Socket-and-locknut head for hydraulic cylinder

Abstract

 ©7 A hydraulic, pneumatic, oleodynamic cylinder or the like, comprises a tubular liner (1) defining a chamber closed by end heads (2); the liner (1), in correspondence with its end portions, presents an annular shoulder element which fits into a centering seat in the side wall (5) of the head (2) and a threaded locknut (8) is screwed against the annular shoulder element of the liner (1) and inside the wall (5) of the head (2).

Description

[0001] This invention refers.to a hydraulic or pneumatic cylinder or the like, with head-locking device, of the type comprising a tubular liner defining a cylindrical chamber closed by two lateral heads mechanically secured to the liner itself. There are known hydraulic, pneumatic, oleodynemic or similar cylinders, of the aforementioned type, in which the extreme heads of the cylinder are mechanically secured to the intermediate liner by means of stay rods arranged outside and parallel to the axis of the cylinder itself. There are also equally known cylinders whose heads are screwed directly onto the threaded ends of the liner, or welded to the liner.

[0002] The methods of assembling the heads in the known cylinders, present a number of problems and in particular do not offer satisfactory operating reliability - fluid seal - or extreme simplicity in construction and assembling; in fact, their setting, during construction and assembling calls for specialized personnel provided with sophisticated equipments. In particular, the use of stay rods calls for rectangular-shaped heads which must be machined and drilled at the corners in order to allow the passage of the stay rods themselves with subsequent longer production times and higher manufacturing costs; the stay rods are moreover,subjected tti different degrees of elongation which present the correct assembling of the heads and their precise axial positioning.

[0003] The use of heads screwed directly onto the ends of the liner, apart from calling for the machining of the latter in order to form the thread, also rarely enables the correct axial positioning of the heads and, consequently, the precise length of the cylinder, in relation to the piston stroke, due to the fact that the axial positioning of the heads depends both upon the pitch of the thread and upon the correct tightening of the head.

[0004] The use of welding, besides calling for the use of particularly sophisticated machines, very often gives rise to the distortion of the lining and the impossibility of disassembling the cylinder. Moreover, the correct axial positioning of the heads, in relation to the piston stroke, becomes even more critical; just consider that for cylinders operating at high pressures of over 200 Atm, a difference of a few tenths of a millimeter is not allowed.

[0005] Lastly, a problem common to all types of known cylinders, which causes considerable difficulty when fitting the cylinder onto any type of power-consuming machine, consists in the impossibility of orientating the heads in different directions, once assembled, in order to adapt the position of the fluid inlets to the feeding ducts which are usually rigid and have pre-established positions. Moreover, in known cylinders, operating at low pressures, the cylinder liner consists of a simple tube of limited thickness, which is subject to stress which causes it to become oval during the machining and assembling of the cylinder itself..

[0006] 'A scope of the invention is to provide a hydraulic, pneumatic,oleodynamic cylinder or the like, provided with a device for securing the heads to the liner, in order to overcome the aforementioned problems and, in particular, to ensure a high degree of operational reliability together with extreme structural and assembling simplicity.

[0007] A further scope of the invention is to provide a hydraulic, or pneumatic cylinder or the like, as described above, in which the same means for assembling and securing the heads to the liner, act as stiffening elements and prevent the ovalization of the liner itself.

[0008] A still further scope of the invention is to provide a cylinder, as described, in which the heads can be rotated with respect to the liner, in order to align the fluid inlets precisely with the feeding ducts, and can then be locked in the desired position, thereby ensuring the perfect alignment and correct axial positioning of the heads.

[0009] According to the invention, a hydraulic, pneumatic, oleodynamic or similar cylinder is thus provided, with a device for locking the heads, said cylinder comprising a tubular liner defining a chamber closed by end heads mechanically secured to the liner itself, characterized by the fact that the locking device comprises an annular shoulder element on the outside of each cylindrical end of the liner and a locknut which is screwed against said annular shoulder element and on the inside of a peripheral wall of the closing head; said annular shoulder element of the liner and said peripheral wall of the locknut presenting opposing flat surfaces for the axial positioning of the head and coaxial cylindrical surfaces for centering the head with respect to the liner itself.

[0010] Some embodiments of the invention will be described hereunder with reference to the accomanying drawings in which:

Fig.l. shows an exploded view of one half of a cylinder according to a first embodiment;

Fig.2. shows a cross-sectional view similar to that of the previous figure, but with the parts assembled;

Fig. 3. shows a partial cross-section of a second embodiment;

Fig. 4. shows a partial cross-section of a third embodiment.

[0011] The first embodiment of the invention will now be described, with reference to figures 1 and 2. As shown, the cylinder substantially comprises a tubular liner 1 the ends of which are closed by a respective head 2 into which tightly penetrates the corresponding end of the liner 1. In particular, as shown in the example in figure 1, each end of the liner 1 ends with a cylindrical portion la which extends with a portion 1b, with respect to an annular shoulder element acting as an axial stop for the head 2 and as a centering element for the head itself.

[0012] The annular shoulder element 3, as shown, is designed to enter a circular seat 4 provided inside a peripheral wall 5 of the head, which extends from the end wall 6.

[0013] Both the annular element 3 of the liner and the annular seat 4 in the head present opposing flat shoulder surfaces 3a, 4a arranged at right-angles to the axis of the cylinder, in order to ensure th the correct axial positioning of the parts, and also comprise cylindrical surfaces 3b, 4b, coaxial to the cylinder, in order to achive and maintain a perfect centering or coaxial alignment of the head 2 with respect to the liner 1.

[0014] In this example, the annular shoulder 3 on the liner is integral with the body of the liner and in a slightly retracted position with respect to the extreme edge of the liner itself; in this way the cylindrical extension 1b of the liner penetrated into a corresponding seat7 inside and close to the end wall of the head, in such a way that by making the extension 1b and the seat 7 with equal diameters, barring machining allowances, an additional centering effect is achieved between the liner 1 and the head 2. Consequently, due to the particular shape of the locking device according to the invention, it is possible to keep the axial length of the cylindrical extension 1b of the liner slightly shorter than the axial length or depth of the seat 7 so that the end of the liner does not strike against the end wall 6. of the head. This not only makes the correct assembly of the parts very much easier, but also their construction due to the fact that it is not necessary to keep to precise machining tolerances.

[0015] Reference 8 indicates a locknut fitted on the corresponding end of the liner 1, which can be screwed on the inside of the cylindrical wall 5 of the head, to tighten it against the annular shoulder 3 of the liner itself. Consequently, the open end of the cylindrical wall 5 of the head 2 is provided with an internally threaded seat 9, into which is screwed the externally threaded body 8a of the locknut 8, as shown; the locknut 8 also presents a rear flange 8b provided with notches to enable it to be gripped with a normal wrench.

[0016] The enable the locknut 8 to be fitted onto the cylindrical end la of the liner, it is necessary for its internal diameter to be larger than the external diameter of the annular shoulder 3 of the liner.

[0017] In the case of figures 1 and 2, the head 2 is locked to the liner 1 by means of the interposition of a split ring 10 between the locknut 8 and the annular shoulder 3. This intermediate ring 10 is made elaxtically deformable in a radial direction by means of a crosswire cut 10a to allow it to cross over the annular shoulder 3 on the liner during assembly..

[0018] The intermediate thrust ring 10 may present a cross-section of any shape whatsoever, however this ring advantageously presents an L-shaped cross-section so as to define a collar 11 which penetrates into the locknut 8 in such a way as to avoid any distortion, as well as an annular flange 12 designed, on one side, to form a shoulder surface against the front end 8c of the locknut, and on the other side against a radial surface 3c of the annular shoulder 3, situated on the opposite side of the previous front shoulder surface 3a. A washer 13 is provided in an annular seat 14 made on the inside of the peripheral wall 5 of the head, to form a seal between the liner 1 and the head 2.

[0019] The assembling of the head 2 onto the cylinder liner 1 can be clearly seen in figures 1 and 2; in fact, it is simply necessary to fit the locknut 8 onto the cylindrical end la of the liner, then to fit on the ring 10, pulling it open elastically to enable it to pass over the annular shoulder 3, then, after having correctly orientated the head, with respect to the fluid feeding duct, by simply rotating the head itself, it is possible to insert the end of the liner 1 into the head and screw the locknut 8, tightening.it securely in order to firmly and finally assemble the parts. It is obvious that this assembling operation can be carried out very simply by any unskilled worker as the annular shoulder 8 on the liner and the relative seat 4 in the head will always ensure the correct centering and proper axial positioning of all the parts.

[0020] A second simplified embodiment is shown in the detail of figure 3 which embodies the principles of this invention.

[0021] Unlike the previous case, the locking device used in figure 3 does not make use of the intermediate split-ring 10, moreover, the annular shoulder element consists of a ring 15, split or made in two parts, placed in a seat 16 machined on the outer surface of the liner 1. In this case too, the shoulder ring 15 is in a retracted position with respect to the extreme edge of the.liner and co-operates with a seat in the peripheral wall of the head 2 to define an axial stop, and for keeping the parts centered. The head is also locked to the liner 1 by means of a locknut 8, as in the previous case. The extension of the body of the liner beyond the seat 16 of the ring, also serves for centering and for forming a seal. This solution, suitable for certain applications in which particularly sturdy types are not required, is advantageous as it is more simple and less expensive than the first.

[0022] Figure 4 of the drawings shows a third solution which is even more advantageous and more economical than the first two, and is especially suitable for cylinders operating at low pressures. The example in figure 4 also comprises a cylindrical liner 1 and a closing head 2, at each end, mechanically fixed to the liner 1 by means of a locknut 8 screwed onto the head itself. Unlike the previous cases, the annular shoulder on the liner, in this case, consists of the extreme edge 17, which is bent or curved outwards radially, starting from a tubular section cut to the desired length from a steel tube of even thickness. In this case, the machining operations necessary for machining the annular shoulder 3 in the previous examples, are totally eliminated, as they are replaced by a simple operation consisting of bending the extreme edges of the liner. The original tubular section is not weakened therefore; on the contrary, the presence of the radial flange 17 defining the aforementioned annular shoulder helps to strengthen the cylinder liner, preventing its ovalization, both during its manufacture and during the assembling of the cylinder itself.

[0023] This third solution proves to be advantageous as it makes it possible to immediately produce cylinders of any length whatsoever. In fact, having the.heads and locknuts at one's disposal, it is simply necessary to cut the tubes to the required length, fit the two loclmuts facing in the right direction and then shape the extreme edges, bending them radially outwards, to complete the construction of the cylinder in the desired dimensions. Moreover, in all the various solutions, it is possible to orientate the heads freely, rotating them by the desired angle in order to make the usual fluid inlets (not shown), match perfectly with the ducts for feeding the fluid to the cylinder itself.

Claims

1. Hydraulic, pneumatic, oleodymic cylinder or the like, with device for locking the heads, said cylinder comprising a tubular liner defining a chamber closed by end heads mechanically secured to the liner itself, characterized by the fact that the locking device comprises an annular shoulder element (3,15,17) on the outside of each cylindrical end (1a) of the liner (1), and a locknut (8) screwable against said annular shoulder element (3,15,17) and inside a peripheral wall (5) of the closing head (2); said shoulder element (3,15,17) of the liner (1) and said peripheral wall (5) of the head (2) comprising opposing flat surfaces (3a,4a) for the axial positioning of the head (2) and coaxial cylindrical surfaces (3b,4b) for centering the head (2) with respect to the liner (1) itself.

2. Cylinder as claimed in claim 1, characterized by the fact that an annular thrust element (10) is interposed between the locknut (8) and the aforesaid annular shoulder element (3).

3. Cylinder as claimed in claim 2, characterized by the fact that said thrust element (10) is in the form of a split ring, elastically expandable in a radial direction.

4. Cylinder as claimed in claim 2 or claim 3, characterized by the fact that said thrust element (10) presents an L-shaped cross-section.

5. Cylinder as claimed in claim 1, characterized. by the fact that the liner (1) extends beyond the annular shoulder element (3,15,17) with a cylindrical portion (1b) which penetrates into a corresponding seat (7) in the cylinder head (2).

6. Cylinder as claimed in claim 1, characterized by the fact that said annular shoulder element (3) is integral with the body of the liner (1).

7. Cylinder as claimed in claim 1, characterized by the fact that said annular shoulder element is in the form of a ring (15) in an annular seat (16) provided on the outer surface of the liner (1).

8. Cylinder as claimed in claim 1, characterized by the fact that the liner (1) consists of a tubular section of even thickness and by the fact that the annular shoulder element, at each end of the liner (1) consists of the outwardly bent edge (17) of the tubular section.

9. Hydraulic, pneumatic, oleodynamic cylinder or the like, comprising a tubular liner defining a chamber closed by end heads mechanically secured to the liner itself, characterized by the fact that said liner (1) consists of a tubular section having the end edges which are curved radially outwards, said curved edges of the liner defining an annular shoulder flange (17), having a flat front surface for axial positioning against the end wall (6) of the head (2), and a cylindrical surface for centering with respect to the internal surface of the side wall (5) of the aforesaid head.

Drawing