US3648946A

US3648946A - Fluid time delay automatic retractor

Info

Publication number: US3648946A
Application number: US29160A
Authority: US
Inventors: Robert W Stoffel
Original assignee: Allied Chemical Corp
Current assignee: Allied Corp
Priority date: 1970-04-16
Filing date: 1970-04-16
Publication date: 1972-03-14
Anticipated expiration: 1989-03-14
Also published as: CA947264A

Abstract

A seat belt retracting assembly including a U-shaped support bracket rotatably supporting a reel on a shaft. A locking pawl is rotatably supported by a pin extending between the side walls of the bracket for moving to and from a locked position in engagement with a pair of spaced parallel plate-like ratchet members defining the ends of the reel. An output impeller is disposed about the shaft exteriorly of one of the side walls of the bracket and is in sealing engagement with the shaft and defines a fluid chamber. The output impeller has an arm extending therefrom with a shoulder which engages a pin extending through the adjacent side wall from the locking pawl. An input impeller is disposed about the shaft within the fluid chamber. A spiral spring is disposed about the shaft for gripping engagement with the shaft during rotation in the extending direction but which allows the shaft to freely rotate therewithin when the shaft is rotating in the retracting direction. A coil spring is disposed about the spiral spring and engages the input impeller whereby upon initial extending rotation of the reel means, the input impeller will be rotated to react through fluid in the fluid chamber with the output impeller to hold the shoulder thereof in engagement with the extension of the locking pawl to maintain the locking pawl out of the locked position. Once the initial extending rotation of the reel means has been terminated, the wound up coil spring will unwind and continue to rotate the input impeller to continue to hold the output impeller in positive engagement with the extension of the locking pawl to prevent the locking pawl from moving into locked engagement with the ratchet members until a predetermined period has elapsed after termination of the initial extending rotation of the reel means. A clutch plate, which is in frictional engagement with one of the ratchet members and includes a slot through which the extension from the locking pawl extends, is disposed between one of the ratchet members and the adjacent side wall for maintaining the locking pawl out of the locked position until there is an additional extending rotation of the reel means in response to which the clutch plate positively moves the locking pawl to the locked position.

Description

United States Patent Stoffel FLUID TIME DELAY AUTOMATIC RETRACTOR Primary Examiner-Stanley N. Gilreath Assistant ExaminerWerner l-l. Schroeder Attomey-Marvin Bressler and Jonathan Plaut [57] ABSTRACT A seat belt retracting assembly including a U-shaped support bracket rotatably supporting a reel on a shaft. A locking pawl is rotatably supported by a pin extending between the side walls of the bracket for moving to and from a locked position in engagement with a pair of spaced parallel plate-like ratchet ('1 1" 4 8 1 p 56 .54 as I i 5] Mar. 14, 1972 members defining the ends of the reel. An output impeller is disposed about the shaft exteriorly of one of the side walls of the bracket and is in sealing engagement with the shaft and defines a fluid chamber. The output impeller has an arm extending therefrom with a shoulder which engages a pin extending through the adjacent side wall from the locking pawl. An input impeller is disposed about the shaft within the fluid chamber. A spiral spring is disposed about the shaft for gripping engagement with the shaft during rotation in the extending direction but which allows the shaft to freely rotate therewithin when the shaft is rotating in the retracting direction. A coil spring is disposed about the spiral spring and engages the input impeller whereby upon initial extending rotation of the reel means, the input impeller will be rotated to react through fluid in the fluid chamber with the output impeller to hold the shoulder thereof in engagement with the extension of the locking pawl to maintain the locking pawl out of the locked position. Once the initial extending rotation of the reel means has been terminated, the wound up coil spring will unwind and continue to rotate the input impeller to continue to hold the output impeller in positive engagement with the extension of the locking pawl to prevent the locking pawl from moving into locked engagement with the ratchet members until a predetermined period has elapsed after termination of the initial extending rotation of the reel means. A clutch plate, which is in frictional engagement with one of the ratchet members and includes a slot through which the extension from the locking pawl extends, is disposed between one of the ratchet members and the adjacent side wall for maintaining the locking pawl out of the locked position until there is an additional extending rotation of the reel means in response to which the clutch plate positively moves the locking pawl to the locked position.

14 Claims, 7 Drawing Figures PAIEMEW 14 1912 3,648 946 SHEET 1 [1F 2 INVEN'I'OR.

2066 Wa 9w ATTORNEY FLUID TIME DELAY AUTOMATIC RETRACTOR This invention relates to safety seat belt assemblies of the type utilized in automobiles or similar vehicles as occupant restraining devices. It has been common practice to use rollup or retracting assemblies which wind up or retract at least onehalf of the disconnected seat belt sections so that such sections do not remain loosely disposed on the seat when not in use. Since an occupant rarely realizes the amount of belt remaining in the retraction device once he has extended the belt therefrom, such assemblies are deficient by providing a potential safety hazard. This occurs because the biasing action, which tends to retract the seat belt into the retraction device, is such that an occupant may buckle a seat belt and believe that both sections of the seat belt are fully extended thereby to be taut or tight and cannot be further extended. In may cases, however, the seat belt is not fully extended and in the event of a crash or sudden stop the seat belt will fully extend to allow the passenger to move forward a dangerous amount.

The problem has been attacked by the development of various retracting assemblies wherein the retracting assembly is locked to prevent further extension of the seat belt once the seat belt has been extended a predetermined amount or after the expiration of a predetermined period subsequent to the initial extension of the seat belt. Such retracting assemblies have not proven entirely satisfactory, however, because in those which provide the locking function after a predetermined length of the belt has been extended, the amount of belt extended is not always of the proper length and in those providing the locking function after a predetermined time the time delay components utilized have not provided the necessary reliability.

Accordingly, it is an object and feature of this invention to provide a retractable seat belt assembly including control means responsive to movement of the retractor means for utilizing energy therefrom during the extending movement thereof in the extending direction from the fully retracted position to prevent movement of the locking means to the locked position during the extending movement and for a predetermined period of time after the extending movement.

In correlation with the foregoing object and feature, it is another object and feature of this invention to provide such a control means including an input means and output means operable in response to movement of the input means for preventing movement of the locking means to the locked position and energy means responsive only to extending movement of the retractor means for moving the input means during the extending movement and for the predetermined period thereafter.

Other objects and attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a plan view of the preferred embodiment of the instant invention;

FIG. 2 is a side elevational view partially broken away and in cross section of the preferred embodiment of FIG. 1;

FIG. 3 is a view taken substantially along line 3-3 of FIG.

FIG. 4 is a cross sectional view taken substantially along line 4--4 of FIG. 2;

FIG. 5 is a view similar to FIG. 3 but showing the assembly in the locked position;

FIG. 6 is a view similar to FIG. 4 but showing the assembly in an intermediate unlocked position; and

FIG. 7 is a fragmentary perspective exploded view of the preferred embodiment.

Referring now to the drawings wherein like numerals indicate like or corresponding parts, a retractable seat belt assembly constructed in accordance with the instant invention is generally shown at 10.

The assembly 10 includes a seat belt 12 which is made of flexible webbing or clothlike material and is attached to a metal tongue or plate 14. The tongue 14 is adapted to be inserted into a buckle assembly (not shown).

The assembly 10 also includes retractor means 16 movable in a retracting direction for retracting the seat belt I2 to a fully retracted position and movable in an extending direction for permitting extension of the seat belt 12.

The assembly 10 includes the locking means generally indicated at 18 and movable between locked and unlocked positions for respectively preventing and allowing extending movement of the retractor means in the extending direction.

The assembly 10 further includes control means generally shown at 20 which is responsive to extending movement of the retractor means 16 for preventing movement of the locking means 18 to the locked position until the expiration of a predetermined period after the termination of the extending movement. The control means 20 is responsive to movement of the retractor means 16 for utilizing energy from the retractor means 16 during extending movement thereof in the extending direction from the fully retracted position to prevent movement of the locking means 18 to the locked position during extending movement and for a predetermined period after the termination of the extending movement. The control means 20 comprises a fluid clutch means operatively interconnecting the retractor means 16 and the locking means 18 for preventing movement of the locking means toward the locked position during movement of the retractor means 16 in the extending direction and during the predetermined period thereafter.

The control means or clutch means 20 includes an input means or impeller 22 disposed in a fluid chamber 24. Also included is an output means or impeller housing 26 which is responsive to the input impeller 22 for preventing movement of the locking means 18 to the locked position. Additionally, there is included energy means 28 responsive to extending movement of the retractor means 16 for imparting the energy developed by the retractor means 16 to the input impeller 22 during the extending movement and during the predetermined period thereafter. The energy means 28 is responsive only to extending movement or rotation of the retractor and is not responsive to retracting movement or rotation of the retractor means 16.

The retractor means 16 includes a support means, comprising the U-shaped bracket generally indicated at 30, and reel means generally indicated at 32. The reel means 32 is rotatably supported by the U-shaped bracket 30 and the seat belt 12 is connected to the reel means 32 to be wound thereon and unwound therefrom. The U-shaped bracket 30 includes a base and a pair of parallel spaced

sidewalls

34 and 36. The base has an opening 38 therein whereby the assembly may be attached to a structure such as a structural member in an automobile.

The reel means 32 includes a shaft 40 which extends through the

sidewalls

34 and 36 to be rotatably supported thereby. A stub shaft 42 is a part of the main shaft 40, albeit, it is shown as an independent member, since it is connected thereto as by press fitting, tongue and grooves, or the like, so as to be rotatable with the main shaft portion 40. The reel means 32 further includes a cylinder 44 concentrically disposed about the shaft 40 and circular

platelike ratchet members

46 and 48 secured to the respective ends of the cylinder 44. The

ratchet members

46 and 48 are supported by the shaft 40 for rotation relative to the U-shaped bracket 30. The cylinder 44 has a slot 50 extending therealong and a seat belt 12 is connected to the shaft, as by being looped thereabout and sewn together, and extends through the slot 50 so as to be wound and unwound abut the cylinder 44 between the

ratchet members

46 and 48. Disposed exteriorly of the sidewall 36 is a biasing means generally indicated at 52 for urging the

ratchet members

46 and 48 and the cylinder 44 to rotate in the retracting direction. Although the biasing means 52 is shown merely asa housing, it is of a type well known in the prior art wherein the housing encloses a coiled band-type spring having one end connected to the shaft 40 and the other end secured to the housing to urge the shaft 40 and the entire reel means 32 to rotate in the seat belt winding direction.

The locking means 18 includes a pin 54 extending between and through the

sidewalls

34 and 36 and a locking pawl 56 rotatably supported by the pin 54 for engaging the

ratchet members

46 and 48 when in the locked position to prevent rotation of the

ratchet members

46 and 48 in the counterclockwise direction as viewed in FIGS. 4 and 6.

The first wall 34 of the U-shaped bracket 30 includes a slot 58 extending therethrough. The locking pawl 56 has an extension 60 extending therefrom and through the slot 58.

The output impeller 26 has an arm 62 with a shoulder 64 thereon for engaging the extension 60 as illustrated in FIG. 3.

There is also included operative means comprising the clutch plate 66 for maintaining the locking pawl 56 out of the locked position after the expiration of the predetermined period and for thereafter moving the locking pawl 56 to the locked position in response to additional extending movement of the retractor means 16. More specifically, the clutch plate 66 is rotatably supported on the shaft 40 between the first sidewall 34 and the adjacent ratchet member 46. A spring 68 (as shown in FIG. 2) reacts between the first sidewall 34 and the clutch plate 66 to urge the clutch plate 66 into frictional driven engagement with the adjacent ratchet member 46. The clutch plate 66 has a generally V-shaped slot with

legs

70 and 72 therein through which the extension 60 extends so that the clutch plate 66 is operable with the extension 60 for maintaining the locking pawl 56 out of the locked position after the predetermined period has expired (the condition illustrated in FIG. 6) and for thereafter moving the locking pawl 56 to the locked position in response to additional extending rotation of the adjacent ratchet member 46.

The energy means 28 includes a flat band-type coil spring 74 and a one-way drive means comprising a wirelike spiral spring 76 and a coupling collar 78. The coil spring 74 is wound in response to extending movement or rotation of the reel means 32. This is accomplished by the one-way drive means, comprising the spiral spring 76 and the coupling collar 78, which transmits drive to wind the coil spring 74 during extending movement or rotation of the reel means 32 but does not transmit drive to the coil spring 74 during retracting movement or rotation of the reel means 32. The outer coil of spring 74 is bent backward as indicated at 80 in FIG. 7 and is connected to the input impeller 22 so as to be nonrotatable relative to the input impeller 22. The inner coil is bent over at 82 and is connected to the coupling collar 78 for winding thereby. The coil spring 74, the coupling collar 78, and the spiral spring 76 are all disposed coaxially with the axis of rotation of the reel means 32, i.e., the axis of the shaft 40 and its extension stub 42.

The output impeller 26 actually takes the form of a housing and includes a cover 84 and a cap 86, all of which are preferably made of plastic. The cover 84 is sonic welded or adhesively secured to the main portion of the output impeller 26 and the cap 84 and the main portion of the output impeller 26 are in sealing engagement about the stub portion 42 of the shaft. A seal 88 is provided and the output impeller 26 as well as the cover 84 are rotatable relative to the stub shaft 42. The cap 86 snaps into engagement with the cover 84. The cover 84 and the cap 86 along with the main portion 26 define the output impeller and the output impeller defines the fluid chamber 24. The input impeller 22 is disposed about the stub shaft portion 42 within the fluid chamber 24. The input impeller 22 has blades 90 extending radially outwardly from the stub shaft 42 from one face thereof. It will be noted the other face of the input impeller 22 is recessed and the coil spring 74 is disposed in the recess. The output impeller member 26 has blades 92 disposed radially outwardly of the input impeller blades 90. In other words, the output impeller blades 92 are disposed circumferentially or concentrically about the input impeller blades 90.

The spiral spring 76 is wrapped about the stub shaft 42 in a very snug manner so that upon rotation of the reel means 32,

and hence the shaft 40 and stub shaft 42, in the counterclockwise direction indicated with the arrow in FIG. 6 or in the clockwise direction indicated with the arrow in FIG. 7, the spiral spring 76 will bindingly engage the stub shaft 42 and rotate therewith to rotate the coupling collar 78. The spiral spring 76 rotates the coupling collar 78 by an extension or arm 94 of the spiral spring 76 being disposed in a slot 96 in the coupling collar 78. The coupling collar 78 also includes a projection 98 which engages the bent portion 82 on the innermost coil of spring 74 so that upon rotation of the coupling collar 78 in the direction indicated with the arrow in FIG. 7, the projection 78 will contact the inner coil of the spring 74 to wind the spring 74.

As will be appreciated from the foregoing description, the chamber 24 is filled with fluid and the blades of the input impeller 22 react through the fluid with the blades 92 of the output impeller 26 to urge the output impeller to rotate in the same direction.

In operation, the seat belt 12 is normally fully retracted and.

the extension 60 is in the position illustrated in FIG. 3. When the extension 60 is in the position illustrated in FIG. 3, it is maintained there by coaction with the shoulder 64 of the output impeller 26 thereby preventing the locking pawl 56 from moving to the locked position in engagement with the

ratchet members

46 and 48. As the seat belt 12 is extended so as to rotate the reel means 32 in the extending direction (counterclockwise as viewed in FIGS. 4 and 6), the shaft 42 is rotated to effect rotation therewith of the spiral spring 76. The spiral spring 76 rotates with the stub shaft 42 because it is urged into gripping relationship therewith because of the direction of rotation. Upon rotation of the spiral spring 76, the coupling collar 78 is rotated to engage the inner coil of the coil spring 74 to effect a winding of the coil spring 74. At the same time, however, the input impeller 22 is rotated by the coil spring 74. During rotation of the input impeller 22, the output impeller 26 is urged to rotate in the counterclockwise direction as viewed in FIG. 3 because of the action of the blades 90 of the input impeller upon the blades 92 of the output impeller 26, through the fluid in fluid chamber 24. As the output impeller 26 is urged to rotate in the counterclockwise direction as viewed in FIG. 3, the shoulder 64 is maintained in engagement with the extension 60 to prevent the locking pawl from moving toward the locked position. So long as the reel means is being rotated in the unwinding direction, the condition of FIG. 3 will exist. Once, however, the belt 12 is no longer being extended from the assembly, the stub shaft 42 will cease to rotate in the direction indicated by the arrow in FIG. 7, but the input impeller 22 will continue to rotate because the coil spring 74 has been wound up and will then proceed to unwind. Thus, until the coil spring 74 is fully unwound, which takes a predetermined period after termination of the extending movement of the belt, the output impeller and the arm thereof including the shoulder 64 will be maintained in the position illustrated in FIG. 3 to prevent the locking pawl 56 from moving to the locked position.

While the assembly is in this initial position, the clutch plate 66 is also urged to rotate in the counterclockwise direction as viewed in FIG. 4 and the extension 60 will be disposed at the uppermost end of the slot leg 70. Upon termination of the extending movement of the belt there always occurs a slight retraction and in response to such slight retraction the clutch plate 66 will move to the position illustrated in FIG. 4 with the extension 60 at the apex of the V-shaped slot therein. If there is no further extending movement, the extension 60 will remain in the position illustrated in FIG. 6 and will continue to be prevented from allowing the locking pawl 56 to move to the fully locked position. When the clutch plate 66 is in the position illustrated in FIG. 6, the shoulder 64 has been disengaged from the extension 60 so that the extension60 is free to move along the slot 58 toward the locked position but is prevented from doing so by the clutch plate 66. When the assembly is in the condition illustrated in FIG. 6 and there is a subsequent extending movement of the belt 12, the frictional engagement between the ratchet member 46 and the clutch plate 66 causes the clutch plate 66 to rotate in the counterclockwise direction as viewed in FIG. 6 whereby the extension is moved along the slot leg 72 as the slot leg 72 forces the extension 60 forwardly thereby positively moving the locking pawl 56 into the locked position engaging the

ratchet members

46 and 48 to prevent further rotation in the extending direction of the

ratchet members

46 and 48.

It will be appreciated that it is possible to eliminate the clutch plate 66 from the assembly since the control means in and of itself allows the extension of the seat belt 12 from the fully retracted position and prevents the movement of the locking pawl 56 to the locked position so long as the seat belt is being extended and for a predetermined period of time after the extension of the seat belt 12 is terminated. The predetermined period of time after extension of the seat belt is attained because the coil spring 74 stores up energy due to the rotation of the reel means 32 during the belt extension so as to continue the rotation of the input impeller 22 after termination of rotation of the reel means 32 to continue to urge the output impeller 26 to rotate in the counterclockwise direction as viewed in FIG. 3 to maintain the shoulder 64 in engagement with the extension 60.

The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than oflimitation.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A retractable seat belt assembly comprising: a seat belt; retractor means movable in a retracting direction for retracting said seat belt and movable in an extending direction for permitting extension of said seat belt; locking means movable between locked and unlocked positions for respectively preventing and allowing movement of said retractor means in said extending direction; and fluid clutch means operatively connected to said locking means comprising an input impeller disposed in a fluid chamber, an output impeller having at least a portion disposed in said fluid chamber, and energy means interconnecting said retractor means and said input impeller for causing said input impeller to act upon said output impeller for a predetermined period after terminating extending movement of said retractor means whereby movement of said locking means towards said locked position during movement of said retractor means in said extending direction and during a predetermined period thereafter is prevented.

2. A retractable seat belt assembly comprising: a seat belt; retractor means movable in a retracting direction for retracting said seat belt to a fully retracted position and movable in an extending direction for permitting extension of said seat belt; locking means movable between locked and unlocked positions for respectively preventing and allowing extending movement of said retractor means in said extending direction; control means responsive to extending movement of said retractor means for preventing movement of said locking means to said locked position until the expiration of a predetermined period after the termination of said extending movement; and operative means for maintaining said locking means out of said locked position after said predetermined period and for thereafter moving said locking means to said locked position in response to additional extending movement of said retractor means.

3. An assembly as set forth in claim 2 wherein said control means includes; input means, output means responsive to said input means for preventing movement of said locking means to said locked position, and energy means responsive to extending movement of said retractor means for imparting the energy developed thereby to said input means during said extending movement and said predetermined period thereafter.

4. An assembly as set forth in claim 2 wherein said control means includes; input means, output means operable in response to movement of said input means for preventing movement of said locking means to said locked position, and energy means responsive only to extending movement of said retractor means for moving said input means during said extending movement and said predetermined period thereafter.

5. An assembly as set forth in claim 4 wherein said energy means includes a coil spring which is wound in response to extending movement of said retractor means.

6. An assembly as set forth in claim 5 wherein said energy means further includes a one-way drive means for transmitting drive to wind said coil spring during extending movement of said retractor means and for transmitting no drive to said coil spring during retracting movement of said retractor means.

7. An assembly as set forth in claim 6 wherein the outer coil of said spring is connected to said input means and the inner coil thereof is connected to said one-way drive means.

8. An assembly as set forth in claim 7 wherein said control means includes a fluid chamber, said input means includes an input impeller, said output means includes an output impeller, said impellers being coaxial so that said output impeller is responsive to said input impeller through fluid in said chamber. v

9. An assembly as set forth in claim 8 including operative means for maintaining said locking means out of said locked position after said predetermined period and for thereafter moving said locking means to said locked position in response to additional extending movement of said retractor means.

10. An assembly as set forth in claim 8 wherein said retractor means includes support means and reel means rotatably supported by said support means, said seat belt being connected to said reel means to be wound thereon and unwound therefrom, said coil spring being disposed coaxially with the axis of rotation of said reel means.

11. An assembly as set forth in claim 10 wherein said reel means includes a shaft, said output impeller being disposed about said shaft and in sealing engagement therewith, said shaft being rotatable relative to said output impeller, said output impeller defining said fluid chamber, said input impeller being disposed about said shaft within said fluid chamber, said input impeller having blades extending radially from said shaft, said output impeller having blades disposed radially outwardly of said input impeller blades.

12. An assembly as set forth in claim 11 wherein said oneway drive means comprises a spiral spring wrapped about said shaft for winding said coil spring.

13. An assembly as set forth in claim 12 including a coupling collar disposed about said spiral spring for rotating with said spiral spring and engaging said inner coil of said coil spring to wind said coil spring.

14. An assembly as set forth in claim 13 wherein said support means includes a generally U-shaped bracket having a base and parallel sidewalls, said shaft extends through said sidewalls, said reel means includes a cylinder concentrically disposed about said shaft, a circular platelike ratchet member secured to each end of said cylinder, said ratchet members being supported by said shaft for rotation relative to said bracket, said cylinder having a slot extending therealong, said seat being connected to said shaft and extending through said slot to be wound and unwound about said cylinder, biasing means urging said ratchet members and said cylinder to rotate in the retracting direction, said locking means includes a pin extending between said sidewalls and a locking pawl rotatably supported by said pin for engaging said ratchet members when in said locked position, a clutch plate rotatably supported on said shaft between a first of said walls and the adjacent ratchet member, a spring reacting between said first wall and said clutch plate for urging the latter into frictional driven engagement with said adjacent ratchet member, said locking pawl having an extension extending therefrom, said clutch plate includes a slot therethrough in which said extension is disposed so as to be operable with said extension for maintaining said locking pawl out of said locked position after said predetermined period has expired and for thereafter moving said locking pawl to said locked position in response to additional extending rotation of said adjacent ratchet member, said first wall includes a slot therethrough and said extension extends therethrough, and said output impeller includes an arm with a shoulder thereon for engaging said extension.

Claims

8. An assembly as set forth in claim 7 wherein said control means includes a fluid chamber, said input means includes an input impeller, said output means includes an output impeller, said impellers being coaxial so that said output impeller is responsive to said input impeller through fluid in said chamber.

12. An assembly as set forth in claim 11 wherein said one-way drive means comprises a spiral spring wrapped about said shaft for winding said coil spring.

14. An assembly as set forth in claim 13 wherein said support means includes a generally U-shaped bracket having a base and parallel sidewalls, said shaft extends through said sidewalls, said reel means includes a cylinder concentrically disposed about said shaft, a circular platelike ratchet member secured to each end of said cylinder, said ratchet members being supported by said shaft for rotation relative to said bracket, said cylinder having a slot extending therealong, said seat being being connected to said shaft and extending through said slot to be wound and unwound about said cylinder, biasing means urging said ratchet members and said cylinder to rotate in the retracting direction, said locking means includes a pin extending between said sidewalls and a locking pawl rotatably supported by said pin for engaging said ratchet members when in said locked position, a clutch plate rotatably supported on said shaft between a first of said walls and the adjacent ratchet member, a spring reacting between said first wall and said clutch plate for urging the latter into frictional driven engagement with said adjacent ratchet member, said locking pawL having an extension extending therefrom, said clutch plate includes a slot therethrough in which said extension is disposed so as to be operable with said extension for maintaining said locking pawl out of said locked position after said pre-determined period has expired and for thereafter moving said locking pawl to said locked position in response to additional extending rotation of said adjacent ratchet member, said first wall includes a slot therethrough and said extension extends therethrough, and said output impeller includes an arm with a shoulder thereon for engaging said extension.