US3552267A

US3552267A - Multistage telescopic hoist

Info

Publication number: US3552267A
Application number: US770310A
Authority: US
Inventors: Sherman W Bushnell Jr
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-10-24
Filing date: 1968-10-24
Publication date: 1971-01-05
Anticipated expiration: 1988-01-05
Also published as: GB1244538A

Abstract

A multistage telescopic hoist operable by pressurized compressible fluid is provided with an internal check valve and hollow probe mechanism associated with a tubular base section and at least a lowermost tubular section telescopically contained within the base section to provide lowering of the hoist without oscillation tendency.

Description

United States Patent Sherman W. Bushnell, Jr. 1213 East Cherry St., Wash. 770,310

Oct. 24, 1968 Jan. 5, 1971 Inventor Appl. No. Filed Patented MULTISTAGE TELESCOPIC HOIST 4 Claims, 3 Drawirg Figs.

U.S. Cl 91/168, 91/451, 91/422 1nt.Cl FlSb 11/18 Field of Search 91/168,

45 1 (cursory); 92/5 1--53(cursory) [56] References Cited UNITED STATES PATENTS 2,257,324 9/1941 Behm et a1 91/168 2,872,904 2/1959 Van Den Beemt 91/168 FORElGN PATENTS 877,869 9/1961 ireat Britain 91/168 Primary ExaminerPaul E. Maslousky A!t0rneySeed, Berry & Dowrey ABSTRACT: A multistage telescopic hoist operable by pressurized compressible fluid is provided with an internal check valve and hollow probe mechanism associated with a tubular base section and at least a lowermost tubular section telescopically contained within the base section to provide lowering of the hoist without oscillation tendency.

PATENTED m 5 m1 3552.267

I'NVENTOR.

AT TORNEYS SHERMAN W. BUSHNELL JR.

more particularly, is of the specialized type in which the lowest stage of largest diameter raisesand retracts first rather than'having the uppermost stage of smallestdiameter be the first to extend and retract.

When such a hoist is used for raising loads such as ducts, installation, ceiling boards, etc: for a'workman to a given height,

it isnormally preferred to have the hoist retract as rapidly as possible after the load has been removed. In certain instances it is advantageous-to beable, to adjust the height of the load with precision. When such adjustment requires a lowering of the hoist by a dumping of fluid a relatively slow discharge rate is required in order toadequately control the descent rate whereas when it is desired to rapidly'lower the hoist under a no-load condition to pickup another load a quick discharge of the fluid is required. The present invention aims to provide improved means for dumping the hoist at both slow and fast discharge rates to fulfill the described performance requirements. and to do so in an unusually simple and economical manner. v

The invention also aims to provide lowering of the hoist 3 without shattering or oscillating tendencies being encouncombination of parts hereinafter described and claimed.

' FlG. 1 is a perspective of a partially "extended telescopic hoist; i 3

HO. 2 is a vertical crossjsectiondetail of the hoist of this invention; and 1 FIG. 3 is a cross section taken along the line 3-'-3 of FIG. 2

In brief, the invention comprises a plurality of telescopic cylinders provided with a compressible pressurized fluid. The intermediate cylinders are closed at their lower ends and the uppermost cylinder and intermediate cylinders serving as pistons to lift the cylinders responsive to the introduction-of pressurized fluid into the base cylinder. The pistons of the intermediate cylinders have center openings therethrough for the passage of fluid from one cylinder to the next. At least the lowermost of the intermediate cylinders is provided with a check valve which closes the pistonopening. The check valve may take the form of a weighted ball adapted to be lifted from its seaton the piston, when the cylinder is retracted, by a vertical probe mounted in the base of the base cylinder. The probe is hollowand connected to a discharge valve for rapid lowering of the hoist, and also has adequate clearance with respect to the piston opening to permit a throttled flow of air in either section 14, a plurality of tubular intermediate sections 15, and

an elongated tubular upper section 16 telescopically contained one in another with the base section having the largest diameter and the upper section having the smallest diameter. All of these sections may be cylindrical. The hoist fits into spaced

sockets

17, 18 presented by the tripod unit 12 and a pressure tank 19-is carried by means of a mounting bracket attached to the tripod. The tank 19 contains a suitable fluid such as carbon'dioxide under pressure and has suitable pressure regulators and gauges. Flexible hoses 21 transfer fluid to and from the base of the hoist through a handheld manually operable flow control valve assembly connected to the manifold and the hoist via lengths of flexible hose 21. The valve assembly 20 is a three-way valve by which pressure fluid from the tank can be directed to' the hoist or fluid can be dumped from the hoist to the atmosphere. ln addition both such flows can be shut off. The base section of the hoist is closed at its direction through the piston opening when pressurized fluid is supplied or dumped from the bottom cylinder. If desired,

more than one of the intermediate cylinder pistons may be provided with check valves and the probe length extended lower end by an annular .base plate 22 containing porting for the su )ply and discharge of the gasfrom the tank. This porting includes a vertical center passage 23 which extends downwardly from the upper face of the plate to a radial passage 23' connecting by an external elbow 24 to an exhaust valve unit 25. A second vertical passage 26 radially offset from the first, also connects with a radial passage 26' to the outside whereat a fitting connects to the'hose 21. The valve assembly 25 has its valve 27 seated at 28' by a compression spring sleeved on the valve stem 31. Manual unseating of the valve to exhaust from the hoist through port 32 is performed by swinging a toggle 33 pivoted to the stern in opposition to the spring 30. The valve unit 25 also serves as a pressure relief valve since it will unseat in response to a predetermined pressure in the hoist. The intermediate sections 15 of the hoist are of similar const'ruction except for diameter and each is closed at its lower end by stepped piston 34 having a peripheral ceiling gasket 36 in sliding contactwith the inner wall of the next lower section of the hoist. The pistons are each connected to its respective tubular section by an inwardly extending annulus 35 roll formed in the section which fits into a circumferential groove formed in the piston. An elastic O-ring 37 is provided near the top of each piston and a cylindrical spacer sleeve 38 is located between each of the tubular sections and abuts as an upper limit against a rib 40 roll formed at the upper end of each section to limit the degree of extension of the hoist sections relative to one another. I

Each of the pistons 34 of the intermediate sections 15 are formed with an upper well 41 having a tapered bottom wall 42 which merges with an axial bore 43 continuing downwardly through the piston. Carried in the wells are respective weighted balls 44 larger in diameter than the axial bores 43 to serve as check valves when the respective stage of the hoist is extended. As part of the present invention a center probe 45 is press fitted into the center bore 23 of the base plate and projects upwardly a distance approximating the combined thicknesses of the pistons of the intermediate sections. This provide a passage 46 around the probe from one section of the check valves close to isolate the'cylinders from one another.

Referring to the drawings, the present invention is illustrated applied to a hoist 10 carrying at the top a load support I ing assembly and mounted on a collapsible tripod assembly 12. The hoist assembly comprises an elongated tubular base hoist to another when the probe extends through the axial center bores 43. Such gas flows into or out of the hoist through theoffset vertical passage 26 and radial bore 26 and via the flexible hose 21 to the hand control valve 20. From this valve a further length of the base 21 connects with the tank 19.

When the hoist sections are all completely collapsed, their pistons rest one upon another on the base section 22 as shown in FIG. 2 and the probe 45 extends upwardly through all of the distance of the intermediate sections. In this position the 7 probe displaces all-of the check valve balls so that there is communication from one hoist section up to the other in the space around the probe within the vertical bores.

' To raise the hoist from this position the hand control valve is set such as to feed pressurized gas from the container through the hose and passages in the base section up into the space between the base section and, the lowermost piston. Since .the bottom area of this piston is greater than the pistons of the other sections, the lower hoist section moves upwardly first and continues'if the supply of pressurized fluid is continued, until the lower piston is fully extended at which time the probe will be fully withdrawn from all of the pistons. The pressurized gas then liftsthe check valve ball in the first cylinder from its seat permitting the flow of the gas in the space between the first and second pistons thereby causing the second cylinder to rise upwardly relative to the first and if the flow of gas is continued from the tank, the second cylinder continues upwardly until it is further extended and then the next higher check valve opens and the process continues until the desired hoist height has been achieved. At this point the supply of gas is cut off at the hand control set and the balls then settle into their seats and isolate each cylinder from the other.

1 From this time on, upward height adjustmentcan be .made

by transferring'fluid to or from the hoist cylinder, by use of the hand control valve. When it is desired to have an upward adjustment,'the inflowing air unseats all the check valves and then causes the next highest nonfully extended section of the hoist to rise accordingly. On the other hand, if the adjustment is to be downward, venting at the hand'control set causes the discharge of gas from the base section only and hence causes the adjustment to occur in the area o'f largest crosssection as is preferred to permit a fine-adjustment. I

When it is desired to speedily retract the hoist as when the load has been removed and a new load is to be applied, the operator, instead of using a handv setfor venting, merelylifts the handle of the check valve at the base of the hoist. As a result, the air is quickly vented through'the center of the probe on the base section and then when the'first piston reaches the base the probe unseats its check valve ball and vents the space between the first and the second pistons. When this isaccomplished, the next ball up is unseated by the probe and this contimes until allofthe balls have been 'unseated and all 'of the chambers have been ventedthroughthe relief valve. FIG, 1' illustrates the parts in the condition after the bottom two'cylindrical sections have been vented when the next higher section is in the process of being vented through the probe.

The clearance between the outside of the probe and the boresand the pistons is made such that the flow capacity of thespace is no greater than that of the hose and out through the hand valve. This is done so that the lower piston will not oscillate or chatter at the point of un'seating of the lower ball byv the probe. If this were not so the high pressure fluid above the probe would flow into the lowermost chamber above the base plate and cause the lowermost piston to raise thereby again shutting off the lower check valve. Then when additional venting of the lower chamber had continued the ball would again be raised'by. the probe and the same action repeated, possibly several? times before the desired degree of venting has'been achieved. i 2

ll it is desired to automatically restrict the upward expansion of the hoist assembly. toa predetermined height. the handle on the pressurerelief valve can be connectedasby a string to the top of the hoist so. that when the string is taut the handle is lifted and the pressure reliefi valve dumped, ,i, s I

It is thus seen that the-hand set is used tom ng'.the hoistpr for minute adjustment thereof, and that'wher rt 'sadjustrnent is downward the contraction '.is .taken ,by t lowermost cylinder first. It is; -also that-when'it f :desired to qui ckly lower the cylinderjthe prgssurerelief valve is opened and-the upper cylinder lowers first; .1 y ,1 f s in many applications, th fi neadjustment providedbythe ball check valves will not be requiredover the full height range of the hOlSL-ii't such applications, a single ball valvepositioned in.the well 41 of the lowermost ij termediate cylinder will provide the necessary ine"hig& t adjustment. Thus, probe 45 need only be of a ength su cient to extend through the piston of the lowermost 'interriiediate cylinder.

l. A multistage telescopic hoistrcofnprising a plurality of elongated concentric telescopically associated, tubular sections of progressively smallercross section? closed at itslower end, a top section of the smallest cross section'iclosed atone'of its'end, and a bottom intermediate section-=having a piston on its lower end slidably' mounted in a base section and having an openingtherethroughja hollow probe of lessjouter-diar'neter than the diameter of 'the"opning,-allowin'g fli'id communication therebetween mounted near the lower end of theZbase section and projecting upwardly lengthwise of the base section in alignment with said opening to extend therethrough but not I seal the opening when said intermediate section is-retracted,

ball check valve means adapted to closez'said piston opening whensaidpiston isabove the probe and adapted to be opened by the probe whensaidinterrnediate' section is retracted, pressurized fluid supply control means communicating withtth'e bottom side of said piston through a'bo re in the lowertend of said base section for extending and retracting the hoist and dump valve means communicating with the interior of the probe through a bore in the lower end of said base section for rapidly ventingwfluids from the hoist.

2. The hoist of claim 1 including at least one other intermediate tubul'ar sectionhavinga piston a t-its lower end with an unobstructed opening theret-hrough the piston of said other intermediate section-being adapted to seat on the piston of the first-named intermediate'section when retracted. t-

3. The hoist of clairn 1 wherein the relative diameters between the probe the piston opening are such that they will provide a restricted exhaust flow of the fluid.

4. The hoist of claim 1 and further including a concentric contiguous sleeve surrounding the'exterior portionof each of the tubular sections adapted to abut the piston ofitssect'ion and an inwardly projecting shoulder of the tubular section having the next larger cross-sectional area whereby extension of each sleeve is limited] I T the

Claims

1. A multistage telescopic hoist comprising a plurality of elongated concentric telescopically associated tubular sections of progressively smaller cross section, closed at its lower end, a top section of the smallest cross section closed at one of its end, and a bottom intermediate section having a piston on its lower end slidably mounted in a base section and having an opening therethrough, a hollow probe of less outer diameter than the diameter of the opening, allowing fluid communication therebetween mounted near the lower end of the base section and projecting upwardly lengthwise of the base section in alignment with said opening to extend therethrough but not seal the opening when said intermediate section is retracted, ball check valve means adapted to close said piston opening when said piston is above the probe and adapted to be opened by the probe when said intermediate section is retracted, pressurized fluid supply control means communicating with the bottom side of said piston through a bore in the lower end of said base section for extending and retracting the hoist and dump valve means communicating with the interior of the probe through a bore in the lower end of said base section for rapidly venting fluids from the hoist.

2. The hoist of claim 1 including at least one other intermediate tubular section having a piston at its lower end with an unobstructed opening therethrough the piston of said other intermediate section being adapted to seat on the piston of the first-named intermediate section when retracted.

3. The hoist of claim 1 wherein the relative diameters between the probe and the piston opening are such that they will provide a restricted exhaust flow of the fluid.

4. The hoist of claim 1 and further including a concentric contiguous sleeve surrounding the exterior portion of each of the tubular sections adapted to abut the piston of its section and an inwardly projecting shoulder of the tubular section having the next larger cross-sectional area whereby extension of each sleeve is limited.