil by a substrate support, such as a platform with pins or other object supports, and secured relative to the stencil. Solder paste is then dispensed by moving a wiper blade or squeegee across the stencil to pass the solder paste through apertures in the stencil and onto the circuit board. Solder paste is typically dispensed onto the stencil from a standard solder paste supply cartridge. After the printing operation is completed, the circuit board is released, lowered and removed from the stencil and transported to another location within the printed circuit board production line.

As the squeegee moves across the stencil, the solder paste rolls in front of the squeegee, which causes the solder paste to mix as desired to achieve the desired viscosity to help fill the apertures in the stencil or stencil. A pair of baffles are provided on opposite sides of the doctor blade which can hold solder paste in the path of travel of the doctor blade for better mixing and dispensing of the solder paste.

Disclosure of Invention

According to a first aspect of the present disclosure, there is provided a squeegee assembly for a stencil printer, comprising: a scraper mounting seat; a scraper having a travel path for scraping material to be dispensed; a doctor blade holder including a connecting portion and a supporting portion connected to each other, the supporting portion being located below the connecting portion and supporting the doctor blade, the doctor blade holder being connected to the doctor blade mount through a top surface of the connecting portion, wherein the connecting portion has a pair of first end portions located at opposite sides of a travel path of the doctor blade, the supporting portion has a pair of second end portions located at opposite sides of the travel path of the doctor blade, the pair of second end portions being retracted with respect to the pair of first end portions, respectively, to form a pair of mounting spaces located below the connecting portion; a pair of shutters held at a pair of second ends of the support portion such that the pair of shutters are located at opposite sides of a travel path of the doctor blade, wherein the pair of shutters are movable up and down with respect to the support portion, and wherein the pair of shutters are located at least partially in the pair of installation spaces, respectively; a pair of mounting blocks connected to the connection portion of the blade frame, the pair of baffles being respectively located between a pair of second ends of the support portion and the pair of mounting blocks; and a pair of elastic pieces respectively connected to the pair of mounting blocks and respectively extending above the pair of baffles, the pair of elastic pieces being configured to be elastically deformed by being pushed by the baffles when the pair of baffles move upward and to enable the pair of baffles to move downward by a restoring force.

According to the above-described wiper assembly, the pair of shutters are respectively connected to the pair of mounting blocks so as to be movable up and down.

According to the scraping and sweeping assembly, the top surface of the baffle comprises an acting surface for interacting with the elastic sheet, the acting surface is located outside the installation space, and the elastic sheet extends to the upper portion of the acting surface.

According to the scraping and sweeping assembly, the top surface of the baffle further comprises an avoidance surface, the avoidance surface is lower than the acting surface, and the avoidance surface is located in the installation space.

According to the scraping and sweeping assembly, the baffle is provided with at least one guide groove extending along the up-down direction; the sweep assembly also includes at least one fastener that mates with the at least one guide slot to moveably connect the baffle to the pair of mounting blocks.

The scraping assembly comprises a first part and a second part which are connected with each other, wherein the first part is positioned in the installation space, the second part is positioned outside the installation space, and the elastic sheet is connected to the top surface of the second part.

According to the above-described wiper assembly, the active surface of the baffle is located substantially on the extended surface of the top surface of the second portion of the mounting block when the baffle is in its lowermost position.

According to the above-described scraping assembly, the pair of baffles are configured to hold the material to be dispensed in the travel path of the scraper blade.

According to the above-described scraping assembly, the scraper has a length perpendicular to its travel path, and the distance between the pair of baffles is slightly larger than the length of the scraper.

According to a second aspect of the present disclosure, there is provided a stencil printer comprising a wiper assembly according to the first aspect described above.

Drawings

FIG. 1 is a perspective view of a stencil printer in accordance with one embodiment of the present disclosure;

FIG. 2A is a perspective view of one view of a wiper assembly according to one embodiment of the present disclosure;

FIG. 2B is a perspective view of another view of the wiper assembly of FIG. 2A;

FIG. 2C is a partially exploded view of the sweep assembly shown in FIG. 2A;

FIG. 3A is an assembly view of the doctor blade holder and doctor blade of the doctor assembly of FIG. 2A;

FIG. 3B is an assembly view of the doctor blade holder and doctor blade of the doctor assembly of FIG. 2A from another perspective;

FIG. 3C is an exploded view of one view of the doctor blade holder and doctor blade in the doctor assembly shown in FIG. 2A;

FIG. 3D is an exploded view of another view of the doctor blade holder and doctor blade in the doctor assembly shown in FIG. 2A;

FIG. 4 is a perspective view of a baffle in the wiper assembly shown in FIG. 2A;

fig. 5 is an assembled perspective view of the baffle and mounting block of the wiper assembly shown in fig. 2A.

Detailed Description

Various embodiments of the present disclosure are described below with reference to the accompanying drawings, which form a part hereof. It is to be understood that, although directional terms, such as "front", "rear", "upper", "lower", "left", "right", "top", "bottom", etc., are used in this disclosure to describe various example structural portions and elements of this disclosure, these terms are used herein for convenience of description only and are determined based on the example orientations shown in the drawings. As embodiments of the present disclosure may be arranged in a variety of orientations, these directional terms are used by way of illustration only and should not be considered limiting.

Fig. 1 is a perspective view of a stencil printer 100 in accordance with one embodiment of the present disclosure. As shown in fig. 1, the stencil printer 100 includes a frame 110 that supports various components of the stencil printer. The components of stencil printer 100 include a controller 120, a display 125, a stencil 130, and a print head assembly or print head 140 for applying solder paste. The stencil 130 and the print head 140 may be suitably coupled or connected to the frame 110. In one embodiment, the print head 140 may be mounted on a print head holder 150, and the print head holder 150 may be mounted on the frame 110. The carriage 150 enables the print head 140 to move in the Y-axis direction under the control of the controller 140. The print head 140 may be placed over the stencil 130 and the front or rear blades of the print head 140 may be lowered in the Z-axis direction into contact with the stencil 130. The squeegee of the print head 140 can then be moved past the stencil 130 by the carriage 150 to cause solder paste to be printed onto the circuit board.

Stencil printer 100 may also include a conveyor system comprising rails 160 that are used to transport printed circuit boards (sometimes referred to as "printed wiring boards," "substrates," or "electronic substrates") to a print position within stencil printer 100. The track 160, also referred to herein as a "feed mechanism," is configured to provide, load, or transport circuit boards to and from the work area of the stencil printer 100. Stencil printer 100 has a support assembly 170 to support a circuit board.

In some embodiments, the print head 140 may be configured to obtain solder from a source such as a dispenser (e.g., a cartridge of solder paste) that provides solder paste to the print head during a printing operation. Other methods of providing solder paste may be used instead of a solder paste cartridge. For example, solder paste may be manually deposited between the blades or the solder paste may be from an external source. Further, in some embodiments, the controller 120 may be configured to control the operation of the stencil printer 100 using a personal computer having a Microsoft DOS or Windows XP operating system with application specific software. The controller 120 may be networked with a master controller that is used to control a production line that manufactures circuit boards.

In some embodiments, stencil printer 100 operates as follows. The circuit board is fed into the stencil printer 100 in the X-axis direction via the conveyor rail 160. The support assembly 170 lifts and secures the circuit board in the printed position. The print head 140 then lowers the desired print head blade in the Z-axis direction until the print head blade contacts the stencil 130 at the desired pressure. The print head 140 is then moved through the stencil 130 in the Y-axis direction by the print head carriage 150. The print head 140 deposits solder paste through the apertures in the stencil 130 and onto the circuit board. Once the print head 140 has completely passed over the stencil 130, the squeegee is lifted off the stencil 130 and the circuit board is lowered back into the conveyor rail 160. Subsequently, the circuit board is released and output from the stencil printer 100 so that a second circuit board may be loaded into the stencil printer 100. For printing on the second circuit board, the other blade would be lowered along the Z-axis into contact with the stencil and the print head 140 would be moved across the stencil 130 in a direction opposite to that used for the first circuit board.

Still referring to fig. 1, an imaging system 180 may be provided for aligning the stencil 130 with the circuit board prior to printing and inspecting the circuit board after printing. In one embodiment, the imaging system 180 may be disposed between the stencil 130 and the support assembly 170 supporting the circuit board. The imaging system 180 is coupled to an imaging support 185 to move the imaging system. In one embodiment, the imaging support 185 may be connected to the gantry 110 and the imaging support 185 includes a cross beam that extends between side rails of the gantry 110 so that the imaging system 180 may move back and forth in the Y-axis direction over the circuit board. The imaging support 185 may also include a transport device that is enclosed outside the imaging system 180 and is configured to move along the length of the beam in the X-axis direction. The structure of the imaging support 185 for the mobile imaging system 180 is well known in the solder paste printing arts. The arrangement is such that the imaging system 180 may be positioned anywhere below the stencil 130 and above the circuit board to acquire images of the circuit board or a predetermined area of the stencil, respectively.

In one embodiment, the print head 140 includes a frame member 145 that forms a portion of the carriage 150. The frame member 145 is disposed to move along a printing direction, for example, a Y-axis direction. Specifically, the frame member 145 is configured to slide along a linear rail (not shown in fig. 1) of the frame 110 of the stencil printer 100 at opposite ends thereof. This configuration allows the printhead carrier 150 to move in the Y-axis direction. In one embodiment, the frame member 145 supports a wiper assembly having front and rear blades and a movement mechanism configured to independently move the blades. Each doctor blade is arranged to move in the Z-axis direction from a higher position spaced from the stencil to a lower position engaging the stencil and applying pressure to the stencil under the control of a respective movement mechanism.

Fig. 2A-2C illustrate an overall structure of the wiper assembly 200 according to one embodiment of the present disclosure, wherein fig. 2A is a perspective view of one view of the wiper assembly 200, fig. 2B is a perspective view of another view of the wiper assembly 200 of fig. 2A, and fig. 2C is a partially exploded view of the wiper assembly 200 shown in fig. 2A. As shown in fig. 2A-2C, the wiper assembly 200 includes a wiper 220, a wiper mount 210 for mounting the wiper 220, and a wiper frame 220. Doctor blade 220 is, for example, a front doctor blade, and only the front doctor blade and its mounting member are shown in the wiping assembly 200 of fig. 2A-2C, with the rear doctor blade and its mounting member removed for ease of illustration. The scraper 220 has a travel path for scraping the material to be dispensed (solder paste), which extends in the Y-axis direction. Doctor blade holder 230 is used to support doctor blade 220 and doctor blade mount 210 is used to attach doctor blade holder 230 to a doctor blade movement mechanism (not shown).

The scraping assembly 200 further includes a pair of baffles 250 and a pair of mounting blocks 260 that respectively hold the pair of baffles 250 on opposite sides of the travel path of the scraper 220. A pair of baffles 250 are used to hold solder paste in the path of travel of the squeegee 220 so that the squeegee 220 can sweep the solder paste so that the solder paste can pass through the apertures in the stencil 130 and onto the circuit board beneath the stencil 130. A pair of mounting blocks 260 are coupled to the blade holder 230, and a pair of shutters 250 are respectively coupled to the pair of mounting blocks 260 to be movable up and down (along the Z-axis), so that the pair of shutters 250 can be moved up and down with respect to the blade holder 230 and the blade 220 held on the blade holder 230.

The squeegee 220 is required to exert a certain pressure on the stencil when sweeping the solder paste, and therefore the squeegee mount 210 is lowered relative to the stencil 130 to deform the squeegee 220 so as to exert the pressure. In order to keep the solder paste on the travel path of the squeegee 220, the lowermost ends of the pair of shutters 250 and the lowermost ends of the squeegee 220 when in operation need to be in contact with the stencil 130. Therefore, in order not to affect the operation of the squeegee 220 while maintaining the solder paste on the traveling path of the squeegee 220, the shutter 250 needs to be able to move up and down with respect to the mounting block 230. That is, the shutter 250 needs to move upward when the scraper 220 deforms by applying pressure to the template, and the shutter 250 needs to move downward when the scraper 220 returns to its original state without applying pressure to the template. In this way, the lowermost end of the shield 250 can always remain in the same plane as the lowermost end of the squeegee (i.e., both are in contact with the stencil 130), the shield 250 can always hold solder paste in the path of travel of the squeegee 220, and the operation of the squeegee 220 is not affected. In order to enable the barrier 250 to move up and down with respect to the mounting blocks 260 along with the deformation of the scraper 220, the scraping assembly 200 further includes a pair of elastic pieces 270, and the pair of elastic pieces 270 are respectively connected to the pair of mounting blocks 260 and respectively extend above the pair of barriers 250. And the pair of elastic pieces 270 are configured to be elastically deformed by being pushed by the shutter 250 when the pair of shutters 250 moves upward, and to enable the pair of shutters 250 to move downward by a restoring force.

As shown in fig. 2C, mounting block 260 is connected to doctor frame 230 by fasteners 283, spring plate 270 is connected to mounting block 260 by fasteners 282, and baffle 250 is connected to mounting block 260 by fasteners 285.

Fig. 3A-3D illustrate a specific structure of the blade holder 230 and a mounting structure of the blade 220 of the wiper assembly 200 of fig. 2A. Among them, fig. 3A is an assembly view of one view of blade holder 230 and blade 220, fig. 3B is an assembly view of the other view of blade holder 230 and blade 220, fig. 3C is an exploded view of one view of blade holder 230 and blade 220, and fig. 3D is an exploded view of the other view of blade holder 230 and blade 220. As shown in fig. 3A-3D, the blade holder 230 includes a connection portion 310 and a supporting portion 350 connected to each other, and the supporting portion 350 is located below the connection portion 310 for supporting or holding the blade 220. The doctor blade holder 230 is connected to the doctor blade mount 210 by a top surface 312 of the connection 310. The connection part 310 has a pair of first ends 313, 315 located at opposite sides of the travel path of the scraper 220, and the support part 350 has a pair of second ends 353,355 located at opposite sides of the travel path of the scraper 220. The pair of second ends 353,355 of the support portion 350 are respectively retracted inward with respect to the pair of first ends 313, 315 of the connection portion 310 to form a pair of mounting spaces 370 under the connection portion 310, the mounting spaces 370 being for mounting the pair of shutters 250 and the pair of mounting blocks 260.

The support portion 350 of the doctor blade holder 230 includes a first portion 352 and a second portion 354 that are removably coupled together. The first portion 352 is connected at its top to the connection portion 310, for example, integrally formed with the connection portion 310. The second portion 354 is removably attached to the side of the first portion 352 facing the solder paste to be scraped by the fastener 380. The scraper 220 is sheet-like and is clamped between a first portion 352 and a second portion 354 of the support 350. The squeegee 220 has a blade portion 322 and a squeegee surface 325, the blade portion 322 protruding from the bottom of the squeegee frame 230, the squeegee surface 325 facing the second portion 354, but a large portion of the squeegee surface 325 is exposed without being obscured by the second portion 354, so that a large portion of the squeegee surface 325 is accessible to the solder paste to be squeegee. Doctor blade 220 is held in doctor blade holder 230 as a whole obliquely with respect to the Z-axis direction, and is inclined rearward with respect to the advancing direction. In operation, blade 220 applies pressure to the stencil from a side of scraping surface 325, thereby causing blade 322 to flex toward first portion 352.

The length of the scraper blade 220 (i.e., the dimension perpendicular to its wiping path) is substantially equal to the distance between the pair of second ends 353,355 of the support section 350, so that when the scraper blade 220 is installed in place in the support section 350, both ends of the scraper blade are aligned with the second ends 353,355 of the support section 350, respectively. The pair of shutters 250 are held at the pair of second ends 353,355 of the support portion 350 by the pair of mounting blocks 260, respectively, with a distance between the pair of shutters 250 slightly greater than a distance between the pair of second ends 353,355 of the support portion 350. Thus, the distance between the pair of baffles 250 is slightly greater than the length of the doctor blade 220. By doing so, it is possible to make the pair of shutters 250 as close as possible to the squeegee while being able to move up and down, thereby better holding the solder paste on the traveling path of the squeegee.

Fig. 4 and 5 show specific structures of the barrier 250 and the mounting block 260, wherein fig. 4 is a perspective view of the barrier 250 in the wiper assembly 200 shown in fig. 2A, and fig. 5 is an assembled perspective view of the barrier 250 and the mounting block 260 in the wiper assembly 200 shown in fig. 2A.

As shown in fig. 4, the baffle 250 is generally rectangular with a top surface 410 that is generally stepped. Specifically, the top surface 410 includes an active surface 412 for interacting with the spring 270 and a relief surface 414 below the active surface 412. When the baffle 250 is mounted in place, the relief surface 414 is located in the mounting space 370 of the support portion 350 (i.e., below the connection portion 310), while the active surface 412 is located outside the mounting space of the support portion 350. In the up-down direction, the working surface 412 can be moved above the installation space 370. The baffle 250 is provided with an elongated guide groove 420, and the guide groove 420 extends in the up-down direction to allow the baffle 250 to be connected to the mounting block 260 to be movable up-down. In some embodiments, the number of guide slots 420 is two, which are located below the active face 412 and the relief face 414, respectively. The bottom end 430 of the baffle 250 and the lowermost end of the doctor blade 220 are both in contact with the stencil 130 during operation.

As shown in fig. 5, the mounting block 260 includes a first portion 510 and a second portion 520 that are connected to each other. When the mounting block 260 is mounted in place, the first portion 510 is located in the mounting space 370 of the support 350 (i.e., below the connection portion 310), and the second portion 520 is located outside the mounting space 370. The proximal end of the spring 270 is attached to the top surface 523 of the second portion 520, and the distal end of the spring 270 extends above the active surface 412 of the bezel 250.

The baffle 250 is connected to the mounting blocks 260 by the fasteners 285, the number of the fasteners 285 is the same as the number of the guide grooves 420, each of the mounting holes 420 is matched with one of the fasteners 285, and the fasteners 285 can move up and down in the guide grooves 420. The baffle 250 includes a lowermost position and an uppermost position. When the shutter 250 is at the lowermost position, the shutter 250 is at the lowermost position of its moving track, and the fastener 285 is at the uppermost end of the guide groove 420. When the shutter 250 is at the highest position, the shutter 250 is at the uppermost part of its moving track, and the fastener 285 is at the bottommost end of the guide groove 420.

When the baffle 250 is in its lowermost position, the active surface 412 of the baffle 250 is substantially located on an extended surface of the top surface 523 of the second portion 520 of the mounting block 260, and the spring plate 270 presses against the active surface 412 of the baffle 250 and exerts a certain pressure on the active surface 412. When the blade 220 starts to press the die plate 130 to perform the wiping operation of the solder paste, the edge portion 322 of the blade 220 is compressively deformed from one side of the wiping surface 325, and the shutter 250 moves upward away from its lowermost position by the die plate 130 with the deformation of the blade 220. In this process, the elastic piece 270 receives an upward pushing force applied from the shutter 250 to elastically deform, thereby accumulating a restoring force. When the shutter 250 is no longer subjected to the force of the form 130, the shutter 250 moves downward to its lowest position by the restoring force of the spring plate 270. Thus, the lowermost end of the dam 250 can always remain coplanar with the lowermost end of the squeegee 220, and the dam 250 does not affect the operation of the squeegee 220 while maintaining solder paste in the path of travel of the squeegee. In addition, as the service time becomes longer, the edge portion 322 of the blade 220 may be deformed. By providing the shutter 250 to be movable up and down, the bottommost end of the shutter 250 can always be kept coplanar with the bottommost end of the scraper 220, regardless of whether the edge portion 322 of the scraper 220 is deformed or not.

For the wiper assembly 200, the top surface of the wiper blade holder 230 (i.e., the top surface 312 of the connection portion 310) is limited in size by the wiper mount 210, with the top surface 312 having a length that is at least as long as the general length of the bottom surface of the wiper mount 210 to facilitate installation between the wiper blade holder 230 and the wiper mount 210. The wiper blade assembly 200 of the present disclosure forms an installation space under the connection part 310 by dividing the wiper blade holder 220 into two parts having different length dimensions, i.e., the connection part 310 and the support part 350, and causing both ends of the support part 350 defining the length thereof to be retracted inward with respect to the end of the connection part 310 defining the length thereof. And the present application arranges the barrier plates 250 and the mounting portions of the mounting block 260 under the connection portion 310 such that a pair of barrier plates 250 are respectively located at both ends of the support portion 350. Thus, the distance between the pair of shutters 250 may not be limited by the distance between both ends of the connection portion 310 of the doctor blade holder 220, but may be adjusted according to the length of the doctor blade 220, allowing the doctor blade holder 230 to accommodate a smaller sized doctor blade 220. Therefore, the size of the scraper that can be used in the wiper assembly 200 according to the present application can be small, so that the production requirement of gradually miniaturizing the size of the circuit board can be satisfied.

It should be noted that, although the baffle 250 is shown mounted on the mounting block 260 in the embodiment in the drawings, in other embodiments, the baffle 250 may be mounted on both ends of the support portion 350 of the scraper blade 230, which is within the scope of the present application.

While the present disclosure has been described in conjunction with the examples of embodiments outlined above, various alternatives, modifications, variations, improvements, and/or substantial equivalents, whether known or that are or may be presently or later be envisioned, may be apparent to those of ordinary skill in the art. Further, the technical effects and/or technical problems described in the present specification are exemplary rather than limiting; the disclosure in this specification may be used to solve other technical problems and to have other technical effects and/or may solve other technical problems. Accordingly, the examples of embodiments of the disclosure as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit or scope of the disclosure. Accordingly, the present disclosure is intended to embrace all known or earlier developed alternatives, modifications, variations, improvements and/or substantial equivalents.

Claims

1. A squeegee assembly (200) for a stencil printer, comprising:

a doctor blade mount (210);

a scraper (220), the scraper (220) having a travel path for scraping material to be dispensed;

a doctor blade holder (230), the doctor blade holder (230) comprising a connecting portion (310) and a supporting portion (350) connected to each other, the supporting portion (350) being located below the connecting portion (310) and supporting the doctor blade (220), the doctor blade holder (230) being connected to the doctor blade mount (210) by a top surface (312) of the connecting portion (310), wherein the connecting portion (310) has a pair of first ends (313, 315) located on opposite sides of a travel path of the doctor blade (220), the supporting portion (350) has a pair of second ends (353, 355) located on opposite sides of the travel path of the doctor blade (220), the pair of second ends (353, 355) being retracted with respect to the pair of first ends (313, 315), respectively, to form a pair of mounting spaces (370) located below the connecting portion (310);

a pair of shutters (250) held at a pair of second ends (353, 355) of the support portion (350) such that the pair of shutters (250) are located at opposite sides of a travel path of the scraper (220), wherein the pair of shutters (250) are movable up and down with respect to the support portion (350), and wherein the pair of shutters (250) are located at least partially in the pair of installation spaces (370), respectively;

-a pair of mounting blocks (260), the pair of mounting blocks (260) being connected to the connection portion (310) of the doctor blade holder (230), the pair of baffles (250) being located between a pair of second ends (353, 355) of the support portion (350) and the pair of mounting blocks (260), respectively; and

a pair of elastic pieces (270), the pair of elastic pieces (270) being respectively connected to the pair of mounting blocks (260) and extending above the pair of baffles (250), respectively, the pair of elastic pieces (270) being configured to be elastically deformed by being pushed by the baffles (250) when the pair of baffles (250) move upward and to enable the pair of baffles (250) to move downward by a restoring force.

2. The wiper assembly (200) as set forth in claim 1 wherein:

the pair of shutters (250) are respectively connected to the pair of mounting blocks (260) so as to be movable up and down.

3. The wiper assembly (200) as set forth in claim 2 wherein:

the top surface (410) of the baffle (250) comprises an active surface (412) for interaction with the spring plate (270), the active surface (412) being located outside the installation space (370), wherein the spring plate (270) extends above the active surface (412).

4. The wiper assembly (200) as set forth in claim 3 wherein:

the top surface (410) of the baffle (250) further comprises an avoidance surface (414), the avoidance surface (414) is lower than the action surface (412), and the avoidance surface (414) is located in the installation space (370).

5. The wiper assembly (200) as set forth in claim 2 wherein:

at least one guide groove (420) extending along the up-down direction is arranged on the baffle plate (250);

the wiper assembly (200) further includes at least one fastener (285), the at least one fastener (285) cooperating with the at least one guide slot (420) to movably connect the barrier (250) up and down to the pair of mounting blocks (260).

6. The wiper assembly (200) as set forth in claim 3 wherein:

the mounting block (260) comprises a first portion (510) and a second portion (520) connected to each other, the first portion (510) being located in the mounting space (370) and the second portion (520) being located outside the mounting space (370), wherein the resilient tab (270) is connected to a top surface (523) of the second portion (520).

7. The wiper assembly (200) as set forth in claim 6 wherein:

the active face (412) of the baffle (250) is located substantially on an extension of the top surface (523) of the second portion (520) of the mounting block (260) when the baffle (250) is in its lowermost position.

8. The wiper assembly (200) as set forth in claim 1 wherein:

the pair of baffles (250) are configured to hold material to be dispensed in a travel path of the scraper (220).

9. The wiper assembly (200) as set forth in claim 8 wherein:

the blade (220) has a length perpendicular to its travel path, and the distance between the pair of baffles (250) is slightly greater than the length of the blade (220).

10. A stencil printer, comprising:

the sweep assembly (200) according to any one of claims 1-9.