Note: Descriptions are shown in the official language in which they were submitted.
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1 Field of the Invention:
This invention relates to methods and apparatuses
for rapidly shifting loads.
More particularly, the invention relates to a method
of producing repeated movement by means of alternately operating
hydraulic jacks consisting of cylinder and piston units and having
both supply sides and pressure sides. In this method the pressure
sides of the jacks are interconnected in such a manner as to form
a closed pressure medium system, while the supply sides of the
jacks are connected to a source of pressure medium so that they
are alternately supplied with pressure medium to bring about the
movement contemplated, the pressure medium in said closed system
being caused to flow between the pressure sides of the jacks when
said movement is performed. The pistons of the jacks are thus ;
returned during operation of the jacks, without necessitating
supply of pressure medium for the return movement from the pressure
medium source proper. ~;
The invention also relates to a method of shifting a
load by means of a group of simultaneously operating hydraulic
jacks. This further method is characterized by temporarily
relieving individual jacks of load during the shifting movements
thereof in that the support for said jacks is moved during shifting
in a direction toward the load. Therefore, a continuous raising
or lowering movement of a load need not be interrupted because
an individual jack has to be relieved of load. After being
relieved of load the jack can be loaded again in that its support
is moved during shifting in a direction away from the load.
The apparatus for practising the method is a jointing
device for rod-shaped lifting elements, said device comprising
a frame having at its ends oppositely directed wedge-type jaw
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1 housings or like means which are adapted to engage the lifting
element on either side of the joint thereof so that the load on ;
the lifting element at said joint is transmitted to the frame.
Moreover, the invention relates to a method of returning
a loaded or unloaded lifting element by means of alternately
operating hydraulic jacks employed for the lifting of the element
and consisting of cylinder and piston units, said jacks having
supply sides and pressure sides as well as wedge-type jaws serving -
to bring about the engagement at the lifting operation. According
to`this further method, the return movement of the lifting
element is produced by the lifting of a counterweight attached to
said element, by alternately supplying the pressure sides with
pressure medium for said lifting operation, and the jacks are
provided with wedge-type jaws acting oppositely to the wedge jaws `;
serving to realize the lifting operation. The use of the counter-
weight will eliminate the risk that the lifting element by its own
weight will carry the piston in the jack along, thereby providing
an uncontrolled rapid lowering movement.
Fin~lly, the invention relates to a method of returning
; 20 a loaded or unloaded lifting element by means of alternately
operating hydraulic jacks employed for the lifting of said element -
and consisting of cylinder and piston units, said jacks having
both supply sides and pressure sides as well as wedge-type jaws ;
serving to bring about the engagement at the lifting operation.
This method comprises providing the jacks with wedge-type jaws
;~ acting in a direction opposite to the wedge-type jaws serving to
- realize the lifting operation, and by interconnecting the one
sides of the jacks in such a manner as to form a closed pressure
- medium syst~em, while connecting the other sides of the jacks to
~ 30 a source of pressure medium in such a manner as to be alternately
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1 supplied with pressure medium for the movement of the lifting
element, the pressure medium in the closed system beiny caused to
flow via a counterpressure valve or like means between the two
sides of the closed system at the movement o lifting elemen~.
The counterpressure valve employed in this method has fundamentally
the same function as the counterweight of the immediately preceding
method.
Brief Description of the Drawings:
,
The invention will be more fully described herein-
below with reference to the accompanying arawings in which:
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Figures l - 12 diagrammatically illustrate how a
~; jack in a group of simultaneously operating hydraulic lifting jacks
is temporarily relieved of load and is then again loaded, and ~;
also show a specific coupling between the pressure sides of the
jacks as well as a preferred embodiment of the jointing device `~
for rod-shaped lifting elementsi
Figures 13 and 14 illustrate a method of returning a
lifting element; "~
J Figures 15 and 16 illustrate another method of returning
a lifting element. ~-
Description of the Preferred Embodiments:
1 designates a jack assembly which is one of a group
of identical jack assemblies, each of which co-operates with a
lifting wire rope or other rod-shaped lifting element 2. The jack
assembly 1 comprises two conventional superimposed cylinder and
piston units 3 and 4, the pistons 5 of which are provided with
wedge-type jaws 5 for engaging the lifting element 2 during a
lifting operation. In the usual manner the jaws 6 slide on a
conical surface, and alternately jaws of the upper and lower units
3 and 4 engage the lifting element 2, or one displaced relative to
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1 the lifting element. See, for example, Figures 1 and 2, as well
as Ahlgren et al ~.S. Patent No. 3,685,801, issued August 22,
1972. The jack assembly 1 is placed on a cylinder and piston
unit 7 which cooperates directly or via spacers 8 with a fixed
support 9 through which the lifting element 2 passes.
The hydraulic cylinder and piston units 3 and 4 of the
jack assembly 1 are adapted to provide a repeated movement by
means of the alternately acting pistons 5 which have both first
or supply sides and second or pressure sides with respect to the
piston. The first or pressure sides of all of the jack assemblies
1 are interconnected via conduit means including a pipe 10. The
second or supply sides are connected via pipes 11 and 12 to an
external pressure source (not shown) so as to be alternately
supplied with pressure medium for the movement contemplated. When
pressure medium is supplied through one pipe 11 or 12, respectively,
pressure medium will thus be discharged through the other pipe
12 or 11, respectively. At the movement of the pistons 5 the
pressure medium is caused to flow between the pressure sides through
the pipe 10. It will be seen that when all of the pressure sides
or first sides of the units 3 and 4 are interconnected through
pipes 10, there exists a closed pressure medium system. ~
The pressure medium in the closed system is initially ~`
supplied through the pipe 13, Figures 1 and 2, which after
supply has been realized is shut off by means of a shut-off valve
13a. By supplying the closed system formed by the pressure sides
of the jacks with a quantity of pressure medium larger than that
; which corresponds to the volume of one of the pressure sides and
i the conduit means 10, the stroke length of the jacks 3 and 4 is
reduced. For example, if additional fluid in excess of the
volume of the first or pressure chamber is introduced to the
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1 closed system, the piston in the other cylinder of the system will
be forced downward.
Normally, the closed system is supplied via the pipe
13 with a quantity o~ pressure medium larger than that which it
shall contain during repeated movements. The excess pressure
medium is then caused to leave the system through the ovexflow valve `~
14 when one of the supply sides is connected to the pressure
medium source. When the desired quantity of pressure medium has --
left the closed system, the counterpressure in the overflow
valve 14 is adjusted so that said valve will function as a safety
valve.
It should be noted that the apparatus of Figures 3 - 12
also has the overflow valve 14, but that it is not shown for the
sake of simplicity; and because when the apparatus is operating,
the overflow valve functions as a safety valve.
As noted in Figure 1, the piston 5 in the cylinder and
piston unit 4 has been moved to its upper extreme position by ;
the action of pressure medium supplied through the pipe 12, the
jaws 6 associated with said piston 5 having carried the lifting
element 2 along. At the same time the piston 5 in the cylinder
and piston unit 3 has been moved by the intermediary of the
pressure medium in the closed system to its lower extreme position,
; the pressure medium at the supply side of the cylinder and piston
- unit 3 in turn having escaped through the pipe 11. In Figure 2,
the piston 5 of the cylinder and piston unit 3 is shown to have
effected its lifting movement with the jaws 6, having clamped
against the lifting element 2 while the piston 5 in the cylinder
and piston unit 4 by the intermediary of the pressure medium in
the closed system has been returned to its lower extreme position
~30 In Figure 3, a further lifting movement has been realized, which
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1 will appear from the position of -the joint 15 of the lifting
element 2.
In Figure 4, the jack assembly 1 has been relieved of
load during the lifting movement thereof, in that the support
structure for said jack assembly 1 during lifting -- simultaneously
with a lifting operation or between two successive lifting
operations -- has been moved in the direction opposite to the
lifting direction. The other jack assemblies 1 (not shown) have
on the other hand, retained their positions in relation to said :~
support structure during the lifting movement, and as a consequence
will wholly or partly take over the load from the thus relieved
:; jack assembly 1. The movement of the support structure against
the lifting direction has been performed by the piston 7a of the
cylinder and piston unit 7 having been pushed inwardly in the :~
cylinder which is shown in Figure 4 to now co-operate with the
fixed support 9 over spacers 16. The spacers 8 which previously . .
co-operated with the piston 7a of the cylinder and piston unit
7, as shown in Figures 1 to 3, have been dispensed with.
In Figure 5, the piston 7a of the cylinder and piston
unit 7 during the continued lifting movement of the jack assembly
1 has been moved outwardly in the cylinder into engagement with
the fixed support 9 which is now penetrated from the underside by :
the upper ends of rod-shaped portions of a jointing device 17 for
the element 2.
The jointing device 17 comprises a frame having at
---. its ends oppositely directed or oppositely acting wedge-type jaw
; housings 18 and 19 which are adapted to engage the lifting element
2 on either side of the joint 15 -- which has the same cross-
section as that of the lifting element 2 in order to pass through
the jack assembly 1 -- so that the load in the lifting element 2
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1 at the joint 15 may be transmitted to the Erame. More particularly, ~ -
the jointing device 17 comprises transverse members 20 and 21
to which the wedge-type ,aw housings 18 and 19 are mounted, and
also a number of longitudinal rod-shaped elements 22 which in'ter~
connect the transverse members 20 and 21. The upper end portions
23 of elements 22 protrude above the upper transverse member 21.
Because the cross-section of the joint 15 is the same as that of
the lifting element 2, the joint 15 may pass through the jaws 6 of
- jacks 3 and 4, and the jaw housing 18 and 19 of jointing device 17.
In Figure 6, the end portions 23 are shown to be
; provided with supporting elements 24 which, as they engage the
upper side of the fixed support 9, carry the jointing device 17.
` It will also be noted that the spacers 16 have been dispensed with,
so that the jack assembly 1 rests only by means of the piston 7a
of the cylinder and piston unit 7 on the fixed support 9.
In Figure 7, there has again occurred a movement
against the lifting direction, inasmuch as the piston 7a of the
cylinder and piston unit 7 has been pushed inwardly in the cylinder.
By this movement the supporting elements 24 have been brought into
engagement with the support 9.
In Figure 8 the wedge-type jaw housing 19 has been ;~ -~
brought out of its engagement with the lifting element 2, so that ;
the transverse member 21 has been moved slightly along the elements
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22. As the lifting movement continues, load-relieved jack assembly ~
1 will again raise the lifting element 2 as will appear ~rom the ~ ;
position of the joint 15 in Figure 9; and the jointing device 17
retaining its position beneath the fixed support 9. When the
joint 15 has passed the jack assembly 1 as shown in Figure 9, the
~ jack assembly can again be loaded because the support ~or said
assembly during lifting has been moved in the lifting direction.
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1 Thus, in Figure 10, the piston 7a of the cylinder and
piston unit 7 has been moved outwardly in the cylinder, thereby
raising the jack assembly. Spacers 16 are then placed between the
cylinder of the cylinder and piston unit 7 and the fixed support.
In Figure 11, the piston 7a o~ the cylinder and piston
unit 7 has been moved inwardly in the cylinder, and therea~ter the
spacers 8 have been placed between said piston 7a and the fixed
support 9.
In Figure 12, the jack assembly 1 has resumed its original
position shown in Figure 1. l`he piston 7a of the cylinder and
piston unit 7 has thus been moved outwardly in the cylinder so
that said piston is supported by the intermediary of the spacers 8
against the fixed support 9. ~`
When a loaded or unloaded lifting element is returned
by means of alternately operating hydraulic jacks employed for
the lifting of said element, each consisting of cylinder and ;~
piston units and having both supply sides and pressure sides as
well as wedge-type jaws for the engagement of the lifting element
during a lifting operation, there is the risk that a conventional
lifting element which usually consists of a lifting wire rope
may take the piston along, thus running a~ay when the two parts
of the lifting wire rope balance one another. This risk is
eliminated by a method whose steps are illustrated in Figures
13 and 14. The return movement of the lifting element 30 is thus
brought about by lifting a counterweight 31 fastened to the said
element 30, and such lifting is realized by alternately supplying
the pressure sides of the jacks 32 and 33 with pressure medium
- for said lifting operation. This also presupposes that the jacks
32 and 33 are provided with wedge-type jaws 36 and 37 serving to
; 30 bring about said lifting movement and acting oppositely to the
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1 wedge-type jaws 34 and 35, said jaws 36 and 37 being alternately
engaged with and disenga~ed from the ~element 30. In other words,
jacks 32 and 33 may be operated in th~e usual manner as discussed
above for lifting a load on lifting element 30; and when the
lifting element is unloaded, for lifting the counterweight 31 by
operating the jacks in the reverse manner and supplying pressure
medium to the sides of the jacks which were previously the pressure
sides from an external pressure source (not shown), and by - -
connecting the sides of the jacks which were previously the supply
sides in a closed pressure medium system. As noted above, the
wedge-type jaws 34 and 35 engage the lifting element 30 during a
lifting operation, and the wedge-type jaws 36 and 37 engage the
lifting element 30 during a return operation; because of the
oppositely directed forces within the jacks 32 and 33 depending
on which side of each jack is connected to the external pressure
source. The return run of the lifting element 30 co-operates with
a suitable runway 38 about which it is curved and from which it
thus extends down to the counterweight 31 suspended thereon.
The above-mentioned risk in returning a loaded or un- ;
loaded lifting element is eliminated also by means of a method
whose steps are illustrated in Figures 15 and 16. In this case
too, the method is performed by alternately operating hydraulic
jacks 42 and 43 consisting of cylinder and piston units, said jacks
having both supply sides and pressure sides as well as wedge-type
jaws 44 and 45 for the engagement at the lifting operation.
.
According to this method, the jacks 42 and 43 are provided with
wedge-type jaws 46 and 47 acting oppositely to the wedge-type
jaws 44 and 45. The operation of jacks 42 and 43 is the same as the
operation of jacks 32 and 33, with wedge-type jaws 44 and 45
30 engaging the lifting element 40 during a lifting operation and ;
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1 wedge-type jaws 46 and 47 engaging the lifting element 40 during
a return operation. As well, one side of each of the jacks 42
and 43 is interconnected to the other jack in a manner so as to
form a closed pressure medium system 49, while the other sides
of each of the jacks 42 and 43 are connected via the pipes 50 and
Sl to a source of pressure medium in such a manner as to be
alternately supplied with pressure medium for the movement of the
lifting element 40, the pressure medium in the closed system 49 being
caused to flow via a counterpressure valve or like throttling
means 52 between the two sides of the closed system at said
movement of the lifting element. The means 52 in the closed
system 49 thus prevents the pistons in the jacks 42 and 43 from
running away in their cylinders.
When the return movement of the lifting element 40
is performed by continuea coaction with the wedge-type jaws 44
and 45 for the engagement at the lifting operation, the pressure
sides of the jacks 42 and 43 are interconnected in a manner to form
the closed pressure medium system 49. In the opposite case, when
the return movement of the lifting element 40 is performed by
20 coaction with the wedge-type jaws 46 and 47 acting oppositely to -
the jaws 44 and 45 serving to bring about lifting, the supply sides
of the jacks 42 and 43 are interconnected so that they will form
a closed pressure medium system. It should be observed that the
return movement of the lifting element 40 occurs not only before
the lifting of a load but that it may occur also before the lowering
of a load. The lifting element 40 may suitably be a rod element
which can take up both tension and compression.
The counterpressure valve 52 is equipped with an
operating means 53 for its setting. The closed pressure medium
system 49 includes a number of non-return valves which force the
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1 pressure medium flowing between the two sides of the system always
to pass the counterpressure valve 52 against the action thereof.
The counterpressure valve 52 therefore can be of the non-return
valve type.
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