Cranks

Today, cranks are an indispensable unit when it comes to safely installing industrial elements that can be used as manual controls on machines and systems or even on agricultural machinery or other units. In this article we will discuss how cranks have made their place in the industrialization of mechanical engineering or other technical equipment. Without cranks, a machine park or other mechanical equipment would no longer be conceivable today. Imagine, for example, that you have a bath system that can be adjusted in width so that you can adjust or set certain widths of this system quickly and without tools by means of a crank on this mechanical device. So there is always a crank in the middle of the system and this is usually connected to a spindle. By turning the crank, the spindle is now set in motion and can initiate the adjustment via the spindle nut. No external tool is required for this procedure. The crank is tightly enclosed by the hand alone and can be tightly enclosed by folding down the lady's and index finger. The handle of the crank is now firmly in the palm of the hand and enclosed so that a rotary movement can be carried out. Now we come to the construction of a crank that consists of mechanical parts. Basically, a crank is made of two separate parts and is also assembled. The crank body is always the starting point for the actual crank drive. This crank base body has two ends, which are provided with attached end pieces whereby the cross drillings run, which on the one hand ensure that the crank can be put on a shaft or axle and firmly connected to it by certain fastening elements. Now a frictional connection is established between the crank body and the shaft. If there is a rotary or circular motion of the crank body, this rotary motion can be transmitted to the shaft by transmitting the torque. There is always a handle at the other end of the crank. This handle ensures that the palm of the hand and the fingers can firmly enclose the handle and carry out the rotary movement. The basic materials used for the cranks are actually always plastics in all variations. These plastic cranks are the basis when it comes to installing an inexpensive and lightweight drive crank. Of course aluminium cranks are also used. These are also very light, not so cheap, but made of a metal. The highest level of a crank material is the crank made of stainless steel. Two alloys are used for this material. On the one hand it is the stainless steel V2A which is usually also used on cooking tables in the food industry to crank up lids or in many other areas. However, if you want to use the stainless steel crank in connection with chemical plants or in the vicinity of acids and alkalis, you should always use the stainless steel V4A, which is also used in connection with salt water.

In the previous article we have already been able to explain the basic structure of a crank. But a crank is still much more complex in construction, as some of you can imagine. That is why we would like to go a little deeper in this article, concerning a crank element, which consists of a basic body and a handle element, which is attached to the crank body. This handle can be designed in different versions and can be adapted to the requirements of the respective technical system. In the case of a crank element which has a fixed handle, the structure is as follows. The basic body of the crank consists of the same segments as always. Two holes, each located at one end and inserted at the opposite end. Like a bicycle crank. One side is firmly connected to the shaft and the other side is attached to the handle. If, in a technical application, only a small torque force is to be transmitted to a shaft and the rotations for the corresponding adjustment unit are only a few revolutions, cranks can also be equipped with a fixed and non-rotating handle. In this design, the handle element is mounted non-rotatably and is connected directly to the crank body by a fixed thread. A decoupled rotary movement cannot be performed by the handle element. The operator's hand slides over the handle with each rotation and must generate the torque and transmit it to the crankcase. The situation is different if the handle elements are not firmly connected to the axis of the grip but can perform a separate rotary movement. In this case the pin and the crank of the main body are firmly connected by the axle piece, but there are still some bearings on the axle which allow the rotary movement of the grip. The handle of the entire crank is thus decoupled and can be rotated with every movement. The hand is firmly attached to the handle and does not have to slide over the handle of the crank. An extended possibility of cranks to make the cranking process even more comfortable and to execute higher torques as well as to let several unproblematic rotary movements follow. These cranks can also be made of plastic, aluminium or even stainless steel in V2A or the V4A version.

In the previous articles we have already been able to give you some information about cranks with the construction of a rigid axis of the handle and also a crank with a rotating handle, which is completely decoupled in the axial rotary movement during a rotary movement. This and last article will be about the cranks, which have built in another level of possibilities and can be equipped not only as a rigid handle position with a rotating handle element, but also the handle can be folded in or the handle and the whole crank body. We would also like to start with the foldable version of this crank element. On the outside of the crank body, where the fixed handle is screwed into the crank body with the axle, there is a joint which is installed on the axle which is screwed into the body. This joint on the crank enables the operator to fold out the handle for cranking and to fold it back in again after the cranking process. This way, the entire crank has no more annoying grip piece to get stuck on. This joint on the axle is equipped in such a way that it can only be folded to 90 degrees and cannot overturn. Also with this crank element it is so that the axle can be supplied with a fixed grip or also with a rotating grip. However, it is often not only sufficient to fold up the handle element on the crank and take it out of a danger zone, but the entire basic body of the crank can also be folded in again via a joint piece on the shaft. Only with these complex crank pieces is it possible to completely fold in a crank from a danger zone. The crank body can then be folded over 180 degrees on the opposite side at a joint or folded in 90 degrees in the direction of the shaft. This means that there is no longer a disturbing piece on a machine. Especially on machines and systems with little space and room, fully foldable cranks are a very important product to avoid creating a danger zone in the machine area.

Further websites on the subject of cranks

1. https://de.wikipedia.org/wiki/Kurbel
2. https://de.wikipedia.org/wiki/Tretkurbel
3. https://de.wikipedia.org/wiki/Handkurbel