DE69702683T2 - Pneumatically operated device - Google Patents

Description

The present invention relates to a pneumatic cylinder device comprising a cylinder body, means for supplying a fluid under pressure to the interior of this body, a first movable piston in a first axial chamber provided in the rear part of the cylinder body and at least one second movable piston in a second axial chamber located in front of the first axial chamber. The device also comprises a wall for separating the two axial chambers, which has an axial bore, and a rod for connecting the pistons, which can slide in a sealed manner in this bore. This rod has a through-bore which opens on the one hand into the first axial chamber behind the first piston and on the other hand into the second axial chamber behind the second piston. The pistons are connected to a feed member provided in the front part of the cylinder body. The means for supplying the pressurized fluid comprise a slide valve which is controlled by control means between a first position in which the fluid is directed into at least one axial chamber behind the piston provided in this chamber in order to bias the advance member forwards, and a second position in which the fluid is directed into at least one axial chamber in front of the piston provided in this chamber in order to bias the advance member backwards.

A device of this type is known from the patent granted in the USA under No. 3,485,141. The feed member can be used, for example, to stamp or punch workpieces, for example metal pieces, by interacting with a fixed member of a corresponding shape. It can also, as in the case of the patent granted in the USA under No. 3,410,180, carry a wedge-shaped head which, during the feed, forces the jaws of a pair of pliers in the direction of closing them, while during the return movement it allows these jaws to open. In this case, the device can be used to hook clamps or the like.

The feed element can therefore be loaded either forwards or backwards directly under the action of the fluid. A device of this type for frequent use should be able to be manufactured at as reasonable a price as possible. The circulation circuit of the fluid, often compressed air, must therefore be as simple as possible, without the need for long, precisely dimensioned pipes. It should also be noted that if such a device is desired, in particular for clamping clamping bands, it must be handled in a very confined space such as a vehicle engine.

The fluid circulation circuit from Swiss Patent No. 570.242 is quite complicated. It has an inlet for compressed air in the rear part of the cylinder body, three parallel channels extending forward over a relatively significant length, two slide valves that are movable in bores with conical valve seats, and a third slide valve that is movable in an axial bore. The number of these parts and their arrangement is incompatible with the realization of the device at a relatively moderate cost and in a limited space. In order to enable the device, the cylinder body of which is held in the user's hand, to be operated, it is necessary for the control means to extend in a central area of the cylinder body. In order to reconcile this requirement with an inlet for pressurized medium and the slide valves arranged in the rear part of the cylinder body, the control means of the device described in Swiss Patent No. 570.242 are formed by a very long lever that requires a lot of space. This is clearly a disadvantage from the point of view of manufacturing costs. It should also be noted that the larger the surface of the control element, the greater the risk of unintentional actuation.

The present invention proposes an improvement of the device of the aforementioned type while eliminating the above-mentioned disadvantages.

This aim is achieved in that the partition wall has a transverse bore in which the slide of the slide valve is provided, a first line connecting the transverse bore to an inlet for pressurized fluid, a second line connecting the transverse bore to the rear region of the second axial chamber behind the second piston, and a third line connecting the transverse bore to the front region of the first axial chamber in front of the first piston, wherein in the first position of the slide valve the first and second lines are connected and separated from the third line, whereas in the second position of this valve the first and third lines are connected and separated from the second line.

It is understandable that, thanks to the invention, the various lines can be incorporated in the partition in a very simple manner, thereby making it possible to reduce its length considerably. In addition, this arrangement makes it possible to use only a single slide valve, which is arranged in a single bore into which various fluid circulation lines open at sensibly distributed points. It should also be noted that, due to the fact that the slide of the slide valve is located in the bore which is itself provided in the partition, this slide is already located in a central area of the cylinder body. It is therefore easier to also arrange the control means of this slide in a central area, thereby making it possible to reduce its length.

Preferably, these control means comprise a lever arranged substantially transversely to the cylinder body, which has a first end connected to this body in the region of the partition and mounted so as to pivot about a substantially axially directed pivot axis, and a second end suitable for cooperating with a free end of the slide of the valve.

The length of the lever (measured axially) is greatly reduced because it is located directly in the area of the partition wall. Because this lever is essentially aligned transversely ated and can be set in a pivoting movement about an axis directed essentially axially to the cylinder body, it is possible to equip the latter with a lever arm sufficient for easy operation. In addition, this arrangement makes it possible to increase safety by giving the whole a compact shape which limits the risks of jamming and accidental operation.

The invention will be better understood and its advantages will appear more clearly from the following detailed description of an embodiment given as a non-limiting example.

In the description reference is made to the attached drawings in which:

- Fig. 1 is an axial sectional view of a device according to the invention and shows the feed member in its rear position,

- Fig. 2 is a cross-sectional view along the line II-II of Fig. 1,

- Fig. 3 is a plan view of Fig. 1,

- Fig. 4 is a section analogous to Fig. 1 and shows the feed member in the front position.

- Fig. 5 is a partial section along the line V-V of Fig. 1 and

- Fig. 6 is a partial section along the line VI-VI of Fig. 4, analogous to Fig. 5.

Figures 1 to 4 show a pneumatic cylinder device with a cylinder body 10. A first axial chamber 12 is provided in this cylinder body in the rear part of the same, while a second axial chamber 14 is provided in front of the first in the cylinder body. In addition, a third axial chamber 16 is provided in front of the second.

A first, a second and a third piston, designated by the reference numerals 18, 20 and 22 respectively, are arranged in and movable in the first, second and third axial chambers respectively. These pistons are connected to each other by a rod. More precisely, this rod comprises a first connecting rod 24 which connects the pistons 18 and 20, and a second connecting rod 26 or "additional connecting rod" connecting the pistons 20 and 22. The axial chambers 12 and 14 are separated by a partition 28 which has an axial bore 30 in which the first connecting rod 24 slides. To make this sliding movement tight, a seal 32 is arranged in a groove of this bore and cooperates with the outer circumference of the rod 24.

Likewise, an additional partition wall 34 separates the chambers 14 and 16. It also has an axial bore, this time designated by the reference numeral 36, in which the second connecting rod 26 slides. The sliding movement is sealed by a seal 38, which is arranged in a bore groove 36.

The pistons are connected to a feed member 40, which is provided in the front part of the cylinder body. More precisely, this feed member is fixed to the front end of the rod connecting these pistons, i.e. in the example shown, to the front end 42 of the second connecting rod 26. For this purpose, the feed member has an internal thread 44 which cooperates with the threaded end 42 of the rod 26.

In the example shown, the front end 40a of the feed element 40 is wedge-shaped, i.e. it is widened towards the rear.

Support arms 46 are arranged on the front part of the cylinder body. These arms 46 are fastened to the front end of the cylinder body by means of a fastening ring 48 which is provided with an internal thread which interacts with an external thread of the front end of the cylinder body 10. These arms 46 carry holding plates 50 arranged at a distance from one another. Two gripper arms 52 are mounted between these holding plates. Their front ends 52a are designed in the form of clamping jaws. Their rear ends in turn have rollers 52b which can interact with the wedge-shaped feed element. The middle part of the gripper arms 52 is each connected to the holding plates via a pivot axis 54. Spreading springs 56 are arranged inside the gripper arms in the region of the axes 54. Thus, when the feed member is in its rear position, as in the case of Fig. 1, the springs 56 load the arms so that their front ends are spaced apart. On the other hand, when the feed member is in its front position, as in the case of Fig. 4, it cooperates with the rollers 52b to move the rear ends of the arms 52 apart and consequently to bring their front ends 52a closer together, which are then able to clamp a clamping band.

The rod 24 has an axial through-bore 60 which opens with its rear end 60a into the first axial chamber 12 behind the first piston 18 and which opens near its front end 60b into the second chamber 14 behind the second piston 20. For this purpose, the through-bore 60 is connected near its front end to a transverse through-bore 62 which opens on the axial peripheral wall of the rod 24 behind the piston 20.

Since the rod 24 is connected to a second rod 26, the axial through-bore 60 also opens at the free front end 60b. The rod 26 in turn also has an axial through-bore, which is designated by the reference numeral 64 and is connected at its rear end to the front end 60b of the axial through-bore 60 of the first connecting rod 24. The through-bore 64 also opens into the third axial chamber 16 behind the third piston 22. For this purpose, it is connected to a transverse line 66 which opens at the axial circumference of the second connecting rod 26 behind the third piston 22. The front end 64b of the through-bore 64 is also closed.

At the rear of the cylinder body 10 there is a branch connection 67 for receiving the end of a pipe for supplying a fluid under pressure, which generally consists of a flexible supply line for compressed air. This branch connection is extended towards the front by a line 68 which is arranged on the side of the cylinder body and extends axially into the area of the partition wall 28. The length of this line is therefore slightly greater than the length, ie the axial dimension of the first chamber 12. With the holes of the connecting rods, this is the only line of the device according to the invention which is relatively long.

The means for supplying the pressurized fluid comprise a slide valve, which is visible in the sectional views of Figures 2, 5 and 6. It should be noted that, in order to simplify the drawings, this valve is not shown in its entirety in Figures 1 and 4.

The slide 70 of the valve can be actuated into a first position, namely that of Figs. 4 and 6, in which the fluid is directed into at least one axial chamber behind the piston located in this chamber, whereby the feed member 40 can be loaded forwards. The slide can also be actuated into a second position, namely that of Figs. 1, 2 and 5, in which the fluid is directed into at least one axial chamber in front of the piston located in this chamber, so that the feed member 40 is loaded rearwards.

The slide 70 is movable in a transverse bore 72 provided in the partition 28 between the first and second axial chambers 12 and 14. As can be better seen in Fig. 2, the bore extends parallel to a diameter of the cylinder body and is separated from the central bore 30 of the partition 28. In Figs. 1 and 4, only the bore 72 is shown without the slide 70.

The various fluid circulation lines provided in the partition 28 will now be described. As can be seen from Fig. 1, the latter comprises, first of all, a first line connecting the bore 72 to the pressurized fluid supply line. More precisely, this first line 75 comprises a substantially radial first portion 74 connected to the front end of the line 68 and extending to a plane P which represents a plane of symmetry of the bore 72 parallel to the axis "A" of the cylinder body. It is precisely in this plane P that the sections of Figs. 5 and 6 are made. The first line 75 comprises a second portion 76 which parallel to this plane P and connects the first section 74 with the bore 72. For the purpose of easier machining, this second section has a part 78 which originally opened at one of the ends (the rear end) of the partition 28 and is closed by means of a plug 80. The opening position of the line 76 in the bore 72 is indicated schematically in Fig. 2.

With reference to Figures 5 and 6, it can be seen that the partition 28 has a second duct 82 connecting the transverse bore 72 to the rear part of the second axial chamber 14. This second duct 82 has a single axial section. Its rear end opens into the transverse bore 72, while its front end opens into the front face 28a of the partition 28, which also forms the rear face of the axial chamber 14. Regardless of the position of the second piston 20 inside this chamber, the second duct 82 therefore opens behind this second piston.

The partition 28 has a third duct 84 which connects the transverse bore 72 to the front part of the first axial chamber 12. Like the second duct 82, the third duct also has a single axial section. Its front end opens into the transverse bore 72, while its rear end opens into the rear face 28b of the partition 28, which also forms the front end of the first axial chamber 12. As a result, the third duct 84 opens in front of the first piston 18 inside the first axial chamber, regardless of the position of the first piston 18.

The partition 28 is long enough to accommodate these various lines. Its length is, for example, in the order of two to three times the diameter of the bore 72.

The slider 70 comprises a substantially cylindrical body 86 having two beaded zones 88 and 90 provided with seals and spaced apart from one another.

In the first position of the slide, which is shown in Fig. 6, it can be seen that the first line 75, more precisely its section 76, is connected to the second line 82 is connected while the third line 84 is disconnected. In contrast, in the second position shown in Fig. 5, the first and third lines 75 and 84 are connected while the second line 82 is disconnected.

Indeed, if one looks at the transverse bore 72 from its opening 72a, from which the free end of the slide can protrude, to its bottom 72b, one can see that the third, first and second lines 84, 75 (76) and 82 are connected in succession to the transverse bore 72.

The openings of these three lines in the bore are provided at regular intervals. The distance between the two beads 88 and 90 of the valve body is very slightly greater than the distance between two lines. If the valve is now pushed forward towards the bottom of the bore, the lines 76 and 82 can be brought into communication because their openings are located between the beads 88 and 90, while the line 84 is separated from the other two by the bead 90. If, on the other hand, the valve is moved away from the bottom of the bore, the openings of the lines 84 and 76 are located between the beads 88 and 90 and thus communicate with each other, while the opening of the line 82 is separated from the other two by the bead 88.

The function of the device is as follows. When the slide 70 is pushed towards the bottom 72b of the bore 72, which is possible because the air in front of the bead 88 can be pushed out via the vent opening 92, the fluid entering via the lines 68, 74 and 76 can reach the rear part of the second chamber 14 via the second line 82 of the partition 28. This fluid is intended to push the second piston 20 back forwards. At the same time, the fluid penetrates via the bore 62 into the bore 60 of the rod 24 and is thus guided to the rear part of the first axial chamber 12, so that its effect is also exerted on the rear part of the first piston 18. Likewise, the fluid entering via the bore 62 is guided through the bores 64 and 66 of the additional connecting rod 26 to behind the third piston 22, so that its effect is also exerted on the rear surface of the third piston 22. The action of the fluid is thus exerted on the three pistons simultaneously, which is why its effectiveness is increased.

It should be noted that means are provided for evacuating the fluid present in the front part of the chambers when the pistons are pushed back forwards. As regards the first chamber 12, the duct 84 is connected to the outside via a hole 94 provided on the guide ring 96 of the rod 98 of the slide 70. As regards the chamber 14, the fluid present in the front part of this chamber is evacuated directly via a hole 100 provided in the wall of this chamber at the front end thereof. Finally, the fluid present in the front part of the third chamber 16 can of course be evacuated upstream of this chamber, since no sealing system is provided between the advancement member, the support arms 46 and the ring 48.

On the other hand, when the slide 70 is pushed back so that it moves away from the bottom 72b of the bore 72, which position is determined by the abutment-like interaction of the bead 90 and the ring 96, the air entering through the ducts 68, 74 and 76 can enter the front part of the first axial chamber 12 through the third duct 84 of the wall 28. The group formed by the pistons and their connecting rods is thus displaced rearwards by the fluid applied to the front of the first piston 18. It is not necessary to reinforce the effect achieved by applying fluid to the other pistons. Since the rear parts of the chambers 12, 14 and 16 communicate with each other via the bores of the piston rods, the air displaced into these rear parts when the group is pushed back is again in the rear part of the second chamber 14 and can be displaced outwards via the second line 82 of the partition 28 which, when the slide is in its second position, is directly connected to the outside air via the vent opening 92.

The control means of the slide valve comprise a control lever 102 mounted substantially transversely. As can be better seen in Fig. 2, this lever 102 has a first end 102a connected to the cylinder body 10 in the region of the partition 28. This first end 102a is mounted so as to pivot about a pivot axis 104, which can be better seen in Figs. 1 and 4, which are directed substantially along the axis A of the cylinder body. The second end 102b of the lever 102 cooperates with the free end 99 of the slide 70.

It should be noted that this lever is directly connected to the partition 28 and is consequently located only in a central area of the cylinder body. In an effort to limit the space required by the device, the partition has a transverse slot 29 in which the first end 102a of the lever is housed. When the second end 102b of the lever is pressed so that the slide 70 is again displaced towards the bottom 72b of the bore, the lever 102 is almost entirely housed in the slot 29. In the example shown, the first and second ends of the lever are at a relative distance from each other to provide a sufficient lever arm. Thus, the lever extends over more than a quarter of the circumference of the cylinder body. This is also the case in the case of the slot 29, which houses most of it. Since the lever is angled, so is the slot 29.

The device advantageously comprises elastic means for naturally biasing the slider 70 towards its second position in which the advancement member is displaced backwards. This makes it possible to proceed in such a way that the natural position of the device is that in which the pliers arms 52 are inactive and their actuation requires a positive action on the slider 70, which action ceases as soon as the lever is stopped being actuated. In the example shown, these elastic means are formed by a simple spring 106 which is mounted on the one hand on the inside of the widened free end 99 of the slide and, on the other hand, on the outside of the guide ring 96 fixed in the bore 72 in which the rod 98 of the slide slides. Other types of elastic means could also be provided, for example a helical spring, possibly arranged between the bottom 72b of the bore and the inner end of the slide located on this side of the bead 88.

The device advantageously has means for damping the movement of at least one of the pistons at the end of the displacement stroke in at least one of the displacement directions of the feed member. Since the pistons are connected to one another by the connecting rods, these means dampen the displacement of the assembly consisting of the piston, rod and feed member.

In the example shown, these damping means are formed by a bead 108 made of relatively flexible material, for example of the rubber type or similar, which is attached to the back of the first piston 18. When the assembly consisting of the piston and the connecting rod is moved backwards into the position shown in Fig. 1, this bead 108 therefore cooperates with the back of the first chamber 12.

It may also be provided to provide the front face of one of the pistons, for example the rear piston again, with a bead of the same type to cushion the forward movement. In the example shown, the piston 18 in fact comprises a metal core 18a and an outer ring 18b made of relatively flexible material surrounding this core and provided with beads. It is advantageous for the maximum advance position of the assembly, which clearly defines the front end position of the advance member 40, to be very precisely defined so that the active position of the jaws 52a is also precisely defined. From this point of view, the device advantageously comprises first stop means provided in one of the axial chambers near its front end and second stop means provided on the piston located on this chamber near the front surface of this piston. Thus, when the assembly consisting of piston, connecting rod and feed member is pushed forward, the first and second stop means act together to determine the maximum feed position of this assembly.

In the example shown, these stop means are very simple, since the first stop means are formed by the front face of the third chamber 16, which front face is itself formed by the rear ends 46b of the support arms 46, while the second stop means are formed by the front face 22a of the third piston 22. It can obviously be provided to realize these stop means in another axial chamber. The exact position of the arms 46 is however determined by screwing in the mounting ring 48. This makes it possible to define the position of the first stop means precisely, by providing a possibility of adjustment.

In order to simplify the sliding movement of the pistons and to avoid any risk of jerking, the device advantageously comprises at least one annular bearing bush 110 provided in the axial bore 30 of the partition 28 and made of a material with a low coefficient of friction. This bearing bush can thus cooperate with the external periphery of the connecting rod 24 and thus facilitate the sliding of the latter in the bore. A similar bearing bush 112 is also provided in the bore 36 of the additional partition, if one is present. Of course, the provision of these bearing bushes does not preclude the installation of seals 32 and 38 in the bores.

The peripheral surfaces of the various pistons which interact with the axial walls of the chambers are provided with seals 118, 120 and 122. The front and rear ends of the connecting rods 24 and 26 interact by means of a screw connection. In order to fix the pistons on these rods, washers 124 are provided on the rear side of the pistons 20 and 22. The rear end of the connecting rod 24 is threaded. The rear side of the first Piston 18 has a recess 126 for receiving a fastening nut 128 which is screwed onto the rear end of the rod. The position of the piston with respect to the rod is fixed by means of a washer 130 arranged on the front side of this piston and cooperating with a shoulder of the rod.

Finally, it should be noted that the cylinder body comprises three main elements formed by blind tubes. The first tube 132 defines the first chamber 12. Its rear and side walls comprise the branch lines for the entry of fluid under pressure. The cavity of the second tube 134 forms the second axial chamber 14. The rear wall of this tube forms the partition between the chambers 12 and 14. It is therefore precisely this wall that is provided with the bore 72 and the various tubes mentioned above. This wall is connected by screwing to the front end of the first tube 132. Likewise, the cavity of the third tube 136 forms the third axial chamber 16, while its rear wall forms the partition 34 between the chambers 14 and 16. This rear wall is screwed to the front end of the second tube 134. Of course, seals 138 are arranged in the screw connection zone between the various pipes to guarantee the tightness of the chambers.

Claims (8)

1. Pneumatic cylinder device comprising a cylinder body (10), means for supplying a fluid under pressure to the interior of the body, a first movable piston (18) in a first axial chamber (12) provided in the rear part of the cylinder body and at least one second movable piston (20) in a second axial chamber (14) located in front of the first axial chamber, the device further comprising a wall (28) for separating the two axial chambers, which has an axial bore (30), and a rod (24) for connecting the pistons (18, 20) which can slide in a sealed manner in this bore, this rod having a through-bore (60) which opens on the one hand into the first axial chamber (12) behind the first piston (18) and on the other hand into the second axial chamber (14) behind the second piston (20), the pistons being connected to a feed member (40) provided in the front part of the cylinder body (10), the means for supplying the pressurized fluid comprise a slide valve (70, 72) which is controlled by control means between a first position in which the fluid is directed into at least one axial chamber behind the piston provided in this chamber in order to load the feed member forwards, and a second position in which the fluid is directed into at least one axial chamber in front of the piston provided in this chamber in order to load the feed member backwards, characterized in that the partition (28) comprises a transverse bore (72) in which the slide of the slide valve (70) is provided, a first line (74, 76) connecting the transverse bore (72) to an inlet of the pressurized fluid (67, 68), a second line (82) connecting the transverse bore (72) to the rear region of the second axial chamber (14) behind the second piston (20), and a third line (84) connecting the transverse bore (72) to the front region of the first axial chamber (12) in front of the first piston (18), wherein in the first position of the slide (70) of the slide valve, the first and second lines (74, 76; 82) are in communication and separated from the third line (84), whereas in the second position of this slide the first and third lines (74, 76; 84) are connected and separated from the second line (82). 2. Device according to claim 1, characterized in that the control means of the slide valve (70, 72) comprise a substantially transversely mounted control lever (102) having a first end (102a) connected to the cylinder body (10) in the region of the partition (28) and pivotally mounted about a substantially axially directed pivot axis (104), and a second end (102b) suitable for cooperating with a free end (99) of the slide (70) of the slide valve. 3. Device according to claim 1 or 2, characterized in that it comprises elastic means (99) for naturally biasing the slide (70) of the slide valve into its second position. 4. Device according to one of claims 1 to 3, characterized in that the transverse bore (72) has a bottom (72b) and an opening (72a) opposite this bottom, from which the free end of the slide (70) of the slide valve can protrude, and in that the third, first and second lines (84, 76, 82) are connected one after the other to the transverse bore (72) in the direction from the opening (72a) to the bottom (72b) of this bore (72). 5. Device according to one of claims 1 to 4, characterized in that it comprises means (108) for damping the movement of at least one of the pistons at the end of the displacement in at least one of the displacement directions of the feed member. 6. Device according to one of claims 1 to 5, characterized in that it comprises first stop means (46b) provided in one (16) of the axial chambers (12, 14, 16) near its front end and second stop means (22a) provided on the piston (22) in this chamber near its front surface, the first and second stop means being able to cooperate with one another to define the extreme advance position of the advance member (40). 7. Device according to one of claims 1 to 6, characterized in that it comprises at least one in the axial bore (30) has an annular bearing bush (110) made of a material with a low coefficient of friction and cooperating with the connecting shaft (24). 8. Device according to one of claims 1 to 7, characterized in that it comprises a third movable piston (22) in a third axial chamber (16) located in front of the second axial chamber, an additional partition (34) separating the second and third axial chambers (14, 16) and having an axial bore (36), and an additional connecting rod (26) connecting the second and third pistons (20, 22) to one another and being able to slide in a sealed manner in this axial bore, this additional connecting rod having a through-bore (64) connected to the through-bore (60) of the connecting rod (24) of the first and second pistons (18, 20) and opening into the third axial chamber (16) behind the third piston.