Patent Publication Number: US-2021177212-A1

Title: Safety system, a method for selecting an operating mode, and a lid for a kitchen device

Description:
FIELD 
     This invention relates to a safety system for a kitchen device, a method for selecting an operating mode of a kitchen device, and a lid for a kitchen device. 
     BACKGROUND 
     Kitchen devices performing a variety of stirring, processing, blending and/or heating of ingredients have recently become popular in the consumer and commercial markets. These devices may be referred to as multicookers. A problem that has emanated from the increasing popularity of such multicookers is that stirring and/or blending heated substances such that they have large amounts of kinetic energy can present a substantial risk to users operating the device. Therefore, safety systems have been integrated into devices performing kinetic operations such as stirring or blending on heated ingredients to decrease the risk of users being exposed to and/or injured by the heated ingredients. 
     However, presently known safety systems are primarily designed to maintain a closed volume in a vessel used by the kitchen device by securing a lid to the vessel, and ensuring that the lid remains secured to the vessel while the ingredients have significant kinetic energy. A substantial disadvantage of this arrangement is that a common task in preparing meals, the reduction of a combination of ingredients including water by heating the combination such that water evaporates and escapes, is either not possible, or restricted by limited escape paths being available to the steam. 
     Further, it is presently not possible for the kitchen device to select a mode of operation, and apply safety limits to a motor and in the kitchen device providing the stirring, processing, and/or blending functionality depending on the intended and possible use of the kitchen device. 
     Finally, present kitchen devices having blending and heating functionality are not able to reduce ingredients by evaporation, as the safety standards require an access restriction to the moving blade of the kitchen device. 
     SUMMARY OF INVENTION 
     It is an object of the present invention to at least substantially address the above discussed disadvantages, or at least provide a useful alternative to the above arrangements. 
     In a first aspect, the present invention provides a safety system for a kitchen device having a vessel and a lid, the safety system comprising: 
     a processor; 
     a retaining arm adapted to, in a retaining position, retain the lid against the vessel; 
     a first sensor adapted to communicate a retaining signal to the processor when the retaining arm is in the retaining position; and 
     a second sensor adapted to communicate a function signal to the processor, the function signal indicating a function of the lid, 
     wherein the processor is adapted to select an operating mode of the kitchen device in response to the retaining signal and the function signal. 
     Preferably, the operating mode includes a limitation on a speed of a motor of the kitchen device. 
     Preferably, the limitation on the speed of the motor is effected by a safety relay disconnecting a power delivery circuit to the motor when a maximum speed is measured by a motor speed sensor. 
     Preferably, the retaining arm is movable between a free position and the retaining position. 
     Preferably, the safety system further comprises: 
     a securing hook, the securing hook being movable between a free position and a securing position, wherein, in the securing position, the securing hook secures the retaining arm in a secured retaining position, and wherein a third sensor is adapted to communicate a securing signal when the securing hook is in the securing position. 
     Preferably, there are at least two second sensors and the retaining arm is adapted to contact the lid on at least two separate contact areas, each contact area having at least one second sensor. 
     Preferably, the function comprises an indication of the type of lid present on the vessel and the type of lid is determined by the processor by determining which, if any, of the second sensors communicate a function signal. 
     In a second, aspect the present invention provides a lid to be used with the safety system according to the first aspect, wherein the lid has a surface geometry adapted to cause the second sensor to communicate the function signal to the processor. 
     Preferably, the surface geometry includes one or more protrusions adapted to interact with the second sensor. 
     In a third aspect the present invention provides a method for selecting an operating mode of a kitchen device, the method comprising the steps of: 
     placing a lid on a vessel of the device; 
     operating a retaining arm of the device, the retaining arm being adapted to retain the lid in position on the vessel; 
     determining a position of the retaining arm using a first sensor; 
     determining a function of the lid using a second sensor; 
     communicating the position of the retaining arm and the function of the lid to a processor; and 
     the processor selecting an operating mode on the basis of the position of the retaining arm and the function of the lid. 
     Preferably, the retaining arm is movable between a free position and a retaining position, and wherein the method further comprises the steps of: 
     determining, when the retaining arm is in an unlocked position, whether the second sensor senses a presence of the lid on the vessel; and subsequently 
     when the processor receives an indication that the second sensor senses the presence of the lid on the vessel, the processor prevents use of the kitchen device and outputs an error signal. 
     Preferably, the error signal is a prompt to clean the second sensor. 
     Preferably, the method further comprises the steps of: 
     operating a power switch of the device; 
     determining whether the retaining arm is in the retaining position; and 
     if the retaining arm is in the retaining position, the processor outputs a prompt to move the retaining arm to the free position. 
     Preferably, the method further comprises the steps of: 
     operating a securing hook from a free position to a securing position to secure the retaining arm in a secured retaining position; 
     a third sensor communicating the position of the securing hook to the processor; and 
     the processor supplying power to the motor when the processor receives an indication from the third sensor that the securing hook is in the securing position. 
     Preferably, the method further comprises the step of: 
     the processor preventing use of the kitchen device and outputting an error signal, if the processor has not received an indication that the securing hook is in the securing position within 4 seconds of operating the securing hook. 
     Preferably, the operating mode includes a limitation on a speed of a motor of the kitchen device. 
     Preferably, the method further comprises the step of: 
     measuring the speed of the motor using a motor speed sensor; and 
     limiting the speed of the motor by a power delivery circuit being disconnected by a safety relay when the speed of the motor is above a predetermined maximum motor speed. 
     Preferably, there are at least two second sensors and the retaining arm is adapted to contact the lid on at least two separate contact areas, each contact area having at least one second sensor. 
     Preferably, the function comprises an indication of the type of lid present on the vessel and the type of lid is determined by the processor by determining which, if any, of the second sensors communicate a function signal. 
     In a fourth aspect, the present invention provides a lid for a vessel used with a kitchen device, the vessel including a floor and upwardly extending sidewalls ending at a rim surrounding an opening to a space within the vessel, the lid including: 
     a central hub; 
     a rim; and 
     a structure extending between the central hub and the rim, the structure including one or more first apertures such that an unobstructed space of the structure is at least 20% of the opening and a continuous rectangular portion of the unobstructed space does not exceed 78 mm×25.4 mm. 
     Preferably, the structure further includes: 
     an intermediate member separating one or more second apertures from the one or more first apertures; 
     one or more outer connectors connecting the intermediate member to the rim to support the intermediate member, thereby forming the one or more first apertures; and 
     one or more inner connectors connecting the intermediate member to the central hub to support the central hub, thereby forming the one or more second apertures. 
     Preferably, the one or more outer connectors are equally spaced such that the unobstructed space extends adjacent the rim continuously for at least 100° for allowing access of a scraper through the lid to the upwardly extending sidewalls. 
     Preferably, the one or more outer connectors are located at a single location such that the unobstructed space extends adjacent the rim continuously for at least 350°. 
     Preferably, the central hub extends a first distance radially from a center point of the lid; 
     the intermediate member is located at a second distance radially from the center point; and 
     the rim is located at a third distance radially from the center point, 
     wherein the difference between the first distance and the second distance is approximately 65 mm, and 
     wherein the difference between the second distance and the third distance is approximately 50 mm. 
     Preferably, the unobstructed space of the structure is at least 80% of the opening. 
     In a fifth aspect, the present invention provides a lid for a vessel used with a kitchen device, the vessel including a floor and upwardly extending sidewalls ending at a rim surrounding an opening to a space within the vessel, the lid including: 
     a central hub; 
     a rim; and 
     a structure extending between the central hub and the rim, the structure including one or more first apertures such that an unobstructed space of the structure extends adjacent the rim continuously for at least 100° for allowing access of a scraper through the lid to the upwardly extending sidewalls. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Preferred embodiments of the present invention will now be described, by way of examples only, with reference to the accompanying drawings: 
         FIG. 1  is a perspective cut-away view of a kitchen device employing an embodiment of the safety system according to the invention. 
         FIG. 2  is a perspective cut-away view of the kitchen device of  FIG. 1  with a retaining arm in the retaining position. 
         FIG. 3  is a front section view of the retaining arm of the kitchen device of  FIG. 1 . 
         FIG. 4  is a detailed front section view of the retaining arm of the kitchen device of  FIG. 1 . 
         FIG. 5  is a right-side cut-away view of the kitchen device of  FIG. 2  with the retaining arm in a free position. 
         FIG. 6 a    is a perspective view of a vessel to be used with the kitchen device of  FIG. 1 . 
         FIG. 6 b    is a perspective view of the vessel of  FIG. 6 a    with a first embodiment of a reduction lid placed thereon. 
         FIG. 6 c    is a perspective view of the vessel of  FIG. 6 a    with a food processor lid placed thereon. 
         FIG. 6 d    is a perspective view of the vessel of  FIG. 6 a    with a standard lid placed thereon. 
         FIG. 7  is a schematic top view of the lids of  FIGS. 6 b    to  6   d.    
         FIG. 8  is a schematic block diagram of an embodiment of the safety system according to the present invention. 
         FIG. 9  is a schematic block circuit diagram of the safety system of  FIG. 8 . 
         FIG. 10  is a schematic flowchart of the safety system of  FIG. 8 . 
         FIG. 11  is a further schematic flowchart of the safety system of  FIG. 9 . 
         FIG. 12  is a perspective view of the kitchen device of  FIG. 1  with a second embodiment of the reduction lid placed thereon. 
         FIG. 13  is a cut-away perspective view of the kitchen device of  FIG. 12 . 
         FIG. 14  is a detailed top plan view of the kitchen device of  FIG. 12 . 
         FIG. 15  is a detailed top plan view of the kitchen device of  FIG. 1  with a third embodiment of the reduction lid placed thereon. 
         FIG. 16  is a detailed top plan view of the kitchen device of  FIG. 1  with a fourth embodiment of the reduction lid placed thereon. 
         FIG. 17  is a detailed top plan view of the kitchen device of  FIG. 1  with a fifth embodiment of the reduction lid placed thereon. 
         FIG. 18  is a detailed cut-away side view of the kitchen device of  FIG. 12  in use. 
         FIG. 19  is a detailed cut-away side view of the kitchen device of  FIG. 12  in use. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A kitchen device  1 , such as the kitchen device  1  shown in  FIG. 1 , may include a safety system  4  according to the present invention. As shown in  FIG. 1 , the kitchen device  1  typically has a body  3  and a vessel  5 , having a rim  6 , mounted thereon. As shown in  FIG. 9 , the kitchen device  1  also has a power switch  2 . A lid  21  is also provided and, in use, placed on the vessel  5 . The lid  21  has a rim  23  extending beyond the rim  6  of the vessel  5 , and an upper surface  25 . On the upper surface  25  there are located two projections  27 . The projections  27  have a rounded leading edge  29  and an upright stop edge  31 . Extending from the upright stop edge may be a contact edge  33 . A guiding edge  35  extends between the leading edge  29  and the stop edge  31 . The guiding edge  33  has a notch  36 . The guiding edges  33  are adapted to guide the retaining arm  7  into a correct alignment with the contact edges  33  as shown in  FIG. 2 . The notch  36  provides tactile feedback to the user that the retaining arm  7  is in the correct alignment. 
     The safety system  4  includes a retaining arm  7  and a securing hook  9 . The retaining arm  7  has a pair of longitudinally extending members  37 . The members  37  are, at a first end  37   a , attached to the body  3  using a hinge  39 . At a second end  37   b , the members  37  are joined by a perpendicularly extending rounded member  38 . The retaining arm  7  also has a channel  41  located at each second end  37   b  of the members  37 . A lid detection switch  43  is located in each channel  41 . 
     As shown in  FIG. 3 , the retaining arm  7  has a rotating projection  8  located at each first end  37   a  of the members  37 . The rotating projections  8  engage with the hinge  39  to allow pivoting of the retaining arm  7  with respect to the body  3  about a hinge axis  45 . Also, as shown in  FIGS. 3 and 4 , the channels  41  are substantially vertical slots with a rounded end point 
     The retaining arm  7  pivots between a free position, as shown in  FIG. 1 , and a retaining position, as shown in  FIG. 2 . The channels  41  are adapted to receive the contact edges  33  when the retaining arm  7  is in the retaining position, thereby retaining the lid  21  on the vessel  5 . A retaining arm position switch  40  is located adjacent the retaining arm  7 , such that the retaining arm  7  actuates the retaining arm position switch  40  when the retaining arm  7  is in the retaining position. 
     The retaining arm  7  is attached to a side of the hinge  39  facing away from the body  3 . On another side of the hinge  39  facing towards the body  3  there is an extension arm  47 . The extension arm  47  extends from the hinge  39  in a direction opposite the retaining arm  7 . The extension arm  47  is linked to the pivoting of the retaining arm  7  and also pivots about the hinge axis  45 , albeit at a phase angle of 180°. 
     As shown in  FIG. 5 , a securing pin  49  extends away from the extension arm  47  in a normal direction from the body  3 . The securing hook  9  has a recess  51  at a first end  9   a . The securing hook  9  pivots about a second hinge  53  between a free position shown in  FIG. 1 , and a securing position shown in  FIG. 2 . As shown in  FIG. 5 , a second end  9   b  of the securing hook  9  extends beyond the second hinge  53 . The second end  9   b  is connected to a drive mechanism  55  driven by a securing motor  57 . A hook position switch  59  is located adjacent the first end  9   a  of the securing hook  9  such that the securing hook  9  actuates the hook position switch  59  when in the securing position. 
     As shown in  FIGS. 6 a  to 6 d   , multiple configurations of the kitchen device  1  are possible, specifically the lid  21  may take a number of forms.  FIG. 6 a    shows the vessel  5  without a lid  21 .  FIG. 6 b    shows the vessel  5  with an embodiment of a reduction lid  21   b .  FIG. 6 c    shows the vessel  5  with a food processor lid  21   c .  FIG. 6 d    shows the vessel  5  with a standard lid  21   d . Referring to  FIG. 7 , the reduction lid  21   b  has a first edge  33   a  of the contact edges  33 , while the reduction lid  21   b  does not have a second edge  33   b  of the contact edges. The food processor lid  21   c  has a second edge  33   b  of the contact edges  33 , while the food processor lid  21   c  does not have the first edge  33   a . Finally, the standard lid  21   d  has both first and second edges  33   a ,  33   b  of the contact edges  33 . 
     As shown in  FIGS. 8 and 9 , the safety system  4  also has a processor  10  that operates a securing motor controller (not shown) for driving the securing motor  57 . The processor  10  also operates a main motor controller  13  for driving the main motor  15 . A speed of the main motor  15  is monitored using a motor speed sensor (not shown) that sends a speed signal indicating a motor speed to the processor  10 . The safety system  4  further includes a safety relay  17  that responds to instructions from the processor  10  and can interrupt a power supply to the main motor  15 . 
     The processor  10  also communicates with the retaining arm position switch  40 , the lid detection switch  43 , and the hook position switch  59  to determine whether the switches  40 ,  43 ,  59  have been actuated. Specifically, the lid detection switch  43  is actuated when the contact edge  33  makes contact with the lid detection switch  43  inside the channel  41 . Actuation of the lid detection switch  43  provides a signal to the processor  10  indicating the presence of the lid  21 . 
     As shown in  FIG. 12 , the kitchen device  1  may further include a lid  321  according to a second embodiment of the reduction lid  21   b . The lid  321 , similarly to the lid  21 , as seen in  FIG. 14 , has a rim  323  surrounding an opening  324 , and an upper surface  325  extending beyond the rim  6  of the vessel  5 , as shown in  FIG. 13 . On the upper surface  325  there are located two projections  327  substantially similar to projections  27 . The retaining arm  7 , when the retaining arm  7  is in the retaining position, retains the lid  321  on the vessel  5 . As shown in  FIG. 13 , a blade  304  is located in the vessel  5 , to be driven by the main motor  15  to process food. Yet further, a heater element  308  is mounted to a floor  311  of the vessel  5  so that it is in thermal communication with the contents of the vessel  5 . The heater element  308  is operable by the processor  10 . 
     As shown in  FIG. 14 , the lid  321  includes a generally structure  329 , the structure includes a set of outer apertures, being a set of six outer apertures  331  shown in  FIG. 14 , a set of inner apertures  333 , being a set of six inner apertures  333  shown in  FIG. 14 , and a central hub  335 . The central hub  335  extends from a center point  336  of the lid  321  to a radius of 55 mm. 
     The set of outer apertures  331  includes a subset of larger outer apertures  331   a  and a subset of smaller outer apertures  331   b . The outer apertures  331  are separated from the inner apertures  333  by an intermediate member  337 . The intermediate member  337  is located at a radial distance of 120 mm from the center point  336 . 
     The intermediate member  337  is connected to the rim  323  by a set of outer connectors, being six outer connectors  339  shown in the embodiment of  FIG. 14 . The six outer connectors  339  are preferably arranged in pairs, each pair preferably located 120° apart from the other, and separate the outer apertures  331  from one another such that each outer aperture  331  extends for at least 100° adjacent the rim  323 , or about 25% of a perimeter of the rim  323  to allow access of a scraper  347 , as shown in  FIG. 19 , through the lid  321  to the upwardly extending sidewalls  357  of the vessel  5 . In alternative embodiments, the outer aperture  331  may extend for as little as 10% of the rim  323 . The outer apertures  331  meet the rim  323  at a radial distance of 170 mm from the center point  336 . The central hub  335  is connected to the intermediate member  337  by a set of inner connectors, being six, preferably equally spaced, inner connectors  341  shown in  FIG. 14 . The inner connectors  341  separate the inner apertures  333  from one another. The central hub  335  includes a set of hub apertures, being a set of six, preferably equally spaced, hub apertures  343 . 
     The outer apertures  331 , inner apertures  333 , and hub apertures  343  together form an unobstructed space S 1 . As shown in  FIG. 14 , a continuous rectangle  355  may be defined in the unobstructed space S 1  such that the area within the continuous rectangle  355  is entirely filled with at least a portion of the unobstructed space S 1 . The structure  329  is dimensioned, as explained above, such that a continuous rectangle  355  having dimensions equal to or larger than 78 mm×25.4 mm in the plane of the unobstructed space S 1  cannot be validly defined, as per the process explained above, in the unobstructed space S 1 . Thereby, as shown in  FIG. 18 , access of a hand  345  of an operator through the opening  324  is hindered. 
     Further embodiments of the lid  321  for the kitchen device  1  will now be described, wherein similar features fulfilling similar functions are numbered in centennial increments. 
       FIG. 15  shows a further embodiment of a lid  421  for the kitchen device  1 . In this embodiment the lid  421  has a set of two outer connectors  439  grouped at a single location, thereby separating a single smaller outer aperture  431   b  from a single larger outer aperture  431   a . Thereby, the single larger outer aperture  431   a  extends for at least 350° adjacent the rim  423 , or about 95% of a perimeter of the rim  423 . The two outer connectors  439  support an intermediate member  437 , which is connected to a central hub  435  by a set of three equally spaced inner connectors  441 , thereby forming a set of three inner apertures  433 . Similarly, in this embodiment, the central hub  435  has a set of three hub apertures  443 . The outer apertures  431 , inner apertures  433 , and hub apertures  443  together form the unobstructed space S 1 . The structure  429  is dimensioned such that a continuous rectangle  355 , similarly to  FIG. 14 , having dimensions equal to or larger than 78 mm×25.4 mm in the plane of the unobstructed space S 1  cannot be validly defined, as per the process explained above, in the unobstructed space S 1 . 
       FIG. 16  shows a further embodiment of a lid  521  for the kitchen device  1 . In this embodiment the lid  521  has a set of two outer connectors  539  separating a single smaller outer aperture  531   b  from a single larger outer aperture  531   a . The two outer connectors  539  support an intermediate member  537 , which is connected to a central hub  535  by a single inner connector  541 , thereby forming a single inner aperture  533 . Preferably, the inner connector  541  is located radially opposite the smaller outer aperture  531   b . Similarly, in this embodiment, the central hub  535  has a set of three hub apertures  543 . The outer apertures  531 , inner aperture  533 , and hub apertures  543  together form the unobstructed space S 1 . When the central hub  535 , the intermediate member  537 , and the rim  523  are dimensioned as specified above, the unobstructed space S 1  is at least 20% of the opening for a vessel  5  having a rim  6  with a diameter of 205 mm. However, the unobstructed space S 1  is more preferably more than 40%, even more preferably more than 60%, and, as shown in the embodiment of  FIG. 16 , especially preferably more than 80% of the opening for a vessel  5  having a rim  6  with a diameter of 205 mm. The structure  529  is dimensioned such that a continuous rectangle  355 , similarly to  FIG. 14 , having dimensions equal to or larger than 78 mm×25.4 mm in the plane of the unobstructed space S 1  cannot be validly defined, as per the process explained above, in the unobstructed space S 1 . 
       FIG. 17  shows a further embodiment of a lid  621  for the kitchen device  1 . In this embodiment the lid  621  is intended for a non-circular vessel (not shown) and has a generally rectangular, or more preferably square, shape. The lid  621  has a set of two outer connectors  639  grouped at a single location thus separating a single smaller outer aperture  631   b  from a single larger outer aperture  631   a . The single larger outer aperture  631   a  extends adjacent the rim  623  for about 95% of a perimeter of the rim  623 . The two outer connectors  639  support an intermediate member  637 , which is connected to a central hub  635  by a single inner connector  641 , thereby forming a single inner aperture  633 . The central hub  635  has a side length of 55 mm and includes a center point  636 . The intermediate member  637  is a rectangular, or more preferably square, member having a side length of 120 mm. The lid  621  has a rim  623  that is substantially rectangularly, or square, shaped, the rim  623  having a side length of 170 mm. Similarly, in this embodiment, the central hub  635  has a set of three hub apertures  643 . The outer apertures  631 , inner aperture  633 , and hub apertures  643  together form the unobstructed space S 1 . The structure  629  is dimensioned such that a continuous rectangle  355 , similarly to  FIG. 14 , having dimensions equal to or larger than 78 mm×25.4 mm in the plane of the unobstructed space S 1  cannot be validly defined, as per the process explained above, in the unobstructed space S 1 . 
     A person skilled in the art would appreciate that the individual elements of the embodiments of  FIGS. 14 to 17  may be combined or altered, for example the structure  329  of  FIG. 14  could be embodied in a generally rectangular shape, similar to the lid  621  of  FIG. 17 . 
     Use of the kitchen device  1  will now be discussed. 
     As shown in  FIG. 10 , upon actuation of the power switch  2 , step  101 , the processor  10  determines, at step  103 , whether the retaining arm  7  is in the retaining position by determining whether the retaining arm position switch  40  is actuated. The processor  10  then determines, at steps  105 ,  107 , whether either of the lid detection switches  43  are actuated. If this is the case and a user has demanded, at step  109 , operation of the main motor  15 , the processor  10  issues a prompt, at step  111 , to move the retaining arm  7  to the free position. If neither of the lid detection switches  43  are actuated, the processor  10  determines, at step  113 , that no lid  21  is present on the vessel  5  and prevents power supply to the main motor  15 . 
     If the retaining arm  7  is not in the retaining position, either because the power switch  2  was actuated when the retaining arm  7  is in the free position, or because the processor  10  issued a prompt for the retaining arm  7  to be moved to the free position at step  111 , the processor  10  determines, at steps  115 ,  117  whether either of the lid detection switches  43  are actuated. If either of the lid detection switches  43  is actuated, the processor  10  determines, at step  119 , whether the retaining arm  7  is in the retaining position, by polling the retaining arm position switch  40 . If the retaining arm position switch  40  is not actuated, this indicates that the lid detection switches  43  are giving a false positive. This could be caused by debris actuating the lid detection switches  43 , or by a technical fault in the lid detection switches  43 . The processor  10  thus, at step  121 , prevents power supply to the main motor  15  and issues a prompt for the user to reset the power switch  2  and/or an error signal indicating a problem with the lid detection switches  43 . 
     If the retaining arm position switch  40  indicates that the retaining arm  7  is in the retaining position, the processor  10 , at step  123 , determines that the initial safety check has been completed and proceeds with further safety procedures described below. 
     The processor  10  now uses the securing motor controller to drive the securing motor  57  such that the securing hook  9  descends and engages the pin  49  in the securing position. This secures the retaining arm  7  in a secured retaining position as shown in  FIG. 2 . In the secured retaining position, the retaining arm  7  is prevented from moving substantially from the retaining position, due to the engagement of the securing hook  9  with the pin  49 . The hook position switch  59  is actuated when the securing hook  9  is in the securing position. The processor  10  verifies that the securing hook  9  has moved to the securing position by polling the hook position switch  59 . If the securing hook  9  has not moved to the securing position within four seconds of the processor  10  using the securing motor controller to drive the securing motor  57 , the processor  10  outputs an error message and reverses a drive direction of the securing motor  57  to return the securing hook  9  to the free position. 
     As shown in  FIG. 11 , the processor  10  now selects the operating mode of the kitchen device  1 . Step  131  is substantially equivalent to step  101 , i.e. the power switch  2  is actuated. Step  133  comprises the safety procedure of steps  103  to  123 . The processor  10  now selects, at steps  135 ,  137 ,  139 ,  141 , the operating mode of the kitchen device  1 . 
     At step  135  the processor  10  determines whether both lid detection switches  43  are not actuated. If this is the case, it indicates that no lid  21  is positioned on the vessel  5 . The processor  10  then disconnects, at step  137 , the safety relay  17  to prevent power supply to the main motor  15 . 
     At step  139  the processor  10  determines whether the lid detection switch  43  on the second edge  33   b  is actuated and the lid detection switch  43  on the first edge  33   a  is not actuated. If this is the case, it indicates that the reduction lid  21   b  is present atop the vessel  5 . The processor  10  then, at step  141 , sets a predetermined safety speed limit of, for example, 500 rpm. At step  143 , the processor  10  connects the safety relay  17  to supply power to the main motor  15 . At step  145  the motor speed sensor measures the speed of the main motor  15  and communicates the speed signal to the processor  10 . At step  147 , the processor  10  determines whether the motor speed indicated by the speed signal is higher than the predetermined safety speed limit. If this is the case, the processor at step  137 , disconnects the safety relay  17  to prevent power supply to the main motor  15 . 
     At step  149 , the processor  10  determines whether the lid detection switch  43  on the first edge  33   a  is actuated and the lid detection switch  43  on the second edge  33   b  is not actuated. If this is the case, it indicates that the food processor lid  21   c  is present atop the vessel  5 . The processor  10  then, at step  151 , sets a predetermined safety speed limit of, for example, 3000 rpm. Similarly to the process described above, step  143  follows to supply power to the main motor  15 , and in steps  145 ,  147  the processor  10  monitors the speed of the main motor  15 . If necessary, that is when the motor speed is higher than the predetermined safety speed limit, the processor  10 , at step  137 , disconnects the safety relay  17  to prevent power supply to the main motor  15 . 
     At step  153 , the processor  10  determines whether both lid detection switches  43  are actuated. If this is the case, it indicates that the standard lid  21   d  is present atop the vessel  5 . The processor  10  then, at step  155 , sets a predetermined safety speed limit of, for example, 15000 rpm. Similarly to the process described above, step  143  follows to supply power to the main motor  15 , and in steps  145 ,  147  the processor  10  monitors the speed of the main motor  15 . If necessary, that is when the motor speed is higher than the predetermined safety speed limit, the processor  10 , at step  137 , opens the safety relay  17  to prevent power supply to the main motor  15 . 
     The lids  321 ,  421 ,  521 ,  621  are used in substantially the same way as the reduction lid  21   b . The unobstructed space S 1  allows evaporation of water, and thus permits reduction of foods contained in the vessel  5 . 
     Advantages of the kitchen device  1  will now be discussed. 
     The kitchen device  1 , using the safety system  4 , is able to discern between lids  21  that are able to safely contain hot ingredients being blended or mixed at high velocities, and lids  21  that require a limitation on the motor speed to prevent hot ingredients from causing injuries or damage. This ability allows the use of partially, or completely, open lids  21  enabling cooking operations such as reducing sauces, frying meats, or safely using a food processor (not shown) in the vessel  5 . 
     The use of a separate safety relay  17 , rather than performing the control of the motor speed when it is above the predetermined safety speed limit, ensures that the reduction, or complete shut off, of power supply to the main motor  15  is reliable and immediate. Performing this control through the main motor controller  13  could be subject to faults in the software or hardware of the more complex main motor controller  13 . 
     The position switches  40 ,  43 ,  59  allow the processor  10  to precisely, and deterministically, check whether the safety system  4 , for example the retaining arm  7 , the securing hook  9 , and the lid  21 , are in their respective positions for safe operation. 
     The securing hook  9  ensures, in the securing position, that the retaining arm  7  remains substantially in the secured retaining position. While it may be possible that the retaining arm  7  moves from the secured retaining position to some degree, the securing hook ensures that the retaining arm  7  is not accidentally removed from the lid  21 , causing an interruption to the cooking process, or a safety hazard. This arrangement also provides peace of mind to the user, that the retaining arm  7  is secured in the secured retaining position and the hot ingredients are safely contained in the vessel  5 . 
     The retaining arm  7  contacts the lid  21  on at least two contact areas, being channels  41 . The retaining arm  7  thereby retains the lid  21  safely against the vessel  5  in multiple degrees of freedom. 
     By determining after providing power to the kitchen device  1 , at steps  103 ,  105 ,  107 ,  109 , whether the retaining arm  7  is in the locking position and engaged with the lid  21 , and thereafter prompting the user to move the retaining arm  7  to the free position, the processor  10  ensures that the lid detection switches  43  are tested for correct functionality before power is supplied to the main motor  15 . The processor  10  performs that test at steps  115 ,  117 ,  119 ,  121 . If the lid detection switches  43  are not functioning appropriately, the processor  10  issues a prompt to clean the lid detection switches  43 , or contacting a suitable service provider. This ensures that on every start-up of the kitchen device  1 , the lid detection switches  43  are functioning correctly, increasing the safety of the kitchen device  1 . 
     Similarly, the processor  10  determines, at steps  103 ,  105 ,  107 ,  113 , whether a lid  21  is present at all on the vessel  5 . 
     The choice of which combination of lid detection switch  43  causes which operating mode to be selected by the processor  10  also increases safety of the kitchen device  1 . Since the receipt of no function signal from the lid detection switches  43  causes the safety relay  17  to be disconnected, a fault in the circuitry of the lid detection switches  43  reverts the kitchen device  1  to a default, safe, non-operational state. 
     The lid  321 , as well as the further lid embodiments  421 ,  521 ,  621 , prevents access of a user&#39;s hand to the blade  308  during operation of the kitchen device  1 , as shown in  FIG. 18 . Thus, safe operation of the kitchen device  1  can be ensured, while ensuring the unobstructed space S 1  is as large as possible to facilitate the reduction operation. 
     The lid  321 ,  421 ,  521 ,  621  also provides desirable access to a sidewall of the vessel  5 , by ensuring that the outer apertures  333 ,  433 ,  533 ,  633  are continuous for large portions of the perimeter of the rim  323 ,  423 ,  523 ,  623 , so that, for example, a scraper may easily be moved continuously along the sidewall of the vessel  5 , without hitting one of the outer connectors. 
     Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. 
     For example,  FIGS. 6 a  to 6 d    show an embodiment of the retaining arm  207 , where the retaining arm  207  has a rounded member  238  and a second rounded member  237  that is pivotable about a hinge  239 .