Home » Issue 21 21-2020 » Company insights » 5 in one sweep (Theodor Leeb)

5 in one sweep

Theo Leeb

In his interview with terraHORSCH Theo Leeb talks about the advantages of pulse nozzles and the success of other innovations that, one year after the Agritechnica, successfully stood their test in the field.

terraHORSCH: Let’s look back on the past year. There were a lot of innovations. How did they settle in the market?
Theodor Leeb: The big highlights we presented were the tandem sprayer Leeb 12 TD, the new self-propelled sprayer line PT and our PrecisionSpray with the pulse nozzle technology.

terraHORSCH: We already talked about the Leeb 12 TD and the new self-propelled sprayer line in the last two issues of terraHORSCH. Can you give us an update how the machines performed in the field?
Theodor Leeb:
Let’s start with the tandem sprayer 12 TD. Right at the beginning we thought that it would be a niche product. An important product, but still a niche product for customers with specific requirements with regard to efficiency and logistics. With a large tank capacity, you want to increase the hectare output and ease the logistic problem in case of large distances between the farm and the fields. But the real demand was an absolutely positive surprise. The new product settled in the market in a very short time and is well accepted. This surely is due to the two-tank system that solved the challenge with regard to tandem sprayers in a new and innovative way. The total capacity is 12,000 litres divided in 7,000 litres at the front and 5,000 litres at the rear. When spraying both tanks are emptied step by step in such a way that there always is more mixture in the front tank than in the rear one. This technology has proven its worth in hilly terrain as there always is enough vertical load on the tractor. Thus, traction is improved significantly. The customers are very surprised by the low horsepower requirement of the 12 TD.

terraHORSCH: At the Agritechnica, the Leeb PT was presented as the basis for a self-propelled sprayer line that HORSCH will launch all over the world. After the successful introduction of the new Leeb PT, the first Leeb VL (Variable Large) has already worked in the markets. What are the first experiences?
Theodor Leeb:
First of all, we are extremely satisfied with the first serial year of the PT. The feedback we got from our customers, mainly from Central Europe, was very positive. The Leeb VL is a new self-propelled sprayer version for the global market that this year was presented for the first time at an exhibition in Russia and in the meantime has worked several thousand hectares, for example in Eastern Europe. The Leeb VL is equipped with telescopic axles and a new individual wheel suspension. The variably adjustable track width is available with two ranges – between 2.60 and 3.50 m and from 3 to 4 m. Both can be equipped with an optional height adjustment of up to 2 m. To begin with the Leeb VL will be available with a tank capacity of 6,000 l and 8,000 l – and later also with 4,000 l. From the track width you can see that these sprayers are intended for the export markets. Moreover, with the VN (Variable Narrow) line we will launch a version for Europe that also disposes of a variably adjustable track width. There also are two ranges: from 1.80 to 2.25 m or from 2.25 to 3 m. The customer can choose the version that suits him best. As an option, the track adjustment from 2.25 to 3 m can be equipped with a height adjustment of up to 2 m. The Leeb VN will be available with a tank capacity of 5,000 l or 6,000 l and with regard to the range of application reminds one a little bit of the Leeb PT 350.

terraHORSCH: For quite a long time HORSCH did not offer an individual nozzle switch-off. Why?
Theodor Leeb: 
Frankly speaking, the technical additional effort was out of all proportion to the benefit as we had a very finely graduated section control with up to 42 sections.

terraHORSCH: But the technical effort for a pulse system like you presented at the Agritechnica must not be underestimated either.
Theodor Leeb:
That’s right. But the additional benefit due to a significantly larger working range of the nozzle, the independence of pressure and thus of drop size and operational speed as well as curve compensation or VariableRate per section absolutely justify this effort. The demand is enormous. And the feedback on the machines that are working in the field at the moment are extremely positive. No-one would return to the previous system. Quite the contrary. There is no discussion at all. But let’s talk about the advantages one after another.

terraHORSCH: Which requirements that now turned out to have so many advantages were the trigger that made you deal with the pulse nozzles as a hardware and PrecisionSpray as the intelligent HORSCH control system behind it in the first place?
Theodor Leeb:
It originally resulted from the dilemma of the North American farmers who wanted to go very fast with only one nozzle. It was not possible to cover the desired speed range from 5 km/h to 25 km/h with one nozzle calibre. And this is why the first developments in this sector started in the US. The pulse width modulation is a system that for a start can open and close nozzles at high-frequency. This is carried out via a small electromagnet that by means of an oscillating metal piston opens and closes a borehole. The so-called Hertz number indicates the opening and closing frequency. Our system for example works with 20 Hertz, i.e. the nozzles opens closes 20 times in one second. One cycle (nozzle opens and closes) takes 0.05 seconds. The high frequency is important to guarantee a sufficiently accurate longitudinal distribution. Higher frequencies, however, would make little sense as in this case the adjustment range of the Duty Cycle would be limited.

terraHORSCH: Now you mention another term that is important for the further understanding and the functioning: Duty Cycle. What exactly is it?
Theodor Leeb:
The system can adapt the opening and closing duration as a percentage dependence of the cycle time. This is the so-called Duty Cycle. The Hertz number of a system indicates the frequency how often a nozzle can be opened and closed in one second, and the Duty Cycle indicates how many percent of an interval is opened. With a Duty Cycle of 0 % the nozzle is closed. With 50 % the nozzle is open during one half of the cycle time and closed during the other half. With a Duty Cycle of 100 % the nozzle would always be open, and you would work like with a conventional plant protection sprayer. We can control the application rate steplessly via different Duty Cycles and, thus, opening times independent of the spraying pressure. A reasonable working range for the Duty Cycle is 30 - 100 %. This means that the output of a nozzle can be reduced to 30 % by the pulse width modulation (PWM) – while the pressure and thus the drop spectrum is kept up. An example: If a 05 nozzle is mounted, the output of a 015 nozzle can be achieved with a Duty Cycle of 30 %. This results in a working range between 015 and 05 – and all that infinitely variable. This illustrates that with the PWM system we basically use larger nozzle calibres and therefore do no longer have any clogging problems. So much for the functioning and the terms.

terraHORSCH: But that virtually is an individual nozzle control.
Theodor Leeb (smiles):
That’s right. But the advantages of our system are striking. The individual nozzle control a lot of people dwell on actually is only one aspect. Due to the numerous practical experiences our focus is on completely other arguments that are far more practice-oriented.
At any rate, for the farmers it is an innovative technology which prepares them perfectly for the future. For who knows which regulations the legislators all over the world will introduce in the plant protection sector in the future.

terraHORSCH: You already mentioned that the farmer will only have one nozzle that will no longer clog.
Theodor Leeb:
Yes, you do no longer have to hold a lot of nozzles available like before to always have the appropriate set at hand for any application rate and operational speed. On the other hand, the spraying characteristics are no longer influenced by changing nozzles. That means: Regardless of changing operational speeds or different application rates, the application quality and the cover pattern always remain constant as the adaption to the operational speed is no longer made via the pressure but via the Duty Cycle. The pressure and the drop spectrum remain constant. If the operational speed or the application rate increases, the nozzles do no longer have to be adapted. With the pulse width modulation this is carried out automatically by changing of the Duty Cycle. 

In short, the advantages are:

  • Infinitely variable adaption of the volume flow while the pressure and the drop size remain constant
  • Constant drop spectrum when using one nozzle -> few different nozzle calibres are required
  • Curve compensation
  • VariableRate with graduation to virtual 3-meter sections
  • Individual nozzle switch-off for SectionControl

terraHORSCH: We already know the term curve compensation from the Maestro single grain seed drills. When cornering with large working widths the sowing density on the inside of the curve is reduced and on the outside it is increased.
Theodor Leeb:
The same principle applies in plant protection and we tackle a very concrete arable problem: The problem of resistant weeds has increased considerably. The weeds often grow from the field boundaries into the population. The problem is that this often is where you have to corner and because of the different speeds of the outside and the inside of the boom an overdose or an underdose may occur. This can be compensated via the curve compensation. With PrecisionSpray the application rate of every nozzle is adapted to the curve speed via the whole boom and thus an exact application with a constant active agent amount is achieved.

terraHORSCH: So you can cover everything with one single nozzle. But which nozzle is the right one? Or does it work with all nozzles?
Theodor Leeb:
Basically: The longer a nozzle and the larger the air chamber is, the more acute is the risk that the liquid impulses are damped and the nozzle starts to „spit“. Most of the short bubblejet nozzles, however, work very well. In North America, where pulse width modulation has already been used for about 20 years, the farmers mainly use standard flat jet nozzles or special low drift nozzles. But here in Germany, they are either not allowed or do not comply with the 90-% drift class. To be able to give a recommendation, we carried out our own tests in the laboratory and in the field with 90%-nozzles as well as with double flat jet nozzles. From a technical point of view these nozzles from the manufacturers Lechler, Agrotop and Teejet work excellently with our PrecisionSpray. The question that still is unanswered is: Does a 90-% nozzle also comply with the 90% drift class with a PWM system? To answer this question, we are working at full blast the nozzle with manufacturers and the Julius-Kühn-Institute on a corresponding registration. We expect the first results for Germany at the beginning of 2021. Our PrecisionSpray system has already been acknowledged by the Julius-Kühn-Institute with regard to reliability, practical suitability and accuracy of the cross distribution. There are technical possibilities to comply with the current stipulations for customers who already have a PWM system. For if you use a Duty Cycle of 100 %, the nozzle behaves like in a standard plant protection sprayer and the current 90-% registration apply. Thus, you can rely on PrecisionSpray already today without having to worry that you might violate applicable stipulations.

terraHORSCH: At the Agritechnica, in addition to PrecisionSpray you also exhibited a system to monitor the nozzles. What are your experiences in this sector?
Theodor Leeb: You are talking about our NozzlePlugControl - a system that consists of small radar sensors that are mounted in front of the nozzle bodies. To guarantee the practical suitability, we tested several machines with this sensor system in the field during the past season. The tests were very successful. The sensor primarily monitors the area behind the machine which is difficult to see for the driver. The special feature is that our sensor really analyses the quality of the spraying fan and the spraying pattern and thus offers more than a mere flow control. It often happens that a little contamination disturbs the formation of the spraying fan, but the output quantity still is ok. Thus, this option does not only guarantee maximum operational reliability, but also takes some workload off the driver. Our NozzlePlugControl (NPC) will soon be available for our self-propelled sprayers as well as for the LT, GS and TD lines.