“Expert Opinion”: Quick-hitch Operation Overview

Health and Safety along with operator training are the two most important factors when operating a quick-hitch. It is of great importance that operators understand the relationship between their excavator and any quick-hitch used with it. They must for example, know exactly how the locking system on the quick-hitch works for maintenance / operation purposes and also how the excavator is able to control each function of the quick-hitch.

Quick-hitch installation
Excavators are not normally factory fitted with a quick-hitch by the original equipment manufacturer, but instead, this component is usually bought from an independent dealer in a separate transaction and subsequently retrofitted to the machine.

Most quick-hitch manufacturers utilize the same installation procedures and equipment, which might include things like:

* hoses;
* high pressure solenoids; and
* fittings.

However, there are a few quick-hitch manufacturers who use low pressure solenoids. The difference in the operating pressure of each solenoid creates extreme risk and high potential for serious mechanical/operation failure should the solenoid and quick-hitch be mis-matched. A good example of this is when a second hand pre-piped machine fitted with a low pressure solenoid is retrofitted with a new quick-hitch requiring a high pressure solenoid. In such an instance the fitter assumes the ‘old’ solenoid will do the same job and proceeds to fit the new quick-hitch to the existing pipe-work unaware of the high risk he has just taken.

In such instances, the quick-hitch will continue to operate even with the wrong solenoid fitted; thereby ‘appearing’ perfectly safe. But unknown to the operator, when they next apply excess force to a digging attachment using this incorrect configuration, the moving jaw controlled by the hydraulic ram in the quick-hitch can be forced off the rear pin of the attachment. This is due to inadequate pressure being sent by the control solenoid to keep the ram securely engaged.

Most quick-hitch manufacturers interact the auto-locking mechanism in their quick-hitches with the machine’s hydraulic ram movement. Indeed, some auto locking quick-hitches unlock when the ram and moving jaw reach maximum stroke. This type of mechanism could be described as high risk should it be fitted onto an excavator with a low pressure solenoid; because when the rear pin is forced off the rear jaw controlled by the hydraulic ram, the pressure in the system is still high enough to send the ram to max stroke and hence also cause auto lock failure at this point. The operator will only be aware there is something wrong when the bucket falls off the quick-hitch, which is often untimely and can result in other onsite workers becoming seriously injured or killed.


Moving attachments around site

The ability for the machine operator to raise an attachment off the ground using the front open jaw of the quick-hitch is undoubtedly the main cause of buckets being lost from quick-hitches in the entire industry. We know each year about the number of deaths and serious injuries caused by the untimely release of attachments from quick-hitches, but we have no recorded information on the number of near misses. From my expert knowledge of quick-hitch devices and my vast experience in direct sales to end users of this type of equipment I am confident in saying that on average operators accidentally drop attachments from quick-hitches about once a week. And it is always the same set of circumstances which are apparent in each case.

Operators are under too much pressure at work, and often skip time consuming activities such as:

(a) inserting safety pins into quick-hitches;

(b) making a full connection to attachments when they want to move buckets around site; and

(c) carrying out a connection test each time they change attachments.

Known attachment pick-up practices

Over 90% of excavators are sold along with a collection of attachments, usually four digger buckets, consisting of:

1 x digging bucket;

2 x trenching buckets; and

1 x grading bucket.

These four buckets travel along with the excavator from site to site and it is common place to see an excavator operator carrying a digging bucket and one trenching bucket inside a grading bucket. In-fact, some operators build the buckets into the grading bucket in such a way that they can carry all four buckets. The need for the operator to keep these attachments near to hand, causes them to make time saving exercises on how they transport all four attachments around site with the machine. Some operators -- less adept at building buckets together on the grading bucket -- simply catch the front pin of each attachment in the open front jaw of the quick-hitch, raise them off the ground and hurl them down the site with the machine.
The correct way to move attachments around site is of course, to make a full connection with the quick-hitch and place each attachment individually. Both experienced operators and onsite health and safety staff are fully aware of these common practices and both seem quite prepared to turn a blind eye to the risks of moving attachments in this manner. Indeed, it would seem that complacency has set in across the construction industry regarding these known bad practices.

Operator Training

Lack of operator training on how the hydraulic system on an excavator is energised is also of serious concern to the present discussion. When using a hydraulic quick-hitch device, the most prominent and best indicator as to when the quick-hitch is safe, is the control switch inside the cab fitted with a warning buzzer. Basically, it is understood that when the switch is in the “OFF” position and the buzzer is sounding, the quick-hitch is open and disengaging the attachment, and when the switch is in the “ON” position with the buzzer silent the quick-hitch is closed and has engaged the attachment.

Unfortunately, the mere activation of this switch will not cause an adequate amount of pressure in the hydraulic system for the function to be completed. This is due to the fact that when an operator lets go of the joysticks for machine control in the cab to operate the quick-hitch switch, the engine revs cut down automatically to idle. This also cuts down the high hydraulic pressure. To create the high oil pressure required to complete each quick-hitch function, the operator must toggle the linkage joystick inside the cab to bring the machine revs and pressure up, to a level which will cause the ram in the quick-hitch to actuate.

Failure to understand how the hydraulic system on an excavator is energised is the main contributing factor to failed attachment pick-ups. Even experienced operators have on many occasions been confused as to how to raise the pressure in the quick-hitch hydraulic lines. The most common related scenario of failed pick-up, is when an operator connects the front pin of the attachment with the open front jaw of the quick-hitch and curls it into the machine, then activates the switch in the cab to the “ON” position and then begins to slew the machine into a new work position. As the operator is using the joystick in the cab to perform this function, they wrongly believe that it is putting up the high hydraulic pressure on the quick-hitch lines needed to complete attachment pick-up. However it is only the joystick movements which control the linkage that put up the high pressure in the quick-hitch hydraulic lines.

Now that the operator has misinterpreted this, as soon as they open up the attachment to go to work, the rear jaw of the quick-hitch controlled by the ram will miss the second pin and the attachment will fall off. This is a major problem with the current operation system used by the majority of quick-hitch manufacturers, and is primarily down to the fact that quick-hitch manufacturers and excavator manufacturers do not work close enough together to eliminate this mechanical loop hole in the system.

The new CJM auto-locking coupler has been developed to combat all the known operator errors and known risky practices along with mechanism failures we have learned about; from accidents involving attachments being untimely released from couplers. Comprising just two body parts, with a hydraulic ram to operate it and being held together by two retaining pins, its simple yet elegant design offers the most reliable solution to preventing the four most likely causes of unintended attachment release. That is:

(a) The operator is unable to pick-up an attachment without safely securing it into the front jaw of the coupler due to the mechanism operation.

(b) In the event of hydraulic ram failure, the front pin remains locked.

(c) If either the switch is accidentally operated in the cab or the solenoid fails, the CJM coupler will continue to lock the front pin of the attachment.

By virtue of its operating design and inherent auto locking systems, the CJM coupler has taken account of the broadest range of failure scenarios. Resultantly, it thereby offers the safest quick-hitch solution available in the industry today.