Posted by Simon Johnston
What is a Double Locking Quick Coupler?
Double Locking, Dual Locking and Multi Locking. Locking quick hitches can share various names but with the same general meaning.
Double Locking is a simple way of saying that the hydraulically operated Quick Coupler has mechanical locking devices to hold both pins of an attachment in place during operation.
How do they work?
In principle a "Force Locked" Double Locking Quick Hitch works like this:
There are two mechanical locking jaws that are hydraulically operated. When actuated via in cab controls they lock, this is usually (but not always) accomplished by the crowd action function of the excavator which pressurises the hitch driving the locking function. The same is in reverse when unlocking, a true compliant coupler should only release an attachment when actuated to do so, that is when the operator sets out . This is important as discussed below.
What should it accomplish?
Simply put it, it should make it easier to pick up attachments and then reliably hold them in place while operating, even should something unforeseen occur.
Compliance should also be necessary for any hitch including those that are Double Locking.
The majority of Quick Hitches available on the market today, particularly in New Zealand and Australia use a 'Force Locked' style of locking attachments into the coupler.
As defined in the ISO standard 13031:2016 'Force-Locked Engagement Systems' require continuous application of force to keep the attachment in place as the working force would otherwise release it.
The ISO standard then sets out what these couplers need to achieve in order to be compliant. That is to automatically lock the attachment in place upon engagement, provide indications that the operator can easily identify as being secured as well as continuing to keep the attachment in it's operating position even in the event of full hydraulic power loss.
Additionally they must not allow the attachment to swing in the event of lost engagement force. Swinging from the front pin is hazardous and is completely non-compliant.
Why choose the A2Lock?
The A2Lock features a Double Locking quick coupler that is both "Force Locked" and "Form Locked"
The addition of a form locked device on the rear sliding jaw adds redundancy to the check valve on the ram, this means that should the ram itself fail the attachment will stay locked in its operating position. The check-valve does this by not allowing hydraulic fluid in the ram from flowing back through the hoses releasing pressure. Instead pressurised hydraulic fluid needs to be actuated in the revers direction for it to then push the fluid out. In essence it needs functioning hydraulics to operate.
The fixed position of the pin prevents the rear form lock from moving which also holds the rear jaw in place. It is only by the rams powered actuation pulling the form lock up from the pin that the sliding jaw can then move to fully unlock the rear pin and then move to push the front lock up from the front pin. This addition of double redundancy means that should the check valve fail, or the ram was to break the front and rear pins will stay completely locked in their working position, with working forces not able to overcome them.
Lastly the A2Lock complies with ISO 13031:2016, take no chances with safety, choose the Quick Coupler that meets the standard.
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