Abstract:
A tool support incorporates height adjustment and locking features in common components. A pivoting door is used to control the engagement of a height adjustment threaded shaft with the bearing flange of the power tool, with the position of the pivoting door controlled by a manual actuator. In one position the manual actuator allows the door to pivot outward to disengage the height adjustment shaft from the bearing flange. In a second position the manual actuator moves the door to engage the height adjustment shaft with the bearing flange to permit “micro” height adjustment by rotation of the height adjustment shaft. In a third position the manual actuator presses the door into the height adjustment shaft to effectively lock the shaft in position.

Description:
PRIORITY CLAIM 
       [0001]    This application is a non-provisional filing of and claims priority to co-pending provisional application No. 61/920,901, filed on Dec. 26, 2013, the entire disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to hand-held power tools, and more particularly hand-held power tools having a base for supporting the tool, such as trim routers. 
         [0003]    One form of conventional trim router or laminate trimmer power tool is shown in  FIGS. 1-2 . The power tool  10  is carried by a tool support  12  that provides a base or foot plate  15  for supporting the tool on a workpiece. The tool support  12  includes a clamping cuff  14  that is configured to support the tool  10  with the working end  11  at a user-selected height above the workpiece. In order to adjust the working height, the tool support  12  includes a height adjustment assembly  20  with a thumb screw  22  that is used to manually rotate a threaded post  24  within a threaded socket defined between the tool  10  and the tool support  12 . A clamping device  16  is provided to clamp opposite halves  12   a,    12   b  of the support about the tool once the user-selected height has been attained. 
         [0004]    As seen in  FIGS. 1-2 , the conventional tool support  12  for a trim router  10  relies upon two separate components at two locations on the support to adjust and fix the power tool at the desired working height. There is a need for an apparatus that simplifies the adjustment and locking features of a support for a power tool. 
       SUMMARY 
       [0005]    The present disclosure contemplates a tool support that incorporates height adjustment and locking features in common components. In one aspect, a pivoting door is used to control the engagement of a height adjustment threaded shaft with the bearing flange of the power tool, with the position of the pivoting door controlled by a manual actuator. In one position the manual actuator allows the door to pivot outward to disengage the height adjustment shaft from the bearing flange. In a second position the manual actuator moves the door to engage the height adjustment shaft with the bearing flange to permit “micro” height adjustment by rotation of the height adjustment shaft. In a third position the manual actuator presses the door into the height adjustment shaft to effectively lock the shaft in position. It can be appreciated that a single component, the manual actuator, allows the tool operator to lock, unlock and perform height adjustment of the tool. 
         [0006]    A tool support is provided for supporting a power tool at adjustable heights relative to a base of the tool support. In one aspect, the tool support includes a clamping cuff connected to the base and configured to receive the elongated body of the power tool therethrough at adjustable heights above a work surface. The body of the power tool includes a bearing flange in sliding engagement with the clamping cuff. The clamping cuff defines an opening with the bearing flange accessible through the opening and a door movably mounted to the clamping cuff for movement toward the bearing flange through the opening. In one feature, the door and the bearing flange each include a threaded half-bore that together form a threaded bore when the door is directly adjacent the bearing flange. A height adjustment mechanism includes a thumbwheel driven threaded shaft disposed between the door and the bearing flange and configured to threadedly engage the threaded half-bore in the bearing flange when the door and the bearing flange are directly adjacent such that rotation of the threaded shaft adjusts the height of the elongated body of the power tool relative to the base. An actuator is provided for selectively moving the door and the bearing flange directly adjacent to form the threaded bore. 
         [0007]    In one aspect, the tool support includes a force generating component that generates a different force corresponding to the position of the actuator, with one force operable to push the door directly adjacent the bearing flange to form the threaded bore, and a greater force operable to squeeze the threaded shaft between the half-bores sufficiently to prevent vertical movement of the power tool relative to the base 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0008]      FIG. 1  is a perspective view of a conventional trim router and tool support. 
           [0009]      FIG. 2  is a side view of the conventional trim router shown in  FIG. 1 . 
           [0010]      FIGS. 3 a , 3 b    are front and side views of a tool support for a trim router according to one aspect of the present disclosure. 
           [0011]      FIG. 4  is an enlarged side view of the tool support shown in  FIG. 3  showing the actuation knob of the support in a first position according to one feature of the present disclosure. 
           [0012]      FIG. 5  is a bottom cross-sectional view of the tool support shown in  FIG. 4 . 
           [0013]      FIG. 6  is an enlarged side view of the tool support shown in  FIG. 3  showing the actuation knob of the support in a second position according to one feature of the present disclosure. 
           [0014]      FIG. 7  is a bottom cross-sectional view of the tool support shown in  FIG. 6 . 
           [0015]      FIG. 8  is an enlarged side view of the tool support shown in  FIG. 3  showing the actuation knob of the support in a third position according to one feature of the present disclosure. 
           [0016]      FIG. 9  is a bottom cross-sectional view of the tool support shown in  FIG. 8 . 
           [0017]      FIG. 10  is an enlarged partial phantom view of the actuator shown in  FIGS. 4-9 . 
           [0018]      FIG. 11  is an enlarged partial cross-sectional view showing a thumb screw interface according to one aspect of the present disclosure. 
           [0019]      FIG. 12  is an exploded view of the tool support and actuator according to the present disclosure. 
           [0020]      FIG. 13  is an enlarged perspective view of the leaf spring shown in  FIG. 12 . 
           [0021]      FIG. 14  is perspective view of a wave spring stack for use with the tool support. 
           [0022]      FIGS. 15 a - c    are side and top perspective views of a wave spring arrangement according to one aspect of the present disclosure. 
           [0023]      FIG. 16  is a perspective view of a cam plate according to a further aspect of the present disclosure. 
           [0024]      FIGS. 17 a - d    show the wave spring arrangement and cam plate of  FIGS. 15-16  incorporated into a tool support according to the present disclosure. 
           [0025]      FIGS. 18 a , 18 b    show the wave spring arrangement and cam plate in a first position. 
           [0026]      FIGS. 19 a , 19 b    show the wave spring arrangement and cam plate in a second position. 
           [0027]      FIGS. 20 a , 20 b    show the wave spring arrangement and cam plate in a third position. 
           [0028]      FIGS. 21 a , 21 b    show the wave spring arrangement and cam plate in a fourth position. 
           [0029]      FIGS. 22 a , 22 b    show perspective and top views of a modified cam plate. 
           [0030]      FIG. 23  is a top view of the modified cam plate of  FIG. 22  with a detent spring according to a further aspect of the present disclosure. 
           [0031]      FIG. 24  is a perspective view of an adjustable pre-bias feature according to the present disclosure. 
           [0032]      FIGS. 25 a , 25 b    are cross-sectional and perspective views of an adjustable pre-bias feature according to a further aspect of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the disclosure is thereby intended. It is further understood that the present disclosure includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles disclosed herein as would normally occur to one skilled in the art to which this disclosure pertains. 
         [0034]    A tool  10  is shown in  FIGS. 3 a - b    mounted within a tool support  30  according to the present disclosure. The tool support  30  includes a base  31  configured to rest on the work surface, and a clamping cuff  32  configured to clamp to the bearing flange  50  of the power tool  10  at adjustable heights. The tool support may be provided with a safety lever assembly  80  that is configured and operates similar to the safety levers of prior devices. However, the safety lever assembly  80  is not required for the height adjustment and locking features of the tool support disclosed herein. In another embodiment, the safety lever assembly  80  may be used as an indicator to the user that the tool is engaged into a height adjustment system (as described herein). The assembly  80  may thus incorporate a human readable indicator. 
         [0035]    The clamping cuff defines an opening through which the bearing flange is accessible and a door  40  at the opening and pivotably mounted to the clamping cuff  32  at a hinge  41 . The hinge includes a biasing element  41   a  ( FIG. 4 ), such as a torsion spring, leaf spring, spiral spring, serpentine spring or other suitable spring element configured to bias the door to an open position outward or away from the clamping cuff. In a further embodiment, the material of the hinge  41  may be adapted to form the biasing element. In yet another embodiment, an electric or electronic component, such as a transistor, may be used to form the biasing element. An actuator  42  is provided that controls the position of the door  40  and controls both the height adjustment and locking features of the tool support  30 , as described below. 
         [0036]    As shown in the detail views of  FIGS. 4-11 , the actuator  42  includes a knob  47  that is configured to be manually rotated. The knob  47  is rotatably attached to a mounting boss  45  on the clamping cuff  32  by way of a mounting screw  44 . The knob is rotatable to three distinct positions defined by detent recesses  60   a,    60   b,    60   c  formed on the surface of the clamping cuff, as best seen in  FIG. 10 . The knob  47  may include a detent post or cap  62  that is biased by a spring  63  to project outward from the actuator surface  48  of the knob, as shown in  FIG. 7 . The cap  62  clicks into one of the detents  60   a,    60   b,    60   c  when the knob is appropriately aligned. The three positions correspond to a “macro” height adjustment position ( FIGS. 4-5 ), a “micro” height adjustment position ( FIGS. 6-7 ) and a locking position ( FIGS. 8-9 ). 
         [0037]    In the “macro” height adjustment position, the knob  47  is rotated to its uppermost position corresponding to the indicia  43   a.  The indicia  43   a  signifies that the clamping cuff  32  is “unlocked” relative to the bearing flange  50  of the power tool  10 . In this position, the power tool  10  may be manually moved up and down relative to the tool support to effect a “macro” adjustment of the height of the power tool, and more pertinently to position the working end  11  near or in contact with the working surface beneath the base  31 . The knob  47  includes an actuator surface  48  that faces the door  40  and more particularly the free or opening end  40   a  of the door. A detent projection  54  is defined at the opening end  40   a  of the door in a position beneath the actuator surface  48 . The knob  47  defines a recess  52  in the actuator surface facing the door that is configured to receive the detent projection  54 . When the recess  52  is aligned with the projection the biasing spring  41   a  biases the door  40  outward to the position shown in  FIG. 5  so that the projection  54  seats within the recess  52 . 
         [0038]    The height adjustment assembly  34  includes a thumb wheel  35  and a threaded shaft  37 . The thumb wheel and threaded shaft are carried by the door  40 , and more specifically by a threaded half-bore  38  defined in the door, as shown in  FIGS. 5 and 11 . The threaded shaft  37  is supported in threaded engagement with the half-bore  38  in the door. The bearing flange  50  of the power tool  10  defines the mating threaded half bore  39  so that when the bearing flange and door are directly adjacent the two half-bores combine to form a continuous threaded bore for the height adjustment threaded shaft  37 . Rotation of the thumb wheel  35  rotates the shaft  37  and the threaded engagement between the shaft and the threaded half-bore  39  in the bearing flange causes the flange  50  to move up and down, depending upon the direction of rotation of the thumb wheel. When the knob  47  is rotated to this position the post  62  clicks into the recess  60   a  and the user has an audible indication that the clamping cuff  32  is able to receive the power tool  10 . 
         [0039]    The tool support  30  may be provided with a guide pin  33  ( FIG. 12 ) that operates as an alignment pin projecting inward from the inner surface  32   a  of the clamping cuff  32 . The guide pin may interface with a corresponding vertical groove (not shown) defined in the outer surface of the power tool or bearing flange  50  to establish the proper circumferential position of the power tool. The guide pin  33  may be mounted, attached or fixed to the clamping cuff in a conventional manner, or may be monolithic component integrated into the inner surface  32   a  of the cuff  32 . 
         [0040]    The macro-adjustment position is provided when the knob  47  is aligned with indicia  43   a , as shown in  FIGS. 4 . When the knob  47  is rotated to this position the post  62  clicks into the recess  60   a  and the user has an audible indication that the clamping cuff  32  is able to receive the power tool  10 . In this position, the door  40  is essentially open, meaning that it is offset from the bearing flange  50  so that the threaded half-bore  39  of the bearing flange is offset sufficiently from the threaded half-bore  38  of the door so that the threaded shaft  37  is unable to engage the threads of the bearing flange half-bore. In this position, the power tool can be moved freely up and down within the clamping cuff. It is, however, contemplated that the bearing flange and clamping cuff will form a close running fit so that there may be some slight resistance to the relative vertical movement. 
         [0041]    After the power tool  10  has been positioned within the tool support  30  in a desired “macro” position, the knob  47  can be rotated to the position shown in  FIGS. 6-7  corresponding to the “micro” height adjustment position. In this position, the cap  62  engages the middle recess  60   b  in the clamping cuff adjacent the indicia  43   b  signifying that the height of the power tool can be adjusted using the thumb wheel  35 . As shown in  FIG. 7 , in this position the free end  40   a  of the door  40  is pushed inward toward the bearing flange  50  of the power tool. This movement may be caused by the detent projection  54  contacting a shallow detent recess  52  in the actuator surface  48  of the knob  47 . 
         [0042]    The tool support includes a force generating component for applying a selectable force to the door to first move the door into a position immediately adjacent the bearing flange to form the threaded bore between the two half-bores  38 ,  39 , and then to subsequently apply a greater force to clamp the threaded shaft  37  between the half-bores. In one embodiment, the force generating component includes a leaf spring  67  mounted to the actuator surface  48  of the knob, as best shown in  FIGS. 9 and 10 . The leaf spring  67  can be configured as shown in  FIGS. 12-13  to include three portions  67   a,    67   b,    67   c.  The end of the leaf spring adjacent the portion  67   a  is fastened to the knob by a mounting screw  68  ( FIG. 9 ) so that the leaf spring  67  bears against the free end  40   a  and detent projection  54  of the door  40  and so that the portions  67   a,    67   b,    67   c  are essentially cantilevered at the mounting screw. The portion  67   b  at the opposite end of the spring  67  contacts a channel  65  defined in the actuator surface  48  of the knob  47 . As best seen in  FIG. 13 , leaf spring the portion  67   c  is a transition from the portion  67   a  to the portion  67   b  that bears against the channel  65  in the knob. This transition  67   c  provides the spring force for the leaf spring in a conventional manner. The portion  67   b  is also free to slide within the channel  65  as the spring is depressed by contact with the detent projection  54 . 
         [0043]    Returning to  FIG. 7 , in the micro-adjustment position the intermediate portion  67   b  of the leaf spring  67  bears against the detent projection  54  with sufficient force to push the door inward in directly adjacent relation with the bearing flange  50 , and thus to push the threaded shaft  37  into threaded engagement with the other threaded half-bore  39  in the bearing flange  50 . It can be noted that the cap  62  may be configured to engage the intermediate recess  60   b  (see  FIG. 10 ) with an audible and/or tactile indication that the knob is in the “micro” height adjustment position. 
         [0044]    In the macro-adjustment position shown in  FIGS. 4-5 , the knob  47  is rotated upward so that the free end of the leaf spring  67  adjacent the portion  67   b  is in contact with the detent projection  54  of the door  40 . At this position, the spring force of the leaf spring  67  is at its lowest. The spring may be further configured so that in the macro-adjustment position the detent projection is aligned with the transition portion  67   c.  As the knob is rotated downward (or clockwise in the figures), the leaf spring contacts the detent projection at locations of the spring nearer and nearer to the fixed mounting at the anchored end of portion  67   a.    
         [0045]    Once the “micro” height adjustment is completed, the knob  47  can be rotated to the locking position depicted in  FIGS. 8-10 . The knob is rotated to its lowermost position adjacent the indicia  43   c  signifying that the clamping cuff  32  is locked onto the bearing flange  50  and tool  10 . In this position, the actuator surface  48  may be configured to push against the detent projection  54  with sufficient force to press the door into the threaded shaft  37 , which thus presses the shaft into the other half-bore  39  with sufficient force to prevent or restrict rotation of the threaded shaft within the bore. Alternatively, the leaf spring  67  is rotated with the portion  67   a  in contact with the detent projection  54 . In the locking position, the full spring force of the leaf spring  67  bears against the detent projection to push the free end  40   a  of the door inward. The inside surface of the free end  40   a  of the door  40  may be configured to contact the outer surface of the bearing flange  50  when the door is pushed inward by the leaf spring bearing against the detent projection. In another embodiment, the inner surface of the door  40  may be offset outwardly from the surface of the bearing flange so that the full force of the biasing element  67  is transferred to the threads to lock the threads and thumbwheel from further adjustment or rotation. It can again be noted that the cap  62  may be configured to engage the uppermost recess  60   c  (see  FIG. 10 ) with an audible and/or tactile indication that the knob is in the locking adjustment position. It is contemplated that the force applied to lock the threaded shaft within the threaded half-bores need only be sufficient to hold the vertical position of the tool relative to the base. In other words, as long as the threads of the threaded shaft  37  are in engagement with the threads of both half-bores  38 ,  39 , it is necessary for the threaded shaft to essentially unwind or counter-rotate to allow the power tool to drop due to gravity. The inherent friction between the threads will help deter such movement. This inherent friction can be increased by squeezing the threaded shaft between the half-bores by some greater amount than is necessary to form the threaded bore. Thus, while the force applied in the locking position may not be sufficient to prevent manual movement of the threaded shaft by the thumbwheel, it can be enough to prevent counter-rotation of the threaded shaft due to the force of gravity on the power tool, which in turn prevents vertical movement of the power tool from the selected height. 
         [0046]    In one alternative, the leaf spring may be replaced with a wave spring or a nested wave spring configuration  90  as shown in  FIG. 14 . The use of a wave spring arrangement eliminates the potential stress that may arise in the leaf spring at the fixed mounting location. The use of a nested wave spring configuration  90  provides a high clamping force with much reduced stress load on the spring than for the cantilevered leaf spring. The wave spring arrangement can incorporate multiple wave springs nested together, as depicted in  FIG. 14 . This facilitates production of each wave spring which may have a small thickness, and facilitates calibration of the spring force based on the number of layers nested in the wave spring arrangement. 
         [0047]    The wave spring configuration can be modified as illustrated in  FIGS. 15 a - c   . In particular, the wave spring configuration  100  can include a generally flat base portion  101   a  subtending about half the circumference of the wave spring configuration, and two wave portions  101   b,    101   c  occupying the other half of the circumference. In one embodiment the waves  101   b ,  101   c  are spaced apart 110° from each other. The base portion  101   a  is non-functional, meaning that it does not generate a spring force between the knob  47  and door  40 . The base portion  101   a  may incorporate an anti-rotation tab  102  that projects upward into a complementary groove in the knob to prevent the spring from rotating relative to the knob. The wave spring configuration  100  may include a single spring or two or more nested wave springs. As a further alternative, the wave spring arrangement is not fully circumferential but instead may be modified to truncate or remove the base portion  101   a.    
         [0048]    In order to accommodate this modified wave spring  100 , the tool support is modified to incorporate a cam plate  110 , as illustrated in  FIG. 16  between the wave spring configuration  100  and knob  40  on one hand, and the door  40  and clamping cuff  32  on the other. The cam plate  110  includes an upper surface  112  against which the wave spring configuration  100  bears at different stages of rotation of the knob  47 . The cam plate includes a lower cam surface  114  that contacts the door  40  so that the wave spring and cam plate can operate as a force generating component to apply a force to the door as discussed above. In one embodiment, the door  40  is modified to replace the detent projection  54  with a roller arrangement  54 ′, as shown in  FIG. 17 a   . An axle  54   a  is mounted within the edge of the door and a roller  54   b  is mounted for rotation on or rotation with the axle. The use of the roller arrangement  54 ′ in lieu of the detent projection  54  reduces the friction between the door and the knob as the knob is rotated between the three positions. 
         [0049]    The upper surface  112  of the cam plate is configured to accommodate the wave spring arrangement  100 . In particular, the cam plate  110  includes a generally flat portion  112   a  to receive the flat base portion  101   a  of the spring arrangement. The upper surface includes opposite transition portion  112   b  that lead to a wave engaging portion  112   c  which receives the wave portions  101   b,    101   c  of the spring arrangement. The node  101   d  between the two wave portions  101   b,    101   c  contacts the body of the knob  47 , as depicted in  FIG. 17   b.    
         [0050]    The cam surface  114  of the cam plate  110  is configured so that contact with the roller  54   b  transmits spring force from the spring arrangement  100  to the roller arrangement  54 ′ and ultimately to the door  47  in a manner similar to the leaf spring  67  described above. The spring force is variable depending on the portion of the cam surface  114  that is in contact with the roller  54   b.  As shown in  FIG. 17 c   , the cam surface  114  includes five zones. The first zone  114   a  is always offset from the roller  54   b  so that no spring force is exerted on the roller arrangement. The first zone corresponds to the macro-adjustment position, signified by the indicia  43   a  when the knob is rotated to its uppermost position, as shown in  FIG. 4 . As the knob is rotated, the second zone  114   b  contacts the roller which gradually pushes the cam plate  110  upward against the spring arrangement  100 . The third zone  114   c  corresponds to the micro-adjustment position signified by the indicia  43   b  as shown in  FIG. 6 . A fourth zone  114   d  gradually increases the spring force as the cam plate is pushed further upward. When the knob is rotated to its lowermost position corresponding to the locking position  43   c  shown in  FIG. 8  the roller  54   b  is in contact with the fifth zone  114   e.  In this zone the cam plate is pushed upward into the knob to its fullest extent and the spring arrangement  100  is compressed to its limit within the knob. In this zone the spring force exerted against the roller arrangement  54 ′ and door  40  is the greatest in order to lock the components as described above. 
         [0051]    The base  31  and clamping cuff  32  may be integrally formed, such as by casting from a hard durable material. The door  40  may be formed of the same material as the clamping cuff. The door may be mounted to the clamping cuff by the hinge  41  which may be in the form of a typical pivot rod and sleeve arrangement. Other hinge arrangements are contemplated, such as a “living hinge” in which the door is integrally formed with the clamping cuff. The biasing element  41   a  may be a torsion spring, as described above, or another element capable of biasing the free end  40   a  of the door outward and away from the clamping cuff 
         [0052]    The 0 degree position corresponding to the macro-adjustment position indicator  43   a  is shown in  FIGS. 18 a , 18 b   . In this position the roller  54   b  is offset from the zone  114   a  of the plate  110  so no spring force is exerted on the roller arrangement  54 ′ or the door  40 . As shown in  FIG. 18 b   , the clamping cuff  32 ′ defines a circumferential channel  32   a  for receiving the cam plate  110  as the wave spring arrangement  100  pushes against the knob  47  and cam plate  110 .  FIGS. 19 a , 19 b    illustrate the initial contact between the roller  54   b  and the cam surface  114 , in particular at the zone  114   b.  In this position the cam plate  110  has been moved upwards into the knob just in contact with the wave spring arrangement  100 . In one embodiment this contact occurs after about 20 degrees of rotation of the knob and before the knob is at the micro-adjustment position  43   b.    
         [0053]      FIGS. 20 a , 20 b    show the orientation of the roller, cam plate and wave spring arrangement when the knob is rotated to the micro-adjustment position  43   b.  In particular, the roller  54   b  contacts the zone  114   c  of the cam plate  110  which pushes the cam plate further upward into the knob, thereby compressing the wave portions  101   b,    101   c  between the cam plate and the knob. This compression results in a spring force against the roller arrangement  54 ′ and door  40  to bring the threaded bore halves  38 ,  39  together about the threaded shaft  37  to thereby permit the fine height adjustment for the tool. In one embodiment this orientation occurs at about 40 degrees of rotation of the knob  47 . 
         [0054]      FIGS. 21 a , 21 b    show the roller  54   b  contacting the final zone  114   e  of the cam plate  110  when the knob has been rotated to the locking position  43   c.  As the knob is rotated from the micro-adjustment position to the locking position, the roller  54   b  moves along the transition zone  114   d  so that the spring force gradually increases. In the position shown in  FIGS. 21 a , 21 b   , the wave spring arrangement  100  is at its greatest compression between the cam plate and knob so that the spring force is thus at its greatest to lock the threaded shaft  37  within the bore halves and thereby lock the vertical position of the tool. In one embodiment this orientation occurs at about 80 degrees of rotation of the knob  47 . 
         [0055]    In one embodiment, the wave spring arrangement  100  can have a free uncompressed height in the macro-adjustment position ( FIGS. 18 a , 18 b   ) of about 0.300 in. (7.62 mm). In the micro-adjustment position ( FIGS. 20 a , 20 b   ) the wave spring arrangement can be compressed to a height of about 0.269 in. (6.832 mm) for a spring force of about 10 lbf. In the locking position ( FIGS. 21 a , 21 b   ) the spring is further compressed to a height of about 0.216 in. (5.48mm) for a clamping spring force of about 26 lbf. 
         [0056]    In one aspect, the cam plate  110  may be configured to translate uniformly upward as the knob  47  is rotated and the roller  54   b  bears against the successive zones  114   b - 114   e . Alternatively, the cam plate  110  may include a fulcrum  116 , best shown in  FIG. 20 a   , about which the cam plate pivots. The fulcrum  116  is generally opposite the transition zone  114   d  but it is understood that the cam plate  110  will pivot upward about the fulcrum as the roller contacts the transition zone  114   b  and continues through the remaining zones  114   c - 114   e.  The cam plate  110  may be pivotably fastened to the knob at the fulcrum  116 , such as by a pivot pin passing through the knob and fulcrum. 
         [0057]    In the embodiment of  FIGS. 4-10 , the knob  47  includes a spring-biased cap  62  that engages one of three recesses  60   a,    60   b,    60   c  corresponding to the three functional positions  43   a ,  43   b,    43   c  of the knob. In the embodiment of  FIGS. 15-17  incorporating the wave spring arrangement and cam plate, the detent positioning feature for the knob can be incorporated into the cam plate. Thus, as shown in  FIGS. 22 a , 22 b   , a cam plate  120  can be modified from the cam plate  110  to incorporate the detent feature. The cam plate  120  can include an upper surface  121  and cam surface  122  that can be the same as the upper and cam surfaces of the prior cam plate  110 . However, the cam plate  120  includes three detent channels  125   a,    125   b,    125   c  defined in the inner circumferential surface  124  of the cam plate. These three channels are configured to receive a detent spring, such as the detent spring  130  shown in  FIG. 23 . The detent spring  130  includes a base  131  that is fastened to a hub  140  defined on the clamping cuff  32 . The knob is pivotably mounted on the hub  140  and the cam plate  120  is connected to the knob to rotate with the knob as described above. The detent spring  130  is thus held in a fixed position relative to the knob, cam plate and detent channels  125   a,    125   b,    125   c.  The detent spring  130  further includes a detent portion  132  that is configured to seat within any of the channels, such as the channel  125   a  depicted in  FIG. 23 . The free end  133  of the spring rides along the hub  140  so that the spring can deflect as needed to release from a channel when the knob is rotated relative to the hub and detent spring. 
         [0058]    In a further modification, an adjustable pre-load may be applied to the cam plate in addition to the spring force applied to the plate by the wave spring arrangement  100 . Thus, as shown in  FIG. 24  a cantilevered spring  150  may be mounted on a cam plate  110 ′,  120 ′ that has been modified to included support steps  152 ,  153  for supporting the opposite ends of the cantilevered spring  150 . A set screw  155  supported in a modified knob  47 ′ bears against the cantilevered spring  150  to push down on the spring. This downward force is translated to the cam plate  110 ′,  120 ′ through the support steps  152 ,  153  to apply a pre-load. The amount of pre-load can be adjusted by threading the set screw  155  into or out of the knob. 
         [0059]      FIGS. 25 a , 25 b    show a further adjustable pre-load component incorporating a set screw  160  threaded into a bore  161  defined in the mounting screw  44  used to fasten the knob  47  to the housing. The set screw  160  bears against a washer  165  disposed concentrically about the hub  44   a  of the mounting screw and positioned between a shoulder  44   b  of the mounting screw  44  and a shoulder  166  of the knob. As the set screw  160  is threaded into the bore  161  in the mounting screw it bears against the shoulder  166  of the knob, which in turn is resisted by the wave spring arrangement  100 . The set screw  160  can thus be used to adjust the pre-load on the wave spring arrangement  100 . 
         [0060]    While the invention has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications and further applications that come within the spirit of the invention are desired to be protected. 
         [0061]    For instance, in the illustrated embodiments the force generating component operable to apply the force to the door is accomplished through a knob that is rotatably mounted to the clamping cuff. Alternatively the actuator knob  47  may be mounted for movement relative to the clamping cuff other than in a rotary movement. For instance, the knob may be mounted to slide vertically or horizontally relative to the clamping cuff, with appropriate modification to the actuator surface  48 , leaf spring  67 , wave spring arrangement  100 , and cam plate  110 , for instance. In the case of a linear movement, the circumferential features of the force generating components may be arranged linearly so that the linear movement of the actuator knob produces the same force changes described above. Similarly, while the threaded shaft  37  of the height adjustment assembly  34  is integrated with a thumbwheel  35 , the thumbwheel can be replaced with another arrangement for rotating the threaded shaft, such as a gear train or lever arrangement. 
         [0062]    It is further contemplated that in the macro-adjustment position the force generating component may generate no force or only a minimal force on the door. The minimal force is not sufficient to permit threaded engagement of the threaded shaft to the half-bore of the bearing sleeve.