WO2009133581A1

WO2009133581A1 - Anti-fall device in particular for hydraulic presses

Info

Publication number: WO2009133581A1
Application number: PCT/IT2009/000169
Authority: WO
Inventors: Gianfranco Maracani; Federico Albertini; Federico Redana
Original assignee: Gauss Automazione S.P.A.
Priority date: 2008-04-28
Filing date: 2009-04-16
Publication date: 2009-11-05
Also published as: ITBS20080090A1

Abstract

The invention concerns an anti-fall device (10) for machines (11 ), such as blanking, braking presses and the like, that have a movable platen or ram (14) moving, by means of a main hydraulic cylinder connected to them, along guide bars (15) above a fixed work table (12). The device comprises a redundant auxiliary hydraulic cylinder (20, 21 ) connected to the movable platen or ram (14) and fed by its own hydraulic circuit (22) and connected to said main control cylinder of the movable platen or ram (14) so as to download and recollect the hydraulic fluid from and to its jacket, only in reply to the movements of the movable platen or ram dynamically from the main cylinder.

Description

"ANTI-FALL DEVICE IN PARTICULAR FOR HYDRAULIC PRESSES"

_* * _*

Field of the Invention

This invention concerns the hydraulic presses field and refers in particular to a safety device for these machines. State of the Art

Some machines, such as blanking machines, forming presses and the like, usually have a fixed work table on a bedplate and a platen or ram, movable vertically along columns or guide uprights between an opening position, in which the platen is raised, away from the work table, and a closed position, in which the platen is lowered on to the fixed table.

These presses can be the mechanical or hydraulic type depending on the operating systems of the work table or movable ram. In the so-called hydraulic presses, the movements of the fixed work table or ram, between one position and another, are carried out by means of at least one control cylinder, which is fixed to a cross member at the top of the bedplate and which has a stem connected to the movable platen. Therefore, the control cylinder is fed by a respective hydraulic circuit that leads up to a control unit and which is in correlation also with the means that control the usual movable protection barriers of the machine, so as to prevent the machine operating if and while said barriers are open.

With the object of maintaining their effective safety and to provide the operators working on it with protection, the type of presses taken into consideration have been equipped according to the rules (EN 693 rev. 2004), also with an anti-fall device with the function of automatically stopping the movable platen to avoid it dropping towards the fixed work table due to breakdowns or inefficiencies in relative command or control means.

According to the known technique, an anti-fall device is basically mechanical and consists of a rack positioned vertically and fixed and moving with the movable platen and of a pawl inserted on a fixed part of the machine, controlled to interact with the toothing of the rack. However, the action of this safety device may not be continuous and immediate, and in fact become discontinuous due to the fact that the pawl must find each time a tooth on the rack to engage with, consequently the movable platen may move further along its stroke before stopping and be the cause of possible damage.

Always according to the known technique, an anti-fall device was also proposed that consisted in a column movable together with the movable platen of the press and in a friction brake system, placed around said column, controlled to operate with the latter and stop the movable platen when required. This other safety device has a continuous action along the column and therefore in each part of the stroke of the movable platen, but it is particularly complex and costly. In addition, then, both the above safety devices have a drawback which, if for some cause or reason, they remain in the operating position without automatically disengaging, the movements of the movable platen by the relative control system can cause damage to them or even their destruction. Objects and Summary of the Invention

One object of this invention is to provide an anti-fall device without mechanical members, simple and reliable and set up to rapidly intervene and stop a movable platen in any position, in answer to a failure warning and/or a breakdown of the system that controls the operation of the machine and/or when the protection devices of the machine are not in the safeguarding position.

A further object of the invention is to provide an anti-fall device which is purely hydraulic, which always remains in the active blocked position and disengages only when the movable platen can be moved correctly and/or when the protection means of the machine are in the safety position.

The anti-fall device in accordance with the invention applies to presses and, in general, to machines with a platen or ram, movable above a fixed work table and operated by a single main control hydraulic cylinder and is characterized in that it comprises a redundant auxiliary hydraulic cylinder connected to the movable platen or ram and fed by an own hydraulic circuit correlated with an hydraulic feed circuit of the main control cylinder of said movable. Brief Description of the Drawings The invention will however be described in greater detail in the following specification, making reference to the attached indicative and not limiting drawings, in which:

Fig. 1 shows a schematic exemplifying view of a press;

Fig. 2 shows a diagram of the hydraulic control cylinder of the movable platen and the safety cylinder with relative hydraulic feed circuits. Detailed Description of the Invention

As shown the anti-fall device 10 of the invention is associated with a press 11 or similar machine with a fixed work table 12 on a bedplate 13 and a platen or ram 14 movable vertically along tie bars or guide uprights 15 between an opening position, in which the ram 14 is at a distance from the fixed work table 12, and a closed position, in which the ram 14 is lowered onto the fixed work table 12.

The movements of the work table or movable ram 14, between the opening and closing positions are commanded by a main hydraulic cylinder with a jacket 16 that is fixed to a cross member 17 joining the top of the guide bars 15 and a piston with a stem 18 fixed to the work table or ram

14.

The main control cylinder 16 is fed by a respective hydraulic circuit 19, well known in itself, a part of which is shown in Fig. 2. According to the invention, the anti-fall device 10 consists of an auxiliary hydraulic cylinder, in a vertical position, provided with a jacket 20 fixed to the top cross member 17 and a piston with a stem 21 fixed to the work table or movable ram 14 to follow the upward movements of the latter, without however the supporting function of the movable platen or ram. The auxiliary hydraulic cylinder is connected to an independent hydraulic circuit 22 that is preferably gravity fed, it being provided with an entry 22' connected directly to a tank 23, which includes a safety block made up of a monitored safety valve 24 and an explosion-proof maximum safety valve 25. The function of the safety block is guaranteed by the redundancy of such a system.

Configured in this way, the auxiliary hydraulic cylinder, with its safety function, is always potentially active and with its piston which follows the movements of the movable platen or ram. In fact, the hydraulic fluid contained in it, is discharged towards, and recalled by the feed circuit 22 only during correction functioning of the machine, that is to say, only in the presence of a force applied by the control cylinder to the movable platen or ram for their movements between a closed and open position. In other words, the auxiliary hydraulic cylinder is enabled to intervene to stop at the right moment and restrain the work table or movable ram in any high position if and each time, due to abnormal external events or to any type of breakdown, the function of the main control cylinder fails both during the upward and the downward movements of the movable platen or ram.

Claims

"ANTI-FALL DEVICE IN PARTICULAR FOR HYDRAULIC PRESSES" * * * C L A I M S

1. An anti-fall device (10) for machines (11), such as blanking, forming presses and the like, having a movable platen or ram (14) moving, by means of a main hydraulic cylinder connected to them, along guide bars (15) above a fixed work table (12) , characterized in that it comprise a redundant auxiliary hydraulic cylinder (20, 21 ) connected to the movable platen or ram (14) and fed by an own hydraulic circuit (22) and connected to said main control cylinder of the movable platen or ram (14) so as to download and recollect the hydraulic fluid from and to its jacket, only in reply to the movements of the movable platen or ram dynamically from the main cylinder.

2. An anti-fall device (10) according to claim 1 , wherein the auxiliary hydraulic cylinder is lined-up vertically and has a jacket (20) anchored to a top cross member (17) connecting the guide bars of the movable platen or ram and a piston with a rod (21 ) fixed to said movable platen or ram (14) to follow the movements.

3. An anti-fall device according to claims 1 and 2, wherein the auxiliary hydraulic cylinder is gravity fed by a tank directly by the respective delivery hydraulic circuit.

4. An anti-fall device according to the previous claims, wherein the delivery hydraulic circuit of the auxiliary hydraulic cylinder includes a safety block comprising at least one monitored safety valve (22) and an explosion-proof maximum safety valve (25).

5. An anti-fall device (10) according to any of the previous claims, wherein the auxiliary hydraulic cylinder does not have a supporting function, but only to stop the movable platen or ram (14) in any position in height in the absence of every function of the main cylinder on said movable platen or ram.