Note: Descriptions are shown in the official language in which they were submitted.
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CONNECTION FOR TWO-PART HANDLE
~ACKGROUND OF THE INVENTION
1. Field of the Invention.
This invention relates to a construction for a handle. More particularly
this invention relates to a connection for a sturdy elongated handle that is
5 constructed in two portions. The novel connection enables the handle to
resist flexion, torque, and distraction at the jointure thereof.
2. Description of the Prior Art.
In certain applications elongated handles for supporting an instrument
are required to be assembled in two portions, an upper portion for
10 mounting the instrument and a lower hand grip portion. Such handles may
be hollow tubular casings that contain electronic circuitry, wiring, sensors,
or the like, and are fitted with connectors for an instrument, suGh as a
hand-held optical device. To achieve strength, it is desirable that a distal
portion be made of metal. In order to provide a suitable diameter for
15 grasping by the hand, and to maintain a light weight, aesthetic appearance,
the proximal pGrtion cou!d be plastic, another non-metal material, or even
another metal. In many work environments it has been found that the
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junction between the two parts fails when the handle is subjected to
repeated flexion, torque, axial distraction or compression.
Prior art approaches to securing two sections into assembly as a
single handle include providing internal or external threads on each section,
and screwing the two together. This requires relative rotation between the
two portions to achieve a threaded connection and complicates the
installation of wiring that extends across the junction. Press fitting two
sections together, with or without adhesives, is often mechanically
unreliable, and in the case of thin metal or plastic housings, the result is
relatively weak, because the stress forces are concentrated at the interface
between the two sections. Furthermore it is difficult to repeatedly disas-
semble and reassemble the two portions.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to provide an
improved elongated handle comprised of two joined sections that is able to
resist mechanical stresses.
It is a further object of the present invention to provide a rugged
handle that is light weight, has a pleasing appearance, and is conveniently
dimensioned for grasping by the hand.
It is yet another object of the present invention to provide an
elongated handle that can be repea~edly disassembled and reassembled
for replacement of components housed therein.
It is still another object of the present invention to provide a rugged
elongated handle constructed of a metal portion and a plastic portion, or
two other dissimilar materials connected thereto.
These and other objects of the present invention are attained by an
elongated handle for holding an instrument that includes a proximal
elongated hand grip portion for grasping in the hand of a user. The
elongated hand grip portion has a length and cross sectional configuration
so as to be grasped by the hand with the fingers in gripping relation
thereto. A distal portion is connected with the elongated hand grip portion
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and has a mounting assembly for receiving an instrument fastened thereto.
An internal splint is disposed in the elongated hand grip portion and in the
distal portion, and extends across the interface therebetween. The splint
secures the elongated hand grip portion in assembly with the distal portion
5 distributes mechanical stresses beyond the interface.
In accordance with one aspect of the invention either the distal portion
or the elongated hand grip portion is provided with at least two flexible,
longitudinally ribbed tabs extending outwardly thereof. At least two of the
tabs having outwardly extending cross longitudinal ribs. The other section
10 has internal longitudinal grooves that receive the longitudinal ribs, and
further having a cross longitudinal groové formed in the internal surface for
engaging the cross longitudinal ribs. The internal splint bears on the tabs
to urge the longitudinal ribs and the cross longitudinal ribs into locking
engagement with the longitudinal grooves and the cross longitudinal groove
1 5 respectively.
In accordance with another aspect of the invention, the internal split is
a self threading screw, and the hand grip section is formed of a plastic
material that can be threaded by the screw.
In accordance with yet another aspect of the invention, the distal
20 section is metal, and a secure plastic-to-metal connection is formed by the
arrangement.
BRIEF DESCRIPTION OF THE DRAWING
For a better understanding of these and other objects of the present
invention, reference is made to the detailed description of the invention
25 which is to be read in conjunction with the following drawings, wherein:
FIG. 1 is a side elevation of a handle embodying the teachings of the
invention, with a bayonet adapter for an instrument secured thereon;
FIG. 2 is a sectional view of the handle shown in FIG. 1;
FIG. 3 is an exploded view of the handle shown in FIG. 1;
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FIG. 4 is a perspective view of a component of the handle shown in
FIG. 1;
FIGS. 5 and 6 are enlarged fragmentary views of the component
shown in FIG. 4;
FIG. 7 is an end view of the handle shown in FIG. 1;
FIG. 8 is a side elevation of the component shown in FIG. 4;
FIG. 9 is an end view of the handle shown in FIG. 1, opposite the end
depicted in FIG. 7;
FIG. 10 is an fragmentary enlarged perspective view of the distal
portion of the handle shown in FIG. 1; and
FIG. 11 is a side elevation of the end portion shown in FIG. 10.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Turning now to the drawings, and in particular to FtGS. 1 - 3, a
handle, referenced generally at 10 comprises an elongate proximal hand
grip section 12 that mates with a distal section 14. A mounting assembly 16
for holding an instrument is threadably attached to the distal section 14.
The mounting assembly 16 is preferably fitted with a bayonet adapter 22
that accepts interchangeable instruments such as a medical ophthalmo-
scope head, an otoscope head, a sensor, or the like (not shown). While
the invention is explained with reference to an instrument handle, it will be
appreciated by those skilled in the art that the invention can be practiced
with other kinds of haridle assemblies as well.
The hand grip section 12 is a hollow shaft fabricated of plastic, and
can be made by any suitable technique, such as injection molding. The
plastic construction is desirable for aesthetic appearance, and to provide a
light weight device that can be conveniently manipulated by the user. The
hand grip section 12 has a series of longitudinal grooves 13 distributed
about its circumference for ease in gripping by the hand or the fingers. A
mating adapter 15 is disposed at the distal end of the hand grip section 12.
The distal section 14 can also be understood with reference to FIGS.
10 and 11. It is a tubular structure, preferably of metal construction to
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provide strength and scuff resistance. Its proximal internal wall portion 17
receives the mating adapter 15 of the hand grip section 12. Its distal
portion 19 is relatively enlarged, and provided with internal threads 21 for
attachment to the mounting assembly 16, and further provided with an
internal shoulder 23 that projects inwardly to seat the mounting assembly in
a predetermined position. The mounting assembly 16 is connected to
cabling 24 that passes through the interior of the distal section 14, and the
hand grip section 12 to a suitable power source or to electronics (not
shown) for processing signals that may-be generated by an instrument
mounted on the mounting assembly 16. Optionally miniature electronics 26
can be housed within the mounting assembly 16. External threads 44 are
provided for engagement with threads ~1 of the distal section 14.
Because of the disparity in load resistance between the relatively light
plastic hand grip section 12, and the more robust distal section 14, the
connection therebetween has always been likely to fail during repeated
use. The connection at the metal-to-plastic interface will be described with
reference to FIGS. 2- 6. The mating adapter 15 comprises four curved
outstanding tabs 32, 32 and 34, 34 that form an extension of the tubular
hand grip section 12. Each tab 32, 34 is provided with an outwardly
projecting longitudinal rib 31 on its outer surface. The two tabs 32, 32 are
further provided with an outwardly projecting circumferential rib 33 that is
orthogonal to the longitudinal rib 31. The tabs 34 are provided only with a
longitudinal rib 31. The tabs 32, 34 are slightly resilient, so that they bear
outwardly against the internal wall portion 17 of the distal section 14 when
inserted therein. The internal wall portion 17 is provided with four longitudi-
nal grooves 41 that engage the longitudinal ribs 31 when the mating
adapter 15 is inserted into the distal section 14. When the adapter 15 is
fully inserted the circumferential ribs 33 snap into a circumferential groove
43 to seat the mating adapter 15 within the distal section 14. The mating
engagement of the circumferential ribs 33 in the circumferential groove 43
prevents longitudinal separation of the hand grip section 12 and the distal
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section 14 when a distractive force is applied. Also, the engagement of the
longitudinal ribs 31 in the longitudinal grooves 41 prevent the hand grip
section from rotating relative to the distal section 14.
A self threading screw 40 is disposed inside the distal section 14 to
5 further secure the distal section 14 to the hand grip section 12. The screw
head 42 bears upon a shoulder 46 that is formed on the interior wall of the
distal section 14 just beyond the end of the mating adapter 15. The
threads of the screw 40 bite into the plastic structure of the hand grip
section 12, and draws the distal section 14 and the hand grip section 12
10 together, as well as expanding the mating adapter 15 to urge it more firmly
against the internal wall portion 17 and thereby also preventing the
circumferential ribs 33 from separating from the mating circumferential
groove 43. Even if the screw 40 loosens significantly, the two handle
portions 12, 14 will remain rigidly attached. When the screw 40 is inserted
15 its threaded portion is separated from the outer wall of the hand grip
section 12 by the tabs 32, 34. The tabs 32, 34 also isolate the screw 40
from the housing of the distal section 14. Torsion and flexion forces thus
cannot act directly on the screw threads and thereby loosen the screw.
The screw 40 should be preferably tightened to a torque value of about 25
20 inch-pounds. It has been found 10 inch-pounds is too low, and 40 inch-
pounds too high for satisfactory performance. Using a self-threading screw
also avoids the necessity of molding the threads in the interior of the plastic
handle, which reduces the cost of manufacture. Pre-threading the interior
of the plastic handle and using an appropriately matched screw would also
25 be suitable, and may be required for handles that are constructed of
materials cannot handle for self-threading screws. The screw 40 is long
enough to extend well beyond the metal-to-plastic interface, and it
distributes stresses away from the interface. This significantly increases
the durability and reliability of the jointure, and the handle is more capable
30 of resisting flexion.
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While this invention has been explained with reference to the
structure disclosed herein, it is not confined to the details set forth and thisapplication is intended to cover any modifications and changes as may
come within the scope of the following claims:
