AU615778B2 - Turntable - Google Patents

Description

I~_ii__:iil: I I 6 15778 COMPLETE SPECIFICATION FOR OFFICE USE Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: Class Int. Class 0 0 00 Related Art: TO BE COMPLETED BY APPLICANT

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S 0 0* Name of Applicant: Address of Applicant: hctual Inventor/s: Address for Service: Complete Specification SAFETECH PTY. LTD.

56 Albert Street, Moe, Victoria 3825 BRUCE NAYLOR COX SMITH SHELSTON BEADLE 207 Riversdale Road Box 410) Hawthorn, Victoria, Australia for the invention entitled:

TURNTABLE

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0i~ The following statement is a full description of this invention, including the best method of performing it known to me/us: Page 1 Our Ref: #3849 TNB:GD 38saf i i I I I n 1- IL l iri pmnx I \06.

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TURNTABLE

Field Of The Invention This invention relates to turntables.

Background Of The Invention Turntables are widely used in industry to allow heavy oooo objects, palletised loads and the like to be easily rotated so that an operator may have complete access to the objects or load without having to move around the objects or load.

Most currently available turntables are substantial

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structures, and many of them are set into the floor of a building so as to present a flat surface for loading and unloading purposes. Freestanding turntables are also available, but they are invariably of such a height as to 0 require the load to be positioned on the turntable by means of a forklift truck, since hand trolleys or pal let trucks are unab e conveniently to mount the turntable.

*0 As result of the above factors, the turntables which have been available in the past are unsuitable for smaller operations which may not have a forklift truck, or for situations in which the use of a forklift truck would be unwarranted or impossible, for example due to confined space, use on mezzanine floor or use in "clezn" area.

Brief Srmary of the Invention and Objects It is an object of the present invention to provide a low-profile turntable which may be loaded using a hand truck or pallet trolley, which is relatively inexpensive, and which may be transported from one location to another.

890810,!pjdspe.00i ,safetech.spe, p S- 3 The invention therefore provides a turntable comprising a bottom metal plate, a top metal plate and central hub means interconnecting said plates, a carrier plate mounted on said hub means between said bottom and top plates, said carrier plate supporting an array of circumferentially spaced balls which hold the top and bottom plates in spaced relation so that the top plate is free to rotate with respect to the bottom plate.

By constructing a turntable using essentially flat 1C plates, the need for tracks for the balls to be machined

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into the surfaces of the plates is avoided. Experiments have shown that the balls quickly create their own tracks in the surfaces of the plates, but after a short period of use the tracks do not become any deeper. In this way, the expense of accurate machining of tracks is avoided, and it 3 has been found that the tracks formed by the bal is are far more accurate than machined tracks in any event. Thus, smooth rotation of the tur table is ensured at all times.

While the invention is equally applicable to turntables of different sizes, it is preferred that the turntable should have a relatively low profile to enable it to be used in conjunction with hand trolleys and pallet trucks. In this regard, it is also preferred that ramp means should be provided at the free edge of the bottom plate, with one free edge of the ramp means terminating adjacent to the free edge of the top plate. In a particularly preferred form this free edge is positioned slightly below the level of the top face of the top plate so that a pallet or other object supported by the top plate and projecting beyond the free 890810, Ipjdspe.001 ,safetech.spe, 4 edge thereof does not bind on the ramp and inhibit rotation.

In a presently preferred embodiment of the invention, the carrier plate is formed with at least two concentric circular arrays of openings within each of which balls are mounted for rotation. The balls are of course hardened balls of the type commonly used in ball bearings, for example, hard chrome steel alloy balls.

The balls are preferably more positively retained in their openings by means of a generally upstanding plastic carrier having a central cylindrical opening within which each ball is freely received. The space between the surface of the bal 1 and the inner diameter of the carrier is selected so that the bal 1 is free to rotate and so that a suitable lubricant may be held within the space. This space further allows for slight out of round of carrier plate and allows the bal ls to always run in a true circular path.

To avoid the dislodgement of the balls from their oo carriers due to distortion of the top plate under load or during handling of the turntable, a preloading force is applied to the top plate so as to positively hold the top plate in engagement with the balls. In one preferred form of the invention, this is achieved by slightly dishing the bottom plate ana selecting the balls of the innermost array to be slightly smaller in diameter than the balls in the outermost array. In this way, the top plate may be preloaded into engagement with the inner most balls to thereby hold the balls in each array captive between the bottom and top plates.

890810,!pjdspe.001 ,safetech.spe, I 5 i i i Brief Description of the Drawings In order that the invention may be more readily understood, one' presently preferred embodiment of the invention will now be described with reference to the accompanying drawings in which Figure 1 is a perspective view from above of a turntable embodying the invention; Figure 2 is a fragmentary plan view of the turntable, partly broken away to show its components.

Figure 3 is a fragmenting sectional elevation of the turntable taken along the line 2-2 in Figure 1; Figures 4, 5 and 6 are enlarged sectional elevation of details 4, 5 and 6 in Figure 3; Figure 7 is a perspective view of a lifting accessory for use with the turntable, and Figure 8 is a perspective view showing an alternative elevating lever in use.

Description of Preferred Embodiment Referring firstly to Figures 1 to 6 of the drawings, the turntable T embodying the i:nvention comprises a bottom plate 1 formed from mild steel and having a central aperture 2 within which an upstanding hollow spindle 3 is suitably secured, for example by welding. The spindl e 3 is internally threaded at 4, for a purpose to be described below, and has a vertical keyway 5 and a circumferential circlip receiving groove 6.

A top plate 7 of similar material to the bottom plate 1 has a central opening 8 surrounding which a downwardly depending hub 9 (Figs. 3 and 4) is secured, say by welding.

890810, pjdspe.001 ,safetech.spe, -6- If desired, a plastics cover plug C may engage the opening 8 as shown in broken outline in Figure 4. The hub has a central opening 10 dimensioned to receive the spindle 3 and is stepped at 11 to receive a preloading washer 12 having a locating tab received in the keyway 5 to prevent the washer 12 rotating with respect to the spindle 3. The groove 6 is adapted to receive a circlip 13 to hold the top plate 7 and preload washer 12 in its preloaded condition, as will be described further below.

A ball carrier plate 14 formed from relatively thin galvanized steel sheeting has a central opening 15 within which the spindle 3 is received, as wel l as two concentric arrays 16 and 17 of openings 18 and 19, each of which receives a nylon bal 1 carrier 20 (Figs. 3 and 5) having a central cylindrical opening 21, a bottom flange 22 and an overlying abutment 23 which operates to retain the carrier within its aperture 18 or 19 in the carrier plate 14.

Each carrier 20 receives a hard chromium alloy ball 24, the balls 24 in the innermost array 16 of openings 18 having a slightly smaller diameter than the balls 24 in the outermost array 17. In the present embodiment, in which the top plate has a diameter of the order of 1100 mm, the diameter of the balls in the outer array is of the order of 13 mm while the diameter of the balls in the inner array is of the order of 11 mm. The balls 24 are freely received in each opening 21 to allow for rotation and to provide space for lubricant.

To ensure that the ba ls 24 are subjected to a positive preload to prevent their detachment from the turntable in 890810, pjdspe.001 ,safetech.spe, LI_ 7 use or during transport, the bottom plate 1 is formed in a slightly dished manner, and this, in combination with the smaller diameter of the inner array 16 of balls 24 means that the top plate 7 must be preloaded to engage the array 16 of balls 24, the assembly being maintained in its preloaded state by means of the preload washer 12 and the circlip 13. It has been determined that the required 0 S amount of dishing of the bottom plate 1 is achieved by the heat absorbed by the plate 1 during the welding of the ramp and spacer to the edge of the plate, as described below.

*0 A seal 25 (Figs. 3 and 6) in the form of a circular brush seal 26 carried in a groove 27 formed in a mild steel seal retainer 28 is secured by welding to the bottom plate 1 I at a position spaced a short distance from the periphery of *i the ball carrier plate 14 so that the brush seal 26 contacts the lower face of the top plate 7 to prevent the ingress of *0 dirt and the like into the bearing region of the turntable.

As mentioned above, a ramp 29 in the form of a rolled annular plate 30 welded to the edge of the bottom plate 1 and supported in its inclined position by a spacer bar 31, is welded to the bottom plate 1 and to the ramp plate As mentioned above, the welding of this plate and the bar to the bottom plate 1 causes sufficient thermal distortion of the bottom plate 1 to render the plate 1 slightly dished whereby the preloading described above may be conveniently achieved.

In the currently preferred embodiment, the overall height of the turntable is of the order of 22 mm, which is significantly lower in profile than any of the prior art 890810,Ipjdspe.001 ,safetech.spe, S- 8 freestanding turntables known to the applicant. Thus, the turntable may be easily loaded with a palletized load, or any other type of load, by the use of a hand trolley or hand operated pallet truck. It will be noted that the upper most corner of the ramp plate 30 lies just below the level of the upper face of the top plate 7 so that the overhanging portions of a pallet or load will not foul the ramp plate S so that the top plate 7 is free to rotate relative to the bottom plate 1.

It will also be noted that the upper and lower faces of the bottom plate 1 and the top plate 7 are not formed with machined tracks for the arrays 16 and 17 of balls 24. It has been found that by using standard grade mild steel (grade 250) in combination with hardened chromium alloy balls 24, the balls quickly form their own tracks in the bottom plate 1 and the top plate 7. It has further been found that the grooving of the plates 1 and 7 does not continue indefinitely but ceases after a relatively short o 9 period of use so that an adequate, but not extensively deep, track is forme for each ai'ray 16 and 17 of balls 24. A person skilled in the art will appreciate that the accurate machining of tracks in steel plates of the above type is extremely difficult to achieve with any accuracy, and the above means of forming suitable tracks is not only significantly less expensive, but is also far more accurate.

If desired, the top plate may be driven to rotate by means of some suitable, drive means. For example, a chain drive may engage a sprocket secured to the top plate 7, the chain extending through suitable openings in the ramp 29 and 890810, pjdspe.001 ,safetech.spe, U I -9-

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i: i: i:i-e i" k i over suitable idler gears to a drive motor located in a position remote to the turntable. Alternatively, a motor drive of suitably low profile may be positioned between the plates 1 and 7 to engage a gear secured to the top plate 7 in some suitable manner.

To enable the .urntable T to be transported to place to place, a carrier member 32 as shown in Figure 7 of the drawings may be used. The carrier member 32 comprises a generally rectangular steel rod frame 33 which carries a stop cage 34 extending at a right angle from one side of the frame 33, and a central downwardly depending threaded lug which is adapted to engage the thread 4 formed in the spindle 3. The frame 33 is shaped to receive the tyne F of a forklift truck while the stop cage 34 prevents the tyne projecting too far through the frame 33. In this way, the turntable T may be easily lifted and transported from place to place by means of a forklift truck.

In the event that a forklift truck is not available, Sthe wheeled elevating lever 36 shown in Figure 8 of the 20 drawings may be used to elevate the turntable T in the manner shown to enable a hand pallet truck H to be positioned under the turntable to facilitate transportation in this way. As will be seen in Figure 5 of the drawings, the lever 36 has an end portion 37 shaped to engage a notch 38 formed in the periphery of the ramp 29 so that the end portion engages under the ramp plate 30 to enable the lever to be pivoted about its wheels 40 to thereby elevate one side of the turntable T.

It will be appreciated that the various components of 890810,!pjdspe.001 ,safetech.spe, r: 4 'i '6 i:I t~s 3 :i a 1 is r a :i

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the turntable described above may be manufactured from suitable alternative materials. For example the ball carrier 14 may be made from a suitable plastics material in which the bal l retainers are integral ly moulded.

Similarly, the top and bottom plates may be made from other suitable metals or from suitably rigid plastics materials where the loads to be carried are not particularly high.

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Claims (1)

11- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: i 1. A turntable comprising a bottom metal plate, a top metal plate and central hub means interconnecting said i plates, a carrier plate mounted on said hub means between said bottom and top plates, said carrier plate supporting an array of circumferentially spaced balls which hold the top and bottom plates in spaced relation so tha.t the top plate is free to rotate with respect to the bottom plate. 2. The turntable of Claim 1, wherein the overall height of the turntable is relatively small to enable the turntable to be loaded by means of a hand trolley or pal let truck, and ramp means associated with said bottom plate and terminating adjacent the free edge of said top plate. 3. The turntable of Claim 2, wherein the free edge of said ,T ramp means terminates at a position slightly below the level of the top face of said top plate. 4. The turntable of any preceding claim, wherein said carrier plate is formed with two concentric circular arrays of openings, and a ball located within each opening in a manner which leaves it free to rotate. The turntakb claim 4, wherein each of said balls are housed within a generally upstanding plastics carrier having a central cylindrical opening within which each ball is freely received. 6. The turntable of any preceding claim, wherein said top plate is held to said hub means in a manner which applies a preloading force to said top plate to positively retain the balls between said plates. 7. The turntable of Claim 6, wherein said bottom plate is 890810, pjdspe.001 ,safetech.spe, -12 slightly dished and the balls of the innermost array are selected to be slightly smaller in diameter than the balls in the outermost array whereby the top plate may have said preloading force applied thereto to cause engagement between said balls in said innermost a'-ay and said top plate. 8. The turntable of Claim 7, wherein said bottom plate is dished by applying heat to the pei iphery of said bottom *t o plate. S 9. The turntable of any preceding claim, wherein said hub means includes a central upstanding spindle secured to said 6* bottom plate and a central hub member carried by said top plate and engaging said spindle, said top plate being held in engagement with said spindle by means of a circlip or other suitable device. 10. A turntable substantially as hereinbefore described U *0 S with reference to the accompanying drawings. methods, processes, compounds and compositio e-erred to or indicated in the specifija ion and/or claims of the 0 application ind ally or collectively, and any and all DATED THIS 10th August 1989 SMITH SHELSTON BEADLE Fellows Institute of Patent Attorneys of Australia. Patent Attorneys for the Applicant SAFETECH PTY LTD \gVr C 90810, pjdspe.001 ,safetech.spe,