WO1998016748A1

WO1998016748A1 - Pneumatic cylinder assembly

Info

Publication number: WO1998016748A1
Application number: PCT/SE1997/001726
Authority: WO
Inventors: Peter Rasmussen
Original assignee: Peter Rasmussen
Priority date: 1996-10-15
Filing date: 1997-10-15
Publication date: 1998-04-23
Also published as: SE506033C2; SE9603768D0; EP0932769A1; SE9603768L

Abstract

A pneumatic cylinder assembly (1) comprises an outer cylinder element (2), an inner cylinder element (3), which is telescopically displaceable in the axial direction (a) relative to the outer cylinder element, and a piston element (4), which is telescopically displaceable in the axial direction (a) relative to the inner cylinder element (3). The elements (2-4) together define a pressure chamber (6', 11') for extension of the inner cylinder element (3) from the outer cylinder element (2) and of the piston element (4) from the inner cylinder element (3), and pressure chambers (6'', 11'') for retraction of the inner cylinder element (3) into the outer cylinder element (2) and of the piston element (4) into the inner cylinder element (3). At least one non-centrally arranged telescopic tube (23, 24) extends in the axial direction (a) through the cylinder elements (2, 3) and the piston element (4). The tube (23, 24) is adapted to lock the piston element (4) against rotation relative the outer cylinder element (2) and to establish a tight connection between a pressure medium connection (27, 28) at the rear end wall (5) of the outer cylinder element (2) and a pressure medium connection intended for a pneumatic or hydraulic tool, such as a gripping jaw, connected to the piston element (4).

Description

PNEUMATIC CYLINDER ASSEMBLY

The present invention relates to a pneumatic cylinder assembly comprising an outer cylinder element, an inner cylinder element, which is axially telescopically displaceable relative to the outer cylinder ele- ment and which is essentially accommodated therein, and a piston element, which is telescopically displaceable in the axial direction relative to the inner cylinder element, the outer cylinder element having a rear end wall, which backwards closes a circular-cylindrical first cylinder chamber, and a front end wall having a central circular opening, which has a smaller diameter than the cylinder chamber and through which extends the inner cylinder element in a sealed manner, the inner cylinder element having a rear end wall, which backwards defines a circular-cylindrical second cylinder chamber and which laterally projects beyond the inner cylinder element into sealed abutment against the outer cylinder element, and a front end wall having a circular opening, which has a smaller diameter than the second cylinder chamber, the piston element having a rear end wall, which backwards defines the piston element and laterally projects beyond the piston element into sealed abutment against the inner cylinder element, and a circular-cylindrical piston rod portion, which in a sealed manner extends through the opening in the front end wall of the inner cylinder element and in the front part is closed by an end wall, the first cylinder chamber being divided by the rear end wall of the inner cylinder element into a rear pressure chamber, which for pressurisation/pressure relief has an air duct at the rear end wall of the outer cylinder element, for extending the inner cylinder element from the outer cylinder element, and into a front pressure chamber, which for pressurisation/pressure relief has an air duct at the front end wall of the outer cylinder element, for retracting the inner cylinder element into the outer cylinder element, the second cylinder chamber being divided by the rear end wall of the piston element into a rear pressure chamber, which for pressurisation/pressure relief communicates with the rear pressure chamber of the first cylinder chamber, for extending the piston element from the inner cylinder element, and into a front pressure chamber, which for pressurisation/pressure relief has an air duct at the front end wall of the inner cylin- der element, for retracting the piston element into the inner cylinder element.

A pneumatic cylinder assembly of the above-mentioned type is disclosed in Patent Specification US-A-2, 625, 135. The cylinder assembly described in this specification is intended to be mounted on the axle of a motor vehicle to serve as a lifting jack when necessary. The known assembly is with its elements telescoped very compact but yet has a great length of stroke and is besides, thanks to the circular-cylindrical elements, inexpensive to anu- facture and very robust. The known assembly is not usable for materials handling since its telescoping elements cannot be locked against rotation.

The object of the present invention is, on the basis of the prior-art cylinder assembly, to provide an equally compact and inexpensive cylinder assembly, which both is locked against rotation and permits easy connection of tools for materials handling.

This object is achieved by a pneumatic cylinder assembly of the type mentioned by way of introduction by at least one non-centrally arranged telescopic tube extending in the axial direction through the cylinder chambers and through the piston element, said tube being adapted to lock the piston element against rotation relative to the outer cylinder element and to estab- lish a pressure-medium-tight connection between a pressure medium connection at the rear end wall of the outer cylinder element and a pressure medium connection intend- ed for a pneumatic or hydraulic tool, such as a gripping jaw, connected to the piston element.

Thanks to the non-central arrangement of the telescopic tube inside the cylinder assembly, the piston ele- ment of the cylinder assembly is in a very simple manner locked against rotation in relation to the outer cylinder element of the cylinder assembly. As a result, it is possible to choose circular cross-sections for the cylinder elements and the piston element, which facilitates both the manufacture of the elements and the mutual sealing thereof, and even the telescopic tube can be made from tubes of circular cross-section, which confers the advantages mentioned above. Moreover, the inventive assembly will be very compact since tools connected thereto do not require the supply of pressure medium by means of space- requiring piping arranged on the outside, which besides, especially when handling materials, always runs the risk of getting jammed or being damaged.

Preferably, the pressure medium connection at the rear end wall of the outer cylinder element is arranged on the lateral exterior of the cylinder element, and a pressure medium duct is formed in said rear end wall between the pressure medium connection and the telescopic tube. This arrangement contributes still more to the reduction of the axial dimensions of the inventive assembly and also facilitates the mounting of the assembly with the flat rear end wall resting against a flat base .

Preferably, the air duct for pressurisation/pressure relief of the rear pressure chamber of the first cylinder chamber opens on the lateral exterior of the outer cylinder element. The advantage of this solution is the same as above, i.e. the flat rear end wall remains free in order to facilitate mounting of the assembly on a flat base.

Besides, a connecting means for attaching the tool preferably is arranged at the end wall of the piston rod portion, the connecting means being either a screw thread or a bayonet fitting, which serves to attach the tool and also accomplishes a pressure medium connection between the tool and the telescopic tube. Also this solution con- tributes to a great extent to making the inventive assembly as compact as possible.

If desired, besides at least one additional cylinder element of the same type as the inner cylinder element can be telescopically displaceably arranged between the inner cylinder element and the piston element. This solution makes it possible to extend in a simple way the length of stroke of the cylinder assembly while maintaining its function.

Finally, two telescopic tubes for individual pres- sure medium supply to the tool are preferably arranged in parallel in the cylinder assembly. The two telescopic tubes contribute to an improvement of the locking against rotation and affords greater freedom in the choice of tools. A preferred embodiment of the invention will now be described in more detail with reference to the accompanying drawing, which is a part-sectional view and shows a longitudinal section through an inventive cylinder assembly. The cylinder assembly 1 shown in the drawing comprises an outer cylinder element 2, an inner cylinder element 3, which is telescopically displaceable in the axial direction a relative to the outer cylinder element and which is accommodated therein, and a piston element 4, which is telescopically displaceable in the axial direction a relative to the inner cylinder element 3 and which is accommodated in the inner cylinder element 3.

The outer cylinder element 2 has a rear end wall 5 in the form of a circular flat cover, which backwards closes a circular-cylindrical first cylinder chamber 6. The outer cylinder element 2 also has a front end wall 7 having a central circular opening 8. The opening 8 has a smaller diameter than the cylinder chamber 6 and through the opening extends in a displaceable manner the inner cylinder element 3 sealed by means of an O-ring 9.

The inner cylinder element 3 has a rear end wall 10, which backwards defines a circular-cylindrical second cylinder chamber 11, which has a smaller diameter than the first cylinder chamber 6. The rear end wall 10 projects laterally, i.e. transversely of the axial direction a, beyond the inner cylinder element 3 into abutment against the outer cylinder element 2 while an O-ring 12 is inserted therebetween. The inner cylinder element 3 also comprises a front end wall 13 having a central circular opening 14. The opening 14 has a smaller diameter than the second cylinder chamber 11 and is defined inter- nally by an O-ring 15.

The piston element 4 has a rear end wall 16, which backwards defines the piston element 4 and which laterally projects beyond the piston element 4 into abutment against the inner cylinder element 3 while an O-ring 17 is inserted therebetween, which during displacement of the piston element 4 slides in a sealed manner against the inside of the piston element 4. Besides the piston element 4 has a circular-cylindrical piston rod portion 18, which in a sealed manner extends through the opening 14 in the front end wall 13 of the inner cylinder element 3. In the front part, the piston rod portion 18 is closed by an end wall 19, which defines the end wall of a third cylinder chamber (not shown) inside the piston element 4, which cylinder chamber has a smaller diameter than the first and the second cylinder chamber 6 and 11.

The first cylinder chamber 6 is divided by the rear end wall 10 of the inner cylinder element 3 into a rear pressure chamber 6', which for pressurisation/pressure relief has an air duct 20 in the lateral exterior of the outer cylinder element 2 at the rear end wall 5, and into a front pressure chamber 6", which for pressurisation/ pressure relief has an air duct 21 in the lateral exte- rior of the outer cylinder element 2 at the front end wall 7. The duct 20 serves for pressurisation for extending the inner cylinder element 3 from the outer cylinder element 2, and for pressure relief of the rear pressure chamber 6' when retracting the inner cylinder element 3 into the outer cylinder element 2, and the air duct 21 serves for pressurisation of the front pressure chamber 6" for retracting the inner cylinder element 3 into the outer cylinder element 2 and for pressure relief of the front pressure chamber 6" when extending the inner cylinder element 3.

The second cylinder chamber 11 is divided by the rear end wall 16 of the piston element 4 into a rear pressure chamber 11' and a front pressure chamber 11", which for pressurisation/pressure relief has an air duct 22 in the lateral exterior of the inner cylinder element 3 adjacent to the front end wall 13.

After a preceding extension through pressurisation via the air duct 20, the air ducts 21, 22 are, during retraction through pressurisation via the duct 21, adapted first to pressurise the front pressure chamber 6" via the air duct 21 and retract the inner cylinder element 3 into the outer cylinder element 2 and then to pressurise the front pressure chamber 6" via the air duct 22 and retract the piston element 4 into the inner cylinder element 3.

In the embodiment shown, two non-centrally arranged telescopic tubes 23, 24 extend in the axial direction a through the two cylinder chambers 6, 11 in the cylinder elements and through the cylinder chamber in the piston element 4. The telescopic tubes 23, 24 extend from the rear end wall 5 and up to the end wall 19. They each consist of three telescopically displaceable tubular parts, of which only the tubular parts 23', 24' in the outer cylinder element 2 and the tubular parts 23", 24" in the inner cylinder element 3 are shown in the Figure. The tubular parts are sealed relative to each other, for instance by means of O-rings (not shown) and are of circular cross-section.

As is evident from the drawing, two ducts 25, 26 are formed in the rear end wall 5 of the outer cylinder element, the ducts 25, 26 extending in the lateral direction of the cylinder assembly and communicating each with a telescopic tube 23, 24 and a pressure medium connection, in this case a pressure medium connection 27, 28, in the lateral exterior of the rear end wall 5. Also in the end wall 19 of the piston element 4 there are ducts which, however, are not shown in the Figure. These ducts which are not shown are adapted to be connected to, for instance, a gripping jaw or a suction cup, which may come into use when the inventive cylinder assembly 1 is used for the handling of materials. The gripping jaw or suction cup can be mounted, for instance, by means of a screw thread 29 or by means of a suitable bayonet fitting, which may then also establish a compressed air connection between the gripping jaw or suction cup and the telescopic tubes 23, 24.

It will be appreciated that the invention within the scope of the appended claims can be varied in different ways in respect of the number of cylinder elements and telescopic tubes and the attachment and connection of the pneumatic or hydraulic tool, and that it is the locking against rotation and the power transmission based on compressed air or hydraulic fluid and effected via the telescopic tubes 23, 24 that are the gist of the invention.

Claims

1. A pneumatic cylinder assembly comprising an outer cylinder element (2), an inner cylinder element (3), which is telescopically displaceable in the axial direction (a) relative to the outer cylinder element and which is essentially accommodated therein, and a piston element (4), which is telescopically displaceable in the axial direction (a) relative to the inner cylinder element (3), the outer cylinder element (2) having a rear end wall (5), which backwards closes a circular-cylindrical first cylinder chamber (6), and a front end wall (7) having a central circular opening (8), which has a smaller dia- meter than the cylinder chamber (6) and through which extends the inner cylinder element (3) in a sealed manner, the inner cylinder element (3) having a rear end wall (10) , which backwards defines a circular-cylindrical second cylinder chamber (11) and which laterally projects beyond the inner cylinder element (3) into sealed abutment against the outer cylinder element (2), and a front end wall (13) having a central circular opening (14), which has a smaller diameter than the second cylinder chamber (11), the piston element (4) having a rear end wall (16), which backwards defines the piston element (4) and laterally projects beyond the piston element (4) into sealed abutment against the inner cylinder element (3), and a circular-cylindrical piston rod portion (18), which in a sealed manner extends through the opening (14) in the front end wall (13) of the inner cylinder element (3) and in the front part is closed by an end wall (19), the first cylinder chamber (6) being divided by the rear end wall (10) of the inner cylinder element (3) into a rear pressure chamber (6')_r which for pressurisation/pressure relief has an air duct (20) at the rear end wall (5) of the outer cylinder element (2), for extending the inner cylinder element (3) from the outer cylinder element (2) , and into a front pressure chamber (6"), which for pressurisation/pressure relief has an air duct (21) at the front end wall (7) of the outer cylinder element (2), for retracting the inner cylinder element (3) into the outer cylinder element (2) , the second cylinder chamber (11) being divided by the rear end wall (16) of the piston element (4) into a rear pressure chamber (11'), which for pressurisation/pressure relief communicates with the rear pressure chamber (6') of the first cylinder chamber (6), for extending the piston element (4) from the inner cylinder element (3) , and into a front pressure chamber (11"), which for pressurisation/pressure relief has an air duct (22) at the front end wall (13) of the inner cylinder element (3) , for retracting the piston element (4) into the inner cylinder element (3), c h a r a c t e r i s e d in that at least one non-centrally arranged telescopic tube (23, 24) extends in the axial direction (a) through the cylinder chambers (6, 11) and through the piston element (4), said tube (23, 24) being adapted to lock the piston element (4) against rotation relative to the outer cylinder element (2) and to establish a pressure-medium-tight connection between a pressure medium connection (27, 28) at the rear end wall (5) of the outer cylinder element (2) and a pressure medium connection intended for a pneumatic or hydraulic tool, such as a gripping jaw, connected to the piston element (4).

2. A pneumatic cylinder assembly as claimed in claim 1, c h a r a c t e r i s e d in that the pressure medium connection (27, 28) at the rear end wall (5) of the outer cylinder element (2) is placed on the lateral exterior of the cylinder element (2), and that a pressure medium duct (25, 26) is formed in said rear end wall (5) between the pressure medium connection (27, 28) and the telescopic tube (23, 24). 3. A pneumatic cylinder assembly as claimed in claim 1 or 2, c h a r a c t e r i s e d in that the air duct (20) for pressurisation/pressure relief of the rear pressure chamber (6') of the first cylinder chamber (6) opens on the lateral exterior of the outer cylinder element (2) . . A pneumatic cylinder assembly as claimed in any one of claims 1-3, c h a r a c t e r i s e d in that a connecting means for attaching the tool is arranged at the end wall (19) of the piston rod portion (18).

5. A pneumatic cylinder assembly as claimed in claim 4, c h a r a c t e r i s e d in that the connect- ing means is a screw thread (29) .

6. A pneumatic cylinder assembly as claimed in claim 4, c h a r a c t e r i s e d in that the connecting means is a bayonet fitting, which serves to attach the tool and also establishes a compressed air connec- tion between the tool and the telescopic tube (23, 24) .

7. A pneumatic cylinder assembly as claimed in any one of claims 1-6, c h a r a c t e r i s e d in that at least one additional cylinder element of the same type as the inner cylinder element (3) is telescopically dis- placeably arranged between the inner cylinder element (3) and the piston element (4).

8. A pneumatic cylinder assembly as claimed in any one of claims 1-7, c h a r a c t e r i s e d in that two telescopic tubes (23, 24) for individual pressure medium supply to the tool are arranged in parallel in the cylinder assembly.