Are magnetic transmissions applicable for the food and beverage industry?
Can magnetic slip clutches be dispensed with by using magnetic transmissions? An application example.
1. Introduction
In the food industry, magnetic slipping clutches are used to limit torque, e.g. for bottle capping systems. For this purpose, an electric motor, a gearbox and a magnetic slipping clutch are connected in series. With the aid of magnetic transmissions which, due to their operating principle, combine the functionality of the gearbox and the slipping clutch, the component of the magnetic clutch can be dispensed with.
2. Magnetic Transmissions for food and beverage
Magnetic transmissions have the same kinematics as planetary gears and can therefore be used in the same or similar applications. Magnetic transmissions consist of an outer magnetic wheel, a modulator and an inner magnetic wheel, analogous to the ring gear, the planet carrier and the sun gear of a planetary gear, respectively. Since the transmission of power via the magnetic forces is purely force-fitted, there are various application scenarios for the magnetic transmission. In the food industry, two advantages of force-fitted torque transmission are relevant - freedom from lubrication and overload limitation.
Since there are no gears rubbing against each other in a magnetic transmission and torque is transmitted by magnetic forces, no lubricant is required. This is a great advantage, especially when an open design is required in the food industry, where the transmission is mounted openly in the spray and process zone.
A magnetic transmission has a maximum transmittable torque. If this torque is exceeded, the components slip against each other. This behavior is the same as in a magnetic slip clutch, which slips in the event of an over-torque. This advantage of the magnetic transmission simplifies the design of the application by eliminating the need for the magnetic slip clutch. Figure 1 shows the torque behavior of a magnetic transmission under overload. In the event of an overload, the transmission ratio drops and no or considerably less torque is transmitted. Only when the application is stopped – or driven at low speeds - the magnetic transmission is able to transmit torque again.
Figure 1: Torque behavior of a magnetic transmission under overload conditions. [2]
An exemplary application for these two advantages in the food industry can be found in systems that close bottles (see figure 2). A defined torque is required to screw the lids. A combination of a drive (e.g. electric motor and gearbox) and a magnetic slip clutch is used for this purpose. The magnetic slip clutch is particularly suitable for the food industry because, compared to a mechanical slip clutch, it does not generate any abrasion that can contaminate the food.
Figure 2: Application case bottle capping machine. The caps are screwed onto the bottles with a defined, adjustable torque. [1]
Figure 3: Motor-gearbox combination. The magnetic transmission enables a defined overload torque. The stainless steel version in hygienic design enables use in the spray and process zone. [3]
The use of a magnetic transmission eliminates the need for a slipping clutch. An exemplary design is a motor (asynchronous or synchronous) with integrated magnetic transmission made of stainless steel in hygienic design (see Figure 3). With this magnetically-geared motor, it is possible to enable applications in the food industry where a defined limited torque is required.
3. Conclusions & Outlook
Magnetic slipping clutches are used in the food industry, e.g. in bottle capping systems in which lids are screwed onto filled bottles with a defined torque. Due to the overload protection function inherent to the magnetic transmission, they can be used in all applications in the food industry in which the drive is to slip at a defined torque. Here, the magnetic transmission can be used alone, with a synchronous motor or also with an asynchronous motor, in stainless steel and with hygienic design.
Dr. Stefan Vonderschmidt,
Geschäftsführender Gesellschafter Georgii Kobold GmbH & Co. KG
Dipl.-Psych. Andreas Vonderschmidt, B.Sc.
Geschäftsführender Gesellschafter Georgii Kobold GmbH & Co. KG
Copyrights
[1] Istockphotos 498062781©pia_ch
[2,3] © Fotograf Waldemar Hamper, www.hamper-fotografie.de