CYLINDER AND TOTAL ROD STOPPAGE SYSTEM

Abstract: The gas cylinder is of the type used for example in punching installations or tools, and comprises two hermetic and independent chambers (7) and (8), the first placed axially to the corresponding rod (6) and the latter placed annularly and externally, with said two chambers externally communicated through branches (16) and (17) which end in a common chamber (14) of a pressure accumulator (11), in which is defined a second chamber (13) which can be charged with nitrogen and is provided with a movable piston (12) for the filling and corresponding pressure balancing between chambers (14), (7) and (8). Ana electrovalve (18) can be closed at will after attaining the pressure balance between said three chambers (14), (7) and (8), preventing rod (6) from recovering its original position after the force exerted on it during operation ceases.

Description: OBJECT OF THE INVENTION The invention relates to a cylinder associated to a system by which the corresponding cylinder rod is locked in its end position of its stroke, also allowing to control and adjust the return of said rod to its initial position. The invention is mainly applicable to cylinders as those used for example in punching installations or tools, without prejudice of its use in any other practical cases requiring these characteristics. It is therefore the object of the invention to lock a gas cylinder rod at the final position of its stroke, preventing its return when the external force which causes the gas to compress ceases, with the expansion of the gas and the ensuing return of the rod to its initial position occurring only by activation of an electrovalve. BACKGROUND OF THE INVENTION In gas cylinders used in punching installations when the external pressure on the rod stops the rod quickly returns to its original position due to the expansion of the previously compressed gas, as the external pressure exerted during the work of the cylinder acts against a gas which is compressed, so that its force of expansion after the external pressure stops or after its work is performed will return the rod to its original position. However, this quick, practically instantaneous return of the gas cylinder rod can result in damage to the part being worked upon, whether by direct action or by indirect action through the tools or machine parts located between the cylinder and the part. DESCRIPTION OF THE INVENTION The cylinder disclosed presents a number of specific characteristics which in combination with a system comprising a pressure accumulator and an electrovalve solves the above described problem in a simple, effective and reliable manner, as the assembly of cylinder, accumulator and electrovalve conform an elastic force system which allows to control the return of the cylinder rod at will. More specifically, the cylinder of the invention comprises two hermetic and independent chambers, one which is arranged axially to the corresponding rod, which runs inside a bushing concentric to the outer cylindrical body of the cylinder, so that between said outer wall and said bushing inside which the rod moves axially, the second chamber is defined which may be in communication with the rod but not with the axial chamber in which it moves. The two chambers, which contain the hydraulic oil, are externally communicated by a pressure accumulator formed by a cylindrical body with two chambers, one charged with nitrogen through an external charging valve to a given pressure and the other meant to transfer the pressure through a piston interposed between this second chamber and the nitrogen-filled chamber of the accumulator being described, in order to balance pressures in the gas cylinder chamber and in the second chamber of the accumulator. An electrovalve is installed in the branch which communicates the external chamber of the cylinder to the second chamber of the accumulator. This valve can be opened and closed at will, so that when open to it maintains pressure in the external chamber and locks the inwards axial displacement of the rod by means of an external force, that is, during the active operation of the cylinder. Thus, if the external force on the rod ceases due to the chamber being closed, because of the electrovalve the rod cannot return to its original position unless this electrovalve is opened, and thus allows hydraulic oil to pass from said chamber to the second chamber of the accumulator, and naturally towards the axial chamber of the cylinder itself, allowing the rod to recover its original position. The accumulator, in addition to transmitting pressure when charged with nitrogen to the cylinder chambers until the pressure balance of the system is restored, also absorbs through the pressurised gas chamber the excess pressure produced by the volume reduction of the cylinder chambers. On its part the electrovalve installed in the branch which communicates the external cylinder chamber to the corresponding accumulator chamber is meant to control at will the flow of oil between the two chambers of the cylinder when said electrovalve is actuated with an external electrical signal. DESCRIPTION OF THE DRAWINGS These characteristics of the invention will become clearer in view of the accompanying drawing of a preferred embodiment, which form an integral part of the description and where for purposes of illustration only and in a nonlimiting manner the single figure represents a sectional view of the cylinder associated to the pressure accumulator and the electrovalve interposed in one of the branches which communicate the cylinder with the pressure accumulator itself. PREFERRED EMBODIMENT OF THE INVENTION As can be seen in the figure, the cylinder which is preferably employed in punching installations or devices comprises an external cylinder (1) which on one of its ends incorporates a flange by which it is attached to a base (2), with two passages (3) and(4). Between base (2) and the free open end of cylindrical body (1) is mounted a bushing (5) on which moves axially the corresponding cylinder rod (6), all such that in said general cylinder are defined two chambers (7) and (8), the first (7) axial to rod (6) and therefore inside bushing (5), and the second (8) placed annularly between bushing (5) and the external wall of cylindrical body (1), with this second chamber (8) having a lateral orifice (9) in bushing (5) for communicating said chamber (8) and rod (6). Passage (4) leads to the second chamber (8) and passage (3) leads to the first chamber (7). The cylinder is further provided with a bushing (10) placed in correspondence with the end of bushing (5), so that said bushing (10) acts as a mechanical stop ending the stroke of rod (6). In said cylinder are provided the corresponding gaskets establishing a hermetic seal between the chambers and the participating elements. The cylinder and total rod stoppage system is further provided with a pressure accumulator comprising a cylindrical body (11) with a piston (12) which defines two chambers labelled (13) and (14), in which one is a gas chamber (13) which receives nitrogen gas through a charging valve (15), and the other, the third chamber (14), is filled with hydraulic oil, as are the aforementioned chambers (7) and (8) of the cylinder, since this cylinder communicates with chamber (14) through branches (16) and (17), the first connected by passage (3) to the first chamber (7) and the second connected by passage (4) to the second chamber (8). Therefore, chambers (7) and (8) of the cylinder are independent, although they are communicated externally by branches (16) and (17) in combination with chamber (14) of the pressure accumulator. This third chamber (14) is naturally independent of and totally sealed from gas chamber (13) of the accumulator. In branch (17) is placed an electrovalve (18) meant to control oil flow between chambers (7) and (8) of the cylinder, using an external electrical signal as described further below. The operation is as follows: When an external axially oriented force is applied to the cylinder rod (6) the end of its working stroke is reached, so that said rod (6) is retracted inwards, and hydraulic oil of the first chamber (7) passes through branch (16) to chamber (14) and through branch (17) to the second chamber (8), so that through orifice (9) oil is allowed though chamber (8) into the chamber defined inside piston (5) when rod (6) retracts. Previously gas chamber (13) of the pressure accumulator has been charged with nitrogen through valve (15) to a given pressure, so that this pressure is transmitted through piston (12) to the entire system and the pressures in chambers (7), (8) and (14) are balanced. Once this pressure balance is attained electrovalve (18) is closed, so that when pressure on rod (6) ceases or when the cylinder stops acting, said rod (6) will be locked in its retracted position as the aforementioned pressure balance prevents rod (6) from recovering its original position, that is, it will not move in the direction of expansion as the pressure balance prevents this. However, if valve (18) is actuated and opened, oil in chamber (8) will return freely through branch (17) to chambers (14) and (7) respectively, allowing a controlled expansion of said rod (6), that is, its movement towards its original position with bushing (10) acting as a stop for the end of the stroke. Finally, as an option a second electrovalve can be installed in branch (16) which may be useful in certain applications, particularly to prevent a possible rebounding effect of cylinder rod (6).

Claims: Cylinder and total rod stoppage system, of those used for example in punching installations or tools, of the type which recover their original position by means of hydraulic pressure after the force exerted axially by a rod (6) itself in its operation ceases, two hermetic independent chambers (7, 8) being defined inside a cylindrical body (1) of the cylinder, the first chamber (7) placed axially to said rod (6) and the second chamber placed annularly and externally to a first bushing (5) which defines the first chamber (7) and in which moves said rod (6), characterised in that said first and second hermetic chambers (7, 8) are externally communicated by the total stoppage system which comprises: a gas accumulator (11) in which are also defined two hermetic and independent chambers, namely a gas chamber (13) charged with nitrogen and a third chamber (14) which contains hydraulic oil, as do the first and second chambers (7, 8), such that the gas chamber (13) and the third chamber (14) of the gas accumulator (11) are separated by an interposed piston (12), a first branch (16) which communicates the third chamber (14) to the first chamber (7) , and a second branch (17) which communicates the third chamber (14) to the second chamber (8) of the gas cylinder, and which incorporates an electrovalve (18) controlled externally and at will. Cylinder and total rod stoppage system, as claimed in claim 1, characterised in that the cylinder, in correspondence with the bottom end of the first bushing (5) inside which moves the rod (6) and in which is defined the first chamber (7), is provided with a second bushing (10) which acts as a mechanical stop for the end of stroke in the motion of the rod (6) towards its original expansion position; and with the wall of the first bushing (5) provided with an orifice (9) which communicates the second chamber (8) and the rod (6), allowing to lock the latter in its retracted position, which was brought about by an external axial force exerted on it, after balancing pressures between the first, second and third chambers (7, 8, 14) opening the electrovalve (18).

Inventors: ORIVE CANTERA ISAAC, ORIVE CANTERA MERCEDES, ORIVE CANTERA NURIA, ORIVE CANTERA, ISAAC, ORIVE CANTERA, MERCEDES, ORIVE CANTERA, NURIA
Applicants: NITROGAS S L, NITROGAS, S.L.
Application year: 1999
Main classification: B30B15
IPC codes: B30B15, F15B1