United States Patent: 3552267

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( 62946 of 62948 )

United States Patent	3,552,267
Bushnell, Jr.	January 5, 1971

MULTISTAGE TELESCOPIC HOIST

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.

Inventors:	Bushnell, Jr.; Sherman W. (N/A, WA)
Appl. No.:	04/770,310
Filed:	October 24, 1968

Current U.S. Class: 91/168 ; 91/422; 91/451

Current International Class: B66F 11/04 (20060101); B66F 3/24 (20060101); B66F 3/25 (20060101); F15B 15/00 (20060101); F15B 15/16 (20060101); F15b 011/18 ()

Field of Search: 91/168,451(CURSORY) 92/51--53(CURSORY)

References Cited [Referenced By]

U.S. Patent Documents


2257324	September 1941	Behm et al.
2872904	February 1959	Van Den Beem

Foreign Patent Documents


877,869	Sep., 1961	GB

Primary Examiner: Maslousky; Paul E.

Claims

I claim:

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.

Description

This invention relates to multistage telescopic hoists of the type in which the sections extend and retract sequentially, and more particularly, is of the specialized type in which the lowest stage of largest diameter raises and retracts first rather than having the uppermost stage of smallest diameter 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 is normally preferred to have the hoist retract as rapidly as possible after the load has been removed. In certain instances it is advantageous to be able 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 to adequately control the descent rate whereas when it is desired to rapidly lower the hoist under a no-load condition to pick up 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.

The invention also aims to provide lowering of the hoist without shattering or oscillating tendencies being encountered. Still another object is to provide such a hoist which can be raised and adjusted by a hand control valve remote from the base of the hoist.

Other more particular objects and advantages of the invention will with the foregoing, appear and be understood in the course of the following description and claims, the invention consisting in the novel construction and in the adaptation and combination of parts hereinafter described and claimed.

FIG. 1 is a perspective of a partially extended telescopic hoist;

FIG. 2 is a vertical cross section detail of the hoist of this invention; and

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 piston opening. The check valve may take the form of a weighted ball adapted to be lifted from its seat on the piston, when the cylinder is retracted, by a vertical probe mounted in the base of the base cylinder. The probe is hollow and 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 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 such that the check valve may be sequentially lifted from their seats when the cylinders are retracted.

With the described arrangement each check valve is open when the cylinder section with which it is associated is essentially completely retracted to thereby permit exhausting of the fluid from the space thereabove. When on the other hand the hoist has been extended to the desired height after loading, the check valves close to isolate the cylinders from one another. Then, if fluid is discharged from the base of the hoist the larger or lower section will retract before any of the higher sections. As a result, height adjustments are made with the largest possible stage diametrically speaking.

Referring to the drawings, the present invention is illustrated applied to a hoist 10 carrying at the top a load supporting assembly and mounted on a collapsible tripod assembly 12. The hoist assembly comprises an elongated tubular base 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 20 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. In addition both such flows can be shut off. The base section of the hoist is closed at its lower end by an annular base plate 22 containing porting for the supply and discharge of the gas from 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 stem 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 construction except for diameter and each is closed at its lower end by stepped piston 34 having a peripheral ceiling gasket 36 in sliding contact with 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.

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 probe is hollow and has a sloped upper end and is beveled at its lower end to communicate with the radial passage 23' leading to the toggle valve 25.

The outer diameter of the probe is purposely made smaller than the diameter of the center bores of the pistons so as to provide a passage 46 around the probe from one section of the hoist to another when the probe extends through the axial center bores 43. Such gas flows into or out of the hoist through the offset 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 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 lifts the 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.

From this time on, upward height adjustment can 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 of largest cross section as is preferred to permit a fine adjustment.

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 hand set for venting, merely lifts 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 is accomplished, the next ball up is unseated by the probe and this continues until all of the balls have been unseated and all of the chambers have been vented through the 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 bores and the pistons is made such that the flow capacity of the space 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 unseating of the lower ball by 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.

If it is desired to automatically restrict the upward expansion of the hoist assembly to a predetermined height, the handle on the pressure relief valve can be connected as by a string to the top of the hoist so that when the string is taut the handle is lifted and the pressure relief valve dumped.

It is thus seen that the hand set is used for raising the hoist or for minute adjustment thereof, and that when this adjustment is downward the contraction is taken by the lowermost cylinder first. It is also seen that when it is desired to quickly lower the cylinder, the pressure relief valve is opened and the upper cylinder lowers first.

In many applications, the fine adjustment provided by the ball check valves will not be required over the full height range of the hoist. In such applications, a single ball valve positioned in the well 41 of the lowermost intermediate cylinder will provide the necessary fine height adjustment. Thus, the probe 45 need only be of a length sufficient to extend through the piston of the lowermost intermediate cylinder.

* * * * *

Current U.S. Class:	91/168 ; 91/422; 91/451
Current International Class:	B66F 11/04 (20060101); B66F 3/24 (20060101); B66F 3/25 (20060101); F15B 15/00 (20060101); F15B 15/16 (20060101); F15b 011/18 ()
Field of Search:	91/168,451(CURSORY) 92/51--53(CURSORY)