US2927771A - Hoist - Google Patents

Description

i ed States Patent HOIST Application September 23, 1957, Serial No. 685,461 Claims. (Cl. 254-167) This invention relates generally to hoists of the winch type which utilize a frame mounting a cable-winding drum provided with ratchet teeth engagable by the acting end of a stop pawl that is movably carried by the frame, an operating lever mounted upon the frame for oscillation relative thereto, a feed pawl carried by the lever for movement thereupon to advance its acting end into engagement with the ratchet teeth, and means, operable at will, for yieldingly holding the feed pawl acting end away from such engagement. More particularly, my present invention is concerned with a single operating means for the stop pawl comprising a camspring unit which transmits a predetermined delayed motion from the advancing feed pawl to the stop pawl, and vice versa, whereby to produce a controlled sequential and alternate engagement of the two pawls with the ratchet teeth of the cable-winding drum whenever a reverse movement of the latter is to be efiected. By such means, a positive, step-by-step, load-induced, unwinding movement of the drum may be assured whenever desired.

A hoist of the kind described may be operated both for lifting or pulling a load and thereafter for lowering or releasing the load, usually in response to gravity. In changing from a lifting to a lowering operation, the bias of a spring which normally urges the feed pawl into ratchet-engaging position may be reversed whereby to retract this pawl to a normally over-riding position relative to the ratchet teeth. When done, this pawl which is movably mounted on the operating lever is advanced by the latter toward the stop pawl which normally remains engaged with the ratchet teeth to sustain the load. The feed pawl near the conclusion of such advance engages the cam-spring unit which then operates, first to deflect the feed pawl into engagement with the ratchet wheel and, with further stroking of the lever, to rotate the said Wheel; and secondly, the cam-spring unit is itself deflected by the engaged feed pawl to impart a delayed retraction of t the stop pawl away from the ratchet wheel to a position of disengagement relative thereto. At the conclusion of the feed pawl advance the operating parts are ready for a lever-controlled reverse movement of the ratchet wheel during which the feed pawl is retracted the necessary distance for the stop pawl to re-engage the next adjacent ratchet tooth, thereby permitting a controlled lowering of the load for a fixed distance equal to the spacing between two adjacent ratchet teeth.

The means which effects disengagement of the stop pawl in response to advance of the over-riding feed pawl comprises a novel and improved cam-spring unit whose features of construction offer special advantages. Since a hoist of the kind herein described is subjected to hard and careless usage, protection to the fullest extent possible should be provided for its operating parts which are necessarily exposed to contact. The present cam-spring unit affords such protection since its associated spring element is accommodated wholly within the confines of the cam body by which it is carried. To enhance the spring range of action, a coil (or coils) is provided in its structure and through the formation of a protecting seat therefor, provided in the cam body, a longer life for the spring element is assured. Such a cam-spring unit is itself capable of maintaining the stop pawl normally in operative engagement with the ratchet teeth without other supplementary means, so is advantageous in holding to a minimum the number of parts requisite for successful operation of the hoist under a wide variety of working conditions. When called upon to urge the stop pawl away from the ratchet teeth, a delayed action is assured by the present cam-spring unit, but one that is also fast and dependable when action commences. It is with objects and purposes such as these, and with others also to be hereinafter mentioned, that the present invention is concerned.

A suggestive exemplification of the present cam-spring unit incorporated into a winch-type hoist for advantageous use therein is illustrated in the accompanying drawing wherein:

Figure l is a front (or rear) elevation of the hoist complete except for its operating lever (shown in its fully retracted position) of which but a small portion of its anchored end is indicated;

Figure 2 is a vertical sectional view through the frame, taken on line 2-2 of Figure 1, showing in elevation the principal operating parts of the hoist in a substantially advanced position, i.e. in a first stage of their movements during the cycle of lowering or releasing the load; and

Figures 3-5 are schematic views of the hoist operating parts in the positions which they occupy in three successive stages of the operating cycle immediately following the first stage as illustrated in Figure 2.

Referring to the drawing, there is illustrated a substantially rectangular frame 10 to which the usual anchoring hook or eye (no-t shown) may be swivelly mounted in one end wall along its axis. The lower end wall of the frame is also provided with a bushed opening 11 through which a cable 15 is guided in its movements during normal operation of the hoist.

The frame 10 supports a transverse shaft 16 journaled for rotation within bushed apertures (not shown) provided in the frame walls. Carried fast on the shaft 16 is a ratchet wheel-drum comprising a cylindrical body 17, an annular flange 18 on one end thereof, and a ratchet wheel 19 on the other. As by a hand wheel 14 affixed to one end of the shaft 16, the latter and the drum 17 may be turned to a desired rotative position whenever the hoist is free of a load. A U-shaped member 20 having approximately the same transverse dimension as the frame 10 has its two legs rotatably mounted on the shaft 16 and, as shown, one leg is positioned intermediate the flange 18 and the proximate side of the frame with the other leg adjacent the opposite frame side, but externally thereof. An operating handle 21 (see Fig. 1) is secured at one end within an elongated sleeve 22 carried fast on the external leg of the U-shaped member 20. Both of the legs of this member are apertured at 2.? to receive the shaft 16. The handle in combination with the U-shuped member 2% constitutes an operating lever for the hoist and at times will be so referred to hereinafter.

A transverse pawl shaft 25 is rotatably supported by the U-shaped member 20. A feed pawl F is rotatably mounted on this shaft substantially in alignment with the ratchet wheel 19 and held in such alignment by appropriate means in conjunction with hubs 27 and 28 which are extended outwardly on opposite sides of the pawl. An arm 29 extending radially from a collar 30 that is fast on the shaft 25 (see Fig. 2) is apertured to receive and support one end of a wire spring 31 in the form of an L-shaped toggle having its other end pivotally mounted in an aperture 32 of the connecting section of the U-shaped member 20. The feed pawl F is provided with a pair of spaced ears 33 and 34 between which the spring 31 extends. When the shaft 25 is biased to lifting position, the spring 31 lies past its center point to press against the ear 33 and bias the feed pawl F into engagement with the teeth of the ratchet wheel 19; whereas, with the shaft 25 rotated back approximately a fourth revolution, the spring 31 is biased in the opposite direction and pressed against the car 34, thereby swinging the feed pawl F away from engagement withthe ratchet teeth and into an over-riding position relative to the ratchet wheel 19 (see Fig. 2). To limit the rotation of the feed pawl F when in its overriding position, a stop lug (not shown) may be provided on the U-shaped member 20, in line with current practice, to abut and hold the spring 31 in this direction of its bias; and to facilitate manual rotation of the shaft 25 a radial knob 36 is fastened to its end at a point exteriorly of the U-shaped member 20 (see Fig. 1).

A shaft 37 is extended between the sides of the frame and journaled for rotation therein. This shaft supports a stop pawl S having oppositely extended hubs, one in engagement with the proximate frame side wall and the other, designated as 38 (see Fig. 1), adjacent a split ring 39 longitudinally fixed on the shaft 37 whereby to hold the pawl in substantial alignment with the teeth of the ratchet wheel 19 for engagement therewith. Pivotally mounted on the frame 10 intermediately of one of its sides and the stop pawl S is an elongated cam C in the form of a plate of substantial thickness having at one point an outwardly extended hump 40, and near one end of the plate an aperture for receiving a supporting pin 42 that is laterally extended inwardly from the adjacent side wall of the frame 10 wherein it is anchored. The cam plate is thereby pivotally mounted at one end so that its opposite free end may swing toward and from the ratchet engaging end of the stop pawl S. In its free end portion the cam C is recessed as by the provision of a framed opening 43 extending through its body between opposite faces thereof. This recess which is elongated in the direction of the plate length extends laterally at one end into the hump portion 40 of the plate and is suitably curved therein to form a seat 44 to receive and support one side of a coil (or coils) 45 formed in a wire spring W.

The spring end portion 46 adjacent the coil 45 is fitted into a bore extending longitudinally through the cam hump portion 40 to provide an anchorage wherein the spring W is fixedly held. An arm which is extended away from the coiled portion of the spring to traverse the elongated opening 43 of the cam C is curved in its free end portion to provide, in effect, a cam 48 for sliding engagement with a stud 49, the stud being projected laterally into the said opening from the stop pawl S to which it is anchored at a point near its ratchet engaging end.

The spring cam 48 maintains at all times a pressure engagement with the stud 49 which occupies a position between the spring and the lower frame side defining the opening 43, as viewed in Figs. 3-5. The cam C, together with its spring cam 48, constitutes a cam-spring unit and will at times be so referred to herein.

The spring W normally serves to bias the acting end of the stop pawl S into engagement with a tooth of the ratchet wheel 19 independently of any other means for this purpose (see Fig. 2). This results from the fact that the tension force exerted upon the stud 49 by the spring cam 48 proceeds in a dircction which tends to swing the acting end of the stop pawl S toward the ratchet wheel 19 and into engagement with its proximate tooth. The tension of the spring W may be supplemented. if desired. by other means to assist in holding the stop pawl S in engagement with the ratchet wheel: such an expedient, however, is not necessary for successful operation of the hoist, and this fact should be kept clearly in mind. For this purpose, a simple wire spring 50 coiled about the shaft 37 with opposite ends 51 and 52 anchored to the frame 10 and pawl hub 38, respectively, will sufiice.

The engagement of the spring cam 48 with the stud 49 is one that is sliding to permit free pivotal movement of the stop pawl S when swinging toward or from the teeth of the ratchet wheel 19. To assure that the spring cam 48 will not slide endwise of the stud, while exerting its force thereupon in an effective direction at the point of its engagement therewith, the spring cam 48 is curved toward the stud which is formed with a circumferential groove 53 at the point of such engagement to accommodate the spring cam therein. Additionally, to maintain intact the operative connection between the spring cam 48 and the stud 49 a kerf 54 is provided in the body of the cam C to extend throughout that portion thereof required for the full movement range of the spring cam 48 while maintaining its pressure engagement with the stud 49. This kerf which receives the free end portion of the spring W serves as a guideway therefor and protection thereto, whereby to obviate any interference with its proper functioning.

The stop pawl S is extended away, oppositely from its acting end, outwardly and beyond its pivotal axis, as at 55, to a point which may be clear of the frame 10 so as to be accessible for manipulation at such times as it is desired to free the drum 17 for reverse rotation, as when the cable 15 wound thereon is to be carried to a load for attachment thereto. The cable end which is attached to the drum is secured thereto in any suitable way.

In operation to raise or pull a load, the knob 36 is, if desired, initially turned to retract the feed pawl F from engagement with the ratchet wheel 19, and pressure applied to the manipulative end 55 of the stop pawl S to retract its acting end from engagement with the ratchet teeth so that the cable 15 may be freely moved to a load. Thereafter, with the knob 36 turned to normal load position, the lever 21 may be stroked forwardly, i.e. downwardly as shown in the drawings, to wind the cable onto the drum 17 and thereby to lift or pull the load. This stroking of the lever which is repeated as often as necessary causes the feed pawl F, normally engaged with the ratchet wheel, to impart an intermittent rotation thereto while the stop pawl S also remains engaged therewith to prevent reverse rotation of the drum whenever the lever 21 is stroked reversely, i.e. upwardly as viewed in the drawing, to its initial position preparatory to another downward or forward stroke.

When a load is to be lowered or released, the feed pawl F is biased to an over-riding position by suitably turning the knob 36. A forward stroking of the operating lever 21, i.e. a downward movement thereof, will then carry the feed pawl F freely over the ratchet wheel 19 to the point of its contacting the cam C which lies in its path of movement near the end of its downward stroke (see Fig. 2). The feed pawl F which is equipped with a laterally extending contact lug 56 then slidingly engages the proximate face of the elongated cam C and in so doing the feed pawl F is rocked against the tension of its spring 31 to swing fully into engagement with the proximate tooth of the ratchet wheel 19 (see Fig. 3). Continued advance of the feed pawl F will transmit a turning movement to the ratchet wheel 19- in a counter clockwise direction as viewed in the drawing; a rocking movement of the cam C will also take place. its free end portion swinging downwardly to compress the spring W carried thereby. It is necessary both for the ratchet wheel 19 to turn slightly and for the spring W to be compressed in order to clear the way for movement of the'stop pawl S away from the ratchet wheel. In Fig. 3 the start of that movement is indicated as consequent upon compression of the spring W to its maximum point where it may engage with the cam frame to receive a positive thrust force therefrom. In this movement the feed pawl F bears unyieldingly with an increasing pressure against the cam C to swing its free end in a direction that is away from the ratchet wheel 19; and during this stage of the operation the spring W, when pressed against the top frame side of the cam C, will be in a state of maximum compression (see Fig. 3) ready to exert its own tension force to supplement the positive force of the cam in dislodging the stop pawl S from its position of engagement with the ratchet wheel.

With continued advance of the feed pawl F, the cam C and spring W, together or singly (depending upon the load and other factors), will exert upon the stud 49 an increasing pressure suflicient to overcome the frictional resistance encountered from the pressure engagement of the ratchet wheel with the acting end of the stop pawl S; the latter will then swing out and away from the ratchet wheel to disengage completely therefrom. in this disengaging movement the tension of the spring W will yield to the greater force exerted by the cam C, but at the moment the stop pawl S has been retracted to a point clear of the ratchet wheel the frictional resistance opposing this movement will suddenly end, with the result that the acting end of the stop pawl S will fly out and snap away from the ratchet wheel to permit of a reverse movement thereof under the control of the lever 21 working through the engaged feed pawl F.

It will be observed that the spring cam 48 in an early stage of the operating cycle acts as a cushion to yield while the cam C undergoes swinging movement. and thereafter, while compressed to its point of maximum tension. or under pressure from the cam C, or both. will exert upon the stop pawl S a force, positive or otherwise, such as is requisite for rocking the pawl speedily and reliably to a position of disengagement relative to the ratchet wheel. This disengaging movement of the stop pawl, it will be noted, is positively delayed, and for an interval that is predetermined inter alia by the contour of the cam, until after the feed pawl F has definitely completed its movement toward and into engagement with the ratchet wheel. so as to eliminate all possibility of control failure.

In the operation just described, the feed pawl F is first cammed into engagement with the ratchet wheel 19. but at a point which is two'teeth removed from the one vacated by the stop pawl S in the same operation. The result is that the winding drum 17 is freed for reverse movement for the distance of one tooth only while complete control is manually maintained over the lowering or releasing of the load. With each disengagement of the stop pawl S from the ratchet wheel 19, the spring W which is carried within the confines of the cam C is effective to impart an accelerated outward movement to the pawl, thereby assuring complete and rapid separation of its acting end from the ratchet wheel at a moment which follows sequentially but closely upon conclusion of advance of the feed pawl F into engagement therewith, thereby to permit controlled lowering or release of the load.

In summary, the cam C which is unyielding serves inter alia as a carrier for the stop pawl spring W which is, in effect, a yieldable tensioned cam. This cam unit is movable through a fixed path between two positions. and the spring W comprised in this unit is itself movable independently of the cam C. The stop pawl S is also movable through a fixed path between two positions wherein it alternately engages and disengages the ratchet wheel. The cam C is operated in response to engagement from the feed pawl F when advanced through a circular path. In the movements which ensue there is a first stage (see Fig. 2) in which the feed pawl F is itself cammed into engagement with the ratchet wheel. Through this stage the tension force of the spring W resists movement of the cam C which remains effective to hold the stop pawl S in its engaged position with the ratchet wheel. Continued advance of the feed pawl F initiates a second stage in the movement (see Fig. 3)

wherein the ratchet wheel 19 is rotated slightly and the cam C is rocked to enhance the compression of its spring W. The stop pawl S initiates its movement of disengagement relative to the ratchet wheel during this second operational stage of the cycle. A third stage is reached (see Fig. 4) when the cam spring unit has completed disengagement of the stop pawl S from the ratchet wheel. A fourth stage in the movement starts with reverse stroking of the lever 21 and retraction of the feed pawl F from its foremost advanced position, the stop pawl S meanwhile remaining away from the ratchet wheel until the latter has started its reverse movement in response to the pulling force exerted on the cable 15 by the load attached thereto; this fourth stage ends with return movement of the stop pawl S toward the ratchet wheel (see Fig. 5) for reengagement with a tooth thereof that is one removed from the tooth previously engaged by the stop pawl whereby to limit correspondingly the distance of wheel movement in the reverse direction. During this last stage of the operational movement the feed pawl .F is maintained in engagement with the ratchet wheel 19 while the spring W acts to bias the stop pawl S against that wheel and direct it into its final position of engagement therewith.

Due to the rough and often careless treatment that portable hoists of the kind here under description are commonly subjected to when placed in service, the more vulnerable of the operating parts are occasionally damaged. The spring W here employed to bias the stop pawl S into engagement with the ratchet wheel and also. at a predetermined point in the operating cycle, to accelerate disengagement of the same pawl from the ratchet wheel, is one part that should be adequately protected. in the present cam-spring unit such protection is afforded in full measure by enclosing it within the confines of the cam body where it is beyond contact range. Its coil (or coils) which is a sensitive part of such spring is furthermore amply supported within the seat that is provided for its reception, thereby assuring for it a long life of dependable service. Once assembled and tested, the hoist of this invention can be counted upon to perform satisfactorily and safely for an indefinite life span.

An earlier disclosure of many of the present improvements as herein claimed is contained in my application filed November 20, 1956 under Serial No. 623,467 issuing later on October 7, 1958 as Patent No. 2,854,852 of which this case is a continuation in part.

I claim:

I. The combination with a hoist of the winch type which utilizes a frame mounting a cable-Winding drum provided with a ratchet wheel engageable by the acting end of a stop pawl carried by the frame and swingable about a fixed axis thereon, an operating lever mounted upon the frame for oscillation relative thereto, a feed pawl carried by the lever for swinging movement about a fixed axis thereon to advance its acting end into engagement with the ratchet wheel, and means yieldingly holding the feed pawl acting end away from such engagement, of means for operating the stop pawl alternately into and out of engagement with the ratchet wheel comprising a movable unyielding cam engageable by the feed pawl when advanced in response to forward stroking of the lever while the feed. pawl is disengaged from the ratchet wheel, the cam when so engaged being movable thereby through a limited distance independently of the stop pawl. and a yieldable tensioned cam extending between the unyielding cam and stop pawl, carried by one and in motion-transmitting slidable connection with the other. the unyielding cam, when moved one way, operating to shift the yieldable tensioned cam to a posilion in which it biases the stop pawl toward the ratchet wheel and, when moved the opposite way, operating to shift the yieldable tensioned cam to a second position in which it biases the stop pawl away from the ratchet wheel.

2. The combination with a hoist of the winch type which utilizes a frame mounting a cable-winding drum provided with a ratchet wheel engageable by the acting end of a stop pawl carried by the frame and swingable about a fixed axis thereon, an operating lever mounted upon the frame for oscillation relative thereto, a feed pawl carried by the lever for swinging movement about a fixed axis thereon to advance its acting end into engagement with the ratchet wheel, and means for yieldingly holding the feed pawl acting end away from such engagement, of a single operating means for the stop pawl comprising an unyielding cam pivoted to swing about a fixed axis and positioned to be engaged by the feed pawl when advanced in response to forward stroking of the lever while the feed pawl is disengaged from the ratchet wheel, the cam when so engaged being movable thereby through a limited distance independently of the stop pawl, and a yieldable tensioned cam extending between the unyielding cam and the stop pawl, carried by one and in motion-transmitting connection with the other, the unyielding cam, when rocked through a first stage of movement, operating through the yielding cam to exert a tension force on the stop pawl to urge the acting end of the latter into engagement with the ratchet Wheel, and the unyielding cam, when rocked through a second stage of its movement, operating through the yielding cam to exert a camming force on the stop pawl tending to move the acting end of the stop pawl out of engagement with the ratchet wheel.

3. The combination with a winch mechanism comprising a frame mounting a rotatable ratchet wheel, an oscillatible lever whereon is carried a movable feed pawl engageable with the ratchet wheel but biased away therefrom, and a stop pawl movable toward and from the ratchet wheel, of a motion transmitting connection between the two pawls mounted on the frame comprising a movable unyielding cam engageable by the feed pawl, when the latter is advanced in response to operation of the lever in one direction while disengaged from the ratchet wheel, to displace the feed pawl through a first stage of movement into engagement with the ratchet wheel for subsequent rotation thereof and, in a continuing advance of the feed pawl through a second stage of movement while rotating the ratchet wheel, to move the unyielding cam from a first to a second position, and a single tensioned cam carried by the unyielding cam for bodily movement therewith between first and second positions in each of which it is slidingly and yieldingly engaged with the stop pawl to exert thereon its tension force alternately in two difierent directions to bias the stop pawl into engagement with the ratchet wheel when in the first position, and away from such ratchet wheel engagement when in the second position.

4. A stop pawl operating means according to claim 1 in which one portion of the yieldable tensioned cam is anchored to the unyielding cam with another portion disengaged therefrom to provide a contact portion free for pressure engagement with the stop pawl for operation thereof.

5. A stop pawl operating means according to claim 1 in which the yieldable tensioned cam is a wire spring carried by the unyielding cam and anchored thereto in one end portion whereby its opposite end portion is freed for sliding pressure engagement with the stop pawl for operation thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,236,616 Snow Aug. 14, 1917 2,470,019 Coiling May 10, 1949 2,501,253 Anglernyer Mar. 21, 1950 2,633,328 Wallace Mar. 31, 1953 2,738,954 Du Bois Mar. 20, 1956 2,816,733 Du Bois Dec. 17, 1957

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