US1421590A - Lifting jack - Google Patents

Description

A. AND H. E. SHRIEVES.

LIFTING JACK.

. APPLICATION FILED JUNE 4. 1920.

Patented July 4, 1922.

ALBERT SHRIEVES AND HENRY EDWIN SHRIEVES, 0F SUTTON COLDFIELD, ENGLAND.

LIFTING JACK.

arten.

Specification of Letters Patent. v

Patented July 4., 1922.

Application filed June 4, 1920. Serial No. 386,422.

T 0 all whomit may concern:

Be it known that we, ALBERT SHRIEVES and HENRY EDWIN SHmnvns, subjects of the King of Great Britain, residing at Kings Chambers, The Parade, Sutton Coldfield, in the county of Warwick, England have invented certain new and useful Tmprovements in Lifting Jacks; and we do hereby declare the following to be a full, clear, and exact description of the same.

This invention relates to lifting jacks and has for its object to provide a simplified and improved construction of such devices.

A. lifting jack constructed in accordance with the present invention comprises a base with which is associated a. guide member in which slides the lifting pillar, ratchet teeth on the pillar, a pivoted operating lever carrying a lifting pawl adapted to engage with said teeth so as to be capable of lifting the pillar in its guide with a step by step movement, and a retaining pawl also adapted to engage with said teeth in such manner as to prevent return movement of the pillar.

Both the pawl carried by the operating lever and the retaining pawl are preferably acted upon by a spring tending normally to press them into engagement with the teeth upon the pillar. and preferably a device such as a cam is provided which may be operated to allow both of said pawls to disengage from the teeth upon the pillar so that the latter may be moved into its lowest position.

Referring to the drawings Figure 1 is a perspective View showing the cam in the position in which operation of the lever will raise the pillar.

Figure 2 is a longitudinal section with the cam in the position shown in Figure 1.

Figure 3 is a view similar to Figure 2 but with the cam in the position in which operation of thelever will lower the pillar.

Figure 4 is a perspective view of the cam removed.

In the construction as shown on the drawings the base member may be made as a casting and may include a base proper 1 and a guidemember 2 extending vertically therefrom. This guide member may form part of a standard which may be made integral with. the base and the standard may include a second upright member 3 connected to the guide member by suitable horizontal webs 4.

The lifting pillar may consist of a member 5 of rectangular or any other suitable cross section adapted to slide in the guide member. The lifting pillar may be prov ded with longitudinal slots 6 in opposite sides adapted to be entered by projections 7 in the guiding member. One side of the lifting pillar is provided with ratchet teeth 8 and the upper end of the lifting pillar may be provided with a pivot upon which is rotatably mounted a curved member 9 adapted to suit 'the axle or the like of a vehicle.

The operating lever 10 may be pivoted to the standard adjacent the lifting pillar. One end of the operating lever is preferably forked and the other end may terminate in a socket 11 into which may be placed a bar or rod. Pivotally mounted to the forked end of the operating lever is a pawl 12, the one end of which engages with ratchet teeth upon the lifting pillar and the other end of which, upon the other side of the pivot 13 may be provided with an eye 14.

The retaining pawl 15 may be arranged below the operating lever and may be pivoted to the standard. This retaining pawl has one end adapted to engage with the teeth upon the lifting pillar and its other end, upon the other side of the pivot 16 may also be provided with an eye 17.

The eye upon the pawl carried by the operating lever and the eye upon the retaining pawl may be connected together by a link 18 consisting of a length of wire or rod. This link between the two eyes is connected to the free end of a leaf spring 19 which is attached to the standard. The arrangement is such that the tendency of the leaf spring is to press both pawls into engagement with the teeth on the lifting pillar.

Between the leaf spring and an adjacent part of the standard is preferably disposed a cam like member 20 which can be operated by a handle 21 working between two stops 22 upon the standard. This cam like member is so constructed that when in one position it forces the spring into a position in which spring pressure is transmitted to the two pawls to keep them in engagement with the teeth upon the lifting pillar, but when the cam is in the other position the spring acts upon the link in such a manner as to move the two pawls upon their pivots to bring their operative ends out of engagement with the teeth upon the lifting pillar.

The two pawls are preferably arranged so that the retaining pawl engages with a fresh tooth each time that the pawl carried by the operating lever reaches the end of a lifting stroke. 7

In operation the lifting jack is arranged with the lifting pillar beneath the article it is desired to raise and a rod or bar is inserted in the socket end of the operating lever. The operating lever is then worked to and fro on its pivot sothat the lifting pillar is raised tooth by tooth. During the lifting movement the retaining pawl serves to prevent return movement of the lifting pillar. Then the jack is no longer required the lifting pillar can be returned to its lowest position by operating the cam, which may have a cranked handle, so as to permit both pawls to move away from the teeth upon the lifting pillar. When the cam is operated for the release, the pawl 15 is moved clear of the rack but if the jack is supporting a weight the pawl 12 will be kept in engagement with the teeth of the rack. The handle is then operated to lower the rack thus bringing its free end 23 into engagement with the upper part of the pawl 15 and again forcing said pawl into engagement with the rack but taking the next tooth to the one it took before. Simultaneously the spring 19 causes the upper pawl 12 to move clear of the teeth.

The handle is then lowered until the pawl 12 engages the next tooth and pawl 15 again leaves the rack. This operation is repeated to give a lowering step by step motion to the pillar.

Both in the lifting and lowering operations the pawl 12 may be guided into and out of engagement with the teeth of the ratchet rack by the end of a set screw 24. This set screw may also be used for locking the aawl 12 in engagement with the rack.

W hat we claim then i In a lifting jack, a frame, a rack verti 'cally movable therein, a lever pivotally mounted in the frame, a pawl for engaging the rack and pivotally connected to said lever, a second pawl below the lever, for engaging the rack, means coacting with said lever to operate said second pawl, and an adjustable abutment member mounted in the frame and arranged for engagement with and disengagement from the first named pawl, to cause the said pawl to engage the rack earlier in the operative movement or to take up wear in the parts, and to also enable the jack to be locked in any position.

In witness whereof we afiix our signatures.

ALBERT SHBIEVES. HENRY EDWIN snmnvns.

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