Sheet Manufacturing Apparatus and Sheet Production Method

The present application is based on, and claims priority from JP Application Serial Number 2024-088751, filed May 31, 2024, the disclosure of which is hereby incorporated by reference herein in its entirety.

The present disclosure relates to a sheet manufacturing apparatus and a sheet production method.

In the related art, an apparatus for manufacturing a sheet from fibers derived from used paper or the like has been known. For example, JP-A-2016-112740 discloses a sheet manufacturing apparatus in which fibers accumulate in air and are then formed into a sheet.

However, a problem of the apparatus described in JP-A-2016-112740 is handling of a material that is accumulating when the apparatus is stopped.

A sheet manufacturing apparatus includes a defibrator that defibrates a fiber material to form a defibrated material, an accumulator that accumulates the defibrated material on a transport body to form an accumulating material, a forming machine that forms the transported accumulating material to produce a sheet, and a return mechanism that sends a residual accumulating material that is the defibrated material being accumulating to the defibrator on condition that the accumulator has stopped or is stopped during accumulation.

A sheet production method includes defibrating a fiber material to form a defibrated material, accumulating the defibrated material on a transport body to form an accumulating material, and forming the transported accumulating material to produce a sheet, in which a residual accumulating material that is the defibrated material being accumulating is returned to a defibrator and accumulates on the transport body in response to an instruction to stop accumulation given during accumulation.

In the following embodiment, a sheet manufacturing apparatusthat produces a sheet by a dry process from a fiber material such as used paper containing fibers and a sheet production method using the sheet manufacturing apparatuswill be exemplified and described with reference to the drawings. The sheet manufacturing apparatus of the present disclosure is not limited to a dry type and may be a wet type. In the present specification, “dry type” means not to be performed in a liquid but to be performed in air such as the atmosphere.

In each of the following drawings, XYZ-axes are given as coordinate axes orthogonal to each other, a direction indicated by each arrow is set as a positive direction, and a direction opposite to the positive direction is set as a negative direction. The Z-axis is a virtual axis extending in a vertical direction, a +Z direction is an upward direction, and a −Z direction is a downward direction. The −Z direction is the vertical direction. In addition, in the sheet manufacturing apparatus, a leading side in a transport direction of a fiber material, an accumulating material, a sheet, or the like is downstream, and a going-back side in the transport direction is upstream. For convenience of illustration, the size of each member is different from the actual size.

As illustrated in, the sheet manufacturing apparatusaccording to the present embodiment includes a first unit group, a second unit group, and a third unit group. The first unit group, the second unit group, and the third unit groupare supported by a frame (not illustrated). In, directions in which fiber materials such as paper pieces C, a sheet P, waste paper P, a slit piece S, scraps, and the like move are indicated by white arrows, and directions in which a residual accumulating material V moves are indicated by dashed arrows.

The sheet manufacturing apparatusmanufactures the sheet Pfrom the paper pieces C which are fiber materials containing fibers such as used paper. In the sheet manufacturing apparatus, the first unit group, the third unit group, and the second unit groupare arranged from a −Y direction to a +Y direction in side view in a −X direction.

The paper pieces C are transported from the first unit groupto the second unit groupthrough a pipethat crosses the inside of the third unit group. The paper pieces C are defibrated in the second unit groupto form a defibrated material, which is an aggregate of fibers, and a binder and the like are added to the defibrated material. The defibrated material is transported to the third unit groupthrough a pipe. The defibrated material is formed into an accumulating material W in the third unit groupand is then formed into a strip-shaped sheet P. The strip-shaped sheet Pis cut into the sheet Pin the first unit group.

The first unit groupincludes a buffer tank, a fixed-quantity supply unit, a merging unit, and the pipe. In the first unit group, these components are arranged in this order from upstream to downstream. The first unit groupalso includes a first cutting unit, a second cutting unit, a tray, a waste paper tray, and a shredding unit.

Moreover, a sheet transport unitis disposed from the third unit groupto the first unit group. The sheet transport unittransports the strip-shaped sheet P, a single-cut sheet P, the sheet P, the waste paper P, and the slit piece S. The first cutting unitand the second cutting unitcut the strip-shaped sheet Pinto the sheet Phaving a predetermined shape.

The sheet Pthat is produced is stacked in the tray. The waste paper Pproduced according to a stop operation of the sheet manufacturing apparatusis stacked in the waste paper tray. Details of the waste paper Pwill be described later.

Moreover, the first unit groupincludes a water supply unit. The water supply unitis a water storage tank. The water supply unitsupplies water for humidification to each of a first humidification unitand a second humidification unit, which will be described later, through a water supply pipe (not illustrated).

The paper pieces C are input from a raw material input portto the buffer tank. The paper pieces C contain fibers such as cellulose and are, for example, pieces of shredded used paper. Humidified air is supplied to the inside of the buffer tankfrom the second humidification unitincluded in the third unit group.

The paper pieces C to be defibrated are temporarily stored in the buffer tankand are then transported to the fixed-quantity supply unitaccording to the operation of the sheet manufacturing apparatus. The sheet manufacturing apparatusmay include a shredder that shreds the paper pieces C and the like upstream of the buffer tank.

The fixed-quantity supply unitincludes a weighing deviceand a supply mechanism (not illustrated). The weighing deviceweighs a mass of the paper pieces C. The supply mechanism supplies the paper pieces C weighed by the weighing deviceto the merging unitlocated downstream. That is, the fixed-quantity supply unitweighs the paper pieces C by each predetermined mass using the weighing deviceand supplies the paper pieces C to the merging unitlocated downstream by the supply mechanism.

Both digital and analog weighing mechanisms can be applied to the weighing deviceSpecific examples of the weighing deviceinclude a physical sensor such as a load cell, a spring scale, and a balance. In the present embodiment, a load cell is used as the weighing deviceto weigh several grams to several tens of grams, but the present disclosure is not limited thereto.

A known technique such as a vibration feeder can be applied to the supply mechanism. The supply mechanism may be included in the weighing device

The weighing and supplying of the paper pieces C in the fixed-quantity supply unitare batch processing. That is, the paper pieces C are intermittently supplied from the fixed-quantity supply unitto the merging unit. The fixed-quantity supply unitmay include a plurality of weighing devicesand the plurality of weighing devicesmay be operated at different times to improve the weighing efficiency.

The sheet manufacturing apparatusincludes a return mechanism. The return mechanism includes a box, a tube, the merging unit, the pipe, and a suction blower (not illustrated) of a suction unit. In the return mechanism, the merging unitis disposed in the first unit group, and the boxis disposed in the third unit group.

The pipeis extended from the first unit groupto the second unit grouppassing through the third unit groupand connects the merging unitand the defibrator. The tubeis extended from the third unit groupto the first unit groupand connects the boxand the merging unit. The suction blower of the suction unit, which will be described later, is connected to the tubethrough a pipe (not illustrated).

The return mechanism temporarily stores the residual accumulating material V in the boxand then transports the residual accumulating material V to the merging unitthrough the tube. The return mechanism then merges the residual accumulating material V with the paper pieces C and the slit piece S in the merging unitand sends them to the defibrator. The slit piece S is a scrap generated when the strip-shaped sheet Pis cut into the sheet Phaving a predetermined shape. The slit piece S is shredded by the shredding unitand supplied to the merging unit.

The residual accumulating material V is a defibrated material that is accumulating and produced when the operation of the sheet manufacturing apparatusis stopped. The residual accumulating material V is not mixed with the paper pieces C during a normal operation of the sheet manufacturing apparatus, in which the sheet Pis produced, and is mixed with the paper pieces C only when the sheet manufacturing apparatusis stopped. That is, in the pipe, the paper pieces C and the slit piece S flow during the normal operation, and the residual accumulating material V flows in addition to the paper pieces C and the slit piece S during the stop operation. Details of the residual accumulating material V, the slit piece S, the shredding unit, and the like will be described later.

The return mechanism sucks air from a position of an accumulatorby the above-described suction blower of the suction unit. Specifically, the above-described suction blower of the suction unitpromotes accumulation of the defibrated material by a generated airflow. The above-described airflow moves from the suction unitto the merging unitthrough the tube. The residual accumulating material V is transported from the boxto the merging unitby the above-described airflow. In addition, the return mechanism blows out the air sucked by the above-described suction blower at a position of the defibrator. More specifically, the defibratorgenerates an airflow from the merging unitto the defibrator.

As described above, the residual accumulating material V, the paper pieces C, and the like pass through the inside of the tubeof the return mechanism and are sent to the defibratorby a wind force. As a result, compared to a configuration in which the residual accumulating material V and the like are transported by a transport belt or the like, it is possible to avoid a decrease in transportability due to the thickness of the residual accumulating material V and the like.

As illustrated in, the shredded slit piece S and the residual accumulating material V supplied from the above-described boxare merged with the paper pieces C in the merging unit. In the return mechanism, the pipeand the tubeeach have a circular cross section. In, a portion of the tubeon the above-described boxside and a portion of the pipeon the above-described defibratorside are not illustrated.

During the normal operation of the sheet manufacturing apparatus, the paper pieces C and the slit piece S are mixed while being transported inside the pipeby the above-described wind force. During the stop operation of the sheet manufacturing apparatus, the paper pieces C, the shredded slit piece S, and the residual accumulating material V are mixed while being transported inside the pipeby the above-described wind force.

Returning to, the second unit groupincludes the defibrator, which is a dry type defibrator, a separator, a pipe, a mixing unit, and the pipe. In the second unit group, these components are arranged in this order from upstream to downstream. The second unit groupalso includes a control unit, a capturing unit, a compressor, a power supply unit, and a pipeand an airflow pipeconnected to the separator.

The paper pieces C and the like transported through the pipeflow into the defibrator. The defibratordefibrates the paper pieces C, which are fiber materials containing fibers, and the like by a dry method and generates a defibrated material containing fibers. A known defibrating mechanism can be applied to the defibrator.

In the present embodiment, a defibrating mechanism including a rotary blade is used as the defibrator. The defibrating mechanism generates fibers by shredding and defibrating the paper pieces C with the rotary blade. In the description of the defibratorto the accumulator, the paper pieces C, the shredded slit piece S, and the residual accumulating material V may be referred to as the paper piece C for convenience.

Tangled fibers contained in the paper piece C are untangled by the defibratorto form a defibrated material containing fibers, and the defibrated material is transported to the separator.

The separatorsorts the defibrated fibers. Specifically, the separatorremoves components contained in the fibers and unnecessary for manufacturing the sheet P. The separatorseparates relatively long fibers from relatively short fibers. The relatively short fibers, which may lower the strength of the sheet P, are sorted and removed by the separator. The separatoralso removes impurities such as coloring materials and additives contained in the paper piece C.

A known separation mechanism can be applied to the separator. In the present embodiment, a disk-type separation mechanism including a separation filter is used as the separator. The separation mechanism sorts and separates relatively short fibers and impurities that pass through the separation filter from relatively long fibers that do not pass through the separation filter. The relatively long fibers are used as the defibrated material for the material of the accumulating material W.

Humidified air is supplied to the inside of the separatorfrom the second humidification unitof the third unit group. As a result, the defibrated fibers are not easily charged, and attachment of the fibers to each other and adhesion of the fibers to the separatorare suppressed.

Relatively short fibers and the like are removed from the defibrated fibers in the separator. The defibrated fibers are then transported to the mixing unitthrough the pipeby an airflow generated by a blower (not illustrated) disposed at a leading end of the airflow pipe. Unnecessary components such as relatively short fibers and impurities are sucked by a suction device (not illustrated) of the capturing unitand are discharged from the pipeto the capturing unit.

The capturing unitincludes a filter (not illustrated). The filter filters out unnecessary components such as relatively short fibers transported through the pipeby an airflow.

The compressorgenerates compressed air. The above-described filter may be clogged with fine particles or the like of the unnecessary components. The filter can be cleaned by blowing the compressed air generated by the compressoronto the filter to blow off adhering particles.

The power supply unitincludes a power supply device (not illustrated) that supplies power to the sheet manufacturing apparatusand the control unit. The power supply unitdistributes power supplied from the outside to each component of the sheet manufacturing apparatus.

A powder supply unitsupplies a binder, which is a powder, to the mixing unit. The mixing unitmixes the defibrated material and the binder supplied from the powder supply unitin air. The binder need only be able to bind fibers to each other in a forming machine, which will be described later. In the present embodiment, starch is used as the binder, but a thermoplastic resin or the like may also be used.

The powder supply unitincludes a powder storage unit and a powder transport unit (not illustrated). The powder storage unit is attachable to and detachable from a main body of the powder supply unit. The powder storage unit can be removed from the powder supply unitto be filled with the binder or transported. The powder transport unit supplies a fixed amount of binder per unit time to the mixing unitwhile transporting the binder.

The powder supplied from the powder supply unitto the mixing unitis not limited to the binder and may be other additives such as a coloring material, for example. In addition, the above-described powder may be a mixture of the binder and other additives. Moreover, the sheet manufacturing apparatusmay include a plurality of powder supply units.

The mixing unitmixes a binder and the like with the defibrated material, which is fibers, in air. Although not illustrated, the mixing unitincludes a flow path through which the defibrated material is transported and a fan. The fan of the mixing unitmixes the binder and the like in air while transporting the defibrated material downstream using a generated airflow. The defibrated material then flows into the pipefrom the mixing unit.

The control unitis electrically connected to each component of the sheet manufacturing apparatusand integrally controls the operation of the sheet manufacturing apparatus. Although not illustrated, the control unitincludes a central processing unit (CPU) and a storage unit including a random access memory (RAM), a read only memory (ROM), and the like. Various programs for controlling the sheet manufacturing apparatusare stored in the storage unit. The control unitmay include dedicated hardware (application specific integrated circuit: ASIC) that executes at least some of various processes. That is, the control unitmay be configured as one or more processors that operate according to a computer program (software), one or more dedicated hardware circuits such as ASICs, or a circuit including a combination thereof.

The processor includes a CPU and a memory such as a RAM and a ROM. The memory stores program codes or instructions configured to cause the CPU to perform processes. The memory, that is, a computer-readable medium includes any medium that can be accessed by a general-purpose or dedicated computer.

The third unit groupaccumulates and compresses the defibrated material containing the binder and forms the defibrated material into the strip-shaped sheet P. The third unit groupincludes the accumulator, the transport unit, the box, the first humidification unit, the second humidification unit, a drainage unit, the forming machine, and the sheet transport unit. In the third unit group, the accumulator, the transport unit, and the forming machineare arranged in this order from upstream to downstream. That is, the transport unitis disposed between the accumulatorand the forming machine.

The transport unitincludes an accumulation transport unitand a back surface transport unit. The transport unittransports the accumulating material W formed in the accumulatorto the forming machinelocated downstream. In the transport direction of the accumulating material W, the accumulation transport unitis disposed upstream of the back surface transport unit. A downstream portion of the accumulation transport unitand an upstream portion of the back surface transport unitpartially face each other in the vertical direction. The boxis disposed corresponding to a downstream end portion of the accumulation transport unit. The first humidification unitis disposed below the back surface transport unit.

The accumulatoraccumulates the defibrated material containing the binder and the like using an airflow and gravity to form the accumulating material W. The accumulatorincludes a drum member, a blade memberdisposed in the drum member, a housingthat houses the drum member, and a suction unit. The defibrated material is taken into the drum memberfrom the pipe.

The accumulation transport unitis disposed below the accumulator. The accumulation transport unitincludes a mesh belt, which is a transport body, and five tension rollers (not illustrated) for tensioning the mesh belt. The suction unitfaces the drum memberwith the mesh beltinterposed therebetween in a direction along the Z-axis.