Vehicle mounted hook hoist for loading, transporting and dumping containers

A vehicle mounted hoist for loading, transporting and dumping containers including a tail frame pivotally mounted at a tail frame pivot pin to the rear of a vehicle; a jib assembly pivotally mounted to the tail frame at a jib assembly pivot pin forwardly of the tail frame pivot pin, the jib assembly including a telescopically extendable jib with an outboard end to which is connected a hook configured to engage with a complementary configured apparatus on a container; a pair of hydraulic cylinders connected between the vehicle and the jib assembly and operable to pivot the jib assembly about one of the pivot pins; and, a locking assembly connected with the tail frame and the jib assembly and having a locked condition wherein the jib assembly is locked to pivot as a unit with the tail frame about the tail frame pivot pin, and having an unlocked position wherein the jib assembly is unlocked from the tail frame and able to be pivoted about the jib assembly pivot pin, and wherein the locking assembly is operably connected with the jib so that complete retraction of the jib changes the locking assembly from the locked to the unlocked condition only when the first hydraulic cylinders are retracted and the jib assembly and the tail frame are both in a rest position lying substantially horizontal atop the vehicle.

FIELD OF THE INVENTION 
The present invention relates to the field of transportable containers and 
vehicles for picking up, transporting, setting off, and dumping such 
containers. 
BACKGROUND OF THE INVENTION 
There exists a type of container hoist called a hook hoist which includes 
an L-shaped hoist arm pivotally mounted at the rear of a trailer. A part 
of the arm called a "jib" is telescopically extendable and has a hook 
mounted to the outboard end thereof. The arm is connected at its end 
opposite the jib to the trailer via a tilt frame such that, when unlocked 
with the tilt frame, hydraulic cylinders pivot the hoist arm back 
approximately 150.degree. where it may engage with a container and be 
pivoted forwardly, thereby lifting the container up onto the vehicle 
chassis. Extension of the jib pulls the container forwardly to the desired 
transport position. When the hoist arm is locked with the tilt frame, 
actuation of the same cylinders causes the hoist arm and tilt frame to 
pivot as a unit about the tail end of the trailer, thereby dumping the 
container mounted thereon. The locking mechanism is designed so that the 
hoist arm is automatically, mechanically unlocked from the tilt frame upon 
retraction of the telescopically mounted jib. 
If the mechanism locking the hoist arm with the tilt frame is disengaged 
while the two are pivoted upwardly with a container, the whole assembly 
may come crashing down with considerable damage to hoist and container. 
Various safety mechanisms have been designed to prevent this occurrence. 
In one such mechanism a hydraulic interlock mechanism precludes hydraulic 
operation (i.e., extension or retraction) of the jib whenever the 
hoist-arm-pivoting cylinder assembly is not Fully retracted, thereby 
precluding the possibility of accidently unlocking the hoist arm from the 
tilt frame while the hoist arm is pivoted. Unfortunately, this also 
precludes extension of the jib at the conclusion of a container unloading 
sequence, such extension stroke being useful to drive a container onto a 
loading dock. 
What is needed is a hoist mechanism which provides the dual 
loading/unloading and dumping capability and which includes a safe 
interlock mechanism to allow for extension or retraction of the hoist arm 
at any time where the hoist arm and tilt frame are locked together and 
pivoted away from horizontal, without the danger that hoist arm and tilt 
frame will accidentally become disengaged.

SUMMARY OF THE INVENTION 
Generally speaking, a vehicle mounted hoist for loading, transporting and 
dumping containers includes a tail frame pivotally mounted at a tail frame 
pivot pin to the rear of a vehicle; a jib assembly pivotally mounted to 
the tail frame at a jib assembly pivot pin forwardly of the tail frame 
pivot pin, the jib assembly including a telescopically extendable jib with 
an outboard end to which is connected a hook configured to engage with a 
complementary configured apparatus on a container; a pair of hydraulic 
cylinders connected between the vehicle and the jib assembly and operable 
to pivot the jib assembly about one of the pivot pins; and, a locking 
assembly connected with the tail frame and the jib assembly and having a 
locked condition wherein the jib assembly is locked to pivot as a unit 
with the tail frame about the tail frame pivot pin, and having an unlocked 
position wherein the jib assembly is unlocked from the tail frame and able 
to be pivoted about the jib assembly pivot pin, and wherein the locking 
assembly is operably connected with the jib so that complete retraction of 
the jib changes the locking assembly from the locked to the unlocked 
condition only when the first hydraulic cylinders are retracted and the 
jib assembly and the tail frame are both in a rest position lying 
substantially horizontal atop the vehicle. 
It is an object of the present invention to provide an improved hoist for 
loading, transporting and dumping containers. 
It is another object of the present invention to provide an improved 
vehicle mounted, hook hoist with a locking assembly which safely enables 
pivoting of a jib assembly about a jib assembly pivot pin to load and 
unload a container and enables pivoting of a jib assembly as a unit with a 
tail frame about a tail frame pivot pin to dump a container mounted 
thereon. 
Further objects and advantages of the present invention will become 
apparent from the following description of the preferred embodiment. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
For the purposes of promoting an understanding of the principles of the 
invention, reference will now be made to the embodiment illustrated in the 
drawings and specific language will be used to describe the same. It will 
nevertheless be understood that no limitation of the scope of the 
invention is thereby intended. 
Referring now to FIG. 1, there is shown a vehicle mounted hook hoist 10 for 
picking up, transporting and dumping containers in accordance with the 
preferred embodiment of the present invention. Hoist 10 is generally 
connected to a subframe 11 for pivotal movement about a tail frame pivot 
pin 12 via a pair of hydraulic cylinders 14 (one shown). Subframe 11 is 
mounted to the chassis 18 of vehicle 16 as is known in the art. Hoist 10 
generally includes a jib assembly 18, a tail frame 19, and a locking 
assembly 23. Tail frame 19 is pivotally connected at its rear by tail 
frame pivot pin 12 to subframe 11 (see FIG. 2). Jib assembly 18 generally 
includes a jib sleeve 20 and an L-shaped jib 21 with a hook 22 connected 
at the outboard end thereof. 
Referring now to FIGS. 3, 4, 5 and 7, the specific components of hoist 10 
will now be described. Tail frame 19 generally consists of a pair of 
parallel, box-shaped frame members 26 and 27 which are held rigidly 
together by cross member 28 (FIG. 1) and angled stop member 29. Also 
spanning between frame members 26 and 27 are tail frame pivot pin 12 and 
jib assembly pivot pin 31. The forward end 32 of each frame member 26 and 
27 defines a planar, jib-locking surface 33. Surface 33 is slanted 
forwardly, downwardly, as shown in FIGS. 4 and S, with respect to the 
longitudinal axis 34 of each frame member 26 and 27. Jib assembly 18 
comprises jib sleeve 20, jib 21 with hook 22, and two pairs of generally 
parallelogram-shaped braces 37, 38, 39 and 40. Jib sleeve 20 has a 
generally rectangular cross-section and telescopically receives one leg 42 
of jib 21 thereby. Four nylon wear pads 48 are mounted on the four sides, 
at the forward end of the inside of jib sleeve 20 and four nylon wear pads 
49 are mounted on the four sides, at the rearward end of the outside of 
leg 42, as shown in FIG. 6, to enhance the telescopic sliding action of 
leg 42 within sleeve 20. A double acting hydraulic cylinder assembly 43 is 
connected by cylinder mount pin 44 at the rear end of jib sleeve 20. The 
opposite end of hydraulic cylinder assembly 43 is connected at the forward 
end of leg 42 in a conventional manner. Cylinder assembly 43 operates to 
extend and retract jib 21 between a retracted position (as shown in solid 
lines at 45 in FIG. 1) and an extended position (as shown in phantom at 46 
for FIG. 1). Jib assembly 18 may be configured to permit extension of jib 
21 from retracted position 45 to an extended position which is farther 
than that indicated at 46 in FIG. 1. This would be particularly useful to 
push a container onto the dock when jib assembly 18 is completely pivoted 
to the rear as indicated at 47 in FIG. 1. Also, as described herein, 
further rearward extension of jib assembly 18 may be achieved by extension 
of cylinders 14 to pivot tail frame 19 from horizontal after jib assembly 
18 has been pivoted to a rearpivot position as indicated at 47. 
Jib 21 further defines an upstanding arm 50 which is generally orthogonal 
to leg 42 (FIG. 6). At the top of arm 50 is rigidly connected a C-shaped 
hook 22 which is configured to engage with a mating cross bar 51 or 
similar structure mounted to the front of a container 52. Jib sleeve 20 is 
mounted for pivotal movement about jib assembly pivot pin 31 by virtue of 
parallelogram-shaped braces 37-40 as will now be described. 
Inner braces 38 and 39 (FIG. 3) are substantially identical and are rigidly 
fixed as by welding to the opposing sides of jib sleeve 20. Outer braces 
37 and 40 are also substantially identical and are rigidly connected to be 
mutually parallel with braces 38 and 39 by plates 54 and 55 and box 
channels 56 welded therebetween. Braces 37-40 and jib sleeve 20 thereby 
pivot as a unit about jib assembly pivot pin 31 which extends through 
braces 37-40, frame members 26 and 27 and jib sleeve 20, as shown in FIG. 
3. A cylinder mounting pin 57 is mounted at and between the outboard ends 
of braces 39 and 40. Symmetrically, a cylinder mounting pin 57 is mounted 
at and between the outboard ends of braces 37 and 38. The piston rods 58 
of hydraulic cylinders 14 are mounted for pivotal movement to pins 57. 
Cylinders 14 are anchored at their opposite ends in an appropriate 
position to chassis 15 of vehicle 16. Stop member 29 includes a stop plate 
60 which is disposed at an angle to frame members 26 and 27 appropriate to 
engage in planar fashion a nylon wear pad 61 mounted to the top surface of 
connecting plates 54. 
Locking assembly 23 generally includes a pair of spring-loaded latches 64, 
a connecting rod 77, a connecting plate 65, a link 66, a spring-bias 
assembly 67 and a pushpost 68. Each of the two latches 64 is pivotally 
mounted by a latch pivot pin 69 to a corresponding inner brace 38, 39. 
FIG. 3 and FIGS. 4,5 and 6 show two alternative embodiments. In FIG. 3, 
box channels 56 are positioned more forwardly and latches 64 are mounted 
generally below box channels 56 (relative to when jib assembly 18 is in 
the horizontal rest position depicted in FIG. 4). In FIGS. 4, 5 and 6, box 
channels 56 are positioned more rearwardly and latches 64 are mounted 
forwardly of box channels 56. The embodiments are otherwise intended to be 
the same with latches 64 engaging the planar, jib-locking surfaces 33 in 
the same manner as described herein. Each spring-loaded latch 64 defines a 
planar, frame member engaging surface 70, which defines a forward angle 
with a radial line 71 extending from pin 69 to the middle of surface 70, 
the angle .alpha. being greater than 90.degree.. Surfaces 33 of frame 
members 26 and 27 are engaged to be coplanar with surfaces 70 when jib 
assembly 18 is locked with tail frame 19 as described herein. Each latch 
64 also defines a channel 72 into which is received a coil spring 73, the 
spring being held within the channel by a pin 74. A longitudinal slot 75 
is defined across the entire width of each latch 64, in communication with 
channel 72. The width of each slot 75 is less than the diameter of channel 
72 so that spring 73 is contained within the corresponding channel 72. A 
connecting rod 77 engages with both latches 64 to cause them to pivot 
about their respective pin 69 in unity by extending between the latches 64 
and through each of their slots 75 and channels 72, as shown in FIG. 3. 
Each spring 73 extends within channel 72 between the retaining pin 74 and 
the rod 77, springs 73 thereby biasing rod 77 to the rear end 78 of each 
channel 72. Rod 77 is connected as by welding to one end of connecting 
plate 65. The opposite end of plate 65 is pivotally connected by a pin 79 
to one end of link 66. Brace 39 defines a cutout area 80 to provide access 
to pin 79 for servicing. A bracket assembly 81 is mounted to the inside of 
jib sleeve 20 as by welding and includes a transversely mounted pin 82 to 
which is mounted link 66 for pivotal movement thereat. One end of a rod 84 
is pivotally connected at 85 to the upper end of link 66. The opposite end 
of rod 84 slidably extends through a hole 86 in bracket assembly 81 as 
shown in FIG. 5. Rod 84 defines a spring rest 87, and a coil spring 88 
surrounds rod 84 and extends in compression between spring rest 87 and an 
upper arm 89 of bracket assembly 81 to bias linkage 66 in the 
counterclockwise rotated position as viewed in FIG. 4. Link 66 thereby 
pulls both latches 64 counterclockwise (as viewed in FIGS. 4 and 5), via 
its connection through pin 79, plate 65 and rod 77, into a locking 
condition. When jib sleeve 20 is in a horizontal rest position atop 
vehicle 16, as shown in FIG. 4, and when latches 64 are in a locking 
condition, the frame member-engaging surfaces 70 of latches 64 are 
juxtaposed trader the planar, jib-locking surfaces 33 of frame members 26 
and 27. In this position, if cylinders 14 are extended away from a fully 
retracted position, biasing jib assembly 18 to rotate clockwise (as viewed 
in FIG. 4), jib assembly 18 will be positively locked with tail frame 19 
and the two will pivot as a unit about tail frame pivot pin 12. 
Pushpost 68 is rigidly mounted as by welding to the rear, inside end of leg 
42 as shown in FIG. 5 and is configured to engage with link 66 when leg 42 
is completely retracted by hydraulic cylinder assembly 43. That is, when 
cylinder assembly 43 completely retracts leg 42 and jib 21, pushpost 68 
pushes the top of link 66, rotating it about pin 82 and pushing plate 65 
and connecting rod 77 forwardly. When jib sleeve 20 is in the horizontal 
rest position relative to tail frame 19, as shown in FIGS. 4 and 5, and 
cylinders 14 are retracted, there will be a small bit of clearance between 
surfaces 70 and 33. Thus, as shown in FIG. 5, when pushpost 68 engages 
with and rotates link 66 clockwise there is virtually no force resisting 
the leftward movement of rod 77 (as viewed in FIG. 5). Springs 73 are 
therefore not compressed, and, instead, latches 64 are rotated clockwise 
and disengaged from frame members 26 and 27. In other words, when tail 
frame 19 and jib assembly 18 are all in the horizontal rest position, 
complete retraction of jib 21 rotates link 66 and disengages latches 64 
from tail frame 19. Subsequent extension of cylinders 14 pivots jib 
assembly 18 alone about pin 31 and relative to tail frame 19, as shown in 
FIG. 3. 
Referring now to FIGS. 2 and 6, when jib assembly 18 is locked with tail 
frame 19, extension of cylinders 14 causes both jib assembly 18 and tail 
frame 19 to pivot as a unit about tail frame pivot pin 12. Because angles 
.alpha. of surfaces 70, and correspondingly, coplanar surfaces 33, are 
greater than 90.degree. as described above, an unlocking rotation of 
latches 64 would require a slight clockwise pivoting of tail frame 19 
about pin 31 relative to jib assembly 18 (as viewed in FIG. 5), which 
action is in opposition to a resulting force F acting from surface 33 
against surface 70. Force F is produced by the combination of the weight 
of the jib assembly 18 and tail frame 19. If cylinder assembly 43 is 
powerful enough, jib 21 could be retracted to cause pushpost 68 to rotate 
link 66, pushing rod 65 forward to rotate latches 64. Because the inside 
end 90 of surface 33 is radially farther from the pivot pin center 91 than 
the outside end 92, clockwise rotation of latch 64 (arrow 93) would force 
surface 33 toward center 91; that is, tail frame 19 would be lifted 
relative to latch surface 70, against the weight of tail frame 19, jib 
assembly 18 and any container 52 thereon. However, in the present 
invention, the spring constant k of spring 73 is selected, relative to the 
weights and dimensions of the components described above and chosen for a 
particular hoist, so that the forced forward movement of connecting rod 77 
upon complete retraction of leg 42 of jib 21 will compress spring 73 
rather than rotate latch 64, as shown in FIG. 6. That is, the force 
required to compress spring 73 is less than the force required to pivot 
latches 64 against the force of the combination of weights of jib assembly 
18, tail frame 19 and a container thereon, acting at surfaces 70 and 33. 
The result is that, when jib assembly 18 is locked with tail frame 19, 
they may only be unlocked by complete retraction of jib 21 when tail frame 
19 and jib assembly 18 are pivoted down to their horizontal rest positions 
shown in FIGS. 1 and 5. This means that jib 21 may be extended or 
retracted within its complete range at any other time, regardless of the 
rotated positions of jib sleeve 20 and tail frame 19. This becomes most 
beneficial when unloading a container by pivoting jib assembly 18 about 
jib assembly pivot pin 31 frown position 45 (FIG. 1) to the rearpivot 
position 47 (FIG. 1). Further extension of cylinders 14 will rotate tail 
frame 19 about tail frame pivot pin 12 to the end of the stroke of 
cylinders 14. It may then be desired to actuate cylinder assembly 43 
within jib sleeve 20 and extend jib 21 to push the container 52 rearwardly 
onto a loading dock. 
Referring to FIGS. 3 and 4, a longitudinal rail 94 extends inwardly from 
both subframes 11. A tail frame rest 95 is fixed to the insides of each 
subframe 11 and atop the corresponding longitudinal rail 94. When tail 
frame 19 and jib assembly 18 are in the horizontal rest position, jib 
assembly pivot pin 31 nests within and is supported by tail frame rests 
95. 
The configuration of locking assembly 23 of hoist 10 provides for 
self-locking of jib assembly 18 with tail frame 19. Each latch 64 defines 
a beveled surface 97 on its lower portion and the top of each forward end 
32 of frame members 26 and 27 defines two slanted surfaces 98 and 99. When 
leg 42 of jib 21 is not completely retracted, and spring-bias assembly 67 
is biasing latches 64 in the locked condition, pivoting jib assembly 18 
counterclockwise to the horizontal rest position (as viewed in FIG. 5) 
will cause beveled surface 97 to engage with the slanted surfaces 98 and 
99 of tail frame 19, which action will pivot latches 64 clockwise until 
they clear the lower surfaces 33 of forward ends 32, at which point 
latches 64 will rotate counterclockwise and lock jib assembly 18 with tail 
frame 19, as shown in FIG. 4. 
While the invention has been illustrated and described in detail in the 
drawings and foregoing description, the same is to be considered as 
illustrative and not restrictive in character, it being understood that 
only the preferred embodiment has been shown and described and that all 
changes and modifications that come within the spirit of the invention are 
desired to be protected.