CA1248787A - Adjustable torque limiting assembly - Google Patents
Adjustable torque limiting assemblyInfo
- Publication number
- CA1248787A CA1248787A CA000471490A CA471490A CA1248787A CA 1248787 A CA1248787 A CA 1248787A CA 000471490 A CA000471490 A CA 000471490A CA 471490 A CA471490 A CA 471490A CA 1248787 A CA1248787 A CA 1248787A
- Authority
- CA
- Canada
- Prior art keywords
- wrap spring
- torque limiting
- pair
- limiting assembly
- assembly
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING OR HOLDING
- B25B23/00—Details of, or accessories for, spanners, wrenches, screwdrivers
- B25B23/14—Arrangement of torque limiters or torque indicators in wrenches or screwdrivers
- B25B23/141—Mechanical overload release couplings
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- One-Way And Automatic Clutches, And Combinations Of Different Clutches (AREA)
Abstract
ABSTRACT
An adjustable torque limiting assembly includes a first wrap spring mechanism which provides a readily adjustable torque transmission limit and a second coaxially disposed wrap spring mechanism which provides a mechanical signal that the torque limit has been reached. This signal may be utilized to terminate an energy supply to a prime mover associated with the torque limiting assembly. The first wrap spring mechanism generally includes a wrap spring in which the spring moment and thus the slip or overrunning torque threshold may be readily adjusted. The second wrap spring assembly likewise includes a wrap spring which is activated only subsequent to slip of the first wrap spring and enlarges to engage a concentrically disposed control sleeve. The control sleeve then rotates and activates an associated shut-off mechanism. Drive from the first wrap spring assembly to an output shaft is through an overrunning clutch assembly which allows energy in the wrap springs to dissipate and the springs to wind down and return to their start positions when power to the torque limiting assembly is removed.
An adjustable torque limiting assembly includes a first wrap spring mechanism which provides a readily adjustable torque transmission limit and a second coaxially disposed wrap spring mechanism which provides a mechanical signal that the torque limit has been reached. This signal may be utilized to terminate an energy supply to a prime mover associated with the torque limiting assembly. The first wrap spring mechanism generally includes a wrap spring in which the spring moment and thus the slip or overrunning torque threshold may be readily adjusted. The second wrap spring assembly likewise includes a wrap spring which is activated only subsequent to slip of the first wrap spring and enlarges to engage a concentrically disposed control sleeve. The control sleeve then rotates and activates an associated shut-off mechanism. Drive from the first wrap spring assembly to an output shaft is through an overrunning clutch assembly which allows energy in the wrap springs to dissipate and the springs to wind down and return to their start positions when power to the torque limiting assembly is removed.
Description
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TITLE
ADJUSTABLE TORQUE LIMITING ASSEMBLY
BACKGROUND OF THE INVENTION
The instant invention relates generally to adjustable torque limiting assemblies and more specifically to adjust-able torque transmitting assemblies which are capable of providing an indication or signal that the preselected torque threshold has ~een reached.
Mechanical assemblies designed to determine torque throughput and utilize such determination to limit such torque by slip or by terminating the flow of energy to an associated prime mover are common power train components.
Such assemblies, for example, are an integral portion of power tools which are utilized to tighten fasteners, secure threaded components and generally tighten coupling mecha-nisms to a desirable level of torque. For purpcses of illustration, a specific example is known as a nut runner;
a device having an electric or, more typically, pneumatic motor which drives a through gear reduction device to tighten threaded fasteners such as bolts, nuts and the ' like. In such applications, it is desirable to quickly, repeatedly and accurately tighten the fastener such that the associated components are secuxed together with a '-, necessary, predetermined force. Numerous approaches have ,~ been taken, particularly with,pneumatic motors to achieve ;; this goal, motor back pressure sensors, stall torque ' controllers and strain yauges coupled to associated ; 30 electronic~ and controls, to name but three. Mechanical ~' devices such as back pxessure sensors typically suffer from an inability to be readily adjusted whereas such electronic ` de~ices may be delicate and complex.
A second drawback of all systems wherein operation of the prime mover continues until the sensed torque achieves ; a predetermined threshold at which time energy flow to the .~ '.
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TITLE
ADJUSTABLE TORQUE LIMITING ASSEMBLY
BACKGROUND OF THE INVENTION
The instant invention relates generally to adjustable torque limiting assemblies and more specifically to adjust-able torque transmitting assemblies which are capable of providing an indication or signal that the preselected torque threshold has ~een reached.
Mechanical assemblies designed to determine torque throughput and utilize such determination to limit such torque by slip or by terminating the flow of energy to an associated prime mover are common power train components.
Such assemblies, for example, are an integral portion of power tools which are utilized to tighten fasteners, secure threaded components and generally tighten coupling mecha-nisms to a desirable level of torque. For purpcses of illustration, a specific example is known as a nut runner;
a device having an electric or, more typically, pneumatic motor which drives a through gear reduction device to tighten threaded fasteners such as bolts, nuts and the ' like. In such applications, it is desirable to quickly, repeatedly and accurately tighten the fastener such that the associated components are secuxed together with a '-, necessary, predetermined force. Numerous approaches have ,~ been taken, particularly with,pneumatic motors to achieve ;; this goal, motor back pressure sensors, stall torque ' controllers and strain yauges coupled to associated ; 30 electronic~ and controls, to name but three. Mechanical ~' devices such as back pxessure sensors typically suffer from an inability to be readily adjusted whereas such electronic ` de~ices may be delicate and complex.
A second drawback of all systems wherein operation of the prime mover continues until the sensed torque achieves ; a predetermined threshold at which time energy flow to the .~ '.
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- 2 - 71636-1 prime mover is terminated, is that in such devices, almost without exception, the drive components such as the motor and gear train are directly coupled to the driven fastener. In this situation, in spite of the fact that the monitoring device has sensed attainment of the torque limit and -terminated energy flow to the motor, the momentum of the drive train will be transmitted to the fastener, generally over-torquing it. Initially, it would seem that this difficulty could be corrected by simply lowering the required torque threshold by an amount commensurate with the momentum energy. However, the rate at which the motor decelerates as it approaches the torque limit due to the hardness or softness of the joint will effect the momentum energy applied to the fastener and render such a simple compensation scheme generally ineffective.
It thus becomes apparent that an improved torque limiting assembly will both permit ready adjustment of the torque trans-mission limit as well as providing a means whereby all or a major portion of the drive train energy can be prevented from reaching the driven device.
SUMMARY OF THE INVENTION
It is therefore an object of the instant invention -to provide an adjustable torque limiting assembly wherein the -torque transmission threshold is readily adjustable.
According to one aspect of the instant invention there is provided an adjustable torque limiting assembly comprising, in combination, a wrap spring having a pair of ends, an input member having means for engaging said pair of ends of said wrap spring, means associated with said input member for adjusting -~ ,.
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It thus becomes apparent that an improved torque limiting assembly will both permit ready adjustment of the torque trans-mission limit as well as providing a means whereby all or a major portion of the drive train energy can be prevented from reaching the driven device.
SUMMARY OF THE INVENTION
It is therefore an object of the instant invention -to provide an adjustable torque limiting assembly wherein the -torque transmission threshold is readily adjustable.
According to one aspect of the instant invention there is provided an adjustable torque limiting assembly comprising, in combination, a wrap spring having a pair of ends, an input member having means for engaging said pair of ends of said wrap spring, means associated with said input member for adjusting -~ ,.
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- 3 - 71636-l the angular position of one of said pair of ends relative to the other of said pair of ends, and an output member disposed within said wrap spring, said output member having a cylindrical portion engaged by at least a portion of said wrap spring.
According to another aspect of the instant invention there is provided an assembly for limiting torque transmission comprising in combination, a first wrap spring having a pair of ends, input member having means for engaging said pair of ends of said first wrap spring, means associated with one of said pair of ends of said first wrap spring for adjusting the angular position of said one of said pair of ends relative to the other of said pair of ends, an inner sleeve disposed within said first wrap spring, an output member, an overrunning clutch operably disposed between said sleeve and said output member, a second wrap spring disposed to engage portions of said input member and said output member, and an outer sleeve disposed about said second wrap spring.
According toafurther aspect of the instant invention there is provided an assembly for limiting torque throughput ~0 comprising, in combination, a first wrap spring having a pair of ends, an input member having a pair of means for engaging a respective one of said pair of ends of said first wrap spring, means associated with one of said pair of ends of said first wrap spring for adjusting the angular position of said one of said pair of ends relative to the other of said pair of ends, a cylindrical sleeve disposed within said first wrap spring, an output member, an overrunning clutch assembly operably disposed between said cylindrical sleeve and said output member, a second ~L2~
According to another aspect of the instant invention there is provided an assembly for limiting torque transmission comprising in combination, a first wrap spring having a pair of ends, input member having means for engaging said pair of ends of said first wrap spring, means associated with one of said pair of ends of said first wrap spring for adjusting the angular position of said one of said pair of ends relative to the other of said pair of ends, an inner sleeve disposed within said first wrap spring, an output member, an overrunning clutch operably disposed between said sleeve and said output member, a second wrap spring disposed to engage portions of said input member and said output member, and an outer sleeve disposed about said second wrap spring.
According toafurther aspect of the instant invention there is provided an assembly for limiting torque throughput ~0 comprising, in combination, a first wrap spring having a pair of ends, an input member having a pair of means for engaging a respective one of said pair of ends of said first wrap spring, means associated with one of said pair of ends of said first wrap spring for adjusting the angular position of said one of said pair of ends relative to the other of said pair of ends, a cylindrical sleeve disposed within said first wrap spring, an output member, an overrunning clutch assembly operably disposed between said cylindrical sleeve and said output member, a second ~L2~
- 4 - 71636-1 wrap spring disposed to engage portions of said input member and said output member, and a sensing element concentrically disposed about said second wrap spring and rotatable between a first position and a second position.
Further objects and advantages of the instant invention will become apparent by reference to the following description of the preferred embodiment and attached drawings.
BRIEF DESCRIPTION O~ THE DRAWINGS
Figure 1 is a full, sectional view o~ an adjustable torque limiting assembly according to the instant invention;
Figure 2A is an exploded, perspective view of a portion of the elements of an adjustable torque limiting assembly accord-ing to the instant invention; and Figure 2B is an exploded, perspective view of the remaining elements of an adjustable torque limiting assembly according to the instant invention.
DESCRIPTION OF THE PREFERRED EMBODI~ENT
Referring now to Figures 1, 2A and 2B, an adjustable torque limiting assembly according to the instant invention is illustrated and generally designated by the reference numeral 10.
The assembly 10 includes and is generally contained within an elongate cylindrical housing 12. The housing 12 includes a threaded, reduced diameter portion 14
Further objects and advantages of the instant invention will become apparent by reference to the following description of the preferred embodiment and attached drawings.
BRIEF DESCRIPTION O~ THE DRAWINGS
Figure 1 is a full, sectional view o~ an adjustable torque limiting assembly according to the instant invention;
Figure 2A is an exploded, perspective view of a portion of the elements of an adjustable torque limiting assembly accord-ing to the instant invention; and Figure 2B is an exploded, perspective view of the remaining elements of an adjustable torque limiting assembly according to the instant invention.
DESCRIPTION OF THE PREFERRED EMBODI~ENT
Referring now to Figures 1, 2A and 2B, an adjustable torque limiting assembly according to the instant invention is illustrated and generally designated by the reference numeral 10.
The assembly 10 includes and is generally contained within an elongate cylindrical housing 12. The housing 12 includes a threaded, reduced diameter portion 14
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which may be engaged within complementary threads in the housing of a prime mover (not illustrated) such as an electric or pneumatic motor. On the end of the housing 12, opposite the reduced diameter portion 14, is an internally threaded region 16 which receives a complementarily threaded housing 18 which may be associated with a final drive device (not illustrated).
A first wrap spring assembly 20 generally includes an input shaft 22 which is supported by an anti-friction bearing such as a ball bearing assemhly 24 and which preferably includes an integrally formed input hub 26 having splines 28 disposed about its periphery. Concen-trically disposed about and receiving the splines 28 of the input hub 26 and extending generally axially away from the input shaft 22 is a coupling annulus 32 having complemen-tary splines 34 disposed orl its inner surface. Also received and retained within the coupling annulus 32 is a spring receiving adjustment hub 36 having complementary splines 38 which engage the splines 34 within the coupling annulus 32. The adjustment hub 36 defines a centrally disposed through opening 40 and an axially oriented spring receiving channel 42 extending outwardly from the opening 40. A tangentially disposed threaded passageway 44 aligns generally with the spring receiving channel 42 and receives a complementarily threaded adjustment screw 46. Access to the threaded adjustment screw 46 is achieved through an aperture 48 in the coupling annulus 32. It should be understood that since the splines 34 and 38 inhibit rela-tive rotation between the coupling annulus 32 and the adjustment hub 3~, the passageway 44 and the adjustment screw 46 must be aligned with the aperture 48 during assembly of these elements in order that access to the adjustment screw 46 can be achieved. A suitably sized and positioned access port 50 formed in the housing 12 facili-tates access to the adjustment screw 46 when the couplingannulus 32 is appropriately rotated and the apertura 48 is
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which may be engaged within complementary threads in the housing of a prime mover (not illustrated) such as an electric or pneumatic motor. On the end of the housing 12, opposite the reduced diameter portion 14, is an internally threaded region 16 which receives a complementarily threaded housing 18 which may be associated with a final drive device (not illustrated).
A first wrap spring assembly 20 generally includes an input shaft 22 which is supported by an anti-friction bearing such as a ball bearing assemhly 24 and which preferably includes an integrally formed input hub 26 having splines 28 disposed about its periphery. Concen-trically disposed about and receiving the splines 28 of the input hub 26 and extending generally axially away from the input shaft 22 is a coupling annulus 32 having complemen-tary splines 34 disposed orl its inner surface. Also received and retained within the coupling annulus 32 is a spring receiving adjustment hub 36 having complementary splines 38 which engage the splines 34 within the coupling annulus 32. The adjustment hub 36 defines a centrally disposed through opening 40 and an axially oriented spring receiving channel 42 extending outwardly from the opening 40. A tangentially disposed threaded passageway 44 aligns generally with the spring receiving channel 42 and receives a complementarily threaded adjustment screw 46. Access to the threaded adjustment screw 46 is achieved through an aperture 48 in the coupling annulus 32. It should be understood that since the splines 34 and 38 inhibit rela-tive rotation between the coupling annulus 32 and the adjustment hub 3~, the passageway 44 and the adjustment screw 46 must be aligned with the aperture 48 during assembly of these elements in order that access to the adjustment screw 46 can be achieved. A suitably sized and positioned access port 50 formed in the housing 12 facili-tates access to the adjustment screw 46 when the couplingannulus 32 is appropriately rotated and the apertura 48 is
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aligned with the access port 50. The access port 50 may be closed `or sealed with a sliding ~ate or plug (both not illustrated) in order to, first of all, prevent foreign matter from entering the housing 12 and, second of all, control access to the adjustment screw 46. Ready or limited access to the adjustment screw 46 may be elected by the selection of a closure which may be removed by a common tool such as a screwdriver or may only be removed by a specially coded or.unique tool, thereby lessening the likelihood of unauthorized adjustment. An anti-friction bearing such as a ball bearing assembly 52 rotatably supports the adjustment hub 36. A spring retainer 54 maintains the position of the ball bearing assembly 52 on an axially extending output shaft 56. Lastly, a cylindrical spring retaining sleeve 58 having splines 60 disposed at one end which are engaged by the splines 34 of the coupling annulus 32 extends generally concentrically about the output shaft 56 in a direction away ~rom the input shaft 22 and is supported at its other end by an anti-~riction bearing such as the ball bearing assembly 62.
The roller bearing assembly 62 and a wave washer 64 are both received within a complementarily sized enlarged diameter region 66 of the cylindrical spr.ing retaining sleeve 58. Extending axially along the inside o~ the spring retaining sleeve 58, generally adjacent the region 66, is a spring retaining channel 68. The spring retaining sleeve 58 also includes a reduced diameter region 7~ which is received within other elements o~ the ass~mbly 10.
Another anti-friction bearing such as a ball bearing assembly 72 is disposed about the output shaft 56 and spaced from the ball bearing assembly 52 by an annular spacer 74 disposed about the output sha~t 56. The ball bearing assembly 72 radially centers and supports an axially extending cylindrical clutch sleeve 76. The clutch sleeve 76 is disposed concentrically about the output sha~t 56 and supported at its opposite end by an anti-friction _7_ ~2~7~7 bearing such as a roller bearing assembly 78. Disposed between the ball bearing assembly 72 and the roller bearing assembly 78 and positioned concentrically about the output shaft 56 and within the clutch sleeve 76 are a pair of overr`unning clutch assemblies 80. The clutch assemblies 80 are conventional and rotationally couple the clutch sleeve 76 to the output shaft 56 upon relative rotation in one direction and free wheel or uncouple these components upon rotation in the opposite direction. Finally, the first wrap spring assembly 20 includes a first wrap spring 84 positioned generally concentrically about the clutch sleeve 76. The wrap spring 84 consists of a plurality of turns, a larger portion of turns 86A consisting of approximately 8 to 10 turns having an inside diameter which creates an interference fit about the clutch sleeve 76 and a smaller portion of turns 86B consisting of a smaller number of turns having an inside diameter equal to or somewhat greater than the outside diameter of the clutch sleeve 76.
The spacing between the smaller portion of turns 86B and the clutch sleeve 76 in Figure 1 is somewhat exaggerated for purposes of illustration and the wrap spring 84 is illustrated in Figure 2A in its relaxed state. At both ends of the wrap spring 84, the spring 84 is formed into an axially extending tang. A first tang 88A is received in the axially extending spring receiving channel 68 formed in the spring retaining sleeve 58 and a second tang 88B is received within the spring receiving channel 42 of the adjustment hub 36.
A second wrap spring assembly 100 generally includes an output hub 102 which is concentrically disposed about the output shaft 56. The output hub 102 includes a keyway 104 which receives a k~y 106. The key 106 extends through a complementarily sized radially oriented slot 108 in the sidewall of the output shaft 56 and into a stub shaft 110 35` thereby securing these three elements together. The stub shaft 110 may include splines or gear teeth 112 which mate -8~ 8~
with power receiving components disposed within the housing 18. The hub 102 also includes a cylindrical spring receiving surface 114 having a diameter equal to the outside diameter of the spring retaining sleeve 58. In a region directly adjacent the output hub 102, the output shaft 5~ is rotatably supported by an anti-friction bearing such as a ball bearing assembly 116. The ball bearing assembly 116 is in turn fixedly and concentrically supported within the housing 12 within a stepped circular spacer 120. The circular spacer 120 includes a through channel 122 extending radially inwardly from its periphery.
Tangentially disposed in one of the sidewalls of the channel 122 is a blind opening 124 ~hich receives a compression spring 126. A cylindrical control sleeve 130 is disposed concentrically within the housing 12 and generally adjacent the inner wall thereof. The control sleeve 130 includes a longitudinally oriented tab 132 which extends into the channel 122 of the mounting support 120 and which engages the end o~ the compression spring 126 extending from the blind opening 124. At the opposite end of the cylindrical control sleeve 130 is an inclined surface or ramp 134 which extends through a small cir-cumferential angle, typically less than about 10 and obliqu~ly interconnects a ~irst surface and a second, axially distinct surface. Abutting the ramp 134 and translated axially due to rotation of the ramp 134 and the cylindrical control sleeve 130 is an axially extending ; control rod 138. The control rod 138 is received within and extends axially through a suitably disposed aperture 142 formed in the housing 12. The control rod 138 may be connected to any suitable mechanical, electrical or pneu-matic control. The control will be actuated when the adjustable torque limiting assembly 10 has reached the predetermined torque transmission level. Finally, the second wrap spring assembly 100 includes a second wrap spring 144. The second wrap spring 144 includes ~irst and ~ .
9 ~ 7 third end portions of turns 146A and 146C, respectively, which each occupy approximately one-third of the axial length and, in their relaxed state, have an inside diameter smaller than the outside diameter of the spring retaining sleeve 58 and the surface 114 on the output hub 102. The second wrap spring 1~4 also includes a second middle portion of turns 146B which occupies the remaining one~third o~ its axial length and, in its relaxed state, has an inside diameter equal to or slightly less than the outside diameter of the spring retaining sleeve 5~. The second wrap spring is illustrated in Figure 2B in its relaxed state.
With reference now to all of the dxawing figures and particularly Figure 1, the operation of the adjustable torque limiting assembly 10 will now be described. Unless otherwise notedt the following description relates to an assembly 10 wherein drive to tne input shaft 22 is in a clockwise direction when viewing the assembly 10 from the input shaft 22 end, that is, from the left end as illus-trated in Figure 1.
As those familiar with the operation of wrap springclutches will readily appreciate, the maximum torque transmitted by a wrap spring to a driven hub it is disposed about when the torque is applied to the spring in such a - 25 direction as to unwind or disengage the spring from the hub is a function of, among other variables, the moment in the spring and the number of turns engaging the hub. The moment in a wrap spring is the result of an initial inter-ference between the-spring and the hub and is normally a finite value dependent primarily upon the radial interfer-i ence between the at-rest inner dia~eter of the spring and .. the outside diameter of the hub, the geometry of the spring and the properties of the spring material.
Turning now specifically to the ad~ustable wrap spring assembly 10 and specifically the first wrap spring 20, it should be noted that the first wrap spring ~4 is of left -10~
hand sense when the input shaft 22 rotates clockwise as stated above. The first wrap spring 84 includes approxima-tely nine turns o~ rectangular wire constituting the larger portion of turns 86A having a preselected inside diameter sized to provide specific radial interference with the clutch sleeve 76.- Commensurate with such interference, -a preselected moment as induced in the first wrap sprin~
84. The first wrap spring 84 also includes several a smaller portion of turns 86B adjacent the adjustment hub 36 which, as noted previously, initially have an inside diameter equal to or slightly larger than the sleeve 76 and thus do not interfere with the sleeve 76 and furthermore initially have no moment induced therein. The end of the first wrap spring 84 adjacent the smaller portion of turns 15 86B is adjustably received within the adjustment hub 36.
The opposite end of the wrap spring 84, specifically the tang 88A, is received within the spring receiving slot 68 of the spring retaining sleeve 58. It should thus be appreciated that this assembly effectively permits adjust~
~0 ment of the preload moment on the first wrap spring 84 by virtue of repositioning the tang 88B by movement of the threaded adjustment screw 46. It can be appreciated that : proper sizing of the spring receiving channel 42 and appropriate selection of the torsional spring rate of the : 25 turns of the smaller portion of turns 86B of the first wrap spring 84 will permit adjustment of the tang 88B of the -~ first wrap spring 84 through an angle large enough to induce a moment in the turns of the smaller portion 86B
equal to or slightly greater than the moment induced in the ~ 30 turns of the larger portion 86A by virtue of their ; interference with the sleeve 76. This condition represents a practical preload limit since if this were the case, the turns of the larger portion of turns 86A would lift off the sleeve 76 and no torque could be transmitted to the sleeve 76 by the first wrap spring 84. Thus it will be appreciated that the moment induced by the turns of the :
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larger portion 86A of the first wrap spring 8~ by virtue of their interference with the sleeve 76 remains a fixed magnitude. The reaction to that moment will b~ shared by varying degrees by the sleeve 76 and the moment adjusted into the turns of the smaller portion 86B by the adjustment screw 46. Thus, that portion of the moment borne by the sleeve 76 varying from all to nothing depending upon the adjustment, becomes the moment in the turns of the smaller portion 86A and thus determines the slip point o~ the first wrap spring 84.
The power flow path through the ~irst wrap spring assembly 20 is generally from the input shaft 22 and input hub 26 through the coupling annulus 32 and to the spring retaining sleeve 58, the tang 88A o~ the first wrap spring 84, to the sleeve 76, through the overrunning clutches 80 which transmit rotational energy to the output sha~-t 56 when their outer housings are driven in a clockwise direc~
- tion but freewheel on the output shaft 56 when they are similarly driven in a counterclockwise direction and through the output shaft 56. It will thus be readily understood that depending upon the setting of the adjust-ment screw 46 and thus the moment in the turns of the larger portion 86A of the first wrap spring 84, torque through the first wrap spring assembly 20 will be transmit-ted up to the limit determined by the preselected moment.
- When the first wrap spring assembly 20 has reached and exceeded its torque limit, slipping and a rotational speed disparity between the input and output members, i.e., the input shaft 22 and the output shaft 56, are the prime manifestations of such torque limi~ attainment. It is, however, highly desirable to provide a mechanical or mechanically driven indicatibn that such torque limit has been achieved. This is desirable since rapid shu~ down of ;- power sources obviates the necessity for the torque trans-mittin~ elements of the assembly 10 to be designed for extended or conti~uous overrunning dutyO The second wrap -12- ~ 7~
spring assembly 100 provides a mechanical indication that the torque limit condition of the first wrap spring assem-bly 20 has been achieved. This indication may be utilized by a variety of means to mechanically terminate an air supply to a pneumatic motor, mechanically trip an electric switch which removes power to a motor or actuate any associated controlling equipment as can be readily under-stood. The second wrap spring 144 is of right hand sense.
The fi~rst and second portions of turns 146A and 146B, respectively, of the second wrap spring 144 engage the outside surface of the spring retaining sleeve 58 whereas the third portion of turns 146C on the right end engages the surface 114 of the output hub 102. The first and third portions of turns 146A and 146C are approximately equal in diameter and interfere with the surfaces upon which they rest to induce a predictable fixed moment in the second wrap spring 144. The middle or second portion of turns 146B is sized slightly smaller than the adjacent contacted surface of the spring retaining sleeve 58. When the Eirst wrap spring assembly 20 is in its overrunning condition, a difference in the speeds of rotation of the spring retaining sleeve 58 and output hub 102 will exist causing the middle or second portion of turns 146B to lift off the outer surface of the spring retaining sleeve 58. ~ift off occurs when the torque exceeds the small moment due to the minimal initial interference of the middle or second por~ion of turns 146B with the sleeve 58. As torque continues to increase, the second or middle portion of turns 146B will continue to expand in a predictable manner related linearly to the torque. At a predictable value of - torque, the second or middle portion of turns 146B of the . spring 144 will expand and engage the inside surface of the cylindrical control sleeve 130. The cylindrical control -` sleeve 130 is loosely disposed within the housing 12 and frictional engagement will rotate the control sleeve 130, compress the spring 126 and move the control rod 138 along . . ~
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-13~ 7~'7 the ramp 134. This activity will axially translate the control rod 138 and provide an indication that the torque limit of the assembly 10 has been reached. It should, of course, be understood that various sensing and indicating means may be utilized to detect rotation of the cylindrical control sleeve 130 and that the ramp 134 and associated control rod 138 are but one means.
From the foregoing description, it should be apparent that the actuation point of the control sleeve 130 and thus the limit torque of the two clutch assemblies 20 and 100 acting together is additive. The maximum torque transmitted to the output shaft 56 by the second wrap spring assembly 100 is equal to the torque required to engage the middle portion of turns 146B with the cylindrical control sleeve 130.
When the foregoing activity has occurred and power to the adjustable torque limiting assembly 10 through the input shaft 22 has been terminated, the assembly 10 must be reset. In order to reset, the output hub 102 must advance clockwise relative to the spring retaining sleeve 58 in order to wind down the middle portion of turns 146B of the second wrap spring 144 and allow the spring 126 to rotate the control sleeve 130 to its initial or start position.
When load or input torque is removed, the torque stored in the spring 144 can either advance the output hub 102 or backdrive the cylindrical spring retaining sleeve 58 and ; the associated input components. In order to do this, the torque in the second wrap spring 144 would have to be capable of slipping the first wrap spring assembly 20. The inclusion of the overrunning clutches 80, however, enables the output hub 102 to advance clockwise relative to the other components.
Several features, advantages and additional obser-vations of the adjustable torque limiting assembly 10 should be made. First of allp the precise si~e or scale and thus torque carrying capability of the assembly 10 is -14- ~&~
broad. Therefore, although the foregoing description may suggest utilization of assembly 10 with power tools, it should be understood and appreciated that the general design and construction disclosed herein may be scaled downwardly to accommodate and transmit torques in the range of a few inch-ounces or scaled upwardly ~o accommodate and transmit many foot-pounds of torque.
When the assembly 10, having springs 84 and 144 and clutches 80 as described, is driven in reverse, that is, in a direction counterclockwise as viewed from the input shaft 22 end the second wrap spring assembly 100 locks up since the drive tends to tighten the second wrap spring 144.
Therefore, the first wrap spring assembly 20 is completely bypassed and full input torque and power is transferred through the assembly 10 to the output shaft 56 and stub shaft 110 in reverse.
It should also be appreciated that the first and second wrap spring assemblies 20 and 100, respectively, may be disposed and may operate independently as individual elements in a power transmission system. Operation o~ the second wrap spring assembly 100 has been described above and corresponding operation will occur when the assembly 100 is utilized as a separate entity.
The operation of the first wrap spring assembly 20 as a separate entity is the same as that described above.
However, since the second wrap spring assembly 100 locks up in the reverse directions (counter-clockwise and with the states spring senses), effectively bypassing the irst spring asembly 20, its operation as a separate entity is significantly different than that described above. Thus, operation o~ the first wrap spring assembly 20 having a spring 84 and clutches 80 as described above in a reverse direction, i.e., counterclockwise when viewed from the input sha~t 22 end and independent o~ the second wrap spring assembly 100, will now be described. When so rotat-ing, input torque will tend to wrap the ~irst wrap spring -15- ~Z~ 7 84 more tightly. Rotating in this direction, force will be applied to the tang 88A of the first wrap sprin~ 84 by the opposite edge of the spring receiving slot 68 in the sleeve 58. If the slot 68 were radially enlarged, no force could be transferred to the tang 88A received therein but would instead be transferred to and through ~he tang 88B received within the adjustment hub 36~ In this case, the force applied to the tang 88B and thus the spring 84 would be in the same direction as the adjusted torque. Any torque applied to the turns of the smaller portion 86B which is greater than the adjusted tor~ue will further deflect the turns beyond the deflection due to adjustment. Continued counterclockwise deflection of the tang 88B will cause separation from the slot 68 and sleeve 58, thereby removing all moment or preload from the larger portion of turns 86~.
With this preload removed, the slip threshold torque of the first wrap spring assembly 20 will become equal to the torque induced by interference. The inner wrap spring assembly 20 therefore is adjustable in one direction but provides a constant overrunning or 51ip torque value in the opposite direction. This ~olds true for all values of adjustment except zero in which case the overrunning torque is zero in both directions.
It should also be noted that the splined coupling annulus 32 provides a significant manufacturing benefitO
Typical manufacturing tolerances in the size as well as the finishes of components in the areas relating to the first wrap spring 84 will cause variation in the initial moment induced by interference between the first wrap spring 84 and the cylindrical sleeve 76. Given the nature of the splined couplings associated with the annular coupling 32, this initial moment can always be designed to equal or exceed the target clutch torque. Any variation above this target torque can be permanently adjusted out during the assembly process by inducin~ the difference as a small preload in smaller portion of turns 8~B of the first wrap spring 84 when the tang ~8B is initially engaged in the adjustment hub 36 and maintaining such preload by the angular positioning and engagement of the splines 60 with the splines 34 of the coupling annulus 32 as the sleeve 58 is engaged therewith.
Finally, it should be understood that if the adjust able torque limiting assembly 10 is to be utilized in an application where the input shaft 22 rotates in a counter~
clockwise direction as viewed from the input end of the housing 12, the sense of the first wrap spring 84 should be right hand, the overrunning clutches 80 should lock, i.e., transfer torque, when their outer housings are driven in a counterclockwise direction relative to the output sha~t 56 and overrun when driven in the opposite direction and the second wrap spring 144 should be of left hand sense then, the foregoing discussions of operation of the assembly 10 in the reverse direction will apply when the input shaft 22 is rotated clockwise.
mhe foregoing disclosure is the best mode devised b~
the inventor for practicing this invention. It is appar-ent, however, that apparatus incorporating modifications - and variations will be obvious to one skilled in the art of adjustable torque limiting devices. Inasmuch as the foregoing disclosure is intended to enable one skilled in the pertinent art to practice the instant invention, it should not be construed to be limited thereby but should be construed to include such aforementioned obvious vaxiations and be limited only by the spirit and scope of the follow-ing claims.
. . ~ , .
aligned with the access port 50. The access port 50 may be closed `or sealed with a sliding ~ate or plug (both not illustrated) in order to, first of all, prevent foreign matter from entering the housing 12 and, second of all, control access to the adjustment screw 46. Ready or limited access to the adjustment screw 46 may be elected by the selection of a closure which may be removed by a common tool such as a screwdriver or may only be removed by a specially coded or.unique tool, thereby lessening the likelihood of unauthorized adjustment. An anti-friction bearing such as a ball bearing assembly 52 rotatably supports the adjustment hub 36. A spring retainer 54 maintains the position of the ball bearing assembly 52 on an axially extending output shaft 56. Lastly, a cylindrical spring retaining sleeve 58 having splines 60 disposed at one end which are engaged by the splines 34 of the coupling annulus 32 extends generally concentrically about the output shaft 56 in a direction away ~rom the input shaft 22 and is supported at its other end by an anti-~riction bearing such as the ball bearing assembly 62.
The roller bearing assembly 62 and a wave washer 64 are both received within a complementarily sized enlarged diameter region 66 of the cylindrical spr.ing retaining sleeve 58. Extending axially along the inside o~ the spring retaining sleeve 58, generally adjacent the region 66, is a spring retaining channel 68. The spring retaining sleeve 58 also includes a reduced diameter region 7~ which is received within other elements o~ the ass~mbly 10.
Another anti-friction bearing such as a ball bearing assembly 72 is disposed about the output shaft 56 and spaced from the ball bearing assembly 52 by an annular spacer 74 disposed about the output sha~t 56. The ball bearing assembly 72 radially centers and supports an axially extending cylindrical clutch sleeve 76. The clutch sleeve 76 is disposed concentrically about the output sha~t 56 and supported at its opposite end by an anti-friction _7_ ~2~7~7 bearing such as a roller bearing assembly 78. Disposed between the ball bearing assembly 72 and the roller bearing assembly 78 and positioned concentrically about the output shaft 56 and within the clutch sleeve 76 are a pair of overr`unning clutch assemblies 80. The clutch assemblies 80 are conventional and rotationally couple the clutch sleeve 76 to the output shaft 56 upon relative rotation in one direction and free wheel or uncouple these components upon rotation in the opposite direction. Finally, the first wrap spring assembly 20 includes a first wrap spring 84 positioned generally concentrically about the clutch sleeve 76. The wrap spring 84 consists of a plurality of turns, a larger portion of turns 86A consisting of approximately 8 to 10 turns having an inside diameter which creates an interference fit about the clutch sleeve 76 and a smaller portion of turns 86B consisting of a smaller number of turns having an inside diameter equal to or somewhat greater than the outside diameter of the clutch sleeve 76.
The spacing between the smaller portion of turns 86B and the clutch sleeve 76 in Figure 1 is somewhat exaggerated for purposes of illustration and the wrap spring 84 is illustrated in Figure 2A in its relaxed state. At both ends of the wrap spring 84, the spring 84 is formed into an axially extending tang. A first tang 88A is received in the axially extending spring receiving channel 68 formed in the spring retaining sleeve 58 and a second tang 88B is received within the spring receiving channel 42 of the adjustment hub 36.
A second wrap spring assembly 100 generally includes an output hub 102 which is concentrically disposed about the output shaft 56. The output hub 102 includes a keyway 104 which receives a k~y 106. The key 106 extends through a complementarily sized radially oriented slot 108 in the sidewall of the output shaft 56 and into a stub shaft 110 35` thereby securing these three elements together. The stub shaft 110 may include splines or gear teeth 112 which mate -8~ 8~
with power receiving components disposed within the housing 18. The hub 102 also includes a cylindrical spring receiving surface 114 having a diameter equal to the outside diameter of the spring retaining sleeve 58. In a region directly adjacent the output hub 102, the output shaft 5~ is rotatably supported by an anti-friction bearing such as a ball bearing assembly 116. The ball bearing assembly 116 is in turn fixedly and concentrically supported within the housing 12 within a stepped circular spacer 120. The circular spacer 120 includes a through channel 122 extending radially inwardly from its periphery.
Tangentially disposed in one of the sidewalls of the channel 122 is a blind opening 124 ~hich receives a compression spring 126. A cylindrical control sleeve 130 is disposed concentrically within the housing 12 and generally adjacent the inner wall thereof. The control sleeve 130 includes a longitudinally oriented tab 132 which extends into the channel 122 of the mounting support 120 and which engages the end o~ the compression spring 126 extending from the blind opening 124. At the opposite end of the cylindrical control sleeve 130 is an inclined surface or ramp 134 which extends through a small cir-cumferential angle, typically less than about 10 and obliqu~ly interconnects a ~irst surface and a second, axially distinct surface. Abutting the ramp 134 and translated axially due to rotation of the ramp 134 and the cylindrical control sleeve 130 is an axially extending ; control rod 138. The control rod 138 is received within and extends axially through a suitably disposed aperture 142 formed in the housing 12. The control rod 138 may be connected to any suitable mechanical, electrical or pneu-matic control. The control will be actuated when the adjustable torque limiting assembly 10 has reached the predetermined torque transmission level. Finally, the second wrap spring assembly 100 includes a second wrap spring 144. The second wrap spring 144 includes ~irst and ~ .
9 ~ 7 third end portions of turns 146A and 146C, respectively, which each occupy approximately one-third of the axial length and, in their relaxed state, have an inside diameter smaller than the outside diameter of the spring retaining sleeve 58 and the surface 114 on the output hub 102. The second wrap spring 1~4 also includes a second middle portion of turns 146B which occupies the remaining one~third o~ its axial length and, in its relaxed state, has an inside diameter equal to or slightly less than the outside diameter of the spring retaining sleeve 5~. The second wrap spring is illustrated in Figure 2B in its relaxed state.
With reference now to all of the dxawing figures and particularly Figure 1, the operation of the adjustable torque limiting assembly 10 will now be described. Unless otherwise notedt the following description relates to an assembly 10 wherein drive to tne input shaft 22 is in a clockwise direction when viewing the assembly 10 from the input shaft 22 end, that is, from the left end as illus-trated in Figure 1.
As those familiar with the operation of wrap springclutches will readily appreciate, the maximum torque transmitted by a wrap spring to a driven hub it is disposed about when the torque is applied to the spring in such a - 25 direction as to unwind or disengage the spring from the hub is a function of, among other variables, the moment in the spring and the number of turns engaging the hub. The moment in a wrap spring is the result of an initial inter-ference between the-spring and the hub and is normally a finite value dependent primarily upon the radial interfer-i ence between the at-rest inner dia~eter of the spring and .. the outside diameter of the hub, the geometry of the spring and the properties of the spring material.
Turning now specifically to the ad~ustable wrap spring assembly 10 and specifically the first wrap spring 20, it should be noted that the first wrap spring ~4 is of left -10~
hand sense when the input shaft 22 rotates clockwise as stated above. The first wrap spring 84 includes approxima-tely nine turns o~ rectangular wire constituting the larger portion of turns 86A having a preselected inside diameter sized to provide specific radial interference with the clutch sleeve 76.- Commensurate with such interference, -a preselected moment as induced in the first wrap sprin~
84. The first wrap spring 84 also includes several a smaller portion of turns 86B adjacent the adjustment hub 36 which, as noted previously, initially have an inside diameter equal to or slightly larger than the sleeve 76 and thus do not interfere with the sleeve 76 and furthermore initially have no moment induced therein. The end of the first wrap spring 84 adjacent the smaller portion of turns 15 86B is adjustably received within the adjustment hub 36.
The opposite end of the wrap spring 84, specifically the tang 88A, is received within the spring receiving slot 68 of the spring retaining sleeve 58. It should thus be appreciated that this assembly effectively permits adjust~
~0 ment of the preload moment on the first wrap spring 84 by virtue of repositioning the tang 88B by movement of the threaded adjustment screw 46. It can be appreciated that : proper sizing of the spring receiving channel 42 and appropriate selection of the torsional spring rate of the : 25 turns of the smaller portion of turns 86B of the first wrap spring 84 will permit adjustment of the tang 88B of the -~ first wrap spring 84 through an angle large enough to induce a moment in the turns of the smaller portion 86B
equal to or slightly greater than the moment induced in the ~ 30 turns of the larger portion 86A by virtue of their ; interference with the sleeve 76. This condition represents a practical preload limit since if this were the case, the turns of the larger portion of turns 86A would lift off the sleeve 76 and no torque could be transmitted to the sleeve 76 by the first wrap spring 84. Thus it will be appreciated that the moment induced by the turns of the :
... . . . .
:... . -- : :
.~
larger portion 86A of the first wrap spring 8~ by virtue of their interference with the sleeve 76 remains a fixed magnitude. The reaction to that moment will b~ shared by varying degrees by the sleeve 76 and the moment adjusted into the turns of the smaller portion 86B by the adjustment screw 46. Thus, that portion of the moment borne by the sleeve 76 varying from all to nothing depending upon the adjustment, becomes the moment in the turns of the smaller portion 86A and thus determines the slip point o~ the first wrap spring 84.
The power flow path through the ~irst wrap spring assembly 20 is generally from the input shaft 22 and input hub 26 through the coupling annulus 32 and to the spring retaining sleeve 58, the tang 88A o~ the first wrap spring 84, to the sleeve 76, through the overrunning clutches 80 which transmit rotational energy to the output sha~-t 56 when their outer housings are driven in a clockwise direc~
- tion but freewheel on the output shaft 56 when they are similarly driven in a counterclockwise direction and through the output shaft 56. It will thus be readily understood that depending upon the setting of the adjust-ment screw 46 and thus the moment in the turns of the larger portion 86A of the first wrap spring 84, torque through the first wrap spring assembly 20 will be transmit-ted up to the limit determined by the preselected moment.
- When the first wrap spring assembly 20 has reached and exceeded its torque limit, slipping and a rotational speed disparity between the input and output members, i.e., the input shaft 22 and the output shaft 56, are the prime manifestations of such torque limi~ attainment. It is, however, highly desirable to provide a mechanical or mechanically driven indicatibn that such torque limit has been achieved. This is desirable since rapid shu~ down of ;- power sources obviates the necessity for the torque trans-mittin~ elements of the assembly 10 to be designed for extended or conti~uous overrunning dutyO The second wrap -12- ~ 7~
spring assembly 100 provides a mechanical indication that the torque limit condition of the first wrap spring assem-bly 20 has been achieved. This indication may be utilized by a variety of means to mechanically terminate an air supply to a pneumatic motor, mechanically trip an electric switch which removes power to a motor or actuate any associated controlling equipment as can be readily under-stood. The second wrap spring 144 is of right hand sense.
The fi~rst and second portions of turns 146A and 146B, respectively, of the second wrap spring 144 engage the outside surface of the spring retaining sleeve 58 whereas the third portion of turns 146C on the right end engages the surface 114 of the output hub 102. The first and third portions of turns 146A and 146C are approximately equal in diameter and interfere with the surfaces upon which they rest to induce a predictable fixed moment in the second wrap spring 144. The middle or second portion of turns 146B is sized slightly smaller than the adjacent contacted surface of the spring retaining sleeve 58. When the Eirst wrap spring assembly 20 is in its overrunning condition, a difference in the speeds of rotation of the spring retaining sleeve 58 and output hub 102 will exist causing the middle or second portion of turns 146B to lift off the outer surface of the spring retaining sleeve 58. ~ift off occurs when the torque exceeds the small moment due to the minimal initial interference of the middle or second por~ion of turns 146B with the sleeve 58. As torque continues to increase, the second or middle portion of turns 146B will continue to expand in a predictable manner related linearly to the torque. At a predictable value of - torque, the second or middle portion of turns 146B of the . spring 144 will expand and engage the inside surface of the cylindrical control sleeve 130. The cylindrical control -` sleeve 130 is loosely disposed within the housing 12 and frictional engagement will rotate the control sleeve 130, compress the spring 126 and move the control rod 138 along . . ~
:
-13~ 7~'7 the ramp 134. This activity will axially translate the control rod 138 and provide an indication that the torque limit of the assembly 10 has been reached. It should, of course, be understood that various sensing and indicating means may be utilized to detect rotation of the cylindrical control sleeve 130 and that the ramp 134 and associated control rod 138 are but one means.
From the foregoing description, it should be apparent that the actuation point of the control sleeve 130 and thus the limit torque of the two clutch assemblies 20 and 100 acting together is additive. The maximum torque transmitted to the output shaft 56 by the second wrap spring assembly 100 is equal to the torque required to engage the middle portion of turns 146B with the cylindrical control sleeve 130.
When the foregoing activity has occurred and power to the adjustable torque limiting assembly 10 through the input shaft 22 has been terminated, the assembly 10 must be reset. In order to reset, the output hub 102 must advance clockwise relative to the spring retaining sleeve 58 in order to wind down the middle portion of turns 146B of the second wrap spring 144 and allow the spring 126 to rotate the control sleeve 130 to its initial or start position.
When load or input torque is removed, the torque stored in the spring 144 can either advance the output hub 102 or backdrive the cylindrical spring retaining sleeve 58 and ; the associated input components. In order to do this, the torque in the second wrap spring 144 would have to be capable of slipping the first wrap spring assembly 20. The inclusion of the overrunning clutches 80, however, enables the output hub 102 to advance clockwise relative to the other components.
Several features, advantages and additional obser-vations of the adjustable torque limiting assembly 10 should be made. First of allp the precise si~e or scale and thus torque carrying capability of the assembly 10 is -14- ~&~
broad. Therefore, although the foregoing description may suggest utilization of assembly 10 with power tools, it should be understood and appreciated that the general design and construction disclosed herein may be scaled downwardly to accommodate and transmit torques in the range of a few inch-ounces or scaled upwardly ~o accommodate and transmit many foot-pounds of torque.
When the assembly 10, having springs 84 and 144 and clutches 80 as described, is driven in reverse, that is, in a direction counterclockwise as viewed from the input shaft 22 end the second wrap spring assembly 100 locks up since the drive tends to tighten the second wrap spring 144.
Therefore, the first wrap spring assembly 20 is completely bypassed and full input torque and power is transferred through the assembly 10 to the output shaft 56 and stub shaft 110 in reverse.
It should also be appreciated that the first and second wrap spring assemblies 20 and 100, respectively, may be disposed and may operate independently as individual elements in a power transmission system. Operation o~ the second wrap spring assembly 100 has been described above and corresponding operation will occur when the assembly 100 is utilized as a separate entity.
The operation of the first wrap spring assembly 20 as a separate entity is the same as that described above.
However, since the second wrap spring assembly 100 locks up in the reverse directions (counter-clockwise and with the states spring senses), effectively bypassing the irst spring asembly 20, its operation as a separate entity is significantly different than that described above. Thus, operation o~ the first wrap spring assembly 20 having a spring 84 and clutches 80 as described above in a reverse direction, i.e., counterclockwise when viewed from the input sha~t 22 end and independent o~ the second wrap spring assembly 100, will now be described. When so rotat-ing, input torque will tend to wrap the ~irst wrap spring -15- ~Z~ 7 84 more tightly. Rotating in this direction, force will be applied to the tang 88A of the first wrap sprin~ 84 by the opposite edge of the spring receiving slot 68 in the sleeve 58. If the slot 68 were radially enlarged, no force could be transferred to the tang 88A received therein but would instead be transferred to and through ~he tang 88B received within the adjustment hub 36~ In this case, the force applied to the tang 88B and thus the spring 84 would be in the same direction as the adjusted torque. Any torque applied to the turns of the smaller portion 86B which is greater than the adjusted tor~ue will further deflect the turns beyond the deflection due to adjustment. Continued counterclockwise deflection of the tang 88B will cause separation from the slot 68 and sleeve 58, thereby removing all moment or preload from the larger portion of turns 86~.
With this preload removed, the slip threshold torque of the first wrap spring assembly 20 will become equal to the torque induced by interference. The inner wrap spring assembly 20 therefore is adjustable in one direction but provides a constant overrunning or 51ip torque value in the opposite direction. This ~olds true for all values of adjustment except zero in which case the overrunning torque is zero in both directions.
It should also be noted that the splined coupling annulus 32 provides a significant manufacturing benefitO
Typical manufacturing tolerances in the size as well as the finishes of components in the areas relating to the first wrap spring 84 will cause variation in the initial moment induced by interference between the first wrap spring 84 and the cylindrical sleeve 76. Given the nature of the splined couplings associated with the annular coupling 32, this initial moment can always be designed to equal or exceed the target clutch torque. Any variation above this target torque can be permanently adjusted out during the assembly process by inducin~ the difference as a small preload in smaller portion of turns 8~B of the first wrap spring 84 when the tang ~8B is initially engaged in the adjustment hub 36 and maintaining such preload by the angular positioning and engagement of the splines 60 with the splines 34 of the coupling annulus 32 as the sleeve 58 is engaged therewith.
Finally, it should be understood that if the adjust able torque limiting assembly 10 is to be utilized in an application where the input shaft 22 rotates in a counter~
clockwise direction as viewed from the input end of the housing 12, the sense of the first wrap spring 84 should be right hand, the overrunning clutches 80 should lock, i.e., transfer torque, when their outer housings are driven in a counterclockwise direction relative to the output sha~t 56 and overrun when driven in the opposite direction and the second wrap spring 144 should be of left hand sense then, the foregoing discussions of operation of the assembly 10 in the reverse direction will apply when the input shaft 22 is rotated clockwise.
mhe foregoing disclosure is the best mode devised b~
the inventor for practicing this invention. It is appar-ent, however, that apparatus incorporating modifications - and variations will be obvious to one skilled in the art of adjustable torque limiting devices. Inasmuch as the foregoing disclosure is intended to enable one skilled in the pertinent art to practice the instant invention, it should not be construed to be limited thereby but should be construed to include such aforementioned obvious vaxiations and be limited only by the spirit and scope of the follow-ing claims.
. . ~ , .
Claims (20)
1. An adjustable torque limiting assembly comprising, in combination, a wrap spring having a pair of ends, an input member having means for engaging said pair of ends of said wrap spring, means associated with said input member for adjusting the angular position of one of said pair of ends relative to the other of said pair of ends, and an output member disposed within said wrap spring, said output member having a cylindrical portion engaged by at least a portion of said wrap spring.
2. The torque limiting assembly of claim 1 wherein said wrap spring, in a relaxed state, includes a first plurality of turns having an inside diameter smaller than the outside diameter of said cylindrical portion of said output member.
3. The torque limiting assembly of claim 1 wherein said pair of ends of said wrap spring define generally axially extending tangs.
4. The torque limiting assembly of claim 1 further including an output shaft and an overrunning clutch operably disposed between said output member and said output shaft.
5. The torque limiting assembly of claim 1 wherein said input member includes an input shaft and a cylindrical sleeve portion for receiving said wrap spring.
6. The torque limiting assembly of claim 5 further including a coupling annulus wherein said coupling annulus, said input shaft and said cylindrical sleeve include splines, said splines of said coupling sleeve being complementary to said splines on said input shaft and said cylindrical sleeve.
7. The torque limiting assembly of claim 1 further including an output shaft, an overrunning clutch operably disposed between said output shaft and said output member, a second wrap spring disposed to engage portions of said input member and said output member and a cylindrical member concentrically disposed about said second wrap spring and rotatable between a first position and a second position.
8. The torque limiting assembly of claim 7 further including means associated with said cylindrical member and movable between a first axial position corresponding to said first position of said cylindrical member and a second axial position corresponding to said second position of said cylindrical member.
9. The torque limiting assembly of claim 7 wherein said wrap spring is of left hand sense and said second wrap spring is of right hand sense.
10. The torque limiting assembly of claim 1 wherein said means associated with said input member includes a threaded adjustment mechanism generally tangentially oriented with respect with said one to the axis of said wrap spring.
11. An assembly for limiting torque transmission comprising, in combination, a first wrap spring having a pair of ends, input member having means for engaging said pair of ends of said first wrap spring, means associated with one of said pair of ends of said first wrap spring for adjusting the angular position of said one of said pair of ends relative to the other of said pair of ends, an inner sleeve disposed within said first wrap spring, an output member, an overrunning clutch operably disposed between said sleeve and said output member, a second wrap spring disposed to engage portions of said input member and said output member, and an outer sleeve disposed about said second wrap spring.
12. The torque limiting assembly of claim 11 wherein said first wrap spring, in a relaxed state, includes a first plurality of turns having an inside diameter smaller than the outside diameter of said inner sleeve.
13. The torque limiting assembly of claim 12 wherein the senses of said first wrap spring and said second wrap spring are opposite.
14. The torque limiting assembly of claim 11 wherein said first wrap spring assembly, in a relaxed state, includes a second plurality of turns having an inside diameter at least as large as the outside diameter of said inner sleeve.
15. The torque limiting assembly of claim 14 wherein said ends of said first wrap spring are a pair of tangs extending axially from said turns.
16. The torque limiting assembly of claim 11 wherein said input member and said output member both include cylindrical surfaces having equal outside diameters.
17. The torque limiting assembly of claim 16 wherein said second wrap spring, in a relaxed state, includes two end adjacent regions having a first inside diameter and a third, intermediate region having a second, larger inside diameter and said larger inside diameter is less than said outside diameter of said cylindrical surface of said input member.
18. The torque limiting assembly of claim 11 wherein said second wrap spring, in a relaxed state, includes two end adjacent regions having a first inside diameter and a third, intermediate region having a second, larger inside diameter.
19. The torque limiting assembly of claim 11 further including means for biasing said outer sleeve toward one of two rotational positions.
20. An assembly for limiting torque throughput comprising, in combination, a first wrap spring having a pair of ends, an input member having a pair of means for engaging a respective one of said pair of ends of said first wrap spring, means associated with one of said pair of ends of said first wrap spring for adjusting the angular position of said one of said pair of ends relative to the other of said pair of ends, a cylindrical sleeve disposed within said first wrap spring, an output member, an overrunning clutch assembly operably disposed between said cylindrical sleeve and said output member, a second wrap spring disposed to engage portions of said input member and said output member, and a sensing element concentrically disposed about said second wrap spring and rotatable between a first position and a second position.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US56877384A | 1984-01-06 | 1984-01-06 | |
| US568,773 | 1984-01-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1248787A true CA1248787A (en) | 1989-01-17 |
Family
ID=24272677
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000471490A Expired CA1248787A (en) | 1984-01-06 | 1985-01-04 | Adjustable torque limiting assembly |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPH0694887B2 (en) |
| CA (1) | CA1248787A (en) |
| DE (1) | DE3500324C2 (en) |
| GB (1) | GB2152600B (en) |
| SE (1) | SE8500058L (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3802740A1 (en) * | 1988-01-30 | 1989-08-03 | Hilti Ag | MOTORIZED HAND DEVICE |
| FR2654791B1 (en) * | 1989-11-20 | 1994-10-21 | Mitsubishi Electric Corp | DEVICE FOR TRANSMITTING A ROTATION WITH TORQUE LIMITING TRANSMISSION MECHANISM. |
| JP2794976B2 (en) * | 1991-04-03 | 1998-09-10 | 富士ゼロックス株式会社 | Torque limiter |
| DE10303235B4 (en) * | 2002-01-29 | 2011-03-31 | Makita Corp., Anjo | Torque-transmitting mechanisms and power tools with such torque-transmitting mechanisms |
| DE102015220920B4 (en) * | 2014-12-15 | 2023-02-16 | Schaeffler Technologies AG & Co. KG | Assembly with a friction device |
| US10024415B2 (en) | 2015-11-02 | 2018-07-17 | Gates Corporation | Isolating decoupler |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB613011A (en) * | 1943-11-01 | 1948-11-22 | William Carleton Starkey | Improvements in or relating to load limiting clutches |
| US3450214A (en) * | 1966-03-03 | 1969-06-17 | Ingersoll Rand Co | Fluid-powered wrench with automatic shut-off |
| GB1158075A (en) * | 1967-07-31 | 1969-07-16 | Ingersoll Rand Co | Power wrench |
| DE2200035C3 (en) * | 1971-01-06 | 1984-09-27 | Rockwell International Corp., Pittsburgh, Pa. | Tool for tightening fasteners such as screws |
| GB1522700A (en) * | 1974-12-19 | 1978-08-23 | Rockwell International Corp | Torque-limiting clutch |
| SE425769B (en) * | 1977-03-22 | 1982-11-08 | Atlas Copco Ab | Screwdriver with Friction Coupler |
| JPS5929987Y2 (en) * | 1981-08-19 | 1984-08-27 | 通子 宮崎 | Foldable portable Japanese embroidery frame |
-
1985
- 1985-01-04 GB GB08500213A patent/GB2152600B/en not_active Expired
- 1985-01-04 CA CA000471490A patent/CA1248787A/en not_active Expired
- 1985-01-07 JP JP75485A patent/JPH0694887B2/en not_active Expired - Lifetime
- 1985-01-07 DE DE19853500324 patent/DE3500324C2/en not_active Expired - Fee Related
- 1985-01-07 SE SE8500058A patent/SE8500058L/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| SE8500058D0 (en) | 1985-01-07 |
| DE3500324C2 (en) | 1994-04-28 |
| GB2152600B (en) | 1988-05-11 |
| JPS60227026A (en) | 1985-11-12 |
| GB2152600A (en) | 1985-08-07 |
| SE8500058L (en) | 1985-07-07 |
| DE3500324A1 (en) | 1985-07-18 |
| JPH0694887B2 (en) | 1994-11-24 |
| GB8500213D0 (en) | 1985-02-13 |
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| MKEX | Expiry |