Patent Application
20140373696
The background of related machines, devices, and practices in the use of table and/or other saws having a deck, or support surface, on which a workpiece is placed to be cut.
This statement will restrict any lengthy elaboration in defining what a table saw is, or how it is used, as the reader can be spared this redundancy. Suffice it to state, a table saw is a machine, or body of a machine of convenient height, having a flat deck, or support surface, on which a workpiece is rested while being cut by a blade, or dada set, or other cutting tool, projecting through the deck from below, and powered in most instances by an electric motor. In this statement “table saw” will be the assumed machine with which the invention is utilized, although use with other types, such as bandsaws and inverted routers, would be practicable. Further, “blade” will include any and all cutters; and it is implied that workpieces of materials other than wood can be involved.
The most common operation performed on a table saw is the rip cut, wherein an element known as the “fence” is secured to the saw so as to be adjustable in its lateral spatial relation to the blade, allowing the operator to select the width of workpiece to be removed from one which is wider. The objective is to keep the stock, or workpiece, tight against the fence so as to produce a straight uniform cut, and prevent danger arising from the work drifting away from said fence, thus becoming bound up and resulting in a violent reversal of movement. This is the situation that results most commonly in an injury to the operator. Therefore there are many devices, or prior art, put forth in the field that address these hazards, many of high merit.
The workpiece is advanced over the blade manually unless propelled by a power feeder. The use of a power feeder, or stock feeder, allows greater accuracy and safety, and its position can be biased, or “crabbed” to impart lateral force, pressing the workpiece tightly against the fence. However, the mounting of a power feeder on the deck of the saw restricts the lateral travel of the fence, and so limits the width of material that can be cut. Thus it is set aside often because of inconvenience, and the re-installation deferred fix various reasons. The purpose and advantage of the present invention is to facilitate the use of guides or feeders mounted directly on the fence, thus eliminating the restriction of lateral movement of the fence, and increasing the convenience and safety of such operations.
The “T-square” style fence is today most widely used, as it can be attached as an after-market accessory to most saws, and is now supplied by numerous makers. These fences have many merits, and accomplish good results when used by an operator with sufficient skills; but suffer one common deficiency, to wit, the distal end is not fastened to the deck of the saw. This condition makes it vulnerable to loss of alignment from rough handling of materials, and precludes the use of the invention(s) herein described, in that the downward force of a stock feeder, or any non-motorized spring-loaded workpiece guide of substantial force, would simply lift the distal end of the fence. These fences lock into position laterally by use of a cam at the front, in a cross-head, tightening onto a rail by the downward movement of a handle. The basic body of one of these has been used in the development of the invention(s) herein described, as the inventor desired to retain the cam-locking feature, which also becomes an essential element in the invention.
After conducting searches available through the USPTO and a website accessing the European database, the inventor found no results particularly related to this invention. Herein are cited patents relevant to some of the elements of the invention:
In response to the objectionable aspects of the use of fences and feeders noted above, the present invention combines the two tools, or elements, into an integrated tool consisting of a feeder, or powerful spring-loaded workpiece guide, mounted directly on the body of the fence, said fence being firmly held to the deck of the saw with a switchable magnet or electromagnet.
As previously mentioned, this invention(s) has been developed to allow the direct mounting of a stock feeder or spring-loaded workpiece guide on a conventional “T-square” style fence for reasons of safety, convenience, freedom of movement, and improved performance and efficiency.
Any person skilled in the art of fabrication, precise measuring, cutting of various materials accurately, drilling and tapping, layout, and associated skills, can built this invention, given access to materials, tools, and supplied with the elements involved. To begin, one must have or construct a body, or housing (17), together with an attached clamping head (14), so comprising a “T-square” type table saw fence. It is highly preferred to use such a body, or housing, in that its dimensions, being a standard 2″×3″ square tubing, provide adequate space for the magnet and the elements of the mechanism to be assembled. Those skilled in the art will appreciate that larger housings could be utilized to accommodate more powerful magnetic elements, or smaller ones for lighter duty, and that the present invention could be susceptible to variations or modifications other than those specifically described, and it is to be understood that the present invention encompasses all such variations that fall within its spirit and scope.
A switchable magnet manufactured by the Magswitch™ company of Westminster, Colo., using the remarkable new magnetic metallurgy, was chosen for use in this prototype for its appropriate dimensions and effective holding power, which is 176 kg. (400 pounds) when activated in contact with substantial ferrous material. The next design task was to install said magnet (19-b) near the distal end of the housing (17) in such a way that it is permitted no movement or rotation except a slight ability to be lifted away from the deck (16) of the saw by small lift springs(20), so as not to be sliding in contact with the deck (16) when not activated, and the operator is moving the entire assembly in lateral motion. Moreover, the materials providing this restriction of movement must be of a non-magnetic nature, as the magnetic field when activated extends in all directions. To accomplish this a close-fitting sleeve (19) was fabricated of phenolic plate ½″ (12.7 mm) thick and secured to the floor of the housing (18) by drilling and countersinking screw-holes in the floor (18) of the housing (17), and tapping threaded holes into the underside of the sleeve to receive flat-head 10/24 machine screws. A rectangular hole, or port, is cut in said floor, as seen in
For the preferred embodiment, this handle, found to be epoxy-glued onto threads which were at the top of the shaft that turns the magnet's core (21), was removed and replaced with the primary spur gear (24) obtained from McMaster-Carr™, catalog #6325K71, by some machining and the use of a tension pin passing through the gear and the shaft. This gear was chosen for its appropriate dimensions and durability. As the switching of the magnet requires a rotation of 180 degrees, with this gear that rotary motion translates to 50 mm. (2″) of travel along the root of the teeth. This distance transfers into the linear motion of the racks (26, 27) as required, which is imparted to said racks from the downward motion of the fence handle (40), through the bell-crank (29) and connecting rods (30, 31). Said racks are found at McMaster-Carr™, catalog #6295K13. Thus by graphic calculation the distance of the pivot-points of the rod ends (32) from the rotational center of the bell-crank was determined, as was the distance of the rod-end of connecting rod #2 (31) from the axis of the cam. In the prototype the bell-crank was made of phenolic also, but could be of other materials. Likewise, the swiveling rod-ends on connecting rods could be replaced with clevises, such variations not defeating claims made here. Fine tuning the timing of the switching of the magnet relative to the locking of the cam is readily done by adjusting the length of either of the connecting rods where they have threaded rod-ends (32) (McMaster-Carry™ 60645K111). The clamping head (14) must square up the fence to the rail (15) a moment before the magnet is activated, which occurs when the magnet's core (21) is rotated 180 degrees. Thus, at about 80 degrees of downward swing of the handle (40), the clamping to the rail is accomplished. 90 degrees of downward swing yields two inches (50 to 52 mm.) of rack travel, which yields 180 degrees of rotation of the magnet's core (21). In the nature of the switchable magnet, as it approaches activation at about 150 degrees, it urges rotation to finish the motion. In the non-automatic version the operator simply turns a knob (33) (in
As readily seen in the drawings, two racks were required to defeat any binding torque on the magnet in its sleeve, the secondary rack (27) pushing on the primary gear (24) diametrically opposed to the primary rack (26), which pulls. The two racks pass through guide blocks (34) so as to be held in close engagement with the gears (24, 28) and parallel to one another, the guides being two layers of ½″ or equivalent phenolic with grooves facing inward to form the guide's channel, glued or screwed together. The guides are attached to the floor of the housing in the same manner as the sleeve. At the primary gear the racks are likewise held in engagement by being trapped in grooves in the sidewalls of the sleeve (19). The secondary, or idler gear (28), which transmits force to the secondary rack (27) is mounted on a shaft (35) which is projected up from its idler block (36), and this block is fastened to the floor of the housing with a single screw to permit the gear to self-align. A good stable hardwood with varnish is appropriate. These features are best recognized in
The primary rack (26), which pulls, was ground and drilled to accept an offset pin (37) having a spacer (38) to bring the linear force in closer alignment to the bell-crank (29). Said bell-crank (29) is linked to the primary rack (26) by connecting rod #2 (31) with the use of a swiveling rod-end (32). Connecting rod #1 (30) has a similar rod-end pivoting in the bell-crank (29), whose axle (39,
Please observe in
Please observe in
With the mechanism complete and in good working order, the top, or roof (17-b), of the housing was reattached to the housing (17), with the stock feeder's mounting base bolted to the feeder mounting plate (10) near to the axis of the saw-blade's arbor, to avail the operator the maximum availability of reach provided by the feeder's mounting apparatus. This re-attachment was accomplished by providing additional sidewalk to the housing made of ½″ hardwood plywood, which are necessarily taller than those of the tubing that comprised the housing (17), due to the vertical dimension of the magnetic element (19-b). Tabs were welded onto the original steel roof and tapped so as to receive countersunk screws from the outside of the added walls. In production the dependence on the plywood as structure would be eliminated.
At this stage the power stock feeder was assembled to its mounting base and the entire prototype was put into use, working flawlessly in many repeated trials, i.e., downward pressure was applied on the workpiece of more-than-sufficient force needed to obtain traction and propel the workpiece over the blade, with no indication of failure, even when downward pressure was emphasized at the maximum distance from the fence allowed by the mounting apparatus of the stock feeder being used.
Of course all things physical have limits, and the user would do well to exercise caution and common sense in the setup and testing of any machinery. It is recommended that a builder or user of this invention conduct a test, with the saw blade retracted downward from any projection above the deck, then applying sufficient downward pressure on the guide or feeder to, in the case of non-motorized guides, obtain traction sufficient for good results, or in the case of a motorized feeder, obtain sufficient traction to propel the workpiece, without any threat of dislodging the magnetic element.
From the description above, a number of advantages become evident. The reader will see the improved facility in the use of saw fences and feeders, and the enhanced efficiency of the operator. Variations or modifications of elements and/or mechanisms described herein shall not affect the value and novelty of the invention. Thus, the scope of the invention should be determined by the appended claims and not limited to the preferred embodiment illustrated.
