Three-point hitch

A three-point linkage, also known as three-point linkage, is a technology developed in the 20th century hydraulic device to tractors to couple and raise Attachments ( attachments ).

The brief also referred to as three-point component is often found on the back of a tractor ( rear linkage ). Attached to the front of the tractor is talk of a front lift. The downward movement is either hydraulically or in simpler systems by its own weight of its elements ( lower link ) or the attachments. Three point is called the system, because the attachments are mounted at three points on the tractor.

Construction

Low on the rear of the tractor are two levers mounted in the longitudinal direction. These are referred to as a link. The lower links are mounted with horizontal oriented transversely to the direction of the shafts or bolts on the tractor. At the free ends of the lower links the field devices are attached. Set the lower two points of the three-point linkage dar. The deep cultivation tensile forces are transmitted to the drive axle, which increases the traction. The lower links are raised, either directly or via a lever system, each with a hydraulic cylinder.

Next above the lower link another lever is mounted centrally. He is referred to as top link. The rearward end of the third point on a three-point suspension. The upper link is designed as a threaded spindle or with heavier tractors and field devices as a double-acting hydraulic cylinder. Due to the change in length of the slope of the attachment can be adjusted.

The attachment points of the upper and lower links are often designed as fishing hooks.

In the attachment is a so-called " A-frame" exists; in this fishing hooks are hooked. When lifting into the transport position the attachment is tilted by the kinematics of the articulation of unequal length in the direction of the tractor and thus shifts the focus of the attachment to the bearing plane of the vehicle. As a desirable for road transport, handling stability of the tractor is obtained.

Function

With the hydraulic three-point hitch allows the field devices

• Transporting stable and secure
• Into working position easily and quickly on the field
• Tune to a certain working depth and automatically regulate exactly in tillage.

Benefits of an automatic draft control:

• Depending on the setting of the dead weight of the hydraulic field device ensures an improvement in the traction on the rear wheels of the tractor.
• It affects more pressure on the rear wheels, making the slip, and thus reduces tire wear.
• Even with high tensile forces, the front axle is not raised. A better steerability is the result.
• All-wheel drive traction on all wheels can be exploited.
• Relieves the driver
• Better quality of work due to constant device position.
• Less wear on the three-point hitch and implements.

Depending on the set working depth and soil conditions, different forces acting on the upper and lower links. The link required to transfer the control of the hydraulic pressure and tensile forces. If only the forces or the movements of the upper arm into consideration, it is called " top link controlled ". By " lower link control " refers to Hubwerksregelungen, in which the control signals are tapped on the lower link.

According to the following scheme, the driving of the hydraulic cylinder is controlled:

• More draw resistance = the hoist lifts the plow
• Less draw resistance = the hoist lowers the plow from deeper.

Depending on the implementation of compressive and tensile forces in control signals are distinguished following systems:

MHR

SHR

EHR

The electronic control system is generally more sensitive and faster than a mechanical control. The elimination of mechanical components, an electronic linkage is wear and less maintenance. The EHR is standard in modern tractors. The draft control can regulate traction dependent or position- dependent. A mixture of two control modes are possible.

Also other functions can be realized through the use of electronics.

• Setting different transport heights for different devices.
• Vibration attenuation during transport.
• Floating position with electronically limited endpoints.
• Traction control
• Programmable working sequences - for example, automatic lifting and lowering for rotating the turning plow at the headland
• Control the working position and the programmed work sequences with the help of GPS navigation data.

At the lower links a drawbar can be attached if required. With old tractors without the three-point hitch bar was rigidly connected to the tractor.

Quick coupler and Dimensions

The three-point fixings are standardized today and equipped with quick couplers. Depending on the PTO power these are divided into the categories 1 to 4. In addition, there is the category 0 for small municipal tractors. The categories are defined as follows:

History

The inventor of the three-point hitch is the Irishman Harry Ferguson. He received in 1918 by the British Department of Agriculture commissioned to increase through the development of agricultural equipment, the efficiency of food production.

In 1928 he designed the prototype of a new trailer system. The aim should be to transfer some of the weight of the attached implement to the tractor to use the power of a lightweight tractor better. From the Duplex Hitch, he developed the three-point linkage. To demonstrate his idea and future manufacturers effectively, he planned to construct its own tractor. He used transmission parts by David Brown and a Hercules engine that came from the USA.

In 1933, Ferguson made ​​in his workshop in Belfast the world's first tractor with hydraulic three-point linkage, the Black Tractor, before. The name was derived from its black finish. The Black Tractor is now at the London Science Museum. In the following years he teamed up with the British tractor manufacturer David Brown. In 1936, the first series tractor with the Ferguson System, the Ferguson Brown Type A

In 1938, Ferguson joined up with the American automobile and tractor manufacturer Henry Ford. 1938 appeared the first Ford tractor with the three point hitch, the Typ 9N.

Ferguson separated from Ford after a long dispute in 1947. Thereupon he built from 1947 to 1953 even tractor. In 1953 he sold his factory to the Canadian agricultural machinery manufacturer Massey- Harris. This Massey Ferguson was created.

In 1979, an electronic hitch control (EHR ) from Bosch was brought to series production with an articulated tractor tractor Massey -Ferguson for the first time.

Historic agricultural impact

The three-point linkage has influenced the agriculture of the 20th century sustainable. Intensive rational, because labor -saving, soil preparation was made possible by their introduction.