Patent Application
20080282862
The invention relates to repetitive fences for use with cross-cutting saws. More specifically, the invention relates to a repetitive fence for attachment to a cross-cut saw, such as a miter saw, chop saw, radial arm saw, table saw, or the like with reference to a blade of the saw.
Industrial machine tools such as numerically controlled milling machines and the like have been provided with adjustable stages, chucks, and other devices for holding a work piece with respect to a working tool such as a drill press, milling head, band saw, or the like. Typically, such devices hold the work piece in place while the working tool itself moves with respect to the work piece. More sophisticated machinery also permits the automatic feeding of material stock (e.g., bar stock) to the working tool for placement with respect thereto. Such systems employ feedback mechanisms to assure that the working material is actually in place, and is properly aligned with the working tool. Homeowners utilizing woodworking tools such as table saws, miter saws (compound, sliding) radial arm saws, and the like cannot be provided with such automated mechanisms in a cost effective manner. Thus, the home hobbyist, cabinet maker or the like must necessarily measure and mark the work piece to be cut at a desired dimension and then proceed by manually placing the work piece with respect to the cutting blade or the like. As a consequence, woodworkers have adopted the motto, “measure twice, cut once.” Thus, it is acknowledged that measuring a proper cutting dimension on a work piece is a source of error for a home craftsman utilizing a cutting tool which does not have automatic means for positioning the work piece with respect to the cutting tool or vice versa. In recognition of this disadvantage, power tool manufacturers have for some time provided various saws (e.g., table saws) with manually positionable fences which can be set at a calibrated distance from a cutting tool, such as a saw blade. In this manner, once the fence has been set by the user, repeated cuts can be made at this dimension without the necessity of having to mark the work piece, and thus measure the cut in advance. Although devices such as rip fences, miter guides, and the like dramatically reduce cross-cut errors, the user must manually and carefully reset the fence for every different dimension cut. Unless the user has carefully worked out the various cut dimensions in advance, such as to organize the various work pieces (particularly with respect to standard dimension lumber) in a logical sequence, the manually adjustable fence may be repositioned numerous times with respect to the completion of a single project (e.g., a book case). This disadvantage is exacerbated when the various cut dimensions may not be known in advance during a planning stage. By way of example, a carpenter installing baseboard or crown molding in a home will arrive at the jobsite and by necessity take numerous wall and ceiling measurements, transfer these measurements to a work piece by marking and then make all the various cuts. If a standard conventional manual repetitive fence is used, a great deal of organizational forethought is necessary to minimize adjustment of the fence throughout completion of a typical job.
Therefore, a need exists for a repetitive cross-cut fence which minimizes the number of adjustments which are necessary for operation of the fence for a typical job.
A further need exists for a repetitive cross-cut fence which is easily adjustable for a variety of various cross-cut lengths while minimizing user error.
Yet another need exists for repetitive cross-cut fence which is easily readable and settable by a user.
It is therefore an object of the present invention to provide for a repetitive cross-cut fence which minimizes the number of adjustments which are necessary for operation of the fence for a typical job.
It is a further object of the present invention to provide for a repetitive cross-cut fence which is easily adjustable for a variety of various cross-cut lengths while minimizing user error.
It is yet another object of the present invention to provide for a repetitive cross-cut fence which is easily readable and settable by a user.
The invention achieves the above objects, and other objects and advantages which will become apparent from the description which follows, by providing a repetitive fence for attachment to a cross-cut saw with reference to a saw blade. The invention includes an extensible member having a work piece stop member adjacent to a distal end thereof for receipt of an end of a material to be cross-cut, such as a length of standard dimension lumber. A drive mechanism is operatively connected to the extensible member for moving the stop member to a pre-selected distance. A mensuration device is operatively connected to the stop member for determining a relative position between the saw blade and the stop member. A visual display is provided for displaying the relative position between the stop member and the saw blade so that the user is provided with visual feedback as to the position of the repetitive fence.
In preferred embodiments of the invention, the drive mechanism includes a coiled, drive tape having a main portion wound round a hub, an end portion connected to the extensible member, and a plurality of apertures positioned a regular intervals thereon for engagement with teeth on a drive sprocket. The drive sprocket has a first pulley portion thereon, and the drive mechanism further includes a drive gear having a second pulley portion thereon. The first and second pulley portions are operatively interconnected by a drive belt such that rotation of a drive gear causes the drive tape to extend and retract the stop member. The drive belt preferably has a tension selected such that the drive belt can slip on the pulleys to permit the stop member to be manually extended and retracted when the drive gear is stationary. In this way, the visual display at all times advises the user of the relative position of the stop member with respect to the saw blade regardless of the manner in which the extensible member is extended or retracted.
In an alternate embodiment of the invention, the drive mechanism includes a prime mover connected to the drive gear preferably through a worm gear and the extensible member has a plurality of relatively slidable arms. The arms may telescope or nest inside one another. The prime mover may be an electric motor, such as an electronically controlled stepper motor, or a manual crank. The mensuration devise is preferably a position sensor which measures an amount of drive tape played either in or out to determine the relative position of the stop member with respect to the blade. An optical encoder may be used for this purpose. The optical encoder may read a bar code on the tape, or the apertures within the tape, or both. The repetitive fence is preferably provided with an electronic keyboard for measurement input, an electronic digital display for displaying the relative position of the stop member with respect to the saw blade, and an electronic logic device, such as a microprocessor. In a method of the present invention, the logic device employs a computer program which permits the user to input the dimensions to be cut, and the number of cuts to be made in a standard dimensional lumber. The logic unit then orders the cuts in an optimal sequence so as to minimize the number of cuts to be made, adjustments of the extensible member, and the amount of waste material generated by the cuts.
A first embodiment of a repetitive fence for cross-cutting materials, such as lumber in accordance with the principals of the invention is generally indicated at reference 10 in
As best seen in
The first arm 32 has a flange 70 defining screw apertures 72 for mounting the telescopic arm assembly 30 to a base unit 80. The base unit includes an electronic, numeric keypad section 82, an electronic command key pad section 84 including an “enter” key 86, and a digital alpha-numeric read-out display 88 of the liquid crystal, light emitting diode, or the like type. The base unit 80 may also incorporate a cam actuated locking lever 90 to manually fix the position of the drive tape 58 and thus the distal end 57 of the fourth movable arm 38 with respect to the base unit 80.
As will be apparent to those of ordinary skill in the art, translating the fourth movable arm 38 longitudinally with respect to the first fixed arm 32 and base unit 80 plays the drive tape 58 onto and off of the drive reel 60, and vice versa. The base unit 80 is therefore provided with a vertically oriented drive reel axle 92 so as to prevent translation of the drive reel 60 with respect to the base unit 80 while permitting the drive-reel 60 to rotate thereabout.
The base unit 80 may be provided with an upper housing 94, and a lower housing 96 manufactured from thermo-plastic materials, or metal. The distal free-end 57 of the fourth movable arm 38 is provided with a stop member 100 attached thereto, such as by screws (not shown). The stop member 100 also has pivotally connected thereto, a base plate 102 which may be used to support the free end of material to be cut, such as a wooden board.
The first fixed arm 32 is preferably provided with conventional scale markings 104 such as in inches (or centimeters) indicating the distance thereon from a hypothetical saw blade, such as saw blade 22. Thus, the repetitive fence 10 is mounted to the out-feed table 16, or the like, such that an initial index mark 106 is located a known distance from the hypothetical saw blade, such as twelve inches. Thus, when initially setting up the repetitive fence 10 with respect to a saw blade, such as the saw blade 22, the user must measure the “zero distance” twelve inches from the saw blade, position the index mark 106 thereat and either clamp down or screw down the repetitive fence 10 to the in-feed table at that position. The repetitive fence should also be positioned in a perpendicular relationship with the cut of the saw blade 20 for right angle cross-cuts.
As best seen in
It will be understood by those of ordinary skill in the art that by moving the distal free-end 57 of the fourth movable end arm 38 inwardly or outwardly, with respect to the base unit 80 and first fixed arm 32, both the barcode 64 and drive aperture 62 will move past a fixed reference point associated with either the base unit 80 or the first fixed arm 32. The repetitive fence 10 is therefore provided with an electronic mensuration device 112 defining crescent-shaped slots 114 for passage there through of the drive tape 58.
The electronic mensuration device 112 is electronically and cooperatively connected with the digital read-out 88 such that the position of the free-end 57 and stop member 110 with respect to the base unit 80 (and therefore saw blade 22) may be displayed. The mensuration device 112 includes a printed circuit board 116 incorporating an electronic logic unit 117 such as a microprocessor, programmable logic array, microcontroller to the like for detecting and interpreting electronic signals from photo detectors 118. The photo detectors read the passage of the drive apertures 62, barcode 64, or both to determine the absolute position of the free-end 57 with respect to the base unit 80. The electronic mensuration device 112, logic unit 117, and photo detectors 118 are all electronically interconnected on the printed circuit board 116 so as to provide a reading on the read-out display 88 indicative of the distance of the end member 100 with respect to the saw blade 22. Depending on the particular methodology employed by the electronic mensuration device 112, the reading may be of an extremely high accuracy, far greater than that achievable with a tape measure and pencil marking by a conventional woodworker. Conversely, it will be apparent that by driving the metal tape drive 58, either inwardly or outwardly with respect to the housing 80, the stop member 100 can be positioned at any desired location as indicated by the read-out display 88.
Those of ordinary skill in the art will be familiar with a wide variety of mathematical and electronic techniques for determining the absolute position of a series of regularly spaced apertures, or a periodic barcode with respect to an optical measuring device. Mitutoyo Corporation, Japan manufactures a wide variety of devices suitable for this purpose. One such implementation using Mitutoyo sensors is described in U.S. Pat. No. 5,225,830 issued on Jul. 6, 1993 to Andermo et al. The disclosure which is herein incorporated by reference. Although the preferred system implemented by the electronic mensuration device 112 is of the absolute positioning type, for lower cost applications, a relative positioning sensing system may also be suitable. The electronic command keypad section 84 preferably has dedicated buttons assigned thereto which when struck cause the read-out 88 to provide desired units such as one-eighth inch, quarter inch, or metric units.
In order to facilitate automatic operation of the repetitive fence 10, the base unit 80 is provided with an electronic motor 120. The motor is preferably of the D.C. stepper type. The motor has a shaft 122 having a worm gear 124 journaled to a free-end thereof. The worm gear 124 engages a drive gear 126 journal for rotation with respect to a spindle portion of the lower housing 96. The drive gear has a pulley portion 128 concentrically mounted thereon. The lower housing also has a drive sprocket 130 journaled for rotation on a separate spindle portion thereof also having a concentric pulley portion 132. The drive sprocket has a plurality of radially directed teeth 134 having a tooth pitch equal to the periodicity of the drive apertures 62 on the metal drive tape 58. The drive teeth 134 are engaged with the drive apertures 62. The pulley portions of the drive sprocket 132 and drive gear 126 are engaged with a resilient drive belt 136, manufactured from rubber, a synthetic polymer or any other suitable material. The drive belt 136 translates rotary motion of the shaft 122 to linear motion of the drive tape 58. The electronic numeric key pad section 82 of the housing 80 is electronically interconnected with the logic unit 117 by way of the printed circuit board such that a user can input a desired dimension on the key pad 82 and such dimension will appear on the display 88. By pushing the “enter” key 86, the logic unit 117 will command the motor 120 to drive the tape 58 until the stop member 100 arrives at the desired location. Such arrival may be confirmed by the user observing the display 88. The user may also input a desired dimension to the repetitive fence 10 by other means which advantageously employ the repetitive fence's ability to electronically move the stop end 100 to a desired dimension. Those of ordinary skill in the art are well aware that a variety of electronic tape measure-type devices have been reduced to practice in the prior art. U.S. Pat. No. 5,691,923 to Alder et al., issued Nov. 25, 1997 and U.S. Pat. No. 5,983,514 issued to Lindsey on Nov. 16, 1999 each disclose electronic tape measures having means for outputting an electronic representation of the distance measured. In this preferred embodiment, the base unit 80 of the repetitive fence 10 is preferably provided with an electronic measurement input 138 in the form of an infrared receiver, I.E.E.E. RS 232 port, or the like for interfacing with an electronic tape measure or the like. Said prior art, electronic tape measure may download an entire sequence of measurements to the electronic logic unit 117 for actuation into a linear positioning of the stop member 100. The user may increment the drive tape 58 to each subsequent, received measurement merely by depressing the “enter” key 86. Thusly, an entire sequence of measurements (e.g., a series of measurements of room wall dimensions for crown or floor molding) may be electronically downloaded to the repetitive fence 10 by an electronic type measure without ever having to physically transfer those measurements by way of retractable tape or the like to the material to be cut, and then marking the material. Numerous errors, wasted time, and wasted material are thus avoided by the invention and its concomitant method of use.
Further advantages of the invention will be apparent to those of ordinary skill in the relevant art upon reviewing the logical flow diagram shown in
After the user has completed all of the indicated cuts of that dimension, the user inputs a cut completed command 162 by way of one of the dedicated keys on the key pad 84. If the last ordered cut has not been made, the cut order is decremented 164 and the new, current cut dimension is displayed on the display 88. This process 166 is repeated until the last completed cut command 161 has been received. The logic unit or microprocessor 117 then sets a “last cut flag” 168 and stops the process 170.
In addition to the electronic advantages described above with respect to automatically inputting a series of cuts to be made, the repetitive fence 10 also permits manual override of any pre-selected dimensions. As stated above, the resilient drive belt 136 has a tension selected such that the drive sprocket 130 may slip with respect to the drive gear 126 upon manual displacement of the movable stop member 100 from any rest position. Advantageously, the display 88 will record any such displacement as a new position reading. Thus, the user may “interrupt” a programmed sequence of cuts with a manual cut to a desired distance merely by translating the movable stop member 100 to any desired position as indicated by the display 88. The user may then move stop member 100 to the previous position and commence with the automated sequence of cuts.
An alternate embodiment of the invention 101 shown in
Other embodiments and variations of the invention will be apparent to those of ordinary skill in the relevant art upon reviewing this disclosure. Thus, the invention is not to be limited to the above description, but is to be determined in scope by the claims which follow.
