Pin router

Details Pin router Pin router

1999-07-06

2001-09-18

Bray, W. Donald (Department: 3725)

Woodworking

Shaping machine

Vertical spindle

C144S371000, C144S134100, C409S110000

Reexamination Certificate

active

06289952

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to router tables, pin routing machines and mechanisms for positioning router bits, particularly bits used in plunge routers mounted in router tables.
BACKGROUND OF THE INVENTION
Adjusting the height of a router bit when the router is fixed in a table is frequently difficult. Doing so is particularly difficult when using a plunge router because a plunge router is not well designed for making small adjustments in the projection of the router bit by moving the router body relative to the base. Furthermore, plunge routers are designed to be used upright, and they typically include springs that balance the router weight so that the router body will not drop uncontrollably toward the base when the body and base are unlocked. When the router is upside down in a router table, the router body and base are urged apart from each other by the force of gravity and/or springs, introducing further grief in achieving desired adjustments in bit location.
Many plunge routers have a threaded adjusting rod attached to the router base and passing through or adjacent to a ledge or other structure that is part of, or is attached to, the router body. A nut or pair of locking nuts positioned on this adjusting rod and bearing against the ledge serves to fix the position of the router base relative to the body. After-market devices for adjusting the position of the base are available in which an internally threaded nut is attached to one end of a tube and a knob is attached to the other to tube end (where the knob is sufficiently clear of the router body to be readily accessible, at least when the router is an upright position). The nut is threaded onto the adjustment rod, and rotation of the knob rotates the nut around the rod and against the ledge. The knob on such devices can be relatively inaccessible, however, when the router is mounted under a router table, and its rotation moves the router body relative to the router base too slowly when substantial changes in router bit position are being made but too quickly for truly accurate adjustments because of the typically coarse pitch of the adjusting rod thread.
As a result, there is a substantial need for a mechanism for securing and conveniently and accurately adjusting the position of a plunge router when it is mounted upside down in a router table so that the projection of the router bit above the table can be closely controlled.
One of the many attractive capabilities of a router is its ability to be used with a pattern to accurately and quickly manufacture multiple parts corresponding to the pattern. In some instances, this is possible utilizing a router bit with an attached ball bearing follower that bears against the pattern. Some products cannot be made, however, with such a pattern following bit. For instance, such bits cannot be used to form a hollow area within a workpiece using a cove cutter. This type of operation can be done with a pin routing machine, which is typically a dedicated tool like that depicted in U.S. Pat. No. 4,893,661.
An attachment has been suggested in order to provide a router table with pin router capability in U.S. Pat. No. 5,345,984, but that design suffers from several practical limitations. Additionally, the full benefit of pin routing capabilities can be achieved only if it is possible to raise the cutter into the workpiece. Accordingly, there is a continuing need for practical pin router apparatus usable with a router table and a conventional fixed base or plunge base cabinet shop router.
SUMMARY OF THE INVENTION
This invention is a mechanism that moves a tool or a portion of it relative to another portion of the tool or other structure. The mechanism attaches to a plunge router, particularly when the router is used in a router table, to conveniently and accurately move the router body relative to the router base and lock the two in desired relative positions so that the adjustment of the position of a router bit relative to a router table may be also be accomplished conveniently and accurately. The mechanism is attached to the router base and bears against a ledge or other portion of the router body so that the body and base can be drawn toward each other or permitted to separate from each other.
In the embodiment of the invention described below, this is accomplished by attaching a plunger or piston to a threaded adjustment rod that is attached to the router base. (Such threaded rods are typically supplied with plunge routers). The piston is positioned to slide within a cylindrical opening or sleeve within a mechanism body. The position of the piston, and therefore the position of the router body relative to its base, is controlled for relatively coarse position adjustments by a pivoting handle and, for fine adjustments in position, by a micro-adjust mechanism positionable in the bottom or lower end of the body. The micro-adjust mechanism utilizes a threaded spindle that may be moved axially by very small increments by rotating a knob on the lower end of the spindle. The piston rests on the top of the spindle and, therefore, is raised and lowered by the same small increments of axial movement of the spindle.
The mechanism body is an elongated sleeve having a cross-sectional shape similar to the letter Omega (&OHgr;). The piston travels within a generally cylindrical passage in the body adjacent to an elongated groove defined by two parallel plates protruding from one side of the body. One end of the handle is positioned between the plates and pivots on a stud or screw that extends through the plates. The handle is attached by links to a piston arm that slides between the plates and within the groove and attaches to the piston. The handle may also be attached by a chain, rod or other link to a foot pedal so that changes in the position of the router body relative to its base may be made without use of the operator's hands. By providing multiple positions at which the link to the piston may be attached to the handle, the position of the handle (for a particular router bit position), and the excursion of the handle necessary to move the piston a particular distance, may be adjusted. Multiple attachment points on the handle for the chain, rod or other link to the foot pedal also make possible adjustment of the pedal excursion (for a particular range of bit movement). Such multiple attachment points also make it possible to adjust the force necessary to achieve a particular bit movement, since the mechanical advantage can be varied. Generally a relatively large handle excursion will result is a relatively small bit movement so that relatively little force is needed and a desired bit location is easy to achieve.
Each of the piston and the micro-adjust cylinder that are positioned within the cylindrical passage in the mechanism body may be locked in the body by squeezing it closed utilizing any of a variety of mechanisms for doing so, such as threaded studs or screws operated by knobs or handles to draw the plates toward each other.
The pin router fixture of this invention is a casting having a foot that rests on a router table top and that is either bolted to the top or clamped to it. The casting rises from the table and gracefully curves toward the center of the table, where it terminates in a sleeve with a vertical bore that is centered above the router. The sleeve captures a guide pin mechanism that holds a selected size of interchangeable guide pins directly above the axis of rotation of the router cutter or bit. The mechanism permits the guide pin to be raised up and held in a raised position or dropped down to a lower, operational position, and held there with the assistance of a spring. The entire guide pin mechanism may be raised or lowered to position the guide pin as desired.
Clamping blocks used to clamp the pin router arm to the router table, particularly a thin top such as a sheet steel one, are adjustable so that, once adjusted for a particular router table top, the pin router arm may be removed and replaced quickly and accurately.
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