A choker hook has a main body and a latch member rotatable relative to the main body. The latch member is biased by a spring thereby to form a pocket to hold the ferrule of a choker cable used in logging operations. The latch member has a toe piece which contacts the surface of a log when the choker hook is rotated by the choker cable relative to the log. The force between the toe piece and its attached latch member will tend to rotate the latch member relative to the main body when the effect of the force on the choker hook is such that the toe piece is brought into contact with the outside of the log. The ferrule pocket will open and the ferrule and attached cable will be released thereby releasing the log being transported without manual intervention at the point of log release.

INTRODUCTION 
This invention relates to a log handling system and, more particularly, to 
a self-release type choker hook used with the log handling system. 
BACKGROUND OF THE INVENTION 
In forestry operations, felled trees are moved from their felling area to a 
roadside or other desired location, referred to as a landing, where they 
are loaded on trucks for transportation to the mill. The logs may be moved 
to the landing by an aerial cable system which transports the logs in a 
suspended or partially suspended manner using a mainline connected to a 
winch or yarder, the latter being used as a means of traction. A second 
cable or haulback returns the rigging to the felling area so that 
additional logs may be transported. 
In one form of this cable system, the butt rigging hardware joins the ends 
of the mainline and the haulback. Shorter cables or chokers are suspended 
from the butt rigging and are placed by the chokerman in a noose-like 
attachment around the log or logs being transported to the landing. In so 
doing, the chokerman places a ferrule or knob formed on the lower end of 
the choker cable, into the socket of a steel choker hook which is slidably 
connected to the mid-section of the choker cable and which is able to 
slide along its entire length. As the mainline pulls the logs towards the 
landing, the chokers are drawn tightly around the logs. 
Following the transport of the log from the felling area to the landing, 
the log is lowered to the ground and the ferrule is manually disengaged 
from the choker hook thereby releasing the log from the choker. Pulling on 
the haulback will reverse the cable system and return the empty chokers to 
the felling area for more logs. 
A second technique for moving logs to a landing or roadside utilizes a 
tracked or rubber-tired tractor called a skidder. Chokers are, however, 
also used in this hauling techinque to secure the logs to the back of the 
skidder as the logs are transported by the pulling motion of the skidder. 
In the prior art, the ferrule was required to be removed from the choker 
hook manually by a chaser or the skidder operator. This operation is 
dangerous, requires additional labour and is inefficient. 
Self-release chokers have attractive features which reduce many of the 
deficiencies set out above. However, most of such chokers are costly 
and/or complex. In our U.S. application Ser. No. 08/202,573 filed Feb. 28, 
1994 now U.S. Pat. No. 5,597,191, a self-release choker hook is disclosed 
which is intended to overcome the above problems. However, it has been 
found that while this choker operates well for logs of a certain size 
range, the self release operation for logs outside this range is not 
consistent. 
SUMMARY OF THE INVENTION 
According to the invention, there is provided a choker hook used with a 
choker cable used for encircling and transporting a log and having a 
ferrule on one end of the cable, said choker hook comprising a main body, 
a latch member having an outer end and being rotatable relative to said 
main body between closed and open positions, a ferrule pocket formed 
between said main body and said latch member, said latch member being 
operable to hold said ferrule in said ferrule pocket in said closed 
position and to release said ferrule from said pocket in said open 
position, said latch member being movable from said closed to said open 
position when the outer end of said latch member is forced into contact 
with said log circled by said choker cable.

DESCRIPTION OF SPECIFIC EMBODIMENT 
Reference is now made to the drawings and, in particular, to FIG. 1 wherein 
a choker hook according to the invention is generally illustrated at 10 
and which is shown in its operating position wherein a choker cable 11 
having a ferrule 12 is wrapped about and encircles a log 13, the ferrule 
12 and attached cable 11 being retained by the choker hook 10. 
Choker hook 10 comprises a main body 14 having a cable passageway 20 
through which cable 11 is freely movable and a latch member 21 which is 
rotatable between open and closed positions about axis 22 and relative to 
main body 14. A pin 25 extends along axis 22 and serves as the hinge about 
which the latch member 21 rotates relative to the main body 14. A roll pin 
26 maintains the pin 25 in its desired position and is removable so as to 
allow disassembly of the latch member 21 from main body 14. 
One or more pair of compression springs 23 (only one of which is shown) are 
mounted between the main body 14 and the latch member 21 internally of the 
choker hook 10 as viewed in FIG. 2A; that is, the springs 23 are not 
visible from the outside of the choker hook 10 when the latch member 21 is 
in its closed position. The range of movement and the necessity for 
satisfactory spring flexing and alignment will determine whether the 
spring ends require a mount which will allow some degree of spring-end 
oscillation 24 or a simpler circular recess or pocket arrangment 31, both 
of which are illustrated in FIGS. 2A, 2B and 2C. The compression springs 
23 act to bias the latch member 21 towards its closed position as seen in 
FIGS. 1, 2A and 2B. Latch member 21 is prevented from further rotation in 
its closed position by contact with main body 14 about a portion 32 of the 
outside circumference of the main body 14. 
A ferrule pocket 33 is formed by the main body 14 and the latch member 21 
although, as viewed in FIG. 2A, a substantial portion of the ferrule 
pocket 33 is defined by the inner surface of the main body 14. A keeper 34 
is formed on the inner surface of the latch member 21. Keeper 34 extends 
along the latch member 21 in a slant or sloping configuration such that 
ferrule pocket 33 has an opening for receiving ferrule 12 which is larger 
at the end 35 (FIG. 1) of the latch member 21 remote from the outside 
surface 41 of the U-shaped opening 40 as will be described. Keeper 34 is 
adapted to positively maintain the ferrule 12 in the ferrule pocket 33 
until the latch member 21 is operable to release the ferrule 12 as will 
also be described. 
The U-shaped opening 40 is formed in the main body 14 and allows the 
insertion and removal of cable 11 when the ferrule 12 is inserted and 
released from the ferrule pocket 33. 
The U-shaped opening 40 has an outside surface 41 and an internal surface 
42 (FIG. 2C). The outside surface 41 is generally flat and in a plane 
which is perpendicular to the axis of rotation 22 of the latch member 21. 
The internal surface 42, however, while also being generally flat, slopes 
upwardly from the outer entrance 44 of the U-shaped opening 40; that is, 
the thickness of the main body 14 at the outer entrance 44 of the U-shaped 
opening 40 is thinner at the outer entrance 44 than internally of the 
U-shaped opening 40. The purpose of the sloped internal surface 42 is to 
enhance the movement of the ferrule 12 out of the ferrule pocket 33 when 
the latch member 21 moves to its open position as will be described 
hereafter. 
OPERATION 
In operation and with reference to the aerial cable system of FIG. 1, a 
chokerman (not shown) will manually encircle the felled log 13 with the 
choker cable 11 which is attached to a mainline (not shown). The choker 
hook 10 is freely slidable on choker cable 11 and the choker hook 10 will 
be positioned on the log 13 such that the ferrule 12 on the end of the 
choker cable 11 remote from the main line is insertable into the ferrule 
pocket 33 under the keeper 34. The cable 11 will be manually pulled tight 
so that the ferrule 12 is adequately secured within the ferrule pocket 33 
of choker hook 10. The chokerman will signal or otherwise advise the 
mainline operator that the log 13 is free to be transported. 
The movement of log 13 will then commence and the transport force exerted 
on log 13 by cable 11, indicated by "F" in FIGS. 2A-2C, will move the log 
13 and choker hook 10 in the directions indicated. 
When the log 13 has reached the landing and been lowered to the ground, 
partial tension will be maintained on the choker cable 11 as the yarder 
pays out on the mainline and pulls in on the haulback. This will change 
the direction of pull on the choker cable 11 relative to the log 13. As 
this direction of pull, shown as force F, moves from the position shown in 
FIG. 2A to that shown in FIG. 2B, the choker hook 10 will rotate relative 
to the log 13 and the outer end 43 of the latch member 21 will contact the 
surface of the log 13. In this position, the cable 11 will have moved from 
the inner position in U-shaped opening 40 which is the position 
illustrated in FIGS. 1 and 2A towards the outside entrance 42 of the 
U-shaped opening 40. 
The force "F" will continue to rotate the choker hook 10 into the position 
illustrated in FIG. 2C wherein the latch member 21 is forced open by its 
contact with log 13 and the increasing force in cable 11 to rotate the 
choker hook 10. Latch member 21 will rotate relative to the main body 14 
about axis 22 and against the bias of compression springs 23. The cable 11 
will pass out of the outside opening 43 of the main body 14 and the 
ferrule 12 will follow the cable 11 because the latch member 21 and keeper 
34 are no longer holding the ferrule 12 within the ferrule pocket 33. 
Thus, the ferrule 12 will be released, the log 13 will no longer be bound 
by the choker cable 11 and the choker cable 11 and choker hook 10 will be 
returned by the haulback for attachment to another log. It will be noted 
that the cable 11 and ferrule 12 are released without manual operator 
intervention at the site of the desired transportation position for log 
13. 
In the skidder log hauling technique earlier described, the skidder is 
reversed or makes a U-turn in order to reverse direction of force on the 
choker cable and thereby release the choker hook. 
A further embodiment of the invention is illustrated in FIGS. 3 and 4A-4C. 
In this embodiment, the main body 101 and latch member 102 are positioned 
such that the compression springs 103 are visible from the outside of the 
choker hook 100 and are readily replaceable by removing the pin 110 and 
dismantling the choker hook 100. Also, the ease of assembly of the choker 
hook 100 is enhanced. The latch member 102 will rotate relative to main 
body 101 about axis 104 which is defined by pin 110 with the compression 
springs 103 continuing to provide a bias to the latch member 102 which 
tends to close the ferrule pocket 111 (FIG. 4A) and retain the ferrule 112 
of cable 113 within the ferrule pocket 111. 
The release action, however, is precisely the same as the release action 
performed by the embodiment of FIGS. 1 and 2A-2C. As the log 13 is 
transported to the landing, the force "F" in cable 113 will be generally 
as illustrated in FIGS. 3 and 4A. When the log 13 is lowered in the 
landing, the operator will change the direction of pull "F" on the cable 
113 such that the choker hook 100 is rotated into the position illustrated 
in FIG. 4B wherein the latch member 102 comes into contact with the 
surface of the log 13. As the direction of pull continues to change to 
that force "F" shown in FIG. 4C, the latch member 102 will rotate about 
axis 104 relative to main body 101 and against the bias provided by the 
compression springs 103. The ferrule 112 and cable 113 will be released 
from the ferrule pocket 111 of the choker hook 100. 
It is contemplated that the latch member 102 may have an adjustable outer 
extension 114 (FIG. 5A) which would be connected to the latch member 102 
with bolts 120. This extension 114 may be made in different lengths or 
removed altogether (FIG. 5B). The extension 114 allows adjustment to the 
amount of rotation of the hook 100 before the extension 114 makes contact 
with the log 13. This, in turn, provides a control to the angle of 
inclination between force "F" and the surface of the log 13 required to 
actuate the latch 102 and release the ferrule 112 from the ferrule pocket 
111. This control over the conditions for choker release will provide some 
compensation for the changing conditions of each cable system as they 
affect the relative inclination of the logs to the rigging. In addition, 
the use of the extension 114 facilitates replacement of the extension 114 
in the event of wear and without dismantling the choker hook 100 in its 
entirety. 
It is further contemplated that latch members 102 of different sizes could 
be used with the main body 101 depending upon the specific logging 
operation intended to be conducted. Thus, the ferrule pocket 111 could be 
opened generally at the time required for releasing transported logs for a 
variety of ground slope and topographical conditions and cable system 
configurations. 
While compression springs 23, 103 have been illustrated as being used with 
the two embodiments described, it is contemplated that tension or torsion 
springs or an appropriate elastomer could also be readily adapted to fit 
the configuration of the choker hooks 10, 100. Other devices could also be 
used that provide a bias to the latch members 21, 102 relative to the main 
bodies 14, 101, respectively, so that the ferrule pockets 33, 111 tend to 
remain closed under operation until the choker hooks 10, 100 are rotated 
by the operator with the cable 11 such that the latch members 21, 102 
contact the surface of log 13. 
Yet a further embodiment of the invention is illustrated in FIGS. 6 and 
7A-7C. In this embodiment, the configuration of the choker hook 200 more 
closely resembles the configuration of the prior art choker hook which 
does not utilise a release mechanism. This configuration has advantages in 
that the insertion of the ferrule 212 into the ferrule pocket 211 is 
accomplished in the same way as the insertion of the ferrule 212 into the 
ferrule pocket (not shown) of the prior art choker hook referred to above. 
That is, there exists an eye 205 into which the ferrule 212 formed on 
cable 213 is inserted. The cable 213 is rotated through approximately 
ninety (90) degrees and the ferrule 212 is pulled into its nested position 
within the ferrule pocket 211 without movement of the latch member 202. 
This is advantageous since kinks in the cable 213 close to the ferrule 212 
are not uncommon. If the ferrule 212 needs to be pulled into the ferrule 
pocket 211 rather than simply rotated in accordance with the present 
embodiment, such setting of the ferrule in accordance with the previous 
embodiments of the invention can be difficult due to the cable kinks. 
A bore 217 is machined through the main body 201 and the latch member 202 
and a pin 210 is inserted in the bore 217. A first slot 209 is machined 
into one end of the pin 210 and a second slot 208 is machined in the main 
body 201 as illustrated in FIG. 6. A roll pin 207 (FIGS. 7A-7C) is 
inserted through the latch member 202 as illustrated in order to remove 
any relative movement between the pin 210 and the latch member 202 such 
that when the latch member 202 rotates, the pin 210 will likewise rotate 
with the latch member 202. 
A torsional spring wire 203 is inserted through a hole 218 machined into 
the main body 201 and pin 210. The spring wire 203 has a first bend 219 
formed at one end which is adapted to fit into the slot 209 in pin 210 and 
a second bend 220 formed in the spring wire 203 which is adapted to fit 
into the slot 208 in main body 201. Thus, when latch member 202 and pin 
210 rotate together because of the coupling effect created by roll pin 
207, an increased torsional force in spring wire 203 will result tending 
to bias the latch member 202 to return to its normal operating position. 
A predetermined initial torsional force in spring wire 203 is desired 
thereby to firmly keep latch member 202 in contact with a first stop 215 
on main body 201 during the log transportation phase. This initial force 
is created by inserting spring wire 203 into pin 210 and hole 218 without 
the insertion of roll pin 207. After insertion of the spring wire 203, pin 
210 is rotated by a screwdriver placed in slot 209 or otherwise 
counter-clockwise as viewed in FIG. 6. When the appropriate amount of 
initial torque is reached, roll pin 207 is inserted to maintain the pin 
210 and spring wire 203 in such position relative to the latch member 202. 
In operation, the ferrule 212 will be inserted through the eye 205 and the 
ferrule 212 and attached cable 213 will be rotated about ninety degrees 
such that the ferrule 212 takes the position illustrated in FIGS. 6 and 
7A. The logs will then be transported from their felled position, the 
principal force from the transporting cable being illustrated as "F" in 
FIG. 7A. 
When the desired end position of the transported logs is reached, the 
direction of force "F" in the transporting cable is changed to that 
illustrated in FIG. 7B. This will bring the latch member 202 into contact 
with the surface of the log 13 and provide a force on the latch member 202 
tending to rotate the latch member 202 and pin 210 in the direction 
indicated about axis 204 (FIG. 6) and against the torsion in spring wire 
203. As the direction of force continues to change to that illustrated in 
FIG. 7C, the latch member 202 and pin 210 will rotate relative to the main 
body 201 of choker hook 200 until the latch member 202 contacts the second 
stop 216 on main body 201. In this position, the ferrule 212 will be 
release from the ferrule pocket 211 and the choker hook 200 can be 
returned to the felling area to transport further felled logs. 
While a torsional spring wire 203 together with a pin 210 have been 
described with the FIG. 6 embodiment, different spring and pin 
configurations are readily envisioned that will maintain the latch member 
202 in contact with the first stop 215 on the main body 201 and while will 
allow the latch member 202 to return to its normal configuration from 
contact between the latch member 202 and the second stop 216. 
Many further embodiments of the invention will readily occur to those 
skilled in the art to which the invention relates and the specific 
embodiments described should be taken as illustrative of the invention 
only and not as limiting its scope as defined in accordance with the 
accompanying claims.