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Arrow-white How does the Sure-Grip work?

Posted by Jacob Hart
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May 27, 2021

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9 mins read

Quick coupling systems and it's safe operation are one of the most important safety systems on excavators today. With earthworks operations undertaken in close proximity with tradies, specialists and engineers, attachment and work tool retention is of utmost importance.

The ISO 13031 standard was produced from the need for a safety standard for automatic quick hitches. However, as earthmoving equipment, tools, and work requirements progressed, traditional hitch systems were not without their flaws presenting risks to the health of a company's staff.

This article will explore how the Sure-Grip hydraulic quick hitch functions and meets the ISO 13031:2016 requirements for safe operation.

 

ISO 13031 2016
International Organization for Standardization (derived from the Greek ‘isos’ meaning equal) The specific standard, indicated by a numerical sequence The year the latest version of the standard was published

 

(i) What is the ISO 13031:2016 standard?
Find out more about this standard by clicking here, including the abstract of requirements.

(ii) What about AS 4772-2008?
The Australian Standards Authority follows a similar pattern to the International Organisation for Standardisation when defining standards. The difference is the ISO standard defines just fully automatic quick hitches, whereas AS standards defines a range of hitch systems.

In the case of AS (Quickhitches for excavators and backhoe loaders), it contains all the same principles of safe operation as the ISO standard, with ISO, generally considered the gold standard by which all other standards creation bodies across the globe work with to adapt to their countries needs and requirements, but aren't always as strict or specific as the ISO version.

 

What does a Quick Hitch do for you? 

Before we dig into the details of the Sure-Grip functions, let's outline what a fully automatic quick hitch must do.

A fully automatic quick hitch must do these things:

  • Pick-up attachments with coupler operation undertaken from the cab, no manual operation from outside the excavator is required to complete the locking of the tool.
  • Visually identify that the attachment or tool is locked in place.
  • Retain the attachment and excavator tool safely and reliably, even should unexpected damage to hydraulics or in part to the quick hitch occur.
  • Release attachments with coupler operation undertaken from the cab and with no manual operation from outside the excavator required to complete the unlocking and release of the tool.

A fully automatic excavator hydraulic quick hitch needs to pick up and hold attachments without outside manual operation. Reliably hold it in place even should something unexpected occur and show the operator in the cab that the attachment is locked correctly. Then in reverse, release it without external manual operation.

Sure-Grip quick hitch on volvo excavator

How the Sure-Grip Quick Hitch works

The Sure-Grip quick hitch uses a forced-locked engagement system. 

Defined in the ISO 13031:2016 standard is an excavator Quick Hitches ability to continue engagement of the attachment and stop disengagement. One of these types of locking systems is the 'force-locked engagement system'.

The Sure-Grip coupler uses a hydraulic cylinder that provides continuous engagement on the attachment pins to stop unintended disengagement.

Using a hydraulic cylinder means that the hitches locking system needs continued engagement force (hydraulic pressure) to ensure the coupler stays engaged with the attachment.Sure-Grip quick hitch components exploded view

The Sure-Grip's engagement system is a sliding jaw (1), the engagement force is the hydraulic cylinder (2); these work together to form the initial function of the Sure-Grip quick hitch.

But more than just a hydraulic cylinder is needed to meet ISO standards for full compliance, as further described in the additional locking systems.

 

Sure-Grip Locking Systems

Primary locking system (captive spring)

The primary locking system is required to prevent disengagement of the attachment, stopping accidental release if the engagement force is lost, reduced or removed, ensuring the attachment stays in the working position (does not swing).

The Sure-Grip uses a large captive spring fitted around the hydraulic cylinder that provides a continuous force on the sliding jaw to stay in the engaged/locked position. If the force provided by the hydraulic cylinder (engagement force) is lost or removed, the spring will ensure the sliding jaw continues to maintain sufficient engagement to remain locked.

Sure-Grip quick hitch locking spring

 

Secondary locking system (front lock)

The secondary locking system provides further redundancy, so the attachment stays attached to the coupler in the working position should a fault in the engagement system occur.

The front lock aids the captive spring in maintaining engagement as the attachment would have to overcome the spring engagement force AND the fixed front lock to become detached.

NOTE: The Sure-Grip's front lock is not designed to produce a swinging attachment in the event of an engagement system failure; with the correct connection of the attachment, it will not swing. Only a sliding jaw miss-engagement and subsequent use without the visual and bump check will produce a swinging attachment; it's important to follow correct quick hitch procedures to prevent health and safety risks.

The secondary lock is located on the front pin and is activated by the sliding jaw. When the sliding jaw disengages from the attachment and fully retracts, the tongue lifts the front lock allowing the attachment to release.

When the primary locking system is activated to engage an attachment, the sliding jaw will release the front lock, allowing it to snap into its default state, locking the front pin. 

The front lock cannot be released without the hydraulic cylinder retracting the sliding jaw back to the fully unlocked position. 

Locked

Sure-Grip quick hitched in locked positionUnlocked

Sure-Grip Quick Hitch in unlocked position

The Sure-Grip's primary and secondary locking systems, the heavy-duty captive spring (1) and the secondary locking system – the front form lock (2).

Other safety features of the Sure-Grip

Like most other quick hitches on the market, the Sure-Grip is fitted with a check valve. The check valve prevents the loss of cylinder pressure if hydraulic pressure is lost. The check valve achieves this by not allowing hydraulic fluid in the ram from flowing back through the hoses, releasing pressure. Instead, pressurised fluid needs to flow in the opposite direction to allow hydraulic fluid to pass through. In short, it needs functioning hydraulics to operate from both lines.

Internal quick hitch locking cylinder and safety valve

Why a Sure-Grip is the best Quick Hitch base

The Sure-Grip quick hitch has been developed continuously over two decades to suit New Zealand and Australia's earthmoving industry by keeping it simple to operate without compromising safety.

Sure-Grip Quick Hitch Benefits:

• 3-year warranty*
• ISO, AS, EU Compliance
• Nationwide support in AU / NZ
• Same base used on Heli-Tilt and Ram-Tilt

 

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