JP6673014B2 - Backup ring and liquid feed pump using the backup ring - Google Patents

Description

  The present invention relates to a backup ring used to support the back surface of a plunger seal that seals a pump chamber in a plunger-type liquid transfer pump, and a liquid transfer pump provided with the backup ring.

  A plunger-type liquid feed pump continuously sucks and discharges liquid into and out of a pump chamber by reciprocating in one direction while sliding the tip of a plunger in a pump chamber provided in a pump head. It is. The pump head is detachably attached to the tip of the pump body, and a drive unit for driving the plunger is provided on the pump body side. A crosshead reciprocated in one direction by, for example, a cam mechanism is accommodated in the pump body, and a base end of the plunger is held by the crosshead.

  The tip of the plunger projects from the tip of the pump body toward the pump head, and is inserted into the pump chamber of the pump head. A portion of the pump head where the plunger is inserted into the pump chamber is provided with a resin plunger seal that tightly holds the outer periphery of the plunger for the purpose of preventing liquid leakage from the pump chamber to the pump body.

  In a liquid sending pump used in a high-performance liquid chromatograph, since the liquid sending pressure becomes high, a high pressure is applied to the plunger seal, and the plunger seal is deformed, causing problems such as wear and deterioration. In order to prevent such a problem, a back-up ring is arranged on the back surface of the plunger seal (the surface opposite to the pump chamber), and the back surface of the plunger seal is supported to prevent deformation of the plunger seal. Reference 1).

JP 2001-254686 A

  When the liquid supply pressure exceeds 100 MPa, the plunger seal is deformed by high pressure, and a part of the plunger seal enters between the outer surface of the plunger and the inner surface of the backup ring, thereby deteriorating the plunger seal or inhibiting the driving of the plunger. Problem. Therefore, the inner diameter of the backup ring is designed so that the gap between the plunger and the backup ring is as small as possible.

  Usually, the position of the center axis of the plunger at the time of liquid feeding is determined by the position of the plunger seal that tightly holds the outer peripheral surface of the plunger, but if the center position of the backup ring and the center position of the plunger seal are misaligned. When the plunger reciprocates, the outer surface of the plunger comes into contact with the inner surface of the backup ring, the center axis of the plunger is displaced from the center position of the plunger seal, and the plunger does not contact the inner surface of the plunger seal with an equal force. There is a problem that the inner surface of the seal is partially worn. Also, when the plunger comes into contact with the backup ring, abrasion powder of the plunger and the backup ring is generated, and the abrasion powder enters between the plunger and the plunger seal, which may extremely shorten the life of the plunger seal. Therefore, it is desirable that the center of the plunger seal and the center of the backup ring be coaxial.

  The backup ring is fitted into a concave portion provided on the surface of the pump head on the pump body side. If the dimensional difference between the outer diameter of the backup ring and the inner diameter of the concave portion of the pump body is large, the position of the backup ring is not stable and the positional deviation of the backup ring with respect to the plunger seal is likely to occur. On the other hand, when the dimensional difference between the outer diameter of the backup ring and the inner diameter of the concave portion of the pump body is reduced, the outer peripheral surface of the backup ring comes into contact with the inner surface of the concave portion of the pump head, so that the backup ring can be stably inserted. However, when the backup ring is fitted into the recess, it must be press-fitted, and the backup ring cannot be easily attached to and detached from the pump head. In addition, if the user tries to forcibly attach or detach it, there is a risk that not only the backup ring but also parts such as the plunger seal and the pump head may be damaged.

  If the thickness of the backup ring is reduced, the contact area between the pump ring and the inner surface of the concave portion of the pump head is reduced, and the frictional resistance when attaching and detaching the backup ring to and from the pump head is reduced. It is also possible to design a small dimensional difference from the inner diameter of the recess. However, when the thickness of the backup ring is reduced, the strength is reduced accordingly, and the backup ring cannot be used for high-pressure liquid supply. Therefore, there is a limit in reducing the thickness of the backup ring.

  Therefore, an object of the present invention is to facilitate attachment and detachment of the backup ring to and from the pump head and to stabilize the positioning of the backup ring with respect to the pump head without reducing the strength of the backup ring.

  The backup ring according to the present invention has a maximum outer diameter on the side of a plunger seal supporting surface that is in contact with the back of a plunger seal that seals a pump chamber provided in a pump head of a plunger type liquid transfer pump and that supports the plunger seal. And a small outer diameter portion having an outer diameter smaller than the maximum outer diameter portion in at least a part of the portion other than the maximum outer diameter portion. That is, in the backup ring of the present invention, the outer peripheral surface of the maximum outer diameter portion is in contact with the inner surface of the concave portion of the pump head into which the backup ring is fitted, while the outer peripheral surface of the small outer diameter portion is in contact with the inner surface of the concave portion of the pump head. Do not touch.

  The outer diameter of the maximum outer diameter portion is preferably substantially the same as the inner diameter of the recess formed in the pump head. Then, the positioning of the backup ring with respect to the pump head is stabilized, and the contact between the inner peripheral surface of the backup ring and the outer peripheral surface of the plunger is suppressed. The fact that the outer diameter of the maximum outer diameter portion is substantially the same as the inner diameter of the concave portion means that the dimensional difference between the two diameters is, for example, 0.01 mm or less.

  As an example of a preferred embodiment of the backup ring, there can be cited one in which the small outer diameter portion also has a cylindrical shape. In this embodiment, there is a step on the outer peripheral surface of the backup ring due to the difference in outer diameter between the plunger seal support surface side and the opposite surface side. Such a structure can be easily formed by processing by cutting using rotation, and an increase in cost can be suppressed.

  Further, as another example of the preferred embodiment of the backup ring, as the outer peripheral surface of the small outer diameter portion moves from the plunger seal support surface side to the surface side opposite to the plunger seal support surface, the outer diameter increases. One having a tapered shape inclined so as to be small can be given. Such a structure can also be easily formed by machining using rotation, and an increase in cost can be suppressed.

  A liquid pump according to the present invention includes a liquid inlet for sucking a liquid, a pump chamber for storing the liquid sucked from the liquid inlet, and a liquid outlet for discharging the liquid in the pump chamber. A head, a plunger whose distal end is inserted into the pump head and slides in the pump head, and a ring-shaped seal attached to the plunger insertion portion of the pump head and sealing a gap between the pump head and the plunger. It has a plunger seal and a backup ring of the present invention provided on the back side of the plunger seal and supporting the back surface of the plunger seal.

  The backup ring according to the present invention has a cylindrical maximum outer diameter portion having a maximum outer diameter on the plunger seal support surface side, and at least a part of the portion other than the maximum outer diameter portion has an outer diameter smaller than the maximum outer diameter portion. The outer peripheral surface of the maximum outer diameter portion is in contact with the inner surface of the concave portion of the pump head into which the backup ring is fitted, while the outer peripheral surface of the small outer diameter portion is formed of the concave portion of the pump head. Since it does not contact the inner surface, the area of contact with the inner surface of the concave portion of the pump head can be reduced without reducing the thickness of the backup ring. This reduces the frictional resistance when attaching and detaching the backup ring to and from the pump head, facilitates attachment and detachment of the backup ring to and from the pump head, and improves maintainability.

  Further, since the contact area between the inner surface of the concave portion of the pump head and the inner surface of the concave portion of the pump head is reduced, even when the outer diameter of the maximum outer diameter portion is closer to the inner diameter of the concave portion of the pump head, when the backup ring is fitted into the concave portion of the pump head. The increase in frictional resistance is suppressed. The closer the outer diameter of the maximum outer diameter portion to the inner diameter of the concave portion of the pump head, the more stable the positioning of the backup ring with respect to the pump head, and the more the contact between the inner peripheral surface of the backup ring and the outer peripheral surface of the plunger is suppressed.

  Since the liquid feed pump according to the present invention uses the above-mentioned backup ring, the backup ring can be easily mounted on the pump head. Further, if a backup ring whose outer diameter of the maximum outer diameter portion is closer to the inner diameter of the concave portion of the pump head is used, the positioning of the backup ring with respect to the pump head is performed more stably, and the gap between the inner peripheral surface of the backup ring and the outer peripheral surface of the plunger. Contact is suppressed, and wear of the backup ring, plunger, and plunger seal is suppressed.

It is a figure which shows one Example of the liquid feed pump provided with the backup ring, (A) is sectional drawing of the front-end | tip part of a pump body, (B) is sectional drawing which expands and shows the pump chamber vicinity of (A). It is. It is sectional drawing of the pump chamber vicinity of the liquid feed pump for demonstrating the other Example of the backup ring.

  One embodiment of the liquid feed pump will be described with reference to FIG.

  In the liquid sending pump of this embodiment, a pump head 8 is mounted on a tip of a pump body 2 with a cleaning chamber 12 interposed therebetween. A crosshead 4 is movably accommodated in the pump body 2. The crosshead 4 is constantly pushed in a direction away from the pump head 8 (rightward in the figure) by an elastic body 6 such as a spring, and is rotated around a cam (not shown) provided on the base end side of the crosshead 4. Follow the surface. The crosshead 4 reciprocates within the pump body 2 in a direction approaching the pump head 8 and in a direction away from the pump head 8 (left and right directions in the figure) by following the peripheral surface of the rotating cam.

  The base end of the plunger 3 is held at the tip of the crosshead 4. The tip of the plunger 3 penetrates through the cleaning chamber 12 and is inserted into a pump chamber 8 a provided inside the pump head 8. The tip of the plunger 3 slides along the wall surface of the pump chamber 8a due to the reciprocating motion of the crosshead 4. The pump head 8 has a liquid inlet channel 8b for sucking the liquid into the pump chamber 8a and a liquid outlet channel 8c for pushing the liquid from the pump chamber 8a. Check valves 9a and 9b for preventing backflow are connected to the liquid inlet channel 8b and the liquid outlet channel 8c, respectively.

  On the surface of the pump head 8 on the pump body 2 side, a concave portion 20 communicating with the pump chamber 8a is provided. The plunger seal 10 and the backup ring 11 are fitted into the recess 20 from the pump chamber 8a side. The concave portion 20 includes a concave portion 20a for fitting a front side portion (a left side portion in the figure) of the plunger seal 10 and a concave portion 20b provided on the pump body 2 side with respect to the concave portion 20a and having an inner diameter larger than the concave portion 20a. Become. The back side portion (right side portion in the figure) of the plunger seal 10 and the backup ring 11 are fitted into the concave portion 20b.

  The plunger seal 10 slidably holds the outer peripheral surface of the plunger 3 so as to prevent liquid leakage from a gap between the inner wall of the pump chamber 8a and the peripheral surface of the plunger 3. The backup ring 11 supports the back surface of the plunger seal 10 (the surface opposite to the pump chamber 8a). The surface of the backup ring 11 opposite to the surface on the side of the plunger seal 10 (the plunger seal support surface) is supported by the wall surface of the cleaning chamber 12. Details of the plunger seal 10 and the backup ring 11 will be described later.

  The cleaning chamber 12 includes a flow path through which the cleaning liquid flows, and a space for cleaning the outer peripheral surface of the plunger 3 penetrating the flow path with the cleaning liquid. A cleaning seal 16 that slidably holds the outer peripheral surface of the plunger 3 is provided in the insertion portion of the plunger 3 in the internal space of the cleaning chamber 12 to prevent leakage of the cleaning liquid. The back surface of the cleaning seal 16 is supported by the wall surface of the pump body 2.

  In this liquid feed pump, the plunger 3 is driven in a direction away from the pump chamber 8a (rightward in the figure), so that the pressure in the pump chamber 8a is reduced, the check valve 9b is closed, the check valve 9a is opened, and the liquid inlet is opened. The liquid is sucked into the pump chamber 8a from the flow path 8b. Conversely, when the plunger 3 is driven in a direction (left direction in the drawing) to be inserted into the pump chamber 8a, the inside of the pump chamber 8a is pressurized, the check valve 9a is closed, the check valve 9b is opened, and the pump The liquid is pushed out from the chamber 8a to the liquid outlet channel 8c. The liquid feeding is performed by repeating this operation.

  The plunger seal 10 is made of an elastic material such as a polyethylene resin. Around the plunger 3 of the plunger seal 10, there is provided a rectangular space 10a having an opening on the pump chamber 8a side for storing the liquid leaking from between the inner wall of the pump chamber 8a and the outer periphery of the plunger 3. The space 10a is provided in a ring shape coaxial with the plunger 3, and the cross-sectional shape of the plunger 3 in the axial direction is rectangular. In this embodiment, a ring-shaped elastic member is provided in the space 10a.

  The inner diameter of the backup ring 11 that supports the back surface of the plunger seal 10 is larger than the inner diameter of the plunger seal 10 and smaller than the hole 14 that penetrates the plunger 3 in the wall surface of the cleaning chamber 12 that supports the backup ring 11. The backup ring 11 is a ring-shaped member made of, for example, PEEK resin.

  The backup ring 11 includes two cylindrical portions, a maximum outer diameter portion 11a and a small outer diameter portion 11b. The maximum outer diameter portion 11a is provided on the plunger seal support surface side (the left side in the figure) and is a portion of the backup ring 11 having the maximum outer diameter. The outer diameter of the maximum outer diameter portion 11a is substantially the same as the inner diameter of the concave portion 20b of the pump head 8, and the outer diameter of the small outer diameter portion 11b is smaller than the outer diameter of the maximum outer diameter portion 11a. As a result, a gap is formed between the outer peripheral surface of the small outer diameter portion 11b and the inner surface of the concave portion 20b.

  That is, there is a step on the outer peripheral surface of the backup ring 11, and only the peripheral surface of the outer peripheral surface on the plunger seal support surface side contacts the inner surface of the concave portion 20b, and the other peripheral surfaces do not contact the inner surface of the concave portion 20b. Thereby, the contact area with the inner surface of the concave portion 20b becomes smaller than when the entire outer peripheral surface of the backup ring 11 is in contact with the inner surface of the concave portion 20b, and friction when the backup ring 11 is fitted into the concave portion 20b or removed from the concave portion 20b. Resistance is reduced. Therefore, attachment and detachment of the backup ring 11 with respect to the pump head 8 are easy.

  The thickness of the backup ring 11 is such that the backup ring 11 has a strength that can withstand liquid transfer under high pressure conditions, for example, about 2 mm. Further, the thickness of the maximum outer diameter portion 11a whose outer peripheral surface is in contact with the inner surface of the concave portion 20b and positions the backup ring 11 is such a thickness as to be able to withstand the deformation pressure from the plunger seal 10 side during liquid feeding under high pressure conditions. , For example, about 0.9 mm.

  The thickness of the maximum outer diameter portion 11a may be any thickness as long as it can withstand the deformation pressure from the plunger seal 10 during liquid feeding under high pressure conditions, but the inner surface of the concave portion 20b and the outer peripheral surface of the backup ring 11 may be used. The thickness of the maximum outer diameter portion 11a may be 50% or less of the entire thickness of the backup ring 11 in order to sufficiently reduce the frictional resistance between the backup ring 11 and the attachment / detachment of the backup ring 11 to / from the pump head 8. preferable.

  In order to stably position the backup ring 11 with respect to the pump head 8, it is preferable that the dimensional difference between the inner diameter of the concave portion 20b and the outer diameter of the maximum outer diameter portion 11a is 0.01 mm or less. When the entire outer peripheral surface of the backup ring 11 is in contact with the inner surface of the concave portion 20b, if the dimensional difference between the inner diameter of the concave portion 20b and the outer diameter of the maximum outer diameter portion 11a is set to 0.01 mm or less, the inner surface of the concave portion 20b is Although the frictional resistance between the ring 11 and the outer peripheral surface becomes too large, it becomes difficult to attach and detach the backup ring 11 to and from the pump head 8, but as in this embodiment, the backup ring 11 is smaller than the maximum outer diameter portion 11a. With the outer diameter portion 11b, such a dimensional difference can be designed.

  The structure of the backup ring 11 is not limited to that of the above-described embodiment. For example, as shown in FIG. 2, the outer peripheral surface of the backup ring 11 may have a tapered shape that is inclined so that the outer diameter decreases toward the pump body 2 (right side in the figure) from the middle. In this case, a portion 11a of the backup ring 11 on the side of the plunger seal support surface (the left side in the figure) is a maximum outer diameter portion, and the outer diameter of the maximum outer diameter portion 11a is substantially the same as the inner diameter of the recess 20b. Then, a portion closer to the pump body 2 than the maximum outer diameter portion 11a becomes a small outer diameter portion 11b having an outer diameter smaller than the maximum outer diameter portion 11a.

  According to the structure of FIG. 2, as in the embodiment of FIG. 1, the contact area with the inner surface of the concave portion 20b is smaller than when the entire outer peripheral surface of the backup ring 11 is in contact with the inner surface of the concave portion 20b. The frictional resistance at the time of fitting into or removing from the recess 20b is reduced.

  The backup ring 11 has a maximum outer diameter portion 11a having an outer diameter substantially equal to the inner diameter of the concave portion 20b on the plunger seal support surface side, and a small outer ring having an outer diameter smaller than the maximum outer diameter portion 11a in other portions. Any structure may be used as long as a diameter portion is provided.

2 Pump body 3 Plunger 4 Cross head 6 Elastic body 8 Pump head 8a Pump chamber 8b Liquid inlet channel 8c Liquid outlet channel 9a, 9b Check valve 10 Plunger seal 11 Backup ring 11a Maximum outer diameter portion 11b Small outer diameter portion 12 Cleaning Chamber 14 hole 16 cleaning seal 20a, 20b recess

Claims (4)

A backup for supporting the plunger seal in contact with the back surface of a plunger seal that seals a pump chamber provided in the pump head is entirely fitted into a concave portion provided in a pump head of a plunger type liquid sending pump. A ring,
The backup ring has a cylindrical maximum outer diameter portion having an outer diameter substantially equal to the inner diameter of the concave portion on the plunger seal support surface side in contact with the back surface of the plunger seal , and includes a portion other than the maximum outer diameter portion. have a Shosoto径portion having a smaller outer diameter than the maximum outer diameter to at least a portion, resulting in a gap between the outer peripheral surface and the inner surface of the concave portion of the small outer diameter portion, the backup ring. The backup ring according to claim 1, wherein the small outer diameter portion also has a cylindrical shape. The outer peripheral surface of the small outer diameter portion is defined in claim 1 having an inclined tapered shape so that the outer diameter decreases toward the side opposite to the plunger seal supporting surface from said plunger seal support surface Backup ring. A pump head having a liquid inlet for sucking liquid, a pump chamber for storing liquid sucked from the liquid inlet, and a liquid outlet for discharging liquid in the pump chamber;
A plunger having a distal end inserted into the pump head and sliding within the pump head;
A ring-shaped plunger seal attached to the plunger insertion portion of the pump head and sealing a gap between the pump head and the plunger;
Said whole recess provided in the pump head is arranged on the rear side of the plugged and the plunger seal, backup ring according to any one of claims 1 to 3 for supporting the back of the plunger seal, Liquid sending pump equipped with.

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