JPS62790Y2

JPS62790Y2 -

Info

Publication number: JPS62790Y2
Application number: JP11814680U
Authority: JP
Priority date: 1980-08-22
Filing date: 1980-08-22
Publication date: 1987-01-09
Also published as: JPS5743887U

Description

[Detailed explanation of the idea]

本考案は工業用原材料又は工業製品などを洗浄
するための処理槽に係り、高速で自動的に給排水
を行う設備を備えた洗浄処理槽に関するものであ
る。従来、洗浄処理槽用の自動給水設備としては、
高所に設けた洗浄用水の貯蔵槽と低所に設けた洗
浄処理槽との間を接続する管路中に電磁弁を設け
て洗浄用水の流下流量を制御する装置が用いられ
たが、電磁弁は一般に流路面積が狭いので充分の
流量が得られず、従つて給水に長時間を必要とし
た。また、従来、上記洗浄処理槽内の廃水を排水す
るため、その底面に電磁弁又は空気シリンダによ
つて開閉作動される弁が設けられていたが、前記
いずれの型式の弁を用いても、それぞれ次のよう
な不具合があつた。即ち、電磁弁を用いた場合、電磁弁は一般に流
路面積が狭いので充分の流量が得られず、排水に
長時間を要する。特に洗浄処理槽の排水は槽内の
静水圧によつて行うため、排水が進行して槽内の
水深が減小すると排水速度が遅くなる。空気シリンダによつて開閉作動される弁として
は第１図又は第２図に示すような弁が実用化され
ている。第１図の弁装置は洗浄処理槽の底板１に
排水孔２を穿ち、空気シリンダ３によつて動かさ
れる平面形の弁４で前記排水孔２を覆う構造のも
ので、５は水密を保つため弁４に接着されたゴム
パツキングである。第２図の弁装置は、底板１に
上方に広がる円錐弁シート６を削成し、これに適
合する円錐弁７が空気シリンダ３に取につけられ
て動かされるようになつている。８は水密を保つ
ため円錐弁７に接着されたゴムパツキングであ
る。上記いずれの空気シリンダ作動の弁装置にお
いても、弁４又は弁７は弁シートに対して下方に
向けて押しつけられて水密を保つ構造になつてい
る。このようになつていると、弁の頂面に掛かる
水圧がこの弁を弁シートに押しつける方向に働く
ので、閉弁した状態を保ち易いという長所が有る
が、弁を上方に動かして開弁しようとするときは
水圧に抗して弁を上昇させねばならない。このた
め開弁作動が迅速に行われ難いという欠点があ
る。また、弁を開閉するためにこの弁を空気力で
上昇させたり下降させたりしなければならないの
で、空気シリンダ３は複動型のものを用いねばな
らない。このため空気シリンダの構造が複雑であ
り、これに附属する操作弁（図示せず）や配管も
複雑となる。また、これらの弁４もしくは同７に
はいずれもそれぞれゴムパツキング５もしくは同
８が接着されているが、このようにゴム等の弾性
材を用いたパツキングを接着するには特殊設備及
び特殊技術を要するので、製造コストが割高とな
る。本考案の目的は、高価な電磁弁や、ゴムパツキ
ングを接着した弁を用いないで、迅速に給、排水
を行い得る洗浄処理槽を提供するにある。本考案は上記目的を達成するため、１基の洗浄
処理槽と２基の洗浄水貯蔵槽とを１組とし、両者
の間をそれぞれサイホン管で接続すると共に、上
記サイホン管の頂部を偏平に形成して、該部にお
ける管内壁の頂面と底面との間隔を該サイホン管
の他の部分の内径よりも小さくし、かつ、前記洗
浄処理槽の底面に排水用の開口部を設けて、この
開口部にパツキンを介して、下方に向けて開いた
形の円錐弁シートを取りつけ、この弁シートに対
して円錐弁を下方から対向密接させることによ
り、水圧を利用して開弁作動が行われるようにし
たことを特徴とする。次に、本考案の一実施例として、蒸溜水による
半導体材料の洗浄処理装置を第３図乃至第８図に
ついて説明する。第３図は洗浄装置全体の正面図で、１基の洗浄
処理槽９に対して２基の洗浄水貯蔵槽１０，１
０′が設けられている。第４図は側面図である。
洗浄水貯蔵槽１０，１０′それぞれの底面に急速
給水用サイホン管１１，１１′の一端が連通固着
され、他端は接ぎ配管１２，１２′によつて洗浄
処理槽９の頂部に接続されている。前記サイホン
管１１，１１′の詳細については第６図について
後述する。洗浄水貯蔵槽１０と同１０′とは同様の構成で
あるから、共通事項については第４図に表わされ
ている洗浄水貯蔵槽１０について説明する。この
洗浄水貯蔵槽内へ給水管１３から洗浄液である蒸
溜水が注入されるようになつており、槽内の水面
を検知するため水面検出管１４が連通固着されて
いる。１５は水面検出管１４内に挿入されている
フロート、１６はこのフロートの位置を電気的に
検出する水面検出器である。第４図に示されるごとく、洗浄処理槽９内には
被洗浄物１７を乗せる多孔板１８が仕切板１９に
よつて水平に支えられている。接ぎ配管１２を通
つて流下した洗浄水は、そのまま矢印Ａの如く洗
浄処理槽９内に流入させることもでき、又はシヤ
ワー管２０に導かれて被洗浄物１７の上に注ぐこ
ともでき、適宜に切り替え操作できるようになつ
ている。また洗浄処理槽９の底部にはバブリング
管２１が設けられていて、空気を吹き込んで撹拌
し得るようになつている。２２は脚である。洗浄処理槽９の底面には弁装置２３が設けられ
ている。その詳細を第５図について説明する。洗浄処理槽９の底板１に開口部２４が穿たれて
いる。そしてこの部の下面にパツキング２５を介
して弁シート板２６がボルトで取りつけられてい
る。この弁シート板２６には下開き方向の円錐弁
シート２６ａが形成されている。前記のパツキン
グ２５は弾性材料で作られた比較的厚手のものを
用い、若干の弾性変形の余裕を残してボルトで締
めつけられている。底板１の下方に、シリンダ取付板２７が支柱２
８を介して取りつけられている。このシリンダ取
付板２７は空気シリンダ２９のシリンダヘツド
と、空気シリンダ２９の取付ブラケツトとを兼ね
た部材である。このシリンダ取付板２７にピスト
ンロツドを兼ねた弁棒３０が挿通され、この弁棒
３０にピストン３１が固着されている。そして前
記シリンダ取付板２７に蓋状のシリンダ３２が取
りつけられて空気シリンダ２９が形成されてい
る。前記弁棒３０に固着された円錐弁３３が前記弁
シート板２６に形成された円錐弁シート２６ａに
対向、密接するようになつている。前述のサイホン管１１の詳細を第６図、第７図
及び第８図について説明する。第６図は従来一般
に用いられているサイホン管の頂部付近を示し、
１本の管をＵ字形に曲げたもので、各部等径であ
る。第７図は本実施例に用いられたサイホン管１
１の正面図、第８図は同じく側面図で、頂部が偏
平に加工されている。線Ａ−Ｂは、頂部における
管の内壁の底面のレベルを示しており、管内水面
がこのＡ−Ｂレベル以下であれば、このサイホン
管１１がサイホン作動をしない限界の水位を意味
している。H₂はサイホン管の頂部における管内
壁の底面から頂面までの高さを示している。サイホン管１１の頂部が偏平に加工されている
ので、第６図に示すものに比して、管内面の断面
積を変えないで、同部の高さ寸法H₁よりも前記
の高さ寸法H₂が小さくなつている。次に第３図について給水作動の説明をする。２
基の洗浄水貯蔵槽１０，１０′は交互に使用する
ように設けられているものであつて、常にいずれ
か一方の洗浄水貯蔵槽はＡ−Ｂレベル、即ちサイ
ホン管１１の頂部における管内壁下面のレベルま
で洗浄水を入れておく。洗浄処理槽９に給水するには、洗浄水貯蔵槽１
０又は１０′いずれか一方の、既にＡ−Ｂレベル
まで洗浄水が溜まつている貯蔵槽に洗浄水を注加
する。水面がH₂だけ上昇して、サイホン管１１
の頂部の、内壁面の最高レベルに達すると、サイ
ホン作用によつて槽内の洗浄水はサイホン管１１
および接ぎ配管１２を通つて洗浄処理槽９内に流
下する。流下し始めると洗浄水貯蔵槽１０内の洗
浄水は全量洗浄処理槽９内に流入する。この流入
管路は、その途中に弁類が介装されていないので
流動抵抗が少なく、速やかに全量の流下が進行す
る。本実施例においては、前記サイホン管１１の
最頂部は既述の如く偏平に形成され、頂部におけ
る内壁の上下面間距離がH₂となつているので、
上述の注入操作において洗浄水貯蔵槽１０内水位
がH₂だけ上昇すると流下が開始される。このH₂
寸法が従来形のサイホンにおけるH₁寸法よりも
小さいので、従来形に比して流下開始までの所要
時間が短かい。洗浄水が洗浄処理槽９内に流下すると、同槽内
で洗浄処理を行う。この間空気シリンダ２９内に
圧縮空気を供給させておく。圧縮空気によつてピストン３１が上向きの空気
圧力を受けると、これに取りつけられた円錐弁３
３が円錐弁シート２６ａに押しつけられる。ゴム等弾性物体のパツキングを介しないで、固
体の弁を固体の弁シートに密着させることによつ
て水密を保つことは、周知のごとく技術的に容易
でない。それは、弁および弁シートが正確に作ら
れていても両者の心と平行とを合わせることが困
難だからである。この為従来は弁とシートとの当
たり面にゴム等を接着していたのであるが、本考
案に於ては円錐弁３３にも弁シート２６ａにもゴ
ム等を接着せず、その代りに、弁シート板２６
を、弾性材料製のパツキング２５を介して底板１
に対して弾性的に取付けている。上記パツキング
２５が弾性を有しているので、円錐弁３３と弁シ
ート板２６ａに形成された弁シート２６ａとの間
の微小の心狂いや平行度狂いは、このパツキング
２５によつて吸収され、円錐弁と弁シートとが実
用上充分な程度に密接する。排水する際、空気シリンダ２９に供給していた
圧縮空気を遮断して、シリンダ内を大気圧にする
と、円錐弁３３は主として水圧によつて押し下げ
られて開弁する。従来の弁装置（第１図、第２
図）においては、開弁作動が水圧に抗して行われ
る構造であるため、開弁スピードを上げ難かつ
た。しかし、円錐弁３３は上方に向けて弁シート
に押しつけられて水密を保つようになつているた
め、この円錐弁に掛かる水圧、並びに該円錐弁、
弁棒３０、及びピストン３１の自重が開弁力とし
て働き、このため開弁作動が迅速に行われる。その上、上述のように水圧が開弁力として働く
ので空気シリンダ２９は複動型にする必要が無
く、単動型で充分な機能を発揮し得る。このため
空気圧関係機器が簡略化され、製造コストが安
い。また前記空気シリンダ２９が支柱２８を介して
底板１に取りつけられているため、排水の流路面
積を充分に取り易く、かつ空気シリンダ２９の取
り外し取りつけが容易で整備性が良い。以上のように、給水、排水が迅速に行われるの
で、洗浄処理槽の実動効率が良く、しかも１基の
洗浄処理槽に対して２基の洗浄水貯蔵槽を設けて
交互に使用するようにし、給水を終つた洗浄水貯
蔵槽には洗浄水を注入して次回給水の準備をとと
のえておくように運転管理することにより、洗浄
The present invention relates to a processing tank for washing industrial raw materials or industrial products, and relates to a washing processing tank equipped with equipment for automatically supplying and draining water at high speed. Traditionally, automatic water supply equipment for cleaning treatment tanks is
A device was used to control the flow rate of cleaning water by installing a solenoid valve in the pipe connecting the cleaning water storage tank installed at a high place and the cleaning treatment tank installed at a low place. Since the valve generally has a narrow flow path area, a sufficient flow rate cannot be obtained, and therefore a long time is required for water supply. Furthermore, conventionally, in order to drain the waste water in the cleaning treatment tank, a valve that is opened and closed by a solenoid valve or an air cylinder has been provided on the bottom of the tank, but no matter which type of valve is used, Each of them had the following problems. That is, when a solenoid valve is used, since the solenoid valve generally has a narrow flow path area, a sufficient flow rate cannot be obtained, and drainage takes a long time. In particular, since drainage from the cleaning treatment tank is carried out by the hydrostatic pressure within the tank, as drainage progresses and the water depth within the tank decreases, the drainage speed slows down. As a valve that is opened and closed by an air cylinder, a valve as shown in FIG. 1 or 2 has been put into practical use. The valve device shown in Fig. 1 has a structure in which a drain hole 2 is bored in the bottom plate 1 of the cleaning treatment tank, and the drain hole 2 is covered with a planar valve 4 operated by an air cylinder 3, and 5 maintains watertightness. This is a rubber packing adhered to the reservoir valve 4. In the valve arrangement of FIG. 2, an upwardly extending conical valve seat 6 is cut out in the bottom plate 1, and a conical valve 7 adapted to the seat is mounted on an air cylinder 3 for movement. 8 is a rubber packing adhered to the conical valve 7 to maintain watertightness. In any of the above-mentioned air cylinder operated valve devices, the valve 4 or the valve 7 is pressed downward against the valve seat to maintain watertightness. This arrangement has the advantage that the water pressure applied to the top of the valve acts to press the valve against the valve seat, making it easier to keep the valve closed, but let's move the valve upwards to open it. When doing so, the valve must be raised against the water pressure. Therefore, there is a drawback that it is difficult to open the valve quickly. Furthermore, since the valve must be raised or lowered by pneumatic force in order to open or close the valve, the air cylinder 3 must be of a double-acting type. Therefore, the structure of the air cylinder is complicated, and the operating valves (not shown) and piping attached thereto are also complicated. In addition, rubber packing 5 or 8 is adhered to each of these valves 4 or 7, but special equipment and special techniques are required to adhere such packing using elastic materials such as rubber. Therefore, the manufacturing cost is relatively high. The object of the present invention is to provide a cleaning tank that can quickly supply and drain water without using expensive solenoid valves or valves with rubber packing attached. In order to achieve the above object, the present invention combines one cleaning treatment tank and two cleaning water storage tanks as a set, connects them with siphon pipes, and flattens the top of the siphon pipes. forming a pipe, the distance between the top surface and the bottom surface of the inner wall of the pipe in the part is smaller than the inner diameter of the other part of the siphon pipe, and an opening for drainage is provided in the bottom face of the cleaning treatment tank, A conical valve seat that opens downward is attached to this opening via a gasket, and the conical valve is brought into close contact with the valve seat from below to open the valve using water pressure. It is characterized by being made to appear. Next, as an embodiment of the present invention, an apparatus for cleaning semiconductor materials using distilled water will be described with reference to FIGS. 3 to 8. FIG. 3 is a front view of the entire cleaning device, showing two cleaning water storage tanks 10 and 1 for one cleaning treatment tank 9.
0' is provided. FIG. 4 is a side view.
One end of a rapid water supply siphon pipe 11, 11' is connected and fixed to the bottom of each of the cleaning water storage tanks 10, 10', and the other end is connected to the top of the cleaning treatment tank 9 by a connecting pipe 12, 12'. There is. Details of the siphon tubes 11, 11' will be described later with reference to FIG. Since the wash water storage tank 10 and the wash water storage tank 10' have the same construction, the common features will be explained with respect to the wash water storage tank 10 shown in FIG. 4. Distilled water, which is a cleaning liquid, is injected into the cleaning water storage tank from a water supply pipe 13, and a water surface detection pipe 14 is connected and fixed in order to detect the water level in the tank. 15 is a float inserted into the water surface detection tube 14, and 16 is a water surface detector that electrically detects the position of this float. As shown in FIG. 4, inside the cleaning tank 9, a perforated plate 18 on which an object to be cleaned 17 is placed is supported horizontally by a partition plate 19. The cleaning water that has flown down through the joint pipe 12 can be allowed to flow directly into the cleaning treatment tank 9 as shown by arrow A, or can be led to the shower pipe 20 and poured onto the object to be cleaned 17, as appropriate. It is now possible to switch to and operate. Further, a bubbling pipe 21 is provided at the bottom of the cleaning treatment tank 9 so that air can be blown into the tank for stirring. 22 is a leg. A valve device 23 is provided on the bottom surface of the cleaning treatment tank 9. The details will be explained with reference to FIG. An opening 24 is bored in the bottom plate 1 of the cleaning treatment tank 9. A valve seat plate 26 is attached to the lower surface of this portion via a packing 25 with bolts. This valve seat plate 26 is formed with a conical valve seat 26a that opens downward. The packing 25 is made of an elastic material and is relatively thick, and is tightened with bolts, leaving some room for elastic deformation. Below the bottom plate 1, a cylinder mounting plate 27 is attached to the support column 2.
It is attached via 8. This cylinder mounting plate 27 is a member that serves both as a cylinder head of the air cylinder 29 and as a mounting bracket for the air cylinder 29. A valve rod 30, which also serves as a piston rod, is inserted through the cylinder mounting plate 27, and a piston 31 is fixed to the valve rod 30. A lid-shaped cylinder 32 is attached to the cylinder mounting plate 27 to form an air cylinder 29. A conical valve 33 fixed to the valve stem 30 faces and is in close contact with a conical valve seat 26a formed on the valve seat plate 26. Details of the aforementioned siphon tube 11 will be explained with reference to FIGS. 6, 7, and 8. Figure 6 shows the vicinity of the top of a conventionally commonly used siphon tube.
It is a single tube bent into a U shape, and each part has the same diameter. Figure 7 shows the siphon tube 1 used in this example.
1 is a front view, and FIG. 8 is a side view as well, and the top portion is processed to be flat. The line A-B indicates the level of the bottom surface of the inner wall of the pipe at the top, and if the water level in the pipe is below this A-B level, it means the limit water level at which the siphon pipe 11 does not perform siphon operation. . H ₂ indicates the height from the bottom to the top of the inner wall of the siphon tube at the top. Since the top of the siphon tube 11 is processed to be flat, compared to the one shown in FIG. 6, the height dimension of the same portion is lower than the height dimension H ₁ without changing the cross-sectional area of the inner surface of the tube. H ₂ is getting smaller. Next, the water supply operation will be explained with reference to FIG. 2
The washing water storage tanks 10 and 10' are provided so as to be used alternately, and one of the washing water storage tanks is always at the A-B level, that is, the inner wall of the pipe at the top of the siphon pipe 11. Add cleaning water to the bottom level. To supply water to the cleaning treatment tank 9, use the cleaning water storage tank 1.
The cleaning water is poured into the storage tank, either 0 or 10', which has already accumulated cleaning water up to the A-B level. The water level rises by H ₂ and the siphon tube 11
When the washing water reaches the highest level of the inner wall surface at the top of the tank, the washing water in the tank flows through the siphon pipe 11 due to the siphon action.
and flows down into the cleaning treatment tank 9 through the joint pipe 12. When the water starts flowing down, the entire amount of the washing water in the washing water storage tank 10 flows into the washing processing tank 9. This inflow pipe has no valves interposed in the middle, so there is little flow resistance, and the entire amount flows down quickly. In this embodiment, the top of the siphon tube 11 is formed flat as described above, and the distance between the upper and lower surfaces of the inner wall at the top is _H2 , so that
In the above-described injection operation, when the water level in the cleaning water storage tank 10 rises by _H2 , the water starts flowing down. This H ₂
Since the dimensions are smaller than the _H1 dimension of conventional siphons, the time required to start flowing is shorter than that of conventional siphons. When the cleaning water flows down into the cleaning treatment tank 9, the cleaning treatment is performed in the same tank. During this time, compressed air is supplied into the air cylinder 29. When the piston 31 receives upward air pressure from compressed air, the conical valve 3 attached to it
3 is pressed against the conical valve seat 26a. As is well known, it is technically not easy to maintain watertightness by bringing a solid valve into close contact with a solid valve seat without packing with an elastic material such as rubber. This is because even if the valve and valve seat are made accurately, it is difficult to align their centers and parallelism. For this reason, in the past, rubber or the like was glued to the contact surface between the valve and the seat, but in the present invention, rubber or the like is not glued to either the conical valve 33 or the valve seat 26a, and instead, Valve seat plate 26
is attached to the bottom plate 1 through a packing 25 made of an elastic material.
It is attached elastically to the Since the packing 25 has elasticity, minute misalignment and parallelism between the conical valve 33 and the valve seat 26a formed on the valve seat plate 26a are absorbed by the packing 25. The conical valve and the valve seat are brought into close contact with each other to a practically sufficient extent. When draining water, the compressed air supplied to the air cylinder 29 is cut off to bring the inside of the cylinder to atmospheric pressure, and the conical valve 33 is pushed down and opened mainly by water pressure. Conventional valve device (Fig. 1, 2
In the case shown in Figure), the valve opening operation was performed against water pressure, so it was difficult to increase the valve opening speed. However, since the conical valve 33 is pressed upward against the valve seat to maintain watertightness, the water pressure applied to the conical valve and the conical valve
The weight of the valve stem 30 and piston 31 acts as a valve opening force, and therefore the valve opening operation is performed quickly. Furthermore, since water pressure acts as the valve opening force as described above, there is no need for the air cylinder 29 to be a double-acting type, and a single-acting type can provide sufficient functionality. This simplifies pneumatic equipment and reduces manufacturing costs. Further, since the air cylinder 29 is attached to the bottom plate 1 via the support column 28, it is easy to secure a sufficient flow path area for drainage, and the air cylinder 29 can be easily removed and attached, resulting in good maintainability. As described above, since water is supplied and drained quickly, the actual operating efficiency of the cleaning treatment tank is high, and two cleaning water storage tanks can be installed and used alternately for one cleaning treatment tank. By managing the operation in such a way that the cleaning water storage tank is injected with cleaning water after the water supply has finished, and is ready for the next water supply.

【表】本考案によれば、簡単な構成で迅速に給水、排
水を行なうことができるので、洗浄処理槽のアイ
ドルタイムが減小し、その能率を顕著に向上させ
ることができる。[Table] According to the present invention, water can be quickly supplied and drained with a simple configuration, so the idle time of the cleaning tank can be reduced and its efficiency can be significantly improved.

[Brief explanation of the drawing]

第１図および第２図は従来一般に用いられてい
る排水弁の断面図、第３図は本考案の一実施例の
正面図、第４図は同じく一部を断面した側面図、
第５図は本考案の一実施例の排水弁部分の断面図
第６図は従来用いられていたサイホン管の頂部付
近の外観正面図、第７図は本考案の一実施例のサ
イホン管の頂部付近の外観正面図、第８図は同じ
く側面図である。１……洗浄処理槽の底板、９……洗浄処理槽、
１０，１０′……洗浄水貯蔵槽、１１，１１′……
サイホン管、１７……被洗浄物、１８……多孔
板、２０……シヤワー管、２１……バブリング
管、２３……弁装置、２４……開口部、２５……
パツキング、２６……弁シート板、２６ａ……円
錐弁シート、２７……シリンダ取付板、２８……
支柱、２９……空気シリンダ、３０……弁棒、３
１……ピストン、３２……蓋状のシリンダ、３３
……円錐弁。 1 and 2 are cross-sectional views of conventionally commonly used drain valves, FIG. 3 is a front view of an embodiment of the present invention, and FIG. 4 is a partially sectional side view.
Fig. 5 is a cross-sectional view of the drain valve portion of an embodiment of the present invention. Fig. 6 is an external front view of the vicinity of the top of a conventionally used siphon pipe. Fig. 7 is a sectional view of the siphon pipe of an embodiment of the present invention. The external front view of the vicinity of the top and FIG. 8 are also side views. 1...Bottom plate of the cleaning treatment tank, 9...Cleaning treatment tank,
10, 10'... Washing water storage tank, 11, 11'...
Siphon pipe, 17...Object to be cleaned, 18...Perforated plate, 20...Shower pipe, 21...Bubbling pipe, 23...Valve device, 24...Opening, 25...
Packing, 26... Valve seat plate, 26a... Conical valve seat, 27... Cylinder mounting plate, 28...
Strut, 29... Air cylinder, 30... Valve stem, 3
1... Piston, 32... Lid-shaped cylinder, 33
...conical valve.

Claims

[Scope of utility model registration request]

The main cleaning treatment tank and the two cleaning water storage tanks are communicated via siphon pipes, and
The top of the siphon pipe is formed flat so that the distance between the top and bottom surfaces of the inner wall of the pipe in this part is smaller than the inner diameter of the other part of the siphon pipe, and an opening is formed in the bottom plate of the cleaning treatment tank. A conical valve seat opening downward is attached to this opening via packing, and an air cylinder device having a conical valve that fits the conical valve seat is attached to the bottom of the cleaning treatment tank. A cleaning treatment tank equipped with an automatic rapid water supply and drainage device characterized in that it is attached via a column.