Patent Publication Number: US-2009236453-A1

Title: Drive Mechanism

Description:
BACKGROUND TO THE INVENTION 
     This invention relates to a drive mechanism. The drive mechanism is particularly useful in a manual grinder for peppercorns, salt crystals and other edible grindable product. 
     In our New Zealand patent specification 528182 there is described and claimed an easy-to-use manual grinder for peppercorns, salt crystals and other edible grindable products. The manual grinder, as described in NZ 528182, is a manual grinder that can be held in one hand and operated. This is principally achieved by the manual grinder having an operating lever which is hinged and, therefore, can be operated on a squeeze and release type operation. The lever is described as controlling a linearly moveable toothed element (e.g. rack) which engages with a toothed wheel on a drive shaft. The mechanism thereby translates a linear movement into a rotary movement which is imparted to the grinding elements. 
     Another example of a manual grinder with a rack and pinion type drive mechanism can be found in U.S. patent specification 
     With such drive mechanisms a problem arises from the lost motion inherent in the mechanism. This primarily is due to backlash clearance of the teeth in a ratchet which is included in the drive mechanism so that upon release of the control lever the shaft is not rotated in a reverse direction. 
     The lost motion means, in practical terms, that the maximum amount of rotation of the grinding elements for each stroke of the mechanism is not achieved. Hence the grinding effect is inefficient. For example, many operations of the operating lever will be necessary to effect the required grind of material. This can be frustrating to the end user and for those who may lack hand span or strength it could, in extreme cases, result in the grinder not being useable by the end user. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a linear to rotary drive mechanism which can be incorporated in a product such as a manual grinder to provide a positive non-reversible drive or, at least, to provide the public with a useful choice. 
     According to one broad aspect of the invention there is provided a drive mechanism including a first toothed element, a second toothed element engaged with the first toothed element, the second toothed element being movable in a first direction to cause movement of the first toothed element and in the second direction to cause reverse movement of the first toothed element, a split sleeve into a bore of which a shaft can be engaged, the split sleeve is coupled to the first toothed element such that relative movement between the split sleeve and first toothed element can occur when the rack is moved in said first direction where, upon engagement, contraction of the bore creates a driving contact between the split sleeve and shaft, and said movement of the second toothed element in the second direction is in the absence of the driving contact whereby the split sleeve and first toothed element can move independent of the shaft. 
     In the preferred form of the invention the second toothed element is a linear toothed element such as a rack. Preferably the first toothed element is an annular gear element with at least part of the split sleeve located within the annular gear element. 
     In the preferred form of the invention the split sleeve is pivotally coupled to the gear element. Preferably abutment surfaces limit the amount of movement of the split sleeve relative to the gear element. 
     In the preferred form of the invention a pivot pin, which creates the pivot coupling of the split sleeve to the gear element, has an axis of rotation which is offset to the axis of the bore. 
     In a preferred form of the invention bias means is provided to bias the split sleeve toward engagement of the abutment surfaces. 
     According to a second broad aspect of the present invention there is provided a manual grinder for the grinding of edible grindable product, the grinder including a body into which grindable product can be located for grinding by grinding elements located at an outlet end of the body, a shaft rotatably located within the body, an operating member located externally of the body, a drive mechanism according to the first broad aspect of the invention, and coupling means whereby the operating handle is coupled to the second tooth element of the drive mechanism whereby movement of the operating handle will cause the second toothed element to move in the first direction and thereby cause operation of the grinding elements, there being biasing means for causing the second toothed element to move in the second direction. 
     In a preferred form of the invention the grinder further includes friction creating means which acts on the shaft when the second toothed element moves in the second direction to thereby prevent any contact between the split sleeve and the shaft causing rotation of the shaft. 
     In the preferred form of the invention the operating handle is a lever pivotally coupled to the body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following more detailed description of the drive mechanism of the invention according to a preferred form, reference will be made to the accompanying drawings in which: 
         FIG. 1  is a cross-sectional illustration through the centre of the drive shaft of a manual grinder incorporating the drive mechanism, 
         FIG. 2  is a view similar to  FIG. 1  but showing the operating handle at the end of its stroke, 
         FIG. 3  is an exploded view of the manual grinder of  FIGS. 1 and 2 , 
         FIG. 4  is a more detailed cross-section of the top part of the manual grinder of  FIGS. 1 to 3 , 
         FIG. 5  is a perspective view illustrating a part assembly of the drive mechanism according to the present invention incorporated in a manual grinder of the type describe in our New Zealand patent specification 528182 with the operating handle in the “open” or rest position, 
         FIG. 6  is a similar view but with part of the mechanism removed in the interests of clarity, 
         FIG. 7  is a view similar to  FIG. 6  but with the operating handle at the other end in its movement (i.e. the “closed” or compressed position), 
         FIG. 8  is a view similar to  FIG. 7  but with the portion of the drive mechanism removed from  FIG. 7  now shown, 
         FIG. 9  is a perspective view of the drive wheel and split sleeve elements of the drive mechanism according to the present invention, 
         FIG. 10  is a planned view of the arrangement shown in  FIG. 9 , 
         FIG. 11  is a perspective view of the drive ring and split sleeve separately, 
         FIG. 12  is a perspective view of the split sleeve with the pivot pin and spring shown in place, 
         FIG. 13  is a plan view similar to  FIG. 10  showing the split sleeve in the driving contact position, 
         FIG. 14  is a view similar to  FIG. 13  but showing the split sleeve in the non driving position, and 
         FIG. 15  is a perspective view of a shaft to which the drive mechanism can be connected. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
     The drive mechanism according to the present invention is suitable for use in products or devices where a linear action is required to be translated into a rotary movement with immediate effect. Thus, as stated previously, the present invention has particular application to a manual grinder especially of the type disclosed in our New Zealand patent specification 528128. Therefore, for the purposes of describing the present invention, the drive mechanism will be described in conjunction with a manual grinder of the type disclosed in NZ 528128. Therefore, the content of NZ 528128 is incorporated herein by way of specific reference. 
     Referring to  FIG. 1  there is shown a manual grinder  10  of the type shown and described in NZ 528128. As described in NZ 528128 a lever handle  11  is preferably in the form of a lever pivotally or hingedly coupled at a lower end to a body  12  of the manual grinder  10 . The body  12  is hollow and located within the body  12  is a drive shaft  14 . The drive shaft  14  is coupled at its lower end to a movable (rotatable) grinder element G at the outlet or lower end of the body  12 . This grinder element G is located operatively within a fixed grinder element G′. 
     As described in NZ 528128 and our New Zealand patent specification 527450 the grinder element G is adjustable in axial position on the end of the shaft  14  and hence relative to the fixed grinder element G′ by an adjustable arrangement A. Consequently, by moving the position of the externally accessible knob K the adjuster A can be altered so as to adjust the position of the grinder element G relative to grinder G′. In this way the grind can be adjusted between fine and coarse settings. 
     As can be seen in  FIGS. 1 and 2  the shaft  14  is located in the body  12  between a lower bearing arrangement B and an upper bearing arrangement which is formed by a well  19  formed as part of (preferably integrally) with a cover  17  hereinafter described. 
     Accordingly, the shaft  14  is supported within the body  12  and is prevented from any appreciable longitudinal movement in the direction of the axis of rotation of the shaft  14 . Consequently, the adjustment of the moveable grinder element G takes place axially independently of the shaft  14  i.e. without any axial movement of the shaft  14  being required. 
     In the preferred form of the grinder the grinder element G is a  7  start ceramic element as can be seen in  FIG. 3 . The grinder element G′ is preferably also ceramic with a multiplicity of inclined teeth. 
     Extending transversely to the lever handle  11  is a push element  21 , which incorporates a rack  22  formed by a plurality of teeth  23 . The teeth  23  of rack  22  meshingly engage with the teeth of a gear element which in the preferred form of the invention is a toothed ring  15 . The actual number of teeth  23 , of rack  22 , which engage with drive ring  15  is illustrated in  FIG. 10 . 
     The drive ring  15  and rack  22  thus form two elements of the drive mechanism according to the present invention. The third element is a split sleeve  16 . 
     As with the arrangement disclosed in NZ 528128 the top of the body  12  is closed by a cover  17  in which is an opening  18 , through which the grindable material can be loaded into the body  12 . According to this particular form of the invention, the cover  17  includes a pair of spaced parallel grooves  20  into each of which a projecting portion  20   a  of the push element  21  is slidingly engaged. 
     As can be seen in  FIG. 1  the push element  21  is essentially hollow. Thus, as the lever  11  is pivotally moved toward the body  12 , the combination of the gear ring  15  and split sleeve  16  move into the confines of the push element  21 . There is a cut away portion  24  in the floor  25  of the push element  21  so as to provide a clearance for the shaft  14 . 
     As is illustrated in  FIG. 1  a spring  26  engages at one end on an abutment  27  on the upperside of the push element  21 . A rod  28  engages through the spring  26  and abutment  27 . End  29  of the rod  28  is engaged within the upper casing  45 , which fits onto the top of the body  12  as is disclosed in NZ 528128 and shown in  FIGS. 1 ,  2  and  4  hereof. While only one spring and rod combination is illustrated a second combination of rod and spring engages with second abutment  27   a  (see  FIGS. 5 and 8 ). 
     Thus, as the lever  11  is moved toward the body  12  the springs  26  compress and provide a restoring force to the lever  11  upon the user releasing pressure on the lever  11  (this action is as described in NZ 528128). Thus, when a pull or “squeeze” type action is applied to the lever  11  by the end user, the toothed ring  15  rotates and, as will hereinafter described, via the split sleeve  16 , applies a torque to the shaft  14  thereby rotating the shaft. However, upon the lever  11  being released the interaction of the rack  22  and the toothed ring  15  causes the ring  15  to rotate in the opposite direction. As will be described. no torque or driving force is applied to the shaft  14  during this counter rotation. 
       FIG. 10  of the drawings illustrates that the toothed ring  15  has about its peripheral outer edge a plurality of teeth  30 , which mesh with teeth  23  of rack  22 . The teeth extend about nearly all of the peripheral edge except for a non-toothed portion  31 , which includes an area of reduced thickness thereby forming a web  32 . An opening  33  (see  FIG. 11 ) extends through the web  32  and is positioned closer to an inner edge surface  34  which is flat. 
     The split sleeve  16  (see  FIGS. 11 and 12 ) has a straight-sided portion  35  and extending therebelow a frustro conical portion  36 . The internal dimensions of the bore  37 , which extends through the split sleeve  16 , are such that when the shaft  14  is to fitted therein, there is a snug fit but yet one which permits the split-sleeve to rotate on the shaft. This will hereinafter become apparent. 
     In a preferred form of the invention the shaft  14  has fitted thereto a sleeve  14   a  of plastic material (see e.g.  FIG. 15 ). This sleeve  14   a  engages in the bore  37  of split sleeve  16 . Preferably the sleeve  14   a  is formed by over-moulding the shaft  14  with TPU/polyurethane or other material suitable for the end purpose. Equally a metal, preferably knurled, shaft could be used. 
     Projecting laterally of the upper portion  35  of split sleeve  16  is a pair of flanges  38 . The distance between these flanges  38  is slightly more than the thickness of the web  32 . These flanges  38  each have an opening  39 , which are aligned. When the flanges  38  are located over the web  32  the openings  29  become aligned with hole  33  in the web  32 . A pin  40  (see  FIG. 9 ) can thus be engaged through the aligned openings  33  and  39  to capture the flanges  38  onto the web  32 . The pin  40  has its axis of rotation offset to the central longitudinal axis of bore  37  of split sleeve  16 . 
     The flanges  38  include abutments surfaces  51  (see  FIG. 1-2 ) which are located opposite abutment surfaces  52  of the first toothed element  15 . Because of the position of the pivot pin  40  and a clearance between the abutment surfaces  51  and  52 , the split sleeve  16  is capable of angular displacement relative to the toothed gear element  15  about the axis of pivot  40 . Thus under the influence of the spring  44  (described in hereinafter) the movement of the split sleeve  16  relative to the toothed element  15  is not restricted but the degree of movement of the split ring  16  in the reverse direction is limited by contact between the abutment surfaces  51  and  52 . This reverse movement is one which will occur upon the rack  22  retracting to the rest position of the lever  11 . 
     The split sleeve  16  is thus capable of limited angular displacement (relative to toothed ring  15 ) about the longitudinal axis of pin  40 . 
     A gap  41  extends for the full length of the sleeve  16  so as to form the split in the sleeve. 
     In the peripheral wall surface of the upper portion  35  of split sleeve  16 , and adjacent the split  41 , there is a profiled portion which forms a projection  42 . This, as is shown in  FIG. 12 , can engage with a profiled edge portion  43  of ring  15  for reasons, which will hereinafter be apparent. The edge portion  43  is formed by the inside peripheral wall of the toothed ring  15  being profiled inwardly toward the centre of the toothed ring  15 . 
     Preferably, a spring  44  is engaged between the flanges  38  and has one end engaged in a recess (not shown) in the outer peripheral surface of the top portion  35  of the split sleeve  16 . The other end of spring  44  engages against the flat surface  34  of web  32 . 
     The upper casing  45 , which engages onto body  12  over the cover  17 , forms a housing in which the drive mechanism is located. A chute or funnel  46  extends from an open end on the top of the casing  45  to fit at a lower end in the opening  18  in the cover  17 . A lid  47  covers the open top of the chute  46  but is rotatable away to uncover the open end by virtue of the cover  47  having a split stub shaft  48  which engages through an annular boss  49  which projects upwardly from the top of the upper casing  45  (see  FIG. 4 ). 
     As a consequence the lid can be rotated to one side to expose the open end of the chute  46  and thereby enable the grindable material to be poured into the body  12 . It will be appreciated that this action can be achieved without any disassembly of the manual grinder, this being typically a problem with known manual grinders where at least some form of disassembly is required to achieve this function. Furthermore, with the present invention the chute  46  ensures that no grindable material gets into the area in which the drive mechanism is located. The drive mechanism is thus effectively in a closed housed relative to the grindable material. 
     As can be seen more clearly in  FIGS. 1 and 2  the split sleeve  16  when installed on the end of the shaft  14  has the frustro-conical portion  36  located in the well  19 . Extending about the portion of the top of the shaft  14 , which extends through the well  19  is one or, as shown, two resilient rings  50 . These engage between the wall of the well  19  and the over-moulded sleeve  14   a.  The reason for the ring(s)  50  will hereinafter become apparent in the following description of the operation of the drive mechanism. 
     The tangential direction and-position (on the periphery of toothed ring  15 ) of the force applied to the toothed ring  15  by the rack  22  causes a relative movement to occur between the ring  15  and split sleeve  16  as the lever  11  is moved from the “rest” position of  FIG. 1  to the full stroke position of  FIG. 2 . As a result the edge potion  43  of toothed ring  15  and projecting profile  42  of split sleeve  16  come into contact. This contact results in a deforming of the split sleeve  16  which effectively causes a reduction of the internal diameter of bore  37 . This creates an immediate gripping effect (or driving contact) between split sleeve  16  and the shaft  14  (via the over-moulded sleeve  14   a ) to occur. 
     It will be appreciated by those skilled in the art that other means for providing a contact to cause contraction of bore  37  could be employed. 
     As a result the linear motion of rack  22  is translated into a rotary motion of toothed ring  15  such that rotation of shaft  14  takes place. This gripping or clamping effect occurs immediately the toothed ring  15  ( FIG. 2 ) commences rotation. 
     Upon the lever  11  having reached the full extent of its inward movement toward the body  12 , the lever  11  is released. The push element  21  thus moves under the action of springs  26  to drive  24  moves back to its “rest” position. Immediately, the return travel of the lever  11  commences the split sleeve  16  “opens” thereby releasing any grip on the shaft  14 . Consequently, the combination of split sleeve  16  and toothed ring  15  rotates independently of the shaft  14 . 
     If a pepper or peppers remain in the space between the grinding elements G and G′ the frictional effect will generally retain the shaft  14  so that it does not rotate in a reverse direction. However, when this holding effect against relative movement between the grinding element G and G′ does not exist or is slight (say if the material to be ground is a “light” material e.g. herbs) the friction to keep the grinding mechanism G/G′ and shaft  14  to rotate in a reverse direction might not exist or be sufficient. Therefore, a so-called “friction brake” is provided by the ring(s)  50  which sets up a friction in the well so as to counter any reverse rotation of the shaft  14 . It will be appreciated by those skilled in the art that the frictional contact between the ring(s)  50  and the surface of the well will be greater than any frictional contact between the split sleeve  16  an over-moulded sleeve  14   a  in the reverse direction. 
     It will be appreciated by those skilled in the art that other means of applying a friction “brake” can be used. However, according to the preferred arrangement of one or more resilient rings  50  a simple neat, yet effective, friction brake is created. As a result the shaft  14  and with it the grinding mechanism G/G′ does not occur in a reverse direction even if the grinder is empty or there is few/light grinding material in the grinding mechanism. 
     In a preferred form of the invention the overmoulded shaft  14  is formed so as to overcome a problem that typically can arise with known condiment grinders/mills. With known designs it is not uncommon for a cavitation effect to arise as a result of rotation of the shaft within the condiment. Thus, with say peppercorns, the corns become packed in the grinder body in such a manner that the corns do not enter into the grinding mechanism. To overcome this problem the user generally needs to shake the grinder to loosen up the peppercorns so that they once again freely move into the grinder mechanism. 
     Because of the overmoulding the present invention permits one or more spiral flutes, grooves, recesses or the like to be formed in the overmoulding. Thus, in  FIG. 15  one embodiment is shown where a pair of spiral flutes  54  are formed in the overmoulded material. Therefore as the shaft  14  rotates, the flutes  54  apply a mixing action on the condiment such that it does not cavitate or otherwise pack in the container body  12 . 
     A further advantage is that the flutes  54  enable a user, viewing the shaft  14  through the transparent body  12 , to see the shaft turning when the lever  11  is squeezed and stationary when the lever  11  is released. 
     In effect, therefore, the mechanism is such as to achieve a radial clamping force resulting from a linear force, which is normal to the axis of the shaft  14  and tangential to the periphery of the toothed ring  15 . These clamping and release actions on the shaft  14  are achieved immediately the lever  11  commences its inward travel/outward travel. The drive is thus unidirectional. Any lost motion which may occur will be as a result of backlash of the teeth of the rack engaging the tooth ring. However, this backlash is only present when movement commences and not during the grinding action. Accordingly, a maximum degree of rotation of the shaft  14  is achieved during each movement of the lever  11  toward the body  12 .