GB2471720A

GB2471720A - Excavator quick hitch mechanism

Info

Publication number: GB2471720A
Application number: GB0912031A
Authority: GB
Inventors: Patrick Roache
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-07-10
Filing date: 2009-07-10
Publication date: 2011-01-12
Also published as: GB0912031D0

Abstract

A quick hitch mechanism for attaching an excavator bucket of the type having a spaced pair of horizontal mounting pins (9,10), the hitch mechanism has a fixed hook (11) engageable with the first (10) of the pins and a first pivoted hook (3) movable by a hydraulic ram (8) from a disengaged position to a closed position in which it engages the second (9) of the pins when said fixed hook engages the first pin. A second pivoted hook (7) is movable towards a closed position wherein it cooperates with the fixed hook (11) to prevent disengagement of the first pin from the fixed hook, and a linkage (5) is pivotally connected at the ends thereof to the first and second pivoted hooks (3,7), whereby rotation of said first pivoted hook causes rotation of the second pivoted hook.

Description

EXCAVATOR QUICK HITCH MECHANISM

Field of the Invention

This invention relates to a quick hitch mechanism for an excavator bucket.

Background to the Invention

A quick hitch mechanism mounts on the end of an excavator arm and enables the excavator operator more readily to mount and dismount an excava-tor bucket or the like. Some mechanisms provide a manual latching and I'm latching arrangement, while more recent mechanisms have hydraulically- controllable latches so that the operator can mount and dismount a bucket with-out manual intervention, except for the need to insert a locking in manually to prevent accidental release of the bucket in use. There have, however, been many reported accidents where failure to secure the bucket correctly using quick hitch mechanisms, and in particular failure to insert the locking pin, has resulted in the bucket becoming detached during use. In some cases this has led to fatalities where the bucket has fallen on people working beneath it.

There is a need for a quick hitch mechanism which is simple and reliable to operate and which ensures that the bucket cannot accidentally be released.

Summary of the Invention

Accordingly, the invention provides a quick hitch mechanism for an exca-vator bucket, the bucket having a spaced pair of horizontal mounting pins, the hitch mechanism having a fixed hook engageable with the first of the pins and a first pivoted hook movable by a hydraulic ram from a disengaged position to a closed position in which it engages the second of the pins when said fixed hook engages the first pin, a second pivoted hook movable towards a closed position wherein it cooperates with the fixed hook to prevent disengagement of the first pin from the fixed hook, and a linkage pivotally connected at the ends thereof to the first and second pivoted hooks, whereby rotation of said first pivoted hook causes rotation of the second pivoted hook.

The linkage preferably comprises first and second link members tele-scopically slidable relative to each other, and a compressible spring between the two members such that, when the first pivoted hook engages the second pin, the spring is under compression, whereby the spring urges the second piv- oted hook towards the closed position thereof. The linkages are preferably ad-justable in length, and the compression of the spring may also be adjusted to ensure that, regardless of the spacing of the bucket pins, the same amount of spring pressure is always applied to the second pivoted hook to ensure that both bucket pins are firmly retained by the mechanism when the excavator is in use.

The mechanism preferably comprises a pivoted lock bar movable be-tween a lock position, wherein it engages the first pivoted hook to prevent movement thereof from the closed position thereof, and release position allow-ing movement of the first pivoted hook to the disengaged position thereof. The lock bar may be configured to move to a default locking position under gravity, or it may be spring-biased to such a position, a secondary hydraulic ram being provided to lift the lock bar against the spring pressure, releasing the first hook to rotate when the main ram in the mechanism is operated. This provides a fail-safe configuration.

Brief Description of the Drawings

In the drawings, which illustrate diagrammatically exemplary embodi-ments of the invention: Figures 1 and 2 are side-elevations of a quick hitch mechanism accord- ing to a first embodiment, respectively in the engaged and disengaged posi-tions; Figures 3 and 4 are enlarged views of the linkage, again respectively in the engaged and disengaged positions; Figure 5 is a side elevation of a quick hitch mechanism according to a second embodiment; and Figure 6 is an enlarged view of the lock bar forming part of the mecha-nism shown in Figure 5.

Detailed Description of the Illustrated Embodiment

Referring first to Figures 1 and 2, a quick hitch mechanism comprises a steel body 1 having spaced apart side plates in which aligned pairs of holes 2 are provided by which it may be mounted, using mounting pins (not shown), on the end of an excavator arm or the like. Between the two sides is pivotally mounted a first latching hook 3, the pivot being at the upper end thereof in the Figure. Mounting bushes 4 are provided at the sides of the first latching hook 3, and these mount a pair of sliding linkages 5 which are attached at their ends to mounting bushes 6 extending from a second latching hook 7, which is also pivo- tally mounted between the sides of the body 1. In this manner, as the first latch- ing hook 3 is rotated, the second latching hook 7 is also caused to rotate. A hy-draulic ram 8 is also pivotally mounted between the sides of the body 1 and is connected at its other end to the first latching hook 3 so that extension of the ram 8 causes the first hook 3 to rotate to a position where it can engage and hold a first of the mounting pins 9 of the excavator bucket (not shown). The ro-tation of the first hook 3 causes the linkages 5 to rotate the second hook 7 into a position wherein it prevents a second of the mounting pins 10 of the excavator bucket from being released from a fixed hook or mounting slot 11 in the body 1.

Figure 1 shows this position, while Figure 2 shows the hydraulic ram 8 retracted to pull both hooks 3 and 7 into their disengaged positions to allow the quick hitch mechanism to be released from the bucket, leaving the bucket on the ground as the excavator arm is lifted away.

A lock bar 12 is also rotated the mounted between the sides of the body 1, and when the mechanism is positioned with the hooks 3 and 7 lowermost, ready for a engagement with a bucket, the lock bar 12 rotates under the influ- ence of gravity to a position wherein, when the first hook 3 is moved by the hy- draulic ram 8 to engage the pin on the bucket, the lock bar 12 slides into en-gagement with the underside of the first hook 3 and so prevents movement of the hook to disengage the pins on the bucket. In order to be able to release the bucket from the mechanism, the lock bar must be lifted manually.

The linkages 5 each consist of a fork member 5a and a partially screw threaded bar Sb which is slidably mounted in the fork member and is retained in it by means of a head portion Sc. The threaded bar engages a screw threaded hole in a second fork member Sd at the opposite end, thereby permitting some adjustment of the maximum length of the linkage. The threaded bar also carries a nut Se which serves as an adjustable retainer for a helical compression spring 5f, the other end of which is seated against the outside of the fork member 5a.

Figure 3 shows the linkage 5 in the engaged position of the mechanism shown in Figure 1. It will be seen that the arrangement of the hooks and the linkage is such that the movement in the linkage created by the rotation of the first hook 3 is greater than that required to rotate the second hook 7 into its closed position.

As a consequence, the threaded bar slides within the fork member, compress-ing the spring, which thus serves to maintain an additional force on the second hook 7 to ensure that it will always be in the closed position when the first hook 3 is in its closed position. Figure 4 shows the relaxed position of the linkage 5 as in Figure 2. The nut permits adjustment to ensure that the spring is always compressed when the hooks are in their closed position, thus ensuring that there is no risk of accidental release of the bucket pins in use.

Referring now to Figures 5 and 6, a preferred embodiment has a helical compression spring 15 mounted so as to urge the lock bar 12 downwardly to its locking position as a default position. A small hydraulic ram 16 mounted coaxi-ally within the spring 15 is configured to lift the lock bar 12 into its disengaged position when retracted in response to retraction of the main rain 8 (the supply of hydraulic fluid to the small hydraulic ram 16 is in tandem with flat to the main ram 8). Because the lock bar 12 requires hydraulic pressure in the ram 16 to move it to the locked position, the system is fail safe. If the excavator breaks down, or a hose in the hydraulic system bursts, the hitch cannot be opened.

The possibility, therefore, of accidental release of the bucket is prevented.

Claims

CLAIMS1. A quick hitch mechanism for an excavator bucket, the bucket hav-ing a spaced pair of horizontal mounting pins, the hitch mechanism having a fixed hook engageable with the first of the pins and a first pivoted hook movable by a hydraulic ram from a disengaged position to a closed position in which it engages the second of the pins when said fixed hook engages the first pin, a second pivoted hook movable towards a closed position wherein it cooperates with the fixed hook to prevent disengagement of the first pin from the fixed hook, and a linkage pivotally connected at the ends thereof to the first and sec-ond pivoted hooks, whereby rotation of said first pivoted hook causes rotation of the second pivoted hook.
2. A mechanism according to Claim 1, wherein the linkage com-prises first and second link members telescopically slidable relative to each other, and a compressible spring between the two members such that, when the first pivoted hook engages the second pin, the spring is under compression, whereby the spring urges the second pivoted hook towards the closed position thereof.
3. A mechanism according to Claim 2, comprising means for adjust-ing the distance the first and second linkages can slide relative to each other.
4. A mechanism according to Claim 2 or 3, comprising adjustable means for pre-compressing the compressible spring.
5. A mechanism according to any preceding claim, further compris-ing a pivoted lock bar movable between a lock position, wherein it engages the first pivoted hook to prevent movement thereof from the closed position thereof, and release position allowing movement of the first pivoted hook to the disen-gaged position thereof.
6. A mechanism according to Claim 5, comprising a lock bar spring biasing the loch bar into the lock position thereof, regardless of the orientation of the mechanism, and a hydraulic ram operable in opposition to the lock bar spring to move the lock bar to the release position thereof.
7. A mechanism according to Claim 6, wherein the lock bar spring is a helical compression spring and the hydraulic ram is mounted co-axially within the spring.
8. A quick hitch mechanism for an excavator bucket, substantially as described with reference to and/or as shown in the drawings.