1. Field of the Invention
The present invention relates to an endoscope cover assembly for covering an endoscope and a cover-system endoscope in which the endoscope is combined with the endoscope cover assembly.
2. Description of the Related Art
Recently, endoscopes have been widely used in the medical field. Because the endoscope is inserted into the human body, mucilage or dirt adheres to the insertion section of the endoscope, sometimes hindering observation or treatment. To remove the mucilage and dirt, a plurality of pipes for feeding water to the front end of the insertion section to clean the observational window, or for sucking dirt are provided in the insertion section of the endoscope.
After use on a patient in the medical field, an endoscope is cleaned or disinfected to prevent disease by infection.
Cleaning and infection procedures take a great deal of labor necessitating a relatively long time, thereby limiting the availability of endoscopes.
For this reason, so-called cover-system endoscopes have been recently used, according to which the endoscope is covered with an endoscope cover assembly which is discarded each time a treatment is completed, simplifying the cleaning and disinfection procedures after use.
U.S. Pat. No. 4,646,722 has disclosed a disposable endoscope cover assembly for covering the entire external surface of the insertion section of the endoscope when the endoscope is used, which is removed from the endoscope after use, eliminating the necessity of cleaning and disinfecting the endoscope.
Japanese Patent Laid-Open No. 2-54734 has disclosed an endoscope cover assembly for covering the external surfaces of an endoscope, which is disposable after use. Such high-efficiency cover-system endoscopes have been disclosed, which minimize the down time of the endoscope and reduce the idle time of doctors.
The above U.S. Pat. No. 4,646,722 has also disclosed a side-view type endoscope in which the endoscope cover assembly is expanded by operating an erecting mechanism provided at the front end of the insertion section of the endoscope in order to change the direction of an opening of a medical treatment instrument channel.
According to the construction described above, the endoscope cover assembly is interposed between the erecting mechanism and the medical treatment instrument to prevent contamination of the erecting mechanism.
However, the above systems have the following disadvantages. The first one concerns the durability of the endoscope cover assembly. When the medical treatment instrument is erected, the endoscope cover assembly must be expanded, thus requiring a small operating force. To achieve this purpose, it is necessary to make the endoscope cover assembly thin, but it is difficult to provide the endoscope cover assembly with sufficient strength to withstand this force. During the operation of the erecting mechanism, the endoscope cover assembly receives a local force, so that it is likely to tear. If it tears, the endoscope becomes subject to contamination so that the purpose of preventing contamination is lost.
Additionally, the endoscope cover assembly is sometimes pinched between the erecting mechanism and the endoscope front end component. In this case also, the endoscope cover assembly may be torn exposing the endoscope to contamination.
The second problem concerns the free-play allowance and assembly precision of the endoscope cover assembly which occur when the endoscope cover assembly is mounted on the aforementioned side-view type endoscope. The assembly position of the endoscope and the endoscope cover assembly may differ along the axis of the insertion section of the endoscope depending on the manufacturer of the endoscope cover assembly. Thus, in respective endoscope cover assembly products which are to be mounted in the endoscope, the erecting mechanism and the medical treatment instrument introducing channel are likely to be deviated from each other. Thus, when a clamp, which is one type of the medical treatment instruments, is erected, the erecting angle of the clamp may differ slightly depending on the kind of endoscope cover assembly product, sometimes precluding a required erecting angle. As a further problem, the erecting angle of the clamp may differ slightly. For example, a procedure for introducing the medical treatment instrument to a duodenal papilla in which the erecting mechanism is frequently used requires great precision and thus may be greatly affected by the aforementioned slight differences making it impossible to introduce the medical treatment instrument as desired.
A third problem occurs because it may be necessary to clean and disinfect the endoscope when the endoscope becomes contaminated by breakage of the endoscope cover assembly or the like. However, with the aforementioned construction, sufficiently cleaning and disinfecting the endoscope takes a great deal of labor because the construction of the endoscope is complicated and particularly because the erecting mechanism is exposed.
In addition to the constructions disclosed in U.S. Pat. No. 4,646,722, the following patent application Nos. have disclosed endoscopes which have erecting mechanisms for the medical treatment instrument.
Japanese Utility Model Laid-Open No. 63-17450 has disclosed an erecting base which is disposed parallel to the center of the field of view of an observational window with a wire for erecting the erecting base connected to a cutout provided at the erecting base. According to this construction, when the wire is pulled, the medical treatment instrument is pressed toward the center of the field of view to direct the medical treatment instrument to the center of the field of view.
According to the construction of the erecting base disclosed in Japanese Utility Model Laid-Open No. 63-17450, the wire is connected to a cutout provided on the erecting base. Thus, the wire approaches the inside face of the erecting base, that is, a face which substantially supports the medical treatment instrument. In this case, although there is no problem in protruding a medical treatment instrument having a relatively large diameter, a flexible medical treatment instrument is likely to be hooked by the wire, so that it cannot protrude to the front end of the endoscope.
If the pressing force of the wire is large, the flexible medical treatment instrument may be crushed thereby losing its function. For example, a tube injecting contrast medium which is used for imaging the pancreatic duct and bile duct is inserted from the duodenum into the duodenum mamilla, bile duct or pancreatic duct. Thus, a very flexible contrast tube may be crushed by the pressing force of the wire when the erecting base is erected, making it impossible to inject the contrast medium.
It is desirable to provide an endoscope having an erecting base which is capable of controlling the erection of the medical treatment instrument so that the medical treatment instrument is located in the center of the field of view of the observational window without being destroyed or damaged when the medical treatment instrument is erected. The same is demanded for the cover-system endoscope.
For example, Japanese Patent Laid-Open No. 64-5895 has disclosed an erecting base which is formed of an elastic material to guide the medical treatment instrument smoothly without avoiding a portion which bends sharply when the erecting base is erected.
The erecting base which is composed of the aforementioned elastic material is erected if the erecting wire connected to the erecting base is pulled; it is restored to its original position (placed down) if the erecting wire is released. However, because the aforementioned erecting base is formed of an elastic material formed of a sheet as thin as 0.03 mm-0.5 mm, it is twisted when the erecting wire is pulled, so that the direction of the protrusion of the medical treatment instrument may not be stabilized. Due to the twisting, sometimes the medical treatment instrument is not protruded properly, and thus this erecting base has room for improvement.
The following problems exist concerning the medical treatment instrument which will be erected by the erecting mechanism.
There are a variety of medical treatment instruments available including a flexible one like the aforementioned contrast medium tube made of resin and another requiring a large force when it is bent like a basket clamp for destroying calculus. Depending on the type of medical treatment instrument, the force required for erecting the instrument varies.
Of the aforementioned cover-system endoscopes, for example, a type employing a side-view type endoscope is suitable for treatment inspecting the bile duct system through duodenum Vater's mamilla. In most cases, the treatment uses flexible instruments and consists of imaging the bile duct, cutting off the mamilla and the like. A basket clamp or the like which requires a large erecting force is seldom used.
Depending on the object and purpose of observation, different medical treatment instruments are used. In erecting mechanisms which erect an instrument with a uniform driving force, it is difficult to adjust the mechanism so that the instrument is erected by a suitable force. Moreover, a high-level skill is required.
Further, the cover-system endoscope has the following problems as well as those described above.
Generally, a reusable type endoscope is used several hundred times by cleaning and disinfecting it after each use. That is, such endoscopes are rigidly constructed so as to withstand several hundred treatments, making them expensive. Even if the initial cost of the medical treatment instrument is increased to some extent, the overall cost for operating the endoscope system is not greatly affected.
On the other hand, if the same structure as the medical treatment instrument guiding device of the reusable type endoscope is provided on the endoscope cover assembly, the cost of the endoscope cover assembly increases.
The cost of the endoscope cover assembly in the cover-system endoscope must be reduced because the endoscope cover assembly is disposed of and replaced each time a treatment is finished. Thus, it is desirable that used parts be as inexpensive as possible.
Next, the construction for erecting the aforementioned erecting mechanism will be described below. An erecting mechanism disclosed in Japanese Utility Model Laid-Open No. 63-17450 is erected by pulling an erecting wire for which an operating member needs to be provided on the operator's side. It is desirable for the aforementioned operating member to be easily operable. Because the endoscope cover assembly is detachable from the endoscope, it is important that the aforementioned operating member not be an obstacle in detaching or attaching it.
Further, because operations for curving the endoscope sometimes must be performed while the erecting mechanism is operated, if it takes a great deal of labor to perform both operations, a medical treatment may take a long time and in some cases, the treatment may be insufficient. This is the reason that a cover-system endoscope which facilitates operating the aforementioned erecting mechanism and curving the endoscope is demanded.
In addition to those described above, the following problems can be addressed. That is, because, according to the cover-system endoscope, the endoscope is covered with the endoscope cover assembly, the endoscope is painful to patients when the diameter of the insertion section covered with the endoscope cover assembly increases. Thus, it is desirable to reduce the diameter of the insertion section while maintaining the erecting function. The reduction of the diameter leads to a reduction of the required inspection time. It is also necessary for the insertion section to be inserted smoothly with the endoscope cover assembled with the endoscope cover assembly.
If a gap is caused between the observational window/illumination window of the endoscope and the transparent cover of the endoscope cover assembly when the endoscope is inserted and mounted in the endoscope cover assembly, the following problem is generated. That is, part of the illumination light transmitted from the illumination window of the endoscope is reflected by the inside face of the transparent cover and the reflected light enters the observational window, thereby causing a flaring reflection in observed images.