EP0689902A1

EP0689902A1 - Connection for two-part handle

Info

Publication number: EP0689902A1
Application number: EP95420176A
Authority: EP
Inventors: William R. Witkowski; John D. Connors
Original assignee: Welch Allyn Inc
Current assignee: Welch Allyn Inc
Priority date: 1994-07-01
Filing date: 1995-06-30
Publication date: 1996-01-03
Also published as: CA2152522A1

Abstract

An elongated handle (10) has a proximal elongated plastic section (12) joined to a distal metal section (14). The plastic section (12) is provided with a plurality of flexible, longitudinally ribbed tabs (32,34) extending outwardly thereof, at least one of which has an outwardly extending cross longitudinal rib (33). The distal section has internal longitudinal grooves (41) that receive the longitudinal ribs (31), and also has a circumferential groove (43) formed in its internal surface for engaging the cross longitudinal rib (33). A self threading screw (40) from the distal portion (14) into the proximal portion (12) engages the tabs (32,34), urging them outward into locking engagement with the longitudinal and circumferential grooves (41,43). The screw (40) distributes mechanical stresses away from the metal-plastic interface, and is isolated from the distal section (14) by the tabs (32,34), so that the screw (40) does not loosen when the handle (10) is subjected to flexion and torsion.

Description

BACKGROUND 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 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 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, such 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 grasping by the hand, and to maintain a light weight, aesthetic appearance, the proximal portion could be plastic, another non-metal material, or even another metal. In many work environments it has been found that the 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 disassemble 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 repeatedly 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 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 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 has internal longitudinal grooves that receive the longitudinal ribs, and further having a cross longitudinal groove 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 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 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 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;
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 FIGS 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 ophthalmoscope 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 handle 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 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 21 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 longitudinal 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 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 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 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 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 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 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 of resisting flexion.
While this invention has been explained with reference to the structure disclosed herein, it is not confined to the details set forth and this application is intended to cover any modifications and changes as may come within the scope of the following claims:

Claims

An elongated handle comprising:
a proximal section;
a distal section connected to said proximal section to define an interface therebetween;
internal splint means disposed in said proximal section and in said distal section, said splint means extending across said interface for securing said proximal section in assembly with said distal section and for distributing mechanical stresses beyond said interface;
one of said distal section and said proximal section being provided with at least one flexible, longitudinally ribbed tab extending outwardly thereof, a said tab having an outwardly extending cross longitudinal rib;
the other of said distal section and said proximal section having at least one longitudinal groove formed in an internal surface thereof for engaging said longitudinal rib, and further having a cross longitudinal groove formed in said internal surface for engaging said cross longitudinal rib;
said internal splint means bearing on said tab to urge said longitudinal rib and said cross longitudinal rib into locking engagement with said longitudinal groove and said cross longitudinal groove respectively.
The handle in accordance with claim 1, wherein one of said distal section and said proximal section has a shoulder formed therein, and said internal splint means comprises threaded means that bears on said shoulder and is threaded into the other of said distal section and said proximal section.
The handle in accordance with claim 2, wherein said threaded means comprises a hollow self-tapping screw having a head that bears on said shoulder and having a threaded portion that is threaded into said other of said distal section and said proximal section.
The handle in accordance with claim 3, wherein said proximal section and said distal section each comprise hollow shells for receiving said screw therein.
The handle in accordance with claim 1, wherein one of said distal section and said proximal section is constructed of a first material, and the other of said distal section and said proximal section is constructed of a second material.
The handle in accordance with claim 5, wherein said first material comprises metal and said second material comprises plastic.
An elongated handle comprising:
a plastic proximal elongated hand grip section for grasping in the hand of a user, said elongated hand grip section having a length and cross sectional configuration so as to be grasped by the hand with the fingers in gripping relation thereto;
a metal distal section connected with said elongated hand grip section to define an interface therebetween;
screw means disposed in said elongated hand grip section and in said distal section, said screw means extending across said interface for securing said elongated hand grip section in assembly with said distal section and for distributing mechanical stresses beyond said interface;
one of said distal section and said elongated hand grip section being provided with at least two flexible, longitudinally ribbed tabs extending outwardly thereof, at least one of said tabs having an outwardly extending cross longitudinal rib;
the other of said distal section and said elongated hand grip section having longitudinal grooves formed in an internal surface thereof for engaging said longitudinal ribs, and further having a cross longitudinal groove formed in said internal surface for engaging said cross longitudinal rib;
said screw means bearing on internal surfaces of said tabs to urge said longitudinal ribs and said cross longitudinal rib into locking engagement with said longitudinal grooves and said cross longitudinal groove respectively.
The handle in accordance with claim 7, wherein said screw means comprises a self tapping screw.
The handle in accordance with claim 8, wherein threads of said screw engage internal surfaces of said tabs.