US3647325A

US3647325A - Concrete pump

Info

Publication number: US3647325A
Application number: US721343A
Authority: US
Inventors: Frederick S Johnson
Original assignee: CONSOLIDATED CONCRETE Ltd
Current assignee: CONSOLIDATED CONCRETE Ltd
Priority date: 1968-04-15
Filing date: 1968-04-15
Publication date: 1972-03-07
Anticipated expiration: 1989-03-07

Abstract

A concrete pump having a pair of cylinders fed from a common hopper and pumping into a common outlet. An inlet valve in the hopper and an outlet valve in the outlet are actuated by piston and cylinder assemblies which in turn control the movement of the concrete pumping pistons in the cylinders.

Description

United States Patent Johnson 1 Mar. 7, 1972 [541 CONCRETE PUMP 2,957,4'30 10/1960 Naff ..103/170x 3,279,382 10/1966 Bennett.. ..103/49 1 lnvenm Frederick Johnson Calgary Alberta, 3,279,383 10/1966 Smith ..103/227 Canada 3,326,135 6/1967 Smith ..103/49 [73] Assignee: Consolidated Concrete Limited, Chinook 3,327,641 6/1967 Kloslerman-u- Mun/49 Qmtep calgarygAlbenafcanadggwpartim 3,398,693 8/1968 Schomann ..103/49 terest Primary Examiner-William L. Freeh 221 Filed: Apr. 15, 1968 Anomgf Kent Ade 21 A LN .1 721 43 l 1 pp 57 ABSTRACT 52 US. Cl ..417/508, 417/454, 92/244, A P having a P cylindm fed fwm 417/533 mon hopper and pumping into a common outlet. An inlet 51] 1111. c1 ..F04b 39/68, F04b 15/02, F04b 23/04 valve in the hopper and an Outlet valve in the Outlet are [58] Field 61 Search ..103/49, 153 c, 227 c, 170; ated by Piston and cylinder assfimblies which in mm control 230/223; 417/508, 454 533 92/244 the movement of the concrete pumping pistons in the cylindets.

[56] References Cited sclaims, 0p UNITED STATES PATENTS 2,677,581 5/1954 TQXIOILJL .,..,...92 244 221 E /2 F E 24 7 F- i [HI I I PAIENTEDHAR 1 mm 3,647. 325

SHEET 1 [IF 4 ,2 V c HYDRAUL/C 83 84 POWER SUPPLY 313, 84' I'- PILOT L/GHT/ REMOTE TOGGLE I SWITCH ll liL l'l GOVERNOR II I: I I06 I07 COIL GOVERNOR RELAY v CAM OPERATED mum/T SWITCH l 1- #54 HYDRAULIC 2 H6 SOLENOID TWO POSITION 4 5 I02 TOGGLE SWITCH (REVERS/NG SWITCH) 2.2L EL /2 E 207 I"; f- I H Ii? T F 26A 7 204 a 5:? if??? I f E 34A 36A PATENTEUHAR 7 I972 SHEET 3 [1F 4 CONCRETE PUMP This invention relates to new and useful improvements in concrete pumps.

Theprincipal essence of the invention is to provide a device of the character herewith described which enables concrete to be fed from a common hopper alternately into a pair of concrete pumping cylinders situated side by side, control being by novel feed valve assembly. The two concrete pumping cylinders feed into a common discharge conduit and a simple discharge valve assembly is also actuated to receive the concrete from the two cylinders alternately.

Another object of the invention together with the foregoing object is to provide a device of the character herewithin described which is fluid operated and which furthermore, utilizes the fluid pressure to change the length of the pumping stroke thus minimizing the difficulties due to plugging or jamming of the concrete pump.

A yet further object of the invention is to provide a device of the character herewithin described in which the head end of the assembly including the hopper, feed valve assembly, and discharge conduit with the discharge valve assembly, is pivotally mounted to the pumping portion so that it can be swung to one side thus enabling access to the interior of the pumping portion and to the valve assembly for cleanout and maintenance purposes. This eliminates the necessity of stripping down or dismantling the entire pump assembly which is usual with conventional concrete pumps.

A yet further object of the invention is to provide a device of the character herewithin described in which there is no possibility of contamination between the hydraulic fluid and the concrete, the two being separated by water carrying a lubricant for the pistons.

Still another object of the invention is to provide a device of the character herewithin described in which the construction of the concrete pumping piston reduces considerably any danger of grit or gravel remaining between the flexible seals of the walls of the cylinder thus reducing wear.

Still another object of the invention is to provide a device of the character herewithin described which is easy to maintain, which pumps concrete with the minimum change of direction of the concrete, and which is otherwise well suited to the purpose for which it is designed.

With the foregoing considerations in view, and such other objects, purposes or advantages as may become apparent from consideration of this disclosure and specification, the present invention consists of the inventive concept which embraces or includes the method, process, construction, arrangement of parts, or new use of any of the foregoing, as herein particularly exemplified in one or more specific embodiments of such concept, reference being had to the accompanying figures in which:

FIG. I is an electrical schematic diagram of the operating portion of the device.

FIG. 2 is a schematic view of the fluid pressure portion of the device.

FIG. 3 is a fragmentary top plan view of the head end portion swung away from the pumping portion.

FIG. 4 is a view similar to FIG. 3, but with the head end portion clamped in operating position.

FIG. 5 is an end view of the head end portion per se, substantially along the line 5-5 of FIG. 3.

FIG. 6 is a side elevation of FIG. 4.

FIG. 7 is a top plan viewof the device segmented in part to show the interior thereof.

FIG. 8 is a side elevation of the device.

FIG. 9 is a top plan view of the concrete pumping components sectioned in part. 1

FIG. 10 is an enlarged fragmentary view of one portion of the concrete piston.

In the drawings like characters of reference indicate corresponding parts in the different figures.

Proceeding therefore to describe the invention in detail, reference should first be made to FIGS. 7 and 8 in which reference character 10 illustrates generally, supporting framework taking the form of a pair of spaced and parallel longitudinally extending frame members.

The device collectively designated 11 is situated between these frame members 10 and comprises a pumping unit which consists generally of a pair of concrete pumping components collectively designated [2 and 13 situated in side by side relationship and being fed from a common concrete supply hopper 14 extending upwardly from the forward ends thereof. These concrete pumping components feed concrete to a common discharge conduit 15 situated upon the other side of the hopper 14, it being understood that concrete may then be conveyed by conduit to the location where it is needed.

An hydraulic fluid reservoir I6 is supported upon the framework above the concrete pumping components together with a water tank 17 and fluid reservoirs l8 and I9 are secured one to each of the longitudinal side members 10.

Each of the concrete pumping components l2, 13 of the pumping unit 11 consists of a

concrete pumping cylinder

20, 20A consisting of sleeves held between a common rear plate 21 and a front plate 22 in the usual manner and having main seals 23 provided, said main seals also being conventional.

Extending concentrically upon the other side of rear plate 21 are actuating

cylinders

24, 24A connected to a source of fluid pressure, the details of which are shown in FIG. 2 and which will subsequently be described.

Piston rods

25, 25A are provided for each of the pairs of

cylinders

20, 24 and 20A, 24A, it being understood that these pairs of cylinders are concentrically located on a common axis. Inasmuch as the construction of the two piston and cylinder assemblies are similar, similar reference characters have been given, but are distinguished by the fact that all of the components of concrete pumping components 13 are followed by the letter A.

On the forward end of piston rod 25A, there is provided a piston collectively designated 26A, the details for which are shown in FIGS. 9 and 10.

The end 27A of the piston rod 25A is screw threaded and receives an anchor nut 28A. Next, a rear or back plate 29A is screwed onto the end 27A with nut 30A secured thereto, to facilitate this screw threading action. Following this disc 29A is a rear flexible disc or cup 31A, then a spacer disc 32A, a further spacer disc 33A, and a front flexible disc or cup 34A held in place by a front disc 35A all of which is clamped by means of front nut 36A screw-threadably engaging the end 27A. This nut 36A clamps the entire assembly together against the anchor portion 28A. Also of note is the piston ring 37A held by spacer disc 32A.

The flexible discs or

cups

31A and 34A are preferably made of synthetic rubber or the like and are provided with an annular recess 38A on the rear side thereof adapted to receive the annular rim 39A formed on the front sides of the

spacer discs

32A and 33A respectively. Also of note is the rear side rim 40A of the

discs

29A and 35A clearly shown in FIG. 10.

This configuration is of importance inasmuch as when the piston is on the return stroke (to the left with reference to FIG. 9) the flexible disc 34A is permitted to roll out towards the axis of the cylinder as shown in phantom in FIG. 10, around the perimeter of disc 35A, thus allowing particles of sand or the like to dislodge. The opposite action takes place with the flexible cup or disc 31A when the piston is moving in the opposite direction. This means that the only cleaning action required is the metal piston ring 37A situated around the spacer 32A. These spacers serve to align and contain the piston ring 37A and back up the

flexible discs

31A and 34A. Furthermore, the disc 35A acts as a piston front plate and a threaded cover 41A is screwed onto the extremity of the screw-threaded portion 27A to protect the thread from damage while in contact with concrete during the pumping operation.

Any sediment that does pass this piston and is cleared by the action of the flexible cup or disc 31A, will be carried to the lubricating fluid reservoir 19 to settle out and this sediment together with any hydraulic oil which may have leaked from the actuating

cylinders

24 or 24A can be drained off periodically.

Conduits

42 and 42A connect the reservoirs l8 and 19 to the

concrete pumping cylinders

20 and 20A respectively as shown in FIGS. 7 and 8, it being understood that these conduits connect to the cylinders on the rear side of the

pistons

26, and 26A, the rear side being defined as the sides to the left of the pistons with reference to FIG. 9.

The

piston rods

25, 25A pass through apertures in the rear plate 21 and into the

cylinders

24 and 24A respectively, hydraulic seals 43A preventing the passage of hydraulic fluid past these rods and into the concrete cylinders.

Conventional

hydraulic pistons

44 and 44A are secured to the ends of these piston rods within the

cylinders

24 and 24A respectively, these pistons being shown schematically in FIG.

The portions of the concrete pumping components consisting of the front plate 22, the

cylinders

20 and 20A,

cylinders

24 and 24A, and the piston and piston rod assembly therewithin, form what is defined as the pumping portion of the concrete pumping components.

Reference to FIGS. 3 and 4 show the head end portion collectively designated 45 of the

concrete pumping components

12 and 13 of the pumping unit 11. This head end portion includes a mounting plate 46 pivotally secured by vertical pivot pin 47, to one side of the front plate 22 spanning the

concrete cylinders

20 and 20A. This head end portion is normally clamped into the position shown in FIG. 4 by means of bolt 48 situated opposite to pivot pin 47 as shown clearly in FIG. 4.

This head end portion includes the aforementioned hopper 14, a feed valve assembly collectively designated 49, a discharge valve assembly collectively designated 50, and the common discharge conduit together with the means to actuate the feed valve assembly 49 and discharge valve assembly This hinging attachment of the head end with the majority of the functional components therein, permits the head end to be swung away from the pumping portion so that the interiors of both may be cleaned out after use or made accessible for easy servicing if desired.

The hopper is conventional in configuration having sloping sides 51 converging to a base float 52 and communicating with a base 53. This base in turn communicates with a concrete intake area 54 separated into two portions by a dividing barrier and valve stop wall 55 extending upwardly from the base 56 thereof and shown in FIG. 5. This divides the intake area 54 into two

areas

57 and 57A which align with the aforementioned concrete cylinders 20, A respectively through corresponding apertures (not illustrated) in the front plate 22 of these components. v

Situated within the base 53 is the aforementioned feed valve assembly 49.

It consists of a horizontally situated mounting spindle 58 extending through the walls 59 of the base 53. Secured to the spindle or shaft 58 is an apex boss 60 of a valve element 61 said valve element being defined by a pair of walls 62 extending from the apex or boss 60 at an angle from one another just less than 90. A curved base wall 63 extends between the two walls 62, but inwardly from the ends 64 thereof as clearly shown in FIG. 5.

When in the position shown in FIG. 5, the upper wall 62 engages the sidewall 59 of the base 53 and the lower wall 62 engages the stepped recess 65 on the outer end of the barrier or valve stop 55 so that concrete within hopper 51 can only flow by gravity to the intake area 57 and thus into the concrete cylinder 20.

However, when the valve element is moved through almost 90, the lower wall 62 now engages the opposite wall 59 of the base 53 and the end 64 of the upper wall 62, in turn engages the stepped upper side 65' of the barrier or valve stop 55 so that concrete can now only flow from the hopper 14, to the intake area 57A and thence to the concrete cylinder 20A.

It will be noticed that the base or lower wall 63 of the valve element is spaced from the upper side 66 of the barrier 55 by an amount defining the maximum size of aggregate or stone in the concrete. This prevents any stones or gravel from jamming when the valve is operating thus ensuring that the valve can operate fully from one position to the other without interference.

An hydraulic piston and cylinder assembly 67 extends between a crank arm 68 secured to spindle or shaft 58 and supporting structure (not illustrated), said assembly 67 being connected to the hydraulic system for actuation as will hereinafter be described.

Situated within the discharge conduit 15, is the aforementioned discharge valve assembly 50. This consists of a vertically situated spindle or shaft 69 situated centrally within the discharge conduit and in alignment with the barrier or divider 55. A vertically situated guiding plate 70 (FIG. 4) is secured to the shaft 69 and moves from a position shown in FIG. 4 through the arc indicated by reference character 71. When in the position shown in FIG. 4, concrete can only flow from the concrete cylinder 20, but when moved through the degree of movement defined by are 71, concrete can only flow from concrete cylinder 20A.

An hydraulic piston and cylinder assembly 72 extends operatively between a crank arm 73 secured to shaft 69 and a point of anchoration 74. This piston and cylinder assembly 72 is also connected to the hydraulic system as will hereinafter be described, with reference to FIG. 2.

The hydraulic schematic is shown in FIG. 2 and consists of a pump 75 driven from the power takeoff 76 connected to the source of power indicated by reference character 77.

Fluid is driven by the pump from the reservoir 16, through filters 78 and conduits 79, to outlet conduit 80. Conduit 80 connects to cross conduit 81, one branch of which connects to a four-way directional double solenoid valve 82 which is conventional in construction and is operated by means of

solenoid

83 and 84. r

A return conduit 85 extends from the valve 82, back to return conduit 86, and thence to reservoir 16.

A conduit 87 extends from the valve to a cross conduit 88 which in turn extends between one end of each of the piston and

cylinder assemblies

67 and 72 as clearly shown. Another conduit 89 also extends from the valve to a cross conduit 90 which in turn extends between the other ends of the piston and

cylinder assemblies

67 and 72 so that by switching the valve 82, both of the pistons of the

assemblies

67 and 72 can be moved in the same direction at the same time and then reversed in direction at the same time.

A cross conduit 91 extends between the inner ends 92, 92A of the

cylinders

24, 24A respectively and a conduit 93 extends from this cross conduit 91, firstly to return conduit 86 through one-way valve 94 and secondly, through conduit 95 and oneway valve 96, to conduit 97 which in turn communicates with bypass release valve 98. A further conduit 99 extends from this release valve back to the return conduit 86 and a further conduit 100 extends from this release valve to the aforementioned main conduit 80 from pump 75.

A four-way directional valve 101 is provided with a singleacting solenoid 102 and the other branch 81A of conduit 81 communicates with this valve together with a return branch conduit 86A which in turn communicates with return conduit 86.

A conduit 103 extends also from the valve to one end 104A of the cylinder 24A and a further conduit 105 extends from the valve to one end 104 of the cylinder 24.

Solenoid 102 is normally in the of position under which circumstances the valve 101 is closed.

Valve 82 is normally in the position in which conduit 81 is connected to conduit 85 so that the pump, which is idling under these conditions, circulates fluid from the reservoir, through conduit 81, through valve 82, to conduit 85 and thence back to the reservoir via return conduit 86.

When the pump is to be used, actuation is commenced by the main switch 106 (FIG. 1) or a remote switch 106A. This actuates a l2-volt DC power supply and increases the motor's speed of the source of power by picking up the relay 107 and coil 108 through pressure switch 109, relay 110, ratchet relay 111, so that relay 111A actuates the hydraulic solenoid 84. This switches valve 82 so that conduit 81 connects with conduit 89 and conduit 87 connects with conduit 85 as indicated by the double-headed arrows within the valve box.

This means that oil under pressure flows from the pump, through conduit 81, to conduit 89 and thence to cross conduit 90 thus moving the pistons in

cylinders

67 and 72 upwardly with respect to FIG. 2. This moves the discharge valve 70 to the position shown in FIG. 2 and also moves the feed valve 49 to the position shown in FIG. 2. At the same time, a cam 112 secured to shaft 58, operates a limit switch 113 which is connected to solenoid valve 102 which in turn actuates valve 101. The limit switch is set to operate solenoid 102 only when the piston of cylinder 67 is halfway along the stroke thereof. This means that the majority of the movement of the feed valve 49 and the discharge valve 70 is taking place while the

pistons

26, 26A are stationary thus letting them move with the minimum of interference from the concrete under pressure.

When valve 101 is actuated, conduit 81A connects to conduit 103 and conduit 105 connects to conduit 86A as indicated by the double-headed arrow within valve 101.

Fluid under pressure flows through conduit 103 to one end 104A of cylinder 24A thus moving piston 44A to the right with respect to FIG. 2 or in the direction of arrow 114. This, at the same time, of course, moves piston 26A in the same direction thus forcing any concrete within concrete cylinder A towards the discharge. As this piston 26A moves in the direction of arrow 114, the discharge valve 70 is in the position opposite to that shown in FIG. 4 thus closing off the concrete cylinder 20 and opening the discharge to concrete cylinder 20A. As piston 44A moves forwardly, fluid in front thereof passes through conduit 91 into the end 92 of cylinder 24 thus driving piston 44 to the left with respect to FIG. 2 or in the direction of arrow 115. This, of course, moves piston 26 in the direction of arrow 115 thus creating a vacuum on the side thereof remote to piston 44. As this movement commences, the feed valve is in the position shown in FIG. 5 thus opening the hopper 14 to the intake area 57 and thence to concrete cylinder 20 which fills with concrete in a combination of gravity and suction feed.

As mentioned, fluid flowing through conduit 91 will move piston 44 in the direction of arrow 115 as fluid is kept in line 93 due to the

valves

94 and 96 being closed. Fluid will continue to flow through

conduits

81 and 89 until pistons are at the end of the stroke within

cylinders

67 and 72. From a point halfway along the stroke, this movement has been facilitated by concrete completely filling the respective

concrete cylinder

20 or 20A.

Should piston 44A reach the end of its stroke before piston 44, one-way valve 96 will open allowing a small quantity of fluid to flow from line 97 to line 93. At the same time, fluid in cylinder 24 will return to the reservoir 16 by way of line 105, valve 101 and conduit 86A to 86. The cause of this small amount of fluid loss would be leakage of the front hydraulic cylinder seals or hydraulic lines. A leak in the hydraulic lines or conduits would be detected by visual inspection, but leakage due to seals could be carried off by the lubricating fluid within

cylinders

20 or 20A to the lubricating

fluid reservoirs

18 and 19 so that the hydraulic fluid would not contaminate the concrete within the cylinders.

Should the piston 44 reach the end of its stroke before piston 44A, one-way valve 94 will open and allow a small quantity of fluid to escape through line or conduit 93, one-way valve 94 and thence to the reservoir 16 through conduit 86. This condition would be caused by hydraulic fluid passing worn piston rings in the

main pistons

44 or 44A or by a stoppage of the concrete being pumped, said stoppage commonly being called a plug.

Pressure in the system would increase causing one-way valve 96 to open momentarily thus allowing oil pressure or fluid pressure to build up and at the same time pressure switch 109 would open and close contact in the ratchet solenoid 111A or 1118 thus causing a rapid change of hydraulic fluid flow. This allows the operator time to shut off the

main switch

106 or 106A before damage occurs to the machine.

However, if this is not done, bypass release valve 98 will open and combined with one-

way valves

94 and 96, will allow hydraulic fluid to circulate back to the reservoir 16 through conduits 100, 97, valve 96, conduit 95, valve 94, conduit 99 and thence to 86 to the reservoir.

After the plug or stoppage has been removed or free of itself, the length of the stroke of the

piston

44A or 44 would increase automatically due to the one-way valve 94 allowing fluid to escape as mentioned above until the two pistons are in sequence once again.

With the use of pressure as the method of changing stroke most of the plugging in the pump outlet or main delivery line is eliminated due to the fact that the pumping

pistons

26 and 26A advancing do not have to reach the end of the stroke before hydraulic pressure alternately increases or decreases to free a formation of cross rock or any foreign object.

Once the pistons have reached the end of the stroke as aforesaid, the cycle is reversed by ratchet relay switch 111 switching from 11A to 11B (reversing switch 116 is used only to change cam operated limit switch 113 from normally open to normally closed so that concrete in line can be returned to hopper which is done manually on toggle switch 116 moving from 116A to 11613. This places solenoid 11B in sequence thus actuating hydraulic solenoid valve 83 which causes fluid to flow from conduit 85, through conduit 87 to above the pistons within

cylinders

67 and 72 and to move them downwardly in a direction opposite to that shown in FIG. 2.

Pilot lights

83 and 84 are in circuit with

solenoid valves

83 and 84 respectively so that the operator can ascertain the situation at all times.

Various modifications can be made within the scope of the inventive concept disclosed. Accordingly, it is intended that what is described herein should be regarded as illustrative of such concept and not for the purpose of limiting protection to any particular embodiment thereof, but that only such limitations should be placed upon the scope of protection to which the inventor hereof is entitled, as justice dictates.

What is claimed to be the present invention is:

1. In a concrete pump which includes supporting structure and a source of fluid pressure; a pumping unit comprising a pair of concrete pumping components mounted in side by side relationship on said supporting structure, means operatively connecting said concrete pump components to said source of fluid pressure whereby said concrete pump components are actuated alternately, a concrete holding hopper situated above said concrete pumping components and being operatively connected therewith, a feed valve assembly in the base of said hopper, means to actuate said feed valve assembly whereby concrete flows from said hopper alternately to each of said concrete pumping components, a common concrete discharge conduit operatively connected to the discharge ends of said concrete pumping components, a discharge valve assembly in said discharge conduit, and means to actuate said discharge valve assembly whereby concrete is discharged alternately from each of said concrete pumping components into said discharge conduit, each of said concrete pumping components including a concrete pumping cylinder mounted in said supporting structure, intake means at one end of said cylinder communicating between said cylinder and said base of said hopper, a piston rod having a piston on one end thereof reciprocal in said cylinder, said piston rod extending through the other end of said cylinder, sealing gland means at said other end of said cylinder through which said rod reciprocates, a lubricating fluid reservoir in said framework, said reservoir communicating with said concrete pumping cylinder on the side of said piston remote from said intake means, an actuating cylinder extending rearwardly of and in alignment with said concrete pumping cylinder, the other end of said piston rod reciprocating in said actuating cylinder, piston means on said other end of said piston rod, said actuating cylinder being operatively connected to said source of fluid pressure, and means connecting the pair of actuating cylinders whereby they reciprocate in opposite direction to one another alternately, said piston on said one end of said piston rod including a screw-threaded end portion, a backplate mounted on said end portion, a rear flexible disc against said backplate, at least one spacer disc against said flexible disc, a piston ring around said spacer disc, a front flexible disc against said spacer disc, a front plate against said front flexible disc, and means to clamp the foregoing together on said end portion, said flexible discs being cup shaped and facing in opposite directions to one another, said flexible discs having an annular recess on the rear faces thereof engageable by said spacer disc, said flexible discs having the property of rolling inwardly towards the axis of said piston rod when moving in a nonpumping direction.

2. The device according to claim 1 in which said means to actuate said feed valve assembly includes a fluid-operated piston and cylinder assembly operatively connected to said source of fluid pressure and mounted adjacent said hopper, said piston and cylinder assembly being operatively connected to said feed valve assembly and also being operatively connected to said means to actuate said concrete pumping components.

3. The device according to claim 1 in which said means to actuate said discharge valve assembly includes a fluidoperated piston and cylinder assembly operatively connected to said source of fluid pressure and mounted adjacent said discharge valve assembly, said piston and cylinder assembly being operatively connected to said discharge valve assembly.

4. The device according to claim 2 in which said means to actuate said discharge valve assembly includes a fluidoperated piston and cylinder assembly operatively connected to said source of fluid pressure and mounted adjacent said discharge valve assembly, said piston and cylinder assembly being operatively connected to said discharge valve assembly.

5. A concrete pump as defined in claim 1 wherein said hopper includes a base, and hinged means connecting said hopper base to said pumping unit.

6. A concrete pumping unit as defined in claim 1 wherein said concrete pumping unit is provided with a front end plate having outlet openings therein and a head portion hingedly connected to said front end plate and including said concrete holding hopper, said valve assembly, said concrete discharge conduit and said discharge valve assembly.

7. In a concrete pump which includes supporting structure and a source of fluid pressure; a pumping unit comprising a pair of concrete pumping components mounted in side by side relationship on said supporting structure, means operatively connecting said concrete pump components to said source of fluid pressure whereby said concrete pump components are actuated alternately, and a head portion connected to said pumping unit and comprising a concrete holding hopper situ' ated above said concrete pumping components and being operatively connected therewith, a feed valve assembly in the base of said hopper, means to actuate said feed valve assembly whereby concrete flows from said hopper alternately to each of said concrete-pumping components, a common concrete discharge conduit operatively connected to the discharge ends of said concrete pumping components, a discharge valve assembly in said discharge conduit, and means to actuate said discharge valve assembly whereby concrete is discharged alternately from each of said concrete pumping components into said discharge conduit, each of said concrete pumping components including a concrete pumping cylinder mounted in said supporting structure, intake means at one end of said cylinder communicating between said cylinder and said base of said hopper, a piston rod having a piston on one end thereof reciprocal in said cylinder, said piston rod extending through the other end of said cylinder, sealing gland means at sai other end of said cylinder through which said rod reciprocates, a lubricating fluid reservoir in said framework, said reservoir communicating with said concrete pumping cylinder on the side of said piston remote from said intake means, an actuating cylinder extending rearwardly of and in alignment with said concrete pumping cylinder, the other end of said piston rod reciprocating in said actuating cylinder, piston means on said other end of said piston rod, said actuating cylinder being operatively connected to said source of fluid pressure, and means connecting the pair of actuating cylinders whereby they reciprocate in opposite direction to one another alternately, said piston on said one end of said piston rod including a screw-threaded end portion, a backplate mounted on said end portion, a rear flexible disc against said backplate, at least one spacer disc against said flexible disc, a piston ring around said spacer disc, a front flexible disc against said spacer disc, a front plate against said front flexible disc, and means to clamp the foregoing together on said end portion, said flexible discs being cup shaped and facing in opposite directions to one another, said flexible discs having an annular recess on the rear faces thereof engageable by said spacer disc, said flexible discs having the property of rolling inwardly towards the axis of said piston rod when moving in a nonpumping direction.

8. In a concrete pump as defined in claim 7 hinge means connecting said head portion to said pumping unit.

Claims

3. The device according to claim 1 in which said means to actuate said discharge valve assembly includes a fluid-operated piston and cylinder assembly operatively connected to said source of fluid pressure and mounted adjacent said discharge valve assembly, said piston and cylinder assembly being operatively connected to said discharge valve assembly.

4. The device according to claim 2 in which said means to actuate said discharge valve assembly includes a fluid-operated piston and cylinder assembly operatively connected to said source of fluid pressure and mounted adjacent said discharge valve assembly, said piston and cylinder assembly being operatively connected to said discharge valve assembly.

7. In a concrete pump which includes supporting structure and a source of fluid pressure; a pumping unit comprising a pair of concrete pumping components mounted in side by side relationship on said supporting structure, means operatively connecting said concrete pump components to said source of fluid pressure whereby said concrete pump components are actuated alternately, and a head portion connected to said pumping unit and comprising a concrete holding hopper situated above said concrete pumping components and being operatively connected therewith, a feed valve assembly in the base of said hopper, means to actuate said feed valve assembly whereby concrete flows from said hopper alternately to each of said concrete pumping components, a common concrete discharge conduit operatively connected to the discharge ends of said concrete pumping components, a discharge valve assembly in said discharge conduit, and means to actuate said discharge valve assembly whereby concrete is discharged alternately from each of said concrete pumping components into said discharge conduit, each of said concrete pumping components including a concrete pumping cylinder mounted in said supporting structure, intake means at one end of said cylinder communicating between said cylinder and said base of said hopper, a piston rod having a piston on one end thereof reciprocal in said cylinder, said piston rod extending through the other end of said cylinder, sealing gland means at said other end of said cylinder through which said rod reciprocates, a lubricating fluid reservoir in said framework, said reservoir communicating with said concrete pumping cylinder on the side of said piston remote from said intake means, an actuating cylinder extending rearwardly of and in alignment with said concrete pumping cylinder, the other end of said piston rod reciprocating in said actuating cylinder, piston means on said other end of said piston rod, said actuating cylinder being operatively connected to said source of fluid pressure, and means connecting the pair of actuating cylinders whereby they reciprocate in opposite direction to one another alternately, said piston on said one end of said piston rod including a screw-threaded end portion, a backplate mounted on said end portion, a rear flexible disc against said backplate, at least one spacer disc against said flexible disc, a piston ring around said spacer disc, a front flexible disc against said spacer disc, a front plate against said front flexible disc, and means to clamp the foregoing together on said end portion, said flexible discs being cup shaped and facing in opposite directions to one another, said flexible discs having an annular recess on the rear faces thereof engageable by said spacer disc, said flexible discs having the property of rolling inwardly towards the axis of said piston rod when moving in a nonpumping direction.