Elevator Buffers
Elevator buffers are safety devices that prevent elevator carriages from falling to the pit bottom by absorbing kinetic energy. This helps to reduce passengers’ injury in case of an impact.
Oleo’s range of high speed elevator buffers is designed to allow installation of elevators into even higher buildings. Its range has been developed using computer modelling and analysis as well as its own in house dynamic test facility, enabling optimisation of force control.
Safety
Elevator buffers provide protection from the potential for damage and injury in case of an elevator car free fall. These buffers are usually a combination of oil and springs, which absorb the kinetic energy that is released as a result of a car or counterweight’s movement down an elevator shaft.
The maximum distance that an elevator can travel before hitting the buffer has a significant effect on the safety of the elevator system. This is why it is important to consider the speed of the cab or counterweight in the calculation of a guide travel.
When a traction-driven elevator reaches over rated speeds, the overspeed governor monitors the movement of the cab and activates an over-speed switch to stop the car. This is also how the brake is activated in this type of elevator.
Depending on the design of the elevator, there are different types of elevator buffers. These include hydraulic buffers, energy dissipation buffers and spring buffers.
Hydraulic buffers are a common solution for elevators that do not exceed 1.6m/s. They use oil to cushion the impact of the descending cabin or counterweight and can be installed in either the lift pit or at the top floor.
There are several tests that an elevator buffer must pass in order to ensure its safety. These include drop tests, which involve dropping a mass at the maximum allowed mass range of the buffer in free fall.
Another type of test involves using a weight to simulate the car load, elevator buffer and measuring its deceleration while it falls on the buffer. The results of these tests are used to ensure that the buffer can safely slow down the elevator.
A further test is used to determine the maximum g force that can be applied to the descending cabin, which is also a safety measure. This test is useful to ensure that the buffer will not be damaged by passengers or other elements, and that the braking force does not affect their comfort.
These are just some of the safety measures that elevator buffers can take to make them safer. The next step is to find a good quality buffer that is compatible with your particular elevator.
Performance
Elevators are an important vertical transportation tool, and when they stop suddenly or fall to a dangerous position they can cause serious damage to passengers. To prevent this, elevators are equipped with safety devices such as emergency stop switches and deceleration buffers.
To meet safety requirements, elevator buffers must perform according to code specifications and drop tests. This means that the buffer must be able to stop an elevator car without deceleration or loss of lift function.
Oleo employs computer modelling and analysis to refine elevator buffers performance, comparing simulations directly with test results from our own in house dynamic test facility. This enables us to optimise the elevator buffer for cost, safety and reliability.
The first step is to consider the design of the buffer and determine the optimum combination of parameters that satisfy safety requirements. The combination of design parameters consists of the natural frequency, damping ratio and maximum displacement.
It is also necessary to consider the nonlinearity, velocity dependence and gravity of damping in the buffer. This is a difficult task, and requires the development of analytical models that are able to take all these factors into account.
However, these calculations are a time-consuming and expensive process, which is why it is not always possible to obtain the desired results from these methods. Therefore, a simpler method is required to reduce the complexity of the system and achieve the same level of accuracy.
In order to achieve this, we must use a model that reflects the dynamic mechanism of the elevator and the hydraulic buffer. Currently, there are two methods to simulate the dynamics of the elevator and the buffering process: (1) simulation via finite element (FE) analysis and (2) computational fluid dynamics.
FE simulation is particularly useful for determining the influence of the structure on the dynamic characteristics of the hydraulic buffer and elevator carriage. It is more economical and accurate than a modeling via computational fluid dynamics.
For evaluating the performance of the buffer, drop tests with a freefalling mass are performed. These tests must take place at a temperature of 0degC to 25degC and must be conducted with the buffer in its extended or compressed state. After the freefalling mass has dropped to a certain height, it must remain on the buffer for at least 5 minutes and must then be released to determine whether or not it will return freely to its extended state. This is the only way to ensure that the buffer is capable of performing to code requirements and to protect the passengers.
Design
Elevator buffers are designed to protect passengers by preventing a car from descending beyond its normal limit and softening the force with which it runs into the pit during an emergency. There are two main types of elevator buffers: energy accumulation type and energy dissipation type.
Among these, the latter is more common, as it has an advantage of absorbing a greater amount of kinetic energy during free-falling, while also being much lighter than its predecessors. It is therefore suitable for a wide range of speeds.
The design of elevator buffers is a complex and difficult task, but it is possible to take a few important measures in order to improve their performance and safety. Firstly, the distance between the counterweight and buffer is an important consideration.
As a result, it is necessary to consider whether the clearance between the counterweight and the buffer should be reduced or increased when designing or installing elevators. It is especially important to ensure that the clearance between the counterweight and the buffer does not exceed a certain range, so that passengers are protected during the fall of the elevator.
Another important factor in determining the impact speed of the elevator is the mass of the car and its travel height. These parameters are usually measured during the production process of elevators.
Finally, FE analysis is elevator buffer conducted to determine the relationship between the acceleration of the elevator carriage and the time in which it impacts the buffer. This analysis is a necessary step for estimating the load and g forces, which affect passengers’ safety when traveling at high speeds.
The analysis results show that the influence of the distance between the counterweight and the buffer on the speed of the elevator car is significant. As a result, it is important to increase the clearance between the counterweight and the buffer.
In the present study, a simplified model is established to calculate the acceleration of the elevator carriage when it impacts the hydraulic buffer. The relationship between the acceleration of the elevator carriage and time is obtained, and the corresponding stress nephogram is shown in Figure 6.
Installation
Elevator buffers are a safety device that prevent the elevator car from hitting the floor in case of elevator cable breakage or a reverse situation such as free fall. They are typically located at the base of the elevator shaft and have to meet a number of technical specifications that vary according to the region in which they are installed.
They must also be able to bring an impacting elevator car back down to its original position after a crash. This requires the buffer to be able to compress a test weight before it hits the ground, and then return the plunger to its fully extended position within a prescribed time.
One of the most common types of buffers is a spring-return oil buffer which uses oil to cushion the descending car or counterweight. These devices are most commonly found on hydraulic elevators and speed less than 200 feet per minute.
These buffers have a tendency to be exposed to water and floods so they require routine cleaning and painting as well as being subjected to the testing specified in the NFIP for these components. These tests are performed to ensure that the oil remains leak-free and meets their performance specifications.
In addition, these devices must be able to withstand the rigors of drop tests and retardation tests in which they are subjected to compressed force. The spring-return type buffers must be designed to withstand these forces without appreciable deformation or damage.
To achieve this, the buffer is placed on a foundation that is designed to withstand these forces without appreciable distortion or deformation. This foundation is then filled with a high-quality elevator oil that is compatible with the buffer and its operating environment.
Then, the buffer is subjected to a drop test using the specified load and height to determine whether it can be compressed by the test weight before it hits the ground. This is then followed by a retardation test to measure the delay that the buffer has to return to its fully extended position after the drop test.
In addition, both embodiments of this invention provide a barrier located in the pit directly beneath the underslung pulley box 2 or other equipment mounted under the car 1. This barrier physically deters personnel from inadvertently stepping into the area of reduced vertical clearance thereby enabling the regulatory minimum free vertical clearance C to be determined as existing between the pit floor 14 and the lowest parts of the car 1 rather than between the pit floor 14 and the underslung pulley box 2. These measures enable the installation of a buffer in an area where there is a lower regulatory threshold value of free vertical clearance than would otherwise be necessary, thus saving valuable space in an elevator installation.
