Patent Document

FIELD OF THE INVENTION 
       [0001]    The invention relates to a magnetic switch for use more particularly though not exclusively for a food processor. 
       BACKGROUND OF THE INVENTION 
       [0002]    Food processors conventionally comprise a base enclosing an electric motor having a shaft on which various tools such as knives or scrapers can be mounted. The drive shaft projects into a bowl adapted to enclose the tools and the products which have been or are being processed. In some cases the bowl is removably mounted on the base for ease in cleaning. The bowl is closed by a removable cover, the main purpose of which is to prevent material from being thrown out of the bowl. The devices have to be fitted with a safety means because they can be very dangerous as tools are driven at high speed in the bowl and any contact with a rotating tool may result in serious injury. 
         [0003]    The motor must be stopped either when the bowl is not properly fitted on the base or when the bowl is properly fitted on the base but the cover is not locked on the bowl. The idea, of course, is to prevent any contact with the rotating tool. This result can be obtained by disposing a working contact in the base, the contact being connected in series in the motor supply circuit and being open or closed depending on whether the bowl and cover are properly positioned, i.e., the cover is locked to the bowl and the bowl is locked to the base. 
         [0004]    One solution has already been proposed in U.S. Pat. No. 4,741,482 to Coggiola et al. (“the &#39;482 patent”), which also describes other solutions prior to the &#39;482 patent. The &#39;482 patent relates to a magnetic safety device for a food processor comprising a base from which a drive shaft extends and is adapted to receive various tools, the processor also comprising a first element detachably mounted on the base and bearing means for securing to the base so as to hold it in a given position, a second element bearing means for locking to the first element in a given position, and a duct extending along a generatrix of the first element so that in the operating position a substantially punctiform region of the base is geometrically in line with the axis of the duct and a point on the second element, characterized in that at least one contact is disposed in the base and at least one permanent magnet is secured to one of the two elements. 
         [0005]    However, the device cannot be considered perfectly because the contact can be actuated by placing a magnet inserting a pointed object into the orifice in the base when the bowl is not in position, thus rotating the drive shaft. When the bowl is in position, it is also possible to start the motor by pressing the top end of the pusher. Finally, there may be difficulties in cleaning and maintaining the pusher, which is pushed upwards by a spring. 
         [0006]    The aim of the invention is to obviate the aforementioned disadvantages and construct a safety device which is more reliable. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention relates to a magnetic switch for, inter alia, a food processor comprising a base from which a tower and a drive shaft extend. Within inside of the tower, near its top, are disposed four magnets that control an electrical contact in the base, which contact either enables or disables a motor disposed in the base. The drive shaft is adapted to receive various tools that rotate to process various food products. The food processor also comprises a bowl detachably mounted on the base, said bowl having means for securing to the base so as to hold it in a given position, and a bowl cover having a chute. The bowl cover also comprises means for locking to the bowl and four magnets, which magnets are aligned with the four magnets disposed within the top of the tower extending from the base of the food processor. A pusher is used to push products down the chute without any possible contact between a hand and a rotating tool. The pusher comprises an actuator that push down the magnets of the bowl cover, thus activating the magnets disposed in the tower. Once the tower magnets are activated, the electrical contact in the base enables the motor and allows the food processor to operate. 
         [0008]    The &#39;482 patent describes a food processor comprising a bowl and a bowl cover, the bowl having a duct extending along a generatrix of the bowl. The duct is adapted to receive a pusher, which, when both the bowl and the bowl cover are in proper position, enables an actuating means to engage a hole in the base and act on a mechanical contact within the base. The bowl further comprises a magnet that actuates a magnetically-controlled contact within the base when the bowl is properly positioned. The mechanical and magnetically-controlled contacts are connected in series in the supply circuit of the motor. Thus, the tool cannot be driven by the motor unless the bowl is properly mounted on the base and the bowl cover is properly mounted on the bowl. The safety feature of the prior patent, however, can be defeated by inserting a pointed object in the hole of the base to actuate the mechanical contact and concurrently placing a magnet above the magnetically controlled contact. 
         [0009]    The present invention, in contrast, does not require a hole in the base to actuate a contact within it to supply power to the motor. Instead, the present invention utilizes, in the bowl cover, four magnets, the magnetic pole arrangement for which alternates. The proper polarity arrangement of the magnets repel the four magnets in the tower, which then actuates the magnetically-controlled contact in the base, which then enables the motor. The safety feature thus requires not only that the bowl and bowl cover are properly in place but also that the pusher is also in place. Further, the safety device cannot be inactivated unless by a person in possession of four magnets in proper polarity arrangement, which greatly reduces the risk of improperly starting the motor. 
         [0010]    Other features and advantages of the invention will be clear from the following description of preferred embodiments of the invention. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings, which are incorporated in and constitute a part of this invention, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE INVENTION 
         [0011]    The foregoing aspects and other features of the present invention are explained in the following description, taken in connection with the accompanying drawings, wherein: 
           [0012]      FIG. 1  is a diagrammatic view of a food processor comprising a magnetic safety device according to the invention; 
           [0013]      FIG. 2  is a top view of the food processor of  FIG. 1 ; 
           [0014]      FIG. 3  is a right side view of the food processor of  FIG. 1 ; 
           [0015]      FIG. 4  depicts a bowl cover comprising a magnetic safety device according to the invention; 
           [0016]      FIG. 5  depicts a pusher used in conjunction with a food processor to actuate a magnetic safety device according to the invention; 
           [0017]      FIG. 6  depicts a base of the food processor of  FIG. 1 ; 
           [0018]      FIG. 7  is a sectional view of a tower of the base depicted in  FIG. 6 , wherein a magnetic safety device according to the invention is not actuated; 
           [0019]      FIG. 8  is a sectional view of a tower of the base depicted in  FIG. 6 , wherein a magnetic safety device according to the invention is actuated; 
           [0020]      FIG. 9  is a sectional view of a magnetic safety device according to the invention; and 
           [0021]      FIG. 10  is a sectional view of a magnetic safety device according to the invention. 
           [0022]      FIG. 11  is a sectional view of a magnetic safety device according to the invention. 
           [0023]      FIG. 12  is a sectional view of a magnetic safety device according to the invention. 
           [0024]      FIG. 13  is a sectional view of a magnetic safety device according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Reference will now be made in detail to embodiments of the invention that are illustrated in the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps. The drawings are in simplified form and are not to precise scale. For purposes of convenience and clarity only, directional terms, such as top, bottom, up, down, over, above, below, left, and right may be used with respect to the drawings. These and similar directional terms should not be construed to limit the scope of the invention in any manner. The words “connect,” “couple,” and similar terms with their inflectional morphemes do not necessarily denote direct and immediate connections, but also include connections through mediate elements or devices. 
         [0026]    Referring to the drawings,  FIGS. 1-3 , in particular, food processor  10  comprises a base  20  from which a tower  30  and a drive shaft  160  ( FIG. 6 ) extend. Base  20 , as known in the art, encloses an electric motor (not shown) mounted so that its axis is vertical and extends through a top wall of base  20 . Alternatively, the vertical output shaft (not shown) of a speed reduction gear can extend through the top wall of the base and its input shaft can be coupled to the motor drive shaft  160 , which can be disposed parallel to a bowl  40 , which is detachably mounted on base  20  and has means for securing to base  20  so as to hold it in a given position, generally known in the art. 
         [0027]    Bowl  40  is generally cylindrical in shape and has a bottom  45  formed with an aperture (not shown) for the end of the drive shaft  160  or the output shaft of a speed reduction gear, when bowl  40  is mounted on base  20 . As known in the art, a tool comprising radial knives (not shown) can be coupled by any appropriate means to the end of the drive shaft  160  in bowl  40  mounted on base  20 . 
         [0028]    As shown in  FIGS. 1-4 , food processor  10  further comprises a bowl cover  50  that is detachably mounted on bowl  40  and has means for securing to bowl  40  such as flanges  150 , as known in the art. Bowl cover  50  further has a chute  55  and four magnets  90 , which are housed in magnet housing  80 . As discussed more fully below, and as shown in  FIGS. 9 and 10 , when bowl  40  and bowl cover  50  properly are in position, magnets  90  are aligned with the four magnets  120  disposed within the top of tower  30  extending from base  20  of food processor  10 . 
         [0029]      FIG. 5  depicts a pusher  60  that is used to push products down chute  55  of bowl cover  50  without any possible contact between a hand and a rotating tool. Pusher  60  comprises an actuator arm  70  having an actuation finger  140  that pushes down the magnets  90  of bowl cover  50 , thus activating magnets  120  disposed in tower  30 . 
         [0030]      FIG. 6  is a top view of the base  20  without either bowl  40  or bowl cover  50  thereon. In the particular embodiment depicted in  FIG. 6 , there is shown tower  30 , on-switch  100 , pulse/off-switch  110 , and raised surface  170 . Bowl  40  rests on raised surface  170  and stops  180  are used to properly position bowl  40  on base  20 . 
         [0031]    As can be seen in  FIGS. 7 and 8 , within the top of tower  30  are disposed four magnets  120  that control an electrical contact  130 , which is connected in series in the motor supply circuit (not shown), is known in the art and is an on-off standard microswitch. Magnets  120  reside in magnet housing  190  having a rod  210 . Magnet housing  190  rests on spring  200  and moves vertically toward or away from switch  220 .  FIG. 7  depicts spring  200  in an uncompressed state, whereas  FIG. 8  depicts spring  200  in a compressed state. As depicted in  FIG. 7 , when spring  200  is uncompressed, electrical contact  130  is not actuated. When contact  130  is not actuated, the supply circuit for the motor is open and the motor cannot start. However, when spring  200  is sufficiently compressed, rod  130  makes contact with switch  220 , thereby actuating contact  130 . When contact  130  is actuated, the supply circuit for the motor is closed and the motor can be started by, e.g., pressing on-switch  100  or pulse/off-switch  110 . 
         [0032]      FIGS. 9 and 10  depict a cross section of housing  80 , which comprise four magnets  90 . Housing  80  is kept in the position depicted in  FIG. 9  by means of sealing rubber  240 . When bowl  40  is properly mounted on base  20  and bowl cover  50  is properly mounted on bowl  40 , magnets  90  are in alignment with magnets  120  in tower  30 . Although magnets  120  are aligned with magnets  90 , the air gap is sufficiently great so as to prevent repulsion of like magnetic poles. However, when pusher  60  is fully pushed down chute  55 , finger  140  pushes on the top of magnet housing  80  causing the air gap between magnets  120  and  90  to cause repulsion of like magnetic poles, causing magnet housing  190  in tower  30  to move toward switch  220  of contact  130 . At full repulsion of magnets  120 , switch  220  of contact  130  closes the supply circuit for the motor, thus allowing the motor to be started. 
         [0033]    Thus the tools on drive shaft  160  cannot be driven in rotation unless (a) bowl  40  is mounted on base  20  in the correct position, (b) bowl cover  50  is mounted on bowl  40  in the correct position for magnets  90  to be aligned over magnets  120  and (c) pusher  60  is fully pushed down chute  55  so as to push magnet housing  80  toward magnets  120  so as to actuate switch  220  of contact  130 . If bowl  40  is not properly mounted on base  20 , bowl cover  50  cannot be properly in place so as to have magnets  120  and  90  properly aligned. In addition, even if bowl  40  and cover  50  are properly in position, if pusher  60  is not pushed down chute  55 , the supply circuit is open and the motor cannot start. 
         [0034]    In order to reduce the air gaps, magnets  90  come in contact with a very thin bottom wall of magnet housing  80 . Likewise, magnets  120  come in contact with a very thin top wall of magnet housing  190 . 
         [0035]    Another embodiment of the invention is depicted in  FIGS. 11-13 . Bowl cover  50 ′ comprises magnet housing  80 ′, which houses two magnets  90 ′. Pusher  60 ′, which is used to push products down a chute (not shown) of bowl cover  50 ′, comprises an arm  70 ′ that houses two magnets  95 ′. As shown in  FIG. 13 , when bowl  40  and bowl cover  50 ′ properly are in position, magnets  90 ′ are aligned with two of the four magnets  120  disposed within the top of tower  30  extending from base  20  of food processor  10 . Moreover, as shown in  FIG. 13 , when pusher  60 ′ is pressed fully down the chute (not shown) of bowl cover  50 ′, two magnets  95 ′ are aligned with the other two of the four magnets  120  disposed within the top of tower  30 . As depicted in  FIG. 13 , magnets  120  are repulsed by magnets  90 ′ and  95 ′, causing rod  210  to trigger switch  220  and thus closing contact  130  and the supply circuit to the motor. 
         [0036]    As shown in  FIG. 11 , if only bowl cover  50 ′ is properly in place over two of magnets  120 , i.e., without pusher  60 ′, spring  200  is compressed only slightly but not enough to activate switch  220 . Likewise, as shown in  FIG. 12 , if only pusher  60 ′ is in place without bowl cover  50 ′, magnets  95 ′ may be aligned with two of magnets  120  and spring  200  is compressed only slightly but not enough to activate switch  220 . Thus the tools on drive shaft  160  cannot be driven in rotation unless (a) bowl  40  is mounted on base  20  in the correct position, (b) bowl cover  50 ′ is mounted on bowl  40  in the correct position for magnets  90 ′ to be aligned over two magnets of four magnets  120  and (c) pusher  60  is fully pushed down the chute (not shown) of bowl cover  50 ′ which causes alignment of magnets  95 ′ to be aligned over the other two magnets of magnets  120 . If bowl  40  is not properly mounted on base  20 , bowl cover  50 ′ cannot be properly in place so as to have magnets  90 ′ properly aligned over two of magnets  120 . In addition, even if bowl  40  and bowl cover  50 ′ are properly in position, if pusher  60 ′ is not pushed down the chute (not shown) of bowl cover  50 ′, the supply circuit remains open and the motor cannot start. 
         [0037]    It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.

Technology Category: a