Patent Abstract:
A method of creating a switch to be disposed along a longitudinal axis of a device, comprising providing a hollow body defining an interior cavity, disposing a switching element movably within the interior cavity, the switching element defining a switch-making position and a switch-breaking position and having a biasing element, coupling an electrically-conductive contact to the switching element to define a switch-making state when the switching element is in the switch-making position and a switch-braking state when the switching element is in the switch-braking position, and imparting a variable longitudinal bias to the switching element with the biasing element to place the switching element in one of the switch-making position and the switch-braking position until an external force imparted to the switching element along the switching axis exceeds the longitudinal bias thereby causing the switching element to move to the other one of the switch-making position and the switch-braking position.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is:
         a divisional of U.S. application Ser. No. 11/750,622, filed May 18, 2007, now U.S. Pat. No. 7,479,608 (which application claimed the priority, under 35 U.S.C. §119, of U.S. Provisional Patent Application 60/801,989 filed May 19, 2006, 60/810,272, filed Jun. 2, 2006, 60/858,112, filed Nov. 9, 2006, and 60/902,534, filed Feb. 21, 2007);   a divisional of U.S. application Ser. No. 12/270,518, filed Nov. 13, 2008, now U.S. Pat. No. 7,714,239;   a divisional of U.S. application Ser. No. 12/728,471, filed Mar. 22, 2010, now U.S. Pat. No. 8,269,121; and   a divisional of U.S. application Ser. No. 13/571,159, filed Aug. 9, 2012,
 
the entire disclosures of which are all hereby incorporated herein by reference in their entireties.
       

    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     n/a 
     FIELD OF THE INVENTION 
     The present invention lies in the field of switches, in particular, a force switch. The device can be used along with any tool in which a particular longitudinal force needs to be overcome prior to reaching a given detected force. 
     BACKGROUND OF THE INVENTION 
     In various applications, a compressible material is compressed between two surfaces for modification of the material in some way after being compressed. The material can be compressed too little, too much, or in an acceptable range of compression. It would be beneficial to provide an electrical switch that can indicate when the acceptable minimum compression force has been exceeded. It would further benefit if the switch actuates over a small gap and is longitudinally in-line with the device in which the switch is incorporated. It would also be beneficial if the minimum force setting of the switch could be pre-set to given force values. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention overcomes the above-noted and other deficiencies of the prior art by providing an electronic switch that actuates over a small gap (on the order of 25 to 200 micrometers), is longitudinally in-line with the device in which the switch is incorporated, and switches dependent upon a longitudinally expanding external force that can be pre-set over a given floor force value. 
     A characteristic of the force switch described herein is that the longitudinal forces that the force switch can withstand are significantly higher than that existed in the past. With a force switch having approximately a 6 mm diameter, for example, an approximately 5 to 8 pound longitudinally pulling force changes the switch state while, at the same time, being able to withstand almost 300 pounds of longitudinal pulling or compressive force. This is an almost twenty-fold difference. 
     There are many uses for the force switch in various different technology areas. 
     In a first exemplary area of technology, the force switch can be used to measure compressive forces imparted upon tissue by medical devices. In many medical procedures, tissue is compressed between two surfaces before a medical device is caused to make a change in the compressed tissue. If the tissue is compressed too little, then the change sought to be effected might not be sufficient. If the tissue is, on the other hand, compressed too much, the change sought to be effected might actually destroy the area of interest. When compressing such tissue, there are measurable force ranges that fall between these two extremes. Knowing the “safe” force range can allow the user to select a pre-tensioning of the force switch to change its state (i.e., indicate to the user the pre-tensioned force has been exceeded) within the “safe” range of that tissue. 
     The force switch described herein can be constructed in a customized way to have the state-changing pre-tension match the “safe” range of the tissue to be operated upon. 
     One type of medical device that is used to change a state of tissue is a medical stapling device. Ethicon Endo-Surgery, Inc. (a Johnson &amp; Johnson company) manufactures and sells such stapling devices. Circular stapling devices manufactured by Ethicon are referred to under the trade names PROXIMATE® PPH, CDH, and ILS. Linear staplers manufactured by Ethicon under the trade names CONTOUR and PROXIMATE also can use the force switch. In each of these exemplary staplers, tissue is compressed between a staple cartridge and an anvil and, when the staples are ejected, the compressed tissue is also cut. In this specific example, the tissue can be compressed too little (where blood color is still present in the tissue, too much (where tissue is crushed), or just right (where the tissue is blanched). Staples delivered have a given length and the cartridge and anvil need to be at a given distance so that the staples close upon firing. Therefore, these staplers have devices indicating the relative distance between the two planes and whether or not this distance is within the staple length firing range. However, these staplers do not have any kind of active compression indicator that would also optimize the force acting upon the tissue that is to be stapled. The force switch described herein provides such a feature. Some exemplary procedures in which these staplers could use the force switch include colon dissection and gastric bypass surgeries. 
     With the foregoing and other objects in view, there is provided, in accordance with the invention, a method of creating a switch to be disposed along a longitudinal axis of a device, comprising providing a hollow body defining an interior cavity; disposing a switching element movably within the interior cavity, the switching element having a longitudinal switching axis disposed parallel to the longitudinal axis of the device and defining a switch-making position at a first longitudinal position along the switching axis and a switch-breaking position at a second longitudinal position along the switching axis, the second longitudinal position being different from the first longitudinal position, and a biasing element; coupling an electrically-conductive contact to the switching element to define a switch-making state when the switching element is in the switch-making position and a switch-braking state when the switching element is in the switch-braking position; and imparting a variable longitudinal bias to the switching element with the biasing element to place the switching element in one of the switch-making position and the switch-braking position until an external force imparted to the switching element along the switching axis exceeds the longitudinal bias thereby causing the switching element to move to the other one of the switch-making position and the switch-braking position. 
     In accordance with another feature of the invention, the switching element is a piston. 
     In accordance with a further feature of the invention, the electrically-conductive contact is physically coupled to the switching element and is moveable along the switching axis between the switch-making position and the switch-breaking position. 
     In accordance with an added feature of the invention, the method further comprises defining a second interior cavity by a stop element in which the switching element is movably disposed, the stop element being at least partly disposed in the interior cavity of the hollow body. 
     In accordance with an additional feature of the invention, the switching element further comprises a bias device. 
     In accordance with yet another feature of the invention, the biasing element is disposed about at least a portion of the switching element between the stop element and the bias contact. 
     In accordance with yet a further feature of the invention, a magnitude of the longitudinal bias is dependent upon a longitudinal position of the stop element within the interior cavity of the hollow body. 
     In accordance with yet an added feature of the invention, the switching axis is disposed coincident with the device axis. 
     In accordance with yet an additional feature of the invention, the biasing element imparts the longitudinal bias to place the switching element in the switch-breaking position to create a normally open switch configuration. 
     In accordance with again another feature of the invention, the biasing element imparts the longitudinal bias to place the switching element in the switch-making position to create a normally closed switch configuration. 
     In accordance with again a further feature of the invention, a distance between the first longitudinal position and the switch-breaking position is between approximately 25 μm and approximately 750 μm. 
     In accordance with again an added feature of the invention, a distance between the first longitudinal position and the switch-breaking position is between approximately 75 μm and approximately 200 μm. 
     In accordance with again an additional feature of the invention, a range of force sufficient to cause the switching element to move between the switch-making state to the switch-breaking state is between approximately 3 ounces and approximately 20 pounds. 
     In accordance with still another feature of the invention, a range of force sufficient to cause the switching element to move between the switch-making state to the switch-breaking state is between approximately 5 pounds and approximately 8 pounds. 
     In accordance with still a further feature of the invention, the method further comprises electrically insulating the electrically-conductive contact from the hollow body and the switching element. 
     In accordance with still an added feature of the invention, the method further comprises forming a switch sub-assembly having the electrically-conductive contact, a switch housing longitudinally fixed and electrically conductively connected to the hollow body and at least partially surrounding the electrically-conductive contact, a switch insulator electrically insulating the electrically-conductive contact from the switch housing, and a piston contact movably disposed in the switch housing and longitudinally fixedly and electrically conductively connected to the piston. 
     In accordance with still an additional feature of the invention, the switching element has a first exterior, the bias contact has a second exterior having a larger diameter than the first exterior, the interior cavity of the hollow body has a first interior substantially equal in diameter to the second exterior, the second interior cavity has a second interior substantially equal in diameter to the first exterior, the bias contact has a third exterior substantially equal in diameter to the first interior, and the electrically-conductive contact has a fourth exterior smaller in diameter than the first interior. 
     In accordance with still an additional feature of the invention, the method further comprises electrically connecting an electric indication circuit to the switching element and the electrically-conductive contact, the electric indication circuit having an indicator operable to transmit state-change information to signal a user that a state change of the switching element has occurred. 
     In accordance with yet an additional feature of the invention, the biasing element is a compression spring compressed between the bias contact and the stop element around the switching element to bias the switching element in a direction away from the stop element. 
     Other features that are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a force switch, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Advantages of embodiments the present invention will be apparent from the following detailed description of the preferred embodiments thereof, which description should be considered in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view from a side of an exemplary embodiment of a force switch according to the invention. 
         FIG. 2  is a longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 1  through a near half of the switch; 
         FIG. 3  is a longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 1  through a near half of the switch; 
         FIG. 4  is a longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 1  through a near half of the switch; 
         FIG. 5  is a longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 1  through a near half of the switch; 
         FIG. 6  is a longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 1  through approximately a longitudinal axis of the switch; 
         FIG. 7  is a longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 1  through a far half of the switch; 
         FIG. 8  is an enlarged, longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 6  with the switch in an un-actuated position; 
         FIG. 9  is an enlarged, longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 6  with the switch in an actuated position; 
         FIG. 10  is a perspective view from a side of another exemplary embodiment of a force switch according to the invention. 
         FIG. 11  is a longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 10  through a near half of the switch; 
         FIG. 12  is a longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 10  through a near half of the switch; 
         FIG. 13  is a longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 10  through approximately a longitudinal axis of the switch; 
         FIG. 14  is a longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 10  through a far half of the switch; 
         FIG. 15  is a longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 10  through a far half of the switch; 
         FIG. 16  is an enlarged, longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 13  with the switch in an un-actuated position; and 
         FIG. 17  is an enlarged, longitudinally cross-sectional perspective view from a side of the force switch of  FIG. 13  with the switch in an actuated position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Aspects of the invention are disclosed in the following description and related drawings directed to specific embodiments of the invention. Alternate embodiments may be devised without departing from the spirit or the scope of the invention. Additionally, well-known elements of exemplary embodiments of the invention will not be described in detail or will be omitted so as not to obscure the relevant details of the invention. 
     Before the present invention is disclosed and described, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. 
     While the specification concludes with claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the drawing figures, in which like reference numerals are carried forward. The figures of the drawings are not drawn to scale. 
     Referring now to the figures of the drawings in detail and first, particularly to  FIGS. 1 to 9  thereof, there is shown a first exemplary embodiment of a force switch  1 .  FIGS. 10 to 17  illustrate a second exemplary embodiment of the force switch  1 . As will be described in more detail below, the first exemplary embodiment represents a “normally open” switch configuration and the second exemplary embodiment represents a “normally closed” switch configuration. Where features of the switch  1  are similar in the two embodiments, for ease of understanding, similar reference numerals will be used. 
     The force switch  1  can be incorporated into a device where force along the longitudinal axis of the device needs to be measured and an action needs to be taken when that force exceeds a given predetermined value. This force switch  1  can be used, for example, in a medical device, but is not limited to the exemplary embodiment of a medical device. As will be described in further detail below, the force switch  1  can be used with a circular surgical stapling device such as is disclosed in U.S. Pat. No. 5,104,025 to Main 
       FIGS. 1 to 9  represent different portions of the force switch  1 .  FIG. 6  provides an example view through the longitudinal axis  2  of the force switch  1  that allows one to see all parts of the switch  1 . A contact piston  10  provides a central part around which other parts of the switch  1  may be explained. A nose piece or tip  20  is fastened to the distal end  12  of the contact piston  10 . The distal end  12  and an internal bore  22  of the tip  20  are illustrated with straight lines in  FIGS. 4 to 9 , however, in a first exemplary embodiment, the distal end  12  can be provided with external male threads and the bore  22  can be provided with internal female threads. Alternatively, the tip  20  can be press-fit, glued, welded, or otherwise connected to the distal end  12  of the contact piston  10 . In the configuration shown in  FIGS. 4 to 9 , a proximal portion  24  of the internal bore  22  has a non-threaded flat portion for receiving therein the distal-most end of the piston  10  such that, when completely threaded into the bore  22 , the proximal portion  24  acts as a stop for further threading of the distal end  12  therein. 
     At the proximal end of the piston  10 , a widening  14  is provided on the outside surface of the piston  10  and an internal bore  16  is formed in the interior thereof. 
     A hollow body tube  30  is disposed around at least a portion of the contact piston  10 . One exemplary embodiment of the interior of the tube  30  includes a relatively narrower proximal bore  32  and a relatively wider distal bore  34  (although the opposite configuration is also possible). The bores  32 ,  34  surround a proximal portion of the piston  10  that includes a central shaft  18  thereof and the widening  14 . The exterior shape of the widening  14  and the interior shape of the proximal bore  32  are substantially equal. Accordingly, in a circular configuration, the interior diameter of the proximal bore  32  is substantially equal to the outer diameter of the widening  14 . As used herein, substantially equal means that there is only a sufficient clearance between the two parts to allow one to slide within the other. Thus, if a given first material requires a particular first spacing between the outer surface of the piston  10  and the inner surface of the body tube  30  to permit the piston  10  to move therein, then that first spacing exists between the two parts  10 ,  30 , whereas, if a given second material requires a smaller (or larger) spacing between the outer surface of the piston  10  and the inner surface of the body tube  30  to permit the piston  10  to move therein, then that that second spacing exists between the two parts  10 ,  30 . 
     There are two parts between the piston  10  and the body tube  30 , an adjustable end cap  40  and a bias device  50 . The exterior shape of the end cap  40  and the interior shape of the distal bore  34  are substantially equal. Accordingly, in a circular configuration, the interior diameter of the distal bore  34  is substantially equal to the outer diameter of the end cap  40 . Thus, when the end cap  40  is inserted into the distal bore  34 , the cap  40  substantially closes an interior space defined by the interior surfaces of the distal and proximal bores  34 ,  32 , the exterior surface of the central shaft  18 , the distal transverse surface of the widening  14 , and the proximal end surface of the cap  40 . The bias device  50  is disposed inside this interior space. The bias device  50  and the cap  40  act together with the widening  14  to bias the piston  10  in a given direction, in this case, in the proximal direction. Force of the bias device  50  can be dependent upon the position of the cap  40 . For example, if the cap  40  is closer to the widening  14 , the bias device  50  can exert a first biasing force and if the cap  40  is further from the widening  14 , the bias device  50  can exert a second biasing force. Depending upon the bias device  50  used, the first force can be greater than the second, or vice-versa. It is beneficial, but not required, if the cap  40  is adjustable between various locations along the body tube  30 . In such a configuration, the bias device  50  can be adjusted to a user-desired pre-bias. 
     One embodiment of the cap  40  and bias device  50  is shown in  FIGS. 2 to 9 . The following description, however, will be directed to the view of  FIG. 8 . In this embodiment, the distal bore  34  has a larger diameter than the proximal bore  32 . The end cap  40  has exterior threads  42  that mate with non-illustrated internal female threads of the distal bore  34 . In such a configuration, the cap  40  can be rotated into the distal bore  34  along any longitudinal point within the distal bore  34 . With the proximal bore  32  having a smaller diameter than the distal bore  34 , the distal endpoint  36  of proximal bore  32  forms a stop for insertion of the cap  40 . The cap  40  is formed with an interior bore  44  having a shape substantially equal to the outer shape of the central shaft  18  of the piston  10 . Thus, while the cap  40  can be screwed into the distal bore  34  such that longitudinal forces will not press the cap  40  out from the distal bore  34 , the central shaft  18  of the piston  10  can move longitudinally freely within the bore  44  and with respect to the cap  40 . 
     The bias device  50  is embodied, in this example, as a compression spring  50 . As such, when the spring  50  is placed around the central shaft  18  of the piston  10  up to the distal transverse surface of the widening  14 , and when the threaded cap  40  is also placed around the central shaft  18  and screwed at least partially within the distal bore  34 , the spring  50  can be compressed between two extremes defined by the longitudinal connection distance that the cap  40  can traverse between being securely but barely inside the distal bore  34  and fully inserted therein up to the stop  36 . 
     Because the piston  10  moves, it can form one contact of an electrical switch for signaling a state of the piston  10 . Another contact needs to be provided that is electrically insulated from the piston  10 . Thus, the piston  10  needs to be associated with a switch sub-assembly so that the electrical switch is in a first state when the piston  10  is in a first longitudinal position and in a second state when the piston  10  is in a second longitudinal position (the first and second states being off/on or on/off). This switch sub-assembly is formed at a proximal end of the piston  10  and the body tube  30  and, in the following text, is shown in two exemplary embodiments. The first embodiment, the “normally open” switch has been mentioned as being related to  FIGS. 1 to 9 . The second embodiment relates to  FIGS. 10 to 17  and is a “normally closed” switch. 
     The normally open switch sub-assembly is explained with regard to  FIGS. 8 to 9 . A switch bushing  60  has a distally projecting stub  62  that is inserted into the proximal end of the body tube  30 . This stub  62  can be connected to the body tube  30  in any number of ways (e.g., by bonding, welding, adhesive, press-fit, screw threads). The proximal end of the switch bushing  60  is attached to a mounting body  70 . In one embodiment, each of the piston  10 , the tip  20 , the body tube  30 , the cap  40 , the switch bushing  60 , and the mounting body  70  are electrically conductive and provide a first electrical contact of the force switch  1 . However, the tip  20  and cap  40  need not be conductive. To form a second electrical contact that, when put into electrical connection with the first contact, completes an electrical circuit (or interrupts an electrical circuit as shown in  FIGS. 10 to 17 ), an insulating body needs to be disposed between the second contact and the first contact needs to be operatively moved into (or out of) contact with the second contact. 
     Various switch embodiments disclosed herein include parts that are electrically conductive and actually form part of the electronic circuit. The switch according to the present invention, however, is not limited to embodiments where parts of the switch form the circuit. An alternative configuration can take advantage only of the mechanical switch-breaking aspects of the invention to have the movement of the piston actuate a separate electrical switch adjacent the switch, e.g., the piston. Such an external switch can be embodied as what is referred to in the art as a tact switch because such a switch is very small. Various microswitches can be used as well if there is sufficient room for such larger switches. 
     In the exemplary embodiment of  FIGS. 1 to 9 , the second electrical contact is formed by a contact ring  80  and the insulating body is formed by an insulating stub  90 . The part that connects the ring  80  and the insulating stub  90  to the piston  10  is a T-shaped connecting bar  100 . Each of the ring  80 , the stub  90 , and the bar  100  are nested in their shape so that they can fit in an easy assembly into the switch bushing and the body tube  30 . The insulating stub separates the contact ring  80  from the connecting bar  100 , which is in electrically conductive contact with the piston  10  and the switch bushing  60 . 
     More specifically, the internal bore  16  is shaped to receive a distal boss  102  of the connecting bar  100 . The connection between the distal boss  102  and the internal bore  16  can be like any of the embodiments of the connection between the piston  10  and the tip  10 . If the boss  102  has an external male thread, for example, then the internal bore  16  has a corresponding female internal thread. Such an exemplary configuration makes attachment of the connecting bar  100  and the piston  10  easy with regard to manufacturing costs and time. 
     The contact ring  80  has an internal bore  82  having a shape dimensioned to correspond substantially to the outer shape of a distal contact portion  92  of the insulating stub  90 . This external outer shape of the distal contact portion  92  can take any polygonal shape, such as circular, ovular, rectangular, square, star, triangular, for example. Regardless of this outer shape, the shape of the internal bore of the contact ring  80  corresponds thereto so that the contact ring  80  can be inserted thereon and fixed (whether by press-fit, adhesive, bonding, welding, or any other connection process) thereto so that control of contact between the ring  80  and any other portion of the first contact can be made with high precision. 
     After the contact ring  80  is connected to the insulator stub  90 , the combined assembly can be connected to the connecting rod  100 . The external shape of an intermediate portion of the rod  100  is made to correspond to an internal shape of a bore  94  extending through the insulator stub  90 . Again, the outer shape of the intermediate portion of the rod  100  can take any polygonal shape, such as circular, ovular, rectangular, square, star, triangular, for example. Regardless of this outer shape, the shape of the internal bore of the insulator stub  90  corresponds thereto so that the insulator stub  90  can be inserted thereon and fixed (whether by press-fit, adhesive, bonding, welding, or any other connection process) thereto so that control of contact between the ring  80 , mounted to the stub  90 , and any other portion of the first contact can be made with high precision. 
     With such a connection, the connecting rod  100  electrically contacts the piston  10  (and, thereby, the tip  20 , the body tube  30 , the cap  40 , the switch bushing  60 , and the mounting body  70 ). The outer shape/diameter of the contact ring  80  is dimensioned to be smaller than the inner shape/diameter of the switch bushing  60  and insertion of the contact ring  80  inside the switch bushing  60  creates a transverse gap  110  therebetween. Thus, the contact ring  80  is electrically isolated from the switch bushing  60  on the outer side thereof by the transverse gap  110  and is electrically isolated (insulated) from the connecting rod  100  on the inner side thereof by being in direct contact with the outside surface of the insulator stub  90 . 
     To make an electric circuit including the contact ring  80  and any electrically conducting part of the first contact ( 10 ,  20 ,  30 ,  40 ,  60 ,  70 ), an electrical connection must be made at the contact ring  80 . One exemplary embodiment for such a connection is illustrated in  FIGS. 5 to 9 . Specifically, the connecting bar  100  is formed with the proximal longitudinal bore  103  extending from the proximal transverse exterior surface  104  up to and including at least a part of the intermediate portion the connecting rod  100  that is located at a longitudinal position where the contact ring  80  is disposed. A further transverse bore  106  is formed to connect the longitudinal bore  103  with an interior surface of the contact ring  80 . In such a configuration, an insulated wire  206  can be threaded through the longitudinal  103  and transverse  104  bores and fastened (e.g., by welding) to the interior surface of the contact ring  80 . For ease of such a connection, the contact ring  80  can be formed with a depression (or a series of depressions) on the inside surface for receiving the electrical portion of the wire while the insulating portion of the wire remains in contact with the entirety of the longitudinal  103  and transverse  104  bores of the connecting rod  100 . 
     Such an electrical connection is, for example diagrammatically shown in  FIG. 7 , where circuitry  200  is disposed between the contact ring  80  and the mounting body  70 . This exemplary circuitry includes a power source  202  and a contact indicator  204  (i.e., an LED) that lights the LED when the electrical circuit is completed. If the mounting body  70  and the insulated wire  206  are each connected to the circuitry  200  (as shown in  FIG. 7 ), then, when electrical contact occurs between the contact ring  80  and any part of the first contact ( 10 ,  20 ,  30 ,  40 ,  60 ,  70 ), the LED  204  will illuminate. 
     With the above exemplary configuration set forth, the functioning of the switch  1  between the first and second states can be described with regard to a comparison between  FIGS. 8 and 9 . The piston  10  is longitudinally fixed to the tip  20  and to the connecting rod  100 . Further, the insulator stub  90  and the contact ring  80  are longitudinally fixed to the exterior of the connecting rod  100 . The piston  10  is slidably disposed inside the bore  44  of the cap  40  at the distal end and is slidably disposed inside the proximal bore  32  of the tube body  30 . Thus, the entire piston sub-assembly ( 10 ,  20 ,  80 ,  90 ,  100 ) can move in a longitudinal direction because a longitudinal gap  112  exists between the distal transverse surface of the contact ring  80  and a proximal end surface  64  of the stub  62  of the switch bushing  60 . It is this gap  112  that forms the space over which the force switch  1  can function. 
     The bias device (e.g., compression spring)  50  disposed between the adjustable cap  40  and the distal transverse surface of the widening  14  imparts a proximally directed force against the piston  10  when the cap  40  is adjusted to compress the spring  50 . This force, referred to herein as a pre-tension, keeps the contact ring  80  at a distance from the electrically conductive stub  62  of the switch bushing  60 —which is defined as the longitudinal gap  112 . Without any external force imparted on the force switch  1 , the pre-tension will always keep the contact ring  80  at this position and electrical contact between the first contact and the contact ring  80  will not occur. A distally directed external force F imparted upon the tip  20  could alter this situation. See  FIG. 9 . If the force F is not as great as the pre-tension force imparted by the spring  50 , then the spring will not compress any further than it has already been compressed by the adjustable cap  40 . However, if the force F is greater than the pre-tension force imparted by the spring  50 , then the spring will compress and the tip  20  along with the remainder of the piston sub-assembly—the piston  10 , the connecting rod  100 , the insulating stub  90 , and the contact ring  80 —will move in a distal longitudinal direction. The distal longitudinal direction is limited by the proximal end surface  64  of the stub  62  of the switch bushing  60  because contact between the end surface  64  and the distal side of the contact ring  80  completely prevents further movement of the tip  20 . This configuration, therefore, provides an electrical switch that has an adjustable longitudinal pre-tension force that must be overcome before the switch  1  can actuate and complete the electrical circuit that is “open” until the contact ring  80  touches the switch bushing  60 .  FIG. 9  shows the piston sub-assembly ( 10 ,  20 ,  80 ,  90 ,  100 ) in the actuated distal position and  FIG. 8  shows the piston sub-assembly in the un-actuated proximal position 
     One exemplary process for assembly of the force switch  1  of  FIGS. 1 to 9 , has the spring  50  inserted over the central shaft  16  of the piston  10 . The cap  40  is also screwed into the proximal bore  34  of the body tube  30 . The piston-spring sub-assembly is, then inserted through the interior bore  44  of the cap  40  and the tip  20  is fastened (e.g., screwed) onto the distal end  12  of the piston  10 . This forms a piston sub-assembly. 
     The insulating stub  90  is attached to the intermediate portion of the connecting bar  100  by being placed, first, over the distal boss  102  and, second, over the intermediate portion. Similarly, the contact ring  80  is attached to the insulating stub  90  by being placed thereover. The ring  80  is longitudinally connected to the insulating stub  90  and the stub  90  is longitudinally connected to the intermediate portion of the connecting bar  100 . The insulated wire  206  is passed through the bore of the mounting body  70  and through both the longitudinal  103  and transverse  106  bores of the connecting rod  100  and electrically connected to the interior surface of the contact ring  80  without electrically connecting the wire  206  to any portion of the mounting body  70  or the connecting bar  100 . This connection forms a switch sub-assembly that is ready to be connected to the piston sub-assembly. 
     Either or both of the distal boss  102  of the connecting bar  100  or the stub  62  of the switch bushing  60  can have threads for connecting the boss  102  to the piston  10  and/or the stub  62  to the body tube  30 . As such, the entire switch sub-assembly can be connected (both physically and electrically) to the piston sub-assembly. With these two sub-assemblies connected together, only the mounting body  70  needs to be connected to the proximal end of the switch bushing  60 . Such a connection can take any form, for example, the connection can be a weld or a mated set of screw threads. 
       FIGS. 10 to 17  illustrate a second exemplary embodiment of the force switch  1  having a “normally closed” switch configuration. 
       FIGS. 10 to 17  illustrate different portions of the force switch  1 .  FIG. 14  provides an example view approximately through the longitudinal axis  2  of the force switch  1  that allows visualization of all parts of the switch  1 . The contact piston  10  provides a central part around which other parts of the switch  1  may be explained. The tip  20  is fastened to the distal end  12  of the contact piston  10 . The distal end  12  and the internal bore  22  of the tip  20  are illustrated with straight lines in  FIGS. 13 to 15  and  17 , however, in the exemplary embodiment, the distal end  12  can be provided with external male threads and the bore  22  can be provided with internal female threads. Alternatively, the tip  20  can be press-fit, glued, welded, or otherwise connected to the distal end  12  of the contact piston  10 . In the configuration shown in  FIGS. 13 to 15  and  17 , the proximal portion  24  of the internal bore  22  has the non-threaded flat portion for receiving therein the distal-most end of the piston  10  such that, when completely threaded into the bore  22 , the proximal portion  24  acts as a stop for further threading of the distal end  12  therein. 
     The piston  10  has a proximal end at which the widening  14  is provided to extend radially the outside surface of the piston  10 . The internal bore  16  is formed in the interior of the piston  10  at the proximal end. 
     As shown in the enlarged view of  FIG. 16 , a hollow body tube  120  is disposed around at least a portion of the contact piston  10 . As compared to the first embodiment of the body tube  30 , the interior of this tube  120  has a constant diameter bore  122 . The bore  122  has a shape substantially equal to an exterior shape of the widening  14  and surrounds the central shaft  18  of the piston  10 . Accordingly, in a circular configuration, the interior diameter of the bore  122  is substantially equal to the outer diameter of the widening  14 . 
     There are two parts of the force switch  1  disposed between the piston  10  and the body tube  120 : a spring stop puck  130  and a bias device  50 . The exterior shape of the spring stop puck  130  and the interior shape of the bore  122  are substantially equal. Accordingly, in a circular configuration, the interior diameter of the bore  122  is substantially equal to the outer diameter of the spring stop puck  130  so that the spring stop puck  130  slides within the bore  122  substantially without play but also without substantial friction. This spring stop puck  130  differs from the end cap  40  in that it floats entirely separate within the body tube  120 . More specifically, as the tip  20  is threaded onto the distal end  12  of the piston  10 , the proximal transverse surface pushes against but is not fixed to the distal transverse surface of the puck  130 . In such a configuration, it would, at first glance, seem to indicate that the compression spring  50  could only be set to one given compression value because the puck  130  has a fixed longitudinal length. This would be correct except a set of pucks  130  are provided, each having different longitudinal lengths. Therefore, the pre-tensioning of the spring  50  is adjusted by selecting one of the set of pucks  130 . Also, it is not necessary to thread the tip  20  entirely onto the distal end  12  of the piston  10  as shown in  FIG. 13 , for example. Thus, if the tip  20  is not entirely threaded on the piston  10 , user-desired pre-tensioning of the bias device  50  occurs by providing a specifically sized puck  130  and threading the tip  20  onto the piston  10  at a predefined distance. Alternatively, the puck  130  can solely determine the pre-tension if the tip  20  is entirely threaded onto to the piston  10 . One embodiment of the stop puck  130  and bias device  50  is shown in  FIGS. 10 to 17 . The following description, however, is directed to the view of  FIG. 13 . The stop puck  130  is formed with an internal bore  132  having a shape substantially equal to the outer shape of the piston  10  so that the piston  10  can traverse through the puck  130  without hindrance. 
     When the spring stop puck  130  is within the bore  122 , the stop puck  130  substantially closes an interior space defined by the interior surfaces of the bore  122 , the exterior surface of the central shaft  18 , the distal transverse surface of the widening  14 , and the proximal transverse surface of the puck  130 . The bias device  50  is disposed inside this interior space. The bias device  50  and the stop puck  130  act together with the widening  14  to bias the piston  10  in a given direction, in this case, in the proximal direction. Force of the bias device  50  is dependent upon the longitudinal length of the stop puck  130 . 
     The bias device  50  is embodied, in this example, as a compression spring  50 . As such, when the spring  50  is placed around the central shaft  18  of the piston  10  up to the distal transverse surface of the widening  14 , and when the stop puck  130  is also around the central shaft  18  and the tip  20  is attached to the piston  10 , the spring  50  is compressed or pre-tensioned therebetween. 
     Because the piston  10  moves, it can form one contact of an electrical switch for signaling a state of the force switch  1 . Another contact needs to be provided that is electrically insulated from the piston  10 . Thus, the piston  10  needs to be associated with a switch sub-assembly so that the electrical force switch  1  is in a first state when the piston  10  is in a first longitudinal position and in a second state when the piston  10  is in a second longitudinal position (the first and second states being off/on or on/off). This switch sub-assembly is formed at a proximal end of the piston  10  and the body tube  120  and, in the following text, applies to the second exemplary “normally closed” embodiment. 
     The switch bushing  60  has a distally projecting stub  62  that is inserted into the proximal end of the body tube  120 . This stub  62  can be connected to the body tube  120  in any number of ways (e.g., by bonding, welding, adhesive, press-fit, screw threads). The proximal end of the switch bushing  60  is attached to a mounting body  70 . In one embodiment, each of the piston  10 , the tip  20 , the body tube  120 , the stop puck  130 , the switch bushing  60 , and the mounting body  70  are electrically conductive and provide a first electrical contact of the force switch  1 . However, the tip  20  and stop puck  130  need not be electrically conductive. To form a second electrical contact that, when put into electrical connection with the first contact, interrupts an electrical circuit as shown in  FIGS. 10 to 17 , an insulating body needs to be disposed between the second contact and the first contact needs to be operatively moved out of contact with the second contact. 
     In the exemplary embodiment of  FIGS. 10 to 17 , the second electrical contact is formed by a contact pin  140  and the insulating body is formed by an insulating bushing  150 . The part that connects the insulating bushing  150  and the contact pin  140  to the piston  10  is a T-shaped, electrically conductive, contact screw  160 . The insulating bushing  150  and the contact pin  140  are nested in their shape so that they can fit in an easy assembly into the switch bushing  60  and the mounting body  70 . The insulating bushing  150  physically and electrically separates the contact pin  140  from the mounting body  70  and the switch bushing  60 , which is in electrically conductive contact with at least the piston  10  and the switch bushing  60 . 
     More specifically, the internal bore  16  is shaped to receive a distal boss  162  of the contact screw  160 . The connection between the distal boss  162  and the internal bore  16  can be like any of the embodiments of the connection between the piston  10  and the tip  10 . If the boss  162  has an external male thread, for example, then the internal bore  16  has a corresponding female internal thread. Such an exemplary configuration makes attachment of the contact screw  160  and the piston  10  easy with regard to manufacturing costs and time. A transverse end surface  164  of the contact screw  160  also provides a stop for indicating complete insertion of the distal boss  162  inside the internal bore  16  of the piston  10 . 
     The insulating bushing  150  has an internal bore  152  having a shape dimensioned to correspond substantially to the outer shape of a proximal contact portion  142  of the contact pin  140 . This external outer shape of the proximal contact portion  142  can take any polygonal shape, such as circular, ovular, rectangular, square, star, triangular, for example. Regardless of this outer shape, the shape of the internal bore  152  of the insulating bushing  150  corresponds thereto so that the insulating bushing  150  can be inserted thereon and fixed thereto (whether by press-fit, adhesive, bonding, welding, or any other connection process) so that control of contact between the contact pin  140  and any other portion of the first contact can be made with high precision. 
     After the insulating bushing  150  is connected to the contact pin  140 , the combined insulating sub-assembly can be connected to the mounting body  70 . The external shape of a proximal portion of the insulating bushing  150  is made to correspond to an internal shape of an internal bore  72  extending through the mounting body  70 . Again, the outer shape of the proximal portion of the insulating bushing  150  can take any polygonal shape, such as circular, ovular, rectangular, square, star, triangular, for example. Regardless of this outer shape, the shape of the internal bore of the mounting body  70  corresponds thereto so that the insulating bushing  150  can be inserted thereon and fixed thereto (whether by press-fit, adhesive, bonding, welding, or any other connection process) so that control of contact between the contact pin  140  (mounted in the insulating bushing  150  and the mounting body  70 ) and any other portion of the first contact can be made with high precision. 
     With such a connection, the contact screw  160  electrically contacts the piston  10  (and, thereby, the body tube  120 , the switch bushing  60 , and the mounting body  70 , and possibly even the tip  20  and the stop puck  130  if desired). The outer shape/diameter of a distal transverse widening  144  of the contact pin  140  is dimensioned to be smaller than the inner shape/diameter of the switch bushing  60  and insertion of the contact pin  140  inside the switch bushing  60  creates a transverse gap  110  therebetween. Thus, the transverse gap  110  electrically isolates the distal widening  144  of the contact pin  140  from the inside of the switch bushing  60 , and the proximal contact portion  142  of the contact pin  140  is electrically isolated (insulated) from the mounting body  70  and the switch bushing  60  on the outer side thereof by being in direct contact with the interior bore  152  of the insulating bushing  150 . 
     To make an electric circuit between the contact pin  140  and any electrically conducting part of the first contact (e.g.,  10 ,  20 ,  60 ,  70 ,  120 ,  130 ), an electrical connection must be made at the contact pin  140 . One exemplary embodiment for such a connection is illustrated in  FIGS. 11 to 17 . Specifically, the contact screw  160  is formed with a proximal transverse widening  166  extending radially from the intermediate portion thereof and defines a proximal transverse surface  168 . The bias device  50  biases the piston  10  and, thereby, the contact screw  160  in a proximal direction to electrically conductively contact the distal transverse surface  148  of the contact pin  140  to the proximal transverse surface  168  of the contact screw  160 . Because such contact needs to only be made between these two surfaces to complete an electrical circuit of the switch sub-assembly, the outer shape/diameter of the proximal widening  166  of the contact screw  160  can be any size or shape that slides within the interior bore  66  of the switch bearing  60 . 
     The other electrical contact of the contact pin  140  resides on the proximal side of the contact pin  140 . In one exemplary embodiment, a longitudinal bore  146  is formed from the proximal transverse surface of the contact pin  140  inward and receives therein an insulated wire  206 . The conductor of this wire  206  can be fastened (e.g., by welding) to the interior surface of the longitudinal bore  146 . Such an electrical connection is, for example diagrammatically shown in  FIG. 7 . In such an exemplary configuration, the power source  202  supplies power to the contact indicator  204  (LED) and lights the LED when the electrical circuit is completed, which will always be the case in this normally closed configuration of the force switch  1 . Conversely, when electrical contact between the first contact and the contact pin  140  is removed, the LED  104  will turn off. Of course, the indicator need not be visual (e.g., the LED  104 ). It can also be audible (e.g., speaker with sound) or tactile (e.g., vibration), or any combination thereof. 
     It is also possible to provide circuitry  300  between the contact pin  140  and the mounting body  70  that lights the LED  204  only when the electrical circuit is opened (i.e., not completed). Any logic circuitry can be used to control the LED  204  based upon the two states of the force switch  1  shown in  FIGS. 10 to 17 . For example, the logic  300  including a NOR gate and an AND gate can be connected to the force switch  1  circuit as shown in  FIG. 13 . In such a configuration, when the switch  1  is in its normally closed state, the LED is off and when contact is broken, as shown in  FIG. 17 , the LED will illuminate. 
     With the above exemplary configuration set forth, the functioning of the switch  1  between the first and second states can be described with regard to a comparison between  FIGS. 16 and 17 . 
     As set forth above, the contact pin  140  is longitudinally secured within the insulating bushing  150  and the insulating bushing  150  is longitudinally secured within at least one of the switch bearing  60  and the mounting body  70 . The body tube  120  is longitudinally secured to the distal end of the switch bearing  60 . The stop puck  130  is disposed, freely longitudinally, between the spring  50  and the tip  20 . The piston  10  is longitudinally fixed to the tip  20  and to the contact screw  160  and this piston sub-assembly slides within the body  120  biased in the proximal direction by the spring  50 . Accordingly, the entire piston sub-assembly ( 10 ,  20 ,  130 ,  160 ) can move in a distal longitudinal direction to compress the spring  50  inside the body tube  120  and this compression distance forms a space  134  (see  FIG. 17 ) over which the force switch  1  functions as a switch. 
     The bias device (e.g., compression spring)  50  disposed between the puck  130  and the distal transverse surface of the widening  14  imparts a proximally directed force against the piston  10  when the puck  130  compresses the spring  50 . This force, referred to herein as a pre-tension, keeps the contact screw  160  against the electrically conductive distal transverse surface of the contact pin  140 . Without any external force imparted on the force switch  1 , the pre-tension will always keep the contact pin  140  at this position and electrical contact between the first contact and the contact pin  140  will remain. A distally directed external force F imparted upon the tip  20  could alter this situation. See  FIG. 17 . If the force F is not as great as the pre-tension force imparted by the spring  50 , then the spring  50  will not compress any further than it has already been compressed by the puck  130 . However, if the force F is greater than the pre-tension force imparted to the piston  10  by the spring  50 , then the spring  50  will compress further and the tip  20 , along with the remainder of the piston sub-assembly ( 10 ,  130 ,  160 ) will move in a distal longitudinal direction. The distal longitudinal direction is limited by the greatest compression distance of the spring  50 , which, in most applications of the force switch  1 , will not occur. This configuration, therefore, provides an electrical switch that has an adjustable longitudinal pre-tension force that must be overcome before the switch  1  can actuate and complete the electrical circuit that is “closed” until the contact screw  160  no longer touches the contact pin  140 . The switching distance of the force switch  1  of  FIGS. 10 to 17  is defined by the longitudinal gap  112  existing between the proximal transverse surface of the stub  62  and the distal transverse surface of the widening  166 .  FIGS. 17 and 19  show the piston sub-assembly ( 10 ,  130 ,  160 ) in the actuated distal position and  FIG. 16  shows the piston sub-assembly in the un-actuated proximal position. 
     One exemplary process for assembly of the force switch  1  of  FIGS. 10 to 17 , the distal end of the switch bushing  60  having the projecting stub  62  is fastened longitudinally to the proximal end of the body tube  120 . The piston  10  inserted inside the body tube  120  and the spring  50  inserted over the central shaft  16  of the piston  10  inside the body tube  120 . The puck  130  is placed over the distal end  12  of the piston  10  and the tip  20  is fully or partially screwed onto the exterior threads of the distal end  12  of the piston  10 . At this point, if the tip is fully screwed onto the piston  10 , the piston  10  will impart the pre-tension force onto the stub  62  of the switch bushing. To avoid this force, the tip  20  can be only partially screwed onto the distal end  12  of the piston  10 . The contact screw  160  is, then, screwed into the internal bore  16  of the piston  10  at the proximal end thereof to capture the stub  62  between the widening  14  of the piston  10  and the widening  166  of the contact screw  160 . This forms a piston-spring sub-assembly. 
     The mounting body  70  is longitudinally fixedly connected to the contact pin  140  with the insulating bushing  150  therebetween. Because of the nested shapes of these parts, the order of the connection is limited only by the costs and time for manufacturing the connections. Alternatively, the insulating bushing  150  and the contact pin  140  can be placed inside the distal end of the mounting body  70 , but, in such a case, these two parts could move longitudinally if the distal end of the force switch  1  is tilted downward. This forms a contact pin sub-assembly. 
     The piston-spring and contact pin sub-assemblies are connected together by fastening, longitudinally, the mounting body  70  to the switch bushing  60 . If the tip  20  is fully screwed onto the piston  10 , then the fastening will have to overcome the pre-bias force of the spring  50 . If, however, the tip  20  is minimally screwed onto the piston  10  such that no pre-bias exists in the spring  50 , then, after all longitudinal fastening has occurred, the tip  20  can be fully screwed onto the distal end  12  of the piston  10  to place the spring  50  in the pre-tensioned state. The conductor of the insulated wire  206  is attached in the longitudinal bore  146  of the contact pin  140  to complete the circuit  300 . 
     In each case of the normally open and normally closed configurations, the longitudinal gap  112  has a length of between approximately 25 μm (0.001″) and approximately 750 μm (0.030″), or in a shorter range between approximately 75 μm (0.003″) and approximately 200 μm (0.008″). 
     The conductive parts of the force switch  1  can be of stainless steel, copper, nickel-plated copper, nickel-plated brass, for example. Where the conductor of the insulated wire  206  needs to be soldered, each of these materials will be sufficient. 
     The range of force that the force switch  1  applicable for switching between the two states can be between approximately 3 ounces to approximately 20 pounds, or a shorter range of approximately 5 pounds to approximately 8 pounds. 
     With regard to the mechanics of selecting the spring  50 , the desired pre-tension force is selected to be within or at the mid-range of the range of a given spring  50 . In other words, the change in state of the force switch will occur not close to a maximum of the spectrum of the spring  50  pre-tension but, instead, somewhere in the middle of the spectrum. 
     The circuitry described above only provides a binary output—whether or not the force on the external object that is transmitted through the force switch  1  is greater or less than the pre-tensioning. If the force switch is provided with a strain gauge, also referred to as a load cell, then a continuous force output can be displayed to the user in which, for example, a row of LEDs gradually light up dependent upon the amount of force or an LCD or LED numerical field increments numerical values corresponding to the amount of force imparted through the force switch  1 . 
     The force switch  1  above will now be described with respect to use in an intraluminal anastomotic circular stapler as depicted, for example, in U.S. Pat. No. 5,104,025 to Main et al. (“Main”), and assigned to Ethicon Endo-Surgery, Inc. This reference is hereby incorporated herein in its entirety. As can be seen most clearly in the exploded view of FIG. 7 in Main, a trocar shaft 22 has a distal indentation 21, some recesses 28 for aligning the trocar shaft 22 to serrations 29 in the anvil and, thereby, align the staples with the anvils 34. A trocar tip 26 is capable of puncturing through tissue when pressure is applied thereto. FIGS. 3 to 6 in Main show how the circular stapler 10 functions to join two pieces of tissue together. As the anvil 30 is moved closer to the head 20, tissue is compressed therebetween, as particularly shown in FIGS. 5 and 6. If this tissue is overcompressed, this surgical stapling procedure might not succeed. The interposed tissue can be subject to a range of acceptable compressing force during surgery. This range is known and is dependent upon the tissue being stapled. The stapler shown in Main cannot indicate to the user any level of compressive force being imparted upon the tissue prior to stapling. However, if the force switch  1  described herein is substituted for the trocar shaft 22, then the stapler 10 will be capable of showing the user when the compressive force (acting along the longitudinal axis  2  of the force switch  1 ) has exceeded the pre-tension of the switch  1 . This pre-tension can be selected by the user to have a value within the range of acceptable tissue compressive force. 
       FIGS. 1 and 10  of the present application show a tip  20  having a pointed distal end that can function within at least the CDH surgical stapler manufactured and sold by Ethicon Endo-Surgery, Inc. The proximal end of the trocar shaft 22 in Main requires a male threaded screw for attachment to the head 20. Other circular staplers require an opposing tang embodiment that is shown in  FIGS. 1 and 10  of the present application. Thus, the mounting body  70  can be in the form illustrated in  FIGS. 1 to 17  or in the form shown in FIG. 7 in Main. The tip  20  and mounting body  70  can be customized to fit into any kind of similar surgical device. 
     The foregoing description and accompanying drawings illustrate the principles, preferred embodiments and modes of operation of the invention. However, the invention should not be construed as being limited to the particular embodiments discussed above. Additional variations of the embodiments discussed above will be appreciated by those skilled in the art. 
     Therefore, the above-described embodiments should be regarded as illustrative rather than restrictive. Accordingly, it should be appreciated that variations to those embodiments can be made by those skilled in the art without departing from the scope of the invention as defined by the following claims.

Technology Classification (CPC): 8