Fluid jack and locking device

A jack comprising a cylinder and a piston, the piston being reciprocal in the cylinder by means of pressure fluid. A piston rod extends out through an end wall of the cylinder. An abutment is fixed to the cylinder or connected to the piston rod. A restricting member, connected to the piston rod or the cylinder, is axially displaceable thereon for engagement with the abutment in any relative position between the piston and the cylinder. A locking device can be connected to the cylinder or the restricting member to lock the latter when engaging the abutment.

The present invention relates to a jack comprising a cylinder and a piston 
which is reciprocal in the same by means of a pressure medium and which 
has a piston rod extending out through an end wall of the cylinder. 
Jacks of this kind can be used to secure an article to a base in which the 
cylinder and piston rod of the jack are coupled to the article and base, 
respectively, and the article is kept pressed in an unmovable position 
against the base by means of a tension or pressure force which is 
generated by the pressure fluid being fed into the cylinder at one side of 
the piston. 
Jacks of this type can, for example, be used to secure loads such as 
containers on platforms, to batten down the hatches on ships and the like. 
During latter years it has also become usual to transport on the decks of 
ships or tow boats very heavy articles up to 20,000 tons, e.g., platforms 
for drilling for oil. These heavy articles must be very securely fastened 
to the base in order to avoid displacement during transport by sea. Up to 
now this anchorage has usually been achieved by the article being welded 
to the deck and to supports arranged on the deck. This, however, has 
considerable disadvantages. The welding takes time, and is expensive, and 
necessitates the use of a cutting torch to remove the welded connections 
at the place of destination, which is likewise expensive and 
time-consuming. If the destination is an oil drilling rig or other place 
situated at sea, a further problem arises in that the transport is 
dependent on weather conditions, relatively calm weather being essential 
during the entire time it takes to release the article, and an unexpected 
turn for the worse in the weather after the article has been partly 
loosened can result in a catastrophe. 
Previous suggestions to use hydraulic jacks for securing articles, 
especially during transport on the high seas, have, however, been 
abandoned for the reason that the necessary clamping power could not be 
guaranteed with assurance as it is dependent on hydraulic pressure which 
can drop through leakage or totally disappear through pipe failure, or the 
like. 
The present invention is intended to produce a jack which can be locked 
mechanically after the necessary tension or pressure force has been 
achieved in a hydraulic manner, so that said force remains constant 
independent of the hydraulic pressure. At the same time it renders it 
possible to provide and remove the mechanical locking with ease and 
comparative speed.

In both embodiments, the hydraulic part of the jack 1 in a known manner 
comprises a cylinder 2 and in said cylinder a reciprocable piston 3 having 
a piston rod 4 which extends out through one end wall 5 of the cylinder 2. 
The passage of the piston rod is sealed by means of a conventional packing 
box 6 which is only shown schematically and is adapted to the desired 
maximum pressure. The piston 3 is also provided with a conventional piston 
seal 7. In a known manner, the cylinder 2 is equipped with ports 8 and 9 
for the supply and drainage of the pressure fluid to and from the spaces 
on both sides of the piston 3, so that the jack is double-acting. The 
closed end wall 10 of the cylinder 2 and the free end of the piston rod 4 
are furthermore provided with means by the help of which said elements can 
be connected to an article and a base, respectively. Said means may be of 
any suitable form and are shown as an attachment ring 11 on the cylinder 2 
and a threaded end piece 12 of the piston rod 4. 
In the embodiment according to FIG. 1, the end of the piston rod 4 
protruding from the cylinder 2 is provided with an externally threaded 
portion 14. A tubular sleeve 15, serving as a restricting means and being 
provided with an internal thread, is screwed on to the threaded portion 14 
of the piston rod 4 and extends towards the adjacent end wall 5 of the 
cylinder 2, so that the tubular sleeve 15 surrounds the piston rod 4 
without abutting against the same. At the end facing the cylinder, the 
tubular sleeve 15 is provided with an annular flange 16 which extends 
radially and has a flat end surface. 
A nut 17, serving as a locking means, is passed over the tubular sleeve 15 
and has an annular flange 18 which is directed radially inwards and 
arranged at the end of the nut facing away from the cylinder 2. The nut 17 
is intended to cooperate with an external thread 19 at the adjacent end of 
the cylinder 2. 
In between its ends the tubular sleeve 15 is furthermore provided with a 
short male threaded portion 20 which is intended to cooperate with a 
female thread at the annular flange 18 of the nut 17 when the nut is not 
screwed on to the thread 19 of the cylinder 2. 
The jack according to FIG. 1 is used in the following manner. 
The jack is connected to the article which is to be secured and to the base 
for the article by means of the connecting means 11,12. The nut 17 is 
thereby attached to the tubular sleeve 15 over the threaded portion 20 
thereof, as shown in phantom lines. Upon introduction of pressure fluid to 
the cylinder at either side of the piston 3, the necessary clamping 
tension or pressure force is developed between the article and the base. 
While maintaining the hydraulic pressure in the cylinder 2, the tubular 
sleeve 15 is rotated by means of a handle 21, for example, and is thereby 
screwed along the threaded portion 14 of the piston rod 4 until the end of 
the tubular sleeve 5, having the external annular flange 16, is forcefully 
pressed against the adjacent end wall 5 of the cylinder 2. Thereafter the 
nut 17 is also turned, by means of the handle 22, so that it is screwed 
out of the threaded portion 20 of the tubular sleeve 15 and thereafter 
onto the thread 19 of the cylinder 2. The nut 17 is tensioned so that its 
internal annular flange 18 is heavily pressed against the external annular 
flange 16 of the tubular sleeve 15. The jack is thereby mechanically 
locked at the desired tension or pressure force, in that the displacement 
of the piston 3 in one direction is prevented through the abutment of the 
tubular sleeve 15 against the end wall 5 of the cylinder 2 and in the 
opposite direction in that the nut flange 18 abuts against the sleeve 
flange 16. The pressure fluid introduced can thereafter be extracted if 
desired without changing the force exerted by the jack. The clamping force 
is removed by turning the nut 17 and the tubular sleeve 15 in the opposite 
direction after reintroduction of the fluid pressure in the cylinder 2. 
The embodiment according to FIG. 2 substantially corresponds to that 
described above. It also includes a tubular sleeve 23 but this acts as a 
fixed abutment means corresponding to the end wall 5 of the cylinder 2 in 
the embodiment according to FIG. 1. The tubular sleeve 23 is rotatably but 
axially indisplaceably connected to the piston rod 4, preferably by 
engagement between a radial abutment surface of the piston rod 4 and a 
stop ring 34 attached thereto. The tubular sleeve 23 extends over the 
piston rod end of the cylinder 2 without contacting the same and a radial, 
external, annular flange 24 is arranged at the free end thereof and has a 
flat radial end surface forming said fixed abutment means. 
The cylinder 2 is provided with a male thread which cooperates with a 
female thread of an annular member 26. By turning, said annular member 26 
can thus be axially displaced along the cylinder 2 and with a flat end 
surface be pressed against the flat end surface of the tubular sleeve 23, 
whereby the annular member 26 serves as a restricting means in like manner 
to the tubular sleeve 15 of the embodiment according to FIG. 1. 
The annular member 26 also has a male thread which is intended to cooperate 
with a nut 27 serving as a locking means. The nut 27 is passed over the 
tubular sleeve 23 and has an annular flange 28, which is directed radially 
inward and is pressed into abutment with the external annular flange 34 of 
the tubular sleeve 23, when the nut 27 is screwed on to the male thread of 
the annular member 26 and is tightened. 
The jack according to FIG. 2 is used in the same manner as the jack 
according to FIG. 1. When the desired tension or pressure force has been 
achieved by introduction of pressure fluid into the cylinder 2, the 
annular member 26 is displaced by turning so far along the cylinder 2 that 
the end surface thereof is forcefully pressed against the end of the 
tubular sleeve 23 having the annular flange 34. Thereafter the nut 27 is 
screwed on to the male thread of the annular member 26 and tightened, so 
that the internal annular flange 28 is pressed against the annular flange 
24 of the tubular sleeve 23. The jack is thereby mechanically locked in 
the position corresponding to the desired clamping force and the hydraulic 
pressure in the cylinder 2 can be removed if desired. 
In order to further secure the jack in the desired position, the annular 
member 26 may be provided with a radially extending locking screw 29, the 
end of which can be pressed into locking engagement with the outer surface 
of the cylinder 2. At the edge turned away from the cylinder 2, the 
annular member may furthermore be provided with a radial, external annular 
flange 30 having an axial threaded bore for a second locking screw 31, the 
end of which may be inserted into one of a number of blind holes 32 in the 
adjacent end surface of the nut 27, or may only be pressed into locking 
engagement with said end surface. These two locking screws 29,31 prevent 
unintentional turning of the annular member 26 and the nut 27, 
respectively. 
Between its ends, the tubular sleeve 23 may furthermore comprise a short 
threaded portion (not shown) corresponding to the threaded portion 20 of 
the embodiment according to FIG. 1 and intended to cooperate with a female 
thread on the annular flange 28 of the nut 27 to support the nut 27 when 
the same is not threaded on to the annular member 26. 
The annular member 26 and the nut 27 may also be provided with handles (not 
shown) corresponding to the handles 21,22 of the embodiment according to 
FIG. 1. 
By the aid of any one of the jacks described above, the desired clamping 
force can thus be achieved by means of introduction of pressure fluid into 
the cylinder 2 of the jack and the jack may thereafter be mechanically 
locked in a position corresponding to the desired clamping force, so that 
this force is maintained independent of the hydraulic pressure. The 
locking of the jack may furthermore be achieved or removed in a rapid and 
simple manner, so that the time required to secure and release the article 
is comparatively short.