Abstract:
The present invention provides a means for preventing, in a cylinder cabinet, the improper securing of a gas container due to human error or the like. The cylinder cabinet comprises a securing means for securing a gas container therein, a control means for managing and controlling a series of steps for carrying out a gas container-exchange operation, and a detection means for detecting whether the gas container is properly secured. When the detection means detects that the new container is improperly secured, the control means places the gas container-exchange operation on stand-by until the container is properly secured.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a casing in which a gas container is accommodated, hereinafter referred to as a cylinder cabinet. More specifically, the present invention relates to a safety measure involving a means for detecting whether a gas container is firmly fixed in a cylinder cabinet, particulary after said gas container has been exchanged. 
     2. Description of the Prior Art 
     Many of the gases used as a feed material in the semiconductor-manufacturing industry, gases such as SiH 4 , PH 3  and NF 3 , possess various dangerous properties, for instance, combustibility (explosiveness), toxicity and corrosiveness. When such a gas is used it is stored in a portable gas container referred to as a gas bomb or gas cylinder. One is also legally obligated to use a gas container accommodated in a casing referred to as a cylinder cabinet for reasons of safety. 
     When the amount of gas remaining in a gas container becomes small, the gas container must be exchanged in a timely fashion with a new gas container. In the case where a new gas container is disposed at a predetermined position within a cylinder cabinet, said gas container is usually secured within the cylinder cabinet to prevent it from falling down. As to the means for securing the gas container, particularly to the wall face of a cylinder cabinet, prior art means include a chain or steel band attached to the wall face of the cylinder cabinet for tightening and thereby securing the gas container. 
     In exchanging a gas container, safety precautions require that there also exist a method for confirming that the exchanged container has been properly secured. However, there is the distinct possibility of human error in such operations. While the release and securing of a gas container are repeatedly carried out whenever a gas container is exchanged, carelessness of the worker can cause the container to be loosely secured, or not secured at all within the cylinder cabinet. Such an error creates a danger that the container will fall down, thereby leading to a gas leak. It would be very desirable and important to the industry, therefore, if a cylinder cabinet was provided which could prevent any failure to properly secure a gas cylinder therein by human error. Safety would be thereby greatly improved. 
     SUMMARY OF THE INVENTION 
     In order to achieve the aforementioned objective, the present invention provides a cylinder cabinet having a means for securing a gas container accommodated therein, a control means for managing and controlling a series of steps which are carried out in a gas container-exchange operation, and a detection means which detects whether the gas container is suitably secured or not. When the detection means detects that a new gas container is not properly secured by said securing means after the gas container has been replaced in a gas-exchange operation, the control means places the gas container-exchange operation on standby, not transferring it to the next step. 
     Therefore, in a case where a worker has forgotten to properly secure a gas container, the cylinder of the present invention does not permit the gas container-exchange operation to progress ahead. As a result, the worker realizes the container must be properly secured and can attend to same. 
     In a preferred embodiment, the securing means is a band of the type that tightens around and thereby secures the body of a gas container, with a pressure 
     In a preferred embodiment, the securing means is a band of the type that tightens around and thereby secures the body of a gas container, with a pressure sensor attached on the inner face of said band. The pressure sensor can thereby detect whether a suitable tightening force has been applied, and thereby whether the gas container has been properly secured or not. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWING 
     FIG. 1 is a perspective view showing the inside of a cylinder cabinet according to the present invention, and particularly the means for securing a gas container. 
     FIG. 2 is a schematic illustrative view showing the construction of a cylinder cabinet according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In referring to the figures of the drawing, preferred embodiments of the present invention will be described in detail, with the same designation being given to the same or corresponding part. 
     The reference numerals employed are as follows: 
       10 —cylinder cabinet,  12 —gas container,  16 —securing band,  26 —lock mechanism,  34 —pressure sensor,  36 —controller. 
     FIG.  1  and FIG. 2 of the drawing schematically show a cylinder cabinet  10  according to the present invention. In the illustrated embodiment, it is devised that a gas container  12  is secured by steel bands  16  attached on the rear wall face  14  of the cylinder cabinet  10 . In order to restrain the upper part and lower part of said gas container  12 , a pair of bands  16  are provided high and low. Only one of these high and low securing bands  16  will be described herein because they are of the same structure. 
     The securing band  16  is one which becomes an annulus surrounding the body of the gas container  12  when the gas container  12  is fixed or secured in place, and it comprises a plurality (i.e. five in the illustrated embodiment) of circular curved portions  18   a ,  18   b ,  18   c ,  18   d  and  18   e . The curved portion  18   c  is formed integratedly with a bracket  22  attached on the rear wall face  14  of the cylinder cabinet  10  by bolts  20 , or the like. This curved portion  18   c  is thicker and is more rigid as compared with the other curved portions, because it must function to receive the gas container  12  carried therein. As to the other curved portions  18   a ,  18   b ,  18   d  and  18   e , it is preferable that they are relatively thin and exhibit some elasticity to act as a tightening force on the body of the gas container  12 . 
     The curved portions adjacent to each other are mutually connected by a hinge  24 , except for the curved portion  18   a  and the curved portion  18   e . Thus, these curved portions are capable of swinging in a horizontal plane, and hence it becomes possible that a gas container  12  can be placed into the inside of the securing band  16  by opening the curved portions, as can be seen from the band  16  in the upper part of FIG.  1 . 
     Adjacent ends of the curved portions  18   a ,  18   e  will be locked in a closed state by means of a lock mechanism  26 . Although various types of mechanisms can be used as the lock mechanism  26 , a mechanism of the type illustrated in the drawings is suitable, in which a ring  30  attached on one curved portion  18   e  is clinched onto a hook  28  fixed on the other curved portion  18   a  and said ring  30  is pulled in a toggle manner by a lever  32  so as to be secured on the hook  28 . The illustrated securing band  16  is constructed such that a small clearance is provided between the ends of the curved portions  18   a ,  18   e  so that all the curved portions  18  are brought in soft contact with the body of the gas container  12 . In a case where the adjacent ends of the curved portions  18   a ,  18   e  are locked by use of the aforementioned lock mechanism  26 , the clearance between the curved portions  18   a ,  18   e  gets narrower so that a tightening force is exerted by the securing of band  16  onto the outer peripheral face of the body of the gas container  12 , whereby the gas container  12  can be firmly fixed with respect to the cylinder cabinet and further rotation is prevented. 
     The cylinder cabinet  10  can also have a sensor for detecting whether the ends of the curved portions  18   a ,  18   e  of the band  16  have been closed and locked, thereby detecting whether the gas container  12  has been secured. As such a sensor, many various types of sensors are possible, such as a magnetic or electric access sensor provided between these ends. Generally, however, at least one pressure sensor  34  is preferred which is attached on the inner face of the curved portion  18   e . When the securing band  16  is locked, this pressure sensor  34  is pressed down between the inner face of the band  16  and the outer peripheral face of the body of the gas container  12 , and hence its output signal is changed. Accordingly, it becomes possible to reliably detect whether the gas container  12  has been secured with respect to the cylinder cabinet  10  in fact, without detecting a lock under conditions when a gas container  12  does not exist. An output signal of the pressure sensor  34  will be input to a controller  36  comprising a computer for controlling the whole system of the cylinder cabinet  10 , and this controller  36  will manage and control the steps of the exchange operation for the gas container  12  on the basis of this signal. 
     The gas container  12  secured by the band  16  has a container valve  38  attached on its mouth, and this container valve  38  will be remotely opened or closed by means of an automatic opening and closing apparatus (not shown) which is controlled by the controller  36 . The discharge port  40  of said container valve  38  has a gas supply pipe  44  connected thereto detachably by a pipe joint  42 . Onto the gas supply pipe  44  are connected two pipes  46 ,  48  at a position near to said pipe joint  42 , where one pipe  46  serves to supply a purge gas such as nitrogen gas from a purge gas supply source and the other pipe  48  serves to vent a gas remaining in the pipe  44  to the atmosphere. Each of the pipes  44 ,  46 ,  48  has a shut-off valve  50 ,  52 ,  54  provided therein, and the opening and closing operations of these shut-off valves  50 ,  52 ,  54  are controlled by the controller  36 . 
     An exchange operation including gas container  12  will next be briefly described. 
     In a case where the exchange operation of a gas container  12  is begun, a worker first turns on an input device, for example an exchanging work start-up switch  56 . The controller  36  receives an input signal from said switch  56 , it drives the automatic opening and closing apparatus so that the container valve  38  is closed and at the same time the shut-off valve  50  in the gas supply pipe  44  is closed. In succession, the worker turns on a purge start-up switch  58  to open the shut-off valves  52 ,  54  in the pipes  46 ,  48 . By virtue of this opening operation, a purge gas is permitted to flow in from a purge gas supply source through the pipe  46 , whereby a special material gas existing in the pipe  44  is discharged to the atmosphere through the pipe  48  for vent. 
     If this purging step is completed prior to the removal of the pipe  44 , the controller  36  will release the lock to the door of the cylinder cabinet  10 . The worker can not directly contact the gas container  12  until this stage has been reached, and then he separates the pipe joint  42  and removes the pipe  44  from the gas container  12 . Thereafter, he releases the lock on the band  16  by its lock mechanism  26 , opens the curved portions  18  and carries the gas container  12  out of the cylinder cabinet  10 . The worker then carries a new gas container  12  sufficiently filled with a gas into the cylinder cabinet  10 , and disposes it at its predetermined position. He then conducts the connection of the pipe joint  42  and the placement of the automatic opening and closing apparatus, and further closes and locks the securing band  16 . In the case where the gas container  12  is properly secured at that time, the pressure sensor  34  senses a pressure higher than a predetermined pressure by the tightening force of the securing band  16 . On the basis of an output signal from the pressure sensor  34 , accordingly, the controller  36  will judge that the gas container  12  has been firmly fixed, and transfer the gas container-exchange operation work to a next gas tightness-checking step. 
     If a worker, however, has forgotten to conduct the lock of the securing band  16  by its lock mechanism  26 , or such locking has been incomplete, the output signal of the pressure sensor  34  does not vary, or even if it has varied, such variation is less than a predetermined level. In such a case, the controller  36  does not transfer the gas container-exchange operation to the next gas tightness-checking step. Even if the worker closes the door of the cylinder cabinet  10  and turns on a gas tightness check start-up switch  60 , the gas tightness check will not be conducted and the gas container-exchange operation work will be interrupted and placed on stand-by. Owing to this situation, the worker can recognize that the securing of the gas container  12  is incomplete, and as a result, he is destined to carry out the tightening and securing of the gas container  12  by the securing band  16 , with subsequent confirmation again. At that time, the controller  36  may also optionally display in a display unit  62  an indication that the securing of the gas container  12  is incomplete. 
     If the securing of the gas container  12  has been completed as mentioned above, the gas container-exchange operation will be permitted to progress to the next gas tightness-checking step. Then, a purging step after the attachment of the gas container will be conducted, and as a result, the gas container  12  will be returned to a usual gas supply state. 
     Although the preferred embodiment of the present invention has been described in detail above, it goes without saying that the present invention is not limited to the aforementioned embodiment. For instance, a series of steps in the gas container-exchanging work mentioned above has been merely exemplified. 
     For example, although a securing band  16  has been used as the securing means for a gas container  12  in the aforementioned embodiment, there may also be used a securing means of another type, for example, of a chain type. In a case where the securing means is of another type, it is a matter of course that the type of a detection means for detecting the securing of the gas container  12  must be also changed. In a case where a chain is used, for instance, it is necessary to provide a sensor for detecting that a hook provided on one end of said chain is clinched on a fixing ring on the side of a cylinder cabinet, whereby it is enabled to confirm that the securing operation has been completed. 
     Even when a gas container has not been completely secured in the gas container-exchange operation as described above, according to the present invention, a gas container will be ultimately secured. Accordingly, the present invention is destined to prevent the falling of a gas container which may be caused to happen by the generation of an earthquake or the likes, and to greatly improve the safety of a cylinder cabinet.