GB2060777A - Double-acting jack - Google Patents

Double-acting jack Download PDF

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Publication number
GB2060777A
GB2060777A GB8032228A GB8032228A GB2060777A GB 2060777 A GB2060777 A GB 2060777A GB 8032228 A GB8032228 A GB 8032228A GB 8032228 A GB8032228 A GB 8032228A GB 2060777 A GB2060777 A GB 2060777A
Authority
GB
United Kingdom
Prior art keywords
piston
rod
tubular rod
cylinder
tubular
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Withdrawn
Application number
GB8032228A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Gai A & G Ultraflex SNC
Original Assignee
Gai A & G Ultraflex SNC
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Gai A & G Ultraflex SNC filed Critical Gai A & G Ultraflex SNC
Publication of GB2060777A publication Critical patent/GB2060777A/en
Withdrawn legal-status Critical Current

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20Other details, e.g. assembly with regulating devices
    • F15B15/26Locking mechanisms
    • F15B15/261Locking mechanisms using positive interengagement, e.g. balls and grooves, for locking in the end positions

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Actuator (AREA)

Abstract

A double-acting jack has a piston 20 slidable inside a cylinder 11 and a tubular piston rod 40 slidable over a fixed rod 30 supported by the cylinder blind head 12. The piston 20 is connected to the tubular rod 40 by a pair of springs 21, 22 provided one at either side of the piston between respective faces 23, 24 thereof 25, 26 on the outer surface of the tubular rod. The fixed rod 30 is provided with at least one annular groove 33. In the position shown locking balls 35, 36 disposed in bores 43, 44 in the wall of the tubular rod 40 project into the annular groove 33 thereby locking the rods against relative movement. When the left hand surface of the piston is pressurised the spring 22 compresses to allow the piston to move relative to its piston rod 40. This movement enables the balls to enter a groove 27 in the piston and thus automatically release the lock. <IMAGE>

Description

SPECIFICATION Double effect jack The present invention relates to a double effect jack.
The present invention consists in a double effect jack which having arrived at one of its two end positions is not displaced until its movement is again controlled even when there is a drop in the working fluid pressure. The use of hydraulic, pneumatic jacks and jacks which in general are controlled by any kind of working fluid, requires that, together with the jacks there should be safety means, which prevent displacement of the relative jack-cylinder position when for any reason, for example a failure, there is a drop in the working fluid pressure which has driven the jack into the required position.
It is known to use pneumatic or hydraulic jacks which are capable of discontinuous operation, so that, once the desired position is reached, it is necessary to provide for mechanical stop means, which are capable of taking pressure of the jack cylinder tubes and chambers.
According to a first aspect of the invention, a double effect jack comprises a piston longitudinally movable within a cylinder, the piston being actuated by fluid pressure, and mechanical means for automatically locking the piston with respect to an end of the cylinder.
According to a second aspect of the invention, a double effect jack is provided with stop means for at least one predetermined position, and for at least the two end-of-stroke positions, of the type providing for a cylinder with a blind head, on one side, and a bored head for the passage of the piston rod, on the other side, a sliding piston inside said cylinder together with a tubular rod, slidable along a drive rod integral with the cylinder blind head, wherein said piston is connected with an axial clearance to the tubular rod by means of a pair of shoulders provided on the outer surface of the tubular rod and a by a pair of springs provided at the two sides of the piston between each face of the piston and the shoulder associated thereto, wherein the cylinder bore of the piston through which passes the tubular rod is provided with two annular grooves and the tubular rod is provided with at least one bore in its thickness, in correspondence with the median axial position (P) of the piston in respect with the tubular rod; wherein at least one annular groove is provided in the drive rod and at least one locking ball is provided in each of said bores in the tubular rod wall; the diameter of said locking ball being greater than the wall thickness of the tubular rod on one side, and on the other smaller than the sum of the wall thickness of the tubular rod plus the depth of the grooves of the piston as well as smaller than the sum of the tubular rod wall thickness plus the depth of the grooves of the drive rod.
The purpose of the present invention is to obtain a double effect pneumatic or hydraulic jack in which, once one of the two end positions of the cylinder-piston unit is reached the position is automatically maintained even if the working fluid pressure should fall to zero. A reverse movement of the piston will then take place only after the working fluid under pressure will again be fed to the cylinder in the desired direction.
The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 A shows in cross-section one end of a jack according to the invention, adjacent to its blind head; Figure 1 B shows in cross-section the other end of the jack shown in Figure 1 A, adjacent to its bored head, for the passage of a piston rod; and Figures 2 to 6 are sections of part of the jack shown in Figures 1 A and 1 B, limited to the piston and to the adjacent cylinder areas; in Figures 2 to 6 the piston is shown in different successive positions starting from the position in which the piston is near its blind head (Figure 1 A) through to the position where the piston is near the bored head (Figure 6) to allow for the passage of the piston rod.
Figures 1 A and 1 B show a double effect jack 10 having a cylinder 11, a first end head 12, which is blind, and a second end head 13, which is bored to allow for the passage of a piston rod.
There is a movable piston 20 within the cylinder 11, the piston being provided with an annular seal 29. For movement inside the cylinder 11, the piston 20 is driven by a rod 30 which is fastened at one end 31, for example by screwing, to the bottom of the blind head 12 of the cylinder.
Whereas the rod 30, at its other end 32, partially crosses the bored head 13, from which it receives only a radial centring.
The axial movement of the piston 20 is associated with the axial movement of a tubular rod 40 which is in turn connected to the piston 20 at one end 42, internally adjacent to the blind head 12. The tubular rod 40 crosses the bored head 13 and slides along the drive rod 30. The other end 41 of the tubular rod 40, which faces the bored head 13 is rigidly connected to a push rod 50. The push rod is generally solid, and is used to transmit the transverse movement of the piston 20 from the jack 10 to the mechanism to be controlled, which is not shown in the drawings.
Figure 1 B shows the connection between the end 41 (also called the outer end) of the tubular rod 40 and the push rod 50. The push rod has an annular groove 51 onto which - by means of rolling -- is pushed the wall of the tubular rod 40 which therefrom forms a firm connection with the push rod 50. It can be seen that, when the piston 20 is moved towards its extreme position near the blind head 12, as shown in Figures 1 A and 1 B, the outer end 32 of the drive rod 30 contacts the inner end 52 of the push rod 50, which is firmly connected to the tubular rod 40. In other cases, there may be a clearance between the free end 32 of the drive rod 30 and the inner end 52 of the push rod 50; this is because of the relative position of the assembly 40-50 on the one hand and of the assembly 10-30 on the other hand.
The assembly consisting of the tubular rod 40 and the push rod 50 follows the displacement of the piston 20, whereas the cylinder 10 and rod 30 work as drive elements. According to the invention, the piston 20 and the tubular rod 40 are not rigidly connected to one another. A pair of springs 21 and 22 in fact permits suitable relative movement between the piston 20 and the inner end 42 of tubular rod 40.
The springs 21 and 22 are located between faces 23 and 24 of the piston 20 and two elastic locking rings 25 and 26 respectively. The locking rings 25 and 26 are fastened to the outer surface of the tubular rod 40 near the inner end area 42 of the tubular rod.
The elastic characteristics of the two springs and the geometrical dimensions of the concerned constructional elements are such that, jn respect to the position of the piston 20 shown in Figure 1 A and which corresponds to a centered position, the piston is movable in either direction, with respect to the tubular rod 40 by two equal distances shown as 'd' in the drawing. The piston 20 can therefore slide along the tubular rod 40 by a distance equal to 2xd.
The central bore of the piston 20 which serves as a guide surface for the piston displacement in respect of the tubular rod 40 is provided with two annular grooves 27, 28 which are spaced from the median transversal plane P of the piston by the same distance 'd'.
When the position of the piston 20 is centred in respect to the tubular rod 40, there are two diametrically opposed bores 43 and 44 on the tubular rod 40 which are aligned with a first annular groove 33 of the drive rod 30. This occurs when the piston 20 is at its inner end position.
Two balls 35 and 36 acting as stop members are partially inserted into the groove 33 and the bores 43 and 44 of the tubular rod 40, in order to allow for relative transverse movement of the piston 20 in respect of the tubular rod 40.
Therefore, as in the position shown in Figure 1 A, the springs 21 and 22, in the absence of pressure on both the right and left of the piston 20, maintain the piston 20 in a centered position with respect to the elastic locking rings 25 and 26.
In this position, the tubular rod 40 and the drive rod 30 are removably held fixed relative to each other by the locking balls 35 and 36, the diameter of each ball being substantially equal to the sum of the depth of groove 33 and of the thickness of the wall of the tubular rod 40. Until the piston 20 is pushed to the right or to the left by fluid pressure, the push rod 50 and the tubular rod 40 are locked in respect of the drive rod 30, and therefore the jack is in a locked position.
When pressure is applied, for example against the face 23 to the left of the piston, and the rod 40 and the rod 30 are still removably held fixed relative to each other by means of the balls 35 and 36, the piston 20 is moved to the right to the position shown in Figure 2, thereby overcoming the reaction force of the spring 22. In such a position, the spring 22 is entirely compressed, and the recovery of the clearances between the various spires is equal to the above defined distance 'd'.
Thus, the grooves 27 of the piston 20 aligns with the openings 43 and 44. If the pressure continues to act on the face 23 of the piston 20, the piston 20 via the compressed spring 22 and the ring 26, transfers the force to the tubular rod 40, which is pushed to the right. As at the beginning of this movement (Figure 2), the groove 27 is aligned with the bore 43 and 44, the balls 35 and 36 can come out of the groove 33, and enter the opening formed by the groove 27 and the bore 43 and 44 respectively of the tubular rod 40, and become rigidly fixed with respect to axial movement of the piston 20 and the tubular rod 40 as shown in Figure 3. In this relative position of the piston 20 and the tubular rod 40, the 200-50 assembly reaches the outer end of the drive rod 30, which is here provided with a second annular groove 34 (Figure 4).
The spring 22 is always compressed. The groove 27 of the piston 20 aligns with the second groove 34 of the drive rod 30 (Figure 5) even, if the pressure acting On the left face of piston 20 still maintains the spring 22 compressed, the alignment of the grooves 27 and 34 and the bores 43 and 44, the pressure frees from the rigid coupling the piston 20 and the tubular rod 40.
When the pressure on the left face of the piston 20 ceases, the compressed spring 22 pushes to the left the piston 20 by a distance equal to 'd'.
This relative movement is accompanied by the movement of the stop balls 35 and 36 into the opening made up by the thickness of the rod 40 (bores 43 and 44) and the depth of the annular groove 34 (Figure 6).
The piston is now in the position shown in Figure 6, perfectly symmetrical to the position shown in Figure 1 A. In the absence of any pressure on one of the two piston faces, the piston is maintained in a centered position with respect to the passages 43 and 44 of the spring 21 and 22. At the same time the rod 40 is removably held fixed, against any axial displacement relative to the drive rod 30. The jack is thus again locked.
The passage of the piston, and hence of the jack, from the position shown in Figure 6 to the position shown in Figure 1 A is the inverse to the above-described manner of operation. - It is on the other hand important to note that the drive rod 30 may have more than two grooves, and that the grooves can be located in an intermediate position along the drive rod. It is thus possible to lock the piston-cylinder assembly in any desired intermediate position, as well as in alignment with the end positions shown in the drawings. Moreover it is evident that the drive rod can also only have one groove, and the groove does not necessarily have to align with one of the two piston end positions.

Claims (8)

1. A double effect jack comprising a piston longitudinally movable within a cylinder, the piston being actuated by fluid pressure, and mechanical means for automatically locking the piston with respect to and end of the cylinder.
2. A double effect jack as claimed in claim 1, wherein the piston is actuated pneumatically or hydraulically.
3. A double effect jack provided with stop means for at least one predetermined position, and for at least the two end-of-stroke positions, of the type providing for a cylinder with a blind head, on one side, and a bored head for the passage of the piston rod, on the other side, a sliding piston inside said cylinder together with a tubular rod, slidable along a drive rod integral with the cylinder blind head, where said piston is connected with an axial clearance to the tubular rod by means of a pair of shoulders provided on the outer surface of the tubular rod and by a pair of springs provided at the two sides of the piston between each face of the piston and the shoulder associated thereto, wherein the cylindrical bore of the piston through which passes the tubular rod is provided with two annular grooves and the tubular rod is provided with at least one bore in its thickness, in correspondenca with the median axial position (P) of the piston in respect with the tubular rod; wherein at least one annular groove is provided in the drive rod and at least one locking ball is provided in each of said bores in the tubular rod wall; the diameter of said locking ball being greater than the wall thickness of thetuburar rod, on one side, and on the other smaller than the sum of the wall thickness of the tubular rod plus the depth of the grooves of the piston as well as smaller than the sum of the tubular rod wall thickness plus the depth of the grooves of the drive rod.
4. A double effect jack as claimed in Claim 3, wherein the two grooves provided on the inner surface of the axial bore of the piston are equally spaced from the median plan (P) of the piston, and said distance 'd' from the mediam transverse plane (P) of the piston is equal to the maximum shortening of each of the two above mentioned springs provided at the two sides of the piston.
5. A double effect jack as claimed in Claim 3, wherein the said annular shoulders provided on the outer surface of the tubular rod and defining the relative axial movement between said piston and the tubular rod are obtained by means of elastic locking rings housed in corresponding grooves of the outer surface of the tubular rod.
6. A double effect jack as claimed in Claim 3, wherein on the outer surface of the drive rod there is provided a groove for each of the desired lock positions of the piston with respect to the cylinder.
7. A double effect jack as claimed in any one of the preceding Claims, wherein the said drive rod is fastened, preferably by screwing, to the inner face of the blind head of the clyinder.
8. A double effect jack as claimed in Claim 1 and substantially as herein described with reference to and as illustrated in the accompanying drawings.
GB8032228A 1979-10-12 1980-10-07 Double-acting jack Withdrawn GB2060777A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
IT12772/79A IT1124200B (en) 1979-10-12 1979-10-12 DOUBLE ACTING JACK WITH STOPPING VEHICLES FOR THE TWO END OF STROKE POSITIONS, EVEN EVEN WITHOUT PRESSURE OF THE ENGINE FLUID

Publications (1)

Publication Number Publication Date
GB2060777A true GB2060777A (en) 1981-05-07

Family

ID=11143191

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8032228A Withdrawn GB2060777A (en) 1979-10-12 1980-10-07 Double-acting jack

Country Status (4)

Country Link
DE (1) DE3038391A1 (en)
FR (1) FR2467310A1 (en)
GB (1) GB2060777A (en)
IT (1) IT1124200B (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2174455A (en) * 1985-05-03 1986-11-05 Hollingsworth Fluid-operated ram
CN103195771A (en) * 2013-04-18 2013-07-10 苏州市东吴滚针轴承有限公司 Cylinder for needle cage orifice punch
CN110388353A (en) * 2019-08-22 2019-10-29 三一重机有限公司 A kind of hydraulic cylinder and steam turbine

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR803805A (en) * 1935-03-28 1936-10-09 Elektronmetall Gmbh Variable length spacer for airplanes
DE866757C (en) * 1939-12-12 1953-02-12 Messerschmitt A G Device for the mechanical locking of working pistons in hydraulic working cylinders, especially for aircraft adjustment parts
DE923412C (en) * 1941-07-19 1955-02-10 Teves Kg Alfred Hydraulic servomotor
FR1004826A (en) * 1947-05-20 1952-04-03 Self-locking device of a movable member
FR1391478A (en) * 1964-04-28 1965-03-05 Plessey Uk Ltd Automatic locking device for cylinders actuated by fluid pressure
AT302107B (en) * 1970-10-27 1972-10-10 Hoerbiger Ventilwerke Ag Pneumatic or hydraulic actuating cylinder with a device for mechanically locking its actuating piston
DE2906819C2 (en) * 1979-02-22 1983-05-26 EHP Hugo Krüger KG Elektrik-Hydraulik-Pneumatik, 5828 Ennepetal Pressurized gas-actuated double lifting cylinder, especially for domed rooflights

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2174455A (en) * 1985-05-03 1986-11-05 Hollingsworth Fluid-operated ram
US4684074A (en) * 1985-05-03 1987-08-04 Hollingsworth Uk Ltd. Fluid-operated ram
CN103195771A (en) * 2013-04-18 2013-07-10 苏州市东吴滚针轴承有限公司 Cylinder for needle cage orifice punch
CN110388353A (en) * 2019-08-22 2019-10-29 三一重机有限公司 A kind of hydraulic cylinder and steam turbine
CN110388353B (en) * 2019-08-22 2024-04-30 三一重机有限公司 Hydraulic cylinder and steam turbine

Also Published As

Publication number Publication date
IT7912772A0 (en) 1979-10-12
DE3038391A1 (en) 1981-04-23
FR2467310A1 (en) 1981-04-17
IT1124200B (en) 1986-05-07

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Legal Events

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)