EP3983324A1

EP3983324A1 - Dock leveler hydraulic unit

Info

Publication number: EP3983324A1
Application number: EP20730243.1A
Authority: EP
Inventors: Sven Roos
Original assignee: Assa Abloy Entrance Systems AB
Current assignee: Assa Abloy Entrance Systems AB
Priority date: 2019-06-13
Filing date: 2020-06-02
Publication date: 2022-04-20
Also published as: WO2020249421A1

Abstract

A hydraulic unit (100) for a dock leveler (200), wherein said hydraulic unit (100) comprises an hydraulic pump (106) driven by an electric motor (102), a hydraulic oil reservoir (101), at least one oil conduit (108, 110) being configured to draw and/or return hydraulic oil from/to said oil reservoir (101), at least one connector (111, 112) for connecting equipment to be powered by said hydraulic unit (100).

Description

DOCK LEVELER HYDRAULIC UNIT

Technical Field

The present invention relates to the technical field of dock levelers for facilitating access to for instance a truck bed from a loading dock, more specifically to a hydraulic unit for a dock leveler, to a dock leveler comprising such a hydraulic unit and to a method for replacing the oil in a hydraulic unit for a dock leveler.

Prior Art

Dock levelers are used to allow access to truck beds or similar from a loading dock, forming a ramp onto which for instance a fork truck may be driven. Dock levelers may be either be manually operated, where the ramp is raised and lowered by hand. Often however, the leveler is powered either by electric motors and/or by hydraulic power. The present disclosure relates especially to hydraulically operated dock levelers.

A typical dock leveler comprises some sort of a support structure, which may be a frame or similar which is fastened to the loading dock. In the case of concrete loading docks, the support structure, or at least a part thereof, may be cast into the concrete and thus form a part of the loading dock itself.

The ramp is pivoted/moved in relation to the support structure by means of hydraulic cylinders and various safety systems may also be provided in order to avoid unintentional movement of the ramp etc.

Dock levelers are often installed where they become subjected to harsh environments. For instance are they often subjected to both varying temperatures as they are often placed outside, as well as periodically having to withstand a significant amount of dust and particles. Both these factors, along with several others, affects the oil of the hydraulic system of the leveler. This may in extreme cases adversely affect the functioning of the dock leveler and in the worst case even the safety systems.

Manufacturers of dock levelers therefore provide strict servicing intervals and sometimes tailored oils having correct viscosity etc for the environment each dock leveler is intended to function in.

Given that the maintenance of a dock leveler can be a complicated task, requiring considerable man hours each time, it is desired to provide a hydraulic unit where servicing is facilitated and where the safety of the system can thus be improved.

It is also desired to facilitate recycling of the used oil. Summary

It is therefore an object of the invention to at least partly overcome one or more of the above-identified limitations of the prior art. According to a first aspect of the teachings herein is a hydraulic unit for a dock leveler provided. The hydraulic unit comprises an hydraulic pump driven by an electric motor, a hydraulic oil reservoir, at least one oil conduit being configured to draw and/or return hydraulic oil from/to said oil reservoir, at least one connector each controlled by at least one valve for connecting equipment to be powered by said hydraulic unit. The oil reservoir is further removably connected to the hydraulic unit. Having a removable oil reservoir formed as a separate part greatly alleviates the work necessary to replace the oil in the hydraulic unit. Costs will thus be lowered for maintenance of the hydraulic unit, while safety is improved as it is made easier to replace the oil ensuring intended functionality of the components of the hydraulic unit.

The oil reservoir may be connected to the hydraulic unit by means of a threaded connection. The threaded connection securely holds the oil reservoir in place while allowing rapid replacement of the oil reservoir.

The oil reservoir may be connected to the hydraulic unit by means of a quick- connect or a clamp-connection, forming alternative quick means of removing/attaching the oil reservoir to the hydraulic unit.

The suction oil conduit may further comprise a filter being arranged near the bottom of the of the oil reservoir when the oil reservoir is connected to the hydraulic unit, ensuring that as much oil as possible can be used by the hydraulic unit.

The electric motor may be connected to a manifold, the manifold comprising the at least one connector and a pump housing is attached to the manifold covering the hydraulic pump, and the oil reservoir may be connected to the pump housing.

In a second aspect is a hydraulically operated dock leveler provided. The dock leveler comprises a support structure for attachment to a loading dock, a moveable ramp being pivotable in relation to the support structure. The dock leveler further comprising at least one hydraulic cylinder for controlling the movement of the dock leveler, and a hydraulic unit according to the first aspect being connected to the at least one hydraulic cylinder for powering the movements of the dock leveler. A dock leveler is thus provided, where maintenance of the hydraulic unit is facilitated. In one embodiment, one hydraulic cylinder is arranged on either lateral side of the ramp for achieving movement of said ramp, and wherein each hydraulic cylinder is connected to the hydraulic unit.

The dock leveler may comprise a lip arranged distally on the ramp and being pivotable in relation to the ramp. The movement of the lip may be powered by a hydraulic cylinder connected to the hydraulic unit. The lip provides a latch which can rest against for instance the truck bed or similar surface which is docked to the loading dock, transferring some of the load from the ramp onto the truck bed.

In a third aspect is an oil reservoir for use with a hydraulic unit according to the first aspect for a dock leveler according to the second aspect provided. The oil reservoir is configured to hold the hydraulic oil necessary for operation of the hydraulic unit, and the oil reservoir is removably connectable to the hydraulic unit. Providing an oil reservoir for a hydraulic unit which can be removed from the hydraulic unit itself simplifies maintenance of the hydraulic unit. Since the old oil is removed together with the reservoir, spillage is reduced and recycling of the oil facilitated.

The oil reservoir may functions as a storage and distribution container for hydraulic oil and is reusable after replacement of used hydraulic oil. After that the used oil in the oil reservoir is taken care of, the reservoir itself may be cleaned and filled with new oil. The oil reservoir can then be sealed and the reservoir serve as a distribution and storage oil container.

The oil reservoir may be connectable to the hydraulic unit by means of a threaded connection.

In one embodiment, the oil reservoir is connectable to the hydraulic unit by means of a quick-connect or a clamp-connection.

In one embodiment, the oil reservoir comprises a portion of the suction conduit being integrated with the oil reservoir and being connectable to a suction conduit portion arranged in the hydraulic unit.

The suction conduit portion integrated with the oil reservoir may in one embodiment comprise the oil filter. The oil filter will consequently also be replaced each time the oil reservoir is changed, improving the oil quality further.

In a fourth aspect is a method for replacing the hydraulic oil of a hydraulic unit of the first aspect for a dock leveler according to the second aspect provided. The method comprises securing the dock leveler to allow maintenance to be performed, providing a new hydraulic oil reservoir and removing the old hydraulic oil reservoir from the hydraulic unit and installing the new hydraulic oil reservoir to the hydraulic unit. The method reduces the man-hours necessary for changing the oil in the hydraulic unit, improving cost efficiency of the dock leveler itself.

Embodiments of the invention are defined by the appended dependent claims and are further explained in the detailed description section as well as in the drawings.

It should be emphasized that the term“comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. All terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [element, device, component, means, step, etc]" are to be interpreted openly as referring to at least one instance of the element, device, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly state

Brief Description of the Drawings

The present invention will be described further below by way of example and with reference to the enclosed drawings. In the drawings:

Figure 1 shows a perspective view of a dock leveler according to one embodiment,

Figure 2 shows a front view of a dock leveler according to one embodiment,

Figure 3 shows a schematic drawing of a hydraulic unit according to one embodiment,

Figure 4 shows a perspective view of a dock leveler according to one embodiment,

Figure 5 shows a perspective view of a hydraulic unit according to one embodiment, and

Figure 6 shows a schematic flowchart of the method for replacing hydraulic oil in a hydraulic unit according to one embodiment.

Detailed Description of Embodiments

Embodiments of the invention will now be described with reference to the accompanying drawings. The 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 so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

The terminology used in the detailed description of the particular embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements.

Fig. 1 and Fig. 2 shows a perspective and a front view of a dock leveler 200.

The dock leveler 200 is seen with its support structure 203 mounted to a loading dock 300. The support structure 203 may be in the shape of a frame as seen in Figs 1 and 2, but may also be embodied as any form of attachment structure that can be used for securing the dock leveler 200 to the loading dock 300.

The ramp 201 is moveable in a pivoting fashion around a hinge against the support structure 203 arranged towards the rear of the dock leveler 200, in a

conventional manner. The ramp 201 needs to be able to pivot in order to accommodate and allow access into e.g. truck beds with varying heights. The ramp 201 may also be fitted with a lip 202, which is arranged distally on the ramp 201 and which may also pivot by a hinge which attaches it to the ramp 201. The lip 202 may thus in use of the dock leveler 200 be configured to be placed against the truck bed and thus transfer some of the load that is placed on the ramp 201 to the truck bed.

On the underside of the ramp 201, made visible through the ramp 201 in Fig. 1, and visible from the underside in Fig. 2, is a hydraulic unit 100 arranged. The hydraulic unit 100 powers the movement of the ramp 201, and optionally the movement of the lip 202. The hydraulic unit 100 itself is connected to a power source, such as a mains supply.

The dock leveler 200 further comprises at least one hydraulic cylinder 204, preferably one connected to each lateral side of the ramp 201. The hydraulic cylinders 201 are naturally connected to the hydraulic unit 100 which provides hydraulic oil to these in order to move the ramp 201 in a pivoting fashion. In one embodiment, a third hydraulic cylinder 205 is also provided which is attached to the lip 202 and thus allows hydraulic operation of the lip 202 as well. It is to be understood that the teachings herein are not limited to a specific number of hydraulic cylinders, but is applicable to dock levelers having any number of hydraulic cylinders. Each of the hydraulic cylinders 204, 205 may be provided with safety valves, for instance such as to limit the flow rate to/from the cylinders below a maximum allowed value. Furthermore, the hydraulic unit 100 may be provided with safety valves such as a pressure relief valve etc.

A control interface 600 may be provided which allows a user to control the motion of the ramp 201 and optionally the lip 202. Movement of the ramp 201 may also be achieved partially or fully automatically by means of various sensors (e.g. motion sensors, pressure sensors, flow sensors etc.) detecting the presence of a truck bed etc and controlling the movement of the ramp 201 accordingly.

In Fig. 3, the hydraulic unit 100 is seen without the cover that is present in Figs 1 and 2. The hydraulic unit 100 comprises an hydraulic pump 106 driven by an electric motor 102. The teachings herein are not limited to a particular type of electric motor, the skilled person would realize that any electric motor suited to the power the hydraulic pump 106 could be used.

A hydraulic oil reservoir 101 is provided for storing the hydraulic oil of the system and at least one oil conduit 108, 110 being configured to draw and/or return hydraulic oil from/to said oil reservoir 101. Preferably, oil is drawn from suction conduit 108 and returned to the reservoir through return conduit 110. The hydraulic unit 100 further comprises at least one connector 111, 112 for connecting equipment to be powered by the hydraulic unit 100. The connectors 111, 112 are controlled by means of a solenoid valve 104, and it is possible that one valve 104 is used for each connector or that one valve 104 controls several connectors 111, 112.

The hydraulic unit 100 may further comprise a manifold 103, the manifold may comprise the connector(s) 111, 112. A pump housing 105 may also be provided being attached to the manifold 103 and covering the hydraulic pump 106 and at least a portion of the oil conduits 108, 110. The oil reservoir 101 may be connected to the pump housing 105 by means of the connection 113.

When oil is drawn from the hydraulic reservoir 101 and pumped into the cylinders 204, 205, it will cause air to be drawn into the hydraulic unit 100 to replace the volume of the oil pumped out. This air should preferably be filtered to avoid particles ending up in the oil, and hence may an air filter 107 be provided.

As mentioned, the hydraulic unit 100 must function under a wide variety of conditions which include a large span of different surrounding temperatures and in dirty and dusty environments. Consequently, the hydraulic oil needs to be replaced relatively often to ensure that the oil in the hydraulic unit 100 meets the requirements for assuring the safety of the system. If oil replacement is overlooked for a long time, it may result in that safety valves does not functions as intended or that the pump output differs from the intended pump output. Replacing the oil in prior art hydraulic units 100 is a time consuming and laboursome task. The oil must be drained from the hydraulic reservoir with the reservoir still in place and the oil must be collected in some sort of container to discard or recycle it. It is also difficult to remove all the old oil from the system without removing the entire hydraulic unit 100 from the dock level er 200. The complexity of the oil replacement procedure, which needs to be performed approximately every other year or sometimes more often, could in itself be a risk as it is possible that it may cause some users extend the oil replacement intervals beyond the recommended limits.

A further problem with prior art solutions is that oil spillage is common, causing unnecessary contamination to the surroundings.

It is therefore desired to facilitate oil replacement, not only to improve the safety of the system by providing simpler and more cost effective maintenance of the hydraulic unit 100, but also to make it easier to recycle the used oil and to reduce spillage.

For achieving this, the oil reservoir 101 is made as a separate part which is removable from the remainder of the hydraulic unit 100. The oil reservoir 101 should preferably have a volume sufficiently large such that it may hold all the oil necessary for operation of the system, and volume will hence vary depending on the number of cylinders etc. Preferably, the oil reservoir 101 is made out of high density polyethylene (HDPE), but also other materials are considered such as aluminum or other polymeric materials. A wall thickness of a HDPE oil reservoir 101 may be in the range of 1.5 to 5 mm, preferably approximately 3 mm. Other wall thicknesses are also possible and falls within the scope of the present disclosure. The oil reservoir 101 should be able to withstand temperatures of at least 80° C.

By providing an oil reservoir 101 that is easily removable from the hydraulic unit 100, the oil replacement is greatly facilitated. The dock level er 200 is simply placed and secured in a servicing position, i.e. one where as much oil as possible is pumped into the oil reservoir 101 and one where maintenance can be performed safely. The oil reservoir 101 is then removed, preferably be means of unscrewing it from a preferably threaded connection 113, from the hydraulic unit 100. A new oil reservoir 101 is provided, containing the correct amount and characteristics of hydraulic oil for the intended dock level er 200, and is simply attached to the hydraulic unit 100 which is then ready to be activated again.

The old oil reservoir may be sealed with a cap that was provided with the new oil reservoir and which was removed to mount the new oil reservoir on the hydraulic unit 100. The old reservoir along with the used oil stored therein may then be sent for recycling of the oil while the oil reservoir 100 itself may be reused or recycled in case it has been damaged etc. The hydraulic oil suction conduit 108 is at its end preferably provided with an oil filter 109, which filters the oil before it arrives at the pump 106 and is further delivered to the hydraulic cylinders 204, 205. The suction conduit 108 preferably extends such that its end where it draws hydraulic oil, and where the filter 109 is preferably placed, is arranged near the bottom of the oil reservoir 101 as shown in Fig.

3. The filter 109 does not necessarily have to be arranged at the end of the suction conduit 101, it may just as well be arranged at another position along the conduit 108. The oil filter 109 and the opening in the oil reservoir 101, which forms part of the connection 113 to the hydraulic unit 100, should be configured such that the filter 109 can pass through the opening of the oil reservoir 101.

In one embodiment, the suction conduit 108 is formed in two parts, where one part is integrated with the oil reservoir 101 and the other part only extends from the pump 106 to the connection 113. The two parts of the suction conduit 108 are then connectable to each other when the oil reservoir 101 is attached to the hydraulic unit 100. In one embodiment, also the oil filter 109 is integrated on the suction conduit 108 portion in the oil reservoir 101. Correspondingly, the return conduit 110 may also be connectable to the oil reservoir in a similar fashion when the oil reservoir 101 is connected to the hydraulic unit 100.

Figure 4 and 5 depicts a dock lever and hydraulic unit according to an embodiment. According to said embodiment, the hydraulic unit 100 may extend in a longitudinal direction. Thus, a proximal end of the hydraulic unit 100 is adjacent to the dock leveler 200, i.e. the ramp 201. A distal end of the hydraulic unit 100 is distant from the dock leveler 200, i.e. the ramp 201.

In one embodiment, the oil reservoir 101 may be arranged at the distal end of the hydraulic unit 100. This allows for easier removal and replacement of the oil reservoir since the oil reservoir is more accessible. The longitudinal direction may be a vertical direction. The distal end may be a bottom end of the hydraulic unit 100. Thus, the oil reservoir 101 may constitute a bottom end of the hydraulic unit 100. Thereby, the risk for spillage is substantially reduced since the oil reservoir may be removed in a vertical direction without risk for the content of said oil reservoir spilling out. Hence, the connector 111, 112 may be adapted to receive the oil reservoir 101 in a vertical direction.

In one embodiment, the hydraulic unit 100 may be mounted to the dock leveler 200, i.e. the ramp 201, by means of a mounting bracket 117. The mounting bracket 117 may be fix to the ramp 201 and to the hydraulic unit 100. In one embodiment, the mounting bracket 117 is further fix to the manifold 103.

Turning to Fig. 6 showing an schematic outline of a method 1000 for replacing the hydraulic oil of a hydraulic unit 100 in a dock level er 200. The method comprises securing 1001 the dock leveler 200 to allow maintenance to be performed. This may include placing the ramp 201 in a position where as much oil as possible is returned to the oil reservoir 101. It may also include securing the ramp 201 such that it cannot be moved unintentionally during the maintenance work.

The method further comprises providing 1002 a new hydraulic oil reservoir 101. The new hydraulic oil reservoir 101 comprises the new oil, having the correct specification and properties necessary for the dock leveler 200 at hand.

The old hydraulic oil reservoir 101 is removed 1003 from the hydraulic unit 100, preferably be simply unscrewing it from the connection 113. The connection 113 may however also be formed by a clamp connection or other types of quick connectors.

The new hydraulic oil reservoir 101 preferably comes with a cap over the opening in the reservoir 101 that is to form part of the connection 113, the cap can be reused to seal the old oil reservoir 101 that is removed from the hydraulic unit 100. After the old oil reservoir 101 is removed, the new oil reservoir 101 can be attached or installed 1004 to the hydraulic unit 100. The hydraulic unit 100 is then ready to be activated, tested and be put back into use.

Thus, the new hydraulic oil reservoir 101 may be provided with the cap. The method may further comprise removing the cap from the new hydraulic oil reservoir 101 and securing said cap to the old hydraulic oil reservoir 101 after removing 1003 said old hydraulic oil reservoir 101 from the hydraulic unit 100.

It should be mentioned that the inventive concept is by no means limited to the embodiments described herein, and several modifications are feasible without departing from the scope of the appended claims. In the claims, the term“comprises/comprising” does not exclude the presence of other elements or steps. Additionally, although individual features may be included in different claims, these may possibly

advantageously be combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. In addition, singular references do not exclude a plurality. The terms“a”,“an”,“first”,“second” etc do not preclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.

Claims

1. A hydraulic unit (100) for a dock leveler (200), wherein said hydraulic unit (100) comprises:

- an hydraulic pump (106) driven by an electric motor (102),

- a hydraulic oil reservoir (101),

- at least one oil conduit (108, 110) being configured to draw and/or return hydraulic oil from/to said oil reservoir (101),

- at least one connector (111, 112) each controlled by at least one valve (104) for connecting equipment to be powered by said hydraulic unit (100),

characterized in that the oil reservoir (101) is removably connected to the hydraulic unit (100).

2. Hydraulic unit (100) according to claim 1, wherein the oil reservoir (101) is connected to the hydraulic unit (100) by means of a threaded connection.

3. Hydraulic unit (100) according to claim 1, wherein the oil reservoir (101) is connected to the hydraulic unit (100) by means of a quick-connect or a clamp- connection.

4. Hydraulic unit (100) according to any one of the preceding claims, wherein the suction oil conduit (108) comprises a filter (109) being arranged near the bottom of the of the oil reservoir (101) when the oil reservoir (101) is connected to the hydraulic unit (100).

5. Hydraulic unit (100) according to any one of the preceding claims, wherein the electric motor (102) is connected to a manifold (103), said manifold (103) comprising the at least one connector (111, 112), wherein a pump housing (105) is attached to the manifold (103) covering the hydraulic pump (106), and wherein the oil reservoir (101) is connected to the pump housing (105).

6. A hydraulically operated dock leveler (1), wherein said dock leveler (1) comprises:

- a support structure (203) for attachment to a loading dock (300), - a moveable ramp (201) being pivotable in relation to the support structure

(203),

- at least one hydraulic cylinder (204, 205) for controlling the movement of the dock leveler (1), and

- a hydraulic unit according to claim 1 being connected to the at least one hydraulic cylinder (204, 205) for powering the movements of the dock leveler (1).

7. Dock leveler (1) according to claim 6, wherein one hydraulic cylinder (204) is arranged on either lateral side of the ramp (201) for achieving movement of said ramp (201), and wherein each hydraulic cylinder is connected to the hydraulic unit (100).

8. Dock leveler (1) according to claim 6 or 7, wherein the dock leveler (1) comprises lip (202) arranged distally on the ramp (201) and being pivotable in relation to said ramp (201), and wherein the movement of said lip (202) is powered by a hydraulic cylinder (205) connected to the hydraulic unit (100).

9. Hydraulic oil reservoir (101) for use with a hydraulic unit (100) according to claim 1 for a dock leveler (200) according to claim 6, said oil reservoir (101) being configured to hold the hydraulic oil necessary for operation of the hydraulic unit (100), wherein said oil reservoir (101) is removably connectable to the hydraulic unit (100).

10. Hydraulic oil reservoir (101) according to claim 9, wherein the oil reservoir (101) functions as a storage and distribution container for hydraulic oil and is reusable after replacement of used hydraulic oil.

11. Hydraulic oil reservoir (101) according to claim 9 or 10, wherein the oil reservoir (101) is connectable to the hydraulic unit (100) by means of a threaded connection. 12. Hydraulic oil reservoir (101) according to claim 9 or 10, wherein the oil reservoir (101) is connectable to the hydraulic unit (100) by means of a quick-connect or a clamp-connection.

13. Hydraulic oil reservoir (101) according to any of claims 9 to 12, further comprising a portion of the suction conduit (108) being integrated with the oil reservoir (101) and being connectable to a suction conduit (108) portion arranged in the hydraulic unit (100).

14. Hydraulic oil reservoir (101) according to claim 13, wherein the suction conduit portion (108) integrated with the oil reservoir (101) comprises the oil filter

(109).

15. A method (1000) for replacing the hydraulic oil of a hydraulic unit (100) according to claim 1 for a dock leveler (200) according to claim 6, said method comprising:

- securing (1001) the dock leveler (200) to allow maintenance to be performed,

- providing (1002) a new hydraulic oil reservoir (101),

- removing (1003) the old hydraulic oil reservoir (101) from the hydraulic unit (100) and

- installing (1004) the new hydraulic oil reservoir (101) to the hydraulic unit

(100).

16. Method (1000) according to claim 15, wherein the new hydraulic oil reservoir (101) is provided with a cap, said method further comprising removing the cap from the new hydraulic oil reservoir (101) and securing said cap to the old hydraulic oil reservoir (101) after removing (1003) said old hydraulic oil reservoir (101) from the hydraulic unit (100).