WO2017039461A1

WO2017039461A1 - A container weighing system

Info

Publication number: WO2017039461A1
Application number: PCT/NZ2016/050138
Authority: WO
Inventors: Gregory John FAHEY; Mark James Fahey
Original assignee: Bison Group Limited
Priority date: 2015-09-04
Filing date: 2016-09-01
Publication date: 2017-03-09

Abstract

A container weighing method uses fixed weighing legs configured to support shipping container that is in position on a vehicle platform. The vehicle platform is lowered to place the container weight entirely on the weighing legs. Each weighing leg includes a weighing mechanism, such as a load cell, to measure the load exerted by the container.

Description

A CONTAINER WEIGHING SYSTEM

FIELD OF THE INVENTION

The invention relates to a method and apparatus for weighing shipping containers which are situated on truck-trailers.

BACKGROUND TO THE INVENTION

Shipping containers are widely used for transport of goods. Containers are stacked on large freight ships and may also be transported by train or truck. These containers are substantially standardised, although there can be variations depending on the manufacturer and various sizes of container are used. For example, 20 foot containers are around 20 feet long by 8 feet wide by 8 feet six inches high while 40 foot containers are around 40 feet long by 8 feet wide by 8 feet six inches high. There are also so- called "high-cube" containers that are 40 feet long by 8 feet wide by 9 feet six inches high or 45 feet long by 8 feet wide by 9 feet six inches high.

These containers have empty weights from 2200kg to 4800kg and maximum gross weights (including the container itself) of around 30,000kg. The convenience and efficiency provided by the use of ISO standardised containers for freight handling has led to their ubiquitous use throughout the world, on ocean, rivers, railroad and road. Their homogeneity however disguises one very important physical property; the mass of the container. The external appearance gives no indication whether the container is filled with a cargo of granite, or is in fact empty. The container's weight can only be determined by weighing, which can be a challenging exercise without dedicated and often expensive equipment.

This uncertainty around container weights creates hazards for the container freight industry. In the past this has led to containers being lost overboard, stacks of containers collapsing, damage to cranes, equipment and trailer chassis, damage to roads, and most catastrophically, injury and loss of life. In January 2007, the containership MSC Napoli suffered a structural failure and broke up off the coast of the UK, becoming the second most expensive maritime disaster in history. A sample of 660 containers salvaged from the deck found 20% were more than 3 tonnes different from their declared weights. The largest difference was 20 tonnes. As a consequence of this incident and others, the International Maritime Organisation (IMO) issued new regulations requiring the weights of all shipping containers to be verified with calibrated and certified equipment prior to loading onto vessels. To satisfy the requirements of ports, the verified weight information is required in advance of preparation of the vessel's stowage plan. Such requirements to declare container weights are not new to road transport authorities and freight operators. Freight operators often try maximise their payloads to gain efficiency, however over-loaded trucks are notoriously destructive of roads, as well as a major safety hazard to other road users. Road transport regulations are commonly based on maximum gross vehicle weight and axle loading distribution, and penalties for breaches of compliance are standard practise in many jurisdictions. In order to check compliance, trucks are often weighed by driving the truck over a ground- imbedded weighbridge or portable axle-weighing pads. Due to unavailability of weighbridges or congestion at public facilities, some operators prefer to fit their trucks with on-board weighing systems. One commonly used system, for example, determines the weight of the payload from measurement of air pressure or spring deflection in the truck and trailer's suspension system (US 20070181350 A1 ). Adding the vehicle's tare weight to the payload weight from a suspension-based weighing system provides the gross vehicle weight and axle loadings. There are however some subtle differences between the new IMO regulations and what has become standard practice for road transport freight operators. One very simple challenge, for example is to determine the weight of two 20 foot containers on a single trailer, which is a very common configuration. The IMO regulations require the weight of each container to be verified separately; i.e. an aggregate of the two containers' weight is not acceptable. Neither weighbridges nor suspension-based onboard weighing systems are able to resolve the weight of each container. While these weighing methods can provide the gross vehicle weight, determining from this the weight of even a single container on a trailer requires the tare weight of the vehicle to be known, and this may not be constant. For example there may be variations in tare weight due to the amount of fuel the truck is carrying, whether the weight of the driver, spare tyres, tyre irons, chains and other equipment is included or not.

To satisfy the accompanying legal responsibilities, the IMO regulations require the use of calibrated and certified equipment for the container weight verification measurement. Most weighing equipment can be calibrated to some degree of accuracy, but certification requires more rigour. Even the least precise accuracy class of the international metrology bodies OIML and NTEP requires 100 divisions of the measurement scale, implying an accuracy of ±0.5%. Suspension-based on-board weighing systems typically have an accuracy of around ±3%. Such systems are not commonly certified as fit for trading, contractual or legal purposes. A further disadvantage of suspension-based on-board weighing systems is that the suspensions of both the truck and semi-trailer units must be equipped with the weight measurement devices, and must be calibrated together. As a consequence the semitrailer and truck are not independent. If another truck is used to tow the trailer which is not equipped and calibrated with a compatible device, then payload weight information cannot be obtained.

Another form of on-board weighing system uses load cells to directly measure the weight of the container on the trailer (US70091 18 B2). It is necessary that the full weight of the container be carried by the load cell in order to accurately measure the container's weight. In some configurations these load cells are integrated with the twist-locks, which connect to the corners of the container. In doing so, the weight of the container cannot be allowed to bear on the trailer's chassis beams, which is the most structurally efficient method. The load cells and the structural elements connecting the twist-locks to the chassis beams load are subject to the full static load of the container, plus high dynamic loads from loading and transit, which make the weigh system and trailer itself prone to damage.

On-board weighing systems that employ a lifting mechanism as part of their design have been proposed (US3545558, US5635680 and US5369222) allowing the weighing instrument to be isolated from load while retracted. These systems avoid the issues caused by impact and dynamic loads, however they are relatively expensive and require a custom trailer dedicated to the task of weighing.

Yet another potential method for weighing containers is shown in AT373849B. This invention is a system primarily for lifting and lowering containers, consisting of hydraulic legs attached to the container. The legs may contain load cells and weigh the container during this operation. This system requires legs performing a lifting function, which adds significant cost, weight and complexity to the apparatus. Other conventional means of weighing containers involve sensors in the spreaders of cranes and other container handling equipment. While this weighing apparatus can be efficient and accurate, such high capacity equipment is inherently heavy and expensive, and as a result is not always available at the location where containers need to be weighed.

For a logistically convenient design, it would be desirable to have a simple, accurate, weighing system that provides a means to weigh shipping containers while in situ on a trailer-chassis. The design should ideally work with existing trailers. It should be mobile and portable, light-weight, fast to use, and easily handled by a single person. It should allow the weight of individual containers to be measured, and should provide a high level of accuracy. The present invention provides the benefit that no lifting apparatus is necessary to perform the weighing operation, and the weight of the container can be determined in any location, independent of a weighbridge or expensive lift equipment. This may enhance efficiencies by avoiding diversion of the truck and container to a weighbridge and can improve safety because the weight of the container can be established before transport operations commence. The system could also be used to determine the gross vehicle weight and the axle load distribution.

It is an object of the invention to provide an improved container weighing system, which addresses at least some of the various limitations of existing container weighing equipment cited above, or at least to provide the public with a useful choice.

SUMMARY OF THE INVENTION

According to one aspect there is provided a container weighing method, including the steps of:

a. attaching upper ends of a plurality of weighing legs to a container whilst it is supported by a vehicle platform;

b. lowering the vehicle platform until the full weight of the container is carried by the legs; and

c. weighing the container based on the force exerted upon the legs.

According to a further aspect there is provided a static weighing leg, including:

a. an upper end, configured to attach to a container whilst the container is supported by a vehicle platform;

b. a lower end, configured to support the leg on a ground surface; and c. a load cell configured to pass the load applied to the upper end of the leg; There is further provided a container weighing system, including:

a. a plurality of static weighing legs including:

. upper ends, configured to attach to a container;

i. lower ends, configured to support the legs on a ground surface; and iii. load cells configured to pass the load applied to upper ends of the legs; and

b. a controller configured to determine one or more weight properties of the container based on the force exerted on the legs. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a single 40 foot shipping container on a trailer;

Figure 2 shows two 20 foot shipping container on a trailer;

Figure 3 shows a single 20 foot shipping container on a trailer;

Figure 4 shows a weighing leg detached from the container;

Figure 5 shows a single 20 foot shipping container on a trailer with weighing legs attached;

Figure 6 shows a single 20 foot shipping container on a trailer with weighing legs attached and the trailer lowered;

Figure 7 shows a weighing leg supporting the container while the trailer is

lowered;

Figure 8 shows detail of a weighing leg;

Figure 9 shows an alternative embodiment of the weighing leg with an

integrated load cell and foot plate; and

Figure 10 shows a diagram of the weighing data communication. DETAILED DESCRIPTION

Below is described an exemplary weighing system for providing a simple and accurate means of weighing shipping containers situated on an adjustable-height truck and trailer.

Typical configurations of a shipping container in road transport mode are shown on truck and trailer 1 in Figure 1 to Figure 3. Shipping containers with lengths of 40 foot (container 2) and 20 foot (container 3) are commonly transported on road trailers. The present invention provides a means of weighing individual containers and is independent of the transport configuration. The weighing system is lightweight, portable, inexpensive (relative to existing container lifting and weighing equipment) and sufficiently accurate to allow it to be certified for legal purposes such as container weight declarations.

The weighing operation is performed by attaching upper end 4 of the weighing leg 5 to the container's lower corner castings 6, as shown in Figure 4. The lower end 7 of the weighing leg reaches to the ground. Figure 5 shows an embodiment with four weighing legs 5 attached to the container. The truck and trailer 1 are lowered by removing the air from the air suspension systems of the truck and trailer until the full weight of the container (container 3 is carried by the weighing legs 5 as shown in Figure 6 and Figure 7. The load carried by each leg passes through a load cell 8 which produces a calibrated electrical output signal that is proportional to the magnitude of the load, and allows the load to be determined. The total weight of the container (container 3 is determined by adding together the loads carried by each individual weighing leg 5. After the weighing operation is complete, the truck and trailer 1 are raised by re-filling the air suspension until the weight of the container is again carried by the trailer. The weighing legs 5 can then be detached from the container. The weighing leg itself consists of an upper end 4 which attaches to the container by means of the twist-lock feature 9. The twist-lock pockets 12 are standard on the corner castings of ISO shipping containers. The twist-lock feature engages with the correspondingly shaped pocket on the corner casting, and is rotated 90 degrees to lock. The rotation of the twist-lock fitting 9 is effected by rotating handle 10. In some embodiments the connection may be tightened after rotation of the twist-lock fitting 9 by a suitable screw thread or other tightening mechanism. The twist-lock feature may include a means 1 1 to limit the rotation of the twist-lock, providing end-stops at 0 degrees and 90 degrees that align the twist-lock feature with the locked and unlocked positions.

It is preferable that the attachment of the upper leg 4 to the container (container 3 prevents rotation of the weighing leg relative to the container. This provides stability when the container is standing on the weighing legs 5. By creating this moment constraint at the upper leg 4 it allows the lower leg 7 to meet the load cell 8 or the ground at a single point, which is convenient for weight measurement purposes. The moment constraint at the attachment of the upper leg 4 is achieved with features 13 that engage around the edges of the container, adjacent to the corner casting. If no rotational constraint were provided at the attachment to the container, stability would need to be provided by a moment constraint at the lower end of the leg, for example with a wide base, to prevent the legs and container from collapsing when the support of the trailer is removed. Although suitably stable, this alternative design complicates the design of the weighing function.

The length of the weighing legs can be adjusted to accommodate the different heights of trailers. The upper portion 14 and lower portions 15 of the leg engage telescopically with each other, and the length of the weighing leg is set by a locking pin mechanism 16. Once set to length, the weighing legs' lengths remain static throughout the weighing operation. It will be appreciated that a range of other adjustment mechanisms may be employed such as complementary screw threads.

The locking pin mechanism 16 may be constructed with pin holes just in the upper portion of the leg. This allows the lower portion 15 of the weighing leg to slide freely when extending the leg length, but the travel when retracting the leg length is limited by the position of the locking pin mechanism 16. An advantage of this design is that once the upper end 4 of the leg is attached to the container, the lower portion 15 of the weighing leg will reach the ground, thereby indicating the location where a separable foot 17 containing the load cell should be positioned. Yet another advantage is that only the weight of the upper portion 14 needs to be lifted by the operator when attaching to the container (container 3 because the weight of the lower portion 15 rests on the ground. The locking pin mechanism 16 may use two holes to control its orientation. Fitting the pins is aided by having one pin slightly longer than the other. The shorter pin is still long enough that it can engage sufficiently to carry the load, should it be used in the lower hole.

A disadvantage of the locking pin mechanism 16 described here is that during handling it may unintentionally slide and pinch or injure the operator's hand. To avoid this injury hazard, a damper may be fitted inside the leg between the moving upper 14 and lower 15 portions. The damper would prevent the upper portion 14 dropping freely and reduce the risk of injury. The damper may be a self-contained gas-spring system which assists the operator when lifting the upper portion 14 during attachment.

A further disadvantage of the locking pin mechanism 16 is that some travel is required between the upper 14 and lower 15 portions of the weighing leg 5 before the locking pin mechanism 16 and the weighing leg 5 begins to carry load. Alternatively a thread- style locking mechanism may be employed, which provides continuous adjustment.

The load from the weighing leg 5 needs to be distributed over the ground with the aid of a foot plate 18, to avoid the weighing leg 5 sinking into the ground. The load cell 8 is situated in the load path between the attachment point at the upper end of the leg 4 and the foot plate 18 at the lower end 7 of the weighing leg. For accurate weighing it is critical that the full load passes through the load cell and that no load, even frictional, can by-pass the load cell. Ideally the foot plate 18 is rotationally free relative to the weighing leg 5, for example with a ball joint, allowing it to adapt to the angle of the ground. The leg of Figure 8 is lighter to handle because its weight is divided into several components. Yet another advantage is that the separable weighing device is more convenient for calibration purposes. However the one-piece, integrated version shown in Figure 9 may be preferable in some circumstances. With regards to its own weight, the weighing leg 5 may be made lighter by constructing it from materials with a high strength to weight ratio, for example a carbon fibre reinforced plastic composite material.

Ease of handling may be supplemented with the placement of handles on the weighing leg in ergonomically appropriate positions. Each weighing leg contains electronics 19 which measure the output of the leg's load cell and determine the magnitude of the load. The electronics 19 and load cell 8 can be calibrated by applying a known reference load, and adjusting the calibration settings in the electronics 19 so that the same reading is produced. The electronics transmit the weight reading from each leg to a controller 20, shown in Figure 1 0. The data transmission may be wireless. The controller 20 sums together the weight readings from each leg to determine and display the total weight of the container. When calculating the sum, the net weight of the legs must be deducted, because the legs themselves are also weighed by the load cells.

The controller 20 may take the form of a dedicated electronic enclosure, or be a generic device like a smart-phone. The controller 20 may gather additional information associated with the container weight data including one or more of: time, date, location, container ID, container seal number, cargo information, shipping information, name of shipper, and image data.

The controller 20 may also determine the weight distribution from the loads of the individual weighing legs. This is achieved by comparing the ratio of loads from pairs of weighing legs (e.g. front to back, and side to side). By knowing the weight distribution and the dimensions of the container, the position of the centre of mass can be determined from front to back and side to side (i.e. in the horizontal plane). The vertical position of the centre of mass cannot be determined. Container packing guidelines recommend that the centre of mass of the container be no more than ±5% from the centre of volume of the container.

The controller may include a means to verify the integrity of the data, for example by checksums or other algorithms, to verify the data has not been tampered with, or otherwise maintain the integrity of the data. The information acquired be the controller 20 may be stored in a local database, or transferred to an internet cloud database 21 for storage, further processing and dissemination.

This invention provides a novel solution for weighing containers that are situated on an adjustable-height truck and trailer. It is logistically convenient and allows a high level of accuracy to be achieved because the tare weights of the truck and trailer do not have to be accounted for. An enormous advantage is that no additional lifting equipment is required to perform the weighing, meaning that the weighing legs are a simple static construction. Without the need for the capability to lift the container during the weighing operation, the weighing legs are light enough (in the order of 20 kg) to be handled by a single person. If the legs were to have lifting capability sufficient to lift a fully loaded shipping container, it would be impossible for a single person to carry them. Furthermore, the cost of the weighing leg without lifting functionality is many times less, as is the complexity.

As a result of these benefits, the weighing legs are mobile and portable, light-weight, and fast to use. The container can be weighed in any location, independent of a weighbridge or other expensive handling equipment. This may enhance efficiencies by avoiding diversion of the truck and container to a weighbridge and can improve safety because the weight of the container can be established before transport operations commence.

While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of the Applicant's general inventive concept.

Claims

I . A container weighing method, including the steps of:

c. weighing the container based on the force exerted upon the legs.

2. A method as claimed in claim 1 wherein the container is a shipping container.

3. A method as claimed in any one of the preceding claims wherein an air suspension system of the vehicle platform is used to lower the container.

4. A method as claimed in any of the preceding claims wherein the vehicle platform is raised following weighing of the container to support the container.

5. A method as claimed in any of the preceding claims wherein the upper ends of the legs are configured to prevent rotation of the legs relative to the container.

6. A method as claimed in any of the preceding claims wherein leg length is adjustable and set by a locking mechanism.

7. A method as claimed in any of the preceding claims wherein leg length is telescopically adjustable.

8. A method as claimed in any of the preceding claims wherein lower ends of the plurality of legs are configured to stand the legs on a ground surface.

9. A method as claimed in claim 8 wherein the lower ends of the legs include feet for distributing the load carried by the legs onto the ground.

10. A method as claimed in claim 9 wherein the feet swivel on ball-joints to adapt to the angle of the ground.

I I . A method as claimed in any of the preceding claims wherein the legs are supported on weighing devices.

12. A method as claimed in any of the preceding claims wherein the legs include load cells configured to measure the load applied to the upper ends of the legs by the weight of the container.

13. A method as claimed in claim 12 wherein the load cells are located near lower ends of the legs.

14. A method as claimed in any preceding claim including a controller configured to determine one or more weight properties of the container.

15. A method as claimed in claim 14 wherein the controller calculates the total load carried by all legs.

16. A method as claimed in claim 14 or claim 15 wherein the weight properties include one or more of: weight sensed by the individual weighing devices, total container weight, weight distribution, and centre of mass.

17. A method as claimed in any one of claims 14 to 16 wherein the controller is configured to associate container weight data with one or more of: time, date, location, container ID, container seal number, cargo information, shipping information, name of shipper, and image data.

18. A method as claimed in any one of claims 14 to 17 wherein the controller is configured to transmit gathered data to a remote computer, database or cloud storage.

19. A method as claimed in any one of claims 14 to 18 wherein the controller is configured to implement a verification process in order to verify that weight data has been properly obtained without tampering.

20. A method as claimed in any one of the preceding claims including sensors for indicating whether the load cell measurement axis is vertical.

21 . A method as claimed in any one of the preceding claims wherein the upper ends of the legs attach to corner castings of the container.

22. A method as claimed in claim 21 wherein the upper ends of the legs twist-lock to corner castings of the container.

23. A method as claimed in claim 21 or claim 22 wherein the upper ends of the legs include features that engage with the corners of the container to provide moment constraint.

24. A static weighing leg, including:

b. a lower end, configured to support the leg on a ground surface; and c. a load cell configured to pass the load applied to the upper end of the leg.

25. A weighing leg as claimed in a claim 24 wherein the upper end of the leg is configured to prevent rotation of the leg relative to the container.

26. A weighing leg as claimed in any of claims 24 to 25 wherein leg length is adjustable.

27. A weighing leg as claimed in any of claims 24 to 26 wherein leg length is set by a locking mechanism.

28. A weighing leg as claimed in any of claims 24 to 27 wherein leg length is telescopically adjustable.

29. A weighing leg as claimed in any of claims 24 to 28 wherein the lower end of the leg includes a foot for distributing the load carried by the leg onto the ground.

30. A weighing leg as claimed in claim 29 wherein the foot swivels on a ball-joint to adapt to the angle of the ground.

31 . A weighing leg as claimed in claim 30 wherein the load cell is located near the lower end of the leg.

32. A weighing leg as claimed in any one of claims 24 to 31 wherein the upper end of the leg is configured to attach to a corner of the container.

33. A weighing leg as claimed in claim 32 wherein the upper end of the leg twist-locks to the corner casting.

34. A weighing leg as claimed in claim 32 or claim 33 wherein the upper end of the leg includes features that engage with a corner of the container to provide moment constraint.

35. A container weighing system, including :

a. a plurality of static weighing legs including:

i. upper ends, configured to attach to a container;

ii. lower ends, configured to support the legs on a ground surface; and iii. load cells configured to pass the load applied to upper ends of the legs; and

b. a controller configured to determine one or more weight properties of the container based on the force exerted on the legs.

36. A system as claimed in claim 35 wherein the controller calculates the total load carried by all legs based on the sum of forces applied to the load cells.

37. A system as claimed in claim 35 or claim 36 wherein weight distribution is determined by comparing the load applied to pairs of cells.

38. A system as claimed in claim 37 wherein the centre of mass is calculated by the controller based on the weight distribution and the dimensions of the container.

39. A system as claimed in any one of claims 35 to 38 wherein the controller includes a database configured to associate container weight data with one or more of: time, date, location, container ID, container seal number, cargo information, shipping information, name of shipper, and image data.

40. A system as claimed in any one of claims 35 to 39 wherein the controller includes a communication device to transmit gathered data to a remote computer, database or cloud storage.

41 . A system as claimed in any one of claims 35 to 40 wherein the controller includes a verification module to implement a verification process in order to verify that weight data has been properly obtained without tampering.

42. A system as claimed in any one of claims 35 to 41 including sensors for indicating whether the load cell measurement axis is vertical.