US3920022A

US3920022A - Surgical instrument

Info

Publication number: US3920022A
Application number: US462383A
Authority: US
Inventors: Macey A Pastor
Original assignee: Individual
Current assignee: Individual
Priority date: 1974-04-19
Filing date: 1974-04-19
Publication date: 1975-11-18
Anticipated expiration: 1992-11-18

Abstract

A surgical pencil embodies interfitting relatively rotatable core and cap having eccentrically positioned bores at their forward ends. The two bores are aligned to readily receive and release the shank of a surgical tool when the core and cap are in a first position of relative rotation and are misaligned so as to firmly grasp and insure good electrical contact with the tool shank when the core and cap are in a second position of relative rotation. A resilient cantilevered finger on the core carries a longitudinally extending detent for selective engagement with a number of mating ribs carried by the cap to releasably retain the parts in selected position of relative rotation and to audibly indicate the amount and degree of relative rotation. The instrument is configured to allow one-handed operation to securely lock a tool thereto or to release it so that it will simply drop from the instrument handle.

Description

Pastor Nov. 18, 1975 [54] SURGICAL INSTRUMENT- [76] Inventor: Macey A. Pastor, 62222 Nita Ave.,

' 1 Woodland Hills, Calif. 91364 [22] Filed: Apr. 19, 1974 [21] Appl. No.2 462,383

[52] US. Cl. 128/303.13 [51] Int. Cl. A61B 17/36 [58] Field of Search..... 128/303.l3, 303.l4,.303.15, l28/303.16, 303.17, 303.18, 303.19; 279/6,

FOREIGN PATENTS OR APPLICATIONS France 403/350 Primary firaminer -channing L. Pace Attorney, Agent, or Firm-Gausewitz, Carr &

. Rothenbe rg [57] ABSTRACT A surgical pencil embodies interfitting relatively rotatable core and cap having eccentrically positioned bores at their forward ends. The two bores are aligned to readily receive and release the shank of a surgical tool when the core and cap are in a first position of relative rotation and are misaligned so as to firmly grasp and insure good electrical contact with the tool shank when the core and cap are in a second position of relative rotation. A resilient cantilevered finger on the core carries a longitudinally extending detent for selective engagement with a number of mating ribs carried by the cap to releasably retain the parts in selected position of relative rotation and to audibly indicate the amount and degree of relative rotation. The instrument is configured to allow one-handed operation to securely lock a tool thereto or to release it so that it will simply drop from the instrument handle.

11 Claims, 9 Drawing Figures US. Patent Nov. 18, 1975 Sheet 2 on 3,920,022

SURGICAL INSTRUMENT BACKGROUND OF THE INVENTION 1. Field of the Invention:

The present invention relates to surgical instruments and more particularly concerns an instrument handle for holding interchangeable tools.

2. Description of Prior Art In many types of surgical procedures, a slender, elongated blade is employed, often electrically energized. Blades are of many different types and configurations for different procedures and further, different blades at times may be employed in a single operation. For this reason, among others, it is desirable that the blades be readily removed and inserted into the instrument handle and, particularly, that they be securely fastened in placed when inuse.

Although sterilization is available for instruments that are repeatedly used, it is desirable and preferable, if possible, to employ devices that are sufficiently simple and inexpensive to permit use in a single procedure so that the device may be discarded rather than sterilized for reuse.

Where electrical energization of the instrument blade is employed, it is necessary that a good electrical contact be made with the blade. Nevertheless, the instrument body and the user must be fully and completely insulated from the conductive parts without undue heating.

A number of surgical pencils of the prior art, such as those shown in the U.S. Pat. Nos. to Peters (3,494,364), Guiorguiev (3,035,580), Wappler (1,717,480 and 1,932,258), Marton (2,110,735), Goode et al (3,597,582), and Miller (3,532,095), employ relatively complex and expensive instrument bodies, generally too costly to be disposable. Further, these arrangements embody different types of tool-holding chucks, such as spring-operated devices, which may either hold the tool shank too loosely or too tightly, whereby the tool may be inadvertently detached, or may be too difficult to remove when desired. The wet gloves often worn by a surgeon make it even more difficult to exert a firm pull on the smooth shank of common surgical blades.

Various types of eccentric fastening devices are exemplified by the U.S. Pat. Nos. to Bochory (3,447,820), the patent to Sharp (2,677,813), and the several patents to Hixon (2,093,079; 2,159,153; 2,182,896; and 2,264,754). These eccentric connectors are large and bulky, often requiring a number of different relatively movable parts. Further, they are not adapted for use with a surgical instrument.

Accordingly, it is an object of the present invention to provide an instrument of the type described which eliminates or minimizes disadvantages common in prior artdevices and affords improvements that allow ready interchangeability of instrument blades in a simple and inexpensive instrument.

SUMMARY OF THE INVENTION body portions so that the tool-receiving bores may be aligned with each other when the body portions are in a release position of relative rotation and will be relatively misaligned to firmly grasp the shank of a tool received in both of the bores when the body portions are relatively rotated to a locked position. The arrangement is such that the relative rotation may be a onehanded operation with the operator simply employing his fingers to twist the forward portion relative to the rear portion held in the same hand. According to another feature of the invention, a simplified releasable locking means is provided to insure a firm gripping of the tool shank.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a surgical instrument constructed in accordance with the principles of the present invention;

FIGS. 2 and 3 are longitudinal sections, with parts broken away, of the instrument shown in FIG. 1, showing the parts in fastened and release position;

FIG. 4 is a fragmentary perspective view of one end of the core, illustrating the resiliently mounted locking rib;

FIGS. 5 and 6 are sectional view taken on lines 55 and 66 of FIGS. 2 and 3, respectively;

FIG. 7 is a section taken on line 7-7 of FIG. 2; and

FIGS. 8 and 9 are sections taken on lines 88 and 99 of FIGS. 5 and 6, respectively.

DETAILED DESCRIPTION As illustrated in FIG. 1, an electrical surgical pencil releasably holds a tool 10 having a blade 12 and a substantially cylindrical shank 14. The pencil comprises a forward body portion or cap 16 and a rear body assembly 18 which is mounted to the forward body portion 16 for rotation relative thereto about an axis substantially aligned with the longitudinal center line of the pencil.

The forward body portion 16 comprises a slender elongated outer tubular element 20 having a first tool receiving bore 22 formed in the front end thereof and extending inwardly from the front tip 24 of the outer tubular sleeve 20.- At a suitable distance from the front end, a distance of approximately one half inch, for example, the tool receiving bore 22 terminates and communicates with an inner enlarged bore 26 which extends rearwardly throughout the remaining length of the outer tubular element to the rear end 28 thereof.

The rear body assembly 18 is formed of a core or inner tubular element 30 and a rear sleeve 32 which is secured thereto to provide a suitable rearward extension of the inner tubular element 30. Element 30 has a front end 34 which is formed with a cylindrical outer surface that is rotatably received within the inner enlarged bore 26 of element 20. The outer peripheral surface of the inner tubular element 30, at the rearward end thereof as indicated at 36, also has a substantially cylindrical surface (except for certain ribs formed therein as will be more particularly described hereinafter) which rotatably rides within the inner cylindrical surface of the rearward end of the element 20. Accordingly, the inner tubular element 30, together with its fixed rearward extension 32, is firmly and smoothly rotatably mounted to and within the outer tubular element 20.

Inner element 30 is also formed with a tool receiving bore 38a extending from the front end therein, which bore is defined by a metallic sleeve 38 having a flanged front end 40. Flange 40 is captured between the front end of the inner tubular element 30 and the shoulder 42 formed by the stepped transition from the tool receiving bore 22 to the enlarged inner bore 26 of the cap 20.

Sleeve 38 receives and is crimped upon a bared end 44 of an insulated electrical conductor 46 that extends through the hollow body of core 30 and through the hollow body of the rear extension 32 for connection to a suitable source of electrical energy (not shown).

Cap 20 has a plurality of circumferentially spaced longitudinally extending grooves 51 formed in its outer surface to facilitate gripping by the fingers of the user. If desired, rear extension 32 may be similarly formed with longitudinally extending grooves to facilitate gripping thereof. Conveniently the outer tubular element or cap 16 is made identical in size and shape to the rear extension 32 except for the formation of certain resilient locking ribs and a circumferentially extending slot, more particularly described below, that is formed in the cap 20.

The enlarged inner bore 26 of cap 20 is centered on an axis substantially aligned with the longitudinal axis of the entire instrument. The cylindrical outer surface of the front end 34 of core 30 is centered upon an axis coaxial with the axis of the surface of bore 26, so that relative rotation of the cap 20 and core 30 occur about a single axis of rotation. However, for the purpose of providing a chuck to insure rapid and positive gripping of the tool shank 14, when the latter is inserted into the tool receiving

bores

22 and 38a, the

bores

22 and 38a are centered upon an axis that is displaced from the axis of relative rotation of the cap and core.

Bores

22 and 380 are positioned so that in one position or condition of relative rotation of the cap 20 and core 30, the two bores are mutually aligned. This position of alignment is illustrated in FIG. 3 and the sections thereof shown in FIGS. 6 and 9. With this mutual alignment of the two tool-receiving

bores

22 and 38a, the tool shank I4 is relatively loosely received in both of the bores since the bores are formed with substantially mutually equal diameters that are slightly larger than, or at least will provide a relatively loose fit for, a tool shank of maximum diameter within the tolerance allowed in the tool manufacture. This arrangement allows the instrument to be used with tools of relatively widely varying tolerance. Thus, in this unlocked or aligned position, illustrated in FIGS. 3, 6 and 9, the tool shank is readily received within the two

bores

22 and 38a and, further, may be readily removed therefrom, for example, simply by pointing the tool receiving end of the instrument downwardly and allowing the tool to drop by virtue of its own weight.

Relative rotation of the cap 20 and core 30 through a relatively small angle, on the order of 90 or less, moves the parts to a locked position illustrated in FIGS. 2, and 8. In this locked position, the relative rotation of the core and cap has moved the two

bores

22 and 38a to positions of mutual misalignment, the position of bore 38a being indicated in the dotted lines in FIG. 5 and the position of bore 22 being indicated in solid lines in FIG. 5. In this position of relative misalignment, the tool shank 14 is tightly grasped by the tool receiving bores and pressed firmly into contact with and over a relatively large area of the electrically conductive sleeve 38 which defines the bore 38a. This contact insures not only a secure locking of the tool shank within 4 the instrument handle, but also insures a good electrical contact with the shank of the metallic tool.

As best illustrated in FIG. 7, the rear end portion 50 of the cap 20 is formed with a plurality of ribs 52a, b, 0, etc., which project radially inwardly therefrom and collectively define radially inwardly facing grooves 54a, b, c, etc., therebetween. Near the rear end 36 of the core 30 (as best seen in FIG. 4) there is provided a cantilevered resilient finger 56 which is conveniently formed from the body of the core 30 by means of a substantially U-shaped slot 58 cut through the core body. Formed upon the free or cantilevered end of the spring finger 56 is a radially outwardly projecting detent or rib 60 which has a longitudinal extent substantially equal to the longitudinal extend of the ribs 52a, b, c, etc. Also formed upon the spring finger and projecting radially outwardly therefrom, just forward of the rib 60, is a lug 62 that projects into a circumferentially extending slot 64 fonned in the rear end portion of the core just forward of the ribs 52 a, b, c, etc.

The resiliently mounted rib 60 cooperates with the ribs 52a, 52b, 52c, to form releasable locking or latching means that will restrain relative rotation of the cap and core, and which yet may be readily released by depressing the lug 62 a distance sufficient to at least partially disengage rib 60 from one of the grooves 54a, 54b, 54c, and thus permit relative rotation of the parts. Preferably, a visual indicator such as groove 65 provided with a suitably contrasting color or stripe, is formed on the lug 62 for cooperation with other indicia such as the printed word Lock, for example (not shown), that may be affixed to the rear end portion 50 of the cap 20. These indicia afford a visual indication of the position or condition of the pencil indicating whether it is in locked (gripping) or unlocked (release) position. Further, the locking rib 60 will provide a series of audible clicks and discrete tactile sensations as the rib 60 rides over successive ones of the ribs 52a, b, c, etc., during relative rotation. Thus, there is provided a combination of visual, audible and tactile indications of the locked or unlocked condition of the instrument which greatly facilitates proper positioning to insure locked condition of the surgical tool and also be provide a psychological assurance to the user.

It will be readily appreciated that the described instrument may be made of many of many different types of material and by many different manufacturing techniques. Nevertheless, for those situations where simplicity, cost and rapidity of manufacture are desirable goals, as for use in a disposable instrument for example, the parts are preferably injection molded of a suitable electrically non-conductive plastic such as Delrin or Lexan for example. As previously indicated, the cap 20 and the rear extension 32 of the core assembly 18 are made substantially indentical except for the slot 64 and ribs 52 formed in the cap. Core 30 is alsoinjection molded, including the resilient finger 56, rib 60 and lug 62 thereof. Further, core 30 is formed with a radially outwardly projecting circumferential stop 58 to facilitate precise positioning of the rear extension 32.

The instrument parts are readily assembled by sliding the rear extension 32 up on the core 30 into firm abuttment with stop 58. These parts may be suitably bonded to each other as by adhesive or sonci welding for example. Then the end 44 of conductor 46 is crimped into the end of sleeve 38 and threaded through body of the core 30 until the flange 40 of the sleeve 48 bears against the forward end of the front portion 34 of the core. It may be noted that the sleeve '38 is a relatively loose fit within the core 34 since it will be retained in place by the captureof its flange 40 between the front end of the core 34 and the shoulder 42 of cap 20. Now the lug 62 is depressed to move the spring finger 56 radially inwardly and allow the inner surface of the rear end of cap to be slid over the'front end of the core 30 until the lug 62is registered with slot 64. The lug is released and the two parts are then locked againstrelative axial motion, although the slot 64 and lug 62 allow the required amount of relative rotation. Assembly is now completed and the; instrument is ready for use. It will be seen that the entire apparatus is readily and inexpensively made, particularly since little precision is required and tolerances may be relatively large. Resilience of the rearwardly extendingportions of the core 30 where they rotatably engage the inner surfaces of the rear portions of cap 20 allows significant tolerances in dimensions of these parts. Further, relatively large tolerances may be employed in the dimensions of the metallic sleeve 38 and the bore formed in front end 34 of core 30 because of the nature of the locking operation of eccentric tool receiving bores. Still further, the eccentric bores allow use of tool shanks with relatively large tolerances since locking upon a tool shank of somewhat smaller than nominal diameter requires only a slightly greater amount of relative angular rotation. Locking upon a tool shank of somewhat larger than nominal diameter requires a lesser amount of relative rotation of the core and cap. A wide range of blade shapes and types may be employed whether or not electrically energized, including loops, needles and various types of cutting configurations.

The locking and unlocking of a tool shank is readily performed by one hand. For example, the rear body portion or core 30 together with its rear extension 32 may be grasped between the palm of the hand and the fourth and fifth fingers, while the thumb and forefinger grasp the forward body portion or cap 20 to achieve a simple and positive relative rotation between locked and unlocked positions.

In an exemplary embodiment, the entire instrument, without a blade, may have a length of between six and seven inches and an overall outer diamter of a quarter to three-eighths of an inch. Enlarged inner bore 26 may have a diameter of approximately one-quarter inch, with .the wall thickness of the cap at the enlarged bore being about one-sixteenth of an inch. Tool shank receiving bores 22 and 38a mayhave a diameter, depending upon the nominal size of a tool shank, which is in the order of one-eighth inches. Offset of the axis upon which the tool receiving bores are centered with respect to the axis of relative rotation is 0.008 inches in this exemplary embodiment, and the circumferential extent of the slot 64 is slightly more than 90 whereby a relative rotationof approximately 90 is available. It will be readily understood that the described dimensions are illustrative only since principles of the invention may be applied to a number of different configurations and sizes of devices made by other and different manufacturing techniques.

There has been described an improved, disposable, electrosurgical pencil formed of few and inexpensively made parts, providing simple and secure operation for one-handed release and locking of interchangeable instrument tools. r

The foregoing detailed description is to be clearly understood as given by way of illustration and example only, the spirit and scope of this invention being limited solely by the appended claims. What is claimed is:

1. A surgical instrument comprising a rear body por- 5 tion adapted to be held in the hand of an operator,

a forward body portion mounted to said rear body portion for rotation about a first axis and adapted to be grasped and rotated by the fingers of the hand in which the rear body portion is held,

said body portions respectively having first and second tool receiving bores positioned atrespective forward ends thereof and of substantially equal diameters, each said bore centered upon an axis displaced from said first axis,

said bores being aligned with each other when said body portions are in a first release position of relative angular rotation about said first axis, and being relatively misaligned when said body portions are in a second gripping position of relative angular rotation, whereby a tool shank may be freely inserted into or withdrawn from said aligned bores when the body portions are in said release position and said tool shank will be firmly grasped by the relatively misaligned bores when the body portions are in said gripping postion, said body portions being readily displaced between said gripping and release positions by a one-handed operation in which said forward body portion may be grasped between the operators thumb and another finger and said rear body portion may be grasped between the operators palm and other f'mgers of the same hand to accomplish movement of the body portions between said gripping and release positions, said forward body portion comprising an outer elongated tubular element having said first tool receiving bore formed in a front end thereof and having an enlarged inner bore extending from an inner end of said first tool receiving bore to the rearward end of said tubular element, said rear body portion comprising an inner tubular element having a front end portion rotatably received in a forward portion of said enlarged inner bore of said outer tubular element to provide at least part of the rotatable mounting of said body portions, said tool receiving bore of said rear body portion extending through said front end portion of said inner tubular element in end-to-end relation to the tool receiving bore of said outer tubular element,

said inner tubular element including an outer peripheral surface rotatably engaged with an inner surface of the inner bore of said first tubular element at a rear end thereof to provide a part of the rotatable mounting of the two body portions,

inner tubular element being axially inserted into said first tubular element and including means for restraining relative rotation of said tubular elements in any one of a plurality of positions of relative rotation.

2. The instrument of claim 1 wherein said means for limiting relative rotationcomprises a circumferentially extending slot formed in said outer tubular element and a lug' carried by said inner tubular element projecting radially outwardly therefrom into said slot, and means for resiliently restraining radially inward motion of said at lug, whereby the lug may be displaced radially inwardly against the resilient restraint thereof to allow relative axial motion of said first and second tubular element 7 and whereby said lug, when it projects through said slot, effectively prevents relative axial motion of said first and second tubular elements but permits a limited relative rotation thereof.

3. The instrument of claim 1 wherein said means for restraining relative rotation of said elements comprises a plurality of interengaging ribs mounted respectively on the inner surface of said outer tubular member and on the outer surface of said inner tubular member.

4. The instrument of claim 2 including means on said outer tubular member cooperating with said lug for providing an indication of the relative angular position of said tubular elements.

5. The instrument of claim 1 including a resilient finger formed in the body of said inner tubular element and a lug upstanding from said finger.

6. The instrument of claim 1 wherein said means for restraining relative motion of said tubular elements in positions of relative rotation comprises a first longitudinally extending rib resiliently carried by said inner tubular member and projecting radially outwardly therefrom, and a plurality of circumferentially spaced longitudinally extending ribs carried by the outer tubular member and projecting inwardly therefrom for selective engagement with said first resiliently carried rib as said tubular elements are relatively rotated.

7. The instrument of claim 1 wherein said inner tubular element includes a spring finger formed therein and having a radially outwardly projecting lug and a radially outwardly projecting longitudinally extending rib formed on said finger, a circumferentially extending slot formed in said outer tubular member for receiving said lug and cooperating therewith to limit relative rotation of said tubular elements, and at least one radially inwardly facing groove formed on the inner surface of said outer tubular member for cooperation with said outwardly projecting rib to restrain a relative rotation of said tubular elements.

8. A tool holder comprising an elongated tubular cap having a first tool receiving bore extending from one end of said cap and centered upon a first tool axis, an elongated tubular core mounted within said cap for rotation relative to the cap about an operating axis, said core having a second tool receiving bore extending from one end of the core, said second tool receiving bore being of a diameter substantially equal to the diameter of said first tool receiving bore and centered upon a second tool axis,

said first and second tool axes being substantially mutually aligned and displaced from said operating axis when said cap and core are in a first angular position of relative rotation about said operating axis, whereby a tool shank maybe readily inserted and removed from a position extending within both bores, and whereby relative rotation of said core and cap to a second angular position will displace one of said tool axes relative to the other and cause said first and second tool receiving bores to grip said tool shank, and

means for releasably retaining said core and cap in said second angular position, said cap being formed with an enlarged bore extending from said first tool receiving bore toward the other end of said cap, said one end of said elongated core being rotatably received in a forward portion of said enlarged bore of the cap, said core having a rearward portion ro- 8 tatably received within the enlarged bore of said cap at a rear portion thereof to provide a rotatable support for said core within said cap at both the front and rearward ends of said cap and core, said cap and core being formed of electrically nonconductive material, at least one of said tool receiving bores being defined by an electrically conductive sleeve, an electrical conductor connected with said conductive sleeve and extending rearwardly through said elongated core and cap, said cap being formed with a circumferentially extending slot and a plurality of circumferentially spaced longitudinally extending ribs adjacent said slot, said ribs extending radially inwardly of said cap, said elongated core being formed with a spring finger having a radially outwardly projecting lug fixed thereto and extending into said circumferentially extending slot of said cap, said finger having a longitudinally extending and radially outwardly projecting rib formed thereon for cooperation with said radially inwardly projecting ribs of said cap to provide a releasable restraint of relative rotation of said core and cap.

9. A tool holding chuck comprising a core having a first bore extending into the core from one end thereof,

a cap having a second bore extending into the cap from one end thereof and having a diameter substantially equal to the diameter of said first bore,

means for mounting said cap core for relative rotation about a first axis,

said first and second bores being centered upon axes displaced from said first axis and being mutually aligned when said core and cap are in a release position of relative rotation wherein a tool shank may be loosely engaged within both of said bores,

means for relatively rotating said core and cap toward a gripping position whereby said bores are relatively radially displaced from each other and said tool shank is gripped thereby, means independent of said bores for limiting relative rotation of said core and cap through a path of limited length whether or not a tool shank is inserted in said chuck, and

means for releasably latching the core and cap in any one of a plurality of position s of relative rotation within said path, said last named means comprising a plurality of interengaging ribs on said core and cap, at least one of said ribs being resiliently mounted.

10. The chuck of claim 9 wherein said means for relatively rotating said core and cap comprises a portion of the cap forming a first handle extending rearwardly from said one end thereof to provide a first surface remote from said tool to be grasped by an operator, and further comprises a portion of the core forming a second handle extending rearwardly of said one end thereto to provide a second surface remote from said tool to be grasped by an operator, whereby said tool may be readily gripped or released by operation of said first and second handles at a distance from said tool.

11. The apparatus of claim 9 wherein said means for limiting relative rotation of said core and cap comprises a circumferentially extending slot in one of said core and cap and a lug on the other of said core and cap projecting into said slot.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3, 920, 022 DATED November 18, 1975 |NVENTOR(S) acey A. Pastor It rs certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 4, line 15, extend should be extent C 1, line 64, sonci should be sonic 0 C01. 4, line 67, 48 should be 38 C01, line 55, before word inner insert Word said Signed and Scaled this sixth Day Of April 1976 i [SEAL] I Attest: i

RUTH C. MASON C. MARSHALL DANN Alfsll'ng H ('Hmmissioncr qflatvnls and Trademarks i i F i I i

Claims

1. A surgical instrument comprising a rear body portion adapted to be held in the hand of an operator, a forward body portion mounted to said rear body portion for rotation about a first axis and adapted to be grasped and rotated by the fingers of the hand in which the rear body portion is held, said body portions respectively having first and second tool receiving bores positioned at respective forward ends thereof and of substantially equal diameters, each said bore centered upon an axis displaced from said first axis, said bores being aligned with each other when said body portions are in a first release position of relative angular rotation about said first axis, and being relatively misaligned when said body portions are in a second gripping position of relative angular rotation, whereby a tool shank may be freely inserted into or withdrawn fRom said aligned bores when the body portions are in said release position and said tool shank will be firmly grasped by the relatively misaligned bores when the body portions are in said gripping postion, said body portions being readily displaced between said gripping and release positions by a one-handed operation in which said forward body portion may be grasped between the operator''s thumb and another finger and said rear body portion may be grasped between the operator''s palm and other fingers of the same hand to accomplish movement of the body portions between said gripping and release positions, said forward body portion comprising an outer elongated tubular element having said first tool receiving bore formed in a front end thereof and having an enlarged inner bore extending from an inner end of said first tool receiving bore to the rearward end of said tubular element, said rear body portion comprising an inner tubular element having a front end portion rotatably received in a forward portion of said enlarged inner bore of said outer tubular element to provide at least part of the rotatable mounting of said body portions, said tool receiving bore of said rear body portion extending through said front end portion of said inner tubular element in end-to-end relation to the tool receiving bore of said outer tubular element, said inner tubular element including an outer peripheral surface rotatably engaged with an inner surface of the inner bore of said first tubular element at a rear end thereof to provide a part of the rotatable mounting of the two body portions, inner tubular element being axially inserted into said first tubular element and including means for restraining relative rotation of said tubular elements in any one of a plurality of positions of relative rotation.

2. The instrument of claim 1 wherein said means for limiting relative rotation comprises a circumferentially extending slot formed in said outer tubular element and a lug carried by said inner tubular element projecting radially outwardly therefrom into said slot, and means for resiliently restraining radially inward motion of said lug, whereby the lug may be displaced radially inwardly against the resilient restraint thereof to allow relative axial motion of said first and second tubular element and whereby said lug, when it projects through said slot, effectively prevents relative axial motion of said first and second tubular elements but permits a limited relative rotation thereof.

8. A tool holder comprising an elongated tubular cap having a first tool receiving bore extending from one end of said cap and centered upon a first tool axis, an elongated tubular core mounted within said cap for rotation relative to the cap about an operating axis, said core having a second tool receiving bore extending from one end of the core, said second tool receiving bore being of a diameter substantially equal to the diameter of said first tool receiving bore and centered upon a second tool axis, said first and second tool axes being substantially mutually aligned and displaced from said operating axis when said cap and core are in a first angular position of relative rotation about said operating axis, whereby a tool shank maybe readily inserted and removed from a position extending within both bores, and whereby relative rotation of said core and cap to a second angular position will displace one of said tool axes relative to the other and cause said first and second tool receiving bores to grip said tool shank, and means for releasably retaining said core and cap in said second angular position, said cap being formed with an enlarged bore extending from said first tool receiving bore toward the other end of said cap, said one end of said elongated core being rotatably received in a forward portion of said enlarged bore of the cap, said core having a rearward portion rotatably received within the enlarged bore of said cap at a rear portion thereof to provide a rotatable support for said core within said cap at both the front and rearward ends of said cap and core, said cap and core being formed of electrically non-conductive material, at least one of said tool receiving bores being defined by an electrically conductive sleeve, an electrical conductor connected with said conductive sleeve and extending rearwardly through said elongated core and cap, said cap being formed with a circumferentially extending slot and a plurality of circumferentially spaced longitudinally extending ribs adjacent said slot, said ribs extending radially inwardly of said cap, said elongated core being formed with a spring finger having a radially outwardly projecting lug fixed thereto and extending into said circumferentially extending slot of said cap, said finger having a longitudinally extending and radially outwardly projecting rib formed thereon for cooperation with said radially inwardly projecting ribs of said cap to provide a releasable restraint of relative rotation of said core and cap.

9. A tool holding chuck comprising a core having a first bore extending into the core from one end thereof, a cap having a second bore extending into the cap from one end thereof and having a diameter substantially equal to the diameter of said first bore, means for mounting said cap core for relative rotation about a first axis, said first and second bores being centered upon axes displaced from said first axis and being mutually aligned when said core and cap are in a release position of relative rotation wherein a tool shank may be loosely engaged within both of said bores, means for relatively rotating said core and cap toward a gripping position whereby said bores are relatively radially displaced from each other and said tool shank is gripped thereby, means independent of said bores for limiting relative rotation of said core and cap through a path of limited length whether or not a tool shank is inserted in said chuck, and means for releasably latching the core and cap in any one of a plurality of position s of relative rotation within said path, said last named means comprising a plurality of interengaging ribs on said core and cap, at least one of said ribs Being resiliently mounted.