1. Chainwheels for low noise chains
t: pitch of the chain
D: Tip diameter
Dt: pitch diameter
z: number of teeth of the chainwheel
The definition of the tip diameter is obtained with the below formula:
D = t.cot
A low noise chain consists of a series of toothed links connected by linking elements that allow a movement between two adjacent links. There are low noise chains with central conduction and chains with lateral conduction. Characteristics of a low noise chain:
- The chain is situated at the external surface of the wheel, equal a belt, and the teeth stick outside the chain. The chain grips with the wheel through teeth that are located at the bottom of the chain. The chain teeth and the chain wheel teeth are so constituted that by wear at the linking elements the pitch increases, the chain accordingly tend to move out on the tooth surfaces, so to grip on a larger pitch diameter; the result of this move is that the pitch of the chain and the pitch of the wheel increase to the same extent.
- The load on the teeth is divided across all the teeth within the contact arc, regardless of the extension by wear.
- The links do not show any gliding on or of the teeth, which carries a soft and practically noiseless gripping; this transmission was also engineered for transmitting power or higher speeds than this was allowed for roll chains.
- The return of the “low noise chain” can amount 99% and for the full transfer from 96% to 97% under favourable conditions; of 94% upto 96% there is a guarantee with well designed transmission under average operating conditions.
- The lifetime and maintenance of low noise chains depends mainly on the design of the complete chain drive, the tension arrangement included. At very loose chains the balancing of the chain will speed up the wear. A good tension arrangement can double the lifetime. A slight clearance is required with a minimum of +/-3 mm. Although the chain is getting higher positioned on the teeth upon stretching of the pitch, this stretching is not moderated by the straight section of the chain, which means that this section is slacking at wear.
Except for the tooth shape the pinions and wheels for low noise chain transmissions resemble those for roll chain transmissions. As shown in the picture the wheels for low noise chain have “flat” active tooth flanks. The tooth tips can be both rounded and angular.
The tip root clearance below the active tooth flank is not properly defined, but should be adequate to let move the tooth tips of the chain freely. The normalized tooth shape is meant to grip with chain plates whose outer (active) sides form a enclosed angle of 60°. One also sees that the angle formed by the flanks of a given tooth (60°-) decreases according to the number of teeth is smaller, so that for a pinion with 12 teeth this angle is zero. In other words, the tooth flanks will be parallel. As a practical tip is recommended to choose for 21 or more teeth and to avoid less than 17 teeth. The hobbing of low noise chainwheels shall be carried out by means of reference gear hobs (gear hobbing process for series production), through a double gearprofile hob (2 flanks) or with a normal disc hob with parallel flanks. Since the hobbing pressure angles vary acoording to the numbers of teeth, the availability of appropriate hobbing tools will determine the hob possibility and cutting time.
The choice of a low noise chain transmission will not only depend on the ability to transfer and the ratio between driving and driven axes, but also by factors such as the speed of the fastest rotating axis, the available space, the dimensions of the wheels, the nature of the load and other factors. As a first step in the selection of such a transmission the pitch of the chain and the number of teeth of the pinion should be choosen. Usually various combinations of chain pitch and wheel dimensions can be chosen. It is advisable to consult the manufacturer of the chain when designing a chain transmission and choose to do, taking into account the size and length of the chain, centre distance, lubricating capabilities, preparation of the housing, etc…
2. Chainwheels for transport chains
do: pitch diameter
da: tip diameter
da = do + ≈d
df: foot circle diameter df = do – d
A: pitch between the roll pulleys
B: pitch of the the roll pulleys
d: roll diameter do = tanβ =
3. Chainwheels for chains
Chains according to DIN 766A – 766B – 766HA – 766HB – 5687 – 763 – 764 – 764H
D: pitch diameter
N: number of teeth
d: diameter of the chain of the link
Pitch: pitch of the chain
The diameter of the chainwheel is obtained by the following formula:
D = with