WO2019145908A1

WO2019145908A1 - Device for hydraulic cylinders and the like

Info

Publication number: WO2019145908A1
Application number: PCT/IB2019/050633
Authority: WO
Inventors: Paolo Sprega
Original assignee: SPREGA, Matteo; SPREGA, Alessandro
Priority date: 2018-01-25
Filing date: 2019-01-25
Publication date: 2019-08-01
Also published as: IT201800001899A1

Abstract

The Device (1) for hydraulic cylinders and the like comprising: - at least one connecting body (2): - associable with a cylinder (3) in which a piston (4) is sliding, at an end position of the cylinder (3); and - provided with a sliding chamber (7) associable in communication with the cylinder (3); - at least one interaction element (8), sliding in the sliding chamber (7) along a predefined direction (9) and adapted to interact with the piston (4) for the passage from an inactive position, wherein the piston (4) is moved away from the end position and the interaction element (8) is at least partly facing in the cylinder (3), to an active position, wherein the piston (4) is at the end position and the interaction element (8) is pushed by the piston (4) along the predefined direction (9); - detection means (17, 18, 19, 20, 21) of the active position adapted to associate a presence signal with the active position and comprising one magnetic element (17) which is integral to the interaction element (8) and adapted to induce a magnetic field variation when the interaction element (8) switches from the inactive position to the active position and vice versa.

Description

DEVICE FOR HYDRAULIC CYLINDERS AND THE LIKE

Technical Field

The present invention relates to a device for hydraulic cylinders and the like, such as hydraulic cylinders, pneumatic cylinders and other cylinders inside which a piston slides.

Background Art

The need is well known to determine the position of the piston(s) sliding inside a cylinder, in particular the end-of-stroke positions, in order to improve the control of the activities that are taking place and of the working cycles.

To this aim, several types of device have been developed that are able to mechanically detect the presence of the piston when it is in the end-of-stroke positions and to transduce such presence into an electric signal.

A first type of known device is a connecting body to a head of a hydraulic cylinder or the like, inside which there is a sliding tip which is adapted to enter in contact with the cylinder piston when this is brought to the head.

The tip is inserted into a chamber communicating with the inside of the cylinder.

The chamber has a larger section than the section of the tip extremity intended to interact with the piston.

The tip, in the absence of the piston, is partially inserted into the cylinder and kept in such a position by the action of a spring and by the balancing of the fluid pressures acting on the extremities of the tip.

When the piston reaches the head and, therefore, is in the“end-of-stroke” position, it interacts with the tip by lifting it up.

In the body of the device there is also a proximity sensor which is adapted to detect the presence of the tip when this is lifted up.

The sensor detects the presence of the lifted tip and sends a signal of presence that indicates the arrival of the piston to the end-of-stroke position, thus obtaining a detection of the position of the piston itself.

One drawback of this first type of device is related to the use of the proximity sensor, or inductive sensor. In fact, this type of sensor has working temperatures ranging from -20°C to +70°.

Outside this temperature range there are malfunctions, such as self-ignition of the sensor resulting in incorrect position detection, or other malfunctions related to high temperatures.

This compromises the use of this first type of devices in the hydraulic cylinders where the temperatures of the pressurized working fluid normally reach 45- 55°C and to which the effect must be added of the outside temperature which, in particular conditions such as summer conditions or in rooms characterized by high ambient temperatures, can easily cause the temperature of the fluid to exceed the maximum value of 75°C.

A second type of known devices, similarly to the first type described above, provides a connecting body for the connection to a head of a hydraulic cylinder or the like, inside which there is a sliding tip which is adapted to enter in contact with the piston of the cylinder when this is brought to the head.

On the sliding direction of the tip is positioned a switch which, depending on its on-off state, transmits an electric signal.

The piston inside the cylinder lifts the tip up by pushing it against the switch, causing it to pass from the off configuration to the on configuration.

In this way, the electric signal sent by the switch indicates the presence of the piston at the end-of-stroke position.

When the piston changes its position, the tip slides downwards and the switch returns to the off configuration.

This second type of device also has some drawbacks.

One drawback relates to the life span of the switch.

The switch, in fact, is provided with mechanical contacts which are subjected to stress for each on and off cycle.

This causes wear and tear thereof, which means that the switch or the entire device needs to be replaced.

On average, the switches used in known devices have a life span of about 50000 cycles. For both the first type of known devices and the second type of known devices described above, the lifted tip must necessarily reach a predefined position in order for presence detection to be successful.

In the first case, one extremity of the tip must be moved to a position where it can be detected by the inductive sensor.

In the second case, the extremity of the tip must be moved to a position where the switch can be pressed, nor further forward, with the risk of pressing the switch too much until it breaks, and neither further back, with the risk of not pressing the switch and, therefore, failing detection.

A certain degree of precision is therefore required to position the tip.

For this reason, in the known types, special solutions are used to satisfy a hydraulic balance aimed at obtaining several equally pressurized chambers with different sections in which are exploited the different conditions of force and pressure induced by the increase/decrease in the working fluid pressure.

To make these chambers, sealing gaskets are used which are positioned between the tip and the wall of the chamber, as well as venting channels obtained inside the tip itself.

In this way it is possible to precisely control the positioning of the tip, checking the stability thereof and minimizing the risk of failure in presence detections. There are however some drawbacks related to the magnitude of the pressures involved and the complexity in manufacturing the device.

The working fluid pressure values are very high and, in the pressurized chambers delimited by the various gaskets, result in a force applied on the tip which counter-acts the lifting motion.

As a result, the force with which the tip presses on the piston is also great and can produce grooves and damage the surface of the piston itself.

This makes necessary to treat the piston in order to give it greater hardness, with a consequent increase in the production and/or maintenance costs of the cylinder.

In addition, the presence of gaskets and vents makes it more complex to manufacture the device. In fact, the gaskets are subjected to wear and tear and do not withstand high temperatures, thus requiring frequent maintenance or replacement jobs.

The presence of vents, on the other hand, prevents the use of the device dipped in water or in environments where there are jets of water.

Description of the Invention

The main aim of the present invention is to devise a device for hydraulic cylinders and the like that makes it easier to determine the end-of-stroke position of the pistons in the cylinders.

One object of the present invention is to devise a device for hydraulic cylinders and the like that has improved resistance to high temperatures and to high pressures.

Another object of the present invention is to devise a device for hydraulic cylinders and the like that is easy to operate and easy to install on newly produced and already existing cylinders.

Another object of the present invention is to devise a device for hydraulic cylinders and the like the electric reliability of which has improved.

Another object of the present invention is to devise a device for hydraulic cylinders and the like that allows overcoming the aforementioned 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 device for hydraulic cylinders and the like 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 descriptions of the following preferred, but not exclusive, embodiments of a device for hydraulic cylinders and the like, illustrated by way of an indicative, but non-limiting example, in the attached tables of drawings in which:

Figure 1 is a cross-sectional view of a first embodiment of the device according to the invention;

Figure 2 is a cross-sectional view of a second embodiment of the device according to the invention; Figures 3 and 4 are schematic views of an application of a first embodiment of the device according to the invention to a hydraulic cylinder;

Figures 5 and 6 are schematic views of an application of a second embodiment of the device according to the invention to a hydraulic cylinder;

Figures 7 to 10 are cross-sectional views of a third embodiment of the device according to the invention;

Figure 11 is a partly cross-sectional view of details of possible embodiments of devices according to the invention.

Fmbodiments of the Invention

With particular reference to these illustrations, reference numeral 1 globally indicates a device for hydraulic cylinders and the like.

In a first embodiment, illustrated in Figures 1, 3, 4 and 11, the device 1 comprises a connecting body 2 associable with a cylinder 3 in which a piston 4 is sliding.

The cylinder 3 shown in the illustrations is of the type of a hydraulic cylinder the actuation of which is given by pressurizing a mineral, vegetable or synthetic fluid, but different cylinders cannot be ruled out, e.g. with pneumatic or hydraulic actuation.

In particular, the connecting body 2 is associable with the cylinder 3 at an end position of the cylinder itself.

The connecting body 2 has a connecting portion 5, associable with the cylinder, and a head 5a associated with the connecting body 2 and defining a gap 6 substantially isolated from the inside of the cylinder 3.

The connecting body 2 is provided with a sliding chamber 7 associable in communication with the cylinder 3.

As can be seen from the illustrations, the sliding chamber 7 is located inside the connecting portion 5 and communicates with the internal chamber of the cylinder 3 in which the piston 4 can slide.

In this way, the mineral fluid useful for the operation of the cylinder 3 can flow inside the sliding chamber 7.

The device 1 comprises at least one interaction element 8 sliding in the sliding chamber 7 along a predefined direction 9.

Usefully, the predefined direction 9 is the direction of longitudinal extension of the sliding chamber 7.

The interaction element 8 is adapted to interact with the piston 4 for the passage from an inactive position (Figure 4) to an active position (Figure 3).

In the inactive position, the piston 4 is moved away from the end position and the interaction element 8 is at least partly facing in the cylinder 3.

In the active position, the piston 4 is at the end position and the interaction element 8 is pushed by the piston itself along the predefined direction 9.

Usefully, the device 1 comprises at least one spring element 10 associated with the interaction element 8 and exerting a thrust along the predefined direction 9 for keeping the interaction element 8 in the inactive position.

Advantageously, the interaction element has an elongated body 11 comprising a contact end 12 which is adapted to interact with the head of the piston 4 when this moves to the end position.

The elongated body 11 also has extensions 13 that extend transversely to the sliding chamber 7.

The total width of the extensions 13 and of the interaction element 8 is equal to the width of the cross section of the portion of sliding chamber 7 in which the extensions themselves slide.

In the present embodiment, the sliding chamber 7 has a first portion 14 having a section equal to the section of the elongated body 11, and a second portion having a section equal to the width of the extensions 13 and of the section of the elongated body 11.

This characteristic allows balancing the fluid pressures acting on the interaction element 8.

In other words, the sum of the pressures acting on the interaction element 8 is cancelled because the sliding chamber 7 communicates with the cylinder 3 and because the interaction element 8 has extensions 13 which are proportionate to the width of the sliding chamber itself.

In this way the piston 4, in order to lift up the interaction element 8, does not have to overcome the resistance due to the increase in pressure of the mineral fluid, but only the resistant force of the spring element 10 and of the weight of the interaction element itself.

These characteristics facilitate the lifting up of the interaction element 8 and avoid the formation of grooves on the piston head due to excessive pressure exerted by the contact end 12 on the piston head.

Embodiments of the extensions 13 and of the interaction element 8 different to those shown in Figures 1 to 6 cannot be ruled out.

As an example, Figure 11 shows different solutions for the interaction element 8, wherein the extensions 13 have a flat profile, which is orthogonal to the elongated body 11.

In Figure 11 the upper portions of the device 1 have been schematically illustrated.

Figures 7 to 10 show an interaction element 8 having a different shape from that described above, but with a similar function.

A bushing 16 is inserted inside the sliding chamber 7.

In particular, with reference to Figure 1, inside the second portion 15 of the sliding chamber 7, in the proximity of the junction between the first portion 14 and the second portion 15, an anti-friction bushing 16 is inserted having the function of a guide, which is adapted to facilitate the linear sliding of the interaction element 8.

The bushing 16 has diametrical holes, for sake of simplicity not illustrated, that allow the mineral fluid to flow inside the second portion 15.

Different embodiments cannot be ruled out, wherein the sliding chamber has a single constant section and, in this case, the interaction element 8 has an elongated body without extensions 13, just as different solutions cannot be ruled out wherein the sliding chamber 7 has several portions of different sizes and the interaction element 8 has extensions 13 which are proportionate to the size of the sections of the portions of such sliding chamber.

Usefully, the device 1 comprises detection means 17, 18, 19, 20, 21 for detecting the active position which are adapted to associate a presence signal with the active position.

The detection means 17, 18, 19, 20, 21 detect when the interaction element 8 is in the active position and, consequently, send a relative presence signal by transmitting it to a control unit or to another unit adapted to receive this signal to use or show the information it carries with it.

The signal, in fact, indicates the presence of the piston 4 in the end position and can be used to program and monitor the working cycles of the piston 4, or for other operations based on the detection of the extreme end-of-stroke positions of the piston 4.

According to the invention, the detection means 17, 18, 19, 20, 21 comprise at least one magnetic element 17 made integral to the interaction element 8 and adapted to induce a magnetic field variation when the interaction element 8 passes from the inactive position to the active position and vice versa.

In particular, the magnetic field variation occurs in the proximity of the sliding chamber 7 and is given by the movement of the interaction element 8 along the predefined direction.

In this first embodiment, the detection means 17, 18, 19, 20, 21 comprise at least one magnetic sensor element 18 adapted to detect the magnetic field variation for the transmission of a presence signal.

In particular, the magnetic sensor element 18 undergoes a variation in its electric state as the magnetic field changes, by transducing this variation into a presence signal.

Preferably, the magnetic sensor element 18 is positioned inside the gap 6.

In this way, the magnetic sensor element 18 does not enter in contact with the mineral fluid.

Solutions other than that shown in the figures, e.g. having several magnetic sensors, cannot be ruled out.

Advantageously, the detection means 17, 18, 19, 20, 21 comprise at least one ferromagnetic body 19 arranged in the proximity of the sliding chamber 7.

In particular, the ferromagnetic body 19 faces at least partly into the sliding chamber 7. The interaction element 8 is moveable close to the ferromagnetic body 19 in the passage from the inactive position to the active position so as to bring the magnetic element 17 in the proximity of the ferromagnetic body 19 for the transmission of the magnetic field variation.

In particular, the approaching/removal of the magnetic element 17 with respect to the ferromagnetic body 19 involves a polarization/depolarization of the ferromagnetic body exactly due to the magnetic field variation induced by these displacements.

Usefully, the magnetic sensor element 18 is positioned in the proximity of the ferromagnetic body 19 to detect the magnetic field variation in an indirect manner. In this way, the magnetic sensor element 18 is affected by the polarization/depolarization of the ferromagnetic body 19, changing its electric state and sending a corresponding presence signal when the ferromagnetic body 19 is polarized.

Preferably the magnetic sensor element 18 and the magnetic element 17 are positioned on the opposite side with respect to the ferromagnetic body 19.

The operation of the present invention in this first embodiment is as follows. When the cylinder 3 moves to the end position (Figure 2), the interaction element 8 is pushed along the predefined direction 9 and, moving into the sliding chamber 7, approaches the ferromagnetic body 19.

Thanks to the approaching of the magnetic element 17, a magnetic field variation is obtained that polarizes the ferromagnetic body 19.

The magnetic sensor element 18, being affected by the polarization of the ferromagnetic body 19, varies the electric state thereof, transmitting a signal that, in the light of what has been described, indicates the presence of the piston 4 in the end position.

After the piston 4 has moved from the end position, the spring element 10 pushes the interaction element 8 along the predefined direction 9, but opposite the thrust previously provided by the piston 4.

In this way the interaction element 8, and therefore the magnetic element 17, moves away from the ferromagnetic body 19 and depolarizes it. The depolarization is detected by the magnetic sensor element 18 which, consequently, returns to the initial electric state, interrupting the signal or sending a second signal indicating the absence of the piston 4 in the end position.

In a second embodiment, illustrated in Figures 2, 5 and 6, the device 1 is similar to the one described in the first embodiment and differs by the fact that the detection means 17, 18, 19, 20, 21 comprise electric contact means 20, 21 having a fixed contact portion 20 and a moveable contact portion 21.

As shown in Figures 2, 5 and 6, the fixed contact portion 20 comprises two electric ends 22 connected to an electric system 23 in turn connected to a control unit such as the one described in the first embodiment.

Similarly, the moveable contact portion also comprises two electric ends 22 connected to the electric system 23.

The electric ends 22 define, therefore, two pairs of electric contacts.

Solutions cannot be ruled out wherein there is only one electric end 22 on the moveable contact portion 21 and only one electric end 22 on the moveable contact portion 21, to define only one pair of electric contacts.

The moveable contact portion 21 is at least partially responsive to the magnetic field variation due to the displacement of the interaction element 8 and varies from a spaced away position (Figure 6) to a contact position (Figure 5).

In the spaced away position, the moveable contact portion 21 is moved away from the fixed contact portion 20 and the interaction element 8 is in the inactive position.

In the contact position, the moveable contact portion 21 is at least partly placed in contact with the fixed contact portion 20 and the interaction element 8 is in the active position.

In the contact position, the electric ends 22 are brought in contact with each other, closing the electric system 23 and sending therefore an electric signal that can be translated as presence signal of the piston 4 in the end position.

Usefully, the moveable contact portion 21 comprises a second magnetic element 25 which is responsive to the magnetic field variation. The moveable contact portion 21 is entrained from the spaced away position to the contact position when the interaction element 8 is in the active position.

In particular, when the interaction element 8 is pushed to the active position by the piston 4, the magnetic field variation is such that the magnetic element 17 is able to attract the second magnetic element 25 in the direction of the interaction element 8.

In this way, the moveable contact portion 21 is entrained in motion and brought in contact with the fixed contact portion 20.

In particular, the electric ends 22 are brought in contact with each other.

Advantageously, the moveable portion comprises a return spring 24 which is adapted to push the moveable contact portion 21 from the contact position to the spaced away position when the interaction element 8 is in the inactive position. This characteristic makes it easier for the moveable contact portion 21 to return to the spaced away position, reopening the electric system and, therefore, generating an absence of electric signal indicating the absence of the piston in the end position.

The operation of this second embodiment is similar to the operation of the first aforementioned embodiment.

The operation of the second embodiment differs by the fact that, when the interaction element 8 is pushed by the piston 4 to the active position, the magnetic element 17 produces a magnetic field variation that makes possible the attraction of the second magnetic element 25.

Consequently, since the second magnetic element 25 is entrained towards the magnetic element 17, the entire moveable contact portion 21 is entrained in contact with the fixed contact portion 20.

In this way, the electric ends 22 are brought in contact and the electric system 23 is closed, transmitting an electric signal to the control unit.

When the piston 4 leaves the end position, the spring element 10 returns the interaction element 8 to the inactive position and the magnetic field produced by the magnetic element 17 is no longer able to attract the second magnetic element 25. When the attraction force of the magnetic element 17 is no longer present, the return spring 24 will return the moveable contact portion 21 to the spaced away position.

As a result, the electric ends 22 will be spaced away and the electric system will be reopened, indicating the absence of the piston 4 from the end position.

Figures 7 to 10 illustrate a third embodiment of the device.

This third embodiment has the same characteristics as the first embodiment (Figures 7 and 9) or as the second embodiment (Figures 8 and 10) and differs by the fact that it comprises a terminal fitting 26 communicating with the inside of the cylinder 3 to let in/out the mineral fluid used for the operation of the cylinder itself.

Figures 7 and 8 show an“eye-shaped” terminal fitting, which wraps at least part of the connecting body 2 of the device 1.

The mineral fluid can pass from the terminal fitting 26 to the cylinder 3 through the sliding chamber 7.

In this third embodiment, the connecting body 2 comprises one or more connecting channels 27 which are adapted to place the sliding chamber 7 in communication with the inside of the cylinder 3.

Figures 9 and 10 show a terminal fitting 26 of different shape, but functionally similar to that of Figures 7 and 8.

It has in practice been ascertained that the described invention achieves the intended objects and, in particular, the fact is underlined that the device for hydraulic cylinders and the like allows promoting the determination of the end- of-stroke position of the pistons in the cylinders.

The device devised, in fact, is applicable in the proximity of the front or rear heads of hydraulic cylinders and allows physically detecting, through the interaction element, the presence of the piston when it arrives at the end positions.

Thanks to the detection means described above, the device is able to transduce such presence into an electric signal of magnetic or magneto-mechanical nature, which can be used by the control units for the automation of various types of machining process.

The device devised also has improved resistance to high temperatures and high pressures.

The special interaction element and the particular shape of the sliding chamber, together with the action of the spring element, improve the stability of the interaction element itself when it is in the inactive position, and facilitate the lifting up of the interaction element itself by the piston.

The piston, in fact, will only have to overcome the resistance of the spring element to lift up the interaction element, without having to undergo an excessive load.

In this way the piston is preserved from the wear and tear action of the contact with the interaction element and the life span of the mechanical components is improved.

In addition, the device devised has improved electric reliability, due to the fact that the electric signal does not arise from direct contact with the interaction element (wear) or from direct detection of the position of the interaction element itself (inaccuracy).

The electric signal, in fact, derives from the magnetic field variation produced by the displacement of the interaction element in the sliding chamber.

Ultimately, the device for hydraulic cylinders and the like devised is applicable to the hydraulic cylinders used in various sectors, from agricultural, construction, road, industrial, forestry machinery, to the naval, railway and other sectors.

The use of the device devised allows the appropriate control units to acquire and control the linear end-of-stroke positions (extended stem/retracted stem) useful for automating the relative machine cycles.

Claims

1) Device (1) for hydraulic cylinders and the like comprising:

- at least one connecting body (2):

associable with a cylinder (3) in which a piston (4) is sliding, at an end position of said cylinder (3); and

provided with a sliding chamber (7) associable in communication with said cylinder (3);

- at least one interaction element (8), sliding in said sliding chamber (7) along a predefined direction (9) and adapted to interact with said piston (4) for the passage from an inactive position, wherein said piston (4) is moved away from said end position and said interaction element (8) is at least partly facing in said cylinder (3), to an active position, wherein said piston (4) is at said end position and said interaction element (8) is pushed by said piston (4) along said predefined direction (9);

- detection means (17, 18, 19, 20, 21) of said active position adapted to associate a presence signal with said active position;

characterized by the fact that said detection means (17, 18, 19, 20, 21) comprise at least one magnetic element (17) which is integral to said interaction element (8) and adapted to induce a magnetic field variation when said interaction element (8) switches from said inactive position to said active position and vice versa.

2) Device (1) according to claim 1, characterized by the fact that it comprises at least one spring element (10), associated with said interaction element (8) and exerting a thrust along said predefined direction (9) for keeping said interaction element (8) in said inactive position.

3) Device (1) according to one or more of the preceding claims, characterized by the fact that said detection means (17, 18, 19, 20, 21) comprise at least one magnetic sensor element (18) adapted to detect said magnetic field variation for the transmission of a presence signal.

4) Device (1) according to one or more of the preceding claims, characterized by the fact that said detection means (17, 18, 19, 20, 21) comprise at least one ferromagnetic body (19) arranged in the proximity of said sliding chamber (7), with said interaction element (8) which is moveable close to said ferromagnetic body (19) during the switch from said inactive position to said active position to bring said magnetic element (17) in the proximity of said ferromagnetic body (19) for the transmission of said magnetic field variation.

5) Device (1) according to one or more of the preceding claims, characterized by the fact that said magnetic sensor element (18) is positioned in the proximity of said ferromagnetic body (19) to detect said magnetic field variation in an indirect manner.

6) Device (1) according to one or more of the preceding claims, characterized by the fact that said magnetic sensor element (18) and said magnetic element (17) are positioned on the opposite side with respect to said ferromagnetic body (19).

7) Device (1) according to one or more of the preceding claims, characterized by the fact that said detection means (17, 18, 19, 20, 21) comprise electric contact means (20, 21) having a fixed contact portion (20) and a moveable contact portion (21) at least partially responsive to said magnetic field variation, said moveable contact portion (21) varying from a spaced away position, in which it is moved away from said fixed contact portion (20) and said interaction element (8) is in said inactive position, to a contact position, in which it is at least partly placed in contact with said fixed contact portion (20) and said interaction element (8) is in said active position.

8) Device (1) according to one or more of the preceding claims, characterized by the fact that said moveable contact portion (21) comprises at least a second magnetic element (25) which is responsive to said magnetic field variation.

9) Device (1) according to one or more of the preceding claims, characterized by the fact that said moveable contact portion (21) is entrained from said spaced away position to said contact position when said interaction element (8) is in said active position.

10) Device (1) according to one or more of the preceding claims, characterized by the fact that said moveable contact portion (21) comprises a return spring (24) which is adapted to push said moveable contact portion (21) from said contact position to said spaced away position when said interaction element (8) is in said inactive position.

11) Device (1) according to one or more of the preceding claims, characterized by the fact that said interaction element (8) comprises at least one extension (13) which extends transversely to the sliding chamber (7).

12) Device (1) according to one or more of the preceding claims, characterized by the fact that the total width of said extension (13) and of said interaction element (8) is equal to the width of the cross section of the portion of sliding chamber (7) in which said extension (13) is sliding.