Abstract:
A novel device and method for the efficient, regular and highly maneuverability administration of medical liquids, especially anesthetics. The system of the present invention includes a light-weight, hand-held injection device which is connected to an operating pedal and a control unit. The control unit stores a number of preprogrammed injection procedures having specific injection flow rates and volumes, and provides the user with the ability to create and store a plurality of user-defined procedures. The control unit and injector allow precise selection, control and monitoring of the injection flow rate and volume. The operating pedal provides “hands-free” control of the procedures, as well as a means to select various sub-procedures, such as an Aspiration mode, Introduction mode, or Preparation mode, in addition to the Injection mode.

Description:
FIELD OF THE INVENTION 
     This invention pertains to the field of medical liquid injection systems and, in particular, to programmable medical liquid injection systems. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Medical liquid injection devices are currently used to administer medical liquids, such as anesthetics. However, prior medical liquid injection devices lack the desired precision, regularity and maneuverability to be of substantial use to medical practitioners, especially in the field of dentistry. 
     The present medical liquid injection system provides a novel device and method for the efficient, regular and highly maneuverability administration of medical liquids, especially anesthetics. The system of the present invention includes a lightweight, balanced, hand-held injection device which is connected to an operating pedal and a control unit. The control unit stores a number of preprogrammed injection procedures having specific injection flow rates and volumes, and provides the user with the ability to create and store a plurality of user-defined procedures. The control unit and injector allow precise selection, control, monitoring and adjustment of the injection flow rate and volume. The operating pedal provides “hands-free” control of the procedures, as well as a means to select various sub-procedures, such as an Aspiration mode, Introduction mode, or Preparation mode, in addition to the Injection mode. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a complete understanding of the above and other features of the invention, reference shall be made to the following detailed description of the preferred embodiments of the invention and to the accompanying drawings, wherein: 
     FIG. 1 is a schematic diagram of the medical liquid injection system of the present invention; 
     FIG. 2 is a schematic diagram of the injection device of FIG. 1; 
     FIG. 3 is a schematic diagram of the operating pedal of the injection device of FIG. 1; 
     FIG. 4 is a schematic diagram of the control unit of the injection device of FIG. 1; 
     FIG. 5 is a block diagram of the components of the control unit of the injection device of FIG. 1; 
     FIG. 6 is an exploded view of the harpoon/cartridge assembly device; 
     FIG. 7 is an assembly view of the harpoon/cartridge device of FIG. 6; 
     FIG. 8 is an exploded view of the injection device; 
     FIG. 8A is an enlarged view of the harpoon; 
     FIG. 9 is a cross-sectional, elevational view of the injection device of FIG. 8; 
     FIG. 10 is an exploded view of the operating pedal; 
     FIG. 11 is a top, plan view of the operating pedal of FIG. 10; 
     FIG. 12 is a side elevational view of the operating pedal, taken along line  12 — 12  of FIG. 11; 
     FIG. 13 is a side elevational view of the operating pedal, taken along line  13 — 13  of FIG. 11; and 
     FIG. 14 is a side elevational, close-up view of the injection device showing the means to permit free rotation of the cartridge case, cartridge and needle with respect to the body of the injection device. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings, and initially to FIG. 1 thereof, the medical liquid injection system  10  of the present invention includes three primary components: The injection device  12 , the operating pedal  14  and the control unit  16 . The injection device  12  and the control unit  16  are connected to the operating pedal  14  by shielded cables  13 ,  15 , which provide power to the control unit  16  and injection device  12  and transmit information and control signals among the components. 
     The injection device  12  is of a reduced size, with a pen-like configuration and a reduced, balanced weight. This allows a high degree of maneuverability and accuracy in the use of the injection device  12 , especially during extended or successive procedures. The operating pedal  14  contains four switches which are operated by pressing on the toe or heel, or either side of the foot pad  28 . Thus, the foot pad  28  provides four separate controls which are conveniently accessible. The control unit  16  includes a keyboard  17  for entering data and selecting procedures, a display readout  19 , and a sound producing device (not shown), such as a speaker. 
     Referring to FIG. 2, the injection device  12  includes a needle  18 , a motor  20  having a drive shaft  22 , a reducer  24  connected to the drive shaft  22 , a threaded shaft  23  connected to the reducer  24 , and a motion sensor  25  which senses the motion of the threaded shaft  23  induced by the motor  20  and reducer  24 . The threaded shaft  23  imparts forward and backward movement to a hollow piston  128  which is threaded internally. The injection device  12  also includes an connection port  26  for receiving electrical power and motor control signals from the operating pedal  14 , and for transmitting the signal generated by the motion sensor  25  to the operating pedal  14 . Through the motion sensor  25 , the injection system  10  precisely monitors and adjusts, if necessary, the flow rate and volume of liquid expelled from the needle  18 . 
     Referring to FIGS. 3-4 and  10 - 13 , the operating pedal  14  includes a foot pad  28 , which is pivotal in two substantially orthogonal axes generally toward the four primary points of a compass, that is up, down, right and left. The operating pedal  14  also includes a power supply port  30 , an on/off switch  32 , and two connection ports  34 ,  36  for transmitting power and control signals to and from the injection device  12  and control unit  16 . The operating pedal  14  also includes a dual transformer for supplying reduced voltages to the injection device  12  and control unit  16 . 
     The operating pedal  14  also includes two pairs of motion sensors, such as the four micro-switches  42  (operated by movement of the foot pad  28 ), a micro-controller  38 , and a motor interface  40  which interface generates power signals for the motor of the injection device  12 . 
     Referring to FIG. 5, the control unit  16  includes a micro-controller  44 , the keyboard  17 , the display  19 , a memory  46  for semi-permanent storage of procedures and for temporary storage of current operating parameters (e.g., volume of liquid dispensed during a current procedure), and a connection port  48  for receiving power and for transmitting and receiving signals to and from the operating pedal  14 . 
     The liquid injection system  10  provides a number of modes of operation including: a Preparation mode, which calibrates the injector for the particular liquid cartridge to be used; an Introduction mode, which provides a low-rate, intermittent i dose of anesthetic for painless insertion of the needle; an Injection mode, which provides a steady, programmable flow rate for delivering the anesthetic to the desired location; an Aspiration mode which slightly retracts the hollow piston  128 , pauses and then returns the hollow piston  128  to its original position to allow visual inspection of the withdrawn liquid; and a Programming mode whereby a user can store injection procedures in the memory of the control unit  16 . The Preparation, Introduction and Aspiration modes are pre-programmed in the memory of the control unit  16  and preferably cannot be altered by the user. The control unit  16  also preferably includes a number of pre-programmed injection procedures select the keyboard  17  of the control unit  16 , which also cannot be altered. 
     The Preparation mode is required because the location of the rubber stopper, or bung, in the cartridge (see FIGS. 6 and 7) can vary depending on the manufacturer and type of cartridge. When the Preparation mode is activated, the motor  20  of the injector device  12  is activated to advance the hollow piston  128  at a speed which would correspond to a liquid flow rate of about 0.3 ml/min. When the operator observes a first drop of anesthetic forming at the end of the needle of the injector  12 , the Preparation mode is ceased. During the Preparation mode, the control unit  16  does not increment the value corresponding to the volume amount of liquid expelled from the cartridge. Thus, upon completion of the Preparation mode, the injection device  12  is properly calibrated for the currently installed anesthetic cartridge. 
     The Preparation mode is preferably initiated by depressing the foot pad  28  of the operating pedal  14  to the side (e.g., the right side), and holding the foot pad  28  down until the first drop of liquid is observed on the tip of the needle, and then releasing the foot pad  28 . Preferably, to initiate the Preparation mode, the hollow piston  128  of the injection device  12  must be in a fully retracted, or “zero” position, which can be achieved by depressing a Restart key on the control unit  16  or by cycling the On/Off switch of the operating pedal  14 . This will prevent unintended or accidental initiation of the Preparation procedure. 
     The Introduction mode provides a pre-programmed, timed, alternating flow rate, suitable for inserting the needle. It is intended that, during the higher of the two flow rates, the user will advance the needle toward the intended destination, and that during the lower of the two flow rates, the user will cease advancing the needle to allow the anesthetic to anesthetize the area immediately preceding the needle, thereby providing for painless insertion of the needle. The higher of the two flow rates is preferably about 0.15 ml/min, and has a duration of about 5 seconds. This is immediately followed by the lower of the two flow rates, which is preferably about 0.075 ml/min, with a duration of about 2.5 seconds. This sequence repeats for the duration of the introduction procedure allowing the medical liquid to penetrate the tissue surrounding the needle (including hard tissues) without stressing the nerves, thus avoiding the pain from the insertion of the needle. 
     During the period corresponding to the low flow rate in the Introduction mode, the control unit  16  preferably emits a sonorous signal and displays a warning message, such as “Stop the. Needle”, to indicate that the user should cease advancing the needle. The Introduction mode is preferably initiated by depressing the foot pad  28  of the operating pedal  14  backward (e.g., by the heel). 
     The Injection mode is the mode wherein the anesthetic is delivered to the intended destination. The injection system  10  provides for programmable injection flow rates of about 0.3 ml/min to 1.0 ml/min, in about 0.05 ml/min increments, and for programmable total injection volumes of about 0.1 ml to about 1.8 ml, in about 0.1 ml increments. During activation of the Injection mode, the control unit  16  preferably emits a sound after about every 0.1 ml is expelled from the needle, or another predetermined amount. Upon completion of the pre-programmed injection volume, a different sound is emitted and the control unit  16  displays a message, such as “Final Dose”, indicating the completion of the injection procedure. The injection procedure can be interrupted and resumed by releasing, and then depressing, respectively, the foot pad  28  of the operating pedal  14 . Thus, the user has complete control over the injection procedure. 
     In a fully operative mode of the injection system  10 , all three components of the injection system  10  (i.e., the injection device  12 , operating pedal  14  and control unit  16 ) are used. The desired injection procedure (either pre-programmed or entered manually immediately prior to the procedure) is selected using the keyboard  17  of the control unit  16 , and, once selected, the procedure is initiated by depressing the foot pad  28  of the operating pedal  14 , preferably frontwards, thereby activating the Injection mode. 
     In a limited operation mode of the injection system  10 , only the injection device  12  and the operating pedal  14  are used. The limited Injection mode can be activated by depressing the foot pad  28  preferably frontward (to deliver a pre-programmed, fixed-rate injection flow of 0.3 ml/min), or to the right (for a pre-programmed, fixed-rate injection flow of 1.0 ml/min). Thus, the limited Injection mode provides two fixed alternative injection speeds. 
     The Aspiration mode is used to prevent accidental intravenous injection of anesthetic. In the Aspiration mode, the motor  20  of the injection device  12  operates in reverse for a short period to withdraw the hollow piston  128  a short distance to withdraw a maximum of about 0.2 ml of fluid in about 1.33 seconds. The motor  20  then pauses for about 1 second to allow visual inspection of the withdrawn liquid for blood, and then operates in a forward direction to return the hollow piston  128  to its original position, again in about 1.33 seconds. The Aspiration mode is preferably activated by a relatively quick depression of the foot pad  28  of the operating pedal  14  to, for example, the left. During the Aspiration mode, which can last for approximately 3.66 sec, the operating pedal  14  remains inactive and the control unit  16  displays a message, such as “Stop the needle”, to instruct the user to cease advancing the needle. The aspiration mode can preferably be activated during an intermission of either an Introduction or Injection procedure. 
     In the Programming mode, the control unit  16  is used to enter the desired injection flow rate and the desired injection volume (i.e., the dosage). For example, in the Programming mode, the up/down keys of the keyboard of the control unit  16  are used to select an Injection Rate item. Then the left/right keys are used to select an injection rate value from a list of 15 available rates. The Confirm key is used to store the selection. The desired injection volume is selected in a similar manner by selecting an Injection Volume item and then an injection volume value from a list of 18 available volumes. Upon selection and storage of the desire rate and volume, the injection procedure (and the other procedures) are initiated with the operating pedal  14 . 
     In an automatic mode, the desired injection procedure is selected by number, from a database of pre-programmed procedures stored in the memory of the control unit  16 . Preferably, a plurality of injection procedures are permanently stored in the control unit  16  such the injection rates and volumes cannot be altered or lost. In this manner, a user can become familiar with, and can rely on the accuracy and integrity of the fixed procedures. 
     For example the following six (6) injection procedures can be permanently recorded in the memory of the control unit  16 : (1) The Advanced Subperiosteal Anesthetic Technique (ASAT), for the anterior region of the maxilla, including the canine teeth (rate 0.3 ml/min, volume 0.3 ml); (2) the Advanced Subperiosteal Anesthetic Technique (ASAT), for the anterior region of the mandible and the posterior region of the maxilla, including the pre-molars and molars (rate 0.3 ml/min, volume 0.6 ml); (3) the Spongy Ossy Zone/Alveolar Crest (CAZOE), for the molars of the mandible (rate 0.3 ml/min, volume 0.9 ml); (4) Spongy Ossy Zone/Alveolar Crest (CAZOE), for the molars (rate 0.3 ml/min, volume 1.2 ml); (5) Palatine Injection, for anterior/posterior nerve block, as well as to complement any molar anesthesia at the palatal root (rate 0.3 ml/min, volume 0.3 ml); and (6) Convention Technique, for supraperiosteal, inferior alveolar nerve blocks and others (rate 1.0 ml/min, volume 1.8 ml). 
     A particular pre-programmed injection procedure is selected using the keyboard  17  of the control unit  16 , such as the up/down keys, and is initiated with the operating pedal  14 . A user can record additional procedures by using the left/right keys of the keyboard  17  to select an available procedure number (e.g.  7 ), then, using a combination of the up/down and the and left/right keys, enter and Confirm: (1) a name for the new procedure, (2) the desire flow rate, and (3) the dosage volume. 
     Referring to FIGS. 6-7, a harpoon/cartridge assembly device  66  is used to ensure that the harpoon  60  is properly seated in the rubber stopper  62  (i.e., the bung) of the cartridge  64 . As best seen in FIG. 8A, the harpoon  60  has a conical portion  318  having threads (not shown), a collar  320 , and a shaft  322 , which has a cross section which is generally non-circular. An outer portion  324  of the shaft  322 , which is spaced a distance from the collar  320  is threaded and has a partially circular cross section. An inner portion  325  of the shaft  322  is not threaded and has a maximum diameter (measured from the center of curvature of the threads) less than that of the minimum diameter of the outer threaded portion thereof. 
     Referring again to FIGS. 6-7, the harpoon/cartridge assembly device  66  includes a harpoon seat  326  having a recess  328 . The recess  328  has an outer portion  330  with a depth and cross section corresponding to that of the collar  320  of the harpoon. The recess  328  also has an interior portion  331  which is sized and shaped to closely receive the non-circular shaft  322  of the harpoon  60 . 
     The harpoon/cartridge assembly device  66  also includes a cartridge support  332  which has a through opening  333  having a first portion  334  sized and shaped to closely receive a cartridge  64 , and a second portion  336 , sized and shaped to closely receive the end of the harpoon seat  326  having the recess  328 . The diameter of the harpoon seat  326  and the second portion  336  of the through opening  333  of the cartridge support  332  is larger than the diameter of the first portion  334  of the through opening  333 . Therefore, the inward movement of the harpoon seat  326  (and the harpoon  60  seated therein) is limited by the wall  338  between the first and second portions  334 ,  336  of the through opening. The inward movement of a cartridge  64  is limited by the harpoon seat  326 . Preferably, the harpoon seat  326  and the cartridge support  332  are connected by a leash, as shown. 
     To mount the harpoon  60  to the cartridge  64 , the following steps are taken: 
     (1) The harpoon  60  is seated in the harpoon seat  326 , 
     (2) the harpoon seat  326  is inserted into the cartridge support  332  through the first portion  334  of the through opening  333 , until the harpoon seat  326  abuts the wall  338 , 
     (3) the cartridge  64  is inserted into the cartridge support  332  through the second portion  336  of the through opening  333 , until the rubber stopper  62  contacts the threaded conical portion  318  of the harpoon  60 , and then 
     (4) the cartridge  64  is rotated together relative to the harpoon seat  324  and urged into the cartridge support  326  to thread the rubber stopper onto the harpoon  60 . When the rubber stopper  62  is fully threaded onto the harpoon  60 , the collar  320  contacts the rubber stopper  62 , preventing further movement. Then the cartridge  64  and harpoon  60  are withdrawn from the cartridge support  326  and are ready to mount to the injector  12 . 
     Referring to FIGS. 8 and 9, the precision injector  12  is a small, pen-like device suitable for operation with one hand. The injector  12  includes the motor  20 , and first and second spur gears  120 ,  122 . The first spur gear  120  is connected to a drive shaft  22  of the motor  20  and the second spur gear  122  is connected to a threaded shaft  23  aligned directly above and parallel to an axis of rotation of the drive shaft  22  of the motor  20 . A proximal end  125  of the threaded shaft  23  adjacent the second spur gear  122  is supported by a bearing  126 . A hollow piston  128 , with an internal thread is threaded over the threaded shaft  23 . A distal end  132  of the hollow piston  128 , opposite the bearing  126 , is supported by a bushing  130 . Thus, it can be appreciated that, rotation of the motor  20  will cause the hollow piston  128  to move frontward or backward according to the direction of rotation of the motor  20  (clockwise or counter-clockwise), and that the hollow piston  128  will travel at a velocity proportional to the rotational speed of the motor  20 , establishing the injection rate. 
     The hollow piston  128  is threaded internally, along a relatively short length adjacent the proximal end  131  thereof. Thus, when the threaded portion  127  of the hollow piston  128  travels beyond the threads of the threaded shaft  23 , the threaded portion  127  of the hollow shaft  128  becomes disengaged from the thread of the threaded shaft  23 . 
     The proximal and distal ends  125 ,  129  of the threaded shaft  23  include areas of reduced cross section which lack threading to prevent over-travel of the hollow piston  128 . To re-engage the threads of the threaded shaft  23 , the hollow piston  128  includes a clutch assembly comprised of two spaced-apart c-clips  146 ,  148  mounted within circular channels in the hollow piston  128 . Between the c-clips  146 ,  148  is a washer  150  intermediate two springs  152 ,  154 . The washer contacts wall portions  310 ,  312  of the shells  314 ,  316  of the injector device  12  when the hollow piston  128  is in the forwardmost or rearmost overtravel positions, respectively. When the hollow piston is in rearward overtravel position (as in FIG.  9 ), the washer  150  compresses the forward spring  152  which urges the hollow piston  128  forward such that the threaded portion  127  thereof contacts the thread of the threaded shaft  23 . The clutch assembly works in a complementary manner in the case of forward overtravel. Thus, it can be appreciated that the clutch assembly serves to maintain the end threads  127  of the hollow piston  128  in contact with end threads of the threaded shaft  23  when the threads disengage such that, upon a change of direction of the motor  20 , the threads re-engage. 
     To prevent the hollow piston  128  from rotating along with the threaded shaft  23 , one of the c-clips  146  or  148  includes outwardly extending wing portions  136  (see FIG. 8) which engage channels (not shown) in the shell halves  314 ,  316  of the injector device  12 . In addition, the circular channel in the hollow piston  128  in which the one C-clip  146  or  148  is mounted is not complete and therefore prevents the hollow piston  128  from turning relative to the C-clip, and the threaded shaft  23 . Therefore, it can be appreciated that upon rotation of the threaded shaft  23 , the hollow piston  128  must translate forward or backward. 
     As described above, the harpoon  60  is threaded into the rubber stopper  62  of the medical liquid cartridge  64  using the harpoon/cartridge assembly device  66 . The cartridge/harpoon assembly is then inserted within a cartridge case  133  which is then connected to the body of the injector  12 . The cartridge case  133  includes threads  135  on a proximal end  137  thereof which engage a threaded connector  134  threaded to the bushing  130 . The bushing  130  is fixedly located within a cavity  138  formed in the body of the injector  12  by the left and right shells  314 ,  316 . A sealing ring  140  is located between the threaded connector  134  and the threaded bushing  130 , and jointing material  142  is located adjacent the bushing  130 , opposite the sealing ring  140 . 
     As best seen in FIG. 14, the threaded connector  134  forms a cavity  350  for receiving the proximal end  137  of the cartridge case  133 . The cavity  350  includes an internally threaded portion  352  intermediate a bottom wall  354  and an opening  356  of the cavity  350 . The threaded portion  352  is dimensioned to engage the threads  135  of the cartridge case and generally divides the cavity  350  into inner and outer portions  358 ,  360 ; the inner portion being bounded by the bottom wall  354  and the threaded portion  352 , and the outer portion being bounded by the threaded portion  352  and the opening  356 . The distance between the bottom wall  354  and the threaded portion  352  is greater than the width of the threaded portion  135  of the cartridge case  133 , and the diameter of the inner portion  358  of the cavity  350  is greater than the maximum diameter of the threads  135  of the cartridge case  133 . Thus, when the cartridge case  133  is fully threaded into the threaded connector  134 , the threads  135  of the cartridge case  133  pass beyond the threaded portion  352  of the threaded connector  134  and into the inner portion  358  of the cavity  350 , which allows the cartridge case  133  to rotate freely with respect to the body of the injector  12 . However, in this position the cartridge case  133  is trapped between the threaded portion  352  and bottom wall  354  of the threaded connector  134 . 
     Walls  361  of the outer portion  360  of the cavity  350  of the threaded connector  134  closely receive an outer wall  362  of the cartridge case  133  to stabilize the cartridge case  133  in the fully installed position. 
     The distal end  132  of the hollow piston  128  includes an internal thread  366  dimensioned to engage the threaded portion  324  of the harpoon  60 . The internal thread  366  of the distal end  132  of the hollow piston  128  has a length less than a distance between the collar  320  and the threaded portion  324  of the harpoon  60 , and less than or equal to the length of the threaded portion  352  of the threaded connector  134 . Also, the internal diameter of the thread  366  of the hollow piston  128  is greater than a maximum diameter of shaft  322  of the harpoon  60  between the collar  320  and the threaded portion  324  of the harpoon  60 . Thus, when the cartridge case  133  (and cartridge/harpoon assembly) is fully threaded into the threaded connector  134 , the threaded portion  324  of the harpoon  60  will be fully threaded past the thread  366  of the hollow piston  128 ; and the cartridge case  133  and the cartridge/harpoon assembly can rotate freely with respect to the body of the injector  12 . This allows free angular (i.e., rotational) orientation of the needle  18  (which preferably has an inclined tip), without altering the orientation of the entire injector  12 . 
     It can be appreciated that when the hollow piston  128  is extended from the position shown in FIG. 14 (e.g., during the Injection Mode), the distal end  132  of the hollow piston  128  will contact the collar  320  of the harpoon  60 , thus exerting an outward force on the rubber stopper  62  of the cartridge  64 . This force will urge the cartridge  64  and cartridge case  133  outward until the threads  135  of the cartridge case  133  abut the threads  352  of the threaded connector  134 , which prevents further outward movement of the cartridge case  133 . Additional extension of the hollow piston  128  will cause the rubber stopper  62  of the cartridge  64  to plunge into the cartridge  64  thereby expelling the liquid therein. Similarly, when the hollow piston  128  is withdrawn (e.g., during the Aspiration Mode), the threads  366  of the hollow piston  128  abut the threads  324  of the harpoon  60  thereby exerting an inward force on the harpoon  60 . Since the harpoon  60  is firmly threaded into the rubber stopper  62 , this causes the rubber stopper to be withdrawn resulting in a withdrawal of liquid into the cartridge  64 . 
     Referring again to FIG. 8, the injector  12  includes a ring  156  fixedly connected to the threaded shaft  23 , which ring  156  has a plurality of holes  158  preferably  8 . As shown, the ring  156  can be integrally formed with the second spur gear  122 . Aligned on opposite sides of the holes  158  is an optical reader  160  which generates a pulse upon the passage of one of the holes. The signal from the optical reader  160  is transmitted to the control unit  16  for monitoring and adjusting the speed and duration of operation of the motor  20 . 
     The injector  12  includes sealing material to prevent the ingress of water and contaminants. A first sealing material  166  is located between the left and right shells  314 , 316 . The sealing ring  140  is located between the threaded connector  134  and the threaded bushing  130 . Another sealing material  168  is located around the cable connection port  164 . Thus, the internal components of the injector are hermetically sealed. This provides that the injector  12  can be cleaned and sterilized in the convention manner, such as with an autoclave. 
     The external shells  314 ,  316  of the injector  12  are preferably formed from injection molded polypropylene and, when assembled, have dimensions of preferably about 116 mm×40 mm×18 mm. The motor  20  is preferably a high precision motor such as motor model 1319S Micro motor, available from Mini Motors AS, CH-6980 Croglio, Switzerland. 
     Referring to FIGS. 10-13, the operating pedal  14  includes a lower casing  200  which houses a ball joint  202  seated in a cavity  204 . The ball joint  202  is rotatably secured to the lower casing  200  by a ball joint support  206 . A movable cross arm  208  is fixed to the ball joint  202  above and through the ball joint support  206  and extends upwardly through a cover  210  fixed to the lower casing  200 . The cover  210  includes a cross-shaped opening  212  sized and shaped to allow the passage of the movable cross arm  208  therethrough. A foot pad  28 , which includes an arched, upwardly-extending heel registration flange  216  is fixedly connected to the movable cross arm  208  for engagement by the foot of the operator. 
     Microswitches  42 , such as the electromechanical microswitches shown, are located below each arm  220  of the movable cross arm  208 . Thus, the microswitches  42  can be activated by rotating the foot pad  28  with respect to the casing  200 . Springs  218  located below each arm  220  bias the cross arm  208  and foot pad  28  in a horizontal or neutral position. 
     The operating pedal  14  also includes two cable connector ports  34 ,  36  (preferably RJ-45 modular connectors), a power switch  32 , a fuse  33 , 110V/220V voltage selector switch  37 , a power connector  41  and a transformer  39 . The transformer  39  preferably provides power for all the components of the injection system  10 , the power being transmitted to the injection device  12  and the control unit  16  via the cables. 
     Referring to FIGS. 4 and 10, the electronic circuits  232 ,  234  in the operating pedal  14  receive a signal from the optical reader  160  in the injection device  12  to measure and monitor the actual rotational speed of the shaft  23  of the injection device  12 . As a result of the analysis of the signal, software-based PWM (i.e., Pulse With Modulation) is applied to a power circuit of the motor interface  40  which feeds power to the motor  20  until the motor reaches the correct rotational speed. The circuit also stops and drives the motor in both directions using a FET H-Bridge output stage. 
     It should be understood, of course, that the specific form of the invention herein illustrated and described is intended to be representative only, as certain changes may be made therein without departing from the clear teachings of the disclosure. Accordingly, reference should be made to the following appended claims in determining the full scope of the invention.