US3501968A - Drive mechanism - Google Patents

Description

(5- D. FREDELL March 24, 1970 I DRIVE MECHANISM 3 Sheets-Sheet 1 Filed Aug 5, 1967 9 o I 2 I p 'qlllll mnmrlllll INVENTOR. GARY D. FREDELL ATT R NEYS.

March 24, 1970 e. n. FREDELL 3,501,968

DRIVE MECHANISM Filed Aug 5, 1967 3 Sheets-Sheet 3 mum FIG.2

MI 4/// INVENTOR.

GARY D. FREDELL ATTORNEYS March 24, 1970 e. D. FREDELL 3,501,968

DRIVE MECHANISM Filed Aug 5, 1967 5 Sheets-Sheet 3 FIG.4

FIG.5

INVENTOR. GARY D. FREDELL NEYS.

United States Patent US. Cl. 74-128 9 Claims ABSTRACT OF THE DISCLOSURE A shaft supporting a ratchet wheel is rotatably supported in a frame with a pawl reciprocating into and out of engagement with the teeth of the ratchet, thereby to impart rotation to the shaft. Lock means cooperate with the pawl and the ratchet wheel to restrict rotation of the ratchet wheel with each'actuation to a predetermined amount in a single direction with the ratchet wheel being otherwise restricted from any movement in either direction. 1 I Y 1 This invention is directed to a drive mechanism, and more particularly to a mechanism in which reciprocating linear motion is converted to rotary motion.

A great number of prior art mechanisms have been developed in which reciprocating linear motion is converted to rotary motion. One type of such prior art mechanisms employs a ratchet wheel on a shaft, a pawl which is adapted to engage the teeth on the ratchet wheel and some appropriate mechanism to reciprocate the pawl into and out of engagement with the ratchet teeth. The path of reciprocation of the pawl is normally tangential to the ratchet wheel and as the pawl approaches the ratchet wheel it engages a ratchet tooth and rotates the ratchet wheel a predetermined amount. One advantage of a mechanism such as this is that a predetermined incremental rotation may be imparted wi.h a relatively simple mechanism.

The prior art has also devised means to prevent unwanted rotation of the ratchet wheel. Typically, the prior art approach has employed some form of a locking dctent or pawl which engages the ratchet wheel to prevent reverse rotation of the wheel. These locking detents or first position generally beneath the feedboard to a second engagement with the teeth of the ratchet wheel but are permitted to ratchet over the teeth as the ratchet wheel is rotated by the drive pawl. As the drive pawl is returned to its normal position to pick up the next tooth on the ratchet wheel, the lock detent or pawl remains in engagement with the teeth of the ratchet wheel and precludes reverse rotation of the wheel.

Mechanisms such as those hereinabove described have some shortcomings. Thus, although the prior art has provided means for preventing reverse rotation of the ratchet wheel, the prior art has made no provision whatsoever for restraining rotation of the ratchet wheel in the drive direction. The locking detent or pawl is wholly ineffective to prevent additional rotation of the ratchet wheel in the drive direction since it is designed to ratchet over the teeth of the wheel when the wheel rotates in this direction. As a result, the ratchet wheel is normally free to rotate in the drive direction when the drive pawl is disengaged from the ratchet teeth. Indeed, in some such mechanisms even when the drive pawl is in engagement with the ratchet teeth, the drive pawl does not prevent additional rotation of the ratchet wheel in the drive direction. It will be appreciated that devices such as these are not satisfactory when a carefully controlled movement of the drive wheel is desired.

It is an object of this invention to provide a drive A lock pawl is pivotally 3,501,968 Patented Mar. 24, 1970 mechanism in which reciprocating linear motion is COH- verted into rotary motion.

It is a further object of this invention to provide a drive mechanism in which the rotary motion of a shaft is controlled both in direction and amount of rotation.

It is a still further object of this invention to provide a drive mechanism in which a drive pawl is reciprocated into and out of engagement with the teeth of a ratchet wheel, and in which means are provided to prevent any rotation of the ratchet wheel when the drive pawl is disengaged from the ratchet teeth.

Another object of the invention is to provide a ratchet mechanism in which the ratchet wheel may not rotate more than a predetermined amount in one direction with each actuation of the mechanism.

It is another object of this invention to provide a drive mechanism which converts linear motion into rotary motion with the linearly moving mechanism serving to lock the rotary mechanism from movement during a portion of the linear cycle.

It is still another object of this invention to provide a drive mechanism in which linear motion is converted into rotary mo.ion and in which the mechanism is failsafe in that it is impossible for the rotary mechanism to rotate in any direction without a prederminted linear movement.

More specifically, this invention broadly contemplates a shaft supporting a ratchet wheel with the shaft being rotatably supported in a frame. A pawl is provided to reciprocate into and out of engagement with the teeth of the ratchet, thereby, to impart rotation to the shaft. Lock means cooperate with the drive pawl to prevent ro:ation of the shaft beyond a predetermined movement for each reciprocation of the pawl, and lock means cooperate with the ratchet wheel to prevent rotation of the ratchet wheel in any direction when the drive pawl is disengaged from the ratchet wheel.

The preferred construction of the invention contemplates a frame supporting a shaft for rotation with a ratchet wheel secured to the shaft. A solenoid-operated reciprocating plunger is supported on the frame with a drive pawl carried by the plunger and which is adapted to be reciprocated into and out of engagement with the teeth on the ratchet wheel. A guide is positioned adjacent the pawl and serves to limit movement of the pawl in a direction radially away from the ratchet wheel. supported on the frame and is biased into engagement with the wheel to prevent reverse rotation of the ratchet wheel. In addition, the plunger carries a lock bar which engages the lock pawl when the drive pawl is disengaged from the ratchet wheel. This lock bar cooperates with the lock pawl to prevent the lock pawl from being pivoted out of engagement with the ratchet wheel, thereby, preventing rotation of the ratchet wheel in any direction when the drive pawl is disengaged from the wheel.

Referring to the drawings wherein like reference numerals indicate like parts in the various views:

FIGURE 1 is a sectional view through the drive mechanism.

FIGURE 2 is a top plan view of the drive mechanism of FIGURE 1.

FIGURE 3 is a partial sectional view similar to FIG- different portion of the operating cycle.

FIGURE 4 is a sectional view of a modified form of the invention.

FIGURE 5 is a sectional view of the modification of FIGURE 4 illustrating the parts in a different position of actuation.

Referring now to the drawings, and particularly the embodiment of FIGURE 1, the drive mechanism indicated generally by the reference numeral 10, is supported on a frame 11 which may be mounted on any supporting structure. A shaft 12 is rotatably supported by bearings 13 in the frame 11. The shaft 12 may carry on its one end an appropriate driving element such as a gear 15. Secured to the shaft 12 is a ratchet wheel 16, on the periphery of which there are formed a plurality of ratchet teeth .17.

A plate 18 is supported on the frame 11 and the plate, in turn, supports a solenoid indicated generally by the. reference numeral 19. The solenoid includes a solenoid coil 20 and a solenoid plunger or armature 21. A bottom stop 22 provides a bottom limit for the reciprocation of the plunger 21. The plate 18 includes an aperture 23 through which the upper end of the plunger 21 projects.

An upwardly opening bore or slot 24 is provided in the upper end of the plunger 21 and receives therein a pawl 25. A pin 26 pivotally supports the pawl 25 in the bore 24. A leaf spring 27 is secured at the inner end of the bore and is adapted to engage a flat surface 28 formed on the inner end of the pawl. The flat surface defines a chord on the otherwise circular end of pawl 25 with one end 29 of the surface serving as a fulcrum point against which spring 27 abuts. A lock bar 30 encircles the upper end of plunger 21 and is secured thereto with a spring 31 received over the plunger 21 and interposed between the lock bar 30 and the upper surface of the plate .18 to bias the plunger 21 in a direction away from the bottom stop 22.

As an upper stop. for the plunger 21, there is provided a stop bar and guide 33 which issupported by the frame 11. A guide block 34 is secured to the guide 33 with the guide block extending between a bifurcated portion of lock bar 30 defining arms 35.

The pawl 25 is defined by substantially parallel opposed sides with a beveled surface 37 formed on the outer extremity of the pawl 25 defining a nose 38 adapted to engage the ratchet teeth 17 in the manner shown in FIGURE 1. As will be understood by those in the art, reciprocation of the plunger 21 will cause the pawl 25 to be reciprocated therewith, and as the pawl engages the ratchet teeth 17 on the ratchet 16, a rotary motion will be imparted to the shaft 12.

In many applications it is desirable to prevent reverse rotation of the ratchet wheel 16. Moreover, it is often desirable to assure that the ratchet wheel 16 is advanced but a predetermined amount with each actuation of the mechanism.

As a means to accomplish both of these purposes, there is provided a locking arrangement which includes a locking pawl or detent 40 which is pivotally mounted on a shaft 41 supported by the frame 11. The pawl is normally biased by a spring 42 in a clockwise direction about the shaft 41, as viewed in FIGURE 1. The pawl 40 includes a nose portion 43 which is adapted to cooperate with the ratchet teeth 17. The pawl 40 further includes a tail portion 44 which includes a flat surface 45 and a tapered surface 46 adjacent surface 45. The tail portion 44 is of such a configuration and so dimensioned that it is normally spaced from the path of reciprocation of lock bar 30 when pawl 40 is in engagement with ratchet wheel 16.

The above-described mechanism operates in the following manner:

With the parts of the mechanism in the position shown in FIGURE 1, it will be appreciated that the shaft 12 is effectively restrained from any rotation. Thus, any tendency of the shaft 12 to rotate in the clockwise direction will be restrained by the engagement of the pawl 25 with the ratchet tooth 17. Similarly, the engagement of the pawl 40 with ratchet teeth 17 also prevents counter-clockwise rotation of the shaft 12. The spring 42 maintains engagement of the pawl 40 with the ratchet wheel, while pawl 25 is maintained in engagement with the ratchet wheel by the blocking engagement of surface 36 on guide 33 with pawl 25.

When it is desired to impart rotation to the shaft 12, the solenoid 19 is actuated which causes the plunger 21 to be drawn toward the bottom stop 22. As the plunger 21 is displaced, the pawl 25 is disengaged from the ratchet wheel, and the action of the spring 27 against the fulcrum oint 29 on the pawl causes the pawl 25 to pivot in a. counter-clockwise direction around the pin 26. However, though the pawl 25 is now disengaged from the ratchet wheel 16, the shaft 12 is still restrained from rotating in the clockwise direction due to the continued engagement of the pawl 40 with the teeth 17. Moreover, as the plunger 21 is moved downward, the lock bar 30 moves to a position in which it is directly opposed to the surface on tail 44 of the pawl 40. Thus, although pawl 40 normally ratchets over teeth 17 when wheel 16 rotates counter-clockwise, lock bar 30 blocks pawl 40 so that it can no longer pivot to accommodate the rotation of wheel 16, thereby effectively locking the ratchet wheel against movement in any direction.

As the solenoid is de-energized, the spring 31 returns the plunger 21 to the position shown in FIGURE 1. As the plunger is returned to its original position, the pawl 25 picks up a different tooth of the ratchet wheel and imparts rotary movement to the shaft .12. Because the lock bar 30 has now been displaced from a position of direct opposition to the tail portion 44 of the pawl 40, the pawl is free to pivot about the shaft 41 without interfering with the rotation of wheel 16.

It will be appreciated that this mechanism prevents any rotation of the shaft 12 from external sources and limits the rotation of the shaft to a single ratchet tooth with each actuation of the solenoid 19. The mechanism is entirely failsafe in that all steps in the cycle the ratchet wheel 16 is positively controlled by either the pawl 25 or the pawl 40 or both. Moreover, the engagement of the guide 34 with the lock bar 30 and arms 35 prevents any tendency of the plunger 21 to tilt so that not only are the pawls locked in position, but also the plunger 21 is restrained from movement.

Referring now to FIGURES 4 and 5, there is illustrated an alternate embodiment which achieves the same desirable results as the mechanism of FIGURE 1. Essentially, the same basic arrangement of a frame, solenoid and plunger is employed. A shaft is rotatably supported by the frame and a pawl 51 is pivotably supported by a pin 52 carried by the upper end of the plunger. A

spring 53 biases the plunger to an extended position with,

a guide bar 54 functioning as an upper stop and a guide 55 cooperating with a bar 56 to prevent undesirable tilting of the plunger.

Rather than employing a single ratchet wheel as in the embodiment of FIGURE 1, the embodiment of FIG- URE 4 employs two ratchet wheels. Thus, there are secured on the shaft 50 a ratchet wheel having ratchet teeth formed around the periphery thereof. However, the teeth 59 on the ratchet wheel 57 face in the direction opposite to the direction of the teeth 60 on ratchet wheel 58.

The pawl 51 includes a stepped shoulder 61 which is adapted to engage the teeth 60 on the ratchet 58. The pawl further includes a nose portion 62 which extends in a direction longitudinal of the pawl 51. In addition, the pawl includes an arm or lock bar 63 which is formed at the outer extremity of the pawl with the arm 63 having a transverse dimension relative to the pawl 51. The arm '63 is adapted toengage the teeth 59 on the ratchet wheel 57. A spring 64 tends to bias pawl 51 in the same manner as in the embodiment of FIGURE 1. The embodiment of FIGURE 4 also includes a lock or check pawl 65 which cooperates with the teeth of ratchet wheel 58 to prevent reverse rotation.

The embodiment of FIGURE 4 functions in the following manner:

With the parts of the mechanism in the position illustrated in FIGURE 4, it will be appreciated that the shaft 50 is restrained from any movement whatsoever. Thus, the tooth 60 on the ratchet wheel 58 in engagement with the shoulder 61 of the pawl 51 is restrained from movement relative to the pawl. Should the wheel 58 tend to rotate in a clockwise direction, the check pawl 65 will restrain such tendency. In the event that the ratchet wheel should tend to rotate in the counterclockwise direction, the tooth 60 will engage the longitudinal surface of the shoulder 61. Any tendency of the pawl 51 to be pivoted about the pin 52 is prevented through the inter-engagement of the pawl with the lock bar 54. Similarly, any attempt to tilt the plunger is restrained through interengagement of the lock bar 56 with the guide 55.

When it is desired to impart rotation to the shaft 50, the solenoid is actuated and the plunger is retracted in the manner of the embodiment of FIGURE 1. As the plunger is retracted, the pawl 51 is disengaged from the teeth on the ratchet wheel 58. As the plunger is retracted, the pawl 51 is permitted to pivot in a counterclockwise direction around the pin 52'under the bias of spring 64. As the pawl 51 is pivoted in a counterclockwise direction, the arm 63 engages the teeth 59 on the ratchet wheel 57. Any tendency of the shaft 50 to rotate in the counterclockwise direction when the arm 63 is in engagement with the ratchet wheel 57 will merely tend to move the plunger upward. However, since the plunger is electrically held energized, the shaft 50 is prevented from rotation. When the solenoid is de-energized, the plunger will be displaced under the bias of spring 53 and the shoulder 61 on the pawl 51 will engage the next tooth on the ratchet wheel 58 and impart a rotary movement to the shaft 50.

It will be appreciated that this latter embodiment may utilize the engagement of member 56 with check pawl 65 in the same manner as in the embodiment of FIGURE 1. However, since arm 63 is effective to prevent rotation of shaft 50 in the counterclockwise direction when the solenoid is energized, member 56 need not be employed.

It is thus apparent that both embodiments employ the linearly reciprocating member as the means to lock the rotary mechanism when the drive pawl is disengaged from driving engagement with the ratchet wheel. Moreover, both embodiments employ the drive pawl as the means to limit the amount of rotary motion imparted to the ratchet wheel, thereafter locking the wheel from further rotation in the drive direction. Thus, rotation of the shaft is fully controlled in direction and amount at all times.

Having thus descried my invention, I claim:

1. An improved mechanism for converting linear motion to rotary motion in which the mechanism includes a shaft rotatably supported on a frame, a single ratchet wheel secured to the shaft, a drive pawl adapted to reciprocate into and out of driving engagement with said ratchet wheel means, reciprocating drive means connected to said drive pawl to rotate said wheel means in one direction and lock means cooperating with said ratchet wheel means to prevent rotation in the other direction, the improvement comprising:

additional lock means operative to prevent rotation of said wheel means in said one direction when said drive pawl is out of driving engagement with said wheel means.

2. The mechanism of claim 1 wherein said improvement further comprises guide means fixedly supported on said frame adjacent to the path of reciprocation of said drive means,

said guide means being operative to limit the rotation of said wheel means in said one direction when said drive pawl is in driving engagement with said wheel means.

3. An improved mechanism for converting linear motion to rotary motion in which the mechanism includes a shaft rotatably supported on a frame, ratchet wheel means secured to the shaft, a drive pawl adapted to recip rocate into and out of driving engagement with said ratchet wheel means, reciprocating drive means connected to said drive pawl to rotate said wheel means in one direction and lock means cooperating with said ratchet wheel means to prevent rotation in the other direction, the improvement comprising:

additional lock means operative to prevent rotation of said wheel means in said one direction when said drive pawl is out of driving engagement with said wheel means; said lock means comprises a lock pawl pivotally supported on said frame;

said additional lock means comprising a lock bar on said drive means,

said lock bar cooperating with said lock pawl to prevent pivoting movement of said lock pawl when said drive pawl is out of driving engagement with said wheel means. 4. An improved mechanism for converting linear motron to rotary motion in which the mechanism includes a shaft rotatably supported on a frame, ratchet wheel means secured to the shaft, a drive pawl adapted to reciprocate into and out of driving engagement with said ratchet wheel means, reciprocating drive means connected to said drive pawl to rotate said wheel means in one direction and lock means cooperating with said ratchet wheel means to prevent rotation in the other direction, the improvement comprising:

additional lock means operative to prevent rotation of said wheel means in said one direction when said drive pawl is out of driving engagement with said wheel means; said additional lock means includes an arm projecting from said drive pawl,

said arm being spaced from said ratchet wheel means when said drive pawl is in driving engagement with said wheel means and in engagement with said wheel means when said drive pawl is out of driving engagement with said wheel means.

5. The mechanism of claim 4 wherein said wheel nlieafns comprises a pair of ratchet wheels secured to said s a t,

said drive pawl being adapted to engage one of said wheels and said arm being adapted to engage the other of said wheels. 6. An improved mechanism for converting linear motlon to rotary motion in which the mechanism includes a shaft rotatably supported on a frame, ratchet wheel means secured to the shaft, a drive pawl adapted to reciprocate into and out of driving engagement with said ratchet wheel means, reciprocating drive means connected to said drive pawl to rotate said wheel means in one direction and lock means cooperating with said ratchet wheel means to prevent rotation in the other direction, the improvement comprising:

additional lock means operative to prevent rotation of said wheel means in said one direction when said drive pawl is out of driving engagement with said wheel means; said drive means comprises a solenoid having a reciprocating armature,

a recess in the upper end of said armature,

said drive pawl being pivotally supported in said recess,

spring means in engagement with said drive pawl,

said spring means normally pivoting said pawl toward said ratchet wheel means, and

guide means fixedly supported on said frame adjacent the path of reciprocation of said drive pawl,

said guide means being operative to limit the pivoting movement of said pawl in a direction away from said ratchet wheel means.

7. An improved mechanism for converting linear motion to rotary motion in which the mechanism includes a shaft rotatably supported on a frame, ratchet wheel means secured to the shaft, a drive pawl adapted to reciprocate into and out of driving engagement with said ratchet wheel means, reciprocating drive means connected to said drive pawl to rotate said wheel means in one direction and lock means cooperating with said ratchet wheel means to prevent rotation in the other direction, the improvement comprising:

additional lock means operative to prevent rotation of said wheel means in said one direction when said drive pawl is out of driving engagement with said wheel means; said drive pawl is pivotally supported on said drive means,

biasing means cooperating with said drive pawl to pivot said drive pawl toward said ratchet wheel means, and

stop means operative to limit the pivoting movement of said drive pawl away from said ratchet wheel means.

8. The mechanism of claim 7 wherein said stop means is radially spaced from the periphery of said wheel means a distance substantially equal to the Width of said drive pawl.

vent pivoting movement of said lock pawl when said drive pawl is out of driving engagement with said wheel means.

References Cited UNITED STATES PATENTS 1,565,336 12/1925 Seufert 74128 2,900,840 8/1959 Greve 74-1421 2,829,530 4/1958 Holden 74-128 MARK M. NEWMAN, Primary Examiner W. S. RATLIFF, JR., Assistant Examiner US. Cl. X.R. 74126

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