VARIABLE SPEED REVERSIBLE METAL DETECTING SAW MILL SYSTEM

A perpendicular axis saw blade includes a blade body with an outer blade body edge to which a plurality of primary saw teeth are affixed at spaced intervals to form a primary teeth per inch (TPI). The blade also includes a plurality of primary gullets. Each primary gullet is located between two of the plurality of primary teeth and has a primary gullet depth and primary gullet capacity. Each of the plurality of the primary teeth includes a primary tooth tip, a primary tooth leading edge, a primary tooth trailing edge. Secondary saw teeth affixed at spaced intervals to the primary tooth trailing edge or at least one primary gullet form a secondary TPI. The primary teeth cut a workpiece during a machining operation. A user or system can use the secondary teeth to cut through a foreign object detected in the workpiece without damaging any primary teeth.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to the field of cutting and subtractive manufacturing, and more specifically to an optimized saw blade and sawmill apparatus for use in milling operations that cut materials along a perpendicular, moving saw axis.

2. Description of Related Art

Subtractive manufacturing refers to machining processes in which a piece of raw material, such as wood or metal, is cut into a desired final shape and size by a controlled material-removal process.

Milling is a controlled material-removal process that typically uses bandsaws or rotary saws to remove portions of material by advancing (or feeding) a workpiece to come into come into contact with cutting teeth positioned on an oscillating or rotating saw blade. The saw blade is typically a bandsaw blade or a circular saw blade.

During a milling operation, the cutting surface on the tip of each saw blade tooth penetrates the workpiece, pushing, shaving or shearing off a continuous chip of material as the tooth moves. This chip remains in the gullet, the space between the tooth tip and the inner surface of the blade. Once the tooth is free from the workpiece, the chip falls away from the gullet, freeing the tooth to cut away another chip during the next oscillation or rotation.

A defining characteristic of a milling apparatus is that the workpiece moves perpendicular to the axis of movement of the bandsaw and circular saw blades. A further defining characteristic of milling is the precise geometry of the saw blade teeth, which have a cutting surface and curvature that simultaneously cuts into the work piece and removes material in carefully controlled manner to perform precise shearing.

Milling systems have become increasing sophisticated with the integration of computer numerical control (CNC) technologies. Many systems incorporate multiple milling functions, and include sensors to monitor the status of the cutting tools and the workpieces. Many attempts have been made in the prior art to increase throughput (feed rate) without damaging saw blade components and causing system down time and error due to damage to the saw blades.

There are several factors that affect cutting efficiency: saw blade and tooth design, band speed, feed and gullet capacity.

Saw blades must be carefully engineered, drawing upon material science concepts and a large body of research as to the relationship of tooth geometry and the materials being cut. Saw tooth geometry is highly specific to the type of material being cut. Furthermore, the size and shape of the material to be cut dictates the blade's teeth per inch (TPI) for the material.

Blades can be made from one piece of steel, or built up of two pieces, depending on the performance and life expectancy required. A hard back saw blade is a one-piece blade made of carbon steel with a hardened back and tooth edge. A flex back saw blade is a one-piece blade made of carbon steel with a hardened tooth edge and soft back. A bi-metal saw blade is a high-speed steel edge material that has been electron beam welded to a fatigue resistant spring steel backing. Such a design provides better cutting performance in certain situations.

Increased band speed increases cutting efficiency. Efficient cutting removes as much material as possible as quickly as possible by using as high a band speed as the machine can handle. Band speed is restricted, however, by the machinability of the material and how much heat the cutting action produces. Too high a band speed or very hard materials produce excessive heat, resulting in reduced blade life and potential damage to the workpiece.

Feed refers to the depth of penetration of the saw blade tooth into the material being cut. However, the machinability of the material being cut and blade life expectancy limits the feed. A deeper feed results in a lower shear plane angle (angle at which the chip shears off) and faster cutting, but dramatically reduced blade life. A light feed increases the blade life, but also increase the shear plane angle and decreases cutting efficiency.

Gullet capacity also affects cutting efficiency. As the tooth scrapes away the material during a cut, the chip curls up into the gullet. A blade with the proper clearance for the cut allows the chip to curl up uniformly and fall away from the gullet. If too much material is scraped away, the chip will jam into the gullet area causing increased resistance. This loads down the machine, wastes energy and can cause damage to the blade.

It is a problem known in the art that even brief contract of a woodcutting saw blade with metal during a wood milling operation could cause significant damage to the blade, as well as substantial downtime for a milling facility. In theory, such damage can occur from any foreign material embedded in the wood. Furthermore, such damage can also occur in operations cutting other substances, such as metal or cork, when a saw blade encounters foreign objects in the workpiece.

Attempts have been made to mitigate this damage, such as use of sensors. One design uses a sensor embedded in the surface supporting the workpiece to detect metal before it comes into contact with the saw blade. However, if the workpiece is too thick for accurate detection or the metal does not properly align with the sensor, detection may not occur in time to prevent damage to the blade.

There is an unmet need for technology that can protect milling systems from costly damage caused by undetected, embedded objects made of metal and other materials that damage specialized saw blades.

There is a further need for more versatile and durable saw blades than those that are currently known in the art.

BRIEF SUMMARY OF THE INVENTION

One embodiment of the present invention is a perpendicular axis saw blade. The blade includes a blade body having an outer blade body edge to which a plurality of primary saw teeth are affixed at spaced intervals to form a primary teeth per inch (TPI). The blade also includes a plurality of primary gullets. Each primary gullet is located between two of the plurality of primary saw teeth and has a primary gullet depth and primary gullet capacity. Each of the plurality of the primary saw teeth includes a primary tooth tip, a primary tooth leading edge and a primary tooth trailing edge. A plurality of secondary saw teeth affixed to the primary tooth trailing edge at spaced intervals form a secondary TPI.

One embodiment of the present invention is a perpendicular axis saw blade. The blade includes a blade body having an outer blade body edge to which a plurality of primary saw teeth are affixed at spaced intervals to form a primary teeth per inch (TPI). The blade also includes a plurality of primary gullets. Each primary gullet is located between two of the plurality of primary saw teeth and has a primary gullet depth and primary gullet capacity. Each of the plurality of the primary saw teeth includes a primary tooth tip, a primary tooth leading edge and a primary tooth trailing edge. A plurality of secondary saw teeth affixed to the primary tooth trailing edge at spaced intervals form a secondary TPI.

Another embodiment of the present invention is a perpendicular axis saw system for performing subtractive machining on a workpiece. The system includes at least one material sensor for determining the presence of a foreign object within a workpiece and at least one computer control component. The material sensor is configured to transmit at least one alert signal when a foreign object has been detected within the workpiece. The computer control component is configured to receive or process the at least one alert signal from the at least one material sensor and to perform at least one saw blade control function to control operation of a perpendicular axis saw blade (as detailed above).

TERMS OF ART

As used herein, the term “alternate” means a saw blade design where every tooth is set in an alternating sequence. Used for quick removal of material when finish is not critical.

As used herein, the term “blade body” means the body of the blade not including tooth portion.

As used herein, the term “clearance angle” means the angle between the tooth back and the axis of motion of the saw blade.

As used herein, the term “control operation” refers to an operation or function performed by a computer processor or control unit to alter, analyze or measure the movement, operation, state or function of a mechanical part.

As used herein, the term “direction of movement” refers to the course of motion of a component (e.g. axial, rotational, etc.)

As used herein, the term “feed” or “feed rate” refers to the depth of penetration of the tooth into the material being cut. Variables affecting feed or feed rate may include but are not limited to the type material being cut, the saw blade material, blade life expectancy or optimization.

As used herein, the term “foreign object” refers to an object located at least partially within a workpiece and having a composition different from said workpiece.

As used herein, the term “gullet” means the curved area at the base of the tooth. A gullet may be described using measurements including but not limited to gullet depth and gullet capacity.

As used herein, the term “gullet capacity” means the amount of material removed from a work piece that a gullet can contain.

As used herein, the term “gullet depth” means the distance from the tooth tip to the bottom of the gullet.

As used herein, the term “kerf” refers to the void in a workpiece created by removal of material by the cut of the blade.

As used herein the term “leading” or “leading edge” means a cutting edge of a tooth or blade.

As used herein, the term “material” refers to a metal, ceramic, composite, carbon fiber, alloy, coating or other material or substance known in the art that may be used to form, construct, coat or treat a saw blade.

As used herein, the term “material sensor” refers to any sensor known in the art capable of detecting any differential within a material being cut that may be indicative of the presence of a foreign object.

As used herein, the term “perpendicular axis saw” means a saw that removes material along a perpendicular axis to the piece being cut.

As used herein, the term “perpendicular axis saw blade” refers to a saw blade used for subtractive manufacturing, which moves at a perpendicular axis of movement to axis of movement of the workpiece material being cut.

As used herein, the term “primary” refers to any measurement or characteristic of a primary tooth.

As used herein, the term “primary saw tooth” means a saw tooth that creates a kerf in a workpiece.

As used herein, the term “raker” means a saw blade design with a three-tooth sequence with a uniform set angle (left, right, and straight).

As used herein, the term “saw tooth geometry” includes but is not limited to the following variables and characteristics of a saw tooth: tooth back, tooth face, tooth rake angle and clearance angle.

As used herein, the term “secondary” refers to any measurement or characteristic of a secondary tooth.

As used herein, the term “secondary saw tooth” means a saw tooth which cuts through foreign material in a workpiece.

As used herein, the term “set” refers to the displacement from the centerline of the array of teeth to one or the other side of the centerline of the array of teeth to allow clearance of the body of the blade through the cut.

As used herein, the term “single level set” means a saw blade design where the blade geometry has a single tooth height dimension as a result of bending each tooth at the same position with the same amount of bend on each tooth.

As used herein, the term “skip” means a saw blade design with a wide gullet. A skip blade design may be suited for non-metallic applications such as wood, cork, plastics and composition materials.

As used herein, the term “state” refers to any metric identifying movement, position, speed, structural alteration or damage, location, temperature, structure, friction, lubrication or any other status or state of a system component.

As used herein, the term “subtractive manufacturing” or “subtractive machining” refers to manufacturing or machining processes in which a piece of raw material, such as wood or metal, is cut into a desired final shape and size by a controlled material-removal process.

As used herein, the term “teeth per inch (TPI)” means the number of teeth per inch as measured from tooth tip to tooth tip.

As used herein, the term “thickness gauge” means the dimension from side to side on the blade.

As used herein, the term “tooth back” means the non-leading surface of the tooth, which does not remove material from the workpiece during milling.

As used herein, the term “tooth face” means the leading surface of the tooth, which removes material from the workpiece during milling.

As used herein, the term “tooth pitch” means the distance from the tip of one tooth to the tip of the next tooth.

As used herein, the term “tooth rake angle” or “rake angle” means the angle of the tooth face measured with respect to a line perpendicular to the cutting direction of the saw.

As used herein, the term “tooth set” means the number of teeth per inch and the angle at which they are offset. Tooth set affects cutting efficiency and chip carrying ability.

As used herein, the term “variable design” or “variable positive design” means a saw blade configuration with variable tooth spacing and/or gullet capacity.

As used herein, the term “vari-set” means a saw blade design where the tooth height/set pattern varies with product family and pitch. The teeth have varying set magnitudes and set angles, providing for quieter operation with reduced vibration. Vari-set is efficient for difficult-to-cut materials and larger cross sections.

As used herein, the term “wavy set” means a saw blade design wherein the tooth set varies within groups of teeth set to each side within a set pattern. The teeth have varying amounts of set in a controlled pattern. In various embodiments, a wavy set may reduce noise, vibration and burr when cutting thin, interrupted applications.

As used herein, the term “width” means the dimension of a saw blade as measured from the tip of the furthest-extending tooth to the back of the blade.

As used herein the term “workpiece” means the material being cut, shaped or worked upon.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1a,1band1cillustrate alternate embodiments of perpendicular axis saw blade100.FIGS. 1aand 1cdepict configurations of bandsaw blades, whileFIG. 1bdepicts a rotary saw blade. Perpendicular axis saw blade100is designed to cut different materials by being able to cut in either direction.

Perpendicular axis saw blade100incorporates a blade body10, a plurality of primary saw teeth20and a plurality of secondary saw teeth30. Blade body10has outer blade body edge11. Primary saw teeth20are designed to cut a workpiece in a primary direction, while secondary saw teeth30are designed to cut embedded foreign objects located in the workpiece in a reverse or secondary cutting direction.

Each primary saw tooth20attaches to at least one outer blade body edge11, in a spacing that provide a particular value for primary teeth per inch (TPI) T1. In certain embodiments, T1is variable. Each primary saw tooth20includes a primary tooth tip21, a primary tooth leading edge22and a primary tooth trailing edge23. Primary gullets25extend between the primary tooth trailing edge23of one primary saw tooth20and the primary tooth leading edge22of another primary saw tooth20. Each primary gullet has a primary gullet depth D1and a primary gullet capacity C1.

In the embodiment ofFIGS. 1aand1b,a plurality of secondary saw teeth30are affixed to primary tooth trailing edge23, in a spacing that provide a particular value for secondary TPI T2. In certain embodiments, at least one secondary saw tooth30is comprised of a different material than at least one primary saw tooth20. In certain embodiments, T2is variable. In the exemplary embodiment, T2is greater than T1. Each secondary gullet35extends between one secondary saw tooth30and another secondary saw tooth30. Each secondary gullet35has a secondary gullet depth D2and a secondary gullet capacity C2. In the exemplary embodiment, C1has a value greater than that of C2and D1has a value greater than that of D2.

In the embodiment ofFIG. 1c,secondary saw teeth30are located between primary saw teeth20.

FIG. 2illustrates an exemplary embodiment of perpendicular axis saw system200. Each perpendicular axis saw system200includes at least one perpendicular axis saw blade100, as above, at least one material sensor240, at least one optional status sensor245and at least one computer control component250. This invention is based upon the new perpendicular axis saw blade100configuration requiring that perpendicular axis saw blade100be able to move in two directions relative to the workpiece. Bandsaws and circular saws are only produced and known to operate in one blade motion or rotation, respectively. Therefore, the concept of running perpendicular axis saw system200“backwards” or in such a way as to make a perpendicular axis saw blade100move in a reverse or backward motion is considered a part of this invention.

In use, material sensor240determines the presence of a foreign object F within a workpiece W. Upon detection, material sensor is configured to transmit at least one alert signal to computer control component250. In certain embodiments, status sensor245identifies a status of perpendicular axis saw blade100.

Computer control component250is configured to receive or process the alert signal and perform at least one saw blade control function. The saw blade control function controls operation of perpendicular axis saw blade100. In embodiments where perpendicular axis saw blade100moves axially, the saw blade control function may reverse the direction of the axial motion or stop the movement entirely. In embodiments where perpendicular axis saw blade100moves rotationally, the saw blade control function may reverse the direction of the rotational motion or stop the movement entirely.

In certain embodiments, computer control component250performs a rate function utilizing a feed rate of perpendicular axis saw system200and a distance X relative to perpendicular axis saw blade100to perform a rate control function. This rate control function may be performed before perpendicular axis saw blade100contacts the workpiece, and may alter the feed rate to optimize the cutting motion of perpendicular axis saw blade100.

The workpiece cutting mode of perpendicular axis saw system200is provided via perpendicular axis saw blade100moving in one cutting direction, which for descriptive purposes will be described as “primary.” The foreign object cutting mode is provided via perpendicular axis saw blade100moving in the opposite direction or “secondary.” To utilize perpendicular axis saw blade100as described, perpendicular axis saw system200has to be able to have a control feature, such as computer control component250, allowing the selective rotation of its band wheels in a clockwise or counter-clockwise direction of rotation. This is because rotational direction of the band wheels determines the primary or secondary cutting direction of perpendicular axis saw blade100, which in the case of this invention determines which cutting mode perpendicular axis saw system200presents to the workpiece.

In step302, material sensor240detects a foreign object in a workpiece in perpendicular axis saw system200.

In step304, material sensor240transmits an alert signal to computer control component250.

In optional step306, computer control component250calculates the time it will take the foreign object to reach perpendicular axis saw blade100. In the exemplary embodiment, this calculation is a rate function utilizing a feed rate of perpendicular axis saw system200and a distance X of the foreign object relative to perpendicular axis saw blade100.

In optional step308, computer control component250performs a rate control function to alter the feed rate of perpendicular axis saw system200.

In step310, computer control component250performs at least one saw blade control function to control operation of perpendicular axis saw blade100. In one embodiment, the saw blade control function stops the movement of perpendicular axis saw blade100. In another embodiment, the saw blade control function reverses a direction of movement of perpendicular axis saw blade100. This reversal may be rotational or along an axis.

It is not normal, nor has a saw been observed or invented, that has a scanner to detect a metal object while cutting a timber so as to control a saw blade's cutting motion. Timber is commonly scanned for metal in industry, but only prior to or after being processed through a saw, not while being sawed. Therefore, the novel method of scanning for imbedded objects to affect the blade cutting direction/rotation while sawing is also a part of this invention.

It should be further understood that the drawings are not necessarily to scale; instead, emphasis has been placed upon illustrating the principles of the invention. Moreover, the terms “about,” “substantially” or “approximately” as used herein may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related.