Abstract:
An electrosurgical pencil adapted to receive an electrode controllable by an electrical signal for performing surgical operations. This pencil includes a housing, a circuit, and switch that is activatable from outside the housing for closing the circuit. The housing receives the electrode. The circuit is a flexible circuit and is positioned such that it is in direct contact with the electrode when the electrode is received in the housing.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a division of U.S. patent application Ser. No. 14/114,476 filed Oct. 28, 2013, which is a 371 filing of International patent application no. PCT/DK2012/050176 filed May 18, 2012, which claims priority to Danish patent application no. PA 2011 70251 filed May 19, 2011. 
     
    
     BACKGROUND 
       [0002]    The invention relates to an electrosurgical pencil adapted to receive an electrode controllable by an electrical signal for performing surgical operations, comprising: a housing, a circuit, switching means adapted to be activated from outside the housing for closing the circuit, wherein the housing comprises receiving means (for receiving the electrode. The invention further relates to a kit of parts comprising an electrosurgical pencil and a method of providing an electrosurgical pencil and a kit of parts. 
         [0003]    Electrosurgical pencils are used during operations for, for example, cutting in tissue or coagulating blood by delivering a high voltage, high- or radiofrequency current from a source of electricity to an electrode of the pencil. Depending on the waveform of the current, the pencil has a cutting or coagulating effect on the tissue. Some pencils are provided with means for evacuating smoke from the operation site as the smoke is known to contain viral DNA, bacteria, carcinogens and irritants. 
         [0004]    Generally, electrosurgical pencils are constructed of two elongate housing parts assembled lengthwise, one of which is provided with hole for accommodating control buttons. The pencil is at the forward end provided with a bore, through which an electrode/blade projects. From the rearward end a cable extends from an aperture. The cable is connected to a printed circuit board inside the housing. 
         [0005]    Such a pencil is known from US 2009/0062791. This pencil further comprises a switch module, comprising the printed circuit board upon which two dome switches are positioned. The buttons are located above the respective dome switches. A resilient sleeve encloses the printed circuit board and the dome switches inside the housing. The resilient sleeve acts as a gasket to prevent the escape of low pressure air from the interior of the housing at the buttons, and to prevent the smoke and other debris from contaminating the switches. A wire conducts a radio frequency electrosurgical waveform from the printed circuit board to an electrode anchor unit. The anchor unit comprises several conductive elements. 
         [0006]    Another such pencil is known from U.S. Pat. No. 4,625,723. Here, a resilient strip of electrically conductive metal or alloy connects the electrode and the printed circuit board. Push buttons under which a dome member and a metal disc are provided, bridges contacts to the printed circuit board when the button is pushed. 
         [0007]    Though pencils of this kind are widely used, they suffer from a number of disadvantages, among others the large number of different parts that are used complicate the production process and the many parts clutters the limited space available in the pencil so the space cannot be used to provide an effective suction channel. Additionally, the many parts make the device larger and not particularly comfortable to work with. 
       SUMMARY OF THE INVENTION 
       [0008]    It is therefore the object of the invention to provide an electrosurgical pencil with improved energy transmission and a simple construction that eases the production process considerably. 
         [0009]    This is achieved with a flexible printed circuit, wherein the flexible circuit is positioned such that the flexible circuit is in direct contact with the electrode, when the electrode is positioned in the receiving means. 
         [0010]    According to a first aspect of the invention an electrosurgical pencil is provided, which is adapted to receive an electrode controllable by an electrical signal for performing surgical operations, comprising: a housing, a circuit, switching means adapted to be activated from outside the housing for closing the circuit, wherein the housing comprises receiving means for receiving the electrode wherein the circuit is a flexible circuit, wherein the flexible circuit is positioned such that it is in direct contact with the electrode, when the electrode is positioned in the receiving means. 
         [0011]    By positioning the circuit in direct contact with the electrode, a better contact between the electrode and flexible circuit is provided as no intermediate elements are required. Additionally, the construction is simpler and requires fewer steps in the production of the pencil. Usually, a metal bushing would be required, but now the receiving means can be provided in the same material as the main housing part where the receiving means may be located. Furthermore, the pencil is less cluttered on the inside and thereby opens up for the possibly of integrating a suction channel, while at the same time keeping the pencil slim and easy to handle. Additionally, the advantage of the flexible circuit is that only one switch is activated when the flexible circuit is indirectly pressed. In case of a less flexible circuit, such as a printed circuit board, all switching means would be activated when the circuit is pressed, as the pressure would be distributed and hence applied to all the switches below the circuit. 
         [0012]    The flexible circuit may further comprise a first portion and a second portion, wherein the second portion is substantially parallel with the first portion, when mounted in the housing. By bending the flexible circuit and making the two portions parallel in the mounted position, the complete flexible circuit does not have to be integrated in the receiving means and thereby the housing parts are easier to produce. 
         [0013]    The switching means may comprise a switch and an actuator. Dividing the functionality between the switch and the actuator improves the flexibility of design and ease of manufacture even further. In preferred further developments of this embodiment, the first portion of the flexible circuit is positioned between the actuator and the switch, and the back of the switch is facing the actuator. By turning the switch so to speak upside down, the flexible circuit together with the actuator provides two layers of insulation without using an extra material layer. Additionally, this position of the switch gives a better response to the user and makes the actuator easy to press so that the switch is activated even if only the edge of the activator is pressed. Furthermore, a more resilient material may be used for the actuators. 
         [0014]    The housing may comprise a sheath, wherein the thickness of the sheath is greater than 0.35 mm in the area of the switching means. The thickness provides a better protection in general and against tearing in particular. 
         [0015]    At least a part of the second portion of the flexible circuit may be positioned between the electrode and the receiving means, when the electrode is positioned in the receiving means. This provides a better contact between the flexible printed circuit and the electrode, as the flexible printed circuit is shaped according to the form of the electrode and the receiving means and thereby provides a larger area of contact. 
         [0016]    The receiving means may be a bushing. The bushing is a preferred receiving means and is easily formed in the main housing part. The bushing may be provided in various shapes, such as conical, pyramid shaped etc. 
         [0017]    A tapered form of the bushing on its inner side makes it possible to use various sizes of electrodes and at the same time securing a large area of contact with the flexible circuit. This is i.a. advantageous when using electrodes of slightly varying transverse dimensions. 
         [0018]    The electrosurgical pencil may further comprise a suction channel. The suction channel may be provided along the length in the interior of the pencil. This eliminates the need for any external suction devices as the smoke generated by using the electrosurgical pencil may be hazardous. By integrating the suction channel into the pencil the pencil is more comfortable to work with and provides a better view for the surgeon of the operation site. 
         [0019]    In a preferred embodiment, the exterior of the electrosurgical pencil has a substantially triangular shape. By giving the pencil a substantially triangular shape a good grip and good ergonomics are provided. Additionally, the substantially triangular shape provides a better view of the operation site for the surgeon, as the “flat” sides of the triangle takes up less viewing space as compared to the rim of a cross-sectionally circular pencil. Additionally, when suction is provided in the pencil and a suction tube is mounted on the proximal end of the second housing part, the surgeon is less inclined to allow turning of the pencil in response to the torsional load exerted by the suction tube when handling the pencil. With the substantially triangular shape the surgeon will automatically hold the pencil in the most comfortable position, where he has access to the actuators. He will thereby not be inclined to allow the pencil to turn, as he would if it was circular. 
         [0020]    The suction channel may have a substantially triangular shape. This shape makes the most use of the space available in the substantially triangular shape of the exterior of the pen. If a circular suction channel was provided the suction volume would be substantially decreased. 
         [0021]    The substantially triangular shape may be defined by the area ratio between a first triangle which circumscribes the substantially triangular shape and a second triangle inscribed in the substantially triangular shape, which area ratio preferably is between 1:1 and 3:1. This ratio provides a shape that possesses sufficient properties as to optimum use of space and still lies comfortably in the hand. 
         [0022]    A radius of curvature in at least one corner of the substantially triangular shape may be between 1 mm and 5 mm, preferably between 2 mm and 4 mm. By having rounded corners, provided by this radius of curvature, there are no sharp edges, while at the same time the triangular shape is still present. 
         [0023]    The flexible circuit may comprise at least a partial gold coating for creating a contact between the electrode and the flexible circuit. By using gold a better contact between the electrode and the flexible circuit is obtained and the gold does not corrode. 
         [0024]    The electrosurgical pencil may comprise a main housing part, provided with at least one indentation adapted to receive a corresponding switch. One or more indentations may be provided in correspondence with the number of switches. By providing the housing with an indentation, the switch cannot shift and the switch or switches cannot be seen or felt as bumps on the outside of the housing. 
         [0025]    The electrosurgical pencil may comprise a second housing part, provided with a guide recess for receiving a cable. The recess makes it easier to install the cable as it is easier to slide the cable into a recess ending in a hole than it is to simply put the cable through a hole without any guiding means. The recess additionally provides support for the cable when mounted. 
         [0026]    A first housing part, attachable to a main housing part, may be provided wherein the first housing part may comprise a slit adapted to engage with the flexible circuit. The slit is both adapted to engage with the flexible circuit as well as with the first support member, keeping the flexible circuit in a correct position with respect to the main housing part. 
         [0027]    Any of the first, second and main housing parts may be adapted to be assembled crosswise. By assembling the parts this way, the manufacture and assembly operations are facilitated. 
         [0028]    In a second aspect of the invention, a kit of parts is provided. The kit comprises an electrosurgical pencil as defined, a tube, a cable, and a connector. This makes it possible to provide the parts necessary for carrying out the surgical operation or operations desired. 
         [0029]    Preferably, the tube is attachable to a proximal end of the electrosurgical pencil, the cable is connected to the electrosurgical pencil and extends through the tube and the connector is attachable at the distal end of the tube, wherein the connector is provided with a cable recess for guiding the cable out of the tube. This provides for a secure and reliable design, which is furthermore easy to handle. 
         [0030]    In a preferred development of this embodiment of the kit, a suction channel is provided in the tube and the cable is separated from the suction channel by a partition wall in the tube, which enhances the security and ease of operation even further. 
         [0031]    According to third and fourth aspects of the invention, a method of assembling an electrosurgical pencil and a kit of parts, respectively, is provided. 
         [0032]    The terms first, second and main housing parts do not indicate any specific configuration, order or position of the housing parts. The parts may be positioned in a different order, such that for example the main housing part is actually positioned at the most distal end of the pencil. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]    In the following, the invention will be described in further detail with reference to the drawings, where 
           [0034]      FIG. 1  is a perspective view of an electrosurgical pencil according to the invention, 
           [0035]      FIG. 2  is a vertical cross sectional lengthwise view, 
           [0036]      FIG. 3  is an exploded view of an electrosurgical pencil according to the invention, 
           [0037]      FIG. 4  is a cross sectional crosswise view, 
           [0038]      FIG. 5  is a horizontal cross sectional lengthwise view, 
           [0039]      FIG. 6  is a perspective view of parts of the housing, 
           [0040]      FIGS. 7   a - b  are perspective views of a second embodiment of an electrosurgical pencil according to the invention, 
           [0041]      FIG. 8  is an exploded view an electrosurgical pencil according to the invention, 
           [0042]      FIGS. 9 and 9   a - b  are vertical cross sectional lengthwise views, where the respective ends of the device has been magnified in  FIGS. 9   a - b,    
           [0043]      FIGS. 10   a - d  are different views of the connector, 
           [0044]      FIGS. 11   a - b  are different views of the connector with a cable mounted, 
           [0045]      FIG. 12  is an example of the triangular shape of the pen, 
           [0046]      FIGS. 13   a - c  show a second embodiment of a detail of an electrosurgical pencil according to the invention in a non-extended position, 
           [0047]      FIGS. 14   a - c  show a second embodiment of the detail of the electrosurgical pencil of  FIG. 13 , where the electrode is in an extended position, 
           [0048]      FIGS. 15   a - c  show a second embodiment of the detail of the electrosurgical pencil of  FIG. 13  in another position. 
           [0049]      FIGS. 16   a - b  shows a second embodiment of an extension device in a perspective view and a cross sectional view, respectively. 
           [0050]      FIG. 17  shows the pencil with a second embodiment of the second housing part  6 . 
           [0051]      FIGS. 18   a - b  show the pencil as seen in  FIG. 17  with a tube connected thereto. 
           [0052]      FIGS. 19   a - e  show a third embodiment of the electrosurgical pencil in three different positions and two cross sectional views, respectively. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0053]      FIGS. 1-6  represent a first embodiment and parts thereof.  FIGS. 7-9  show a kit of parts where further features have been added to the first embodiment.  FIGS. 10   a - d  and  11   a - b  show a connector which is a part of the kit of parts.  FIG. 12  show an example of a substantially triangular shape and it shows how this is defined. 
         [0054]    When referring to the respective ends of the different parts of the pencil and the kit of parts, the end closest to the opening for receiving the electrode is referred to as the distal end of each part, while the opposite end is referred to as the proximal end for each part. 
         [0055]    One embodiment of a pencil according to the invention is shown in  FIGS. 1-6 . Here, the pencil  100  is in an assembled state, in which the individual parts and elements are mounted. As seen from the outside the pencil comprises two actuators  71 , here in the form of buttons, but it may also be rocker buttons. In the embodiment shown, the pencil  100  further comprises a sheath  7  in a soft and or resilient material such as silicone or rubber. Additionally, the pencil  100  comprises a first housing part  5  and a second housing part  6 . An electrode  1  is projecting from the first housing part  5 . As will be described in further detail below, the pencil  100  has a substantially triangular shape with rounded corners. The housing parts are adapted to be assembled crosswise but may also be assembled lengthwise, or configured in any other manner. 
         [0056]    The first embodiment of the invention will now be described with reference to  FIGS. 2-5 . In addition to the features discloses in  FIG. 1  the pencil may additionally comprise an electrode  1 . 
         [0057]    The electrosurgical pencil  100  may be reusable and the electrode  1  disposable. The pencil may also be disposable. The disposable version may have an electrical cable embedded in a suction tube positioned at the end of the suction channel of the pencil. The reusable pencil may have the electrical cable attached to the end of the pencil however the cable may be positioned outside the suction tube. 
         [0058]    The part of the electrode  1  adapted to be mounted in the receiving means  41  is between 2.2 and 2.6 mm in diameter. The overall cross-sectional dimensions of the electrode may be between 1-3 mm in diameter. The electrode  1  is adapted to be mounted in a bushing or other receiving means  41  of the main housing part  4 . 
         [0059]    The electrode may be selected from the group consisting of a blade electrode, a needle electrode, a ball electrode, a conization electrode, a loop T-bar electrode, an arthroscopic electrode, an electrode extender, all of them with or without non-stick coating. This ensures that the pencil can be used for a variety of purposes. 
         [0060]    In the embodiment shown, the housing generally designated  4567  comprises the first, second and main housing part  4 , 5 , 6  and the sheath  7 . The electrosurgical pencil may consist of a housing, a flexible circuit, an electrode receiving means and a switch, wherein the pencil is adapted to be connected to a cable and an electrode. 
         [0061]    The housing parts  4 , 5 , 6  and parts of the kit of parts, including tube  9  and a connector  10 , are made from any suitable material or polymer, such as ABS, PSU, high density polymer (HDPE) or low density polymer (LDPE), or polyvinylchloride (PVC). The housing is free from phthalates, but may also be made in a phthalate containing material. 
         [0062]    The transverse dimension  350  of the housing  4567  is around 14.5 mm measured from a corner of the substantially triangular shape, to the opposing side, at the widest point. The overall dimension of the housing  4567  may be slightly larger, such as less than 16 mm, or less than 14.5 mm, such as 12 mm, measured from a corner of the substantially triangular shape, to the opposing side, at the widest point. 
         [0063]    The length of the pencil  100  is less than 15.5 cm. The pencil may also be longer such as less than 20 cm, or less than 17 cm. 
         [0064]    The weight of the pencil  100  is 14 g. The pencil  100  may be heavier and weigh less than 16 g, or less than 18 g. 
         [0065]    The housing  4567  may be formed in one piece or the second housing part  6  and main housing part  4  may be formed in one piece, or the first housing part  5  and the main housing part  4  may be formed in one piece. The first housing part  5  is adapted to slide into the main housing part  4  forming a fluid tight seal between the two. 
         [0066]    The second housing part  6  is adapted to slide into the main housing part  4  forming a fluid tight seal between the two. The second housing part  6  is further provided with a compartment  61  adapted to accommodate the end of the first portion  21  of the flexible circuit  2 . The compartment  61  is separated from the suction channel  8 . 
         [0067]    The second housing part  6  is additionally provided with a guide recess  62  for receiving an electric cable. At the bottom of the recess the second housing part  6  is provided with an aperture, such that the cable can be connected with the flexible circuit  2  inside the housing. The first portion of the flexible circuit  21  extends into the second housing part  6  from the main housing part  4 . The space  61  for the cable inside the second housing part and for the flexible circuit  2  is separated from the suction channel  8 . 
         [0068]    The first housing part  5  is hollow and tapered at the distal end and has an aperture from which the electrode projects. The first housing part  5  is triangular in shape and has rounded corners. The triangular shape makes the tip of the pen comfortable to hold, which is particularly useful when doing child surgery or other fine surgery that require a large degree of precision. In this case the surgeon will often hold the distal end of the pen. The pencil may be controlled via a foot pedal instead of via the actuators, as a more steady hand may be required. It may also be other shapes such as circular or have sharp corners. It is further provided with a first slit  51  and a second slit  52  at the proximal end. The slits are positioned directly opposite each other. The slits  51 ,  52  may be positioned elsewhere along the edge of the first housing part. 
         [0069]    The first and the second housing parts are provided with notches  55 ,  65 , which, in an assembled state, define a shore area there between, where the sheath  7  is positioned. 
         [0070]    The main housing part  4  has a triangular shape with rounded corners. It may also be other shapes such as circular or have sharp corners. The main housing part  4  comprises receiving means  41 , in form of a bushing, which is tapered. The receiving means  41  may be straight, conical, pyramid shaped or polygon shaped or be circular at the opening of the receiving means and polygon shaped at the bottom of the receiving means  41  or vice versa. The top of the aperture of the receiving means  41  where the flexible circuit enters the receiving means is rounded, meaning that in a cross section of the pencil an exterior circumference of the receiving means is circular. The flexible circuit is thereby curved cross-wise in the point where it is folded, and enters the receiving means. In a cross-section of the pencil an exterior circumference of the receiving means may be flat on the top, however keeping its shape of the interior circumference. A wedge segment may have been removed from the top of the opening of the receiving means. This removes the stress on the flexible circuit, that in this specific point is bent around 180 degrees and by flattening the top of the opening, the flexible circuit is only bent in one plane instead of two, as a circular exterior circumference of the receiving means requires the flexible circuit to adapt to the curved shape of the receiving means. 
         [0071]    The receiving means  41  is positioned in the center at the distal end of the main housing part  4  facing the first housing part  5 . The receiving means  41  may also be in the form of a number of rings for supporting the electrode  1  or a number of bars or rods running in parallel to the electrode  1 . The receiving means is made of plastic and/or is cast in one with the main housing part  4 . 
         [0072]    A first support member  44  is provided at the distal end inside the main housing part  4 . The first support member  44  is retracted from the edge of the distal end of the main housing part  4 . It functions both as a support for the receiving means  41  and it functions as a stopper for the first housing part  5  when this is slid into an assembled position. When assembled, the crease of the flexible circuit  23  is positioned between the support member  44  and the edge of the first housing part  5 . A first slit  51  in the first housing part is adapted to engage with the flexible circuit  2  as well as with the first support member  44 . The second portion of the flexible circuit  22  is adapted to engage with the first housing part  5  and is therefore narrower than the first portion of the flexible circuit  21 , as the second portion is adapted to enter the receiving means and have to adapt to the shape electrode. 
         [0073]    A second support member  43  is provided opposite the first support member  44 . When assembled the second support member  43  engages with the second slit  52 . The second support member also provides support for the receiving means  41 . 
         [0074]    One or more indentations  42  are provided along the length of the main housing part  4 . These indentations  42  are used to accommodate the switches  3  in order to keep the pencil slim. 
         [0075]    The interior of the main housing part  4  surrounding the receiving means  41  forms a suction channel  8 , which extends through the first housing part  5 , main housing part  4  and the second housing part  6 . The suction channel  8  is used to evacuate smoke and aerosols and particles from the surgical site. The suction channel  8  within the housing parts  4 ,  5 ,  6  has in the embodiment shown a substantially triangular shape  330 . The suction channel may also have other shapes, such as a circular shape. 
         [0076]    The flexible circuit  2  comprises a first portion  21  and a second portion  22  and a middle crease  23 . In the embodiment shown, the first portion of the flexible circuit is 67 mm long, 7.5 mm wide and around 0.14 mm thick. This corresponds to a volume of approximately 70 mm 3 . The second portion is about 37 mm long and 2 mm wide and 0.14 mm thick. The second portion is cut out of the first portion of the flexible circuit and does therefore not add to the volume. By cutting the second portion out of the first portion of the flexible circuit a smaller, and square shaped, circuit may be produced and less waste may be generated during production. The second portion of the flexible circuit may be other sizes and it may be produced separately from the first portion. The first portion comprises the control structure while the second portion  22  is adapted to connect with the electrode  1  in the bushing  41 . The flexible circuit  2  is of a paper thin flexible material, such as a foil, with a control structure printed upon it. When mounted the flexible circuit  2  is folded as shown on the figure with three creases. When assembled the first crease abuts against the edge of the receiving means  41 , the middle crease  23  abuts against the bottom of the first slit  53  of the first housing part  5  and the second crease abuts against the edge  46  of the main housing part  4 . The flexible circuit  2  may be arranged in other ways, such that there for example is only one crease. The flexible circuit may also be folded more times or it may not be folded at all. 
         [0077]    The flexible circuit may be selected from the group consisting of a flexible circuit board, a flexible printed circuit and flexible printed circuit board. 
         [0078]    The second portion  22  is substantially parallel to the first portion  21 , when mounted in the receiving means  41  of the housing  4567 . This is achieved by folding the flexible circuit  2  approximately 180 degrees. However, in the mounted position when the second portion of the flexible circuit is in the receiving means, the angle is slightly less than 180 degrees, which can be seen from  FIG. 8 . But the two portions  21 ,  22  are still even in this position, substantially parallel. Several foldings may be used to achieve the same effect. The first portion of the flexible circuit may be positioned between the actuator  71  or button and the switch  3 . The flexible circuit is provided with a gold coating, on a part of the second portion  22  of the flexible circuit  2 . It may also be provided with another conducting coating such as silver, copper or tin. The flexible circuit is to a great extent covered by a film, such that the conducting parts are not exposed. However, on the second portion of the flexible circuit  22 , this foil is not present, at least on one side, and the conducting part of the circuit is therefore be in direct contact with the electrode  1 , when the electrode  1  is in the receiving means  41 . At least a part of the second portion of the flexible circuit  22  is to be positioned between the electrode  1  and the receiving means  41 , when the electrode  1  is positioned in the receiving means  41 . In  FIG. 4  it can be seen how the second portion  22  of the flexible circuit is shaped according to the shape of the electrode  1 , such that an optimal contact is obtained between the second portion of the flexible circuit  22  and the electrode. 
         [0079]    A sheath  7  made of a resilient material, such as silicone or rubber, encloses mainly the middle part  4 . It isolates the flexible circuit, which is the only conducting part connecting the electrode with the cable, from the user. Additionally it provides the actuators/buttons  71  from where the user can control the activation of cutting and coagulating power from the generator. The suction may be controlled via these buttons as well. The sheath  7  is adapted to snugly fit the main housing part  4  with the flexible circuit  2  and the switches  3  in position for use. The thickness of the sheath  7  is greater than 0.35 mm in the area covering the switch  3 . The sheath  7  may be expended with and instead a non-resilient housing part may used. This part may in turn be provided with apertures in which buttons may be positioned for activating the pencil. 
         [0080]    The pencil further comprises two micro switches  3 . The switches  3  form part of the switching means. Other switches that may be used include a dome, a metal dome switch, a metal tactile switch, a membrane switch or a membrane keypad. The switches  3  are attached to the flexible circuit  2 . The switches  3  are positioned between the flexible circuit  2  and the main housing part  4 . The switches  3  are positioned upside down such that when the user presses the button, he actually pushes on the back of the switch. This is possible because the flexible circuit is so thin that the flexible circuit  2  flexes and thereby does not simultaneously activate both switches. If a non-flexible circuit had been used, the pressure on the button would have activated both switches. The flexible circuit  2  thereby makes it possible to activate the switch from the back side. It is thereby the resistance of main housing part that activates the switch. In this way there is no exposed circuit facing towards the activator  71 . Thereby two layers of insulation from the circuit are provided in the form of the sheath  7  including the activators  71  and the flexible circuit  2 , which does not have any conducting parts on the face facing the sheath  7 . The volume of the flexible circuit  2  and the switches  3  is minimal and takes up less than 0.15 cm 3  of space. The volume of one switch is less than 35 mm 3 . The conducting part and the switch may be sized such that the volume of the two parts is less than 0.5 cm 3  or less than 0.3 cm 3 . The switch may be less than 60 mm 3 , or less than 40 mm 3 . This small volume maximizes the space for a possible suction channel within the housing. 
         [0081]    This means that the volume of an optional suction channel  8  is optimized as the only remaining parts are the housing and the means for supporting and receiving the electrode. 
         [0082]    When using a flexible circuit  2  and micro switches  3  or small switches in general, the electrode  1  may extend beyond the most distal switch  3 , such that the distance from the tip of the electrode to the actuator positioned on top of the switch is minimized. When doing surgery the actuators will be close to where the surgeon&#39;s fingers are positioned and thereby he will not have to rearrange the pen in his hand to reach the actuators. 
         [0083]    When one of the buttons  71  is pressed down, the first portion of the flexible circuit  21  is adapted to flex and the switch  3  is pressed against the indentation  42  in the main housing part  4 . A signal is sent to the control structure on the flexible circuit  2  and the electrode  1  is activated. When the button  71  is pushed down the user may hear a clicking sound or feel a tactile feedback such that the user is aware that the pencil has been activated. 
         [0084]    When the pencil  100  is in use, it is connected to a generator (not shown), by a cable  11 . The patient is provided with a grounding plate somewhere on the body. The electrode thereby forms one pole and the patient forms the other. The generator to which the pencil is connected to delivers power with a frequency of minimum 350 kHz. 
         [0085]    The kit of parts in  FIGS. 7-9  comprises an electrosurgical pencil  100 , a tube  9 , a cable  11  and a connector  10 . The kit may comprise any other features as disclosed in the first embodiment. Each of the features is independent of each other unless explicitly stated so, and may therefore be added to the kit independently of each other. The tube  9  is adapted to be mounted on the second housing part  6  at the proximal end. The second housing part  6  is provided with one or more projections for retaining the tube  9 , such the tube  9  can be securely mounted. The tube  9  is made in a plastic material. The tube  9  may function as a suction channel for guiding smoke, aerosols and particles to a container for collection. The tube is therefore connected to the suction channel  8 . The tube  9  may furthermore be used for guiding the cable such that it does not get in the way when the surgeon works. At the proximal end of the tube  9  a connector  10  may be mounted. The connector  10 , such as a splicing sleeve, is made in a polymer material. It is provided with a cable recess  101  such as the one provided in the second housing part  6 , and is used for guiding the cable  11  to the exterior of tube  9 . A seal that is sufficiently tight such that no particles can escape is provided between the cable  11  and the connector  10 . The cable is provided within the suction channel. The cable  11  may be separated from the suction channel in the tube  9  by a partition wall. Such a separation provides the possibly to makes the electronic pencil reusable, along with further features. The connector  10  may be provided with barbs  63  as seen in  FIG. 17 . Further views of the connector  10  is shown in  FIG. 10   a - d  and with a cable mounted, in  FIGS. 11   a - b.    
         [0086]      FIG. 12  shows an example of the substantially triangular shape. The substantially triangular shape has the advantages that it is easier for the surgeon to see the tip of the electrode during surgery, as a circular shaped housing would be blocking some of the view that the substantially triangular shape exposes instead. The rounded corners of the triangle are defined by the radius of curvature R 1 . The radius of curvature is 2 mm at the distal end of the first housing part  5  and around 4 mm at the proximal end of the second housing part  6  at the widest point. The radius of curvature may vary locally. The sides of the substantially triangular shape are also defined by a radius of curvature R2. This is 8 times larger than R1 in any cross section of the pencil and provides a less curved line. It may also be from 3 to 10 times larger or merely a straight line. The substantially triangular shape  330  cuts through the corners  340  of the second equilateral triangle  320 . The triangles  310 ,  320  are positioned with the second equilateral triangle  320  within the first equilateral triangle  310  such that their sides are parallel. 
         [0087]    In the embodiment shown, the substantially triangular shape is defined by the area ratio between a first triangle  310  which circumscribes the substantially triangular shape and the second triangle  320  inscribed in said substantially triangular shape, is between 1:1 and 3:1. A ratio approaching 1:1 means that the substantially triangular shape is in fact virtually triangular including straight lines between the respective corners of the triangle. In the other end of the interval, the ratio 3:1 provides for a satisfying grip due to the curved outline. In the embodiment shown, the ratio is approximately 2.34. 
         [0088]    The substantially triangular shape may be seen in only some or parts of the housing parts, such as the first, second and main housing parts, where the remaining parts may have a substantially circular shape. The distal end of the first housing part  5  may have a substantially triangular shape, while the proximal end of the first housing part  5  may have a substantially circular shape or vice versa. The housing may have any other cross-sectional shape. 
         [0089]    In  FIG. 13   a - c ,  14   a - c , and  15   a - c , an embodiment of an extension device is shown. Each of the  FIGS. 13-15  shows a lengthwise cross sectional view, a, a lengthwise cross sectional perspective view, b, and a perspective view, c, in three different positions of extension. 
         [0090]    The extension device  300  comprises an extender  50 . It is usable for either extending the suction channel and/or extending the electrode. The extender  50  is adapted to be positioned on the first housing part in the first embodiment. The first electrode extender is provided with a receiving means for the second electrode extender  112 . The receiving means may be in the form of a bushing. 
         [0091]    The extender  50  comprises a first extender part  501  and a second extender part  502 . The first extender part  501  is adapted to slide in the second extender part  502 . The second extender is tapered at the distal end. The second embodiment further comprises a first electrode extender  111  and a second electrode extender  112 . The second electrode extender  112  is adapted to slide in the first electrode extender  111 . The electrode  1  is positioned in the second electrode extender  112 , but may be separate there from. The first and second electrode extenders are made of a conducting material. The first electrode extender  111  is adapted to be positioned in the receiving means  41  in the first embodiment. The second electrode extender  112  may project from the opening in the second extender part  502  when in the most retracted position. 
         [0092]    In order to keep the second extender  502  and/or the second electrode extender  112  in the selected position, the fit of the first extender  501  and the first electrode extender may be sufficiently tight such that their respective positions are kept during an operation. 
         [0093]    The second extender  502  and the second electrode extender  112  may be positioned in any position between the most retracted and most extended position. They may keep this position during an operation or the surgeon may adjust the position of the respective parts during the operation. 
         [0094]    In  FIG. 13  both the extender  50  and the electrode extender parts  111 ,  112  are in a non-extended position, such that the second extender  502  and the second electrode extender  112  are retracted as far back as possible and provides the shortest possible extender  50  and electrode extender parts  111 ,  112 . 
         [0095]    In  FIG. 14  the extension device  300  is in an extended state. Here the second electrode extender  112  is positioned in its most extended position. The extension of the electrode may be used for reaching hard to reach places in the body, where the suction channel or second extender part  502  are not serving a purpose or are getting in the way, respectively. 
         [0096]    In  FIG. 15  the second electrode extender  112  and the second extender  502  are positioned in their most extended position. Here, if an extra long pencil and suction are required, this position serves both purposes. 
         [0097]    The extension and retraction of the respective parts are performed by pulling and pushing the second parts  112  and  502 , respectively. 
         [0098]    Any parts of the second embodiment  300  may be combined with any parts of the first embodiment  100 . In particularly the extension device  300  may be positioned as an extension on the first housing part  5 . The first electrode extender  111  may be positioned in the receiving means  41 , thereby creating an electrosurgical pencil with a telescopic suction channel and a telescopic electrode. 
         [0099]      FIGS. 16   a - b  show a second embodiment of an extension device in a perspective view and a cross sectional view, respectively. Here an electrode extender  212  is comprised in a separate extension piece  510 . The extension piece  510  comprises a pipe piece  511  and an electrode extender  212 . The pipe piece  511  is made of a transparent material, such that it is easier for the surgeon to see, what he is working with, as the pipe piece  511  doesn&#39;t block his view. The pipe piece  511  is made from plastic or other material that will not show on an X-ray picture. However, the electrode extender  212 , which is made of a conducting material, such as metal, and which extends through the length of the pipe piece  511 , will show on an X-ray picture, in case the extension piece  510  should be lost in a patient. Additionally, or alternatively, the pipe piece  511  may be made of other materials for example a polymer comprising barium sulfate. The barium sulfate makes the pipe piece  511  visible on an x-ray picture. 
         [0100]    The extension piece  510  is adapted to be attached to an electrosurgical pencil of any of the other embodiments. The pipe piece  511  is adapted to be attached to the first housing part  5  and the electrode extender  212 , which is provided inside the pipe piece  511 , is adapted to be positioned in the receiving means  41  of the pencil as seen on the preceding embodiments. When the extension piece  510  is pushed onto the pencil, the electrode extender  212  is connected to the flexible circuit and a stable electronic connection is created. At the distal end of the electrode extender  212 , the electrode may be positioned. Because an electrode extender  212  is used, there is no need to used different lengths of electrodes, and the surgeon may therefore use the same electrode no matter the required length of the pencil. 
         [0101]    Additionally the extension piece  510  is adapted to be positioned on another extension piece  510 , making the pencil even longer, which is particularly useful when operating on larger patients. The extension piece  510  thereby fits onto itself. So instead of having to store different lengths of extender pieces, only one kind of extension piece is needed for providing different lengths. When a second extension piece  510  is attached to first extension piece  510 , the electrode extender  212  of the first extension piece is pushed to a side such that the overlapping lengths of each electrode extender merely abut each other. Alternatively each end of the electrode extender  212  may be formed as a plug and a socket, as seen in  FIG. 13 . 
         [0102]    The electrode  1  is further provided with an insulation sheath  513 , for holding on to the electrode  1  when inserting or removing electrode  1  from the pencil. The insulation sheath  513  may be dispensed with. 
         [0103]      FIG. 17  shows a second embodiment of the second housing part  6 . The second housing part  6  has here been provided with barbs  63 . One or more barbs  63  may be provided. This is to ensure that the tube (not shown) conveying the material sucked from the patient&#39;s body is properly fixed. The tube is simply pushed over the barbs and as the material of the tube is slightly expanded where the barbs are positioned inside the tube, the tube stays fixed, but may be removed from the pencil by pulling the tube. The tube is, as in the previous embodiments, able to rotate around its axis. The tube may also be fixed such that it is unable to rotate. The cable providing the pencil with power may be positioned inside or outside the tube. 
         [0104]      FIGS. 18   a - b  show the embodiment in  FIG. 17  with a tube mounted directly on the pencil. Because the second housing part  6  is provided with barbs as seen in  FIG. 17 , it is possible to mount the tube directly on the pencil and the connector, as seen in  FIGS. 8-10 , can be dispensed with. 
         [0105]      FIGS. 19   a - c  show a third embodiment of the electrosurgical pencil  400  in a non-extended position and in a position with an extended first housing part and in a position with an extended electrode  1 , respectively. What differs from the embodiment in  FIG. 2  is that the flexible printed circuit  2 , comprising a first portion  421  and a second portion  422 , is longer. The first housing part  35  is also longer compared to the housing part in  FIG. 2 . The first housing part  35  is adapted to slide inside main housing part  4 , such that the user is able to telescopically to extend the pencil  400  as seen in  FIG. 19   b . When the user pulls the first housing part  35 , the electrode  1  and the flexible printed circuit  2  will follow. The flexibility of the flexible printed circuit  2  is used such that the flexible printed circuit  2  remains in contact with both the electrode  1  and the switching means  3 . The pencil  400  is provided with a locking means (not shown) such that it may be impossible to pull the first housing part  35  completely out of the pencil  400 . 
         [0106]    Because the sheath  7  is made of silicone or a similar material, there is friction between the first housing part  35  and the sheath  7 , which keeps the first housing part  35  in position during use. Another means for creating friction between the two may be used. Friction means may also be provided between the main housing part  4  and the first housing part  35 . 
         [0107]    In addition to the above mentioned differences the electrosurgical pencil  400  further differs from the embodiment in  FIG. 2  in that it is provided with sliding means making possible to extend the electrode  1  from the first housing part  35  as seen in  FIG. 19   c . The sliding means  451 ,  443  can clearly be seen in  FIG. 19   d . This feature is particularly useful when the surgeon is operating in deep cavities. The first housing part  35  is provided with sliding means comprising a guide  451 . The first housing part  35  accommodates an element, which element comprises the support member  443  and  444  and the receiving means  41  for holding the electrode  1 . The sliding means also comprises a support member  443 , which is adapted to slide in the guide  451 . The extension of the electrode  1  is accomplished by pulling the electrode  1 , which remain in the receiving means  41  and in contact with the flexible printed circuit  2  while being extended from the first housing part  35 . In order to detach the electrode  1  from the receiving means  41 , the electrode  1  must be turned first. 
         [0108]    A cross section of the embodiment of the electrosurgical pencil  400  can be seen in  FIGS. 19   d  and  19   e . The cross section in  FIG. 19   e  is indicated on  FIG. 19   a  by the line X 1 -X 2 . 
         [0109]    Like parts in each of the several figures are identified by the same reference. Any feature from any embodiment may be combined with each other independently of other features and no feature is essential unless explicitly mentioned in the claims. When referring to a pen, pencil or electrosurgical pencil, we are referring to an electrosurgical pencil.