FIELD OF APPLICATION
[0001] The invention relates to a load-lifting device, for example a trolley jack of the
type used to help lift vehicles or other heavy objects.
STATE OF THE ART
[0002] In the industrial state of the art, many load-lifting devices for lifting heavy objects,
for example vehicles, are known. Some such devices are jacks (trolley, bottle, etc.),
which lift a load pushing it from below and cranes, which lift a load pulling it from
above. In some cases, the load-lifting devices have wheels in order to move with respect
to the floor.
[0003] For example, trolley jacks are devices commonly used in car repair garages and other
mechanical work environments, which enable the heavy objects, such as vehicles, to
be lifted. A trolley jack generally comprises a main body, with respect to which some
type of lifting element is movably disposed that, duly actuated by means of a hydraulic
system or similar, is capable of raising itself, exerting sufficient force underneath
the vehicle or heavy object to cause the lifting thereof. Examples of lifting elements
are articulated lifting arms, telescopic mechanisms capable of extending vertically
or at an inclined angle and, in any case, with a vertical upward component, etc. Additionally,
trolley jacks comprise actuating means so that the user can actuate the hydraulic
system or similar and the consequent ascent of the lifting element. Similarly, the
jack comprises actuation means for enabling the controlled descent of the lifting
element, wherein said descent must be carried out in a controlled manner, as the lifting
element generally descends when loaded, i.e. while bearing the weight of the vehicle
and, therefore, avoiding imbalances, tipping or falls is vital for guaranteeing safety.
[0004] Known trolley jacks are capable of moving by means of wheels, rollers or other rolling
elements comprised in the main body. Given that the main body is generally disposed
very close to the floor and has a relatively low height, jacks usually comprise a
lever that projects upwards from the main body to provide the user with a gripping
zone for pulling or pushing the jack from one place to another, or for turning the
trolley around.
[0005] As regards the distribution of the wheels on the jack, a known solution consists
of disposing two rotary wheels in the rear zone of the jack (the zone closest to the
lever and, therefore, the user) and two fixed wheels in its front zone. Another known
solution consists of the jack also having one additional fixed wheel placed on a lifting
element in the form of a folding arm, wherein said additional fixed wheel only rests
on the floor when the arm is not raised. In this case, when the lifting element ascends,
the additional fixed wheel ascends together with said lifting element and the jack
then rests on the two remaining fixed wheels and on the two rotary wheels. However,
if the lifting element is not raised, the fixed wheel rests on the floor. In this
second scenario, the additional fixed wheel, resting on the floor, makes it possible
for a force applicator of the vehicle, i.e. a point or surface of the lifting element
that exerts a lifting force on the vehicle, to follow the same angle as the lever,
thereby improving manoeuvrability with respect to the previous solution without an
additional fixed wheel.
[0006] Trolley jacks are devices that can be quite heavy. For example, a jack capable of
lifting 2 tonnes may weigh approximately 45 kg; a jack capable of lifting 6 tonnes
may weigh up to 81 kg.
[0007] Due the heavy weight of some trolley jacks, in practice it is not always easy to
move or turn a jack around, despite having wheels and even an additional fixed wheel
in the lifting element. The complication of the rotation can be observed in the fact
that, in current trolley jacks, it is necessary to greatly rotate the lever to achieve
a rotation of a certain magnitude of the front end of the jack, which is where the
point of the lifting element destined for vertically pushing the vehicle is located.
If the jack is very heavy, causing the rotation of the lever requires a significant
effort and therefore entails risks for the user, who must usually repeat this task.
[0008] The invention is particularly aimed at designing a trolley jack that simplifies and
facilitates the rotation thereof, reducing the effort that must be made by the user.
This is aimed at improving the manoeuvrability of the jack to facilitate the positioning
thereof, for example to help the user to position the jack appropriately with respect
to the vehicle before proceeding to lift it.
[0009] In addition, the invention is generally aimed at achieving a load-lifting device
which, being provided with wheels or rolling elements for moving along the floor,
has improved manoeuvrability with respect to conventional rolling load-lifting devices.
BRIEF DESCRIPTION OF THE INVENTION
[0010] The subject matter of the invention is a load-lifting device comprising a main body
with respect to which a lifting element is capable of ascending or descending to lift
a heavy object, wherein said lifting element comprises a force applicator capable
of exerting an upward force on the object. The main body can rest and move along the
floor by means of rolling elements. A particular feature of the device according to
the invention is that it comprises at least one rear rolling element located in rear
zone of the device which can be actuated by the user in order to manoeuvre the device;
at least one front rolling element, located in a front zone of the device closer to
the force applicator than the rear zone; and an intermediate rotating rolling element.
The intermediate rotating rolling element is connected to the main body by means of
an elastic element. Said elastic element tends to cause a separation of the intermediate
rotating rolling element with respect to the main body until all the rolling elements
(front, rear and intermediate rotating elements) are not on the same plane. In addition,
said elastic element is capable of deforming itself until the rolling elements are
on the same plane. The intermediate rotating rolling element is located between the
rear zone and the front zone. Also according to the invention, the proportion of mass
of the device distributed between the intermediate rotating rolling element and the
rear rolling element is greater than the proportion of mass distributed between the
intermediate rotating rolling element and the front rolling element. That is, the
centre of gravity is behind the intermediate rotating rolling element.
[0011] The device according to the invention works as follows. When not loaded, i.e. with
the force applicator not exerting force on the object, the elastic element separates
the intermediate rotating rolling element sufficiently so that the rolling elements
of the device are not on the same plane. Consequently, as a consequence of the position
of the centre of gravity and of the action of the force of gravity, the rear rolling
elements and the intermediate rotating rolling element rest on the floor, whilst the
front rolling elements remain in the air. However, when loaded, wherein the lifting
element exerts an upward force on a heavy object, consequently receiving the corresponding
force of reaction of the heavy object, the elastic element is flexed sufficiently
so that all the rolling elements are located on the same plane and, therefore, the
front rolling elements rest on the floor.
[0012] In this way, the device according to the invention has the following advantages.
On the one hand, having an intermediate rotating rolling element closer to the rear
zone of the device (a zone that can be actuated by the user in order to manoeuvre
the device) than the front rolling elements, added to the fact that when not loaded
the front rolling elements do not rest on the floor, endows the device with great
manoeuvrability. Manoeuvrability is understood to be the maximisation of the rotation
of the front zone of the device, where the force applicator or zone of the lifting
element that pushes the heavy object, for a same rotation angle of the rear zone of
the device, is usually found, where the actuation lever or other actuation means which
can be actuated by the user is disposed. This reduces the effort that must be made
by the user, as in order to perform the same rotation of the force applicator the
user must rotate the lever or other actuation means less, compared to conventional
devices. On the other hand, the fact that when loaded the front rolling elements rest
on the floor makes it possible to endow the device with great resistance, since said
front rolling elements, particularly if they are fixed, may be designed with a high
capacity to support the weight of the load of the device. In turn, the intermediate
rotating rolling element only has to provide manoeuvrability and it will not have
to bear heavy weights, since when loaded the weight is borne to a greater extent by
the front rolling elements.
BRIEF DESCRIPTION OF THE FIGURES
[0013] The details of the invention can be observed in the accompanying figures, which do
not aim to limit the scope of the invention:
- Figure 1 shows a perspective view of an embodiment of a device in accordance with
the invention, in this case in the form of a trolley jack;
- Figure 2 shows a side view of the jack of Figure 1 when not loaded or idle;
- Figure 3 shows an expanded cross-sectional front view in accordance with the cross-section
plane A-A illustrated in Figure 2;
- Figure 4 shows a side view of the jack of Figure 1 under a loaded condition;
- Figure 5 shows an expanded cross-sectional front view in accordance with the cross-section
plane B-B illustrated in Figure 4; and
- Figures 6, 7 and 8 show schematic elevation views of the state of the art and of the
jack according to the invention represented in the preceding figures.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Figure 1 shows a perspective view of an embodiment of a load-lifting device in accordance
with the invention. In the embodiment represented, the load-lifting device is a jack
(1) of the type known as a trolley jack. As can be observed in the figure, the jack
(1) comprises a main body (2) with respect to which a lifting element (3), intended
for exerting a force on a heavy object to cause the lifting thereof and also intended
for sustaining the heavy object during lowering thereof, is capable of ascending or
descending. In the embodiment of the figure, the lifting element (3) is a lifting
arm capable of folding with respect to the main body (2), as schematically indicated
by an arrow (4). The lifting element (3) has a force applicator (5) at its end, said
force applicator precisely being the zone responsible for exerting the upward force
on the object to cause the lifting thereof. In the embodiment represented, the force
applicator (5) is a circular flat surface intended for coming into contact with the
underbody of a vehicle or with a lower surface of the object to be lifted. The jack
(1) has been represented resting on a floor (6). The main body (2) can move with respect
to said floor (6) by means of different rolling elements. More specifically, the jack
(1) comprises at least one rear rolling element (7) located in a rear zone (8) of
the jack (1). The rear zone (8) of the jack (1) is the zone that can be actuated by
the user in order to manoeuvre the jack (1), specifically actuating a handle (9a)
of an actuation lever (9). In this particular case, the jack (1) comprises two rear
rolling elements (7) in the form of fixed wheels, i.e. two wheels whose rotation axis
does not change direction. In addition, the jack (1) comprises at least one front
rolling element (10) located in a front zone (11) of the device closer to the force
applicator (5) than the rear zone (8). In this case, the front rolling element (10)
is a single cylinder or roller that is fixed, i.e. whose rotation axis does not change
direction. The jack (1) also comprises an intermediate rotating rolling element (12).
In the embodiment represented, the intermediate rotating rolling element (12) is a
wheel which is capable of rotating on itself according to a central rotation axis
(14) in order to roll with respect to the floor (6). The intermediate rotating rolling
element (12) is also capable of rotating with respect to a vertical rotation axis
(14), causing the rotation axis (13) to have a variable direction. In addition, the
intermediate rotating rolling element (12) is fixed elastically to the main body (2),
said elastic connection enabling the vertical position of the intermediate rotating
rolling element (12) to vary. Elastic connection is understood to be that the intermediate
rotating rolling element (12) is fixed to the main body (2) by means of an elastic
element (16).
[0015] Also in accordance with the invention, the proportion of mass of the jack (1) distributed
between the intermediate rotating rolling element (12) and the rear rolling elements
(7) is greater than the proportion of mass distributed between the intermediate rotating
rolling element (12) and the front rolling element (10). That is, the centre of gravity
of the jack (1), when not loaded, is located behind the intermediate rotating rolling
element (12), between the intermediate rotating rolling element (12) and the rear
zone (8) of the jack (1).
[0016] Figure 2 shows a schematic side view of the jack (1) of Figure 1 in a situation wherein
the lifting element (3) is disposed folded against the main body (2) and wherein the
jack (1) is not loaded, i.e. not exerting a force on an object. In this situation,
as can be observed, the lowest points of the rolling elements (7, 11, 12) are not
disposed on the same plane, but rather the lowest point of the intermediate rotating
rolling element (12) is located below an imaginary plane (15) that joins the lowest
points of the rear rolling elements (7) and of the front rolling element (10). In
this situation, due to the fact that the centre of gravity of the jack (1) is located
behind the intermediate rotating rolling element (12), between the intermediate rotating
rolling element (12) and the rear zone (8), the intermediate rotating rolling element
(12) and the rear rolling elements (7) rest on the floor (6) while the front rolling
element (10) remains in the air. Therefore, in an unloaded situation only the rear
rolling elements (7) and the intermediate rotating rolling element (12) are actuated,
achieving maximum manoeuvrability, as explained below.
[0017] Figure 3 shows a front cross-sectional view of the jack (1) of the preceding figure,
wherein it can be clearly observed that the intermediate rotating rolling element
(12) is disposed fixed to the main body (2) by means of an elastic element (16), which
in this case has the shape of a band extending between two inner walls (2a, 2b) of
the main body (2). The intermediate rotating rolling element (12) is disposed fixed
to the central zone of said band and is capable of varying its height in accordance
with the deformation of the band.
[0018] Figure 4 shows the jack (1) of Figure 2 when loaded, i.e. in a situation wherein
the lifting element (3) is exerting a force on a heavy object (17), schematically
represented as an irregular polygon and, consequently, the object (17) exerts a reaction
force (F) on the lifting element (3). The lifting element (3) is shown in its lowest
position, without yet having begun to rotate in an upward direction as the arrow (4)
indicates. Under this load situation, the reaction force (F) on the lifting element
(3) is transferred to the main body (2), due to being the lifting element (3) fixed
thereto. Due to the fact that the intermediate rotating rolling element (12) is disposed
resting on the floor (6) and the fact that there is an elastic connection between
the intermediate rotating rolling element (12) and the main body (2) which enables
a relative vertical movement between the two, the reaction force (F) applied to the
main body (2) causes the main body (2) to descend with respect to the intermediate
rotating rolling element (12) while the elastic element (16) is flexed. A point is
reached wherein the elastic element (16) is flexed sufficiently for the front rolling
element (10) to rest on the floor, as can be observed in the figure. In this way,
when loaded the front rolling element (10) bears the weight of the object (17) rather
than the intermediate rotating rolling element (12), which is less capable of bearing
weight due to being rotary.
[0019] Figure 5 shows a front cross-sectional view of the jack (1) of the preceding figure,
wherein it can be clearly observed that the elastic element (16) has become deformed,
enabling the descent of the main body (2) with respect to the intermediate rotating
rolling element (12), which is disposed resting on the floor (6).
[0020] The elastic element (16) is configured such that it exerts an elastic force that
tends to cause the descent of the intermediate rotating rolling element (12) with
respect to the main body (2) until the lowest points of the rolling elements (7, 10,
12) are not on the same plane. That is, it tends to return the jack (1) to the idle
position of Figure 2, wherein the lowest point of the intermediate rotating rolling
element (12) rests on the floor while the lowest point of the front rolling element
(10) is in the air. Therefore, when not loaded, the jack (1) automatically returns
to said idle position.
[0021] Figures 6, 7 and 8 show schematic elevation views of two jacks known in the state
of the art and of the jack (1) according to the invention represented in the preceding
figures, with the aim of illustrating the improved manoeuvrability achieved with the
jack of the present invention. Figure 6 shows a conventional jack (100) equipped with
two rotating rear wheels (107) in its rear zone (108), two fixed front wheels (110)
in its front zone (111) and an actuation lever (109) disposed in its rear zone (108).
When a user rotates the actuation lever (109) pushing a handle (109a) thereof towards
the left or towards the right, the rear wheels (107), due to being rotary, rotate
freely, while the front wheels (110), due to being fixed, do not rotate freely. Consequently,
the pivot point (150) of this first conventional jack is disposed between the front
wheels (110), which are fixed and equidistant therebetween, in front of the force
applicator (105) (zone of the jack (1) intended for exerting force on the object to
be lifted). Therefore, when the user rotates the handle (109a) of the actuation lever
(109) describing an arc (A1) such as the one illustrated in the figure, it causes
the practically null rotation of the front zone (111) and a very small rotation of
the force applicator (105), indicated by the arc (B1). That is, the user must greatly
rotate the rear zone (108) of the jack (100) to achieve a very small rotation of the
front zone (111) and the force applicator (105), thereby requiring a large effort.
Figure 7 shows another conventional jack (200), in this case equipped with two rotary
rear wheels (207) in its rear zone (208), two fixed front wheels (210) in its front
zone (211) and one intermediate fixed wheel (212). In this conventional second jack
(200), the intermediate fixed wheel (212), due to being fixed, serves as a pivot point
(250) of the jack. Therefore, a rotation arc (A2) similar to that of the rotation
arc (A1) of the preceding figure causes the force applicator (205) to describe an
arc (B2) greater than the arc (B1) of the preceding figure. This is equivalent to
saying that the conventional jack (200) of this figure requires the user to make a
greater effort to rotate the front zone (211) thereof compared to the conventional
jack (100) of the preceding figure and, consequently, is more manoeuvrable. However,
figure 8 shows the jack according to the invention, equipped with two rear wheels
or rolling elements (7) in its rear zone (8), a front roller or rolling element (10)
in its front zone (11) and an intermediate wheel or rotating rolling element (12).
When not loaded, the front rolling element (10) does not rest on the floor, due to
which the pivot point (50) of the jack is disposed in the zone of the rear rolling
elements (7), due to being fixed and the intermediate rotating rolling element (12)
being rotary. Specifically, the pivot point (50) is disposed between the rear rolling
elements (7) and equidistant therebetween, very close to the actuation lever (9).
The actuation lever (9) is represented in a more forward position compared to the
actuation levers (109, 209) of the two preceding figures, but if it had been represented
disposed in the same manner, its handle (9a) would be positioned at the point represented
in the present figure. Therefore, if a user were to rotate the handle (9a) describing
an even smaller arc (A3) than the arcs (A1, A2) of the preceding figures, the front
zone (11) would be rotated and, in particular, the force applicator (5) would describe
an arc (B3) considerably larger than in the two preceding figures. That is, the manoeuvrability
achieved by the jack (1) of the invention is very high, since it would be sufficient
for the user to slightly rotate the rear zone (8) of the jack in order to greatly
rotate the front zone (11), where the force applicator (5) is located.
[0022] In the embodiment represented, as can be observed in figure 4, when loaded the lowest
points of all the rolling elements (7, 10, 12) are disposed on the same plane, such
that all the rolling elements (7, 10, 12) rest on the floor (6). In this situation
wherein all the rolling elements (7, 10, 12) are resting on the floor (6), the weight
of the jack (1) and of the object (17) or load is preferably borne by the rear rolling
elements (7) and the front rolling element (10), and not by the intermediate rotating
rolling element (12), even though the latter is in contact with the floor (6).
[0023] As mentioned earlier, in the embodiment represented the elastic element (16) is a
band connected to the main body (2) and whereto the intermediate rotating rolling
element is fixed (12). Alternatively, the elastic element (16) may be a spring or
damper connected to the main body (2) and whereto the intermediate rotating rolling
element (12) is fixed. Other embodiments along these lines are not ruled out.
[0024] In the embodiment represented, the intermediate rotating rolling element (12) is
disposed approximately in the centre of the main body, seen from above. In alternative
embodiments, the intermediate rotating rolling element (12) in accordance with the
invention can be found in other points of the main body (2) at a certain distance
from the centre and disposed between the rear rolling elements (7) and the front rolling
elements (10).
[0025] In accordance with the invention, both the front rolling elements and the rear rolling
elements may be fixed -as in the embodiment represented in the figures- or rotary.
Fixed is understood to mean that their rotation axis does not change direction. Rotary
is understood to mean that their rotation axis may change direction.
[0026] The fact that the rear rolling elements are fixed, as in the embodiment of the figures,
has certain advantages that can be observed in the jack (1) of the figures. On the
one hand, the resulting jack (1) may be narrower. On the other, the rear rolling elements
(7) may be large and consequently cause the jack (1) to be much more pleasant and
easy to handle.
[0027] In the embodiment represented, the force applicator (5) is a circular flat surface
intended for coming into contact with the underbody of a vehicle or with a lower surface
of the object to be lifted. The invention envisages different force applicators, capable
of pushing the object or load upwards (for example, a piston shaft) or capable of
pulling on the object from above (for example, a hook or claw).
1. A load-lifting device comprising a main body (2) with respect to which a lifting element
(3) is capable of ascending or descending to lift a heavy object (17), wherein said
lifting element (3) comprises a force applicator (5) capable of exerting an upward
force on the object (17), wherein the main body (2) can rest on and move along a floor
(6) by means of rolling elements,
characterised in that it comprises:
- at least one rear rolling element (7) located at a rear zone (8) of the device which
can be actuated by the user in order to manoeuvre the device;
- at least one front rolling element (10), located in a front zone (11) of the device
closer to the force applicator (5) than the rear zone (8);
- an intermediate rotating rolling element (12) located between the rear zone (8)
and the front zone (11) of the device and connected to the main body (2) by means
of an elastic element (16), wherein said elastic element (16) tends to cause a separation
of the intermediate rotating rolling element (12) with respect to the main body (2)
until the rolling elements (7, 8, 9) are not on the same plane and wherein the elastic
element (16) is capable of being deforming until the rolling elements (7, 8, 9) are
on the same plane; and wherein
- the proportion of mass of the device distributed between the intermediate rotating
rolling element (12) and the rear rolling element (7) is greater than the proportion
of mass distributed between the intermediate rotating rolling element (12) and the
front rolling element (10).
2. The device, according to claim 1, characterised in that the rear rolling elements (7) are fixed.
3. The device, according to claim 1, characterised in that the rear rolling elements (7) are rotary.
4. The device, according to claim 1, characterised in that the front rolling elements (10) are fixed.
5. The device, according to claim 1, characterised in that the front rolling elements (10) are rotary.
6. The device, according to claim 1, characterised in that the elastic element (16) is a band connected to the main body (2) and whereto the
intermediate rotating rolling element (12) is fixed.
7. The device, according to claim 1, characterised in that the elastic element (16) is a spring connected to the main body (2) and whereto the
intermediate rotating rolling element (12) is fixed.
8. The device, according to claim 1, characterised in that the elastic element (16) is a damper connected to the main body (2) and whereto the
intermediate rotating rolling element (12) is fixed.
9. The device, according to claim 1, characterised in that one or more of the rolling elements is a wheel.
10. The device, according to claim 1, characterised in that one or more of the rolling elements is a ball.
11. The device, according to claim 1, characterised in that one or more of the rolling elements is a roller.