The main parts of diesel forklift- History of forklift (Part 3)

Later, the German company STILL forklift created a very economical hybrid diesel-electric device instead of a diesel engine. In Europe, the United States and Japan, forklifts with diesel engines are losing their leading position in the market. This is not only due to stricter environmental standards. One important reason is warehouses, distribution centers and workshops that rely on electricity to regulate temperature have built up. Obviously, forklift powered by diesel oil is obviously excluded from the internal logistics.

Nevertheless, diesel forklifts continue to be used in the European market. There are several reasons for this. First, the cost is relatively cheap compared with electric forklift. It is easy to purchase and has less investment in energy consumption and maintenance. Secondly, diesel engine is still a reliable, easy to maintain, powerful and efficient power plant. Of course, the biggest drawback is the emission of smoke and dust. With the change of engine speed and the use of sulfur-containing diesel, the smoke emission will further increase. To some extent, this problem can be solved by a particulate filter. According to the variety and type, harmful emissions can be reduced by 70% to 98%. But even today, up to 4% to 5% of diesel forklifts are equipped with such dust filters.

Through X-ray, we can clearly see the location of the main parts and 3D structure of the electric forklift

Compared with diesel, the forklift also uses a gaseous fuel – Petroleum and natural gas. This by-product of petroleum refining, when used as fuel supply, is usually a corresponding reconfiguration of the gasoline engine. Forklift buyers can choose a hybrid or pure gas fuel.

In the case of a hybrid system, the driver can “switch” the forklift from gas to gasoline. When it is not possible to add gasoline directly, the driver can use the gas in the spare cylinder as fuel. And vice versa. In general, forklift trucks run out of gasoline and the indicator lights signal when the driver must connect the spare cylinder. However, when using gasoline and natural gas fuel, the engine power is different. Therefore, it is not reasonable to match and make the best use of it. Forklift users will choose to use gas engines in most cases, and the use of pure gasoline engines on forklifts is rarely found in Europe. More than 95% of the gasoline engines on forklifts use processed gas fuel.

Lifting device

Using new materials and manufacturing rigid structures with higher bending capacity and strength. The manufacturer can reduce the weight of forklift gantry, improve the stability and safety of cargo landing at higher altitudes. By the beginning of the 21st century, the maximum gantry height of conventional forklift with counterweight is about 8m. For high outrigger forklift is about 10m, for some combined forklift and stacker, the maximum height is about 12M.

In automated warehouses, high-level stackers with lifting heights of 15 to 18 m are not uncommon. In order to ensure the movement of goods at this height. The transport equipment is equipped with special anti-vibration and impact compensation systems to prevent uneven floors.

In the original forklift, gantry tilting was accomplished by using a mechanical system with gears and racks. It was not until later that the use of individual (or in special cases, the use of dual tilt cylinders) began. At present, the gantry of the forklift is tilted by two hydraulic cylinders. One end of hydraulic cylinder is fixed in the middle of the gantry, another end is fixed at the chassis. For example, Linde forklift has one end of tilt cylinder fixed to the cab top, another to the middle of the gantry. This not only increases the stiffness of the gantry, but also provides a barrier-free view for the forklift driver, and increases the safety of the work.

Hydraulic system

Since the mid-1930s, the hydraulic cylinder is powered by a hydraulic pump, which is driven by the engine. As a result, it’s possible to use chains instead of cables and forks as before to lift the gantry. The first manufacturers of this second generation gantry were towomotor (L-type) and Clark (tructier model) in the United States. Tructier B even has a retractable extension of the lifting gantry.

In the late 1930s, a gantry tilting device appeared. To adjust the inclination, the gear pump with brake is first time to change the tilt speed of the gantry. In 1937, TOWOMOTOR used hydraulic devices to adjust the tilt angle of the telescopic gantry of its Cu Series forklifts. The tilt cylinder is controlled by a hydraulic valve block. The next step is to replace the hydraulic control valve with a multi-way valve. It enables the tilt angle to be changed very precisely with the help of a small joystick. These levers are located next to the driver, even on the right armrest of his seat. Therefore, the control dev ice of forklift gantry becomes more ergonomic, safe and compact. The long rod of the hydraulic valve completely disappeared. Firstly, the hydraulic valve on the inner side of the front wall was located under the cab floor. In the 1990s, the hydraulic system became a high-pressure system, designed for about 200 bar (instead of previous 140 bar). This not only makes the lifting and tilting cylinder more compact but also improves the lifting speed. So that the driver can get a better view between the mast posts.

Only in the mid-1950s. Heavy machinery steering (with rack and pinion) was replaced by the hydraulic servo system invented by Francis W. Davis. We are talking about a hydraulic drive system with a valve, which is first built into the side steering cylinder and then under the steering column, which is located on the side of the forklift. In the 1990s, forklift manufacturers made the double-acting control cylinder into the rear axle, that’s hydrostatic control rear-cylinder steering. Later, in the late 1990s, electrical control devices basically replaced manual hydraulic or hydrostatic. Because of electronic control, the sensor can record the angle and direction of the driver turning the steering wheel.

When the forklift is braked, the hydraulic system greatly improves the operation comfort and safety. Early production forklifts were equipped with mechanical brakes. Later, the mechanical brake was replaced by the main brake hydraulic cylinder. Soon, hydraulic brake amplifiers will become standard equipment on at least medium and heavy-duty forklifts. With its help, the driver can easily get a lot of braking force by pressing the pedal. As mentioned above, hydraulic disc brakes have been used in some heavy-lift Korean forklifts, which greatly reduces maintenance costs.

The hydraulic system is widely used in forklift, which paves the way for the latest development of forklift accessories. As early as the late 1920s, YALE forklift company first provides hydraulic fittings as tilting fork as forklift accessories. Since the 1950s, the company has been providing customers with lateral movable hydraulic fittings (adjustable forks) for forks. In the 1990s, the built-in lateral moving accessories and others, especially on 5-ton or more forklifts, were even considered standard. This not only reduces the overall size but also improves the view through the mast, thus improving safety.

Hydraulic Parts

Forklift Accessory

One of the most common working mechanisms of forklift is the shift mechanism of the lateral displacement fork. The transverse moving fork first appeared during the Second World War, and was installed on the crossbeam of the fork. This reduces the payload by about 10%. The lateral displacement fork is usually built into the bracket, so there is little loss of load capacity. The lateral displacement value of the fork is stipulated by EU standard. For forklift with maximum load capacity less than 5 tons, the lateral displacement shall not exceed 100 mm. In this case, the redundant capacity will not be reduced. The integrated lateral movement mechanism and other accessories provide greater redundant load capacity because of the reduced size and weight. The new lateral shift mechanism has a box-shaped profile. Through this design, the fork and the cargo can be seen better, thus improving the safety of the driver.

Lateral moving mechanism