Elevator Buffer Types

The elevator buffer is a critical part of an elevator safety system. It is used to stop an elevator car in the event of a control system failure or malfunction.

Elevator buffers are available in a variety of forms. This article explores the different types of elevator buffer and discusses their advantages and disadvantages.

Hydraulic Buffers

A hydraulic buffer is a device that absorbs the kinetic energy of an elevator carriage and prevents its falling to the pit bottom. It is commonly used in the vertical transportation industry to provide safety for passengers.

A typical buffer has a heavy fluid container and a piston that extends into the container to force fluid through ports, which causes progressive deceleration. It is most often located in the elevator pit.

Oil buffers are another type of buffer used on traction elevators and are more commonly found on elevators elevator buffer with speeds greater than 200 feet per minute. They contain a mixture of oil and springs to cushion the car or counterweight in case of impact. These devices are more likely to be exposed to flooding and require routine cleaning and painting to assure they meet the proper performance specifications.

The primary disadvantages of the current standard hydraulic buffers are their comparatively expensive construction, deteriorating piston seals that can allow contaminants to enter the system and fluid to escape during operation, and their requirement for regular maintenance. In addition, these units are prone to accelerated wear and tear from high-speed impacting.

Moreover, these buffers must be tested in the field to ensure they meet their specifications and operate properly. They must be tested with the rated load on the elevator car and a counterweight on the buffer to ensure they are not overloaded or undersized.

These tests must be performed by a certified test engineer. These tests are not only required to verify that the buffer meets its specifications, but also to determine if the unit has any potential weaknesses or failure points.

The simulation analysis of dynamic characteristics of the hydraulic buffer has a significant influence on the design of the buffer and the elevator carriage. Hence, it is necessary to develop accurate modeling methods to predict the effect of the hydraulic buffer on the carriage impacting and resulting in its falling to the pit bottom.

Oil Buffers

Elevator buffers are a type of safety device that is required to be mounted at the base of an elevator shaft. They are designed to prevent an elevator car from free falling to the ground if it is struck by an object such as a door or a counterweight.

They must be installed in accordance with elevator code specifications. They must also be tested to ensure they meet these specifications.

There are a variety of different buffer types and each one has a specific purpose. However, the most common type of buffer used on traction elevators is an oil buffer.

These are generally a combination of springs and oil that cushion an elevator car or counterweight during its descent. They are commonly located in the elevator pit and need routine maintenance such as cleaning and painting to keep them in good working order.

The most important characteristic of an elevator buffer is its ability to bring an impacting car or counterweight to rest with minimal deceleration. This is a critical requirement in the elevator code and it must be achieved by precise control of the amount of retardation that the buffer exerts over its stroke.

This is a function of the buffers length, its striking speed and its load rating. In addition, a buffer’s minimum stroke is specified (within EN81.1 and ASME A17.1) as the distance that is necessary to bring an elevator car traveling at 115% of its rated speed to rest with a uniform deceleration of 1g.

A hydraulic buffer can be designed to closely match this idealised performance, but it is difficult to do because the range of elevator masses that are encountered in the real world are much more variable than the impact mass. This means that it is not possible to provide an elevator buffer with the same retardation force across a wide range of loads and it is not desirable to try and do this in an elevator.

This is a key problem in the elevator industry, where passengers are at risk. By reducing the amount of retardation that the buffer exerts during its stroke, a new elevator buffer embodying the invention can minimise this effect.

Spring Buffers

There are a number of different types of buffers used in elevator systems. One of the most common types is the spring buffer, which is designed to stop a descending car or counterweight from hitting the ground hard during an emergency situation.

As with most safety devices, there are a number of specifications that are required to be met by the buffers in order to ensure their operation is safe and effective. These include the manner in which the buffer must bring an impacting elevator car to rest, the height at which the buffer is required to be installed and a number of other considerations that must be taken into account.

The main objective of the design process for any elevator buffer is to achieve an optimum balance between the peak deceleration force and the average deceleration. This is a key performance criterion that most elevator code and industry specifications require to be achieved.

Oleo elevator buffers are able to achieve this idealised performance through the precise control of hydraulic oil flow across an orifice throughout the buffer stroke. This enables them to closely match the idealised peak deceleration performance of an elevator car.

However, the problem with this approach is that it can only be achieved for a single impact mass. This means that when the elevator car mass varies, such as in the case of the passenger load, the performance of an elevator buffer cannot be guaranteed to match this.

For this reason, Oleo employs computer modelling and analysis to refine the performance of its elevator buffers. This allows them to optimise their performance, resulting in reduced costs, improved reliability and increased efficiency of the buffers.

Moreover, these simulations also allow the designers to compare the results of their simulations with the actual performance data they collect on Oleo’s own dynamic test facility. This is a valuable tool for ensuring that the design of an elevator buffer will achieve its intended elevator buffer performance – it’s not possible to know if your elevator buffer will meet its specification until it has been tested on site.

Telescopic Buffers

Telescopic buffers are a type of elevator buffer that can be adapted to different elevator configurations. They are used to reduce the number of elements required in a buffer and can be designed to meet specific requirements for stroke length and overall height.

In elevators, the main purpose of an elevator buffer is to slow the elevator down as it approaches its destination, allowing passengers to disembark safely. In order to accomplish this function, buffers are subjected to a type test to verify they meet the standards set forth in European specifications EN81.1 and ASME A17.1 before they are sold to the market.

Most elevator buffers are based on a single-stage design, consisting of an upper piston, a lower piston, a cylinder, a head bearing and a packing (on each piston). They can be designed with internal or external synchronization, which allows each piston to fully extend before the next piston moves.

An advantage of this design is that it can accommodate a larger freefall distance than a single-stage jack, which makes them ideal for use in higher rise and faster elevators. However, the disadvantage is that they can be difficult to service if there are any leaks or seepage in the system and must be plumb for resynchronization.

To reduce the bouncy ride and the need for resynchronization, some telescopic jacks have air-relief ports on each piston to drain out any air that may be in the system. In addition, if the jack is in automatic mode, it should be programmed to resynchronize after a set number of elevator runs.

Another advantage of a telescopic buffer is that it can be used to replace an in-ground cylinder, which is usually more expensive and requires longer installation times due to the need to drill holes. This can also create potential contamination problems and is less effective than a hole-less design, which is safer and can be easily inspected for leaks and corrosion.

Telescopic buffers are also a good solution for smaller and medium sized elevator applications where the cylinder is located above ground, where it can be easily inspected, maintained and remains safe from oil leaks and corrosion. They are a cost-effective solution for complicated space requirements, modernization or new construction designs that require a cylinder replacement.