US1944351A - Hoist mechanism - Google Patents

Description

Jan. 23, 1934. G LANDRY I I HOIST MECHANISM v Filed March 4, 19:52 s Sheets-Sheet 1 ill I INVENTOR.

I BY M4 ATTORNEYcs.

Jan. 23, 1934. LANDRY 1,944,351

HOI ST MECHANISM Filed March 4. 1932 3 Sheets-Sheet 2 INVENTOR.

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. ATTORNEY.

G. L. LANDRY HOIST MECHANISM Jan. 23, 1934.

Filed March 4, 1932 v 3 Sheets-Sheet 3 INVENTOR.

ATTORNEYos tion to provide an efiiclent two cylinder hydraulic Patented Jan. 23, 1934 um'rso STATES- norszr MECHANISM George Leo Landry, Milwaukee, Wis, assignor to The-Hell 09., Milwaukee, Win, a corporation of Wisconsin Application March 4, 1932. Serial No. 596,685 a 3 can. (Ci. 138-4) The present invention relates in general to improvements in the art raising and lowering bodies and structures, and relates more specificaliy to improvements in the construction and I operation 01 dual cylinder hydraulic hoist mechanisms for effecting relatively high vertical movements or certain types of structures.

An objectoi the invention is to provide improved fluid hoist mechanism which is simple l0 and durable in construction, and which is moreover highly eflicient and flexible in operation.

In the art of hauling certain materials in bulk, the trucks are sometimes equipped with bodies adapted to be elevated vertically with respect to ii the chassis, to a relatively high degree in order that the bulk material may be permitted to gravitate from a. lower opening in the body into a conveniently disposed container or chute. In i order to raise and lower the body vertically with respect to the chassis in this class of truck, various types or hoist mechanisms have been resorted to, but up ,to the present time no satisfactory vertical lift hydraulic hoist for such bodies has been devised.

It is, therefore, an objector the present invenhoist mechanism applicable, among other things, to high lift truck bodies, which mechanism. will conditions.

A further object of the invention is to provide a two cylinder pump actuated hydraulic hoist mechanism wherein the pump delivers fluid to only one of the cylinders but the pistons of both of the cylinders are caused to raise or lower uniformly and at the same time.

A iurther object of the invention is to provide a dual cylinder hoist operated by a pump which delivers fluid to only one of the cylindera'the arrangement being such that when said cylinder is supplied with fluid its piston is raised and causes fluid above the piston in said cylinder to act as a displacement pump for raising the piston in the other cylinder, whereby both pistons travel equally.

A further object of the invention is to provide a dual cylinder hydraulichoist having a minimum of moving parts and which is easily controlled and which raises and lowers uniformly.

A further object 01' the invention is to provide a hydraulic hoist of the class described equipped with an oil reservoir and an automatic replenish ing valve for the purpose of automatically refunction emciently under all normal operating plenishina oil in one of the cylinders should leakage occur.

Another object of the invention is the provision of a dual cylinder pump actuated hydraulic hoist which is extremely simple in construction and on operation, which is strong and durable, and which is well adapted for the purposes set forth.

These and other objects and advantages will appear from the following detailed description.

A clear conception of the embodiment of the agnovel features constituting the present invention and of the mode of constructing and of operating hoists built in accordance therewith, may be had by referring to the drawings accompanying and forming a part of this speciflcationin which like reference characters designate the same or similar parts in the various views:

Fig. 1 is a side view of a truck having a vertically movable body operable'by the improved hoist mechanism, the body being in its normal n lowered position and parts being broken away and in section to show details oi construction;

Fig. 2 is a view similar to Fig. i only showing the truck body and hoist mechanism in an ele-= vated position; go

Fig. 3 is a plan view of the truck chassis d the hoist mechanism;

Fig. i is a semi-schematic view showing in sec tion the improved hoist mech;

Fig. 5'is an enlarged, fragmentary, detail sec- 5 tio'nal view illustrating the fluid supply tank and the replenishing valve associated therewith; and

Fig. 6 is an enlarged detail view, partly, in section, oithe pump and the valve arrangement incorporated therein.

- Referring to Figs. 1, 2 and 3 of the drawings,

it will be observed that a truck body 8, which may be oi any of the well lmown types, is vertically'movably mounted on the rear portion of the chassis 9 01 the truck. The vertically movable mounting of the body is efiected by means oi vertical angle iron'posts 10 carried by the chassis, which are slldably engaged by complementary angle iron members 11 secured to and depending irom the, body 8. For the purpose of w imparting upward movement to the body a, the improved dual cylinder hoisting mechanism is employed. In general, and as herein disclosed,

said hoisting mechanism comprises a rear cylinder 12, a forward cylinder 13 of a larger circumference, movable elements or pistons 14 and 15 associated with the cylinders 12, 13 respectively, a fluid supply tank 16,-a pump 17, and tubular connections for efiecting transfer of fluid in. the system.

The rear cylinder 12 is supported vertically upon the rear portion of the chassis 9 and the forward cylinder 13 is also supported vertically upon an intermediate portion of the chassis, and elongated piston rods 18 and 19 extending vertically upwardly from the'pistons 14 and 15 respectively, and through the upper ends of the cylinders 12 and 1 3, engage and are connected at their upper ends to brackets 20 and 21, respectively, carried by upper front and rear portions of the truck body 8. The piston rod 19 is of considerably greater diameter than the piston rod 18. The pump 17, which is preferably a gear or other positive displacement type of pump, is rigidly mounted on a transverse chassis bar 22 below the body in its lowered position, and the supply tank 16 is mounted in an elevated position adjacent the front portion of the body. The actuating fluid for the hoist mechanism, preferably oil, is permitted to gravitate from the tank 16 to the inlet side of the pump 17 through a supply pipe 23, and an automatic shut-off valve 24, within the inlet or suction side of the pump casing or in the pipe 23 immediately thereadjacent, controls fluid flow into the pump.- A tubular connection 25, having a lowering or by-passing valve 26 therein, leads from the pump 17 into a lower portion of the forward cylinder 13 below the piston 15. It is also to be noted that an elongated pipe 27 extends from the upper portion of the forward cylinder 13 above its piston to the lower portion of the rear cylinder 12, below, its piston. The pipe 27 is connected to branch pipes 28, 28 leading respectively to the tank 16 and to the connection 25. Locatviiln each branch pipe 28, 28' is a valve casing 29 which encloses valve mechanism which will be. referred to more in detailhereinafter. Another elongated tubular connection 30 aifords direct communication between the upper portion of the rear cylinder 12, above the piston 14, and the tank 16.

An important feature of the mechanism re-= sides in the fact that the forward cylinder 13 is of a diameter larger than that of the rear cylinder 12. The relationship of cylinder 13 to cyl-' inder 12, and of piston rod 19 to piston rod 18, must be such that the unobstructed cross-sectional area of thebore of cylinder 13 above the piston 15 must equal the cross-sectional area of the bore of cylinder 12 below its piston 14. This is for the reason that when fluid is forced into cylinder 13 below the piston 15 to elevate said piston, elevation of said piston will displace fluid in the cylinder 13 above the piston and force it through the pipe 27 into cylinder 12 below the piston 14 and by virtue of the displaced fluid and the relative areas before mentioned, the piston 14 will be caused to elevate exactly equal to theelevation of piston 15 at all times and under all conditions.

The pump construction and the valve mechanism associated therewith is illustrated in detail in Fig. 6 and schematically in Fig. 4. It will be observed that the suction line 23 from the tank enters the casing 17 and opens into a valve chamber 31 in which the automatic shut-off valve 24 is movably disposed. A duct 32 leads from said chamber 31 into the gear chamber of the pump proper and another duct 33 in which is positioned a bailcheck valve 34 extends from another portion of the gear chamber and is adapted, under certain operating conditions, to

discharge fluid into a port 35, from which the high pressure line 25 (see Figs. 3 and 4) leads 31, while in another position said valve 26 closes said ducts 37 and 38 so as to prevent by-pa'ssing of fluid, in which case, when valve 24 is positioned as shown in Fig. 6, the fluid must pass through the gear chamber of the pump, as previously mentioned. The lowering or by-pass valve 26 is moved'from open to closed position by manual control means which include an operating lever 39 extending into the cab of the truck (see Figs. 1 and 2) which is adapted to be pivotally moved to reciprocate a rod 40 extending to a lever 41 which is operatively connected with said valve 26. On the other hand, the shut-off valve 24 is automatically operated and controlled by movements of the truck body. Said shut-oil valve has connected thereto a bell-crank lever 42 and to the free end of said-bell-crank lever one end of a link 43 is pivotally connected. The other end portion of said link 43 is pivotally connected to a fixed bracket 44, and adjacent said end portion said link carries a flanged bracket 45., For the purpose of causing the body 8, when moved, to operate thevalve 24, a depending lower front portion of the body may fixedly carry a tripping bar. It has been found to be convenient in practice to secure a bar 46 transversely to the front vertical angles 11 which move with the body, below the body, and when the body is in lowered position said bar 46- engages and depresses the flanged bracket 45, causing, through the link 43, the movement of the bell-crank lever 42 to the position shown in Fig. 1, in which position the valve 24 is as shown in Fig. 1 to allow fluid to flow through the gear chamber of the pump, but closing communication with the by-pass duct- 38. The flanged bracket 45 has secured thereto the lower. end portion of a vertical operating rod 47 which is slidably guided at its upper end portion in a suitable collar or bracket 48. When the body 8 is elevated to its maximum position, a flange on the bar 46 engages a fixed lug or projection 49 on the rod 47 to raise said rod, and through the connections 43 and 42 the valve 24 will be moved to shut off communication with the duct 32 to the pump gear chamber and to open communication ,with the by-pass 38.

To summarize, the operation of the improved hoist is as follows: Initially the body 8 is in its normal lowered position with respect to the chassis illustrated in Fig. 1. In this position the shut-off valve 24 is open with respect to the gear chamber of the pump, and the lower valve 26 is in closed position. To set the hoist intooperation for elevating, a control lever 50 is moved to engage standard power take-oil mecha-- nism 52 with the vehicle transmission, and an elongated shaft 51, extending to the gears of the r pump 17 is revolved to set the-pump into operation. The operation of the pump serves to draw fluid from the tank 16 through the pipe 23 into the suction port of the pump, through the pump chamber, and from thence out of the pump under 'piston 15 will raise the piston and will cause displacementof fluid in the cylinder 13 above the piston.- This displaced fluid is conducted to the lower portion of the smaller cylinder '12 through the pipe 27. Byvirtue of the relationship of the area of the space above the piston in cylinder 13 to the area of the space below the piston 14 in cylinder 12, previously discussed, the piston 14 is raised an amount equal to the elevation of the piston 15. Through the piston rods 18 and. 19 this elevation is imparted to the body 8. When the body reaches the maximum elevation shown in Fig. 2 the shut-off valve 2% is automatically closed with respect to the gear chamber of the pump by the means previously mentioned. Said shut-oil valve is, however, in

open position with respect to the by-pass duct 38 for the lowering valve.

When it is desired to lower the truck body the operating lever 39 for the lowering valve is manually moved, and through the connections previously described the lowering valve 26 is moved from the position shown in Fig. 6 to an open position with respect to the by-pass ducts 37 and 38. Said lowering valve is thereby in direct communication with the high pressure side of the system and fluid will flow throughthe by-pass ductsirom the high pressure side of the system to-the suction side. This action takes place during the descent of the body and'when the body reaches its normal lowered position the shut-off valve 24 will be automatically opened with respect to the pump and closed with respect to the by-pass ducts. The lowering valve is adjusted to its original position and everything is again in readiness for free circulation when it is desired to again elevate the body.

After continued use of the hoist mechanism, it may be found that the rings of the pistons 14, 15 no longer maintain a fluid tight joint, and that leakage around these pistons occurs. Such leakage may result in the tendency of the rods 18, 19 to travel irregularly, and will prevent uniform elevation of the body. In order to overcome this objection, the valves housed within the casings 29 and disposed within the branch pipes 28, 28, are provided. The branch pipe 28, as previously explained, connects the reservoir 16 with the fluid 28 is interposed between the fluid passages or connections 25, 27.

Each of the casings 29 is provided with a bore 53 having reduced cross-section at the upper portion thereof as at 54, andthe junction of the bored portions 53, 54 forms atapered valve seat 55 with which coacts a ball valve 56. In each of these valve mechanisms, the ball valve 56 is urged upwardly into closed position to shut off the flow of fluid, by means of a confined coiled spring 57.

When upward leakage past the piston 14 occurs, there will be a reduction in pressure above the piston 15 as compared to that existing below this piston, when the pistons 14, 15 descend. This reduction in pressure will be sufiicient to cause the upper ball check valve in the branch pipe 28,

to open, thus permitting fluid to flow from the tank .15 through the branch pipe 28 and into the in the branch pipe 28', will automatically become effective to deliver the excess oil or fluid from the connection 27 to the connection 25, thereby likewise restoring the most desirable condition of operation in the system.

. Although the improved duplex cylinder .hydraulic hoisting mechanism has been specifically illustrated and described herein as being applied to a high lift truck body, it is to be understood that the invention is capable of more general application to hoisting mechanisms for structures of various. types-wherein raising and lowering movements of a body are desired. Such' uses of the invention will obviously include mechanisms such as elevators, movable platforms, elevatable vehicle racks for chassis lubrication, and the like. It should also be understood that while the movable elements have been defined as pistons 14, 15, these elements may partake various forms, and other types of fluid pressure generating mechanisms than the gear pump-speciflcally shown, may also be utilized without departing from the .scope of this invention.

Hoists manufactured in accordance with the present improvements have proven highly successful and eificient in commercial operation, and while the actuating fluid utilized is preferably oil, it will be apparent that other fluids may be substituted. The prescnt'hoist is extremely practical for the elevation of bodies which are to be elevated by supports disposed at two separated points, as said hoist permits the use of hydraulic lifting power. which is advantageous over cables and mechanical means, and still insures the elevation of the body without any departure from the normal horizontal plane of thebody, which feature will eliminate any possibility of binding during movements.

It should be understood that it is not desired to limit the invention to the exact details of construction herein shown and described, for various modifications within the scope of the claims may occur'to persons skilled in the art.

What is claimed as the invention is:

1. In combination, primary and secondary cylinders each having a movable piston, a fluid reservoir, a pump, an initial conduit connecting said reservoir and said pump, a second conduit connecting said pump and said primary cylinder below its piston, a third conduit connecting said primary cylinder above its piston withysaid secondary cylinder below its piston, a fourth conduit directly connecting said secondary cylinder above its piston with said reservoir, and a fifth conduit connecting said reservoir with said third conduit. said fifth conduit having therein an automatic check valve for permitting fluid to how therethrough only from said reservoir to said third conduit.

2. In combination, primary and secondary cylinders each having a movable piston, a fluid reservoir, a pump, an initial conduit connecting said reservoir and said pump. a second conduit connecting said pump and saidprimary cylinder below its pistonfa third conduit connecting said Mil primary cylinder above its piston with said secondary cylinder below. its piston, a fourth conmatic check valve for permitting fluid to flow 'therethrough only from said third to said second conduit.

- 3. In combination, primary and secondary 'duit directly connecting said secondary cylinder above its piston with said reservoir, and a filth conduit connecting said reservoir and said third conduit and having therein-an automatic check valve for permitting fluid to flow therethrough only from said reservoir to said third conduit, and

-a sixth conduit connecting said second and third conduits and having therein an automatic check valve for permitting fluid to flow therethrough only from said third to said second conduit.

GEORGE LEO LANDRY.

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