Abstract:
An electrically operated slicing knife includes an axially movable switch guard overlying the switch of the knife. The switch guard is movable to a first position whereat the switch is uncovered and a second position whereat the switch is covered to prevent a user from actuating the switch. A pair of user actuated buttons control ejection of the blade of the knife. When the buttons are in a first position, the blade is locked relative to the knife handle, and the switch guard when positioned to uncover the knife switch maintains the buttons in their locked position. When the switch guard is moved to cover the switch, the buttons can be actuated by a user to unlock the blades from the knife handle.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an electrically powered slicing knife, and in particular to an electric knife having a switch guard functioning to reduce the possibility of injury to a user of the knife when the user desires to remove the blades thereof. 
     Electrically operated slicing knives are among the most popular small kitchen electrical appliances. Most of these slicing knives comprise a pair of blades releaseably secured together and reciprocated by a suitable electric motor contained in a housing. The blades are in sliding contact with each other. 
     During normal usage of the slicing knife, for example, when cutting meat, the blades become dirty and require cleaning. During the cutting operation, the blades are securely held within the knife housing and are connected to the motor. To enable the blades to be readily cleaned, it is desirable that the blades be easily removable from the housing. To minimize the potential of injury to the user, it is important that the knife include means to reduce the possibility that the knife will be accidentally energized when the blades are being either removed from or reinserted into the housing. 
     Accordingly, it is an object of the invention to provide in an electric slicing knife means to minimize the possibility of injury to a user when the user is removing blades from the knife housing. 
     SUMMARY OF THE INVENTION 
     The foregoing object and other objects of the invention are obtained in an electrically operating slicing knife including a housing having an electric motor mounted in the housing. Gear means are provided for converting rotary motion of the motor to reciprocating motion of the blades. A pair of blade holders are connected to the gear means for opposite reciprocating motion with respect to each other. The knife further includes a pair of blade members having adjacent faces in sliding engagement with each other and having a cutting portion and a tang portion. The tang portion of a first blade member is received by a first blade holder, and a tang portion of the second blade member is received by the second blade holder. A resilient member releaseably secures the blade members in the blade holders. A user operated switch selectively connects the motor to a source of electrical power. A guard overlies the switch and is movable between a first position whereat the switch is uncovered to permit activation by the user and a second position whereat the switch is covered to prevent activation by the user. A movable locking means is in operative relationship with the resilient member and the guard. The switch guard moves and retains the locking means in a locking position relative to the resilient member when in the first position. The guard when in the second position enables the user to move the locking means into an unlocking position relative to the resilient member. 
     The object of this invention is also obtained in a method of operating an electrically powered knife comprising the steps of inserting a knife blade into a knife handle for cutting purposes; placing an actuating switch in an on position to operate the blades in a cutting motion while simultaneously preventing the user from removing the blades from the handle; placing the switch in an off position to deactivate the blades; and blocking the switch to prevent user actuation while simultaneously enabling the user to remove the blades from the handle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a perspective view of an electric slicing knife including the present invention in an operating state; 
     FIG. 2 is a view similar to that shown in FIG. 1 but taken from a side opposite to that shown in FIG. 1; 
     FIG. 3 is a perspective view with parts broken away and some omitted for purposes of clarity further illustrating the present invention; 
     FIG. 4 is an exploded perspective view of an electric slicing knife designed in accordance with the present invention with parts omitted for purposes of clarity; 
     FIG. 5 is a further exploded perspective view with parts omitted for purposes of clarity providing additional details of the slicing knife of the present invention; 
     FIG. 6 is a sectional, somewhat diagramatic view of the slicing knife providing further details of the invention; 
     FIG. 7 is a view similar to that shown in FIG. 6 with the knife in a different operating state than that shown in FIG. 6; and 
     FIG. 8 is a longitudinal sectional view of the electric slicing knife in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the various figures of the drawing, there is disclosed a preferred embodiment of the present invention. In referring to the various figures of the drawing, like numerals shall refer to like parts. 
     Referring specifically to FIGS. 1 and 2, there is disclosed an electrically operated slicing knife  10  having a housing generally designated by the reference numeral  12 . A pair of blade members  14  are mounted in housing  12 . Blade numbers  14  have adjacent faces in sliding engagement with each other. Each of the blades includes an ear-like member  22  for enabling a user to manipulate a blade. Each of the ears  22  is made from a thermoplastic rubber overmolded over an ABS plastic substrate or other suitable plastic material. In the preferred embodiment, the thermoplastic rubber has been obtained from Teknor Apex Company, Pawtucket, R.I., and is sold under the trademark “Tekbond”. 
     Housing  12  includes lower and upper housing portions respectively  24 ,  26 . Lower housing portion  24  includes air vents  28 . Upper housing portion  26  includes air vents  29 . Housing  12  is made from polycarbonate plastic. Upper housing portion  26  includes an overmolded section  27 . Section  27  is overmolded with “Tekbond” thermoplastic rubber. Housing  12  further includes a lower housing portion  50  at the end of the housing proximate ears  22 . Housing portion  50  is also overmolded with the “Tekbond” thermoplastic rubber. 
     Housing portion  50  has a pair of openings  21  extending therethrough for accommodating user operated button assemblies  20 . Each assembly  20  includes a button actuator  20 A,  20 B. A user operated switch  16  is mounted in lower housing portion  24 . In the preferred embodiment, switch  16  is a rocker-type switch, which, when actuated by the user to an on position, connects motor  44  (shown in FIG. 8) to a source of electrical power. Switch  16  rotates about integral pivots  80 . Switch  16  mounts spring  70  which maintains switch  16  in an open state. Switch  16  includes axially extending tracks  72 . Switch  16  when placed in an on state actuates switch  74 . A guard  18  is moveable relative to switch  16  for a reason to be more fully explained hereinafter. As shown in FIG. 8, when guard  18  is moved forwardly relative to switch  16  (the solid line position for guard  18 ), switch  16  is exposed for use by the user. When guard  18  is moved rearwardly relative to switch  16  (as shown in dotted or phantom lines), guard  18  overlies switch  16  to prevent the user from actuating the same. Tracks  72  guide the movement of guard  18  relative to switch  16 . Guard  18  includes finger tab  76  for enabling the user to easily move the guard. 
     Referring now in particular to FIGS. 3,  4 , and  5 , further details of electric slicing knife  10  shall be described. Knife  10  includes a blade holder assembly  35  comprising a pair of blade holder members  34 ,  36  which are connected to gear  46  (shown in FIG. 8) for opposite reciprocating motion with respect to each other. Gear  46  converts rotary motion produced by motor  44  to reciprocating motion for effective use by blade holder members  34 ,  36 . Each blade  14  includes a tang portion  32 . Each tang portion  32  is held by a respective one of the blade holder members. In the preferred embodiment, the axial travel of each blade holder is approximately four millimeters. Blade holder assembly  35  further includes resilient means comprising first and second spring members  38 ,  40  for resiliently securing the tang of each blade member in its respective blade holder member  34 ,  36 . Blade holder assembly  35  further includes rear and forward support frames  37 ,  42 . Support frame  37  includes a pair of pads  62  which are aligned with bosses  60  when blade holder assembly  35  is mounted in lower housing portion  24 . Blade holder assembly  35  is secured to housing portion  24  through joining bosses  60  with pads  62  through suitable means such as screws or the like. 
     Forward frame member  42  includes a pair of rearwardly extending legs  67 . Each leg includes an opening  66 . Each opening is aligned with a corresponding boss  64  for connecting forward frame member  42  to housing  24 . Each leg  67  includes a member  69  forming an axially extending opening. The function of each opening shall be explained more fully hereinafter. 
     Switch  16  of knife  10  further includes a guide member  57  having a U-shaped portion formed by plate  78  and axially extending legs  58 . Guide member  57  retains spring  70  of switch  16 , prevents electrical power wires  74  from interfering with movement of blade holder assembly  35 , returns switch  16  in its assembled position and guides the reciprocating motion of blade holder assembly  35 . End  71  of each leg  58  extends within the opening formed in members  69  for aligning guide member  57  relative to forward frame member  42 . Guide member  57  forms the top surface of switch  16 . Screw openings  82 ,  88  in plate  78  are in alignment respectively with bosses  86 ,  84  for connecting guide member  57  to housing  24 . 
     Each button assembly  20  includes a generally vertically extending triangular support member  52 . A split beam-like member  54  extends radially inwardly from the upper end of each triangular member  52 . Beam-like member  54  includes two-spaced horizontally extending arms  55 ,  57  which form an opening  49  therebetween. Finger  45  of frame number  42  extends axially within each opening  49 . Inward radial movement of button assembly  20  is limited through engagement of one of the vertical faces forming opening  49  with one of the side edges of finger  45 . Each button assembly  20  includes a vertically extending pin  56 . 
     Referring specifically to FIGS. 6 and 7, it will be observed that each spring member  38 ,  40  of blade holder assembly  35  terminates in a generally U-shaped portion which forms vertically extending openings  92 ,  94  respectively in spring members  38 ,  40 . FIG. 6 illustrates guard  18  in its forward position wherein guard  18  abuts opposed inner faces  90  of triangular support members  52 . The position of guard  18  in FIG. 6 corresponds to the solid line position for guard  18  shown in FIG.  8 . In FIG. 7, guard  18  is moved rearwardly so that it is no longer abutting the inside faces  90  of triangular support members  52 , but rather is overlying switch  16 . The position of guard  18  in FIG. 7 corresponds to the position shown for guard  18  in dotted or phantom lines in FIG.  8 . 
     With reference to FIGS. 6 and 7, it will be observed that user actuated button  20 A controls movement of the pin  56  within opening  92  of spring member  38 . Thus, inward movement of button  20 A moves spring member radially outwardly relative to the center of housing  12 . Similarly, user actuated button  20 B controls movement of finger  56  in opening  94  of spring member  40 . When guard  18  is in the position shown in FIG. 6 in abutting relationship with faces  90 , buttons  20 A and  20 B are in their outermost position with their respective fingers being moved inward relative to the center of housing  12 . The abutting relationship between the surface of guard  18  and faces  90  prevents user actuated buttons  20 A and  20 B from being moved inward in a direction normal to the longitudinal axis of knife  10 . 
     Similarly, when guard  18  is moved rearwardly so that it is no longer in abuttance relationship with vertical faces  90 , user actuated buttons  20 A and  20 B can be moved inwardly so that their respective fingers move outwardly which in turn moves spring members  38  and  40  likewise outwardly. As shall be explained more fully hereinafter, when guard  18  is in the position shown in FIG. 6 (in solid line in FIG. 8) switch  16  may be actuated by the user to actuate slicing knife  10 . When guard  18  is the position shown in FIG. 7 (and in dotted line in FIG.  8 ), the guard overlies switch  18  to prevent actuation of the switch. 
     Operation of the electric slicing knife as described above shall now be more fully explained. Assume that blades  14  are within blade holder  35  as shown in FIGS. 1,  2 , and  3 . Further assume that the user desired to operate the slicing knife to cut food. When it is desired to operate knife  10 , guard  18  is moved forwardly to enable the user to actuate switch  16 . The position of guard  18  in its forward position is shown, for example, in FIGS. 1,  2 ,  3 , and  6 . As particularly shown in FIG. 6, when guard  18  is moved forwardly, the surface thereof moves into abutting engagement with faces  90  of assemblies  20 . Pins  56  of assemblies  20  are moved inwardly to likewise move spring members  38 ,  40  inwardly relative to blades  14 . With spring members  38 ,  40  in their innermost radial position relative to the longitudinal axis of the blades, the blades are locked in their cutting position. 
     When the user is finished cutting food with knife  10  and desires to clean blades  14 , the user will slide guard  18  rearwardly to override switch  16 . When guard  18  overrides switch  16 , the user cannot inadvertently actuate the switch. With guard  18  in its rearward position, the user can move buttons  20 A and  20 B radially inwardly (as shown in FIG. 7) which in turn moves fingers  56  of assemblies  20  outwardly to likewise move spring members  38 ,  40  outwardly. The outward movement of spring members  38 ,  40  releases blades  14  from their locked position relative to housing  12 . The user then may readily remove the blades from the housing by grasping ears  22  of each blade  14 . 
     It should be understood that while guard  18  has been specifically shown in the preferred embodiment as overlying switch  16 , it is within the scope of the invention for guard  18  to be located in a different position relative to switch  16 . For example, guard  18  may be positioned within switch  16  for movement relative to the switch. Likewise, guard  18  may be positioned behind the switch. 
     While a preferred embodiment of the present invention has been described and illustrated, the invention should not be limited thereto but may be otherwise embodied within the scope of the following claims.