EP0068495A1 - Shock absorbing device for hydraulic cylinder - Google Patents
Shock absorbing device for hydraulic cylinder Download PDFInfo
- Publication number
- EP0068495A1 EP0068495A1 EP82105779A EP82105779A EP0068495A1 EP 0068495 A1 EP0068495 A1 EP 0068495A1 EP 82105779 A EP82105779 A EP 82105779A EP 82105779 A EP82105779 A EP 82105779A EP 0068495 A1 EP0068495 A1 EP 0068495A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- shock absorbing
- peripheral surface
- port
- absorbing member
- back pressure
- 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.)
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Classifications
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- 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
- F15B15/20—Other details, e.g. assembly with regulating devices
- F15B15/22—Other details, e.g. assembly with regulating devices for accelerating or decelerating the stroke
- F15B15/222—Other details, e.g. assembly with regulating devices for accelerating or decelerating the stroke having a piston with a piston extension or piston recess which throttles the main fluid outlet as the piston approaches its end position
Abstract
Description
- This invention relates to a shock absorbing device for a hydraulic cylinder capable of imparting to a piston the function of absorbing the force of shocks in a plurality of stages at the terminating portion of a stroke of the piston of the hydraulic cylinder.
- In the majority of hydraulic cylinders operated hydraulically, it is usual practice to move the piston rod assembly at high speed to increase operation efficiency. The piston rod assembly moving at high speed has high kinetic energy, so that it is necessary to provide means for absorbing high energy of inertia to bring same to a halt at the end of its stroke. If the piston rod assembly were allowed to impinge on the end wall of the cylinder when it is brought to a halt, a high force of impact would be exerted on the end wall to thereby cause considerable damage thereto. Thus a shock absorbing device for absorbing the energy of inertia possessed by the piston rod assembly has been provided to absorb the force of shocks at the end of the stroke of the piston.
- One type of shock absorbing device known in the art is disclosed in Japanese Patent Application Laid-Open No. 35478/72 (corresponding to US Application serial No. 128,822). This shock absorbing device comprises a cylindrical shock absorbing port formed in the end wall of the cylinder housing in a manner to extend axially and communicating at one end with the cylinder chamber and at the other end with a suction and exhaust passageway, and a cylindrical shock absorbing member mounted on the piston and adapted to be inserted in the shock absorbing port at the end of the stroke of the piston to reduce the area of the channel in the shock absorbing port. The device functions such that high resistance is offered to a stream of working fluid discharged, in the terminating stages of the stroke of the piston, from the cylinder chamber through the shock absorbing port by the piston as the shock absorbing member enters the shock absorbing port, to thereby restrict the flow rate of the discharged fluid to impart a shock absorbing function to the piston. Some disadvantages are associated with this device of the prior art. First, the effectiveness of the shock absorbing function may vary depending on the relation between the length of the cylindrical portion of the cylindrical shock absorbing member and the length of the shock absorbing port. To increase the shock absorbing function would require an increase in the lengths. This however, would increase the overall length of the cylinder. Conversely, in the case of a cylinder of restricted cylinder length, it would be necessary to forgo the benefit of shock absorbing function. Secondly, the shock absorbing device of the prior art has a shock absorbing characteristic such that the instant the shock absorbing member enters the shock absorbing port, deceleration of very high order would take place in the piston and no great deceleration would occur thereafter. Stated differently, the device would only perform a shock absorbing function or energy absorbing function in a single stage. Thus a very high force of impact would be exerted on the hydraulic cylinder the instant the shock absorbing member enters the shock absorbing port, and a high force of impact would be applied to the end wall of the cylinder housing when the piston impinges thereon when it is brought to a halt. Thirdly, the provision of the axially extending shock absorbing port and the suction and discharge passageway communicating with the end portion of the shock absorbing member in the end wall of the cylinder housing would increase the axial length of the end wall of the cylinder housing. Fourthly, it is only in the annular throttling passageway defined between the inner peripheral surface of the shock absorbing port and the outer peripheral surface of the shock absorbing member that the shock absorbing function is performed, so that the clearance between the inner and outer peripheral surfaces constituting the throttling passageway would exert great influences on the shock absorbing performance. Thus it would become necessary to increase the precision with which working and assembling are performed, which would be troublesome.
- This invention has been developed for the purpose of obviating the aforesaid disadvantages of the prior art. Accordingly, one of the objects of the invention is to provide a shock absorbing device for a hydraulic cylinder which is free from the defects of the shock absorbing device for a hydraulic cylinder of the prior art described in the background of the invention.
- Another object of the invention is to provide a shock absorbing device for a hydraulic cylinder operative to absorb the energy of inertia of the piston assembly at least in two stages.
- According to the invention, there is provided, in a hydraulic cylinder comprising a housing including a cylindrical side wall and at least one end wall, and a piston assembly including a piston slidably arranged in the housing for axial sliding movement for cooperating with the housing to define therein a working space, a shock absorbing device comprising means for defining a shock absorbing hole formed in the end wall and extending axially of the housing., passageway means communicating with the shock absorbing hole, and a shock absorbing member mounted on the piston assembly in a manner to align with the shock absorbing hole and adapted to enter the shock absorbing hole in terminating stages of a stroke of the piston to throttle the flow of fluid in the shock absorbing hole, characterized in that said passageway means comprises a port opening in the shock absorbing hole at its inner peripheral surface defining the hole, said port being located in a position in which the area of its opening is reduced by the shock absorbing member.
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- Fig. 1 is a sectional view of a hydraulic cylinder incorporating therein the shock absorbing device comprising one embodiment of the invention;
- Figs. 2 and 3 are sectional views showing, on an enlarged scale, the shock absorbing device of Fig. 1 mounted on the head cover side with the piston located in different operation positions;
- Fig. 4 is a sectional view showing, on an enlarged scale, the shock absorbing device of Fig. 1 mounted on the head cover side;
- Fig.. 5 is a diagrammatic representation of the shock absorbing characteristic of the embodiment shown in Figs. 2-and 3;
- Figs. 6 and 7 are sectional views of the shock absorbing device comprising another embodiment, shown as mounted on the head cover side with the piston located in different operation positions;
- Fig. 8 is a graph showing the piston speed and the head cover acceleration in the shock absorbing stroke of the embodiment shown in Figs. 6 and 7;
- Fig. 9 is a diagrammatic representation of the pressure characteristic of the embodiment shown in Figs. 6 and 7 exhibited in the shock absorbing stroke;
- Fig. 10 is a graph showing the piston speed and the head cover acceleration of a shock absorbing device of the prior art in the shock absorbing stroke;
- Fig. 11 is a sectional view of the shock absorbing device comprising still another embodiment mounted on the rod cover side similar to the embodiment shown in Figs. 6 and 7;
- Figs. 12 and 13 are sectional views of modifications of the embodiment shown in Fig. 6;
- Figs. 14 and 15 are sectional views of the shock absorbing device comprising still another embodiment mounted on the head cover side with the piston located in different operation positions;
- Fig. 16 is a sectional view of the shock absorbing device comprising still another embodiment mounted on the rod cover side similar to the embodiment shown in Figs. 14-15;
- Figs. 17-19 are sectional views of the shock absorbing device comprising still another embodiment mounted on the head cover side with the piston located in different operation positions;
- Fig. 20 is a graph showing the piston speed and the head cover acceleration of the embodiment shown in Figs. 17-19 in the shock absorbing stroke;
- Fig. 21 is a sectional view of the shock absorbing device comprising a further embodiment mounted on the rod cover side similar to the embodiment shown in Figs. 17-19; and
- Figs. 22 and 23 are sectional views of modifications of the embodiments shown in Figs. 17-19.
- Referring to Fig. 1, the hydraulic cylinder comprises a cylinder housing including a cylinder 1 and a
head cover 2 androd cover 3 secured to opposite ends of the cylinder 1. Thehead cover 2 is formed therein with ashock absorbing hole 4 adapted to receive therein a shock absorbing member subsequently to be described, aport 5 opening in theshock absorbing hole 4 at its side, and a supply anddischarge passageway 6 communicating with theport 5. Likewise, therod cover 3 is formed therein with ashock absorbing hole 7, aport 8 and a supply anddischarge passageway 9. The rod cover 3 guides arod 10 for sliding movement, and therod 10 has apiston 11 defining hydraulic chambers A and B in the cylinder 1 in which it is slidably fitted. Anut 12 for securing thepiston 11 to therod 10 and theshock absorbing member 13 are located at an end surface of thepiston 11 on thehead cover 2 side, and anothershock absorbing member 14 is located at an end surface of thepiston 11 in contact therewith. - The
shock absorbing members rod 10 orpiston 11. Alternatively, shock absorbing rings held by therod 10 through rubber rings may be used. - As shown on an enlarged scale in Figs. 2 and 3, the
shock absorbing hole 4 includes a cylindrical innerperipheral surface 4A at which theport 5 opens in theshock absorbing hole 4. Meanwhile, theshock absorbing member 13 is aligned with theshock absorbing hole 4 and has a cylindrical outerperipheral surface 13A of an outer diameter slightly smaller than the diameter of the innerperipheral surface 4A. Thus, as theshock absorbing member 13 is received in theshock absorbing hole 4, a minuscule annular gap or throttle passageway C is defined between the innerperipheral surface 4A of theshock absorbing hole 4 and the outerperipheral surface 13A of theshock absorbing member 13. Theport 5 is positioned such that, as shown in Fig. 3, it is closed by the outerperipheral surface 13A of theshock absorbing member 13 at the end of a stroke of thepiston 11. - Likewise, as shown in Fig. 4, the
shock absorbing hole 7 formed in therod cover 3 includes a cylindricalinner surface 7A, and theshock absorbing member 14 includes a cylindrical outerperipheral surface 14A. The outerperipheral surface 14A of theshock absorbing member 14 cooperates with the innerperipheral surface 7A of theshock absorbing hole 7 to define therebetween an annular gap D and closes theport 8. - Operation of the shock absorbing device shown and described hereinabove will be described. Upon a pressure fluid being fed into the chamber B from the supply and
discharge passageway 9 via theport 8, thepiston 11 moves rightwardly in the figure at high speed in a compression stroke and enters a shock absorbing stroke, in which the forward end of theshock absorbing member 13 enters theshock absorbing hole 4 to define the annular throttle passageway C between the innerperipheral surface 4A of theshock absorbing hole 4 and the outerperipheral surface 13A of theshock absorbing member 13. This throttles the flow of the pressure fluid from the chamber A to the supply anddischarge passageway 6 via theshock absorbing hole 4, so that a high pressure prevails in the chamber A to offer high resistance to the movement of thepiston 11. At the same time, the resistance offered by the flow of the pressure fluid through the throttle passageway C is conducive to rapid deceleration of thepiston 11. This condition is represented in Fig. 5 by a curve PP'. Then a shock absorbing function mainly attributed to resistance to the flow offered by the throttle passageway C is performed, and thepiston 11 shows slow deceleration as indicated by a curve P'Q. During this shock absorbing operation, theshock absorbing member 13 continues its movement into theshock absorbing hole 4 and the length of the annular throttle passageway C increases with an attendant increase in the resistance offered thereby to the flow of the pressure fluid. However, the deceleration of thepiston 11 is not so high. A position represented by Q in Fig. 5 is a position (shown in Fig. 2) in which the forward end of theshock absorbing member 13 is positioned against theport 5. - Further movement of the
shock absorbing member 13 into the shock absorbing hole gradually reduces the area of the opening of theport 5 as it is closed by the outerperipheral surface 13A of theshock absorbing member 13. This creates a high resistance offered to the pressure fluid as it flows through theport 5 into the supply anddischarge passageway 6 from aspace 4B in thehole 4 after it has flown through the annular throttle passageway C into thespace 4B, to thereby decelerate thepiston 11. The flow resistance offered by theport 5 grows by leaps and bounds as the area of the opening of theport 5 is reduced, so that thepiston 11 shows a rapid deceleration as indicated by a curve QR in Fig. 5. A point R shown in Fig. 5 is a point at which the outerperipheral surface 13A of theshock absorbing member 13 fully closes the port 5 (as shown in Fig. 3) immediately before thepiston 11 reaches the end of the stroke. Thereafter the piston assembly reaches the end of the stroke and abuts against the end wall of the cylinder 1, thereby being brought to a halt (as represented by a point T in Fig. 5). As described hereinabove, in this embodiment, it is possible to decelerate thepiston 11 until its speed is reduced to a very low level by a shock absorbing operation performed in two stages, shock absorption in the first stage being performed by the action of the throttle passageway C (represneted by a curve PQ) and shock absorption in the second stage being performed by the throttling action of the passageway C and the port 5 (represented by the curve QR). - Meanwhile, in the shock absorbing device of the prior art described hereinabove, shock absorption is performed only by the throttling action of the throttle passageway C. Thus the piston speed is reduced as indicated by a curve PQS. As a result, the piston still has high speed when it reaches-the end of its stroke and a high force of impact is produced at the end of its stroke. To reduce the speed of the piston satisfactorily at the end of its stroke, one has only to reduce the gap between the shock absorbing member and the shock absorbing hole or the width of the throttle passageway C and increase its length. This would entail an increase in the overall length of the cylinder and make it necessary to increase the precision with which machining and assembly of the parts are performed. The shock absorbing device of the prior art incorporating therein the aforesaid improvements has a shock absorbing characteristic such that the speed is reduced abruptly as indicated by a dash-and-dot line PR in Fig. 5. Thus, it will be appreciated that the embodiment of the present invention is superior to the device of the prior art in that a better shock absorbing characteristic is obtained without requiring to increase the precision of machining and assembling of the parts and to increase the length of the cylinder.
- The aforesaid description refers to the shock absorbing device mounted on the
head cover 2 side. - The shock absorbing device mounted on the
rod cover 3 side operates in like manner, so that the description thereof shall be omitted. - In the embodiment shown and described hereinabove, the inner peripheral surface of the shock absorbing hole and the outer peripheral surface of the shock absorbing member are both cylindrical in shape. However, the invention is not limited to this specific shape and one or both of them may be tapering. The use of a tapering inner peripheral surface and/or an outer peripheral surface causes a reduction in the cross-sectional area of the annular gap C or D defined therebetween as the shock absorbing member progressively enters the shock absorbing hole, thereby increasing the shock absorbing effect.
- Figs. 6 and 7 show an embodiment distinct from the embodiment shown in Figs. 2 and 3. In Figs. 6 and 7, parts similar to those shown in Figs. 2 and 3 are designated by like reference characters and their description is omitted. In this embodiment also, a
shock absorbing hole 21 having a cylindrical innerperipheral surface 21A is formed in thehead cover 2, and aport 23 of a suction anddischarge passageway 22 opens in theshock absorbing hole 21 at the innerperipheral surface 21A. Meanwhile theshock absorbing member 13 has a cylindrical outerperipheral surface 13A cooperating with the innerperipheral surface 21A of theshock absorbing hole 21 to define therebetween an annular throttle passageway C and operating to close theport 23. In this embodiment, theshock absorbing hole 21 extends farther than theport 23 to form aback pressure chamber 24, and theshock absorbing member 13 is constructed such that, as shown in Fig. 7, the forward end of the cylindrical outerperipheral surface 13A moves past theport 23 to enter theback pressure chamber 24 at the end of a stroke of the piston and cooperates with the innerperipheral surface 21A of theshock absorbing hole 21 to define adjacent and posterior to the port 23 a minuscule annular gap or annular throttle passageway E. The annular throttle passageway E functions such that when theshock absorbing member 13 enters theback pressure chamber 24, the pressure fluid in the latter is restricted in its flow to theport 23 to thereby generate a pressure in theback pressure chamber 24. - In operation, as the
piston 11 progressively moves rightwardly in Fig. 6, theshock absorbing member 13 enters theshock absorbing hole 21. Flow of the pressure fluid from the chamber A to theport 23 is suddenly restricted by the throttle passageway C, to perform shock absorption of the first stage. Further movement of theshock absorbing member 13 into theshock absorbing hole 21 results in gradual reduction in the opening of theport 23 as it is closed by the outerperipheral surface 13A of theshock absorbing member 13, thereby perform shock absorption of the second stage. Theshock absorbing member 13 continues its movement into theshock absorbing hole 21 even after the former has fully closed theport 23, to generate a high pressure in theback pressure chamber 24, which offers resistance to the movement of theshock absorbing member 13 into theshock absorbing hole 21. Combined with the resistance offered by the high pressure in theback pressure chamber 24, the resistance offered by the throttle passageway E to the flow of the pressure fluid from theback pressure chamber 24 through the throttle passageway E to theport 23 performs shock absorption of the third stage. Thus the shock absorbing device of the embodiment in conformity with the invention performs shock absorption in three stages. - Figs. 8 and 9 are graphs showing shock absorbing characteristics of the embodiment shown in Figs. 6 and 7 as actually measured. In Fig. 8, a curve (a) represents a change in piston speed, and points i, ii, iii and iv indicate positions in which shock absorption is initiated immediately before the
shock absorbing member 13 enters theshock absorbing hole 21, theshock absorbing member 31 begins to close theport 23 of the suction anddischarge passageway 22, theshock absorbing member 13 has completely closed theport 23 and thepiston 11 has reached the end of its stroke, respectively. Meanwhile, a curve (2) represents a change in the acceleration of thehead cover 2. In Fig. 9, P l. P 2' P3 and P4 represent the internal pressure of the hydraulic chamber B (see Fig. 1), the internal pressure of the hydraulic chamber A, the internal pressure of theback pressure chamber 24 and the internal pressure of the supply and discharge passageway 22 (see Fig. 7) respectively. In the graphs shown in Figs. 8 and 9, a section i - ii represents a first stage shock absorption in which the internal pressure P2 of the chamber A gradually rises and offers resistance to thepiston 11 while the latter is decelerated by the throttling action of the throttle passageway C. A section ii - iii represents a second stage shock absorption in which in addition to the aforesaid shock absorption, theport 23 of the suction anddischarge passageway 22 is gradually throttled and the piston is decelerated. A section iii - iv represents a third stage shock absorption in which, following full closure of theport 23, the back pressure p 3 is proaucea in thenacK pressure cnamber 24 to aece- lerate thepiston 11. - Fig. 10 is a graph showing the data obtained with the shock absorbing device of the prior art relying on the throttle passageway alone for effecting shock absorption. As shown, a curve (a) represents a change in the speed of the piston, and a curve (b) indicates a change in the acceleration of the
head cover 2. In Fig. 10, it will be seen that in the shock absorbing device of the prior art, shock absorption is performed only in one stage and that even at the end of a shock absorbing operation, thepiston 11 still has a substantial speed as indicated at a point X. Thepiston 11 is brought to a halt at the.end of its stroke by impinging on thehead cover 2, so that a high force of impact is exerted on thehead cover 2 and high acceleration is generated in thehead cover 2 as indicated at a point Y. On the other hand, in the embodiment shown in Figs. 6 and 7, smooth deceleration of thepiston 11 can be obtained as shown in Fig. 8 and a good shock absorbing characteristic is exhibited. The change in the acceleration of thehead cover 2 is almost nil as indicated by the curve (b), indicating that no high force of impact is exerted thereon. - Fig. 11 shows a modification of the shock absorbing device mounted on the
rod cover 3 side. - In the figure, the cylindrical outer
peripheral surface 14A of ashock absorbing member 14 extends beyond aport 32 opening in ashock absorbing hole 31 at its - - innerperipheral surface 31A into aback pressure chamber 33, to define annular throttle passageways D and F on opposite sides of theport 32. Like the embodiment shown in Figs. 6 and 7, the embodiment shown in Fig. 11 performs shock absorption in three stages. - In the embodiments shown in Figs. 6, 7 and 11, the shock absorbing hole and the shock absorbing member have cylindrical inner and outer peripheral surfaces respectively. However, the invention is not limited to this form of the shock absorbing hole and member, one or both of the shock absorbing hole and member may be tapering in form.
- Fig. 12 shows a modification of the embodiment shown in Figs. 6 and 7. This modification has a tapering
groove 41 formed in a portion of the cylindrical outerperipheral surface 13A of theshock absorbing member 13 facing theport 23. The taperinggroove 41 has a progressively increasing depth in going toward the forward end of theshock absorbing member 13. - Thus as the
shock absorbing member 13 enters theshock absorbing hole 21 and closes theport 23, the taperinggroove 41 provides a channel for the pressure fluid to flow to theport 23, thereby avoiding sudden deceleration of the piston. The depth of the taperinggroove 41 is reduced as theshock absorbing member 13 enters theshock absorbing hole 21, so that the throttling effect increases and a good deceleration characteristic can be exhibited. Moreover, when the piston moves from its position shown in Fig. 12 leftwardly as pressure fluid is supplied through the supply and discharge passageway, pressure fluid is immediately supplied from theport 23 through the taperinggroove 41 to theback pressure chamber 24. As compared with the embodiment shown in Figs. 6 and 7 in which pressure fluid is supplied to theback pressure chamber 24 through the throttle passageway E alone, the embodiment shown in Fig. 12 is capable of quickly and smoothly effecting movement of theshock absorbing member 13, out of theshock absorbing hole 21. - Fig. 13 shows an embodiment which comprises, in addition to the parts of the embodiment shown in Figs. 6 and 7, a first ancillary passageway mounting a
check valve 42 allowing pressure fluid to flow from the supply anddischarge passageway 22 to the chamber A, and a second ancillary passageway mounting acheck valve 43 allowing pressure fluid to flow from the supply anddischarge passageway 22 to theback pressure chamber 24. In this embodiment also, the pressure fluid from the suction and discharge passageway.22 is fed into the chamber A and theback pressure chamber 24 through thecheck valves discharge passageway 22 and thepiston 11 has moved into'an expansion stroke, to thereby enable movement of theshock absorbing member 12 out of thehole 21 to be smoothly effected. - Figs. 14 and 15 show a still another embodiment in which a
shock absorbing hole 50 is defined by a cylindrical innerperipheral surface 50A and a tapering innerperipheral surface 50B extending beyond theport 23 and aback pressure chamber 51 is defined by a tapering innerperipheral surface 50B. Meanwhile theshock absorbing member 13 has a cylindrical outerperipheral surface 13A of a length Lc substantially equal to the length Lt of a cylindrical innerperipheral surface 50A and a tapering outerperipheral surface 13B at the forward end of the former. The tapering outerperipheral surface 13B operates in such a manner that it enters theback pressure chamber 51 and cooperates with the tapering innerperipheral surface 50B to define between thesurfaces piston 11 causes theshock absorbing member 13 to enter theshock absorbing hole 50, to allow the throttle passageway G to perform a first stage shock absorption. The first stage shock absorption lasts while the cylindrical outerperipheral surface 13A of theshock absorbing member 13 moves in a stroke covering the distance corresponding to the length Ls of the throttle passageway. Then as theshock absorbing member 13 further moves, the area of the opening of theport 23 is gradually reduced by the cylindrical outerperipheral surface 13A of theshock absorbing member 13, to thereby perform a second stage shock absorption. At the end of the second stage shock absorption, the tapering outerperipheral portion 13B of theshock absorbing member 13 enters theback pressure chamber 51 as shown in Fig. 15, to cause a back pressure to be generated therein. At the same time, the pressure fluid in theback pressure chamber 51 flows through the throttle passageway G into theport 23, so that resistance is offered by the passageway G to the flow of the pressure fluid..Thus, the shock absorbing action performed by the throttling of theport 23 gradually by the cylindrical outerperipheral portion 13A of theshock absorbing member 13 and the shock absorbing action performed by the back pressure in theback pressure chamber 51 and the throttle passageway G are set in motion simultaneously, to thereby bring about rapid deceleration of thepiston 11. At this time, as the tapering outer periperal surface 13B.of theshock absorbing member 13 nears the tapering innerperipheral surface 50B of theshock absorbing hole 50, the cross-sectional area of the throttle passageway G shows a sudden reduction and the resistance offered to the flow of the pressure fluid therethrough rapidly increases. Thus a positive shock absorbing action can be performed to bring thepiston 11 to a halt. The tapering surfaces 13B and 50B defining the throttle passageway G may be parallel to each other or angles of inclination a and β may be equal to each other as shown in Fig. 14. However, the angle of inclination S of theshock absorbing hole 50 is preferably greater than the angle of inclination a of theshock absorbing member 13. When a < S, a thin blade orifice can be formed between the forward end of the tapering outerperipheral surface 13B of theshock absorbing member 13 and the tapering innerperipheral surface 50B of theshock absorbing hole 50, so that it is possible to offer resistance to the pressure fluid flowing through the orifice without the fluid being influenced much by the temperature and viscosity of the fluid. - Fig. 16 shows an embodiment in which the same concept as incorporated in the embodiment shown in Figs. 14 and 15 is incorporated in a shock absorbing device mounted on the rod cover side. In this embodiment, a tapering inner
peripheral surface 60B is formed in a portion of ashock absorbing port 60 extending beyond aport 32. The operation of this embodiment is similar to that of the embodiment shown in Fig. 14, so that detailed description shall be omitted. - Figs. 17, 18 and 19 show still another embodiment in which, as in the embodiment shown in Fig. 6, the
shock absorbing member 13 has a cylindrical outerperipheral surface 13A and a tapering outerperipheral surface 13B, while ashock absorbing hole 70 has a cylindrical innerperipheral surface 70A and aport 23 opening in thehole 70 at the cylindrical innerperipheral surface 70A. Theshock absorbing hole 70 is additionally formed with an annular steppedportion 70C disposed beyond the innerperipheral surface 70A between it and an innerperipheral surface 70B of smaller diameter than the innerperipheral surface 70A, as distinct from theshock absorbing hole 21 shown in Fig. 6. The steppedportion 70C is located in a position spaced apart from the entrance of the shock absorbing hole 70 a distance corresponding to the length Lc of the cylindrical portion of theshock absorbing member 13. - In operation, as the cylindrical outer
peripheral surface 13A of theshock absorbing member 13 enters theshock absorbing hole 70, a throttle passageway C is defined between the cylindrical outerperipheral surface 13A and the innerperipheral surface 70A of theshock absorbing hole 70, so that the throttle passageway C performs a first stage shock absorption. This shock absorbing action lasts while the cylindrical outerperipheral surface 13A moves a distance corresponding to the length Ls of the throttle passageway C. Further movement of theshock absorbing member 13 causes the cylindrical outerperipheral portion 13A to gradually close the opening of theport 23, to additionally perform a shock absorbing action by the throttling of the flow of the pressure fluid through theport 23, to thereby perform a second stage shock absorption. Furthermore, as the cylindrical outerperipheral surface 13A of theshock absorbing member 13 moves past the opening of theport 23 as shown in Fig. 18, the forward end of theshock absorbing member 13 enters aback pressure chamber 71, to cause a back pressure to be generated therein. Thus the resistance offered to the flow of the pressure fluid by the back pressure in theback pressure chamber 71 and by the throttle passageway E perform a shock absorbing action, thereby setting in motion a third stage shock absorption. When further movement of theshock absorbing member 13 brings same to a position shown in Fig. 19, an annular orifice H is defined between the tapering outerperipheral surface 13B of theshock absorbing member 14 and the steppedportion 70C of theshock absorbing hole 70. Thus as the area of the orifice H is reduced, the back pressure in theback pressure chamber 71 rises because the latter is brought to a closed condition, to thereby offer increased resistance to theshock absorbing member 13. At the same time, the resistance offered to the flow of the pressure fluid from theback pressure chamber 71 to the throttle passageway E through the orifice H performs a shock absorbing action, thereby enabling a fourth stage or last stage shock absorption to be performed. - As described hereinabove, in the embodiment shown in Figs. 17-19, shock absorption is carried out in four stages, to enable smooth deceleration of the
piston 11 to be obtained. Fig. 20 shows the results of actual measurements of a change in the speed of the piston and a change in the acceleration of the head cover done in the embodiment shown in Figs. 17-19. In the figure, a curve (a) represents the speed of the piston, and a curve (b) indicates the acceleration of the head cover. As can be clearly seen in the figure, this embodiment enables smoother deceleration of thepiston 11 to be obtained than the embodiment shown in Fig. 8. - The concept of the embodiment shown in Figs. 17-19 can, of course, be incorporated in a shock absorbing device mounted on the
rod cover 3 side. - Fig. 21 shows an embodiment of this concept in the shock absorbing device mounted on the
rod cover 3 side, in which a shock absorbing hole 80 has a cylindrical innerperipheral surface 80A of a major diameter, a cylindrical innerperipheral surface 80B of a minor diameter and a steppedportion 80C interposed therebetween. The steppedportion 80C operates in such a manner that a minuscule annular orifice is defined between the tapering outer peripheral surface 14B of theshock absorbing member 14 and the steppedportion 80C. In this embodiment also, shock absorption is performed in four stages, like the embodiment shown in Figs. 17-19. - Figs. 22 and 23 show modifications of the embodiment shown in Fig. 17. Like the embodiment shown in Fig. 12, the modification shown in Fig. 22 is formed with a tapering
groove 41 in theshock absorbing member 13. In the modification shown in Fig. 23,check valves shock absorbing member 13 out of the hold is offered as described by referring to the embodiment shown in Figs. 12 and 13. - While preferred embodiments of the invention have been shown and described hereinabove, it is to be understood that they are merely for purposes of illustration and not limiting the scope of the invention.
- It will be apparent that various changes and modifications may be made therein without departing from the spirit and scope of the invention which is defined in the appended claims.
Claims (9)
Applications Claiming Priority (8)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP96790/81U | 1981-06-30 | ||
JP9679081U JPS584804U (en) | 1981-06-30 | 1981-06-30 | cylinder device |
JP15573681U JPS5860003U (en) | 1981-10-20 | 1981-10-20 | cylinder device |
JP155736/81U | 1981-10-20 | ||
JP18784181U JPS5891004U (en) | 1981-12-16 | 1981-12-16 | cylinder device |
JP187841/81U | 1981-12-16 | ||
JP33416/81U | 1982-03-10 | ||
JP3341682U JPS58135506U (en) | 1982-03-10 | 1982-03-10 | cylinder device |
Publications (2)
Publication Number | Publication Date |
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EP0068495A1 true EP0068495A1 (en) | 1983-01-05 |
EP0068495B1 EP0068495B1 (en) | 1986-03-12 |
Family
ID=27459785
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP82105779A Expired EP0068495B1 (en) | 1981-06-30 | 1982-06-29 | Shock absorbing device for hydraulic cylinder |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0068495B1 (en) |
DE (1) | DE3269801D1 (en) |
Cited By (5)
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US4807514A (en) * | 1987-04-13 | 1989-02-28 | Gratzmueller C A | Differential hydraulic jack with damping system for the control of electric circuit-breakers |
EP0734495A1 (en) * | 1994-10-13 | 1996-10-02 | ROSE, Nigel Eric | Fluid actuated engines and engine mechanisms |
EP0751315A1 (en) * | 1995-06-27 | 1997-01-02 | KNORR-BREMSE SYSTEME FÜR NUTZFAHRZEUGE GmbH | Hydropneumatic clutch servo, especially for motor vehicles |
EP1677010A1 (en) * | 2005-01-03 | 2006-07-05 | Volvo Construction Equipment Holding Sweden AB | Cylinder cushion device |
CN112780633A (en) * | 2021-01-06 | 2021-05-11 | 安徽鼎图液压设备有限公司 | Double-cylinder hydraulic oil cylinder |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3323422A (en) * | 1965-08-02 | 1967-06-06 | Cessna Aircraft Co | Cushion stop for hydraulic cylinders |
DE2603041A1 (en) * | 1976-01-28 | 1977-08-04 | Licentia Gmbh | Hydraulically driven circuit breaker - has dampening system with non return valves mounted in region of working cylinder bore |
US4064788A (en) * | 1976-07-29 | 1977-12-27 | Parker-Hannifin Corporation | Cushioning means for hydraulic cylinder |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3704650A (en) * | 1971-03-29 | 1972-12-05 | Caterpillar Tractor Co | Hydraulic jack stroke cushioning means |
-
1982
- 1982-06-29 EP EP82105779A patent/EP0068495B1/en not_active Expired
- 1982-06-29 DE DE8282105779T patent/DE3269801D1/en not_active Expired
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3323422A (en) * | 1965-08-02 | 1967-06-06 | Cessna Aircraft Co | Cushion stop for hydraulic cylinders |
DE2603041A1 (en) * | 1976-01-28 | 1977-08-04 | Licentia Gmbh | Hydraulically driven circuit breaker - has dampening system with non return valves mounted in region of working cylinder bore |
US4064788A (en) * | 1976-07-29 | 1977-12-27 | Parker-Hannifin Corporation | Cushioning means for hydraulic cylinder |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4807514A (en) * | 1987-04-13 | 1989-02-28 | Gratzmueller C A | Differential hydraulic jack with damping system for the control of electric circuit-breakers |
EP0734495A1 (en) * | 1994-10-13 | 1996-10-02 | ROSE, Nigel Eric | Fluid actuated engines and engine mechanisms |
EP0734495A4 (en) * | 1994-10-13 | 1998-10-28 | Nigel Eric Rose | Fluid actuated engines and engine mechanisms |
EP0751315A1 (en) * | 1995-06-27 | 1997-01-02 | KNORR-BREMSE SYSTEME FÜR NUTZFAHRZEUGE GmbH | Hydropneumatic clutch servo, especially for motor vehicles |
EP1677010A1 (en) * | 2005-01-03 | 2006-07-05 | Volvo Construction Equipment Holding Sweden AB | Cylinder cushion device |
CN112780633A (en) * | 2021-01-06 | 2021-05-11 | 安徽鼎图液压设备有限公司 | Double-cylinder hydraulic oil cylinder |
Also Published As
Publication number | Publication date |
---|---|
EP0068495B1 (en) | 1986-03-12 |
DE3269801D1 (en) | 1986-04-17 |
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