Patent Grant
8733089
The present invention relates to a fluid-dynamic circuit, particularly adapted to control the movements of drive members for driving implements and tools on operating machines, such as tire demounting machines.
Various technical fields use automatic or semiautomatic machines with tools mounted to the free end of an operating arm, which is movably attached to a support of the machine and moves with a single degree of freedom.
These tools shall be caused to contact an object upon which they are designed to operate, while ensuring that no excessive contact forces are generated between the tool and the object, to prevent any damage during such contact.
For this reason, it is highly advantageous to use detection means to detect the contact between the tool and the object to be acted upon, which detection means generally controls drives of additional automatic members that shall be only actuated when contact has occurred between the tool and the object.
A further very useful feature is the possibility of controlling the stroke and position of the arm and to cause it to reach a predetermined limit stop position which typically coincides with the contact between the tool and the object or with a predetermined position of the arm, to control the operation of the automatic members which, as mentioned above, shall be only operated once such limit stop position has been reached.
The tool supporting arm is typically driven by a double-acting fluid-dynamic actuator, which is interposed between the arm and the support of the machine in which the arm slides.
In order to obtain the above described features, the operation of the actuator must be controlled to limit the sliding speed of the piston in the jacket and the drive force that will be exerted on the object as contact occurs between the latter and the arm-supported tool.
Two possible alternative solutions are used in the prior art to control the arm stroke, and hence the action of the actuator.
In a first solution, one or more proximity sensors (selected from those known in the art) are mounted to the machine support, to the arm and, when needed, also to the tool.
Thus, a warning signal, typically an electric or pneumatic signal may be used to detect when the arm reaches the predetermined limit stop position, which signal is transmitted by the sensors to one or more control units of the machines, which are designed to control the operation of the automatic members.
Nevertheless, this first solution suffers from certain drawbacks.
A first drawback is that the areas in which the proximity sensors shall be mounted and positioned must be located and prepared on the arm support and possibly on the tool.
Furthermore, these operations shall be carried out in a particularly accurate manner, to avoid any inaccurate arm position detection.
A second drawback is that means have to be provided for transmitting and carrying signals from the sensors to the control unit, such as cables, pipes, optical fibers, and this involves an increase of machines' manufacturing costs, because in addition to sensor costs, seats have to be formed, by suitable processing, on the arm, the support and possibly the tool, for mounting such sensors.
Furthermore, if the sensor mounting positions are not easy to reach, the sensors must be calibrated according to their non-optimal location with respect to a limit stop position or the end position that the arm is required to reach.
A further drawback is that the sensors that are designed to generally detect a contact between a tool and an object upon which the latter is designed to act are typically mechanical sensors and hence clearances may exist between components that might cause inaccurate detections with respect to the positions that have been reached by the tool relative to the object.
Therefore, for improved accuracy, high-precision sensors must be used, which will have a proportionally higher cost.
A further drawback is that the lines that carry the signals between the sensors and the control unit are often mounted, at least partially, in the proximity of the object and this increases the risk of contact with the object or with parts that might come off therefrom during further processing.
In the second solution the arm is still moved by means of an actuator, but detection of a predetermined limit stop position of the arm occurs by measuring changes in the force of the actuator, namely by measuring the pressure thereof, which considerably increases above the normal operating value when the actuator is under a stress, because the arm and the tool have reached the limit stop position that stops any further sliding movement although the pushing action of the actuator continues.
Such second solution provides an advantage over the first solution, in that the lines required transmitting the signals indicating that the arm has reached its limit stop position or a predetermined position, are the lines that are used to connect the actuator to fluid source, also known as power source.
According to the second solution, a further parameter may be also used to detect that the arm has reached a limit stop position, i.e. the change in the energy (typically electric energy) absorbed by the actuator during normal operation and when the limit stop position has been reached; when this state is reached, energy absorption considerably increases due to the resistance opposed to the actuator.
Therefore, in short, this second solution is generally preferable, as long as pressure forces and changes thereof can be measured as the arm moves in its support.
Furthermore, this second solution has a much simpler construction than the first solution and hence, a lower cost and improved reliability with time.
However, this second solution also has various drawbacks.
A first drawback is that the speed of the arm relative to its support has to be controlled and limited, both to prevent kinetic reactions from causing the arm to slide beyond a predetermined end position with no limit stop abutment, and to allow accurate detection of the changes in pressure or (electric) force absorbed by the actuator.
Furthermore, the thrust imparted by the actuator shall be detectable by reading a single physical quantity and should not require comparison of two different quantities, which would involve the use of more advanced electronic systems and mapping thereof, requiring particularly expensive components and accordingly expensive calibration thereof.
Even when using constant voltage-controlled electromechanical actuators, in which the current absorbed by the actuator provides a reliable reading of the force exerted thereby, absorbed current detection requires high cost sensors, as well as high cost control unit components to analyze the absorbed and detected current value.
Furthermore, when the arm has a substantially straight motion, the electromechanical actuators designed to impart this motion are also costly, as they are typically composed of a rotary motor and a rack or recirculating-ball screw transmission.
If constant-flow hydrostatic actuators are alternatively used, in which the hydrostatic fluid pressure in the pressure chamber is directly proportional to the force exerted by the actuator, other drawbacks occur.
A first drawback of this solution is that hydrostatic actuators require a hydraulic station to supply hydraulic pressure, even in machines that would not require it as such, such as most light industrial automation machines, typically operated by compressed air.
Furthermore, the hydraulic circuit has to be controlled by solenoid valves which in turn require an electronic controller to be connected thereto, thereby increasing construction costs.
In addition, the detection of hydraulic pressure in the pressure chamber of the actuator requires electronic pressure transducers, which are also expensive, as well as expensive electronic components for interpreting the signals generated by these transducers.
Finally, a further drawback of the prior art in general is that an operator is required to manually hold the actuation control to move an operating arm to a predetermined position.
One object of the invention is to improve the state of the art.
Another object of the invention is to provide a fluid-dynamic circuit that allows accurate control of the movements of an operating arm of a machine tool, both in terms of speed and in terms of strength of the contact force between a work tool mounted to the operating arm and an object to be worked upon by the tool.
A further object of the invention is to provide a fluid-dynamic circuit that can reduce the manufacturing costs of the machine on which it is mounted.
Another object of the invention is to provide a fluid-dynamic circuit that allows predetermined movements to be performed by an operating arm without requiring an operator to hold a control as the operating time is being displaced.
In one aspect the invention relates to a fluid-dynamic circuit comprising: a source of a pressurized fluid; distributor valve means for distributing said pressurized fluid to transport lines; a feeding line for feeding said pressurized fluid, which is interposed between said source and said valve means; at least one main user apparatus which is reciprocatingly operated by actuator means which comprise a slider slideably and sealably fitted in a sliding seat of a containing element divided thereby into a first chamber and a second chamber in opposite positions and having variable volumes; and at least one second and one third transport lines for said pressurized fluid, which are interposed between said distributor valve means and said first chamber and second chamber respectively, wherein a first derived transport line is interposed between said valve means and at least one of said second and third transport lines, and has normally closed quick discharge means mounted thereto, whose opening is designed to be controlled by actuator means.
Therefore, the invention affords the following advantages:
controlling the speed and length of the stroke of an operating arm driven by a fluid-dynamic actuator, thereby avoiding any violent impact between the tools supported by the operating arm and an object to be worked upon by the tools;
holding an operating control actuated in a selected work or rest position, to move an operating arm in a first direction or in a second direction opposite thereto;
preventing any overrun of the operating arm, caused by inertia or by clearances between the components of an operating machine having the operating arm mounted thereto.
Further characteristics and advantages of the invention will be more apparent from the detailed description of preferred, but non-exclusive embodiments of a fluid-dynamic circuit of the invention, which are described as non-limiting examples with the help of the annexed drawings, in which:
Referring to the above figures, same reference numerals will be used to designate common parts in all the versions as shown in
Referring to
A first pillar 5 extends in a substantially vertical direction from the base 2 and supports at its upper end 6 a guide element 7, in which a quadrangular-section bar 8 is slideably received.
The bar 8 has a support head 9, at one end facing toward the self-centering turntable 3, for receiving a hexagonal post 10 in a special inner seat, which post is coupled with the inner seat with a single degree of freedom, like the bar 8 relative to its guide element 7.
In practice, the post 10 and the first pillar 5 are substantially parallel.
A bead removing device 12 is mounted at one side of the base 2, for removing tire beads, once they have been deflated, from the edges of the rims on which they are mounted.
Next to the first pillar 5, a second pillar 13 is mounted to the base 2, parallel to the first pillar 5 and with carriages 15 sliding therealong on guides 14, for supporting a series of operating arms 16, 17 and 18 which have, at their ends facing toward the self-centering turntable 3, corresponding tools 19, 20, 21 for use to work upon the wheels 4.
As shown in
Referring to
The action of the actuator 24 moves or retracts the arm 18, equipped with a tool 21, toward or away from an object, e.g. a wheel 4, that has to be contacted to be worked upon thereby.
Referring to
As shown in
As is shown, the second transport line 111 is connected at its opposite end to a first chamber 113 of a sliding seat of a piston 114 which divides the seat, generally referenced 116, into this and an opposite second chamber 115.
In practice, the piston 114 and the seat 116 are part of a main user apparatus, i.e. the linear actuator 24, which comprises a pneumatic cylinder 117 having a shaft 118 which, in this case, coincides with the shaft 27, and having one end extending out of the seat 116 and with a contact element 119 mounted thereto for abutment against one of two limit stop elements 120 or 121 according to the direction of displacement of the piston 114 in the seat 116.
In this first version of the circuit 100, a flow regulator 122 is mounted along the third transport line 112 and is namely designed to regulate the compressed-air flow along the second transport line 112 in one direction, i.e. toward the second chamber 115, whereas in the opposite direction the flow is free.
A first derived transport line 123 is connected to the second transport line 111, and has a first coupling end proximate to the third port 108 and a second connection end proximate to an inlet port 125 that allows access to the first chamber 113.
The second chamber 115 also has its access port, referenced 125 with the concurrent end of the third transport line 112 connected thereto.
Quick discharge means 126 are arranged along the first derived line 123, which are designed to be normally closed, but may be opened when air pressure in the first derived line 123 increases, as further discussed below.
The quick discharge means 126 have a port 127 for connection to the first derived line 123, a port 128 for connection to the second transport line 111 and a quick discharge port 129.
A second derived line 130 is provided on the third transport line 112, namely between the flow regulator 122 and the access port 125, and connects it to an auxiliary control circuit 131, which is designed to control at least one additional user apparatus controlled by said main user apparatus, i.e. the linear actuator 24, and described below.
Referring now to
In this case, the connection 132 is obtained by means of a slide valve 133 that has two alternate work positions, namely a normal position 134 in which it is closed, and a discharge position 135 in which it is open, against elastic counteracting means 136.
Furthermore, in
Referring now to
In greater detail, the additional quick discharge valve 137 comprises an inlet port 138 which is connected to the port 128 of the quick discharge means 126 by means of a pneumatic connection line 139, an exit port 140 which is connected to the second transport line 111 and a discharge port 141.
The additional quick discharge valve 137 also comprises therein a connection line between the inlet port 138 and the discharge port 141, which is regulated by a one-way valve 142.
Referring now to
Referring now to
Referring to
Namely, the end of the third derived line 145 opposite to the end for connection to the second port 107 is connected to the third transport line 112 at one point between the flow regulator 122 and the inlet port 125 of the second chamber 115.
This third derived line 145 also has further quick-discharge means 146 mounted thereto, which are substantially similar to the quick-discharge means 126, and have an inlet port 147, an exit port 148 and a discharge port 149.
As shown in
Referring to
More in detail, the auxiliary control circuit 131 comprises a pressure stabilizer 150, which is mounted to a second pressurized-fluid feeding line, referenced 151, which connects the source 101 to an inlet port 152 of the pressure stabilizer 150, the latter also having an exit port 153 connected, through an additional transport line 154 for pressurized fluid, to one end of an additional slide valve 155.
The latter has two work positions 156 and 157, an inlet port 158, which is connected to the source 101 through an additional transport line 159, a discharge port 160 and an exit port 161 which is connected through an additional transport line 162 to a port 163 that provides access to a sliding chamber 164 of a linear actuator 165.
The latter has a piston 166, which is slideably mounted in the sliding chamber 164 and has a shaft 167 extending out of it.
The piston 166 slides in the sliding chamber 164 against the action of the elastic counteracting means, i.e. a compression spring 168.
Referring to
The operation of the fluid-dynamic circuit in the versions referenced 100, 600, 700, 800, 900 is described below, a “forth” motion being understood as the motion of the contact element 119 toward the limit stop element 120 and a “back” motion being understood as the motion of the contact element toward the limit stop element 121.
Therefore, in the first case, the operating arm 18 moves toward a wheel 4, whereas in the second case it retracts from it.
Referring to the version of the fluid-dynamic circuit 100 as shown in
More in detail, the operator has stably selected the work position 104 and the compressed air fed from the source 101 passes through the feeding line 102 and is conveyed into the second transport line 111, which carries it into the first chamber 113, through the inlet port 124 thereof.
Therefore, the pressure in the first chamber 113 increases and pushes the piston 114 toward the limit stop element 121.
At the same time, the second chamber 115 appears to be in an air emptying configuration, as it is connected to the fourth discharge port 109 through the third transport line 112 and a by-pass 122A belonging to the flow regulator 122.
In this work configuration, the first derived line 123 is also connected to the fourth discharge port 109 and hence no pressurized air reaches the quick discharge means 126, which hence remain in a closed state.
In this work configuration, the sliding speed of the piston 114 is controlled by the pressure differential between the first and second chambers 113 and 115.
Referring to
The operator has actuated the slide valve 103 by stably moving it to the work position 105.
In this configuration, the compressed air supplied from the source 101 through the first coupling port 106 and the second connection port 108 is simultaneously conveyed into the third transport line 112 and the first derived line 123.
Through the third transport line 112, pressurized air moves past the flow regulator 122 that has a flow regulating function and is introduced into the half-chamber 115.
The second transport line 111 is connected both to the fifth discharge port 110 through the second connection port 107 and to the quick-discharge means 126 through the connection port 128 thereof.
As shown in
Pressure acts on the connection port 127 and moves the quick-discharge means 126 into the discharge position 135, by overcoming the counteracting force of the elastic means 136, namely the compression spring 136.
In this configuration, the time for emptying the half-chamber 113 is much shorter than the time for filling the second camber 115.
Therefore, the piston 114 (and hence the operating arm 18) moves toward the limit stop element 120 at a speed controlled by the section of the passage of the flow regulator 122.
Once the contact element 119 has abutted against the limit stop element 120 and hence the operating arm 18 has carried the tool 21 to the proper work position relative to the wheel 4, pressure in the second chamber 115 starts to increase until it reaches a predetermined adjustable threshold that operates the auxiliary control circuit 131, the latter actuating, in this case, the linear actuator 165, as shown in
In more detail, the pressure of compressed air in the second chamber 115 acts upon the additional slide valve 155 through the second derived line 130 and switches it to the work position 157.
When the slide valve 155 is in this work position 157, as shown in
Therefore, the pressurized air that comes from the source 101 through the additional transport line 15 and passes into the additional transport line 162 is introduced into the sliding chamber 164 of the linear actuator 165.
Pressure acts upon the piston 166, which compresses the counteracting spring 1269 and moves toward it.
The shaft 167 of the piston 166 conforms, or is connected to, a stop pin (not shown), which is designed to fit into, or be extracted from a corresponding seat (also not shown) formed in the arm 18, transverse to the direction of movement of the latter, as designated by the arrow “A” in
Referring to
These switch into the work position 135 and the two connection 128 and quick-discharge 129 ports are connected to each other.
This causes the one-way valve 142 to open and the exit port 140 to be directly connected with the discharge port 141 of the quick-discharge valve 137: such connection allows discharge of the first chamber 113 which is emptied very quickly, thereby affording a controlled-speed travel of the piston 114 toward the limit stop element 120.
Referring to the fluid-dynamic circuit 700 as shown in
This allows the displacement speeds of the piston 114 to be controlled in both directions, i.e. both toward the limit stop element 120 and toward the limit stop element 121 because, depending on the work position 104 or 105 of the slide valve 103, compressed air is fed to the first chamber 113 or the second chamber 115 in a gradual manner, by adjusting the sections of the passages, and hence the flow rates, of the flow regulators 122 and 143.
In the fluid-dynamic circuit version 800 as shown in
Referring to the fluid-dynamic circuit version 900 as shown in
When the second chamber 115 is set to quick discharge, it is quickly emptied, while the first chamber 113 is progressively filled with pressurized air, whose flow is regulated, as mentioned above, by the flow regulator 143.
In practice, in the fluid-dynamic circuit version 900, both the forward and the back strokes of the piston 114 (and hence the arm 18) have controlled speeds and are not exposed to interferences caused by resistances which, in prior art fluid-dynamic circuits, are produced by temporarily residual pressures in the emptying half-chamber.
Referring to
However, when the additional slide valve 155 is in the work position 156 as shown in the figure, the additional quick-discharge valve 169 allows quick discharge of the sliding chamber 164 of the linear actuator 165, by retracting the shaft 167 from the position in which the sliding motion of the arm 18 is stopped, as described above.
It can be noted that, in this work position, the discharge 160 and exit 161 ports of the additional slide valve 155 are connected to each other.
Therefore, the additional transport line 162 is connected in a discharge configuration through the discharge port 160, and the one-way valve 172 opens and provides direct connection between the exit port 171, with the access port 163 to the sliding chamber 164 connected thereto, and the discharge port 173.
The above disclosed invention was found to fulfill the intended objects.
The invention is susceptible to a number of changes and variants within the inventive concept.
Furthermore, all the details may be replaced by other technically equivalent parts.
In practice, any materials, shapes and sizes may be used as needed, without departure from the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| M02009A0275 | Nov 2009 | IT | national |
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| 2945522 | Nelson | Jul 1960 | A |
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| 20060201321 | Loedige et al. | Sep 2006 | A1 |
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| Number | Date | Country | |
|---|---|---|---|
| 20110114209 A1 | May 2011 | US |
