WO1994010458A1

WO1994010458A1 - Cylinder-piston combination

Info

Publication number: WO1994010458A1
Application number: PCT/FI1992/000297
Authority: WO
Inventors: Matti Luojus
Original assignee: Matti Luojus
Priority date: 1992-11-03
Filing date: 1992-11-03
Publication date: 1994-05-11
Also published as: EP0667935A1; AU2882092A

Abstract

A cylinder-piston combination driven by a pressure medium, said combination being comprised of a cylinder (3) whose interior houses an elongated cylinder barrel, a dual-element piston assembly (1, 2) adapted movable in opposite direction in the axial direction of the cylinder barrel, and the piston rod of the outer piston (1) of said piston assembly having a tubular structure and said piston (1) being sealed against the inner surface of the cylinder (3) and the inner piston (2) of said piston assembly being appropriately dimensioned to be able to enter the bore of the tubular piston rod of the piston (1) and to be movable in respect to said piston rod, and said combination further incorporating a piston element (6) which is adapted to fit about the piston rod of the inner piston (2) and is sealed against and is capable of sliding along said piston rod of the inner piston and is sealed against said inner surface of the cylinder (3), and said cylinder (3) having appropriate connection ports (4, 8, 14, 20) for routing the pressure medium into the cylinder and out thereof. The piston element (6) is provided with elements (10, 11, 13) for locking said piston element disengageably to the inner piston (2), and the inner piston (2) is provided with channels (22) for routing the pressure medium entering via the port (4) to the interior of the outer piston (1), and at least one end of the cylinder (3) is provided with elements (15, 16, 17, 18) for locking at least one of the piston rods of the pistons (1, 2) in place.

Description

CYLINDER-PISTON COMBINATION

The present invention concerns a cylinder-piston combina¬ tion according to the preamble of claim 1.

A cylinder-piston combination related to the object of the invention is presented in the international patent applica¬ tion WO 88/09441 filed by the applicant of this patent. The construction and function of the abovementioned publication has been improved by further development.

More specifically, the invention is implemented by constructions according to the characterizing part of claim 1. The subsequent dependent claims disclose a number of preferred embodiments of the invention.

By virtue of the invention a cylinder-piston combination can be made to provide a pressurized area corresponding the full inner diameter of the cylinder barrel during the outward stroke of piston rods, whereby a higher working thrust is attained. Thus, a smaller-diameter cylinder can be employed to deliver the equal thrust as with prior-art constructions. The construction according to the present invention achieves an improved operating reliability of a cylinder-piston combination. The use of a check/control element adapted to channels formed in the inner piston facilitates the pressurization of the unpressurized inter¬ mediate volume remaining between the piston rods in the conventional construction, thus preventing the formation of a vacuum. Locking elements adapted to the ends of the cylinder give an appreciably improved locking force of the piston rod over prior-art constructions.

In the following, the invention will be examined in greater detail with reference to the attached drawing, in which Fig. 1 shows a partially sectional view of the cylinder- piston combination according to the invention contracted to its shortest length,

Fig. 2 shows one end of the cylinder-piston combination according to the invention when the outer piston is in its extreme position with the piston rod fully extended,

Fig. 3 shows the opposite end to that of the cylinder- piston combination according to the invention illustrated in Fig. 2 when the inner piston is in its extreme position with the piston rod fully extended,

Fig. 4 shows a longitudinal view of the cylinder-piston combination sectioned along the line IV - IV of Fig. 2,

Fig. 5 shows the cylinder end illustrated in Fig. 3 in an enlarged view when the inner piston is in its extreme position with the piston rod fully contracted,

Fig. 6 shows a detail of the cylinder-piston combination in a partially sectioned perspective view.

Figure 1 shows the cylinder-piston combination with the piston rods of pistons 1, 2 fully contracted into a cylinder 3, whereby the combination attains its shortest external length. The bore of the cylinder 3 delineates a volume in which coaxial pistons 1, 2 are adapted to move. The outer piston 1 is arranged to slide tightly along the bore of the cylinder. According to the drawing the piston rod of the outer piston 1 exits at the right end of the cylinder. The piston 1 has a tubular structure permitting the inner piston 2 to enter the volume delineated by the bore of the piston 1. The rod of the inner piston 2 exits according to Fig. 1 at the left end of the cylinder 3. Thus, the piston rods of the pistons 1 and 2 exit at opposite ends of the cylinder.

The volume delineated by the bore of the cylinder 3 and the inner piston 2 and the piston rod thereof and the end sur¬ face of the outer piston 1 is adapted to house a piston element 6 later referred to as the lock piston. The lock piston 6 is adapted to mate tightly via seals with the bore of the cylinder 3. Similarly, the lock piston also mates tightly via seals with the piston rod of the inner piston 2. The lock piston 6 is designed to carry one or multiple locking pieces 10. The locking pieces, which are circum- ferentially spaced on the lock piston perimeter, are adapted movable, advantageously radially. The locking pieces are shown in Fig. 2 in their disengaged position (upper position) , whereby the lock piston 6 and the inner piston 2 can be moved independently from each other. In Figs. 3 and 6 the locking pieces 10 are shown in their engaged position, whereby the lock piston 6 is locked to the inner piston 2. The lock piston is designed to have an annular recess to receive the inner piston 2. The locking pieces are adapted to the outer rim of the annular recess. A radially compressive resilient element 11 is arranged to encircle the locking pieces, and thus, also the lock piston. Furthermore, to the lock piston 6 is adapted a release element 13 of the locking pieces which moves the locking pieces from the engaged position to the disengaged position. The release element has advantageously the shape of a bushing with a bevelled outer rim at the end facing the locking pieces. The inner edges of the locking pieces 10 facing the release element 13 are tapered corre¬ spondingly. The bushing 13 is adapted axially movable at that end of the lock piston 6 which faces the outer piston 1. When pushed by the outer piston 1, the bushing 13 slides into the lock piston, whereby the bevelled rim of the bushing facing the locking pieces raises the locking pieces 10 to the upper position thereof. In the situation illustrated in Fig. 6, the locking pieces 10 have their ends facing the inner piston 2 machined for a shoulder or similar extension, which in the engaged position of the locking pieces is pressed against the end surface of the inner piston 2, thereby locking the inner piston 2 to the lock piston 6. The structure of the lock piston 6 is elucidated in a greater detail in Fig. 6. The arrow in the drawing indicates the direction for the motion of the lock piston 6 and the inner piston 2. The release element 13 is advantageously adapted on the inner circumference of the lock piston. The longitudinal movement of the release element is limited by a mounting element such as a screw (not shown) .

At the ducts of connection ports 4, the inner piston 2 is designed to have channels 22 or similar ducts through which the pressure medium can enter via the inner piston 2 the volume contained between the outer piston 1 and the inner piston 2, thus imposing the pressure on the entire area of the cylinder barrel envelope. The channel 22 is advanta¬ geously provided with a check/control element 7, preferably a valve, which allows free flow of the pressure medium from the port 4 to the volume contained between the pistons 1,2, but prevents reverse flow in the opposite direction.

At least that cylinder end which faces the inner piston 2 in the cylinder 3 is provided with elements 16, 17 suited to locking the piston rod of the inner piston 2 in place. The piston rod is advantageously locked by means of a lock element 16 movable by way of the pressure medium, said ele¬ ment being advantageously movable in the axial direction of the piston rod. The lock element 16 is provided with one or multiple locking pieces 17, which can be pressed against a shoulder 23 formed on the piston rod of the inner piston 2. The locking system body piece 23 is dimensioned to permit radial motion of the locking pieces 17. The locking pieces 17 are adapted to move toward the piston rod when the lock element moves to the right in the situation illustrated in the drawings. The locking pieces are shown in the engaged position in Fig. 5. Correspondingly, the locking pieces are shown in the disengaged position in Fig. 3. The operation of the lock elements 16 and the locking pieces 17 are con¬ trolled by means of the pressure medium flowing via connec¬ tion ports 15, 18 made into the cylindrical body piece of the locking system.

The cylinder 3 is provided with connection ports 4, 8, 14, 20 for routing the pressure medium to the interior of the cylinder 3 and/or away from the interior of the cylinder. The ports are employed for controlling the operation of the cylinder-piston combination. The ports are advantageously circumferentially spaced in a ring so that the envelope of the cylinder 3 is provided with holes at a port, said holes being used for routing the pressure medium at several points of the cylinder perimeter to the interior of the cylinder.

E.g., the left-side end surface of the lock piston 6 is advantageously pressurized via the port . The port 8 is advantageously employed for admitting the pressure, e.g., to control the operation of the lock piston 6 and to pressurize the right-side end of the lock piston 6 and the pressurized end of the inner piston 2. The port 14 is advantageously employed to route the pressure on, e.g., the right-side pressurized end of the outer piston 1. The ports are used in a conventional manner described in, e.g., the publication WO 88/09441.

The cylinder-piston combination has a number of seals placed between, e.g., the pistons, piston rods and cylinder body. These seals are not indicated by reference numbers in the drawings, but such sealing elements are easily recog¬ nizable from the drawings by those skilled in the art.

In the following the operation of the cylinder-piston combination is described by virtue of a work cycle, said work cycle being comprised of an initial position in which the pistons 1, 2 are in their inner positions, during the stroke of the work cycle the pistons are actuated by the pressure medium so that the piston rods are pushed outward from the cylinder 3 to their extended positions, and at the end of the work cycle the pistons 1, 2 are back in their initial positions.

With reference to the annexed drawings the cylinder-piston combination operates as follows:

In Fig. 1 the piston rods of the pistons 1, 2 are shown in their contracted positions. The pressure medium is routed via the connection port 4 to the interior of the cylinder, whereby the lock piston 6 expels the piston 1 outwardly in the interior of the cylinder 3. The lock piston 6 moves in the volume contained between the piston rod of the inner piston 2 and the barrel of the cylinder 3. The lock piston communicates via the seals with both said components. On the other hand, the pressure medium can also enter via a channel adapted to the piston rod of the inner piston 2 and a valve member 7 adapted into said channel to the interior of the piston rods 1, 2 and between said rods. This arrangement makes it also possible to pressurize the interior of the piston 1, whereby the thrust expelling the piston 1 becomes higher, since the thrust-generating surface becomes now as large as the entire section of the interior of the cylinder 3. The piston 1 is moved to its extreme position to the right as shown in Fig. 2.

Fig. 2 illustrates the situation in which the pressure medium is routed to the cylinder via the connection port 8 Simultaneously, the pressure medium is routed via the port 18 (Fig. 5) , whereby the lock element 16 is moved to the left thereby disengaging the locking pieces 17 from the piston rod of the piston 2. Then, the piston rod of the piston 2 is permitted to move outward from the cylinder (to the left) . By virtue of the pressurized medium routed via the port 8, the imposed pressure causes the locking pieces 10 mounted about the lock piston 6 to become compressed advantageously radially inward, thereby locking the inner piston 2 to the lock piston 6. The number of the locking pieces 10 is advantageously two or more. Additionally, the lock piston 6 has advantageously a resilient compressive element 11 adapted to it so as to assure the engaging function of the locking pieces 10. As the lock piston 6 is in the abovedescribed manner locked over the inner piston

2, the entire cross-sectional cylinder area can be utilized for generating the thrust which moves the piston 2 to the left. Fig. 3 shows the inner piston 2 moved to its leftmost extreme position.

When the inner piston 2 is desired to be moved to the right, inward into the cylinder, the pressure medium is routed via the port 4 to the interior of the cylinder 3. Then, the lock piston and the piston 2 locked to it are moved to the right. When the release element 13 of the lock piston 6 meets the piston 1 at the other end of the cylinder, the release element is pushed inward, thereby pushing the locking pieces 10 outward, whereby the locking is released and the inner piston 2 unlocked.

To reach the initial position shown in Fig. 1 from the position shown in Fig. 2, the pressure medixam is routed via the port 14 to the interior of the cylinder. Simultaneous¬ ly, the pressure medium is routed via the port 15 into the cylinder. Then, the lock element 16, which is movable in the axial direction of the piston rod, pushes the locking pieces 17 against the shoulder 23 designed to the piston rod of the piston 2, thereby locking the piston rod of the piston 2 in place. The pressure of the pressurized medium routed via the port 14 moves the piston 1 to the left, simultaneously pushing the lock piston 6 ahead it to the left end of the cylinder barrel.

To those versed in the art it is evident that the scope of the invention is not exhausted by the exemplifying embodi¬ ments described above; instead, the invention can be varied within the disclosed claims. For example, compressed air can be used to replace hydraulic fluid as the pressure medium.

Claims

CLAIMS :

1. A cylinder-piston combination driven by a pressure medium, said combination being comprised of a cylinder (3) whose interior houses an elongated cylinder barrel, a dual- element piston assembly (1, 2) adapted movable in opposite direction in the axial direction of the cylinder barrel, and the piston rod of the outer piston (1) of said piston assembly having a tubular structure and said piston (1) being sealed against the inner surface of the cylinder (3) and the inner piston (2) of said piston assembly being appropriately dimensioned to be able to enter the bore of the tubular piston rod of the piston (1) and to be movable in respect to said piston rod of the inner rod, and said combination further incorporating a piston element (6) which is adapted to fit about the piston rod of the inner piston (2) and is sealed against and is capable of sliding along said piston rod and is sealed against said inner surface of the cylinder (3) , and said cylinder (3) having appropriate connection ports (4, 8, 14, 20) for routing the pressure medium into the cylinder and out thereof, c h a r a c t e r i z e d in that said piston element (6) is provided with elements (10, 11, 13) for locking said piston element disengageably to the inner piston (2) , and that the inner piston (2) is provided with channels (22) for routing the pressure medium entering via the port (4) to the interior of the outer piston (1) , and that at least one end of the cylinder (3) is provided with elements (15, 16, 17, 18) for locking at least one of the piston rods of the pistons (1, 2) in place.

2. A cylinder-piston combination as defined in claim 1, c h a r a c t e r i z e d in that said piston element (6) incorporates one or multiple locking pieces (10) or similar members, which are adapted to be movable, advantageously radially to the longitudinal axis of the piston (1, 2) by means of the pressure medium acting on the piston element (6) .

3. A cylinder-piston combination as defined in claim 1 or 2, c h a r a c t e r i z e d in that said piston element (6) is adapted to incorporate a release element (13) for moving the locking pieces (10) at least from the engaged position thereof to the disengaged position thereof.

4. A cylinder-piston combination as defined in any fore¬ going claim 1...3, c h a r a c t e r i z e d in that said piston element (6) is adapted to incorporate a resilient compressive element (11) encircling the locking pieces (10) .

5. A cylinder-piston combination as defined in any fore¬ going claim 1...4, c h a r a c t e r i z e d in that the channels (22) of the inner piston (2) are adapted to in- corporate a control/check element (7) .

6. A cylinder-piston combination as defined in any fore¬ going claim 1...5, c h a r a c t e r i z e d in that said elements for locking the piston rod in place comprise a lock element (16) carrying one or multiple locking pieces (17) mounted on it.

7. A cylinder-piston combination as defined in claim 6, c h a r a c t e r i z e d in that said lock element (16) has the shape of a bushing and is comprised one or multiple members and is advantageously adapted coaxial about the piston (1, 2) so as to be movable in the direction of the longitudinal axis of the piston rod.

8. A cylinder-piston combination as defined in claim 6 or 7, c h a r a c t e r i z e d in that said locking pieces (17) are adapted to be movable essentially radially to the longitudinal axis of the piston (1, 2) .

9. A cylinder-piston combination as defined in any fore- going claim 1...8, c h a r a c t e r i z e d in that said locking elements (16, 17) for locking the piston rod in place are adapted to be located within a body (21) forming an extension of the cylinder (3) , said body (21) incorporating connection ports (15, 18) for routing the pressure medium actuating the lock element (16) to the interior of the body (21) and out therefrom.

10. A cylinder-piston combination as defined in any fore¬ going claim 1...9, c h a r a c t e r i z e d in that a shoulder (23) is provided on the piston rod of the piston (2) for ensuring the locking function.