SAFETY DEVICE FOR SPRING/DAMPER UNITS Technical Field

The present invention relates to a safety device for spring/damper units. Background Art

Spring/damper units generally have a tubular containment jacket that is closed hermetically at one end by a bottom provided with a gas filling valve and at the opposite end by a head that is perforated for the passage of a stem with a piston, which performs a translational motion within such jacket; the jacket, the bottom and the head define the stroke chamber for the piston, while such piston, together with the jacket and the bottom, forms the chamber for compression and expansion of the gas that is present therein within the head.

These spring/damper units are used typically but not exclusively also in situations, such as molds, die-forming presses, and the like, in which they can be subjected to pressures that might damage them; such damage can cause the spring/damper unit to become unusable, forcing replacement and interruption of the machine or system in which it is placed to work, but such damage can also be such as to harm an operator who is in the vicinity, as in the case of an explosion due to overpressure or breakage with uncontrolled escape of pressurized gas.

This damage can occur mainly for two reasons. A first reason is linked to a retracting stroke of the stem with the piston that is longer than allowed from the constructive standpoint for that specific spring/damper unit.

This so-called overtravel, which can be caused for example by an unexpected increase in load on the stem of the unit, which forces such stem to retract into the body of the unit for an unexpected length, can generate an overpressure inside the unit which the structure of the unit as a whole might be unable to sustain; the unit may thus splay or break at the connecting

points between the parts that compose it, or its sealing elements might fail, and in all the cited cases an unexpected, unwanted and dangerous rapid escape of gas can occur.

A second reason for damage may occur due to the inflow of lubricating liquids, by which such spring/damper units can be affected in many of their applications, such as die-forming presses or the like, within the compression and expansion chamber in which the gas is compressed by the movement of the piston.

The presence of substantially incompressible liquid within the unit determines a smaller free volume available for compression of the gas; the normal stroke of the stem and of the piston causes an overpressure, which, in a manner similar to what has been described above for an overpressure due to overtravel, can cause structural failures of the spring/damper unit, with all the consequent dangers. Disclosure of the Invention

The aim of the present invention is to provide a safety device for spring/damper units that is capable of making safe and reliable a spring/damper unit both in case of overtravel of the stem-piston and in cases of overpressure caused by other unwanted events, such as for example seepage of incompressible fluid into the jacket of the unit.

Within this aim, an object of the present invention is to provide a safety device that is simple to provide and assemble.

Another object of the present invention is to provide a safety device with which even known types of spring/damper unit can be equipped. Another object of the present invention is to provide a safety device which, if activated, can be replaced easily with another identical one.

Another object of the present invention is to provide a safety device for spring/damper units that can be manufactured cheaply with known systems and technologies. This aim and these and other objects, which will become better

apparent hereinafter, are achieved by a safety device for spring/damper units, characterized in that it comprises at least one part of the bottom or jacket of a spring/damper unit provided with a breakable partition that is subjected to the pressure determined by the gas compressed within a compression and expansion chamber of a spring/damper unit, said chamber being formed between said bottom, said jacket and the piston of the unit, said breakable partition having such a thickness as to break in the presence of a pressure inside said chamber that is greater than, or equal to, a preset pressure value, said breakable partition being associated with a longitudinally elongated element that lies within said compression and expansion chamber for such a length as to affect part of said piston during its descent before it performs a stroke that exceeds the predefined stroke, said longitudinally elongated element being supported by way of yielding supporting means adapted to allow, in the presence of a preset force that pushes, in the direction of operation of the unit, against said longitudinally elongated element, so that said element moves so as to break said breakable partition or so that it breaks itself, causing the opening, on the bottom or on the jacket, of an outlet for the gas toward the outside. Brief description of the drawings Further characteristics and advantages of the invention will become better apparent from the following detailed description of two preferred but not exclusive embodiments thereof, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a sectional side view of a spring/damper unit provided with a safety device according to the invention in a first embodiment thereof;

Figure 2 is a sectional side view of a detail of the device according to the invention;

Figure 3 is a transverse sectional view of the device according to the invention;

Figure 4 is a perspective view of part of the striker;

Figure 5 is a sectional side view of a spring/damper unit provided with a device according to the invention in a second embodiment thereof;

Figure 6 is an enlarged-scale view of a detail of Figure 5, illustrating the device according to the invention in a second embodiment thereof. Ways of carrying out the Invention

With reference to the figures, a safety device for spring/damper units according to the invention is generally designated by the reference numeral 10. The safety device 10 comprises a part of a bottom 1 1 of a spring/damper unit 12, which is provided with a breakable partition 13.

The breakable partition 13 is designed to be subjected to the pressure determined by the gas that is compressed within a chamber 14 for compression and expansion of the spring/damper unit 12, the chamber 14 being formed between the bottom 1 1 , a jacket 1 1a and a piston 15 of the spring, as shown in Figure 1.

The breakable partition 13 has such a thickness that it breaks in the presence of a pressure inside the chamber 14 that is higher than, or equal to, a preset pressure value. A longitudinally elongated striker 16 is positioned, by way of yielding supporting means described in greater detail hereinafter, at and proximate to the breakable partition 13.

The longitudinally elongated striker 16 has a stem 17 that protrudes into the compression and expansion chamber 14 for such a length as to affect a part of the piston 15 during its descent before the piston 15 performs a stroke that exceeds the predefined one.

The yielding means that support the longitudinally elongated striker 16 allow, in the presence of a preset force that pushes on the stem 17 in the direction of the longitudinal axis of the unit 12, a movement of the striker 16 so as to break the breakable partition 13.

In the embodiment of the device 10 according to the invention, described here by way of non-limiting example of the invention, the part of the bottom 1 1 is constituted by a body 18 that can be fixed detachably to the bottom 11 and has a first compartment 19, which opens onto the outside of the unit 12, and a second compartment 20, which is open onto the chamber 14; the two compartments 19, 20 are mutually separated by the breakable partition 13.

In this embodiment, the body 18 is constituted by a plug that is threaded externally to be screwed into a corresponding complementarily threaded through hole 21 formed in the bottom 11.

The first compartment 19 is provided by the hexagonal maneuvering recess formed on a head 18a of the body 18, while the second compartment 20 is shaped to accommodate a spike 22 of the longitudinally elongated striker 16. The yielding means for supporting the longitudinally elongated element 16 proximate to the breakable partition 13 are constituted by an internally threaded collar 23, which is designed to receive by screw coupling a corresponding threaded portion 24 of the striker 16.

In the embodiment described here of the longitudinally elongated striker 16, the threaded portion 24 extends contiguously with the spike 22, and at least one groove 25 is provided thereon which is adapted to determine, when the threaded portion 24 is screwed onto the collar 23, a channel 26 designed to connect the chamber 14 and the second compartment 20. The second compartment 20 is substantially cylindrical, and the spike

22, which is cone-shaped, is arranged inside it so that its tip is in contact with the breakable partition 13.

In particular, the threaded portion 24 has four grooves 25, which run parallel in the direction of the axis of the longitudinally elongated striker 16 and are provided symmetrically with respect to such axis.

The operation of the safety device according to the invention is as follows.

During the assembly of the unit 12, the body 18, to which the striker 16 has already been screwed, is screwed to the bottom 11. When the unit 12 is loaded, the gas that is in the chamber 14 passes through the channels 26 into the second compartment 20, thus pressurizing the breakable partition 13.

When the spring/damper unit 12 is operating, if a critical overpressure, i.e., an overpressure that is equal to or greater than a preset value, occurs inside the chamber 14 due to seepage of liquids into it, the breakable partition 13 breaks, allowing the safe discharge of the pressurized gas.

There is, therefore, a "guided" and controlled rupture, which prevents the spring/damper unit 12 from breaking in other points that cannot be determined beforehand and are more dangerous for an operator who is in the vicinity.

In the case of overtravel of the piston 15, it pushes against the stem

17; when this thrust causes yielding of the threaded coupling between the collar 23 and the portion 24 of the longitudinally elongated striker 16, it is transferred to the region of contact between the tip of the spike 22 and the breakable partition 13.

An even greater thrust causes breakage of the breakable partition 13 by the spike 22 and the safe escape of the gas.

In a second embodiment, shown in Figures 5 and 6 and designated therein by the reference numeral 1 10, the device is characterized in that the breakable partition 113 is provided on a part of the jacket I l ia, instead of on a part of the bottom 1 1 1 as in the first embodiment described above.

This part of the jacket I l ia is provided by a body 118 that can be fixed reversibly to the jacket I l ia, from which the longitudinally elongated element 1 16 extends.

The body 118 and the longitudinally elongated element 116 are crossed by a dead hole 119, which runs along the direction of the axis of the longitudinal element 116.

The dead hole 119 is open onto the outside of the unit 112 and is closed toward the inside of the unit 112 by the partition 1 13.

The longitudinally elongated element 116 protrudes monolithically from the reversibly fixable body 1 18 and toward the interior of the chamber 1 14.

One groove 125 for initiating breakage under the thrust of the piston 1 15 is formed at a transverse cross-section of the longitudinal element 116.

In this second embodiment of the invention, which also is a non- limiting example of the invention, the body 118 is a plug that is threaded externally to be screwed into a corresponding complementarily threaded through hole 121. The outer compartment 119a of the hole 119 is provided by hexagonal maneuvering recess formed on the body 1 18.

The operation of the device 110 entails that as the piston 1 15 descends, if it continues descent by going beyond the limit of its preset stroke, it encounters the longitudinally elongated element 116, which protrudes at right angles to the jacket I l ia into the chamber 1 14.

The overtravel of the piston 115 causes the impact of the piston 1 15 against the longitudinal element 1 16 and the breakage of the latter at the height of the fracture groove 125.

In this manner, the pressurized gas is free to discharge outside the unit 1 12 through the hole 119.

If instead there is an overpressure inside the chamber 1 14 regardless of the stroke of the piston 1 15, then, in a manner similar to what has been shown for the first embodiment of the invention, the partition 113 breaks, allowing the discharge of the pressurized gas through the hole 1 19. In practice it has been shown that the invention thus conceived

achieves the proposed aim and objects.

In particular, the present invention provides a safety device for spring/damper units that is capable of making a spring/damper unit safe and reliable both in case of overtravel of the piston and in cases of overpressure determined by other unwanted events, such as for example seepage of incompressible fluid into the jacket of the spring/damper unit.

Moreover, the present invention provides a safety device 10 and 1 10 that is simple to manufacture and assemble, by way of the body 18 and 1 18, which can be provided in practice by a plug that can be screwed to the bottom 1 1 or to the jacket I l ia, and by way of the coupling between the body 18 and the longitudinally elongated striker 16, which is also provided by a threaded coupling, or by way of the coupling between the body 1 18 and the longitudinally elongated element 1 16, these last being monolithic.

Further, the present invention provides a safety device with which even known types of spring/damper unit can be equipped.

Moreover, the present invention provides a safety device which, if activated, can be replaced easily with another identical one, since the integrity of the spring/damper unit 12 and 1 12 is not compromised by malfunction and the device 10 and 1 10 can be replaced easily by unscrewing the body 18 and 1 18.

Moreover, the present invention provides a safety device for spring/damper units that can be manufactured cheaply with known systems and technologies.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

In practice, the materials employed, so long as they are compatible with the specific use, as well as the dimensions, may be any according to requirements and to the state of the art. The disclosures in Italian Patent Application No. PD2007A000378

from which this application claims priority are incorporated herein by reference.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.