[0001] The present invention relates to a mobile crane for lifting immobile patients and
moving them in a longitudinal direction of the crane, the crane comprising a wheel
supported driving chassis having a base portion oriented generally crosswise of said
longitudinal direction and carrying an upstanding crane post and a pair of mutually
spaced, generally forwardly projecting, wheel supported floor engaging beams, which
are connected with adjustment means for generally varying the transverse distance
between the beams, while the crane post is connected, topwise, with a crane arm projecting
forwardly over the area as effectively supported by the floor engaging beams and connected
with means for hoisting a patient to and from a position hanging in the crane.
[0002] Cranes of this type are used for local transportation of entirely immobile patients
e.g between a bed and an examinaton locality, and it is of course of utmost importance
that the person hanging in the crane is extremely safely supported during the transportation.
This implies that the driving chassis shall show a considerable length and width.
As far as the length is concerned there are no special problems, but with respect
to the width the limitation will occur that the crane shall have to be moved through
usually narrow door openings, whereby the driving chassis shall have to be or become
correspondingly narrow. The associated narrowness is so pronounced that it will not
provide for any safe support of the patient during the movements occurring during
the transportation and by the handling of the patient at the end stations of the transportation,
and it is, therefore, an already established standard that the floor engaging beams
are connected with an actuation handle, by means of which they can be caused to be
mutually moved in the horizontal plane between a narrow position, in which they are
located relatively close to each other, normally parallel with each other so as to
be able to pass through a narrow door opening, and a widespread position, normally
forwardly diverging from each other from respective pivotal connections with fixed
outer ends of the said transverse base portion, in which position the crane and therewith
the patient is supported with increased safety.
[0003] The actuation handle is normally constituted by a long lever, which projects upwardly
along the crane post and is topwise provided with a handle grip, which is seizable
for pivoting the handle lever about a lower longitudinal axis, the lower end of the
lever being connected with a mechanism for spreading and narrowing the floor support
beams. This mechanism may comprise an eccentric cam disc, which is rotated by the
pivoting of the actuation handle and is operatively connected with a lever or link
system for displacing the floor support beams between the narrow and the widespread
position thereof.
[0004] Due to the required narrowing of the drive chassis, e.g. by the passage through door
openings, it is required in practice that the crane is handled by a particularly competent
operator in order to make sure that a patient hanging in the crane will not be scared
by the decreased safety as connected with the required narrowing of the drive chassis,
e.g. by the passage of a door opening. Normally the patient will be very sensitive
to any sign of the operator becoming extra alert, should a situation of danger occur.
The said handle should be pushed or pulled in the transverse direction of the crane
with a considerable force, not least in case of a heavy patient moved over an uneven
floor, and the operator will have to support the crane post in the opposite direction
for avoiding a lateral displacement of the entire crane, and preferably at the same
time even support the patient against oscillation. Moreover, the operator shall not
only move the handle to a new position, but cause it to be arrested in the new position,
normally by engaging it into a holding notch in a guide rail mounted along the movement
path of the handle; such a locking is desirable for preventing the floor beams from
changing their mutual positions by themselves, e.g. if one of them abuts a fixed structure.
Critical situations may arise, in which the operator with one hand on the handle just
behind the crane post may be unable to intervene with the required firmness and speed
if some uncontrolled movement of the crane and/or swinging of the patient is started.
Out of deference to the patient the operator should react long before a real danger
is encountered.
[0005] It is the purpose of the invention to provide a crane of the discussed type, which
can be operated with highly increased safety.
[0006] According to the invention the adjustment means for varying the distance between
the floor engaging beams comprise a motor driven, self-locking mechanism, which is
controllable from an easily operable actuator unit in the immediate proximity of the
suspension area of the crane, e.g. a hand carried press button control unit as additionally
provided with actuator means for the operation of the hoisting means. Hereby the adjustment
movements of the floor beams may be effected without subjecting the crane as a whole
to any lateral forces, i.e. no compensation pressure should be applied, and due to
the self-locking character of the moving mechanism the operator may let go of the
actuator, e.g. a press button, at any time without any risk of decreased stability
of the crane. The actuator can be operated with one hand in a position very close
to the patient, and with the use of a hand carried control unit the operator may even
support the patient with the same hand while the actuation is going on.
[0007] The motor driven mechanism will require a power source, the type of which is principally
irrelevant to the invention. It is well known, however, that the hoisting means may
be driven from an electrical accumulator mounted on the crane, and such a power source
will be very suitable also for the present purpose, e.g. for driving an electric gear
motor. It is also known that the hoisting means may be actuated via press buttons
on a small hand carried control box, whereby the operator may support and guide the
patient with both hands during the raising and lowering of the patient, and such a
control box may conveniently be provided with additional control buttons for the floor
beam moving mechanism according to this invention.
[0008] In connection with a servo controlled operation of the floor beams it may be a problem
that these beams may incidentally be moved against more or less fixed objects, e.g.
underneath a bed, whereby the driving mechanism may be damaged or the beams cause
damage. For counteracting such damages an electric drive motor may be connected with
an excess current relay, which will stop the motor at a given overload and trigger
and associated control unit to the effect that the motor cannot be restarted in the
same direction, but only in the opposite direction, whereby the occurred jamming will
be relieved. Thereafter, of course, the motor should be startable again in the original
direction.
[0009] In the following the invention is described in more detail with reference to the
drawing, in which:-
Fig. 1 is a perspective view of a crane according to the invention,
Fig. 2 is a top view of the rear part of the driving chassis of the crane, and
Fig. 3 is a schematic top view of a modified driving chassis.
[0010] The patient crane shown in Figs. 1 and 2 is designated 2 and comprises a driving
chassis 4 having floor supported beams 6, which, at the rear, are pivotally connected,
through hinges 7, with mutually opposed ends of a transverse base member 8, which
carries a central crane post 10 in a dismountable manner by having a socket member
12 for receiving the lower end of the post 10 and a clamp screw 13 for fixing the
post to the socket. At its top end the crane post 10 is connected through a hinge
15 with a crane boom 14, which projects forwardly midways over the area between the
floor beams 6 and has a hanger 17 at its free end for use when a patient in some suitable
carrier equipment is to be suspended in the crane. Between the boom 14 and the post
10 is arranged, in known manner, a telescopic actuator member 16 driven by an electric
motor for controlling the vertical pivoting of the boom about the hinge 15. The motor
is controlled from a hand carried control box 18, which is wire connected with a control
unit mounted inside a box 20 on the post 10, this box also holding an accumulator
for driving the motor.
[0011] The control box 18 houses a magnet enabling the box to be temporarily held on the
boom 14 or on any other iron part, but in use the operator will hold the box in one
hand, which will then be usable both for supporting the patient and for actuating
switch buttons on the box.
[0012] The control box 18 is in a conventional manner provided with a pair of press buttons
22 for the up/down controlling of the boom 14, but here the box is additionally provided
with a pair of press buttons 24 for the controlling of a motor driven mechanism for
pivoting the floor beams 6 about their hinge connections 7 with the transverse base
member 8.
[0013] The crane is supported on swivel wheels 26,28 mounted adjacent the front ends of
the floor beams 6 and adjacent the rear end of rear extensions 30 of these beams,
respectively. On the crane post 10 is arranged a pair of fixed handles 32 for use
by the manual transport of the crane.
[0014] The said mechanism for pivoting the floor beams 6 comprises a gear motor 34, which
is mounted at the rear side of the base member 8, behind the socket 12, and is connected
with a gear housing 36 for rotating a transverse shaft 38. Through cardan joints 40
this shaft 38 is connected with opposed screw spindles 42 received in nut portions
44 on respective connector link arms 46 projecting outwardly to a hinge joint 48 with
the rear end of the respective floor beam extensions 30.
[0015] When the motor 34 is actuated in one or the other direction it will thus work out
that the rear ends of the beam extensions 30 are forced towards or away from each
other, whereby the floor beams will pivot about the hinges 7 between a narrow position,
wherein they are located practically parallel with each other, and a broad position,
wherein they are swung out from each other as indicated in dotted lines, such that
the transverse distance between their front ends will be substantially increased,
whereby, the crane as a whole is broader and thus more safely supported.
[0016] In Fig. 2 it is shown that in connection with the base member 8 end stop sensors
50 may be provided for limiting the movements of the link arms 46 between the positions
correspondingly to the said narrow and broad positions of the floor beams, respectively.
[0017] As mentioned, in an associated control unit may be arranged a protection circuit
which will switch off the current to the motor 34 in response to the floor beams 6
meeting a substantial resistance towards further pivoting, inwardly or outwardly.
Such a situation may be delected in different possible manners, but most conveniently
by a detection of an excess motor current. Preferably the said control unit is designed
such that the motor cannot be restarted in the same direction until it has been restarted
in the opposite direction, whereby both the motor and the moving mechanism will be
safeguarded against overload, just as the operator's attention will be automatically
drawn to the jamming situation. Optionally the control unit may be adapted to automatically
restart the motor invertedly so as to cause the floor beams to be moved slightly backwardly
from the jamming position, in which the movement was interrupted.
[0018] It will be within the scope of the invention to make use of pedal controlled actuator
means for the motor 34, but it will be a natural demand that the operator should be
able to actuate the motor during the movement of the crane as a whole, such as achievable
with the use of the hand carried control box.
[0019] The narrowing and broadening of the crane support chassis should not necessarily
be effected by a pivoting of floor beams 6 about fixed hinges 7. It will be readily
understood that it would be advantageous, though structurally more complicated, if
the beams or corresponding wheel carriers were arranged so as to spread and narrow
not only the front wheels, but also the rear wheels, e.g. by causing the parallel
"narrow" beams to be displaced laterally in a maintained parallel position rather
than by a pivoting movement.
[0020] Such a system is illustrated in Fig. 3. The floor beams 6 are provided with rear,
inwardly projecting arms 54, which are telescopically received in a transverse guiding
tube 56 substituting the vase member 8 of Fig. 1. The rear ends of the beams 6 are
provided with a rearwardly and inwardly projecting angular arm portion 58, the inner
ends of which carry a rigid nut 60 engaging with a transverse screw spindle 62, which
is driven by a gear motor 64. It will be readily understood that the beams may hereby
be shifted between the narrow and the broad position while still being mutually parallel.
1. A mobile crane for lifting immobile patients and moving them in a longitudinal
direction of the crane, comprising a wheel supported driving chassis having a base
portion oriented generally crosswise of said longitudinal direction and carrying an
upstanding crane post associated with patient raising and lowering means, said driving
chassis being arranged and connected with control means such that the general width
thereof is changeable between respective transversely narrow and broad positions,
characterized in that the said control means comprise a motor driven, self-locking
mechanism, which is controllable from an easily operable actuator unit in the immediate
proximity of the suspension area of the crane, e.g. a hand carried press button actuator
unit as additionally provided with actuator means for the operation of the raising
and lowering means.
2. A crane according to claim 1, in which the control means comprise an electrically
driven spindle or gear motor, which is located behind the lower portion of the crane
post and cooperates with opposed, forwardly projecting floor support beams.
3. A crane according to claim 1 and comprising a control unit designed to detect a
jamming condition by the broadening or narrowing movement of the driving chassis and
to hereby stop the motor and prevent a restarting thereof in the same direction until
it has been restarted in the opposite direction.