EP0046788B1 - Hydraulic press mechanism - Google Patents

Abstract

PCT No. PCT/FR81/00034 Sec. 371 Date Oct. 30, 1981 Sec. 102(e) Date Oct. 30, 1981 PCT Filed Mar. 11, 1981 PCT Pub. No. WO81/02543 PCT Pub. Date Sep. 17, 1981.This mechanism makes it possible to obtain in succession a fast approach stroke (C), and then a work stroke with a substantial developed stress, in operations such as riveting or marking, the work stroke being started as the tool (16) comes into contact with the part to be pressed (25). A control stem (4) and a body (9) are movable along one and the same axis (3), means such as a clack (31) providing for their non permanent locking. The stem (4) is integral with a primary piston (8) penetrating into a hydraulic circuit (10, 11) of the body (9); this circuit communicates, on the one hand, with an expansible casing (19) surrounding the body (9) and making it possible to block this body with respect to the frame (1), and on the other hand, with a chamber (12) in which a secondary piston (15), drawn back by a spring (18) and integral with tool (16), slides.

Description

The present invention relates to a hydraulic press mechanism, making it possible to successively obtain a rapid approach stroke, then a working stroke with significant developed force, this mechanism comprising: a member on which the action of controlling the device is exerted for said strokes, and a main body movable along the same axis in a fixed guide bore, means being provided for non-permanent axial locking of the body relative to the control member, the body comprising a first chamber filled with fluid incompressible into which a primary piston penetrates, extending the control member along the axis of the mechanism, this chamber communicating on the one hand with an expandable socket immobilized axially in the body and able to be pressed against the wall of the bore, and on the other hand with a second cylindrical chamber in which a secondary piston is slidably mounted, the latter being integral with a rod comprising the out it intended for the use of the mechanism.

Such a mechanism, known from US-A-3,059,433, can be used for operations such as riveting, marking, clamping of parts and, more generally, for all operations in which the working stroke can be relatively short compared to the magnitude of the approach movement. The operating principle is as follows: the main body is first moved in the bore, being pushed by the control member, until the working tool comes into contact with the part to be subjected the desired operation. When the contact of the tool with this part causes a certain resistance to the penetration of the body, the control member is moved axially relative to the body, which is allowed by the non-permanent locking means between these parts . The primary piston extending the control member then pressurizes the incompressible fluid circuit, causing the expansible bushing to swell which blocks the main body against the bore, thus immobilizing this body axially. The pressurization of the incompressible fluid then causes the advancement of the only secondary piston, which causes the tool to describe its working stroke, with a force "multiplication" effect obtained by the fact that the section of the second cylindrical chamber , in which the secondary piston slides, is provided greater than the section of the primary piston. A rapid approach stroke is thus obtained, followed by a working stroke with a large developed effort, by applying a moderate control effort at a single point of the device, on the control member, the working stroke being in principle triggered automatically the moment the tool comes into contact with the tool to be worked.

In the embodiment known from US-A-3,059,433, as well as in somewhat different known embodiments but still using a primary piston, a hydraulic fluid, a secondary piston and an expandable bushing (see for example the patent FR -A-1 599881), the device is designed as a pneumatic cylinder, as regards its control. Thus, the control member is a rod secured to a third piston subjected to the pressure of the compressed air. To obtain not only the approach and working strokes in the "go" direction, but also the reverse movement of "return" to the starting position, these known devices have a second compressed air supply opposite to the first, and internal conduits allowing this compressed air to be admitted to several places in the device. In particular, the compressed air must be sent through several organs, some of which are mobile, and for example it is necessary to pierce in the main body of long channels located outside the axis of the device, and provide on these channels valves (see US-A-3,059,433 - Figures 4 and 5). The device therefore remains complex and its manufacture is difficult and costly, if it is desired to obtain suitable operation and in particular good sealing of the valves which requires high machining precision. In addition, the return movement being controlled pneumatically and by a supply of compressed air at a location separate from the point used for controlling the approach and work strokes, it cannot be envisaged for the current devices a mechanical control of the 'whole functioning, which can only be conceived if the control action for all the movements is exerted on a single and same organ, and in a single place.

Furthermore, given the entirely pneumatic design of the control, in current devices, the connection between the secondary piston and the main body is poorly controlled. When the tool comes into contact with the workpiece, the pressurization of the incompressible fluid can cause the main body to recede, before the expandable sleeve is tightened firmly against the bore. We therefore do not obtain a certain and immediate immobilization of the body at the end of the approach run.

The present invention overcomes these drawbacks by providing a press mechanism of the kind defined above, which is of simplified structure, therefore of easier and more economical construction, and of more reliable operation, and which can be controlled by a single and same organ and from a single point both for its successive strokes in the forward direction and for its return stroke, so as to make the device compatible with various solutions for its control, and in particular with mechanical actuation.

To this end, the control member, integral with the primary piston, is associated with means allowing its axial displacement control in both directions from a single end of the device, so as to constitute a common single control member for the approach run, the work run and the return run in the rest position.

This arrangement simplifies the device and in particular are removed the internal channels located off the axis.

The assembly can therefore be obtained by using conventional machining modes such as lathe machining. In addition, the control function is completely separate from the internal hydraulic system, and this makes it possible to envisage control by any means, mechanical or fluid, acting on a single member, the device being able to be designed as a "press" operating. from a wide variety of external sources of energy and movement, possibly from a simple manual control.

According to a first possibility, constituting a mechanical solution, the single control member, integral with the primary piston, is a rod provided with a rack engaged with a drive pinion, the latter being mounted on a shaft maneuvered by a member such as a lever, possibly by inserting a torque limiter.

According to another possibility, the single control member, integral with the primary piston, is an additional piston slidably mounted in a cylinder coaxial with the bore in which the main body slides, to constitute a pneumatic or hydraulic control cylinder.

The single control member secured to the primary piston may also be a tube mounted to slide and rotate in the bore where the main body slides, and connected by a thread to this body which means immobilize in rotation, the stroke of approach being obtained by simultaneous translation of the tube and the body, while the working stroke is obtained by screwing the tube onto the body, the tube comprising an operating part, preferably linked to this tube via a limiter of couple. In the latter case, it is the thread which ensures, during the approach stroke, the axial connection between the control tube and the body and during the working stroke, the relative axial displacement of the control member and of the body, with amplification of the effort. The control tube is linked to the primary piston and the operation of the hydraulic part is not changed.

According to another characteristic of the invention, a return spring is mounted in the cylindrical chamber containing the secondary piston, and exerts its action on this secondary piston in the direction opposite to the action of the incompressible fluid. The spring does not only intervene during the "return" stroke caused from the single control member, but also during the "go" movement: the stiffness of the spring prevents the main body from retreating, at the end of the approach stroke, and it makes it possible to be certain that the sleeve is properly inflated and tightened against the bore, therefore that the body is immobilized axially, before the start of the working stroke.

The means for non-permanent locking of the body with respect to the single control member and to the primary piston comprise, for example, a calibrated valve capable of preventing the incompressible fluid from leaving the first chamber, in the direction of the expandable sleeve and of the second chamber, that is to say the one housing the secondary piston, and thus preventing the primary piston from entering the first chamber, so that the control rod in its movement drives the entire body and in particular the piston secondary, until the tool attached to the latter comes into contact with the workpiece. The valve, by the resistance which it offers to the flow of the fluid, opposes the insertion of the primary piston into the body, and this results in a permanent effort which makes it possible to maintain an energetic contact between the tool and the object to be pressed during the entire inflation phase of the sleeve, regardless of the position in space of the device. The action of the valve is therefore combined with that of the aforementioned spring retaining the secondary piston, so that the transition from the approach stroke to the working stroke takes place under the best conditions. Advantageously, a double valve is provided at the bottom of the first chamber, one of these valves, allowing the fluid to flow back from the expandable sleeve and the second chamber, housing the other valve which opposes the flow towards the expandable socket and the second chamber. This double valve allows the fluid to easily flow back to the chamber where it came from, when the single control member is brought back, first causing the recoil of the secondary piston and the release of the main body relative to the bore, then the simultaneous recoil of the control member and the body. Furthermore, the two valves being housed one inside the other can occupy a common position on the axis, which facilitates the production of the device for the reasons already explained above.

In order to be able to compensate for the functional leaks of the hydraulic seals which would adversely affect the proper functioning of the device, the primary piston has, at its end which plunges into the first chamber filled with fluid, a longitudinal groove such that, when this primary piston is in the retracted position, and only in this position, said groove puts the first chamber of the body into communication with a reserve of hydraulic fluid, delimited by the bore in which the body slides and by a movable wall in said bore and pushed by a spring, to produce a automatic compensation for variations in fluid volume.

• Figures 1, 2, 3 et 4 sont des vues en coupe du mécanisme selon l'invention, dans quatre positions successives,. illustrant son principe de fonctionnement;
• Figure 5 est une vue partielle, en coupe et à échelle agrandie, d'une variante avec verrouillage mécanique par bille du piston primaire par rapport au corps;
• Figure 6 est une vue en coupe du mécanisme selon l'invention, dans une autre variante où la commande de la tige se fait par un piston supplémentaire mû par de l'air comprimé ou tout autre fluide;
• Figure 7 est une vue, partiellement en coupe, d'une dernière forme de réalisation, avec commande par translation et rotation combinées;
• Figure 8 est une section suivant 8-8 de figure 7.

In any case, the invention will be better understood with the aid of the description which follows, with reference to the appended schematic drawing representing, by way of nonlimiting examples, some embodiments of this hydraulic press mechanism:

• Figures 1, 2, 3 and 4 are sectional views of the mechanism according to the invention, in four successive positions. illustrating its operating principle;
• Figure 5 is a partial view, in section and on an enlarged scale, of a variant with mechanical locking by ball of the primary piston relative to the body;
• Figure 6 is a sectional view of the mechanism according to the invention, in another variant where the control of the rod is done by an additional piston driven by compressed air or any other fluid;
• Figure 7 is a view, partially in section, of a final embodiment, with control by combined translation and rotation;
• Figure 8 is a section along 8-8 of Figure 7.

FIGS. 1 to 4 represent a machine comprising a frame 1, on which a tube 2 of vertical axis 3 is fixed.

In the bore defined by this tube 2 is slidably mounted a body 9 which carries an expandable sleeve 19, which is immobilized axially on the one hand by a shoulder separating the two parts of distinct diameters from the body 9, and on the other hand by an annular stop orange 20. The body 9 is hollowed out, so as to comprise an upper cylindrical chamber 10 connected, by an intermediate channel 11, to a lower cylindrical chamber 12. At least one radial communication 21 connects the channel 11 to the inside the sleeve 19, which is filled with incompressible fluid, in particular oil. The chamber 12 contains a secondary piston 15 secured to a tool 16 passing through a screwed bottom 17, a spring 18 being compressed between this bottom 17 and the underside of the secondary piston 15.

The upper chamber 10, the channel 11 and the part of the lower chamber 12 situated above the secondary piston 15 are filled with the same incompressible fluid as the expandable sleeve 19.

In the upper chamber 10 penetrates a primary piston 8 which has on its lower part a longitudinal groove 26 of a length such that, when the piston 8 is in the high position (shown in FIG. 1), this groove 26 puts the chamber 10 and a chamber 35 filled with the same incompressible fluid and located above the body 9. The chamber 35, constituting the fluid reserve, is separated from the chamber 10 by a seal 14, retained by a ring 13 screwed to the top of the body 9 (the seal 14 not fulfilling its function in the high position of the piston 8). The chamber 35 is further delimited by another seal 7 interposed between the body 9 and the tube 2, by the inner wall of this tube 2, and by a movable upper bottom 22, which is kept applied against the surface of the liquid by means of 'a spring 23.

The primary piston 8, passing through the ring 13, the chamber 35 and the bottom 22, is extended upwards by a control rod 4 which slides in a recess in the frame 1. The rod 4 is provided with a rack 5, in taken with a drive pinion 6 mounted on a maneuvered shaft, for example, using a lever not shown.

To temporarily link the primary piston 8, and the control rod 4 which extends it, to the body 9, there is provided in the embodiment of Figures 1 to 4 a double valve device which temporarily closes the inlet of the intermediate channel 11 located at the bottom of the chamber 10, and in doing so opposes the penetration of the primary piston 8 into said chamber 10. In the embodiment more particularly described here, one of the valves is disposed inside the other: a first valve 29, pushed down by a spring 30, serves as a housing for a second valve 31, urged upwards by another spring 32.

The part 25 to be worked, for example to be flattened, is placed on the frame 1, in the axis 3 of the device described above. In the initial position (Figure 1), the control rod 4 is raised; the double valve 29-31 obturates the inlet of the channel 11 and prevents any movement of fluid in the hydraulic circuit. The secondary piston 15 occupies, inside the chamber 12, its highest position, and the tool 16 linked to the secondary piston 15 is removed from the part 25.

In a first phase (see FIG. 2), the rod 4 is pushed downwards by the action of the pinion 6, itself maneuvered by the lever already mentioned. The primary piston 8 penetrates in a short stroke in the chamber 10, until the groove 26 located at its lower part is entirely beyond the seal 14. The fluid contained in the chamber 10, which is then closed at its upper part and at its lower part, prevents any greater penetration of the primary piston 8 and this is how the latter carries with it the body 9. The tool 16, linked to the secondary piston 15 which remains in the upper position in the chamber 12 is lowered until it comes into contact with the part 25 after having described an approach stroke C (indicated in FIG. 1).

When contact is established between the tool 16 and the part 25 (see FIG. 2), the body 9 and the tool 16 come to a standstill. By slightly increasing the force exerted on the rod 4, the pressure of the fluid in the chamber 10 increases and reaches a threshold such that the spring 32 of the valve 31 disappears and lets the fluid flow along the arrow 33 (Figure 3 ), through the interior of the valve 29, in the direction of the channel 11. This channel being connected to the expandable sleeve 19, the latter will swell and cause the axial immobilization of the body 9, to which it is linked, by compared to tube 2, therefore compared to frame 1.

Beyond a certain pressure threshold, a function of the setting of the spring 18, the secondary piston 15 is moved downwards in the chamber 12 of the body 9 which remains immobilized and it pushes the tool 16 against the part 25 to be pressed (see figure 3).

The section of the secondary piston 15 is such that the force F resulting from the pressure applied to this piston remains slightly less than the blocking force of the body 9 relative to the tube 2. This force F, due to the fact that the section of the secondary piston 15 is greater than that of the primary piston 8, will on the other hand be higher than the force applied to the rod 4 which is indeed the desired effect (obtaining a low working stroke with large developed force).

After having thus carried out the flattening operation, or the like, on the part 25, the rod 4 is brought up by a reverse rotation of the pinion 6. The primary piston 8, rising with the rod 4, causes a release of the pressure pressure on the secondary piston 15. The latter returns back into the chamber 12 under the upward return action exerted by the spring 18. Similarly, the drop in pressure inside the expandable sleeve 19 causes it to contract . The sleeve thus makes the body 9 free to move relative to the tube 2. The fluid flowing back from the sleeve 19 and from the chamber 12 of the secondary piston 15 lifts the valve 29 and thus passes around it in the direction of the next chamber 10 the path defined by the arrows 34 (Figure 4).

When the primary piston 8 reaches its upper position (Figure 1), the groove 26 which it comprises at its lower part communicates the chamber 10 and the chamber 35; in this way the smallest leak that could have occurred during the cycle described above is compensated for an arrival of fluid pushed by the movable bottom 22 and by its spring 23 out of the chamber 35, in the direction of the chamber 10.

In addition, the primary piston 8, thanks to the shoulder which it also has at its lower part, carries with it upwards the body 9 which thus returns to its starting position. The circulation of fluid from the sleeve 19 and the chamber 12 towards the chamber 10 being completed, the valve 29 returns to its rest position by closing the inlet of the channel 11. The device is thus ready to accomplish another work cycle.

According to a first variant represented by FIG. 5, the temporary connection between the primary piston 8 and the body 9 is made by means of a mechanical locking, with ball for example and constituted in this case by a ball 42 housed in a bore formed radially in the lower part of the piston 8 and also receiving a spring 43 which tends to push the ball 42 towards the outside of its housing.

In the high position of the piston 8, this ball 42 is partially housed in a groove 44 of an annular part 45 placed under the seal 14 and which is fixed relative to the body 9. After the approach phase during which, thanks to this locking, the rod 4 has driven the body 9, the latter being stopped, the ball 42 disappears in its housing, leaving the groove 44, and it leaves the piston 8 to put the hydraulic circuit under pressure according to the cycle previously described.

According to a second variant shown in FIG. 6, the displacement of the rod of the primary piston 8 is obtained by means of an additional piston 36, fixed to the upper part of the piston 8 and mounted to slide inside a cylinder 37 placed along the axis 3 in the upper region of the tube 2 which serves as a guide for the body 9 as well as a bearing surface for the expandable sleeve 19. This cylinder 37 is closed at its upper part by a cover 38.

The piston 36 is driven by a pneumatic or hydraulic fluid, admitted into the upper chamber of the cylinder 37 through an orifice 39 of the cover 38, and it is brought back to the rest position by a spring 40 housed in the lower chamber of the cylinder 37, or indeed by any fluid introduced into this same chamber through an orifice 41.

The assembly thus produced constitutes a rapidly advancing jack and multiplication of force at the end of the stroke, an important advantage of which is that, whatever the position of the piece to be pressed 25 relative to the frame 1 (within the limit of the stroke of the body 9), the final force exerted will be the same and will depend directly on the pressure of the control fluid acting on the piston 36.

According to a last embodiment described here, and shown in Figures 7 and 8, a tube 4 is connected to the body 9 by a thread 47, these two members being slidably mounted in a bore 2 of the frame 1. The body 9 is here immobilized in rotation relative to the frame 1, for example by means of a screw 48 engaged in a groove 49 of the body 9. The tube 4 can on the contrary turn autor of the axis 3, and it is maneuverable by means of a part 50 mounted at its top.

• - une bille 51 logée dans un alésage radial de la piè pièce 50;
• - une rainure interne 52 du tube 4;
• - un ressort 53 poussant la bille 51 dans la rainure 52;
• - un coulisseau 54 sur lequel prend appui le ressort 53;
• - une vis de réglage 55, parallèle à l'axe 3, et vissée dans la pièce 50, la pointe de cette vis 55 coopérant avec une face inclinée du coulisseau 54, pour comprimer plus ou moins le ressort 53.

This part 50 is linked in rotation with the tube 4 by a torque limiting device, which comprises:

• - a ball 51 housed in a radial bore of the workpiece part 50;
• - an internal groove 52 of the tube 4;
• - a spring 53 pushing the ball 51 in the groove 52;
• - A slide 54 on which the spring 53 is supported;
• - an adjustment screw 55, parallel to the axis 3, and screwed into the part 50, the tip of this screw 55 cooperating with an inclined face of the slide 54, to more or less compress the spring 53.

• En premier lieu, il décrit une translation, s'accompagnant d'une translation du corps 9 sur lequel il est provisoirement verrouillé, et amenant l'outil 16 en l'outil 16 en contact avec la pièce à presser 25. Cette première phase, correspondant à la course d'approche, ne diffère pas de ce qui a été déjà décrit plus haut.

The tube 4, constituting the control member, undergoes a displacement in two forms:

• Firstly, it describes a translation, accompanied by a translation of the body 9 on which it is provisionally locked, and bringing the tool 16 into the tool 16 in contact with the part to be pressed 25. This first phase, corresponding to the approach race, does not differ from what has already been described above.

In a second phase, the tube 4, maneuvered using the part 50, is rotated and therefore screwed onto the body 9, which remains immobilized in rotation. By this screwing, the tube 4 sinks into the bore 2 and it drives with it, downwards, the primary piston 8 secured to said tube. As before, the descent of the piston 8 in the hydraulic circuit increases the pressure in the latter and has the effect, on the one hand, of blocking the body 9 relative to the frame, by inflating the expandable bush 19, and on the other hand, to make the tool 16 move against the piece to be pressed 25. The torque limiting device, associated with the piece 50, makes it possible to limit the pressing force of the tool 16 on the piece 25.

This last embodiment allows, with a relatively low screwing torque, and exerted for example by hand, to obtain a force already amplified on the primary piston 8, by the effect of the thread 47, this force being in turn amplified by the secondary piston 15 pushing the tool 16.

The press mechanism described above finds applications in particular in the field of marking and riveting, and it can be controlled, depending on the energy sources available and the efforts to be made, by manual actuation means, mechanical hydraulic, pneumatic or others, acting on the rod 4. Other applications can be envisaged in the clamping field, where rapid advance, followed by a significant clamping force is often sought.

As is obvious, and as follows from the above, the invention is not limited to the sole embodiments of this press mechanism which have been described above, by way of examples.

Claims (9)

1. A hydraulic press mechanism providing successively a rapid approach stroke and a work stroke with a substantial developed stress, including a member (4) on which the control action of the device for said strokes is exerted, and a main body (9), which are movable along the same axis (3) in a fixed guiding bore (2), means (29 to 32; 42 to 45; 47) being providing for the non-permanent axial locking of the body (9) with respect to the control stem (4), the body (9) having a first chamber (10) filled with incompressible fluid into which penetrates a primary piston (8), being an extension of the control stem (4) along the axis (3) of the mechanism, this chamber (10) communicating, on the one hand, with an expansible casing (19) held axially immobile around the body (9) and adapted to be pressed against the wall of the bore (2), and in the other hand, with a second cylindrical chamber (12) in which a secondary piston (15) is slidably mounted, this latter being rigid with a rod (16) having the work tool provided for use in the mechanism, characterised in that the control member (4), which is rigid with the primary piston (8), is associated with means (5, 6; 36 to 41; 50 to 55) enabling its axial movement to be controlled in both directions from one end only of the device, in such a way as to constitute a single common control member for the approach stroke, the work stroke and the return stroke to the rest position.

2. A hydraulic press mechanism according to Claim 1, characterised in that the single control member, rigid with the primary piston (8), is a rod (4) provided with a rack (5) meshing with a drive pinion (6), the latter being monted on a shaft operated by a member such as a lever.

3. A hydraulic press mechanism according to Claim 1, characterised in that the single control member rigid with the primary piston (8),is a supplementary piston (36) slidably mounted in a cylinder (37) co-axial with the bore (2) in which the main body (9) slides, so as to constitute a pneumatic or hydraulic control cylinder.

4. A hydraulic press mechanism according to Claim 1, characterised in that the single control member, rigid with the primary piston (8), is a tube (4) slidably and rotatably mounted in the bore (2) in which the main body (9) slides, and connected by a thread (47) to this body (9), which is prevented from rotating by means (48,49), the approach stroke being produced by simultaneous translation of the tube (4) and the body (9), whilst the work stroke is produced by screwing the tube (4) on the body (9), the tube (4) having an operating member (50) preferably connected to the tube (4) by means of a torque limiting device (51 to 55).

5. A hydraulic press mechanism according to any one of Claims 1 to 4, characterised in that a return spring (18) is mounted in the cylindrical chamber (12) containing the secondary piston (15), and exerts its action on this secondary piston (15) in the opposite direction to the action of the incompressible fluid.

6. A hydraulic press mechanism according to any one of Claims 1 to 3, characterised in that the means for non-permanently locking the body (9) with respect to the single control member (4) and to the primary piston (8), include a calibrated valve (31) adapted to prevent the incompressible fluid leaving the first chamber (10) in the direction of the expansible casing (19) and the second chamber (12), i.e. that housing the secondary piston (15), and thus preventing the primary piston (8) from penetrating the first chamber (10).

7. A hydraulic press mechanism according to Claim 6, characterised in that a double valve (29, 31) is provided at the bottom of the first chamber (10), one of these valves (29), which permits the fluid to flow back from the expansible casing (19) and the second chamber (12), housing the other valve (31) which opposes flow towards the expansible casing (19) and the second chamber (12).

8. A hydraulic press mechanism according to any one of Claims 1 to 3, characterised in that the means for non-permanently locking the body (9) with respect to the single control member (4) and to the primary piston (8), include a ball (42) housed in the primary piston (8) and urged radially by resilient means (43), whilst the internal wall of the body (9) has an annular throat (44) adapted to receive the ball (42).

9. A hydraulic press mechanism according to any one of Claims 1 to 8, characterised in that the primary piston (8) has a longitudinal groove (26) at the end thereof which enters the fluid filled first chamber (10), such that, when the primary piston (8) is in a drawn back position, and only in this position, the groove (26) connects the first chamber (10) of the body (9) with a reserve (35) of hydraulic fluid delimited by the bore (2), in which the body (9) slides, and by a movable wall 22 in said bore (2), said wall being urged by a spring (23) to provide automatic compensation for variations in the volume of fluid.

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