Router depth of cut adjustment

Information

  • Patent Grant
  • 6779954
  • Patent Number
    6,779,954
  • Date Filed
    Wednesday, July 3, 2002
    22 years ago
  • Date Issued
    Tuesday, August 24, 2004
    20 years ago
Abstract
A fixed base router with an adjustable depth of cut comprising a motor unit including a first threads and an output spindle, a router bit operatively connected to the output spindle of the motor unit, an adjustment ring including a second threads for cooperation with the first threads of the motor unit for adjustment of the depth of cut of the router bit, a base for supporting the adjustment ring, and a plurality of clip assemblies for selectably coupling the adjustment ring to the base assembly, and wherein the clip assemblies are simultaneously operable by the fingers of one hand of the person using the router.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates generally to the field of power tools. In particular the present invention relates to a depth of cut adjustment arrangement for a router. More particularly, it relates to a router depth of cut adjustment employing a threaded ring.




2. Discussion




Various types of power tools comprise a cutting tool or bit that is raised or lowered relative to a base that rests on or against the workpiece. Often the tool or bit is attached to the output shaft of a motor unit that can be vertically or axially moved relative to the base. Movement of the motor unit and attached tool bit relative to the base unit determines the depth of cut into the workpiece.




Routers, including some laminate trimmers, are constructed according to this basic design. The router bit is attached to the motor output spindle by means of a tool holder such as a collet or chuck and the bit projects through an opening in the base to contact the workpiece. The motor unit is mounted to the base by means that allow the operator to move the motor and bit axially relative to the base in order to determine the depth of cut of the bit.




Router base and depth of cut systems fall into two commonly recognized categories. They are plunge base routers and fixed base routers (including so-called D-handle bases). Generally speaking, plunge routers comprise a generally planer base element, a motor unit, and a plurality of support columns on which the motor unit is vertically movably mounted above the base. Usually, the motor unit is biased upward or away from the base. Means are provided for finely adjusting the depth of cut and for locking the motor unit at the selected depth/height against the biasing force.




Fixed base routers usually comprise a generally cylindrical base and a motor unit with a cylindrical housing portion. The cylindrical portion of the motor housing fits snugly but movably within an annulus of the cylindrical portion of the base with the motor spindle and router bit projecting downward beyond the lowest portion of the base. The cylindrical portion of the base often includes a longitudinal or axial cut or gap that permits the base diameter to expand or contract slightly under the force of a clamp mechanism that bridges the gap and that can be used to tighten the base onto the motor housing within. Means for adjusting the depth of cut by adjusting the vertical or axial position of the motor unit and bit within the base are also provided. The base clamp is loosened for adjusting the cutting depth and after the desired depth is set with the depth adjusting means the base clamp is tightened to lock the motor housing at the set position.




One known means for adjusting the depth of cut in a fixed base router employs a rack and pinion arrangement. A toothed rack is attached in the axial direction on the exterior of the motor housing while a pinion is attached to the base so as to engage the pinion. Means, such as a knob, are provided for the operator to turn the pinion. Turning of the pinion drives the rack and the attached motor and bit. See for example U.S. Pat. No. 3,466,973 to Rees.




Another well known means for adjusting the depth of cut consists essentially of providing threads on the exterior of the motor unit and matching threads on the base assembly. Screwing the motor unit into and out of the base assembly raises and lowers the motor and cutter like a nut in a bolt. See for example U.S. Pat. No. 1,899,833 to Sacrey and U.S. Pat. No. 2,562,143 to Godfrey et al. Among several disadvantages of this means for adjusting the depth of the router is that the rotation of the router power head within the base assembly is problematic due to the presence of the power cord connected to the motor, which tangles or interferes with the rotation of the motor unit.




A refinement on the threaded motor unit concept is the replacement of a fully threaded base with a threaded ring or nut rotatably mounted on the base element. In such a mechanism, the ring can be manually rotated to raise and lower the power head relative to the base element without relative rotation between the motor unit and base element. See for example U.S. Pat. No. 2,988,199 to Godfrey et al. In some embodiments according to this concept means are provided to restrain the motor from turning within the base. These restraining means can take the form of an axial groove within the annulus of the base that is slideably engaged by a stud or projection on the exterior surface of the motor housing or vice versa. The engagement of the projection and the groove prevents the motor housing from turning within the base.




In some of these ring designs the ring merely rests atop the base element. This presents a problem, however, if the router is inverted. When inverted, the ring and the motor unit will tend to fall out of the base element unless the base clamp, if provided, has been sufficiently tightened to hold the motor by compression. When a router is mounted upside down in a router table, it is necessary to loosen the base clamp to adjust the depth of cut, then, unless additional connecting structure is provided, the problem remains of the motor and ring falling out of the router base.




In a further refinement, the ring can be rotatably connected with the base element so that it can retain and raise or lower the power head even when inverted. See U.S. Pat. No. 2,842,173 to Turner and U.S. Pat. No. 5,613,813 to Winchester et al. A disadvantage of a ring that is permanently axially connected to the base is that it prevents quick removal of the motor unit. Instead the motor must be unscrewed from the ring and base assembly—usually requiring numerous turns of the ring to fully raise and free the motor housing. Quick and easy removal of the motor unit is desirable for convenient access to the motor spindle and collet/chuck when changing router bits. The inability of a fixed ring to quickly release the motor forces design choices between steep thread pitches of approximately 2 inches per revolution or greater, which can lower and raise and free the motor quickly, and fine thread pitches of approximately ½ inch per revolution or less, which provide greater depth control, but require numerous turns to raise and free the motor.




In another variation, the Porter-Cable Model 310 laminate trimmer employs a ring that is held axially atop the cylindrical base by means of a pair of steel leaf spring clips. See FIG.


13


. Th clips


140


are mounted to the exterior of the base


120


and engage a v-shaped circumferential groove


136


around the outer side of the depth adjustment ring


130


. So constructed, the ring


130


is axially secured to the base


120


, but the motor using


114


and ring can be quickly detached and removed from the base.




Due to their small size, sharp edges, orientation and stiffness, the thin steel leaf spring clips


140


of the Porter-Cable Model 310 are extremely difficult to manipulate and do not appear to have been designed with the intention that the tool user actually operate them with his fingers. In practice, the Model 310 motor


114


is removed from the base


120


by a pull on the motor sufficient to overcome the compression force of the clips


140


engaged in the ring groove


136


. Thus, the leaf spring clips


140


act rather as a mere detent mechanism that the motor


114


and ring


130


can be pushed in and pulled out of with only modest force. After adjustment of the depth a cut the base is tightened on the motor with a base clamp, as described above.




Laminate trimmers are essentially, however, very small routers. The motors of laminate trimmers are of less than one horsepower and usually draw less than 5 amps. Such small motors usually weigh less than five pounds. Furthermore, laminate trimmers are not usually used inverted and are not intended for mounting upside down in router tables. For such small lightweight routers that are infrequently inverted, the Model 310 clips provide satisfactory retention of the ring and motor with convenience of removal.




Regular, fixed based, wood working routers, however, have motors of approximately 1 to 3 or more horsepower, draw 5 to 10 or more amps, and weigh 5 or more pounds. Construction professionals and woodworking hobbyists frequently use such routers upside down and want to be able to mount them inverted under a router table for prolonged periods. The Model 310 ring system, however, does not scale up well to retain and operate these larger and heavier motors. The leaf spring clips do not exert sufficient compressive force to hold the ring and heavy motors against the force of gravity and the occasional shock. Moreover, as mentioned above, the size, sharp edges, orientation and stiffness of the Model 310 leaf springs clips make them difficult to manipulate, so that in practice the motor and ring are pulled out of the base with the clips serving as a detent. Furthermore, the structure of the Model 310 clips do not permit the user to loosen the clips with one hand while grasping the motor or base with his or her other hand.




SUMMARY OF THE INVENTION




It is, therefore, one object of the invention to provide a tool with an axial depth of cut adjustment arrangement that both securely retains the motor unit in the base when inverted, but also provides for quick and convenient release of the motor from the base.




It is another object of the invention to provide a retaining mechanism with exposed and graspable elements that will permit the tool user to release the motor from the base by operation of those elements with one hand.




It is still another object of the invention to provide a fixed base router with a threaded depth adjustment ring that can be selectably detachable from the router base.




This and other objects of the invention are attained by a fixed base router, with a height adjustment ring that is in turn removably attached to the base by a manually operable clip. The clip is large enough and resilient enough to retain the motor unit of a large router when inverted and can be manually released.




Because of the provision of a convenient mechanism for release of the motor from the base, another object of the invention is the identification of thread pitch for the motor housing and depth adjustment ring that provides an optimal compromise between fine and accurate depth control and quick and convenient gross adjustment depth adjustment.











BRIEF DESCRIPTION OF THE DRAWINGS




Additional objects and advantages of the present invention will become apparent from a reading of the following detailed description of the preferred embodiments that make reference to the drawings of which:





FIG. 1

is an exterior perspective view of a power tool selectably detachable depth adjustment ring according to the present invention.





FIG. 2

is an exterior perspective view of the motor unit of the power tool of FIG.


1


.





FIG. 3

is an exterior side view of the base assembly of the power tool of FIG.


1


.





FIG. 4

is an axial cross-section view of a portion of the base and depth adjustment ring of the power tool of FIG.


1


.





FIG. 5

is an axial cross-section view of the depth adjustment ring of the power tool of FIG.


1


.





FIG. 6

is an exterior side view of the depth adjustment ring of the power tool of FIG.


1


.





FIG. 7

is an axial cross section view of the base, depth adjustment ring, and clip assembly portions of the power tool of FIG.


1


.





FIG. 8

is an exterior side view of the base, depth adjustment ring, and clip assembly portions of the power tool of FIG.


1


.





FIG. 9

is an expanded cross section view of the base, depth adjustment ring, and clip assembly portions of the power tool of FIG.


7


.





FIG. 10

is a further expanded cross section view of the base, depth adjustment ring, and clip assembly portions of the power tool of FIG.


7


.





FIG. 11

is an exterior side view of the clip lever of the power tool of FIG.


1


.





FIG. 12

is a top view of an alternative embodiment of the base and clip assembly in accordance with the present invention.





FIG. 13

is an axial cross-section view of the depth adjustment and retention portions of a prior art power tool.











DETAILED DESCRIPTION




The present invention provides a depth adjustment mechanism for a power tool. More particularly it provides a depth adjustment mechanism for a power tool wherein a motor unit is axially movable within a base element. While shown through the drawings in various embodiments of a fixed base router, those skilled in the art will appreciate that the invention is not so limited in scope. In this regard, the teachings of the present invention will be understood to be readily adaptable for use in any tool incorporating a motor housing axially movable in a base assembly by means of rotatable ring element threadably engaged with the motor housing.




Turning generally to the drawings in which identical or equivalent elements have been denoted with like reference numerals, and particularly to

FIGS. 1

,


2


, and


3


a power tool is illustrated and designated with the reference numeral


1


. The particular power tool shown is, for example, a fixed base router


1


including a motor unit


10


, a base assembly


20


, and a depth of cut adjustment ring


30


.




The motor unit


10


contains an electric motor (not shown) in a housing comprising a head portion


13


and a cylindrical portion


14


. The motor is powered through a cord


11


and controlled by a switch


12


. Projecting from the bottom of the motor unit


10


is the motor spindle


18


on the end of which is located a collet


4


of the well known kinds. Motor housing cylindrical portion


14


has exterior threads


16


that engage the depth of cut adjustment ring


30


. Motor cylindrical portion


14


also includes an exterior and axially oriented longitudinal slot


17


that serves to prevent rotation between the motor unit


10


and the base


20


by engaging with a stud (not shown) in the interior of the base.




The base assembly


20


includes handles


2


, and an upper portion


21


. Upper portion


21


is generally cylindrical in shape and is split by an axial gap


7


that permits expansion or contraction of the upper portion under the influence of clamp


6


, which is constructed and operates in a well known manner. Upper portion


21


defines a generally cylindrical annulus which is sized to accommodate the cylindrical portion


14


of the motor housing such that when the clamp


6


is released the motor


10


may slide easily within the base


20


, and when the clamp


6


is closed/engaged the cylindrical portion


14


is firmly and nonslidably gripped within the upper portion


21


of the base.




A depth adjustment ring


30


is connected to the top portion


21


of base


20


by means that will be described in detail below. With reference to the attached

FIGS. 4

,


5


and


6


the lower portion


34


of height adjustment ring


30


rests on a shelf


24


inside the upper lip


22


of the base


20


. The outer face of ring


30


also defines a circumferential groove


36


including a first surface


36


A substantially perpendicular to the axis of the ring. An upper portion


35


of ring


30


includes ribs


37


to provide an improved gripping surface for turning the ring. The inner face of ring


30


includes a thread


32


. Due to the selectably detachable feature of the depth adjustment ring according to the present invention, the need for a steep screw pitch that can quickly raise and lower the motor for ease of installation/removal is eliminated. Therefore, a pitch more optimally compromised between course and fine depth adjustment can be selected. Preferably, a screw pitch is employed that will raise or lower the motor unit


10


approximately 1 inch per rotation of the depth adjustment ring


30


.




Referring now to

FIGS. 7

,


8


, and


9


, mounted on the base


20


are at least two clip assemblies


40


. The clip assemblies include a lever


44


that is pivotably mounted to the base


20


. A lip


42


, including a second surface


42


A, on each of the levers


44


selectably and slidably engages the ring groove


36


at first surface


36


A and axially retains the ring


30


on the shelf


24


and inside the upper lip


22


of the base


20


. Alternatively, the clips assemblies could be mounted on the ring and slidably engage a groove on the base.




With additional reference to

FIGS. 10 and 11

, the clip assemblies


40


also include a pin


46


and a spring


48


. As depicted the levers


44


are pivotably mounted to the base


20


in cutouts


26


in the upper portion


21


of the base


20


, including the lip


22


. Pin


46


passes through a hole or ears


47


in lever


44


and engages holes


28


in the base


20


. Lever


44


pivots around or with pin


46


. Alternatively, lever


44


could be pivotably connected to the base


20


by means of studs rotatingly captured in holes in the base.




Spring


48


is depicted as a leaf spring, but could also include a coil spring around pin


46


, a suitably located compression spring, or other known spring types and configurations. Spring


48


biases pivoting lever


44


into a clamped position, wherein lip


42


engages with the ring groove


36


. Spring


48


acts between the base


20


and the inside of the lever


44


to force the lower portion of the lever outward and the upper portion inward against the ring


30


. The lower portion of the lever


44


constitutes a tab


45


that can be pressed with the operator's fingers in order to move the lever


44


to a released position. In the released position the lip


42


of the lever


44


is retracted from the groove


36


, so that the ring


30


and motor unit


10


may be removed from the base


20


.




Preferably router


1


includes two clip assemblies


40


located at positions around the upper circumference of base


20


such as to adequately grip and retain the ring


30


and also to be simultaneously operable by the fingers of one hand, for example the thumb and forefinger. In order to retain the ring


30


to the base


20


it is not necessary that the clips


40


be directly opposite each other, that is they need not be 180° apart around the circumference of the base. As shown in

FIG. 12

, the clips


40


can be spaced apart by less than 180°, for example by approximately 145°, in one direction and still adequately secure the ring


30


to the base


20


. The option to shorten the angular separation between the two clips


40


can allow one hand to span the distance between the clips even on larger diameter routers. It also provides design flexibility to relocate a clip or clips if required by the presence of other structural elements.




While the above description constitutes a preferred embodiment of the invention, it will be appreciated that the invention is susceptible to modification, variation, and change without departing from the proper scope or fair meaning of the accompanying claims.



Claims
  • 1. A portable router with an adjustable depth of cut comprising:a motor unit including a first threads and an output spindle; a router bit operatively connected to the output spindle of the motor unit; an adjustment ring having an axis of rotation and including a groove and a second threads, the second threads for cooperation with the first threads of the motor unit for adjustment of the depth of cut of the router bit, and the groove having a first surface substantially perpendicular to the axis of rotation of the adjustment ring; a base for surrounding the motor unit and rotatably supporting the adjustment ring; at least one clip assembly including a lip with a second surface, the clip movable from between a first position, wherein the lip engages the groove of the adjustment ring, and a second position wherein the lip is disengaged from the groove; and wherein, when the lip is engaged in the groove, the second surface is substantially perpendicular to the axis of rotation of the adjustment ring.
  • 2. The fixed base router of claim 1 wherein the clip assemby includes a lever pivotably mounted on one of the adjustment ring and the base.
  • 3. The portable router of claim 2 wherein the clip assembly further includes spring which biases the lever into the first position.
  • 4. The portable router of claim 3 wherein the lever includes a tab portion for moving the lever to the second position against the biasing action of the spring.
  • 5. The portable router of claim 1 wherein the base defines a gap and includes a clamp assembly, the clamp assembly operable for compressing the gap so as to cause the base to grip the motor unit and prevent movement of the motor unit within the base.
US Referenced Citations (25)
Number Name Date Kind
1532683 Carter Apr 1925 A
2591002 Pedron Apr 1952 A
2630152 Turnbull Mar 1953 A
2842173 Turner et al. Jul 1958 A
2867251 Moretti et al. Jan 1959 A
3332462 Williams Jul 1967 A
3433479 Huck et al. Mar 1969 A
3581787 Bane Jun 1971 A
4244406 Stielper Jan 1981 A
4640324 Lounds Feb 1987 A
4679606 Bassett Jul 1987 A
4688613 Bassett Aug 1987 A
4693656 Guthrie Sep 1987 A
4787794 Guthrie Nov 1988 A
4946323 Kazama et al. Aug 1990 A
5074724 McCracken Dec 1991 A
5078557 McCracken Jan 1992 A
5088865 Beth et al. Feb 1992 A
5176479 McCracken Jan 1993 A
5181813 McCracken Jan 1993 A
5188492 McCracken Feb 1993 A
5590988 Rusconi Jan 1997 A
5613813 Winchester et al. Mar 1997 A
5913645 Coffey Jun 1999 A
6050759 Bone Apr 2000 A
Foreign Referenced Citations (2)
Number Date Country
2035892 Feb 1971 DE
0830923 Mar 1998 EP