Patent Description:
Examples of support roller arrangements are disclosed in documents <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

Powered Low Lifting Fork-Lift Trucks or Powered Pallet Trucks comprises a height adjustably fork which is supported on the ground by front support rollers. These trucks are typically used for moving loading pallets in warehouses. Such pallets are supported on the ground by lower baseboards that are arranged parallel and form two channel-like openings for receiving the forks of the pallet truck. Sometimes, it is not possible to maneuver the truck into a position where the forks may be inserted into the appropriate channels of the pallet and instead the pallet is engaged in a direction transverse to the base boards. The forks of the lift trucks are typically provided with support rollers that support the forks on the ground. These rollers may be arranged in a bogie that pivots in order to enable the rollers to climb up onto and over the baseboards of the pallet. Climbing wheels may further be provided to facilitate the entering of the forks through the pallet. A lift truck comprising climbing wheels and a support roller bogie is disclosed in <CIT>.

However, a problem related to the known lift truck is that the support roller bogie, when hanging in the air between two baseboards of a pallet may be in an inclined orientation. This situation is shown in <FIG>. A problem thereby is that when the forks <NUM> of the lift truck <NUM> proceeds through the pallet <NUM>, the inclined support roller bogie <NUM> may hit the following base board <NUM>. This in turn causes negative effects such as noise, shocks and movement of the pallet <NUM>.

Thus, it is an object of the present invention to provide a support roller arrangement for a lift truck that solves or mitigates at least one of the problems of the prior art.

A further object of the present invention is to provide a support roller arrangement for a lift truck, which allows for smooth engagement between the forks of the lift truck and the pallet.

Yet a further object of the present invention is to provide a support roller arrangement for a lift truck which is of robust and simple construction and that may be realized at a low cost.

According to the present invention, at least one of these objects is met by a support roller arrangement according to the appended claims.

The support roller arrangement according to the present invention provides an advantage in that the bogie is allowed to assume an inclined orientation when climbing up on a baseboard of a pallet. However, as soon as the bogie has passed the baseboard and loses contact therewith it is returned to a predetermined resting position, which may be selected such that the bogie does not hit the subsequent baseboard. This reduces or eliminates the risk that the bogie hits the subsequent baseboard as the forks of the lift-truck proceeds through the pallet. In all, the support roller arrangement provides for easy and smooth engagement of pallets in a direction transverse to baseboards.

Alternatives are set out in the appended dependent claims.

The present invention also relates to a fork lift truck comprising a support roller arrangement according to appended claims.

The support roller arrangement according to the present invention will now be described more fully hereinafter. The support roller arrangement according to the present invention may however be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided by way of example. The scope of the present invention is limited only by the appended claims.

Same reference numbers refer to same elements throughout the description.

Further, in following description, any references to direction or positions or orientation are in relation to a situation in which the support roller arrangement <NUM> is mounted on the engagement means <NUM>, <NUM> of a lift truck <NUM> that positioned on a horizontal ground surface.

<FIG> shows a support roller arrangement <NUM> according to a first alternative of the present invention.

The support roller arrangement <NUM> comprises a bogie <NUM> which comprises a pair of support rollers <NUM>, <NUM> that are rotationally arranged in a bogie frame <NUM>. Turning to <FIG>, the bogie frame <NUM> comprises first and second bogie frame sides <NUM>, <NUM>, which may be arranged parallel and be in the form of metal sheets or plates. Returning to <FIG>, the pair of support rollers <NUM>, <NUM> is arranged in series, i.e. one roller in front of the other, between the bogie frame sides <NUM>, <NUM>. Each roller is rotationally attached to the bogie frame <NUM> by a respective roller pivot shaft <NUM>, <NUM> that extends between the first bogie frame side <NUM> and the second bogie frame side <NUM> and through the respective roller (see <FIG>).

The roller support arrangement further comprises a bracket <NUM> for attaching the bogie <NUM> to a lift-truck <NUM>.

The bracket <NUM> comprises a front end to which the bogie <NUM> is pivotally is attached by the bogie pivot shaft <NUM>. Turning to <FIG>, the bracket <NUM>, may have a first and a second fork tine <NUM>, <NUM> which extend on opposite sides of the bogie <NUM>. The ends of the first and the second fork tines <NUM>, <NUM> thereby constitute the front end of the bracket <NUM>. Turning to <FIG>, the rear end of the bracket <NUM> is configured to be attached to the lift-truck <NUM>. Typically, the rear end of the bracket <NUM> is configured to be attached to the underside of a ground supported load engagement of a lift truck not shown). Such a load engagement means may be in the form of ground supported lift-forks that are movable in vertical direction. The rear end of the bracket <NUM> is typically configured to be pivotally attached to underside of a ground supported load engagement means. For this purpose, the rear end of the bracket <NUM> may comprise diagonally spaced apart openings <NUM> that may be attached to pivot shafts on the underside of the ground supported load engagement means. The bracket <NUM>, together with pivot shafts (not shown) between the load engagement means and the bogie <NUM> thereby forms a linkage which ensures that the pair of rollers <NUM>, <NUM> remain in contact with the ground when the load engagement means <NUM>, <NUM> moved vertically. This feature is known in the art and need not be described further here within.

The bogie <NUM> is pivotally attached to the front end of the bracket <NUM>. For this purpose, the bogie <NUM> comprises a bogie pivot shaft <NUM>. The bogie pivot shaft <NUM> extends from the bogie frame <NUM> and is pivotally journalled in the front end of the bracket <NUM>. The bogie pivot shaft <NUM> may be fixed to the bogie frame <NUM> such that the bogie <NUM> and the bogie pivot shaft <NUM> pivots relative the bracket <NUM>. In the alternative of the support roller arrangement <NUM> shown in <FIG>, the bogie pivot shaft <NUM> comprises a first bogie pivot shaft section <NUM> and a second bogie pivot shaft section <NUM>. The first bogie pivot shaft section <NUM> extends from the first bogie side frame <NUM> and is pivotally received in an opening <NUM> in the first fork tine <NUM>. The second bogie pivot shaft section <NUM> extends from the second bogie frame side <NUM> and is pivotally received in an opening <NUM> in the second fork tine <NUM>. In <FIG>, the first and the second bogie pivot shaft sections <NUM>, <NUM> are separate sections. However, the bogie pivot shaft <NUM> may also be realized as a single shaft. Typically, the first and second bogie pivot shaft sections <NUM>, <NUM> extend respectively from a position between the first and the second roller. This facilitates a horizontal resting position of the bogie <NUM>.

According to the present invention, the roller support arrangement comprises at least one spring device <NUM> which is coupled to the bogie <NUM> and to the bracket <NUM>. The spring device <NUM> is configured to force or move the bogie <NUM> to a predetermined resting position. In detail, the spring device <NUM> is configured to force the bogie <NUM> from an inclined position, in which the orientation of the bogie <NUM> deviates from the resting position, to the resting position. In the resting position, the bogie <NUM> may be level, i.e. oriented horizontally. In detail, the predetermined resting position may be relative a horizontal plane (X) and may be defined by the orientation of a longitudinal axis (A) that extends through the first and the second roller pivot shafts <NUM>, <NUM> relative the horizontal plane (X). For example, as shown in <FIG>, the spring device <NUM> is configured to force the bogie <NUM> to a resting position in which the bogie <NUM> is oriented parallel with the horizontal plane (since <FIG> is a plain side view, the horizontal plane is illustrated with a plain line). In the inclined position, the angular orientation of the bogie <NUM> (and the longitudinal axis (A) deviates from the horizontal plane (X).

According to a first alternative of the present invention, the spring device <NUM> is a torsion spring. The encircled area of <FIG> shows the spring device <NUM>.

<FIG>, shows an exploded view of the support roller arrangement <NUM> according to the first alternative of the present disclosure. Thus, the spring device <NUM>, which may be manufactured of spring steel wire, comprises a coiled portion <NUM> and a first spring end <NUM> and a second spring end <NUM>. The spring device may be dimensioned in view of the bogie in question. That is, in view of factors such as the dimensions and weight of the bogie and the pivoting distance back and forth from a resting position. A suitable spring device in the form of a torsion spring is available commercially from the company Lesjöfors AB under the article no: <NUM>: TSR <NUM>,5X28X25X3.

The coiled portion <NUM>, is arranged around one of the bogie pivot shaft sections <NUM>, <NUM>, in this case the first bogie pivot shaft section <NUM>. Turning to <FIG>, which shows an enlarged view of the circled area of <FIG>, the first spring end <NUM> of the spring device <NUM> is coupled to the bogie <NUM>, in this case attached to first bogie frame side <NUM>. The second end <NUM> of the spring device <NUM> is coupled to the bracket <NUM>, in this case attached to the first fork tine <NUM>. Attachment of the ends <NUM>, <NUM> of the spring device <NUM> may be achieved by bending the ends <NUM>, <NUM> by e. g <NUM>° and inserting them into appropriate openings in the bracket <NUM> and the bogie frame <NUM>.

It is appreciated that a second spring device <NUM>, in the form of a torsion spring, may be arranged around the second bogie pivot shaft section <NUM> and coupled by a first spring end <NUM> to the bogie <NUM>, in this case the second bogie frame side <NUM>, and by second spring end <NUM> to the bracket <NUM> in this case to the second fork tine <NUM>. (this is not shown in the drawings).

In operation, the bogie <NUM> may be forced to pivot in clockwise or anti-clock wise direction, for example as result of the bogie <NUM> climbing up on a pallet baseboard. Pivoting of the bogie <NUM> around the bogie pivot shaft <NUM> causes biasing of the spring device <NUM>. When the bogie <NUM> loses the ground contact and no external forces acts on the bogie <NUM>, the spring device relaxes from its biased state and forces the bogie <NUM> to pivot back to its resting position. Typically, in the resting position, no or small spring forces act on the bogie <NUM>.

<FIG> shows schematically a lift-truck <NUM> according to the present invention in operation of engaging a pallet. Turning to <FIG>, the lift-truck <NUM> may be a fork-lift truck, such as a powered pallet truck, powered stacker truck and low lifting order picking trucks. The lift-truck <NUM> comprises a first and a second vertically movable ground-supported load engagement means <NUM>,<NUM> in the form of a first and a second lifting fork arm (in <FIG> only load engagement means <NUM> is visible). The lift-truck <NUM> further comprises a housing <NUM>. A drive wheel <NUM> is arranged underneath the housing <NUM>. The housing <NUM> comprises a lifting/lowering arrangement <NUM> for raising or lowering the load engagement means <NUM>, <NUM>. For example, the lifting/lowering arrangement <NUM> may comprise a hydraulic piston and cylinder coupled to the load engagement means <NUM>, <NUM> and to hydraulic circuit including a hydraulic pump coupled to a motor (these features are not shown in detail). The housing <NUM> further comprises an electric motor <NUM> for propelling the drive wheel <NUM> of the lift-truck <NUM> and the hydraulic pump. The housing <NUM> further comprises an Electronic Control Unit (ECU) <NUM>, for example a Programmable Logic Controller, which is configurable to control the motor <NUM> and the lifting/lowering arrangement <NUM> and other necessary functions of the lift-truck <NUM>. The lift-truck <NUM> further comprises an operator's control <NUM> arranged on the housing <NUM> and other components (not shown) such as an electric battery and necessary electrical wiring, electronic circuits and hydraulic components as is known to the skilled person.

The load engagement means <NUM>, <NUM> extend from the front of the housing <NUM> and comprises each at least one support roller arrangement <NUM> according to the present invention for supporting the respective load engagement means <NUM>, <NUM> on the ground surface that the lift-truck <NUM> is running on. The support roller arrangement <NUM> comprises, as described above a bracket <NUM> and a bogie <NUM> with a pair of support rollers <NUM>, <NUM> that is attached in known manner, by a linkage (not shown), to the underside of the load engagement means <NUM>, <NUM>. Each load engagement means <NUM>, <NUM> may further comprises a climbing wheel <NUM> which is arranged in front of the bogie <NUM>. The load engagement means <NUM>, <NUM> may further comprises a two auxiliary wheels <NUM> which are arranged behind the bogie <NUM>. The climbing wheel <NUM>, and the auxiliary wheels <NUM> are pivotally attached to shafts (not shown) to the lower side of the load engagement means <NUM>, <NUM> and out of contact with the ground surface.

In <FIG>, the lift-truck <NUM> is in a position where the bogie <NUM> has started to climb up onto the baseboard of the pallet. In this situation, the weight of the lift-truck <NUM> forces the bogie <NUM> to pivot such that the bogie <NUM> is inclined and may roll up onto the baseboard. Pivoting of the bogie <NUM> causes the biasing of the spring device as described hereinabove. The inclined orientation of the bogie <NUM> may remain in more or less degree until the bogie <NUM> has passed the baseboard and is out of contact with the underlying surface as shown in <FIG>. Since no forces now are acting on the bogie <NUM>, the spring device <NUM> relaxes from its biased state and causes the bogie <NUM> to return to its horizontal resting position (see <FIG>). The bogie <NUM> will then easily and without any impact roll over the next bas board of the pallet.

Although a particular embodiment has been disclosed in detail this has been done for purpose of illustration only, and is not intended to be limiting. In particular, it is contemplated that various substitutions, alterations and modifications may be made within the scope of the appended claims.

For example, <FIG> shows a roller support arrangement according to a second alternative of the present disclosure. The roller support arrangement according to the second alternative comprises a bogie <NUM> and a bracket <NUM> for attaching the bogie <NUM> to the load engagement means <NUM>, <NUM> of a lift-truck <NUM>. These features are identical to the bogie <NUM> and bracket <NUM> as described under the first alternative. However, according to the second the alternative of the present invention, the spring device <NUM> is an extension spring having a coiled portion <NUM> and a first and a second spring end <NUM>, <NUM>. The first spring end <NUM> of the draw spring is coupled to the bogie, in this case the first bogie frame side <NUM>, The second end <NUM> of the draw spring is coupled to the bracket <NUM>, in this case attached to the first fork tine <NUM>. In operation, when the bogie <NUM> is inclined during climbing, the draw spring will be biased by the pulling force from the bogie <NUM>. When the bogie <NUM> loses ground contact the spring device <NUM> relaxes and forces the bogie <NUM> to pivot towards a predetermined resting position. Thus, if the bogie <NUM> is raised out of ground contact, the pulling force of the draw spring will force the bogie <NUM> to pivot back form an inclined position to its resting position (as shown in <FIG>).

Claim 1:
A support roller arrangement (<NUM>) for a lift truck (<NUM>) comprising:
- a bogie (<NUM>) with a pair of support rollers (<NUM>, <NUM>);
- a bracket (<NUM>) for attaching the bogie (<NUM>) to a lift truck (<NUM>), wherein the bogie (<NUM>) is pivotally attached to the bracket (<NUM>), wherein a spring device (<NUM>) that is coupled to the bogie (<NUM>) and to the bracket (<NUM>) and configured to force the bogie (<NUM>) towards a predetermined resting position (A) characterized in that
the spring device (<NUM>) is a coiled wire spring with a coiled portion (<NUM>) and a first end (<NUM>) that is attached to the bogie (<NUM>) and a second end (<NUM>) that is attached to the bracket (<NUM>).