EP0103549A1 - Overload protection device for a hydraulic cylinder - Google Patents
Overload protection device for a hydraulic cylinder Download PDFInfo
- Publication number
- EP0103549A1 EP0103549A1 EP83830172A EP83830172A EP0103549A1 EP 0103549 A1 EP0103549 A1 EP 0103549A1 EP 83830172 A EP83830172 A EP 83830172A EP 83830172 A EP83830172 A EP 83830172A EP 0103549 A1 EP0103549 A1 EP 0103549A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- cylinder
- rod
- protected
- hydraulic cylinder
- piston
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 230000006835 compression Effects 0.000 claims abstract description 3
- 238000007906 compression Methods 0.000 claims abstract description 3
- 238000006073 displacement reaction Methods 0.000 claims abstract description 3
- 239000012530 fluid Substances 0.000 description 7
- 230000000694 effects Effects 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B1/00—Installations or systems with accumulators; Supply reservoir or sump assemblies
- F15B1/02—Installations or systems with accumulators
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
- F15B15/08—Characterised by the construction of the motor unit
- F15B15/14—Characterised by the construction of the motor unit of the straight-cylinder type
- F15B15/1423—Component parts; Constructional details
- F15B15/1447—Pistons; Piston to piston rod assemblies
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
- F15B15/08—Characterised by the construction of the motor unit
- F15B15/14—Characterised by the construction of the motor unit of the straight-cylinder type
- F15B15/1423—Component parts; Constructional details
- F15B15/1457—Piston rods
Definitions
- the present invention relates to a device for protecting a hydraulic cylinder against overloading which could damage its structure.
- a hydraulic cylinder is normally used for moving an object in a straight line by means of a rod connected to its piston, and for maintaining the object firmly in position at a desired point along its line of movement.
- the object so moved is kept in position by cutting off the two chambers of the cylinder by means of the distributor .of the pressurised working fluid, or by means of suitable valves connected in the supply and discharge ducts of the chambers.
- the incompressibility of the working fluid generally oil
- the prior art makes use of maximum pressure valves connected to the working chambers of the cylinder, which, by opening at a maximum predetermined pressure, allow part of the pressurised fluid to leave one of the chambers.
- the problem behind the present invention is thus to provide a protection device for a hydraulic cylinder which avoids the failure of the cylinder and the apparatus hydraulically connected thereto when'overloading arises due to any external disturbing forces, and which at the same time allows the rod of the cylinder and hence the object controlled by this rod to be returned automatically to the initial position where the disturbing forces arose.
- a protection device which is characterised in that it comprises an auxiliary hydraulic cylinder in which each working chamber defined by its piston is in constant hydraulic communication through a respective duct with a corresponding chamber of the hydraulic cylinder to be protected, and in that the rod is connected to a resilient member which yields in a direction opposite the direction of any displacement of the rod itself resulting from the surpassing of a force of predetermined value acting on the piston due to the pressure differential created in the hydraulic cylinder to be protected by the exceeding of the maximum pressure allowable within the cylinder to be protected.
- a conventional hydraulic cylinder 1 has its interior divided into working chambers 2, 3 by a piston 4 which slides in a straight line within the cylinder 1.
- a conventional sealing ring 5 is located on the piston 4.
- the piston 4 is rigid with a rod 6 which, in the example illustrated, is of the type which projects from both ends 7, 8 of the cylinder 1 through respective apertures provided with conventional seals 9, 10.
- the working chambers 2, 3 are provided with respective ducts 11, 12 for alternating hydraulic connection to a source of pressurised fluid, generally oil, and to a discharge vessel, not illustrated, through a distributor, also not illustrated since it is conventional.
- the rod 6 has a cylindrical cavity 13 within which is slidable a piston 14 with a seal 15.
- This piston divides the cylindrical cavity 13 into two working chambers 16, 17.
- the whole thus. constitutes an auxiliary hydraulic cylinder.
- a duct 18 effects a constant hydraulic connection between the chamber 16 and the chamber 2 of the cylinder 1 to be protected, while a second duct 19 effects a constant hydraulic connection between the chamber 17 and the working chamber 3 of the cylinder 1.
- the rod 6 of the cylinder 1 also has a cylindrical cavity 20 coaxial with the cavity 13.
- This cavity 20 in the preferred embodiment shown in the drawings, communicates hydraulically with the working chamber 17 of the auxiliary hydraulic cylinder.
- a rod 21 is connected to the piston 14 and, in the embodiment illustrated, projects only from the side facing the chamber 17.
- This rod 21 is extended by a coaxial section 22 which extends longitudinally within the cavity 20 of the side 6.
- a coaxial section 22 which extends longitudinally within the cavity 20 of the side 6.
- annular shoulder 23 At the junction between the rod 21 and its extension 22 there is an annular shoulder 23, while at the free end within the cavity 20 there is a head 24 defining an annular shoulder 25 facing the shoulder 23.
- a helical spring 26 is mounted on the extension 22 and will yield only on the surpassing of a predetermined compression value, the spring being located between two annular elements 27, 28 which, when the spring 26 is not operative, bear against the shoulders 23, 25 of the extension rod 22, respectively. The latter may slide freely axially of the said annular elements 27, 28.
- the cavity 20 of the rod 6 is provided, in its turn, with two opposing annular projections 29, 30 against which the annular elements 27, 28 engage when the spring 26 is in its non-operative condition.
- the operation of the device is as follows.
- the piston 14 is thus returned to its initial position and, with the return of the previously-displaced hydraulic fluid to the chamber 3 of the cylinder 1, the piston 4 is also returned automatically to the initial position.
- the object (not illustrated) controlled by the rod 6 of the cylinder 1 is also automatically re-positioned exactly in its initial position.
- auxiliary cylinder is formed within a cavity in the rod of the cylinder to be protected and the resiliently yielding member con--stituted by the spring 26 is also housed within a coaxial cavity in the same rod of the cylinder to be protected
- the auxiliary cylinder and its resiliently yielding member may clearly also be formed separately from the rod of the cylinder to be protected without departing from the scope of the invention.
- the basic advantage of the device according to the invention is that of achieving suitable protection against possible overloading and, at the same time, returning the rod of the cylinder to be protected automatically to the initial position where the overloading occurred, without having recourse to special operations.
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Actuator (AREA)
Abstract
A device for protecting a hydraulic cylinder (1) against possible overloading is constituted by an auxiliary hydraulic cylinder (13) in which each working chamber (16, 17) is connected hydraulically by a respective duct (18, 19) to a corresponding working chamber (2, 3) of the protected cylinder (1). The piston rod (21) of the auxiliary cylinder (13) is connected to a spring (26) which yields in a direction opposite the direction of displacement of the rod (21) resulting from the surpassing of a compression force of a value greater than a limit which is predetermined in accordance with the value of the maximum pressure which can be borne by the protected cylinder (1). The device avoids failure of the cylinder (1) and any hydraulic apparatus connected thereto, and also returns the piston rod (6) of the protected cylinder (1) automatically to the initial position from which it was displaced as a consequence of the intervention of the protection device.
Description
- The present invention relates to a device for protecting a hydraulic cylinder against overloading which could damage its structure.
- As is known, a hydraulic cylinder is normally used for moving an object in a straight line by means of a rod connected to its piston, and for maintaining the object firmly in position at a desired point along its line of movement.
- According to the prior art, the object so moved is kept in position by cutting off the two chambers of the cylinder by means of the distributor .of the pressurised working fluid, or by means of suitable valves connected in the supply and discharge ducts of the chambers.
- If, under these conditions, an external force tries to move the rod of the cylinder, the incompressibility of the working fluid, generally oil, does not allow any movement.
- Cases do occur, however, in which the degree of external force applied to the rod of the cylinder is such that the pressures within the cylinder reach values which are unacceptable as regards either the strength of the cylinder itself or the apparatus hydraulically connected thereto.
- In order to avoid failure, the prior art makes use of maximum pressure valves connected to the working chambers of the cylinder, which, by opening at a maximum predetermined pressure, allow part of the pressurised fluid to leave one of the chambers.
- The intervention of the valves, however, results in a movement of the rod and hence of the object connected to the rod, which leaves its correct position.
- Once the external force has ceased, it is thus necessary to act on the hydraulic circuit manually or automatically to return the rod and the object controlled thereby to the initial position where.the external disturbing forces occurred.
- The problem behind the present invention is thus to provide a protection device for a hydraulic cylinder which avoids the failure of the cylinder and the apparatus hydraulically connected thereto when'overloading arises due to any external disturbing forces, and which at the same time allows the rod of the cylinder and hence the object controlled by this rod to be returned automatically to the initial position where the disturbing forces arose.
- This problem is solved in accordance with the invention by means of a protection device which is characterised in that it comprises an auxiliary hydraulic cylinder in which each working chamber defined by its piston is in constant hydraulic communication through a respective duct with a corresponding chamber of the hydraulic cylinder to be protected, and in that the rod is connected to a resilient member which yields in a direction opposite the direction of any displacement of the rod itself resulting from the surpassing of a force of predetermined value acting on the piston due to the pressure differential created in the hydraulic cylinder to be protected by the exceeding of the maximum pressure allowable within the cylinder to be protected.
- The invention will now be more fully described with reference to an embodiment of the device illustrated in the appended drawings, in which:
- Figure 1 is.a longitudinal section of a hydraulic cylinder provided with a protection device according to the invention;
- Figure 2 is a longitudinal section of the cylinder of Figure 1, to the rod of which is applied an external axial disturbing force acting in one direction;
- Figure 3 is a longitudinal section of the cylinder of Figure 1, to the rod of which is applied an external axial disturbing force acting in the opposite direction to that of Figure 2.
- With reference to the drawings, a conventional
hydraulic cylinder 1 has its interior divided intoworking chambers 2, 3 by a piston 4 which slides in a straight line within thecylinder 1. A conventional sealing ring 5 is located on the piston 4. - In a conventional manner, the piston 4 is rigid with a rod 6 which, in the example illustrated, is of the type which projects from both
ends cylinder 1 through respective apertures provided withconventional seals - The working
chambers 2, 3 are provided withrespective ducts - In accordance with the invention, in a preferred embodiment,. the rod 6 has a
cylindrical cavity 13 within which is slidable apiston 14 with aseal 15. This piston divides thecylindrical cavity 13 into twoworking chambers duct 18 effects a constant hydraulic connection between thechamber 16 and thechamber 2 of thecylinder 1 to be protected, while asecond duct 19 effects a constant hydraulic connection between thechamber 17 and the working chamber 3 of thecylinder 1. - The rod 6 of the
cylinder 1 also has acylindrical cavity 20 coaxial with thecavity 13. Thiscavity 20, in the preferred embodiment shown in the drawings, communicates hydraulically with theworking chamber 17 of the auxiliary hydraulic cylinder. Arod 21 is connected to thepiston 14 and, in the embodiment illustrated, projects only from the side facing thechamber 17. - This
rod 21 is extended by acoaxial section 22 which extends longitudinally within thecavity 20 of the side 6.. At the junction between therod 21 and itsextension 22 there is anannular shoulder 23, while at the free end within thecavity 20 there is ahead 24 defining anannular shoulder 25 facing theshoulder 23. - A
helical spring 26 is mounted on theextension 22 and will yield only on the surpassing of a predetermined compression value, the spring being located between twoannular elements spring 26 is not operative, bear against theshoulders extension rod 22, respectively. The latter may slide freely axially of the saidannular elements - The
cavity 20 of the rod 6 is provided, in its turn, with two opposingannular projections annular elements spring 26 is in its non-operative condition. - The operation of the device is as follows.
- Supposing that an external disturbing force F2 greater than the maximum force F1 envisaged for the normal operation of the
cylinder 1 arises and acts on the rod 6 of thecylinder 1 to be protected, while the rod 6 is retained in a predetermined position by means of the conventional blocking of theducts chambers 2, 3 in thecylinder 1. - This same increased pressure differential also occurs between the
chambers auxiliary cylinder 13, which are in constant communication with thechambers 2, 3 of thecylinder 1 to be protected by means of theducts - As a consequence of the increase in the pressure differential, the
piston 14 is moved towards the left, as seen in Figure 2, in that thespring 26, the predeterm--ined load limit being surpassed, yields and is compressed towards the left between theannular elements element 27 being retained against theprojection 29 of thecavity 20. - Under these conditions, some of the working fluid present in the chamber 3 flows into the
chamber 17 of the auxiliary cylinder, allowing the piston 4 of the protectedcylinder 1 to move towards the right, again as seen in Figure 2, avoiding any failure. - Simultaneously, some of the fluid moved by the
piston 14 in thechamber 16 flows into thechamber 2 of the protected cylinder which, its volume being increased, is able to receive it. Clearly, the volumes displaced in the two directions are equal. When the disturbing force F2 ceases and the force less than or equal to the maximum force F1 envisaged for the normal operation is restored, thespring 26 expands and returns to the initial condition betweenprojections cavity 20. - The
piston 14 is thus returned to its initial position and, with the return of the previously-displaced hydraulic fluid to the chamber 3 of thecylinder 1, the piston 4 is also returned automatically to the initial position. - Thus, the object (not illustrated) controlled by the rod 6 of the
cylinder 1 is also automatically re-positioned exactly in its initial position. - An entirely similar operation occurs again when a disturbing force F3 acts on the rod 6 in the opposite direction from the force F2.
- In this case, the
piston 14 of theauxiliary cylinder 13 moves towards the right, as seen in Figure 3, and thespring 26 is compressed between theannular elements projection 30 of thecavity 20. - Although the invention has been described with reference to a preferred embodiment in which the auxiliary cylinder is formed within a cavity in the rod of the cylinder to be protected and the resiliently yielding member con--stituted by the
spring 26 is also housed within a coaxial cavity in the same rod of the cylinder to be protected, the auxiliary cylinder and its resiliently yielding member may clearly also be formed separately from the rod of the cylinder to be protected without departing from the scope of the invention. - The basic advantage of the device according to the invention is that of achieving suitable protection against possible overloading and, at the same time, returning the rod of the cylinder to be protected automatically to the initial position where the overloading occurred, without having recourse to special operations.
- Moreover, in accordance with the preferred embodiment of the. invention, there is also achieved the advantage that the structural compactness of the protection device renders it more efficient.
Claims (5)
1. Device for protecting a hydraulic cylinder (1) against overloading, characterised in that it comprises an auxiliary hydraulic cylinder in which each working chamber (16, 17) defined by its piston (14) is in constant hydraulic communication through a respective duct (18, 19) with a.corresponding working chamber (2, 3) of the hydraulic cylinder (1) to be protected, and in that the rod (21) of said piston (14) is connected to a resilient member (26) which yields in a direction opposite the direction of any displacement of the rod (21). itself resulting from the force acting on the piston (14) due to the pressure differential in the hydraulic cylinder (1) to be protected surpassing a prede--termined value due to the pressure within the cylinder (1) to be protected exceeding its maximum allowable value.
2. Protection device according to Claim 1, characterised in that the auxiliary hydraulic cylinder (13) and the resiliently yielding member (26) connected to its piston rod (21) are housed within respective parts of a longitudinal cavity (13, 20) in the piston rod (6) of the hydraulic cylinder (1) to be protected.
3. Protection device according to Claim 2, characterised in that the auxiliary hydraulic cylinder is constituted by a cylindrical portion of the inner wall of the longitudinal cavity (13) in the piston rod (6) of the cylinder (1) to be protected.
4. Protection device according to Claim 1, characterised in that the resiliently yielding member is constituted by a spring (26) which can yield to a compression force of a value predetermined in dependence on the value of the maximum pressure allowed within the hydraulic cylinder (1) to be protected, the spring (26) being mounted coaxially on an extension (22) of the rod (21) of the piston (14) of said auxiliary cylinder (13) between two annular end elements (27, 28) slidably mounted on the said rod extension (22) between two end shoulders (23, 25) thereof, the annular elements (27, 28) bearing against respective opposing annular projections (29, 30)-on the inner wall of the axial cavity (13) in the rod (6) of the cylinder (1) to be protected when the spring
(26) is in its non-operative condition.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IT8223204A IT1152387B (en) | 1982-09-10 | 1982-09-10 | PROTECTION DEVICE AGAINST OVERLOADS IN A HYDRAULIC CYLINDER |
IT2320482 | 1982-10-15 |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0103549A1 true EP0103549A1 (en) | 1984-03-21 |
Family
ID=11204858
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP83830172A Withdrawn EP0103549A1 (en) | 1982-09-10 | 1983-09-05 | Overload protection device for a hydraulic cylinder |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0103549A1 (en) |
IT (1) | IT1152387B (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3606148A1 (en) * | 1986-02-26 | 1987-08-27 | Bbc Brown Boveri & Cie | SPRING SUSPENSION OF A STEERING PISTON |
DE4424927A1 (en) * | 1994-07-14 | 1996-01-18 | Kaup Gmbh & Co Kg | Hydraulic drive set for conveyor technology |
DE10027731C1 (en) * | 2000-06-03 | 2001-11-29 | Festo Ag & Co | Operation unit activated by fluid action has contraction tube between head pieces and that can be radially expanded and exert axial tension force and has force overload prevention |
DE102015118839A1 (en) * | 2015-11-03 | 2017-05-04 | Tkr Spezialwerkzeuge Gmbh | Hydraulic unit for a mobile hydraulic tool |
CN109854282A (en) * | 2019-03-11 | 2019-06-07 | 中铁二局第四工程有限公司 | Automatic compacting device and tunnel waterproof board spreading machine people |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1347730A (en) * | 1962-10-26 | 1964-01-04 | Single-acting hydraulic cylinder | |
FR1555347A (en) * | 1967-04-26 | 1969-01-24 | ||
US4007667A (en) * | 1975-08-15 | 1977-02-15 | Fauchon Engineering Works Limited | Hydraulic positioning and shock-absorbing apparatus |
FR2414130A1 (en) * | 1978-01-09 | 1979-08-03 | Leduc & Fils Rene | Double acting hydraulic jack - has built-in pressure relief with spring-loaded piston which uncovers transfer ports |
WO1981003527A1 (en) * | 1980-06-05 | 1981-12-10 | Tampella Oy Ab | Hydraulic piston cylinder device with a valve element |
-
1982
- 1982-09-10 IT IT8223204A patent/IT1152387B/en active
-
1983
- 1983-09-05 EP EP83830172A patent/EP0103549A1/en not_active Withdrawn
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1347730A (en) * | 1962-10-26 | 1964-01-04 | Single-acting hydraulic cylinder | |
FR1555347A (en) * | 1967-04-26 | 1969-01-24 | ||
US4007667A (en) * | 1975-08-15 | 1977-02-15 | Fauchon Engineering Works Limited | Hydraulic positioning and shock-absorbing apparatus |
FR2414130A1 (en) * | 1978-01-09 | 1979-08-03 | Leduc & Fils Rene | Double acting hydraulic jack - has built-in pressure relief with spring-loaded piston which uncovers transfer ports |
WO1981003527A1 (en) * | 1980-06-05 | 1981-12-10 | Tampella Oy Ab | Hydraulic piston cylinder device with a valve element |
Non-Patent Citations (1)
Title |
---|
OELHYDRAULIK UND PNEUMATIK, vol. 6, no. 10, October 1962, page 379, Mainz, DE. * |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3606148A1 (en) * | 1986-02-26 | 1987-08-27 | Bbc Brown Boveri & Cie | SPRING SUSPENSION OF A STEERING PISTON |
US4774876A (en) * | 1986-02-26 | 1988-10-04 | Bbc Brown, Boveri Ltd. | Sprung suspension of an actuating piston |
DE4424927A1 (en) * | 1994-07-14 | 1996-01-18 | Kaup Gmbh & Co Kg | Hydraulic drive set for conveyor technology |
DE4424927C2 (en) * | 1994-07-14 | 1998-06-04 | Kaup Gmbh & Co Kg | Telescopic spreader for container loading |
DE10027731C1 (en) * | 2000-06-03 | 2001-11-29 | Festo Ag & Co | Operation unit activated by fluid action has contraction tube between head pieces and that can be radially expanded and exert axial tension force and has force overload prevention |
DE102015118839A1 (en) * | 2015-11-03 | 2017-05-04 | Tkr Spezialwerkzeuge Gmbh | Hydraulic unit for a mobile hydraulic tool |
DE102015118839B4 (en) * | 2015-11-03 | 2017-06-01 | Tkr Spezialwerkzeuge Gmbh | Hydraulic unit for a mobile hydraulic tool |
CN109854282A (en) * | 2019-03-11 | 2019-06-07 | 中铁二局第四工程有限公司 | Automatic compacting device and tunnel waterproof board spreading machine people |
Also Published As
Publication number | Publication date |
---|---|
IT8223204A0 (en) | 1982-09-10 |
IT1152387B (en) | 1986-12-31 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Designated state(s): AT BE CH DE FR GB LI LU NL SE |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
|
18D | Application deemed to be withdrawn |
Effective date: 19841122 |
|
RIN1 | Information on inventor provided before grant (corrected) |
Inventor name: ORTELLI, AURELIO |