US3045850A - Dual fork lift attachment - Google Patents

Description

July 24, 1962 1.. E. CARR ETAL DUAL FORK LIFT ATTACHMENT 2 Sheets-Sheet 1 Filed Oct. 17, 1960 a 7 T r W .5 m m. 5 a [70W /r 5 z 4 W, l a a; w d B M NW/ 1 J/ :4 I n a a a; 1 2 4M w July 24, 1962 CARR ETAL 3,045,850

DUAL FORK LIFT ATTACHMENT Filed Oct. 17, 1960 2 Sheets-Sheet 2 N V EN TORS. 100/; 124

3,045,850 Patented July 24, 1962 3,045,850 DUAL F0131; LEFT ATTACHMENT Louis E. Carr, Qedarhurg, and Daniel C. Jones, Port Washington, Wis, assignors to Koehring Company, Miiwaukee, Win, a corporation of Wisconsin Filed Oct. 17, 1969, Ser. No. 63,141) Claims. ((31. 214-626) The present invention relates to material handling equipment and, in particular, lift attachments for use with mobile power units such as trucks or other vehicles.

It is a general object of the present invention to improve the operation and increase the versatility of lift loaders of the type having an extensible mast.

Another object is to provide a lift attachment for loaders which has a pair of load supporting devices to enlarge the useful range of work of loaders of the present type.

A further object is to increase the outward and vertical reach of a platform or fork lift device over that available with conventional mast type loaders. A related object is to increase the load handling capacity of such loaders and fork lifts.

A more detailed object of the present invention is to provide a fork lift attachment having an extensible mast and a pair of forks in which the forks are movable through a given range independently of each other to handle a great variety of materials. It is also an object of the present invention to provide a fork lift which can elevate a load for a given distance without extending the lifting mast.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings, in which:

FlGURE 1 is a perspective of a dual fork lift attachment embodying the present invention which is illustrated mounted on a mobile truck, the latter being shown in dashed outline;

P16. 2 is a side elevation of the attachment of FIG. 1 illustrating two positions of the second or boom lift fork; and

FIG. 3 is a perspective of the attachment of FIG. 1 with the rigid carriage and the boom fork in lowered position.

While the invention will be described in connection with a preferred embodiment, it will be understood that we do not intend to limit the invention to that embodiment. On the contrary, it is the intention to cover all equivalents and modifications which may be included within the spirit and scope of the invention as defined by the appended claims.

Referring now to the illustrated embodiment of the invention of the drawings, a lift attachment is there shown mounted on one end of a wheeled truck 11. In general description, the attachment 10 comprises a vertical mast 12 supported on the truck 11 by a transverse pivot pin 14 which passes through the lower end portion of the mast 12 and has its ends supported by transversely spaced brackets 15 rigidly mounted on the truck 11. To maintain the mast 12 in an upright position and provide limited forward and aft angular adjustment of the mast with respect to the vertical, an hydraulic ram '16 is positioned to interconnect an upper joint on the truck 11 with a point on the mast 12 above the support pin 14. Lengthening the adjustment ram 16 swings the mast 12 forwardly as for loading and unloading and retracting the ram 16 pulls the upper end of the mast 12 rearwardly over the truck 11 for greater stability in transporting the load from place to place.

The mast 12 itself may be of conventional form, having extensible sections. The particular form of mast of the drawings comprises a series of three telescoping, interfitted, elongated box sections. The largest box section 18 forms the top section, the smallest, 19, the bottom section, and the middle sized box section 20, the intermediate section of the mast. An hydraulic ram means (not shown) of conventional construction is employed in the illustrative attachment for raising the top and intermediate sections to extend the mast.

Supported on the top section 18 of the mast is a carriage 22 mounted on the forward side of the mast for vertical movement relative to the top section. The carriage 22 comprises a pair of vertically spaced transverse back bars or members 23, 24, rigidly interconnected by a pair of transversely spaced vertical guide brackets 26 fixed to the rear side of the back bars 23, 24.

Maintaining the carriage 22 in position relative to the mast 12 to prevent forward and sidewise swing, as well as to guide the carriage in an up and down path parallel to the forward side of the mast are cooperating guide means on the mast and carriage. For this purpose, the mast has an elongated rib 27 which provides clearance for a lift chain (not shown) and also forms an elongated guideway or track extending lengthwise of the front side of the mast 12. The rear face of the mast 12 forms guideways or tracks on either side thereof having a guide face directed toward the rear of the attachment.

Cooperating with the tracks are front and rear rollers 23, 29 on the carriage 22. The front carriage roller 28 is relatively short to correspond to the width of the front guideway or track 27 on the mast and is supported by a transverse axle pin 31 received in holes in the upper ends of a pair of transversely spaced brackets 32. The front roller brackets 32 are of generally triangular outline and secured to the central portion of the upper one of the transverse carriage bars 23. The two rear rollers 29 (only one shown) are positioned to engage the rear side of the top section 18 of the mast 112 and are supported on pins 33 which are journaled in the upper rear corners of the vertical guide brackets 26 on the carriage 22. The guide brackets 26 are more or less triangular in outline and extend rearwardly from the carriage 22 along opposite sides of the mast 12 to locate the upper rear corner of each bracket behind the back edge of the top section of the mast and thus support the rear rollers in position to engage the rear sides of mast section 18.

The carriage is further supported by tension means which lifts or elevates the assembly relative to the mast upon extension of the mast sections. For this purpose a pair of roller link chains 36, one on each side of the front guide ribs 27, are connected to the carriage assembly 22 on opposite sides of the front roller support brackets 32. An outer run of chain extends upwardly along the front of the top section 18 and is trained over transversely spaced sprockets 37 journaled at the top of the section 18. The sprockets are positioned such that an inner run of the roller chain proceeds downwardly on the inside of the top mast section 18 behind the front wall of the section and is connected to the intermediate section 2% (not shown). The roller chain 36 has a length approximately equal to the length of the top section 18 so that as the top section and consequently the sprockets 37 move upwardly with respect to the next lower section of the mast, the outer run of chain is shortened to compensate for the increasing length of the inner run, thus lifting the carriage assembly 22 along its guides or tracks. When the top section 18 of the mast is completely raised, the carriage 22 is also raised to the top of the mast 12 and, conversely, when the top section 13 is completely lowered relative to the intermediate section 20, the carriage 22 is at its lowest point on the top section.

'In carrying out the present invention, a dual lift or load 3 supporting means is provided to increase the versatility of the attachement. For this purpose a first lifting device illustrated in the form of a lift fork 39 is mounted directly on the carriage 22. This first or carriage fork 39 comprises a pair of transversely L-shaped tines 4t} positioned with their bottom or foot portions 42 extending forwardly from the mast and carriage and their upright or leg portions '43 extending upwardly in front of the mast and carriage. The two tines 40 are interconnected and supported on the carriage by Welding or otherwise fastening the leg portions 43 to the transverse back bars 23, 24 of the carriage. in use the tines 40 are usually placed under a pallet or similar load support and the lift truck 11 is driven forwardly until the load rests against the back bars 23, 24 of the carriage. The carriage 22 is then lifted to raise the load as desired. Should it be desirable in transporting the load to tilt the mast 12 rearwardly for greater stability, the back bars 23, 24 of the carriage prevent the load from sliding into the mast 12.

The second lifting device of the dual lift means of the present invention is adapted to rest in its lowered position immediately in front of the first portion formed by the carriage fork 3%. The second portion in the illustrated construction also comprises a fork 45 which is supported on an hydraulically actuated boom 46. In the illustrative embodiment of the invention, the boom and boom fork are mounted on the carriage to be raised and lowered thereby. To accomplish this, the lift carriage 22 has two uprights or boom supports 47 fixed to the back bars 23, 24, one upright being spaced outwardly on each side of the mast to provide a stable base. Each of the uprights comprises a pair of parallel, upright plates 43, 49 relatively closely spaced to each other and having their lower forward edges rigidly fixed, as by welding, to the rear face of the carriage back bars 23, 24. The plates 48, 49 extend upwardly and rearwardly to the rear of the back edge of the mast 12. Extending between each set of support plates 48, 49 and pivotally connected to the upper end portion of the plates by a transverse pivot pin 51 is the rear end of a rigid boom arm 52. As seen in FIG. 2 of the drawings, the pivotal connection 51 permits each of the two boom arms 52 to swing upwardly and downwardly for lifting and lowering the boom fork assembly 45.

The boom fork assembly 45 comprises a pair of rigid L-shaped tines 54 interconnected by upper and lower back bars 55, 56 rigidly fixed to the upright legs 57 of the tines 54 at vertically spaced positions. The bottom or foot portions 58 of the tines 54 extend forwardly from the attachment in the same direction as the foot portions 42 of the carriage fork 39. To support the boom fork 45 on the forward end of the boom 46 a lug 60 and connecting pivot pin 61 are provided on the lower back bar 56 for receiving and pivotally connecting the forward end of each boom arm 52. Preferably, the lugs 60 are spaced transversely from each other a distance equal to the spacing between the upright boom supports 47 on the carriage 22 for maintaining the boom arms 52 in substantially parallel relation. To strengthen the boom 46 against relative twisting and side sway, rigid struts 62 are interposed between the boom arms 52 at spaced intervals. In the illustrated attachmeint of the drawings, two such struts 62 are shown connected at their ends to the respective boom arms 52.

'In order to maintain the boom fork level during swing of the boom, a leveling link in the form of a tension member or rod 64- is provided. Preferably, two such tension rods 64 are used, one above each boom arm 52.

Each of the rods 64 is pivotally connected at its rear end to an upward extension 65 on the outer one of the boom support plates 49.

The pivotal connection is made by a shackle 66 adjustably connected as by screw threads to the rear end of the rod 64, and by a pivot pin 67 which passes through the shackle 66 and an aperture in the support plate extension 65. The forward end of each rod 64 is pivotally con nected to the upper back bar 55 of the boom fork assembly by means of a transverse pin 68 and rearwardly extending lugs 69 fixed to the upper back bar. By substantially vertical alinement of the rear and forward pivotal connections, respectively, of the leveling links 64 and boom arms 52, a parallelogram linkage is formed which maintains the boom fork 45 substantially level as it is raised and lowered by swing of the boom 46.

In further carrying out of the invention, means are provided to give free lift to the boom fork 45 relative to the carriage fork 39 and mast 12. For this purpose, hydraulic ram means is provided to swing the boom 46 about its pivotal support 51. To accomplish this, an hydraulic ram 71, preferably of the double acting type, is mounted under each boom arm 52 to exert an upward push on the arm at a point forwardly of its support pivot 51. As seen in the drawings, each ram 71 is positioned between a respective set of upright support plates 43, 49 having its lower or cylinder end 72 pivotally supported near the lower end of the plates at "73 and its upper or rod end 74 pivotally connected to the corresponding boom arm 52 by a lug or shackle 75 fixed to the underside of the arm. A transverse pin 76 having its ends received in suitable apertures in the upright plates 48, 4-9 forms the lower pivotal connection for the ram 71 and a similar pivot pin 77 passing through the shackle 75 and end of the piston rod '74 forms the upper connection.

By actuating the hydraulic ram 71 the boom fork 45 may be raised or lowered as desired relative to the mast 12 and the carriage form 39. To supply pressure fluid to the boom rams '71 at all elevations of the mast, a pair of hydraulic conduits or hoses 80, in the case of a double acting ram, are provided for each ram. To prevent tangling of the hoses 80, a pulley arrangement is utilized to support and keep them straight at all elevations of the mast and carriage. Positioned on each side of the upper end of the top section 18 of the mast are two double grooved pulleys 81, 82 supported side by side on a transversely extending shaft 83 fixed to the mast. The pair of hoses extends upwardly from suitable couplings 84 on the truck 11 which contains the pressure fluid supply (not shown) over one of the two pulleys 81, each hose lying in one of the grooves. The hoses then proceed downwardly, under and around a freely suspended double grooved pulley 85, from there upwardly over the second of the upper double grooved pulley 82, and finally downwardly to the hydraulic ram 71. Hoses for the other of the boom rams are trained in like fashion over identical supported pulleys 81, $2 and under an identical freely suspended pulley 85.

By means of the foregoing pulley arrangement for the hoses 859, the freely suspended pulley 85 by its own weight keeps the hoses taut but is free to move upwardly toward the supported pulleys 81, 82, playing out hose as the mast is extended, and to move downwardly to take up hose as the mast is retracted. If desired, the free pulley 85 may be provided with vertical guide means of any well known form to eliminate sidewise swing of the pulley as the lift truck is moved about.

In the operation of a lift device embodying the present invention, it will be apparent that the dual load supporting means may be used together or individually, thus increasing both the capacity and range of types of work which can be done. For example, the boom fork 45 may be raised by means of the boom rams 71 and a load placed on the carriage fork 39. The boom fork 45 may then be lowered and a second load placed on it for simultaneously transporting and lifting two loads. For this purpose, the pivotal connections 51 are positioned substantially above the carriage 22, and the boom is of sufficient length to locate the boom fork ahead of the carriage fork giving space for holding a load on the carriage fork and at the same time actuating the boom fork 45. It is also noted that with the present load lifting device the hydraulic rams, including the upper pivotal connections of the rams 71, are located behind the carriage to free the carriage fork of any obstruction in loading it.

Also increasing the versatility of the present device is the placing of the boom fork not only ahead of the carriage fork, but also below the carriage fork, when the boom is in its lowest position. Preferably, the boom fork when so positioned is slightly below the surface on which the supporting vehicle is standing. By this arrangement, the boom fork may be used to lift loads which are resting directly on the ground or which are actually below the ground upon which the wheel truck 11 rests.

In addition to concurrent use of both forks to lift separate loads of materials, the position of the boom and boom supporting means permits the boom to be used as a hold-down for large bulky loads on the carriage fork. This is accomplished by raising the boom While loading the carriage fork and then lowering the boom until it rests on the top of the material underneath.

The present loader is capable of other advantageous uses, representative of which are placing loads carried by the boom fork above the highest point of the mast and also forwardly of the mast such as across a trench or through an opening too narrow for the vehicle to enter.

We claim as our invention:

1. A lift attachment for use on a vehicle having a source of pressure fluid comprising, in combination, an extensible mast having elongated, relatively slidable sections including a top section, said mast being adapted to be mounted on said vehicle in a substantially vertical position, a carriage, means for guiding said carriage for movement longitudinally of said top section, means for raising said carriage relative to said top section, a first lift fork mounted on and carried by said carriage and extending forwardly from said mast for movement with said carriage, a second lift fork positioned forwardly of said first lift fork, a boom having its outer end portion pivotally connected to said second load supporting means and having its inner end portion pivotally connected to said carriage at a point upwardly and rearwardly of said first lift fork thereby permitting simultaneous loading of said first and second lift fork, and hydraulic ram means positioned behind said first lift fork and connected at its ends to said carriage and said boom respectively for swinging said boom and second lift fork upwardly relative to said carriage to raise said second lift fork upwardly and forwardly of the top of said top mast section.

2. A lift attachment for use on a vehicle having a source of pressure fluid comprising, in combination, an extensible mast adapted to be mounted on said vehicle in a substantially vertical position and having elongated, telescoping sections including a top section overfitting the next lower section, a carriage having a pair of transverse vertically spaced bars and a pair of vertical plates rigidly interconnecting said bars and extending rearwardly along the sides of said top section of the mast, a front roller mounted centrally of said upper transverse bar and rear rollers mounted on the rear end portions for said vertical plates for engaging the front and back sides respectively of said top section for guiding said carriage for movement longitudinally of said top section, chain means connected to said carriage for raising said carriage relative to said top section upon extending said top section relative to the next preceding mast section, a first lift fork carried by said carriage and extending forwardly from said mast for unison movement with said carriage, a second lift fork for positioning the latter forwardly and below said first lift fork, a boom having its inner end portion pivotally connected to said carriage at a point upwardly and rearwardly of said first lift fork for vertical swing and having its outer end portion connected to said second lift fork for positioning said second lift fork forwardly and below said first lift fork when said bottom is in lowered position, and hydraulic ram means interconnected between said carriage and said boom for swinging said boom and second lift fork upwardly relatively to said carriage to raise said second lift fork above and forwardly of said top mast section when the said carriage is in raised position.

3. A lift attachment for use on a vehicle having a source of pressure fluid comprising, in combination, a mast having elongated, telescoping sections of relatively slidable interfitting box shape and including a top section overfitting the next lower section, said mast being adapted to be mounted on said vehicle in a substantially vertical position, a carriage having front and rear rollers positioned to engage the front and back sides respectively of said top section for guiding said carriage for movement longitudinally of said top section, means connected to said carriage for raising said carriage relative to said top section upon extending said top section relative to the next preceding mast section, a first load supporting means carried by said carriage and extending forwardly from said mast for unison movement with said carriage, a second load supporting means positioned forwardly of said first load supporting means, a boom having its outer end portion pivotally connected to said second load supporting means and having its inner end portion pivotally connected to said carriage at a point upwardly and rearwardly of said first load supporting means, and hydraulic ram means interconnected between said carriage and said boom at a point on said boom outwardly of said inner end portion for swinging said boom and second load supporting means upwardly relative to said carriage to permit loading of said first load supporting means and for raising said second load supporting means above and forwardly of the top of said top mast section.

4. A load lifting attachment for use on a vehicle having a source of pressure fluid comprising, in combination, a mast adapted to be mounted on said vehicle in a substantially vertical position, and having a plurality of relatively movable sections including a top section for extending and retracting said mast, a carriage on the forward side of said top section, means for moving said carriage up and down along said top sect-ion, a first lift fork carried by said carriage, a vertical support bracket positioned on opposite sides of said mast, each of said support brackets including a pair of vertical, transversely spaced support plates having the lower forward side thereof fixedly connected to said carriage for unison movement therewith, said support plates having an upper end portion projecting upwardly and rearwardly of said carriage, a boom assembly including a pair of transversely spaced arms having their inner end portions extending between, and pivotally connected to, the upper end portions of respective pairs of said support plates for vertical swinging movement of said boom, a second lift fork pivotally supported on the outer ends of said arms, said boom arms extending forwardly and downwardly in the lowered position of said boom to position said second lift fork forwardly and below said first lift fork, an hydraulic ram positioned between each pair of the support plates and having its end portions pivotally connected to the support plates and corresponding boom arm respectively for raising and lowering said lift fork relative to said carriage and said mast, and leveling means including a tension member interconnecting an upper portion of said second lift fork and an, upper extension on said support bracket for maintaining said second lift fork substantially horizontal upon swinging of said boom.

5. A load lifting attachment for use on a vehicle having a source of pressure fluid comprising, in combination, a mast adapted to be mounted on said vehicle in a substantially vertical position and having a plurality of relatively movable sections including a top section for increasing and decreasing the length of said mast, a carriage on the forward side of said mast having a pair of tranrsverse vertically spaced bars and a pair of vertical transversely spaced plates interconnecting said bars, first and second vertical support brackets positioned on opposite sides of said mast, each of said support brackets including a pair of vertical, transversely spaced support plates having their forward sides fixedly connected to the carriage bars for unison movement with said carriage, said support plates having an upper end portion projecting upwardly and rearwardly of said carriage, a boom assembly including two transversely spaced boom arms, each of said arms having its inner end portion positioned between the upper end portions of a corresponding pair of said support plates and pivotally connected thereto for vertical swinging movement of said boom, a lift fork pivotally supported on the outer ends of said arms, a pair of hydraulic rams positioned respectively between said pairs of support plates, each of said rams having its lower end portion pivotally supported by said support plates and its upper end portion connected to the corresponding boom arm for raising and lowering said lift fork relative to said carriage and said mast, and a tension member pivotally connected at its end portion between an upper portion of said lift fork and an upper extension on said support bracket for maintaining said fork substantially horizontal upon swinging 'of said boom.

References Cited in the file of this patent UNITED STATES PATENTS

Images