HYDRAULICALLY OPERATED CRANES

APPAREILS HYDRAULIQUES DE LEVAGE

English Abstract

ABSTRACT
A hydraulically operated crane of either the jib or bridge type
it the hoist block supported from a trolley movable along the sup-
port structure provided by the jib or bridge. The rope and sheave
system to control the lifting and lowering of the hoist block provides
a balanced fleet through system and the actuating power for the system
is provided by a special hydraulic multiplying linear motor mounted in
the jib or bridge. The arrangement of the sheaves is such that move-
ment of the multiplying linear motor causes travel of the hoist rope
to be balanced about the hoist block with the rope taken in or let out
evenly over the trolley sheaves.

Claims

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:



1. A hydraulically operated crane comprising a
support structure including a hollow cylindrical traveling
bridge having a cylindrical wall and trolley tracks on the
outside of said wall, a trolley traversible across said
cylindrical bridge on said tracks, said tracks being so
located for the trolley to produce a tangential load
through the cylindrical wall with no local bending of
said wall, a hoist block supported from said trolley, a
rope and sheave system of the balanced fleet through type
to control the lifting or lowering of the hoist block, said
rope and sheave system comprising a rope, a multiplying
system, trolley sheaves on said trolley, end sheaves
mounted on the support structure at each end of the
cylinder and a diverter sheave mounted on the support
structure, the rope being reeved through the hoist block
and trolley sheaves and about the end sheaves, with one
end of the rope then returning directly to the multiplying
system and the other end of the rope passing about the
diverter sheave prior to returning to the multiplying
system, and a separate rope and sheave system to control
the traversing of the trolley across the bridge.
2. A hydraulically operated crane comprising a
support structure, trolley tracks on said support
structure, a trolley supported on said tracks, a hoist



block supported from said trolley, a balanced fleet through
rope and reeve system supported by said structure to
control the lifting and lowering of the hoist block, a
hydraulic multiplying linear motor having one end anchored
in the support structure to provide operating power for
the hoist block, said linear motor having twin opposed
hydraulic cylinders, tie rods connecting the cylinders
in line with the length of tie rods between adjacent ends
of the cylinders determining the operating stroke of the
linear motor, a reeve sheave carrier connected in the space
between the cylinders to each operating piston extending
from the cylinders, two reeve sheaves mounted on said reeve
sheave carrier, end return sheaves at each end of said
support structure, two trolley sheaves mounted on said
trolley and a diverter sheave supported in said support
structure with the operating rope for the hoist block
having the ends anchored to a support base associated
with the linear motor with the rope from one anchor point
passing about one reeve sheave mounted on the reeve carrier
supported by the pistons of the linear motor, and the end
return sheaves at the end of the structure before being
returned to the trolley sheave and about the hoist block
and the rope from the other anchor point passing about the
second reeve sheave on the reeve carrier supported by the
pistons of the linear motor and about the diverter sheave
before returning to pass about the end return sheaves at


21

the opposite end of the structure and then to the second
trolley sheave about the hoist block.
3. A crane as claimed in claim 2 wherein the pistons
in the linear motor are hollow with stopped ends adjacent
the reeve carrier so that in use the interior of the piston
is filled with oil under pressure.
4. A crane as claimed in claim 2 wherein the ends
of the rope for the hoist block are mounted on a mounting
plate fixed to the end of one cylinder and at an angle
designed so that the frictional forces which operate on
the piston are balanced.
5. A crane as claimed in claim 2 wherein the support
structure comprises a hollow cylindrical travelling bridge
with trolley tracks on said cylindrical travelling bridge
to support the trolley to the side of said cylindrical
travelling bridge.
6. A crane as claimed in claim 5 wherein the linear
motor and associated sheaves and rope reeving used in the
crane are mounted within the cylindrical travelling bridge.
7. A crane as claimed in claim 2 wherein the travers-
ing mechanism for the trolley comprises a rope and sheave
system with the actuating power for this system being
provided by a hydraulic multiplying linear motor.
8. A crane as claimed in claim 2 wherein a greater
number of reeve blocks may be supported by the reeve
22


carrier to provide a greater mechanical advantage between
the operating stroke of linear motor and the distance moved
by the hoist blocks.
9. A crane as claimed in claim 2 wherein the hydraulic
control circuit or the crane includes a hydraulic pump, a
directional control valve to actuate the hydraulic motor
in a forward or reverse direction and to connect the
exhaust circuits to a control valve and metering valve
with the control and metering valve used to regulate the
speed and acceleration of the hydraulic motor.
10. A crane as claimed in claim 9 wherein the control
valve comprises a three positional hydraulic valve in one
position delivering oil to one side of the hydraulic motor,
in another position delivering oil to the other side of
the hydraulic motor and in the third position closing off
the flow of oil with the exhaust flow of oil from the
control valve passing through the metering valve that can
be opened or closed or maintained in a particular position
using an operator controlled interface valve which inter-
face valve in a first position allows a flow of oil to
pass to open at a regulated rate the metering valve and
in a second position allows a flow of oil to close at
a regulated rate the metering valve and in the third
position allows no oil to pass through the metering valve
thereby effecting no alteration to the positioning of the
metering valve.

23


11. A hydraulically operated crane comprising a
support structure having a hollow cylindrical travelling
bridge, trolley tracks on said cylindrical travelling
bridge to support the trolley to a side of said travelling
bridge, a hoist block supported from said trolley, a
balanced fleet through rope and reeve system supported by
said structure to control the lifting and lowering of the
hoist block, a hydraulic multiplying linear motor having
one end anchored in the support structure to provide
operating power for the hoist block, said linear motor
having twin opposed hydraulic cylinders, tie rods con-
necting the cylinders in line with the length of tie rods
between adjacent ends of the cylinders determining the
operating stroke of the linear motor, a reeve sheave
carrier connected in the space between the cylinders to
each operating piston extending from the cylinders, two
reeve sheaves mounted on said reeve sheave carrier, and
return sheaves at each end of said support structure, two
trolley sheaves mounted on said trolley and a diverter
sheave supporter in said support structure with the
operating rope for the hoist block having the ends
anchored to a support base associated with the linear
motor with the rope from one anchor point passing about
one reeve sheave mounted on the reeve carrier supported by
the pistons of the linear motor, and the end return sheaves
at the end of the structure before being returned to the
24

trolley sheave and about the hoist block and the rope from
the other anchor point passing about the second reeve
sheave on the reeve carrier supported by the pistons of
the linear motor and about the diverter sheave before
returning to pass about the end return sheaves at the
opposite end of the structure and then to the second
trolley sheave about the hoist block.
12. A crane comprising
hollow cylindrical load trolley supporting girder
means,
support means for said hollow cylindrical girder
means,
trolley track means on the outside of the hollow
cylindrical girder means for traversing a load along the
hollow cylindrical girder, and
a load trolley supported upon said trolley track
means with the trolley track means arranged so that the
line of action of the load forces is applied tangentially
to said hollow cylindrical girder means.
13. A crane as claimed in claim 12 wherein the hollow
cylindrical girder means comprises a single hollow
cylindrical girder with the trolley track means comprising
in turn an action rail attached to the outside of the
single hollow cylindrical girder with the line of action
of the load forces supported by the action rail applied
tangentially substantially through the center line of the



wall of the single hollow cylindrical girder and with a
reaction rail attached to the opposite outside of the
hollow cylindrical girder.
14. A crane as claimed in claim 13 wherein the action
rail is supported by a support plate located so that the
line of action of the load passes substantially centrally
through the support plate and the wall of the single hollow
cylindrical girder substantially at the horizontal axis of
the girder.
15. A crane as claimed in claim 14 wherein the
reaction rail is supported in a manner similar to the
action rail with the reaction force passing substantially
through the centre of the wall of the hollow cylindrical
girder.
16. A crane comprising
twin parallel hollow cylindrical girders,
support means for said twin parallel hollow
cylindrical girders,
action trolley tracks on the outside of adjacent
surfaces of each of the said twin parallel hollow
cylindrical girders for traversing a load along said
twin parallel hollow cylindrical girders, and
a load trolley supported upon the action trolley
tracks between the twin parallel hollow cylindrical girders
so that the load is divided and the line of action of each
component is applied tangentially to the associated hollow
cylindrical girder.


26

17. A crane as claimed in claim 16 wherein each action
rail is supported by a support plate located so that the
line of action of the load passes substantially centrally
through the support plate and the wall of the associated
hollow cylindrical girder substantially at the horizontal
axis of the girder.
18. A crane comprising
hollow cylindrical load trolley supporting girder
means,
support means for said hollow cylindrical girder
means,
trolley track means on the outside of the hollow
cylindrical girder means for traversing a load along the
hollow cylindrical girder,
a load trolley supported upon said trolley track
means with the trolley track means arranged so that the
line of action of the load forces is applied tangentially
to said hollow cylindrical girder means, and
reinforcing means associated with said hollow
cylindrical girder means.
19. A crane as claimed in claim 18 wherein said
reinforcing means comprises
a reinforcing member welded to the top of each
hollow cylindrical girder making up the hollow cylindrical
girder means at the centre top to strengthen and raise the
neutral axis of said hollow cylindrical girder.
27

20. A crane comprising hollow cylindrical load trolley
supporting girder means,
support means for said hollow cylindrical girder
means,
trolley track means on the outside of the hollow
cylindrical girder means for traversing a load along the
hollow cylindrical girder,
a load trolley supported upon said trolley track
means with the trolley track means arranged so that the
line of action of the load force is applied tangentially
to the said hollow cylindrical girder means, and
hogging means mounted towards the base of said
hollow cylindrical girder, said hogging means comprising
a tensioning member extending the length of said hollow
cylindrical girder means and anchored substantially to
the ends thereof and tensioning means acting to induce a
tension in said tension member.
21. A crane as claimed in claim 20 wherein a hydraulic
hoist ram and associated rope and sheave system is mounted
in the interior of the hollow cylindrical crane towards
the base thereof with the anchor point of the hoisting
cylinder attached to a lever pivotally supported on an
anchor point and providing on the opposite side of the
pivotal anchor point a mounting for said tensioning member
with the tensioning member extending the length of the
girder on the under side thereof so that the reaction


28


force generated by the lifting cylinder is transmitted
through the lever to tension the tensioning member.
22. A crane as claimed in claim 20 wherein a hydraulic
cylinder is incorporated in a tensioning rod running
towards the bottom of said hollow cylinder with said
hydraulic cylinder generating the required tensioning
force in the tensioning rod.




29

Description

ABSTRACT
-
A hydraulically opera-ted crane of either the jib or bridge type
with the hoist block supported from a trolley movable along the sup-
port structure provided by the jib or bridge. The rope and sheave
system to control the lifting and lowering of the hoist block provides
a balanced fleet through system and the actuating power for -the system
is provided by a special hydraulic multiplying linear motor mounted in
the jib or bridge. The arrangement of the sheaves is such that move-
mint of the multiplying linear motor causes travel of the hoist rope
to be balanced about the hoist block with the rope taken in or let out
evenly over the trolley sheaves.

TITLE
"Improvements in or relating to hydraulically operated cranes".
This invention relates to hydraulically operated cranes.
BACKGROUND
_
The use of hydraulic power to operate cranes has been known and
examples appear in the patent literature from an early time. Some of
the more recent and more sophisticated examples can be found in United
States Patent Specification Nazi, 2984191, 3872671, 3872674 and
3907120. Examples are also found in British patent literature and
reference is made to British Patent Specification Noah and
Noah.
Despite recognizing the possibility of adopting hydraulic prime
movers the hydraulic crane has not met with any significant commercial
25 success. There are many reasons which contribute to this but print
supply among the statewide or acknowledged disadvantages is -the tendency
for hydraulic motors to leak or discharge oil. This is viewed as very
undesirable in most situations where cranes will operate.

I believe the advantages which can be secured from the successful
operation of a hydraulic crane considerably outweighs the disadvan-
taxes particularly in view of the very high component cost necessary
in an electrically powered crane and the high maintenance costs
required to ensure satisfactory long term operation of such a crane.
By way of an example of such a disadvantage reference is specifically
made to the energy dissipation means which must be incorporated in an
electrically powered crane and these overheat and can lead to high
maintenance costs or failure. I believe all these disadvantages can
lo be overcome by the adoption of a hydraulically operated crane.
THE Present INvENTIorl
Accordingly it is an object of the present invention to provide a
hydraulically operated crane which will allow the advantages of a
hydraulic system as opposed to an electrically operated crane system
to be fully realized while also minimizing what has traditionally been
accepted as the disadvantages of the hydraulic system.
It is another objective to introduce a means whereby forces in the
hydraulic operating system are balanced tending to minimize wear or
stress on some components and allowing for balanced and controlled
movement of the load.
Accordingly in one aspect the invention consists in a hydraulic
gaily operated crane comprising a support structure incorporating
-trolley tracks, a -trolley traversable across said support structure, a
hoist block supported from said trolley, rope and sheave system in
said support structure to control the lifting or lowering of the hoist
block and a separate sheave system in said support structure to
control the traversing o-f the trolley across the support structure,
with the rope and sheave system for the hoist providing a balanced


I 3
fleet through system and with the actuating power for this system pro-
voided by a hydraulic multiplying linear motor mounted in said support
structure.
The support structure will usually comprise the jib of a power
crane or the bridge of a traveling or fixed bridge crane.
A balanced fleet through system is easily achieved in the ire-
versing mechanism by inserting a hydraulic multiplying linear motor in
the support structure attached to the rope system controlling the
movement or position of the trolley along that structure.
Lo In the case of the hoist block the balanced fleet through system
comprises two revved sheaves movable by the hydraulic multiplying
linear motor, a diverter sheave fixed in the structure and having the
rope from one of the revved sheaves attached to the hydraulic
multiplying motor passed thereabout, end return sheaves in the struck
lure, trolley sheaves and a hoist block the construe lion and
arrangement being such that with the introduction of the diverter
sheave movement of the linear motor causes travel of the hoist rope to
be balanced about the hoist block with the rope taken in or let out
evenly over the trolley sheaves.
The hydraulic multiplying linear motor used can assume any known
configuration which will move the revved sheaves to achieve the
motions previously set forth. However, I have devised a hydraulic
multiplying linear motor of particular configurations which I believe
overcomes a number of the difficulties previously accounted with
hydraulic systems and which would have an application outside -that
specifically described with reference to the balanced fleet through
system or indeed the crane itself.
Accordingly the hydraulic multiplying linear motor comprises twin


opposed hydraulic cylinders, pistons operably arranged in said Solon-
dons with each piston connected to the power takeoff point, tie rods
connecting the operating cylinders over the operating length of the
motion possible with the pistons, said motor being supported at least
by fixing the end of one cylinder in the support structure and
appropriately supporting the other cylinder.
In the present invention the hydraulic multiplying linear motor is
connected so that -the revved sheave carrier is mounted at the power
take-of point.
The opposed pistons connected to the power take-off are hollow
with stopped ends adjacent the power take-off point so that in use the
interior of the piston is filled with oil under pressure. This has
two advantages. It means the weight of the assembly tending to create
any bowing or bending moment in the structure has a counter-balancing
effect as a consequence of the bourbon effect. Also the piston having
oil under pressure is a better load carrier in the operating con-
dictions experienced by the hydraulic multiplying linear motor.
Preferably the cylinder head assembly carries the sealing rings
and guide bush in a manner which ensures easy maintenance and replace-

mint.
Preferably the ropes are anchored relative to the reeve sheaves so
that the forces generated upon load being applied through -the ropes
-tends to balance, preventing or minimizing bending or eccentric load
being placed on the pistons of the hydraulic multiplying linear motor.
US The opposed cylinder linear motor also operates in conjunction
with the control mechanism adopted to take advantage of the metering
out principle for speed control.
The cylinders in the linear motor are balanced with the input to

lo 3

one cylinder balancing the output from the other cylinder in a manner
such that the reserve supply of oil required in the system does not
vary substantially. This allows a system to be operated either under
a closed and controlled atmosphere or where there is little movement
of air into and out of the reservoir tank thereby minimizing the dirt
and other extraneous material what might otherwise be introduced into
the system.
The support structure member for a traveling bridge crane pro-
fireball comprises a hollow cylindrical structural member, a trolley
Lo engaged about part of the circumference of the cylindrical structural
member and running on rails substantially diametrically opposed
through the cylindrical structural member and with the linear motor
and associated sheaves and rope reeving used in the crane mounted
within the cylindrical structural member.
The trolley is designed to support a torsional load relative to
the cylindrical structural member.
The hydraulic control circuit for the crane includes including a
hydraulic pump, a directional control valve to actuate a hydraulic
motor in a forward or reverse direction and to connect the exhaust
circuit through a control valve and metering valve with the control
and metering valve used to regulate the speed and acceleration of the
hydraulic motor.
Preferably the control valve delivers a flow of oil to the
metering valve which compresses a biassing spring and opens a needle
I valve.
Preferably the rate at which the oil is delivered -to the metering
valve and the rate from the which the oil is discharged from -the valve
in the control mode is the same and is independent of operator


~22'7~,~3
control.
DRYING DESCRIPTION
One preferred form of the invention and modifications thereof will
now be described with reference to tune accompanying drawings in which
Figure 1 is a part side elevation of a hydraulic crane according
to the present invention,
Figure 2 is d plan view of a crane in the mode of a traveling
bridge crane again embodying the present invention,
Figure 3 is a section -through A-A on figure 1,
Figure 4 is an elevation of a hydraulic multiplying motor
according to the present invention,
Figure 5 is a plan view of the motor as shown in figure 4,
Figure 6 is a detail of the cylinder head and sealing mechanism
adopted therein,
Figure 7 is a section through B-B on figure 5,
Figure 8 is a section through C-C on figure 5,
Figure 9 is a section through D-D on figure 5,
Figure 10 is a schematic arrangement sorbing the rope reeving used
for the hoist,
Figure 11 is a schematic view showing -the rope reeving for the
cross travel,
Figure 12 is the control circuit for the cross travel across the
bridge,
Figure 13 is the hydraulic control circuit for the lifting and
25 lowering, and
Figure 14 is the hydraulic control circuit For the long travel
along the rails 4. PREFERRED EMBODIMENT
The preferred form of the invention will be described with

I 3
reference to a traveling bridge crane although it will be appreciated
that the invention in its various aspects may in the main be applied
to any structure where the load is to be lifted and traversed relative
to the structure. This of course includes tower cranes and other
installations of the like type and also includes Goliath cranes. The
predominant application for the invention will however be in the ire-
violin bridge crane normally found in workshops warehouses or other
areas requiring a lifting capacity.
The hydraulically operated crane 1 has as the main structural
member 2 a cylindrical member formed by rolling or otherwise suitably
forming from steel plates a member having a diameter consistent with
the load to be lifted and the span. For example with a 10 tone
crane of 20 moire span would involve a cylindrical member 2 having a
diameter of approximately 1 Metro. This cylindrical member is carried
on end carriers 3 which in turn are supported on rails carried in
the usual manner on a suitable support structure such as -the top of a
reinforced wall. It will be appreciated in the normal operation the
rails will be parallel rails and the bridge 2 will move backwards

and forwards along those rails.
Attached to one side of the cylinder 2 is a substantially horizon-
tat rail 5 and approximately diametrically opposed thereto is a
Further horizontal rail 6. A trolley 7 shown in figllre 2 comprises a
framework 8 hooked about the member 2 is that wheels 9 supported in
the frame will engage with the rail 5 and wheels 10 will engage with
I the rail 6. In this way the trolley is supported hooked about the
cylindrical structural member 2 with -the load being carried as a
tangential load to the structural member. In this way a torsional
load is applied to the bridge or main structural member 2 which maxim

muses the efficiency of the tubular member. Strengthening ribs 11 are
welded internally in the cylindrical member 2 at intervals at approxi-
mutely 1l/2 metros to minims the likelihood of any localized buckling
or failure as a consecluence of the horizontal loads being applied to
the member.
It will be appreciated that the configuration adopted For the
bridge of the crane could have an application without necessarily
involving the remaining components of the invention. Louvre, it is
highly desirable for this particular mode of bridge -to be used in con-

junction with the remainder of the invention as will be explained
horribly.
A lifting hook 12 is supported from a revved block 13 by a rope 14
which passes about sheaves 15 and 16 fixed to the trolley 7. It is
desirable for maximizing maneuverability of the hook for the diameter
of the sheaves 13, 15 and 16 and 17 and 18 to be kept as small as
practicable. It will also be understood that in -the drawing a single
rope system has been illustrated for simplicity but the invention
could readily be applied to a multiple and particularly a two rope
lifting system. The rope 14 after passing about the trolley sheaves
15 and 16 extends to the end of the bridge to pass about end return
sheaves 17 and 18. The rope 14 after passing about the end return
sheaves 17 then passes about a diverter sheave 19 which is fixed to
the structural bridge before being connected to the sheave carrier at
sheave 20. The rope 14 after passing about the end return sheaves 18
runs directly to the sheave carrier at sheave 21.
The sheave carrier sheaves 20 and 21 are supported on a hydraulic
multiplying linear motor 22 which is illustrated in more detail in
-figures 5 to 9.




The linear hydraulic motor is of a particular design and while i-t
has special application in the present invention would also be apply-
cable in other areas. There are a number of important and novel
features in the design adopted for the linear hydraulic rotor.
The motor comprises two opposed cylinders 23 and 24 preferably
being cylinders of the same diameter having operatively fitted therein
piston rods 25 and 26 which are connected -to the sheave carrier 27.
The cylinders 23 and 24 are spaced apart by tie bars 28 with the
operating distance of the linear motor controlled by the length of the
tie bars.
A detail of the cylinder head as shown in figure 6, the piston 26
passes through a seal 29 and a guide bush 30 which is held in place by
a retainer 31 bolted to the head by bolts 32. This particular
construction allows for ease of maintenance in that split bushes can
be removed when the bolts release the retainer and split seals are
also designed to facilitate on-site maintenance.
Each of the pistons 25 and 26 is hollow with the stopped end adja-
cent the sheave carrier. The volume in each of the cylinders and
pistons is the same so that upon the sheave carrier being reciprocated
through the operating distance the oil displaced from one equates with
the oil introduced to the other. In this way there is no change of oil
in the reserve tank enabling a sealed system to be use or at least
minimizing the air movement into or out of the -tank which as explained
previously has deleterious effects in the operation o-f the system.
The reeving system just described is schematically illustrated in
Figure 10 end provides a balanced fleet -through system. The return
sheaves 17 and 18 are fixed to the support structure as is also the
diverter sheave 19.

- 10 -

~22'7~

The rope 14 is anchored at two points 32 and 33 in a plate 34
which is fixed at an angle to the end of the cylinder 24. This con-
figuration is shown most clearly in figure 10 and it is designed so
that the friction forces which operate on the piston are balanced.
The end 25 of the cylinder 23 is designed to be pinned to the support
structure and the structure is also supported on a stand from under-
neat on flexible brackets at each of the cylinder heads. It thisbway
a stable structure is provided which will ensure that the linear
hydraulic motor operates in a manner which will place the minimum
stress and hence cause minimum wear to the seals. The possibility of
any sag caused through the weight of the revved sheaves, sheave'
carrier and pistons is to some extent off-set by the hollow pistons
which are filled with oil under pressure and therefore tend to
straighten under the bourbon effect. Sag is further reduced by the
straightening effect of the hydraulic forces set up in the tie rods
combined with the vertical flexibility of the supports so that as the
bridge sags under load the reverse effect occurs on the engine.
The hydraulic control system will be described in detail hereafter
but the pressure in the cylinders 23 and 24 are arranged such that the
tie rods are always in tension. The cylinder 24 is the main operating
cylinder and the cylinder 23 is a control cylinder which although
playing a more minor role is still very significant from the point of
view of operating of the linear motor and control.
With reference to figure 10 it will be apparent that operation of
the linear motor reciprocates the revved sheaves 20 and 21. As these
sheaves are moved to the left, the hook will be raised and as the
sheaves are moved to the right the hook will be lowered. In either
mode the rope 14 is either taken up or let down about the trolley


~2~7~163

sheaves 15 and 16 equally and this is caused because the rope 14 from
the anchor point 32 passes about the sheave I and the deflector
sheave 19 prior to returning to the end return sheave 17, in this way
as the sheaves 20 and 21 move to the left the rope 14 will shorten the
5 length of the rope dependent from the sheave 15. Similarly taking the
rope from the anchor point 33 it passes about the sheave 21 and then
the end return sheaves 18 to the sheave 16. Movement in the same
direction will also cause the rope to be raised about the sheave 16.
This balanced fleet through system has d number of control ad van-
ala taxes in that -there is the minimum need to introduce braking or other
controls to otherwise off-set eccentric or out of balance loads which
can develop in the system The movement is more controlled and there
is less likelihood of any jerking or rapid movement because of slack
or rope stretch in the system when there is a change in the direct

tonal movement In the illustrated example the linear motor has multiplying effect of 4 but this could be increased by introducing
more sheaves in the system if -this was desired. With the illustrated
example 1 moire of travel in the sheave carrier attached to the linear
motor results in 2 meters ox movement of the hook Thus the operating
pa stroke of the linear motor needs to be half of the required hook lift
because of -the peculiar and special -features described such
a distance of linear movement is feasible and normally the more
complex reeving pattern which would be involved with more sheaves
attached to the linear motor can be avoided.
Another peculiar advantage which can be achieved in the combined
application o-f aspects according to the present invention is
illustrated in figures 1 to 3 of the drawings where the linear motor
and associated sheaves and rope reeving can be mounted inside -the

Lo 3

cylindrical bridge 2 and below the neutral axis of the girder. This
has a number of significant advantages. First, the lines of the
completed crane are clean without any significant rope visibility in
excess of that which would be visible in a conventional crane. The
linear motor described is intended to minimize wear on components and
hence should no-t be prone to leakage. However, in the event of any
leakage occurring the oil would be discharged into the cylinder 2 and
would not therefore fall into the area being serviced by the crane.
Secondly, the position of the linear motors below the neutral axis of
La the girder not only reduces the deflection under load but also reduces
the tensile stress in the girder. The effect is accentuated by the
'large forces created by the multiplying of the hoist ropes. Finally,
by confining the motor and associated reeving system in the bridge i-t
is confined and will not accumulate as much dirt as might otherwise be
the case.
It is also necessary to ensure that the trolley 7 can be traversed
across the bridge 2. Lucy traversing motion is achieved using a
secondary 'linear motor 36 which is also located in the preferred embo-
dominate within the bridge member 2. The linear motor has not been spew

civically detailed in -the drawings but a schematic showing the opera-
lion is illustrated in figure 11. The rope 37 is attached to the
trolley 7 at points 38 and 39. The rope 37 passes about end return
reeves 40 and 41 before returning to the sheave carrier 42 and the
anchor sheaves 43 and 44. The operation of -this system is similar but
simpler to that previously described. Movement of the linear motor 36
in one direction causes the trolley 7 to move across the bridge in one
direction and movement in the opposite direction causes the return of
the trolley. In -this case do is illustrated there is a multiplying


~L227~L~3

factor of 6 to 1 which means that the length of stroke required in the
linear motor 36 can be less than that required in the main lifting
linear motor.
For light duty work the convention winch drum with an endless rope
driven by a single hydraulic motor would be suitable.
The hydraulic circuitry and control required is also designed to
achieve specific advantages. In the drawings an electric motor 45 is
mounted on a frame 46 associated with one end carriage. The electric
motor drives a hydraulic pump which together with the hydraulic riser-

lo void tank is housed in the chamber 47. The electrical control equip-
mint necessary is also housed in this chamber.
The hydraulic control circuit necessary to operate the crane will be
described horribly. The hydraulic circuits have been designed to
achieve the following unique operating features. First, an operator
may select any desired operating speed from almost zero to the maximum
achievable by the system using a simple standard double depression
type of pendant push button control station. Secondly, both positive
and negative acceleration can be maintained constant irrespective of
the load and are outside the control of the operator. The circuit
adopted has a basic common factor which is applied to the lifting and
the lowering of the load, the traversing of the trolley across the
crane and the
traversing of the bridge along the rails 4 where a bridge crane
control is applied.
This common factor is based on the meter out principle of speed
control which is to control the oil flow through the driving means by
throttling the motion exhausts while the pump itself continues to run
at full speed and full flow. There are many advantages which are



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7~3
gained from this system but the main ones are stability as the
driving means is always to some extent driven even when braking over-
running loads as it occurs on the long travel and lowering and the
fact that it facilitates pump pressure unloading at light loads on the
crane hook and also facilitates the use of the desirable simple and
inexpensive fixed displacement pump. However this does not preclude
the use of a single variable displacement pressure compensated fro
certain applications.
The control circuit will first be described with reference to
lo figure 12 which is -the circuit for the cross travel of the trolley on
the bridge. In the circuits like components will be given like numb
biers and the positive displacement pump 50 driven by the electric
motor 45 shown on the preceding drawings causes the oil to flow to the
directional control valve 51 to the linear motor 36. The valve 51 is
energized by the operator control and the directional arrows indicate
the circuit connections possible. It is therefore apparent that in
one position the pump will deliver oil under pressure to the side aye
and in the other position the high pressure will be delivered to the
side 36b. A relief valve 52 allows for oil to be exhausted in the
event of excessive pressure build up. A spill-off valve 53 operates
to control the pressure on the exhaust side of the circuit. This
pressure has been set approximately 50 psi and if this pressure is
exceeded the spill-off valve 9 operates allowing a bypass of oil back
to the tank 54.
An interface valve 55 connects the exhaust circuit to the metering
valve 56 and -thence back to the tank I The interface valve is
capable of assuming three positions. In the Sinatra position
illustrated the valve is closed preventing any passage of oil. If the


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interface valve is moved to the left oil can flow through to the
metering valve 56. If the valve is moved to the right oil from the
metering valve can flow through to exhaust to the tank 54.
The interface valve is important and must be able to assume any
one of the three stated positions. To achieve this it is necessary
for the control mechanism to be able to assume any one of the three
stated positions. This can be achieved using a valve with two sole-
nods. One solenoid operating as a push solenoid to move the valve to
-the central position and -the second solenoid operating to take over to
RIO move the valve to the accelerating mode if the control circuit is so
actuated.
The flow of oil in the control circuit from the interface valve 55
into the metering valve 56 must be regulated so that there is -the same
pressure drop irrespective of operating mode. As indicated above the
pressure on the exhaust side through the spill-off valve is controlled
at 50 psi. A control aperture 57 in the line between the interface
valve and the metering valve results in a drop of pressure of half
so that pressure at 50 psi is delivered to the metering valve at a
pressure of 25 psi. When the interface valve is changed over to the
decelerating mode the oil in the control chamber of the metering valve
56 is allowed to exhaust back to tank again -through the orifice 57
resulting in a further drop in pressure of 25 pounds, that is from the
25 pounds in the chamber to 0. This means that the flow in either
direction is the same resulting in both acceleration and braking or
deceleration Functioning at the same rate. The metering valve 56 is
designed to control the rate at which oil in the exhaust circuit can
pass back to the tank 54 through the filter 58. If the operator at
the control mechanism pushes the controls necessary for acceleration


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~2~3

the interface valve moves in the drawing to the left so that the 50
pound psi pressure can pass through the valve and through the orifice
57 to the metering chamber. This oil causes the piston 59 to be moved
against the spring 60 opening the aperture 61 and thereby regulating
the rate of oil which can be discharged through to the tank. As soon
as the control circuit is set back to the central position the piston
59 is retained in the same position and hence the rate of movement of
the notion remains constant. As soon as the interface valve is moved
to the braking or the deceleration mode oil is displaced by the spring
60 to pass through the orifice 57 and valve 55 back to the tank I
The rate at which this oil is discharged and hence the rate at which
the orifice 61 is closed is again the same as that for acceleration.
It will be apparent that this mode of operation is quite independent
of the operator who can select a speed by actuating the controls but
cannot control the rate at which that speed is increased or decreased
and this is an important control function in the present invention.
Instead of using a biassing spring the piston 59 can also be post-
toned using a convention single three position closed center direct
tonal control valve operated by solenoids as described above.
If we now consider figure 14 the circuit for controlling the
hoisting and lowering is illustrated. In this instance the hydraulic
linear motor having the cylinders 23 and I is shown connected -to -the
sheave carrier 27. In this case because of special protective
requirelnents additional valves are introduced. It is necessary For
25 the circuit to include protection in the event of failure so that the
load will not be dropped. This is achieved by including a drop check
valve 62. Any failure in pressure will cause this valve to close and
hold the load at the position adopted when the failure occurred. To

i; I

enable the lowering circuit to operate it is necessary for a pilot
control to maintain the drop check valve during the lowering mode.
This increases the pressure in the exhaust side and to prevent the
spill-off valve aye operating at that lime a solenoid valve 63 is used
which can isolate the spill-off valve aye. It is still necessary to
have some pressure relief in the circuit and a pressure relief valve
64 is incorporated -to allow the exhaust oil to be spilled to tank a-t
loll pressure and to provide the low pressure protection necessary for
the cylinder 24. With these modifications the circuit is essentially
Lo the same as that previously described. The constant displacement pump
passes oil through the directional control valve and when the valve is
arranged for lifting it is displaced to the
left. Pressure is exerted in the cylinder 24 and the pressure in the
exhaust circuit is retained at the 50 pounds per square inch pro-

piously referred to which operates through the interface valve and metering valve to effect the speed and acceleration control as pro-
piously described. In the lowering mode the solenoid valve 63 it
energized thereby cutting out the valve aye. The oil is exhausted
through valve 64 to tank 54 and at the same time sufficient pressure
is caused to open the drop check valve 62. The speed and acceleration
control is maintained in the same mode as that previously described.
As the valve aye is not Functioning in this mode it is also necessary
to introduce a pressure reducing valve 65 so that the pressure applied
to the speed and acceleration control through the interface and
metering valve is maintained at 50 psi. The long travel circuit
follows again a similar operating criteria and is illustrated in
figure 14. In this case two separate hydraulic motors 67 and 68 are
located on each side of the traveling bridge and are connected to the
_ 18 -



I 3

wheels of the bridge so that -they will provide motive power to cause
one side or the other side of the bridge to be moved A sensor 69 is
connected to the bridge on one side and operates from one of the horn-
zontal rails or any other datum reference point selected to control
the speeds of the motors and hence maintain the bridge in the correct
configuration. The operator mode through the directional control
valve is similar to that previously described as is also the interface
and speed and acceleration control. The control circuit when in the
braking mode has the motors 67 and 68 operating effectively as pumps.
lo It is therefore desirable to ensure that the oil displaced by the pump
50b does not further contribute to the pressures which will build up.
To this end a pressure relief valve 66 has been incorporated which
will unload the main relief valve 52b in the standstill or braking
conditions.
The directional control valves 51 and 51b are closed center valves
so that when the controls are in the neutral position the valve is set
to block the flow of oil to or from the motors controlling either the
linear movement across the bridge or the motors controlling the long
travel motion along the rail. This effectively operates as parking
brakes for the crane.




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