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This application is the U.S. National Phase of International Application Number PCT/IE2004/000,128 filed on 20 Sep. 2004, which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to an excavator tool quick attachment device and more particularly to a safety mechanism for an excavator tool quick attachment device. 
     Pneumatic/hydraulic latches on quick attachment devices are well known and are generally mounted on a tool engaging portion which has two hooks, one of which is on each end of the device. The excavator operator locates one of the hooks around the first pin of the tool and raises a dipper arm of the excavator. The rams of the dipper arm are manipulated until the second hook is located adjacent the second pin of the tool and a pneumatic/hydraulic latch comprising a hydraulic/pneumatic piston connected between the attachment device and the latch is actuated to lock the second pin of the tool onto the quick attachment device. 
     The problem with this latch is that failure of the hydraulic/pneumatic cylinder could result in the latch opening and allowing the tool such as a bucket to become separated from the quick attachment device with potentially disastrous consequences for anyone in the vicinity. A number of safety pins and other safety mechanisms have been developed but most of these require to be inserted manually. Further secondary safety systems utilising hydraulic systems have also been developed which add extra system maintenance and expense. 
     It is an object of the present invention to overcome the need for manually operable safety pins or complex hydraulic systems, both of which are used to prevent unintended release of the tool from the quick attachment device. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention provides an excavator tool quick attachment device for attaching a tool to a dipper arm of an excavator, the device comprising a body member with an engaging means at or about each end for engagement with two connecting pins disposed on a tool, the first engaging means being a movable engaging means, the device further comprising a drive means mounted between the body member and the movable engaging means for moving the movable engaging means between a tool pin engaging position and a tool pin releasing position, the second engaging means being a second movable engaging means normally biased into a tool pin engaging position by a biasing means, a control means mounted between the first movable engaging means and the second movable engaging means, wherein the control means acts on the second movable engaging means to overcome the biasing force only when the quick attachment device is inverted relative to a normal working position and the drive means is actuated, whereby the tool can not be released when it is in a normal working position in the event the drive means fails or is inadvertently actuated by an operator. 
     The quick attachment device being in an inverted position is commonly referred to in the art as the crouched or valueless position. 
     Preferably, the control means comprises an adjustable length actuating assembly having a catch means to fix the length of the actuating assembly at a predetermined position when the quick attachment device is inverted relative to a normal working position and the drive means is actuated. Advantageously, the use of mechanical components powered by an already present drive means reduces the complexity and cost of a secondary safety mechanism. 
     Ideally, the actuating assembly is pivotally connected to both movable engaging means. 
     Preferably, the actuating assembly is in two parts, the first part having a slot extending along a substantial portion of its longitudinal axis and the second part having two pins spaced apart along its length and extending laterally therefrom, the pins being formed for slidable engagement with the slot of the first part, allowing relative movement between the two parts, the pins movably holding the two parts together. 
     Ideally, the catch means is provided by a notch on the slot which is located above the pins in any normal working position of the tool and the slot is located below the pins only when the quick attachment device is inverted relative to the normal working position. 
     Preferably, when the quick attachment device is inverted and the drive means is actuated to move the first movable engaging means from a tool pin engaging position to a tool pin releasing position, the pins of the second part of the actuator assembly slide along the slot until the leading pin encounters the notch into which it drops under the force of gravity thereby fixing the length of the actuating assembly after which point continued stroke action of the drive means causes the actuating assembly to move the second movable engaging means away from the tool pin engaging position thereby releasing that tool pin. 
     Ideally, the first movable engaging means is provided by a pair of latch hooks pivotally mounted on the body. 
     Preferably, the second movable engaging means is provided by a lock pivotally mounted on the body. 
     Ideally, the drive means is a double acting piston and cylinder unit. 
     Advantageously, the excavation tool quick attachment device includes a tilt mechanism by means of which the device can be titled about a longitudinal pivotal axis. 
     This invention will now be described with reference to the accompanying drawings which show, by way of example only, two embodiments of an excavator tool quick attachment device in accordance with the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a perspective view of a first embodiment of a quick attachment device with a left side plate removed; 
         FIG. 1   a  is a side view of the first embodiment of a quick attachment device mounted on a dipper arm of an excavator in a normal working position; 
         FIG. 2  is a second side view of the quick attachment device with a latch in an open position; 
         FIG. 3  is a side view of the quick attachment device in an inverted position; 
         FIG. 4  is a second side view of the quick attachment device in an inverted position showing the safety mechanism in an open position; 
         FIG. 5  is a detail view taken from the opposite side as the views of  FIGS. 1 to 4  of the safety mechanism in a normal working position; 
         FIG. 6  is a second detail view of the safety mechanism of  FIG. 5  in a second working position; 
         FIG. 7  is a third detail view of the safety mechanism of  FIG. 5  and  FIG. 6  in an uncoupling position; 
         FIG. 8  is a fourth detail view of the safety mechanism in an uncoupled position; 
         FIG. 9  is a plan view of a second embodiment of a quick attachment device according to the invention incorporating a tilting mechanism; 
         FIG. 10  is a first end view of the second embodiment; 
         FIG. 11  is a side view of the second embodiment; 
         FIG. 12  is a second end view of the second embodiment; 
         FIG. 13  is a perspective view of the second embodiment showing the mechanism tilted 45 degrees in one direction; 
         FIG. 14  is a further perspective view of the second embodiment showing the mechanism tilted 45 degrees in the opposite direction. 
         FIG. 15  is a lower perspective view of the second embodiment showing the mechanism in a non-tilted position; and 
         FIG. 16  is an upper perspective view of the second embodiment with the mechanism in the non-tilted position. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings,  FIGS. 1 to 4  show an excavator tool quick attachment device  1  mounted on an excavator dipper arm  2  and  FIGS. 5 to 8  show detail views of the safety mechanism  21  mounted on the quick attachment device  1 . The quick attachment device  1  is of the type having a dipper arm engaging portion  51  and a body portion  52  having receivers or mouths  12 ,  14  for receiving tool pins  11 ,  15  respectively. The device  1  also has two latch plates  3  (one shown) spaced apart and being pivotally connected to the body portion  52  of the attachment device  1  by pivot pin  6 . A hydraulic ram  20  is connected between heels  4  of the latch plates  3  and shaft  5 . Actuation of the ram  20  causes the latch plates  3  to pivot about pin  6  locking or releasing tool pin  11  between a concave potion of the latch plates  3  and a concave portion of mouth  12  of the attachment device  1 . The attachment device  1  has a second mouth  14  for engaging the other tool pin  15  at the opposite end of the device  1 . A safety mechanism indicated generally by the reference numeral  21  (see  FIGS. 5 to 8  in particular) is shown having a lock  22  pivotally mounted adjacent the mouth  14  and a two-part actuating assembly  23 . A first part  24  of the actuating assembly  23  is pivotally connected to the lock  22  and the second part  25  of the actuating assembly  23  is pivotally connected to latch plate  3 . The first part  24  of the actuating assembly  23  has a slot  28  extending along a substantial portion of its length. The second part  25  has two pins  29  extending transversely therefrom and movably connecting the first and second parts  24 ,  25  together with the pins  29  being formed for slidable movement along the slot  28  in response to actuation of the hydraulic ram  20  to pivot the latch plates  3 . The slot  28  has a notch  32  above the pins  29  in a normal working position and below the pins  29  in the inverted position. 
     In use and referring to  FIG. 1  and  FIG. 5 , the latch plates  3  are pivoted into a pin  11  engaging position and lock  22  is biased into a pin  15  engaging position by a biasing element, such as a spring (not shown). In  FIG. 2  and  FIG. 6 , the latch plates  3  are pivoted into a tool pin  11  releasing position by the ram. This could be an intentional actuation or it could have come about as a result of ram failure or inadvertent actuation by an operator. Due to the forces of gravity acting on the free end of the second part  25  and the free end of the first part  24  of the actuating assembly  23  the pin  29  adjacent the free end of the second part  25  slides past the notch  32 . The complete rotation of the latch plates  3  causes the pin  29  adjacent the free end of second part  25  to slide to an area just before the end of the slot  28 . No force is exerted on the lock  22  by the actuating assembly  23  therefore the lock  22  prevents the second tool pin  15  from becoming released unintentionally when the quick attachment device  1  is in a normal working position. 
     In  FIG. 3  and  FIG. 7 , the dipper arm  2  of the excavator has been pulled in towards the excavator and the hydraulic rams  41  of the dipper arm  2  have been activated so that the longitudinal axis of the quick attachment device  1  has been rotated clockwise through 180° into the inverted position compared to  FIGS. 1 and 2 . The hydraulic ram (not shown) is activated and the pins  29  slide along the slot  28 . However, due to the rotation of the attachment device  1 , the notch  32  is now located below the pins  29 . The first pin  29  adjacent the free end of the second part  25  drops down into the notch  32  again due to gravitational force and abuts against the notch  32 . At this point, the lock  22  is still engaging the tool pin  15 . 
     In  FIG. 4  and  FIG. 8 , the hydraulic ram for operating the latch plates  3  has continued with its stroke forcing pin  29  to push first part  24  of the actuating assembly  23  against the lock  22  overcoming the biasing force of the spring. Lock  22  pivots about pin  42  and engaging bar  43  rotates away from mouth  14  of the attachment device  1 . Both pins  11 ,  15  are no longer locked in the mouths  12 ,  14  and movement of the dipper arm  2  allows the tool to drop onto the ground. 
     Referring now to the second embodiment which is shown in  FIGS. 9 to 15 , the excavator tool quick attachment device  101  is provided with a safety mechanism  121  which is similar in construction and operation as the safety mechanism  21  of the first embodiment. 
     The excavator tool quick attachment device  101  additionally includes a tilt mechanism  150  by means of which the device can be tilted in two directions by approximately 45 degrees in each direction. The tilt mechanism  150  comprises two hydraulically operated cylinders  151  and  152  which can tilt the device about longitudinal central pivot  155 . 
     With the device  101  fitted to an excavator it can be used for more versatile operations, for example, grading and digging work at an angle such as in ditches, dykes an drains. The operator can manoeuvre a tool around obstacles more readily within the device  101 . 
     It will of course be understood that the invention is not limited to the specific details herein described, which are given by way of example only, and that various modifications and alterations are possible with the scope of the invention.

Summary:
Excavator tool quick attachment device ( 1 ) is used to attach a tool to a dipper arm ( 2 ) of an excavator. Body member ( 52 ) has two receivers ( 12,14 ) for tool pins ( 11,15 ). Receiver ( 12 ) has a movable latch ( 3 ) powered by an hydraulic ram ( 20 ) for securing and releasing pin ( 11 ) and receiver ( 14 ) has a movable spring loaded lock ( 22 ) for securing and releasing pin ( 15 ). A control assembly ( 21 ) is connected between latch ( 3 ) and lock ( 22 ) but only operates to release lock ( 22 ) when the device ( 1 ) is inverted relative to a normal working position and the hydraulic ram ( 20 ) is activated.