FR2847146A1 - Mixer for culinary preparation, has mixing blade at extremity of stem and electric motor with feeding circuit that has electronic circuit with regulation of feeding parameter to set points related to given speed of output shaft - Google Patents

Abstract

The mixer has a mixing blade fixed at an extremity of a stem and an electric motor with a feeding circuit. The circuit has an electronic circuit (13) with the regulation of feeding parameters to set points related to a given speed of an output shaft (10) of the mixer. The electronic circuit receives an input of the impulses of the rotation of the shaft of the motor, where impulses are generated by an optical sensor (14).

Description

The present invention relates to an apparatus of the mixer type operating at

constant speed, especially

for professional use.

  A mixer of this type generally comprises an engine block to which a mixing stand is attached. The mixing stand is formed by a tube ending in a bell, connected to the casing of the engine block and containing inside a rod whose one end carries splines of coupling with the output shaft of the engine while the other end, located on the side of the bell, is equipped with a knife. The inner rod of the sheath is guided and immobilized by a smooth bearing, the communication of the sheath with the bell being closed by a lip seal preventing the penetration of the mixing product between the rod and the

tubular sheath.

BACKGROUND OF THE INVENTION

  Most mixers currently on the market have a very high no-load speed of around twice the normal operating speed. Indeed, it is advisable to fix the rotation of the knife around nine to ten thousand revolutions per minute in operation, that is to say in the presence of a resistant torque so that there is a real mixing of the product. Below this critical speed, the mixer only ensures mixing of the product without spraying the components and above this speed there is significant cavitation which affects the efficiency of the mixing. Furthermore, the speed at no load or in the presence of a low resistive torque is the cause of an excessive heating of the seal opposing the penetration of the product between the tubular sheath and the rod, which seal under these conditions deteriorates quickly. It follows a mixing stand which is soiled and whose dead volumes are filled with a biological material which can be a source of

  bacterial pollution due to the difficult if not impossible cleaning of these volumes.

OBJECT OF THE INVENTION

  The present invention intends to remedy these disadvantages by proposing a mixer for professional or domestic use in order to produce in particular culinary preparations in which the speed of rotation, whatever the load applied to the mixer, is kept substantially constant at an optimum value of 1 'order of

nine to ten thousand revolutions per minute.

BRIEF DESCRIPTION OF THE INVENTION

  To this end the invention therefore relates to a mixer comprising an electric motor, enclosed in a casing forming the outer casing of the motor, and a mixing head fixed to the end of a drive rod, housed at the inside a tubular sheath detachably connected to the above-mentioned outer casing, the rod being guided in the sheath by a smooth bearing, associated on the side of the knife with a seal, in which the motor supply circuit electrical system includes an electronic circuit for regulating the parameters of this supply to setpoints corresponding to a determined speed of the motor output shaft, the electronic circuit

  receiving as input the pulses generated by an optical sensor of the rotation of the motor output shaft.

  In order to avoid overloads and overheating harmful to the motor, the motor supply circuit

  is equipped with a thermal protection device.

  Other advantages and characteristics of

  the invention will emerge from an embodiment given below.

BRIEF DESCRIPTION OF THE DRAWINGS

  Reference will be made to the appended drawing in which the single figure represents by a schematic section a mixer in accordance with the invention.

  DETAILED DESCRIPTION OF THE INVENTION

  In this figure, there is shown schematically the motor M of a motor unit 1 of a mixer enclosed in a casing 2, which casing constitutes the outer casing of the motor and either directly its gripping member by the user or the support for a grip handle. This casing, in known manner, comprises the start / stop button of the engine and, if necessary, a button for adjusting the nominal speed thereof. A power cord, not shown, allows the motor unit to be connected to a power source. In the lower part, the casing 2 has an orifice, for example threaded or with a rod, through which it is possible to fix a mixer stand 3 conventionally formed of a tubular sheath 4 terminated by a bell 5 and containing a rod 6 of transmission of the movement of the engine to a knife 7 lo20 ge in the bell. At the opposite end of the knife, the rod has a coupling member 8, for example a grooved end capable of being introduced into a coupler 9 in shape correspondence with the end piece and integral with the end of the shaft output 10 of the motor M. The axial support for guiding the rod 6 in the sheath 4 is ensured by known means such as a smooth bearing 11 and the sealing of the annular space between sheath and

  rod on the side of the tool 7 is produced by a lip seal 12.

  The electrical supply of the motor M is equipped with an electronic regulation circuit 13 which makes it possible to adjust the parameters of the electrical supply which are the voltage and the intensity, to set values corresponding to a predetermined speed of rotation. of the output shaft 10 of the motor itself corresponding to a value of the order of nine to ten thousand revolutions per minute of speed of rotation of the knife 7. This control of the intensity and voltage parameters is ensured by monitoring the speed of rotation of the motor output shaft 10 M, monitoring carried out by means of an optical sensor 14 whose pulses are interpreted by the electronic circuit 13 in a servo loop. A device 15 for thermal protection of the motor supply, for example a fuse, allows

  avoid overloading and therefore overheating of this motor.

  This speed regulation of the mixer motor has several advantages. The wear of the bearing there and the heating therefore the deterioration of the seal 12 are greatly reduced because the rod 6 does not reach excessive speed when the mixer does not meet any resistant torque. The constant speed from the start to the end of the mixing, despite the variation of the mechanical characteristics of the product during this mixing, allows on the one hand to optimize the energy consumption of the mixer and on the other hand to reduce the time of mixing. In fact, there is no cavitation phenomenon when the product reaches the end of mixing. Finally, there will have been a significant reduction in the operating sound level of the

blender.

Claims (2)

REVENDI CATIONS   1. Mixer comprising an electric motor (M) enclosed in a casing (1) forming the outer casing of the motor and a mixing knife (7) fixed to the end of a drive rod (6) housed inside a tubular sheath (4) detachably connected to the above-mentioned outer casing (2), the rod (6) being guided in the sheath (4) by a smooth bearing (11) asso10 cie, on the side of the knife ( 7), to a seal (12), characterized in that the supply circuit of the electric motor (M) comprises an electronic circuit (13) for regulating the supply parameters to set values corresponding to a speed determined from the output shaft (10) of the motor (M), the electronic circuit (13) receiving as input the pulses generated by an optical sensor (14) of the rotation of   the output shaft (10) of the motor (M).   2. Mixer according to claim 1, characterized in that the motor supply circuit is equipped   a thermal protection member (15).