NO972053L - Pneumatic cylinder device - Google Patents

Description

The present invention relates to a pneumatic cylinder device comprising a cylinder housing, means for supplying pressure fluid to the inside of the housing, a first piston which is movable in a first axial chamber located at the rear end of the cylinder housing and at least one second movable piston in a second axial chamber located in front of it first axial chamber. The device further comprises a dividing wall which separates the two axial chambers, and has an axial bore, and a connecting rod which connects the pistons to each other and is arranged to be displaced tightly in the bore. The rod has a bore that opens first into the first axial chamber behind the first piston, and then into the second axial chamber behind the second piston. The pistons are connected by an advance element located at the front of the cylinder housing. The means for supplying pressure fluid comprise a slide valve which is controlled by means of a control device for movement between a first position where the fluid is directed into at least one axial chamber behind the piston in the chamber to thereby force the advancing element forward, and a second position where the fluid is directed into at least one axial chamber in front of the piston in the chamber to thereby force the advancing element backwards.

A device of this kind is known from Swiss patent issued under No. 570,242. As an example, the advancing element may act to stamp or puncture parts, e.g. metal parts, by cooperating with a fixed element of suitable shape. Likewise, as in the patent issued in the US under No. 3,410,180, it can have a wedge-shaped head which, when advanced, grips the jaws in a clamp, forcing them in the closing direction, while on return it allows opening of the jaws. In this case, the device can be used for fastening turnbuckles or the like.

The advancing element is forced either forward or backward directly during operation of the fluid.

A device of this kind is widespread and must be able to be produced as cheaply as possible. Therefore, the fluid circuit, often a compressed air circuit, must be as simple as possible, without the need to create long channels with very precise dimensions. It should also be noted, particularly when it is desired to use such a device for tightening clamps, that it must be mounted in a very small space, such as the engine compartment of a vehicle.

The fluid circuit according to Swiss Patent No. 570,242 is quite complicated. It comprises a compressed air supply at the rear of the cylinder housing, three parallel channels that extend towards the front over a relatively large distance, two valves with slides that move in bores with conical valve seats, and a third valve with a slide that is movable in an axial bore. The number and arrangement of such parts is not compatible with making the arrangement compact and relatively cheap. In order for the device to be handled, with the cylinder housing held in the user's hand, the control device must extend into a central area of the cylinder housing. In order to make this requirement compatible with compressed air supply and with slide valves located at the rear of the cylinder housing, the control device according to the device described in Swiss patent no. 570,242 consists of a torque arm which is very long and space-consuming. This is a major disadvantage from a manufacturing cost point of view. It should also be noted that the larger the control element's area, the greater the risk that it will work inappropriately.

The present invention aims to improve the device of the above-mentioned kind, by eliminating the above-mentioned disadvantages.

This purpose is achieved by the partition wall having a transverse bore in which the slide of the slide valve is engaged, a first channel which connects the transverse bore with a pressure fluid supply, a second channel which connects the transverse bore with the rear part of the second axial chamber behind the second piston, and a third channel which connects the transverse bore with the front part of the first axial chamber in front of the first piston, the first and second channels being brought into communication with each other and isolated from the third channel when the slide of the slide valve is in the first position, while the first and third channels are brought into communication with each other and is isolated from the other channel when the slide is in its second position.

It should be understood that due to the invention the various channels can be machined in a very simple way in the partition wall, thereby enabling them with considerable limitation of the length of the channels. Moreover, this device makes it possible to use a single slide valve located in a single bore in which the different fluid flow channels open out in positions which are conveniently separated from each other. It should also be noted that the slide of the valve slide is located in the bore which is itself formed in the partition wall and automatically places the slide in a central area of the cylinder housing. Consequently, it is easier to place means for controlling the slide also in a central area, which makes it possible to reduce the length of the device.

This control device preferably comprises a torque arm which is arranged mainly transversely in relation to the cylinder housing and has a first end which is connected to the housing in the region of the partition wall and mounted to rotate about an axis of rotation which extends mainly axially, and a second end which is suitable for cooperating with a free end of the valve slide.

In this case, the length of the moment arm (measured axially) is very small as it is located directly in the area of the partition wall. The fact that the moment arm extends mainly transversely and that it is suitable for rotating about a pivot axis which extends mainly axially in relation to the housing of the cylinder device has the effect that it nevertheless becomes possible to give it a moment arm which is of sufficient length so that it can be easily operated. Moreover, this arrangement makes it possible to improve safety by giving the device a compact shape that reduces the risk of it catching and working in an inappropriate manner.

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

The description refers to the accompanying drawings, where:

• Figure 1 is an axial section through the device according to the invention, and shows the advancement element in its rear position,

• Figure 2 is a cross-section along the line I I-l I in Figure 1,

• Figure 3 is a ground plan of Figure 1,

• Figure 4 is a section similar to Figure 1, and shows the advancing element in its front position,

• Figure 5 is a fragmentary section along the line V-V in Figure 1, and

• Figure 6 is a fragmentary section, similar to Figure 5, along the line VI-VI in Figure 4.

Figures 1 to 4 show a pneumatic cylinder device comprising a cylinder housing 10. A first axial chamber 12 is formed in the cylinder housing, at its rear end, while a second axial chamber 14 is formed in the actuator housing, in front of the first chamber. Moreover, a third axial chamber 16 is formed in front of the second one.

First, second and third pistons, given reference numbers 18, 20 and 22 respectively, are arranged in the first, second and third axial chambers respectively, and are movable in these. These pistons are connected to each other by a rod. More specifically, the rod comprises a first connecting rod 24 which connects the pistons 18 and 20, and a second or "additional" connecting rod 26 which connects the pistons 20 and 22. The axial chambers 12 and 14 are separated by a partition wall 28 which has an axial bore 30 as the first connecting rod 24 is displaceably engaged in. To seal this displacement, a sealing ring 32 is arranged in a groove in the bore and this sealing ring interacts with the rod 24's outer circumference.

Likewise, a further partition wall 34 separates the chambers 14 and 16. It likewise has an axial bore, this time given the reference number 36, and in which the second connecting rod 26 is displaceably arranged. Displacement is sealed by means of a sealing ring 38 which is arranged in a groove in the bore 36.

The pistons are connected to a feed element 40 located at the front of the cylinder housing. More specifically, this advancing element is attached to the front end of the rod connecting the pistons, i.e. in the example shown at the front end 42 of the second connecting rod 26. To this end, the advancing element has threads 44 that cooperate with threads on the end 42 of the rod 26 .

In the example shown, the front end 40a of the advancing element 40 is wedge-shaped, i.e. it tapers forwards.

The support arms 46 are arranged at the front of the cylinder main part. These arms 46 are attached to the front end of the actuator main part by means of a fastening ring 48 which is designed with threads that cooperate with a thread on the front end of the actuator main part 10. The arms 46 carry support plates 50 which are arranged at a distance from each other. Two clamping arms 52 are mounted between the support plates. The front ends 52a of the clamping arms are designed as slopes. Their rear ends carry wheels 52b adapted to cooperate with the wedge-shaped advancing element. The middle parts of the clamp arms 52 are connected to the support plates via respective pivot axes 54. Spreader springs are arranged between the clamp arms near the pivot axes 54. When the feed element is in its rear position as shown in figure 1, the springs 56 will thus influence the arms so that their front ends are moved apart. When the advancing element is in its forward position, as shown in Figure 4, it will, on the other hand, cooperate with the wheels 52b to thereby spread the rear ends of the arms 52 apart and consequently bring their front ends 52a towards each other to thereby tighten a clamping bracket.

The rod 24 has an axial bore 60 which at its rear end 60a opens into the first axial chamber 12 behind the first piston 18, and which near its front end 60b opens into the second chamber 14 behind the second piston 20. In this regard, the bore 60 near its front end connected with a transverse hole 62 which * opens through the circumferential wall of the rod 24 behind the piston 20.

As the rod 24 is connected to a second rod 26, the axial bore 60 also opens out at its free front end 60b. The rod 26 also has an axial bore, given the reference number 64, the rear end of which is connected to the front end 60b of the first connecting rod 24's axial bore 60. The bore 64 also opens into the third axial chamber 16 behind the third piston 22. In this regard, it is connected by a transverse hole 66 which opens through the circumference of the second connecting rod 26, behind the second piston 22. Moreover, the front end 64b of the bore 64 is closed.

At the rear part of the cylinder main part 10, there is a coupling 67 designed to receive the end of a pipe for the supply of pressurized fluid, generally consisting of a hose for the supply of compressed air. The coupling is extended in the forward direction by a channel 68 which is located on the side of the valve housing and extends axially to the region of the partition wall 28. The length of this channel is thus somewhat greater than the length, i.e. the axial extent, of the first chamber 12. Together with the bores in the connecting rods, it is the only channel in the device according to the invention that must be relatively long.

The means for supplying pressurized fluid includes a slide valve which is shown in the sections according to Figures 2, 5 and 6. It should be noted that, for the sake of simplicity, the valve is not shown in full in Figures 1 and 4.

The valve slide 70 can be moved between a first position as shown in figures 4 and 6, where the fluid is led into at least one axial chamber behind the piston in the chamber, so that the advancing element 40 can be pushed forward, and a second position, as shown in figures 1, 2 and 5, where the fluid is led into at least one axial chamber in front of the piston in this chamber, whereby the advancing element 40 is pushed backwards.

The slide 70 is movable in a transverse bore 72 located in the partition wall 28 between the first and second axial chambers 12 and 14. As can be seen better from figure 2, the bore extends parallel to a diameter of the cylinder main part and is separated from the central bore 30 by the partition 28. In Figures 1 and 4, the bore 72 is shown without the slide 70.

The different fluid flow channels which are designed in the partition wall 28 will now be described. As can be seen from Figure 1, the wall has a first channel which connects the bore 72 with the pressurized fluid supply. More specifically, this first channel 75 has a first length 74 which is mainly radially connected to the front end of the channel 68 and extends to a plane P which is a plane of symmetry for the bore 72 parallel to the axis "A" of the cylinder main part. The sections, according to Figures 5 and 6 extend along this plane P. The first channel 75 has a second length 76 which extends parallel to the plane P and connects the first length 74 with the bore 72. To facilitate machining of this, the second includes length a part 78 which first opens into one of the ends of the partition 28 (the rear end) and which is then closed by means of a plug 80. The position where the channel 76 opens into the bore 72 is schematically shown in figure 2.

It appears from Figures 5 and 6 that the partition wall 28 has a second channel 82 which connects the transverse bore 72 with the rear part of the second axial chamber 14. This second channel 82 has a single axial length. Its rear end opens into the transverse bore 72 while its front end opens into the front end surface 28a of the partition wall 28, which also forms the rear end surface of the axial chamber 14. Regardless of the position of the second piston 20 in the chamber, the second channel 82 will therefore open out behind the second piston.

The partition wall 28 comprises a third channel 84 which connects the transverse bore 72 with the front part of the first axial chamber 12. Like the second channel 82, the third channel comprises a single axial length. Its front end opens into the transverse bore 72 while its rear end opens into the rear end surface 28b of the partition wall 28, which also forms the front end of the first axial chamber 12. Regardless of the position of the first piston 18 in the first axial chamber, the third channel 84 will consequently open in front of the piston.

The partition wall 28 is long enough to accommodate these different channels. Its length can e.g. be approx. two to three times the bore's 72 diameter.

The slide 70 comprises a mainly cylindrical main part 86 with two extended parts 88 and 90 provided with sealing rings and located at a distance from each other.

In the slide's first position as shown in figure 6, it appears that the first channel 75, and more precisely its length 76, is brought into connection with the second channel 82, while the third channel 84 is isolated. In the second position as shown in Figure 5, on the other hand, the first and third channels 75 and 84 are connected to each other, while the second channel 82 is isolated.

If the transverse bore 72 is followed from its opening 72a through which the slide's free end can project, to its end wall 72b, one will see that the third, first and second channels 84, 75 (76), and 82 are connected to the transverse bore 72 in the aforementioned order.

The mouths of these three channels in the borehole are arranged at regular intervals. The distance between the two extensions 88 and 90 on the slide's main part is slightly greater than the distance between two channels. As the slide thus moves towards the end of the bore, the channels 76 and 82 can be brought into communication with each other, as their mouth openings lie between the extensions 88 and 90, while the channel 84 is isolated from the other two because of the extension 90. When, on the other hand, the slide is at a distance from the end of the bore, the openings of the channels 84 and 76 lie between the extensions 88 and 90 and are therefore in communication with each other, while the opening of the channel 82 is isolated from the other two because of the extension 88.

The device works as follows. When the slide 70 is pushed towards the end

72b of the bore 72, which is possible because the air located in front of the expansion 88 can be expelled via the drain hole 92, the fluid flowing in via the channels 68,

74 and 76 flow into the rear part of the second chamber 14 via the second channel 82 in the partition wall 28. This fluid therefore seeks to force the second piston 20 forward. Likewise, the fluid flows via the hole 62 into the bore 60 in the rod 24 and is guided

thereby to the rear end of the first axial chamber 12, so that the fluid also works

on the rear end surface of the first piston 18. Likewise, the fluid that flows in via the hole 62 is led to the rear end surface of the third piston 22 via the bore 64 and the hole 66 in the further connecting rod 26, and thereby also acts on the rear end surface of the third piston 22. The fluid thus acts simultaneously on all three pistons, thereby increasing its efficiency.

It should be noted that the fluid drainage devices are arranged in the forward portions of the chambers which come into operation when the pistons have been fully pushed forward. For the first chamber 12, the channel 84 is brought into connection with the outside via a hole 94 through a ring 96 for controlling the rod 98 of the slide 70. For the chamber 14, the fluid located in the front part of the chamber is diverted directly through a hole 100 which is designed through the wall of the chamber, at its front end. Finally, the fluid located in the front part of the third chamber 16 can naturally flow out from the front part of the chamber, as no sealing system is arranged between the advancing element, the support arms 46, and the ring 48.

When, on the other hand, the slide 70 is pushed away from the end 72b of the bore 72, the position determined by the expansion 90 coming into contact with the ring 96 will enable air flowing in via the channels 68, 74 and 76 to flow into the front part of the first axial chamber 12 via the third channel 84 in the wall 28. The unit consisting of the pistons and their connecting rods thus becomes

forced backwards by the fluid acting on the front end surface of the first piston 18. At this point there is no need to increase the applied force by bringing the fluid to act on the other pistons. Since the rear portions of the chambers 12, 14 and 16 are in communication with each other via the bores in the piston rods, air expelled from the rear portions as the unit is forced backward flows into the rear portion of the second chamber 14 from where it can flow out to the outside via the second channel 82 in the partition wall 28 which is in direct connection with the atmosphere via the drain hole 92 when the slide is in its second position.

The device for controlling the slide valve comprises a torque arm 102 which is arranged mainly in the transverse direction. As is clear from figure 2, this torque arm 102 has a first end 102a which is connected to the cylinder main part 10 in the area of the partition wall 28. This first end 102a is mounted to rotate about a pivot axis 104 which is more clearly seen from figures 1 and 4, and which extends mainly parallel to the axis A of the valve body. The other end 102b of the torque arm 102 cooperates with the free end 99 of the slide 70.

It should be noted that this torque arm is directly connected to the partition wall 28 and is therefore only located in a central area of the cylinder housing. In order to keep the size of the device down, the partition has a transverse slot 29 in which the first end 102a of the torque arm is engaged. When the second end 102b of the torque arm is forced so that it pushes the slide 70 towards the end 72b of the bore, the torque arm 102 is almost completely engaged in the slot 29. In order to achieve a torque arm of sufficient length, the first and second ends of the torque arm in the example shown are relatively far apart. Thus, the torque arm extends over more than a quarter of the circumference of the cylinder housing. Consequently, this also applies to the slot 29, which occupies the essential part of the torque arm. As the torque arm is curved, so is the slot 29.

The device advantageously comprises an elastic device to force the slide 70 naturally to its second position where the advancing element is forced backwards. Thereby, the device's natural position will be the one where the clamping arms 52 are inactive, and the influence of these requires that the slide 70 be exposed to a positive influence, which influence ceases as soon as the torque arm is released. In the example shown, the elastic device consists only of a spring 106 which acts first against the inner end surface of the slide's extended free end 99, and then against the outer end surface of the control wing 96 which is fixed in the bore 72 and in which the slide rod 98 slides. It will also be possible to arrange other types of elastic devices, e.g. a coil spring which is optionally arranged between the end 72b of the bore and the slide's inner end located outside the extension 88.

The device advantageously includes means for damping the movement of at least one of the pistons towards the end of a displacement stroke, at least in one of the directions of movement of the advancing element. As the pistons are connected to each other by means of the connecting rods, such damping means will apply to the displacement of the entire unit consisting of the pistons, the piston rod and the advancing element.

In the example shown, the damping means are constituted by an extension 108 of the relatively flexible material, e.g. rubber or the like, which is formed on the rear end surface of the first piston 18. Thus, when the unit formed by the pistons and their connecting rod is forced backwards to the position according to Figure 1, the extension 108 will cooperate with the rear end surface of the first chamber 12.

It can also be ensured that the front end surface of one of the pistons, e.g. the rear piston is fitted with an extension of the same type to dampen forward displacement. In the example, the piston 18 comprises a metal core 18a and an outer ring 18b which is made of relatively flexible material, which surrounds the core, and equipped with the extensions. It is advantageous that the very forward position of the unit, which is determined by the forward element 40 being in its foremost position, is determined very accurately, so that the effective position of the slopes 52 can also be determined accurately. To this end, the device advantageously comprises first abutment means arranged in one of the axial chambers near their front end, and second abutment means arranged on the piston in the chamber, and near the front end face of the piston. The first and second impact means thus interact with each other when the unit consisting of the pistons, the piston rod and the advancing element is forced forward, thereby determining the unit's foremost position.

In the example shown, these impact means are very simple, as the first impact means are formed by the front end surface of the third chamber 16 which itself is formed by the rear ends 46b of the support arms 46, while the other impact means are formed by the front end surface 22a of the third piston 22. Of course, the impact means can be arranged in other axial chambers. In any case, the exact position of the arm 46 is determined by screw adjustment of the mounting ring 48. This makes it possible to determine the position of the first impact means accurately, while leaving room for adjustment.

In order to facilitate the displacement of the pistons and to avoid the risk of shaking, the device advantageously comprises at least one annular liner 110 which is arranged in the bore 30 in the partition wall 28, and which is made of a material with a low coefficient of friction. The liner can thus cooperate with the outer circumference of the connecting rod 24 and facilitate its displacement through the bore. A similar lining 112 can also be arranged in the bore 36 in the further dividing wall, if it exists. Of course, the use of liners does not exclude that sealing rings 32 and 38 can also be arranged in the bores.

The various main end surfaces of the pistons which cooperate with the axial walls of the chambers are equipped with piston rings 118, 120 and 122.

The front and rear ends of the connecting rods 24 and 26 cooperate in that they are screwed together. In order to fix the position of the pistons on the rods, the rear end surfaces of the pistons 20 and 22 are equipped with a set disc 24. The rear end of the connecting rod 24 is threaded. The rear end surface of the first piston 18 has a recess 126 adapted to receive a retaining nut 128 which is screwed onto the rear end of the rod. The position of the piston in relation to the rod is set by means of a setting disc 130 which is placed on the front of the piston and cooperates with a shoulder on the rod.

Finally, it should be noted that the cylinder housing comprises three main elements which are made up of blind pipes. The first tube 132 forms the first chamber 12. Its back and side walls comprise the channels for connecting the pressurized fluid supply. The cavity in 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 thus this wall which is equipped with the bore 72 and the various channels mentioned above. This wall is screwed to the front end of the first pipe 132. Likewise, the cavity in the third tube 136 forms the third axial chamber 16, while its back wall forms the partition wall 34 between the chambers 14 and 16. This back wall is screwed into the front end of the second tube 134. To ensure sealing of the chambers, sealing rings 138 are of course arranged near the screw connections between the various pipes.

Claims (8)

1. Pneumatic cylinder device comprising a cylinder housing (10), means for supplying pressure fluid to the inside of the housing, a first piston (18) which is movable in a first axial chamber (12) located at the rear end of the cylinder housing, and at least one second movable piston ( 20) in a second axial chamber (14) located in front of the first axial chamber, a partition wall (28) which separates the two axial chambers and has an axial bore (30), and a connecting rod (24) which connects the pistons (18, 20) and is aligned to be displaced in the bore, which rod has a bore (60) which opens first into the first axial chamber (12) behind the first piston (18), and then into the second axial chamber (14) of the second piston (20) , the pistons being connected to a feed element (40) located in the front part of the cylinder housing (10), the means for supplying pressurized fluid comprising a slide valve (70, 72) which is controlled by means of control means to move between a first position where the fluid is led in n in at least one axial chamber behind the piston in said chamber, whereby the advancing element is pushed forward, and a second position where the fluid is led into at least one axial chamber in front of the piston in said chamber, whereby the advancing element is pushed backwards, characterized in that the partition wall (28) has a transverse bore (72) which accommodates the slide of the slide valve (70), a first channel (74, 76) which connects the transverse bore with a pressurized fluid supply (66, 68), a second channel (82) which connects the transverse bore (72) with the rear part of the second axial chamber (14) behind the piston (10), and a third channel (84) which connects the transverse bore (72) with the front part of the first axial chamber (12) in front of the first piston (18), as it first and second channels (74, 76; 82) are connected to each other and isolated from the third channel (84) when the slide of the slide valve is in the first position, while the first and third channels (74, 76; 84) are connected with each other and are isolated from the second channel (82) when the slide is in its second position. 2. Device according to claim 1, characterized in that the means for controlling the slide valve (70, 72) comprise a control torque arm (102) which is arranged mainly in the transverse direction and comprises a first end (102a) which is connected to the cylinder housing (10) in the region of the partition (28) and mounted to rotate about a pivot axis (104) which extends substantially axially. and a second end (102b) adapted to cooperate with a free end (99) of the slide valve slide (70). 3. Device according to claim 1 or 2, characterized in that it comprises an elastic device (99) for pressing the slide valve's slide (70) naturally to its second position. 4. Device according to one of claims 1 to 3, characterized in that the transverse bore (72) comprises an end wall (72b) and an opening (72a) at a distance from the end wall, beyond which the free end of the slide of the slide valve is arranged to project, and that the third, first and second channels (84, 76, 82) are connected in sequence to the transverse bore (72) in the direction from the opening (72a) towards the end wall (72b) of the bore (72). 5. Device according to one of claims 1 to 4, characterized in that it comprises a device (108) for damping the movement of at least one of the pistons at the end of a displacement stroke, in at least one of the displacement directions of the advancing element. 6. Device according to one of claims 1 to 5, characterized in that it comprises a first stop device (46b) which is arranged in one (16) of the axial chambers (12, 14, 16) near its front end, and a second stop device (22a) arranged on the piston (22) located in the chamber near the front end surface of the piston, the first and second abutment means being arranged to cooperate to determine the outer position to which the advancing element (40) can be advanced. 7. Device according to one of claims 1 to 6, characterized in that it comprises at least one annular liner (110) which is arranged in the axial bore (30) in the partition wall, which liner is made of a material with a low coefficient of friction and which cooperates with the connecting rod (24). 8. Device according to one of claims 1 to 7, characterized in that it comprises a third piston (22) which is movable in a third axial chamber (16) located in front of the second axial chamber, a further dividing wall (34) which separates the second and third axial chambers (14, 16) and has an axial bore (36), as well as a further connecting rod (26) which connects a second and third piston (20, 22) and is arranged to seally move in the axial bore, a further connecting rod being a bore (64) which is connected to the bore (60) ) in the connecting rod (24) between the first and second piston (18, 20) and opens into the third axial chamber (16) behind the third piston.