HYDROMECHANICAL-ELECTRIC LIMIT SWITCH APPLICABLE TO HYDRAULIC CYLINDERS

Description

Description of the industrial utility model entitled: “Hydromechanical limit switch applicable to hydraulic cylinders” of HCS Hydraulics Components and Systems Srl, with registered office in Gualdo Tadino (PG) 06023 Via Giacomo Matteotti snc, in the person of the legal representative and Sole Director Mr. Tittarelli Gianni, with domicile at the registered office of the aforementioned Company, deposited at the Chamber of Commerce, Industry, Crafts and Agriculture of Perugia The hydromechanical limit switch is a component that has been designed and manufactured to be applied near the front and rear heads of hydraulic cylinders, or directly on them, with the aim of detecting the position of the relative pistons, when they are in the fully forward position (rod extended) and fully backward position (rod retracted). Each of the two conditions causes the aforementioned limit switch to protrude from a mechanical "witness," the end of which engages either the magnetic field of an inductive electric sensor or the cam of a standard electromechanical limit switch, suitably powered. This will cause the limit switches to switch states, emitting an electrical output signal or interrupting that signal, depending on their wiring, whether it is normally closed and / or normally open (in technical jargon NO / NC). Description text Given that the present invention concerns a device suitable and adaptable to any front and / or rear head of the most varied types of hydraulic cylinders, applicable, obviously respecting the technical rules for the installation of the invention, in a simple, practical and safe manner, it is important to highlight the so-called state of the art in which the invention finds application. There are already components similar to the hydromechanical limit switch available on the market, including: a) Balluff fibre optic sensor, which is mounted on the cylinder heads or in their immediate vicinity directly in an oil bath, following specific technical installation instructions, also providing a metal ring inside the hydraulic cylinder, near the piston, whose external diameter, when detected by the magnetic field of the inductive sensor, determines the switching of the same, and therefore the subsequent electrical signalling of the position reached; b) magnetic limit switches, which involve the construction of the hydraulic cylinder in non-magnetic material (stainless steel or aluminum jacket and piston, and stainless steel rod); this solution involves mounting a plastoferrite ring inside the (non-magnetic) piston. Its magnetic field, when detected by the relevant limit switch, causes the piston to change state, thus generating an electrical output signal, indicating that the cylinder's piston has actually reached the front or rear end-of-travel position; c) inductive electric sensor holder from Fluidotec Tecnologie Oleodinamiche Srl, which, although based on a similar basic principle to the hydromechanical electric limit switch, is a technically and qualitatively far inferior product, despite having substantially the same external configuration. The attached drawing A illustrates the application of n. 2 hydromechanical electric limit switches: the first near the rear head (activated), the second near the front head of the cylinder in question (not activated), as well as the operating principle, which starts from the assumption of having the piston of the hydraulic cylinder (pos. 1) made with the lateral ends in the shape of a truncated cone, which, upon reaching the respective forward or backward end-of-stroke positions, coming into contact with the respective ball (pos, 3) “lift” their own piston (pos. 2) of the limit switch, the opposite end of which invades the magnetic field of action of the inductive electric sensor (pos. 4) thus determining the electrical switching of the same, to be understood as an activated sensor and therefore, position reached. Conversely, the non-activated limit switch stem is kept in the fully out position by the spring preload (pos. 5) but above all by the larger usable upper annular section, which is 25% larger than the lower one, on the ball side; therefore, the hydraulic pressure present inside the integral piston stem means that it tends to always be fully out (downwards). In light of the above, our invention represents, at the same time, the improvement of some existing devices, but above all a real innovation innovation in the field of electrical sensor devices applicable to hydraulic cylinders for the following reasons: 1) The inductive electric sensor, or electromechanical microswitch, applied to the hydromechanical limit switch, works dry because it "captures" the external radial excursion of the piston itself and not in an oil bath as occurs in other types of products; 2) During the design and planning phase, efforts were made to ensure the invention's maximum operational safety by "obliging" it (according to the principle of equal pressure on two different areas) to activate only when the piston of the hydraulic cylinder in question has actually reached its position, and never under any other conditions. On the other hand, with oil-immersed inductive sensors, it often happens that electrical signaling occurs even when it shouldn't, since any metal residue (chips or tiny particles) can be attracted and / or merely "detected" by the sensor as they pass by. 3) In addition to ensuring maximum safety in use, the reliability of the invention was also taken into account during the design phase. While the possibility of malfunction (accidental activation) was avoided, the limit switch piston, due to both its larger upper surface area and the force of the spring, must always remain lowered, and therefore inactive, in all conditions except those requiring the piston to be present. In other words, the hydromechanical limit switch activates, or rather "switches," only when the piston of the corresponding hydraulic cylinder has reached the front and / or rear end position. 4) The specific force with which the sphere presses on its own truncated cone, in the case of the present invention, is far lower than that of other existing and similar sensor holders (e.g., Fluidotec Srl). In fact, in the latter, the sphere presses on the truncated cone with approximately 210 kg of specific force under all dynamic conditions within the hydraulic cylinder, regardless of the pressures and backpressures generated during its operation. In the present case, however, in the absence of backpressure in the cylinder chamber, the force with which the sphere presses on the affected truncated cone is only 3 kg! Any backpressure in the exhaust chamber in this sense becomes an "aggravating factor" of pressing force directly proportional to its own value. In fact, considering, for the sake of argument, a backpressure of 100 bar in the exhaust chamber of our hypothetical sensor holder, the ball presses on the truncated cone with a force of approximately 210 kg.hydraulic cylinder, which is an unlikely condition in the vast majority of hydraulic applications, we will have that the maximum pressing force of the sphere on its own truncated cone of the piston will be 3 kg due to the effect of the compressed spring of its own piston, and 12.56 kg due to the difference in section between the annular chambers (0.1256 square cm x 100 kgcm squared), for a total of 15.56 kg against 210 kg! The resulting advantages are the following: - the truncated cones in contact with the spheres are not subject to premature deterioration due to the lower pressing force and their heat treatment; - the entire mechanical structure of the hydromechanical limit switch is subjected to much more gentle stress when compared to existing sensor holders (e.g. Fluidotec Srl); - the hydraulic pressure required to lift the integral piston rods is remarkably low; - the hydromechanical-electric limit switch, for the technical reasons listed in point 4, is much more stable and safe in operation, against any accidental activations. In light of the above, in addition to having reduced the physical dimensions of the invention, it represents, at the same time, a state-of-the-art improvement of existing technology but above all a true innovation in the field of limit switch devices applied to hydraulic cylinders. In fact, the invention allows to overcome and remedy all the above-mentioned drawbacks, providing a technical solution that allows to obtain: a) that the inductive sensor or electromechanical limit switch mounted on board the invention works dry and not in an oil bath; b) the maximum safety condition of use due to the particular design of the invention; c) long life of the component due to its low operating force; d) the elimination of premature wear of the piston cones. The specific object of the present invention is therefore a device of elements which ensures that a specific piston of a hydraulic cylinder, upon reaching the front or rear end of its travel, by activating the appropriately electrically powered hydromechanical limit switch, can emit and / or cancel an electrical output signal indicating the position reached (rod fully extended or rod fully retracted). From what has been stated, the product as conceived, compared and contrasted with existing ones, stands out as a true innovation. Technical description This utility model will now be described for illustrative but not limiting purposes, with reference to the typical sectional view in the attachment (drawing B): - position 1: contact ball in treated steel; - position 2: integral piston rod in quality steel; - position 3: static stem seals (n° 2); - position 4: threaded stud welded onto the hydraulic cylinder jacket; - position 5: dynamic sealing gasket on the piston; - position 6: annealed copper sealing washer; - position 7: jacket (or casing) of the hydromechanical limit switch; - position 8: static sealing gasket of the cover on the jacket; - position 9: Allen screw for fixing the cover to the shirt (n° 4); - position 10: compression spring in alloy steel; - position 11: hydromechanical limit switch cover; - position 12: inductive electrical sensor (M8xl or M12xl). Operating principle. Hydromechanical limit switches (or electric limit switch sensor holders) applied to the front and / or rear heads of any type of hydraulic cylinder, provide and / or cut an electrical output signal when the piston has reached the respective forward or reverse end-of-travel position. The operating principle of the above invention is based on the concept of an "inclined plane" (see drawing A in the attachment). In the aforementioned cross-sectional drawing, there are two hydromechanical limit switches, one of which is at the end of the backward travel, correctly represented as being switched by the truncated cone of the piston, and therefore active, and the other at the end of the forward travel, which obviously, not being engaged by the corresponding truncated cone on the piston, is inactive. In order to make the operating principle of the invention as clear as possible, we will now describe in technical detail the two phases of the active or inactive hydromechanical electric limit switch. A) Active hydromechanical limit switch (figure 1 drawing A) Still referring to the sectional views of the attached drawings A and B, it can be noted that the rear limit switch of the hydraulic cylinder in question is active, since the left lateral truncated cone of the hydraulic piston (pos. 1 drawing A), while retracting, has impacted against the sphere (pos. 3 drawing A) which, at the same time, has absorbed the axoradial load generated by the same, and has raised its integral piston rod (pos. 2 drawing A), compressing the rear spring (pos. 5 drawing A) invading the magnetic action field of the inductive sensor (pos. 4 drawing A) with its upper end, thus determining the change in state or electrical switching, as you wish to call it. The phase described above is the one in which we will say that the hydromechanical limit switch has been activated. B) Hydromechanical electric limit switch deactivated (figure 2 drawing A) Looking at figure 2 of drawing A we can observe that the hydromechanical limit switch is inactive because the integral piston rod pos. 2, not being raised from its contact sphere pos. 3 since the right truncated cone of the hydraulic piston pos. 1 is outside the field of action and, therefore, in this phase the upper part of the integral piston rod (pos. 2) does not invade the magnetic field of action of the sensor pos. 4, which in this condition, cannot switch or change state, and therefore we will not have any electrical output signal. The one described above is the phase in which we will say that the hydromechanical limit switch is deactivated. Descriptive phases A and B above have illustrated the operating principle of hydromechanical limit switches applied to a type of hydraulic cylinder. Below, the technical descriptive phase of the invention will be illustrated in even greater detail, referring to section B of the attached drawing. Salient technical features. Pos. 1: Contact sphere. It is mechanically riveted into its pre-machined seat on the lower end of its integral piston rod, and its main task is to “dampen”, with its rolling inside its pre-machined seat, the impact with the truncated cone of the hydraulic piston in question. Pos. 2: Integral piston rod. And it is a particular double through rod with integrated central piston; at its lower end the contact ball is riveted, in the central part it has the seat obtained in a closed cavity for the dynamic sealing gasket, and in the upper part " presents a cavity where the lower part of the compression spring is housed, pos. 10 drawing B. Looking carefully at section 2 of the integral piston rod, one immediately understands the importance this component has in the technical economy of the invention in question; in fact, the integral piston rod contains within itself multiple and very unique functions, all of fundamental importance for the proper functioning of the mechanical-electric limit switch. Among the most important and exclusive, we mention two: 1) the internal drilling, offset from the axis (brown in actual fact), allows for hydraulic power to be supplied to the rear portion of the integral piston rod, which has a 25% larger surface area than the front portion where the ball is positioned. In fact, the lower portion, with a diameter of 8 mm, has an area of ​​50.24 square mm, while the upper portion, with a piston diameter of 12 mm minus an upper rod diameter of 8 mm, has a usable cross-section of 62.8 square mm. All of this benefits the functionality, stability, and operational safety of the invention, since by applying equal hydraulic pressure to different cross-sections, the larger cross-section prevails over the smaller one, and therefore the integral piston rod is always in the inactive phase; 2) the other internal hole, off-centre with respect to the axis (in reality light blue) which ends up in the spring slot, is the exhaust for the air which is created during operation between the lower hydraulic chamber and the upper hydraulic chamber of the integral piston rod, which must absolutely be conveyed to the outside, otherwise the invention will not function properly. Pos. 3: Stem seals No. 2 static seal gaskets, of which the lower one provides the seal between the jacket and the lower stem, while the other ensures the seal between the upper stem and the cover of the hydromechanical-electric limit switch; Pos. 4: Threaded stud It must be welded onto the jacket of the hydraulic cylinder at the front and / or rear where you wish to install the hydromechanical electric limit switches, following the assembly instructions; Pos. 5: Piston seal Dynamic piston seal separating the upper and lower chambers of the integral piston rod; Pos. 6: Sealing washer It guarantees not only the hydraulic seal between the jacket and the welding stud, but also the orientation of the sensor positioning with respect to the axis of the hydraulic cylinder; Pos. 7: Shirt It represents the natural casing suitable for containing the heart of the invention and is screwed to the stud welded on the shirt; Pos. 8: Lid seal Gasket that guarantees static sealing in the coupling between the cover and the jacket of the hydromechanical-electric limit switch; Pos. 9: Allen screw No. 4 galvanized Allen screws in 8.8 steel, ensure the mechanical coupling of the cover on the limit switch sleeve; Pos. 10: Compression spring made of alloy steel Pos. 11: Cover. Made of quality brass, it has inside, towards the top, the centering for the compression spring and, laterally, on one of the four sides, the thread where the inductive electric sensor can be screwed; Pos. 12: M8xl or M12xl inductive electric sensor. Special conditions of use for the operator The main technical precautions adopted both in the design and construction phases are the following: 1) minimum overall dimensions of the invention which, applied to a hydraulic cylinder of any diameter, means that its maximum radial protrusion is 50 mm, while seen in plan it is a square with sides of 30 mm; 2) possibility of orienting the cover of the hydromechanical electric limit switch by 90° in order to position the radial protrusion of the inductive electric sensor on the side most suitable for the user; 3) possibility of being able to mount on the device either the M8xl inductive electric sensor, or the M12xl one or any other type of electromechanical, pneumatic, hydraulic limit switch etc.; 4) possibility of installing the invention on both welded type hydraulic cylinders and mechanical type hydraulic cylinders (tie-rodded, bolted, etc.), subject to appropriate mechanical adaptations; 5) the installation of the invention on existing hydraulic cylinders does not modify their length, and consequently no mechanical modifications need to be made to the parts that are to receive the modified cylinder; 6) Possibility of adjusting the front or rear intervention point of the hydromechanical limit switch by approximately 12-13 mm linearly, simply by moving the sensor head away from the upper end of the activated integral piston rod; in fact, by adjusting the inductive electric sensor more or less close to it, it is possible to practically obtain an adjustment with respect to the intervention point of approximately 12-13 mm (advance signal) due to the decrease in intensity of the sensor's magnetic field and the increase in its hysteresis. Possibility of industrial application and use As for the possibilities of industrial applications, the invention can be manufactured and used in the industrial field, specifying that it allows a wide possibility of application on all the hydraulic cylinders existing on the market, obviously with mechanical processes to adapt it to our invention. It is easy to install, does not require highly specialized labor, and replacing any damaged components is very quick and easy. The hydromechanical limit switch is intended to interest the following market segments: - manufacturers of hydraulic cylinders and / or their parts; - end users of hydraulic cylinders (companies manufacturing various types of machines); - dealers of hydraulic components in general; Furthermore, the invention is applicable to all hydraulic cylinders that comply with the following standards: > ISO 6020 / 2 > ISO 6022 > DIN 24554 > ISO 6020 / 3 > DIN 24333 > AFNORNFE 48-025 CETOPRP3H in addition to welded and / or customer-designed cylinders, starting from a bore of 25 mm and up to a diameter of 400 mm and beyond, for maximum operating pressures of 320 bar. Aims and objectives. The objective of the invention is to fully and completely apply it to hydraulic cylinders already manufactured and marketed (obviously) without the invention, as well as, and especially, to newly manufactured ones. This entails an innovative addition to the basic product (hydraulic cylinder), which fully achieves the intended objective, namely, safely monitoring the position of the piston of a hydraulic cylinder in the extended (fully extended) or retracted (fully retracted) positions. HCSSr1. The sole administrator

Claims

Claims. As for the main innovative features that are claimed with respect to the current state of the art, it should be noted that the hydromechanoelectric limit switch is distinguished and characterized by the following features which, as such, are the subject of the following claims: 1) the inductive electric sensor or electromechanical limit switch installed on the invention in question does not work in an oil bath but dry, since it "captures" the upper end of the integral piston rod raised by the truncated cone of the hydraulic piston, which is external to the hydraulic circuit; 2) the commutation of the inductive electric sensor or of the electromechanical limit switch installed on the invention occurs due to the truncated cone of the hydraulic piston which raises the integral piston rod by means of contact with the ball located in the lower part of the same, which absorbs the absoradial impact with the truncated cone of the piston rolling on itself inside the particular housing slot in which it is suitably reaffirmed; 3) as a result of what is specified in the previous point sub. 2), a particular "sweetness" is given to the invention in the switching phase, due to the progressive "gradualness" of the same, which occurs in about 12-13 mm of linear stroke of the hydraulic cylinder, while in other similar components the switching is abrupt and sudden; 4) the particular design of the invention makes it absolutely "stable" and "safe" in operation since the difference between the lower and upper areas of the integral stelopistone is in clear favor of the upper one (+ 25%) also helped by the compression spring; this means that the hydro-mechanical limit switch is always obliged to stay, basically, in the condition of piston completely out (towards the hydraulic cylinder), and that therefore no particular dynamic condition inside the invention could determine a "false" or "undesired" actuation of the same, except for the effect of the piston of its own hydraulic cylinder which reaches its position. This is an absolutely important event which is not always found in other types similar to our hydro-mechanical limit switch; 5) the particular design of the invention also allows to manually adjust the intervention point of the hydro-mechanical limit switch, since, by "approaching" the sensor to the rear end of the integral piston rod (by screwing it clockwise inside its seat), its intervention can be "anticipated" by about 12-13 mm with respect to the "zero" point, because, by doing so, the sensor will almost immediately "feel" the rear end of the integral piston rod which will rise as soon as the the beginning of the truncated cone will begin to rise due to the effect of the maximum magnetic field of the sensor "due" to the minimum distance from the metal part to be detected; obviously, by progressively moving the sensor away from it, unscrewing it inside its threaded slot, it is possible instead to "delay the advance" of the signal progressively up to the point of "zero". This peculiarity does not it is found in all the other components currently on the market, similar to our invention, since in the latter it is not possible to regulate their intervention point which is "fixed"; 6) the multiplicity of integrations present in the integral stelopistone, and more precisely: a) the sphere present at the lower end of the same that softens the impact with the truncated cone, due to its rolling inside its groove; b) decentralized axial drilling to hydraulically feed the upper part of the same; c) the axial decentralized drilling (diametrically opposite to the one mentioned above) to allow the expulsion of the air that is created between the two lower and upper hydraulic chambers sealed, in the spring chamber which, through the upper vent hole, is in communication with the atmosphere; d) the rear drilling that allows the housing of the compression spring; these peculiarities clearly distinguish our invention from competing products, as they are unique in their design philosophy, full of noteworthy additions; 7) the simplicity of installation for the user, since, by making a simple hole in the cylinder liner, and concentrically welding his own stud to be welded to it where the invention is screwed, he has completed the application, while to install similar components to our found, in most in some cases, a "tolerance mechanical reaming" must also be performed in the part where the component is to be screwed; 8) The hydro-mechanical limit switch can receive the inductive electric sensor either radially at choice on one of the four sides of the cover - which is also adjustable - or axially, simply by choosing the radial or axial rear cover, which is not always possible with other similar products; 9) The invention in question can also be supplied in the basic version, which provides only the hydromechanical limit switch with the upper projection of the "free" probe, which can be used to operate any type of limit switch, proximity, electrical, mechanical, pneumatic and / or anything else, testifying to the flexibility and ductility of use of our invention which, also for these peculiarities, is characterized and decisively different from other similar products. H.C.S. S.r.L The Sole Director