US3464527A - Clutch and indexing mechanism for tool spindle - Google Patents

Description

Sept. 2, 1969 w. J. BAKER 3,464,527

CLUTCH AND INDEXING MECHANISM FOR TOOL SPINDLE Filed D90. 13, v1967 //v|//vr0, WILL/AM J. BAKE/i ATTORNEY United States Patent U.S. Cl. 192--.072 3 Claims ABSTRACT OF THE DISCLOSURE A slip clutch having friction drive members and being particularly suitable for use in motor-driven power tools of the type which incorporate means to arrest the tool operating mechanism at a predetermined position. The clutch includes a notched cam disk splined to the tool drive spindle and in frictional driving engagement with a coaxially aligned gear rotatably mounted on the spindle. The friction faces of the cam disk and the gear are held in engagement by a coil spring; and, the gear meshes with the tool motor pinion. Positive engagement of the cam disk notch by a tool operating lever arrests the tool spindle in a predetermined rotary position and results in slippage of the gear relative to the cam disk thereby allowing the motor to decelerate smoothly .and providing variable stopping positions of the motor rotor? Background of the invention Tools used for wrapping electrical conductor wire about a terminal usually employ a rotary bit which receives one end of the wire in a longitudinal groove. The bit is usually driven by suitable motor and drive means housed in the tool proper. The highly repetitious nature of the tool usage makes desirable the prepositioning of the wire-receiving groove in the same angular position after each operation to facilitate insertion of the wire in the bit preparatory to the next tool operating cycle.

T o achieve this predetermined positioning of the wirewrapping bit, various rotation arresting or indexing mechanisms have been developed which function to arrest the bit as well as the entire tool rotary drive mechanism including the motor and associated driving components at the completion of each tool operating cycle.

Other tools of the aforedescribed general character usually employ somewhat complicated mechanical clutch de vices having interfitting dentil or jaw members which operate to engage with one member rotating relative to the other. Generally speaking, the prior art tools operate to start or stop the tool operating mechanism so abruptly that undue stress and wear are encountered on bearings, gear teeth, and other components often resulting in premature failure of these elements. Furthermore, provision for some form of overload release or slip feature is not inherently part of tools employing the aforementioned drive and indexing systems; and, if desired, this torque limiting feature must be added to the already complex operating mechanism further reducing the reliability and increasing the cost of the tool.

Another problem in the design and use of wire-wrapping tools is due to the repeated identical starting position of the tool motor which results from the operation of the indexing mechanism. This repeated starting from the same position may be highly detrimental to the motor, particularly electric motors employing brush and commutator assemblies. It is well known that current inrush during motor starting can severely limit brush and commutator life and that repeated starting from the same brush to commutator relative position will result in destructive sparkling and burning of the commutator bars so involved.

Patented Sept. 2, 1969 ICC One development in positive indexing mechanisms for wire-wrapping tools is disclosed in U.S. Patent No. 3,219,- 067 issued to J. L. Meyer. In the index device of Meyer, smooth motor and drive system deceleration is obtained by absorbing the kinetic energy of rotation with a torsion coil spring which is connected at one end to an index cam and at the other end to the tool drive spindle. However, the drive system stopping position of Meyer is constant; and, in addition, a reversal of motor rotation direction occurs briefly during the indexing phase of the tool operating cycle. This method of indexing not only creates the aforementioned problem of motor commutator bar burning, but also imparts a reversed electromagnetic force to the motor rectifier resulting in possible electrical damage to that component.

Summary of the invention The invention resides in the provision of an indexing clutch mechanism particularly suitable for use with wirewrapping tools powered by electric motors which comprises spring engaged friction drive members interposed between the tool motor and the wire-wrapping bit.

Sufficient frictional engagement of the drive gear with the indexing cam disk is provided to transmit the torque required to perform the wire-wrapping operation. However abrupt arresting or rotation of the indexing cam and tool spindle will cause slippage of the frictionally engaged cam and drive gear relative to each other to absorb tool motor kinetic energy of rotation smoothly by friction braking thereby substantially reducing impact loads on the motor and drive gearing.

Furthermore, the friction braking achieved by the invention prevents any reversal of motor rotation and the undesired reverse generation of electrical energy resulting therefrom.

An object of the invention, i.e. to provide variable relative starting positions of the tool motor commutator and brushes, is accomplished by selecting the engaging force between the friction drive members so that the momentum or rotational energy of the motor is frictionally dissipated through an angle of motor rotation which will provide a substantial number of motor stopping positions. The frictional engaging force is applied by a coil spring member.

Accordingly, the friction drive members also solve the problem of providing a torque limiting or overload release feature as part of the indexing mechanism to prevent tool or wire terminal damage. In reading the following description it will be apparent that the invention performs all of the aforementioned functions desirable in prepositioned rotation arresting mechanisms with a compact structure, simple in construction and reliable in operation.

Brief Description of the drawings FIG. 1 is a sectioned side elevation view of a typical hand-held wire-wrapping tool embodying the present invention.

FIG. 2 is a fragmentary section view taken along the line 2-2 of FIG. 1.

FIG. 3 is an exploded perspective view illustrating the components of the friction indexing clutch mechanism.

Description of the preferred embodiments Referring to FIG. 1 of the drawing, a typical electrio-ally powered wire-wrapping tool is illustrated having a casing 10 preferably consisting of two reversely turned mating halves (one shown in FIG. 1) of molded plastic and held in assembly by a plurality of threaded fasteners 12. The tool casing includes a handle portion 14 for manual gripping by the tool operator.

Extending into the bottom of the tool casing is an electric power cord 16 suitably secured by a strain relief device 18. Power cord leads 20 and 22 extend into the interior of the handle portion of the tool casing where lead 20 is secured to a terminal of a conventional, normally open, switch 24 fastened to the tool casing by pins 26. Contacts housed in the switch 24 may be operated to close by the plunger 28 which in turn is moved by a leaf spring member 30. The switch is closed by the tool operator through digital manipulation of a trigger 32 pivotally secured at 34 and positioned to engage the leaf spring 30. The trigger 32 is biased by a spring 36 to allow the switch 24 to open when digital pressure of the operator is relieved.

Wire lead 38 leaving the switch 24 is in communication with a fuse 40 followed by a lead 42 which together with lead 22 completes the electric circuit to a rectifier unit 44, which converts the alternating current power supply to a filtered direct current power supply suitable for energizing the tool motor 46.

The motor 46 is typical of small direct current types embodying a stator 48 enclosed within a frame consisting of two end members 50 and 52 and a cylindrical sleeve 54. An armature assembly consisting of an armature shaft 56, a commutator '58 and suitable armature windings '60 is supported by the frame members 50 and 52 in bearings 62. The armature assembly is rotatable relative to the stator 48 being separated therefrom by a small air a g lSirect current electric power is supplied to the motor 46 via the leads 64 and 66 connecting the rectifier unit 44 to the motor brushes 68 completing the electric circuitry of the tool.

Extending from a nose portion 70 of the tool casing is a collet 72 and nut 74. The collet is suitably secured to the casing 10 by fasteners, not shown. The collet and nut assembly function to retain an elongated sleeve 76 which in turn is appropriately adapted to house a wirewrapping bit 78 for rotation within the sleeve but proh'ibiting longitudinal displacement therefrom. The sleeve is prepositioned in the collet by a pin 79.

The distal end of the bit 78 includes a wire-receiving groove 80 and a terminal-receiving bore 82. As previously mentioned, it is desirable to preposition the wire-receiving groove to facilitate insertion of the wire into the groove by the tool operator prior to the wrapping operation ln the exemplary tool prepositioning of the wire-receiving groove 80, as shown in FIG. 1, results in longitudinal alignment with a flared wire guide portion 84 on the sleeve 76.

The wire-wrapping bit 78 extends into the bore of the collet 72 terminating with a tang portion 86 which 18 in positive driving engagement with a tang receiving recess 87 formed in a spindle 88. The spindle 88 forms a part of the rotation arresting or indexing mechanism of the tool.

Included with the spindle as part of the indexing mechanism is a cam disk 90 which is axially slidable over splines 92 formed on the spindle 88 (see FIG. 3) but is in positive rotary engagement with the spindle through complementary grooves engaging the splines 92. The cam disk 90 forms the driven member of a friction slip clutch.

Also axially aligned with the spindle 88 is a drive gear 94 comprising the driving member of the clutch and having a bore 96 slightly larger than the diameter of the splines 92 such that the gear 94 is rotatable relative to the spindle. The spindle, cam disk and drive gear may be advantageously made of molded plastic, thereby reducing the inertia of these parts and contributing to a lightweight tool design.

The complete assembly of the indexing mechanism includes a coil spring 98 bearing at one end against a collar 100 on the spindle 88, and at the opposite end against the 4- side of the 9am disk forcing the latter into engagement with the drive gear 94 on coacting friction surfaces 102 and 184, respective-1y. The drive gear 94 is axially retained on the spindle 88 by a pin 186 and an interposed grooved bushing 1-08.

In the assembled position of the indexing mechanism, as shown in FIG. 1, the spindle 88 is rota-t'ively journaled in the collet 72 and has a bushing pressed over the opposite end of the spindle which in turn is journaled in a bore 112 of the motor frame end plate 52. The drive gear 94 is in mesh with a pinion 114 press fitted over the end of the motor armature shaft 56.

Indexing of the tool bit 78 is accomplished by the cam disk 90 coacting with the trigger 32. As best shown in FIG. 2 the cam disk has a spiral cam surface 116 and a radially opening notch 118 which intersects with the cam surface 116 to provide a shoulder 120. The forward end of the upper surface of the trigger 32 has formed thereon an upwardly extending stop 122 which engages the cam disk notch 118 when the trigger is in the released position as shown in FIGS. 1 and 2.

The functions of the indexing mechanism will be better understood from the following description of the operation of the tool. Assuming the tool to be properly readied for performing the wire wrapping operation in a manner well known, upon digital depression of the trigger 32 the pivotal movement will cause the stop 122 to move out of engagement with the notch 118 in the cam disk 90 and sequentially result in engagement of the trigger with the leaf spring 30 causing depression of the plunger 28 to close the switch 24.

The resultant energization of the motor 46 will cause the spindle 88 and bit 78 to be rotat-ively driven through the meshing of the pinion 114 with the drive gear 94 and the frictional engagement of the gear with the cam disk 90. Direction of rotation will be as indicated by the arrow in FIG. 2.

At the completion of the tool operating cycle release of the trigger 32 will result in opening of the switch 24. As the spring 36 urges the trigger to pivot upwardly, the stop 122 will either engage the notch 128 immediately, should the instantaneous position of the cam disk 90 coincide, or the stop will ride the cam surface 116 until the inertial rotation of the motor and drive system effects engagement of the stop with the shoulder and still under the urging of the spring 36 the stop then seats fully in the notch 118. The rotation of the cam disk 90, spindle 88 and bit 78 is thereby arrested in a predetermined position for the next tool operating cycle. The momentum of the motor armature is still substantial upon arrestation of the spindle and bit to the extent that the drive gear 94 will begin to slip relative to the cam disk 90 and spindle 88 as the frictional engaging force of the cam disk and gear is overcome. The result is that the rotational energy of the armature is absorbed smoothly and dissipated as heat generated on the friction surfaces 104 and 102 on the gear and cam disk, respectively. In the aforedescribed manner the motor is braked without severe shock loads being applied to the gear teeth, bearings, and other rotating components of the tool. Also, the desired irregular stopping position of the commutator 58 relative to the stationary brushes 68 is obtained due to the selection of the spring 98 to exert a friction engaging force which will permit absorption of the motor rotational energy in an amount of angular rotation of the motor armature which will permit a substantial number of stopping positions. For example, the selection of a spring having an engaging force which will permit angular displacement of the drive gear relative to the cam disk of 270 will provide four stopping positions of the motor armature, provide slippage for smooth motor braking, and provide adequate driving engagement of the gear and cam disk for the Wire wrapping operation. The spring engaging force could be changed only minutely to provide a substantially greater number of motor stopping positions without having a deleterious eifect on the other mentioned operating characteristics. It will also be appreciated that the friction slip clutch mechanism serves as a torque limiting device to protect the tool components and the wire terminal in the event of sticking of the wire in the bit groove or jamming of the bit on the terminal. Furthermore, the use of the disclosed rotation arresting mechanism need not be limited to tools employing electric motors but could serve to permit smooth braking and provide overtorque protection for tools using pressure fluid motors which are commonly employed for wire wrapping operations.

It will be understood that the above description and acompanying drawings comprehend the preferred structural arrangement of the invention to give a compact and simple device to achieve the desired functions, however, various changes in construction, proportion, and arrangement of the elements may be made without sacrificing any of the advantages or departing from the scope of the appended claims.

What is claimed is:

1. In a tool:

(a) a motor capable of being in an energized condi tion and a deenergized condition;

(b) spindle means operatively connected to said motor to be driven thereby, said spindle means being operable to be arrested in a predetermined position;

(c) slip clutch means drivably coupling said motor and said spindle and operable to frictionally absorb the rotational energy of said motor upon arresting of said-spindle means, said clutch means including:

(1) a driving member comprising a toothed drive gear mounted on said spindle means in axial alignment therewith and in rotatable relationship relative thereto;

(2) a driven member mounted on said spindle in axial alignment therewith and in nonrotatable relationship relative thereto, said driven member including a transverse friction surface engageable with a corresponding transverse friction surface on said driving member;

(3) resilient means operable to hold said driving member and said driven member in frictional engagement for transmitting rotary motion to said spindle upon energization of said motor; and,

(d) indexing means operable to arrest said spindle means in said predetermined position, said indexing means comprising said driven member and an operating member for energizing said tool motor.

2. The invention set forth in claim 1 wherein:

said driven member is interposed between said driving member and said resilient means and said driven member is operable to be engaged by said tool operating member to arrest said spindle in said predetermined position.

3. The invention set forth in claim 1 wherein:

said driven member comprises a notched cam disk operable to engage said tool operating member for positive interfitting engagement of said notch with said operating member thereby arresting the rotation of said cam disk and said spindle means.

References Cited UNITED STATES PATENTS 2,351,997 6/1944 Morrill l92--2 2,539,836 1/1951 Hoffman 310--77 2,949,989 8/1960 Lindstrom et al. 1922 3,344,292v 9/1967 Hurst 310 76 3,367,460 2/1968 Wanner 19224 2,839,603 6/1958 Poll et a1. 192-148 XR 3,172,512 3/1965 Allen et al 192-148 XR BENJAMIN W. WYCHE III, Primary Examiner US. Cl. X.R.

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