Pavement Spring

Aid in the prescription and installation of floor springs.

The floor spring, like its older sister, the air spring, is today a complex mechanism, designed to return the force that is exerted on a coil spring lodged in its body when we open a door by rotating the axis that serves as its pivot.

In essence, the coil spring will, when the door is released, return to its resting position by decompressing itself.

In order for this decompression to be carried out at a controlled speed, the coil spring has been placed inside a cylindrical chamber which, when the spring is compressed, is filled with a special oil that passes through a frank and non-return valve. When the spring wants to return to its original position, it presses the oil inside the chamber so that it returns the space it occupied. The oil output is then controlled through valves that regulate its flow, causing the spring to decompress faster or slower, according to the desired closing speed for the door.

The following aspects must be taken into account when choosing and prescribing a floor closer:

1. The weight of the door, because the floor spring acts as a support pivot, must be calculated to define the type of spring to be applied. Depending on the spring chosen, we can support doors up to a maximum weight of 300 kg.
2. The type of shaft. The axis of the floor spring is its connection to the door. It is therefore important that its shape is compatible with the shape of the fittings provided for the door. By default, German-made floor springs are supplied with a rectangular shaft, as the supplied door attachments are also of that shape. However, if the floor spring is going to be used on glass doors and the accessories for them are French or Portuguese made, it is possible that the spring shaft will have to be replaced by another with a square shape. Triple W offers axles that adjust to the needs of the market.                       

    3. The stop at the opening. Floor springs can be supplied with a preset stopping point at the opening. This means that whenever the door is opened to an opening angle "x", it remains in that position until it receives a push towards closing. Possible stopping          angles are: 85º, 90º, and 105º, depending on the manufacturer.

a) The lower support arm	b) The upper pivot	c) The arm covers.
		These covers are supplied in the colour of aluminium and can be further anodised or lacquered in order to hide the zinc-plated iron of the arms.

For a wooden, iron or aluminium swinging door:

5. The force of the spring.
   This is the strength that the spring must have to be able to close a door with a certain width, mass and wind resistance.

How is it determined? We know, empirically, that some doors close perfectly when they are opened and others, with the same dimensions and weight, do not close correctly when controlled by the same equipment.

In fact, both the natural force of the wind on site and the action of air extractors, namely in industrial kitchens or air currents in stairwells of residential buildings or others can cause a spring calculated with sufficient force to fulfil a mission, to prove to be, once installed, insufficient.

To solve this problem, manufacturers have created springs whose force is adjustable on site by the installer according to needs.

Basically, these springs have a screw that, when tightened or loosened, will compress or decompress the coil spring, giving it the necessary strength in each case. If we don't know what force to choose, we opt for springs with adjustable force.

6. Damping in the opening. Whenever a door is opened violently (escape path) or pushed by the wind towards the opening, it runs the risk of breaking against the adjacent wall or damaging any of its elements.

To avoid this effect, manufacturers have added another feature to their equipment. They put a valve in the spring body that works like the seat belt of cars, that is, when the door is pushed gently it does not offer any resistance, but when pushed violently it stops the opening movement.

7. Care to be taken when installing floor springs.

A good floor spring when well prescribed, that is, when suitable for the door you are going to control, should work for many years without any type of breakdown.

When the springs are manufactured in accordance with EN 1154, they must be able to open and close the door at least half a million times.

We know that in the vast majority of cases this does not happen. 

Is it because the spring is poorly regulated in terms of force or closing speed?
No!

A spring with the speed control valves all open closes the door violently, causing the destruction of the door or its frame, but not the spring.

Is it because when the door is being closed by the spring, users tend to push the door helping it close faster and, with that, drastically increase the oil pressure inside the spring damaging it?
No!

Quality springs prevent this misuse by means of an overpressure valve (14), which discharges the oil into an antechamber when this pressure increases disproportionately.

The fundamental reason for premature failure of floor springs lies in poor installation and has to do with their levelling in relation to the door.

The spring axis, which receives and supports the weight of the door, rests on a tapered needle bearing and must be perfectly aligned with the door in its vertical position.

In the vast majority of cases, the installer does not use the level to level the spring on the floor and, when he does, he limits himself to levelling the spring lengthwise (about 27 cm) but rarely has or uses a small level to level the spring widthways (about 8 cm).

Because the shaft is not flexible, it is supported by a thrust bearing at the bottom and guided by another collar bearing at the top, if it is not perpendicularly aligned with the door, one of two things happens during the opening and closing process:

1.     
The spring body will move in a circle inside its box when it is not properly tightened, seeking to adapt to the movement of the door or,

2.     
The axis will draw a cone of revolution as the door moves.

This movement will tend to break the support bearing liner, a malfunction that is denounced by the strongly audible clicking of many of the doors installed when they open or close.

In addition to this effect, the shaft will also tend to try to widen the sealing o-ring at the top, allowing oil to escape and producing the famous "drool" of hydraulic springs.

1st Caution to be taken: Correctly level the pavement spring during its installation.

Floor springs are applied, as the name implies, to the pavement.

The process of washing the floor with the use of the most varied products, usually caustic and strongly oxidising, destroys the equipment.

Although the spring body is made of cast aluminium and thick enough to resist corrosion, there are some elements that are not as resistant and that communicate directly with the interior of the spring:

- Speed regulating valves.

These are made of brass, small and easily attacked by the strongly aggressive products of the washes.

2nd Care to be taken: Fill the spring box with a good consistent mass, with high resistance to high temperatures and seal the spring cover with good quality silicone.

If the two previous precepts are fulfilled, we will have a well-installed spring with good functioning guaranteed for many years.

All that remains is for us to adjust the valves that are in the upper part of the spring, before closing and completely isolating it, so that the closing speed and final blow are the ones that best suit the situation of the door, in order to guarantee not only a long life but also a smooth and firm operation.

For any questions regarding the use of floor springs, please consult us.