US1541577A

US1541577A - Screw jack

Info

Publication number: US1541577A
Application number: US18031A
Authority: US
Inventors: Alvin L Johnson
Original assignee: Individual
Current assignee: Individual
Priority date: 1925-03-24
Filing date: 1925-03-24
Publication date: 1925-06-09
Anticipated expiration: 1942-06-09

Description

A. L. JOHNSON SCREW JACK Filed March 24. 1925 J M/ J J i f 4, d VAVWIWA,

x x Y Y Y N June 9, 1925.

Patented June 9, 1925.

UNITED STATES ALVIN L. JOHNSON, 0F SPRINGFIELD, MASSACHUSETTS.

` SCREW JACK.

Application filed March 24, 1925.

To aZZ whom t 'may concern:

Be it known that I, ALviN L. JOHNSON, a citizen of the United States, residing at Springfield, in the county of Hampden and State of Massachusetts, have invented a new and useful Screw Jack, of which the following is a specification.

This invention relates to a screw jack of the type in which the means for lifting the load has a double travel. That is, it moves upwardly on an element which supports it which itself also moves upwardly at the same time so that the load support will rise to a height of more than twice the height of the ack when collapsed. Although this jack is capable of general use it is particularly adapted for automobile use on account of the difficulties that have been encountered due to the use of balloon and other over-size tires.

The principal objects of this invention are to provide a jack of this kind in which the work supporting member that projects up out of the jack casing is entirely without screw threads that are exposed, thus avoiding the injuring of the screw threads in the use and abuse of the jack and always keeping them protected from dirt, dust and metal particles.

Another object of the jack is to improve the means for guiding the work supporting element so that it will be guided always at a point nearer its upper end than has been the case heretofore and will also lhave a guide at its lower end;

Another object of the invention is to provide a more simple construction than has been provided heretofore in this type of jack.

Reference is to be had to the accompanying drawings, in which Fig. 1 is a central sectional view of a jack constructed in accordance with this invention, shown in its lowermost position; and

Fig. 2 is a plan of the jack.

The jack preferably is made with -a standard or casing 10 having a comparatively wide base. The main part of this lstandard is in the form of a vertical cylinder having an internal screw thread. In this screw thread turns a screw 11 which is internally and externally threaded in opposite directions all the way from top to. bottom. To the top of this screw is fixed a gear 12 or other element for rotating it so as to cause it to rise in the internal screw thread in Serial No. 18,031.

the casing 10. The gear is shown as operated by a pinion 13 and shaft 14 for the attachment of a handle.

In the interior of the internally vthreaded screw 1l T provide a screw 22 meshing with the internal screw threads of the screw and therefore capable of being moved'up and dougn therein by the turning of the screw. In the top of this nut is a square or other non-circular hole for receiving a similar shaped projection 15 on a plunger 16. This plunger is of square or other non-circular shape and obviously it is'iiXed to move with the screw 22.

0n top of the casing 10 I provide an outer casing 17 in which the

gears

12 and 13 are housed and which has a bearing for the shaft 14. This casing surrounds the upper gear 12 and is provided with a flat top 18 bearing against the top of the gear to receive the thrust. The top has in the center thereof a perforation 19 of the same shape as the plunger 16. The plunger is of the same size all the way from the top to the bottom and the opening 19 is broached or otherwise finished so as to fit this plunger and constitute an accurate guide for it.

In the operation of the jack. assuming it to be in the collapsed position shown in Fig. 1, the shaft and gears are turned by means of the handle. This results, in the first place, in turning the screw 11 which moves it up on account of its engagement with the stationary internal screw threads of the casing 10. This screw therefore rises, taking with it the casing 17 and all the parts supported thereby. But simultaneously another action takes place, namely the rising of the plunger 16 in the screw due to the fact that the nut does not turn. This plunger rises relatively to the screw just as fast as the screw rises. Therefore I get twice the velocity of travel of the plunger that I do of the screw. -Also, the plunger rises so that its upper surface eventually gets to a height approximately three times the elevation of the jack when collapsed, as shown in Fig. 1.

Furthermore, it will be seen that on account of the guide furnished by the hole 19 and the stabilization of the plunger by the screw 22 which is at a considerable disjacks on the market because this guide 19 is located at a considerably higher point than usual. When the plunger rises to the top in the former types of jack there was only one guiding or stabilizing element below the gear. so there was a chance to sway, especially after long wear. In this case we have the nut below and in addition the guide 19 which is above the gear. Thus, the two guiding and stabilizing points are at a maximum distance apart in this type of ack and the upper one is higher than in any such jack on the market. The casing 17 is prevented from turning by one or more studs 20 and slots 21.

As stated above. a very important advantage of this jack lies in the fact that all the screw threads are enclosed in the casing and protected from dust and dirt and particularly metal particles. This is an advantage in the ordinary use of a jack in the Shop and of still more advantage where it is handled out ou the road and may be tipped over and the screw threads filled with dirt, stones, cement and whatever else may be in the roadway. There is a high degree of protection against the entrance of dirt into the casing because of the guiding lit of the opening 19. This is the only opening that is exposed.

This is a comparatively inexpensive jack to make and put on the market and it contains no springl latches that are likely to be placed where they cannot be repaired. On account of their absence the cost of manufacture and assembly is very small indeed.

Although I bave illustrated and described only a single form of the invention I am aware of the fact that modifications can be made therein by any person skilled in the art without departing' from the scope of the invention as expressed in the claims.

Therefore I do not wish to be limited to all the details ot construction herein shown and described, but what I do claim is 1. In a screw jack, the combination of a casing having an internal screw thread with a hollowscrew fitting in said thread and having itself an internal screw thread, a screw within the last named screw thread fitting the same, a Square plunger extending upwardly from the second screw, means at the top of the casing'for turning the hollow screw, and a second casing surrounding the turning means and having a guide having a square opening for preventing the plunger from turning, whereby when the hollow screw is turned it will rise and the plunger and second screw will rise within it ata higher speed.

2. In a screw jack, the combination of a cylindrical casing having an internal screw thread, a hollow screw movable up and down in said screw thread and provided with an internal screw thread, a screw fitting in the second internal screw thread and movable from the top to the bottom thereof, a non-circular plunger extending upwardly from the last named screw to the top of the first screw, a gear fixed to the top of the hollow screw for turning it, and a second casing surrounding the gear and having a passage therethrough fitting the plunger, whereby the plunger will be prevented from turning.

3. In a screw jack, the combination of a easing having an internal screw thread, a hollow screw movable up and down in said screw thread and provided with an internal screw thread, all the way to the bottom, a non-circular unthreaded plunger as long as the screwv and located therein. a short screw on the bottom of the plunger fitting the internal thread, a gear fixed to the top of the screw for turning it, and a guide located above the gear and fitting the noncircular plunger, whereby the plunger is guided and stabilized at two points always at considerable distance apart.

In testimony whereof I have hereunto afl'ixed my signature.

ALVIN L. JOHNSON.

CTI