US1528987A - Lifting jack - Google Patents

Description

March 10. 1925. 1,52s;987

' J. G. PICKERING, JR

LIFTING JACK Filed May 1, 1924 Patented Mar. 10, 1925.

UNITED STATES PATENTOFFICE.

'JEs'sE oEEALnUs PICKERING, .13., 0E NASHVILLE, TENNESSEE.

"LIETING JACK.

Application filed May 1,

To all whom it may concern:

Be it known that I, J ssE Gr. PIoKERING, Jr., a citizen of the United States, residing at Nashville, in the county of Davidson and State of Tennessee, have invented certain new and useful Improvements in Lifting Jacks, of which the following is a specification. y

This invention relates to liftingj'acks and more particularly toian improvement in jacks of the rack type wherein the lifting column is raised step by step through the manipulation of a handaor foot operated lever. v

A primary object of the invention is'to providea simple and practical construction which assures positiveness of action regardless of theposition in which the jack may be placed, while at thesame'time, owing to the novel arrangement of lifting andsustaining pawls, making it possible to obtain a maximum lifting distance with a relatively short rack. That is to say, the present construction makes it possible to raise the object to be lifted the entire height of the lifting rack whereas in many jacks a number of the last notches cannot be brought into play. I

A further object of; the invention is to provide novel means for elevating and lowering the liftmgcolumn of the ]ack,-

whereby the same may be readily raised step by step during, the lifting operation. and may be likewise lowered if the column is'supporting a load, and yet on the other hand will permit of the column rapidly sliding back to collapsed position if it is not under load.

With the above and other objects in. view which .will more readily appear asthe nature of the invention isbetter understood, the same consists in the novel construction, combination and arrangement of parts hereinafter more fully described, illustrated and claimed.

Apreferred and practical embodiment of the invention is shown in the accompanying drawings, inwhich: I

Figure 1 is a side elevation of the im-.

proved jack.

Figure 2 1s a View with" one of the side plates removed showing the'parts in posi-v tion to raise the lifting column.

Figure 3 is a view s'imilar'to Figure. 2 showing the relative position of parts when the reversing control means has been re- 1924. Serial No. 710,277.

Similar reference characters designate corresponding parts throughout the several figures of the drawings.

,According to the embodiment shown in the accompanying drawings it is proposed to. provide a suitable housing or casing designated generally as A and preferably having a side plate or cover B which constitutes the body of the jack and is supported on a suitable stand C. The casing Aland the cover Bflcooperate to provide a lifting'column guide-way D and a chamber E for housing the operating parts for the lifting column. I This lifting column is provided along one side witha plurality of rack teeth or shoulders 2 andcarries at its upper end,

a bearing horn 3 for engaging with the object to be moved.

. Referring more particularly to the means for raising and lowering the lifting bar 1 it will be observed that the same primarily consists of a lifting pawl 4. and a sustaining pawl 5 which alternately come into play to raise and hold the lifting column in the desired position, or according to one of the novel features of the invention, may be both thrown out to permit the lifting column to rapidly telescope within the guideway D. The lifting pawl 4 is pivotally connected as at 6 to a rockable operating lever 7 which in turn is pivoted as at8 to the casing and adapted to be operated by either hand or foot power applied to the portion 9 whichprojects exteriorly of the casing or housin The said lifting pawl 4 is normally forced toward the rack teeth 2 by the spring 10,

and'the lever 7 which carries thesaid spring is preferably maintained in a normal ele 'vated position'by means of a main supporting spring 11. This spring is preferably of fiat form and has its free end bearing against the underside of the lever 7 at the side of the pivot 8 opposite the pivot 6 while the intermediate portion thereof has a relatively fulcruming engagement as indicated at 13 with a shoulder of the casing. As will be observed from Figures 2 and 3 the end 14 of the main spring 11 is engaged by an adjusting screw 15 having a threaded engagement in the bottom wall of the housingyso that the lrmgitudinal adjustment of the screw will move the spring against the fulcrum 13 and thus cause its free end 12 to exert more or less tension against the lever 7.

The sustaining pawl 5 is pivotally supported in the casing as indicated at 16 and is provided with an opening 17 arranged eccentric to the pivot 1a thereby to receive the end 18 of a control spring 19. This spring has an intern'iediate loop 20 and the end 21 thereof is anchored eccentricallyin a reversing disk 22. This reversing disk is rotatably supported in the casing and is provided with an exteriorly projecting shaft portion 23 adapted to receive an adjusting lever 25 as shown in Figure 1 thereby to permit of the disk being moved the distance indicated by the fulland dotted line positions of the lever 25 in Figure 1. When the lever 25 is in the full l ne position the pawl l will be operative to raise the lifting column, and when the lever is in the dotted line position the'pawl 1 and sustaining pawl 5'will cooperate to permit of the descent of the lifting column.

The reversing cam disk also carries therewith, eccentric to its axis, a lifting pawl engaging spring 24. Normally this spring 2 1, which may he of the looped type shown in the drawings or flat, as desired, is held out of contact with the pawl i. thereby per mitting the spr ng 10 to exert its full tendency to throw the pawl toward the rack teeth 2. However, when it is oesired to lower the lifting column 1 and the reversing disk 22 is moved to the dotted line po sition shown in Figure 1, the said spring 21 is moved into engagement with the pawl 4:, thereby counteract ng the effect of the spring 10 siifliciently to keep the nose of the pawl 4 out of the path of the rack teeth 2 until after the pawl l is elevated so that its nose will clear the tooth with which it is normally aligned. The function of the spring 24 is, therefore, to counteract the of feet of the spring 10 to permit of lowering the lifting column 1. That is to say, the spring 24L will yieldingly press the pawl 4; backwardly so that the nose 1 thereof will be moved from beneath the overlying tooth until the lever 7 elevates the nose i sutliciently to clear thetooth and put it into with theloop'ofthe spring 24.- therebynullifying the effect of this spring and permitting the spring 10 to exert its full influence to push the pawl 4 toward the rack into which it is positively guided by the screw or its equivalent f".

The operation of the device is as follows: Assuming that the lifting column 1 is to be elevated and the parts are in the position shown in Figure 2 it will readily be seen that downward movement on the end 9 of the lever 7 will cause the pawl 1 to move upwardly and engage with the tooth a of the column thereby elevating the same as the lever 7 continues to move so as to remove the tooth Z) from engagement with the sustaining pawl 5 and bring tooth 0 into position to rest on said pawl (see Fig. l). The pawl 5 is normally pressed toward the teeth of the rack 2 due to the expansive force of the loop 20 in the intermediate part of the spring 19. c'llherefore, upon each reciprocation of the lever 7 the lifting column will be raised one tooth.

When it is desired to collapse the jack and remove it from beneath the load the revcrsing lever 25 is moved from the full line position shown in Figure 1 to the dotted line position, thereby causing the disk 22 to rotate in the direction of the arrow in Figure 2 and thus pull on the end 21 of the spring 19 and cause the loop 20 to contract, thereby placing the spring 19 in tension which has the effect of rocking the sustaining pawl 5 rcarwardly on its pivot 16. At the same time the spring is pushed over into contact with the lower end 41'? of the lifting pawl i. If the horn 3 of the column 1 is susta ning a load. it will be apparent that the weight of the load on the column will cause the tooth a which engages with the pawl 5 to keep the pawl from responding to the influence of the tensioned spring 19 Therefore. when the device is under load, it is necessary to lift the rack-column 1 slightly to permit the pawl 5 to snap backwardly; and therefore, as shown in Figure 3, the end 9 of the lever 7 is moved downwardly thereby to cause the end 1 of the pawl 4 to elevate and engage the tooth due to the fact that the spring 2 1 shifts the pawl 4t rearwardly so that its nose will clear the tooth 1 normally lying opposite.

lVhen the column is lifted sufficiently to move the tooth n" to release the load from the pawl 5 the latter will snap backwardly and the column will be lowered gradually while the load is sustained on the end 4; of the pawl 4 which is in engagement with the tooth 2. However, as the pawl 41: descends the underside l thereof will engage with the face 5 of the pawl and cam the latter over into position to engage the tooth y, which tooth will sustain the load while the lever 1 jumps back to clear the tooth 2 and be ready to engage the next tooth above.

If the column 1 is not under load the susmediately upon theturning of the cam 22 which places the loop 20 of the spring 19 under tension, and, also, the. spring 2.4.

thrusts the lever 4 backwardly so as to cause thenose 4 to clear the toothy, thereby permitting the rack-column to drop back to initial position. When the reversing cam 22 is moved back to the full line position of the lever 24; in Figure 1 the spring 24 is moved out of engagement with the. lifting pawl 4 and also the loop 20 of the spring 19 is expanded thereby shifting the sustaining pawl 5 into the teeth of the rack 2 and also placingthe pawl 4 under the full pressure of the spring 10 to cause the nose 4* thereof to'work into the teeth of the rack.

\Vhile it will of'course be understood that various changes in the form, shape, and proportion of the various parts may be made, nevertheless, the primary and essential features of the construction will always remainthe same, and'it is believed that without further description, the advantages of operation and manipulation will bereadily apparent to those skilled in the art, and that changes of the type referred to may be readily made within the scope of the appended claims.

I claim 1. A lifting jack comprising a. "rackcolumn, a sustaining pawl, means for causing said pawl to normally engage the rack comprising a reciprocating membe' and a spring having its ends connected tothe sustaining pawl and member eccentrically to the axis of the member and the pivot axis of the pawl, a lifting pawl, pressure means for maintaining the lifting pawl normally in engagement with the rack, and means carried bythe said member for counteracting the eflect of said pressure means on the lifting pawl.

2. A lifting jack comprising a rackcolumn, a sustaining pawl, means for causing said pawl to normally engage the rack comprising a reciprocating disk and a spring having its ends connected to the sustaining pawl and disk eccentrically to the axis of the disk and the pivot axis of the pawl, a lifting pawl, pressure means for maintaining the lifting pawl normally in engagement with the rack and a yielding member carried by said disk and engagingwith the said lifting pawl when the disk is rotated thereby to exert a force on the lifting pawl in opposition to the said pressure means therefor. p

3. A lifting jack comprising a rackcolumn, a sustaining pawl, means for caus-' ingfsaid pawl to normally engage the rack comprising a reciprocating disk and a spring having its ends connected to the sustaining pawl and disk eccentrically to the axis of the disk and the pivot axis of the pawl, a lifting pawl, pressure means for maintaining the lifting pawl normally in engage ment with the rack and a yielding member carried by said disk and engaging with the lifting pawl when the disk is rotated thereby to exert a force on the said lifting pawl in opposition to the said pressure means therefor,.sa1d lifting pawl being formed to recede from the said yielding member as it moves upwardly thereby to permit said pressure means to perform its normal function.

4. A lifting jack comprising a rackcolumn, a sustaining pawl, a lifting pawl, a lever for operating said lifting pawl, a pressure spring for normally maintaining said lifting pawl in engagement with the rack, and a device comprisingadisk mounted for reciprocatory movement, a lever for adjusting the position of said disk, a spring comprising an intermediate loop and having-its end portions respectively connected to the disk and sustaining pawl eccentric to the axes thereof, and a spring eccentrically carried by said. disk and adapted to engage with said lifting pawl.

5. A lifting jack comprising a rackcolumn, a device including a lifting pawl, an operating lever for said pawl, a pressure spring for said pawl, a sustaining pawl, a device having means for controlling the movement of said sustaining pawl and also for counteracting the effect of said pressure spring on the lifting pawl, a bowed spring having one end engaging with said lever and the intern'lediate portion thereof having a fulcruming engagement with the part of the jack casing, and means connected with said spring at one side of its fulcruming point in the casing for adjusting the tension thereof.

6. Av lifting 'jack comprising a rackcolumn, a device including a lifting pawl, an operating lever for said pawl, a pressure spring for said pawl, a sustaining pawl, a device having means for controlling the movement of said sustaining pawl and also for counteracting the effect of said pressure spring on the lifting pawl, a spring engaging said lever and, means for adjusting the tension of said spring.

In testimony whereof I. hereunto aflix my signature in the presence of two witnesses.

JESSE GERALDUS PICKERlNG, Jr.

lVitnesses:

J. H. ROBEY, J. G. AMIs.

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