Abstract:
An adjustable scale typically used with a router table may be reset at any time to facilitate determining the change in height of the router regardless of where the scale is positioned when the router is at a given height. When used with a router table having a table plate with a height adjustment screw for adjusting the height of the router, the scale includes a marker carried by the table plate or the adjustment screw. When carried by the adjustment screw, the marker is rotatable relative to the adjustment screw to align markings thereon with a reference mark on the table plate to reset the scale. Thus, a zero marking may be aligned with the reference mark at any height of the router, and the adjustment screw and marker may then be rotated together to adjust the height of the router and simultaneously measure the height change.

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The invention relates generally to a scale for measuring the distance an object has moved. More particularly, the scale is used for measuring the distance that such an object moves in response to rotation of an adjusting screw. Specifically, the scale is adjustable so that it may be reset to a reference point regardless of the position of the adjustment screw. 
   2. Background Information 
   Router tables and the like typically utilize an adjustment screw for adjusting the height of the carriage and router carried thereby relative to the work surface of the table. It is known in the art to include a scale on the adjustment screw which has markings which are alignable with a reference point or mark on the table in order to determine the change in height of the router as the adjustment screw is rotated. However, a problem that arises with the use of such scales is the need to track and calculate the height adjustment between two positions as the adjustment screw is rotated. That is, when the markings of the scale are not zeroed to the reference point when beginning a height adjustment, the user is required to subtract numbers which may easily cause user error. In addition, when the reference point is positioned between an adjacent pair of markings on the scale, it is more difficult to ascertain the exact starting position of the adjustment screw and thus the exact height of the router or the like. Thus, beginning a height adjustment at such an “in between” position of the markings, the calculation of the height adjustment becomes more difficult. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention provides an apparatus comprising a first table plate member defining a through hole adapted to receive a rotary cutting member of a rotary cutter; a first threaded member rotatably mounted on the table plate member; a carriage which is adapted to carry the rotary cutter and which threadedly engages the first threaded member and is movable toward or away from the table plate member in response to rotation of the first threaded member; a marker carried by and selectively rotatable relative to one of the first members; a reference mark on one of the marker and the first member not carrying the marker; a plurality of markings on the other of the marker and the first member not carrying the marker. 
   The present invention further provides a method comprising the steps of moving a marker relative to a first table plate member defining a rotary cutter member-receiving through hole and a first threaded member rotatably mounted on the first table plate member to align a first mark carried by the marker with a second mark carried by the first member not carrying the marker; and rotating the first threaded member to move a rotary cutter carriage threadedly engaged with the first threaded member toward or away from the first table plate member and to position a third mark on one of the marker and first member not carrying the marker adjacent the mark carried by the other of the marker and first member not carrying the marker. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a front elevational view with portions cut away of a router table and a router mounted thereon with which the adjustable scale of the present invention is used. 
       FIG. 2  is a side elevational view with portions cut away of the router table and router of  FIG. 1 . 
       FIG. 3  is a sectional view taken on line  3 - 3  of  FIG. 1 . 
       FIG. 4  is a sectional view taken on line  4 - 4  of  FIG. 3 . 
       FIG. 5  is similar to  FIG. 3  and shows a handle rotating the adjustment screw and adjustable scale. 
       FIG. 6  is a fragmentary side elevational view similar to  FIG. 2  showing the handle rotating the adjustment screw to move the router to a first height. 
       FIG. 7  is similar to  FIG. 6  and shows a workpiece on the router table being cut by the router bit at the first height. 
       FIG. 8  is similar to  FIG. 5  and shows a manual adjustment of the scale to reset the zero marking at the reference mark while the router is at the first height. 
       FIG. 9  is similar to  FIG. 5  and shows the handle further rotating the adjustment screw and the adjustable scale so that another marking thereon is aligned with the reference mark. 
       FIG. 10  is similar to  FIG. 6  and shows the handle rotating the adjustment screw to raise the height of the router and cutter bit to a second height. 
       FIG. 11  is similar to  FIG. 7  and shows the workpiece being cut with the router bit at the second height. 
   

   Similar numbers refer to similar parts throughout the drawings. 
   DETAILED DESCRIPTION OF THE INVENTION 
   The adjustable scale of the present invention is shown generally at  10  in  FIGS. 3 ,  4  and  8  in use with a router table  12  shown in  FIGS. 1 and 2 . Referring to  FIGS. 1 and 2 , router table  12  includes a plurality of legs supporting a table top  14  and a table plate  16 . Table top  14  and table plate  16  have an upper side each of which is flat and coplanar to define a work surface  18  which is substantially horizontal. Table plate  16  has a lower side  20  and defines a bit-receiving through hole  22  ( FIGS. 2-3 ) extending from the upper side to the lower side thereof. Table plate  16  further defines a second through hole  24  ( FIGS. 3-4 ) extending from the upper to the lower side thereof for receiving therein a portion of an adjustment screw  26 . Hole  22  receives therein a cutting member in the form of a cutter bit  28  having an upper surface  30 . Cutter bit  28  is rotatably mounted on a router  32  having an electric motor for powering rotation of bit  22 . Router  32  includes a pair of handles  34  extending outwardly from the body thereof. Router  32  is mounted on a carriage  36  comprising first and second clamping members  38  and  40 , a threaded rod  42  extending therebetween and a handle  44  threadably engaging rod  42  and rotatable to tighten and loosen the clamping members to clamp router  32  therebetween or release said clamping thereof. Clamping member  38  defines an internally threaded hole  46  and includes a pair of elongated bushings  48  defining through holes  50  for receiving therein a respective pair of guide bars  52  on which bushings  48  are slidably mounted. Guide bars  52  extend downwardly from table plate  16  and are rigidly mounted thereon by mounting screws  54  ( FIG. 3 ). 
   Referring to  FIGS. 3 and 4 , adjustment screw  26  includes a cap  56  which is disposed in hole  24  and an externally threaded rod  58  mounted thereon. More particularly, cap  56  defines an internally threaded hole  60  extending upwardly from the lower end thereof which threadably engages the upper end of rod  58  so that rod  58  is rigidly mounted on cap  56 . Hole  24  in table plate  16  includes a lower narrower portion  62 , a wider counterbore portion  64  and a beveled countersunk portion  66 . Table plate  16  includes an annular flange  68  which extends radially inwardly from a body of plate  16 . Flange  68  has an inwardly facing surface bounding lower portion  62  and an upper horizontal ledge  70  which bounds wider portion  64 . Flange  68  typically includes a bushing (not shown) which bounds narrower portion  62 . Cap  56  is rotatably mounted within hole  24  about a substantially vertical axis and includes a portion which slidably engages the inner surface of flange  68  during rotation thereof. Cap  56  defines an annular recess or groove  72  extending inwardly from the outer surface thereof and spaced downwardly from lower side  20  of table plate  16 . Cap  56  has a tool engaging portion in the form of a hexagonally-shaped opening  74  which is accessible from the upper side of table plate  16  and configured to receive a mating hexagonal portion of a tool in the form of a handle  76  ( FIGS. 5-6 ) used for rotating adjustment screw  26 . Cap  56  defines an annular recess  78  which extends downwardly from the upper end thereof and circumscribes an upper portion of cap  56  and a portion of opening  74 . Recess  78  has a substantially rectangular configuration as viewed from the side and is bounded in part by an annular surface  80  which extends vertically downwardly from the upper end of cap  56  and faces radially outwardly. An annular flange  82  extends radially outwardly from surface  80  and includes upper and lower annular surfaces  84  and  86  each of which is substantially horizontal, with upper surface  84  bounding recess  78 . Flange  82  is disposed in wider portion  64  of hole  24  above flange  68 . Cap  56  further defines an annular recess or groove  88  which extends inwardly from annular surface  80  so that an annular lip  90  overhangs groove  88  adjacent the upper end of cap  56 . 
   Referring to  FIG. 4 , a washer  92  is seated on ledge  70  of flange  68  within wider portion  64  of hole  24 . Lower surface  86  of flange  82  is seated atop washer  92  and slidably engages washer  92  during rotation of cap  56 . Thus, washer  92  is typically formed of a plastic or other type of material which is relatively slippery and has a smooth outer surface to facilitate rotation of cap  56 . The portion of cap  56  which extends below table plate  16  passes through several washers, including a washer  94  which abuts lower side  20  of table plate  16 , a washer  96  spaced therebelow and first and second spring washers  98  and  100  disposed between washers  94  and  96  to provide a downward force on cap  56  via a spring bias. A retaining ring  102  abuts washer  96  and is disposed in annular groove  72  of cap  56  in order to retain adjustment screw  26  on table plate  16  while allowing it to rotate within hole  24 . 
   In accordance with the invention and referring to  FIGS. 3-4 , adjustable scale  10  includes a substantially flat annular marker  104  which is disposed in annular recess  78  and wider portion  64  of hole  24  so that it is rotatably mounted on cap  56 . Marker  104  has a substantially rectangular cross section which is slightly smaller than that of recess  78 . Marker  104  has substantially flat and horizontal upper and lower surfaces  106  and  108 . Upper surface  106  is disposed below work surface  18  a short distance so that upper surface  106  is manually accessible from the upper side of table plate  16 . Lower surface  108  slidably engages upper surface  84  of flange  82  during relative rotation between marker  104  and cap  56 . Marker  104  has a circular outer circumference or surface  110  defining a diameter of marker  104  which is slightly smaller than the diameter of wider portion  64  so that outer surface  110  is spaced slightly inwardly from the portion of table plate  16  defining wider portion  64 . Marker  104  also has a circular inner circumference or surface  112  defining a through hole  114  which receives therein the portion of cap  56  circumscribed by annular surface  80  thereof. Marker  104  thus also circumscribes a portion of opening  74 . Marker  104  further defines an annular recess or groove  116  which extends outwardly from inner surface  112 . A frictional engagement member in the form of an O-ring  118  is disposed partially within groove  116  and partially within groove  88  so that O-ring  118  engages each of cap  56  and marker  104 . O-ring  118  thus provides for a frictional engagement with marker  104  to maintain marker  104  in a fixed relation with respect to cap  56  unless a sufficient force is applied to marker  104  to overcome the frictional engagement with O-ring  116  and thus allow the rotation of marker  104  relative to cap  56 , during which marker  104  slidably engages O-ring  118 . Marker  104  and screw  26  rotate about a common axis. O-ring  118  is typically formed of an elastomeric material or another material which has sufficient flexibility and resilience to allow it to stretch over lip  90  and retract into groove  88 . These characteristics also allow marker  104  to be press fit into place within recess  78  such that the lip of marker  104  disposed below groove  116  forces O-ring  118  inwardly during assembly with O-ring  118  subsequently expanding into groove  116  to mount marker  104  on cap  56 . 
   Referring to  FIG. 3 , upper surface  106  of marker  104  adjacent outer surface  110  is preferably knurled as indicated by the shading at  120  in order to provide a rough surface to facilitate manual rotation of marker  104 . A plurality of markings  122  are evenly circumferentially spaced along the outer circumference of marker  104  and include four markings which are specifically number “0”, “8”, “16” and “24”. While the markings may represent a variety of specific measurements, typically they represent thousands of an inch as it relates to the height change of carriage  36  and router  32  during rotation of adjustment screw  26 . Markings  122  are alignable with a reference point or mark  124  disposed on work surface  118  of table plate  16 . 
   The operation of adjustable scale  10  is now described with reference to  FIGS. 5-11 . Referring to  FIGS. 5 and 6 , handle  76  is rotated as indicated at Arrows A to rotate adjustment screw  26  and marker  104  as indicated at Arrow B to raise carriage  36  and router  32  as indicated at Arrow C so that upper surface  30  of bit  28  is disposed at a first height H 1  above work surface  18 . This rotation of adjustment screw  26  and marker  104  has caused marker  104  to move from the position shown in  FIG. 3  in which the “0” marking  122  is aligned with mark  124  to the position shown in  FIG. 5  in which a marking  122  which would be associated with “26” if numbered is aligned with mark  124 , thus indicating that carriage  36 , router  32  and cutter bit  28  have been raised 26/1000 of an inch, assuming less than one full rotation. 
   As shown in  FIG. 7 , router  32  is operated so that cutter bit  28  cuts a workpiece  126  while at first height H 1 . After this cut has been made and referring to  FIG. 8 , a force is manually applied as indicated at Arrow D to upper surface  106  of marker  104  to rotate marker  104  as indicated at Arrows E relative to cap  56  in order to align the “0” marking  122 A with mark  124 . Marker  104  has thus been reset to a zero position while cutter bit  28  is at first height H 1 . Referring to  FIGS. 9-10 , handle  76  is then rotated as indicated at Arrow F to rotate adjustment screw  26  and marker  104  together as indicated at Arrow G to raise carriage  36 , router  32  and cutter bit  28  so that upper surface  30  thereof has moved to a second height H 2 . More particularly, marker  104  has been rotated from the position shown in  FIG. 8  with marking  122 A aligned with mark  124  to the position shown in  FIG. 9  with the “8” marking  122 B aligned with mark  24 , thus indicating that upper surface  30  of bit  28  has been moved 8/1000 of an inch from height H 1  to height H 2 . As shown in  FIG. 11 , router bit  28  then cuts workpiece  126  when disposed at height H 2 . Adjustable scale  10  thus greatly facilitates the ability to track the change in height of a cutting member when moved from any particular height as represented by height H 1  to any other height as represented by height H 2 . 
   It will be appreciated by one skilled in the art that various changes may be made within the scope of the present invention. For example, it will be understood that the plurality of markings shown on marker  104  may be disposed on the work surface of table plate  16  while a single mark may be located on a marker similar to marker  104 . In addition, it will be understood that a marker may be mounted directly on table plate  16  in a recess formed therein so that such a marker is rotatably mounted on the table plate and out of contact with the adjustment screw, thus still allowing for the relative rotation of such a marker and the adjustment screw wherein the adjustment screw would include a mark or marking alignable with such a marker. In addition, it will be evident that the adjustable scale of the present invention may be used in other settings although it is most preferably used with a router or another rotary cutter. 
   In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. 
   Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.