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Field of application

The invention relates to the field of electric motors.

More in detail, the invention relates to a braking device for direct current electric brushed motors.

State of the art

Direct current electric brushed motors are widely used in automatic systems for doors and gates (sectional doors, up-and-over doors, etc.), in systems for adjusting and moving medical devices (hospital beds, wheelchairs for the disabled, etc.), and in many other civil and industrial applications.

Said electric motors generally have a limited irreversibility coefficient, i.e. a limited capacity to withstand forces that tend to change the rest position reached by the systems connected thereto, generated by the weight of the components of these systems.

Therefore, when said electric motors are not powered they have the tendency to change their rest position together with the systems connected thereto, facilitating incomplete or imprecise movements of these systems and consequent incorrect execution of functions related thereto (partial opening or closing of doors and/or gates, imperfect adjustments of medical devices, etc.).

Known technical solutions currently used to increase the irreversibility coefficient of direct current electric brushed motors provide for opposing the counter-rotation forces generated by the weight of the components of the systems connected thereto with a desired increase of the internal frictions of these motors, obtained by means of specific braking devices associated therewith.

Said known technical solutions in particular provide for associating braking devices of the following types with said electric motors:

- spring-applied brakes, based on electromagnets operated by the power supply supplied to these motors;

- devices for increasing cogging torque, based on mutually interacting magnets, arranged on rotors and stators of these motors.

Said prior art solutions have important negative factors, as:

- spring-applied brakes require a specific power supply and specific activation means (springs), and consequently have high implementation and/or running costs in the systems concerned; - spring-applied brakes are conceived mainly as safety brakes and consequently are too costly to be used as simple braking devices;

- devices for increasing cogging torque produce vibrations and consequently increase the overall noise of the electric motors with which they are associated.

Presentation of the invention

Therefore, the object of the invention is to overcome the aforesaid negative features of known solutions currently used to increase the irreversibility coefficient of direct current electric brushed motors.

The object of the invention is achieved with a braking device for direct current electric brushed motors according to independent claim 1.

Further features of the invention are described in the subsequent dependent claims. The braking device for electric motors forming the subject matter of the invention produces numerous and important advantages, and in particular:

- it allows the irreversibility coefficient of direct current electric brushed motors to be increased;

- it produces minimum friction levels, maintaining substantially unchanged the overall performance of the electric motors with which it is associated;

- it causes minimum levels of vibrations, maintaining substantially unchanged the overall noise of the electric motors to which it is applied;

- it does not require a specific power supply or specific actuation means, thereby maintaining substantially unchanged the engineering and structural configuration of the electric motors to which it is applied.

Brief description of the drawings

Further features and advantages of the invention will be more evident from the more detailed description set forth below, with the aid of the drawings, which show a preferred implementation thereof, illustrated by way of non-limiting example, wherein:

- Fig. 1 shows, in a complete axonometric view, a braking device for direct current electric brushed motors according to the invention;

- Figs. 2-3 show, respectively in an exploded axonometric view and in a horizontal sectional plan view, the internal structural configuration of said device;

- Fig. 4 shows, in an axonometric view, the possible association of said device with a direct current electric brushed motor.

Detailed description of a preferred example of embodiment of the invention

With reference to the details of the figures, a braking device 1 for direct current electric brushed motors M according to the invention substantially comprises:

- a plurality of metal pistons 2, sliding in corresponding seats 5 of a first support 4, applicable to rotors R of electric motors M;

- a plurality of metal teeth (8), integral with a second support 10, applicable to stators S of electric motors M;

- a magnet 1 , comprised between said plurality of metal teeth 8, Said pistons 2 are made of ferromagnetic metal material and are provided on the front with inclined opposite faces 3 and with at least one levelled area on the lateral surface.

Said first support 4 is made of plastic materials and is indicatively discoid in shape.

Said first support 4 comprises radial seats 5 for housing said pistons 3, passing through the structure of the same support, configured to allow linear sliding of said pistons 3 and avoid simultaneous rotations thereof on the respective longitudinal axes.

Said first support 4 comprises a perimeter seat 6 for housing an O-ring 7 for closing said radial seats 5.

Said teeth 8 are also made of ferromagnetic material and are indicatively prismatic in shape, comprising laterally inclined opposite faces 9.

Said teeth 8 are arranged on the top of the second support 10, at the external perimeter of said magnet 11.

Said second support 10 is also made of plastic materials and is also indicatively discoid in shape. Said magnet 11 is made of magnetic material of the rare earth type and is a substantially ring shaped.

Said teeth 8 and said magnet 11 comprise anti-vibration and/or sound- absorbing coverings 12, 13, made of vulcanized rubber or similar materials.

Operation of a braking device 1 for direct current electric brushed motors M according to the invention can be described as set forth below.

When no power supply is present, the magnet 11 instantly attracts the pistons 2 of the first support 4, determining their extension in the corresponding radial through seats 5.

The inevitable counter-rotation of the rotor R of the electric motor M, due to the weight of the components of the system connected thereto, determines a corresponding counter-rotation of the first support 4, integral with said rotor R, with respect to the second support 10, integral with the stator S of said electric motor M.

The counter-rotation of said first support 4 causes any sliding of the pistons 2 on the teeth 8 of the second support 10 and, in any case, drop of said pistons 2 on the magnet 11 comprised between them.

The further counter-rotation of said first support 4 therefore causes stopping of the pistons 2 against the teeth 8 of the second support 10, in this way determining a complete stop of the electric motor M and an advantageous reaching of a stable rest position of the electric motor M and of the system connected thereto.

The coverings 12, 13, provided on said teeth 8 and on said magnet 11 , deaden the noise and/or the vibrations produced by the drop of the pistons 2 on the magnet 11 and by the sliding of the pistons 2 on the teeth 8, in this way facilitating a reduction in the overall noise of the braking device 1 during stopping and blocking of the electric motor M.

When the power supply is present, the normal rotation of the rotor R of the electric motor M determines a corresponding rotation of the first support 4, integral therewith, with respect to the second support 10, integral with the stator S of said electric motor M.

The rotation at full speed of said first support 4 produces a sliding of the inclined faces 3 of the pistons 2 on the corresponding inclined faces 9 of the teeth 8 of the second support 10, adapted to determine the detachment of the pistons 2 from the magnet 11.

The rotation of said first support 4 thus produces a centrifugal force sufficient to determine the retraction of the pistons 2 in the corresponding radial through seats 5, so as to allow regular operation of the electric motor M and simultaneously determine an advantageous limitation of the internal frictions thereof.

During the rotation of said first support 4, the O-ring 7 housed in the corresponding perimeter seat 6 prevents extension of the pistons 2 toward the corresponding radial through seats 5.

The braking device 1 as described produces an advantageous increase of the irreversibility coefficient of direct current brushed electric motors M, comprised between 0.05 Nm and 0.1 Nm.