Abstract:
An ergonomic footswitch having a substantially planar tiltable treadle positioned on a base enables up and down or pitch movement of the footswitch around an axis of rotation located on the horizontal rotational axis of an operator&#39;s ankle. This arrangement reduces fatigue in the operator&#39;s leg and ankle and also permits the operator to vary the speed of an instrument or vary an operational parameter of the instrument via both the up and down motion of the treadle.

Description:
This application claims priority from Provisional U.S. Patent Application No. 60/515,255, filed Oct. 29, 2003. 
    
    
     FIELD OF INVENTION 
     This invention relates to footswitches; more particularly, the present invention relates to footswitches typically used to operate equipment associated with the treatment of a patient. 
     BACKGROUND 
     During the operation of complex equipment used to treat a patient; for example, in a delicate surgical procedure such as ophthalmic surgery, a surgeon, physician, dentist, or veterinarian may use a variety of pneumatic and electronically driven handpieces. The handpieces are operated by a variety of control systems. The control systems, in turn, receive inputs from a variety of different peripheral devices configured to receive manual control inputs. 
     One of the most important manually controlled peripheral devices is a footswitch. Exemplary footswitches are disclosed in a variety of U.S. patents, including U.S. Pat. No. 4,837,857 (Scheller, et al.), U.S. Pat. No. 4,965,417 (Massie), U.S. Pat. No. 4,983,901 (Lehmer), U.S. Pat. No. 5,091,656 (Gahn), U.S. Pat. No. 5,268,624 (Zanger), U.S. Pat. No. 5,554,894 (Sepielli), U.S. Pat. No. 5,580,347 (Reimels), U.S. Pat. No. 5,635,777 (Telymonde, et al.), U.S. Pat. No. 5,787,760 (Thorlakson), U.S. Pat. No. 5,983,749 (Holtorf), and U.S. Pat. No. 6,179,829 B1 (Bisch, et al.), and in International Patent Application Publications Nos. WO 98/08442 (Bisch, et al.), WO 00/12037 (Chen), and WO 02/01310 (Chen). 
     The aforementioned exemplary patents and patent applications focus primarily on the operability or functional attributes of footswitches—not on the ergonomic usability of a footswitch. Accordingly, it is not unusual for an operator of a prior art footswitch to experience foot and/or leg fatigue, particularly when performing repetitive motions over a long period of time. This foot and leg fatigue affects the ability of a physician, surgeon, dentist, or veterinarian to properly control motion inputs to the footswitch. In extreme circumstances, the result of operator fatigue may be inadvertent improper operation of a handpiece. Such improper operation could be injurious to the patient. 
     Therefore, a need remains in the art to provide a footswitch for use by a physician, surgeon, dentist, or veterinarian whose operation is ergonomically designed. Such ergonomic design will reduce foot and leg fatigue and thereby reduce the risk of inadvertent patient injury. 
     SUMMARY 
     The present invention provides a footswitch for use by physicians, surgeons, dentists, veterinarians, and the like. The disclosed footswitch is ergonomically designed for reducing foot and leg fatigue. 
     The disclosed footswitch allows for motion of the operator&#39;s leg and knee which is less fatiguing. This less fatiguing motion comes from co-locating the treadle axis of rotation with the substantially horizontal rotational axis of the operator&#39;s ankle. By co-locating the treadle axis of rotation with the substantially horizontal axis of the operator&#39;s ankle, the rotation of the operator&#39;s foot allows for both up and down control movements. Such up and down control movements may then be used to control the operation or motion of a variety of microsurgical instruments. 
    
    
     
       DRAWINGS 
       A better understanding of the ergonomic footswitch of the present invention and the following description of the embodiments may be held by reference to the drawings wherein: 
         FIG. 1  is a perspective view of the footswitch of the present invention; and 
         FIG. 2  is a side elevational schematic view of the footswitch in partial section showing the rocking motion of the foot pedal. 
     
    
    
     DETAILED DESCRIPTION 
     As best seen in the perspective view of the footswitch  10  shown in  FIG. 1 , the present invention generally includes a base portion  12 , a substantially planar foot pedal or tiltable treadle  14 , and side or wing switches  18 . Commercially available footswitches are made from a variety of materials including stainless steel, titanium, and plastic. 
     As best shown in  FIG. 2 , the motion control assembly  20  contained in the base portion  12  provides the ergonomic design which reduces the foot and leg fatigue of an operator. Specifically, the foot pedal or tiltable treadle  14  is substantially planar. The top side  15  of the foot pedal or tiltable treadle  14  is flat and is sized to engage the bottom of an operator&#39;s foot (not shown). The bottom side  13  of the foot pedal or tiltable treadle  14  includes an arcuate projection  22 . In the illustrated embodiment, the perimeter  24  of arcuate projection  22  matches the contour  26  of an arcuate depression or arcuate slot  28  formed in the top of the base  12 . The contour  26  of the arcuate depression  28  has a curvature with a radius R extending from an origin that is co-linear with the operator&#39;s ankle  100 . The perimeter of the arcuate projection  22  needs not match the contour of the arcuate depression  28 . 
     Friction forces between the perimeter  24  of the arcuate projection  22  and the contour  26  of the arcuate depression  28  may be reduced by the use of anti-friction roller bearings  30  which ride on the contour  26  of the arcuate depression  28  in the space between the arcuate projection  22  and the contour  26  of the arcuate depression  28 . Those of ordinary skill in the art will understand that other anti-friction force systems may be used, such as a low-friction coating made from a low-friction material such as Teflon®. 
     In the illustrated embodiment, the arcuate depression  28  includes a longitudinal slot  32  formed therein. This longitudinal slot  32  provides an opening through which an arcuate gear sector  34  may pass. The arcuate gear sector  34  is positioned to engage a mating gear  36 , such as a spur gear, affixed to a shaft  38  extending from a motor encoder or potentiometer  40 . Thus, when the shaft  38  is caused to rotate in a clockwise direction by the interaction of the arcuate gear sector  34  with the mating gear  36 , a first electrical signal is produced. When the shaft  38  is caused to rotate in a counter-clockwise direction, a second electrical signal is produced. The electrical signal produces a predetermined response in the handpiece being used by the operator. For example, the movement of the foot pedal or tiltable treadle  14  may control the speed of a drill motor in the hands of a dentist, the reciprocal action of a forceps or scissors mechanism, or the operation of a vitrectomy probe in the hands of an ophthalmic surgeon, or the intensity of a light source in the hands of a physician. 
     Optionally, a spring bias mechanism  42  may be used to provide mechanical feedback of the amount of deflection or pitch movement of the foot pedal or tiltable treadle  14  from a home or neutral position. Or the spring bias  42  may simply be used to return the foot pedal or tiltable treadle  14  to a home or neutral position when the procedure requiring the use of the footswitch  10  has been completed. While a mechanical spring  42  is shown in  FIG. 2 , those of ordinary skill in the art will understand that other types of bias may be used such as a fluidic or magnetic bias. 
     As may be best seen in  FIG. 2 , the foot pedal or tiltable treadle  14  is positioned on the base portion  12  so that the rotational or pitch movement of the tiltable treadle  14  is about the ankle axis  100  of the operator. In most prior art footswitches, the axis of rotation is positioned to be close to the center of the operator&#39;s foot. 
     Placement of the foot pedal or tiltable treadle  14  on the base  12  to enable movement about the substantially horizontal rotational axis of the operator&#39;s ankle  100  provides three advantages. First, foot and leg fatigue are reduced, as the operator&#39;s foot is caused to move about the ankle&#39;s natural axis of rotation. Second, the disclosed footswitch  10  may be used to provide a first input by applying pressure to change the pitch of the tiltable treadle  14  by moving the front of the foot pedal or tiltable treadle  14  down, and a second input by applying pressure to change the pitch of the tiltable treadle  14  by moving the rear of the foot pedal or tiltable treadle  14  down. Third, because the key geometric relationship is placement of the substantially horizontal rotational axis  100  of the operator&#39;s ankle over the low point of the foot pedal or tiltable treadle  14 , there is no need for special adjustments to accommodate the length of or width of the operator&#39;s foot. 
     The simplicity of construction of the disclosed footswitch provides greater reliability. The low profile and footprint of the base  12  enables greater stability and rigidity as well as giving the disclosed footswitch a lower profile and smaller size. 
     In an alternative embodiment, the distance between the upper surface and the operator ankle axis can be made to be adjustable to customize the footswitch for those individuals who must use the disclosed footswitch for long periods of time. In yet another alternate embodiment, the distance between the ankle axis and the rear portion of the foot pedal or tiltable treadle  14  may be made to be adjustable to accommodate special-needs operators. 
     In the preferred embodiment, the contour  26  on the top of the arcuate depression  28  in the base  12  has a radius R from an origin which is co-linear from the operator&#39;s ankle  100 . It is this radius R which determines the axis of rotation, together with height H. It has been found that a height H of approximately 5 inches will accommodate nearly all potential operators. 
     While the present system and method has been disclosed according to the preferred embodiment of the invention, those of ordinary skill in the art will understand that other embodiments have also been enabled. Such other embodiments shall fall within the scope and meaning of the appended claims.