KOBA Shock Absorbers & Buffers

Hydraulic Shock Absorbers

Today, the production scale is getting larger, and the production speed is also increasing, so productivity is getting higher. On the other hand, due to the influence of this high speed, the impact force is extremely high, and vibration occurs, deteriorating the working environment and causing problems in production facilities due to fatigue load. Therefore, failure to take appropriate shock and vibration countermeasures may cause damage to the system or equipment.

KOBA has developed innovative shock absorbers through continuous research and development and is supplying various products that are significantly improved compared to existing products, and the developed products are optimized for performance even in systems subjected to high impact forces.
In addition to the sophisticated design, durability has been increased to extend the product's service life, the range of effective weight values has been further widened, and the energy absorption capacity has been doubled compared to the previous model.

Rubber & metal springs or hydraulic and pneumatic devices are used as parts that have the same function as the shock absorber, and the shock absorption characteristics are as follows.

Rubber & Spring	When decelerating a moving object with rubber or spring, the compressive force is not constant — when compressed, the resistance gradually increases. The impact energy is then stored without absorption and is transferred back to the object as is.
Hydraulic & Pneumatics Devices	When decelerating using a single-hole orifice, such as hydraulic cylinders, dashpots, deceleration valves, etc., a large initial resistance is generated. In the case of pneumatic devices, on the other hand, the resistance gradually increases, so that the maximum force is applied at the end of the stroke.
KOBA Shock Absorber	KOBA Shock Absorbers absorb impact energy at constant resistance through all the stroke sections by using multiple orifices to minimize the impact force when moving object is stopped. Thus, KOBA shock absorber can stop moving object softly by minimized impact force.

Shock Absorber’s Overview Structure and Function

1. Shock Absorber consists of Body, Bumper Head, Piston Rod, Adjustment Dial and Lock Nut.
2. The body is composed of a screw thread, which effectively dissipates heat due to shock absorption, and can be used more conveniently by using a screw when mounting.
3. Bumper Head acts as a stopper.
4. Piston Rod transfers the impact energy applied to the Bumper Head to the piston.
5. The Adjustment Dial can adjust the buffering force according to the collision speed, so it can be used conveniently according to the collision load and speed.
6. The lock nut can be used with the thread of the body to accurately and stably fix the mounting position.

Shock Absorber’s Internal Structure and Working Principle

Principal of Energy Absorption

Orifice Feature

Single Orifice
Single Orifice Type has a dashpot structure with gap between piston and Inner tube or one hole.
resistance characteristic is shown as below. Orifice area is same on entire stroke section, so resistance force is increased immediately after collision. And as stroke progress, the speed decreases and resistance force minimized at the end.

Multiple Orifices

• Adjustable

  By using multiple orifices, total oil route dimension is decreasing when the stroke is on-going. It enables to maintain total shock absorption safely and softly. Adjustment dial can provide best deceleration features against various collision cases.

• Self Compensating

  Operation principal is same of adjustable type. When it set to the optimized orifices’ area is applied, adjustment is not possible after that. Diagram A1 shows high velocity – light impact mass, B1 shows low velocity-heavy impact mass.

Technical Information

Model	KHG	KHS
Adjustment type	Self adjustment type	Self adjustment type
Applied fluid	Oil, N2 Gas	Oil
Allowed Speed	0.2~4.5m/sec	0.2~3m/sec
Temperature ranges	-20~80℃	-20~80℃
Return mediator	Nitrogen gas	Coil Spring
Pistion rod	Hard Chrome (25㎛ or more)	Hard Chrome (25㎛ or more)
Body, Bumper head	Epoxy paint coatings	Epoxy paint coatings
Application	Over head crane, Transfer car, Stacker crane, Gantry crane, Transport equipment

Rubber Damping Low damping High spring

Spring Damping Low damping High spring

Hydraulic Buffer Maximum damping Low gas spring

Operation Principle KHG Series

When the moving object collides with the bumper head, the internal check valve is closed, and the oil chamber is compressed. The compressed oil flows into the orifice bar through the multiple orifice hole and it absorbs the shock. In addition, as the piston rod enters the inside of oil chamber, the oil amount as much as the piston rod volume presses the chamber piston to compress the gas chamber (performs the accumulator function), so that the pressure inside the gas chamber is increased, absorbs shock energy over the entire stroke ranges.

When the shock absorption is completed, the compressed gas chamber is forced to the oil chamber area, and the check valve installed in the piston is opened to return the piston rod to its original position.

Operating principle of KHS Series

When a moving object collides with the Bumper Head, the oil escapes through the multi-orifice using the internal piston to absorb the collision energy.
After collision, the compressed piston rod returns to its original state by an external return spring.

Features of Hydro Check

Accurate movement speed control and position control are possible, and speed control is possible finely with any moving equipment, and various types are prepared for each stroke. Hydro Check is convenient to install and adjust, and precise feed can be obtained by finely adjusting the Adjustment Knob in the range of 300°, extending the life of the tool. The piston rod uses a material that is resistant to corrosion, and the body is plated to prevent damage caused by the working environment Snap rings and mounting blocks are used for accessories to simplify installation and to move and fix the location. The oil inside the hydro check is self-filtering, so the speed is controlled constantly, so it is convenient to work in any condition.

Features of Step Check Unit

The Step Check Unit has the same speed control function as the Hydro Check, with the difference that it has an intermediate stop function at the desired location. It is used for long drilling work, work that requires precision, work that requires chip discharge in the middle, and can be customized for special purposes.

Structure & Specification of Gas spring

There are several types of gas springs depending on the application, and the general structure is composed of cylinder, piston rod, and end cover.

Nitrogen gas is compressed inside the cylinder, and the piston's check valve and orifice operate to control the speed during tension and compression, so it can be controlled safely and smoothly.
Gas spring can receive a large load with a wide range of spring characteristics, long stroke, small spring constant, and small size, and it is possible to control the operating speed during compression and extension, so it can be applied and installed in various fields. Compared to general plate springs and coil springs, stable power can be obtained, so it is used throughout the industry.

Comparison of spring performance curves

Install Method

F = (m×g×B)/(A×n×0.95)(N) F: Spring force (N) m: Door weight (kg) A: Distance from hinge to gas spring (m) B: Distance from hinge to door center of gravity (m) N: Mounting quantity of gas spring G: acceleration due to gravity (9.8 m/s 2 )

GAS SPRING should be installed with the body part facing upward as shown in the picture for smooth operation.