US2796996A - Hydraulic elevating apparatus - Google Patents

Description

June 1957 E. o. SUNDlN HYDRAULIC ELEVATING APPARATUS.

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ATTORNEYS June 25, 1957 E. o. SUNDIN 2,

' HYDRAULIC ELEVATING APPARATUS Filed-Aug 5, 1953 V 2 Sheets-Sheet 2 I/vvE/vrm ERic OLov SUI/DIN United States Patent HYDRAULIC ELEVATIN G APPARATUS Eric Olov Sundin, Hudiksvall, Sweden Application August 5, 1953, Serial No. 372,438 Claims priority, application Sweden September 1, 1952 3 Claims. Cl. 212-35 This invention relates to hydraulic elevating apparatus of that kind which is especially adapted to be mounted on self-propelled trucks and which comprises an elevating cylinder vertically mounted on the truck, this cylinder having a'piston rotatably and axially movable therein. The piston supports at its upper end, respectively at the upper end of its piston rod, a boom mounted for swinging movement, said boom having two arms of diiferent lengths, the longer arm of which at its outer end carries a pulley for a cable which at its one (outer) end is provided with a hook or like implement. The shorter arm of said boom is provided at its outer end with a plurality of pulleys for the same cable, this cable being besides passed around a number of similar pulleys corresponding to the number of pulleys of the shorter arm mounted on a pulley bracket rotatably mounted on the elevating cylinder, the outer end of said cable being draulic catch device.

secured to this pulley bracket or to the boom. The

pulley bracket is adapted to be swung in a horizontal plane about the elevating cylinder. The length of the cable is so adapted to the length stroke of the piston and to the number of pulleys on the short arm of the boom and on the pulley bracket that when a stop member on the outer end of the cable abuts against an abutment on the outer end of the long boom arm said piston has not performed its full stroke but can move a further distance upwards in order to swing the long arm of the boom upwardly. As the boom is swung upwardly when the load is lifted the advantage is obtained that the load may be lifted to a considerable height even with rather a short cylinder and rather a short stroke of the piston. A drawback in this device is however that when the load is lowered the boom first is swung to a horizontal position before the stop member on the cable leaves the abutment on the outer end of the long boom arm. This causes the load to be always lowered to the body of the truck at a considerable distance from the elevating cylinder which of course hampers the stowing of the goods on the body of the truck.

The object of this invention is to overcome this drawback. According to the invention it will be possible to lower the load even in the vicinity of the elevating cylinder due to the fact that the apparatus is provided with means for detachably holding the boom in a swung-up position independent of the position of the stop member on the cable in relation to said abutment on the boom. According to the invention, this means for detachably catching the boom in a swung-up position comprises a hydraulic detent device inserted between the lever beam and the upper end of the elevating cylinder and which device is provided with control means for releasing the catching efiect. The detent device works only in one direction, viz. so that the lever beam is prevented from being swung to a horizontal position by the load and its own weight.

In the following reference is had to the accompanying drawings in which Fig. 1 shows a vehicle on which is arranged a device The elevating apparatus is preferably of the type, which is the subject of my Patent No. 2,672,990.

Behind the drivers cabin of a self-propelled truck 1 is a vertical'elevating cylinder 2 into which cylinder a hydraulic liquid is led at a certain pressure from a pump, driven by the truck engine via control means (not shown). In the cylinder 2 is a piston 3 vertically movable and rotatable about its own axis. This piston supports at its upper end a horizontal shaft 4 about which the boom 5 having arms of different lengths is pivoted. Thus the boom 5 may be swung in a horizontal plane as well as in a vertical plane in relation to the body 6 of the truck. At the outer end of the longer arm 7 of the boom 5 a pulley 8 is rotatably mounted, and a cable 9 is passed around the same. The cable carries at its outer end a hook 10 and is besides provided with a stop member 11 which preferably is displaceable along the cable and lockable to the same for cooperation with an abutment 12 on the free end of the longer arm 7 below the pulley 8. The shorter arm 13 is provided with two or more pulleys 14, and a corresponding number of pulleys 16 are rotatably mounted on a pulley bracket 15 swingably mounted on the upper end of the fixed portion of the elevating cylinder 2. The cable 9 is passed around all of these pulleys 8, 13,116. and is secured either to the pulley bracket 15'or to the boom'S.

I In the embodiment showndevice is hydraulically acting. This device consists of a piston 31 adapted to swivel at its one end about a shaft 30 on the boom 5 and is displaceably guided in a cylinder 32, which at the end opposite the piston 31 is swingably mounted about a horizontal shaft 33 on the piston 3. Outside the cylinder 32 a container 34 is provided for a pressure liquid, the same being connected through channels 35, 36 and 37 with the inner part of the cylinder 32. In the channel 36 is arranged a seat for a ball-shaped check valve 39, which closes against a pressure in the cylinder. A valve body 41 is inserted in a channel 40 which connects the channels 35 and 37, and this valve body closes against a seat 43 in the channel 40 under the action of a helical spring 42. By pulling a cable 42 or the like, connection is established between the inside part of the cylinder 32 and the container 34 so that a pressure liquid, e. g. oil, may be pressed from the cylinder into the container 34 this way.

When the boom 5 is swung as described above with the longer arm 7 upwards, for example to the position shown in dash and dot lines in Fig. 3, the piston 31 is pushed outwards to a position which corresponds to the increased distance between the shafts 30 and 33. Then pressure liquid is sucked from the container 34 through the channels 35, 36 and 37 into the cylinder 32.

As the liquid under the pressure of the load of the boom cannot return to the container 34 either through the conduit 36 or through the conduit 40, as the valves 39 and 41 prevent that, the boom will remain in its elevated position. If, however, the connection is opened via the channel 40 by pulling the cable 42, the pressure medium will return from the cylinder 32 to the containers 34 this way, and the boom 5 as a consequence thereof will be lowered down to the horizontal position provided that the valve body 41 has not before that been permitted to close the pressure liquid passage by means of on the drawings a catch the spring 42. Supporting projections or other implements corresponding to the supporting projection 29 may also in this embodimentbe arranged to limit the tilting of the boom to a hoi'iiontal 'p'osit'io'n.

What I claim is:

1. In combination, a hydraulic elevating apparatus adapted to be mounted on a vehicle, comprising a hydraulically extensible support having a fixed and an extensible portion mounted in a vertical position on said yehicle, an extensiblevboom pivoted f or movement ii a vertical plane on the upper 'end of the extensible portion of said support, a singlepulley mounted onthe outer end of said boom, a plurality of pulleys mounted on the other end of said boom, a plurality of pulleys 'rotatably mounted on the fixed portion of said supportpa cable having a 'stop thereon passed over the pulley on the outer end of said boom, over one of the pulleys on the other end of the boom and alternately around the plurality of pulleys on the fixed portion of the support and the other end of the boom and fixed to one of said plurality of pulleys, such that on extension of said support, said boom will be tilted up when the stop engages the pulley on the outer end, and hydraulic catch means pivoted on said boom adjacent said extensible portion of said support to removably engage said extensible portion to hold said boom tilted up relative to said support, whereby said support may be lowered and said cable may be lowered, and said boom will remain tilted, said means having a release means thereon.

2. A combination as claimed in claim 1 in which said hydraulic catch means comprise a piston pivoted on said boom, a cylinder pivoted to the upper end of the extensible portion of said support, said piston movable in said cylinder, a hydraulic fluid reservoir associated with said cylinder, two passageways connecting said cylinder and said reservoir, a check valve in one of said passageways permitting fluid to be drawn from the reservoir into the cylinder, and a spring controlled valve in the other of said passageways to which said release means is attached to permit return of fluid from the cylinder to the reservo1r.

on the upper end of the extensible portion of said support,

a single pulley mounted on the outer end of said boom, a plurality of pulleys mounted on the other end of said boom, a plurality of pulleys rotatably mounted on the fixed portion of said support, a cable having a stop thereon passed over the pulley on the outer end of said boom, over one of the pulleys on the other end of the boom and alternately around the plurality of pulleys on the fixed portion of the support and the other end of the boom and fixed to one of said plurality of pulleys, such that on extension of said support, said boom will be tilted up when the stop engages the pulley on the outer end, that improvemeiit comprising a piston pivoted on said boom, a cylinder pivoted to the upper end of the extensible portion of said support, said piston movable in said cylinder, a hydraulic fluid reservoir associated with said cylinder, two passageways connecting said cylinder and said reservoir, a check valve in one of said passageways permitting fluid to be drawn from the reservoir into the cylinder, and a spring controlled valve in the other of said passageways to which said release means is attached to permit return of fluid from the cylinder to the reservoir.

References Cited in the file of this patent UNITED STATES PATENTS 1,443,376 Morgan et al. Ian. 30, 1923 2,392,004 Sherman Ian. 1, 1946 2,537,755 Harbaugh Jan. 9, 1951 2,645,360 Raymond July 14, 1953 2,672,990 Sundin Mar. 23, 1954

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