Project Description

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Perfect function of a gas spring – despite the extremely difficult installation position

A life without a cup of coffee is hardly imaginable for most of us. Coffee, water, coffee machine on and shortly afterwards the coffee is ready. Behind this, however, there are highly complex manufacturing processes and machines. One of them is the ‘ground coffee compressor’. Freshly ground coffee has a relatively large volume and must therefore be compacted before packaging.

Just as many other machines, the ground coffee compressor also has a maintenance flap. And this flap had to meet the following requirements:

  • It must remain in closed even after the locking device has been released.
  • It should be very easy to open.
  • It must stay reliably open at an angle of approx. 100°.
  • When closing, the gas spring must hold the flap until shortly before the closed position.

Implementing these requirements became more difficult due to the fact that the gas spring could only be installed on top of the flap (outside the compressor) and the pivoting point was far outside the flap. Thus, it was necessary to calculate the mounting position with absolute accuracy and to design the gas spring accordingly. Even a 5 mm displacement of the installation points would have led to malfunction. The technical know-how of the DICTATOR employee was put to test!

Other aspects to consider when determining the type of gas spring:

  • Direct use in food processing: Hence the AISI 304 version and the use of bio-oil with H1 approval. Each gas spring contains a small amount of oil to lubricate the seal and to achieve damping, in this case, when the piston rod extends, i.e. when the flap is opened.
  • Since the gas spring cannot be installed with the piston rod pointing downwards (important for lubricating the seal at the front of the cylinder), it had to be equipped with an oil chamber so that the seal never runs dry.

DICTATOR provided the customer with an exact calculation of the gas spring and its installation position. Since the customer had used a 3D program to design the flap, DICTATOR also provided him with a STEP file of the calculated gas spring, which he could then integrate directly into his design. This allowed the perfect function to be tested in advance on the 3D model.

As for many other areas, the gas spring for such ground coffee compressors are manufactured – in addition to the standard models – for customer-specific projects, even as single units. That’s why DICTATOR was the ideal partner for the company Bauermeister. Even if only one gas spring is required, as in this case, it was a given for DICTATOR to support the customer from the enquiry to the successful completion of the project – and, of course, to manufacture the gas spring as a single unit with the exact required specifications – despite the high effort needed for its calculation.

Maintenance flap with gas springs - 3D drawing, closedMaintenance flap with gas springs - 3D drawing, open

Already in the 3D simulation, the perfect interaction of gas spring and maintenance flap could be checked. For the customer, the fact that DICTATOR provided the gas spring exactly in the required dimensions and with the intended fastenings as a STEP file was time-saving and highly valuable.

Maintenance flap with gas springs - closed

The maintenance flap remains in the closed position even when the locks are released. The gas spring is designed to be neutral in this position.

Maintenance flap with gas springs - half open

First, the flap is opened slightly by hand. Then, the gas spring takes over the opening process all while damping the movement until the open position is reached. This protects the flap and fittings and prevents uncontrolled knocking open.

Maintenance flap with gas springs - open

At an opening angle of approx. 100°, the flap comes to a standstill and remains securely open in this position until it is manually pushed close with a previously calculated force without difficulty until just before the closed position is reached. It is important that the flap only closes the last millimetres by itself, otherwise it may present a hazard for goods and people. This shows how importance a very precise calculation is.

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