Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ATTACHMENT DEVICE
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INTRODUCTION
This invention relates to an attachment device for attaching a sling to a
hoist, particularly but, not necessarily exclusively, an invalid hoist.
It is known to provide an attachment device comprising a headed stud,
which is secured to the lifting arm of a hoist, and a plate-like clip, which
is connected
to a sling. The clip is provided with a slot comprising a first portion
through which
the head of the stud will pass, a second portion through which the head of the
stud
will not pass and a passage joining the first portion to the second portion.
In order
to place the clip on the stud, the first portion of the slot is aligned with
the head of
the stud. The clip is then placed over the stud and moved relative to the stud
until
the shaft of the stud is disposed in the second potion of the slot. The second
portion
of the slot receives the shaft of the stud with a clearance so that the clip
can pivot
about the shaft. The passage receives the shaft of the stud as a friction fit
to
discourage unintentional movement of the clip from an operative position in
which
the shaft of the stud is disposed in the second slot portion to a
disengageable position
in which the shaft of the stud is disposed in the first slot portion.
However, these known clips occasionally unintentionally disengaged from
the studs.
GB 2293857A discloses a clip also provided with a slot having first and
second portions similar to those referred to above and a passage joining the
first
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portion to the second portion. The passage over at least part of its length
has a width
which is less than the cross-sectional dimension of the shaft of the stud and
the clip
has a weakened zone adjacent to each side of the passage so that the clip can
deform
to allow the shaft of the stud to pass along the passage between the first and
second
slot portions. This clip proved unsatisfactory because the manufacturing
tolerances
were hard to hold and this resulted in clips which were often difficult to
disengage.
The present invention seeks to provide an improved attachment device
which overcomes the aforementioned drawbacks.
SUMMARY OF THE INVENTION
According to the present invention, there is provided an attachment device
for attaching a sling to a hoist, the attachment device comprising a headed
stud and
a plate-like clip having a body moulded in plastics material, the body having
a slot
comprising a first portion through which the head of the stud will pass, a
second
portion through which the head of the stud will not pass and a third portion
joining
the first and second portions, the clip including two insert moulded elements
on
opposite sides, respectively, of the third portion, the insert moulded
elements defining
a gate in the third portion intermediate the first and second portions, the
gate having
a width which is slightly less than the cross sectional dimension of the shaft
of the
stud.
Preferably, the insert moulded elements are of more durable plastics
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material than the material of the body of the clip. The inserts may be of
resilient
material but are more preferably of non-resilient material and, in the latter
case, the
inserts, preferably, have a hole extending therethrough from one side to the
other side
of the clip.
The invention will now be more particularly described, with reference to
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of one embodiment of an attachment device
according to the invention; and
Figure 2 is a plan view of the clip shown in Figure 1 on an enlarged scale.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings, the attachment device shown therein comprises
a stud 10 secured to a lifting arm 11 of an invalid hoist, e.g. a hoist
according to GB
2184706B, and a clip 12 connected by a flexible strap 13 to a sling 14.
The stud 10 has a shaft 15 of circular cross section and a round head 16.
The clip 12 is plate-like and of generally rectangular shape. It is made of
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plastics material, typically glass fibre reinforced nylon. The clip 12 has a
slot 17
comprising a first part circular end portion 17a, a second part circular end
portion
17b _ - -spaced from the portion 17a, and a neck portion 17c joining the
portions 17a and
17b.
The diameter of the slot portion 17a is slightly larger than the diameter of
the head 16 of the stud 10. The diameter of the slot portion 17b is less than
the
diameter of the head 16 of the stud 10 and slightly larger than the diameter
of the
shaft 15 of the stud 10 so that when the shaft 15 is disposed in the slot
portion 17b
the clip can pivot freely about the stud 10 but cannot disengage therefrom.
The slot
portion 17c has a width equal to or slightly greater than the diameter of the
shaft 15.
The clip 12 also includes two insert moulded elements 18 and 19 on
opposite sides, respectively, of the neck portion 17c. These insert moulded
elements
18 and 19 define a gate in the neck portion 17c intermediate the first and
second
portions 17a and 17b, respectively. The gate has a width which is slightly
less than
the diameter of the shaft 15. The insert moulded elements 18 and 19 are of
more
durable plastics material than the body of the clip and are typically made of
an acetyl
resin which is a non-resilient material. The inserts 18 and 19 comprise a
generally
cylindrical body part 20 having a hole 21 extending axially therethrough and
an ear
22 projecting from one side of the body 20 in order to prevent the insert
moulded
elements 18 and 19 from rotating in use.
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It will be appreciated that in order for the shaft 15 to pass from the slot
portion 17_a _to the slot portion 17b, the insert moulded elements 18 and 19
must
deform outwardly.
Transverse slots 23 are provided so that the clip can be attached to the strap
13.
In order to place the clip on the stud, the part circular slot portion 17a is
aligned with the head 16 of the stud 10. The clip 12 is then placed over the
stud 10.
A force is then applied to the clip 12 to cause the clip to slide relative to
the stud 10
until the shaft 15 of the stud is disposed in the part circular slot portion
17b. During
the sliding movement, the shaft 15 of the stud 10 outwardly deforms the
elements 18
and 19. These elements 18 and 19 must also be outwardly deformed to allow the
stud
to return to a disengageable position in which the shaft 15 of the stud is
disposed in
the slot portion 17a. The clip is, therefore, unlikely to become
unintentionally
disengaged from the stud. Also, the clip moves past the gate defined by the
elements
18 and 19 with a resounding click. This gives both attendant and user a sense
of
great security.
The gate is preferably mid-way or substantially mid-way between the slot
portion 17a and 17b. The shaft 15 of the stud will therefore self locate
within the
neck portion 17c in abutment with the gate. As soon as a load is applied to
the clip,
the shaft of the stud will move into an engaged position. This will prevent a
situation
in which the clip fails to be engaged.
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The embodiment described above is given by way of example only and
various modifications will be apparent to persons skilled in the art without
departing
from the scope of the invention. For example, the insert moulded elements 18
and
19 could be of resilient material and, in this case, no hole need be provided
therein.
Also, the slot portion 17c need not be rectilinear. It could be of any other
appropriate shape.
