Abstract:
A rotary knife assembly includes a rotary knife with a spinning blade, a motor operable to power the rotary blade, and a flexible drive cable connected between the motor and knife to transmit rotational power to the blade. The assembly includes a safety release feature drivingly intercoupled between the motor and drive cable so as to drivingly disconnect the cable and knife from the motor when excess torque is experienced. The safety release feature is in the form of a breakaway drive lug operable to normally transmit rotational power from the motor to the knife. In the event of binding of the knife or kinking of the drive cable, excess torque serves to break the drive lug in order to disengage the motor from the knife.

Description:
CROSS-RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/716,347, filed Oct. 19, 2012, which is hereby incorporated by reference herein in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention is broadly concerned with rotary knife assemblies, such as those used in the meat-packing industry. As is customary, the knife assembly is provided with a drive motor, a flexible drive line, and a rotary knife. The present invention further concerns a simplified safety feature serving to disengage the rotary knife from the drive in the event of binding or kinking of the knife or drive line. More particularly, the invention is concerned with such assemblies having safety release structure in the form of an easily replaceable breakaway drive lug forming a part of the drive connection between the rotary knife motor and the flexible drive line. 
         [0004]    2. Description of the Prior Art 
         [0005]    Powered knives have long been used in the meat processing industry for dressing an animal carcass. The process of dressing the carcass normally involves removing meat and fat from various bones (i.e., boning), cutting various bones, and trimming the meat. Powered rotary knives enable workers to perform this process with much greater efficiency than traditional, unpowered knives. Among these prior art powered knives are rotary knives that include a rotating annular blade rotatably driven within a knife housing. Rotary knives can be either electrically or pneumatically powered and are able to spin the annular blade at very high rotational speeds. Electrically powered rotary knives include an electric motor and a flexible drive shaft that directly connects the motor and the rotary knife. The prior art flexible drive shaft is drivingly connected to the knife motor with a quick-coupled connection so that drive shaft powers the rotary knife. 
         [0006]    Conventional rotary knives are problematic and suffer from certain limitations. One problem encountered by prior art knives is that the annular blade within the knife housing can be restricted from rotating during operation. For instance, a bone or other obstruction encountered while dressing a carcass can become lodged between the blade and housing and either slow blade rotation or entirely stop the blade. Also, the annular blade and other components of the rotary knife can become worn from extensive use and cause the blade to bind within the housing. During installation, the annular blade can become misaligned within the housing and blade misalignment can also cause excessive wear of knife components and binding of the blade. Furthermore, the high-speed rotational movement of the annular blade, which is ideal for quickly and efficiently processing meat, often serves to accelerate wear of the annular blade and other knife components and can promote blade binding. 
         [0007]    The flexible drive shaft of a conventional electrically powered rotary knife can also experience binding (e.g., by becoming kinked or bent) that also restricts rotation of the drive shaft or of the annular blade. For shaft-driven rotary knives, binding of the blade or shaft is known to expose the elongated flexible shaft to a significant amount of torque and cause the flexible shaft to twist or move unexpectedly. Some prior art shaft-driven rotary knives include a lever mounted on the knife handle that can be depressed by the operator to selectively power the knife (e.g., the lever can be released by the operator when an obstruction binds the blade to remove at least some torque on the shaft drive). However, these conventional rotary knives are not ergonomically designed and are known to cause the operator to experience fatigue in the hand and arm from holding the knife and depressing the lever over a long period of time (e.g., a user will operate the same knife for an eight hour work day, five days per week). 
         [0008]    U.S. Pat. No. 8,250,766 describes an improved rotary knife equipped with a safety feature serving to automatically disengage the drive motor from the drive shaft in the event of an over-torque resulting from knife or cable binding. The safety feature is in the form of a slip clutch assembly, which separates in the event of high torque loadings. While this patent represents a distinct advance in the art, the safety arrangement is somewhat complex and expensive to produce. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention overcomes the problems outlined above and provides a greatly simplified safety release structure for rotary knife assemblies. 
         [0010]    According to one aspect of the present invention the knife assembly includes a motor having a rotatable drive shaft, a rotary knife including a shiftable blade operable to be powered by the motor, and an elongated, flexible drive cable having proximal and distal ends, with the proximal end drivingly connected to the rotary knife. A drive connection assembly is operably coupled between the motor drive shaft and the distal end of the cable, so that the drive cable is operable to transmit rotational power from the motor to the blade. The drive connection assembly also includes safety release structure operable to disengage the motor from the drive cable when excess torque is applied to the safety release structure corresponding with binding of the knife or kinking of the drive cable. The preferred safety release structure includes a breakaway drive lug having opposed end sections and an intermediate breakaway section. The end sections are operably coupled with the drive shaft and the drive cable, respectively. The breakaway section is operable to break when the excess torque is applied to the drive lug. 
         [0011]    Preferably, the breakaway section of the drive lug is of reduced cross-sectional area relative to the cross-sectional areas of adjacent portions of the opposed end sections, in order to assure that the drive lug will reliably break in the event of excess torque conditions. Preferably, one end section comprises an elongated pin member of non-circular cross-section (e.g., square), and the other section comprises an annular member having a non-circular passageway therein. The drive lug is preferably machined of billet aluminum. 
         [0012]    Another aspect of the present invention concerns a breakaway drive lug for a rotary knife assembly, wherein the assembly includes a motor having a rotatable drive shaft, a rotary knife including a shiftable blade powered by the motor, an elongated flexible drive cable having one end thereof operably coupled with the knife, and a drive connection assembly coupled between the motor drive shaft and the end of the cable remote from the knife. The drive lug comprises an integral aluminum body presenting a pair of opposed end sections and an intermediate breakaway section. The end sections are configured for operable connection with the drive shaft of the motor and the drive cable, respectively. One of the end sections preferably comprises an elongated segment having a non-circular cross-section, and the other end section comprises an annular segment having a non-circular central passageway. The intermediate breakaway section has a cross-sectional area less than the cross-sectional areas of adjacent portions of the end sections such that, when excess torque is applied to the drive lug, the breakaway section will fail and the end sections will be drivingly disconnected. 
         [0013]    This summary is provided to introduce a selection of concepts in a simplified form. These concepts are further described below in the detailed description of the preferred embodiments. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 
         [0014]    Various other aspects and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments and the accompanying drawing figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Preferred embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein: 
           [0016]      FIG. 1  is an elevational view of a powered knife assembly constructed in accordance with a preferred embodiment of the present invention, including a motor, rotary knife, a flexible drive shaft, and the breakaway drive lug safety feature; 
           [0017]      FIG. 2  is a fragmentary view in partial vertical section illustrating the drive connection between the motor and the flexible drive shaft, depicting the breakaway drive lug safety feature; 
           [0018]      FIG. 3  is an exploded view of the drive connection illustrated in  FIG. 2 ; 
           [0019]      FIG. 4  is a top perspective view of the preferred breakaway drive lug; 
           [0020]      FIG. 5  is a bottom perspective view of the preferred breakaway drive lug; 
           [0021]      FIG. 6  is a side elevation view of the preferred breakaway drive lug; and 
           [0022]      FIG. 7  is a vertical sectional view taken along line  7 - 7  of  FIG. 6 . 
       
    
    
       [0023]    The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the preferred embodiments. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0024]    The present invention is susceptible of embodiment in many different forms. While the drawings illustrate, and the specification describes, certain preferred embodiments of the invention, it is to be understood that such disclosure is by way of example only. There is no intent to limit the principles of the present invention to the particular disclosed embodiments. 
         [0025]    Turning first to  FIG. 1 , a powered rotary knife assembly  10  is illustrated. The knife assembly  10  is particularly suitable for use in an animal slaughter house for dressing animal carcasses, although other knife applications are within the ambit of the present invention. The rotary knife assembly  10  broadly includes a rotary knife  12 , a flexible drive cable  14  having the proximal end thereof drivingly connected to the knife  12 , a motor  16 , and a drive connection assembly  18  operably coupled between the motor  16  and the distal end of cable  14 , so that the drive cable is operable to transmit rotational power from the motor  16  to the knife  12 . As will be explained in detail hereinafter, the connection assembly  18  includes a simplified breakaway drive lug safety feature. 
         [0026]    In more detail, the knife  12  is a conventional rotary knife operable for trimming, boning, and cutting animal carcasses. To this end, the knife  12  includes a handle  20 , a blade housing  22 , and a rotatable, annular blade  24 . A cable coupler  26  is operably connected with drive cable  14  by means of a conventional transmission (not shown). Additional features of the preferred rotary knife  12  are disclosed in U.S. Pat. No. 8,037,611, which is incorporated by reference herein in its entirety. Those of ordinary skill in the art will appreciate, however, that the knife construction may be varied without departing from the spirit of the present invention. For example, the knife  12  may alternatively have a different blade design (different knife edge shapes), housing design (split housing vs. continuous housing), connection between the blade and housing (e.g., a bushing rotatably supporting the blade on the housing), etc. 
         [0027]    Flexible drive cable  14  is configured to transmit rotational power from motor  16  to the rotary knife  12  while being flexible along its length to permit movement of the rotary knife  12  relative to the motor  16  during knife operation. The drive cable  14  includes an outer sheath  28  and an inner, axially rotatable drive shaft  30 . The distal end of cable  14  includes a coupler  32 , which receives the square-in-cross-section terminal end  34  of the shaft  30  ( FIGS. 2-3 ). The cable  14  is preferably at least about three (3) feet in length from end to end, and typically ranges from about three (3) to ten (10) feet in length. Again, the present invention encompasses other suitable flexible cable designs. For example, the drive shaft may have an alternative cross-sectional shape (non-circular, alternative polygonal, etc.) or be alternatively covered, without departing from the spirit of the present invention. 
         [0028]    The motor  16  is operable to supply rotational power to the knife  12 . In the illustrated embodiment, motor  16  is a conventional electrical motor  36  having a motor housing  38  and a rotatable motor drive shaft  40 . The housing  38  includes a tubular, outwardly projecting, internally threaded fitting  42  presenting a bore which receives the drive shaft  40 . The fitting  42  is equipped with a bushing  44  mounted in the end wall  46  of housing  38 , which rotatably receives the drive shaft  40 . A drive shaft sleeve  48  is mounted on shaft  40  and has a proximal end of a reduced diameter equipped with a metallic insert  50  presenting a square-in-cross-section central passageway  52 . Although an electric motor  36  has been illustrated, it will be understood that a pneumatic motor could be used in lieu thereof. 
         [0029]    The drive connection assembly  18  includes an elongated, tubular connector body  54  having an externally threaded distal end  56 , which is threaded into fitting  42  as shown ( FIG. 2 ), and a hexagonal proximal end  58  having an external, outwardly extending, annular shoulder  59 . The central region of body  54  is provided with a pair of opposed openings  60 , which respectively receive a coupling ball  62 . Internally, the body  54  has an inwardly projecting annular segment  64  defining a lower annular shoulder  66 . The overall assembly  18  further has a shiftable coupler sleeve  68  disposed about the body  54  and having an enlarged socket  70  at the proximal end thereof, and an internal recess  71  adjacent the distal end. A coil spring  72  is disposed about the body  54  and is captively retained between shoulder  59  and the upper end of socket  70 ; the spring  72  serves to bias sleeve  68  upwardly as viewed in  FIG. 2 . It will also be observed that the exterior surface of body  54  adjacent the distal end  56  has a groove  74 , which receives a snap ring  76 , and a spacer  77  (preferably in the form of a synthetic resin collar) is located between snap ring  76  and fitting  42 . 
         [0030]    The coupler  32  has an enlarged head  78  having a continuous ball-receiving groove  80  and an outwardly extending flange  82 . The head  78  also has an annular extension  84 , which receives the square terminal end  34  of drive shaft  30 . 
         [0031]    The preferred drive connection assembly  18  is a fairly traditional quick-coupled connection, as will be explained. The principles of the present invention, however, are equally applicable to other drive connections between the cable  14  and motor  16 . For example, the drive connection may alternatively require the use of tools (rather than a manually shifted sleeve  68 ) to disconnect the cable  14  from the motor  16 . 
         [0032]    Referring to  FIG. 2 , it will be observed that the drive connection assembly  18  also has safety release structure in the form of a breakaway drive lug broadly referred to by the numeral  86 . The lug  86  ( FIGS. 4-7 ) is in the form of an integral body  88  machined of billet aluminum. The body  88  has a square-in-cross-section segment  90 , an opposed, tubular segment  92 , and an intermediate, cylindrical breakaway section  94 . The segment  90  has a chamfered outboard end  96  as well as a radially outwardly extending flange  98 . The tubular segment  92  presents a square tubular central passageway  100 . The intermediate section  94  has a reduced cross-sectional area as compared with the cross-sectional areas of the adjacent portions of the body  88 , namely flange  98  and segment  92 . 
         [0033]    The segments  90  and  92  preferably present non-circular shapes to facilitate driving connection with the motor drive shaft  40  and cable drive shaft  30 , respectively. However, it is entirely within the ambit of the present invention for the segments  90  and  92  to alternatively be circular in shape and otherwise drivingly secured to the shafts  40  and  30 , respectively. For example, with circular shaped segments  90  and  92 , a set screw (or other fastener) or other releaseable connection may be provided with the shafts  40  and  30 , respectively. Furthermore, although the segments  90  and  92  preferably present a polygonal shape, as shown, it is not necessary that each segment shape matches the shape of the corresponding shaft. It is only necessary that enough faces contact one another to transmit torque in the desired manner. 
         [0034]    In greater detail, the segment  90  between chamfered end  96  and flange  98  preferably has a length of about 0.525 inches and a width of about 0.197 inches. The flange  98  preferably has an axial length of about 0.05 inches and a diameter of about 0.487 inches. The preferred segment  92  has a length of about 0.688 inches and a diameter of about 0.487 inches; and the square passageway  100  has a width of about 0.210 inches. With most known knife constructions, the intermediate section  94  preferably has a maximum cross-sectional dimension (or diameter in the illustrated embodiment) of about 0.200 inches. More preferably, the cylindrical intermediate section  94  has a diameter of about 0.145 inches. 
         [0035]    Again referring to  FIG. 2 , it will be seen that the segment  90  of lug  86  is seated within the metallic insert  50  of sleeve  48 , whereas the tubular segment  92  thereof is situated within the tubular extension  84 , and the square terminal end  34  of cable  30  is seated within the passageway  100 . In this way, the lug  86  forms a part of the drive connection between motor shaft  40  and drive cable  14 . It will be appreciated that the interconnection between the lug  86  and cable  14  and motor  16  may be varied without departing from the spirit of the present invention. For example, the orientation of the lug may be reversed so that the tubular segment  92  connects with the motor and the pin segment  90  connects with the cable. Furthermore, the lug may alternatively be provided with the same type of segment (pin or tubular) at both end sections. It is only necessary that the motor and cable be appropriately configured for driving connection with the lug. 
         [0036]    During the assembly of the drive connection, tubular segment  92  of lug  86  is inserted into the extension  84  with the square terminal end  34  of drive shaft  30  within the passageway  100 . Next, the head  78  is inserted into the bore of connector body  54  so that the flange  82  thereof abuts the shoulder  66  and square segment  90  is seated within the insert  50  of sleeve  48 . In this orientation, the coupling balls  62  serve to releasably maintain the head  78  in place. This head placement is accomplished by shifting the sleeve  68  against the bias of spring  72  until recess  71  is aligned with the balls  62 ; the head  78  can then be inserted past the balls  62  until the flange  82  abuts shoulder  66  and segment  90  is properly seated within insert  50 . Release of the sleeve  68  and consequent movement thereof by the extension of spring  72  serves to captively retain the balls within the groove  80  to secure the head  78  in place. 
         [0037]    The spacer  77  is particularly important in the illustrated embodiment because the lug  86  is retrofit to an existing traditional drive connection assembly  18 . Because of the added length of the lug  86  between the shaft end  34  and drive shaft sleeve  48  (which are traditionally directly connected to one another), the spacer  77  ensures that all of the components of the traditional assembly  18  maybe used without modification. More particularly, the spacer  77  limits the extent to which the connector body  54  threads into the fitting  42  (see  FIG. 2 ) so as to accommodate the lug  86 . 
         [0038]    In this assembled orientation, rotation of motor drive shaft  40  serves to correspondingly rotate drive lug  86 , terminal end  34 , and drive shaft  30  to thereby correspondingly rotate blade  24  for cutting purposes. In the event that the blade  24  encounters a bone or the like and binds, or drive shaft  30  is kinked, the motor  36  exerts increasing levels of torque through lug  86 , which can no longer rotate owing to the binding or kinking When this torque reaches a certain magnitude, the intermediate portion  94  of lug  86  breaks, thereby disengaging motor  36  from the drive shaft  30  to stop the rotation of blade  24 . Thereupon, the binding or kinking can be resolved, without injury to the user of the knife assembly  10 . Once the drive lug  86  has broken, it is necessary to replace the now-broken lug with a fresh lug. This can be readily accomplished simply by removal of head  78  from connector body  54  by reversing the above-described steps, installing a new drive lug, and reinserting the replacement lug and head  78  into the body  54 . It is noted that the flange  98  is particularly useful in facilitating removal of the segment  90  from the sleeve  48 , which could otherwise be particularly problematic if the lug sheared immediately adjacent the sleeve  48 . 
         [0039]    It will thus be seen that the present invention provides a very simplified and inexpensive safety feature which avoids the complexities of the prior art designs. 
         [0040]    Although the above description presents features of preferred embodiments of the present invention, other preferred embodiments may also be created in keeping with the principles of the invention. Furthermore, these other preferred embodiments may in some instances be realized through a combination of features compatible for use together despite having been presented independently as part of separate embodiments in the above description. 
         [0041]    The preferred forms of the invention described above are to be used as illustration only and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention. 
         [0042]    The inventor hereby states his intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention set forth in the following claims.