US 3301364 A
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Description (OCR text may contain errors)
1 6 J. D. BENNETT ETAL 3,301,354
TORQUE TRANSFER DEVICE Filed Oct. 15, 1964 F l G.
22 2e 7 2e A y 28 u INVENTORS JOHN D. BENNETT 0nd WALTER CARL CALDWELL, Jr.
BY 2 i v 0 ATTORNE Un ted,v S tes Patent This invention relates to a friction type coupling device which provides a variable amount of torquetransfer between two relatively rotating members.
For purposes of illustration, the present inventionwill be described in connection with a magazine indexing mechanism although it will be readily apparent" that the. invention is of much broader utility and may 'be used, for. example, in connection with the drive of reels of movie film or tape recording reels or in any other mechanism which requires a simple device for transferring variable degrees of torque or drag force between two relatively moving members. his a principal object of the present invention to provide a torque transfer device which is exceptionally simple.
in construction, highly compact and substantially more economical than has been previously possible. a a I It is a further object of the present invention to provide a torque transfer device wherein the degree of torque transfer 'may be varied depending upon the'direction 'of' relative rotation of the two members connectedthereby The above objects as'well as others relating more particularly to the details of construction and o'peration will Patented Jan. 31, 1967 ice 2'- internal diameter of'bore 32' is substantially greater than become more fully apparent from the following de's'c-ription when taken in conjunction with the accompanying drawings in which:
FIGURE 1 is a simplified, elevational view, partly broken away illustrating the present invention in combination with an indexing mechanism for a rotatable magazme; .1
FIGURE 2 is a sectional view of the indexing mechanism taken along the plane indicated byline 2Z" Of FIG- UR-E 1 and indicating the relative-positions oftheMelements when no torque is being transferred;
FIGURE 3 is a sectional view taken al'ong'thfe plane-of;
FIGURE 2 indicating the relative positions of the elements when torque is being transferred in a first direction; and
FIGURE 4 is a sectional view taken along the plane of FIGURES 2 and 3 indicating the relative positions of the elements when torque is being transferred in the opposite direction.
Referring first to FIGURE 1, numeral 10 indicates a support member which includes a stub shaft 12 upon which a magazine 14 is journalled for rotation. By way of example, magazine 14 may be of the type having radial slots 16 adapted to receive transparent slides which are conveyed by the magazine to means (not illustrated) for individually projecting or viewing each of the slides.
In order to rotate the magazine intermittently so as to position the individual slides in the viewing mechanism successively, the magazine carries a plurality of indexing pins 18 which are spaced about the periphery of the magazine and which project outwardly from the rear surface of the magazine. Each of pins 18 is adapted to be en gaged -by one end of a pawl 20 the oposite end of which is connected to and actuated by a crank member 22 which extends through an aperture 24 provided in support member 10. Support member 10 also mounts an abutment 21 which serves to limit the clockwise movement of pawl 20.
As more clearly shown in FIGURES 2-4, crank 22 includes a drive shaft portion 26, a disc portion 28 and a projecting stud 30 the latter of which extends through a bore 32 provided in pawl 20. It will be noted that the the diameter ofstud 30 so that a spring 34 may be ac-' commodated in the annular-space formed between the studand-thebore. For purposes of illustration, the size of "this'annular space has been exaggerated in order to more clearly show the movement of the spring, whereas,
in practice, the diameter of bore 32 need only be equal to the diameter of stud 30 plus twice'the diameter of the spring wire'plus a slight running clearance.
Reference is now made to FIGURE 2 which illustrates the spring configuration when the crank 22 is stationary.
Spring 34 is of conical shape-with the first and last turns being circular-and the intermediate turns being helical.
Thus, the first turn is received in a groove 36 provided in stud 30 and the last turn is received in a recess 38 provided in bore 32. At this point it is to be understood that the first and second turns comprising the leftmost end' of thesp-ring havediameters slightly'less than the diam etersof groove 36 and the main portion of stud 30, re-
spectively. Thus, the first two turns of the spring must be slightly expanded in order to be snapped into position on the stud and, once positioned thereon, these two turns remain "in frictional engagement with the stud.
At the other end of the spring, the lasttwo turns have diameters which are slightly greater than the internal diameters of bore 32 and recess 38. Thus, the lasttwo turns must be slightly contractedin order to 'be snapped into position and, once positioned therein, the last two turns remain in frictional engagement with the surface ofbore 32. Lastly, it will be'noted that the diameters of the turns intermediate those just described are such that, as long as the crank is stationary, these turns do not engage either the stud nor the surface of the bore.
The operation of the mechanism will now be described v with particular reference to FIGURES 1,3 and 4. In
' order to index magazine 14 about-shaft 12 in a clockwise direction, crank 22is driven in a counterclockwise direction as viewed in; FIGURE 1.. As soon as crank 22 bethe relative angular movement between the stud and pawl 20 causes spring 34 to begin to wind itself about the stud and this winding action increases the frictional engagement between the stud and the spring so that the spring does not slip relative to the stud. Thus, the spring continues to wind itself about the stud until the second last turn of the spring disengages the surface of bore 32. At this point, the frictional engagement between the spring and the pawl is thereby reduced so that the last turn of the spring begins to slip within recess 38. However, this slipping action imposes a drag force on the pawl tending to bias the upper end of the pawl into engagement with successive pins 18 as the latter are indexed by the continued reciprocation of pawl 20. Of course, the magnitude of this biasing force is determined by the degree of frictional engagement between the last turn of the spring and the internal surface of recess 38 which, in turn, is dependent upon the amount of tension imposed on the last turn in order to be snapped into the groove upon the initial assembly.
When it is desired to remove the upper end of the pawl from engagement with pins 18 so as to install or remove the magazine, crank 22 is rotated in the opposite direction, i.e., clockwise as viewed in FIGURE l. Rotation of the crank in this direction causes the spring to begin to unwind from the stud so that the intermediate turns of the spring come into frictional engagement with the surface of bore 32. This unwinding action continues until only the last turn of the spring remains in engagement with the pawl, at which point, this turn begins to slip within recess 38 whileimposinga drag force on the pawl. Thus, pawl 20 is retracted from engagement with pins 18 and abuts stop member 21 with a biasing force which is determined by the amount of frictional engagement between recess 36 and the single turn of the spring in frictional engagement therewith. Of course, the magnitude of this biasing force is dependent upon the amount of force which was necessary to initially contract the end of the spring so as to snap it in place in the recess.
From the foregoing description it will be apparent that spring 34 forms :an exceptionally simple coupling the torque transfer characteristics of which are dependent upon the initial diameter relationships between the ends of the spring and the associated surfaces which they engage. It will also be apparent that these diameter relationships may be selected such that a greater or lesser amount of torque or drag force is transferred depending upon the direction of relative rotation between the members. In addition, it will be noted that the spring also serves to retain the pawl on the stud so that the pawl cannot move axially off the stud. Thus, the disclosed invention provides a most compact and economical mechanism for retaining two relatively rotating members in position while being capable of transferring variable amounts of torque therebetween.
From the foregoing description it will also be apparent that the present invention is in no way limited to use with a pawl and crank, but rather, may be employed to transfer various degrees of torque between any two relatively rotating members. Thus, it is to be understood that the foregoing description is intendedto be illustrative of the invention and that the latter is not to be otherwise limited than as specifically set forth in the following claims.
What is claimed is: I
1. Arfrictional drive mechanism comprising a first member having a bore therein, a second member extending into said bore, the diameter of said second member being less than the diameter of said bore so as to define an annular space between said second member and the internal surface of said bore, a spring which, in its relaxed state, takes the form of a conical helix positionedin said space surrounding said second member, one end of said spring being in frictional engagement with said second member and the' other end of said spring being in frictional engagement with the surface of said bore, and'means transmitting rotationalpower to impart a cranking motion to one of said first and second members whereby, upon relative angular movement of said members in one direction, said spring winds about said second member and slips relativeto said first member so as to impart a frictional drag force between said members in a first direction and,.upon relative angular movement of said members in the opposite direction, said spring unwinds from said second member and slips relative to said second member so as to impart a frictional drag force between said members in the opposite direction. I
i 2. A frictional drive mechanism comprising a first member having a bore therein, a second memberextending into said bore, the diameter of said second member being less than the diameter of said bore so as to define an annular space between .said second member and the internal surface of said bore, a spring which, in its re-f laxed state, takes the form of a conicalhelix positioned in said space surrounding said second member, a plurality of turns at one end of said spring being in frictional engagement with said second member and a plurality of turns at the other end of said spring being in fric-- tional engagement with the surface of said bore, and
means transmitting rotational power to impart a cranking motion to one of said first and second members whereby, upon relative angular movement of said mem-' References Cited by the Examiner UNITED STATES PATENTS 1,126,780 2/1915 Jones 64-30 X 2,595,454 5/1952 Greenlee -30 2,895,578 7/1959 Winchell 192-72 X DAVID J. WILLIAMOWSKY, Primary Examiner. BENJA MIN W. WYCHE III, Examiner.