US2138276A - Lifting device - Google Patents

Description

Nov. 29,1938 A. L. JOHNSON 2,133,276 l LiF'IING DEVICE Filed May 6, 1937 2 Sheets-Sheet l A. L. JOHNSON LIFTING DEVICE Filed May 6, 193'? Nov. 29, 1938.

2 Sheets-Sheet 2 Patented Nov. 29, 1938 PATENT OFFICE LIFTING DEVICE Alvin L. Johnson, Ottawa Hills, Ohio, assignor to The Logan Gear Company, Toledo, Ohio, a corporation of Ohio Application May 6, 1937, Serial No. 141,140

6 Claims.

This invention relates to lifting devices and more especially to lifting jacks utilizing dual pawl mechanism for elevating and lowering a lifting element.

The invention embraces the provision of simple yet positive acting dual pawl mechanism for manipulating the lifting element and in which the pawls per se may be fabricated from sheet material and configurated to a section having great strength yet utilizing a minimum amount of metal.

An object of the invention is the provision of a lifting jack of this character in which the lifting element may be of circular section but threaded or grooved to provide spaced teeth for cooperation with the pawl mechanism.

Another object of the invention resides in the provision of a sheet metal housing for the mechanism preferably fabricated of one piece of material and so configurated as to form an elongated guiding means for the lifting element and which is reinforced by ribs formed in the walls of the housing lending strength and rigidity to the same.

A further object of the invention is the provision of a so-called ratchet jack wherein a major number of the elements of the structure may be fabricated of sheet metal in suitable dies, thus materially reducing the cost of producing the elements of the lifting jack yet enhancing the interchangeability of parts for purposes of replacement or repair should this become necessary.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and to combinations of parts, elements per se, and to economies of manufacture and numerous other features as will be apparent from a consideration of the specification and drawings of a form of the invention, which may be preferred, in which:

Figure 1 is a side elevational View of a form of lifting jack of my invention;

Figure 2 is a side elevational view of the upper portion of the lifting jack, part of the housing being broken away and the interior mechanism shown in section for purposes of illustration, this view illustrating the position of the pawl mechanism at one stage during elevation of the lifting element or thrust bar;

Figure 3 is a View similar to Figure 2 showing the position of the pawl mechanism at one stage during the retraction of the lifting element;

Figure 4 is a view similar to Figure 3 showing the pawl mechanism in a diiferent position during retraction of the lifting element;

Figure 5 is a view showing the pawl mechanism and the lifting element in the latters partially extended position; 5'

Figure 6 is a view similar to Figure 5 showing the arrangement for preventing further extension of the lifting element;

Figure '7 is an isometric perspective view illustrating the pawl mechanism and associated parts;

Figure 8 is a side elevational View of the housing structure of my invention;

Figure 9 is a sectional View through the housing structure taken substantially on the line 9-9 of Figure 8.

While I have illustrated the arrangement of my invention as particularly adapted for use in elevating vehicles and the like, it is to be understood that I contemplate the use of my invention wherever the same may be found to have utility.

Referring to the drawings in detail, the arrangement of my invention includes a base member Ill preferably formed of sheet metal having side flanges H and end flanges l2 serving to add strength and rigidity to the base member. Mounted upon the base member is a housing or casing structure I 4 preferably fabricated of one piece of sheet metal and generally of U-shaped configuration as illustrated in Figure 9. The housing is formed with substantially parallel side wall portions l5 and I6 which are joined together at their bight portions by means of a cylindrical configuration ll, the housing having integrally formed lateral-1y extending flanges l8 and I9 which are rigidly secured to the base member by means of rivets 20 or other suitable securing means. It is to be noted that the cylindrical configuration l'l continues to a point where portions of the side Walls project inwardly as at 2i forming a cylindrical guide for a lifting element. The 40 upper portions of the side walls of housing l4 project laterally in closing the upper part of the housing and these flanges as at 25 are brought together forming at the top of the housing a complete cylinder so that when the lifting element is moved to its uppermost position, it is still restrained against tilting with respect to the housing portion by means of this guide. The lower portions of the side walls I 5 and 16 of the housing are provided with reinforcing ribs 22 and 23 which serve to impart substantial rigidity and strength to the housing structure. The parallel side Wall portions of the housing are held in spaced relation by suitable means as, for example, rivets The cylindrical configuration ll of the housing structure forms a guiding tubular configuration within which is slidably positioned a thrust bar or rack 26 which may be in the form of a threaded bar, the threads in themselves acting as rack teeth for engagement with pawl mechanism to be hereinafter described for elevating and lowering the thrust bar or lifting element. The upper portion of the thrust bar is provided with a reduced tenon 21 adapted to receive and position a load engaging member 28, the latter being held to the thrust bar by the swaged portion 29 of the tenon 21.

The thrust bar actuating mechanism of my invention comp-rises a pair of pawls or pawl members 36 and 31, these pawl members being preferably formed of sheet metal to a U-shaped configuration as clearly shown in Figure '7. I have provided a lever member 38 which is preferably formed of sheet metal and having a socket portion 46 adapted to receive an operating handle 4|, the lever 38 being preferably formed of one piece of metal, its lower portions being secured together by rivets as at 42 or by other suitable securing means. The lever member 38 is fulcrumed upon a pin or shaft 44 through openings in the spaced parallel wall portions 45 and 46 of the lever member. The side walls of pawl member 36 are provided with openings to also receive pin 44 in which manner the pawl 36 is pivotally supported upon the fulcrum pin for the lever member 38.

The parallel wall portions 45 and 46 are also provided with aligned openings to receive a pin or shaft 41, which also passes through aligned openings in the side walls of pawl 31, thus form.- ing a support for the pawl 31. As hereinafter designated, the pawl 31 will be referred to as the lifting pawl and the pawl 36 referred to as the retaining pawl. As the threads on the bar 26 are spiralled upwardly, in order to effect a full surface engagement of the pawls with the teeth of bar 26, the extremities of the pawls are slanted upwardly substantially the same amount as the degree of spiral in the threads. In this manner the load is transmitted through the bar 26 to the pawls through a substantial pawl engaging surface which also eliminates any tendency of the spiral threads on the bar 26 to tip the pawls.

Projecting within the side walls of the pawls 36 and 31 are the leg portions 49 and 56 of a hairpin-like spring 5| of rectangular cross section having its bight portion 52 of cylindrical configuration embracing the lever fulcrum pin 44. Each of the pawl members 36 and 31 are provided with aligned openings 53 and 5.4 in the side walls thereof to receive cotter keys 55 and 56, the extremities of the leg portions 49 and 56 of the spring projecting respectively between the leg portions of the cotter keys 55 and 56 as particularly illustrated in Figure 7.

Lever member 38 is also provided with a pin 6! which carries a spring 62 preferably formed of wire having its bight portion 63 contacting with the rear edges of the parallel wall portions of pawl 36 as illustrated in Figure 7 while the free extremities of the spring engage with an edge portion 63 of the lever member 38, the spring being so formed as to exert a counterclockwise pressure against the pawl 36 as shown in Figure 6.

Arranged between the parallel wall portions of lever 38 is a member 64 of U-shaped configuration having its parallel side wall portions formed to embrace the cylindrical bight portion 52 of spring 5| whereby it is thus indirectly supported by the fulcrum pin 44. The member 64 is provided with depending ledge portions 66 and 61. Suitably fulcrumed upon a pivot pin 68 carried by one wall of the housing I6 is a control dog or member 16 having its upper extremity arranged for cooperative relation with the depending ledge portions 66 and 61 for a purpose hereinafter explained, the depending arm of the control dog 16 having a manipulating button 12 projecting exteriorly of the casing and carried by a laterally projecting portion 13 of dog 16, the projecting portion extending through a slot 14 formed in the side wall of the housing permitting the control dog 10 to be oscillated about its pivot point through the medium of the manipulating button 12. The manipulation of the control button acting to move the control dog 10, the latter arranged to shift the member 64, serves as a means for changing the action of the pawls to elevate or retract the thrust bar 26 in a manner to be hereinafter described.

It is to be noted that the lower extremity of the thrust bar or lifting element 26 carries a member 16 swaged thereto as at 11 having a laterally projecting portion arranged to engage the bight portion of pawl 31 when the thrust bar has been elevated to its uppermost position as illustrated in Figure 6 to prevent the thrust bar from moving upwardly beyond a predetermined point as the member 16 prevents further reengagement of the pawl 31 with the thrust bar.

The operation of the structure is as follows: Referring particularly to Figures 2, 5 and 6, there are illustrated various stages or positions of the pawl mechanism during the sequence of movements of the mechanism while the lifting element is being elevated. In Figure 2 the actuating lever member 38 is in its extreme counterclockwise position of oscillation about the fulcrum 44 in which position pawl 31 is urged into engagement with a tooth of the thrust bar 26 under the influence of the branch of the hairpin spring 5|, both leg portions of the spring 5| being urged toward the thrust bar 26 under the influence of member 64, the latter being held in the position shown in Figure 2 by the control dog 10, the button 12 being illustrated in the up position. After the pawl 31 has engaged a tooth of the thrust bar, the handle 38 is oscillated by the operator about its fulcrum 44 in a clockwise direction, as viewed in the drawings, which elevates the thrust bar and the elevating pawl 31 until the retaining pawl 36 under the counter-clockwise influence of the portion 49 of the spring 5| falls into a recess between the teeth in the thrust bar 36. After pawl 36 is in a position projecting beneath one of the teeth of thrust bar 26, movement of the handle member 38 in a counter-clockwise direction moves the lifting pawl 31 out of engagement with a tooth of the thrust bar, the latter being retained in its elevated position by the retaining pawl 36. The oscillation of handle member 38 then lowers the lifting pawl 31 to engage the next successive tooth in the thrust bar or rack 26 and. the elevating operation repeated as above set forth. With the control button located in the up position, as illustrated in Figure 2, repeated oscillation of the lever member 38 continues to elevate the thrust bar 26 until such time as the member 16 is brought into contact with the bight portion 80 of the lifting pawl 31 as particularly shown in Figure 5, the curved portion 8| at the rear of the pawl serving as a cam means engaging with the bight portion 82 of the retaining pawl 36 preventing the latter from reengagement with any tooth of the rack member when the handle 38 is oscillated in a clockwise direction as shown in Figure 5.

When further effort is made to elevate the jack with the thrust bar in this position, the handle member is moved in a clockwise direction to the position shown in Figure 6 in which position the retaining pawl 36 is supporting the load by engagement with a tooth in the thrust bar while the member I6 slides along the face of the cam surface 86 preventing the lifting pawl 31 from engaging a tooth in the thrust bar. By this means, a further elevation of the rack or thrust bar is prevented.

When it is desiredto retract the lifting element and lower the load with which the same may be in engagement, the control button 12 is manipulated to the down position as illustrated in Figure 3, which movement of button 12 swings the control dog Til to the position illustrated in Figure 3. This movement of the dog 16 shifts the member 64 to distort the spring so that the resiliency of the leg portions thereof tends to withdraw the pawls from engagement with the bar 26. In the position shown in Figure 3, the weight of the load is carried upon the pawl 36, and the pawl 31 has been retracted from engagement with the rack under the influence of leg 56 of spring 5|. The oscillation of the handle member 38 in a clockwise direction elevates the pawl 31 and by reason of the cam face 82 of pawl 36 engaging the rear portion 8| of pawl 31, the latter is cammed into a position beneath one of the teeth of the thrust bar 26 and slightly further clockwise oscillation of the handle 38 causes the load to be supported upon the pawl 31 slightly elevating the rack bar 26, relieving the stress of the load upon pawl 36 so that the latter is disengaged and swings away from the bar 26 under the influence of the leg 49 of spring 5! Counterclockwise oscillation of lever 38 about its fulcrum lowers the rack bar, as the latter is then carried upon the pawl 31. As the lever 38 approaches its maximum counter-clockwise position, spring 96 which bears against the rear portion of pawl 36 and acts in opposition to the leg 49 of spring 51 overcomes the resiliency of the spring portion 49 and urges the extremity of pawl 36 into en gagement with the next succeeding tooth on the rack bar sothat the pawl 36 then carries the load. The lever is again moved in a clockwise direction and the pawl 3'! is again cammed into engagement with a tooth in the lifting element so as to carry the load permitting the pawl 36 to be withdrawn by the spring 49 from engagement with the rack. This oscillating action of the handle member 38 may be continued and with each oscillation the rack is lowered the distance of one tooth of the rack bar until the lifting element is at its lowermost position.

It is apparent that within the scope of the invention, modifications and different arrangements may be made other than are herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

What I claim is:

a 1. A lifting device including a base member; a housing, said housing having a tubular guide portion; a toothed lifting element reciprocably carried in said guide portion; a load engaging element carried by said toothed lifting element; a lever fulcrumed upon said housing; a lifting pawl pivotally supported upon said lever; a retaining pawl pivotally carried on the fulcrum of said lever, said pawls being formed of sheet metal to substantial U-shaped configuration; a plate spring of U-shaped configuration having its bight portion embracing the fulcrum of said lever and the leg portions thereof operatively connected to said pawls between their parallel wall portions; and a member carried on the fulcrum of said lever and having portions cooperating with said spring for changing the effect of said spring upon said pawls.

2. A lifting device including a base member; a housing, said housing having a tubular guide portion; a toothed lifting element reciprocably carried in said guide portion; a load engaging element carried by said toothed lifting element; a lever fulcrumed upon said housing; a lifting pawl pivotally supported upon said lever; a retaining pawl pivotally carried on the fulcrum of said lever, said pawls being formed of sheet metal to substantial U-shaped configuration; a hairpin spring embracing the fulcrum of said lever and having the leg portions thereof cooperating respectively with said pawls; a member for retaining said spring in contact with the fulcrum of said lever and having portions cooperating with said spring for changing the eifect of said spring upon said pawls; a dog; and manipulating means carried by said dog for shifting the latter to change the position of said member.

3. A lifting device comprising, in combination, a base member; a housing formed of one piece of sheet metal; said housing being formed with a tubular guide portion; a threaded lifting element reciprocably contained in the tubular guide portion of said housing; a lever fulcrumed upon said housing; a lifting pawl; a retaining pawl, said pawls having cooperative connection with said lever; a spring embracing the fulcrum of said lever and having its leg portions respectively connected to said pawls; means for controlling the action of said spring upon said pawls; and means carried by said lifting element and engageable with one of said pawls urging the pawl away from the lifting element when the same is elevated to its full extended position.

4. A lifting device, comprising, in combination, a base member; a housing formed of one piece of sheet metal and arranged in substantially U- shaped configuration, the bight portion of said housing being tubular; a toothed lifting element reciprocably contained in the tubular portion of said housing; a lever fulcrumed upon said housing; a lifting pawl; a retaining pawl, said pawls having cooperative association with said lever; a U-shaped spring embracing the fulcrum of said lever and having its leg portions respectively connected to said pawls; a second spring having engagement with the retaining pawl opposing the action of the U-shaped spring when the lifting element is being retracted; means for controlling the action of said U-shaped spring upon said pawls; and means carried by said lifting element and engageable with one of said pawls when the lifting element is elevated to its full extended position.

5. A lifting device comprising, in combination,v

element reciprocably mounted in said guide portion; a lever fulcrumed on said housing; a lifting pawl and a retaining pawl cooperatively associated with said lever; a U-shaped spring having its leg portions respectively in cooperative engagement with each of said pawls; and control means for changing the action of said spring upon said pawls including a member carried upon the fulcrum of said lever and embracing the bight portion of said spring.

6. A lifting device including a base member; a housing, and housing having a tubular guide portion; a toothed lifting element reciprocably carried in said guide portion; a load engaging ALVIN L. JOHNSON.

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