A lift truck load handling attachment having a quick-disconnect hook assembly for quick mounting or demounting of the attachment on a lift truck carriage. The hook assembly comprises a hook mounting member fastened to the rearwardly-facing surface of the frame of the load-handling attachment, slideably mounting an upwardly-facing hook for vertical reciprocation of the hook relative to the mounting member. The hook and mounting member respectively have elongate, vertically-oriented interlocking slides for permitting such vertical reciprocation while preventing rearward movement of the hook relative to the mounting member. A locking pin is selectively insertable transversely to limit downward movement of the hook relative to the mounting member, and the vertical slides and pin are located below the engagement surface of the hook when in its engaged position so as to permit direct abutment between the front of the lift truck carriage and rear of the attachment frame. The hook is further selectively lockable by the pin so as to limit upward movement of the hook in a lower position so that the hook can serve as a pedestal. The hook mounting member is adjustable for permitting variation of the height of both the hook and the mounting member relative to the attachment frame.

BACKGROUND OF THE INVENTION 
The invention relates to improvements in a quick-disconnect structure by 
which a load-handling attachment is removably mounted upon a lift truck 
carriage to permit quick mounting or demounting of the attachment. In 
particular, the invention relates to a vertically-slidable, 
upwardly-facing hook structure mounted adjacent the bottom of a 
load-handling attachment for engaging the downwardly-protruding lip of a 
standardized lower horizontal mounting bar on the front of a lift truck 
carriage. 
Quick-disconnect hooks for engaging such standardized lower horizontal 
mounting bars are now commonly used on lift truck load-handling 
attachments. Most such hooks are rotatably mounted to the 
rearwardly-facing surface of the attachment frame so as to pivot about a 
forwardly-extending axis, such as the hooks shown in U.S. Pat. Nos. 
4,230,434 and 4,406,575. Alternatively, other types of quick-disconnect 
hooks pivot about a transverse axis, such as that shown in U.S. Pat. No. 
4,482,286 or, although not pivotable, utilize a transverse locking pin. A 
disadvantage of all of the foregoing hook assemblies is that the pivot 
axis pin or transverse locking pin, as the case may be, must absorb all, 
or at least part, of the reactive force preventing forward movement of the 
attachment relative to the bottom of the lift truck load carriage. Such 
reactive force can be very substantial incident to the pulling or 
withdrawing of a load, or the striking of an obstacle by the attachment or 
load as it is being lowered by the lift truck mast. The shear and bending 
stresses imposed on such pins by such reactive force frequently cause 
bending or breakage of the pins. 
A few prior quick-disconnect hook assemblies feature either a pivotal or 
vertically-slidable hook locked in its engaged position by a transverse 
pin which is not required to absorb such reactive force. However these 
structures have a hook whose forwardly-facing engagement surface, when in 
its engaged position, is located below the upper extremity of the 
hook-mounting member. Such assemblies, if used on the rear surface of a 
load-handling attachment to engage the lower horizontal bar of a lift 
truck carriage, would require a space between the rear surface of the 
attachment and the forward surface of the lift truck carriage sufficient 
to accommodate the hook-mounting member. Any such space reduces the 
load-carrying capacity of a counterbalanced lift truck by increasing the 
forward protrusion of the load-handling attachment by the distance 
required to provide such space. 
Another type of prior quick-disconnect hook assembly features a 
hook-mounting member, mounted on the rear surface of a load-handling 
attachment frame, having a vertically-reciprocating hook whose engagement 
surface, when locked in its engaged position, is located above the upper 
extremity of the mounting member, thereby requiring no space between the 
carriage and attachment frame to accommodate such mounting member. The 
mounting member provides resistance to forward movement of the attachment 
relative to the bottom of the load carriage by enclosure of the hook 
within a surrounding vertical slot in the mounting member. However such 
hook assembly requires a locking pin which projects forwardly into a 
closed depression formed in the mounting member. This, together with the 
face that the mounting member encloses the hook in a surrounding fashion, 
makes the hook assembly susceptible to the build-up of dirt and other 
debris which can eventually impede the proper operation of the locking 
structure and the free vertical reciprocation of the hook. 
Moreover, while at least some of the foregoing structures provide some 
vertical adjustability of the engaged position of the hook, none provides 
any corresponding vertical adjustability of the hook mounting member. Lack 
of vertical adjustability of the hook mounting member relative to the 
frame of the load-handling attachment can cause difficulty in mounting of 
the attachment because the lower horizontal bar of the lift truck carriage 
must temporarily be placed in a position lower than normal, relative to 
the load-handling attachment, during the mounting procedure to enable the 
top of the carriage to be raised into engagement with the upper, 
downwardly-facing hooks of the load-handling attachment. Accordingly, the 
upper extremity of the hook mounting member should be sufficiently low to 
avoid interfering with the abutment of the lower horizontal bar of the 
carriage against the rear surface of the attachment frame when such bar is 
in such temporarily lowered position. Since the distance between the top 
of a lift truck load carriage and the bottom of the lower horizontal bar 
is not uniform from truck to truck, adjustability of the vertical position 
of the mounting member relative to the lift truck attachment frame is 
needed to ensure the necessary clearance. 
SUMMARY OF THE INVENTION 
The present invention compatibly solves all of the foregoing problems of 
prior quick-disconnect hook assemblies by providing a mounting member and 
hook interconnected by a vertically-oriented slide structure which permits 
vertical sliding of the hook relative to the mounting member but prevents 
rearward movement of the hook relative to the mounting member, thereby 
enabling the slide structure to absorb all reactive force resisting the 
forward displacement of the loadhandling attachment relative to the bottom 
of the lift truck load carriage. The slide structure cooperates with a 
selectively insertable transverse locking pin which locks the hook in its 
engaged position without absorbing any of such reactive force. 
The engagement surface of the hook, when in its engaged position, is 
located above the upper extremity of the slide structure so as to require 
no space between the front of the lift truck carriage and the rear surface 
of the load-handling attachment, thereby minimizing the forward protrusion 
of the attachment and maximizing the load-handling capacity of a 
counterbalanced lift truck upon which the attachment is mounted. 
Both the slide structure and transverse locking pin structure, because of 
their open nature, are highly resistant to clogging by dirt or other 
debris which might otherwise impede their functions. 
The mounting member is adjustably attachable to the rear surface of the 
attachment frame at different vertical heights so as to eliminate any 
likelihood of interference with the lower horizontal bar of the lift truck 
carriage during the mounting procedure. 
The foregoing and other objectives, features and advantages of the present 
invention will be more readily understood upon consideration of the 
following detailed description of the invention, taken in conjunction with 
the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
With reference to FIG. 1, a lift truck 10 is depicted having a load-lifting 
mast 12 mounted at the front thereof. Mounted upon the mast 12 and 
vertically-movable with respect thereto is a load carriage 14 having upper 
and lower horizontal attachment mounting bars 16 and 18 respectively 
affixed to the front thereof, bar 16 having an upwardly-extending lip 16a 
and bar 18 having a downwardly-extending lip 18a. A load-handing 
attachment, designated generally as 20, comprises a frame 22 upon which 
are mounted forwardly-extending load-handling members which may be of any 
suitable type, such as a pair of clamp arms 24, only one of which is 
shown. Mounted upon the rearwardly-facing surface 26 of the attachment 
frame 22 are a transversely spaced pair of downwardly-facing fixed upper 
hooks 28 (only one of which is shown) for matingly engaging lip 16a, and a 
transversely spaced pair of upwardly-facing lower quick-disconnect hook 
assemblies 30 (only one of which is shown) for matingly engaging the 
rearwardly facing surface 18b of lip 18a. 
The hook assembly 30 is shown in greater detail in FIGS. 2-8, and comprises 
a hook-mounting member 32 fastened to the rearwardly-facing surface 26 of 
the frame 22 by a pair of cap screws 34 threaded into respective apertures 
36 formed in the frame 22. The mounting member 32 has an upper extremity 
defined by an upper, transversely-extending engagement surface 32a and a 
lower extremity defined by a lower, transversely-extending engagement 
surface 32b. Extending vertically between the upper and lower engagement 
surfaces 32a and 32b are a pair of transversely-spaced, elongate slides 38 
having generally T-shaped cross-sections each having a pair of transverse 
legs 38a. 
Slidably mounted upon the hook-mounting member 32 for vertical 
reciprocation relative thereto is an upwardly-facing hook 40 having a pair 
of transversely-spaced, vertically-oriented T-shaped guides 42 slidably 
interlocking with the slides 38, each guide 42 having a pair of transverse 
channels 42a for slidably engaging the respective legs 38a of the slides 
38. The hook 40 has a forwardly-facing engagement surface 40a for engaging 
the rearwardly-facing surface 18b of the lip 18a when in a raised, engaged 
position as shown in FIGS. 4-7. The guides 42 are open at both the top and 
the bottom, permitting a large range of vertical motion of the hook 40 and 
permitting the hook 40 to be lifted completely off of the hook mounting 
member 32 for assembly and disassembly purposes, or for cleaning of the 
slides and guides. The slide and guide assembly also permits lowering of 
the hook 40 from its engaged position, but it is prevented from sliding 
completely off of the bottom of the mounting member 32 by the provision of 
a pair of lips 44 which interfere with the heads of the respective cap 
screws 34 upon lowering of the hook 40 relative to the hook-mounting 
member 32, as shown in FIG. 8. 
An elongate locking pin 46 is selectively slidably insertable transversely 
through three aligned transverse apertures 48 formed in the hook 40. When 
the hook is in its raised engaged position shown in FIGS. 4-7, the 
inserted pin rests on the upper engagement surface 32a of the mounting 
member 32 so as to prevent downward movement of the hook 40 relative to 
the mounting member 32. In this position the upper engagement surface 32a 
of the mounting member 32 is below the forwardly-facing engagement surface 
40a of the hook 40. This arrangement eliminates any need for the mounting 
member 32 to extend upwardly into a position where it might require space 
between the lower hoirzontal bar 18 of the lift truck carriage and the 
rear surface 26 of the attachment frame 22. 
In order to disconnect the hook 40 from the lip 18a, it is necessary only 
to withdraw the pin 46 thereby permitting the hook 40 to drop downwardly 
by the distance X shown in FIG. 7 until limited by the interference 
between the lips 44 and the cap screws 34. Such downward movement of the 
hook 40 enables a second group of transverse apertures 50 formed in the 
hook to move below the lower engagement surface 32b of the mounting member 
32 such that insertion of the locking pin 46 in the apertures 50 will 
cause the pin to engage the lower engagement surface 32b and prevent 
upward movement of the hook 40 relative to the mounting member 32. In this 
lowered position, the hook 40 acts as a pedestal elevating the bottom of 
the load-handling attachment above the ground 51 to facilitate 
reconnection of the loadhandling attachment to the lift truck carriage, as 
shown in FIGS. 1 and 8. 
The interlocking relationship of the slides 38 and guides 42 of the 
mounting member 32 and hook 40, respectively, resists all forces tending 
to move the bottom of the load-handling attachment 20 forwardly with 
respect to the bottom of the lift truck carriage 14, as previously 
discussed, due to the fact that the channels 42a of the guides 42 impose a 
reactive, rearwardly-directed shear force on the legs 38a of the slides 
38. The fact that the pin 46, when the hook 40 is in its engaged position, 
merely rests upon a horizontal upper engagement surface 32a of the 
mounting member 32, rather than passing through an aperture or the like in 
the mounting member 32, ensures that none of such rearwardly-directed 
reactive shear force will be imposed upon the pin 46, which might 
otherwise bend or break the pin. Moreover, the presence of pin-engaging 
apertures 48 only in the hook 40 ensures that the pin 46 can be inserted 
easily and rapidly since there is no necessity to align apertures in 
relatively movable parts. Finally, the transverse orientation of the 
apertures 48 ensures that they are open-ended and thereby resistant to 
filling with dirt or other debris which might make insertion of the pin 
difficult or impossible. It will be recognized that an equivalent 
structure could comprise transverse apertures in the mounting member 32 
with only horizontal engagement surfaces on the hook 40 to engage the pin 
46. 
Another advantage of the foregoing vertical slide and guide structure is 
that no portion of the mounting member 32 need protrude rearwardly in 
surrounding relationship to the hook 40 in order to provide the necessary 
resistance to forward displacement of the attachment relative to the 
bottom of the lift truck carriage. This provides a relatively open slide 
structure resistant to clogging with dirt or debris, and enables the 
quick-disconnect hook assembly to be relatively narrow in a fore-and-aft 
direction thereby minimizing the likelihood of interference with any other 
lift truck components. 
It will be noted that the lower engagement surface 32b of the mounting 
member 32 is located a greater distance Y (FIG. 2) from the cap screw 34 
than the distance Z by which the upper engagement surface 32a is separated 
from the cap screw 34. This feature permits the mounting member 32 to be 
attached adjustably to the load-handling attachment frame 22 in either of 
two orientations wherein the upper extremity of the mounting member 32 is 
at different vertical heights relative to the attachment frame 22. One 
such orientation is shown in the figures. The other orientation would 
simply involve inverting the mounting member 32 so that the engagement 
surface 32b becomes the upper engagement surface. Such adjustable feature 
varies not only the height of the engaged position of the hook 40, but 
also varies the height of the upper extremity of the mounting member 32 to 
ensure adequate clearance between the member 32 and the lower horizontal 
bar 18 of the lift truck carriage during temporary depression thereof 
while engaging the upper hook 28, as depicted in FIG. 1 and discussed 
previously. 
The terms and expressions which have been employed in the foregoing 
specification are used therein as terms of description and not of 
limitation, and there is no intention, in the use of such terms and 
expressions, of excluding equivalents of the features shown and described 
or portions thereof, it being recognized that the scope of the invention 
is defined and limited only by the claims which follow.