# Technical explanations

## Basic function: Lowering

Propelling force FR

The propelling force FR is the friction force between the conveyor equipment and the pallet. It is a function of the coefficient of friction μ, the weight of the pallet m and acceleration due to gravity g:

FR = µ · m · g

If more than one pallet has been accumulated than the number of pallets n must also be considered:

FR = n · µ · m · g

The coefficient of friction µ is a function of the friction between the conveyor equipment and the pallet.

Examples for the coefficient of friction:

Belt/band:                  µ  = 0,2 - 0,3
Plastic modular belt:  µ  = 0,3 - 0,5
Accumulation
roller chain:               µ  = 0,01 - 0,03

mworkpiece  =  5 kg
mWT            =  2 kg
µ                 =  0,2
g                 =  9,81 m/s²

FR  =  (5 + 2) kg · 0,2 · 9,81 m/s² = 13,7 N In this example, a pallet of total weight 7 kg exerts a propelling force of 13.7 N on a double belt conveyor.

The product brochure and data sheets indicate the maximum propelling force against which the stopper can reliably lower during long-term operation. The propelling force in your system must be less than the specified value.

Example for DBS-20/60:
(Value given for coefficient of friction µ = 0.07):
Maximum propelling force 41 N

Please note that other pallet weights can be reliably lowered at different coefficients of friction. Using the formula above, you can easily convert the maximum propelling force specified by us for other coefficients of friction.

## Basic function: Stopping

Deceleration force FV
(by way of example for damped stopper)

The deceleration force FV is required to slow the pallet down to a halt and dissipate the kinetic energy stored in the pallet. It consists of the damping force (at conveyor speed v and damping stroke s) and the propelling force, which continues to have an effect even during the damping operation:

FV  =  m · v2/2s  + m · g · µ

The scope of application of the various stoppers is indicated in the product brochure and data sheets. Using these tables, it is easy to determine whether the intended stopper is able to damp the expected pallet weight at your required conveyor speed. The damping capacity, e.g. of a DBS -20/60 stopper at 18m/min, is sufficient for both a pallet with a weight of 3.5 kg and for a pallet with a weight of 30 kg.

Beispiel DBS-20/60
(Values given for coefficient of friction µ = 0.07):

Conveyor
speed               Pallet weight

6 m/min               3,5 - 60 kg
9 m/min               3,5 - 40 kg
12 m/min             3,5 - 35 kg
18 m/min             3,5 - 30 kg
24 m/min             3,5 - 24 kg
30 m/min             3,5 - 18 kg
36 m/min             3,5 - 10 kg

Please note that other combinations of the conveyor speed and pallet weight parameters are possible, or may indeed be required, at different coefficients of friction. This is true, in particular, when the propelling force ac-counts for a high proportion of the deceleration force, i.e. in systems with high levels of friction. You can obtain an initial approximation of these values using the formula above.