Device for operating a plurality of pneumatically controlled operative equipments

Abstract

 A device for operating a plurality of pneumatically controlled operative equipments, particularly of the articulated lever type, includes a pressure generator (40) for a gas, which comprises a main cylinder (48) provided with two chambers (56, 58) separated by a slidable piston (54), and an actuator (42) to move the piston (54); fluid lines (34, 36, 60, 62) for connecting the generator unit (40) with at least a chamber (30, 32) of a plurality of pneumatic cylinders (28) of the operative equipments (16), which lines make a closed circuit for the gas, and means (33) for detecting the end-of-stroke position of the levers (18) of said equipments (16), connected with an electronic control unit (ECU). The lines of connection (34, 36, 60, 62) connect the chambers (56, 58) of the main cylinder (48) with the chambers (30, 32) of the cylinders (28) of the equipments (16).

Description

[0001] The present invention refers to pneumatically controlled operative equipments, particularly of the articulated lever type, which comprise an arm that is swingably mounted between a pair of end-of-stroke positions.

[0002] Such known equipments comprise articulated lever pneumatic clampings, used to lock a workpiece, for example in order to allow welding operations to be carried out on the workpiece, as well as other equipments, for example known centering, hooking or translation equipments, of the pneumatically controlled type and comprising an articulated lever.

[0003] In particular, the invention relates to a control device of the type mentioned in the preamble of appended claim 1.

[0004] In the devices of the type known defined above, the operative equipments are usually operated by compressed air selectively fed to the opposite chambers of a double acting cylinder associated with the moving mechanism of the relevant articulated levers.

[0005] However, use of compressed air in such a device involves a series of problems related to the presence of air compressors, for example of the centrifugal or axial type, and of lines for feeding compressed air from the compressors to the various equipments.

[0006] As far as the compressors are concerned, they are usually arranged at a considerable distance from the articulated lever equipments to be controlled, typically outside the sites in which the equipments are installed, owing to the strong noise they generate in operation, and since they need to suck a high volume of air. These compressors are usually kept continuously in motion in order to be able to deliver a design flow rate of compressed air for the maximum request by the various users, also when the required flow rate of air is smaller, which involves unavoidably a waste of power. When the compressed air required by the users is smaller than a preset maximum, the air volume in excess is discharged into the atmosphere. Moreover, the characteristics of the air sucked by the compressors in not easy to be controlled; in fact, it may have a high humidity rate, in which case humidity in the air may cause the operative equipments to be deteriorated with the passing of time or, at any rate, to require a hard maintenance.

[0007] The feeding lines used for connecting the compressors with the several equipments, are of the opened circuit type, so that compressed air delivered from the compressors, after having been used in the various operative equipments, is discharged into the atmosphere. In many cases, it is necessary to take into account the exhaust of compressed air from the equipments, that must not interfere with persons or things close to the same equipments. Moreover, the feeding lines are very extended in length, which unavoidably causes flow resistances that contribute to increase the consumption of the whole control device, beyond involving a relative design complexity in view of the installation of the feeding lines in the sites where the equipments are mounted, as well as a low versatility of the system.

[0008] In conclusion, open circuits used for feeding compressed air, commonly used to operate systems including pneumatic operative equipment units, involve a remarkable waste of energy and a series of management and design problems.

[0009] With the aim of overcoming the above mentioned drawbacks, the subject of the invention is a device having the features set forth in the appended claims.

[0010] By virtue of the fact that the pressure generator unit comprises a main cylinder provided with a first and a second chamber separated by a slidable piston, and an actuator for controlling the movement of the piston, and that the connection lines make a closed circuit for said gas and connect the chambers of the main cylinder with respective first and second chambers of the pneumatic cylinders of the operative equipments, and that the detection means of the operative equipments are connected with an electronic control unit that controls the operation of the actuator of the compressor unit as a function of the position of the articulated levers of the operative equipments and of the inner pressure of the chambers of the main cylinder, it is possible to obtain an operating device that proves to be very effective in operation, which allows maintenance and operating costs of the device to be considerably reduced with respect to known systems, on equal terms of reliability of operation.

[0011] According to a preferred feature of the invention, the gas admitted in the cylinders of the pneumatic equipments, in the main cylinder and in the connection lines, is an inert gas, conveniently nitrogen.

[0012] That allows, in particular, that any problem deriving from humidity of the gas of the operating device can be avoided, and the size of the structure of the main cylinder and of the cylinders of the operative equipments to be kept small, to the advantage of the compactness of the device.

[0013] Further characteristics and advantages of the invention will be made more evident from the following detailed description, provided as a non limitative example only, and referring to the appended drawings in which:

figure 1 is a schematic perspective view showing some main elements of a control device according to the invention,

figure 2 is an enlarged sectional and side elevational view of an articulated lever equipment that can be used in the device of figure 1,

figure 3 is a schematic partially sectional and side elevational enlarged view of a pressurized gas generator of the device of figure 1, and

figure 4 is a diagram schematically showing the relation between the various members of the device of the invention.

[0014] With initial reference to figure 1, a device according to the invention is generally indicated 10.

[0015] The device 10 comprises a frame 12 that, by means of a series of support members 14, supports a plurality of pneumatically controlled operative equipments 16.

[0016] In the specific case shown in the figures, the operative equipments 16 consist of pneumatic controlled locking devices known per se, of the type including an arm, or an articulated lever, 18, movable between a pair of angularly spaced positions. In short, and with particular reference to figure 2, the arm 18 of each operative equipment 16, is articulated to the body 21 of the respective device by means of a shaft 20, and is movable between a closed position and an opened position (shown by continuous and dotted lines in figure 2, respectively) as a result of the axial sliding of a control rod 22. The rod 22 is associated with a toggle articulation mechanism 24 known per se, in order to make irreversible the closing position of the arm 18.

[0017] The rod 22 is provided with a piston 26 at its end opposite to the mechanism 24, which piston is sealingly and slidably mounted within a cylinder 28 fixed to a support flange 29, below the body 21, in order to divide the cylinder 28 in a first and a second chamber 30, 32. The first chamber 30 communicates with a first fluid line 34, while the second chamber 32 communicates with a second fluid line 36. The lines 34 and 36 serve to feed a pressurized fluid to the chambers 30 and 32 in order to cause the piston 26 to move in the cylinder 28, with the aim of causing the arm 18 to rotate. Detection means 33, typically in the form of an end-of-stroke sensor 33 of inductive type, are associated with the body 21 of each equipment 16 in order to sense when the positions of the rod 22 that correspond to the angular end-of-stroke positions of the lever 18, are reached.

[0018] In spite of the fact that in the appended figures the operative equipment 16 is shown in the form of a locking device adapted to lock a sheet 38 indicated by a dotted line in figure 1, usually during execution of welding operations, the invention can be also used for operating pneumatic operative equipments of a different type, such as centering, hooking or translating devices known per se, typically comprising an articulated lever or arm.

[0019] The device 10 includes also a pressure generator unit, indicated 40 on the whole, preferably arranged in a position close to the frame 12 and shown in figure 3 in a greater detail.

[0020] In particular, the unit 40 includes an actuator 42 of a type known per se, preferably controlled by an electric motor 43, from which a linearly movable rod 44 extends. The actuator 42 with the respective motor 43 forms a unit that is usually fixed on a base member in the form of a beam or a slab, indicated 46 in the figures.

[0021] Also, the body of a main cylinder 48 is fixed to the base member 46, inside of which a piston 54 is slidably and sealingly mounted, which divides the interior of the cylinder 48 in a first and a second chamber 56, 58.

[0022] The piston 54 is rigidly connected to a stem 52 that extends from the cylinder 48 towards the actuator 42, and the end of which opposite to the piston 54 is connected with the rod 44, preferably by an articulated joint 52. The two chambers 56 and 58 of the cylinder 48 communicate with respective fluid lines 60 and 62 that extend outside the body of the cylinder 48. A respective pressure transducer 70, 72 is associated with each of the lines 60, 62, in order to detect the pressure of the fluid in each chamber 56 and 58.

[0023] The first chamber 56 of the main cylinder 48 is connected through the fluid lines 60 and 34 with the first chambers 30 of the cylinders 28 of the various operative equipments 16, and the second chamber 58 of the main cylinder 48 is connected through the fluid lines 62 and 36 with the second chambers 32 of the cylinders 28 of the various operative equipments 16, in such a manner that a closed circuit connection is made between the various cylinders 28 and the main cylinder 48.

[0024] Conveniently, the fluid admitted in the cylinders 28 and in the main cylinder 48, as well as in the connection lines 34, 36, 60, 62, and therefore in the whole pneumatic feeding closed circuit of the device 10, is an inert gas, typically nitrogen. This gas allows the device to be optimally operated and, being closed the circuit in which the gas is admitted, the same gas can be controlled so that it does not comprise any trace of humidity in order to avoid any formation of oxides, particularly rust, within the members of the circuit, to the advantage of the reliability of the device 10 in operation. Moreover, the use of this gas and of the pressure generator unit 40, allows very higher pressures to be reached with respect to those commonly used in the known operating devices employing air and compressors of a traditional type. In fact, in the known systems for feeding compressed air, pressures of about 4-6 bar are reached, taking into account of a pressure of about 8-10 bar generated by the compressors, while in the system according to the invention a pressures of about 15-40 bar can be reached, which allows the size of the cylinders 28 and 48 to be kept very compact, with favorable effects for the whole dimensions of the members of the device.

[0025] Moreover, the device 10 comprises an electronic control unit ECU (figure 4), typically consisting of a PLC, that manages its whole operation.

[0026] The motor 43 of the actuator 42, the pressure transducers 70 and 72, and the detection means 33 of the various operative equipments 16 are connected with the unit ECU, in such a manner that the latter controls the operation of the actuator 42 to move axially the rod 44 and the stem 50 along the direction indicated by arrow A of figure 4, with the aim of moving the piston 54 so that the pressure level inside the chambers 56 and 58 of the main cylinder 48 is that required to get the correct operation of the equipments 16, and to control the operation of the equipments 16 according to the proper timing, in order to allow the position of the arms 18 of the equipments 16 to be controlled in the desired manner as a result of the movement of the pistons 26 along the axial direction B (figure 4) of the relevant cylinders 28.

[0027] In particular, the signal detected by the detection means 33 of the equipments 16, referring to the reaching of an end-of-stroke position of the arms 18, are collected by an electric control panel 64 connected with the unit ECU, which contains a series of sensors/switches for signalling the position reached by the arms 18 of the individual equipments 16.

[0028] In the event in which a different movement of part of the arms 18 of the operative equipments 16 is required, respective electrically controlled valves 66 and 68 are interposed along the fluid lines 34, 60 and 36, 62, between the pressure transducers 70, 72 and the cylinders 28 of the equipments 16, so as to allow the moving sequence of the arms 18, typically the reaching of their end-of-stroke positions, to be controlled according to a preset timing. In this case, and as shown in figure 4, two electrically controlled valves 66 are arranged along the fluid line 34, 60, that is between the first chamber 56 of the main cylinder 48 and the first chambers 30 of the cylinders 28, and two electrically controlled valves 68 along the fluid line 36, 62, that is between the second chamber 58 of the main cylinder 48 and the second chambers 32 of the cylinders 28. This allows to cause a different operation of the two units of cylinders 28 connected to each of the two valves 66 and to each of the two valves 68, respectively, typically according to different opening/closing timing of the two aforesaid units of cylinders 28.

[0029] Of course, the electrically controlled valves 66, 68 are connected with the ECU unit in such a manner that the latter controls the opening/closing thereof in order to operate the various equipments 16 connected to it in the preset manner.

[0030] Moreover, each pressure transducer 70, 72 is connected with a respective load/release/safety panel 74, 76.

[0031] In operation of the device 10, and according to a typical operating cycle, initially the unit ECU controls, by a software, opening of all the electrically controlled valves 66, 68 and the carrying out of a test in order to verify that the pressure detected by the transducers 70 and 72, in the chambers 56 and 58 of the main cylinder 48, respectively, is at least equal to a predetermined threshold, typically of about 36 bars.

[0032] Then, the unit ECU controls opening of one electrically controlled valve 66 only and of one electrically controlled valve 68 only and, by operating the actuator 42, it causes the pistons 26 of the cylinders of the relevant equipments 16 to move, so that rotation of the arms 18 of the equipments 16 connected to such electrically controlled valves 66 and 68 is caused.

[0033] When the unit ECU receives the signal, through the respective sensors 33, indicating that the arms 18 of the series of equipments now operated have reached the desired end-of-stroke position, it operates the closing of the previously opened electrically controlled valves 66 and 68, and the opening of the other previously opened electrically controlled valves 66 and 68, to control the movement of the pistons 26 of the cylinders of the remaining equipments 16, so that rotation of the respective arms 18 is caused until they reach the desired end-of-stroke position.

[0034] The transducers 70 and 72 detect the reaching of a predetermined pressure, and send a signal to the unit ECU that controls stopping of the motor 43 and, therefore, of the actuator 42. In particular, the unit ECU controls, by means of the transducers 70 and 72, that the pressure in the chambers 56 and 58 of the actuator 48 is sufficient to ensure the proper operation of the equipments 16 and, in the event the pressure detected in such chambers is insufficient, operates the actuator 42 in order to restore the correct pressure for operation.

[0035] The unit ECU, by means of signals exchanged with the panel 64, checks the status of the position reached by the equipments 16, which is communicated to the panel 64 by the sensors 33 and, as a result of the positive result of such a check, emits a confirmation signal indicating that the desired position has been reached by all the equipments 16, for example if all the arms 18 are in their closing position. In this case, the unit ECU stops operation of the device 10 and allows a new operating cycle to be started according to a preset timing.

Claims

1. Device for operating a plurality of pneumatically controlled operative equipments, particularly of the articulated-lever type, including:

- a gas pressure generator unit (40),

- connection fluid lines (34, 36, 60, 62) extending from the generator unit (40) and to at least one chamber (30, 32) of a plurality of pneumatic cylinders (28) of said operative equipments (16),

- detection means (33) for detecting the end-of-stroke position of the articulated levers (18) of said operative equipments (16),

characterized in that the pressure generator unit (40) comprises a main cylinder (48) provided with a first and a second chamber (56, 58) separated by a slidable piston (54), and an actuator (42) for controlling the movement of the piston (54), in that said connection lines (34, 36, 60, 62) make a closed circuit for said gas and connect the chambers (56, 58) of the main cylinder (48) with respective first and second chambers (30, 32) of the pneumatic cylinders (28) of the operative equipments (16), and in that the detection means (33) of the operative equipments are connected with an electronic control unit (ECU) that controls the operation of the actuator (42) of the compressor unit (40) as a function of the position of the articulated levers (18) of said operative equipments (16) and of the inner pressure of the chambers (56, 58) of the main cylinder (48).

2. Device according to claim 1, characterized in that said control actuator (42) is an electrical actuator intended to control the linear movement of a rod (44) connected with the stem (50) of the piston (54) of the main cylinder (48).

3. Device according to claim 2, characterized in that said rod (44) and said stem (50) are mutually connected by an articulated joint (52).

4. Device according to any one of claims 1 to 3, characterized in that each pneumatic equipment (16) comprises an end-of-stroke sensor (33) connected with the control unit (ECU) through a check panel (64) including sensors/switches, and is adapted to generate a signal of attainment of an end-of-stroke position of all the pneumatic equipments (16).

5. Device according to any one of claim 1 to 4, characterized in that it includes at least a first electrically controlled valve (66) connected to the electronic control unit (ECU) and interposed in the fluid line (36, 62) that connects the first chamber (30) of each cylinder (28) of the pneumatic equipments (16) with the first chamber (56) of the main cylinder (48), and at least a second electrically controlled valve (68) connected to the electronic control unit (ECU) and interposed in the fluid line (36, 62) that connects the second chamber (32) of each cylinder (28) of the pneumatic equipments (16) with the second chamber (58) of the main cylinder (48).

6. Device according to claim 5, characterized in that said electrically controlled valves (66, 68) are connected to the electronic control unit (ECU) through pressure transducers (70, 72) associated with the first and the second chamber (56, 58) of the main cylinder (48), respectively.

7. Device according to claim 6, characterized in that each of said pressure transducers (70, 72) is connected with a respective load/release/safety panel (74, 76).

8. Device according to any one of claims 1 to 7, characterized in that the gas admitted into the cylinders (28) of the pneumatic equipments (16), in the main cylinder (48) and in said connection lines (34, 36, 60, 62) is an inert gas, conveniently nitrogen.

Drawing