Why a new card?
The market for cards has changed, some high volume applications have gone to spunbonded and meltblown process has taken fine web markets.
The future market for cards will be characterized by
- natural fibers
- rapid flexible response to the market
- sandwich products of different fibers (multilayer)
- high operational availability at low maintenance level
- low investment cost
- special characteristic of the web like soft touch, special orientation
- wide range of applications
This made a new design necessary, and new manufacturing processes were applied. The conventional card design is more than 200 years old and most current designs just tried to copy the cast iron design to welded steel. These designs do not take all advantages of laser cutting and sheet metal processing in the design itself. Also the drives still have been with belts. The old designs still use imperial dimensions for the cylinders as it was only copy and paste for decades. The accessibility in old designs is not given as motors and hoods are often placed below the machine. For multilayer products the machines had to be mounted on costly platforms that stretched a long way. It is difficult to change the configuration of the card, going from an air-doffed to a roller-doffed is almost impossible.
These drawbacks have been solved by the compact card design by HERGETH.
The basic machine that includes the chute feed, the feed roll, first carding cylinder, second and third carding cylinder with the carding elements stays always the same.
Carding is done by 5 sections each having 3 carding strips giving a total of 15 carding areas.
Individual carding strips can be replaced by blanks when carding is too much for the processed fibers. So the carding can easily be adjusted to the fibers used. Feed roll and doffer are precisely servo-driven, all other cylinders are individually driven by frequency-controlled motors. The transfer from motor to cylinder is by cardan links. No belts or chains which need more maintenance are used. The speed is exact without slippage of belts.
Fiber flow is from top to down, and covers guide the fibers so fiber agglomerations in the machine are avoided. Only one suction point is needed when working with a doffer.
All motors are placed in a separate part that makes them easily accessible and replaceable. The motors can be installed at the left or at the right side of the machine, where more comfortable.
That also makes it easy to clean the motor fan covers from fibers and keep the temperature low. As there are not belts and chains, the drives and the shafts of the cylinders do not suffer from rotation bend resulting in longer life time.
Each cylinder can be individually monitored and its performance data can be displayed and analyzed in the PLC and on the monitor.
Fewer parts result in less spare parts. There are only 400 and 200 mm (300 mm as an exception) diameter cylinders resulting in very few different bearings. Apart from high speed carbon cylinders the cylinders of same diameter can serve in any position.
The 400 mm carding cylinders can be rolled off the card and rolled in. So if there is a spare set, downtime can be minimized. For flexible production also a second set of cylinders can be kept with different wire to adjust between coarse or fine fibers.
The machine can be reconfigured from air-doffed to roller-doffed or vice versa as the configuration is similar and all the connecting points are incorporated in the basic machine.
A new type of side seal for the cylinders, the h-seal, can be exchanged without taking the cylinders out. The seals stretch right to the wall avoiding an undercut and fibers caught by this.
The carding elements can be slid out to the side if they have to be replaced, but our experience shows that the life of the carding strips is much longer than the carding wire. The setting of the holding bar can be adjusted along the whole width of the card so there is no hanging of carding elements on wide machines. The carding strip holder is spring-loaded, the carding strips can move back when a very hard spot appears reducing damage.
8 temperature sensors monitor the status of the machine.
As the carding cylinders are lined up in one line, setting is easy.
The only cast-iron parts are the pillow-block bearing housings.
The main body is from 15 mm gauge steel laser-cut, bended and welded to form one solid block. The platform of the carding roller bearings is leveled to 1/100 of a millimeter.
The covers of the cylinders are fixed with position pins that can easily be removed. The floating mounting avoids problems due to thermal expansion. Plexiglass, removable inspection windows allow inspection of the machine.
The newly designed shaft bearing fixing allows easy change of bearings without changing the position of the bearing on the shaft. Fretting corrosion is not a problem on the carding cylinder bearings at all.
The chute feed is an essential integrated part of the card. It feeds directly to the feed roll without any draft between chute and feed roll. Special profiles avoid twining of fibers around the individual air separation bars. The design of the bars also allows an open area of more than 50 %. This big area with the high box area allows much higher air volume to pass through the bars giving a more regular bat.
Two ways of feeding are offered. First a circular feed avoiding the dead-end-feed of the conventional chute feeds where slow air speed leads to disintegration of heavy and light tufts. For very bulky material a two-sided feed without partition is used that allows fibers that need more air to better settle in the chute. The two-sided feed uses the same wide chute feed channel without partition avoiding chokes. The new feed system allows extremely accurate CD/ MD and longtime stability.
There are big doors covering the width of the chute if cleaning is desired.
The unidirectional feed to the first carding cylinder avoids bending of fibers. The clamping of the fibers is unique for a non-woven card. At the end of the feed table the feed clamping is done by piano plates that press the fibers to the feed roll. The pressure of the plates is generated by individual pneumatic bellows. This gives the following advantages:
- a) constant pressure over the whole width of the machine. No bend open of the feed table at large width
- b) Flexibility:though the position of the feed plates can be mechanically changed, it is easier and better just to set the clamping pressure at the central pressure reducer to influence the clamping force. In case the metal contact at the feed plate has been engaged, the pressure can be taken away so the feed roll can easily turn reverse.
The piano plates are also used to measure the fiber thickness feed to the card. The displacement of each clamping plate is measured to 1/100 of a millimeter. Each position is processed by the PLC with an individual PID regulator. If a deviation of the set thickness is detected, the depth of the segmented chute feed is changed at the corresponding position to get the fiber profile correct again (optional, not needed with new feed).
The opening of the chute feed is set by a linear motor unit for each section (optional).
For simpler applications just the feed roll speed gets corrected. This helps to keep the product constant.
The compact chute feed and the design of the card with minimum open areas reduce the chance of fibers resting in the machine and building up bumps. Some customers do not clean the machine when changing the material. They just remove a few meters of web.
Due to the design as a vertical card, the surface of the cylinders is optimally used, only small areas have to be closed with covers. This avoids the wind streaks that can be caused by large covers.
Roll-on/ roll-off. The cylinders of the card can easily be rolled on and off the card. First the covers and when necessary carding elements are removed, then on each side a lever is attached, then the pillow block opened and the carding cylinders can be rolled out with the bearing. The reclothed or spare cylinder can be rolled in. By this, it is possible to keep a spare set of rollers to avoid production losses, no soldering or welding in the production area is necessary, thereby increasing the safety. It is also possible to have another set of cylinders to switch from carding coarse fiber to fine carding and vice versa. In conventional cards the wire is lost each time you change and all settings have to be changed.
No big platform necessary even when webs from more than one card are on a common belt. This reduces installation costs and operators do not have to climb up a platform frequently for observing the machine.
What is the difference in the airlay technology?
Conventional airlaid have an opening cylinder and an air current passing by this cylinder to take the fibers out of the cylinder wire. The HERGETH airless uses a kick-off roll that takes the fibers out of the carding cylinder and throws them on a sieve where the fibers are held by a small air suction.
Why the difference?
In order to open fibers the carding cylinder has to be wired or pinned aggressive, i.e. with pins or wire tilted in the rotating direction. Otherwise, there is no good opening and agglomerations of fibers are thrown by the cylinder.
In order to doff the fibers from the cylinder, a non-aggressive pointing, i.e. backward from the cylinder rotating is necessary. If not, fibers tend to run around with the cylinder several times, creating neps.
In order to air-doff the fibers from an aggressive cylinder wire, the air speed should be about 3 times the surface speed of the cylinder. In most installations this is not achieved.
The HERGETH airless doffing of the carding cylinder by a kick-off roll makes sure the carding cylinder can be aggressive doing a good opening job, and the kick-off cylinder having a higher surface speed than the carding cylinder and negative wire clears the carding cylinder well and throws the fibers onto the sieve. This avoids nep creation and much less air is necessary to form a web.
This allows new web building techniques for a better web.
When using powder binder the HERGETH airless system avoids a lot of powder being lost by the air suction. The HERGETH airless system is also less affected in different air flows from left/ right distribution.
Less filter capacity is necessary. No fans are necessary at the top of the machine.
The HERGETH airless system allows easier access to the web building section and the separation knife.
The vertical card is a new approach to replace the old card concept.
There have been known only two major attempts before.
In the early 1970ies Herbert Hergeth introduced the roller train card based on an English invention. Originally, the card had the shape of an inverted V, only later did it evolve as an inclined line. The roller train card uses small cylinders, but is still using the worker and stripper concept for carding due to the arrangement of the rolls or cylinders. Some cylinders work also as strippers for the worker cylinders. The great number of rolls makes the drives relatively complicated and the setting of the big rolls takes time. Due to the setup of the rollers, it is difficult to handle all the covers necessary at this type of card. A difficult point is the uncontrolled area where the rollers are placed in a triangle. Nevertheless quite a number of these cards are used in the industry.
A forerunner of the compact card more closer to textile technology was the Mastercard by John D. Hollingsworth. John D. Hollingsworth was an inventor of metallic wires and introduced the stationary flats. Driven by the success of the metallic wire and stationary carding elements Mr. Hollingsworth designed a non-woven card with stationary flats only. As the card was based on the concept of cotton cards, it was relatively simple. It was also executed as a double card with 2 main cylinders of relatively small diameter (about 600 mm). these cards have been built in small numbers (about a dozen). This interesting development stopped as Hollingsworth was busy with new acquisitions. The trend to smaller cylinders was started by research done by Andre Varga and he introduced them in cotton cards and tandem cards.
The unidirectional feed was introduced to the industry by Herbert Hergeth. His famous scutcher design used the feed principle and also used the displacement of the pedals to measure the weight of the total bat and correct the speed of the feed cylinder.