Product category:
Cranes, hoists, winches, chains and ancillaries
News Release from: Bosch Rexroth | Subject: Inverted tooth chains
Edited by the Manufacturingtalk Editorial
Team on 31 July 2003
Inverted tooth chains have no projecting
rivets
Latest inverted tooth chains feature link plates with laser-welded pin ends, so there are no projecting rivets and the chain presents a smooth contact surface on both sides.
The latest inverted tooth chains from Rexroth feature link plates with laser-welded pin ends There are no projecting rivets and the chain presents a smooth contact surface on both sides, which means it can be mounted directly alongside dead plates or side rails and, as each side is identical, it is suitable for both directions of travel
This article was originally published on Manufacturingtalk on 17 Jul 2001 at 8.00am (UK)
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Incorporating Rexroth's renowned 2-pin rolling pivot joints, a CAD-CAM optimised link plate design and edge rounding to reduce friction, it represents the current state-of-the-art in inverted tooth chain technology.
Silent or inverted tooth chains date back to the turn of the last century, yet the technology is still highly relevant to countless power transmission and materials handling applications in modern industry.
Silent chains provide the drive for high powered motorcycle and car engines and are used in transmission gearboxes; they power machine tools, plastics and woodworking machinery, coilers, coaters, grinders and shredders; convey workpieces, goods trays, pallets and sub-assemblies in the automotive, electronics and engineering sectors; ensure precision transportation of hot and cold product in the glass industry.
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End-users in these and other fields acknowledge inverted tooth chains' capacity to transmit high power and high torque in confined installation spaces, with no slippage, less noise and longer service life, at speeds up to 50m/s and efficiencies up to 99%.
To understand how these substantive operating advantages accrue, it is necessary to revisit the structure of the inverted tooth chain in general and Rexroth products in particular.
Typically machined from case hardened steel, the inverted tooth chain comprises toothed plates or driving links, guide plates that hold the chain in track, and rolling pivot joints consisting of two profiled pins.
Fastened by rivet washers or laser welding, the plates are connected by the pivot joints in a staggered configuration, giving a lamellar construction, and the actual drive or conveyor chain is made up from multiple plates and pivots, according to the required length and width.
The lamellar structure results in a highly compact chain, with load bearing plates making up the entire width; it also features interspaces through which air can escape, thereby eliminating the whistling noises that are encountered with toothed belts.
One of the main design features of Rexroth inverted tooth chains is the two-pin rolling pivot joint.
During chain articulation, the two profiled pivots roll against each other smoothly, removing the sliding friction that occurs with single pin joints and other pintle chain formats, as well as contributing to less wear elongation.
It also minimises the chordal action that causes other chains to vibrate during rotation.
All this results in very high efficiency, minimal chain heating and wear, and extended load and speed capacity, enabling narrower widths to be specified for a given application.
The cause of operating noise in chain drives is the entry impact that occurs when links mesh with the sprocket teeth, the intensity of this resulting from the mass of the chain link, the impact velocity and the angle of contact.
The coefficient of impact for inverted tooth chains is considerably lower than for other types, due to the design of the sprocket and the load-bearing tooth plates.
Sprockets for inverted tooth drives have involute teeth and the toothed plates, whose outer flanks are oriented at an angle of 60deg, engage so deeply in the tooth gaps that both flanks make contact.
As a result, the impact speed is nearly half that of roller chains and noise is greatly reduced, hence the term 'silent chain'.
The lamellar construction also allows chain pitches to be sized smaller, reducing the impact speed and operating noise still further.
Moreover, since all pivot joints wear at the same rate, it means no irregular link stretching and a greatly prolonged service life.
These inherent characteristics promise significant performance advantages for both power transmission and conveyor applications.
For drives, inverted tooth chains deliver extremely smooth and silent operation, high efficiencies up to 99%, low lubrication and maintenance requirements, zero tooth-flank backlash and outstanding durability, with the capacity to transmit high torque and power in confined spaces.
Whilst for conveying duties, they additionally offer no slippage and near-constant surface velocity, functional reliability and long life, a flat and uniform bed for trouble-free transporting of workpieces, space-saving and versatile installations, heat-resistant materials, and conveying chains without a rigid backing, for cooling and other purposes.
Rexroth provides these technical characteristics in a whole series of drive and conveyor chains.
Type 300 is the company's standard tooth chain drive, in pitches between 5/16in and 21/2in, which has widespread, economical applications and comes with a matching range of sprockets between 13 and 150 teeth.
HDL chains are a further development of this design, with a revised pin profile, which caters for higher power requirements and speeds up to 40 m/s.
Whilst the latest HPC generation of 1/2in chains, featuring optimised tooth plate shape and pin joint kinematics, is yet stronger, quieter and faster, now delivering record-breaking speeds up to 50m/s.
Biflex chain drives have double-sided toothed plates, permitting both sides of the chain to mesh with a sprocket and enabling them to drive shafts that operate in counter directions; thus, a typical S-shaped wrap will enable any number of shafts to be driven by one Biflex chain.
Whilst a ZK inverted tooth chain coupling, consisting of two half-width sprockets and a silent chain wrap, enables two shafts to be close-coupled, with great elasticity and the option of radial and angular offsets.
Rexroth's KT type conveyor chains, marketed in 1/2in, 2 x 1/2in and 1in pitches, start with a simple, rugged single-pin system and include two-pin designs with vee-section dog plates, for holding round and profiled workpieces firmly in place.
The latest RS laser-welded chains, with no side projections, two-pin rolling pivot joints and even longer service life, feature extra edge rounding on the link plates, for improved sliding capability, less bottom damage to contact surfaces and reduced risk of 'stumbling' of workpieces, especially narrow-based bottles.
Rexroth also offers stainless steel chains for hygienic and pharmaceutical applications and ceramic pads for enhanced thermal insulation, as well as cleaning disks to prevent dirt accumulation between the plates.
Manufactured in Europe to DIN ISO9001 standards, Rexroth inverted tooth chains have applications across a broad spectrum of industry, including machine tools, plastics and rubber processing, automotive manufacture, building materials production, cranes and elevators, wire and cable making, food production, the glass industry, steel foundries, papermaking, printing and packaging, chemicals and pharmaceuticals, woodworking, ceramics, textiles and general automation.
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