Patent Description:
For example, in various machines such as automobiles and industrial machines, a device for ejecting a constant amount of viscous material from a nozzle of a dispenser and applying the viscous material on a predetermined portion is used in applying viscous material such as an adhesive or sealing material. In the device as such, there is installed a platen (hereinafter, referred to as a piston) which presses a container accommodating the viscous material and is provided with a flow passage for sucking the viscous material. Here, a technique is disclosed in which the piston is moved, and the viscous material is force-fed from the flow passage connected to the piston (refer to Patent Literature <NUM>).

<CIT> relates to a container for a product. <CIT> relates to an emptying device. <CIT> relates to a device for air bubble-free extraction and improved aeration.

In the above application device, the viscous material needs to be supplemented when all of the viscous material inside the container is finished to be force-fed. At this time, the piston is temporarily removed from the container. In supplementing the viscous material into the container, because the viscous material that had been force-fed from the previously used container is adhered on the piston, the viscous material adhered to the piston needs to be removed when the container is replaced to the new one. Regarding this point, the inventor has been intensively studying to improve an efficiency of removal operation of the viscous material that could be adhered to the piston.

Accordingly, an object of the present invention is to provide a viscous material supply device and a viscous material supply method that facilitate the removal operation of the viscous material that could be adhered to the piston.

The viscous material supply device according to an aspect of the present invention to solve the above problem includes a tank, a piston, and a covering sheet. The tank includes a storage space storing viscous material. The piston is slidably inserted into the tank, and the piston is provided with a pressing surface that presses the viscous material and a suction passage through which the viscous material inside the tank flows by pressing force of the pressing surface. The covering sheet includes a covering part covering the pressing surface in the piston and a communication hole communicating with the suction passage. Further, one aspect of the present invention is the covering sheet used in the viscous material supply device, and including the covering part that covers the pressing surface in the piston and the communication hole that communicates with the suction passage.

In the viscous material supply method according to one aspect of the present invention, the tank, the piston, and the covering sheet are prepared. Next, the covering sheet is attached to the piston such that the covering part of the covering sheet covers the pressing surface of the piston and the communication hole of the covering sheet communicates with the suction passage of the piston. Thereafter, the viscous material is pressed by the pressing surface of the piston, and the viscous material is flowed through the suction passage. Further, one aspect of the present invention is an attaching method of the covering sheet. In the method, there are prepared the piston in which the pressing surface and the suction passage are provided, and the covering sheet including the covering part and the communication hole. Then, the covering sheet is attached to the piston such that the covering part of the covering sheet covers the pressing surface of the piston and the communication hole of the covering sheet communicates with the suction passage of the piston.

Hereinafter, an embodiment of the present invention is described with reference to the attached drawings. Note that the following description does not limit the technical scope and the meaning of the term recited in claims. Moreover, dimensional proportions in the drawings are exaggerated for convenience of description, and may differ from the actual proportion.

<FIG> are drawings provided for describing a viscous material supply device according to the present disclosure.

The viscous material supply device <NUM> according to the present disclosure is used for discharging and supplying viscous material. The viscous material supply device <NUM> applies grease, an adhesive, a liquid gasket such as an FIPG (Formed In Place Gasket), sealing material, or other viscous material, as an object to be applied, in a manufacturing process, maintenance and the like of a machine such as an automobile or industrial machine.

Here, the viscous material is viscous material that has fluidity but whose viscosity is relatively low and flow resistance to a pipeline and a nozzle is relatively low, and for example, includes grease, an adhesive, a liquid gasket such as FIPG, sealing material, and the like. A preferable viscosity of the viscous material is <NUM> Pa·s or less. In the following description, a case is described in which a silicone-based gasket that is moisture-cured by a condensation reaction in the atmosphere is used as an example of the viscous material. However, the present invention is not limited to the above.

The viscous material supply device <NUM> according to the present disclosure includes, as shown in <FIG> and <FIG>, a tank <NUM>, a piston <NUM>, a covering sheet <NUM>, a sealing member <NUM>, a pump <NUM>, an air cylinder <NUM>, a dispenser <NUM>, a pipeline <NUM>, and an air bleeding valve <NUM>. The detailed description is made below.

The tank <NUM> has, as shown in <FIG>, a storage space <NUM> storing the viscous material. The tank <NUM> is a member formed in a cylindrical shape and made of plastic such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polyethylene terephthalate, polyamide, or made of metal, and is constituted by having an upper part of the cylindrical shape opened so as to allow the viscous material to be accommodated. However, the shape of the tank <NUM> is not limited to a cylinder as long as the viscous material can be stored, and other than the above shape, can be formed in, for example, a shape of a polygonal column such as a square column or hexagonal column. Also, the shape is not necessarily cylinder or polygonal column, as long as the tank <NUM> is stably installed on the ground. In the present embodiment, the viscous material is directly accommodated in the tank <NUM> without interposing a bag or the like.

The piston <NUM> is slidably inserted inside the tank <NUM>. The piston <NUM> has, as shown in <FIG>, a main body part <NUM>, a pressing surface <NUM>, a suction passage <NUM>, pins <NUM>, a first outer shape part <NUM>, a second outer shape part <NUM>, and nuts <NUM>.

The main body part <NUM> has, as shown in <FIG>, a plate member 21a and a plate member 21b. The plate member 21a is constituted of a shape formed by combining a small-diameter cylinder and a large-diameter cylinder. Although different in sizes, similarly to the plate member 21a, the plate member 21b is constituted of a shape formed by combining a small-diameter cylinder and a large-diameter cylinder. The plate member 21a and the plate member 21b are integrally constituted by the pins <NUM> and the nuts <NUM>. However, a specific shape of the main body part <NUM> is not limited to the above as long as the main body part <NUM> can be slidably inserted inside the tank <NUM> and can press the viscous material stored inside the tank <NUM>.

The first outer shape part <NUM> is, as shown in <FIG>, a portion of the small-diameter cylinder in the plate member 21b, whose outer diameter (outer shape) is constituted smaller than that of the second outer shape part <NUM>. The second outer shape part <NUM> is a portion of the large-diameter cylinder in the plate member 21b, and is separated from the first outer shape part <NUM> downward in <FIG> in a direction that the piston <NUM> slides, and has an outer periphery constituted larger than the first outer shape part <NUM>. On an outer periphery of the first outer shape part <NUM>, the sealing member <NUM> having a disc shape is attached. The large-diameter portion of the cylinder in the plate member 21a and the second outer shape part <NUM> in the plate member 21b have outer diameters formed substantially the same as shown in <FIG>, however, the configuration is not limited to this.

The pressing surface <NUM> is a portion that presses the viscous material in the piston <NUM>. As shown in <FIG>, the pressing surface <NUM> refers to an end surface in an axial direction of the second outer shape part <NUM> in the plate member 21b of the main body part <NUM>. The pressing surface <NUM> refers to a portion in the radial direction from the outer periphery of the second outer shape part <NUM> of the plate member 21b to an outer periphery of the suction passage <NUM>, and is formed in a substantially disc shape.

The suction passage <NUM> is a portion where the viscous material inside the tank <NUM> flows through by pressing by the pressing surface <NUM>. As shown in <FIG>, the suction passage <NUM> is formed by hollowing out the main body part <NUM> at an axis center portion located at an inner part in the radial direction. In the present embodiment, the suction passage <NUM> has a substantially circular cross-sectional shape, however, the cross-sectional shape is not limited to the above as long as the viscous material can be flowed through. The pipeline <NUM> is connected to the piston <NUM>, and the pipeline <NUM> communicates with the suction passage <NUM>. The viscous material stored in the storage space <NUM> of the tank <NUM> flows into the suction passage <NUM> by pressing of the pressing surface <NUM>, and thereafter, flows into the pipeline <NUM>.

The pins <NUM> are erected on a surface opposite to the pressing surface <NUM> in the axial direction of the piston <NUM> as shown in <FIG>, and the covering sheet <NUM> is attached to the piston <NUM>. In the present embodiment, the pins <NUM> are erected with uniform angular intervals at four locations for every <NUM> degrees in a circumferential direction (angular direction), in plan view from the axial direction of the piston <NUM>. However, numbers, locations to be attached, and the angular intervals of the pins <NUM> are not limited to the above as long as the covering sheet <NUM> can be attached to the piston <NUM>, and the pins <NUM> are not necessarily arranged uniformly in the angular direction (circumferential direction). Additionally, the pin <NUM> is formed with a screw portion and is screwed with the nut <NUM>. However, the configuration is not limited to this, and as long as the covering sheet <NUM> can be attached to the piston <NUM>, the screw portion and the nut <NUM> are not necessarily provided.

The covering sheet <NUM> has, as shown in <FIG> and <FIG>, a covering part <NUM>, a communication hole <NUM>, and insertion holes <NUM>.

The covering part <NUM> covers the pressing surface <NUM> in the piston <NUM>. More specifically, the covering part <NUM> covers the pressing surface <NUM> being an end surface in the axial direction of the second outer shape part <NUM> of the plate member 21b of the piston <NUM>. With this configuration, the viscous material can be prevented from being adhered to the pressing surface <NUM> of the piston <NUM> after being force-fed from the tank <NUM>, thereby facilitating removal operation of removing the viscous material from the piston <NUM>. Material of the covering sheet <NUM> is not particularly limited, but polyethylene, polypropylene, and the like are exemplified.

The communication hole <NUM> communicates with the suction passage <NUM> of the piston <NUM> when the covering sheet <NUM> is attached to the piston <NUM>. The communication hole <NUM> is formed in a substantially circular shape similarly to the suction passage <NUM>.

The insertion holes <NUM> are provided at a relatively outer part in the radial direction of the covering sheet <NUM>. The covering sheet <NUM> is, as shown in disclosed but not claimed <FIG>, folded from a state of being located on a side of the pressing surface <NUM> to a state such that the outer periphery of the covering sheet <NUM> is on a side opposite to the pressing surface <NUM>. The insertion holes <NUM> are fitted with the pins <NUM> of the piston <NUM> at portions of the covering sheet <NUM> being folded. With this configuration, axis centers of the suction passage <NUM> of the piston <NUM> and the communication hole <NUM> of the covering sheet <NUM> match with each other.

The covering sheet <NUM> is formed in a substantially rectangular shape in plan view, however, the shape is not limited to the above as long as the pressing surface <NUM> of the piston <NUM> is covered, and apart from the above, may have a circular shape or the like.

The sealing member <NUM> is formed in a cylindrical shape with a substantially disc-shaped cross-section, and is attached to the outer periphery of the first outer shape part <NUM> of the plate member 21b of the piston <NUM>. The sealing member <NUM> seals a portion between the piston <NUM> and the tank <NUM> by being attached at the above position. Material of the sealing member <NUM> is not particularly limited as long as the portion between the piston <NUM> and the tank <NUM> can be sealed, but NBR (nitrile butadiene rubber), acrylic rubber, chloroprene rubber, fluoro-rubber, polyurethane, and the like are exemplified, and the material is selected according to the viscous material.

The pump <NUM> is not particularly limited as long as the pump can force-feed the viscous material pushed out from the tank <NUM> to the dispenser <NUM> and the like, and for example, a gear pump, a plunger pump, a screw pump, a piston pump, and the like are exemplified.

The air cylinder <NUM> is provided to drive the piston <NUM> from an opening part of the tank <NUM> toward a bottom part of the same by air pressure. The dispenser <NUM> is constituted of known components including a syringe, a plunger that can move within the syringe, and the like.

The pipeline <NUM> is provided from the piston <NUM> through the pump <NUM> to the dispenser <NUM>, and the viscous material flows through the pipeline <NUM>. A cross-sectional shape of the pipeline <NUM> is formed in a substantially disc hollow shape, however, the shape is not limited to this. The air bleeding valve <NUM> switches opening/closing between the storage space <NUM> of the tank <NUM> and the outside in a state in which the piston <NUM> is inserted in the storage space <NUM> of the tank <NUM>.

Next, a viscous material supply method and an attaching method of covering sheet <NUM> are described. <FIG> is a flowchart showing the viscous material supply method according to one embodiment of the present invention. In the viscous material supply method, generally, the tank <NUM>, the piston <NUM>, the covering sheet <NUM>, and the like are prepared (ST1, <NUM>). Next, the covering sheet <NUM> is attached to the piston <NUM> (ST3). Thereafter, the viscous material is pressed by the pressing surface <NUM> of the piston <NUM> to force-feed the viscous material into the suction passage <NUM> (ST4). Further, the attaching method of the covering sheet <NUM> includes, in ST2, ST3 of <FIG>, preparing the piston <NUM> and the covering sheet <NUM>, and attaching the covering sheet <NUM> to the piston <NUM>. The detailed description is made below.

First, the components from the tank <NUM> through the air bleeding valve <NUM> required in supplying the viscous material are prepared (ST1, ST2). At this time, the tank <NUM> is filled with the viscous material in advance. Next, the sealing member <NUM> is attached to the piston <NUM>.

Next, as shown in disclosed but not claimed <FIG>, the covering sheet <NUM> is arranged on the side of the pressing surface <NUM> of the piston <NUM>. Then, as shown in disclosed but not claimed <FIG>, an inner periphery in the covering part <NUM> is abutted to the pressing surface <NUM> of the piston <NUM>, and portions opposing to each other at an outer periphery of the covering sheet <NUM> are folded back toward the side opposite to the pressing surface <NUM> with an outer peripheral edge part of the second outer shape part <NUM> of the piston <NUM> as an origin. Then, the insertion holes <NUM> of the covering sheet <NUM> are fitted with the pins <NUM> of the piston <NUM>.

Accordingly, folded-back parts f1, f2 are formed as shown in <FIG>. Next, the insertion holes <NUM> of the covering sheet <NUM> are fitted with the pins <NUM> of the piston <NUM>. Accordingly, the suction passage <NUM> of the piston <NUM> and the communication hole <NUM> of the covering sheet <NUM> communicate with each other and the axis centers of the suction passage <NUM> and the communication hole <NUM> match with each other. Note that "matching" of the suction passage <NUM> and the communication hole <NUM> herein allows to have positional shift of about <NUM>, <NUM>. The piston <NUM> and the covering sheet <NUM> can be inserted into the tank <NUM> in this state. Also, in this disclosed but not claimed state, the folded-back parts f2 of the covering sheet <NUM> are positioned further outward in the radial direction than the sealing member <NUM>. In other words, the sealing member <NUM> seals the tank <NUM> while having the covering sheet <NUM> interposed therebetween.

Note that the covering sheet <NUM> can be attached to the tank <NUM> in a state of having the folded-back parts f1, f2 formed, however, the following procedure can be taken following <FIG>. That is, as shown in disclosed but not claimed <FIG> following <FIG>, portions that have not been folded back at the outer periphery of the covering sheet <NUM> are folded back toward the side opposite to the pressing surface <NUM> with the outer peripheral edge part of the second outer shape part <NUM> of the piston <NUM> as an origin. Then, the insertion holes <NUM> of the covering sheet <NUM> which have not been fitted with the pins <NUM> in <FIG> are fitted with the pins <NUM> of the piston <NUM>. Accordingly, folded-back parts f3, f4 are formed.

When the covering sheet <NUM> is successfully attached to the piston <NUM>, the piston <NUM>, the air cylinder <NUM>, the pump <NUM>, and the dispenser <NUM> are connected. Thereafter, the piston <NUM> is driven by the air cylinder <NUM> and is pushed inside the storage space <NUM> of the tank <NUM>, and the viscous material is flowed through the suction passage <NUM> and the pipeline <NUM> by activating the pump <NUM> and is supplied from the dispenser <NUM> (ST4).

Here, when the viscous material becomes short in supply (ST5: YES), operations of the pump <NUM> and the air cylinder <NUM> are stopped and the supply of the viscous material is stopped (ST6). Then, the piston <NUM> is pulled out from the tank <NUM> (ST7). Further, the pump <NUM> and the piston <NUM> are separated, and the covering sheet <NUM> is removed from the piston <NUM>. Because the viscous material is adhered to the suction passage <NUM> of the piston <NUM>, cleaning is performed (ST8). The pressing surface <NUM> of the piston <NUM> is covered by the covering part <NUM> of the covering sheet <NUM>, therefore, does not require cleaning, and the cleaning operation is correspondingly facilitated. Next, the tank <NUM> is replaced with the new one having the viscous material therein (ST9).

When the cleaning of the piston <NUM> and the replacement of the tank <NUM> are finished, the covering sheet <NUM> is replaced with the new one (ST2). Then, the attaching of the covering sheet <NUM> to the piston <NUM> (ST3) and force-feeding of the viscous material (ST4) are repeated.

When the viscous material is not short in supply in the storage space <NUM> of the tank <NUM> (ST5: NO), and a required amount of the viscous material has not been supplied (ST10: NO), the supply of the viscous material is continued (ST4).

As described above, the viscous material supply device <NUM> according to the present embodiment includes the tank <NUM>, the piston <NUM>, and the covering sheet <NUM>. The tank <NUM> is provided with a storage space <NUM> storing the viscous material. The piston <NUM> is slidably inserted into the tank <NUM>, and the piston <NUM> is provided with the pressing surface <NUM> that presses the viscous material, and a suction passage <NUM> through which the viscous material inside the tank <NUM> flows by pressing force of the pressing surface <NUM>. The covering sheet <NUM> includes the covering part <NUM> that covers the pressing surface <NUM> in the piston <NUM>, and the communication hole <NUM> that communicates with the suction passage <NUM>.

Further, in the viscous material supply method according to the present embodiment, the tank <NUM>, the piston <NUM>, and the covering sheet <NUM> are prepared. Next, the covering sheet <NUM> is attached to the piston <NUM> such that the covering part <NUM> of the covering sheet <NUM> covers the pressing surface <NUM> of the piston <NUM>, and the communication hole <NUM> of the covering sheet <NUM> communicates with the suction passage <NUM> of the piston <NUM>. Thereafter, the viscous material is pressed by the pressing surface <NUM> of the piston <NUM>, and the viscous material is flowed through the suction passage <NUM>. Further, in the attaching method of the covering sheet <NUM> to the piston <NUM>, the piston <NUM> and the covering sheet <NUM> are prepared. Then, the covering sheet <NUM> is attached to the piston <NUM> such that the covering part <NUM> of the covering sheet <NUM> covers the pressing surface <NUM> of the piston <NUM> and the communication hole <NUM> of the covering sheet <NUM> communicates with the suction passage <NUM> of the piston <NUM>.

Accordingly, the pressing surface <NUM> of the piston <NUM> is covered by the covering part <NUM> of the covering sheet <NUM>, preventing the viscous material to be adhered to the pressing surface <NUM>, and correspondingly, the removal operation of the viscous material in the piston <NUM> can be facilitated.

Additionally, in the piston <NUM>, the pins <NUM> for attaching the covering sheet <NUM> to the piston <NUM> are erected on the surface on the side opposite to the pressing surface <NUM>. The covering sheet <NUM> includes the insertion holes <NUM> that are fitted with, when outer portions of the covering part <NUM> are folded back toward the side opposite to the pressing surface <NUM>, the pins <NUM> at the folded back portions. The covering sheet <NUM> is arranged on the side of the pressing surface <NUM> of the piston <NUM>, and an inner part (inner side) of the covering sheet <NUM> is abutted to the pressing surface <NUM> of the piston <NUM>. The outer parts (outer sides) of the covering part <NUM> are folded back to the side opposite to the side of the pressing surface <NUM> of the piston <NUM>, and the insertion holes <NUM> are fitted with the pins <NUM> of the piston <NUM>. As described above, by fitting the insertion holes <NUM> with the pins <NUM> of the piston <NUM>, the axis centers of the suction passage <NUM> and the communication hole <NUM> of the covering sheet <NUM> match with each other.

<FIG> is a cross-sectional view according to a disclosed but not claimed comparative example similar to <FIG>. As in a case of the comparative example of <FIG>, in a case in which a suction passage and a communication hole are aligned with each other in a state where pins <NUM> are not provided in the piston <NUM> and a covering sheet S does not have insertion holes, an operator needs to visually align an axis center CL1 of the suction passage and an axis center CL2 of the communication hole. On the other hand, the viscous material supply device <NUM> of the present embodiment is configured as described above, therefore, the aligning of the suction passage <NUM> and the communication hole <NUM> can be simplified. Moreover, accuracy of the aligning can be improved as compared to that performed visually. Further, when the axis centers of the communication hole <NUM> of the covering sheet <NUM> and the suction passage <NUM> do not match with each other, the suction passage <NUM> may be at least partially covered by the covering sheet <NUM> to obstruct the force-feeding of the viscous material, causing a risk that the viscous material remains in the storage space <NUM> of the tank <NUM>. On the other hand, by matching the axis centers of the communication hole <NUM> and the suction passage <NUM> by the pins <NUM> and the insertion holes <NUM> as described above, the above situation can be prevented and the risk of the viscous material remaining in the storage space <NUM> can be suppressed or reduced.

Additionally, the sealing member <NUM> for sealing the portion between the piston <NUM> and the tank <NUM> is attached at the outer periphery of the first outer shape part <NUM> of the piston <NUM>. The sealing member <NUM> is attached to an outer part of the first outer shape part <NUM> in the radial direction of the piston <NUM> before the viscous material is flowed through the suction passage <NUM> by the pressing surface <NUM> of the piston <NUM>. Accordingly, when the viscous material inside the tank <NUM> is pressed by the piston <NUM>, leaking of the viscous material from the outer periphery of the piston <NUM> can be prevented.

Note that various changes can be made within the scope of the claims. <FIG> is a partial enlarged view showing a disclosed but not claimed modified example of <FIG>. In the above, it has been described that the outer periphery of the covering sheet <NUM> is folded back toward the side opposite to the pressing surface <NUM>, and the insertion holes <NUM> are fitted with the pins <NUM>, however, the configuration is not limited to this.

Apart from the above, an edge part of the insertion hole <NUM> in the covering sheet <NUM> may be provided with, as shown in <FIG>, a reinforcing member <NUM> for increasing a thickness at the edge part of the insertion hole <NUM>. The reinforcing member <NUM> is applied with an adhesive on a side facing (side coming into contact with) the covering sheet <NUM>, and thereby, is constituted integrally with the covering sheet <NUM>. With this configuration, when tension is applied in the covering sheet <NUM> at the pressing surface <NUM> and the side opposite thereto, deformation of the outer peripheral edge part of the insertion hole <NUM> and moreover, positional shift of the communication hole <NUM> can be prevented.

Further, the disclosed but not claimed embodiment is described in which, in the above, the sealing member <NUM> seals the tank <NUM> while having the covering sheet <NUM> interposed therebetween, however, the configuration is not limited to this. According to the single embodiment of the claimed invention, as shown in <FIG> as well, an outside surface <NUM> of the sealing member <NUM> is positioned further outward in the radial direction than the covering sheet <NUM> attached to the piston <NUM> at the first outer shape part <NUM>. In this case, when attaching the sealing member <NUM> to the piston <NUM>, the outside surface <NUM> of the sealing member <NUM> is positioned further outward in the radial direction than the covering sheet <NUM> at the first outer shape part <NUM>.

The covering sheet <NUM> is attached to the piston <NUM> before the sealing member <NUM> is attached to the piston <NUM>. That is, the covering sheet <NUM> is arranged on the side of the pressing surface <NUM>, the inner periphery of the covering part <NUM> is abutted to the pressing surface <NUM>, and the outer periphery of the covering part <NUM> is folded back to the side opposite to the pressing surface <NUM> with the outer peripheral edge part of the second outer shape part <NUM> of the piston <NUM> as an origin. Thereafter, the insertion holes <NUM> are fitted with the pins <NUM>. Accordingly, the axis centers of the suction passage <NUM> and the communication hole <NUM> match with each other. The sealing member <NUM> is then attached to the piston <NUM>.

With this configuration, the sealing member <NUM> is positioned on the outer periphery further than the covering sheet <NUM> at the first outer shape part <NUM>, allowing the sealing member <NUM> to come into contact with the tank <NUM> without interposing the covering sheet <NUM>. Accordingly, a portion between the piston <NUM> and the tank <NUM> can be more firmly sealed.

Further, the embodiment in which the viscous material is directly filled in the storage space <NUM> of the tank <NUM> has been described above, however, the configuration is not limited to this. Apart from the above, not only the viscous material but also a bag that accommodates the viscous material may be accommodated together in the storage space <NUM> of the tank <NUM>.

Claim 1:
A viscous material supply device (<NUM>) comprising:
a tank (<NUM>) provided with a storage space (<NUM>) storing viscous material;
a piston (<NUM>) slidably inserted into the tank, and is provided with a pressing surface (<NUM>) that presses the viscous material and a suction passage (<NUM>) through which the viscous material inside the tank flows by pressing force of the pressing surface;
a covering sheet (<NUM>) including a covering part (<NUM>) covering the pressing surface in the piston and a communication hole (<NUM>) communicating with the suction passage;
a sealing member (<NUM>) attached to an outer periphery of the piston and sealing a portion between the piston and the tank;
characterized by covering sheet comprising a folded back portion (f1, f3) at which the covering sheet is folded back at an outer periphery towards a side of the piston opposite to the pressing surface, wherein the folded back portion includes insertion holes (<NUM>); and
pins (<NUM>) erected on the side opposite to the pressing surface in the piston, wherein the insertion holes of the covering sheet are fitted with the pins to attach the covering sheet to the piston;
wherein the insertion holes are fitted with the pins and wherein axis centers of the suction passage and the communication hole are matched with each other;
the piston further includes a first outer shape part (<NUM>) on which the sealing member is attached and a second outer shape part (<NUM>) separated from the first outer shape part in a direction that the piston slides and whose outer periphery is formed larger than the first outer shape part, and
the sealing member has an outside surface (<NUM>) positioned further outward in a radial direction than the covering sheet attached to the piston, at least in the first outer shape part.