US3858847A

US3858847A - Double chain jack

Info

Publication number: US3858847A
Application number: US369517*A
Authority: US
Inventors: Henry B Chambers
Original assignee: Hydranautics Corp
Current assignee: Hydranautics Corp
Priority date: 1972-06-13
Filing date: 1972-06-13
Publication date: 1975-01-07
Anticipated expiration: 1992-01-07

Abstract

A single jack ram is straddled by two chains resulting in low cost and a balanced load. Ram head latches and cylinder assembly latches are formed as double pins hydraulically operated and which are oriented at right angles to each other to engage consecutive links of the chain when the ram is completely retracted. This eliminates possible misregister of the latches, caused by cumulative pitch error from manufacturing or stretch in operation, if the latches are separated by several links of the chain.

Description

United States Patent. 11 1 Chambers Jan. 7, 1975 DOUBLE CHAIN JACK 2,996,284 8/1961 Welbom 254/107 Inventor: Henry B. Chambers Santa Inez, 3,499,629 3/1970 Horton 1. 254/93 R Cahf' Primary Examiner-Al Lawrence Smith [73] Assignee: Hydranautics, Santa Barbara, Calif. As istant Examiner-Robert C. Watson [22] Filed June 13 1972 Attorney, Agent, or Firm-Clement H. Allen [21] Appl. N0.: 369,517 [57] ABSTRACT A single jack ram is straddled by two chains resulting 521 US. Cl. 254/108 in low cost and a balanced laad- Ram head latches and 51 Int. Cl B66f 1/08 Cylinder assembly lalahaa are fahhad as lauhla Pins [58] Field of Search 254/93 R 105-111 hydraulically Operated and which are Orlamad at right 7 angles to each other to engage consecutive links of the [56] References Cited chain when the ram is completely retracted. This eliminates possible misregister of the latches, caused by UNITED STATES PATENTS cumulative pitch error from manufacturing or stretch 2 i f in operation, if the latches are separated by several am 2,609,953 9/1952 Schramm 254/93 R lnks of the chem" 2,973,566 3/196l Elsner 254/93 R 4 Claims, 5 Drawing Figures BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an improved chain jack, and more particularly to a chain jack having a double chain.

2. The Prior Art A number of chain jacks have been proposed and used by the prior art featuring designs for lifting heavy loads with equal or balanced load distribution. Double ram jacks have employed a single chain between the rams which are actuated by hydraulic cylinders. Single ram jacks with a side arm and parallel single chain are inherently unbalanced but can be used for relatively light loads, and if the ram is maintained aligned by a spaced apart bearing couple in the hydraulic cylinder to counteract the effect of the side load.

This invention provides a balanced load chain jack which can be constructed at low cost and which features more accurate register of lifting and holding latches with the links of the chain. Additionally the jack allows complete disassembly of the hydraulic piston and cylinder assembly while the load is suspended by the holding latches.

BRIEFSUMMARY OF THE INVENTION Summarized briefly, this invention comprises a chain jack having a single ram repetitively actuated by a hydraulic cylinder with latch plates attached to the ram head and to the hydraulic cylinder. Each of the latch plates has cruciform apertures on opposite sides of the ram, the apertures in the ram head latch plate being aligned with the corresponding apertures in the cylinder latch plate. A pair of chains, one on each side of the ram, pass through each pair of aligned cruciform apertures with their top ends, for operation in vertical position, being passed over sheaves mounted on the ram head latch plate. Latches to engage links of the chains are arranged in the ram head and in the plate attached to the cylinder. These latches are oriented at right angles to each other and engage the chains at adjacent or consecutive links when the ram actuating piston is fully retracted into the hydraulic cylinder.

The latches are each formed as a pair of pins actuated in and out of engagement with the chains by hydraulic cylinders which may be manually or automatically controlled by conventional apparatus for lift or lower mode of operation. The latch pins of each pair, when engaged with the chain lie, against under portions of a chain link on each side of the adjacent link, the pins being flattened in their areas of contact with the chain link surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS Construction and operation of this invention will be apparent from the following description thereof and from the annexed drawings in which:

FIG. 1 is a general isometric view of a chain jack embodying features of this invention.

FIG. 2 is a general side view of the chain jack of FIG. 1, without hydraulic auxiliary equipment.

FIG. 3 is a horizontal section of the chain jack of FIG. 2 taken along the line 3-3 of FIG. 2.

FIG. 4 is a horizontal section of the chain jack of FIG. 2 taken along the line 44 of FIG. 2.

FIG. 5 illustrates a latch pin assembly showing flattened surfaces for contact with a chain link.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now particularly to FIGS. 1 to 4 the chain jack comprises a hydraulic cylinder in which rides a piston 12 to which is attached ram 14. Proximate the top of cylinder 10 is attached lower latch plate I6 which, as will be seen best in FIG. 4 has a pair of cruciform apertures 18 on opposite sides of ram 14. The top of hydraulic cylinder 10 terminates slightly above latch plate 16 and is provided with seal member 20 and hearing plate 22.

To the head 24 of ram 14 is attached upper latch plate 26 also provided with a pair of cruciform apertures l8 vertically aligned with similar apertures 18 in cylinder latch plate 16. The apertures in latch plate 26 are best seen in FIG. 3.

Fixedly attached to the top of latch plate 26 are two pairs of diverging, outwardly extending, spaced-apart supports 28. Shafts 30 are journalled through the outer ends of each pair of supports 28 and carry freely rotable grooved sheaves 32. A chain 34 is carried over each of sheaves 32, having its free end as at 36 simply hanging to provide weight to keep chain 34 in place on sheave 32 and passing through aligned apertures 18 in

latch plates

26 and 16.

As will be seen more clearly in FIG. 3 upper latch plate 26 is arranged with two pairs of parallel spaced apart latch pins 38 which are slidably mounted in horizontal holes in latch plate 26, these holes being in the way of apertures 18 with each hole on one side of the center-slot for passage of a chain link in the end-on position. The outer ends of each pair of latch pins 38 are attached to a mount plate 40 attached to a hydraulic cylinder 42 with its extending piston rod slidably passing through mount plate 40 and having its end attached to the edge of latch plate 26 as shown.

As will be seen more clearly in FIG. 4, lower latch plate 16 is also arranged with two pairs of parallel spaced apart latch pins 38 which are slidably mounted in horizontal holes in the way of apertures 18 with a hole being on each side of the center slot for passage of a chain link in the end-on position. The outer ends of each pair of latch pins 38 are attached to a mount plate 40 to which is attached a hydraulic cylinder 42 with its extending piston rod slidably passing through mount plate 40, and having its end attached to the edge of latch plate 16 as shown. As will be seen in FIG. 5 latch pins 38 are fabricated with flattened areas 39 where they contact the links of chains 34.

Operation of latch pins 38 is controlled by hydraulic systems illustrated diagramatically in FIG. I and which cause latch pins 38 to be moved inwardly, alongside both sides of end-on links in chains 34 and under the lower side portions of the adjacent cross chain link immediately above, or outwardly, clear of apertures 18. The hydraulic cylinders 42 in operating latch pins 38 in upper latch plate 26 are actuated simultaneously by exerting oil pressure on either side of their pistons 44 through oil lines 46 or 48 by high pressure pump 50. The return drain is connected to oil reservoir 52, the oil and drain line connections being made to oil lines 46 and 48 selectively by manually operated 4 way valve 54. In like manner hydraulic cylinders 42 cause latch pins 38 to move inwardly in the way of apertures 18 in lower latch plate 16, or outwardly clear of these apertures as previously described for those in upper latch plate 26. The hydraulic cylinders 42 actuating pins 38 in latch plate 16 are similarly connected in pairs to another 4 way valve 54a with a high pressure pump 50a and an oil reservoir 52 a by connecting

oil lines

56 and 58. It will be understood that the hydraulic systems are illustrated diagramatically for clarity, and that additional conventional equipment and controls may be employed and also that hydraulic lines 46 and 48 as well as 56 and 58 will be sufficiently flexible to allow in and out movement of latch pins 38, their mount plates 40 and hydraulic cylinders 42.

Piston 12 connected to ram 14 is actuated in cylinder by connection of

oil lines

60 and 62 to cylinder 10 above and below piston 12 with oil being introduced selectively under pressure to one side by another high pressure pump 64, the other side being connected to drain into reservoir 66, the up or down action of piston 12 and attached ram 14 being controlled by direction of the pressurized oil flow by another 4 way valve 68.

A position indicator in the form of a hanging scale stick may be attached to the underside of upper latch plate 26 and allowed to ride slightly against a visible sharp edge of lower latch plate 16. Indicia on the scale stick can be arranged to show the precise position of upper latch plate 26 relative to lower latch plate 16 so that one or the other set of latch pins can be moved inwardly to support the load on selected chain links.

For simplicity and ease of understanding the chain jack of this invention has been illustrated and described to be operated by manually controlled hydraulic systems, specifically by valves 54 and 54a controlling the in and out movement of the latches and valves 68 controlling the up and down movement of the ram 14. For example, for lift mode of operation assuming the chains 34 carrying a load to be supported by latch pins 38 in their inward position in lower latch plate 16 (as shown in FIG. 2) then the ram 14 is retracted by operation of valve 68 until the marks on scale stick 70 indicate that the latch pins 38 in upper latch 26 are registered properly just below the bottom of the cross links of chains adjacent to and immediately above the links supported by the latch pins in lower latch plate 16. Valve 54 is then turned to introduce pressurized oil into the outer ends of upper latch plate cylinders 42 so that latch pins now are run in and then latch pins 38 in lower latch 16 are retracted by operation of valve 54a so that the chains and the load are supported by the upper latch plate 26.

The upper latch plate 26 may now be raised by introduction of pressurized oil into the bottom of hydraulic cylinder 10 by suitable adjustment of valve 68, and will raise the chains 34 and the load. When upper latch plate 26 has been raised the distance of say one link as indicated by the marks on scale stick 70 the upward movement of ram 14 is stopped by rotating valve 68 to a neutral position then valve 54a is actuated to cause latches 38 in lower latch plate 16 to be moved inward under the bottom sides of the selected link of chain 34 which will be in proper register because of the alignment indicated by the position of scale stick 70. Ram 14 is then lowered slightly until the load is picked up by the latches 38 in lower latch plate 16 and then latch pins 38 in upper latch plate 26 are retracted and the upper latch plate 26 is lowered by operation of valve 68 until upper latch plate 26 is in position so that its latches 38 may be moved inward again under the bottom sides of the links of chains 34 immediately above those engaged by the latch pins in lower latch plate 16. The lift cycle is repeated to raise the chain (and the load) the desired height, withexcess chain hanging over sheaves 32.

For lower mode by operation, the load is first lifted slightly on latches 38 in upper latch plate 26, the latches 38 in the lower latch plate 16 are retracted and the ram and upper latch plate carrying the load is then lowered by operation of valve 68 to allow oil to be forced into reservoir 66 by piston 12 in cylinder 10. When the upper latch plate has been lowered until proper register has again been achieved (as indicated by scale stick 70) latches 38 in lower latch plate 16 are moved inwardly to catch and support the load. Latch pins 38 in upper latch plate 26 are then retracted and upper latch plate 26 with its chain and sheave assembly are again raised for another lowering stroke and the cycle repeated.

While the ram and latch operation of the chainjack of this invention has been illustrated as being manually controlled it will be understood that electrical, hydraulic, mechanical, or other type of automatic control means may be employed to provide repetitive actuation of the ram lift and lower hydraulic cylinder, and the hydraulic cylinders actuating the latch pins in both latch plates. Such automatic control means may use a cam and follower arrangement, or other device to provide properly spaced actuation of the control valves.

The double chain jack of this invention is advantageous in that a single hydraulic cylinder and ram is employed between a pair of chains. Therefore the load on the ram and the hydraulic cylinder is balanced and is wholly vertical. This makes possible the simplest form of hydraulic actuating equipment without need for providing devices to counteract side or off-center loads. Thus the ram, the cylinder and ram and associated structure may be considerably lighter and less expensive than if side or off-center loads would have to be counteracted. A single ram arrangement with balanced load is of course of substantially lower cost than employment of a double ram assembly proposed and used by the prior art.

The cylinder latch plate can be constructed of heavy material to serve as a convenient mount for the jack. This will allow complete disassembly of the cylinder and its piston, and the ram assembly, while the load is supported by the latches in the cylinder latch plate. This is a maintenance advantage in event of a seal leak.

The latch pins as described are preferably fabricated of cylindrical bar stock with flat surfaces in the areas that the pins contact the chain links. This provides a greater area of surface contact and distribution of load over both sides of the chain. The chain jack with chain loads not biased, that is with loads evenly distributed between the two chains, may be used for operation in horizontal attitude in which case the sheaves carrying the chains may not be used. For horizontal operation where the load may be required to be pushed or pulled,

the latch pins 38 are preferably fabricated with flattened areas on two opposite sides as specifically illustrated in FIG. 5. The surfaces of the chain links, will, after a period of rise under heavy load, become themselves slightly upset and flattened at areas of contact with the latch pins. This will not detract materially from the chain link strength and will provide better and more even load support.

Employment of the bar type latches contacting the undersides of the links of the chain is additionally advantageous because this organization permits use of chains assembled from links each having a centralcross bar and often referred to as stud-link chain. This type is stronger than plain welded link chain. The latches, produced from round bar stock are strong and inexpensive to fabricate, and their flattened surface, as described, provide areas for effective distribution of the lifting or moving loads.

Orientation of the two sets of latch pins so that these are at right angles, and close together, is of substantial importance. This permits the two sets of latches to engage adjacent chain links and eliminates mis-register that often occurs when spaced apart latches engage a chain at intervals of several links. If latches are separated by several links at their closest position, that is when the ram is fully retracted in the hydraulic cylinder, cumulative pitch error from manufacturing or chain stretch can cause mis-register of the latches with the chain links. With the latches oriented as described and the latch plates arranged so that the latches will en gage adjacent latches at their closest position, the possibility of mis-register of the latches with the chain links is essentially eliminated at the important position at which the raising latch engages the chain for a lifting stroke.

I claim:

1. A chain jack having a chain, a pair of latch plates having latches for selectively engaging and disengaging the links of said chain, means for moving the said latch plates repetitively from and toward each other, and means for actuating said latches in and out of engagement with the links of said chain, in which the improvement comprises:

a. a single ram connected to a piston in a hydraulic cylinder;

b. a latch plate attached to the head of said ram and a latch plate attached to said hydraulic cylinder, said latch plates each having two cruciform apertures, one on each of opposite sides of said ram, the cruciform apertures in the said ram head latch plate being vertically aligned with the corresponding cruciform apertures in the said cylinder latch plate;

0. two chains passing through said cruciform apertures, one on each of opposite sides of said ram;

d. two pairs of parallel spaced apart latch pins slidably mounted in horizontal holes in each of said latch plates, a pair on each of opposite sides of said ram and in the way of said cruciform apertures for selectively engaging and disengaging said chains passing through said cruciform apertures; and

e. means for repetitively extending and retracting said ram in said hydraulic cylinder and means for engaging and disengaging said latch pins from said chains to cause lifting and lowering of said chains.

2. A chain jack according to claim 1 in which the upper free ends of said chains pass over sheaves rotatably mounted on said ram head latch plate.

3. A chainjack according to claim 1 in which the said latch pins in said latch plate attached to said ram are oriented at right angles to the said latch pins in the said latch plate attached to said hydraulic cylinder.

4. A chain jack according to claim 1 in which said latch pins are cylindrical with flattened surfaces at their areas of contact with the surfaces of the links of said

Claims

1. A chain jack having a chain, a pair of latch plates having latches for selectively engaging and disengaging the links of said chain, means for moving the said latch plates repetitively from and toward each other, and means for actuating said latches in and out of engagement with the links of said chain, in which the improvement comprises: a. a single ram connected to a piston in a hydraulic cylinder; b. a latch plate attached to the head of said ram and a latch plate attached to said hydraulic cylinder, said latch plates each having two cruciform apertures, one on each of opposite sides of said ram, the cruciform apertures in the said ram head latch plate being vertically aligned with the corresponding cruciform apertures in the said cylinder latch plate; c. two chains passing through said cruciform apertures, one on each of opposite sides of said ram; d. two pairs of parallel spaced apart latch pins slidably mounted in horizontal holes in each of said latch plates, a pair on each of opposite sides of said ram and in the way of said cruciform apertures for selectively engaging and disengaging said chains passing through said cruciform apertures; and e. means for repetitively extending and retracting said ram in said hydraulic cylinder and means for engaging and disengaging said latch pins from said chains to cause lifting and lowering of said chains.

3. A chain jack according to claim 1 in which the said latch pins in said latch plate attached to said ram are oriented at right angles to the said latch pins in the said latch plate attached to said hydraulic cylinder.

4. A chain jack according to claim 1 in which said latch pins are cylindrical with flattened surfaces at their areas of contact with the surfaces of the links of said chain.