Tail gate opening/closing device for dump truck

A tail gate opening/closing device for a dump truck in which bracket means are affixed at the upper rear ends of both side walls in the rear part of the carrier section. One end part of a bracket arm is pivotally arranged at each of the ends of the bracket means and each of the other ends is pivotally fastened to the end of a tail gate arm. When material transported such as sand, soil, gravel, etc. is dumped, the carrier section is raised to an angle with the ground causing the material transported to exert pressure on the tail gate so as to open the tail gate in a rearward direction and, at the same time both the bracket arm and the tail gate arm are rotated upwards and the fulcrum of the tail gate arm is also moved upwards. In this way, the tail gate is opened smoothly and the discharge port is opened to the widest extent possible.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an opening/closing device for tail gate in the 
dump truck which is installed at the rear part of the carrier section 
thereof. 
2. Description of the Prior Art 
In a conventional type of dump truck in which a tail gate is opened by 
inclining the carrier section with a dump mechanism so as to discharge or 
dump the material to be transported such as sand, soil and gravel etc., 
the opening/closing device for the tail gate is a simple structure, as 
shown in FIGS. 12 and 13, where the arm (14) of the tail gate (13) is 
pivotally attached, by an axis (15), to the bracket (12) fixed to the 
upper ends of both side walls of the burden carrier (11). Thus, usually 
the tail gate (13) may be rotated rearwardly around a fulcrum point of the 
axis (15). However, in case of loading of sand and soil etc. higher than 
that of the tail gate (13), or in case of performing a fast inclination of 
the burden carrier (11), the upper part of the tail gate (13) is applied 
with a heavy load from the sliding soil and sand etc., so that it becomes 
difficult to rotate the tail gate (13) around the axis (15). Therefore, 
the sand and soil etc. are dropped down over the tail gate (13), the tail 
gate (13) is buried completely by the sand and soil etc., so that it 
sometimes occured that the dump truck may not be moved forward. 
Transmitting of the center of gravity of the dump truck is directed in a 
rearward direction when the sand and soil are discharged, thereby the 
front wheels of the dump truck are lifted up to cause a dangerous 
condition. 
Further, in case of a conventional type of the opening/closing device for 
the tail gate, an opening of the tail gate is narrow, so that if the sand 
and soil contain a relatively large sized rock therein, they may not be 
discharged frequently unless the tail gate is removed therefrom, resulting 
in making a substantially less efficient operation. Narrow opening of the 
tail gate may not enable a high discharging or unloading of the sand and 
soil etc. in a narrow place, so that the conventional type of the dump 
truck shows such a disadvantage as requiring a little wider storing or 
accumulating place. 
In reference to the above disadvantage, the conventional type of the system 
is made such that the bracket (12) is made high and the tail gate arm (14) 
is also extended. However, if the bracket (12) is made high, some 
dangerous conditions are found in which it is struck against the bucket of 
the power shovel etc. during a loading operation of the sand and soil etc. 
And extension of the arm (14) of the tail gate is apt to cause it to be 
easily broken and at the same time it shows such a disadvantage as the 
tail gate may not be operated smoothly when the material to be transported 
is discharged. 
OBJECTS OF THE INVENTION 
It is an object of the present invention to provide an opening/closing 
device for the tail gate in which when the sand and soil etc. are loaded 
over a height of the tail gate or even when the burden carrier is rapidly 
inclined by the dump mechanism, the tail gate is opened widely and 
smoothly and the sand and soil etc. are slid off smoothly. 
It is another object of the present invention to provide an efficient and 
safe transporting operation of the sand and soil etc. 
It is still another object of the present invention to provide a simple and 
rigid structure of the opening/closing device of the tail gate which may 
not be damaged. 
The present invention relates to an opening/closing device for the tail 
gate of the dump truck and has its object to provide an opening/closing 
device for the tail gate of the dump truck characterized in that brackets 
are fixed to the upper ends of both side walls in the rear part of the 
burden carrier, one end of the bracket arm is pivotally arranged at each 
of the end parts of the bracket, respectively, and each of the other ends 
is pivotally arranged to the end part of the arm of the tail gate. 
Other objects, features and additional features of the present invention 
will become more apparent from the following description in reference to 
the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In reference to FIGS. 1 to 4 wherein one preferred embodiment of the 
present invention is shown, reference numeral 10 indicates a member of the 
tail gate opening/closing device, a bracket 12 is arranged at one of the 
mounting blocks 11, and one end part 14 of the bracket arm 13 is pivotally 
mounted on the upper end of said bracket 12 with the axis 15. Further, at 
the other end 16 of the bracket arm 13 is pivotally mounted an upper end 
of the slightly curved tail gate arm 17 with the axis 18. Reference 
numeral 19 shows a receptacle fitting arranged at the mounting block 11 
which is constructed such that the other end part thereof 16 is supported 
by the receptacle fitting 19 when the bracket arm 13 is placed in its 
lateral direction. Reference numeral 20 shows a compressed helical spring, 
one end thereof is fixed to the central part of the bracket arm 13 and the 
other end thereof is fixed to the mounting block 11. 
In FIGS. 2, 3 and 4, reference numeral 21 indicates a carrier section of 
the dump truck 22 and each of said members 10 and 10 is welded to each of 
the upper rear end portions of both side walls. Lower end of each of the 
tail gate arms 17 is welded to the upper end of the tail gate 23, 
respectively. Reference numeral 25 indicates a lock means. 
In accordance with the present invention, as shown in FIG. 5, when the 
carrier section 21 is inclined by a dump mechanism 24 after the lock means 
25 is disengaged, the tail gate 23 is opened in a rearward direction under 
the pressure force of the sliding soil and sand etc., and at the same 
time, the bracket arm 13 and the tail gate arm 17 are rotated in an upward 
direction around fulcrums of the axis 15 and 18, and further the fulcrum 
point of the axis 18 is also moved in an upward direction. Therefore, the 
tail gate 23 may be smoothly opened and at the same time the dump 
discharge port is opened wider than that of a conventional type of the 
tail gate. 
Therefore, even if the soil and sand 26 are piled over a height of the tail 
gate, or the carrier section is rapidly inclined, they may slide down 
without any restrictions from the wide-opened dump discharge port. 
According to the present invention, the tail gate may not be prevented from 
being buried by some falling soils and sands, and the front wheels are not 
lifted up. 
Further, even if substantial big rocks 27 are included in the load to be 
transported, they are not held in the tail gate but may fall freely, so 
that the transported load may be discharged fast, a transporting operation 
may be performed safely and at the same time an efficiency of operation 
may be improved more. 
Further, in accordance with the present invention, the material to be 
transported such as soil and sand etc. may be dumped from a higher 
elevation position than that of a conventional type, so that a narrow 
storing accumulation place or site may effectively be used. 
Further, in accordance with the present invention, there may be provided an 
extremely simple and rigid structure of the opening/closing device and at 
the same time the tail gate may be opened wide in a smooth manner when the 
sand and soil etc. are dumped, so that it is possible to prevent a 
break-down of the bracket arm, a tail gate arm, and a tail gate etc. 
Further, it is possible to replace the tail gate opening/closing device of 
the present invention with a conventional or an existing tail gate 
opening/closing device of the dump truck. 
Arrangement of spring 20 may prevent some shock from being produced when 
the tail gate is opened or closed and further arrangement of the 
receptacle fitting 19 may enable a supporting of the other end 16 of the 
bracket arm, however, spring 20 and the receptacle fitting 19 are not 
necessarily required. 
FIG. 6 shows another preferred embodiment of the present invention and a 
structural feature of the member 30 differing from the member 10 shown in 
FIG. 1 in that the other end of the bracket arm 31 is extended downwardly 
so as to provide a bearing part 32. 
FIG. 7 shows another preferred embodiment of the present invention, a 
structural feature of the member 40 differing from the member 10 shown in 
FIG. 1 is consisted in that it has no arrangement of the receptacle 
fitting 19 and the spring 20. 
In the preferred embodiment of the present invention shown in FIGS. 8 and 
9, a structural feature in which a pivotally arranged part 53 between the 
bracket arm 51 of the member 50 and the tail gate arm 52 is removably 
installed is different from that of each of the preferred embodiments of 
the present invention described above. That is, when a handle 54 at the 
pivotal part is rotated up to a position shown in FIG. 9, one end side 
part of the pivoted portion is opened so as to enable a removal of the 
tail gate arm 52 along with the axis 56 at its end part. The preferred 
embodiment is suitably applied for a small-sized dump truck. 
In a preferred embodiment of the present invention shown in FIG. 10, a 
structural feature in which a bracket arm 61 of the member 60 having two 
linkage plates 61a and 61b is pivotally supported by an axis 62 is 
different from that of each of the preferred embodiments described above. 
In such a bracket arm 61 as above, the tail gate may easily and lightly be 
operated. 
In a preferred embodiment of the present invention shown in FIG. 11, 
similar to the preferred embodiment shown in FIG. 10, two linkage plates 
71a and 71b of a bracket arm 71 of member 70 are pivotally supported by an 
axis 72, and further as a preferred embodiment shown in FIG. 8, one side 
part 75 of the pivoted part 74 is opened by rotating the handle 73, and so 
the tail gate arm 76 may be removed along with its axis 79. The end part 
of the linkage plate 71a is pivotally mounted on a bracket 77 with axis 
78. 
Practical application of the present invention as a tail gate 
opening/closing device for a dump truck may provide a highly useful 
apparatus which may perform a transportation and an unloading of sands, 
soils, gravels and rocks etc.