Table of contents:
- Separation point or overload protection
- Picture gallery
- Series revised
- Automatic engagement with minimal wear
- Prevent costly repairs
Video: The Clutch Engages Again At The Right Moment
Jakob Antriebstechnik has been active in the field of overload protection and torque limiters for several decades. The area of application includes all sophisticated drives in mechanical engineering, from the highly dynamic servo axis of a machine tool to overload protection of conveyor systems. Especially in modern applications with constantly increasing degrees of automation and dynamization, machine damage not only means repair costs, but also rapid financial losses due to increasingly expensive downtimes. Appropriate protection against such scenarios should therefore be a high priority today.
Separation point or overload protection
Safety clutches from Jakob Antriebstechnik are designed as a separation point or overload limiter. At the center of the coupling is a robust and high-precision release mechanism with steel balls as a spring-loaded form-locking body. The drive torque is conducted from the shaft via a key connection or a non-positive, play-free clamp or cone connection into the centrally arranged hub. The hub is designed as a ball cage and serves to accommodate an output-side flange ring, a switching disc with a plate spring and the adjusting nut. Special disc springs press the balls over the pressure or switching disk into hardened spherical caps of the flange ring. In normal operation, the drive torque is transmitted to the flange ring without play.For torque transmission, a compensating element (metal bellows or elastomer star), a toothed or belt wheel or a connecting flange is attached to the flange ring.
Depending on the balancing torque selected, the coupling is able to compensate for significant shaft misalignments. If the set disengagement torque is exceeded, the flange ring rotates relative to the cage hub, the balls are pressed out of the calottes. The drive train is interrupted within a few milliseconds. By tightening the steel balls between the ball cage, hub and flange ring, backlash-free torque transmission and high torsional rigidity are guaranteed.
As in the past, Jakob Antriebstechnik continues to rely on its modular principle in order to be able to guarantee short delivery times with constant quality. This system enables the selection of the optimal design of the overload mechanism for the respective application, as well as the desired attachment types, which cover almost all indirect and direct drives.
In the case of direct drives, the safety coupling for the shaft-shaft connection is supplemented by metal bellows or elastomer attachments. The designers at Jakob Antriebstechnik have recently revised numerous series that can now cover a much wider torque range. This opens up a wide range of other applications for the company's proven torque limiters. In the course of this revision, the maximum disengagement torques of the clutches were tripled from 3000 Nm to 9000 Nm.
There are new versions for both indirect and direct drives. The SKY series covers indirect drives and offers a connection using a cone clamping bush or for larger torques (3000-9000) using a conical shrink disk, while the SKW series is a more cost-effective alternative in which torques are transmitted using a keyway connection. Direct drives, on the other hand, can be protected by the SKY-KS series with metal bellows coupling attachment and cone clamping on both sides. The new sizes also cover a wide range of diameters and are available for bore diameters up to 130 mm.
New distance couplings for center distances up to 6 meters
While in the previous standard series the drive train is reliably disconnected in the event of an overload, the automatic re-engagement function (360 ° synchronous engagement position) can cause considerable wear on the coupling components, especially at high speeds and long overrun times. Unlocking competing products interrupt the drive, but at the same time make it necessary to re-engage the clutch manually using special tools or complex devices.
Automatic engagement with minimal wear
In many applications, however, such a safety coupling is not freely accessible and it is difficult to re-engage it, or it is simply impossible for reasons of space. Jakob Antriebstechnik has now developed a new version (series "F") for these areas of application, which combines automatic re-engagement with the minimal wear and tear of an activation clutch. The re-engagement takes place automatically when the direction of rotation is reversed at low speed. Downtimes can be reduced effectively. If it is not possible to reverse the direction of rotation, it can optionally be re-engaged using a manual process at a standstill.
This new development was stimulated by the demand from a customer who saw no possibility of using a classic torque limiter. In the application in question, tractors were equipped with compressors for loading and unloading. These compressors are driven by a secondary shaft of the internal combustion engine. To protect this drive, classic safety clutches have been used so far, but in the event of an overload and a long overrun due to the automatic re-engagement, this could lead to considerable wear. Sometimes it was so big that the complete drive protection had to be replaced after only one overload. Such a repair not only means a lot of work, but also a downtime in which the tractor cannot be used.
Additional information on the subject of the play-free ball detent mechanism
A patented tensioning of the hardened and polished steel balls between the ball cage of the hub and the calottes of the flange ring guarantees a play-free torque transmission with high torsional rigidity. The mechanism works in reverse for both directions of rotation.
The degressive spring characteristic
The function of the Jakob safety clutches is significantly influenced by the disc springs specially developed for this application. Due to the design in the degressive characteristic curve range, the spring force decreases with increasing spring travel (switching travel), which means that the torque drops immediately when activated. With conventional spring-loaded overload clutches, on the other hand, the spring force and the disengagement torque increase. T. considerably. This results in an undefined functional behavior between response and disengagement.
The dynamic disengagement behavior
Jakob safety clutches are characterized by excellent dynamic disengagement behavior. The reason for this is the degressive spring characteristic as well as the minimized masses (ball and switching disc) that have to be accelerated axially when disengaging. This guarantees that the drive train is interrupted within a few milliseconds in the event of a collision. The product of mass and acceleration (F = m • a) results in a force that must be added to the spring force. In the case of conventional clutches with large proportions of mass to be moved, the static disengagement torque and the switching time can increase several times.
Prevent costly repairs
A clutch that reliably disengages in the event of an overload and only engages again when the direction of rotation is reversed at slow speed can often prevent such expensive repairs and increases the availability of the production systems. The use of such a solution is also conceivable in numerous other areas. (ud)
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