Patent Grant
7040206
This invention relates generally to the field of woodworking tools, and more particularly to the field of accessories for feeding stock safely across a saw table.
A table saw typically includes a flat, horizontally oriented table having an opening formed therein through which a top portion of a circular saw blade protrudes. The saw blade may be 10–12 inches in diameter, for example, and is motor driven to rotate at a speed of 3,000 revolutions per minute or more. A piece of stock material, typically wood, may be cut by moving it across the table to intersect the spinning saw blade. The height of the top of the saw blade above the table may be adjustable within predetermined limits in order to accommodate stock material of various thicknesses.
A fence is provided with a table saw to guide the movement of the stock in a direction parallel to the plane of the saw blade in order to ensure a straight cut and to avoid binding of the non-cutting portions of the saw blade within the stock material. A fence typically includes an elongated metal bar having a flat guide face oriented at a right angle with respect to the table and parallel to the plane of the saw blade. The distance between the fence guide face and the saw blade may be adjustable within predetermined limits in order to accommodate stock material and cut locations having various widths.
It is known to use a push stick to urge the stock material past the saw blade in order to keep the operators fingers at a safe distance from the dangerous rotating blade. The most simple push stick may be simply an elongated piece of excess stock material that is urged against the work piece. A more sophisticated push stick is described in U.S. Pat. No. 6,135,521 as including an ergonomically designed handle, two stepped portions for engagement with the work piece, and non-slip pads for better control. While the push stick of the '521 patent does provide a degree of protection for the one hand of the operator, it still requires the operator to touch the work piece with a second unprotected hand. Furthermore, this style of push stick can apply downward force against only the trailing edge portion of the work piece since it engages the rear edge of the work piece with a stepped portion of the stick. Applying downward force only against the trailing edge portion of the work piece may be inadequate to hold the stock material down. A long piece of stock material being urged into a saw blade with such a tool may be lifted away from the table by the lifting action of the rotating saw blade, thus creating a dangerous kick-back condition where the work piece is thrown upward toward the table saw operator.
U.S. Pat. No. 2,839,100 describes a woodworking accessory that engages the work piece along an extended length in order to keep the operator's hands away from the saw blade at all times. This device engages the stock material with a plurality of screws, thus causing undesirable damage to the work piece. While this device provides improved control of the work piece between the saw blade and the fence guide face, it does not provide any control for the severed portion of the work piece on the far side of the blade away from the fence, commonly called the outside cut material. While the outside cut material is often considered the scrap portion of the stock material, it nonetheless may present a danger to the operator if it is not properly restrained during the cutting operation.
U.S. Pat. No. 4,370,909 describes a hand guard for a table saw including a grooved underside adapted to rest on top of the work piece and a vertically moveable heel for engaging the rear edge of the work piece. Here, again, this tool engages the stock material only near its rear edge and is thus ineffective in restraining the leading edge portion of a long piece of stock material. Furthermore, the tool is narrow and must be positioned against the guide fence, so it is useful for removing only a small width of material from the work piece. The tool is designed to exert a pushing force against the work piece. It includes no means for positively forcing the work piece against the guide fence, thus necessitating the use of the operator's second unprotected hand for maintaining pressure against the fence as the work piece is moved past the saw blade.
Thus, an improved pushing apparatus is needed for moving stock material along a table past a rotating blade in order to provide improved control of the work piece and improved safety for the operator.
An apparatus for guiding a work piece through a cutting device is described herein as including: a body; a first leg attached to the body and extending downward to form a first leg non-slip work piece-contacting surface; a second leg attached to the body and extending downward to form a second leg non-slip work piece-contacting surface; a center leg moveably attached to the body and extending downward between the first leg and the second leg to form a center leg non-slip work piece-contacting surface, the center leg fixable in any one of a plurality of positions; and a handle moveably attached to a top of the body and fixable in any one of a plurality of positions.
In a further embodiment, an apparatus for guiding a work piece through a cutting device is described as including: a body having a top and an underside opposed the top; a first leg attached to the body and forming a first side surface, the first leg extending below the underside of the body to form a first leg work piece-contacting surface; and a center leg attached against the underside of the body and extending below the underside of the body to form a center leg work piece-contacting surface, the center leg moveable to a plurality of positions relative to the first side surface to form a first tunnel having a selected width through which a cutting device may pass, the first tunnel defined by the first leg, the center leg and the underside of the body. The apparatus may further include a spacer removably attached to the first leg and having a spacer side surface remote from the first side surface and having a spacer bottom surface, the spacer attachable to the first leg in a plurality of positions to extend the spacer bottom surface below a plane of the first leg work piece-contacting surface. The spacer may have a non-slip surface and a slip surface opposed the non-slip surface; with the spacer being selectively attachable to the first leg to position one of the slip surface and the non-slip surface as a spacer bottom surface. The apparatus may include a shield comprising a connector to position the shield at a first position relative to the body and a second connector to position the shield at a second position relative to the body. The apparatus may include a tapering device having a first edge extending under the leg closest to the fence to make parallel contact with an edge of the work piece, and a second edge moveable to a plurality of angles with respect to the first edge. The tapering device may include: a bottom plate; a top plate pivotally attached to the bottom plate and fixable at a plurality of angles in relation thereto; a first memory stop connected to the bottom plate for abutting the top plate when it is positioned at a first of the plurality of angles; and a second memory stop connected to the bottom plate for abutting the top plate when it is positioned at a second of the plurality of angles.
In a further embodiment, an apparatus for guiding a work piece through a cutting device is described as including: a structure defining a tunnel through which a cutting device may pass, the structure comprising at least two work piece-contacting surfaces for applying force to a work piece on each of two opposed sides of the cutting device; and a means for adjusting a width of the tunnel to accommodate a plurality of cut geometries. The apparatus may include a means for balancing the structure when the work piece has a width insufficient to make contact with the work piece-contacting surfaces on both opposed sides of the cutting device. The apparatus may further include a means attached to the structure for maintaining an edge of the work piece at a selected one of a plurality of angles with respect to a cut line.
An apparatus for guiding a work piece through a cutting device may include: a structure defining a tunnel through which a cutting device may pass, the structure comprising at least two work piece-contacting surfaces for applying force to a work piece on each of two opposed sides of the cutting device; and a handle attached to the structure and moveably fixable at any one of a plurality of positions along a width of the structure for positioning the handle relative to a line of the cutting device.
An apparatus for guiding a work piece through a cutting device may further include: a structure defining a tunnel through which a cutting device may pass, the structure comprising at least two work piece-contacting surfaces for applying force to a work piece on each of two opposed sides of the cutting device; and a balance support moveably attached to the structure at any one of a plurality of positions to extend a bottom surface to a position below a plane of the at least two work piece-contacting surfaces.
An apparatus for guiding a work piece through a cutting device may include: a structure defining a tunnel through which a cutting device may pass, the structure comprising at least two work piece-contacting surfaces for applying force to a work piece on each of two opposed sides of the cutting device; and each of the at least two work-piece-contacting surfaces comprising a non-slip surface.
An apparatus for guiding an especially long work piece through a cutting device may be embodied as: a first structure defining a first tunnel through which a cutting device may pass, the first structure comprising at least two work piece-contacting surfaces for applying force to a work piece on each of two opposed sides of the cutting device; a second structure defining a second tunnel through which the cutting device may pass after having passed through the first tunnel, the second structure comprising at least two work piece-contacting surfaces for applying force to the work piece on each of two opposed sides of the cutting device; and a bridge connecting the first structure and the second structure to align the first tunnel and the second tunnel along a line of the cutting device.
These and other advantages of the invention will become more apparent from the following description in view of the drawings. Similar structures illustrated in more than one figure are numbered consistently among the drawings.
The inventor has analyzed the forces acting upon a work piece being moved over a table saw blade in order to identify the shortcomings of the prior art pusher designs and in order to evaluate the improved pusher apparatus described herein.
Arrows are used to illustrate the forces that should be exerted on the work piece 22 in order to ensure optimal control of the cutting process and to ensure the safety of the table saw operator. A pushing force is needed in a direction parallel to the direction of the cut C to force the work piece 22 past the saw blade 16. The pushing force should include separate components 30, 32 exerted on the inside cut portion 24 and outside cut portion 26, respectively. The rotation R of the saw blade 16 will create a force opposing pushing force 30, 32 proximate the leading edge of the saw blade 16 where the saw blade 16 is moving forward into the stock material.
Force 34 is necessary to keep the inside cut portion 24 in contact with the fence 18. Importantly, no force in the direction of force 34 should be exerted on the outside cut portion 26 in positions P2 and P3. Any such force acting on the outside cut portion 26 will cause the work piece 22 to engage the trailing portion of the saw blade 16 where it is traveling in an upward direction, thus causing binding of the saw blade 16, burning of the cut surface, and possible kickback of the work piece 22.
Downward forces 36, 38 must be exerted on the inside cut portion 24 and outside cut portion 26, respectively. Downward forces 36, 38 must be of sufficient magnitude proximate the saw blade 16 to overcome the tendency of the rotating saw blade 16 to fling the work piece 22 upward.
Simple prior art pushers, such as the one described above in U.S. Pat. No. 6,135,521, provide a downward force 36 proximate the trailing edge 40 of the work piece 22 where they engage the trailing edge of the work piece 22. Depending upon the length of the work piece 22 and the length of the pusher, the magnitude of such a force may be insufficient proximate the saw blade 16, and the work piece 22 may be lifted away from the table surface 14. Accordingly, downward force 38 and pushing force 32 must be provided by the operator's unprotected hand with the device of U.S. Pat. No. 6,135,521. It is particularly difficult for an operator to provide pushing force 32 in a direction exactly parallel to the line C of the cut, especially due to the tall, narrow structure of the device. Should the operator exert any force in a direction toward the saw blade 16, the work piece 22 will bind with the saw blade 16 and cause burning and possible kick back. This is especially dangerous when making a bevel cut, since the forces generated between the saw blade 16 and the inside cut portion 24 can be very large.
In addition to damaging the top surface of the work piece, prior art pushers of the style of U.S. Pat. No. 2,839,100 also rely on the operator's unprotected hand for providing forces 32, 38. As described above, this is not only unsafe, but it is difficult for the operator to properly maintain such forces without exerting any force toward the fence.
The hand guard described in U.S. Pat. No. 4,370,909 includes a heel for generating pushing force 30, 32, but it has no means for positively engaging the work piece 22 to provide force 34 for keeping the inside cut portion 24 in contact with the fence 18. Contact between the bottom surface of the hand guard and the top surface of the work piece is confined to a limited surface area, with the actual contact between these surfaces being further reduced by the inherent unevenness of the as-manufactured bottom surface of the hand guard. No provision is provided to prevent the work piece from slipping horizontally in relation to this prior art hand guard. Furthermore, depending upon the length of the work piece 22, the downward forces 36, 38 provided at the trailing edge portion of the work piece 22 by such a device may be insufficient to prevent kickback. The operator's unprotected second hand must be used to provide the missing forces for adequate control of the work piece 22.
Apparatus 50 may be formed of component parts that can be attached or removed as desired. Body 52 is the structural base to which other components are attached, either directly or indirectly. Body 52 may be formed to include a slot or keyway 66 on opposed leading and trailing edges for receiving mating tongues or keys 68 formed on respective leading and trailing portions of center leg 60. Center leg 60 is assembled onto body 52 by sliding keys 68 into the opening slot of keyways 66 to position center leg 60 at a selected location along the underside 70 of body 52. The center leg 60 may be affixed at any selected location by tightening thumb screws 72 into mating nuts (not shown) located within the keyway 66, thereby drawing the keys 68 tight against the body 52. The location of center leg 60 defines the respective widths of tunnels 62,64.
First leg 56 and second leg 58 may be assembled onto the sides of body 52 by threading bolts through counter-bored holes in the respective leg into nuts embedded or otherwise retained in body 52. (hardware not shown in Figures) Each of the legs 56, 58 includes a flat side surface 74 adapted for abutting a flat guide surface of a saw table fence. Any mounting hardware exposed along the side surface 74 should be mounted flush or counter-bored below surface 74 so as not to interfere with the smooth movement of side surface 74 across a guide surface. Apparatus 50 may be assembled to include one or both of first leg 56 and second leg 58, depending upon the requirements of a particular operation. The legs 56, 58, 60 each extend away from the underside 70 of body 52 to form respective work piece-contacting surfaces 76. These work piece-contacting surfaces 76 are preferably non-slip surfaces, being formed from a material that does not easily slide over a work piece surface, for example rubber or a thermoplastic elastomer containing a plurality of recesses such as grooves 77. The term non-slip is used herein with its common usage meaning that two surfaces will tend to stick together when a force is applied there between. The term non-slip need not imply a specific coefficient of friction, but rather is meant to include surfaces that are generally soft and adhering, such as rubber or other elastomers. The term non-slip as used herein excludes hard smooth surfaces such as metal or plastic having no special surface treatment, but may include such materials if treated to have a degree of roughness for imparting a non-slip property when forced against a work piece. A typical molded plastic part surface will have an inherent unevenness and hardness such that it will provide a slip surface when pressed against a work piece such as wood. A non-slip material may be molded into or may be attached to the bottom of the respective leg 56, 58 with an adhesive, or a non-slip material may be partially embedded into the bottom surface of the legs, or the material of the legs may be sufficiently roughened to be non-slip. It is preferred that the non-slip material used to form work piece-contacting surface 76 be slightly recessed from the first and second leg side surfaces 74 so as not to interfere with the smooth movement of side surface 74 across a fence guide surface. In one embodiment, the non-slip surface may be an elastomer having a durometer measurement of 35–40. The elastomer is sufficiently soft that it will deform to accommodate the inherent unevenness of a molded plastic surface, thereby further increasing its non-slip property.
Body 52 and legs 56, 58 may include keyways 78 for capturing hardware used to attach handle 54 and/or other accessories. Handle 54 may be moved to any selected position between first leg 56 and second leg 58, then locked into place by tightening bolts 80. Bolt 80 passed through a hole formed in handle 54 and is threaded into a nut disposed within the keyway 78. As will be described more fully below, the location of handle 54 with respect to body 52 may be selected to most advantageously locate the point of application of forces to be applied by an operators hand on the handle 54. Handle 54 may be aligned to be parallel to leg side surface 74 or it may be fixed at an askew position so that the longitudinal axis of the handle 54 is disposed at an angle to the line of the saw blade 16.
The structural components of the apparatus 50 described above and below may be formed of plastic, metal, wood or other known materials of construction. In a preferred embodiment, the component parts are formed of structural foam injection molded plastic, with assembly hardware being formed of metal. Accidental contact between a cutting tool and a plastic apparatus part will not damage the cutting tool and may result in a lower risk of injury to an operator than would otherwise be the case if the apparatus part were formed of metal.
The operation of apparatus 50 with a table saw 10 may be understood with reference made to
Apparatus 50 exerts all of the forces necessary for proper control of the work piece 22 as discussed above with reference to
In the configuration of
There may be certain stock materials and cut dimensions that are beyond the range of adjustment of a particular embodiment of body 52 and legs 56, 58, 60. One such situation is illustrated in
Another embodiment of a spacer is illustrated in
By providing vertically oriented slots 92, 106 for the passage of thumbscrews 90, 104, a spacer 84, 96 may be attached (directly or indirectly via first or second leg) to body 52 at any of a plurality of vertical heights. This feature may be used advantageously when the width of the work piece 22 is too narrow to properly engage both sides of tunnel 64 as illustrated in
Apparatus 50 protects the operator's first hand (not illustrated) as it is placed on the handle 54. The operator may place a second hand 112 on the balance support/spacer 84 and/or on the body 52 to provide additional force against apparatus 50. The body top surface 82 may include ribs 114 or other non-slip structures or materials to provide additional gripping action for the operator's second hand 112.
Another accessory that may be used with apparatus 50 is a shield such as dust shield 120, as illustrated in
Dust shield 120 may be provided with an alternative connector, such as a second set of keys 126 on its underside, as illustrated in
Spacers 84, 96 may be provided with open-ended slots 128, 129 as illustrated in
When making a taper cut on two opposed sides of the same piece of stock material, one may appreciate that the set-up for the second cut must include consideration of the taper that was previously made on the first side of the material. Thus, tapering device 144 may be set to 2° for a first cut, then 4° for a second cut on the opposed side of the same piece of material. When making multiple such pieces, it may be necessary to repeatedly change the setting of tapering device 144 from one angle to another. To facilitate such an operation, two memory stops 166, 168 are provided on bottom plate 146. A first angle is selected and first memory stop 166 is moved in slot 170 to abut top plate 148 and locked into position. A second, greater angle is then selected and second memory stop 168 is moved in slot 172 to abut top plate 148 and locked into position. The device 144 may then be quickly switched between the first angle and the second angle by simply loosening locking knob 164, sliding top plate 148 until it abuts either first memory stop 166 or second memory stop 168, then again tightening locking knob 164.
Tapering device 144 is illustrated in
Tapering device 144 may also be used as a bridge for cutting long pieces of stock material. This can be accomplished by connecting a first body 52 to tapering device 144 via spacer 84 at slot 154 and connecting a second body 52 to tapering device 144 at slot 152, in a manner similar to the way that stabilizing plates 130 are attached in
While the preferred embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those of skill in the art without departing from the invention herein. Non-limiting examples include a component that is described above as being attached to one part of the apparatus may alternatively be attached to a different part of the apparatus in other embodiments. Parts described as being indirectly connected may be connected directly to each other, and vice versa. Component parts may be assembled from individual pieces or may be integrally formed as a single unit. Alternative types of connectors and alternative materials may be used. The apparatus may be used with other types of power tools. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.
This application claims benefit of the Jun. 1, 2001, filing date of U.S. provisional patent application Ser. No. 60/295,378.
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| Number | Date | Country | |
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| 60295378 | Jun 2001 | US |
