US3809248A

US3809248A - Boom extension means

Info

Publication number: US3809248A
Application number: US00218822A
Authority: US
Inventors: K Ohniwa; S Ishikawa
Original assignee: Tadano Iron Works Co Ltd
Current assignee: Tadano Iron Works Co Ltd
Priority date: 1970-02-13
Filing date: 1972-01-18
Publication date: 1974-05-07
Anticipated expiration: 1991-05-07

Abstract

In a boom consisting of more than three boom members telescopically extensibly connected with each other and including a plurality of hydraulic cylinders each having compressed oil chambers on the extending and retracting sides thereof and arranged to extend between adjacent boom members, a boom extension means comprising oil supply and discharge lines connected to an oil pressure source; oil pressure supply and discharge lines connecting said plurality of hydraulic cylinders with each other; a plurality of control valve means each connected to each of the secondly mentioned oil pressure supply and discharge lines which are connected between adjacent hydraulic cylinders, each of said control valve means being so adapted as to be normally maintained in a closed position to permit the flow of oil pressure in the same direction and forcibly biased into an opened position only when the hydraulic cylinder relating to said control valve is operated to an utmost limit of extension or retraction, thereby permitting the flow of oil pressure in a direction opposite to said same direction, the opening and closing operations of said control valve being automatically effected in association with movement of the hydraulic cylinder relating to said control valve.

Description

I United States Patent 11 1 1111 3, I Ohniwa et al. May 7, 1974 BOOM EXTENSION MEANS [57] ABSTRACT [75] Inventors: Kazuhiro Ohniwa; Seuti Ishikawa,

both of Takam t Japan In a boom consisting of more than three boom members telescopically extensibly connected with each [73] Asslgnee s z 'l Tekkosho other and including a plurality of hydraulic cylinders a amatsu apan each having compressed oil chambers on the extend- [22] Filed; Jan. 18, 1972 ing and retracting sides thereof and arranged to extend between adjacent boom members, a boom exten- [21] Appl 218822 sion means comprising oil supply and discharge lines Related US, Application D t connected to an oil pressure source; oil pressure sup- [63] continuation of Sen 11,131, Feb. 13 1970' ply and discharge lines connecting said plurality of hyabandoned. draulic cylinders with each other; a plurality of control valve means each connected to each of the secondly 52 us. c1. 212/55, 52/115, 91/411 R, mentioned Oil Pressure pp y and discharge lines 92/14 which are connected between adjacent hydraulic cyl- [5l] Int. Cl. Fl5b 15/16 indersr' each of Said control Valve means being so 53 Fie|d f Search 55 35, 91/167 R adapted as to be normally maintained in a closed posi- 91/168. 411 R. 4114; 52/115-118; 92/146; 110" to permit the flow 01011 pressure in the same di- 6Q/97 H rection and forcibly biased into an opened position only when the hydraulic cylinder relating to mid con- 5 References m trol valve is operated to an utmost limit oi extension UNITED STATES PATENTS or retraction, thereby permitting the flow of oil pressure in a direction opposite to said same direction, the 823i: 3 3 opening and closing operations of said control valve Primary Examiner- -Evon C. Blunk Assistant Examiner.lohnny D. Cherry Attorney, Agent, or Firm-Shlesinger, Fitzsimmons & Shlesinger being automatically effected in association with movement of the hydraulic cylinder relating to said control valve.

5 Claims, 7 Drawing Figures PATENTEDIH 7 1914 SHEEI 2 [IF 7 TV a N rm n wei PATENTEDMY mm $809,248

SHEEI 3 (1F 7 INVENTOR K h Ohniwaand.

Sean lshk'lrayw ATTORNEY5 PATENTEDIAY 71914 I also-SL248 sum 5 or 7 51 61 Q1 86 c B 75 72 61 71 BYMM/FJ -JM 12k ATTORNEYS BOOM EXTENSION MEANS This is a continuation of application Ser. No. 1 1,131, filed Feb. 13, 1970, now abandoned.

The present invention relates to an extension means of a boom consisting of at least three extensible boom members telescopically fitted to each other.

The most commonly used extension means of a boom consisting of at least three extensible boom members and operated by hydraulic cylinders is so constructed that the hydraulic cylinders are respectively disposed to extend between two adjacent boom members and oil supply lines are disposed in the respective hydraulic cylinders so as to cause these boom members to extend and retract by the working pressure supplied therefrom. The conventional and existing arrangements of the oil pressure supply lines or circuits in the multistage boom extensible means of this type are various: one of them is such that oil pressure supply circuits are respectively arranged at respective hydraulic cylinders of respective boom members, and a valve is connected to each of oil pressure supply lines, thereby to independently control the extending and retracting operations of respective boom members; and the other practice is such that a pair of oil pressure supply and discharge lines or circuits are arranged for respectively connecting the compressed oil chamber on the extending side and the compressed oil chamber on the retracting side of each hydraulic cylinder connected between boom members and a valve is connected therebetween for switching the hydraulic pressure. In the latter case, as a means for regulating the operational sequence of respective boom members, such ways have been selectively or in combination used as connecting adjacent 7 boom members by cables so as to operate each of them in regular sequence; or disposing between adjacent boom members any suitable securing means automatically engaging or disengaging in association with the extending motion of each boom; or making a dimensional difference in the areas on piston rods on which the working pressure is exerted in the directions of extending and retracting pistons of respective hydraulic cylinders.

These conventional boom extension means as described, however, respectively present many disadvantages and inconveniences in viewpoints of structure and operation that to connect a valve for switching the hydraulic pressure to every hydraulic cylinder connected between boom members is not only difficult in piping work but also inconvenient in operating each valve; to use cables or securing means for controlling the operational sequence of respective boom members results in complexity in structure of relevant portions; and to control the operational sequence of boom members by making a dimensional difference in the pressure exerted areas on respective piston rods results in unnecessary enlargement of a boom, because, with increment in numbers of boom members, the working pressure exerted area on the piston rod of the preceding hydraulic cylinder of which the diameter is smaller than that of succeeding cylinder must be larger than that on the piston rod of the succeeding hydraulic cylinder of which the diameter is larger than that of preceding cylinder. This requirement issatisfied by imparting sufficient strength to the preceding cylinder. However, this inevitably results in an unnecessary increase in size and strength of the succeeding hydraulic cylinder.

The present invention overcomes these drawbacks as described. Accordingly, an object of the present invention is to provide an extension means of a multi-stage boom in which the oil pressure is supplied to and discharged from all of the hydraulic cylinders for operating the respective boom members, through oil pressure supply and discharge lines to each of which a valve for switching the hydraulic pressure is connected, and operation of the respective hydraulic cylinders for retracting and extending the boom members is automatically regulated in relation with the operational positions of preceding and succeeding hydraulic cylinders, thereby assuring the regular operational sequence of respective boom members by a simple operation.

In a boom consisting of more than three boom members telescopically extensibly connected with each other and including a plurality of hydraulic cylinders each having compressed oil chambers on extending and retracting sides and arranged between adjacent boom members, the boom extension means comprises oil supply and discharge lines connecting to an oil pressure source; oil pressure supply and discharge lines connecting said plurality of hydraulic cylinders with each other;

a plurality of control valve means each connected to each of secondly mentioned oil pressure supply and discharge lines connected between adjacent hydraulic cylinders, each of said control valve means being so adapted as to be normally maintained in a closed position to permit the flow of oil pressure in the same direc tion and forcibly biased into an opened position only when the hydraulic cylinder relating to said control valveis operated to an utmost limit of extension or retraction, thereby permitting the flow of oil pressure in a direction opposite to said same direction, open and close operations of said control valve being automatically effected in association with movement of the hydraulic cylinder relating to said control valve.

A boom extension means is characterized in that one of oil pressure supply and discharge lines connected to an oil pressure source is directly connected to the compressed oil chamber on the retracting side of the first hydraulic cylinder most adjacent to a base portion of the boom; said one of oil pressure supply and discharge lines being further connected to the compressed oil chambers on the retractingsides of the hydraulic cylinders located in succeeding positions with respect to said first hydraulic cylinder through oil pressure supply and discharge lines connecting adjacent hydraulic cylinders and each having a control valve, said control valves being so adapted as to be normally maintained in closed position to prevent the flow of oil pressure in a discharging direction from the compressed oil chamber on the retracting side of the hydraulic cylinder located in the succeeding position with respect to said control valve to that of the preceding hydraulic cylinder while permitting the flow of oil pressure in a direction opposite thereto, and forcibly biased into an opened position only when said preceding hydraulic cylinder is moved into an utmostly extended position, thereby permitting the flow of oil pressure in said direction of discharging from the succeeding compressed oil chamber on the retracting side, and the other of oil pressure supply and discharge lines is directly connected to the compressed oil chamber on the extending side of the hydraulic cylinder most adjacent to a top end portion of the boom, said other of oil pressure supply and discharge lines being further connected to the compressed oil chambrs on the extending sides of hydraulic cylinders preceding said hydraulic cylinder most adjacent to the top portion of the boom through oil pressure supply and discharge lines connected between adjacent hydraulic cylinders and each having a control valve, said control valves being so adapted as to be normally maintained in closed position to prevent the flow of oil pressure in the discharging direction from the compressed oil chamber on the extending side of the hydraulic cylinder located in a preceding position with respect to said control valve to the compressed oil chamber on the extending side of the succeeding hydraulic cylinder while permitting flow of oil pressure in an opposite direction thereof and forcibly biased into an opened position only when said succeeding hydraulic cylinder is moved into an utmost retracted position, thereby permitting the flow of oil pressure to the compressed oil chamber on the extending side of said succeeding hydraulic cylinder from the preceding compressed oil chamber; opening and closin g operations of said control valve being automatically effected in association with the retracting movement of corresponding hydraulic cylinder.

And, said boom extension means is further characterized in that one of oil pressure and discharge lines is directly connected to the'compressed oil chamber on the extending side of the first hydraulic cylinder most adjacent to the base porition of the boom; said one of oil pressure supply and discharge lines being further connected to the compressed oil chambers on the extending sides of hydraulic cylinders located in the succeeding positions with respect to said first hydraulic cylinder through oil supply and discharge lines each having a control valve, said control valves being so adapted as to be normally maintained in closed positions to prevent the flow of oil pressure in the direction of oil supply from the compressed oil chamber on the extending side of the hydraulic cylinder located in a preceding position with respect to said control valve to that of the succeeding hydraulic cylinder while permitting flow of oil pressure in the opposite direction thereto, and forcibly biased to an opened position when said preceding hydraulic cylinder is extended to the extremity, thereby permitting the supply of oil pressure to the compressed oil chamber on the-extending side of the succeeding hydraulic cylinder, the opening and closing operations of said control valve being automatically effected in association with movement of the hydraulic cylinder relating to said control valve; and the other of said oil pressure supply and discharge lines is directly connected to the compressed oil chamber on the retracting side of the hydraulic cylinder most adjacent to the top end portion of the boom; said other of oil pressure supply and discharge lines being further connected to respective compressed oil chambers on the retracting sides of hydraulic cylinders located in the preceding position with respect to said hydraulic cylinder most adjacent to the top portion of the boom through oil pressure supply and discharge lines each having a control valve, said control valves being so adapted as to be normally maintained inclosed positions to prevent the flow of oil pressure in the direction from the compressed oil chamber on the retracting side of the hydraulic cylinder located in the succeeding position with respect to said control valve to that of the preceding hydraulic cylinder while permitting flow of oil pressure in the opposite direction thereto, and forcibly biased into an opened position only when said succeeding hydraulic cylinder becomes extended to the extremity, thereby permitting the oil flow to the compressed oil chamber on the retracting side of the preceding hydraulic cylinder, the opening and closing position of said control valve being automatically effected in association with movement of the hydraulic cylinders relating to said valve.

The accompanying drawings show two embodiments of the present invention, wherein,

FIG. 1 is a longitudinal sectional side view of a boom consisting of four boom members, partly broken away,

FIG. 2 is a longitudinal sectional view of respective hydraulic cylinders, partly broken away,

FIG. 3 is a longitudinal sectional view illustrating the respective mechanical check valves,

FIG. 4 is a hydraulic diagram showing the pipe lines for supplying and discharging oil to and from the different boom cylinders and showing also the different of control valves of the system,

FIG. 5 is a longitudinal sectional side view a of fourstage boom built according to another embodiment, part being broken away,

FIG. 6 is a longitudinal sectional view of different hydraulic cylinders of this boom, and FIG. 7 is a longitudinal sectional view illustrating mechanical check valves for this boom.

For explanatory convenience and better understanding of this invention, the boom extension means which is used with a boom consisting of four boom members is explained throughout the examples.

In FIGS. 1 through 3 showing the first embodiment, numerals l, 2, 3 and 4 are first, second, third and fourth cylindrical boom members, respectively, which are telescopically and slidably fitted one within another. These cylindrical boom members are similar in construction with the exception that the third boom member 3 is internally divided by a longitudinally extending partitioning wall 3a into an upper space and a lower space. Numeral 11 is a first hydraulic cylinder arranged within the first and

second boom members

1, 2 to extend into the upper space of the third boom member 3 and having a cylinder portion 11a of which the base portion is connected by a pivot 22 to the base portion of the second boom member 2 and a piston rod 11b longitudinally extending therethrough and connected at one end to the base portion of the first boom member 1 by a pivot 21.

Numeral 12 is a second hydraulic cylinder longitudinally arranged between the second and third boom members and having a cylinder portion 12a pivotally connected at its base portion by pivot 24 to the base portion of the third boom member 3 and a longitudinally extending piston rod 12b pivotally connected at 23 at its one end to the base portion of the second boom member 2.

Numeral 13 is a third hydraulic cylinder longitudinally arranged between the third and fourth boom members 3, 4 and having a cylinder portion 13a connected at its top portion to the top portion of the fourth boom member 4 by a pivot 26 and a longitudinally extending piston rod 13b connected at its one end to the base portion of the third boom member 3 by a pivot 25.

Numeral 27 is a roller for carrying the top end of the first hydraulic cylinder 1 1 and numeral 28 is a roller for carrying the top end of the second hydraulic cylinder 12.

The arrangement of the oil pressure supply lines or circuits to the respective hydraulic cylinders l l, 12, 13 will be described. Numeral 29 is anoil pressure supply line connected to a port 30 formed at the base portion of the piston rod 13b of the third hydraulic cylinder 13 and communicating with a compressed oil chamber 130 in said hydraulic cylinder 13. Numeral 31 is an oil pressure supply line connected to a port 32 formed on the base portion of the piston rod 11b of the first hydraulic cylinder 1 l and communicating with a chamber 11d in said hydraulic cylinder. Numeral 33 is a valve for switching the direction of flow of oil pressure to the oil

pressure supply lines

29, 31. Said oil pressure supply line 29 connected to the port 30 moving with the third boom member 3 at the time of extending and retracting operations of the boom member is a flexible hose and sufficiently long to extend according to necessity, and being shortened by any suitable means, for example, a pulley (not shown) connected thereto.

Said port 30 communicates with a chamber 130 in the third hydraulic cylinder 13 through a hollow piston rod 13b while the port 32 communicates with a chamber 11d inthe first hydraulic cylinder 11 through a pipe 34. The

chambers

11c, 12c in the first and second

hydraulic cylinders

11, 12 and the

chambers

12d and 13d in the second and third

hydraulic cylinders

12, 13 are respectively connected to oil chamber 13c when the boom is being extended and to the chamber 11d when the boom is being retracted, namely, to the

oil supply lines

29, 31, respectively, under these conditions In detail, the compressed oil chamber 11c on the extending side of the first hydraulic cylinder 11 is connected to the compressed oil chamber 12c on the extending side of the second hydraulic cylinder 12 through a port 35, an oil pressure supply line 36 with a mechanical check valve D connected thereto, a port 37 and hollow piston rod 12b, said compressed oil chamber 120 on the extending side of the second hydraulic cylinderl2 being further connected, through a port 38 and an oil pressure supply line 39 with a mechanical check valve C, to the port 30 to which is connected the oil pressure supply line 29 communicating with the compressed oil chamber 130 on the extending side of the third hydraulic cylinder 13. The compressed oil chamber 13d on the retracting side of the third hydraulic cylinder 13 is connected to the compressed oil chamber 12d on the retracting side of the second hydraulic cylinder 12 through a pipe 49, a port 40, an oil supply line 41 with a mechanical check valve B and a port 42, said compressed oil chamber 12d on the retracting side of the second hydraulic cylinder 12 being further connected to the compressed oil chamber 11d on the retracting side of the 'first hydraulic cylinder 11 through a pipe 43, a port 44, an oil pressure supply line 45 with a mechanical check valve A and a port 46.

Said mechanical check valve A is secured to the second boom member 2 as best seen in FIG. 3, said mechanical check valve having a valve rod Ab normally maintained in a closed position to prevent the flow of oil in the discharging direction from the compressed oil chamber 12d on the retracting side of the second hy-,

draulic cylinder 12 to the compressed oil chamber 11d on the retracting side of the first hydraulic cylinder 11 but to permit the supply of oil pressure only in the opposite direction thereto. Said mechanical check valve A is so adapted that, as soon as the first hydraulic cylinder 11 is extended to move thesecond boom member 2 into the utmost extended position, its valve rod Ab normally urged to the closed position is forcibly biased to open position by an engaging projection 47 provided on an internal periphery of the first boom member 1. It is automatically returned to and maintained in the closed position to control the fiow of oil in the discharging direction from the compressed oil chamber 12d on the retracting side of the second hydraulic cylinder 12 to the compressed oil chamber 11d on the retracting side of the first hydraulic cylinder 1 1 while permitting oil to flow in the opposite direction, when said hydraulic cylinder 11 and the second boom member 2 are in the other extending and retracting positions. The mechanical check valve B secured to the third boom member 3 is the same as the valve A both in its operation and structure. As soon as the second hydraulic cylinder 12 is operated to the extremity of extension,

namely, the third boom member 3 is extended to the extremity, the valve rod Bb of the valve Ba normally urged to the closed position is brought into engagement with projection 48 provided on an internal periphery of the second boom member 2, thereby to be forced to a biased or opened position. Said valve rod Bb is automatically returned to normally closed position to prevent the flow of oil in the discharging direction to the compressed oil chamber 12d on the retracting side of the second hydraulic cylinder 12 from the compressed oil chamber 13d on the retracting side of the third hydraulic cylinder 13 but permitting the supply of oil only in the opposite direction, when the second hydraulic cylinder 12 is in the other extending and retracting positions. Operation of the mechanical check valve C is such that when the third hydraulic cylinder 13 is operated to the extremity of retraction, namely, the fourth boom member 4 is retracted to the extremity, the valve rod Cb of the valve C, which is normally urged to closed position, is forced by the base portion of the fourth boom member 4 into a biased or opened position; and it is automatically returned to normal closed position to prevent flow of oil in the discharging direction from chamber 12c to chamber 136 while permitting supply of oil only in the opposite direction when said third hydraulic cylinder 13 is in the other retracting and extending positions. The mechanical check valve D is so adapted that, when the second hydraulic cylinder 12 is operated to the extremity of retraction, namely, the third boom member 3 is retracted to the extremity, the valve rod Db normally urged to the closed position is forced by the base portion of the third boom member 3 into a biased or opened position. It is automatically returned to the normal closed position to prevent the flow of oil in the discharging direction from the compressed oil chamber on the extending side of the first hydraulic cylinder 11 to the compressed oil chamber on the extending side of the second hydraulic cylinder 12 but to permit the supply of oil only in the opposite direction. The boom extension means is operated as follows.

When the respective

hydraulic cylinders

11, 12, 13 are put in the retracted position as shown in FIG. 2 and if the valve 33 is operated to connect the oil pressure supply line 29 to the pressure line and connect the oil supply line 31 to the tank line, the oil pressure simultaneously acts on respective

compressed oil chambers

11c, 12c, on the extending sides of respective

hydraulic cylinders

11, 12, 13 in the direction to extend these hydraulic cylinders, since the mechanical check valves C and D constantly permit the flow of oil pressure in the direction of oil pressure supply. In this situation, the discharge of oil from

chambers

12d, 13d on the retracting sides of the second and third

hydraulic cylinders

12, 13 is prevented by the mechanical check valves A and B, hence passage of oil through the

lines

45 and 41 in the discharging direction is also prevented. While discharge from the compressed oil chamber 11d on the retracting side of the first hydraulic cylinder 11 is permitted at this time, only the first hydraulic cylinder 11, namely, the second boom member 2, is caused to extend. And, when the second boom member 2 is moved by the first hydraulic cylinder 11 to the extremity of extension, the mechanical check valve A is forcibly biased by the engaging projection 47 to permit oil discharge from chamber 12d of the second hydraulic cylinder 12 through chamber 11d, whereby the second hydraulic cylinder 12 is operated to cause extending motion of the third boom member 3. When the third boom member 3 is extended to the extremity, the mechanical check valve B is forcibly biased to permit the discharge of oil from chamber 13d through chamber 12d, whereby the third hydraulic cylinder 13 is caused to extend, thereby to move the fourth boom member 4 into the extended position.

If the valve 33 is switched to the other direction to connect the oil pressure supply 31 to the pressure line and the line 29 to the tank line when all of the boom members are in the extended positions, the oil pressure acts on the

compressed oil chambers

11d, 12d, 13d in the direction of retract these cylinders, since the mechanical check valves A and B normally permit passage of the oil pressure in the feed direction. In the situation where all boom members arein the extended position, the discharge of oil from the compressed oil chambers 12c, lie on the extending side of the second and first

hydraulic cylinders

12, 11 is prevented by the mechanical check valves C and D, while the discharge from chamber 13c is only permitted; hence the third hydraulic cylinder 13 is retracted, thereby moving the fourth boom member .4 to the retracting position. When the fourth boom member 4 is retracted to its extremity by operation of the third hydraulic cylinder 13, the mechanical check valve'C is forcibly biased by the base portion of the fourth boom member 4 to permit the oil discharge from the compressed oil chamber 120 on the retracting side of the second hydraulic cylinder. 12 through the chamber 130 on the extending side of the third hydraulic cylinder 13, whereby the second hydraulic cylinder 12 is retracted to cause retraction of the third boom member 3. When the third hydraulic cylinder 13 is retracted to move the fourth boom member 4 into its utmost retracted position, the mechanical check valve C is forcibly biased by the base portion of the fourth boom member 4 to permit the oil discharge from chamber 120 through chamber 13,whereby the second hydraulic cylinder 12 is retracted to cause re traction of the third boom member 3. When the second hydraulic cylinder 12 is fully retracted to move the third boom member 3 into its fully retracted position, the mechanical check valve D is forcibly biased to permit the oil discharge from chamber 11c, whereby the first hydraulic cylinder 11 is retracted to move the second boom member 2 to the retracted position.

The example is shown in which the mechanical check valves A, B, C and D are respectively connected to the oil discharge lines 45, 41 connected to the

chambers

12d, 13d on the retracting sides of the second and third hydraulic cylinders and connected to the oil discharge lines 39, 36 connected to the compressed oil chambers 12c, 110 on the extending sides of the second and first

hydraulic cylinders

12, 11. The control valves to be connected to these

pipe lines

45, 41, 39 and 36 are not limited to the check valves having a structure as described in the foregoing, but may be such valves A, B, C and D as are automatically opened and closed according to the extending and retracting operations of respective

hydraulic cylinders

11, 12, 13, like the mechanical check valves-A, B, C and D as described. The arrangement of the oil pressure supply lines in and between respective hydraulic cylinders to which valves A, B, C and D are respectively connected is diagramatically shown in FIG. 4. So far as these valves A, B, C and D in this example are so constructed that the valve A is caused to open only when the hydraulic cylinder 11 is in the extremity of expansion; the valve B is opened only when the second hydraulic cylinder 12 is extended to the extremity; the valve C is opened only at the extremely retracted position of the hydraulic cylinder 13; and the valve D is opened only at the extremely retracted position of the hydraulic cylinder 12, the respective boom members can be automatically controlled to move in regular sequence, like the fore going embodiment described. i

A further embodiment is shown which is substantially similar to the first embodiment in it construction.

In FIGS. 5 through 7, numerals S1, 52, 53 and 54 are first, second, third and fourth cylindrical boom members telescopically slidably connected to each other and having the same structure with the exception that the third boom member 53 is internally divided by a longitudinally extending partitioning wall 53a into upper and lower chambers. Numeral 61 is a first hydraulic cylinder arranged between the first and

second boom members

51, 52 to extend into the upper spacing of the third boom member. The first hydraulic cylinder 61 has a cylinder portion 61a connected by a pivot 72 to the base portion of the second boom member 52 and apiston rod 61b connected by a pivot 71 to the baseportion of the first boom member 51 most adjacent to the base portion of the boom.

Numeral 62 is a second hydraulic cylinder having a piston rod 62b connected to the base portion of the second boom member 52 at a pivot 73 and a cylinder portion 62a connected by a pivot 74 to the base portion of the succeeding third boom member 53.

A third hydraulic cylinder 63 is arranged between the third and the

fourth boom members

53 and 54, and has a piston rod 63b pivotally connected by a pivot 75 to the base portion of the third member 53 and a cylinder portion 63a pivotally connected to the top portion of the fourth boom member 54 at 76.

Numeral 77 is a roller carrying the top of the first

hydraulic cylinder

61, and 78 is a roller carrying the top of the second hydraulic cylinder 62.

The arrangement of oil pressure supply lines to the first, second and third

hydraulic cylinders

61, 62 and 63 is as follows. An oil pressure supply line 79 is connected to a port 80 provided at the base portion of the piston rod 61b of said hydraulic cylinder 61 and in communication with a compressed oil chamber 61c on an extending side of the first hydraulic cylinder 61. An oil pressure supply line 81 is connected to aport 82 provided at the base portion of the piston rod 63b of said third cylinder 63 and communicating with a compressed oil chamber 63d on a retracting side of the third hydraulic cylinder 63, and a valve 83 for switching the flow of oil is connected to supply

lines

79 and 81. Said supply line 81 is connected to the port 82, which moves with the third member 53, depending upon the extention or retraction of the boom, and is formed from a flexible material and retained retractile by any suitable means.

Said port 80 communicates with chamber 610 through hollow piston rod 61b and port 82 communicates with chamber 63d of the retracting side of the third hydraulic cylinder 63 through a pipe 84. The

other chambers

62c and 63c and chambers 61d and 62d of the first, second and third

hydraulic cylinders

61, 62 and 63 are connected, respectively, to chamber 610 of the extending side of the first cylinder 61, to the line 79, and said chamber 63d and to the line 81.

The chamber 610 is connected to chamber 62c through a port 85, a line 86 to which a-mechanical check valve 54 is connected, a port 87 and the hollow piston rod 62b, said chamber 62c further being connected to the chamber 63c of the third hydraulic cylinder 63 through a port 88, a line 89 to which a mechanical check 58 is connected, a port 90 and the hollow piston rod 63b. The compressed oil chamber 63d of the third hydraulic cylinder 63 is connected to chamber 62d of second hydraulic cylinder 62 through the port 82, a line 91 to which a mechanical check valve C is connected, and a port 92, said chamber 62d further communicating with chamber 61d of the first hydraulic cylinder 61 through a pipe 93, a port 94, and a line 95 to which a mechanical check valve 5D is connected.

The mechanical check valve 5A is secured to the second boom member 52 and so positioned that when the first hydraulic cylinder 61 is extended to its extremity and the second boom member 52 is moved into its utmost extended position, the valve rod 5Ab, normally urged to the closed position, is forcibly biased by an engaging projection 97 provided on the internal periphery of the first boom member 51 into opened position. It is automatically returnedto normal, closed position to prevent the supply of oil to chamber 62c from the first hydraulic cylinder but to permit flow of oil in the opposite direction. The mechanical check valve 5B, similarly to the valve 5A, is normally maintained in closed position to prevent oil pressure supply to chamber 630 of the third hydraulic cylinder 63 and permit flow of oil only in the opposite direction, said mechanical check valve 5B being forced open when the second hydraulic cylinder 62 and the third boom member 53 reach the utmost extension state, because a valve rod SBb of a valve 5Ba normally urged to the closed position is brought into engagement with a projection 98 provided on the inside wall of the second boom member. At the other position of the second hydraulic cylinder 62, valve 5B is mechanically returned to its normal position to check supply to chamber 63c of the third hydraulic cylinder 63 and permit flow of oil pressure in the opposite direction. The mechanical check valve 5C is forcibly opened when the third hydraulic cylinder 63 namely the fourth boom member 54, reaches its utmost retracted position, because a valve rod 5Cb of a valve 5Ca normally kept closed is pushed by the base portion of the fourth member 54 of the boom into biased position and, at the other position of the third hydraulic cylinder 63, mechanically controlled to return to the normal, closed position to check supply to the compressed oil chamber 62d and permit an oil flow in the opposite direction. The mechanical check valve 5D is forcibly opened when the second hydraulic cylinder 62, namely, the third boom member 53 reaches its utmost retracted position, a valve rod 5Db of a valve 5Da normally kept closed is pushed by the base portion of the third boom member 53 into a biased position. At other position of the second hydraulic cylinder 62, valve 5D is mechanically returned to its normal position to check oil pressure supply to the chamber 61d and permit an oil pressure flow in the opposite direction.

In the boom extension means having such piping arrangement as described, if the valve 83 is operated to connect line 79 to the pump line and line 81 to the tank, respectively, the first hydraulic cylinder 61 only is extended to move the second boom member 52 into the extended position, since the

mechanical check valves

5A and 5B operate to close the

lines

86, 89. When the first hydraulic cylinder 61, namely, the second member 52 reaches its utmost extension, the mechanical check valve 5A is opened by the projection 97, thereby supplying oil to chamber 62c, whereby said second hydraulic cylinder 62 is caused to extend. When said second hydraulic cylinder 62, namely, the third member 53 reaches the utmost extension, the mechanical check valve 5B is opened by the projection 98 and the oil is supplied to the chamber 63c of of the third cylinder 63, this third cylinder 63 is extended to move the fourth boom member 54 into its utmost extended position.

Meanwhile, in the

chambers

61d, 62d and 63d of

cylinders

61, 62 and 63, when said

cylinders

61, 62 and 63 are extending, oil is discharged therefrom to the tank through the

lines

95, 91 and 81 because the mechanical check valves 5C and 5D permit the flow in said direction.

When all of the boom members are in their fullest extended positions, if the valve 83 is operated to switch the connection of the oil pressure supply and discharge lines, the third hydraulic cylinder 63 is retracted to move the fourth boom member 54 into the retracted position, since the

lines

81 and 85 are kept closed by mechanical check valves 5C and 5D, so that backpressure is not created in chambers 61d, 62d, due to the load to be applied thereto. Since, at the utmost retraction of said third hydraulic cylinder 63, or the fourth boom member 54, the mechanical check valve 5C is opened by the base portion of the fourth boom member 54 and the oil is applied to chamber 62d of the retracting side cylinder 62; hence the second hydraulic cylinder 62 is retracted to move the third boom member 53 into its fully retracted position. When the boom member 53 reaches to the extremity of retraction, the check valve 5D is opened and the oil is supplied to the chamber 61d of the retracting side, so that the first hydraulic cylinder 61 is retracted to cause the retraction of the second boom member 52.

Check valves A, B, C, D and 5A, 5B, 5C, 5D as employed in the first and third embodiments and valves A, B, C, D as employed in the second example may be so adapted as to be indirectly controlled by solenoids operating according to the extending and retracting operations of respective hydraulic cylinders l1, l2, l3, and 61, 62, 63. The boom extension means according to the present invention is applicable not only in the boom consisting of four boom members but also in the boom consisting of any desired numbers of boom members more than three.

The thus constructed extension means of a multistage boom relating to the present invention has such advantages that the construction and operation are simplified and the respective hydraulic cylinders are automatically operated in regular sequence by operating a single valve means, thereby to provide the smooth extending and retracting motions of respective boom members. v

The boom extension means according to the present invention provides further advantages that since the retracting motion of respective boom members of a multi-stage boom is regulated by controlling the oil discharge and supply from the chambers on the extending sides of respective hydraulic cylinders, the chambers on the retracting sidessof respective hydraulic cylinders become vacuous owing to the loadexerted on boom members, at the time of retraction thereof, hence there is no probability of disturbing said sequence of retraction of respective boom members.

What is claimed is:

1. In a boom consisting of at least three telescopically-connected boom members,

fluid-pressure operated means for extending and contracting said boom, comprising a series of cylinders, the number of which is one less than the number of boom members,

a piston reciprocable in each cylinder,

each piston dividing its cylinder into two chambers, one a retracting chamber and the other a chamber for effecting extension, and each piston having a piston rod attached to it at one side,

each cylinder being connected to one of said boom members and each piston being connected to the next adjacent boom member,

a first conduit for conducting the motive fluid to and from the extension side of the piston reciprocable in the last cylinder of said series,

a second conduit for conducting the motive fluid to and from the retracting side of the piston in the first cylinder in the series,

a reversible valve to which said conduits are connected for reversing the direction of flow of the motive fluid to said conduits,

a first series of lines connecting the chamber on the retracting side of each cylinder with the corresponding chamber in the next adjacent cylinder,

a valve in each said line which is closed, when the boom is retracted, for preventing flow of the motive fluid in one direction through said line while permitting flow in the opposite direction,

a second series of lines connecting the chamber on the extending side of each cylinder with the corresponding chamber in the next adjacent cylinder in the series,

a valve in each of the second series of lines, which is closed, when the boom is extended, for preventing flow of the motive fluid in each line of said second series in said opposite direction while permitting flow in said one direction,

means actuated when the last cylinder of said series is extended to its extremity, for opening the valve in the line with which the first conduit communicates, to connect the chamber in the last cylinder with the corresponding chamber in the next adjacent cylinder to cause extending movement in said next adjacent chamber, and

means actuated, when the first cylinder in said'series is extended to its extremity, for opening the valve in the line, with which the second conduit communicates, to connect the extension chamber in the first cylinder with the corresponding chamber in the next adjacent cylinder to cause extending movement in said next adjacent cylinder, whereby a boom can extend from the second boom member and successively retract from the last boom member. i

2. A boom as claimed in claim 1, wherein said first conduit conducts the motive fluid to and from the chamber on the retracting side of the last cylinder, and said second conduit conducts the motive fluid to and from the chamber on the extending side of the first cylinder.

3. A boom as claimed in claim 1, wherein said first conduit conducts the motive fluid to and from the chamber on the extending side of the last cylinder and said second conduit conducts themotive fluid to and from the chamber on the retracting side of the first cylinder. v

4. In a boom comprising at least three telescopicallyconnected boom members,

fluid-pressure operated means for extending and retracting said boom, comprising a series of hydraulic cylinders disposed between and connecting adjacent boom members, each of said cylinders including a piston reciprocable in said cylinder, each piston dividing its cylinder into two chambers, one a chamber for effecting retraction and the other a chamber for effecting extension, and each piston having a piston rod attached to it at one side and extending through the chamber on the retraction side of the cylinder,

a first conduit for conducting the motive fluid to and from the chamber on the extension side of the first hydraulic cylinder in said series,

a second conduit for conducting the motive fluid to and from the chamber on the retraction side of the last hydraulic cylinder in said series,

a reversible valve to which said first and second conduits are connected for controlling the direction of flow of the motive fluid through said first and second conduits,

a pipe connecting the chamber on the extension side of each hydraulic cylinder, excepting said last one, with the corresponding chamber in the next adjacent hydraulic cylinder in the series,

a first valve in said pipe connecting the chamber on the extension side of each hydraulic cylinder to the corresponding chamber of the next adjacent hydraulic cylinder, said first valve being adapted to be closed for preventing flow of the motive fluid from the first hydraulic cylinder side to the last hydraulic cylinder side, and opened for permitting flow of the motive fluid in either direction through said pipe, said first valve being normally closed,

a pipe connecting the chamber on the retraction side of each hydraulic cylinder, excepting the last one, with the corresponding chamber in the next adjacent hydraulic cylinder in the series,

a second valve in said pipe connecting the chamber means actuated to open the valve in the pipe connecting chambers on the first conduit which correspond to extension side, when the hydraulic cylinder of first cylinder side between the chambers to which the said valve corresponds is extended to its extremity, and

means actuated to open the valve in the pipe connecting chambers on the second conduit which corresponds to retraction side, when the hydraulic cylinder of first cylinder side between the chambers to which the said valve corresponds is retracted to its extremity;

whereby, the boom can extend from its first member side successively and retract from its last member side likewise.

5.' In a boom comprising at least three telescopicallyconnected boom members.

a first conduit for conducting the motive fluid to and from the chamber on the retraction side of the first hydraulic cylinder in said series,

a second conduit for conducting the motive fluid to and from the chamber on the retraction side of the first hydraulic cylinder in said series,

a second valve in said pipe connecting the chamber on the retraction side of each hydraulic cylinder to the corresponding chamber of the next adjacent hydraulic cylinder, said second valve being adapted to be closed for preventing flow of the motive fluid from the last hydraulic cylinder side to the first hydraulic cylinder side, and opened for permitting flow of said motive fluid in either direction through the last-named pipe, said second valve being normally closed,

means actuated to open the valve in the pipe connecting chambers on the first conduit which corre sponds to retraction side, when the hydraulic cylinder of first cylinder side between the chambers to which the said valve corresponds is extended to its extremity, and

means actuated to open the valve in the pipe connecting chambers on the second conduit which corresponds to extension side, when the hydraulic cylinder of first cylinder side between the chambers to which the said valve corresponds is retracted to its extremity;

whereby, the boom can extend from its first member.

side successively and retract from its last member side likewise.

UNITED STATES PATENT OFFII'JE CER'TIFIQATE 0F (JORRECTION Pat nt No- 3, 9 Dated May-7, 197

Inventor(s) Kazuhiro Ohniwa and Seuti Ishikawa It is certified that error appears in the above-identified'patent and that said Letters Patent are hereby corrected as shown below:

Co1umn 8,1ine 39, "chambers" should be .--spaces--.

Column 9, line 24, numeral "5 should be --5A.

Column 10, line #7, numeral "81" should be -9l-. column 13, line 20, "first" should be --last---; in

line M3, "retraction" should be ----extension---; and in line 44, "first" should be --last--.

Column 14, line +0, "first" should be --last--.

Signed and sealed this 5th day of November 19 74.

(SEAL) Attest:

McCOY M. GIBSON JRO c. MARSHALL DANN f Attesting Officer Commissioner of Patents FORM PC4050 uscoMM-oc 60376-Pfl9 U.S GOVERNMENT PRINTING OFFICE: I959 O-JG-33

Claims

1. In a boom consisting of at least three telescopicallyconnected boom members, fluid-pressure operated means for extending and contracting said boom, comprising a series of cylinders, the number of which is one less than the number of boom members, a piston reciprocable in each cylinder, each piston dividing its cylinder into two chambers, one a retracting chamber and the other a chamber for effecting extension, and each piston having a piston rod attached to it at one side, each cylinder being connected to one of said boom members and each piston being connected to the next adjacent boom member, a first conduit for conducting the motive fluid to and from the extension side of the piston reciprocable in the last cylinder of said series, a second conduit for conducting the motive fluid to and from the retracting side of the piston in the first cylinder in the series, a reversible valve to which said conduits are connected for reversing the direction of flow of the motive fluid to said conduits, a first series of lines connecting the chamber on the retracting side of each cylinder with the corresponding chamber in the next adjacent cylinder, a valve in each sAid line which is closed, when the boom is retracted, for preventing flow of the motive fluid in one direction through said line while permitting flow in the opposite direction, a second series of lines connecting the chamber on the extending side of each cylinder with the corresponding chamber in the next adjacent cylinder in the series, a valve in each of the second series of lines, which is closed, when the boom is extended, for preventing flow of the motive fluid in each line of said second series in said opposite direction while permitting flow in said one direction, means actuated when the last cylinder of said series is extended to its extremity, for opening the valve in the line with which the first conduit communicates, to connect the chamber in the last cylinder with the corresponding chamber in the next adjacent cylinder to cause extending movement in said next adjacent chamber, and means actuated, when the first cylinder in said series is extended to its extremity, for opening the valve in the line, with which the second conduit communicates, to connect the extension chamber in the first cylinder with the corresponding chamber in the next adjacent cylinder to cause extending movement in said next adjacent cylinder, whereby a boom can extend from the second boom member and successively retract from the last boom member.

3. A boom as claimed in claim 1, wherein said first conduit conducts the motive fluid to and from the chamber on the extending side of the last cylinder and said second conduit conducts the motive fluid to and from the chamber on the retracting side of the first cylinder.

4. In a boom comprising at least three telescopically-connected boom members, fluid-pressure operated means for extending and retracting said boom, comprising a series of hydraulic cylinders disposed between and connecting adjacent boom members, each of said cylinders including a piston reciprocable in said cylinder, each piston dividing its cylinder into two chambers, one a chamber for effecting retraction and the other a chamber for effecting extension, and each piston having a piston rod attached to it at one side and extending through the chamber on the retraction side of the cylinder, a first conduit for conducting the motive fluid to and from the chamber on the extension side of the first hydraulic cylinder in said series, a second conduit for conducting the motive fluid to and from the chamber on the retraction side of the last hydraulic cylinder in said series, a reversible valve to which said first and second conduits are connected for controlling the direction of flow of the motive fluid through said first and second conduits, a pipe connecting the chamber on the extension side of each hydraulic cylinder, excepting said last one, with the corresponding chamber in the next adjacent hydraulic cylinder in the series, a first valve in said pipe connecting the chamber on the extension side of each hydraulic cylinder to the corresponding chamber of the next adjacent hydraulic cylinder, said first valve being adapted to be closed for preventing flow of the motive fluid from the first hydraulic cylinder side to the last hydraulic cylinder side, and opened for permitting flow of the motive fluid in either direction through said pipe, said first valve being normally closed, a pipe connecting the chamber on the retraction side of each hydraulic cylinder, excepting the last one, with the corresponding chamber in the next adjacent hydraulic cylinder in the series, a second valve in said pipe connecting the chamber on the retraction side of each hydraulic cylinder to the corresponding chamber of the next adjacent hydraulic cylinder, said seconD valve being adapted to be closed for preventing flow of the motive fluid from the last hydraulic cylinder side to the first hydraulic side, and opened for permitting flow of said motive fluid in either direction through the last-named pipe, said second valve being normally closed, means actuated to open the valve in the pipe connecting chambers on the first conduit which correspond to extension side, when the hydraulic cylinder of first cylinder side between the chambers to which the said valve corresponds is extended to its extremity, and means actuated to open the valve in the pipe connecting chambers on the second conduit which corresponds to retraction side, when the hydraulic cylinder of first cylinder side between the chambers to which the said valve corresponds is retracted to its extremity; whereby, the boom can extend from its first member side successively and retract from its last member side likewise.

5. In a boom comprising at least three telescopically-connected boom members. fluid-pressure operated means for extending and retracting said boom, comprising a series of hydraulic cylinders disposed between and connecting adjacent boom members, each of said cylinders including a piston reciprocable in said cylinder, each piston dividing its cylinder into two chambers, one a chamber for effecting retraction and the other a chamber for effecting extension, and each piston having a piston rod attached to it at one side and extending through the chamber on the retraction side of the cylinder, a first conduit for conducting the motive fluid to and from the chamber on the retraction side of the first hydraulic cylinder in said series, a second conduit for conducting the motive fluid to and from the chamber on the retraction side of the first hydraulic cylinder in said series, a reversible valve to which said first and second conduits are connected for controlling the direction of flow of the motive fluid through said first and second conduits, a pipe connecting the chamber on the extension side of each hydraulic cylinder, excepting said last one, with the corresponding chamber in the next adjacent hydraulic cylinder in the series, a first valve in said pipe connecting the chamber on the extension side of each hydraulic cylinder to the corresponding chamber of the next adjacent hydraulic cylinder, said first valve being adapted to be closed for preventing flow of the motive fluid from the first hydraulic cylinder side to the last hydraulic cylinder side, and opened for permitting flow of the motive fluid in either direction through said pipe, said first valve being normally closed, a pipe connecting the chamber on the retraction side of each hydraulic cylinder, excepting the last one, with the corresponding chamber in the next adjacent hydraulic cylinder in the series, a second valve in said pipe connecting the chamber on the retraction side of each hydraulic cylinder to the corresponding chamber of the next adjacent hydraulic cylinder, said second valve being adapted to be closed for preventing flow of the motive fluid from the last hydraulic cylinder side to the first hydraulic cylinder side, and opened for permitting flow of said motive fluid in either direction through the last-named pipe, said second valve being normally closed, means actuated to open the valve in the pipe connecting chambers on the first conduit which corresponds to retraction side, when the hydraulic cylinder of first cylinder side between the chambers to which the said valve corresponds is extended to its extremity, and means actuated to open the valve in the pipe connecting chambers on the second conduit which corresponds to extension side, when the hydraulic cylinder of first cylinder side between the chambers to which the said valve corresponds is retracted to its extremity; whereby, the boom can extend from its first member side successively and retract from its last member side likewise.