US3568804A

US3568804A - Elevating table with improved ball screw drive

Info

Publication number: US3568804A
Application number: US752627A
Authority: US
Inventors: Robert A Olsen
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-08-14
Filing date: 1968-08-14
Publication date: 1971-03-09
Anticipated expiration: 1988-03-09
Also published as: GB1264505A; CA920574A

Abstract

A ball screw drive and suspension system which includes, generally, a ball screw which is supported at the top by a selfaligning bearing and is supported and driven at the bottom by a drive assembly. The load, in the instant case, the roller platform of an elevating table, is supported by a ball nut through a pair of links capable of accepting misalignment between the ball screw and the load supporting mechanism, i.e., the roller platform. With this arrangement, the alignment tolerances between each vertical lift assembly are far more liberal than heretofore possible. The elevating table further includes four load cells which are functionally associated with its roller platform and an indicator mechanism, in a fashion such that articles placed on the roller platform are automatically weighed and the weight indicated.

Description

United States Patent Robert A. Olsen 309 s. Oak St, Palatine, in. 60067 752,627

Aug. 14, 1968 Mar. 9, 1971 e 72] Inventor [21 Appl. No. [22] Filed [45 Patented [54] ELEVATING TABLE WITH IMPROVED BALL Primary Examiner-Harvey C. Homsby AttorneyDominik, Knechtel & Godula ABSTRACT: A ball screw drive and suspension system which includes, generally, a ball screw which is supported at the top by a self-aligning bearing and is supported and driven at the bottom by a drive assembly. The load, in the instant case, the roller platform of an elevating table, is supported by a ball nut through a pair of links capable of accepting misalignment between the ball screw and the load supporting mechanism, i.e., the roller platform. With this arrangement, the alignment tolerances between each vertical lift assembly are far more liberal than heretofore possible.

The elevating table further includes four load cells which are functionally associated with its roller platform and an indicator mechanism, in a fashion such that articles placed on the roller platform are automatically weighed and the weight indicated.

ELEVATING TABLE WITll-I IMPROVED BALL SCREW DRIVE This invention relates generally to improved elevation tables and, more particularly, to improved ball screw tension drives for supporting and elevating the movable platform thereof. More particularly still, the invention relates to improved elevating tables having roller platforms which are adapted to be elevated and to automatically weigh articles placed on them.

Elevating tables of various sorts presently are available, and most of them are generally satisfactory. A major problem with most of these tables, however, is that the drive mechanism, usually a ball-screw-type drive, has a relatively short life expectancy. This is generally contributable to the fact that a rigid support system, i.e., one where the load is coupled directly to the ball nut of the ball screw drive, is used and misalignment due to construction, or deflection under load produces side loads on the ball screw of an unpredicatable nature and, ultimately, premature failure of the ball screw. The possibility of failure can be reduced to some degree by specifying very close alignment tolerances, however, this generally substantially increases construction cost.

Accordingly, an object of the present invention is to provide improved ball screw drive and suspension systems for use with elevating tables, forklifts and the like.

Another object is. to provide improved ball screw drive and suspension systems which eliminate the need for close alignment tolerances.

Still another object is to provide improved ball screw drive and suspension systems wherein the load is supported by a ball nut through a pair of links capable of accepting misalignment between the ball screw and the load-supporting mechanism.

Elevating tables, in many cases, are used for loading and unloading trucks, aircraft and the like, and for transporting articles between various locations. In a great number of cases, the articles need to be weighed, either prior to loading them or upon unloading. This usually necessitates transporting the articles to a weighing station, unloading them onto a weighing platform and then again loading them onto the elevating table after weighed them. This entails a considerable amount of time and labor, and hence, expense. It therefore would be extremely advantageous to have an elevating table which is adapted to not only raise and lower articles placed on the movable platform thereof, but is further adapted to weigh the articles as they are placed on the tables platform.

Accordingly, a still further object of the invention is to provide improved elevating tables having roller platforms which are adapted to be elevated and to automatically weigh articles placed on them.

Still another object is to provide improved elevating tables of this last-mentioned type having improved ball screw drive and suspension systems which eliminate the need for close alignment tolerances between each vertical lift assembly, i.e., each ball screw and guide means.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The above objectives are accomplished with a ball screw drive and suspension system which includes, generally, a ball screw which is supported at the top by a self-aligning bearing and is supported and driven at the bottom by a drive assembly. The load, in the instant case, the roller platform of an elevating table, is supported by a ball nut through a pair of links capable of accepting misalignment between the ball screw and the load supporting mechanism, i.e., the roller platform. With this arrangement, the alignment tolerances between each vertical lift assembly are far more liberal than heretofore possible.

The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, referenceshould be had to the following detailed description taken in connection with the accompanying drawings in which:

FIG. 1 is a perspective view of an elevating table exemplary of the present invention;

FIG. 2 is a partial sectional view taken along lines 2-2 of FIG. 1;

FIG. 3 is a partial sectional view taken along lines 3-3 of FIG. 1, the same being partially broken away to illustrate various features of the elevating table;

FIG. 4 is a perspective view of a ball screw drive and suspension system exemplary of the present invention;

FIG. 5 is an enlarged side plan view of the ball nut and the links affixed to it, the latter being sectioned to illustrate the manner in which they are affixed to the ball nut;

FIG. 6 is a sectional view taken substantially along line 6-6 of FIG. 3, illustrating the manner in which the load support is affixed to the links and is guided within the corner posts of the elevating table;

FIG. 7 is a partial sectional view of one of the link members illustrating an alternative manner in which it can be constructed; and

FIGS. 8 and 9 are a partial side view and a partial front view, respectively, of an alternative construction of the links and the manner in which they can be adapted to support a load.

Similar reference characters refer to similar parts throughout the several views of the drawings.

Referring now to the drawings, in FIG. 1 there is illustrated an elevating table 10 including a base frame 11 which has four cornerposts 12 fixedly secured to it in vertically disposed positions, at each of its opposite corners. A ball screw drive and suspension assembly 20 is retained in each of the cornerposts 12, for raising and lowering a load support 13 including a roller platform 14 and a platform support 15. The base frame 11 has a caster 18 pivotally affixed to it, at each of its four corners, which casters permit the table to be transported from one location to another. Preferably, two casters at one end of the base frame 11 are fixed casters, and the other two at its opposite end are swivel casters. One or more floor locks such as the floor lock 19 (FIG. 3)-are afiixed to thebase frame 11 and are operable to releasably lock the elevating table 10 from moving about during loading or unloading.

As can be best seen in FIG. 4 the ball screw drive and suspension assemblies 20 retained within each of the cornerposts 12 includes a ball screw 21 which is vertically disposed within the cornerpost and is supported at its top by means of a self-aligning bearing 23 which is fixedly secured to a top wall of the cornerpost. The opposite or lower end of the ball screw 21 is coupled by means of a flexible coupling 26 to a drive assembly 27. In the illustrated example, the drive assembly 27 is illustrated as a right angle bevel gear reducer drive, however, any one of a number of different types of drive assemblies such as a worm gear drive or a chain-and-sprocket drive can be used, if desired. A ball nut 22 is affixed to the ball screw 21 and is adjustably positioned along the length of the ball screw as the latter is rotated in the well-known fashion.

The ball screw 21 of each of the assemblies 20 is rotated by means of the drive assemblies 27, and the latter all are driven by motor means 35 which is coupled to them, in the manner illustrated in FIG. 2. The motor means 35 can be an electric motor which can be powered from a 220/440 volt source or from a battery to avoid it being dependent upon a local power source. Alternatively, a gasoline engine can be used, if desired. The motor means 35 is coupled by means of pulley belts 37 to a reducer unit 36. The reducer unit 36 has an output shaft 39 which is coupled to and drives a gearbox 3 3 affixed to one side of the base frame 111. The output shaft 39 can be rotatably supported and retained within a pair of pillow blocks 40 or, alternatively, the latter can be replaced with universal joints. The gearbox 34 is coupled to and drives two of the drive assemblies 27, through drive shafts 28 which are rotatably retained within pillow blocks 32. The drive shafts 28 and the output shaft 39 each includes a pair of flexible couplings 30 which compensate for misalignment and which permit the reducer unit 36, the gearbox 34, or these shafts to be easily removed for servicing. The reducer unit 36 also has an output shaft 38 which is coupled to a similar gearbox 34 affixed to the opposite side of the base frame, for driving the drive assemblies 27 of the ball screw drive and suspension assemblies 20 in the other two comers of the elevating table 10.

A limit switch 41 is coupled by means of sprockets 42 to one of the drive shafts 28 and is operated after a predetermined number of revolutions, in either a clockwise or counterclockwise direction, to open the energizing circuit for the motor means 35, to prevent the load support 13 from being raised or lowered beyond predetermined limits.

As can be best seen in FIGS. 4 and 5, the ball nut 22 of each of the ball screw drive and suspension assemblies 20 has a threaded portion 46, for threadly receiving a threaded collar 47. These collars 47 each have a pair of pins 48 having enlarged head portions 52 threadedly affixed to them in diametrically opposed positions and with ball bushings 49 retained between the enlarged head portions 52 thereof and the peripheral surface of the collars. A pair of links 50, each having an aperture 51 of sufficient size to receive the ball bushing 49 therein, is suspendingly supported from the pins 48 afflxed to each of the collars 47. A similar aperture 56 is formed in the opposite end of each of the links 50, for receiving similar ball bushings 55 affixed to the ends of pins 54 which are affixed to a pair of support arms 57 fixedly secured to the platform support l5, as can be best seen in FIGS. 3 and 6. It can therefore be seen that the load support 13 including the roller platform 14 and the platform support are not coupled directly to the ball nut 22, as in the past, but is instead loosely or flexibly supported by the ball nut 22 through the medium of the links 50. These links 50 compensate for any misalignment between the ball screws 21 and the load support 13, due to construction or deflection under load so that the need for close tolerance alignment between the ball screws 21 and the vertical guide means, in this case, the cornerposts 12, is eliminated. In fact, as much as one-sixteenth of an inch of nominal platform freedom can be provided to accommodate construction tolerances and deflections. In most cases, the load support 13 can be aligned and guided between the cornerposts 12 by means of three small guide blocks 60 affixed to the support arms 57 and to a backplate 61, in the manner illustrated in FIG. 6. Furthermore, the load support 13 is guided by means of guide blocks 60 in only two of the cornerposts. If guided in all four cornerposts, interference could result. Accordingly, it can be seen that aligning and guiding the load support 13 can be accomplished in a very simple fashion.

As can be best seen in FIG. 3, the roller platform 14 is supported atop the platform support 15 in spaced relation to it by means of four load cells 65 (only one of which is shown) supported and retained between load cell support seats 66 affixed by means of threaded screws 67 to the roller platform 14 and the platform support 15, respectively. These load cells 65 are electrically coupled to a scale mechanism 68 (FIG. 1) and are operative to indicate the weight of any object placed atop the roller platform 14 on the dial (not shown) of the scale mechanism 68.

The roller platform 14, as can be best seen in FIGS. 1 and 3, has a number of rows of rollers 70 affixed to it in a fashion such that articles can be placed atop the roller platform and easily transported from one end of it to the other, by means of the rollers.

From the above description of the elevating table 10, it can be seen that it is extremely versatile and is not easily subject to damage due to misalignment as a result of the load support 13 being deflected under load. If deflection should occur, the

misalignment is compensated for by the links 50 so that little if any horizontal force component (the force component perpendicular to the ball screw 21) is brought to bear on the ball nut 22 and/or the ball screw 21. In use, the elevating table 10 can be transported to, for example, the cargo hatch of an airplane and the cargo loaded on its load support 13 while the latter is in its raised position. As the cargo is placed on the roller platform 14, the load cells 65 are activated and convey electrical signals to the scale mechanism 68 to cause the weight of the cargo to be indicated on the dial of the scale mechanism. When the roller platform 14 is loaded, the load support 13 can be lowered and the elevating table 10 transported to an unloading area. This can be accomplished by means of a tow truck or the like, or the roller platform can be provided with an auxiliary power device so that it is selfpropelling. There no, need, as in the past, in those cases where the cargo had to be weighed, to unload the same on a weighing platform, weighing the same and then reloading it back onto the elevating table for transportation to an ultimate storage or transfer area.

In FIG. 7, there is illustrated a link 75 having an apertured bushing 76 therein which is adapted to receive one of the pins 48. The bushing 76 has a resilient sleeve 77 afiixed to its exterior which functions in substantially the same manner as the ball bushing 49 of FIG. 5, to provide a flexible coupling between the ball nut 22 and the load support 13. More specifically, if the load support 13 is deflected, the resilient sleeve 77 about the bushings 76 within the links 75 flex so as to prevent any horizontal force component of major consequence which may damage the ball nut 22 and/or the ball screw 21, from being coupled to the ball nut.

In FIGS. 8 and 9, there is illustrated another link 80 which is in the form of an elongated or oval-shaped ring. The

pins

48 and 54 can have annular grooves 81 formed in them, in which the links 80 can seat.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompany drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention, which, as a matter of language, might be said to fall therebetween.

Iclaim:

1. An elevating table comprising, in combination: a base frame having a plurality of spaced-apart, vertically disposed cornerposts fixedly secured to it, a ball screw drive including a ball screw and a ball nut retained within each of said cornerposts, each of said ball nuts having collar means affixed to them, said collar means each having pin means fixedly secured thereto in diametrically opposed positions, a platformlike load support, a plurality of link means flexibly coupling said load support to said ball nuts, said link means each comprising an elongated barlike member having an aperture adjacent one end thereof, an apertured bushing having a resilient sleeve about its exterior peripheral surface retained within said aperture and adapted to receive one of said pin means therein, the opposite end of said barlike member being secured to said load support, whereby misalignment due either to construction tolerance or deflections of said load support with respect to said cornerposts are compensated for so that substantial horizontal force components are not exerted directly upon said ball nuts and said ball screws, and drive means coupled to and operable to drive said ball screw drives to raise and lower said load support.

2. The elevating table of claim 1, further including a weighing mechanism, and wherein said load support comprises a platform support and a platform supported atop said platform support in spaced relation to it by means of a pluralispaced apart to receive said collar means therebetween in a fashion such that one of said pin means can be affixed to each of said arms, said arms having guide means affixed to them for aligning and guiding said load support with respect to said corhas pairs of arms corresponding in number to the number of 5 P ball screw drives, each of the arms of said pair of arms being

Claims

2. The elevating table of claim 1, further including a weighing mechanism, and wherein said load support comprises a platform support and a platform supported atop said platform support in spaced relation to it by means of a plurality of load cells, said load cells being adapted to couple electrical signals to said weighing mechanism to operate the latter to indicate the weight of objects placed on said platform.

3. The elevating table of claim 1, wherein said load support has pairs of arms corresponding in number to the number of ball screw drives, each of the arms of said pair of arms being spaced apart to receive said collar means therebetween in a fashion such that one of said pin means can be affixed to each of said arms, said arms having guide means affixed to them for aligning and guiding said load support with respect to said cornerposts.