When a continuous rotation damper is mounted on a lid that closes horizontally and torque is insufficient, torque may be secured by incorporating gears. In such a case, the torque calculation method is the same up to the middle as for a partial rotation angle rotary damper.
Under what circumstances would a low torque continuous rotation rotary damper be mounted on a lid that closes horizontally? For lids that close horizontally, it is common to insert a partial rotation angle damper with a fixed housing and shaft on the same axis at the center of rotation, but there are cases where it is difficult to use a partial rotation angle rotary damper due to limitations in axial thickness. In such cases, continuous rotation rotary dampers, which are thinner in assembly, may be used. Continuous rotation rotary dampers are best suited for lids that are light and have a small installation space, such as the lid of an electronic piano.
However, because the continuous rotation rotary damper has a structure that only stirs viscous material, the torque is lower than when a general partial rotation angle rotary damper is mounted. Therefore, it is necessary to incorporate gears and design the rotary damper to withstand higher torques. Due to the structure of the lid, it is common to install segment gears, but the method of calculating torque for rotary dampers is a bit more complicated than for free fall.
In this article, we will explain in detail the torque calculation when a continuous rotation rotary damper is assembled on a segment gear to increase the torque, showing an example.
Torque calculation method when a polyacetal plate 230 mm wide
x 60 mm long x 10 mm thick is used as a lid
(Specific gravity of POM | Polyacetal = 1.42 g/cm3)
The weight M of the lid is calculated as follows
M = (230 x 60 x 10) / 1000 x 1.42 = 195.96 [g] = 0.19596 [kg].
Distance L from the center of rotation to the center of gravity of the lid as approximately half the length,
L = 60 mm / 2 = 30 [mm].
The torque T1 required for lid damping is
T1 = M x g x L = 0.19596[kg] x 9.8[m/S2] x 30[mm] = 57.61[mN･m].
At this time, TOK’s TD88 continuous rotation rotary damper is suitable for the rotary damper assembly space, but TD88 has a maximum torque of 40[mN･m] at 30[min-1], which is insufficient for torque T1, so the gear train is used to gain torque. Therefore, the torque is handled by gaining torque in the gear train. Therefore, based on the standard gears of TD88, we will design it so that the torque of the lid can be used even if it is twice as much as the damper torque.
Gear specifications for TD88: module m = 0.8, number of teeth Z2 = 11
Since to double the torque, the number of teeth must be doubled,
Number of teeth Z1 = 22
The torque T2 required for TD88, compared to the torque T1 of the lid, is calculated by the following calculation.
T2 = Z2/Z1 x T1 = 11 /22 x 57.61 ≒ 28.8 [mN･m].
In other words, a product close to T2 can be selected as “TD88L1-300” with a torque of 30[mN･m].
Caution:
The speed ratio is also 2:1 because it is designed to handle twice the damper torque.
TD88L1-300 produces 30[mN･m] of torque at a rotational speed of 30[min-1], so the average closing speed of the lid at this time is 15[min-1], half of that speed.
If this speed is too slow, the TD88L1-200 with lower 1 rank torque may be more suitable.
Summary of Torque Calculation Method for Rotary Dampers | In the Case of Free Fall
The torque calculation method for the case where a continuous rotation rotary damper is assembled to a segment gear described in this article can be calculated by simply entering numerical values on the automatic torque calculation page. We hope you will find it useful.
TOK rotary damper website also provides torque calculation methods for various other types of rotary dampers, so please take a look at these pages as well.
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