Patent Publication Number: US-6662452-B2

Title: Power operated rotary knife

Description:
FIELD OF THE INVENTION 
     The present invention relates to a power operated rotary knife with an improved blade housing and clamping assembly. 
     BACKGROUND OF THE INVENTION 
     Power operated rotary knives have been used in commercial meat processing operations to trim fat and connective tissue from meat, trim pieces of met from bones, and to produce meat slices. Such knives are often constructed so that they are driven via a long flexible drive shaft. The knife operator wields the knife relatively freely at a meat cutting work station that is remote from the driving motor. 
     The blade of a power operated rotary knife must be replaced periodically. To permit easy removal of the blade from a blade housing, a split blade housing has been employed. Such a split blade housing is disclosed in published PCT Application No. PCT/US00/27488 (International Publication No. WO 01/24977 A2), assigned to the assignee of the present invention and which is incorporated herein in its entirety by reference. 
     A clamping assembly is used to secure the blade housing to a head member of the knife. The clamping assembly includes a clamp body and a pair of clamping screws. The pair of clamping screws extend through holes in the head member and into tapped holes in the clamp body. The clamping screws are tightened to secure the blade housing to the head member. 
     The blade housing includes a slot on its outer periphery to facilitate remove of the blade from the blade housing without the necessity of removing the blade housing or the clamp body from the head member. To remove the blade, the clamping screw nearest the blade housing slot is slightly loosened, a screwdriver is inserted in the slot and levered against the head member to resiliently expand the blade housing diameter and, thereby, release the blade from the blade housing. Upon installing a new blade, the screwdriver is removed from the slot and the blade housing returns to its unexpanded diameter and the clamping screw is tightened. Frictional forces between the blade housing, clamp body and head member maintain the blade housing in its unexpanded condition. 
     It has been found that some operators of such rotary knives fail to tighten the clamping screw sufficiently after installing a new blade. During cutting operations, forces are applied to the split housing that tend to spread it apart. If the clamping screw is not sufficiently tightened, the blade housing diameter may gradually expand during use of the knife. Expansion of the blade housing during use of the knife may result in chattering of the blade, poor cutting performance and downtime as the operator attempts to analyze and remedy the problem. To avoid this problem it would be desirable to provide an inexpensive and reliable structure to increase the frictional force between the blade housing and the clamp body that maintain the blade housing in its unexpanded condition during use of the knife but that still permits easy changing of the blade by loosening of a single clamping screw. 
     SUMMARY OF THE INVENTION 
     The present invention provides for an improved rotary knife comprising an annular blade, a split blade housing for supporting the blade for rotation, a handle assembly including a head member for supporting the split blade housing, and a clamping assembly including a clamp body for clamping the split blade housing to the head member. 
     An important feature of the invention is that a portion of the split blade housing is provided with an area of scoring along a bearing surface that bears against the clamp body. Similarly, the clamp body is provided with an area of scoring along a bearing surface that bears against the blade housing bearing surface. The areas of scoring coact to inhibit movement of one end of the split blade housing with respect to a second end of the split blade housing when the split blade housing is clamped to the head member. Preferably, the scoring of the clamp bearing surface of the blade housing comprises lines of scoring defining a pattern of alternating ridges and grooves and the scoring of the blade housing bearing surface of the clamp body comprises lines of scoring defining a pattern of alternating ridges and grooves. The lines of scoring of the blade housing are configured to inter fit with the lines of scoring of the clamp body, that is, the ridges of the clamp body engage the grooves of the blade housing and the ridges of the blade housing engage the grooves of the clamp body to increase the frictional force between the clamp body and the blade housing. 
     These and other objects, features and advantages of the invention will become better understood from the detailed description of the preferred embodiments of the invention which are described in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a rotary knife of the present invention; 
     FIG. 2 is a perspective view of a split blade housing of the rotary knife of FIG. 1; 
     FIG. 3 is an enlarged perspective view of a portion of the split blade housing of FIG. 2; 
     FIG. 4 is a top plan view of the split blade housing of FIG. 2; 
     FIG. 5 is a sectional view of the split blade housing of FIG. 2 as seen from a plane indicted by the line  5 — 5  in FIG. 4; 
     FIG. 6 is an enlarged plan view showing detail of lines of scoring of the split blade housing of FIG. 2, 
     FIG. 7 is front elevation view of a clamp body of the rotary knife of FIG. 1; 
     FIG. 8 is a bottom plan view of the clamp body of FIG. 7 as seen from a plane indicated by the line  8 — 8  in FIG. 7; 
     FIG. 9 is an enlarged plan view showing detail of lines of scoring of the clamp body of FIG. 7; and 
     FIG. 10 is a perspective view of split blade housing and handle assembly of an alternate embodiment of the rotary knife of the present invention. 
    
    
     BY DESCRIPTION OF THE BEST MODE FOR PRACTICING THE INVENTION 
     A rotary knife  10  embodying the invention is illustrated in the drawings. As illustrated by FIG. 1, the knife  10  comprises a handle  12 , a generally circular, split blade housing  14  supported by the handle assembly  12 , and an annular blade  18  supported by the blade housing  14  for rotation about a central axis. The illustrated knife is connected to a remote electric motor by a flexible drive shaft so that the blade  18  is driven from the electric motor. The motor and drive shaft may be of any suitable or conventional construction and are not illustrated. It should be appreciated that other means may be employed to drive the blade  18 . For example, an air motor may be mounted in the handle assembly  12  and connected to a source of pressurized air via a suitable hose, or an electric motor may be mounted in the handle assembly  12  and connected to a power source by a power cord. 
     The illustrated handle assembly  12  extends away from the blade  18  and blade housing  14  along a line that is transverse to the axis of rotation of the blade  18  allowing a knife operator to wield the knife with one hand. The handle assembly  12  comprises a handle supporting frame member  20 , a head assembly  24  fixed to the frame member  20 . A hand grip (not shown) surrounds frame member  20  and provides a gripping surface for an operator. The frame member  20  is adapted to receive various hand pieces having different configurations to permit an operator to select a hand grip which is most comfortable for the operator&#39;s hand. 
     The frame member  20  rigidly supports the head assembly  24 , a blade driving pinion gear  27  and a pinion gear supporting bearing  27   a  while providing a channel through which the flex shaft (not shown) extends to make a driving connection with the pinion gear  27 . The head assembly  24  secures the blade housing  14  and the blade  18  to the housing while enabling their removal and replacement when desired. The illustrated head assembly  24  comprises a head it member  40  and a clamp assembly  42  that detachably clamps the blade housing  14  and the blade  18  to the head member  40 . The head assembly  24  also includes a conventional lubrication system (not shown) by which a relatively viscous, edible lubricant may be supplied to the pinion gear  27 , the blade  18  and the blade housing  14  via suitable passages. An operator depresses a rubber-like diaphragm of the lubrication systems to force a flow of the lubricant into the pinion gear teeth for which the lubricant flows onto the blade  18  and is circulated about the blade housing  14 . The lubrication system forms no part of the invention and is therefore not described in further detail since it may be of any conventional or suitable construction and may be omitted from the knife  10  altogether if desired. 
     The head member  40  positions the blade housing  14  relative to the handle assembly  12 . The illustrated head member  40  is a generally crescent shaped, cast metal body that defines a semicircular blade housing seating region, a clamp assembly receiving, socket-like cavity  52 , and a boss  54  that surrounds the frame member  20  and projects from the head member body opposite to the cavity  52  and seating region  50 . The pinion gear bearing  27   a  is a tubular member that is fixed in the head member  40  and surrounds a shank of the pinion gear. The clamp assembly  42  includes a steeling mechanism  70  by which the blade  18  can be straightened by a knife operator. The steeling mechanism forms no part of the invention and is therefore not described in further detail since it may be of any conventional or suitable construction and may be omitted from the knife  10  altogether if desired. 
     The clamp assembly  42  firmly maintains the blade housing  14  seated against the seating region  50  to rigidly position the blade  18  while covering the pinion gear  27  which might otherwise be directly exposed to meat, fat, bone chips, etc. The clamp assembly  42  comprises a clamp body  60  and clamping screws  62   a ,  62   b . The clamp body  60  defines a semicircular recess  64  (FIGS. 7 and 8) confronting the head member  40  for receiving the pinion gear  27 , outer peripheral bearing surfaces  66   a ,  66   b  (FIGS. 7 and 8) that engage the blade housing  14  along inner peripheral bearing surfaces  67   a ,  67   b  (FIGS. 1,  2 ,  3  and  5 ) on respective opposite sides of the blade housing split  84 , and clamping screw receiving bosses  68   a ,  68   b  (FIG. 7) that project past the blade housing  14  into the cavity  52 . 
     The clamping screws  62   a ,  62   b  extend through respective holes  69   a ,  69   b  in the rear side of the head member  40  and into respective tapped holes  70   a ,  70   b  (FIG. 7) in the clamp body bosses  68   a ,  68   b . The screws  62   a ,  62   b  are tightened to clamp the clamp body  60  against the blade housing  14 . Each clamp face  66   a ,  66   b  exerts force on the blade housing bearing surfaces  67   a ,  67   b  that depends on the tension in the respective clamping screws  62   a ,  62   b . The illustrated clamping screws  62   a ,  62   b  are unscrewed from the clamp body  60  to release the clamp body  60  and the blade housing  14  from the handle assembly  12 . The screws  62   a ,  62   b  and head member holes  69   a ,  69   b  are preferably constructed so that the screws  62   a ,  62   b  are captured in the holes  69   a ,  69   b  when unscrewed from the clamp body  60 . This prevents the screws  62   a ,  62   b  from being misplaced when changing the blade housing  14 . 
     Advantageously, in the knife  10  of the present invention, the blade  18  may be removed and replaced without the necessity of removing the blade housing  14 . The blade housing  14  has first and second end portions  80 ,  82  extending circumferentially away from opposite sides of the blade housing split  84  along the handle seating region  50  and defines a radially inwardly opening circumferential groove  86  (best seen in FIG. 3) that receives the blade  18 . The blade housing  14  is split to enable-resilient expansion for removing and replacing the blade  18 . 
     The blade housing  14  is constructed and arranged so that the end portion  82  is shiftable along the handle seating region  50  relative to the end portion  80  for expanding the blade housing  14 . The blade housing  14  is centered on the axis of rotation of the blade  18  with the end portions  80 ,  82  forming a blade housing mounting structure that extends circumferentially partially about the blade housing  14  on opposite sides of the split  84  between the head member  40  and the clamp assembly  42 . 
     The illustrated end portions  80 ,  82  include axial extensions  92 ,  94  that are clamped between the clamp body  60  and the head member  40  and are construction for facilitating blade housing expansion for blade removal and replacement. The extension  92  defines an arcuate notch  96  through which the clamp body boss  68   a  extends. The notch  96  closely conforms to the shape of the boss  68   a . When the clamping screw  62   a  is threaded into the boss hole  69   a , the boss  68   a  extends through the notch  96  and prevents the blade housing end portion  80  from moving with respect to the clamp face  66   a.    
     The blade housing extension  94  defines an elongated reduced height section  98  that extends away from the split  84 . The boss  68   b  extends through the reduced height section  98  when the blade housing  14  is supported on the head member  40 . The length of the reduced height portion  98  assures that the blade housing end portion  82  can move freely along the confronting clamp face  66   b  toward and away from the end portion  80  when the clamp screw  62   b  is completely loosened. 
     The blade housing  14  is formed with an expansion structure  120  that enables the housing  14  to be resiliently expanded, while still connected to the head member  40 , when the blade  18  is removed and replaced. The expansion structure  120  comprises one or more, e.g., two spaced apart axial slots  122 ,  124  in the blade housing outer periphery  126  adjacent the head member  40 . To remove the blade  18 , the clamping screw  62   b  is partially, but not completely loosened, thus maintaining some tension in the clamping screw  62   b  and, therefore, some clamping force applied to the blade housing  14 . A screwdriver, or equivalent tool, is inserted in the slot  124  and levered against the head member  40  to resiliently expand the blade housing diameter. The screwdriver is then removed from slot  124  and inserted in slot  122  and levered against the head member to further resiliently expand the blade housing diameter and allow for easy removal of the blade  18  from the blade housing groove  86 . Because the clamping screw  62   b  is only partially loosened and some clamping force on the blade housing  14  remains, the blade housing  14  does not snap back or return to its unexpanded diameter when the screwdriver is removed from the slot  124  and inserted in slot  122 . Similarly, the residual clamping force prevents the blade housing  14  from returning to its unexpanded diameter when the screw drive is removed from the slot  122 . After the blade  18  is removed and replaced with a new blade, the screwdriver is used inserted in slot  122  and then slot  124  to urge the blade housing  14  back to its unexpanded diameter. The clamping screw  62   b  is then tightened to complete the blade replacement process. 
     It has been found that some operators fail to sufficiently tighten the clamping screw  62   b  after replacing the blade  18 . If the clamping screw  62   b  is not sufficiently tightened, the clamping force applied to the blade housing  14  by the clamp body  60  may be sufficient to maintain the blade housing  14  in its unexpanded condition during operation of the knife  10 . During operation of the knife  10 , forces are applied to the blade housing  14  that tend to expand the diameter. The blade housing end portion  80  is prevented from moving by virtue of the intermitting of the notch  96  and the clamp body boss  68   a . However, the blade housing end portion  82  is not similarly constrained and the blade housing end portion  82  may move with respect to the blade housing end portion  80 , the clamp body  60  and the head member  40  if the blade housing  14  is subjected to enough force tending to expand its diameter, that is a force on the blade housing  14  that would tend to enlarge the size of the split  84 . 
     When the clamping screws  62   a ,  62   b  are tightened, there are frictional forces between the clamp body bearing, surface  66   b  and the blade housing bearing surface  67   b  and between the outer periphery  180  of the blade housing end portion  82  and a corresponding bearing surface  190  of the head member seating region  50  that tend to keep the blade housing end portion  82  from moving with respect to the blade housing end portion  80 . One way to increase such frictional forces is to increase the tension of the clamping screws  62   a ,  62   b , i.e., increase the tightness of the clamping screws  62   a ,  62   b . This has several potential problems. First, the threaded holes  70   a ,  70   b  of the clamp body  60  and the threads of the clamping screws  62   a ,  62   b  can only tolerate limited amount of tightening tension before failing. Second, tightening the clamping screws  62   a ,  62   b  requires the operator to use a screwdriver on the screws. Some operators may not be able to tighten the screws to recommended torque values. Third, even if screws  62   a ,  62   b  are checked by maintenance personnel and, if necessary, tightened to recommended torque values prior to use on a shift, an operator changing the blade  18  during the course of a day must loosen the clamping screw  62   b  to remove and replace the blade. There is no guarantee that the clamping screw  62   b  will be sufficiently tightened after blade replacement. 
     Advantageously, in the knife  10  of the present invention, the blade housing  14  and the clamp body  60  include structure for increasing the frictional force between the blade housing and the clamp body for any given tension or tightness of the clamping screws  68   a ,  68   b . The structure includes an area of scoring  140  on the blade housing bearing surface  67   b  and a corresponding area of scoring  142  on the clamp body bearing surface  70   b . As can best be seen in FIGS. 3 and 7, the scoring areas  140 ,  142  comprise a plurality of parallel lines of scoring, the lines oriented being perpendicular to a direction of movement M (FIG. 5) of the blade housing end portion  82 . 
     In one preferred embodiment, the clamp body  60  is an aluminum casting while the blade housing  14  is fabricated of stainless steel. The lines of scoring may easily be implemented by laser scoring. Desirably, the lines of the scoring in the respective scoring areas  140 ,  142  are sized and configured to interfit to increase frictional forces. In one preferred embodiment, the scoring  140  of the blade housing bearing surface  67   b  comprises a series of radial grooves (shown schematically as  150   a ,  150   b ,  150   c  in FIG.  6 ), when viewed in cross section, having a depth d 1  of 0.005 inches, a width w 1  of 0.020 inches and a distance r 1  between adjacent grooves of 0.010 inches, while the scoring of the clamp body bearing surface  66   b  comprises a series of radial grooves (shown schematically as  152   a ,  152   b ,  152   c  in FIG.  9 ), when viewed in cross section, having a depth d 2  of 0.005 inches, a width w 2  of 0.010 inches and a distance r 2  between adjacent grooves of 0.020 inches. 
     The areas of scoring may be viewed as an alternating pattern of grooves and ridges (distance between adjacent grooves). As can be seen from the above dimensions, the grooves  150   a ,  150   b ,  150   c  of the blade housing bearing surface  67   b  (width 0.020 inches) interfit with the ridges  153   a ,  153   b ,  153   c  of the clamp body bearing surface  66   b  (width 0.020 inches). The grooves  152   a ,  152   b ,  152   c  of the clamp body bearing surface  66   b  (width  0 . 010  inches) interfit with the ridges  151   a ,  151   b ,  151   c  of the blade housing bearing surface (width 0.010 inches). A longitudinal extent of the areas of scoring  140 ,  142  is determined by a distance between an edge of the end portion  154  (FIG. 3) where the scoring area  140  commences and the outer edge  156  (FIG. 7) of the clamp body  60 . In one embodiment, the longitudinal extent of the areas of scoring  140 ,  142  is approximately 1⅝ inches. 
     If additional frictional force resisting movement of the blade housing end portion  82  is desired, areas of scoring  140 ,  142  between an outer peripheral bearing surface  180  of the end portion  82  of the blade housing  14  and the corresponding bearing surface  190  of the head member  40  may be provided. This is shown as an alternate embodiment in FIG.  10 . Such scoring areas  160 ,  162  of the outer peripheral bearing surface  180  of the blade housing  14  and the bearing surface  190  of the head member  140  respectively may be in addition to or in lieu of the areas of scoring  140 ,  142 , shown in FIGS. 1-9. 
     If it is desired to use only a two areas of scoring, it is preferable to use the areas of scoring  140 ,  142  because it is recognized that, over long usage of the knife  10 , the lines of scoring will become worn. When the lines of scoring are worn, the respective components will need to be replaced. It is more economical to replace that blade housing  14  and the clamp body  60 , than to replace the blade housing  14  and the head member  40 . 
     While the present invention has been described with a degree of particularity, it is the intent that the invention include all modifications and alterations from the disclosed embodiments falling within the spirit or scope of the appended claims.