US 3494395 A
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Feb. 10, 1970 J. w. GRAHAM 3,494,395
7 ROUTER Filed Feb. 8, 1967 2 Sheets-Sheet l INVENTOR John W. Graham ATTORNEYS Feb. 10, 1970 J. w. GRAHAM 7 3,494,395
ROUTER Filed Feb. 8, 1967 2 Sheets-Sheet 2 II- IIIIII] l 1 l M v 20 L I I N! 5 22 64 H 28 I2 J J 24 44 W36 32 1 J 30 ll. 34
48 I as I a so illl|lll|l I III INVENTOR John M. Graham ATTORNEYS United States Patent 3,494,395 ROUTER John W. Graham, Syracuse, N.Y., assignor to Rockwell Manufacturing Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Feb. 8, 1967, Ser. No. 615,015 Int. Cl. B27c 5/00 US. Cl. 144136 7 Claims ABSTRACT OF THE DISCLOSURE A router or the like having .a base so supporting a rotatable arbor to which a cutter can be attached as to minimize side loads on the arbor. A motor is mounted on the base independently of the arbor and preferably so drive-connected to the latter as to minimize shock loads on and the transmission of vibrations to the motor. A motor-driven fan cools the motor and blows chips and dust away from the work area. The center of mass of the tool lies to the side of the cutter and over the workpiece; and the base configuration allows the cutter to operate near surfaces parallel to the cutter and provides a constant view of the workpiece and cutter. Preferably, mechanism capable of adjusting the depth of out without moving the motor relative to the base is provided.
BACKGROUND AND SUMMARY OF THE INVENTION The present invention relates to improvements in routers or the like and more particularly to improvements in routers which will render such tools more easily, effectively, and widely usable.
Prior to the present invention, it has been customary to construct routers with a base structure having a flat bottom base plate, usually of circular form, with a central through aperture through which projects a router bit. The router bit is mounted coaxially on the lower end of the armature shaft of an electric motor mounted on the base structure above the base plate. The present invention provides an integrated solution to a number of design problems which have existed without solution for many years in routers of this type.
First, there has been the problem of bearing failure. Designers of routers have long been plagued with premature failure. This has been attributed to a number of reasons:
(a) The size of the lower hearing has been limited in outside diameter due to the necessity for allowing the air from the motor to exhaust through ports around its circumference. In the present invention, it is not necessary to direct air around the lower bearing on a combined armature and cutter shaft so that this design limitation is eliminated.
(b) Bearing failures are also believed to have been influenced by the armature shaft flexing due to side loads on the bit. In prior router designs, the shaft diameters through the armature have been dictated primarily by motor design consideration, not the loading which is imposed upon the shaft when a router bit is secured to it at one end. In the present invention, the cutter shaft is independent of motor design considerations and therefore may be made relatively short and stiff.
(c) Bearing alignment is always a critical factor where high shaft speeds are involved as in routers. In prior routers, the bearing alignment has always been an unsatisfactory compromise due to the necessity of supporting the motor parts and the cutter along the same axis. The lower motor housing has been a relatively long thin shell. The field winding of the motor has been mounted 3,494,395 Patented Feb. 10, 1970 designs has been that of motor failure. It has long been suspected that premature motor failure in routers has been associated with the vibrations set up in the armature shaft due to the cutting action of the bit which is mounted on the end of the armature shaft. Many efforts have been made in an effort to keep the armature windings in place in service. These have included tying the windings, using heavy varnish dips and encapsulating. These measures are expensive and have not been completely satisfactory. In the preferred embodiment of the present invention, the cutter bit is isolated from the armature shaft through a resilient connection which renders the vibrations and shock loading of the bit and the shaft upon which it is mounted far less damaging to the armature than in prior art designs.
A further problem has been that of bit run out. This factor results from the accumulation of tolerances in the bit and the various parts used to mount it on the armature shaft in the prior art designs and contributes to all of the problems described above as well as limiting the precision with which fine routing can be done without damage to the work. This problem is particularly critical in the routing of soft metals and bn'ttle plastics. In the present design it is possible to maintain better control over tolerances contributing to bit run out by freeing the shaft which holds the cutter from the many design considerations dictated by the manufacture of the motor parts and their assembly in the router.
In addition to the foregoing deficiencies of prior art router designs, there are several factors relating to the effectiveness with which a user can operate the router. These are balance, depth of cut, view of the work, and chip dispersal.
Because of their power and high speed, routers have always been considered one of the more difficult portable tools to operate. Complicating this is the fact that in prior router designs when the router is used to take a cut from the edge of a piece of material the center of gravity and more than half of the router base are off the work. Consequently, the operator has to apply a twisting torque to the router knobs to keep the machine from tipping. This action makes it difiicult for the operator to feel whether or not the router base is solidly on the surface assuring a square cut. The addition of an edge guide still further aggravates the overhanging weight condition. As a further example, assume the router is being used to cut out a hole in a counter top to receive a sink. In this cutting operation, half of the base plate of the router lies on the material in the center of the hole which is being removed and only the other half remains supported throughout the cut on solid counter top material. As a result, after the out has reached any appreciable length, the router becomes difiicult to support as it tends to pivot about the line of cut. In the present invention, the center of gravity of the router remains over the work providing a stable accurately aligned platform for the cutter bit.
In prior router designs, the entire motor is raised relative to the base structure in order to reduce the depth of cut. This further aggravates the out of balance condition and makes use of the router on a vertical surface substantially impossible. In the present design, it is unnecessary to move the motor since the depth of cut adjustment is associated only with the cutter shaft and is independent of the position of the motor.
A further problem of long standing with routers is V the very limited area of View afforded by the structure of the router base. At maximum cutting depth, the lowered position of the motor housing further reduces the aperture through the base. If any reference marks on the surface of the work are to be used by the operator, the operator must have his head in close proximity to the plane of the work surface to be able to see those reference marks through the opening in the router base about the bottom of the router motor.
Another difficulty with prior art router designs has been that of chip dispersal. The arrangement of the motor in the single shaft router necessitates exhausting the cooling air straight down into the work area. As a result, chips fly in all directions. In the present invention, the exhaust air from the motor can be directed to'blow the chips away from the operator.
A further difficulty with prior art routers is that the minimum distance which one can approach a surface perpendicular to the surface over which the router is being moved is limited by the radius of the motor housing and base.
The basic object of the present invention is to provide an improved router design which eliminates the foregoing difficulties with prior art single shaft routers.
The present invention eliminates these disadvantages of prior art routers by locating the cutter supporting arbor in offset relation to the motor so that the center of mass of the router is offset to one side of the cutter supporting arbor rotation axis. As a result, the cutter supporting arbor or shaft is isolated from the motor armature and therefore can be properly constructed and supported, the router is properly supported and balanced in use, the size of the motor does not establish a minimum distance to which the router can approach a surface parallel to the cutter head supporting arbor rotation axis and the tool can be firmly supported by a workpiece surface at one side of the path of cut into the workpiece of the bit of the router and the other problems outlined above are eliminated.
With these considerations in view, it is therefore a primary object of the present invention to provide an improved router construction in which the center of mass of the router is offset laterally from the axis of rotation of the bit supporting arbor resulting in a stable support for the router by the workpiece.
Another object of the present invention is to provide an improved router or like tool in which the router bit supporting arbor is rotatably mounted beside the router motor to which it is drive connected so that the size of the router motor does not impose a minimum limitation upon the distance to which the router can approach a surface parallel to the router bit supporting arbor rotation axis.
A further object of this invention is to provide a router having a cutter arbor supported and journalled independently of the motor armature shaft.
A still further object of this invention is to provide an improved router in which the armature of the motor is isolated from shock loading from the cutter by a shock absorbing drive connection.
These and other objects of the present invention will become more fully apparent by reference to the appended claims and as the following detailed description proceeds in reference to the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING In the drawing:
FIGURE 1 is a front elevational view of a router embodying the principles of the present invention; 7
FIGURE 2 is a bottom elevational view of the router of FIGURE 1;
FIGURE 3 is a side view of the router of FIGURE 1 but showing the lower portion of the router in section; and
FIGURE 4 is a side elevational view partially in section of a further router constituting a second embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring now in detail to the drawings and particularly to FIGURES l, 2 and 3, the router 10 of the present invention in its preferred embodiment comprises a base structure 12 having a motor support casting 14 and a bottom base plate 16 secured to the motor support 14 by screws 18 (FIGURE 2) and an electric motor 20 (FIGURES 1 and 3) received in the upwardly opening split collar portion of the motor support casting 14 and clamped therein by manipulation of the bolt 22 as in prior router constructions as illustrated in United States Patent No. 2,839,107, issued June 17, 1958 to A. N. Emmons for Combination Straight and Bevel Cutter.
The router of the present invention differs from such prior constructions in that it is provided with a cutter arbor or spindle 24 journalled in a support structure 26 fixed relative to and preferably integral with the motor support structure 14. Arbor 24 is journalled by spaced coaxial antifriction bearings 28 and 30. Axial spacing between the outer races of the bearings 28 and 30 is maintained by an integral internal annular shoulder 32 formed internally of the through bore. 34 extending through the support 26. The arbor 24 is embraced by the inner races of the bearings 28 and 30 the minimum axial spacing of which is established by a collar 36 surrounding arbor 24 between bearings 28 and 30. The lower end of arbor 24 is formed with or has fixed thereto a pulley 38. The upper end of the arbor 24 is threaded as indicated at 40 and receives thereon a nut 42 by which the inner race of bearing 30, the collar 36, and the inner race of bearing 28 are clamped on the arbor 24 between the pulley 38 and the nut 42.
Arbor 24 is journalled by bearings 28 and 30 in spaced parallel relation to the rotation axis of the shaft 44 of the armature (not shown) of the motor 20. A pulley 46 is fixed to the lower end of the shaft 44 and the pulleys 46 and 38 are interconnected by a drive belt 48.
Drive belt 48 on pulleys 38 and 46 may be a conventional V-belt but is preferably of the timing belt type in which teeth are formed internally of the belt and engage teeth on the pulleys to thereby prevent slippage in the drive. In either event the belt 48 forms an elastic shock absorbing connection between the pulleys 46 and 38 so that shock loading of the arbor 24 as it rotates and the bit cuts into the workpiece does not result in transmission of shock loading to the armature shaft 44 and the armature (not shown) thereon to any material extent.
A router bit 50 is received within the lower end of the through bore 52 extending coaxially through the arbor 24. Its shank 54 abuts at its upper end the lower end of an adjusting screw 56 threadedly received within the internally threaded upper end of the bore 52 to thereby establish the upper limit of travel of the cutter or bit 50 within the bore 52. This determines the depth of cut by establisring the magnitude of the distance below the bottom surface 58 of the base plate 16 to which the cutter 50 projects. The cutter '50 is clamped to the arbor 24 by manipulation of a nut 60 which in its clamped position firmly grips and locks the angular position of the cutter 50 relative to the arbor 24.
As is apparent from the drawings and the foregoing description, the embodiment illustrated in FIGURES l, 2 and 3 eliminates all of the deficiencies of the prior art routers explained above. Specifically, by providing a second shaft or arbor 24 to support the cutter 50 which is independent of the motor 20 and the armature shaft 44, the arbor 24 can be made of suflicient size to prevent flexing due to side loads on the bit, the bearings 28 and 30 may be made of sufiicient size and space sufficiently close together to withstand the loads imposed upon them, both bearings 28 and 30 may be mounted within a single rigidly constructed support 26 whereby bearing alignment may be easily established and maintained and, the motor 20 is isolated by the resiliency of the belt 48 from the shock loading and vibrations resulting from the cutting action of the bit 50. In addition, the bit 50 is offset well to one side of the center of gravity of the router which is established primarily by the weight of the motor 20, so that the center of gravity of the router 10 may be placed over the work and the router 10 stably supported while in use. The depth of cut is established by manipulation of the adjusting screw 56 and appropriate movement of the bit '50. This adjustment is independent of the position of the motor 20. It may be made much more easily than in prior art router designs and has no adverse effect upon the location of the center of gravity of the router 10 as a whole. The view of the workpiece through the aperture 62 in the base plate 16 through which the bit 50 projects is not obstructed by the motor 20 or by its support casting 14. The air exhausting from the bottom end of the motor 20 will move over the base plate 16 toward and pass the bit 50 thereby tending to direct the chips away from the operator gripping the router 10 by the handle 64 from the left of the router 10 as viewed in FIGURE 3. As is apparent from FIGURE 2, the axis of rotation of the bit 50 may be brought to within a distance A of a surface parallel to the axis of the bit 50 rather than being restricted to a much greater distance such as the distance B determined primarily by the radius of the motor 20.
A second embodiment of the router of the present invention is illustrated in FIGURE 4. In this embodiment, the router bit 70 is fixed by a clamping nut 72 to the lower end of an arbor 74 journalled by spaced antifricrtion bearings 76 and 78 in a housing 80. The housing 80 is fixed to a base plate 82 through a connection formed by a pair of adjacent bosses 86 and 88 interconnected by a thumb screw 90, an arrangement which permits router bit 70 to be tilted with respect to the base for bevel cuts. The arbor 74 is driven by an electric motor 92 comprising a field winding 94 fixed Within a chamber 96 within the housing 80 and surrounding an armature 98 fixed to an armature shaft 100. Armature shaft 100 is journalled in the housing 80 by spaced aligned antifriction bearings 102 and 104. Shaft 100 and arbor 74 are interconnected by a pair of meshed beveled gears 106 and 108 fixed to shaft 100 and arbor 74 respectively. Electrical current is supplied to the motor 92 through input leads 10 under control of an electrical switch actuated by a finger lever 112.
As is apparent, the embodiment of FIGURE 4 has many of the advantages of the embodiment of FIGURES l, 2 and 3 differing primarily therefrom only in that a gear drive is provided between the armature shaft 100 and the arbor 74 on which the bit 70 is mounted rather than having a shock absorbing connection therebetween as is provided by the belt 48 in the embodiments of FIG- URES 1, 2 and 3.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalence of the claims are therefore intended to be embraced therein.
What is claimed and desired to be secured by Letters Patent is:
1. A power driven router or the like comprising:
(a) a base unit including a base plate having a planar bottom surface portion for contacting a workpiece and guiding a cutter relative thereto and a nose defined by converging edge portions of said base plate with the angle between said edge portions being approximately (b) said base unit further comprising an arbor support structure above and fixedly positioned relative to said base plate;
(c) a cutter-supporting arbor rotatably supported above said base plate at the nose thereof with its axis of rotation normal to the planar bottom surface portion of the base by said arbor support structure;
(d) said base unit further comprising a motor support structure fixed directly to said base plate, said motor support structure being located at a position remote from the nose of and above the base plate;
(e) a motor attached to said base plate by said motor support structure; and
(f) a drive-connection disposed between said motor and said base for transmitting power from said motor to said arbor;
(g) said base having an opening therethrough in alignment with the arbor through which a cutter driveconnected to said arbor can extend; and
(h) the nose of said base plate protruding beyond said arbor support structure and being the only part of the tool projecting therebeyond, whereby the movement of the router cutter toward a structure extending above the workpiece is limited onl by the configuration of the base plate.
2. The tool defined in claim 1, wherein said driveconnecting means comprises a pulley fixed to said motor output shaft, a pulley fixed to said arbor, and a drive belt interconnecting said pulleys, said drive belt and pulleys being toothed to provide a substantially positive drive connection between said motor output shaft and said arbor.
3. The tool defined in claim 1, wherein the converging edges of the base plate are straight and interconnected by a. curved edge portion which is tangent to both of said straight edges and has a center of curvature coincident with the rotation axis of the arbor.
4. The tool defined in claim 1, wherein the means rotatably supporting the arbor above the base plate comprises:
(a) a pair of bearing assemblies surrounding said arbor;
(b) means including bearing support structure fixedly positioned relative to said base plate for maintaining said bearing assemblies in a predetermined axially spaced relation to each other and to said base plate; and
(0) means including a retainer detachably fixed to said arbor above said bearing assemblies for maintaining said arbor in a fixed position in said bearing assembles and for maintaining said bearing assemblies in assembled relationship with said support structure.
5. A power driven router or the like comprising:
(a) a base plate having a planar bottom surface portion for contacting a workpiece and guiding a cutter relative thereto and having a nose defined by converging edges;
(b) a motor attached to said base plate in a position remote from said nose with its axis substantially perpendicular to said planar bottom surface portion;
(0) a rotatable, cutter-supporting arbor mounted above the top surface of said base plate and at said nose with its rotation axis normal to said planar bottom surface portion, said arbor having a coaxial through bore;
(d) a drive-connection for transmitting power from said motor to said arbor;
(e) said base plate having a cutter opening therethrough in alignment with and beneath said arbor whereby a cutter may be inserted through said opening and drive-connected to said arbor;
(f) means for receiving and retaining the shank of a cutter in the lower end of said arbor through bore; and
(g) selectively axially adjustable means mounted in the opposite end of the bore providing a thrust bearing 7 8 for and controlling the depth to which the shank of References Cited: a cutter may be inserted in said lower end of said I bore to thereby regulate the depth of cut of the cutter. ED STATES PATENTS v 6. A base unit according to claim 1, wherein said cutter 2,610658 9/ 1952 1 supporting arbor has an axial through bore and including 2,952,281 9/ 1960 W clamping means at the lower end of said arbor engageable 5 3,111,969 11/1963 with a cutter to retain the cutter in the lower end of said 31346926 10/1967 Pluchmot 4- bore and means in said bore above the lower end thereof FOREIGN PATENTS for limiting the distance which a. cutter can extend into ZZIIIItCZeIlZIJDOI'B and thereby regulating the depth of cut of the 10 1,074,433 3/1954 France.
7. The router of claim 1, wherein the motor support 542165 4/1956 Italy structure comprises an upwardly opening, split collar type DONALD R SCHRAN Primar Examine motor receiving member and selectively releasable means y r for clamping the ends of the collar of said motor receiving U 5 c1 X R member together to retain said motor therein. 1 144 134 I I I 981,146 1/1951 France.