Abstract:
An easy to operate, extremely quiet, efficient can engagement and opening mechanism is provided for use in an opener for a can, and that provides a pair of missing teeth operating endpoints at opposite ends of its opener cycle, along with an eccentrically operating idler gear and cutter gear urging mechanism that produces a non-jamming foolproof mechanism that can be urged forward to a closed and operating position or reversed to a disengagement and non-operating position.

Description:
[0001]    This application is a divisional application of commonly-owned U.S. patent application Ser. No. 12/807,137, filed Aug. 27, 2010, the entire disclosure of which is herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a mechanism for use in a can opener that uses a quiet reversal mechanism that may be provided with a manual or automated drive mechanisms. 
         [0004]    2. Related Background Art 
         [0005]    U.S. Pat. No. 4,365,417 issued to Rosendahl on Dec. 28, 1982 and entitled “TIN OPENER” describes a can opener that uses a missing teeth structure at one end of travel of a cutter gear. The open position of the cutter lies at the end of a number of teeth of the cutter movement gear. In essence, a user turns a butterfly shaped actuator from a first, resting stopped position and in a direction of engagement that causes the cutter blade to move toward and engage the body of a can. At the point in which the cutter and the can, urged by a drive wheel, are closest, the drive gear encounters a “missing teeth” section of the cutter gear so that the drive gear can continue to turn the drive wheel and without having the cutter gear interfered with by the cutter gear&#39;s having stopped at the point where the cutter and the can are closest. The cutter engagement gear can be reversed to move the cutter wheel away from the drive wheel. The mechanism to assist this reversal is the use of a projection that extends outward towards a cover and is arranged to co-operate with a rubber cylinder situated within a circular ridge and an adjacent ridge and is intended to import a rotary movement to the too segment device. In essence, when the concave surface (missing teeth) is centrally opposite a pinion, the rotary movement tends to turn the tooth segment device (cutter gear) in such a way as to cause the teeth in the row of teeth (adjacent the section of missing teeth) to re-engage and cause the cutter gear to move the cutter away from the drive wheel. 
         [0006]    The mechanisms to cause gear re-engagement from a position in which a drive gear opposes the “missing teeth” portion of another gear are many. Most involve a more complex method of re-starting the drive gear against the driven gear by detecting the reverse motion of the drive gear. In some designs a starter “clicking gear” is used to continually present the beginning gear of the reversal to the drive gear. Friction of an idler gear with respect to a driven gear can sometime be counted upon to get the driven gear going in a direction away from the “missing teeth” section of the driven gear. However both of these methods can greatly suffer. First, any “clicking” mechanism operates through continued wear and distracting noise. Second, the use of friction among gears in a highly lubricated environment can result in long terms changes in the ability of the driven gear to reverse. If a can opener becomes un-disengageable from a can or lid, the can opener becomes disposable or in the alternative a significant repair job is needed to free the can lid or can from the mechanism. 
         [0007]    In the case of the Rosendahl device directly, there are several shortcomings that it has in terms of building a can opener that is utilizable in the safest and most secure way by the greatest number of people. The Rosendahl device has a butterfly drive handle which is a pair of oppositely oriented extensions that are each about one to two inches from the rotational center. The operation of the Rosendahl device requires significant dexterity, finger and thumb strength and wrist flexibility. Further, the use of a butterfly actuator involves a series of partial turns interrupted by stopping and thence further partial turns. High dexterity and strength is required. A further undesired by-product of this method of operation is the necessity to grasp the opener with one hand, periodically operate the opener with the other hand, while putting some downward pressure on the can with both hands in order to stabilize the food contents during the opening activity. To prevent spillage, the user orients the opener and the can on a flat surface and operates it in an awkward position sacrificing user comfort in exchange for a necessity to use the table as a stabilizing reference point. A user would not normally think of supporting the can to be opened with the hand supporting the bulk of the opener as the motion would be too much of a jerking motion that would cause a mess. This is because the manual force necessary to open the can is significant, as well as periodically occurring. 
         [0008]    The Rosendahl device generally must be made of a metallic construction. One end of the toothed gear set on the cutter wheel movement gear is made up of a blocking tooth. Once the user reaches the non-operating end of the tooth segment device (toothed gear set on the cutter wheel movement gear) it cannot be rotated further by means of its pinion drive gear. Only a metal construction would have the force of hold against a user “trying” to continue movement of the pinion gear in the opposite direction. In essence one of the stronger failure modes of the Rosendahl devices occurs at the non-working end of its operational range. In a good can opener, the maximum forces should be put to work forming a nip in the can or in opening the can, not in providing strength at a non-operating end point of the opening cycle. 
         [0009]    Another important aspect in which the Rosendahl device falls short is the requirement generally for significant strength on the part of the person opening the can. The fact that the Rosendahl device is required to be made of metal and have strength to defeat damage from turning it in the direction of the non-operating position. Requiring only enough force to make the nip and open the can might also have caused Rosendahl to have considered persons of limited strength and their need to utilize a can opener that they could operate. If the Rosendahl mechanism were optimized, then a motorized version of the design might have been practically possible. However, the single, blind ended cycle of opening would have caused Rosendahl to have included more complex stopping sensors to insure that any motorized force would not challenge the return to the non-operating position. Any motorization of this type of end point can set the mechanics of motorization against the mechanics of operation and create destruction of both. Put another way, the simple provision of the mechanism of Rosendahl into a heavy motorized housing would either have created a significant cost in sensors, electronics to precisely control the cycle, or might have ended with the motorization gearing and the operational gearing destructively fighting with each other. 
         [0010]    What is therefore needed is a mechanism that can provide a mechanically advantaged engagement of the cutter wheel toward the can to form the nip, followed by continuous operation until the can is open. A needed can opener of this type, in order to be available in large quantity at an inexpensive price in order to facilitate its purchase as a perfunctory and useful item, should be amenable to an inexpensive construction while having a long lasting high quality mechanism. The mechanism should not make any discernible noise and should operate consistently regardless of the amount of lubrication within the gear mechanism. Most importantly, a needed can opener mechanism should facilitate use of a can opener into which it is placed by providing ease of manual operation in the case of a manual opener, and low energy consumption/long battery service in the case when the needed can opener mechanism is motorized. 
       SUMMARY OF THE INVENTION 
       [0011]    A mechanism is provided for use in an opener for a can, that provides a pair of missing teeth operating endpoints at opposite ends of its opener cycle, along with an eccentrically operating idler gear and cutter gear urging mechanism that produces an easy to operate, extremely quiet, efficient can engagement an opening mechanism. The opener is actuated to a closed and operating position by turning the main drive in a first direction and then actuated to an open and disengaged position by simple reversal caused by turning the main drive in a second direction opposite from the first direction. This eliminates jamming or a “hard stop” that is seen in many openers, while simultaneously eliminating the need for a locking lever or other holding or freeing mechanism. 
         [0012]    These and other advantages are achieved while using a few number of simple parts, and an idler gear that has an internal diameter that is oversized with respect to an eccentric boss about which it operates, and a including a cutter movement gear that has an actuator cover with a tooth engaging bump for engaging the idler gear when the idler gear shifts its position about the eccentric boss upon change in its direction. 
         [0013]    A combination drive shaft-drive gear-drive wheel operates adjacent to the cutter movement gear and idler gear. The drive gear of the drive shaft has three stable modes of operation with respect to the cutter movement gear, including a non-engagement non-operational position when the drive shaft is being turned in a direction to disengage the cutter wheel, an engagement and operational position when the drive shaft is being turned in a direction to engage the cutter wheel, and a non-engagement but can cutting operational position when the drive shaft is being turned in a direction to and beyond engagement with cutter wheel movement gear and is not engaged with the cutter wheel movement gear but where the drive wheel is engaged in turning and cutting the can being opened. 
         [0014]    The two ended, non-jamming or stopped mechanism allows greater freedom and advantage in both manual and electrically powered can openers. Both electrically and manually driven openers benefit from less expensive parts that would be needed to oppose the stop forces in non-double ended freewheeling operation. For manual can openers the smoother operation makes manual opening much easier, enabling the user to use one hand to steady the well secured can, preferably on a surface, and easily use the other hand to turn an extended crank. The use of lesser cranking force enables the user to better stable the can level as it turns on a surface. The reversal of the crank over only a few turns causes disengagement that is not a surprise spilling disengagement for the user. The pivoting crank handle can be stored with respect to the housing and thus take up minimal space, and in most cases less space than a conventional butterfly can opener. Further, the sharp potentially pinching metal structure relationship found in butterfly can openers is eliminated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Embodiments of the present invention will now be described with reference to the accompanying drawings in which: 
           [0016]      FIG. 1  is a floating perspective view of one embodiment of the invention shown for familiarity and orientation; 
           [0017]      FIG. 2  is a floating perspective view of one embodiment of the invention as in  FIG. 1  and shown at the point of proximity to a can; 
           [0018]      FIG. 3  is a floating perspective view of one embodiment of the invention as in  FIGS. 1 and 2  and showing closed engagement with an the beginning of cutting of a can; 
           [0019]      FIG. 4  is an exploded view of the components of the can opener mechanism seen in  FIGS. 1-3  and illustrating further details of the components thereof; 
           [0020]      FIG. 5  is a schematic view looking down onto the rotary can opener mechanism seen in  FIGS. 1-4  and at the level of the top of the cutter movement gear as a beginning of the explanation of the action of the components in explanation of a full cycle of action; 
           [0021]      FIG. 6  is a schematic view looking down onto the rotary can opener mechanism seen in  FIGS. 1-4  and at the level of the toothed upper portion of the idle gear and showing the interaction corresponding to the view of  FIG. 5  and the non-interaction of the interference bump of the downwardly extending overhang member with the toothed upper portion of the idle gear; 
           [0022]      FIG. 7  is a schematic view looking down onto the rotary can opener mechanism seen in  FIGS. 1-4  and at the level of the toothed upper portion of the idle gear and showing the interaction corresponding to the view of  FIG. 5  but at a moment after a change in direction of the lower drive gear and illustrating contact interaction of the interference bump of the downwardly extending overhang member with the toothed upper portion of the idle gear; 
           [0023]      FIG. 8  is a schematic view looking down onto the rotary can opener mechanism seen in  FIGS. 1-4  and at the level of the top of the cutter movement gear and where the lower drive gear is engaged with the gear teeth of the cutter movement teeth and where the cutter movement gear is mid-way through a change in position; 
           [0024]      FIG. 9  is a schematic view looking down onto the rotary can opener mechanism seen in  FIGS. 1-4  and at the level of the top of the cutter movement gear and where the lower drive gear opposes the other missing teeth portion of the cutter movement gear and where the lower drive gear continues to turn; 
           [0025]      FIG. 10  is a schematic view looking down onto the rotary can opener mechanism seen in  FIGS. 1-4  and at the level of the toothed upper portion of the idle gear and showing the interaction corresponding to the view of  FIG. 9  and illustrating non-interfering non-contact interaction of the interference bump of the downwardly extending overhang member with the toothed upper portion of the idle gear; 
           [0026]      FIG. 11  is a schematic view looking down onto the rotary can opener mechanism seen in  FIGS. 1-4  and at the level of the toothed upper portion of the idle gear and showing the interaction corresponding to the view of  FIG. 9  but at a moment after a change in direction of the lower drive gear and illustrating a re-contact interaction of the interference bump of the downwardly extending overhang member with the toothed upper portion of the idle gear which will enable the cutter movement gear to begin to reverse its direction; 
           [0027]      FIG. 12  illustrates an exploded view of one realization of a manual rotary can opener that utilizes the rotary can opener mechanism seen in  FIGS. 1-11 ; 
           [0028]      FIG. 13  illustrates a perspective view similar to the exploded view of  FIG. 12  and seen with the assembled components of the can opener the same orientation as in  FIG. 12 ; 
           [0029]      FIG. 14  illustrates a perspective view of the can opener showing the upper handle flattened ball section protruding through the through an opening such that the crank assembly is in lock down position; 
           [0030]      FIG. 15  is a perspective view of the can opener as was seen in  FIG. 14  and shown from an upwardly directed perspective position; 
           [0031]      FIG. 16 , is a perspective cut-away view of an electrically driven opener; and 
           [0032]      FIG. 17  is one possible realization of circuitry possibly usable with the can opener shown in  FIG. 16 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]    Referring to  FIG. 1 , a spatial perspective of the mechanism of the invention hereinafter referred to as rotary can opener mechanism  31  is seen as an operating assembly and without the surrounding housing details. Beginning at the top of the assembly, a drive shaft  33  is seen as having an engagement aperture  35 . Drive shaft  33 , for strength may preferably be made of metal. Drive shaft  33  is shown extending through an axial drive gear set  37  having an upper engagement gear  41  and a lower drive gear  43 . 
         [0034]    A number of structures that are preferably integral to a support housing are illustrated in a position isolated from the remainder of the support housing. A housing section  51  represents the base floor of a lower housing section (not shown) that would provide support for all of the connected components seen at the upper left of  FIG. 1 . At the right side of the housing section  51  a drive gear boss  55  is shown for rotatably supporting the drive gear  43  at a proper elevation. 
         [0035]    At the left side of  FIG. 1  and immediately above the housing section  51 , an idle gear  57  having a toothed upper portion  61  and a cylindrical lower portion  63  is seen. The cylindrical lower portion  63  has a flat end (not seen in  FIG. 1 ) that smoothly rides on an upper surface of the housing section  51  with no significant axial downward force. Although not seen in  FIG. 1 , the idle gear  57  has an relatively large diameter internal surface that rides loosely upon a boss (also not shown) that is eccentric and has an effective reduced diameter for portions of the boss that are located away from the closes point to the drive gear  43 . This enables the idle gear  57  to move slightly with regard to a line extending through the center of the eccentric boss (not seen) each time that the idle gear  57  changes direction. When the drive gear  43  is operated, the side of the idle gear  57  feeding teeth into the teeth of the drive gear  43  tends to hug the side of the boss more tightly while the teeth fed out of the drive gear  43  tends to make a larger gap at the side of the boss (not seen). The result is an idle gear  57  that shifts its position slightly depending upon which way it is driven by the drive gear. As will be seen, this slight movement is one design element that enables the can rotary opener mechanism to operate more smoothly. 
         [0036]    Above the idle gear  57  toothed upper portion  61  is seen the cutter movement gear  65 . Cutter gear has having a toothed portion having a series of gear teeth  69 . To one side of the series of gear teeth  69  is seen a concave surface or missing teeth portion  71  that is provided to enable the lower drive gear  43  to turn freely without further actuation of the cutter movement gear. To the left of the missing teeth portion  71  is seen a downwardly extending overhang member  75  that has an interior portion side  77  that opposes the toothed upper portion  61  of the idle gear  57 . Since the idle gear  57  has some movement about a yet unseen boss, it is possible for the toothed upper portion  61  of the idle gear  57  to, in some limited circumstances move closer to and farther from the interior portion side  77  of the downwardly extending overhang member  75  cutter movement gear  65 . Although the idle gear  57  has some lateral movement, the cutter movement gear  65  rotates evenly within the same eccentric boss (not shown) that idle gear  57  moves about with some of the aforementioned lateral freedom. A pivot axle  79  is shown protruding from the cutter movement gear  65  where the cutter movement gear  65  may derive further stability and support from an upper portion of the ‘housing (not shown) that engages the pivot axle  79 . 
         [0037]    Beneath the housing section  51  is seen a wear plate  81  that extends from a position underneath the idle gear  57  and across to a position underneath the lower drive gear  43 . The wear plate  81  is preferably made of a thin metal or highly wear resistant material, as it is subject to moving contact from an upper surface of an upper rim  83  of an upper section of can  85  and that is resting on a side wall  87 . At the right side, and underneath the wear plate  81  is a drive wheel  91 . Drive wheel  91  is preferably metal and metallically affixed to the drive shaft  33  and should have a diameter of about one centimeter and a number of gripping teeth which may preferably be about 18. In one embodiment, the drive shaft is pressed into the drive wheel  91  such that a small amount of the drive shaft  33  can be seen in the center of the drive wheel  91  to which the drive shaft  33  is attached. Other methods of attachment may be by welding or even integral formation of the drive shaft  33  and the drive wheel  91 . 
         [0038]    As the drive wheel  91  and drive shaft  33  are have a unitary relationship it should be noted that the drive shaft  33  and drive wheel  91  may vertically slide through and out the bottom of the upper engagement gear  41  and lower drive gear  43  were it not secured upwardly by some structure associated with engagement aperture  35 . At the other side of the area underneath the housing section  51 , and directly opposite the drive wheel  91  is a cutter washer  93 . The cutter washer  93  will press the upper rim  83  of the can  85  against the drive wheel  91  so that the drive wheel  91  can engage the inside circumferentially inwardly directed surface of the upper rim  83  of can  85  during the cutting or can opening operation. The cutter washer  93  is generally preferably freely rotatable and facilitates rotation of the upper rim  83  of the can  85  by providing a nearly frictionless bearing surface opposing the drive wheel  91  such that the cutter washer  93  will allow the rim  83  of the can  85  to rotate as driven by the drive wheel  91 . 
         [0039]    Below the cutter washer  93  is the cutter  95 , a circular sharply bevelled rotatable metal disc that rotates and cuts the side wall of the can  85  during the cutting process. A square washer  97  is seen below the cutter  95  and is so termed because it has a square aperture  99  that registers against a square member (not seen) within and below the cutter washer  93  to provide that the square washer  97  not rotate with the cutter  95 . The square washer  96  is secured by a cutter screw  101 . The non-rotatability of the cutter washer  93  helps to stabilize the cutter screw  101  by not subjecting the cutter screw  101  to rotational force that might otherwise cause it to disconnect from the other parts of the rotary can opener mechanism  31 . 
         [0040]    Typical drive wheels  91  have been known to be about 1.6 centimeters in diameter with about 25 gripping teeth. The small size of the drive wheel  91  has two important effects. First it enables less turning moment to advance the can. Second, it enables the drive wheel  91  and its associated gearing such as lower drive gear  43  to also be much closer to, smaller, and to take a greater mechanical advantage with respect to the force imparted to the cutter movement gear  65  and without the need for intermediate gearing. The diameter of the cutter washer  93  is about 1.7 centimeters and the diameter of the cutter  95  is about 2.3 centimeters, both sizes of a magnitude normally associated with larger 1.6 centimeter drive wheels. The ratio of the diameter of the drive wheel  91  to the cutter washer  93  is then about 1:1.7 or about 0.58. The ratio of the diameter of the drive wheel  91  to the cutter  95  is then about 1:2.3 or about 0.434. 
         [0041]    Thus the use of a drive wheel  91  enables a greater mechanical advantage by enabling a gear directly related to the same shaft  33  to which drive wheel  91  is attached, namely the lower drive gear  43  to cause rotation of the cutter movement gear  65 , as well as to provide an advantageous mechanical advantage in moving the upper rim  83  of a can to be cut. In addition, and in the open position, the spacing between the drive wheel  91  and the cutter washer  93  is about 0.7 centimeters while the diagonal opening between the drive wheel and the cutter  95  cutting edge is about 0.3 centimeters. In the closed position, the spacing between the drive wheel  91  and the cutter washer  93  is about 0.1 centimeters. The result is that the axial center of the drive wheel  91  is only about 1.45 centimeters from the axial center of the cutter  95  and cutter washer  93 . This closer axial relationship enables more force with components that are either smaller or do not have to withstand greater stresses to achieve such force. The cutter washer  93  and cutter  95  only have to travel 0.6 centimeters, which is 60% of the distance of the diameter of the drive wheel  91 . 
         [0042]    A partial introduction into the workings of the rotary can opener mechanism  31  will be initially seen, but also repeated later, with reference to  FIGS. 2 and 3 . Referring to  FIG. 2 , and respect to the view shown, the series of gear teeth  69  of the toothed portion cutter movement gear  65  are seen while the visually observable cutter assembly components including the cutter washer  93 , cutter  95 , square washer  97  and the cutter screw  101  are positioned away from the drive wheel  91  sufficient for the can  85  upper rim  83  to be positioned between the visually observable cutter assembly and the drive wheel  91 . As the drive shaft  33  is turned clockwise looking down into the end of the drive shaft  33  adjacent the engagement aperture  35 , the series of gear teeth  69  of the cutter movement gear  65  begin to move from left to right as the cutter movement gear  65  begins to turn counterclockwise taken from view looking down onto the cutter movement gear  65 . This rotates the acentrically mounted the visually observable cutter assembly components including the cutter washer  93 , cutter  95  square washer  97  and the cutter screw  101  begin to rotatably displace toward the wall  87  of the can  85 . 
         [0043]    Referring to  FIG. 3 , a side view illustrates the cutter wheel  95  engagement of the wall  87  of the can  85  that is the fully engaged result of the visually observable cutter assembly components being rotatably displaced toward the wall  87  of the can  85 . Note that the full extent of the downwardly extending overhang member  75  is seen and that from the angle of view of  FIG. 3  that it totally obscures any view of the toothed upper portion  61  of the idle gear  57 . To the right of center of the downwardly extending overhang member  75 , an interference bump  103  is illustrated in dashed line format. As will be seen more fully, the interference bump  103  is a circumferentially inwardly projecting protrusion that can provide some engagement with the space between two adjacent teeth of the toothed upper portion  61  of the idle gear  57  but only if the idle gear  57  were laterally shifted toward the downwardly extending overhang member  75 . Recall that downwardly extending overhang member  75  is a part of the concentrically rotatable cutter movement gear  65  and that cutter movement gear  65  cannot laterally shift. Other new details seen in  FIG. 3  include an upper flattened rim  105  that can help the cutter movement gear  65  to be contained and operate with minimum friction against an inside upper wall of a housing in which the rotary can opener mechanism  31  is housed. 
         [0044]    Referring to  FIG. 4 , an exploded view of the components of the rotary can opener mechanism  31  reveal further details of the components seen in side view in  FIGS. 1-3 . At the top of  FIG. 4 , the cutter movement gear  65  is seen to have a central cylindrical member  111  about which the cutter movement gear  65  precisely rotates, as will be shown. Beneath the central cylindrical member  111  is a cutter support member  113  that is mounted acentrically with respect to cylindrical member  111 . The acentrically mounted cutter support member  113  is used to move the cutter  95  mounted thereon closer or farther from the drive wheel  91  upon rotation of the cutter movement gear  65 . At the bottom end of the acentrically mounted cutter support member  113  is a rectangular projecting member  115  for engagement with the square washer  97  to isolate any rotation from and to stabilize the cutter screw  101 . Cutter screw  101  engages a bore (not shown in  FIG. 4  through a center of acentrically mounted cutter support member  113 . 
         [0045]    The axial drive gear set  37  is further seen to have a lower cylindrical member  121  for interfitting and deriving stable rotational support within and from the drive gear boss  55 , and an upper slot opening  123  for slidably accepting the drive shaft  33 . Idle gear  57  is seen as having an internal surface  125 . Below the idle gear  57 , a view from a higher vantage point illustrates the housing section  51 , the previously seen drive gear boss  55 , and seen for the first time is the cutter movement gear boss  131  and its internal surface  133 . The cutter movement gear boss  131  is seen as having an exterior cylindrical surface  135  that is interrupted by a circumferentially outwardly projecting rib  137 . 
         [0046]    The rib  137  acts to force some closeness of the idle gear  57  to the drive gear boss  55  and thus to the lower drive gear  43  a having an upper engagement gear  41  and a lower drive gear  43 , but possibly over a narrower urging face. An alternative mechanism, such as by having an elliptical outer surface (not seen in  FIG. 4 ) will be illustrated. Other possibilities include a thickening (not necessary elliptical) in the direction of drive gear boss  55  combined with a reduced size of the exterior cylindrical surface  135  on the lateral of a line extending away from the area between idle gear  57  to the drive gear boss  55 . In yet other cases, a mere oversize of the idle gear  57  with respect to the drive gear boss  55  will be sufficient to produce the type of laterally shifting action of the idle gear  57  to be described. However the use of a circumferentially outwardly projecting rib  137  emphasizes several aspects of the use of the idle gear  57 . First, an idle gear  57  has teeth that serve to place an engaging bearing load on only a portion of the axial length and narrow arc width urged by the narrow circumferentially outwardly projecting rib  137 . Secondly, the shape and depth of teeth of the toothed upper portion  61  of the idle gear  57  can, with relaxation of other factors determine the lateral angular pivot displacement about the closest point of mesh of the toothed upper portion  61  of idle gear  57  even as idle gear  57  is engaged with the teeth of lower drive gear  43 . 
         [0047]    It is seen that since exterior cylindrical surface  135  has a given cylindrical diameter, that a projection such as circumferentially outwardly projecting rib  137  causes the cutter movement gear boss  131  to have an even greater effective diameter, i.e. the distance between the circumferentially outwardly projecting rib  137  to the side of the exterior cylindrical surface  135  opposite the circumferentially outwardly projecting rib  137 . However, the internal surface  125  of the idle gear  57  has an internal diameter even larger than such even greater effective diameter to enable it to have sufficient looseness to enable an angular pivot displacement about the closest point of mesh of the toothed upper portion  61  of idle gear  57  with respect to the teeth of lower drive gear  43 . 
         [0048]    Below the housing section  51 , the wear plate  81  can be seen as having a pair of apertures including a central cylindrical member and wear aperture  141  that admits the central cylindrical member  111  through the wear plate  81  and provides an expanded area wear and stabilization for the very abbreviated portion of central cylindrical member  111  that extends through it. In a like manner, wear plate  81  has a lower cylindrical member and wear aperture  145  that admits the lower cylindrical member  121  through the wear plate  81  and provides an expanded area wear and stabilization for the very abbreviated portion of lower cylindrical member  121  that extends through it. 
         [0049]    Below the central cylindrical member and wear aperture  141  is located the cutter washer  93  that is seen to have a strong outer wall  147 , a strong inner wall  149 , separated by a channel  151 , and an internal bore  153  that matches the outer diameter of the acentrically mounted cutter support member  113 . The cutter washer  93  is rotatable, but includes a downward rectangular projection  157  that matches a rectangular aperture  159  seen in the cutter  95 . Where the cutter  95  is thus keyed to rotate with the cutter washer  93 , there is some assurance that neither the cutter washer  93  nor cutter  95  will become stuck and wear unevenly. 
         [0050]    Below the cutter  95 , the square washer  97  can be seen as having a central square aperture that is sized for engagement with the rectangular projecting member  115  of the acentrically mounted cutter support member  113 . The rectangular projecting member  115  prevents rotation of the square washer  97  to prevent any exterior rotational movement of the cutter  95  from touching the cutter screw  101 . Thus, the cutter screw  101 , the material within the acentrically mounted cutter support member  113  with which cutter screw  101  is fastened, and the square washer  97  against which an underside  161  of a head  163  of the cutter screw  101  rests will experience no dislodgement friction from the natural turning of the cutter washer  93  and the cutter  95 . 
         [0051]    The operation of the rotary can opener mechanism  31  involves both the cutter movement gear  65  and the idle gear  57  that lies below it. Superimposing both views can lead to confusion, and therefore it can be best explained in a series of side by side views that illustrate the relationship between them. Further, each of the endpoints of travel of the cutter movement gear  65  can have two idle gear  57  positions associated with it. As a result, there are mathematically five states that the cutter movement gear  65  and the idle gear  57  can assume in their normal cycling, and those states are independent of whether the endpoints of travel of the cutter movement gear  65  has been achieved. As shown in  FIGS. 1-4 , the cutter movement gear  65  has a downwardly extending overhang member  75  having an interior portion side  77  that supports a circumferentially inwardly disposed interference bump  103 , that may be a type of inwardly directed tooth and that is sized to provide some slight engagement with the teeth of the toothed upper portion  61  of the idle gear  57 . Such slight engagement will only occur when the axial drive gear set  37  is turning in a certain direction while the cutter movement gear  65  is at one of the two ends of its cycle of travel. Engagement can happen also between endpoints but has little effect as teeth  69  and  43  are also engaged. 
         [0052]    Referring to  FIG. 5 , a view looking schematically down onto the rotary can opener mechanism  31  as seen in  FIGS. 1 and 2  is seen. Upper engagement gear  41  is omitted for clarity of illustration. Rotary can opener mechanism  31  is in an open position and ready to accept the can  85  for opening. The lower drive gear  43  on the drive shaft  33  is shown with a counterclockwise arrow to indicate that cutter movement gear  65  had just arrived at that position through a clockwise movement of the cutter movement gear  65  and that it has just stopped moving while the lower drive gear  43  might have moved for a few moments and thus the counterclockwise arrow about lower drive gear  43 . The position shown would have been arrived at by having the user turn lower drive gear  43  in a direction opposite of the drive direction to create can  85  cutting, also known as toward the open position and perhaps and a little beyond what would be required to open the rotary can opener mechanism  31  as seen in  FIGS. 1 and 2 . The lower drive gear  43  can continue to turn in this opening or release direction so long as it faces the concave surface or missing teeth portion  71  without causing any further movement in the cutter movement gear  65 . 
         [0053]    Referring to  FIG. 6 , a schematic view of both the lower drive gear  43  and idle gear  57  as it appear while the lower drive gear  43  and cutter movement gear  65  are in the state shown in  FIG. 5  is seen. A similar counterclockwise arrow about the lower drive gear  43  is seen as if it were in motion. Note that a gap  171  exists between the exterior cylindrical surface  135  of the cutter movement gear boss  131  and the internal surface  125  of the idle gear  57  on the side of the cutter movement gear boss  131  that is downstream of the exit feed of teeth of the toothed upper portion  61  from the mesh connection of the toothed upper portion  61  of the idle gear  57  and the lower drive gear  43  of the drive shaft  33 . On the side of the cutter movement gear boss  131  exterior cylindrical surface  135  opposite the gap  171 , an area of contact  173  or near contact between the exterior cylindrical surface  135  of the cutter movement gear boss  131  and the internal surface  125  of the idle gear  57  is seen. This on the side of the cutter movement gear boss  131  that is upstream of the exit feed of teeth of the toothed upper portion  61  from the mesh connection of the toothed upper portion  61  of the idle gear  57  and the lower drive gear  43  of the drive shaft  33 . Put another way, an “upstream” side pulls the idle gear  57  close to the boss  131 , and a “downstream” side pushes the idle gear  57  away from the boss  131 . 
         [0054]    If and when the lower drive gear  43  ceases motion, the existence and orientation of the gap  171  contact  173  is not expected to change. Of course, if the rotary can opener mechanism  31  were to attain a position such that gravity might urge the idle gear  57  to shift so that the gap  171  lessened in magnitude so that contact  173  was lost, this is a passive state of affairs and does not affect the position of the gap  171  and contact  173  used herein to explain the action of the idle gear  57 . Also note that the downwardly extending overhang member  75  is on the side of the idle gear  57  having the contact  173  and opposite the side having the gap  171 . So, if the lower drive gear  43  continues to turn counterclockwise with respect to the view of  FIG. 6 , the idle gear  57  will continue to turn such that its toothed upper portion  61  will not have contact with the interference bump  103 . In real terms, a user who has turned the lower drive gear  43  to open up the rotary can opener mechanism  31  reaches a point where the drive shaft  33  simply continues to spin and the orientation of components as shown in  FIG. 6  will continue. This is in marked contrast to a can opener system that relies upon the physical integrity of interfering or jamming gears to halt and withstand movement of the drive shaft  33 . In essence, the rotary can opener mechanism  31  removes the possibility that a user can harm it at either end of its cycle, as will be shown. 
         [0055]      FIG. 7  is a view of the rotary can opener mechanism  31  at the moment where the lower drive gear  43  just begins motion in the clockwise direction (opposite of its counterclockwise motion seen in  FIG. 6 ). After only one tooth is displaced, the gap  171  disappears from the side of the cutter movement gear boss  131  opposite the location of the downwardly extending overhang member  75 . The contact  173  breaks as the idle gear  57  shifts toward the cutter movement gear  65  downwardly extending overhang member  75 , since it is this side of idle gear  57  that begins to be fed into the gear mesh connection mesh connection of the toothed upper portion  61  of the idle gear  57  and the lower drive gear  43  of the drive shaft  33 . This movement of the idle gear  57  toward the downwardly extending overhang member  75  causes the toothed upper portion  61  of the idle gear  57  to engage the interference bump  103 . This engagement is slight, especially since the interference bump  103  is not particularly deep. The only slight work that the idle gear  57  does is to urge the cutter movement gear  65  very slightly toward the teeth of the lower drive gear  43  sufficient for the lower drive gear  43  to begin to engage the series of gear teeth  69  carried by the cutter movement gear  65 . A variation in the structure  137  immediately inside the idle gear  57  is seen as ellipse shaped structure  177  to show another possible variation. 
         [0056]    Once the first of the series of gear teeth  69  carried by the cutter movement gear  65  engages the lower drive gear  43 , the lower drive gear  43  may continue to smoothly and quietly begin to turn the cutter movement gear  65  to cause the cutter  95  to move toward the drive wheel  91 . Referring to  FIG. 8 , a view similar to that seen in  FIG. 5  illustrates angular displacement of the cutter movement gear  65  to a position mid-way of its total travel. Upper engagement gear  43  is shown as having a two directional movement as the view shown in  FIG. 8  can represent the mid point in the path from open (as seen in  FIGS. 1 and 2 ) to closed (as seen in  FIG. 3 ), or closed to open. During the middle portion of the path between closed and open, the lower drive gear  43  is engaged with both the idle gear  57  and gear teeth  69  of the cutter movement gear  65 . The interference bump  103  may or may not ride passively within the teeth of the toothed upper portion  61  as it is not mandatory that the overall number of gear teeth in a complete circle of the toothed upper portion  61  be the same as the number of teeth that form a complete circle as to the series of gear teeth  69 . However, any relative movement between the interference bump  103  and teeth of the toothed upper portion  61  will occur so slowly as to be passive and silent. 
         [0057]    Referring to  FIG. 9 , a view looking schematically down onto the rotary can opener mechanism  31  as seen as in  FIGS. 5 and 8 . Rotary can opener mechanism  31  has just moved cutter movement gear  65  to a closed position and has already caused the cutter  95  to form a nip in the can wall  87  and further turning of the upper engagement gear in the clockwise direction will cause the drive wheel  91  to cause the rim  83  of the can to be fed between it and the cutter washer  93  to perform the can  85  cutting process. As was the case for  FIG. 5 , the lower drive gear  43  can continue to turn so long as it faces the concave surface or missing teeth portion  71  without causing any movement in the cutter movement gear  65 . 
         [0058]    As the cutting operation continues, and referring to  FIG. 10  a gap  171  will exist between the exterior cylindrical surface  135  of the cutter movement gear boss  131  and the internal surface  125  of the idle gear  57  on the side of the cutter movement gear boss  131  that is downstream of the exit feed of teeth of the toothed upper portion  61  from the mesh connection of the toothed upper portion  61  of the idle gear  57  and the lower drive gear  43  of the drive shaft  33 . The gap  171  is seen to occurs on the side of the gear boss  131  opposite the side where the downwardly extending overhang member  75  is located and thus interference bump  103  is not contacted and is unaffected. On the side of the cutter movement gear boss  131  exterior cylindrical surface  135  opposite the gap  171 , an area of contact  173  or near contact between the exterior cylindrical surface  135  of the cutter movement gear boss  131  and the internal surface  125  of the idle gear  57  is seen. This on the side of the cutter movement gear boss  131  that is upstream of the exit feed of teeth of the toothed upper portion  61  from the mesh connection of the toothed upper portion  61  of the idle gear  57  and the lower drive gear  43  of the drive shaft  33 . The contact  173  is on the same side of the boss  131  as the downwardly extending overhang member  75 . The orientation seen in  FIG. 10  continues for so long as the can  85  opening operation continues. If and when the lower drive gear  43  ceases motion, such as when the can cutting operation is completed, and the upper rim  83  is separated from the can wall  87 , a reversal of the direction of turn of the drive shaft  33  and lower drive gear  43  would start the opening process whereby the drive wheel  91  and cutter washer  93 -cutter  95  would move away from each other to release the can  85  rim  83 . A further variation on the shape of the cutter movement gear boss  131  involves elimination of the circumferentially outwardly projecting rib  137  with optional removal of material at the sides of the cutter movement gear boss  131  indicated by removal areas  181 . Any number of other tolerances, structures, and other accommodations can allow the idle gear  57  to shift itself into contact with the interference bump  103 , including its own flexibility. 
         [0059]    Referring to  FIG. 11 , the moment that the lower drive gear  43  begins to turn in the counterclockwise direction, and perhaps after only one tooth is displaced, the gap  171  disappears from the side of the cutter movement gear boss  131  opposite the location of the downwardly extending overhang member  75 . The contact  173  breaks as the idle gear  57  shifts toward the cutter movement gear  65  downwardly extending overhang member  75 , since it is this side of idle gear  57  that begins to be fed into the gear mesh connection mesh connection of the toothed upper portion  61  of the idle gear  57  and the lower drive gear  43  of the drive shaft  33 . This movement of the idle gear  57  toward the downwardly extending overhang member  75  causes the toothed upper portion  61  of the idle gear  57  to engage the interference bump  103 . The engagement is again slight, as before. Once again, the only slight work that the idle gear  57  does is to urge the cutter movement gear  65  very slightly toward the teeth of the lower drive gear  43  sufficient for the lower drive gear  43  to begin to engage the series of gear teeth  69  carried by the cutter movement gear  65 , but with the cutter movement gear  65  now turning in the opposite direction. 
         [0060]    Once the first of the series of gear teeth  69  carried by the cutter movement gear  65  again engage the lower drive gear  43 , the lower drive gear  43  may continue to smoothly and quietly begin to turn the cutter movement gear  65  to cause the cutter  95  to begin to move away from the drive wheel  91 . This continues until the lower drive gear  43  are at a midway point with respect to the series of gear teeth  69  of the cutter movement gear  65 . Further movement of the lower drive gear  43  will cause the cycle to arrive at the stage that was explained with respect to  FIG. 5 . Then, the lower drive gear  43  can continue to be turned in the open position as seen in  FIGS. 5 and 5 , or it can be reversed to re start the cycle as was described beginning with the description given for  FIG. 7 . 
         [0061]    Referring to  FIG. 12 , an exploded view of one realization of a manual rotary can opener  201  that utilizes the rotary can opener mechanism  31  seen in  FIGS. 1-11  is shown. The manual rotary can opener  201  is designed with several objectives in mind, including (1) ease of storage and deployment, (2) stability during can opening operation to reduce spills and the like, and (3) ease of operation during opening so that even a person of limited physical capability can more easily use can opener  201 . The Exploded view not only facilitates the identification of both old and new component parts, it emphasizes the simplicity and modularity of parts necessary to provide significant utility to rotary can opener mechanism  31 . 
         [0062]    Referring to  FIG. 12 , new components will be discussed beginning at the upper left side. An upper handle oval or flattened ball section  205  is seen positioned over a similar shaped lower handle flattened ball section  207 . The lower handle ball section fits onto a rotation stem  209  having an aperture  211  at its upper end to intermit with a lower handle ball threaded member  213 . The lower end of the rotation stem  209  is attached to a crank upper section  215 . Crank upper section  215  has an attachment to a crank lower section  217 . The crank lower section includes a pair of spaced apart pivot fittings  219  each having a pivot aperture  221 . At the inside of the pair of spaced apart pivot fittings  219 , a detent engagement surface  223  is seen. A detent surface  223 A Detent engagement surface  223  is configured to provide a detent resting space for the crank upper &amp; lower sections  215  and  217  in storage position to align with the upper housing section  241 , and in a second unfolded position when in use ( 230 B &amp;  223 B engage). The upper handle flattened ball section  205 , lower handle flattened ball section  207 , rotation stem  209 , crank upper section  215 , crank lower section  217 , and pair of spaced apart pivot fittings  219  may be referred to as a crank assembly  224 . 
         [0063]    Adjacent the crank lower section  217  is a rotation and pivot fitting  225  that provides a rotational crank action for operation of the can opener  201 , and a pivot action for the crank lower section  217 . The pivot fitting  225  has a central main wide slot  227  for accepting the pair of spaced apart pivot fittings  219 . A ball filler fitting  229  will occupy a part of the central main wide slot  227  between the a pair of spaced apart pivot fittings  219  in order to make a smooth appearance, and to cover the pivot fitting mechanical components. Ball filler fitting  229  has a pair of detents  230  that engage detent engagement surface  223  to help hold the crank assembly  224  in place in the closed open position, as well as a central detent  230 B which help hold the crank assembly  224  in place in the closed, stowed position. A crank pivot pin  231  is seen in a position of parallel alignment with a multi bore opening  233 , as well as a pair spaced apart lateral pin apertures  235  seen in the pivot fitting  225 . The crank pivot pin fits through the pair spaced apart lateral pin apertures  235 , the pivot apertures  221  of the pair of spaced apart pivot fittings  219 , the multi bore opening  233 , and the engagement aperture  35  of the drive shaft  33  when the upper end of drive shaft  33  is inserted within the engagement aperture  35  ball filler fitting  229 . Also shown are a pair of finishing caps  237  that are sized to fit into matching spaces and over the exposed ends of the pair spaced apart lateral pin apertures  235  to give the can opener  201  a more finished appearance. 
         [0064]    An upper housing section  241  having a handle portion  243  and gear housing portion  245  overlies in matching exploded alignment with a lower housing section  251  having a handle portion  253  and gear housing portion  255 . The upper housing section  241  has a number of features and structures that enable it to mate with, join, and be secured to the lower housing section  251 . A series of joining fasteners are seen, with three gear housing portion fasteners  261  seen over the gear housing portion  245  and two handle housing portion fasteners  263  shown below the handle housing portion  253 . A pair of finishing caps  265  are seen to be associated with the two handle housing portion fasteners  263  to cosmetically cover countersunk bores into which the fasteners  263  fit. 
         [0065]    An upper housing section  241  has a number of visible features including an upper engagement gear aperture  271  through that the upper engagement gear  41  will protrude to be engaged by the rotation and pivot fitting  225 . Distributed about the upper engagement gear aperture  271  is a series of threaded member engagement apertures  275 . The handle portions  243  and  253  have a through opening  277  for accommodating the upper handle flattened ball section  205 . The handle portions  243  and  253  also have a hanger opening  279  to enable a hanging or lanyard-type storage of the can opener  201 . Lower housing section  251  has a number of visible features including an countersunk aperture bores  281  to accommodate the two handle housing portion fasteners  263 . Within the gear housing portion  255  of the Lower housing section  251  a series of three raised threaded bore fastener supports  285  are seen for providing engagement and material support for the fasteners  261 . Also seen are the previously identified cutter movement gear boss  131  and drive gear boss  55 . Although not directly seen, the gear housing portion  255  of the lower housing section  251  forms the housing section  51  that was shown in  FIGS. 1-4 . Other previously seen components of the can opener  201  are predominantly visible in  FIG. 12  but not discussed. 
         [0066]    Referring to  FIG. 13 , a perspective view similar to the exploded view of  FIG. 12  is seen with the assembled components of the can opener  201  in roughly the same orientation as they were seen in  FIG. 12 . The configuration seen in  FIG. 13  is in a position where the upper and lower handle ball sections  205  and  207  are ready to be turned to cause rotation and pivot fitting  225  to turn while rotation and pivot fitting  225  engages and causes upper engagement gear  41  to turn to operate the mechanism as shown. Turning in one direction causes the rotary can opener mechanism  31  to close and turning in the other direction causes the rotary can opener mechanism  31  to open. 
         [0067]    Referring to  FIG. 14 , a perspective view of the can opener  201  shows the upper handle flattened ball section  205  protruding through the through opening  277  such that the crank assembly  224  is in lock down position. Referring to  FIG. 15 , a perspective view of the can opener  201  as was seen in  FIG. 14  is shown from an upper perspective position. 
         [0068]    Referring to  FIG. 16 , a perspective cut-away view of an electrically driven opener  301  shows a battery  303 , contacts  305  and  307 , and an electric motor  311  switchably powered by the battery  303 . Electric motor  311  is connected through a series of speed reduction gears including a worm gear  315  connected to the motor  311 , a first reduction gear  317 , first reduction gear pinion  319  with the first reduction gear  317  about an axle (not seen in  FIG. 16 ), and engaging a second reduction gear  321 . A second reduction gear pinion  323  turning with the second reduction gear  321  about an axle  325 , engages a drive gear  327 . Although not seen directly, the drive gear  327  engages the upper engagement gear  41 , and operates the rotary can opener mechanism  31  in the same way as was described for  FIGS. 1-11 . The only difference noted is that the cutter gear  65  is located forward of the axial drive gear set  37  that is directly driven by the drive gear  327 . 
         [0069]    A momentary action switch  331  may be located next to a polarity reversing switch  335 . A cam follower  331 B attached to the momentary switch  331  is shown resting against a cam surface  361  which extends from upper flattened rim  105 . A button  337  acts in concert with its mechanically connected actuators  341  and  345  to simultaneously actuate both the momentary action switch  331  and polarity reversing switch  335  simultaneously upon the pressing of the button  337 . The circuitry connecting the above switches can be many and varied, and involve mechanical switches as well as electronic switches. One embodiment will be shown and explained with respect to  FIG. 17 . Meanwhile it can be seen the electric battery powered can opener  301  has a base housing  351  and an upper housing  355 . 
         [0070]    Referring to  FIG. 17 , a schematic electrical diagram is shown where momentary action switch  331  is seen as well as polarity reversing switch  335 . From a state in which the motor  311  is off, a cam structure  361  enables a cutting off of momentary action switch  331 . Pressing the button  337  changes the reverse switch  335  to the opposite position to allow the positive side of the battery  303  to electrically connect to the “+” side of the polarity reversing switch  335 , and to start the motor  311  toward the closure and can opening position. Once the motor  311  has operated for a second or two, the cam  362  holds the momentary action switch  331  in the closed position and the momentary action switch  331  no longer needs to be pressed throughout the cycle. The motor causes the can opener  301  to close about a can  85  and for the opening cycle to continue cutting a can  85  upper rim  83  from a can. As the mechanism achieves the state seen in  FIGS. 9 and 10 . The can continues to be processed until the user again presses the button  337  to reverse the mechanism. This moves the polarity reversing switch  335  to the position opposite that seen in  FIG. 17 , where positive current flows to the non positive side of the motor  311  to cause the motor to reverse itself and begin to open the can opener  301 . This opening process continues normally until the upper rim  83  is released and in any event until the rotary can opener mechanism  31  is stopped. The opening process continues until the state seen in  FIG. 5  is achieved. In this state, due to CAM  361 , the break in the circuit of  FIG. 17  causes the motor  311  to stop. The can opener  301  is now open and waiting for another can opening cycle. 
         [0071]    While the preferred embodiments of the invention have been shown and described, it will be understood by those skilled in the art that changes of modifications may be made thereto without departing from the true spirit and scope of the invention.