CN107158464B

CN107158464B - Automatic fluid infusion formula system of taking off cells

Info

Publication number: CN107158464B
Application number: CN201710397304.XA
Authority: CN
Inventors: 韩卫东; 王红刚; 米维; 雷文诚
Original assignee: Shaanxi Ruisheng Biotech Co ltd
Current assignee: Shaanxi Ruisheng Biotech Co ltd
Priority date: 2017-05-31
Filing date: 2017-05-31
Publication date: 2020-10-30
Anticipated expiration: 2037-05-31
Also published as: CN107158464A

Abstract

The invention discloses an automatic liquid supplementing type cell removing system, and relates to the technical field of biological material processing devices. The invention aims to solve the problems that the cell removing device in the prior art cannot adapt to mass production and the fluid infusion operation is complex. The invention relates to an automatic fluid infusion type cell removing system, which comprises: a cradle comprising a swing tray; a cleaning tank disposed on the swing tray, the cleaning tank including a plurality of cleaning tanks; the liquid feeding device comprises a liquid storage tank, a liquid feeding pipe and a liquid feeding pump, one end of the liquid feeding pipe is communicated with the liquid storage tank, the other end of the liquid feeding pipe extends into the cleaning tank, and the liquid feeding pump is connected with the liquid feeding pipe in series; a liquid level meter for detecting a liquid level within the cleaning tank; and the control unit is respectively connected with the liquid adding pump and the liquid level meter. The invention can be used for the decellularization of biological materials.

Description

Automatic fluid infusion formula system of taking off cells

Technical Field

The invention relates to the technical field of biological material processing devices, in particular to an automatic liquid supplementing type cell removing system.

Background

With the development of economy and society, the medical application of biomaterials is also more and more prominent, and biomaterials refer to materials formed by biological processes, including cells and extracellular matrix. Common biological materials include bovine pericardium and porcine small intestine, and when the biological materials are applied to clinic, the biological materials need to be cleaned, sterilized, disinfected, decellularized and the like.

In the prior art, a shaking table is usually used for decellularization, specifically, a cleaning box is fixed on a tray of the shaking table, biological materials and a decellularization reagent are put into the cleaning box, then the shaking table is started to oscillate, and during the oscillation process, the inner wall of the cleaning box repeatedly slaps the biological materials, thereby realizing the decellularization of the biological materials.

However, the volume of the washing box cannot be made large due to the limitation of the oscillation amplitude of the shaking table, and if the volume is too large, the distance between the two opposite side walls of the washing box is large, so that the biological material moves in the opposite direction without slapping against the inner wall of the washing box in the oscillation process of the washing box, and the cell removal cannot be realized. Therefore, the prior art decellularization cleaning cartridge is generally small in volume to adapt to the oscillation amplitude of the shaking table, and cannot adapt to mass production. In addition, in the process of cell removal, a cell removal reagent generates foams, the reagent amount is gradually reduced, when the amount of the biological material is large, the reagent amount added at one time can not meet the requirement of thorough cell removal of the biological material, liquid supplement is needed when the cell removal reagent amount is reduced to a certain degree, in the prior art, the reagent is manually added into a cleaning box after a shaking table is shut down, the operation is complex, the efficiency is low, and the added reagent amount cannot be accurately controlled.

Disclosure of Invention

The embodiment of the invention provides an automatic liquid supplementing type acellular system, which can increase the processing quantity of biological materials, can automatically and accurately supplement liquid and improve the working efficiency.

To achieve the above object, an embodiment of the present invention provides an automatic fluid infusion type decellularization system, including: a cradle comprising a swing tray; the cleaning box is arranged on the swing tray and comprises a plurality of cleaning tanks, and the cleaning tanks are used for placing biological materials and cell removal reagents; the liquid feeding device comprises a liquid storage tank, a liquid feeding pipe and a liquid feeding pump, one end of the liquid feeding pipe is communicated with the liquid storage tank, the other end of the liquid feeding pipe extends into the cleaning tank, and the liquid feeding pump is connected with the liquid feeding pipe in series; a liquid level meter for detecting a liquid level within the cleaning tank; and the control unit is respectively connected with the liquid adding pump and the liquid level meter, and controls the liquid adding pump to be started when the liquid level detected by the liquid level meter is lower than a preset value.

According to the automatic liquid supplementing type cell removing system, the cleaning box comprises a plurality of cleaning tanks, so that the volume of each cleaning tank can be made to be the maximum volume suitable for the oscillation amplitude of the shaking table, and compared with a cleaning box in the prior art, the processing quantity of biological materials is increased. And owing to set up liquid feeding device and level gauge, consequently, when the liquid level that the level gauge detected is less than the default, the control unit steerable liquid feeding pump opens, in going into the washing tank with the cell removal reagent pump in the liquid storage tank, closes the liquid feeding pump when reaching appointed liquid level height. Therefore, automatic liquid supplementing is realized, the added reagent amount can be accurately controlled, and the working efficiency is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of an embodiment of an automatic fluid infusion type decellularization system according to the present invention;

FIG. 2 is a schematic diagram of the internal structure of an automatic fluid infusion type decellularization system according to an embodiment of the invention;

FIG. 3 is a schematic structural diagram of an inner-layer box of an automatic fluid infusion-type decellularization system according to an embodiment of the invention;

FIG. 4 is a schematic bottom structure view of an inner-layer box of an automatic fluid infusion-type decellularization system according to an embodiment of the invention;

FIG. 5 is a schematic structural diagram of another embodiment of a bubble-absorbing device of an automatic fluid infusion type decellularization system according to the embodiment of the invention;

fig. 6 is a schematic structural diagram of an inner-layer box cover of an automatic fluid infusion type decellularization system according to an embodiment of the invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

Referring to fig. 1 and 2, the automatic fluid infusion type decellularization system of the present embodiment includes: a rocking bed 3, said rocking bed 3 comprising a rocking tray (not shown in the figures); the cleaning box is arranged on the swing tray and comprises a plurality of cleaning tanks 21, and the cleaning tanks 21 are used for placing biological materials and cell removal reagents; the liquid adding device 4 comprises a liquid storage tank 41, a liquid adding pipe 42 and a liquid adding pump 43, one end of the liquid adding pipe 42 is communicated with the liquid storage tank 41, the other end of the liquid adding pipe 42 extends into the cleaning tank 21, and the liquid adding pump 43 is connected with the liquid adding pipe 42 in series; a liquid level meter (not shown in the drawings) for detecting a liquid level inside the cleaning tank 21; and the control unit (not shown in the figure) is respectively connected with the liquid adding pump 43 and the liquid level meter, and when the liquid level detected by the liquid level meter is lower than a preset value, the control unit controls the liquid adding pump 43 to be started.

According to the automatic liquid-replenishing type decellularization system provided by the embodiment of the invention, since the cleaning tank comprises a plurality of cleaning tanks 21, the volume of each cleaning tank 21 can be made to be the maximum volume suitable for the oscillation amplitude of the shaking table 3, and compared with a cleaning box in the prior art, the processing quantity of biological materials is increased. And because the liquid adding device 4 and the liquid level meter are arranged, when the liquid level detected by the liquid level meter is lower than a preset value, the control unit can control the liquid adding pump 43 to be started, the decellularization reagent in the liquid storage tank 41 is pumped into the cleaning tank 21, and the liquid adding pump 43 is closed when the specified liquid level height is reached. Therefore, automatic liquid supplementing is realized, the added reagent amount can be accurately controlled, and the working efficiency is improved.

In fig. 6, the liquid adding device 4 may be provided on any side of the cleaning tank, only for showing the connection relationship between the components of the liquid adding device 4 and the cleaning tank, and the relative positional relationship between the liquid adding device 4 and the cleaning tank is not limited.

In order to facilitate the liquid drainage, as shown in fig. 1, the cleaning tank comprises an outer layer tank body 1 and an inner layer tank body 2 arranged in the outer layer tank body 1, the inner box body 2 can synchronously oscillate along with the outer box body 1, the outer box body 1 is connected with the swinging tray, as shown in fig. 2, 3 and 4, the inner box 2 includes a bottom plate 23 and a side plate 24 disposed around the bottom plate 23, the bottom plate 23 is provided with a partition 25, the partition plate 25 partitions the space inside the inner casing 2 into a plurality of the cleaning tanks 21, the outer layer box body 1 is connected with a liquid discharge pipe 11, the liquid discharge pipe 11 is communicated with the bottom space of the outer layer box body 1, each cleaning tank 21 is provided with a liquid discharge hole 211, the liquid discharge hole 211 is communicated with the bottom space of the outer casing 1, and the liquid discharge hole 211 allows the decellularization reagent to pass through and does not allow the biological material to pass through. Therefore, when liquid is drained, only the liquid discharge pipe 11 needs to be opened, the acellular reagent in the cleaning tank 21 can be discharged from the liquid discharge pipe 11, the outer-layer box body 1 and the inner-layer box body 2 do not need to be detached, the operation is simple, and the production efficiency is high.

In addition, the inner tank 2 may be directly placed with the plurality of independent cleaning tanks 21 in the inner tank 2 without using the partition plate 25, and the outer side walls of the plurality of cleaning tanks 21 may be closely attached to each other and arranged in the inner tank 2. The solution shown in fig. 3 is simple in structure and has low requirements on manufacturing accuracy, and therefore is relatively more economical and practical.

The arrangement of the plurality of cleaning tanks 21 may be various, for example, the plurality of cleaning tanks 21 may be arranged in a row along the same line, or the plurality of cleaning tanks 21 may be arranged in a rectangular array. Compared with the washing tank along a linear array, the washing tank according to the rectangular array is more compact in overall structure and is not easy to deform during oscillation. For example, as shown in fig. 1, the partition plate 25 divides the space inside the inner casing 2 into 16 washing tanks, and the 16 washing tank arrays are 4 rows and 4 columns. Similarly, the partition plate 25 may divide the space in the inner casing 2 into 9 washing tanks, and the 9 washing tank arrays are 3 rows and 3 columns. The specific division and arrangement can be selected according to actual situations, and is not limited herein.

Since the cell removal reagent generates foam during the cell removal process, and the foam accumulation may affect the measurement accuracy of the liquid level meter and also affect the cell removal effect, as shown in fig. 2, it is preferable that an inner tank cover 26 is disposed at an opening of the inner tank 2, and a bubble suction device 5 is disposed on the inner tank cover 26, and the bubble suction device 5 is respectively communicated with upper spaces of the plurality of cleaning tanks 21 for sucking foam generated by the cell removal reagent in the cleaning tanks 21. Therefore, the foam can be sucked by the foam sucking device 5, and the excessive foam accumulation is prevented.

Specifically, the bubble absorbing device 5 may be the structure shown in fig. 5, the bubble absorbing device 5 includes a plurality of bubble absorbing pipes 51, the plurality of bubble absorbing pipes 51 are disposed through the inner tank cover 26, a plurality of first ends of the bubble absorbing pipes 51 are extended into the plurality of cleaning tanks 21 in a one-to-one correspondence manner, a plurality of second ends of the bubble absorbing pipes 51 are communicated with the collecting container 52, and the plurality of bubble absorbing pipes 51 are respectively connected in series with a suction pump 53. Thus, the plurality of suction pumps 53 can control the plurality of suction bubble tubes 51, respectively, and the control accuracy is high.

In another embodiment of the present invention, the bubble absorbing device 5 may have a structure as shown in fig. 2, the bubble absorbing device 5 includes a plurality of bubble absorbing tubes 51, the plurality of bubble absorbing tubes 51 are inserted into the inner case cover 26, first ends of the plurality of bubble absorbing tubes 51 are inserted into the plurality of cleaning grooves 21 in a one-to-one correspondence manner, second ends of the plurality of bubble absorbing tubes 51 are communicated with a collecting tube 55 through a multi-way tube joint 54, the collecting tube 55 is communicated with the collecting container 52, and the collecting tube 55 is connected in series with a suction pump 53. Thus, only one suction pump 53 is required to suck the bubbles from all the cleaning tanks 21, which saves cost and space.

In order to facilitate the observation of the inside of the washing tub 21, the inner case cover 26 is preferably made of a transparent material. Therefore, the conditions in the cleaning tank 21, such as the amount of foam, the level of liquid, the state of biological materials, etc., can be observed through the inner tank cover 26. If abnormal conditions occur, the abnormal conditions can be found in time.

Wherein, in order to realize inlayer box 2 along with outer box 1's synchronous oscillation, can be with the inside dimension of outer box 1 and the outside dimension phase-match of inlayer box 2, when inlayer box 2 installs in outer box 1 promptly, laminate each other between the inside wall of outer box 1 and the lateral wall of inlayer box 2 to make outer box 1 at the in-process of oscillation, inlayer box 2 can't remove for outer box 1, avoid producing the striking between outer box 1 and the inlayer box 2. In addition, also can set up location structure between outer box 1 and inlayer box 2, prevent through location structure that inlayer box 2 from removing for outer box 1, for example can set up the rubber pad between outer box 1 and inlayer box 2, be fixed in on the inside wall of outer box 1 with the one end of rubber pad, the other end supports with the lateral wall of inlayer box 2 and leans on, or is fixed in on the lateral wall of inlayer box 2 with the one end of rubber pad, the other end supports with the inside wall of outer box 1 and leans on. Synchronous oscillation of the inner box body 2 along with the outer box body 1 can be realized.

As shown in FIG. 3, handles 22 are provided on both sides of the upper surface of the inner casing 2, so that the inner casing 2 can be easily taken out of the outer casing 1, and the inner casing 2 can be easily sterilized and cleaned.

For facilitating the filling, as shown in fig. 3, a communication hole 251 is preferably formed at the lower end of the partition plate 25, and two adjacent cleaning tanks 21 are communicated through the communication hole 251. Thus, when the cell-removing reagent is supplied, it is not necessary to supply the cell-removing reagent into the cleaning tanks 21 one by one, and the cell-removing reagent is supplied into one of the cleaning tanks 21 and flows into the other cleaning tank 21 through the communication hole 251. Moreover, the dosage and the concentration of the cell removing reagent in each cleaning tank 21 can be equal by the scheme, so that the cell removing effect of the biological materials cleaned in the same batch is consistent.

As shown in fig. 3, the communication holes 251 are provided around the circumference of the cleaning tank 21, and are provided in two rows in the vertical direction. The communication holes 251 are not required to be formed too much, 1-3 rows are preferably arranged along the vertical direction, if the communication holes are arranged too much, the slapping force of the partition plate 25 to the liquid is reduced, the movement speed of the liquid driving the biological material is reduced, the slapping force between the biological material and the partition plate 25 is reduced, and the cell removing effect is influenced.

In an embodiment of the present invention, as shown in fig. 4, the liquid discharge holes 211 are distributed on the bottom plate 23 of the inner tank 2 and respectively correspond to the plurality of cleaning tanks 21, a communication cavity 28 is formed between the bottom plate 23 of the inner tank 2 and the bottom plate 12 of the outer tank 1, and the plurality of liquid discharge holes 211 on the bottom plate 23 of the inner tank 2 are all communicated with the communication cavity 28. Therefore, when the liquid discharge pipe 11 is opened during liquid discharge, the liquid in the cleaning tank 21 is discharged through the communicating cavity 28 and the liquid discharge pipe 11 in sequence, the operation is convenient, and the inner-layer box body 2 does not need to be detached.

In the above embodiment, the communication chamber 28 can be implemented in various ways, for example, as shown in fig. 2, a support member 27 can be disposed between the bottom plate 23 of the inner case 2 and the bottom plate 12 of the outer case 1, and the support member 27 can separate the bottom plate 23 of the inner case 2 from the bottom plate 12 of the outer case 1, so that the communication chamber 28 is formed between the bottom plate 23 of the inner case 2 and the bottom plate 12 of the outer case 1. Similarly, a hanging structure can be arranged between the side wall of the inner box 2 and the side wall of the outer box 1, so that the inner box 2 is hung in the outer box 1, and a communication cavity 28 is formed between the bottom plate 23 of the inner box 2 and the bottom plate 12 of the outer box 1.

In another embodiment of the present invention, the drain holes 211 may also be distributed on the side plate 24 of the inner casing 2, as shown in fig. 3 and 4, a communication hole 251 is formed at the lower end of the partition plate 25, two adjacent cleaning tanks 21 are communicated through the communication hole 251, and the drain hole 211 is formed at the lower end of the side plate 24. Therefore, when the liquid discharge pipe 11 is opened during liquid discharge, the liquid in the cleaning tank 21 positioned in the middle flows into the cleaning tank 21 on the outermost side through the communication hole 251, then is discharged into the outer tank 1 through the liquid discharge hole 211 at the lower end of the side plate 24, and finally is discharged through the liquid discharge pipe 11, and the inner tank 2 does not need to be detached.

The two arrangements of the drain holes 211 may be one arrangement or two arrangements may be used simultaneously. When only the first embodiment is adopted and the drain holes 211 are formed in the bottom plate 23 of the inner casing 2, the drain holes 211 are easily clogged with the biomaterial and the drainage effect is not good, so that it is preferable to adopt both embodiments.

The diameter of the drain hole 211 is preferably 3 mm, and if the diameter is too large, the biological material is easily stuck, and if the diameter is too small, the drain speed is too slow.

In order to realize automatic drain pipe 11, a drain valve may be connected in series with drain pipe 11, and the opening and closing of the drain valve may be controlled by a control unit to realize automatic drain.

In order to achieve rapid liquid discharge, a liquid discharge pump is preferably connected to the liquid discharge pipe 11 in series, so that the liquid discharge pump can rapidly pump out the decellularized reagent, thereby achieving rapid liquid discharge and improving the working efficiency.

Since the used decellularization reagent usually contains a large amount of impurities, in order to prevent the impurities from clogging the drain valve and the drain pump, it is preferable to provide a filter screen 14 at the inlet of the drain pipe 11 as shown in FIG. 2, so that the filter screen 14 can filter the impurities in the decellularization reagent and prevent the impurities from clogging the drain valve and the drain pump.

The horizontal section of the cleaning tank 21 may be rectangular, square, polygonal circular, etc., and is not limited herein. Since the oscillation amplitude of the shaking table 3 is 30 to 60 mm, it is preferable to set the maximum dimension of the washing tank 21 in the horizontal direction to be less than or equal to 300 mm in order to ensure that the washing tank 21 can be adapted to the oscillation amplitude of the shaking table 3. For example, when the cleaning tank 21 has a rectangular shape, the width of the cleaning tank 21 may be set to 140 mm and the length thereof may be set to 230 mm.

Preferably, the height of the cleaning tank 21 in the vertical direction should be greater than or equal to 100 mm, for example, the height may be selected to be 250 mm, so that the liquid in the cleaning tank 21 can be prevented from splashing when oscillating.

In order to facilitate the liquid discharge, the bottom plate 12 of the outer casing 1 may be disposed obliquely, and the lowest point of the bottom plate 12 of the outer casing 1 is disposed near the liquid discharge pipe 11. Therefore, the decellularization reagent in the outer casing 1 can flow to the inlet of the liquid discharge pipe 11 along the inclined surface, and the remaining of the decellularization reagent at the bottom of the outer casing 1 can be prevented.

In order to avoid the above problem, it is preferable that the inner cover 26 is configured as a flat plate-like structure, the upper edges of the side plate 24 and the partition plate 25 are located in the same plane, and the inner cover 26 is covered on the side plate 24 and the partition plate 25. Therefore, the inner box cover 26 is tightly attached to the side plate 24 and the upper edge of the partition plate 25, so that the biological material cannot be lapped on the partition plate 25 or the upper edge of the side plate 24. As shown in fig. 6, a lid handle 261 may be provided on the inner lid 26.

In addition, as shown in fig. 1, an outer case cover 13 may be disposed at an opening of the outer case 1, so as to prevent external impurities from entering the decellularization reagent and polluting the biological material.

Preferably, the outer box 1 of the decellularization net cage is fixed on the swing tray by clamping through a clamping structure, as shown in fig. 1, the bottom surface of the shaking table 3 is provided with a retractable roller 31, which facilitates the carrying of the shaking table 3.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. An automatic fluid infusion type decellularization system, comprising:

a cradle comprising a swing tray;

the washing box is arranged on the swing tray and comprises an outer box body and an inner box body arranged in the outer box body, the inner box body can synchronously oscillate along with the outer box body, the outer box body is connected with the swing tray, a partition plate is arranged in the inner box body and divides the space in the inner box body into a plurality of washing tanks, communication holes are formed in the lower end of the partition plate, two adjacent washing tanks are communicated through the communication holes, the outer box body is connected with a liquid discharge pipe, the liquid discharge pipe is communicated with the bottom space of the outer box body, each washing tank is provided with a liquid discharge hole, the liquid discharge holes are communicated with the bottom space of the outer box body, and the liquid discharge holes allow the decellularization reagent to pass through and do not allow the biological materials to pass through;

the liquid feeding device comprises a liquid storage tank, a liquid feeding pipe and a liquid feeding pump, one end of the liquid feeding pipe is communicated with the liquid storage tank, the other end of the liquid feeding pipe extends into the cleaning tank, and the liquid feeding pump is connected with the liquid feeding pipe in series;

a liquid level meter for detecting a liquid level within the cleaning tank;

the control unit is respectively connected with the liquid adding pump and the liquid level meter, and controls the liquid adding pump to be started when the liquid level detected by the liquid level meter is lower than a preset value;

the inner-layer box body comprises a bottom plate and side plates arranged around the bottom plate in a circle, the partition plates are arranged on the bottom plate, the liquid discharge holes are multiple, at least one part of the liquid discharge holes are formed in the bottom plate of the inner-layer box body, a communicating cavity is formed between the bottom plate of the inner-layer box body and the bottom plate of the outer-layer box body, and the liquid discharge holes in the bottom plate of the inner-layer box body are communicated through the communicating cavity.

2. The automatic liquid supplementing type cell removing system according to claim 1, wherein an inner box cover is arranged at an opening of the inner box body, and a bubble absorbing device is arranged on the inner box cover and is respectively communicated with upper spaces of the plurality of cleaning grooves for absorbing bubbles generated by the cell removing reagent in the cleaning grooves.

3. The automatic liquid supplementing type acellular system according to claim 2, wherein the bubble absorbing device comprises a plurality of bubble absorbing pipes, the bubble absorbing pipes are arranged on the inner layer box cover in a penetrating manner, first ends of the bubble absorbing pipes correspondingly extend into the cleaning grooves one by one, second ends of the bubble absorbing pipes are communicated with the collecting container, and the bubble absorbing pipes are respectively connected with a suction pump in series.

4. The automatic fluid infusion type decellularization system according to claim 3, wherein the bubble suction device comprises a plurality of bubble suction pipes, the plurality of bubble suction pipes are arranged on the inner layer box cover in a penetrating manner, first ends of the plurality of bubble suction pipes extend into the plurality of cleaning grooves in a one-to-one correspondence manner, second ends of the plurality of bubble suction pipes are communicated with a collecting pipe through a multi-way pipe joint, the collecting pipe is communicated with the collecting container, and a suction pump is connected in series with the collecting pipe.

5. The automated fluid replacement decellularization system of claim 2, wherein the inner box cover is made of a transparent material.

6. The system according to claim 1, wherein at least a portion of the drainage holes are formed at a lower end of the side plate.

7. The automatic fluid infusion type decellularization system according to any one of claims 1 to 5, wherein a bottom plate of the outer case is disposed obliquely, and a lowest point of the bottom plate of the outer case is disposed near the drain pipe.