Patent Abstract:
The present invention is directed to a router depth adjustment mechanism for minimizing rapid course depth adjustment for standard and plunge routers. Routers with rapid or course adjustment mechanisms may permit a router motor housing to drop suddenly, if the user in inattentive. Sudden adjustments may result in damage to the router and even user injury. The mechanism of the present invention includes a threaded shaft and a biased thread engaging member which may be disengaged for rapid adjustment. A restraining device and/or a break may be included to minimize the rate of change.

Full Description:
FIELD OF THE INVENTION 
   The present invention relates to the field of hand tools and particularly to an apparatus for promoting router safety. 
   BACKGROUND OF THE INVENTION 
   For instance, United States Published Patent Application 2002/0043294 A1, entitled: Router, which is hereby incorporated by reference in its entirety, describes a device which permits rapid depth adjustment. While such a device provides the ability to adjust rapidly, rapid adjustment may result in injury to the user and/or damage to the router itself. For example, when an unwary user replaces the motor housing into the router base, such as after changing a bit, the motor housing and motor may drop upon utilizing a course adjustment device, if the motor housing is not grasped. 
   Furthermore, if a user is forced to support the motor housing, such as to prevent damage to the router when adjusting plunge depth, the user&#39;s grasping hand or fingers may be smashed and/or pinched, upon rapid depth adjustment, due to the weight of the router motor and housing. 
   Moreover, routers which include grasping apparatus for aiding in grasping the base or motor housing typically include a lip or rim for at least partially supporting the weight of the router during operation and transfer. A safety problem may occur if the motor housing and grasping apparatus interact to create a pinch point where a user&#39;s finger or hand may be easily caught. 
   Moreover, the router itself may become damaged, such as when an adjustment mechanism is released when the router is implemented with a router table. For instance, if a user actuates the course adjustment device, the router may drop suddenly. 
   Therefore, it would be desirable to provide an apparatus for promoting router safety. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention is directed to an apparatus for promoting router safety when adjusting router depth. As will be appreciated by those of skill in the art, the apparatus of the present invention may be implemented in rotary cut-off tools, both standard and plunge routers, and the like. 
   In a first aspect of the present invention, a router includes a motor housing, a base, an adjustment mechanism and a hand grip attachment. The adjustment mechanism includes a shaft with a threaded portion and a thread engaging member. The shaft is attached to the motor housing and is received in the base wherein the engaging member may selectively engage the threaded portion. The hand grip includes a lip for at least partially supporting the router when grasped. The lip extends generally outward from the base to which it is attached. The lip may be disposed even with or below the end of the base adjacent to the motor housing so as to minimize potential user injury. 
   In an additional aspect of the invention, a router adjustment device includes a base, a motor housing, a frictional zone, and an adjustment mechanism including a shaft and threaded engaging member. The motor housing may adjustably secure within the base for permitting depth adjustment. The frictional zone may be disposed either on the base or motor housing. For instance, the frictional zone is disposed generally at the interface of the motor housing and base. The frictional zone at least partially resists the movement of the motor housing, such as when the thread engaging member is disengaged from the threaded shaft. 
   In a further aspect of the invention, an apparatus for controlling router adjustment includes a base, a motor housing, and an adjustment mechanism. The adjustment mechanism includes a shaft, a threaded engaging member and means for at least partially restraining the motor housing from moving with respect to the base. For instance, the adjustment mechanism contains a spring for generally biasing the shaft to prevent damage and/or injury. 
   In another aspect of the invention, a router adjustment device includes a base, a motor housing, an adjustment mechanism, and a brake element. The motor housing is adjustably secured in the base to permit longitudinal movement. The break element is disposed in the base substantially perpendicular to the motor housing. The break element may be activated to at least partially resist the movement of the motor housing, such as when a course adjust occurs. 
   It is to be understood that both the forgoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the general description, serve to explain the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The numerous advantages of the present invention may be better understood by those killed in the art by reference to the accompanying figures in which: 
       FIG. 1  is an isometric view of a router including hand grip attachment with a support lip terminating generally even with the end of a base; 
       FIG. 2  is an exploded view of a router with a motor housing including an angled portion, for minimizing pinching, adjacent to a base; 
       FIG. 3  is an exploded view of a router adjustment device including a frictional zone for generally minimizing rapid course adjustment; 
       FIG. 4A  is a cut-a-way view of an apparatus for controlling router adjustment including a compression spring for minimizing rapid adjustment; 
       FIG. 4B  is a cut-a-way view of an apparatus for controlling router adjustment including a coiled spring with lever arm for minimizing rapid adjustment; 
       FIG. 4C  is a cut-a-way view of an apparatus for controlling router adjustment including a gasket for minimizing rapid adjustment; 
       FIG. 4D  is a cut-a-way view of an apparatus for controlling router adjustment including a frictional zone mounted to a thread engaging member for minimizing rapid adjustment; 
       FIG. 5A  is cross sectional view of a router adjustment device including a biased breaking element; 
       FIG. 5B  is cross sectional view of a router adjustment device including a biased breaking element capable of automatic actuation by a thread engaging member; and 
       FIG. 5C  is cross sectional view of a router adjustment device including a thread engaging member with a contact zone for minimizing rapid course depth adjustment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. 
   Referring generally now to  FIGS. 1 through 5C , exemplary embodiments of the present invention are shown. 
   Referring to  FIG. 1 , a router  100  is shown. A base  102  and motor housing  104  are included in the router  100 . The base  104  is suitable for supporting the router  100  when the motor housing  104  is upwardly directed. The base  102  adjustably secures the motor housing  104 . For example, the motor housing is capable of being adjusted with respect to the base  102 , such that the router may achieve various cut depths when implemented with a router bit. Typically, bases include a furcation which may be drawn together by means of a clamping mechanism. In additional embodiments, a friction lock may be employed to secure the motor housing within the base. An adjustment mechanism  106  is further included in the router  100 . 
   The adjustment mechanism includes a shaft  108 , with a threaded portion, and a thread engaging member  110 . The engaging member  110  contains a lug or ridge for alternately engaging and releasing at least a portion of the threads included on the shaft  108 . The engaging member  110  may be biased, so the lug engages the shaft when unactuated. For instance, the engaging member  110  is biased by a spring so the motor housing is secured in a first orientation. When a user depresses the engaging member the lug and threads may disengage resulting in a second orientation being obtained. Additionally, fine depth adjustment may be achieved by rotating the shaft  108 . 
   A hand grip attachment  112  is connected to the exterior of the base  102 . The hand grip attachment  112  includes a lip  114  for at least partially supporting the router when grasped. The lip  114  extends generally outwardly from the exterior of the base. The portion of the lip  114  adjacent to the motor housing  104  of the present embodiment is either even with or less than the end of the base  102 . For example, the lip may be even with the base adjacent to the motor housing  104 . In a further embodiment, the top of the lip is below the end of the base. By orientating the top of the lip even with or below the end of the base a user is less likely to have their hand or fingers caught between the lip and the motor housing. For example, an unwary user&#39;s hand may be pinched between the motor housing and hand grip attachment during adjustment. 
   In further examples, the motor housing and/or the top of the lip generally opposing the housing may be angled away from the other so as to further minimize the pinch point. See generally  FIG. 2 , wherein the motor housing is angled generally away from the base/lip to minimize pinching. 
   In an additional aspects, a motor housing is contoured for grasping by a user. For instance, the motor housing is shaped so a user may pinch the motor housing between their fingers and thumb when adjusting depth. Supporting the motor housing in the previous manner may prevent the motor housing from dropping suddenly while changing depth, while promoting safety. In additional embodiments, the motor housing includes a lip for at least partially supporting the motor housing when grasped. Moreover, the motor housing may include an elastomeric coating or formed at least partially of elastomeric material to promote user comfort and minimize muscle fatigue. 
   Referring to  FIG. 3 , a router adjustment device  300  is shown. The adjustment device  300  includes a base  302 , a motor housing  304 , and an adjustment mechanism  306 . The adjustment mechanism includes a shaft  308 , with a threaded portion, and a thread engaging member  310 . The base  302 , motor housing  304  and adjustment mechanism  306 , including the shaft and engaging member  310  operate substantially as described with respect to  FIGS. 1 and 2 . The router adjustment device  300 , of the present embodiment, includes a frictional zone  316 . A frictional zone is included to at least partially resist the movement of the motor housing  304  with respect to the base. The frictional zone  316  is disposed either on the portion of the motor housing  304  received in the base or is disposed in an interior recess of the base  302 . 
   A frictional zone permits course adjustment, via disengaging the engaging member  310 , and fine adjustment, via rotation of the shaft  308 . The frictional zone at least partially inhibits rapid course adjustment which would damage the device  300  or potentially injure a user. 
   Frictional zones may be formed of brass, ceramic material, polymeric materials, elastomeric materials and the like for increasing the coefficient of friction between the friction zone and the generally opposing surface, such as the base. The increase in the coefficient of friction is greater than the coefficient of friction provided by a router or device not containing at least one frictional zone. For instance, the static coefficient of friction between the zone and opposing surface is between 0.15μ and 0.58μ, so as to permit adjustment while offering resistance, and thus increased safety. 
   In additional examples, a second frictional zone is employed to generally oppose the first frictional zone  316 . In examples where two frictional zones are employed, the first and second frictional zones are disposed generally opposite with one zone disposed on the base and the other disposed on the motor housing. 
   Referring to  FIGS. 4A ,  4 B and  4 C an apparatus  400  for controlling router adjustment is discussed. The apparatus  400  includes a base  402 , a motor housing  404  and adjustment mechanism  406 , which operate substantially a previously described. 
   Referring to  FIG. 4A , in a first example, a compression spring  418  is disposed in the base  402  so the shaft  408  is generally biased. For instance, when the shaft  408  included in the adjustment mechanism  406  is disengaged from the engaging member  410  the spring at least partially supports the shaft, and thus the motor housing, such as by contacting a shoulder included on the shaft  408 . By implementing the present apparatus when the engagement member  410  is disengaged from the shaft the spring acts to prevent rapid adjustment which may damage the apparatus or injure the user. The present apparatus retains the ability to permit a wrench to interact with a mechanical connection included on the shaft to permit base end adjustment. In additional examples, a washer may be disposed on the end of the spring  408  contacting the shaft for providing a suitable interface for the spring/shaft. 
   Referring to  FIG. 4B , in a second example, a biased lever is disposed in the base  402  adjacent to the threaded portion of the shaft  408 . In the present example a coiled spring with a lever arm  420  is utilized. The lever  420  acts to at least partially restrain the longitudinal movement of the threaded shaft by alternately engaging and releasing the threads. For example, when the thread engaging member is disengaged from the shaft  408 , the lever  420  may permit gradual change. 
   Referring to  FIG. 4C , in a further example, a gasket  422  formed of elastomeric or polymeric material is disposed in the base adjoining the shaft  408 , included in the apparatus  400 . For instance, the gasket  422  is formed of a semi-rigid plastic which couples to the shaft to at least partially restraining the shaft during longitudinal travel, such as when the shaft  408  is disengaged from the thread engaging member. Additionally, an inner ring formed of a metal such as brass, a ceramic and the like may be utilized to increase the durability of the gasket  422 . For instance, a gasket may include a washer with a metallic inner ring surrounded by an elastomeric material such that the inner ring contacts the shaft  408 . 
   Referring to  FIG. 4D , in an additional example, a frictional zone  424  is attached to the thread engaging member  410 . The frictional zone  424  is disposed in the aperture generally opposite the lug or ridge for engaging the threads included on the shaft  408 . The frictional zone may contact the shaft  408 , thus retarding the longitudinal motion of the shaft, such as when the shaft is disengaged from the threaded engaging member  410 . For instance, when a user inadvertently releases the thread engaging member  410  the frictional zone may come in contact with the shaft, and resulting in a slower travel. 
   Referring now to  FIG. 5A , a router adjustment device  500  is shown. The router device  500  includes a base  502 , a motor housing  504  and an adjustment mechanism  506 , including a shaft  508  and thread engaging member  510 . All of the above are substantially similar as discussed previously. The device  500 , of the present embodiment, further includes a brake element disposed in the base generally perpendicular to the axis motion for the motor housing  504 . 
   For example, the brake element is a biased pin  526  which is suitable for contacting the motor housing. Preferably, the pin  526  is biased in a disengaged orientation. For example, a user may wish to depress the pin  526 , and thus contact the motor housing and at least partially resist or inhibit motor housing motion, such as when performing a course adjustment. The pin  526  may be located so as to permit the user to utilize one hand to manipulate the pin  526  and the thread engaging member  510 . 
   In a further embodiment, the portion of the pin  526  contacting the motor housing may be formed of brass (e.g., a brass plug  527 ), ceramic material, plastic and the like for at least partially retarding the longitudinal motion of the motor housing without marring the motor housing  504 . 
   Referring to  FIG. 5B , in an additional example, the biased pin includes an angled end directed towards a generally opposing angled surface included on the thread engagement member  510 . Employing the present arrangement, the pin  526  automatically engages when the engaging member  510  is actuated, thus resulting in the pin  526  being forced towards the motor housing  504 . 
   Referring now to  FIG. 5C , in a further example, a contact zone  528  mounted to the thread engaging member  510 . For instance, the thread engaging member  510  includes an angled or curved protrusion, directed towards the motor housing, with a contact zone  528  for contacting the motor housing  504  when the engaging member  510  is pressed. The contact zone may be formed of brass, ceramic material, plastic and the like for at least partially resisting the longitudinal motion of the motor housing without marring the motor housing  504 . 
   It is believed that the apparatus of the present invention and many of its attendant advantages will be understood by the forgoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely an explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.

Technology Classification (CPC): 8