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This study was made for Dellner Couplers and is regarding a development of their electrical coupler cover (ECC).

The electrical coupler includes several electrical contacts where the current flows, which lets electrical signals to be transported between all carriages in a train when the electrical couplers are connected to each other. An electrical coupler that is not connected to another one will have an ECC that automatically folds down in in front of the coupler to protect the electrical contacts from dust, water, and damage. The current ECC Dellner Couplers have today is made from an extruded aluminium profile, which has desirable properties in all aspects, except that it’s conductive.

If the ECC encounter the electrical contacts, which can happen during a collision between the train and an animal, the contact between them could cause short circuit since the electricity is always running and can’t be turned off. The development of the ECC is aimed to remove the occurrence of short circuit in case of collision with an animal, but still fulfil the mechanical requirements.

The method used to find a solution was based around well know concept development methods involving problem identification, identifying customer needs to create a target specification on what the ECC must fulfil, search for external and internal ideas for solving similar problems, performing concept screening on several concept ideas, and implement a finite element analysis (FEA) on the final concepts to see which one has the best potential for success. A part of the focus in the method has also been around material exchange by searching for potential materials in a material database.

The results imply that adding thickness to the extruded aluminium profile could be a promising concept, which was discovered in the concept screening and FEA. The FEA of the concept shows lower displacement of the ECC and a decrease of stress level of about 57% compared to the original when being exposed to 10kN, and the result in displacement is ¼ of the original concept when being exposed to 100kN.

The conclusion of this work is that a significant improvement can be made by adding thickness to the cross-section, but it is limited by the strength of the screws and the attachment. The ECC can handle up to 100kN before it will reach the electrical contacts, but the screws can only endure up to 53kN before they rupture. The screws and the attachment are the ones limiting what the electrical coupler can handle, but if the real force of an impact is below 53kN, this solution could be seen as acceptable in terms of the strength.

The concept also involves a significant addition of weight and space required. The weight (+2,4kg) needs to be examined so it doesn’t affect other parts of the coupler negatively, and evaluation needs to be done to find out if the space required (+12mm at the center of the ECC) is available and that the meeting electrical couplers won’t collide in each other when connecting.

A suggestion is to focus on the avoidance of short circuit, rather than the avoidance of reaching the electrical contacts. A more potential solution could potentially be found in a protective coating, which will allow the ECC to deform and not exhaust the screws and the attachment as much. The thicker and stronger geometry of the ECC will set higher requirements for the screws and the attachment.