GB2451304A

GB2451304A - Hitch safety device

Info

Publication number: GB2451304A
Application number: GB0725354A
Authority: GB
Inventors: Anthony Joseph Bianchi
Original assignee: QUICK SWITCH
Current assignee: QUICK SWITCH
Priority date: 2007-12-31
Filing date: 2007-12-31
Publication date: 2009-01-28
Anticipated expiration: 2027-12-31
Also published as: GB0725354D0; GB2451304B; AU2008345445A1; WO2009083730A1

Abstract

An automatic hydraulically-operated quick hitch 10 for connecting a bucket or other tool to an excavator has a sensor 34, e.g. an inductive proximity switch, magnetic switch or microswitch, to detect the presence or absence of a safety pin or safety bar 38. The pin or bar 38 is located directly behind a body portion of a jaw 30 and engages in apertures in the body portion 24 of the hitch to prevent the jaw 30 from opening. A buzzer or warning light in the cab of the excavator warns the operator if the safety pin is not present.

Description

Safety device The present invention relates to a safety device and particularly to a safety device for use with a quick hitch of a mechanical arm, for example, an excavator arm.

An excavator arm typically includes a boom, a dipper arm and a bucket, all powered by hydraulic rams. in use, an excavator operator may have to change a bucket or other tool attachment a number of times per day in order to optimise the productivity of the machine. In some cases, an operator may change a bucket on an excavator up to thirty times per day.

Most excavators are Fitted with a quick hitch or coupler in order to speed up the process of changing a bucket. A standard bucket is usually attached to the end of the dipper arm using two spaced and parallel pins. A quick hitch is a system in which one of the pins is generally located in an open-mouthed substantially C-shaped aperture and the other pin is located in a similar C-shaped aperture, but is secured within the aperture by means of a movable jaw or catch. The C-shaped apertures are arranged such that when the first pin is located in the first aperture and the second pin is *..

* secured in the second aperture and the jaw closed, the bucket is securely held to the quick hitch. S. *. * . S * S

In other arrangements, custom made pins, apertures and lugs may be provided to secure a bucket or other tool, but the principal of holding the bucket or tool to the quick hitch is the same, in that a movable jaw or catch secures a pin of the bucket or tool to the dipper arm.

Some quick hitch systems are operated manually, but the majority of quick hitches are semi-automatic or fully automatic. A manual arrangement requires an operator to open and close the jaw manually, or to open a spring operated latch using a lever.

This involves the operator leaving the excavator cab and is relatively slow and inconvenient.

A semi-automatic quick hitch generally includes a movable jaw, which is powered by a hydraulic ram. The ram can be operated from the cab of the excavator, but because the system relies on the hydraulics of the machine, a safety pin is inserted by hand, which locks the movable jaw in its closed position. The safety pin is also known as a "safety bar" and prevents the jaw from opening in the event of a hydraulic failure or operator error.

A fully automatic quick hitch is operated entirely from within the excavator cab and utilises a movable hydraulic jaw similar to that in a semi-automatic arrangement.

However, an independent locking system for the hydraulic jaw is usually provided, which does not rely on hydraulic pressure. Furthermore, a visible indicator may be provided on the quick hitch, which indicates when the bucket or tool is secure. In one arrangement, a locking pin may protrude from the side of the quick hitch if it is not in a securely locked condition. The protruding pin can be seen from the cab of the excavator by the operator and serves as a warning that the bucket or other tool is not secure.

*... It is an acknowledged problem of semi-automatic or fully automatic quick hitch I...

arrangements that if the hydraulic jaw holding the bucket or tool accidentally retracts due to operator error or hydraulic failure, then the bucket or tool will fall from the S. * dipper arm potentially causing a serious accident. In the last year approximately 13% of investigated excavator incidents in the UK have been caused by an excavator bucket detaching unexpectedly from a quick hitch and injuring or killing a ground worker. In the last year four ground workers have been killed due to the accidental release of a bucket from a semi-automatic quick hitch.

A reason for a semi-automatic quick hitch fiuiling is the omission of an excavator operative to fit the safety pin. Reasons for this omission include the desire to speed up the changing of buckets, reluctance to insert the pin in bad weather because it is necessary to leave the excavator cab, or a misplaced pin. An operative may also incorrectly fit a safety pin.

It is an object of the invention to provide a safety device which reduces or substantially obviates the above mentioned problems.

According to a first aspect of the present invention there is provided a safety device comprising a sensor adapted to be attached to a quick hitch of a mechanical arm for detecting the presence or absence of a safety pin, and alarm means connected to the sensor for indicating when an absence of the safety pin is detected Preferably the alarm means is adapted to be positioned in close proximity to the operator of the mechanical arm. This may be, for example, in an excavator cab.

It is an advantage of the invention that the alarm can be fitted to a quick hitch and is triggered when the safety pin of the quick hitch hydraulic jaw is not inserted, or is not inserted properly, to retain the hydraulic jaw in the locked position. In other words, the operative of the mechanical ann, for example, of an excavator is warned when a bucket or other tool is not securely held to the mechanical arm. This will result in the operative seeking to secure the bucket or tool before continuing with further work and consequently accidents resulting from the imexpected release of buckets or tools from *.*.. quick hitches can be substantially prevented. * S S...

* Preferably the sensor is an inductive proximity switch. * S

Preferably the alarm means is an audible alarm. S. ** * S * * S

Preferably the alarm means is a light.

Preferably a green indicator light is provided to indicate that the safety pin is present.

Preferably a red indicator light is provided to indicate that the safety pin is absent.

Preferably the sensor is connected to a quick hitch by means of a bracket.

Preferably a further sencor is provided for detecting the presence or absence of a further safety pin, the further sensor being connected to the alarm means.

According to a second aspect of the present invention there is provided a quick hitch comprising at least one hydraulically actuated arm for engaging a pin of a tool, a safety pin for locking the at least one hydraulically actuated arm in an engaged position, a sensor for detecting the presence or absence of the safety pin in the engaged position and an alarm means connected to the sensor for indicating when an absence of the safety pin is detected.

Preferably the alarm means is adapted to be positioned proximate an operator of the quick hitch, enabling the operator to be warned by the alarm means.

Preferably the tool is an excavator bucket.

Preferably the sensor is an inductive proximity switch.

Preferably the alarm means is an audible alarm.

1 5 Preferably the alarm means is a light. * ** * . . * ** * S

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the S.....

* accompanying drawings, in which: Figure 1 shows a schematic side view of a quick hitch arrangement;

S *.*

S

Figure 2 shows a side view of a sensor and bracket of the quick hitch safety device of Figure l;and Figure 3 shows a schematic circuit diagram of a circuit controlling the quick hitch safety device of Figure 1.

Refemng firstly to Figure 1, a quick hitch is indicated generally at 10. The quick hitch 10 is pivotally mounted on one side to the distal end of a dipper arm 12 of an excavator about a pivot 14, The other side of the quick hitch 10 is pivotally mounted to a connecting arm 20 about a pivot 22, which is itself pivotally connected to a hydraulic ram 16 about a pivot 1 8. The hydraulic ram 1 6 controls the movement of a bucket or other tool connected to the quick hitch 10.

The quick hitch 10 includes a body portion 24 including a first open-mouthed substantially C-shaped aperture 26 facing in one direction, ie to the left of the drawing as viewed, and a second open mouthed substantially C-shaped aperture 28 facing the bottom of the page, as viewed. In other words, the mouths of the apertures 26, 28 are substantially perpendicularly disposed relative to one-another. A movable jaw 30, shown partly in dotted outline, pivots about a pivot point 31 between a closed position, as viewed, in which the jaw 30 c]oses over the mouth of the aperture 28 and an open position (not shown) in which the jaw 30 is rotated away from the aperture 28, allowing the aperture to receive a pin of an excavator bucket or other tool. The jaw is powered by a hydraulic ram 32, shown in dotted outline.

A sensor 34, for example a proximity switch, is mounted on a bracket 36 and is positioned to detect the presence or absence of a safety pin or safety bar 38. The proximity switch can be a micro-switch, an inductive or a magnetic switch or any *** other switch type capable of detecting the presence or absence of the safety pin 38.

The safety pin 38 is disposed directly behind a body portion of the jaw 30 and engages in apertures in the body portion 24 of the quick hitch 10. When the safety pin *.S...

38 is located in the apertures, as shown, it blocks the path of the jaw 30, which is prevented from opening. The bracket 36 and sensor 34 arc also shown in Figure 2. A cable 40 extends from the sensor 34 back to the cab of the excavator. The bracket 36 is curved to accommodate the curvature of the periphery of the safety pin 38. i'he sensor 34 is mounted in an aperture through the bracket 36, and may be fastened to the bracket by means of a screw thread. The shape of the bracket and proximity of the sensor to the safety pin enable the sensor to detect the presence of absence of the safety pin 38.

Referring to Figure 3, an electrical circuit for use with the sensor 34 is indicated at 42.

The circuit includes the sensor or inductive proximity switch 34, a five-pin relay 44, a buzzer 46, a green indicator light 48 and a red indicator light 50. The lights 48,50 are LED's. The switch 34 is an open type switch capable of sensing mild steel at a distance of 5mm. Mild steel is the material of the safety pin 38. The buzzer 46 and warning lights 48, 50 are mounted in the cab of the excavator. The circuit is powered by a 24 volt supply, indicated at 52, and the sensor 34 is protected by a 5 amp circuit breaker 54. The relay 44 is protected by a 10 amp inline fuse 56. The circuit may be powered by, for example, a 12 volt supply, or any other supply voltage depending on the excavator battery supply voltage.

In use, when a bucket or tool is secured to the quick hitch 10 and the jaw 30 is closed, the safety pin 38 is inserted causing the proximity switch 34 to close. This completes the circuit back to the relay 44. The coil in the relay 44 is energised and the contact moves to illuminate the green indicator light. In this condition, safe operation of the excavator can resume.

However, should the safety pin 38 be removed or simply not be inserted, the proximity switch 34 opens and the coil of the relay 44 is de-energised. This causes the contact to switch, causing the green indicator light 48 to be switched off and the red indicator light 50 to be illuminated. The buzzer 46 is also energised and sounds in 1 5 the cab of the excavator. In this condition, operation of the excavator is unsafe and the operator is warned that the safety pin 38 should be inserted. * .

In the event that a short circuit to the proximity switch 34 occurs, then the circuit ** * breaker 54 will pop out, cutting the power to the coil of the relay 44. This is a fail safe and has the same effect as if the safety pin 38 is removed. The green indicator light is switched off and the red indicator light and buzzer are switched on. This indicates to the operator that a fault has occurred.

The circuit 42 is an example of a suitable circuit, but has the benefit of fail safe operation. it is envisaged that use of the safety device will substantially reduce or even eradicate accidents caused by operator error and hydraulic failure. The safety device can be utilised with manual, semi-automatic and fully automatic quick hitch devices.

Claims

1. A safety device comprising a sensor adapted to be attached to a quick hitch of a mechanical arm for detecting the presence or absence of a safety pin, and alarm means connected to the sensor for indicating when an absence of' the safety pin is detected

2. A safety device as claimed in claim 1, in which the sensor is an inductive proximity switch.

3. A safety device as claimed in claim I or claim 2, in which the alarm means is an audible alarm.

4. A safety device as claimed in any preceding claim, in which the alarm means isalight. * ** * . . * ** * *S.

5. A safety device as claimed in claim 4, in which a green indicator light is adapted to indicate that the safety pin is present. * *

6. A safety device as claimed in claim 4 or 5, in which a red indicator light is adapted to indicate that the safety pin is absent.

S S..

S

7. A safety device as claimed in claim 6, in which the sensor is adapted to be connected to a quick hitch by means of a bracket.

8. A safety device as claimed in any one of claims I to 7, in which a further sensor is provided for detecting the presence or absence of a further safety pin, the further sensor being connected to the alarm means.

9. A quick hitch as claimed in any preceding claim, in which the tool is an excavator bucket.

A quick hitch substantially as claimed herein with reference to and as illustrated in Figures 1 to 3 of the accompanying drawings. Co c\J Ic'

9 A quick hitch comprising at least one hydraulically actuated arm for engaging a pin of a tool, a safety pin for locking the at least one hydraulically actuated arm in an engaged position, a sensor for detecting the presence or absence of the safety pin in the engaged position and an alarm means connected to the sensor.

10. A quick hitch as claimed in claim 9, in which the tool is an excavator bucket.

1]. A quick hitch as claimed in claim 9 or 10, in which the sensor is an inductive proximity switch.

12. A quick hitch as claimed in any one of claims 9 to 11, in which the alarm means is an audible alarm.

13. A quick hitch as claimed in claim 12, in which the alarm means is a light.

14. A safety device substantially as claimed herein with reference to and as illustrated in Figure 1 to 3 of the accompanying drawings.

15. A quick hitch substantially as claimed herein with reference to and as illustrated in Figure 1 to 3 of the accompanying drawings. * *** * * * S*. *

S..... * S SS ** * S S

S S..

S

Amendments to the claims have been filed as follows

1. A quick hitch for a mechanical arm, the quick hitch comprising a body portion having first and second tool-pin apertures therein which are in fixed spaced relationship and which have tool-pin receiving openings which face in different directions, at least one hydraulically actuated arm for closing or substantially closing a said tool-pin receiving opening of the second aperture so as to retain a respective tool-pin in the second aperture, a safety pin aperture provided in the body portion of the quick hitch, a safety pin which is locatable in the safety pin aperture for locking the at least one hydraulically actuated arm in an engaged position by blocking movement of the arm, a sensor for detecting the presence or absence of the safety pin in the engaged position, and alarm means connected to the sensor for indicating when an absence of the safety pin is detected. Co

2. A quick hitch as claimed in claim 1, in which the sensor is an inductive proximity switch.

3. A quick hitch as claimed in claim 1 or claim 2, in which the alarm means is an audible alarm.

4. A quick hitch as claimed in any preceding claim, in which the alarm means is alight.

5. A quick hitch as claimed in any preceding claim, in which a green indicator light is provided to indicate that the safety pin is present.

6. A quick hitch as claimed in any preceding claim, in which a red indicator light is provided to indicate that the safety pin is absent.

7. A quick hitch as claimed in any preceding claim, in which the sensor is adapted to be connected to a quick hitch by means of a bracket.

8. A quick hitch as claimed in any preceding claim, in which a further sensor is provided for detecting the presence or absence of a further safety pin, the further sensor being connected to the alarm means.