Abstract:
A caulking gun apparatus is described. In one embodiment the caulking gun includes an electric motor axially coupled to a plurality of cams having uneven surfaces thereon. In one aspect, the uneven surfaces are in slidable contact with at least one driving lever slidably positioned on a piston shaft. The piston shaft includes a piston end that is configured to engage with a cartridge used to dispense fluids such as caulk. The uneven surfaces are arranged relative one another such that when rotated, two or more of the cams about evenly exchange power transmission from the motor to the piston shaft to provide about an even fluid flow from a dispensing end of the cartridge.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This invention is based on U.S. Provisional Patent Application Ser. No. 60/492,587 filed Aug. 4, 2003 entitled “Hand held Multi Cam Electric Caulking Gun” filed in the name of John O. H. Niswonger. The priority of this application is hereby claimed and it is hereby incorporated herein by reference thereto. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Embodiments of the present invention generally relate to caulking guns. 
   2. Description of the Related Art 
   Generally, caulking guns are designed primarily for dispensing caulk packaged in a cylindrical container or cartridge. The cartridge has a dispensing nozzle on one end that dispenses caulk during a calking operation. The caulk is forced from the cartridge nozzle by forcing a movable wall end disposed within the cartridge toward the nozzle end. Conventionally, hand-held caulking guns use a piston type member, e.g., piston, driven by a shaft to push the movable wall. The piston member and shaft may be hand driven in a mechanical caulking gun as known. Unfortunately, such mechanical caulking guns during use often cause fatigue of the hand of the user thereby limiting the efficiency of the caulking operation. Further, due to varying levels of hand strength and gripping ability a user may apply a non-uniform hand-driven force thereby creating a non-uniform flow of caulk. 
   Electric caulking guns have been developed to help resolve such hand caulking issues by easing the work required by the user to move the movable wall end of the cartridge. Conventional electric caulking guns use a motor, such as a DC motor, in combination with a piston and shaft configured to apply force to the movable wall when a user activates the motor. Electric caulking guns are configured with a motion translation linkage that converts the motor rotation to linear piston motion. Some motion translation systems are designed to provide torque reduction to the motor so the motor size and therefore electrical energy consumption may be reduced. Unfortunately, such conventional motion transmission linkage is generally complicated thereby reducing the energy transmission between the motor rotation and the piston. 
   One type of transmission linkage is a single cam electric caulking gun. Such a single cam electric caulking gun uses a single cam motion to force the position forward while providing some torque reduction. Unfortunately, such a single cam only forces caulk forward when the cam is in a lifting portion of rotation and therefore provides no force to the piston during the cam return or retrograde portion of cam rotation to force the caulk forward. Such a change in caulking force causes a non-uniform flow of caulk from the cartridge. 
   Another type of transmission linkage is the screw type of linkage where the piston is rotatably coupled to a long screw on one end and the motor is coupled to the other end. While the screw provides an even caulking force when rotated, unfortunately, such a screw type of device requires a larger motor as little if any torque reduction may be derived therefrom. Conventionally gears are often used to provide such torque reduction. Unfortunately, gears add complexity and reduce the power transmission between the motor and piston. Moreover, a screw type linkage and gears increase the complexity of the portion of the apparatus dedicated to accommodating retraction of the piston for cartridge replacement. 
   Therefore, what is needed is a caulking gun that provides an even flow of caulk that is efficient to use, inexpensive to build and permits easy cartridge replacement. 
   SUMMARY OF THE INVENTION 
   An aspect of the present invention is a caulking gun apparatus configured to support a cartridge and dispense caulk from the cartridge. The apparatus includes a body configured to hold the cartridge in a dispensing position and a piston shaft configured to engage the cartridge for dispensing of the caulk. The piston shaft has a plurality of driving levers in slidable engagement with the piston shaft. The apparatus further includes a motor means disposed within the body coupled to a motor shaft and a plurality of cams axially coupled to the motor shaft. The plurality cams have uneven surfaces in slidable engagement with at least one of the plurality of driving levers and each of the uneven surfaces include at least one lifting surface and at least one retrograde surface. The lifting surfaces and the retrograde surfaces are positioned such that during rotation of the motor shaft, power transmission is provided from the motor to the piston shaft by the lifting surfaces. Furthermore, such power transmission is exchanged between two or more of the plurality of cams through two or more of the plurality of driving levers within a desired power transmission range. 
   Another aspect of the present invention is A caulking gun apparatus configured to support a cartridge and dispense caulk from the cartridge. The apparatus includes a body configured to hold the cartridge in a dispensing position and a motor means disposed within the body coupled to a motor shaft. The plurality of cams are axially coupled to the motor shaft, and a piston shaft is configured to engage the cartridge for dispensing of the caulk. The piston shaft has a plurality of driving levers in slidable engagement with the piston shaft. The plurality cams have surfaces in slidable engagement with at least one of the plurality of driving levers. The surfaces in slidable engagement describe a plane and each of the plurality of planes forms an acute angle with the motor shaft. The planes are positioned such that during rotation, power transmission from the motor to the piston shaft is exchanged between two or more of the plurality of cams through two or more of the plurality of driving levers within a desired power transmission range. 
   Another aspect of the present invention is a method for supporting a cartridge and dispensing caulk from the cartridge. The method includes configuring a body to hold the cartridge in a dispensing position, disposing a motor means within the body, and coupling the motor means to a plurality of cams, each cam having at least one cam surface. The method further includes configuring a piston shaft to engage the cartridge for dispensing of the caulk, engaging the piston shaft with a plurality of driving levers, slidably engaging the cam surfaces with at least one of the plurality of driving levers, and rotating the cams. The method further includes positioning the cam surfaces such that during rotation of the cams, power transmission from the motor to the piston shaft is exchanged between two or more of the plurality of cams through two or more of the plurality of driving levers within a desired power transmission range. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. 
     It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the present invention may admit to other equally effective embodiments. 
       FIG. 1  is a perspective view of one embodiment an electric caulking gun in accordance with aspects of the invention. 
       FIG. 2  is an exploded perspective view of one embodiment of the caulking gun of  FIG. 1  in accordance with aspects of the invention. 
       FIG. 3  is a perspective view of one embodiment of the caulking gun of  FIG. 1  illustrating an arrangement of an electric motor assembly and a piston shaft assembly in a body half, in accordance with aspects the invention. 
       FIG. 4A  is a side elevation view illustrating one embodiment of a plurality of driving levers in an engagement position with a plurality of cams, in accordance with aspects of the invention. 
       FIG. 4B  is a side elevation view illustrating one embodiment of the plurality of driving levers in an engagement position with the plurality of cams in accordance with aspects of the invention. 
       FIG. 5  is a side elevation view illustrating one embodiment of driving levers in a release position in accordance with aspects of the invention. 
       FIG. 6A  is a plan view illustrating one embodiment of a cam engaged with a driving lever in accordance with aspects of the invention. 
       FIG. 6B  is a perspective view illustrating one embodiment of the cam of  FIG. 6A  in accordance with aspects of the invention. 
       FIG. 7A  is a plan view illustrating one embodiment of a cam engaged with a driving lever in accordance with aspects of the invention. 
       FIG. 7B  is a perspective view illustrating one embodiment of the cam of  FIG. 7A  in accordance with aspects of the invention. 
       FIG. 8  is a side elevation illustrating one embodiment of a plurality of planer cams in accordance with aspects of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention. However, it will be apparent to one of skill in the art that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the present invention. 
     FIG. 1  is a perspective view of one embodiment of an electric caulking gun  100  in accordance with aspects of the invention.  FIG. 2  is an exploded perspective view of one embodiment of the electric caulking gun of  FIG. 1 , in accordance with aspects of the invention. Electric caulking gun  100  includes a body  110 , a piston assembly  105 , and a cartridge ring  106 . Electric caulking gun  100  further includes a cartridge tube  101 , a battery  104 , a trigger  103 , and a retaining ring  107 . A dispensing nozzle  102  is illustrated extending from retaining ring  107 . Cartridge ring  106  secures cartridge tube  101  to body  110 . Electric caulking gun  100  further includes a motor assembly  210  and a release slide  223 . Piston assembly  105  includes a piston shaft  115 , a piston  201 , an engagement spring  205 , a driving lever  204 A, another engagement spring  206 , and another driving lever  204 N. Engagement spring  205 , driving lever  204 A, second engagement spring  206 , and driving lever  204 N are described further below. A caulking cartridge  109  is illustrated internal to cartridge tube  101 . 
   Caulking cartridge  109  is connected to dispensing nozzle  102 . Caulking cartridge  109  and dispensing nozzle  102  are not part of electric caulking gun  100 . Retaining ring  107  may be secured to cartridge tube  101 . Dispensing nozzle  102  of caulking cartridge  109  extends therefrom. Cartridge tube  101  may be secured to cartridge ring  106 . Piston  201  may be mounted axially, for example, on an end of piston shaft  115 . Piston shaft  115  extends from piston  201  axially through cartridge ring  106 . Engagement spring  205  is disposed axially on piston shaft  115  between cartridge ring  106  and first driving lever  204 A. Engagement spring  206  is disposed axially on piston shaft  115  between driving lever  204 A and driving lever  204 N. 
   Body  110  may be constructed, for example from a body half  110 A and another bodyhalf  110 B. Body half  110 A includes a plurality of shaft guides  304 A,B to align and slideably hold piston shaft  115 . Body half  110 A and body half  110 B are adapted to receive motor assembly  210 , battery  104 , cartridge ring  106 , piston assembly  105 , trigger  103 , and slide release  223  therein. When assembled together, body half  110 A and body half  110 B may be configured to position and secure motor assembly  210 , battery  104 , cartridge ring  106 , piston assembly  105 , trigger  103 , and slide release  223  in a functional relationship with respect to each other. 
   Motor assembly  210  includes a battery connector  212  electrically connected to a switch  214 . Battery connector  212  is configured to connect battery  104  to motor  210  through switch  214 . Trigger  103  is configured to close switch  214  as is known in the art. Switch  214  may be closed, for example, by sliding trigger  103  toward switch  214  to electrically short contacts associated therewith. When switch  214  is closed, battery  104  may provide electrical energy to motor assembly  210 . Motor assembly  210  may be actuated by electrical energy supplied by battery  104  as is known. In one embodiment, motor assembly  210  may be configured to be actuated by alternate forms of energy, for example a pneumatic type of energy. 
   In one operational configuration, motor assembly  210  applies a force to driving levers  204 A and  204 N. Driving levers  204 A and  204 N transfer such force to piston shaft  115 , urging piston shaft  115  in a direction of dispensing nozzle  102  as described more fully below. Piston shaft  115  advances through cartridge ring  106 , transferring such force to piston  201  and thereby urging piston  201  into caulking cartridge  109 . Piston  201  transfers such force to caulking cartridge  109  disposed within cartridge tube  101 . Retaining ring  107  constrains caulking cartridge  109  inside of cartridge tube  101  against such force transferred to such caulking cartridge by piston  201 . Caulking material, not illustrated, may thus be extruded from dispensing nozzle  102 . 
     FIG. 3  is a perspective view of one embodiment of electric caulking gun  100  of  FIG. 1  illustrating an arrangement of electric motor  210  and piston assembly  105  in body half  110 B, in accordance with aspects the invention. A ring groove  306  may molded into body half  110  and is configured to accept a ring flange  308  of cartridge ring  106  to secure cartridge ring  106  therewith. 
   In one embodiment, electric motor assembly  210  includes a cam  311 A, a cam  311 N, a motor shaft  302 , and a bushing  301 . Cam  311 N is defined herein to represent at least one cam  311 A–N. Cam  311 A and cam  311 N are axially disposed on motor shaft  302 . Cam  311 A–N includes a cam face  303 . Cam face  303  may define an uneven surface having a lifting phase (defined below) and a retrograde phase (defined below). Cam face  303  may alternatively define a surface, which is about planer. Bushing  301  is slideably disposed on motor shaft  302  and may be seated in body  110  to provide rotational stability to motor shaft  302 .  FIG. 3  illustrates an example of bushing  301  seated in body half  110 B. Body half  110 A (See  FIG. 2 ) may secure bushing  301  to body half  110 B. Bushing  301  secures and orients motor assembly  210  in an operational position. Cams  311 A–N are configured to rotate with respect to rotation of motor assembly  210  in either a clockwise or counter clockwise rotation. Cams  311 A–N are configured to transfer power from motor assembly  210  to piston shaft  115  as described further below. Body half  110 A and body half  110 B may be configured to slidably support slide release  223 . In operation, slide release  223  is configured to engage with driving levers  204 A and  204 N to remove such power transfer therefrom. In one configuration, slide release  223  may be used to disengage driving levers  204 A–N to stop a forward movement of piston shaft  115  and piston  201  as described herein. 
     FIG. 4A  is a side elevation view illustrating one embodiment of driving levers  204 A–N of  FIG. 2  and  FIG. 3  in an engagement position with cams  311 A–N, in accordance with aspects of the invention. In one operational configuration, motor shaft  302  rotates cams  311 A and  311 N about simultaneously. Cam  311 N is illustrated engaging driving lever  204 N during a lifting phase of cam  311 N rotation. During such lifting phase of cam  311 N rotation, cam  311 N exerts a force within a predetermined range of power on driving lever  204 N. In one operation illustrated in  FIG. 4A , driving lever  204 N is urged forward by cam  311 N. Driving lever  204 N grips piston shaft  115  in a jamb angle and translates such force from motor assembly  210  into a forward motion toward cartridge  109 , forcing piston shaft  115  to advance in a forward direction (from left to right in  FIG. 4A ) in a direction of dispensing nozzle  102 . During some portion of such lifting phase of cam  311 N, cam  311 A engages driving lever  204 A in a retrograde phase. During such retrograde phase of such engagement of cam  311 A, engagement spring  206  urges driving lever  204 A to slide along piston shaft  115  in a retrograde direction (i.e., reverse direction), from right to left in  FIG. 4A , e.g., an opposite direction of piston shaft  115 . 
     FIG. 4B  is a side elevation view illustrating one embodiment of the plurality of driving levers  204 A–N in an engagement position with a plurality of cams  311 A–N in accordance with aspects of the invention. In operation, motor shaft  302  is rotated such that cam  311 A engages driving lever  204 A in a lifting phase. During such lifting phase of cam  311 A rotation, cam  311 A exerts a force within a predetermined range of power on driving lever  204 A. In one operation illustrated in  FIG. 4B , driving lever  204 A is urged forward by cam  311 A. Driving lever  204 A grips piston shaft  115  in a jamb angle and translates such force from motor assembly  210  into a forward motion, forcing piston shaft  115  to advance in a forward direction (from left to right in  FIG. 4B ) in a direction of dispensing nozzle  102 . During some portion of such lifting phase of cam  311 A, cam  311 N engages driving lever  204 N in a retrograde phase. During such retrograde phase of such engagement of cam  311 N, engagement spring  205  urges driving lever  204 N to slide along piston shaft  115  in a retrograde direction (i.e., reverse direction), from right to left in  FIG. 4B , e.g., an opposite direction of piston shaft  115 . Thus in operation, during rotation of motor shaft  302 , cam  311 A and respective driving lever  204 A, and cam  311 N and respective driving lever  204 N are configured to cooperatively exchange and share power translation from motor assembly  210  to piston shaft  115 . For example, cam  311 A and driving lever  204 A translate power to piston shaft  115  for a portion of a rotation of motor shaft  302  and cam  311 N and respective driving lever  204 N translate power to piston shaft  115  for another portion of a rotation of motor shaft  302 . 
   In summary, each cam  311 A–N and driving lever  204 A–N operate similar to a cam member and a cam follower respectively, whereby such cam follower follows a surface of such cam member. In operation, as motor shaft  302  is rotated by motor assembly  210 , cams  311 A and  311 N in conjunction with a respective driving lever  204 A and driving lever  204 N cooperate to urge piston shaft  115  forward, thereby pushing piston  201  forward through caulking cartridge  109 . In one operational configuration, cams  311 A and  311 N are about 180 degrees out of phase, therefore when driving lever  204 A is in a predetermined portion of a lifting phase with respect to cam  311 A, driving lever  204 N is in a retrograde phase with respect to cam  311 N. Conversely, when driving lever  204 N is in a predetermined portion of a lifting phase with respect to cam  311 N, driving lever  204 A is in a retrograde phase with respect to cam  311 A. Thus, cam  311 A and driving lever  204 A and cam  311 N and respective driving lever  204 N work in unison to continuously move piston shaft  115  in a forward motion while each driving lever  204 A–N moves, e.g., slides independently back and forth along a portion of piston shaft  115 . 
     FIG. 5  is a side elevation view illustrating driving levers  204 A–N in a release position, in accordance with aspects of the invention. A user of apparatus  100 , for example, may force release slide  223  in a forward direction, e.g., toward caulking cartridge  109 , which disengages driving lever  204 A and driving lever  204 N from cam  204 A and cam  204 N respectively. With driving lever  204 A and driving lever  204 N disengaged, piston shaft  115  may be pulled in the retrograde direction regardless of phase of cam  311 A–N by such user. Thus, in operation release slide  223  may be used to disengage power transmission from motor assembly  210  to piston  201 , and may be used to allow piston shaft  115  to be repositioned with respect to caulking cartridge  109 . 
     FIG. 6A  is a plan view illustrating one of cams  311 A–N engaged with a respective one of driving levers  204 A–N, in accordance with aspects of the invention.  FIG. 6B  is a perspective view further illustrating cam  311 A–N of  FIG. 6A , in accordance with aspects of the invention. Cams  311 A–N are coupled to motor shaft  302  as illustrated in  FIGS. 6A and 6B . In one embodiment, motor shaft  302  is configured to maintain cam  311 A–N rotation with respect to motor shaft  302 . For example, motor shaft  302  may be configured with a “D” shape, as illustrated in  FIG. 6A , however other rotation inhibiting shapes are contemplated such as a square shape, an oval shape, hexagon, and the like. In one configuration, piston shaft  115  may be shaped to prevent driving lever  204 A–N from rotating away from respective cam  311 A–N engaged therewith. For example, such piston shaft  115  may be shaped with a non-round shape such as a hexagonal shape, oval shape, square shape, rectangular shape, and the like. 
   In one configuration, cam face  303  includes lifting face  601  and a retrograde face  602 . As illustrated in  FIG. 6B , for example, when cam  311 A–N may be viewed in perspective, lifting face  601  and retrograde face  602  form an uneven surface in cam face  303  of cam  311 A–N. A lowest point on uneven surface of cam face  303  may be represented as a retrograde point  612 . A highest point of uneven surface of cam face  303  relative retrograde point  612  may be represented by a peak point  611 . Such retrograde point  612  and peak point  611  are merely illustrative, as cam face  303  surface may include a plurality of high and low surfaces thereon. While  FIG. 6A  and  FIG. 6B  illustrate an example of one embodiment of an uneven surface for cam face  303  for cam  311 A and  311 N, such an uneven surface of cam face  303  is not constrained to be identical for each of cams  311 A–N. 
   In one embodiment, moving clockwise for example, lifting face  601  extends from about retrograde point  612  along and around a perimeter of an uneven surface of cam face  303 , to about peak point  611 . Retrograde face extends from about peak point  611  around and along perimeter of such an uneven surface of cam face  303  to about retrograde point  612 . Following lifting face  601  from about retrograde point  612 , in a clockwise direction for example, along perimeter of such uneven surface of cam face  303 , lifting face  601  may progressively extend higher with respect to retrograde point  612  until reaching peak point  611 . Following retrograde face  602  from peak point  611 , in a clockwise direction for example, along perimeter of uneven surface of cam face  303 , retrograde face  602  may progressively descend lower with respect to peak point  611  until reaching retrograde point  612 . For example, a portion of lifting face  601  may be sloped to extend further out from cam  311 A–N relative to retrograde point  612 . As illustrated in  FIGS. 4A–C , for example, when viewed from the side of cam  311 A–N lifting face  601  and retrograde face  602  form such an uneven surface of cam face  303  of cam  311 A–N which is configured to provide cam action to driving lever  204 A–N. While  FIGS. 6A and 6B  illustrate an example of a cam face  303  in which lifting face  601  extends progressively higher with respect to retrograde point  612  while moving in a clockwise direction, a cam face  303  may be configured to extend progressively higher with respect to retrograde point  612  while moving in a counter-clockwise direction. Similarly, retrograde face  602  may descend progressively lower with respect to peak point  611  while moving in a counter-clockwise direction. 
   In one embodiment, lifting face  601  is a portion of uneven surface of cam face  303  defined by an angle {circle around (-)}, while retrograde face  602  is a portion of uneven surface of cam face  303  defined by angle φ. During operation, motor assembly  210  rotates motor shaft  302  (See  FIGS. 2 and 3 ). As motor shaft  302  rotates cam  311 A–N, driving lever  204 A–N engages cam  311 A–N alternately at lifting face  601 , and retrograde face  602 . In  FIG. 6A , cam  311 A–N illustrates an example of driving lever  204 A–N engaging cam  311 A–N at retrograde face  602 . A lifting phase for any cam  311 A–N may be defined as a set of all rotational angles of motor shaft  302  that place respective driving lever  204 A–N in engagement with cam  311 A–N in some portion of such cam  311 A–N lifting surface. Similarly, a retrograde phase for any cam  311 A–N may be defined as a set of all rotational angles of motor shaft  302  that place respective driving lever  204 A–N in engagement with cam  311 A–N in some portion of such cam  311 A–N retrograde surface. For example, when motor shaft  302  is positioned such that driving lever  204 A engages cam  311 A at lifting face  601 , cam  311 A is in lifting phase. When motor shaft  302  is positioned such that driving lever  204 A engages cam  311 A at retrograde face  602 , cam  311 A is in retrograde phase. Similarly, when motor shaft  302  is positioned such that driving lever  204 N engages cam  311 N at lifting face  601 , cam  311 N is in lifting phase. When motor shaft  302  is positioned such that driving lever  204 N engages cam  311 N at retrograde face  602 , cam  311 N is in retrograde phase. 
   For clarity, only two cams  311 A and  311 N along with respective driving levers  204 A and  204 N are illustrated herein. However, it is contemplated that virtually any cam  311 A–N combination greater than one may be used to advantage. For example, in one embodiment, cam  311 A and cam  311 N along with respective driving levers  204 A and  204 N may represent three cams  311 A–N along with three respective driving levers  204 A–N. In such a three cam  311 A–N and three driving lever  204 A–N arrangement, respective lifting surfaces, e.g., lifting surface  601 , may be aligned such that each of such three cam and driving lever arrangements cooperate to provide about continuous forward motion to piston shaft  115  during rotation of motor shaft  302 . 
     FIG. 7A  is a plan view illustrating one embodiment of cam  311 A–N engaged with a respective one of driving levers  204 A–N, in accordance with aspects of the invention.  FIG. 7B  is a perspective view illustrating cam  311 A–N of  FIG. 7A , in accordance with aspects of the invention. This is just one embodiment of cam  311 A–N illustrating an uneven surface of cam face  303 . In one configuration, cam face  303  includes a lifting face  701  and a retrograde face  702 . As illustrated in  FIG. 7B , for example, when cam  311 A–N may be viewed in perspective, lifting face  701  and retrograde face  702  form an uneven surface in cam face  303  of cam  311 A–N. A lowest point on such an uneven surface of cam face  303  may be represented as a retrograde point  712 . A highest point of uneven surface of cam face  303  relative retrograde point  712  may be represented by a peak point  711 . Such retrograde point  712  and peak point  711  are merely illustrative as surface of cam face  303  may include a plurality of high and low surfaces thereon. While  FIG. 7A  and  FIG. 7B  illustrate an example of a common cam face  303  for cam  311 A and  311 N, uneven surface of cam face  303  is not constrained to be identical for each of cams  311 A–N. 
   Lifting face  701  extends in a clockwise direction, for example, from about retrograde point  712  along and around a perimeter of uneven surface of cam face  303 , to about peak point  711 . Retrograde face  702  extends in the clockwise direction, for example, from about peak point  711  around and along perimeter of uneven surface of cam face  303  to about retrograde point  712 . Following lifting face  701  from about retrograde point  712 , in a clockwise direction along perimeter of uneven surface of cam face  303 , lifting face  701  may progressively extend higher with respect to retrograde point  712  until reaching peak point  711 . Following retrograde face  702  from peak point  711 , in a clockwise direction along perimeter of uneven surface of cam face  303 , retrograde face  702  may progressively descend lower with respect to peak point  711  until reaching retrograde point  712 . While  FIGS. 7A and 7B  illustrate an example of a cam face  303  in which lifting face  701  extends progressively higher with respect to retrograde point  712  while moving in a clockwise direction, a cam face  303  may be configured to extend progressively higher with respect to retrograde point  712  while moving in a counter-clockwise direction. Similarly, retrograde face  702  may descend progressively lower with respect to peak point  711  while moving in a counter-clockwise direction. 
   In one embodiment, lifting surface  701  occupies an angle {circle around (-)} of uneven surface of cam face  303 , which may be a substantial portion of 360 degrees for example more than about 180 degrees, while retrograde surface  702  occupies an angle φ of uneven surface of cam face  303 , which may be minor portion of 360 degrees, for example less than about 180 degrees. Angle {circle around (-)} and angle φ may be configured to define a plurality of different lifting faces  701  and retrograde faces  702  in uneven surface of cam face  303 , that may be used to advantage. For example, angle {circle around (-)} and angle φ may be configured to be small relative to 360 degrees such that a plurality of lifting faces  701  and retrograde faces  702  occur within a 360-degree rotation of uneven face of cam face  303 . It is important that angle {circle around (-)} and angle φ may be selected and cam  311 A oriented with respect to cam  311 N so that at least one of cam  311 A or cam  311 N is oriented in a lifting phase during about the entire 360 degrees of rotation of motor shaft  302 . 
   During operation, motor assembly  210  rotates motor shaft  302  (See  FIGS. 2 and 3 ). As motor shaft  302  rotates cam  311 A–N driving lever  204 A–N engages cam  311 A–N alternately at lifting face  701 , and retrograde face  702 . In  FIG. 7A , cam  311 A–N illustrates an example of driving lever  204 A–N engaging cam  311 A–N at lifting face  701 . Again, as in  FIG. 6A  and  FIG. 6B , a lifting phase for any cam  311 A–N may be defined as a set of all rotational angles of motor shaft  302  that place respective driving lever  204 A–N in engagement with cam  311 A–N in some portion of such cam  311 A–N lifting surface. Similarly, a retrograde phase for any cam  311 A–N may be defined as a set of all rotational angles of motor shaft  302  that place respective driving lever  204 A–N in engagement with cam  311 A–N in some portion of such cam  311 A–N retrograde surface. For example, when motor shaft  302  is positioned such that driving lever  204 A engages cam  311 A at lifting face  701 , cam  311 A is in a lifting phase. When motor shaft  302  is positioned such that driving lever  204 A engages cam  311 A at retrograde face  702 , cam  311 A is in a retrograde phase. Similarly, when motor shaft  302  is positioned such that driving lever  204 N engages cam  311 N at lifting face  701 , cam  311 N is in a lifting phase. When motor shaft  302  is positioned such that driving lever  204 N engages cam  311 N at retrograde face  702 , cam  311 N is in a retrograde phase. 
   For clarity, as described herein, only two cams  311 A and  311 N along with respective driving levers  204 A and  204 N are shown. However, it is contemplated that virtually any cam  311 A–N combination greater than one may be used to advantage. For example, in one embodiment, cam  311 A and cam  311 N along with respective driving levers  204 A and  204 N may represent three cams  311 A–N along with three respective driving levers  204 A–N. In such a three cam  311 A–N and three driving lever  204 A–N arrangement, respective lifting surfaces, e.g., lifting surface  701 , may be aligned such that each of such three cam and driving lever arrangements cooperate to provide about continuous forward motion to piston shaft  115  during rotation of motor shaft  302 . 
     FIG. 8  is a side elevation illustrating one embodiment of a plurality of planer cams  800 A and  800 N, in accordance with aspects of the invention. A line D may be an axis of motor shaft  302 . Cam  800 A has a planer cam face  801 A, A line E may be a normal to planer cam face  801 A and intersecting line D. An angle A is formed between line E and intersecting line D. Angle A defines a “tilt” of planer cam surface  801 A with respect to line D. 
   Cam  800 N has a planer cam face  801 N. A line F may be a normal planer cam face  801 N and intersecting line D. An angle N is formed between line F and line D. Angle N defines a “tilt” of planer cam surface  801 N with respect to line D. 
   Cam  800 A and cam  800 N may be mounted at a respective angle A and N relative a longitudinal axis D of motor shaft  302 . Such angles A and N are configured so that during rotation of motor shaft  302 , cam  800 A provides planer cam face  801 A that moves forward and backward with a cam motion relative to driving lever  204 A and piston  201 . Therefore, in one rotation position, planer cam face  801 A is positioned relative driving lever  204 A such that about zero forward pressure is applied to driving lever  204 A, while in another rotation position cam face  303 A extends further toward driving lever  204 A to urge piston shaft  115  and piston  201  forward. Similarly, cam  800 N provides cam face  801 N that moves forward and backward with a cam motion relative to driving lever  204 N and piston  201 . Therefore, in one rotation position, cam face  303 N is positioned relative driving lever  204 N such that about zero forward pressure is applied to driving lever  204 N, while in another rotation position cam face  303 N extends further toward driving lever  204 N to urge piston shaft  115  and piston  201  forward. In one configuration, for example, cam face  303 A and cam face  303 N are aligned relative motor shaft  302  such that while one cam face  303 A–N is providing forward pressure on a respective driving lever  204 A–N, another surface  204 A–N is allowing a respective driving lever  204 A–N to be released and forced in a retrograde direction along piston shaft  115  by respective engagement springs  205  and  206 . For example, consider the case where cam face  303 A may urge piston shaft  115  forward while cam face  303 N is releasing driving lever  204 N to allow such driving lever  204 N to retract along piston shaft  115 . 
   For clarity, as described herein, only two cams  800 A and  800 N along with respective driving levers  204 A and  204 N are shown. However, it is contemplated that virtually any cam  800 A–N combination greater than one may be used to advantage. For example, in one embodiment, cams  800 A and  800 N along with respective driving levers  204 A and  204 N may represent three cams  800 A–N along with three respective driving levers  204 A–N. In such a three cam  800 A–N and three driving lever  204 A–N arrangement, respective lifting faces, e.g., cam face  303 , may be aligned such that each of such three cam and driving lever arrangements cooperate to provide about continuous forward motion to piston shaft  115  during rotation of motor shaft  302 . 
   In a case of an apparatus having for example two cams  800 A–N, as described above Line E and line D define a first cam axial plane. Line F and line D define a second cam axial plane. The first cam plane and the second cam axial plane have line D in common and may be separated by phase angle of about 180 degrees. In a case of an apparatus having for example three cams a third cam axial plane may be determined analogous to the first cam axial plane and the second cam axial plane. All three cam axial planes have line D in common and may be separated by a phase angle of about 120 degrees. In a general case of an apparatus having N cams, N cam axial planes may be defined, all having line D in common. A phase angle between each adjacent pair of cam axial planes may be about 360 divided by an N number of cams. As described herein, cam  800 A is tilted at an angle A and cam  800 N is tilted at an angle N to a respective longitudinal axis D. For a configuration of two or more cams  800 A–N each respective cam  800 A–N is tilted at a respective angle A–B configured to impart about continuous forward motion on piston shaft  115 . For example, consider the case of two cams  800 A–N, angle A and N are configured such that as cams  800 A and  800 N are rotated out of phase about 180 degrees. For a case of three cams  800 A–N, angle A–N is configured such that such three cams  800 A–N are out of phase about 120 degrees. Thus, an associated phase relationship between cams  800 A–N may be computed using the following formula:
 
cam relative phase=360 degrees/(no. of cams)  (1)
 
Where cam relative phase is the relative position along a common longitudinal axis D of each cam  800 A–N, e.g., the relative radial position of each cam  800 A–N with respect to a rotation of motor shaft  302 .
 
   While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.