US3572802A

US3572802A - Fork loader with lift-controlled enclosure

Info

Publication number: US3572802A
Application number: US683239A
Authority: US
Inventors: Viktor Zupancic
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-11-15
Filing date: 1967-11-15
Publication date: 1971-03-30
Anticipated expiration: 1988-03-30

Abstract

A fork loader has a wire-net enclosure giving access to a lifting fork when the latter is in its normal, unloaded state. A clevis articulated to the head of the fork, at an acute angle to the axis of a pneumatic cylinder rigid with the fork, acts through a plunger upon an air cushion in the cylinder when the clevis is lifted by a crane while the fork is weighted down by a load. The free end of the plunger thereupon releases a sickleshaped arm on the pivotal shaft of a swingable front part of the enclosure whereby that part is allowed to drop down in front of the pallet, being subsequently locked in place by a pair of pins released from a withdrawn position by a further advance of the plunger into engagement with a spring-loaded camming lever.

Description

United States Patent Primary Examiner-Andres H. Nielsen Att0rney-l(arl F. Ross ABSTRACT: A fork loader has a wire-net enclosure giving access to a lifting fork when the latter is in its normal, unloaded state. A clevis articulated to the head of the fork, at an acute angle to the axis of a pneumatic cylinder rigid with the fork, acts through a plunger upon an air cushion in the cylinder when the clevis is lifted by a crane while the fork is weighted down by a load. The free end of the plunger thereupon releases a sickle-shaped arm on the pivotal shaft of a swingable front part of the enclosure whereby that part is allowed to drop down in front of the pallet, being subsequently locked in place by a pair of pins released from a withdrawn position by a further advance of the plunger into engagement with a springloaded camming lever.

52 57 57 87 1 5/ j a: I x l n O I I I 60 V/ "'PATENIEU M R 30 ml SHEET 1 BF 2 INVENTOR.

VIKTOR ZUPANCIC SS (QM 6RD Attorney FORK LOADER WITH LIFT-CONTROLLED ENCLOSURE My present invention relates to a fork loader of the type wherein a lifting fork has a pair of depending prongs terminating in generally horizontal tines designed to engage a. load such as a pallet used for the transportation of goods.

The general object of my invention is to provide means for automatically lowering an enclosure, such as a wire-net cage, around the load when the latter is being gripped by the fork for hoisting with the aid of a crane.

This object is realized, pursuant to the present invention, with theaid of a connecting member, specifically a plunger guided in a pneumatic cylinder, which is movably secured to the head portion of the fork and is biased into a normal position from which it can be displaced into an off-normal position, against the force of the biasing means represented by an air cushion in the cylinder, upon the exertion of a lifting force on aghoisting means such as a clevis engaging this connecting member; a mobile front part of an enclosure such as a wire cage,v normally retracted to give access to'the load-engaging -.prongs of the fork, is linked with'a transmission element, such as a curved camming arm, which is engageable by the connecting member in its normal position to hold the front part of the cage retracted while enablingthis-part to descend forwardly of the load upon the lifting of the weighted fork by the aforementioned hoisting means.

According to another feature of my invention, the fork is provided withdetent means suchas a, pair of locking pins normally held in a withdrawn position provided with actuating means, such as a camming lever, engageable by'the connecting member upon the disengagement thereof from the transmission element for the mobile cage part to releasethe detent means in order to latch that part in a swung-down position.

The above and other features of my invention will be described in greater detail hereinafter with reference to the accompanying drawing in which:

FIG. I is an axonometric view of a loading device embodying my invention, shown in an unloaded position .with the front part of its protective cage upwardly retracted;

FIG. 2 is a longitudinal sectional view of the head portion of a lifting fork forming part of the device of FIG. I,.together with associated elements;

FIG. 3 is a view similar to FIG. 2 but showing the pans in a different relative position;

FIG. 4 is a top view of the assembly of FIGS. 2 and 3 shown partly in section on the line IV-IV of FIG. 2;

FIG. 5 is a side-elevational view, with parts broken away, of a modified lifting fork adapted to be used in the device of FIG. I; and

FIG. 6 is an axonometric view of a detail shown within'the circle VI of FIG. I.

The device illustrated in FIG. 1 comprises, essentially, a lifting fork with a head portion 50- having a pair of divergent prongs 51 depending therefrom, these prongs terminating in two short parallel legs- 52 from which tines '53 extend forwardly for engagement with a loading pallet not shown. The legs 52 of the fork are interconnected by a'brace 54, a similar brace 55 extending across the upper portions of the prongs 51. Two

handles

62 and 63 are respectively secured to these .bracesJ-Iead portion 50, which interconnects the upper ends 61 of the prongs SI in a manner more fully described hereinafter, is engaged by a clevis 74, forming part of a hoisting mechanism, through the intermediary of a connecting member 13 (FIGS. 2-4) constituted by the rod of a plunger whose head 11 is received in a cylinder 1 rigid with fork-portion 50. Clevis 74is suspended via a steel cable 75 from a ring 76 adapted to'be engaged by a lifting device such as a crane Cage portion 82 has a cutout 84 clearing the cable 75 in its upwardly retracted position shown in full lines in FIG. I. The two relatively movable cage portions 8i, 82 have frames BI, 83 interlinked with the wire netting thereof.

The connection between the fork 50-53 and the rear part 81 of the cage includes, in addition to the tubes 57, a pair of tubes 56 extending laterally outwardly from the legs 52 in line with the brace 54 and terminating in a pair of cheek plates 44 (FIG. 6), the frame 81 of cage portion 81 being gripped by hooked straps 46 secured to these cheek plates by bolts 45. Also supported on plates 44 are a pair of locking pins 43 biased outwardly by springs 42 within tubular housings 41, the inner ends of the pins 43 being connected to respective tension cables 36 which pass around rollers 37 toward the head portion 50 of the fork. The upper ends of cables 36 are secured to a pair of arms 35 whose other extremities are rigid with a shaft 3|, FIGS. 24, which is pivotally mounted in head portion 50 and also carries a camming lever 32 urged by a spring 34 into a position in which the arms 35 tension the cables 36 to hold the pins 43 withdrawn againstthe force of their loading springs 42. The lower rear comers of the three-sided cage portion 81 forms seats'87 engageable by the pins 43 upon a slackening of cables 36 as more fully described hereinafter. Angle plates 85 at the upper rear corners of this cage portion are secured to the projecting ends of pivotal shaft 57 by connecting tabs 85. As seen in FIGS. 2 and 3, shaft 57' is offset fromthe axis of cylinder 1, i.e., from the direction of movement of plunger 13.

As best seen in FIGS. 2 and 3, shaft57' carries a cam 59 in the form of a sickle-shaped arm having a hub 58 clamped onto said shaft. Plunger I3 is connected through a cross-pin IS with a pair of side bars 27 whose'rear ends are interconnected bya .pin 28 supporting a deflecting roller 29. An air cushion 6 in cylinder I bears upon a piston 2 freely movable within that cylinder, this piston in turn acting through an oil column 14 upon the head 11 of plunger 13. With the plunger 13 unstressed by the clevis 74 as illustrated in FIG. 2, the pressure of air cushion 6 tends to maintain the roller 29 in contact with arm 59.

The ends of cylinder I are sealed by

plugs

7 and 9, the latter being traversed by the rod 13 while the former is provided with an air inlet in a valve in a nose 8. Piston 2 comprises a pair of discs 3 interconnected by a mounting bolt 4 and serving to hold a pair of packing rings 5 in position. A similar packing ring 12 is provided on the circumference of plunger head 11.

The head portion 15 of the lifting fork comprises a pair of angle irons I6'which are interconnected by a tie 17 and are secured to a pair of plates 18 supporting and secured to the overlying ends 6l of prongs 51 as best seen in FIG. I. Brackets 16 are also fastened to a pair of side wings 21 formed with slots 22 which accommodate two pairs of

rollers

24, 26 mounted via

studs

23, 25 on the arms 27 of plunger 13. Studs 23 also serve as pivots for two pairs of

straps

71, 72 which are interconnected by a cross-pin 73 and secured to the lower ends of the arms of clevis 74. A bracket 33, projecting from one of the arms 27, serves as a support for spring 34.

I shall now-describe the operation of the system illustrated in FIGS. I-4 and 6.

In the normal position illustrated in FIG. 2, air cushion 6 is expanded so that piston 2 and, with it, head II of plunger 13 are maintained in their extreme left-hand positions in which the roller 29 at the free end of plunger 13 bears upon the curved arm 59 to hold the cage portion 82 retracted as illustrated in full lines in FIG. I. In this position, the tines 53 of the lifting fork are accessible for engagement with a loading pal let. When the fork is thus weighted down by the load, with its nose 8 pointing upwardly as illustrated in FIG. I, an upward pull upon ring 76 by a lifting crane exerts upon clevis '7 a force in the direction of arrow C, FIG. 3, i.e. at an acute angle to the axis of cylinder I. As a result, a component of the lifting force represented by arrow C acts upon plunger 13 in a sense urging it into cylinder I to compress the air cushion 6 therein,

with concurrent withdrawal of roller 29 from arm 59 whereby the latter is free to swing clockwise (arrow A, FIG. 2) as the mobile cage portion 82 drops down under its own weight in front of the load to occupy the position illustrated in phantom lines in FIG. 1. In this position the seats 87 are aligned with the locking pins 43 which, however, remain retracted until a further inward motion of plunger 13 (to the right in FIG. 3) causes the roller 28 to depress the camming lever 32 against the force of spring 33, thereby slackening the tension cables 36 (arrow B, FIG. 2) sufficiently to let the locking pins 43 enter the seats 87 for latching the front portion 82 onto the rear portion 81 of cage 80. The device of FIG. 1 can now be raised and transported to any desired location where it is set down to relieve the force of gravity acting upon the fork 50- -53 so that the energy stored in air cushion 6 can now return the plunger 13 to its original position; as the roller 28 clears the camming lever 32, spring 34 withdraws the locking pins 43 whereupon the front portion 82 of cage 80 can be raised either manually or by the pressure of roller 28 upon arm 58 to restore the original position.

with the loading device freely suspended from the crane by the ring 76, the direction represented by arrow C is of course vertical. The center of gravity of the load is then vertically aligned with the suspension point represented by the axis of studs 23, as will be well understood. The initial angle between the clevis 74 and the axis of cylinder 1, shown in FIG. 3, is determined by the forward divergence of that axis from the tines 53 as seen in FIG. 1 (cf. also FIG. As the plunger 13 advances from its normal position (FIG. 2) past the intermediate position of FIG. 2 to its working position in which the roller 29 deflects the camming lever 32, the suspension point moves forwardly with reference to the center of gravity of the load.

In FIG. 5 I have shown a modified fork structure in which a fluid chamber 53' lies in the plane of symmetry of the tines 53, one of which is shown partly broken away in the FIG. Blockshaped clamping elements 53" project laterally outwardly toward these tines for gripping engagement with a load. Such an engagement is brought about by the pressure of a hydraulic fluid delivered to chamber 53' through an inlet 99 by a conduit 98 which opens at 97 into a hydraulic cylinder 96 having a piston 95 on a rod 94. A clevis 92 is connected via straps 91 with a cross-pin 93 secured to the free end of piston rod 94 while the cylinder 96 is connected with the head portion 50 of the fork, secured as before to the upper ends 61 of prongs 51, through the intermediary of links 71. Thus, the exertion of an upward force C upon clevis 92, aside from raising the fork head to bring about the aforedescribed swing of cage portion 82, also actuates the clamping means 53".

Iclaim:

I. A loading device comprising a fork with a pair of load-engaging prongs depending from a common head portion provided with elongate guide means; a connecting member movably secured to said head portion by said guide means; biasing means tending to maintain said connecting member in a normal position relative to said head portion; hoisting means engaging said connecting member at an acute angle to said guide means for urging same into an off-normal position, against the force of said biasing means, upon upward movement of said hoisting means with reference to said prongs weighted down by an engaged load; an enclosure for said load including a mobile front part adapted to give access to said load in an upwardly retracted position; and transmission means linked with said front part and engageable by said connecting member in said normal position thereof for normally holding saidfront part in said retracted position while enabling said front part to descend forwardly of the load upon a lifting of the weighted fork by said hoisting means.

2. A device as defined in claim I wherein said guide means comprises a cylinder, said connecting member being a plunger received in said cylinder, said biasing means including an air cushion in said cylinder.

3. A device as defined in claim 2 wherein said plunger has a free end provided with a roller, said transmission means including a pivotal shaft for said front part offset from the direction of movement of said plunger and a cam on said shaft normally in contact with said roller.

4. A device as defined in claim 2 wherein said prongs terminate in a pair of fortines diverging forwardly from the axis of said cylinder whereby the latter is upwardly inclined in a horizontal position of said tines.

5. A device as defined in claim I, further comprising detent means on said fork for latching said front part in its lowered position, and spring-loaded actuating means for said detent means normally holding same in a withdrawn position, said actuating means being positioned for engagement by said connecting member subsequently to disengagement thereof from said transmission means for releasing said detent means from said withdrawn position.

6. A device as defined in claim 1 wherein said hoisting means includes a hydraulic cylinder and piston movable relatively to each other to generate hydraulic pressure upon the exertion of an upward force to a suspension point of said hoisting means, said fork being provided with hydraulic clamping means juxtaposed with said prongs for gripping a load in response to said hydraulic pressure.

7. A loading device comprising a fork with a pair of load-engaging prongs depending from a common head portion; a connecting member movably secured to said head portion; biasing means tending to maintain said connecting member in a normal position relative to said head portion; hoisting means engaging said connecting member for urging same into an offnormal position, against the force of said biasing means, upon upward movement of said hoisting means with reference to said prongs weighted down by an engaged load; an enclosure for said load including a mobile front part adapted to give access to said load in an upwardly retracted position; and transmission means linked with said front part and engageable by said connecting member in said normal position thereof for normally holding said front part in said retracted position while enabling said front part to descend forwardly of the load upon a lifting of the weighted fork by said hoisting means; said hoisting means including a hydraulic cylinder and piston movable relatively to each other to generate hydraulic pressure upon the exertion of an upward force to a suspension point of said hoisting means, said fork being provided with hydraulic clamping means juxtaposed with said prongs for gripping a load in response to said hydraulic pressure.

8. A device as defined in claim 7 wherein said head portion is provided with elongate guide means for said connecting member, said hoisting means being coupled with said connecting member at an acute angle to said guide means.

9. A loading device comprising a fork with a pair of load-engaging prongs depending from a common head portion; a connecting member movably secured to said head portion; biasing means tending to maintain said connecting member in a normal position relative to said head portion; hoisting means engaging said connecting member for urging same into an offnorrnal position, against the force of said biasing means, upon upward movement of said hoisting means with reference to said prongs weighted down by an engaged load; an enclosure for said load including a mobile front part adapted to give access to said load in an upwardly retracted position; transmission means linked with said front part and engageable by said connecting member in said normal position thereof for normally holding said front part in said retracted position while enabling said front part to descend forwardly of the load upon a lifting of the weighted fork by said hoisting means; detent means on said fork for latching said front part in its lowered position; and spring-loaded actuating means for said detent means normally holding same in a withdrawn position, said actuating means being positioned for engagement by said connecting member subsequently to disengagement thereof from said transmission means for releasing said detent means from said withdrawn position.

10, A device as defined in claim 9 wherein said enclosure further includes a rear part fixed with reference to said fork, said detent means comprising a pair of spring-biased locking pins mounted on opposite sides of'said rear part for engagement with corresponding sides of said front part.

11. A device as defined in claim 10 wherein said actuating means comprises a spring-loaded camming lever and flexible link means connecting said levelwith said pins, said transmission means including a pivotal shaft for said front part and a cam on said shaft, said connecting member being provided with a deflecting roller normally in contact with said cam and positioned to engage said camming lever upon disengaging said cam to facilitate a downward swing of said front part.

12. A device as defined in claim 11 wherein said connecting member comprises a plunger, said biasing means including a pneumatic cylinder on said head portion receiving said plunger, said head portion being provided with slotted lateral wings, said plunger carrying said deflecting roller on a free end thereof and being further provided with lateral roller means received in slots of said wings.

Claims

1. A loading device comprising a fork with a pair of loadengaging prongs depending from a common head portion provided with elongate guide means; a connecting member movably secured to said head portion by said guide means; biasing means tending to maintain said connecting member in a normal position relative to said head portion; hoisting means engaging said connecting member at an acute angle to said guide means for urging same into an off-normal position, against the force of said biasing means, upon upward movement of said hoisting means with reference to said prongs weighted down by an engaged load; an enclosure for said load including a mobile front part adapted to give access to said load in an upwardly retracted position; and transmission means linked with said front part and engageable by said connecting member in said normal position thereof for normally holding said front part in said retracted position while enabling said front part to descend forwardly of the load upon a lifting of the weighted fork by said hoisting means.

2. A device as defined in claim 1 wherein said guide means comprises a cylinder, said connecting member being a plunger received in said cylinder, said biasing means including an air cushion in said cylinder.

5. A device as defined in claim 1, further comprising detent means on said fork for latching said front part in its lowered position, and spring-loaded actuating means for said detent means normally holding same in a withdrawn position, said actuating means being positioned for engagement by said connecting member subsequently to disengagement thereof from said transmission means for releasing said detent means from said withdrawn position.

7. A loading device comprising a fork with a pair of load-engaging prongs depending from a common head portion; a connecting member movably secured to said head portion; biasing means tending to maintain said connecting member in a normal position relative to said head portion; hoisting means engaging said connecting member for urging same into an off-normal position, against the force of said biasing means, upon upward movement of said hoisting means with reference to said prongs weighted down by an engaged load; an enclosure for said load including a mobile front part adapted to give access to said load in an upwardly retracted position; and transmission means linked with said front part and engageable by said connecting member in said normal position thereof for normally holding said front part in said retracted position while enabling said Front part to descend forwardly of the load upon a lifting of the weighted fork by said hoisting means; said hoisting means including a hydraulic cylinder and piston movable relatively to each other to generate hydraulic pressure upon the exertion of an upward force to a suspension point of said hoisting means, said fork being provided with hydraulic clamping means juxtaposed with said prongs for gripping a load in response to said hydraulic pressure.

9. A loading device comprising a fork with a pair of load-engaging prongs depending from a common head portion; a connecting member movably secured to said head portion; biasing means tending to maintain said connecting member in a normal position relative to said head portion; hoisting means engaging said connecting member for urging same into an off-normal position, against the force of said biasing means, upon upward movement of said hoisting means with reference to said prongs weighted down by an engaged load; an enclosure for said load including a mobile front part adapted to give access to said load in an upwardly retracted position; transmission means linked with said front part and engageable by said connecting member in said normal position thereof for normally holding said front part in said retracted position while enabling said front part to descend forwardly of the load upon a lifting of the weighted fork by said hoisting means; detent means on said fork for latching said front part in its lowered position; and spring-loaded actuating means for said detent means normally holding same in a withdrawn position, said actuating means being positioned for engagement by said connecting member subsequently to disengagement thereof from said transmission means for releasing said detent means from said withdrawn position.

10. A device as defined in claim 9 wherein said enclosure further includes a rear part fixed with reference to said fork, said detent means comprising a pair of spring-biased locking pins mounted on opposite sides of said rear part for engagement with corresponding sides of said front part.

11. A device as defined in claim 10 wherein said actuating means comprises a spring-loaded camming lever and flexible link means connecting said lever with said pins, said transmission means including a pivotal shaft for said front part and a cam on said shaft, said connecting member being provided with a deflecting roller normally in contact with said cam and positioned to engage said camming lever upon disengaging said cam to facilitate a downward swing of said front part.