US2966227A

US2966227A - Ladder operating apparatus

Info

Publication number: US2966227A
Application number: US656890A
Authority: US
Inventors: Herman J Troche
Original assignee: J H HOLAN CORP
Current assignee: J H HOLAN CORP
Priority date: 1957-05-03
Filing date: 1957-05-03
Publication date: 1960-12-27
Anticipated expiration: 1977-12-27

Description

Dec. 27, 1960 H. J. TROCHE LADDER OPERATING APPARATUS v INVENTOR. HERMAN J. TROCHE 2 Sheets-Sheet 1 ATTORNEYS a;E g

Flled y a, 1957 h. I I li I I 5 [A E 1 y L, a 2 2 w Dec. 27, 1960 H. J. TROCHE 2,966,227

LADDER OPERATING APPARATUS Filed May 3, 1957 2 Sheets-Sheet 2 1N VEN TOR. HERMAN J.TRocHa 361165 TM is 4mm ATTORNEYS United States Patent C) I 2,966,227 LADDER OPERATING APPARATUS Herman J. Troche, Fairview Park, Ohio, assignor to J. H. ghogan Corporation, Cleveland, Ohio, a corporation of Filed May 3, 1957, Ser. No. 656,890

4 Claims. (Cl. 182-66) This invention relates generally to an aerial extension ladder, which is swingable and tiltable with reference to a supporting vehicle or the like to provide access to overhead traflic lights, street lamps and similar objects. The invention is more particularly directed to an improved apparatus for selectively tilting the extension ladder in a vertical plane in either the extended or retracted condition.

The load of an extensible aerial ladder may be counterbalanced to aid an operator in eflectively spotting the ladder assembly at any selected position throughout the tilting range. However, difliculties are encountered in effectively counterbalancing the diflerent loads encountered when attempting to tilt the ladder assembly in extended and retracted conditions respectively. It is therefore a principal object of this invention to provide a ladder tilt ing mechanism which acts independently of the counterbalancing mechanism to permit tilting of the ladder assembly in either its retracted or extended position throughout its tilting range.

Another object of this invention relates to the provision of an improved mechanism for tilting an aerial extension ladder to any selected position throughout its tilting range and for holding it in any attained position regardless of variations in load on the ladder assembly.

Briefly, in accordance with this invention an extensible aerial ladder is pivotally connected adjacent its lower extremity for tilting movement in a vertical plane on top of a rotatable mast and includes a mechanism for counterbalancing the ladder in its retracted condition throughout its tilting range. An independent tilting mechanism in the form of a fluid actuated lift piston coacts between the mast and the extensible ladder to independently tilt the ladder throughout its tilting range in response to the actuation of a manually operated fluid pump. Although the lift piston is single acting in the direction of tilting movement, it includes a check valve arrangement for controlling the flow to and from the lift piston cylinder to selectively lock the piston in any attained position and thereby forestall uncontrolled tilting movement of the ladder assembly due to variations in the load applied to the ladder. The mechanism includes a manually actuated device for releasing the fluid lock on the lift piston to permit uncontrolled lowering of the ladder from any tilted position. The pump includes means for adjusting its stroke to permit an increased application of fluid pressure to the lift piston when the ladder is extended without increasing the effort required by the operator.

In the drawings:

Fig. l is a partial rear view of a utility vehicle supporting the extensible aerial ladder of this invention;

Fig. 2 is an enlarged perspective view of the ladders tilting mechanism in relation to the supporting mast and the extension ladder environment which are shown in dotted lines;

Fig. 3 is a side elevation of the mast and the ladder ladder;

Fig. 4 is a front elevation of the mast;

Fig. 5 is a diagrammatic illustration of the fluid control system for the ladder tilting mechanism; and

Fig. 6 is an enlarged view of a portion of the pump handle assembly.

Referring now more particularly to Fig. 1 of the drawings, the ladder assembly is shown as being mounted upon a vehicle chassis 10 and is of the extensible type, there being an upper section 11 and a lower section 12 mounted telescopically with respect to each other in the customary manner; the upper section 11 being extendable or retractable within the lower section 12. The entire ladder assembly is supported on the vehicle chassis 10 for swinging movement in a horizontal plane and for tilting movement to any desired angle in the vertical plane Within its operating range.

As best shown in Figs. 2 through 4 inclusive, the lower ladder section 12 carries adjacent its lower extremity, a supporting frame 15 which is mounted on a shaft 16 journaled in spaced

brackets

17 and 18 on the upper portion 20 of the rotatable mast. The upper portion 20 of the mast is journaled for rotation on a vertical axis on the lower fixed portion 21 of the mast; rotation being accomplished by means of a crank 23 which rotates a sprocket chain 24 extending about spaced

sprocket wheels

25 and 26, the lower one of which rotates a worm gear 27 that meshes with and travels about a ring gear 28 on the lower portion of the mast. The rotation mechanism, with the exception of the ring gear 28, is carried by the rotatable upper portion 20 of the mast and is easily operated by an operator standing on the floor of the vehicle chassis.

The entire ladder assembly is counterbalanced by means of a coiled spring 30, the lower end of which is anchored to the vehicle floor adjacent the base of the mast and the upper end of which is connected to a cable 31 that extends about a sheave 32 which is rotatably journaled on the upper end of the mast and then anchored at its free extremity to a bracket 33 on the lower section 12 of the ladder frame 15. The counterbalancing spring 30 is designed to counterbalance the load of the ladder assembly when the ladder sections are retracted for any tilted position of the ladder throughout its tilting range. However, the counterbalancing spring is not effective for the increased load when the ladder sections are extended. Tilting of the ladder assembly in a vertical plane is preferably accomplished in accordance with this invention by pro viding a fluid actuated lift piston 35 which operates independently of the counterbalancing spring to positively tilt the ladder assembly in either the retracted or extended condition to any selected position in its tilting range.

The lift piston 35 includes a cylinder 36 whose lower end is pivotally anchored to a bracket 37 extending outwardly from the lower extremity of the upper or rotatable portion 20 of the mast. The free extremity of the piston 35 is bifurcated to pivotally receive a depending dog 38 formed on a bracket 39 which is fixed on a cross member 40 of the ladder supporting frame 15. Thus, when fluid pressure is supplied to the operating end of the cylinder 36, the piston 35 is positioned axially outward and coacts with the supporting frame 15 to tilt the entire ladder assembly in a vertical plane. In its preferred form, fluid actuating pressure is supplied to the lift piston cylinder 36 from a manually operated pump 41 which is also mounted on the rotatable portion 20 of the mast. The pump 41 includes a fluid chamber 42 having a reciprocable piston 43 therein whose piston rod 44 extends external to the chamber and is coupled at its free extremity to a bracket 45 mounted on the lower extremity of a pump handle 46. The pump handle 46 is pivotally supported on a rocker shaft 47 journaled in a bracket 48 on the rotatable portion 20 of the mast. Reciprocation of Ce Patented Dec. 27, 1960;

the pump handle 46 back and 'forth will pump operating fluid from a reservoir T under pressure to a load control valve, indicated generally at 50, which transmits the operating fluid to the lift piston cylinder 36 in a manner to be hereinafter more fullydescribed.

-Referring nowmorefparticularlyito Fig.5 of :the drawings, the lift pistonfiS and the pump 41 :are diagr matically shown oper tively coupled together with the flow control valve and the fluid reservoir "Lin a manner that will permit an operator to spot and .hold the ladder assembly at any tilted position throughout its operating range regardless of'whether the ladder is in the extended or retracted condition. The reservoir T contains a hydraulic fluid such as oil which servesasithe operating fluid in the system and the pump 41 is a conventional double-acting manifold pump with aftwo stage leverage. The lift piston 35 is of the double-acting type whose actuation is controlled by the flow control valve 50 and by a needle type lowering control valve 51 having a torsion spring actuated shut off 57. The life cylinder 36 includes bleeder valves 52 and '53 which are operated to pressuzire the fluid system.

Thus, initially, the system is pressurized by opening an air vent plug 54 on the reservoir T and then actuating the pump handle 46 to extend the lift piston 35 to its maximum height. Then the cylinder bleeder valves .52 and 53 are opened to let trapped air escape, after which the pump is actuated until clear oil flows through the bleeder valves. Thereafter, the bleeder valves are closed and the control valve handle 56 is turned to open the lowering control valve 51 and lower the ladder. The control valve handle 56 is then released, and a torsion spring 57 acts to automatically close the valve. The elevating and bleeding operations may be repea ed until all air has been evacuated from the system. When the lift piston 35 is in its fully extended position, the

cylinder bleeder valves

52 and 53 are closed and the air vent plug 54 on the reservoir is closed. Thereafter, the lowering control valve 51 is opened to lower the ladder and pressurize the system to such a condition that there is a forced feed of operating fluid through the pump.

After the system is pressurized and conditioned for operation, actuation of the pump handle 46 to move the pump piston 43 in the direction A forces operating fluid from the pump chamber 42 through the

check valves

62 and 63 and into the lower chamber 64 of the lift cylinder 36 through passages 66 and 67 to produce an upward force on the lift piston 35. While this is occurring, the operating fluid is forced from the reservoir T into the opposite end of the pump chamber through the check valve 68. The fluid passes through the check valve 69 to the lift cylinder 36 when the travel of the pump piston 43 is reversed. The upper chamber 70 of the lift cylinder 36 is sealed ofl from the lower chamber 64 by 0 rings 71 and 72. Movement of the lift piston 35 starts when the fluid is allowed to escape through a check valve 75. This occurs when the pressure of the fluid from the pump is suflicient to force a differential piston 76 upward to engage and open the check valve 75 and to allow the fluid to flow from the upper chamber 7% to the chamber 64. i ressure of the fluid in the

chambers

76 and 64 is now equal but, because of the difference in the effective areas of the lift piston 35, the piston is forced upward to tilt the ladder assembly vertically. Additional fluid requirements for the lift piston are supplied by continued pumping until the desired elevation of the ladder'assembly is reached.

When a load is imposed on the ladder assembly causing a downward force on the lift piston 35, the pressurized fluid in the lower chamber 64 is automatically increased to equal this load. The differential piston 76 also holds the check valve 75 open because it is forced upward by pressurized fluid passing through the passages 66 and 67 causing a static conditionbetween the cham- '

bers

70 and 64. If the load should suddenly he changed, .as may .occur when .the ladder .is used at higher elevations caused by tugging or pulling operations of the workman tending to cause an upward drift of the ladder, the pressure of the fluid in lower chamber 64 will be decreased to where the check valve 75 would be closed by spring action, thuslocking fluid in the upper chamber 70 and preventing movement of the lift piston 35 to hold the ladder stationary. Unrestricted movement of the differential piston 76 is .maintained by virtue of the air vent 7.8. When the ladder is being lowered and the lowering valve 51 is fully opened, the fluid pressure in the chamber 64 diminishes to an extent where it will not open the check valve 75 and the fluid passes through a check valve 80 to the upper chamber 70. During lowering of the ladder, the fluid from chamber 64 is also being forced into the reservoir T under pressure, thus completing the cycle of operation.

:In the preferred form, the pump 41 is arranged for two speed operation by adjustment of the pump stroke. This is accomplished, as best shown in Fig. 6, by permitting the pump handle to be shifted axially in the supporting bracket 48, :thus .changingthe length of the iorque arm between the rocker shaft 47 and .the bracket 45. The bracket 45 is anchored at the lower extremity by means of a stop plate and locking pin assembly 49 on one side and by a retaining ring 60 on the other side. The handle 46 is provided withaxially spaced notches 61(a) and 61(b) in aportion of .its peripheral surface which selectively engage 'a spring biased key 65 carried by the bracket :48 to hold the .handle in either of two ax al positions. The handle 46 may be disengaged from the key 65 by rotation, whereupon the key .is cammed outwardly by the normal diameter of the handle. A torsion return spring coacts between the lower extremity of the handle 46 and the stop-plate to cause an autom'atic return rotation of the handle after it has been positioned axially. The longer stroke of the pump when the handle 46 is lowered pumps the operating fluid more rapidly for fast elevation of the ladder assembly. H gh pressure pumping for changing the ladder elevation when the ladder is extended is accomplished by shortening the stroke of the pump when the handle 46 is in its upper position.

Thus, there has been provided ,a controlled mechanism for tilting an extensible ladder assembly in a vertical plane and for positively holding the ladder assembly in any attained position regardless of the extended condition of the ladder or of changes in the load acting on the ladder. The holding action of the tilting mechanism is independent of a counterhalancing spring which is effective only when the :ladder is in retracted condition. The tilting mechanism is fluid actuated and provides controlled movement of the ladder to and from any tilted position throughout .its operating range.

I claim:

1. In an aerial extension ladder operably mounted on a support for tilting movement in a vertical plane the combination comprising, fluid-actuated means for selectively tilting the ladder in either direction, said latter mentioned tilting means including a cylinder, a doubleacting piston therein having 'a larger piston area at one end than at the other, means for charging the cylinder with operating fluid, means responsive to fluid pressure for normally holding the ladder against tilting movement in either direction, said ladder holding means including normally closed pressure responsive valve means adapted to interconnect opposite ,ends .of said cylinderwhen opened, and means coacting .du-ring actuation of said tilting means to disable said ladder holding means, said disabling means including means for supplying fluid under pressure to the cylinder and to said pressure responsive valve means whereby'the differential piston area will cause movement of the piston in one'direction, and

means for exhausting operating fiuid from the cylinder to permit return of the piston in the other direction.

2. In an aerial extension ladder operably mounted on a support for tilting movement in a vertical plane the combination comprising, fluid actuated means for selectively tilting the ladder in either direction, said latter mentioned tilting means including a cylinder and a double-acting piston therein having a larger piston area at one end than at the other, means responsive to fluid pressure for normally holding the ladder against tilting movement in either direction, and means coacting during actuation of said tilting means to disable said ladder holding means, said disabling means including a pump, a conduit connecting the pump output with the large area end of the cylinder, a normally closed pressure responsive check valve in said conduit to isolate the cylinder from the pump, a second conduit interconnecting opposite ends of the cylinder together, said ladder holding means including a second normally closed pressure responsive check valve in said second conduit adapted to isolate the opposite ends of the cylinder from each other, a third conduit by-passing said second check valve, a third check valve biased in normally closed position in said third conduit, and means operative in response to fluid pressure in said first conduit to open said third check valve.

3. In an aerial extension ladder having one end pivotally mounted on a support for tilting movement in a vertical plane the combination comprising, fluid-actuated means coacting between the ladder and the support for selectively tilting the ladder in either direction, said latter mentioned tilting means including a cylinder, a doubleacting piston therein having a larger piston area at one end than at the other, a pump for charging said cylinder with operating fluid, means responsive to fluid pressure for normally holding the ladder against tilting movement in either direction, said ladder holding means including normally closed pressure responsive valve means adapted to interconnect opposite ends of the cylinder when opened, disabling means coacting during actuation of said tilting means to disable said ladder holding means, said disabling means including means for supplying fluid under pressure to the cylinder and to said pressure responsive valve means whereby the difierential piston area will cause movement of the piston in one direction, means for exhausting operating fluid from the cylinder to permit return of the piston in the other direction, and other means for independently counterbalancing the ladder in retracted condition throughout its tilting range.

4. The apparatus of claim 3 wherein said independent counterbalancing means includes a coiled spring coacting between the ladder and the support, said spring having a loading sutficient to counterbalance the extension ladder in retracted condition.

References Cited in the file of this patent UNITED STATES PATENTS 865,951 Seagrave Sept. 10, 1907 983,212 Dahill Jan. 31, 1911 1,550,550 McCauley Aug. 18, 1925 1,955,154 Temple Apr. 17, 1934 1,979,041 Lundskow Oct. 30, 1934 2,635,430 Hodges Apr. 21, 1953 2,654,524 Humpal et al Oct. 6, 1953 2,663,150 Dolch Dec. 22, 1953 2,742,216 Arps Apr. 17, 1956 2,864,543 Troche Dec. 16, 1958