Patent Document

The present invention generally relates to power hand tools and, more particularly, to plunge-type routers. 
     BACKGROUND OF THE INVENTION 
     Plunge-type routers are used to cut a variety of shapes in work pieces made of wood and other materials, with the shapes being determined by the kind and shape of router bits used, the depth of cut of the bit and the path of travel by the router bit relative to the work piece. A plunge router is constructed to move the router bit toward and away from the work piece when the router is being operated by hand. The depth of cut of the router bit is typically determined by an adjustable depth stop system which may or may not include means for locking the router in its plunged position. 
     During operation, the plunge router may be supported on the work piece with the bit retracted and placed in the desired position so that when it is turned on and plunged, the router bit advances into the work piece where the operator moves it relative to the work piece to complete the desired routing operation. To do the plunging operation, the operator must exert a downward force on the head assembly, generally by pressing on handles attached to it, to move the router bit into contact with the work piece. The head assembly is typically biased to automatically retract the router bit from the work piece when the downward force imparted by the operator is removed. 
     Plunge routers generally include a plunge adjustment mechanism that enables the operator to control the distance the router bit can move toward the work piece and thereby determine its depth of cut. As is well known to those who have used plunge type routers, the adjustment of the stop system must be carefully done to achieve the desired depth of cut. Because the type and size of various router bits are very different, it is prudent if not absolutely necessary to recalibrate or reset the adjustment means after any manipulation of the router bit to insure that it has been accurately set to achieve the desired depth of cut. There are many other devices that attempt to accurately set the depth adjustable stop to provide an accurate depth of cut including adjustable rods, scales with indicators, micrometer type adjusters and other systems. Such adjustable stop mechanisms in the prior art are generally hand manipulated and some may have a printed scale or other indicia located on the mechanism for use in providing a specified depth of cut. However, it is still necessary for users to carefully measure the depth of cut in one way or another to insure that the desired cut will be made. In this regard, it is often common practice to perform a test cut on a scrap piece and actually measure the result and to iteratively adjust the stop mechanism until the proper result is achieved. 
     SUMMARY OF THE INVENTION 
     A plunge-type router is disclosed which is adapted for either free hand use or mounted beneath a router table. The router has a base and a head assembly with the base being adjustable relative to the head assembly by an adjusting mechanism. The plunge router of the present invention includes an electronic control system with a digital display and control functionality that enables the router to accurately determine a baseline or zero position for a router bit installed in the router and permits the user to input a depth of cut value or other predetermined command. The system then automatically adjusts a motorized depth adjustment mechanism to achieve the appropriate position. The electronic control system enables the storage of multiple depth settings as well as multiple step or macro operations. In this regard, macros may be run to provide incremental cutting necessary for performing multiple passes to achieve a relatively deep depth of cut. 
     The present invention may include as an alternative embodiment a supplemental electronic control panel that can enable a user to install the plunger router in a router table and yet have a control panel clearly visible to the user even though the router is mounted underneath the table surface in an inverted position. The electronic system also enables the choice of either metric or English units of measure. The speed of operation of the main drive motor can be provided on the display, as well as an identification of a macro number or other information relating to the particular operation that is being carried out. In the event of multiple step macro operation, stepping between progressively deeper depths of cut may be manually triggered by the user on the control panel and displayed thereon. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view a preferred embodiment of the plunge router of the present invention; 
     FIG. 2 is a front view of the plunge router shown in FIG. 1; 
     FIG. 3 is a right side view of the plunge router shown in FIG. 1; 
     FIG. 4 is a cross section taken generally along the line  4 — 4  of FIG. 3; 
     FIG. 5 is a perspective view similar to FIG. 1, but shown with portions removed; 
     FIG. 6 is a block diagram of the electronic system that controls the depth adjusting mechanism; 
     FIG. 7 is a perspective view shown with portions removed of an alternative embodiment of the plunge router embodying the present invention; 
     FIG. 8 is a cross section of the embodiment shown in FIG. 7; 
     FIG. 9 is a perspective view of a second alternative embodiment shown with portions removed and particularly illustrating an offset spindle; and, 
     FIG. 10 is a perspective view of a plunge router mounted to a router table and illustrating an auxiliary control panel. 
    
    
     DETAILED DESCRIPTION 
     A preferred embodiment of the present invention is shown in FIGS. 1-5 and indicated generally at  20 . The router  20  has a motor housing assembly  22  that includes a pair of handles  24  preferably integrally formed with the housing assembly. A control panel, indicated generally at  26 , is preferably installed in the motor housing assembly  22  and includes a visual display  28  that is preferably an LCD display, but may be other known types of electronic display such as an LED display, for example. The control panel  26  also includes pushbuttons  30  and  32  which are adapted to raise and lower the router bit relative to a work piece, a menu pushbutton  34  and pushbuttons  36  and  38  which may be used to either change the menu selections or trigger changes in the operation of the router in a manner that will be hereinafter described. A socket  40  is provided for connecting an auxiliary control panel  26 ′ for use when the router  20  is attached to a router table  42 , as shown in FIG.  10 . 
     The motor housing assembly  22  is connected to a base  44  by a depth adjusting assembly, indicated generally at  46 , which includes a pair of plunge posts  48  and  50  that are slidable in cylindrical channels  52  and  54  that are part of the motor housing assembly  22 . A protective cylindrical accordion bellows structure  56  and  58  are provided to protect the interface between the posts and their respective channels and keep the posts from eventually binding up due to wood or other material shavings and dust produced by operation of the router. The motor housing assembly  22  has a conical lower portion  60  with a central opening through which the output shaft  62  of a motor  64  passes. A collet chuck  66  or the like is used to secure a router bit  68  and the router bit  68  and collet chuck  66  extend through an aperture  70  located in the base  44  to adjust the depth of cut, i.e., the position of the bit  68  relative to the bottom surface  72  of the base  44 . The main drive motor is turned on and off by a switch  74  located in the right handle  24 . 
     To adjust the depth of cut, the base is adjusted relative to the housing assembly  22  and therefore the router bit  68 . This is accomplished by a depth adjusting mechanism  46  having one of the posts, such as post  48  as shown in FIGS. 4 and 5, with an attached threaded nut  76 , with the nut engaging a threaded rod  78  that is driven by a motor  80  through a gear mechanism  82 . The motor  80  is preferably a servo motor, but may be a stepper or other suitable motor. During operation, activation of the motor  80  causes its output shaft to drive the gear mechanism  82  and rotate the rod  78  which will then cause the captive nut and post  76  to move upwardly or downwardly relative to the rod and housing assembly  22  depending upon the direction of rotation of the rod  78 . This movement also necessarily adjusts the position of the bit  68  relative to the bottom surface  72  of the base  44 . A tachometer, resolver, encoder or other sensing mechanism  84  is operably connected to the motor  80  to detect rotation of the motor output shaft. Since the pitch of the threads of the rod  78  is known or can be determined, as can the mechanical advantage of drive mechanism  82 , the angular movement of the motor  80  output shaft directly translates into vertical movement of the housing assembly relative to the base and enables the elevation of the router bit to be accurately determined relative to the position of the bottom surface  72  of the base. 
     In accordance with an important aspect of the present invention and referring to the electrical block diagram of the plunger outer depth adjustment control system shown in FIG. 6, the control panel  26  is connected to a controller  86  which preferably includes a nonvolatile memory for storing data relating to the operation of the system. The controller  86  is adapted to provide output signals on line  88  which are applied to drive circuitry  90  of conventional design depending upon the type of motor that is being driven, with the drive output being applied on line  92  to the adjustment motor  80 . The tachometer  84  is operatively connected to the motor  80  and provides signals on line  94  that provide feedback information to one or both of the controller  86  or the drive circuitry  90  depending upon the particular implementation that is used. 
     An external sensor  96  is connected to the controller  86  and provides information for zeroing the router hit  68 . In this regard, zeroing is intended to mean that the very bottom of the router bit  68  is at the same elevation as the bottom surface  72  of the base  44 . A power supply  98  provides proper voltages to the controller  86  and drive circuitry  90 . The controller  86  and memory may be a microprocessor, a digital signal processor and ASIC integrated circuit, as well as many other types of programmable logic devices. The external sensor  96  is preferably one that either “feels” or “sees” the relative position of the work piece and router bit  68 . In this regard, it is contemplated that such external sensors may be a camera or CCD sensor, a laser device, a sensitive pad device or sensing fingers. In the preferred embodiment, the external sensor  96  is a load sensing device adapted to monitor the load on the motor  80  as the outer bit  68  is moved downwardly into contact with the surface of the work piece. If the work piece is flat, then the surface  72  would be in close contact with the work piece and movement of the router bit downwardly into contact with the work piece would provide an accurate zero position for the router. 
     At that moment, it is contemplated that the menu button  34  can be pushed to reveal a reset or zero option which could be entered by pushing an appropriate one of the buttons  36  and  38  depending upon the manner of implementation that is carried out. Once the zero position is entered, then the user can use the menu pushbutton to enable the depth of cut to be entered by using button  32  to increase the depth of cut or alternatively  30  to decrease it. It is also preferred that the pushbuttons  30  and  32 , when held down will result in continuous operation of the motor  80  to either increase or decrease the depth of cut. It is preferred that the depth of cut be displayed on the display  28  during such adjustment. It may also be programmed so that a mere quick depression and release of either of the pushbuttons would result in a definite amount of incremental movement of the bit in the appropriate direction. In this regard, it is contemplated that the elevation of the bit may be changed in {fraction (1/10,000)} th inch intervals in this manner. Alternatively, the menu may be sequenced through predetermined incremental depths such as tenths of an inch or quarters of an inch, for example. If the total depth of cut is ½ inch, for example, the controller may be programmed to operate as a macro which would perform a ½ inch cut in two ¼ inch increments. The menu pushbutton  34  may also have a menu item which enables the router to be converted between American and metric units. It is also contemplated that the control panel  26  include a numeric keyboard so that a user could merely key in the depth of cut that is desired and the system will go there upon activation. 
     It should also be understood that the tachometer  84  may be an optical encoder, resolver or other type of device that is adapted to provide rotary position information relating to the operation of the motor  80 . 
     In accordance with another aspect of the present invention, a first alternative embodiment is shown in FIGS. 7 and 8 wherein instead of a depth adjusting mechanism  46 , a depth adjusting mechanism  46 ′ is illustrated. Rather than having a fixed nut and a threaded rod  78  driven by the motor  80  and drive mechanism  82 , a motor  100  is positioned to drive a gear mechanism  102  that has an output connected to a pinion gear  104  that engages the teeth of an elongated rack  106  which is attached to the post  48 . This embodiment is otherwise substantially similar to the embodiment shown in FIGS. 1-5. 
     In accordance with another aspect of the present invention, a second alternative embodiment is shown in FIG.  9  and includes a housing assembly  22 ′ that has a different shape than that shown in the preferred embodiment and the first alternative embodiment. An important difference is that the collet chuck  66  is attached to a splined shaft  110  which is rotatable in a bracket  112  and also in a rack member  114 . A pulley  116  is provided and is attached to the splined shaft  110  with the pulley  116  being driven by a belt  118  that is driven by another pulley located on the output shaft of the motor  64 . The rack  114  can be vertically moved by the pinion gear  120  that is driven by gear mechanism  122  and drive motor  124 . Thus, when the rack is vertically moved, it vertically moves the shaft  112  as well as the collet chuck  66  and router bit  68  in a vertical direction. Because of the described movement, it should be apparent that the posts  48 ′ and  50 ′ do not move relative to the housing assembly  22 ′ and the base  44 ′ is somewhat larger, including a larger opening in which to observe the work piece during operation. The offset spindle construction enables a user to see the drill bit perhaps better than the other embodiments that have been shown and described. 
     From the foregoing, it should be understood that various embodiments of a plunge router have been shown and described which offer many desirable attributes compared to the prior art. The sophistication of the design provides accurate depth of the cut and adjustment in addition to flexibility its functionality and operation that has not heretofore been achieved. The functionality of the control panel is convenient and straightforward and an auxiliary control panel can be plugged into the router so that a control panel is visible to the user even when the router is mounted in an inverted position beneath a router table. 
     While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims. 
     Various features of the invention are set forth in the following claims.

Technology Category: 7