Chain is unique among power transmission equipment with its facility for add-on attachments that simplify the conveying of products across all sectors of industry, usually at quite low cost. Attachment chain is used widely in general manufacturing industries and in the production of electronics and small electrical components. In addition, its inherent flexibility also means that it is employed in such diverse operations as can making (pin oven chain), book binding and even in the production of casings for sausages.
Attachments Are Low Cost, But Many Are application Specific.
Although attachment chains are low cost conveying devices, they do have one fundamental problem.
The characteristics of the conveyed materials and the working environment are usually different for each application.
This means that many different types of attachment are required.
In fact there are potentially so many types that it would be difficult for chain manufacturers to satisfy all customer requirements for quality, price, and delivery if every type of special attachment chain were made.
Tsubaki divides chain attachments into three categories: Standard, Plus * Alpha and Special.
By their very designation the standard attachments are the most commonly used and feature in this article.
In most applications standard attachments - A, K, SA, SK, E-1, and E-2 types - are used with small pitch conveyor chains to convey materials in one of two ways: either directly on the attachments, or on jigs installed on the attachments.
The attachments can be fitted to a wide range of standard Tsubaki chains, including those used in arduous environments.
For operation in these environments the attachments are designed to fit nickel plated chains, chains employing Tsubaki's unique DP anti-corrosive surface coating, and also stainless steel units.
Another major vehicle for attachment chains is Tsubaki's unique LAMBDA* series, lube-free chain.
The lube-free qualities are particularly useful in conveying applications, in industries like food and electronics, where product contamination is totally unacceptable.
'A' Type Attachment.
The most commonly used attachment is the 'A' type.
This has a bent link plate that extends out on one side of the chain, forming an inverted L-shape.
The attachment interval can vary (for example, on each chain link, every five links, or two attachments in a series with intervals every four links, etc.).
Generally two strands of chains with slats are used with this type of attachment.
In common with most attachments, the 'A' types are subjected to bending force.
If they convey heavy objects, have long jigs installed or receive side loads, twisting force is added to the bending force.
Depending on the application, these forces must be considered by the designer when calculating the type and size of attachment to be employed.
Another consideration is that the shape of the attachment influences the design of the equipment.
If slats do not cover the chain rollers, guide rails may be used to support the chain rollers on the return side.
'A' Type Attachments - Uses.
'A' Type attachments provide a sound and stable base for general conveying applications such as moving boxes or pallets.
They offer advantages over rollers where heavy or fragile items are concerned, as the item remains static and so relatively safe on the conveyor surface.
Another application example is plastic wrapping stations for pallets and boxes.
Here the chain is used to convey the aforementioned items onto wrapping tables where they are wrapped and then dispatched as part of an automated production line.
'K' Type Attachments K type attachments differ from A types in that they can convey objects directly, without jigs or slats.
The K attachment is essentially two A types, one on each side of the chain.
An advantage of the K type is that the top of the attachment is higher than the rollers.
Consequently, slats or jigs can be installed over the chains.
'K' Type Attachment - Uses.
K types perform similar tasks to the A version but are used where heavier objects are being transported, such as loaded pallets and metal products for example.
Increased stability is achieved from a firmer fixing to the load-bearing member.
'SA' Attachment.
In contrast to the 'L' shaped A and K attachments, SA attachments are vertical plates that are extended on one side of the chain.
They have one or two bolt holes (designated SA-1 or SA-2) installed for the fastening of jigs, hooks or slats.
The attachment interval can vary the same as the A attachment.
The SA attachment is simpler and stronger than the A type attachment, and may receive bending and twisting force depending on the direction of the loads.
A guide rail can support the rollers on the return side of the chain if fastening bolts do not extend into the attachment.
'SA' Attachment - Uses.
With a pusher mechanism installed on the attachment, products that are in bar form, such as steel stock or tubing can be lifted or indexed either from a vertical stack, or from a lateral feed mechanism.
The conveying of lighter duty objects such as newspapers is also a popular use for SA attachments.
When a cam is attached to the SA attachment this can act as a trigger, releasing product onto a conveyor from a chute or hopper, for example.
The same arrangement can also be used in a lifting and release application.
Here, a good example is raising a baking tray to 'tip product off' when the tray is removed from an oven.
In addition to these applications, added utility is provided as the holes in the extended plates can be used for hooking items onto a hanger in any continuous or semi-continuous processing application, from dry cleaning to metal plating.
'SK' Attachment.
SK attachments are made by installing SA attachments on both sides of the chain.
Usually they are used with dogs or jigs and are strong enough to stand up to bending or twisting forces.
'E' Attachment - (Extended Pin).
With E attachments the one end of the pin is extended.
Depending upon the application, the extension can be relatively small or, for applications such as can making, quite considerable.
Irrespective of the length of extension required, the extended pins are subjected to bending and shearing forces.
The allowable load of these attachments is based on a bending force concentrated at the centre of the extended pin.
This force can be offset, partly, by employing guide rail supports on the rollers on the return side of the chain.
Where enhanced levels of support are required two sets of E attachment chains can be connected to crossrods, or jigs (such as blocks) may be installed.
'E' Attachment - Uses.
Chains with extended pins or rollers attached are used to perform tasks such as pressure testing of aerosol cans on a production line.
Even longer pins are used to hold cans in a drying machine.
In addition, pairs of chains with rods fitted between them, and with a block or attachment fitted over the attachment have been used as indexing triggers on machines and production lines, and for moving large volumes of sheet materials such as steel, glass and plastics.
Special Attachments.
In a minority of applications standard attachments do not 'fit the bill'.
In these instances Tsubaki can make a number of special attachments to order.
The major considerations when specifying and using these are the accuracy required, the cost and the delivery time.
Because of the enhanced accuracy and the (usually) small quantities involved, cost can be an issue.
Here the potential user should ask himself two questions.
Firstly, can the application - and the final product cost - bear the outlay on bespoke equipment?
Secondly, does the application really require such levels of accuracy anyhow?