Abstract:
A rotary cutter head comprises rotary body, resilient clamping arm, and at least one cutting blade. The clamping arm clamps the cutting blade radially inwardly first rather than in a circumferential direction in order to positively lock the cutting blade radially, and thereby prevent the cutting blade from migrating out of position slightly during high speed rotation of the cutter head.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This patent application claims the benefit of U.S. Provisional Patent Application No. 60/667,810, filed Apr. 1, 2005. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention pertains to an improvement for a cutting tool for use in a rotary power tool. More particularly, the invention relates to rotary cutter heads and cutting blades for use therewith.  
       BACKGROUND OF THE INVENTION  
       [0003]     A rotary cutter head for releasably holding cutting blades is formed with cutting edges which extend radially outwardly of and generally axially along the outer periphery of the cutter head. Cutter heads of this general type are typically used in power machines such as routers, moulders, shapers or tenoners and are typically used to chamfer, round, or otherwise shape an edge portion of a workpiece of either non-ferrous metals, plastics, woods, etc.  
         [0004]     In general, a cutter head of this type is formed with at least one recess for receiving a cutting blade. The recess extends generally radially inwardly from the outer periphery of the cutter head and extends substantially axially in the cutter head. Frequently, the recess extends across the entire width of the cutter head.  
         [0005]     Prior cutter heads of this general type utilize threaded fasteners and a so-called gib to releasably secure the blade in the recess. The gib is shaped to generally conform to the shape of the recess and is sized to allow the gib and the blade to be slidably received in the recess. When installing a blade into the cutter head, the gib and the blade are manually located in the recess. The threaded fasteners are then screwed into threaded openings formed in the cutter head to draw the gib toward one side of the recess so as to wedge or otherwise clamp the blade in the recess. The blade and the gib used in these cutter heads must be manually aligned relative to one another and relative to the recess when they are installed into the recess. Moreover, this alignment must then be maintained until the gib and the blade are secured in the recess.  
         [0006]     In one prior cutter head, the fasteners extend through openings formed in the gib, and the heads of the fasteners engaging the gib to secure the gib and the blade in the recess. In this instance, each time that the blade is changed, the gib and the fasteners must be removed from and reinstalled into the recess.  
         [0007]     In another prior cutter head, the fasteners draw pins through openings formed in the gib. The pins are formed with enlarged heads which engage the gib and which wedge the gib and the blade in the recess. In this case, the gib and the pins need not be removed from the recess to change the blade. However, the gib and the blade must still be manually aligned as the fasteners are tightened. Moreover, the pins and the gib used in this cutter head easily fall out of the recess when the fasteners are inadvertently loosened too far.  
         [0008]     The gib used in some prior cutter heads is formed with a fixed locating pin for establishing relative alignment between the gib and the blade. In such a cutter head, the locating pin is received into an opening formed in the blade before the gib and the blade are placed into the recess. While the fixed locating pin aids in establishing and maintaining alignment between the gib and the blade, the gib and the fasteners must be removed and reinstalled each time the blade is changed. Moreover, the gib and the blade must still be aligned relative to the recess.  
         [0009]     In addition to a gib and the associated fasteners and pins, prior cutter heads are typically equipped with a back-up fastener to prevent the blade from flying out of the cutter head in the event that the gib loosens while the cutter head is rotating or in the event that the fasteners which secure the gib are not tightened before the machine is turned on. The back-up fastener extends through an opening in the blade and must either be backed out or completely removed from the cutter head before the blade can be removed from the recess. The back-up fastener must then either be turned inwardly or reinstalled when a new blade is installed in the cutter head.  
         [0010]     Another prior cutter head is shown in U.S. Pat. No. 5,647,699 to Martin, et. al. This cutter head includes an integral clamping arm on the cutter head clamps a cutting blade into a slot recess formed into the cutter head. The clamp is loosened or tightened by one or more screws. The &#39;699 patent has resulted in a commercially successful product. However, it has been realized that high speed rotation of the cutter head can generate large centrifugal forces which can dislodged the cutter blade slightly. The present invention relates to improvements in the fixing the position of cutting blades in cutter heads.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     The general aim of the present invention is prevent the cutting blade from slipping out of position in a radial direction due to centrifugal forces generated from high speed rotation of the cutter head during operation.  
         [0012]     In accordance with this aim, an aspect of the present invention is directed towards an improved rotary cutter head which includes a clamp that positively locks one or more cutting blades in a radial direction. This positive radial clamping prevents the cutting blade from slipping slightly in a radially outward direction in response to centrifugal force generated by high rotational speeds of the cutter head. According to this aspect, the rotary cutter head includes a rotary cutter head body, at least one clamp which is moveable relative to the body to open and close a clamping recess and one or more cutting blades. The cutting blade has a slot which receives a tab provided by the corresponding clamp. When the clamp member is clamped down, the tab on the clamp member engages the inner side wall of the cutting blade. This causes the base end of the cutting blade to engage the bottom of the recess formed in the rotary cutter head body to positively lock the cutting blade in the radial direction. This prevents the cutting blade from inadvertently slipping radially outwardly during subsequent high-speed rotation of the cutter head.  
         [0013]     One aspect of the present invention is directed toward a cutting blade which is configured to prevent the blade from migrating slightly out of position in the radial direction due to centrifugal force. The cutting blade is intended for use with a rotary cutter head as described above. This cutter head includes a resilient clamping arm that is adapted to clamp the cutting blade in a recess defined in the rotary cutter head. To accomplish this aspect, the cutting blade includes a specially configured slot on the leading face of the cutting blade which is intended to mate with a corresponding tab formed in the clamping arm on the rotary cutter head. The location and size of the slot is such that it provides means for ensuring that the cutting blade clamps in a radially inward direction when installed on the cutter head body. Specifically, the cutting blade slot is sized and positioned to ensure that the base end of the cutter blade and the bottom of the cutter head recess are positively engaged against each other when the cutter blade is clamped into the cutter head. This prevents the cutting blade from wandering radially outward during high speed rotation.  
         [0014]     These and other objects and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a perspective view of a new and improved rotary cutter head incorporating the unique features of the present invention and equipped with cutting blades;  
         [0016]      FIG. 2  is an exploded perspective view of the cutter head;  
         [0017]      FIG. 3  is a side view with certain portions being broken away and shown in cross-section;  
         [0018]      FIG. 4  is an end view of the cutter head;  
         [0019]      FIG. 5  is an enlarged fragmentary cross-sectional view taken substantially along the line  5 - 5  of  FIG. 3 ;  
         [0020]      FIG. 6  is a view similar to  FIG. 5  but shows a clamping portion in a release position and with the cutting blade removed;  
         [0021]      FIG. 7  is an enlarged cross-sectional view taken substantially along the line  7 - 7  of  FIG. 4 ; and  
         [0022]      FIG. 8  is a further enlarged fragmentary cross-sectional view taken substantially along the line  5 - 5  of  FIG. 3 . 
     
    
       [0023]     While the invention is susceptible of various modifications and alternative constructions, a certain illustrated embodiment hereof has been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]     For purposes of illustration, the present invention is shown in the drawings as embodied in a cutter head  10  ( FIG. 1 ) adapted to be installed in a rotary power tool such as a router (not shown) and adapted to releasably hold replaceable cutting blades  11  for shaping the edge portion of, for example, a wood or plastic workpiece (not shown).  
         [0025]     The cutter head  10  includes a body  12  and a shank  14 . The body is formed with front and back surfaces  15  and  16  ( FIG. 3 ), respectively, and with a generally radially facing outer periphery which defines a substantially circular cross-section. The shank extends rearwardly from the center of the back surface and is sized to be received into a chuck or a collet of the rotary power tool such that the shank portion establishes the axis of rotation for the cutter head. Alternately, the body may be formed with a centrally located hole suitable for mounting to an arbor or a spindle of the power tool. The cutter head shown is adapted to be rotated in a counter-clockwise direction when viewed from the front of the cutter head (see  FIG. 4 ).  
         [0026]     The blades  11  are preferably formed from relatively thin (e.g., 0.079 inch), carbide and are ground with relatively sharp cutting edges  18  for engaging and cutting the edge portion of the workpiece. The distance between the base  19  of each blade and the cutting edge of that blade are precisely controlled during the manufacture of the blades to facilitate alignment of the cutting edges in the cutter head as discussed below. The blades may be formed with straight cutting edges or, as shown, they may be formed with profiled cutting edges for forming the edge portion of the workpiece to a predetermined shape.  
         [0027]     The blades  11  are secured into recesses  20  ( FIG. 2 ) which extend generally radially inwardly from the outer periphery of the cutter head body  12  and which extend axially of the body. As a result, the recesses are defined, in part, by leading and trailing surfaces  21  and  22 , respectively, ( FIG. 6 ) which face generally circumferentially and generally toward one another. The blades are located in the recesses abutting the trailing surfaces of the recesses. The portions of the body defining the trailing surfaces are formed with a profile similar to the profile of the cutting edges  18  of the blades. In this way, the body provides relatively solid support for the blades as they engage the workpiece. In addition, gullets  24  are formed in the body adjacent to and on the leading sides of the recesses. The gullets provide clearance for the chips generated by the blades as the blades cut the edge portion of the workpiece.  
         [0028]     The base of each recess  20  is formed with a generally radially outwardly facing surface or registry  25  which is precisely positioned relative to the center of the cutter head  10 . The registry may be formed substantially perpendicular with respect to the trailing surface  22  of the recess, as shown, or it may be formed at an oblique angle relative to the trailing surface. When a blade  11  is installed into the recess, the base  19  of the blade rests on the registry so that the cutting edge  18  of the blade is precisely and repeatably positioned relative to the center of the cutter head.  
         [0029]     In accordance with one aspect of the invention, the body  12  of the cutter head  10  is formed with integral clamping portions or arms  30  which are selectively movable between clamping positions ( FIG. 5 ) and release positions ( FIG. 6 ) relative to the blades  11  in the recesses  20 . Each blade may be slideably inserted into or removed from the recess when the corresponding arm is in the release position. The blade is securely held in the recess when the corresponding arm is in the clamping position. The arm is resiliently biased to the release position but is selectively moved to the clamping position by simply turning screws  33  inwardly relative to the center of the cutter head. The arm resiliently returns to the release position when the screws are turned outwardly. As a result, the blades can be quickly installed into, secured in, and removed from the cutter head.  
         [0030]     More specifically, each arm  30  is defined by an outer peripheral portion of the body  12 . The arm is substantially separated from and is generally spaced radially outwardly from the center portion of the body but is formed with an end portion which is integrally connected to the center portion of the body by a relatively narrow, axially extending strip of material. This narrow strip of material defines an integral hinge  31  which is sized to elastically stretch so as to allow the arm to resiliently pivot radially inwardly and outwardly. The arm is further formed with a free end portion located oppositely of the integral hinge. The free end portion defines a portion of one of the sides of the recess  20 . The arm is preferably located on the leading side of the recess with the free end portion defining the entire portion of the leading surface  21  of the recess. With this arrangement, the leading surface of the recess approaches and recedes from the trailing surface as the arm pivots inwardly and outwardly, respectively.  
         [0031]     The integral hinge  31  is adapted to bias the leading surface  21  of the recess  20  to a position relative to the trailing surface  22  such that the recess is sized to slideably receive the blade  11 . As a result, the integral hinge biases the arm  30  radially outwardly to the release position. In addition, the screws  33  are threaded into threaded openings  34  in the center portion of the body. The heads  35  of the screws engage radially outwardly facing surfaces  36  formed on the arm between the free end portion and the integral hinge. As a result, the screws drive the arm radially inwardly from the release position and cause the leading surface of the recess to clamp the blade against the trailing surface  22  and the registry  25  as the screws are turned inwardly in the threaded openings. Accordingly, the screws are operable to selectively move the arm from the release position to the clamping position.  
         [0032]     In carrying out the invention, the arm  30  is defined by forming an elongated slot  37  in the body  12  of the cutter head  10 . The slot extends from the base of the recess  20  and in the same general direction as the direction of rotation of the cutter head. The slot is formed with a closed end which is radially inwardly of and adjacent to the outer periphery of the body. The integral hinge  31  is defined by the material which is located generally radially outwardly of the closed end of the slot. The closed end of the slot is preferably formed with a relatively large radius to define an enlarged, strain relief opening for reducing the stress concentration at the closed end of the slot due to the flexing of the integral hinge.  
         [0033]     The shape of the slot  37  is not critical in carrying out the invention, but may be formed with any suitable curvature. For example, to aid in forming the registry  25 , the slot shown extends from the base of the recess  20  having an initial angle which is equal to the angle of the registry relative to the trailing surface  22  of the recess. The slot then extends with a curvature which is greater than the general curvature of the outer periphery of the body  12 . Alternately, the slot may be formed extending in a straight line from the recess.  
         [0034]     The width of the recess  20 , i.e., the distance between the leading surface  21  and the trailing surface  22 , is precisely controlled within relatively tight tolerances. Specifically, the recess is sized to slideably but snugly receive the blade  11 . The integral nature of the hinge  31  limits the movement of the arm  30 . The relatively small clearance between the sides of the recess and the blade enables the hinge to stretch within the elastic limit of the hinge material as the arm moves from the release position to the clamping position. As shown in  FIG. 6 , the leading surface is inclined at a small angle as indicated by “A” relative to the trailing surface when the arm is in the release position. In this instance, the angle “A” reduces to zero and the leading surface is parallel with the trailing surface after the arm has been pivoted to the clamping position. Alternately, the leading surface of the recess initially may be substantially parallel to the trailing surface. Advantageously, the recess and the slot  37  may be formed in the same manufacturing operation if they are formed by electrical discharge machining.  
         [0035]     In further carrying out the invention, each arm  30  is formed with holes  39  sized to slideably receive the threaded shank portions  40  of the screws  33 . The holes  39  are located between the free end portion and the integral hinge  31  and extend generally radially through the arm. The threaded openings  34  in the center portion of the body are aligned with the holes  39  in the arm. To prevent the heads  35  of the screws from extending outwardly beyond the outer periphery of the body  12 , the holes  39  are formed with counterbores  42  sized to receive the heads of the screws. The surfaces  36  are defined by the bottoms of the counterbores.  
         [0036]     Advantageously, the cutter head  10  is equipped with screws  26  for establishing the location of the backside of the blades  11  relative to the back surface  16  of the body  12 . More specifically, the screws  26  are screwed into threaded openings  29  ( FIG. 7 ) extending forwardly and axially from the back surface of the body. The threaded openings are located adjacent the recesses  20  and are positioned such that the heads  27  of the screws  26  extend substantially across the recesses. When the back sides of the blades are aligned with the back surface of the body, the profiled cutting edges  18  of the blades are axially aligned relative to one another so as to evenly engage the edge portion of the workpiece.  
         [0037]     With the foregoing arrangement, the cutter head  10  is especially adapted for ease of installation and removal of the blades  11 . With the screws  33  sufficiently backed out of but remaining threaded into the threaded openings  34 , the integral hinge  31  resiliently draws the leading surface  21  of the recess  20  away from the trailing surface  22  of the recess to provide clearance in the recess for receiving the blade. The blade is located and aligned in the recess by simply sliding the blade into the recess until the base  19  of the blade rests against the registry  25  and until the backside of the blade abuts the head  27  of the screw  26 . When the screws  33  are turned inwardly, the heads  35  of the screws  33  engage the bottoms  36  of the counterbores  42  and cause the arm  30  to pivot inwardly about the integral hinge. As a result, the gap between the blade and the sides of the recess closes so that the leading surface clamps the blade against the trailing surface. Advantageously, if the leading surface is at a predetermined angle “A” when the arm is in the release position, the entire leading surface pivots into engagement with the blade when the screws  33  are turned inwardly. Applying a preload torque to the screws  33  firmly clamps the blade in the recess. To release the blade from the recess, the screws  33  are simply turned outwardly to allow the hinge portion to pull the leading surface away from the blade.  
         [0038]     Further in accordance with the invention, the leading surface  21  is formed with an integral tab  44  and the blade  11  is formed with an axially extending slot  45  which is sized to slideably receive the tab. More specifically, the tab extends axially along the leading surface  21  of the recess and generally parallel to the registry  25 . The tab projects into the recess toward the trailing surface  22  and locally restricts the width of the recess. The tab preferably extends along the entire leading surface to allow the recess, the slot  37 , and the tab to be formed in the cutter head  10  during a single electrical discharge machining operation. With this arrangement, the blade is installed into the recess by aligning the slot  45  with the tab and sliding the blade axially into the recess until the blade engages the head  27  of the screw  26 . As a result, the tab prevents the blade from flying out of the cutter head in the event the operator does not tighten the screws  33 .  
         [0039]     Because tab  44  is positioned on leading surface  21  of arm  30 , the tab is generally radially inwardly biased, as indicated by bias arrow  46  ( FIG. 8 ), when screw  33  is radially inwardly driven. The radial inward bias on tab  44  counteracts the centrifugal force, depicted by centrifugal force arrow  48  ( FIG. 8 ), experienced by blade  11  when cutter head  10  is used. The radial inward bias on integral tab  44  further causes a tiny gap to be formed between the outer slot portion  50  of axially-extending slot  45  and outer tab portion  52  integral tab  44 . Moreover, the radial inward bias ensures that when a blade  11  is installed into recess  20 , the base  19  of the blade positively engages and is forcibly biased against the registry  25  so that the cutting edge  18  of the blade is precisely and repeatably positioned relative to the center of the cutter head.  
         [0040]     The axially-extending slot  45  generally defines a slot bottom  51  interposed between an outer slot wall  53  and an inner slot wall  55 . The inner slot wall  55  disposed further radially inwardly than the outer slot wall  53 . In one embodiment, the slot  45  has greater dimensions (e.g., is larger and/or deeper) than the dimensions of integral tab  44 . In other words, integral tab  44  is smaller is size than axially-extending slot  45 . Having these parts so dimensioned ensures that integral tab  44  will provide a radially downward force upon axially-extending slot  45  of blade  11 . In a further embodiment, there is a controlled distance between inward slot portion  54  of axially-extending slot  45  and base  19  of blade  11 . As such, the distance between inward slot portion  54  of axially-extending slot  45  and registry  25  on cutter head  10  can be controlled, ensured and/or maintained while the cutter head is operated. In yet another embodiment, one or both of the inner slot portion  54  and inner tab portion  56  are rounded, as shown, or are oblique, angled, beveled, chamfered, or the like.  
         [0041]     Within a structure of the cutting blade  11  there is provided means for controlling clamping of the cutting blade in a radially inward direction and for preventing radial sliding movement of the cutting blade when clamped in the recess  20 , as is evidenced in the foregoing. More specifically, this means comprises two critical dimensions including the relative width of the cutting blade  11  between the leading and trailing faces of the cutting blade (dimension W), and the relative distance between the base end  19  of the cutting blade and inner wall of the slot (e.g., the portion of the slot wall closest to the base end). This distance has been indicated as dimension D in the drawings. In particular, if the cutting blade  11  is too thick, this will cause the clamping arm  30  to prematurely clamp the cutting blade with the leading and trailing faces  21 ,  22  rather than engage of the base end  19  with the registry  25 . As shown, for example, in  FIG. 8 , the cutting blade  11  is sufficiently thin such that when the blade is clamped into position there is a virtually imperceptibly gap between the leading face of the cutter blade and the clamping arm  30 . Additionally, the position of the inner wall is located relative to the base end  19  of the cutter blade  11  to ensure reliable contact and biasing engagement with the integral tab  44  of the clamping arm  30  as well as positive radially inward clamping of the blade. Thus, the size, configuration and relative location of the slot  45  in the present invention has been closely controlled and modified relative to the prior art to ensure proper positive radial inward clamping of the cutting blade  11 . As such, radial sliding movement of the cutting blade  11  is prevented when the cutting blade is subjected to high rotational speeds during cutting operations. Given that the width W of the cutting blade  11  is ordinarily fixed or substantially fixed in a given application, it is therefore critical that the distance D be provided to ensure that when used in an application with a given rotary cutter head  10  that the blade will positively clamp radially inward rather than being clamped laterally between the leading and trailing faces  21 ,  22 .  
         [0042]     From the foregoing, it will be apparent that the present invention brings to the art a new and improved cutter head  10  in which the blades  11  are more easily installed into and releasably secured in recesses formed in the cutter head when compared to prior cutter heads of the same general type. The uniquely configured arms  30  which are connected to the body  12  by way of integrally formed resilient hinges  31  enable the blades to be clamped into and released from the recesses  20  by simply turning screws  33  inwardly and outwardly, respectively. By virtue of the relatively snug fit between the blades and the recesses, and by virtue of the heads  27  of the screws  26  located on the backside  16  of the cutter head, the blades are easily located in the recesses and repeatably aligned relative to one another. As a result, dull blades can be more quickly removed and replaced with sharp blades without the need to remove and reinstall the screws or other items from the cutter head. In addition, the uniquely configured tabs  44  restrict the radial movement of the blades when they are located in but not firmly clamped in the recesses without the need for separate back-up screws.  
         [0043]     All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.  
         [0044]     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.  
         [0045]     Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.