Abstract:
A system and method for delaying the activation of a powered device, such as a battery powered device. The activation of the device is triggered by contact with a particular environmental characteristic encountered by the device. For example, the system can be configured to activate upon contact with a particular pH value. Upon contact with the particular environmental characteristic, the restraining component (such as a magnetic field or a separating member) that prevents activation of the device is moved, modified, or caused to yield such that the device is activated.

Description:
RELATED APPLICATIONS 
     The present continuation-in-part application claims priority from the utility patent application titled “SYSTEM AND METHOD TO DELAY CLOSURE OF A NORMALLY CLOSED ELECTRICAL CIRCUIT” (application Ser. No. 09/955,160) that was filed on Sep. 19, 2001 now U.S. Pat. No. 6,635,834, and the continuation-in-part application titled “SYSTEM AND METHOD TO DELAY CLOSURE OF A NORMALLY CLOSED ELECTRICAL CIRCUIT (application Ser. No. 10/664,778) filed on Sep. 17, 2003 now U.S. Pat. No. 6,846,994, the contents of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention generally relates to delaying activation of a powered device until its activation is desired. In some embodiments of the invention, an endoscopic camera incorporates a system for delaying activation of the camera in a human body until it is properly situated for use. Different embodiments can involve a wide variety of different devices and different operating environments. 
     Colon cancer is the second leading cause of death in humans. It is curable if it is detected early. The current method of choice for early detection of colon cancer is a colonoscopy. Unfortunately, for many, colonoscopy is an expensive and uncomfortable procedure. Also, there is a risk that the colon may be punctured during the procedure. Consequently, many people opt to avoid or postpone the procedure. As a result, thousands of people die every year because they do not get a colonoscopy. 
     A less intrusive and cheaper method for early detection of cancer has been developed. It is described in U.S. Pat. No. 5,604,531 to Iddan, et al. that issued on Feb. 18, 1997. In this method, a small endoscopic capsule is swallowed. The capsule contains, inter alia, a means for illumination, a video camera, a lens arrangement and a transmitter. The capsule travels through the body, taking pictures along the alimentary canal and transmitting them to a receiver attached to a belt worn by the patient. Patients are permitted to move around normally during the approximately eight hour procedure. Since the device must be small enough to be swallowed, the size of its power source, a battery, and the amount of power it can provide are severely limited. Further, the capsule must be turned on before it is swallowed. Therefore, the principal disadvantage of this device is that the power source is depleted before it completes an investigation of the small intestine and colon. Consequently, the device is unable to investigate for cancer and other abnormalities in these parts of the body. The present invention solves this problem by delaying activation of devices, such as this capsule, until the capsule enters a particular part of the body. 
     There are several patents covering methods used to delay activation of electrically powered devices until they are needed. U.S. Pat. No. 5,057,824 to Stokes that issued on Jul. 30, 1990, uses a normally closed switch held open by a removable spacer. It is designed to be used in security systems to conserve battery power until the device is ready for use. Upon manual removal of the spacer the switch closes and power is supplied. The principle disadvantage of this method is that it must be activated manually, and thus cannot be activated while in an environment that is not directly accessible, such as the human alimentary canal. If the removable spacer method were used to delay activation of the endoscopic capsule in U.S. Pat. No. 5,604,531, it would need to be activated prior to being swallowed; accordingly, the device would still run out of power prior to completing an investigation of the small intestine and colon. 
     U.S. Pat. No. 4,278,077 to Mizumoto that issued on Jul. 14, 1981 uses an induction system to energize an electromagnetic field in a coil around a permanent magnet located in the device. This method energizes the device when it is needed. The principal disadvantage of this device is that it requires the patient to remain in a stationary position during the entire 8 hour process. Furthermore, this method cannot be used to energize the endoscopic capsule described in U.S. Pat. No. 5,604,531 to Iddan, et al. due to size constraints. 
     SUMMARY OF THE INVENTION 
     The present invention is a system and method to delay activation of a powered device (collectively the “system”). The delayed activation of a powered device can be achieved by the delayed closure of an electrical circuit of a battery-powered electrical device. The system can be embodied in a swallowable endoscopic capsule that is intended to operate remotely in an environment in which the pH value changes from one value to another. More specifically, a pH-sensitive material, used either alone or in conjunction with a Hall effect transistor and a magnet, or in conjunction with a Hall effect transistor and a mixture of the pH-sensitive material and a magnetizable material, holds the electrical circuit open, or the Hall effect transistor in a nonconducting mode, until the device is exposed to an environment having a specified pH value. Exposure of the pH sensitive material to an environment having that specified pH value causes the pH-sensitive material to dissolve. The dissolving of the material causes the circuit to close, or the Hall effect transistor to be in a conducting mode, energizing the device. Different embodiments of the system can trigger the delayed activation of a device based on different characteristics of the desired operating environment. 
     Accordingly, several objects and advantages of the invention are to provide a means to delay activation of a powered device by holding it in a deactivated condition until ready for use. 
     An object of the present invention can be to provide a means by which an electrical device can be self-activated at a specific point within an environment that is difficult to access, such as the human alimentary canal. 
     Another object of the present invention can be to use the pH value of an environment to dissolve a pH-sensitive material separating electrical contacts to activate a battery powered electrical device. 
     Still another object of the present invention can be to use the pH value of an environment to dissolve a pH-sensitive material holding a magnet against a battery-powered electrical device, causing the magnet and battery-powered electrical device to separate, causing a Hall effect transistor to conduct, to activate a battery-powered electrical device. 
     Yet another object of the present invention can be to use the pH value of an environment to dissolve a magnetizable coating applied to the outside of a battery-powered electrical device, said coating consisting of a mixture of a pH-sensitive material and a magnetizable material, to activate a battery powered electrical device. 
     Further objects and advantages of the invention are apparent to those skilled in the art from review of the process flow chart, drawings and description of a preferred embodiment and alternate embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The system can be understood more fully from the following description taken in conjunction with the drawings in which: 
         FIG. 1  shows a diagram illustrating an example of a normally closed switch held open by a pH-sensitive material and connected in series between the battery and the electrical circuitry of a swallowable endoscopic capsule; 
         FIG. 2  shows a diagram illustrating an example of a normally closed switch held open by the pH-sensitive material separating the contacts; 
         FIG. 3  shows a diagram illustrating an example of a normally closed switch after the pH-sensitive material has dissolved; 
         FIG. 4  is a process flow chart illustrating an example of a process for delaying activation of a device. 
         FIG. 5  is a schematic view illustrating an example of an embodiment of the system that includes an endoscopic camera unit. 
         FIG. 5   a  is an enlarged detail view of the endoscopic camera unit shown in  FIG. 5 . 
         FIG. 6  is a schematic view illustrating an alternative example of an embodiment of the system that includes an endoscopic camera unit. 
         FIG. 6   a  is an end view of the endoscopic camera unit shown in  FIG. 6 . 
         FIG. 7  is a process flow chart illustrating an example of a process for delaying activation of a device. 
     
    
    
     DETAILED DESCRIPTION 
     One category of embodiments of the system is primarily intended for use with a swallowable endoscopic capsule, as described in U.S. Pat. No. 5,604,531 to Iddan, et al. that issued on Feb. 18, 1997. The endoscopic capsule described in that patent is designed to take pictures of the human alimentary canal. In this prior art, the endoscopic capsule travels through the alimentary canal from the mouth to the stomach, small intestine and colon. Battery capacity is necessarily limited due to size constraints. Its batteries must be activated before it is swallowed, and the device tends to run out of battery power before reaching the colon. 
     The system delays activation of the electronic components of the endoscopic capsule device until just prior to reaching the small intestine so that it has enough remaining battery power to operate while traveling through the small intestine and the colon. 
     Many embodiments of the system described below use a pH-sensitive material, used either alone (as an insulating element) or in conjunction with a Hall effect transistor and a magnet or magnetizable material. The pH-sensitive material can act to hold an electrical circuit open until the device is exposed to an environment having a specified pH value. Exposure of the pH sensitive material to an environment having that specified pH value causes the pH-sensitive material to dissolve. The dissolving of the material causes the circuit to close, or the Hall effect transistor to be in a conducting mode, powering the device. 
     All embodiments described below use a pH-sensitive material designed to dissolve when exposed to an environment having a specified pH value. The preferred material is made by Colorcon Company of West Point, Pa. 19486, described in U.S. Pat, No. 5,811,121 to Wu, et al. that issued on Sep. 22, 1998. That material is sold under the trademark name of SURETERIC. 
       FIG. 2  shows the preferred embodiment having a normally closed switch connected in series between the battery and electrical circuitry of a swallowable endoscopic capsule and held open by a pH-sensitive insulating element  17 . The normally closed switch  12  has a movable contact  15  and a stationary contact  16 . Pursuant to the preferred embodiment of the present invention, the stationary contact  16  is coated with a pH-sensitive element  17  designed to dissolve when exposed to an environment having a specified pH value. The material  17  holds the movable contact  15  separate from the stationary contact  16 , keeping the battery  11  (or some other power source) and the powered device (such as a battery-powered device)  13  inactive. Color may be added to the material  17  to allow for easy identification of differing pH values. The movable contact  15  and stationary contact  16  may be made of various materials, including, but not limited to, brass, copper and phosphor bronze. 
     As shown in  FIG. 1 , the protective covering  14  of the endoscopic capsule contains an opening  18 , allowing the material  17  coated on the stationary contact  16  to be exposed directly to the various environments of the alimentary canal as the capsule travels from the mouth through the stomach, small intestine and colon. Each region through which the capsule travels, during at least part of its journey, has an ever-increasing pH value, starting with a value of pH 1–2 in the stomach and finally reaching a value above pH 7 in the colon. The material  17  that holds the switch  12  open will dissolve upon reaching a region in which the pH value is greater than that of the material  17 . For example, if the stationary contact  16  is coated with a material with a pH of 4, it will dissolve after leaving the stomach and before reaching the colon. Once the material  17  is dissolved, the switch  12  will close, causing the battery  11  to provide power to electrically powered device  3 . 
       FIG. 1  shows a battery  11  inside protective cover  14 , which contains opening  18 . Opening  18  exposes to the outside environment only that section of the capsule containing the switch. It is unnecessary, and may be undesirable, to expose the other capsule components. Positive electrode  11 A of battery  11  is connected to movable contact  15  of a normally closed switch  12  by wire  11 E, and stationary contact  16  of switch  12  is connected to the positive lead  11 B of electrically powered device  13  by wire  1 F. Negative electrode  11 C of battery  11  is connected to the negative lead  11 D of  13  by wire  11 G. 
     As shown in  FIG. 2 , switch  12 , which is normally biased toward its closed position, has movable contact  15  which is held apart from stationary contact  16  by insulating material  17  that is designed to dissolve at a specified pH value. The material  17  prevents electrical current from flowing from positive electrode  11 A to positive lead  11 B. 
       FIG. 3  shows a normally closed switch  12  after the material  17 , shown in  FIG. 2 , dissolves. Accordingly,  FIG. 3  shows a normally closed switch  12  with movable contact  15  closed against stationary contact  16 , allowing current to flow from positive electrode  11 A to positive lead  11 B. 
       FIG. 4  is a process flow chart for the preferred embodiment of the present invention. At step  51 , a battery is connected in series with an electrically powered device, creating a normally closed electrical circuit whereby the device is energized by the battery upon closing of the circuit. The circuit has a movable contact and stationary contact. At step  52 , the pH value of the environment in which it is desired that the device be energized is determined. At step  53 , a material designed to dissolve upon exposure to that environment is selected. At step  54 , either the movable contact and/or stationary contact is coated with the material, separating them such that the circuit is held open. Finally, at step  55 , the material is exposed to the desired environment, causing the material to dissolve, the contacts to close, and electrical power to flow to the device. 
     As an alternative embodiment, the pH-sensitive insulating material is applied directly to the positive and/or negative ends of at least one battery within the circuit. The material holds the circuit open until the material dissolves. When the material dissolves, a movable contact holding the battery in place closes against the battery, allowing current to flow. 
     In two alternative embodiments, the switch means utilized to complete the circuit and power the capsule&#39;s components is a Hall effect transistor or similar circuitry such as a reed switch. The Hall effect transistor is operable to open the capsule&#39;s electrical circuit when it is in the presence of a magnetic field, and to close the capsule&#39;s electrical circuit (thus powering the capsule&#39;s camera and transmitter components) when the magnetic field is absent. A reed switch consists of two magnetic contacts in a tube. When a magnet is close to a reed switch, the two contacts become magnetized and repel each other, blocking electrical current. When the magnet is moved away from the reed switch the contacts demagnetize and move to their original, closed position. 
     In an alternative embodiment schematically shown in  FIGS. 5 and 5   a , small magnet  19  is held in dimple  20  in the end of the endoscopic capsule. The capsule is then coated with the pH-sensitive material, holding the magnet in place against the capsule. The magnet&#39;s magnetic field holds a Hall effect transistor inside the capsule a nonconducting mode. Exposure of the material to an environment having a specified pH value causes the pH-sensitive material to dissolve, causing the magnet and capsule to separate, causing said Hall effect transistor to conduct, energizing said capsule. 
     In another alternative embodiment schematically shown in  FIGS. 6 and 6   a , the pH-sensitive material is mixed with a magnetizable material, such as an iron powder, creating a magnetizable coating. The coating is applied to the outside of the swallowable endoscopic capsule. When the coating is magnetized, the resulting magnetic field maintained between opposite poles at central opening  24  and distal opening holds a Hall effect transistor in a non-conducting mode. Exposure of the coating to an environment having a specified pH value causes the pH-sensitive material to dissolve, destroying the magnetic field. The destruction of the magnetic field causes the Hall effect transistor to conduct, thus activating the camera and transmitter circuitry in the swallowable endoscopic capsule. 
     The embodiment schematically depicted in  FIG. 5  utilizes a magnetic field to hold the electrical switch means in a non-conducting mode until the magnetic field is destroyed.  FIG. 5  shows some, but not all, of the components of an endoscopic capsule: a shell  21 , shell cap  21 A, and an electrical switch means  12 . In this embodiment, magnet  19  is placed in a dimple  20  at the end of shell  21 . A coating  22  is applied to both the magnet  19  and the outside of shell  21 , such that when coating  22  dries and hardens, magnet  19  is held in place in dimple  10  at the end of shell  21 . The preferred magnet is a rare earth magnet. The preferred coating is the pH-sensitive material described above. Alternatively, magnet  19  can be coated in place against the end of shell  21  without the need for a dimple. The magnet  19  will hold an electrical switch means  12 , which is part of the electrical circuit of the endoscopic capsule, in a non-conducting mode. The preferred switch means is either a Hall effect transistor or a normally closed switch means. Exposure of the coating to an environment having a specified pH value causes the coating to dissolve, and causes the magnet to separate from the shell. This separation removes the capsule from the magnetic field, allowing the Hall effect transistor to conduct, thus activating the electronics of the endoscopic capsule where needed. 
       FIG. 6  shows another alternative embodiment. Similar to the second alternative embodiment described above, this embodiment also utilizes a magnetic field to hold the electrical switch means in a non-conducting mode until the magnetic field is destroyed. The main difference is that, rather than using a discrete magnet, this embodiment employs a magnetizable coating  23  on the outside of shell  21  of the endoscopic capsule. The preferred coating  23  is a mixture of the pH-sensitive material, described above, and a powdered magnetizable material. The preferred magnetizable material is powdered iron, powdered rare earth or powdered Alnico. Coating  23  is magnetizable. 
     Coating  23  is applied to the outside of the shell  21 . The area of the coating at the end of the shell  21  has an opening  24  to focus the magnetic field. It is preferable that the shell  21  be coated prior to placing any electronics inside the shell. After coating  23  is applied to the shell  21 , the coating  23  is magnetized. When magnetized, said coating  23  will hold an electrical switch means, which is part of the electrical circuit of the swallowable endoscopic capsule, in a non-conducting mode. The preferred switch means is either a Hall effect transistor or a normally closed switch means. Exposure of the coating  23  to an environment having a specified pH value causes the material to dissolve, which allows the magnetic field formed by the coating  23  to be destroyed, allowing the Hall effect transistor to conduct, or the said switch means to close, thus activating the electronics of the endoscopic capsule where needed. As an example, the electronics of the endoscopic capsule can be activated in the stomach, intestine, colon, or other environment along the alimentary canal, based on the predetermined pH level at which the coating is set to dissolve. 
       FIG. 7  is a process flow chart describing the third alternative embodiment for the present invention. At step  61 , the pH value of the environment in which it is desired that the electronic device be activated is determined. At step  62 , a material designed to dissolve upon exposure to said environment is selected. At step  63 , a powdered magnetizable material is selected. At step  64 , said powdered magnetizable material and said pH-sensitive material are mixed. At step  65 , the mixture is applied to the outside of an endoscopic capsule shell, and is allowed to dry, forming a coating. At step  66 , said coating is magnetized. At step  67 , the electronics and other components of the endoscopic capsule are inserted into the shell, and the shell cap is attached to the shell, and the capsule is sealed closed. At step  68 , the coated endoscopic capsule is exposed to an environment having the pH value determined in step  1  above, causing the coating to dissolve, destroying the magnetic field, and thereby allowing electrical power to flow, activating the electrical device. 
     From the above, it should be understood that the embodiments described, in regard to the drawings, are merely exemplary and that a person skilled in the art may make variations and modifications to the shown embodiments without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as defined by the appended claims. This information is meant to be illustrative and not limiting. 
     The concepts identified and described above can be implemented in a wide variety of different embodiments. For example, a wide variety of different devices can be incorporated into the system. Similarly, a wide variety of different environmental characteristics can be used to trigger the activation of the device. A wide variety of different restraining components, such as magnetic fields and separation members can be used to delay activation of the various devices.