US2227893A - Fence stretcher or hoist - Google Patents

Description

Ja 7, 19 G. w.- BENJAMIN FENCE STRETCHER 0R HOIST Filed March 27, 1940 3 Sheets-Sheet l INVENTOR.

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Jan. 7,

G. w. BENJAMIN 2,227,893

FENCE STRETCHER OR HOIST Filed March 27, 1940 3 Sheets-Sheet 2 1'. I. H m mu W I. J10 17 1.3 W NH i I 'llu u 17 W \l\ .F l 27 I my: w 3.6

Patented Jan. 7, 1941 PATENT OFFICE- FENCE STRETCHERORHOIST George Washington -Benjamin,.Miincie, 1116., as-

signor to Kitsclman Brothers; Muncie; Ind., a corporation of Indiana 2 Application March 2'7,

6 Claims.

My invention relates to wire-stretchers or hoists of the type in which a chain is pulled through a body member by means of force-multiplying mechanism including a manually oscillatable lever pivotally mounted on thebody and provided with pawls which co-operate with the chain.

The primary objects of my invention are to produce a device of thetype described in which, for any given amplitude of lever oscillation, the mechanical advantage will be greater than in other devices of which I am aware'and to produce a chain hoist in which the load can be released under control by the operating lever.

In carrying out my invention in its preferred form, I employ a twisted-link chain in which adjacent links are similarly oriented with reference to the chain-axis. The body of the device is formed with an opening which extends longitudinally through it and in which the chain is freely slidable. The operating lever is pivotally mounted on the body; and, on opposite sides of its axis of pivotal mounting, carries a pair of pawls arranged to engage the chain from opposite sides thereof. Acting between the-pawls is a spring which, when the deviceis being .used under load, serves to draw the pawls toward each other into engagement with the chain. To adapt the device for eifecting a controlled release of the load, I provide means acting between the operating lever and an intermediate point of this spring, such means acting to alter the mannenin which the spring acts on the pawlsand thereby to adapt the device for controlled release under load in a manner which will be explained more fully hereinafter.

The accompanying drawings illustrate myinvention: Fig. 1 is a side elevation of the :device arranged for use in stretching a wire; Fig. 2isa view similar to Fig. 1 but on a largerscale, with parts-oi the device broken away and shown in section and with the operating lever'in-a difierent position; .Fig. 3 is a view similar toFig. 2 showing one condition existing when the device is operating to efiect a controlled release of theload; Fig. 4 is a bottom plan view corresponding to Fig 3; Fig. 5 is a section on the line 5-5 of Fig. 3, but showing the device arranged for operation under load; Fig. 6 is an end elevation of the body illustrating the cross-sectional shape of the chain-receiving opening therein; Fig. '1 is a view similar to Fig. 2, but showing a modified form of pawl-actuating spring acting as it does when the device is operating under load; Fig. 8 is a view similar. to Fig. 7, but showing a condition existing. when the device is operating to effect a con- 1940; Serial No. 326,119

trolledrelease .ofthe load; Fig. 9 is .a section on the line 9-9 of Fig. '8.

The .body I0 of the device may; take any convenientv form, that .illustrated in the drawings being T-shapedsin elevation. and. provided with a U.-shape'yoke. II adapted .forconnection to one of the. objects between. which the device is to operate. The body 'llltisprovided'with an opening extending longitudinally. through it, such opening .slidably receiving a. chain I2. Conveniently, :an intermediate point of the chain. I2 .issecured ;to the yoke II, leavingone endofthe chain :freeto be wrapped around'anwobject, such aszthepost I3; against :which the force exerted by the device will react. Desirably, the ends of .the chain are provided with hooks I4, one for engagement with the yoke .II .andthe other'for connection to the load. Asshown in Fig. l, the latter-hook .-I 4 engages a 1wire+gripper I 5- gripping aiwire .I6 which is to bestretched, but it is tobe understood-that the'load appliedto the chain may be of any. kind.

The chain illustratedin the drawings is made up of twisted links so formed that adjacent links will be. similarly oriented with reference to .the axis of the chain. The opening through the body II] is so shaped in cross-section, as by being provided with longitudinally. extending ribs. H in its sides, that it will hold each link of the chain inJfiXed angular position about the chain. axis. relative to .the body I0..

The operating lever 20 has secured to it a pair of .arms 2I which receive the body I 0 between them. Desirably, there is interposed between the respective arms 2| and the body I0 a pair of; plates22and 23 which are rigid with the arms 2|. A pair of pins 24, each extending through one of the arms 2| and the associated plate, serve to pivotally interconnect the operating lever 20 with the body ID. If desired, the pins 24. may be formed as machined bosses on the sides of the body I0; but howeverthey are formed, their axis is substantially co-planar with the center line of the chain l2 within the body.

,At equal distances from and on opposite sides of the pins .24 there are mounted betweenthe arms :2! a pair of pawls 26 and 21 having teeth 26' and. 21' projecting toward each other through slots.28 in the body I0 into association with the chain. Each of the pawls 26 and 21 is. convenientlymounted upon a bolt 29 extending between the arms 2 I. Each of the teeth 2t and 21' is shaped to enter the chain-links, has a front face which is approximately perpendicular to the center line of the chain and an oblique rear face.

which serves to cam the tooth out of the chainlink as the associated pawl moves rearwardly relatively to the chain l2, all as will be clear from F1 2.

%he pawls 26 and 27 are freely swingable about the bolts 29 on which they are respectively mounted and are normally held in engagement with the chain I2 by a spring acting between them. In the device illustrated in Figs. 1 to 5, the spring acting between the pawls is'an openwound tension spring 32 the ends of which are formed into hooks engaging the bosses 33 on the pawls. As shown, the spring 32 islocated on the same side of the body 16 as the plate 23, and. the forward portion of that plate is desirably oiiset outwardly to form a protective housing for the spring.

In Fig. 1, the device is shown as operating to apply tension to the wire Hi, the handle being shown at the mid-point of a swing to the right. In this condition, the tooth 26"on theIpawl 26 is disposed within one link of the chain and is moving the chain forwardly, or to the left, in.the body Ill. The pawl 21 is moving to the right, or rearwardly, the inclined rear surface of the tooth 21 camming the tooth outwardly against the force exerted on the pawl 21 by the spring 32. A position somewhat nearer the limit of rightward movement of the handle 20 is illustrated in Fig. 2. In the position there illustrated, the teeth 26 and 21' have passed each other; and from Fig. 2 it will be apparent that as rightward movement of the handle 20 continues the. pawl 26, and the chain with it, will move to the left and the pawl 21 to the right until the tooth 21 enters the chain link immediately behind that in which the tooth 26' is located. When this occurs, the handle 23 will be substantially at the limit of its swing to the right; and upon a succeeding swing to the left the pawl 21 will move forwardly carrying the chain with it, while the pawl 26 .moves rearwardly, being camrned outwardly away from the chain by the inclined rear face of the tooth 26'.

It is to be noted that because of the use of the twisted-link chain the pawls 26 and 21 may have the simple opposed relationshipillustrated while still operating to advance the chain one link for each complete swing of the operating lever 28. If the chain l2 were formed of plane, or untwisted, links, only alternate links would be similarly oriented; and with the pawl arrangement illustrated it would then be necessary to advance the chain two links at each swing of the lever 20. This would necessarily involve either a reduction in the mechanical advantage or a reduction in the size, and therefore in the strength, of the chain. With the twisted link chain, however, the opposed teeth 26 and 2l' engage in adjacent links, and it is therefore possible to advance the chain but one link for. each swing of the operating lever 20.

Because of the inclined rear face of the teeth 26 and 21, the chain l2 can always be freely pulled forwardly through the body It. To make it possible to draw the chain freely through the body in the opposite direction, each of the pawls 26 and 21 may be provided with a rearward extension 35. By grasping these two extensions 35 between the thumb and forefinger, the pawls 23 and 21 may be swung apart in opposition. to the spring 32, thus moving the teeth 26 and 21 out of association with the chain so that free rearward movement thereof within the body ill will be permitted.

It will be noted that in the normal operation of the device to advance the chain under load, the forward pawl is not disengaged from the chain until after the rearward pawl has entered into a chain-link and assumed the load. As a result, the device is positive in operation and will always act to prevent accidental release of the load, even if the chain should be stretched to increase the'length of each link and the angle through which the handle must be swung at each operation. If the handle is released with the device under load, the pawl carrying the load will '.move rearwardly, and the other pawl will move forwardly and enter the chain; and a condition of equilibrium will ensue in which, with the handle in one or the other of its extreme positions, the load is positively held and divided substantially equally between the two pawls.

Should the operators hand slip from the handle while making a stroke thereof, or should the handle. break, the device will assume the equilibrium position just described, and the chain will be positively held by both pawls from slipping through the body.

. To adapt the hoist illustrated in Figs. 1 to 5 for use in effecting acontrolled release of a load on the chain I2, I employ a spring 32 which is open-wound, and I provide means for interconnecting an intermediate point of that spring with the operating lever. This means may take the form of a T-shaped member 38 the cross-bar of which is disposed within the spring 32 and the other arm of which projects outwardly between adjacent turns of the spring near the longitudinal center thereof, as will be clear from Fig. 2.- The plate 23, at a point opposite the pivot 24, is provided with a slot-39 (see Figs. 1 and 3) for the reception of the central arm of the T. When the device is being used to advance the chain under load, the central arm of the T 38 occupies the position illustrated in Figs. 1, 2, and 5, where it does not interfere with the action of the spring 32in drawing the. pawls 26 and 21 toward each other. When, however, the device is used, to effect a controlled release of the load (i. e., a con-..

trolled rightward movement of the chain 12 in the body ID) the central arm of the T 38 occupies the slot .39, as shown in Figs..3 and 4', thus serving to limit the movement of the central portionfof the spring32 relative to the operating handle.

. When the device is to be changedfrom-loadadvancing to. load-releasing .condition,,the operating handle is brought'into or near its midposition, under which circumstances-the slot 39.

will be opposite the mid-point of the spring and the central legjof theT 38 can be swung into such slot.: ,If-itbe assumed that the pawl- 26 is carrying theload, as it is in Figs. 2 and 3, the handle is now permitted'to move to the leftcausing a controlled rightward movement of the chain. As will be clear from Fig. 3, which shows the upper half of the spring 32 in compression and cause it to exert on the pawl 26" a force tending tomove that pawl away from the chain. The

' load on thechain [2 holds it in engagement with,

the-forward face of the tooth 26 and creates 'suificient friction to prevent the pawl 26 from 'mo'ving outwardly under the force exerted upon it'by the=compressed upper portion of the spring -32; While the tooth 21', under the influence of the stretchedlower half of i the spring 32,. has entered the chain-link immediately ahead of that withinwhich the tooth 26 is located, its front facehas-not yet been engaged by the chain.

Whenleftward movement of the handle is continuedbeyond the point shown in Fig. 3, the pawl 21 is moved forwardly and the pawl 26 rearwardly, and the chain will move rearwardly with the pawl 26 until it engages the pawl 21. This creates the condition of equilibrium above referred to. If thehandle is now moved through aslight'distance further to the left, the pawl 21 will :advance the chain slightly, whereupon the tooth 26' will be relieved of the load and the compressed upper portion of the spring 32 will move the pawl .26- outwardly until the tooth 26 clears the chain, as is indicated by the dottedline position. The load is now being applied to the operating handle through the tooth 2] and pawl 21'; .and as theoperating lever 29 is permitted to move to the right at a controlled rate of speed, the chain 12 will move rearwardly in the body I while the pawl 26 moves forwardly. During its initial forward movement, the pawl 23 is held out of engagement with the chain by the compressed upper portion of the spring 32, which continues to exert an upward force on the pawl 26 until after it has cleared the chain-link within which it had previously been located. As the operating handle approaches the mid-point of the swing to the right, all parts of the spring 32 will again be under tension; but the tooth 26 will be prevented from entering the link immediately ahead of that which it had previously engaged by reason of the presence therein of the tooth 21', which projects far enough through the chain for this purpose. As the operating handle approaches the rightward limit of its movement, the lower half of the spring 32 will be compressed and will exert on the pawl 2'! a force which will tend to move that pawl out of engagement with the chain but Which will be insufiicient to overcome the friction between the tooth 21 and the chain. At the extreme rightward limit of movement of the operating handle, the pawl 26 will be fully advanced, the tooth 26 will have engaged the chain, the tooth 21 will thereby be freed of load, and the compressed lower portion of the spring 32 will move the pawl 21 downwardly to cause disengagement of the tooth 21' from the chain and to permit the succeeding leftward swing of the operating handle.

In the device illustrated in Figs. '7 to 9, I have employed a different form of spring. The spring there shown consists of a. central eye portion 40 formed of one or more turns of spring wir the ends of which cross adjacent the eye, are bent to provide two generally parallel portions 4 l, and are again bent to re-cross, the extreme ends of the wire being respectively attached to the pawls 26 and 21.

The spring illustrated in Figs. 7 to 9 is so shaped that it normally operates to draw the free ends of the pawls 26 and 2'! toward each other, exactly as does the spring 32 in the device previously described. As the operating lever is oscillated, the eye 48 and parallel legs 4| of the spring swing back and forth in a space between one of the arms 2| and a plate 42 which is secured to the arms by the bolts 29. To connect the spring 4El4| to the operating lever, and thereby adapt the device to efiect a controlled release of a load, I mount in the plate 42 a screw 43 which, when retracted out of the plane of the spring, does not interfere with the free movement thereof but which, when advanced, enters the space between the two legs 4| of the springand limits the movement thereof relative to the. operating handle, as will be clear from Fig. 8. From a comparison of the respective spring-positions shown in Figs. 7 and 8, both of which show the operating handle approximately at the leftward limit of its movement, it will be apparent that as each of the pawls 26 and 2! approaches the rearward limit of its movement the spring will exert an outwardly directed force upon it so that when the load on the chain 12 is transferred from the rear pawl. to the forward pawl the spring will operate to force the former outwardly away from the chain. This action of the spring is illustrated in Fig. 8, where the pawl 26 is shown in full lines in the position it occupies immediately before being relieved of load and indotted lines in the positionit occupies after the load has been transferred to the pawl 21.

I claim as my invention:

1. In a device of the type described, a body having a longitudinally extending guide-way for a chain, a chain slidable in said guide-way, an oscillating operating lever pivotally mounted on said body on an axis perpendicular to said chain, a pair of pawls pivoted to said operating lever on opposite sides of its axis of pivotal mounting and extending forwardly of said body on opposite sides of the chain, the front end of each pawl being provided with a tooth adapted to enter a chainlink and having an oblique rear face adapted to cam the tooth out of the chain-link as the associated pawl moves rearwardly relative to the chain, a spring normally acting directly between said pawls and urging them toward each other and inwardly of the body, and means operable at Will to connect an intermediate point of said spring to said operating lever, said spring being so formed that when it is connected to said operating lever it will urge each pawl inwardly as the pawl approaches the forward limit of its movement and outwardly as it approaches the rearward limit of its movement.

2. The invention set forth in claim 1 with the addition that said spring is an open-wound helical spring disposed forwardly of the pawl-pivots and having its ends connected respectively to said pawls, said connecting means acting when operative to limit axial movement of the center portion of said spring relative to said operating lever whereby the end portion of the spring between said connecting means and each pawl will be compressed as such pawl approaches the rearward limit of its movement.

3. In a device of the type described, a body having a longitudinally extending guide-Way for a chain, a chain slidable in said guide-way, an oscillating operating lever pivotally mounted on said body on an axis perpendicular to said chain, a pair of pawls pivoted to said operating lever on opposite sides of its axis of pivotal mounting and extending forwardly of said body on opposite sides of the chain, the front end of each pawl being provided with a tooth adapted to enter a chainlink and having an oblique rear face adapted to cam the tooth out of the chain-link as the associated pawl moves rearwardly relative to the chain, yielding means acting'on said pawls, and a controlling device associated with said yielding means and selectively operable to cause said yielding means either to urge both pawls inward- 1y at all times or tourge each pawl inwardly when in and near the forward limit of its movement and outwardly when in and near the rearward limit of its movement.

4. In a device of the type described, a body having a longitudinally extending guide-way for a chain, a chain slidable in said guide-way, a pair of pawls disposed on opposite sides of said chain and provided with teeth projecting inwardly and adapted to be received in links of the chain, means mounted on said body for alternately advancing I each pawl while simultaneously retracting the other, yielding means acting on said pawls, and a controlling device associated with said yielding means and selectively operable to cause said yielding means either to urge both pawls inwardly at all times or to urge each pawl inwardly when in and near the forward limit of its movement and outwardly when in and near the rearward limit of its movement.

5. The invention set forth in claim 4 with the addition that said chain is formed of twisted links, adjacent links being similarly oriented with reference to the axis of the chain.

6. In a device of the type described, a body having a longitudinally extending guide-way, a pair of pawls disposed on opposite sides of said guideway and provided with inwardly projecting teeth adapted to extend thereinto, a tension element slidable in said guide-Way and having a longitudinally extending series of openings each of which is adapted to receive the tooth on one or the other of said pawls, means mounted on said body for alternately advancing each pawl while simultaneously retracting the other, yielding means acting on said pawls, and a controlling device associated with said yielding means and selectively operable to cause said yielding means either to urge both pawls inwardly at all times or to urge each pawl inwardly when in and near the forward limit of its movement and outwardly when in and near the rearward limit of its movement.

GEORGE WASHINGTON BENJAMIN.

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