Technical Field

The present invention relates to a grinding head with flap wheels.

Background Art

In particular, the present grinding head is usable in a robotic machining station for sanding and finishing mechanical pieces.

The robotic stations allow the execution of different operations free from the need for direct intervention by operators and an articulated robotic arm is generally housed inside them.

The use of robotic arms allows replacing the manual work of the operators allowing considerably reducing the machining time and the risks for the safety of the operators themselves.

The robotic arm is able to pick up a series of tool heads from special positions and bring them into contact with the mechanical pieces to be machined.

Among these, the grinding heads with flap wheels are used, e.g., for the removal of welding burrs and the final finishing of the mechanical piece through the use of special abrasive flap wheels.

In particular, the flap wheel is assembled on the grinding head by means of a gripping and rotation unit adapted to hold the flap wheel itself and to set it in rotation.

The grinding heads with flap wheels of known type do have some drawbacks.

In particular, in order to carry out the machining of a mechanical piece, the robotic arm brings the grinding head closer to the mechanical piece itself to allow the sanding action of the flap wheel.

However, the contact between the grinding head and the mechanical piece causes a reaction force to arise, opposite that applied by the grinding head itself to approach the mechanical piece.

The reaction force causes mechanical stress on the grinding head which can affect the machining of the mechanical piece or even lead to damage to the grinding head itself.

For this reason, the grinding heads with flap wheels of known type are provided with a basic frame, associable with the robotic arm, and a movable frame, which supports the flap wheel and is associated in a movable manner with the basic frame in order to undergo the reaction forces.

In use, the reaction forces acting on the grinding head with flap wheels are discharged onto the movable frame causing it to oscillate slightly with respect to the basic frame.

This oscillation is controlled by means of a compensation system adapted to counteract the reaction forces between the grinding head and the mechanical piece being machined.

However, this compensation system does not allow for the use of grinding heads with flap wheels of known type for the machining of structurally complex mechanical pieces and/or in which very high sanding quality is required, unless the robotic arm continuously adjusts the movement and position of the grinding head itself.

This inevitably leads to a lengthening of the machining time and of the related costs.

Description of the Invention

The main aim of the present invention is to devise a grinding head with flap wheels that allows carrying out sanding operations of the highest quality and precision.

A further object of the present invention is to devise a grinding head with flap wheels that allows effectively counteracting the reaction forces during the machining of structurally complex mechanical pieces in a quick and effective manner.

Another object of the present invention is to devise a grinding head with flap wheels that allows overcoming the above mentioned drawbacks of the prior art in a simple, rational, easy, effective to use and low cost solution.

The above mentioned objects are achieved by the present grinding head with flap wheels having the characteristics of claim 1.

Brief Description of the Drawings

Other characteristics and advantages of the present invention will be more evident from the description of a preferred, but not exclusive, embodiment of a grinding head with flap wheels, illustrated by way of an indicative, yet non limiting example, in the attached tables of drawings in which:

Figure 1 is an axonometric view of a machining station comprising a grinding head with flap wheels according to the invention;

Figure 2 is a partial and sectional axonometric view of the grinding head according to the invention;

Figure 3 is an axonometric view of the grinding head according to the invention from a different angle;

Figure 4 is a front sectional view of the grinding head according to the invention;

Figure 5 is a front sectional view of the grinding head in a different position of use.

Fmbodiments of the Invention

With particular reference to these figures, reference numeral 1 globally indicates a grinding head with flap wheels.

The grinding head 1 is usable inside a machining station 2 for sanding and finishing at least one mechanical piece M.

In the context of the present treatise, the term “mechanical piece” means a production product intended to be used as a component in mechanical applications. In particular, the mechanical piece is made of a metal material and may have welding burrs to be polished and/or surface portions to be finished. The machining station 2 also comprises at least one movement device A adapted to move the grinding head 1 inside the machining station 2.

Preferably, the movement device A is of the type of an automated robotic arm that allows doing without the intervention of an operator and displacing the grinding head 1 inside the machining station 2 in order to approach / move away from the mechanical piece M.

The machining station 2 is also suitably provided with at least one management and control system 3 operationally connected to at least one of either the grinding head 1 or the movement device A. The management and control system 3, in this case, is of the type of a computerized electronic system which is configured to automatically manage the movement of the movement device A and the operation of the grinding head

1.

The management and control system 3 will be described in more detail later in the present discussion.

The grinding head 1 according to the invention comprises at least one basic frame 4 associable with at least one movement device A and with at least one operating assembly 5.

The operating assembly 5 is associated with the basic frame 4 and is provided with at least one gripping and rotation unit 16, 17 of at least one flap wheel 6 around at least one operational axis L for the machining of the mechanical piece

M.

During the machining of the mechanical piece M, the operating assembly 5 is movable in rotation in both directions of rotation around at least one axis of rotation R.

In particular, during the machining, the operating assembly 5 comes into contact with the mechanical piece M and causes the occurrence of a reaction force, opposite that applied by the grinding head 1 to come into contact with the mechanical piece M.

For this purpose, the operating assembly 5 is hinged to the basic frame 4 so as it is subjected to such a reaction force and to avoid possible damage to the grinding head 1 and/or to the mechanical piece M.

More specifically, the operating assembly 5 comprises at least one holding frame 7 hinged to the basic frame 4 around the axis of rotation R and adapted to support the gripping and rotation unit 16, 17.

In this case, the basic frame 4 comprises a hub portion 4a inside which a corresponding tubular portion 8 of the holding frame 7 is at least partly housed. Specifically, the operating assembly 5 is movable between a balance position, wherein the operating assembly 5 and the basic frame 4 are aligned along an axis of equilibrium E substantially perpendicular to the axis of rotation R, and an unbalance position, wherein the operating assembly 5 is rotated with respect to the axis of equilibrium E by an angle of rotation a.

In particular, the angle of rotation a is comprised between -4° and +4°, wherein the negative values represent the rotation in a clockwise direction and the positive values represent the rotation in a counterclockwise direction.

In the balance position the angle of rotation a is zero and the operating assembly 5 extends towards the mechanical piece M, moving away from the basic frame 4.

The grinding head 1 is suitably provided with a pair of counterweighted elements 9 associated with the holding frame 7, each one arranged on opposite sides with respect to a plane substantially perpendicular to the axis of rotation

R.

The counterweighted elements 9 have the function of balancing the weight of the operating assembly 5 on the axis of rotation R.

During machining, the operating assembly 5 can be subjected to reaction forces in the opposite direction and can be made to rotate clockwise and counterclockwise.

The operating assembly 5 is, in fact, able to machine the mechanical piece M by operating on opposite sides of the mechanical piece itself with respect to a plane of equilibrium P passing through the axis of rotation R and through the axis of equilibrium E; by so doing, it is possible to optimize the machining time and reduce, this way, the costs related thereto.

It is easy to understand, however, that in order to carry out its function effectively and keep the flap wheel 6 in contact with the mechanical piece M, the operating assembly 5 must be able to counteract the reaction forces generated on contact with the mechanical piece M and return to the balance position.

For this purpose, the grinding head 1 is provided with bi-directional pneumatic compensation means 10 adapted to counteract the rotation of the operating assembly 5 around the axis of rotation R from the balance position to the unbalance position in both directions of rotation. In other words, the bi-directional pneumatic compensation means 10 tend to bring the operating assembly 5 back to the balance position and keep it in contact with the mechanical piece M in order to allow the sanding action of the flap wheel 6.

The bi-directional pneumatic compensation means 10 comprise at least one pair of compensation elements 11 inserted at least partly into a housing chamber 12 defined in the basic frame 4.

The compensation elements 11 interact with the operating assembly 5 during the rotation towards the unbalance position.

Each of the compensation elements 11 is movable between a home position and a counteracting position, wherein the compensation element 11 is pushed inside the housing chamber 12 by the operating assembly 5 as a result of the rotation. The compensation elements 11 are substantially aligned along an axis of compensation C that is substantially orthogonal to the axis of rotation R and perpendicular to the axis of equilibrium E.

In more detail, the axis of compensation C is substantially perpendicular to the plane of equilibrium P.

The compensation elements 11 are arranged on opposite sides of the plane of equilibrium P and are movable with respect to the housing chamber 12 sliding along the axis of compensation C between the home position and the counteracting position, in opposite directions.

In other words, the housing chamber 12 extends along the axis of compensation C and the compensation elements 11 partially protrude from the housing chamber 12, from opposite sides thereof.

After having been pushed inside the housing chamber 12 in the counteracting position, the compensation elements 11 are brought back to the home position to bring, in turn, the operating assembly 5 back to the balance position.

For this purpose, the bi-directional pneumatic compensation means 10 comprise actuation means which are adapted to move at least one of the compensation elements 11 from the counteracting position to the home position.

In particular, the actuation means comprise injection means 13 of at least one operational fluid into the housing chamber 12.

The operational fluid is able to counteract the displacement of the compensation elements 11 towards the counteracting position and thus to push the operating assembly 5 towards the balance position.

In more detail, the operational fluid is injected inside the housing chamber 12 at a predetermined pressure value.

Conveniently, the predetermined pressure value is more than 1 bar.

In other words, in the housing chamber 12 the operational fluid is overpressure compared to the atmospheric pressure.

Preferably, the predetermined pressure value is comprised between 2 and 6 bar. In addition, the operational fluid is preferably compressed air.

The bi-directional pneumatic compensation means 10 comprise at least one thrust element 14 associated with the holding frame 7 and adapted to abut against at least one of the compensation elements 11 between the home position and the counteracting position.

In particular, the bi-directional pneumatic compensation means 10 comprise at least one pair of the thrust elements 14 arranged from opposite sides with respect to the plane of equilibrium P, each adapted to abut against a corresponding compensation element 11.

Advantageously, the grinding head 1 comprises at least one position sensor 15 adapted to detect the position of the operating assembly 5 with respect to the basic frame 4, i.e. to determine the angle of rotation a, and to generate at least one electronic positioning data for the operating assembly 5.

In other words, the position sensor 15 allows detecting the instant when the contact occurs between the operating assembly 5 and the mechanical piece M, which determines the displacement from the balance position to the unbalance position.

Preferably, the position sensor 15 is of the magnetic type.

In particular, the position sensor 15 comprises a first sensor element 15a associated with the basic frame 4 and a second sensor element 15b associated with the holding frame 7. In the balance position, the first sensor element 15a and the second sensor element 15b face each other and generate a predetermined magnetic field.

For example, the first sensor element 15a is a Hall effect sensor while the second sensor element 15b consists of a permanent magnet.

When the operating assembly 5 rotates around the axis of rotation R towards the unbalance position, the second sensor element 15b tilts with respect to the first sensor element 15a, thus changing the magnetic field and generating the electronic positioning data of the operating assembly 5.

Appropriately, the management and control system 3 comprises at least one balancing unit 3a operationally connected to the position sensor 15 and to the actuating means and configured to operate the actuating means based on the electronic positioning data of the operating assembly 5.

More in detail, depending on the electronic positioning data of the operating assembly 5 generated by the position sensor 15, the balancing unit 3a can intervene dynamically on the injection means 13, so as to increase or decrease the pressure of the operational fluid inside the housing chamber 12 according to pre-established conditions of use.

The operational fluid operates on the compensation element 11 to bring it back to the home position; the thrust of the compensation element 11 on the thrust element 14 causes the operating assembly 5 to rotate in the opposite direction, towards the balance position.

The application of greater or lesser pressure of the operational fluid in the housing chamber 12 thus results in greater or lesser pressure of the flap wheel 6 on the mechanical piece M.

As described above, the operating assembly 5 is provided with the gripping and rotation unit 16, 17 of the flap wheel 6.

The gripping and rotation unit 16, 17 comprises at least one motor assembly 16 provided with a casing 16a associated with the holding frame 7 and with a drive shaft 16b exiting the casing 16a and rotatable around the operational axis L.

As shown in the figures, the casing 16a extends from the holding frame 7 away from it, towards the mechanical piece M. In the balance position, the casing 16a extends along the axis of equilibrium E. Advantageously, the motor assembly 16 comprises a pneumatic motor.

This makes it possible to create a grinding head 1 with reduced dimensions and provided with smaller size and weight compared to the grinding heads of known type.

The gripping and rotation unit 16, 17 is also provided with retaining means 17 associated with the drive shaft 16b and adapted to grip the flap wheel 6.

In more detail, the flap wheel 6, in order to perform its sanding function, is made to rotate around the operational axis L.

Preferably, the operational axis L is substantially parallel to the axis of rotation

R.

Conveniently, the retaining means 17 comprise at least one threaded element 18 in which a threaded hole 18a is defined that can be coupled with a threaded portion 6a of the flap wheel 6.

In more detail, the retaining means 17 comprise a retaining member 19, of the type of self-centering grippers, inside which the threaded element 18 is inserted. The operation of the grinding head 1 inside the machining station 2 is as follows.

Initially, the grinding head 1 is mounted on the movement device A for the movement of the grinding head itself with respect to the mechanical piece M. The flap wheel 6 is installed by screwing the threaded portion 6a inside the threaded hole 18a of the retaining means 17 and the motor assembly 16 is driven to induce the rotation of the flap wheel itself around the operational axis L.

At this point, the movement device A displaces the grinding head 1 towards the mechanical piece M to allow the interaction of the flap wheel 6 with the mechanical piece itself.

This interaction generates a reaction force that causes the rotation of the operating assembly 5 around the axis of rotation R in one of the directions of rotation, towards the unbalance position.

The rotation causes one of the compensation elements 11 to be displaced towards the counteracting position by the corresponding thrust element 14.

The pressure of the operational fluid in the housing chamber 12 opposes the displacement of the compensation elements 11 and thus determines the force with which the flap wheel 6 is pushed onto the mechanical piece M. During machining, the position sensor 15 detects the rotation and generates the electronic positioning data of the operating assembly 5.

At the end of the machining process or in the event of the flap wheel 6 being replaced, the movement device A moves the grinding head 1 away from the mechanical piece M, and the gripping and rotation unit 16, 17 stops the rotation of the flap wheel 6.

It has in practice been ascertained that the described invention achieves the intended objects and in particular it is emphasized that the grinding head with flap wheels according to the present invention allows carrying out high quality and precision sanding operations and to effectively counteract the reaction forces during the machining of structurally complex mechanical pieces quickly and effectively, thanks to the bi-directional pneumatic compensation means.