US 3260534 A
Description (OCR text may contain errors)
R. E. KNIGHTS July 12, 1966 PALLET TRUCKS 5 Sheets-Sheet 1 A@ n4 MN NNWN R. E. KNIGHTS PALLET TRUCKS July 12, 1966 5 Sheets-Sheet 2 Filed Jan. 24, 1964 July l2, 1966 R. E. KNlGH-rs PALLET TRUCKS' 5 Sheets-Sheet 5 Filed Jan. 24, 1964 United States Patent O 3,260,534 PALLET TRUCKS Robert Edgar Knights, Basingstoke, England, assignor to Lansing Bagnall Limited, Basingstoke, England, a British company Filed Jan. 24, 1964, Ser. No. 340,088 Claims priority, application Great Britain, J an. 31, 1963, 4,076/ 63 1 Claim. (Cl. 280-43.12)
This invent-ion comprises improvements in or relating to pallet trucks.
A pallet truck is a Itruck intended for picking up pallets in a works and conveying them with their load mounted on them to another place in the works. Such a truck normally comprises a pair of yiiat fork arms which are attached at their root ends to a transverse body portion of the truck containing mechanism for raising and lowering the body relatively to the ground and a ground 'wheel which can be steered. From the mechanism within the body there extend, within the fork arms, links which operate rockers at the free ends of the `fork arms, on which rockers are ground rollers; when the body of the truck is raised the rockers are operated to raise the free ends of the fork arms correspondingly. The rollers at the free ends of the fork arms are sometimes called trail wheels.
Normally the fork arms are of an inverted channelshaped section (which permits easy assembly of the links within them) and they are made from heavy-gauge steel sheet. It is the indeavour of the designer to keep the depth of the fork arms in a vertical direction as small as possible because this enables the arms to be more easily ru-n under pallets.
It has now been found that if the fork arms are made in the form of a box-section the depth can be reduced without loss of strength, in spite of the extra space taken by the additional thickness of metal beneath the links, but -in that case the assembly of the links in the fork arms offers a problem.
According to the present invention the free ends of the fork arms are made as separate elements which are secured to the main body of the fork arms in a readily detachable manner.
This has the advantage in the case of the box-section arms of permitting assembly of the linkage endwise through the fork arms while the outer end elements are detached, the detachable elements being fitted in place afterwards. It has the further advantage with arms of the normal type, as well as with the box-section arms, of
permitting ready replacement of the tips of the arms or the substitution of a different shape of tip to suit different operational requirements. The free ends normally become damaged more quickly and therefore the replacement -aspect of the invention is a valuable one in practice. Furthermore, the free end, if made replaceable can be made of a hard-working material such as the material known as S.G. Iron, ywhich is a spheroidal-graphite type of cast iron.
The following is a description, by way of example, of one construction in accordance with the invention:
In the accompanying drawings,
FIGURE 1 is a side elevation of a pallet truck in accordance lwith the invention;
FIGURE 2 is a more detailed side elevation to a larger scale;
FIGURE 3 is a vertical section through the tip of a fork arm upon the line -3-3 of FIGURE 4;
FIGURE 4 is a plan of the part of the construction shown in FIGURE 3, and
FIGURE 5 is a section upon the line 5-5 of FIGURE 2 looking in the direction of the arrows.
A pallet truck is provided of which the body portion 11 stands up above the level of the fork arms 12 at the root end and contains a mechanism which includes a jack 13 and ram 14 (FIGURE 2) for raising and lowering the body 11 and a turntable mounting 15 for a steering wheel 16, coupled to a steering handle 17 which provides not only guidance but also a support for push-button or other controls for the propulsion of the truck. A casing 17 surrounds the drive mechanism for propelling the wheel 16. These parts are well known and do not require detailed description.
There are two parallel fork arms 12, side by side near ground level, which are made shallow and of a boxshaped section as shown in FIGURE 5, Ithe top and bottom surfaces of the box-sectioned arm being stiffened by a central vertical web 22 which extends longitudinally and unites the top and bottom faces of the arm together. In manufacture the arm is made of two pai-rs of at plates 23, 24 which are united together by welding upon the lines 25, 25 after the web 22 has been located in place. The sides of each arm are formed by side plates 28 welded to the top and bottom plates 23 and 24, and on each side of the central Iweb 22 :there 'are rectangular spaces 29 for the passage of link members 26.
lToward the free end of each fork arm 12 the top and bottom plates of the arm are discontinued but the side plates 28 of the box-section are extended onward parallel with one another by means of extension pieces 27 at each side of the arm, welded to the plates 28 and the extensions have the same depth as the main portion of the arm but are slightly thinner, as can be seen in FIGURE 4. The central web 22 is also extended beyond the top and bottom of the arm but to a shorter distance. A long hinge pin 30 extends through the side members 27 and the central web 22 horizontally and on it are pivoted hinge portions of a lever 31, best seen in FIGURE 3, which extends towards the free end of the arm and is itself forked and carries between its free ends a horizontal pivot pin 32. On the pivot pin 32 there swings a bogie member 33 which carries two rollers 34, 35 to run on the yioor, one roller 35 between the pivot pin 32 and the main body of the truck and the other roller 34 on the opposite side of the pivot Ipin 32. These two rollers take the place of the normal single roller of a pallet truck fork arm and as there -are two of them they can be made of somewhat smaller diameter, which helps in keeping the total depth of the construction to the minimum.
The lever 31 which carries the bogie is, at the end where it is hinged to the fork arm, of approximately the same depth as the minimum distance between the top of the fork arm and the ground so that it runs in the normal position with its lower surface 37 just above the ground and its upper surface in line with the top of the fork arm. Above its hinge pin 30 it carries pin joint members 38 for connection to the two links 26 which extend through the two hollow spaces 29 within the fork arm 12 towards the main body `of the truck. These links themselves are forked towards their rear end and they are connected to pivot pins 39 ('FIGURE'Z) on a powerful operating lever 40 within the main body of the truck.
The operating lever has one downwardly depending arm 41 which is connected to the links and a more or less horizontally extending arm 42 which is connected by a pin 43 to the lifting mechanism of the truck body. The result is that when the tr-uck body is lifted (by depressing the ram 14 of its lifting mechanism relatively to the body 11) the links 26 are pushed outward along the fork arms and the bogie 33 is depressed in each lfork arm relatively to the arm so that the free end of the fork arm is lifted to th same extent as the body of the truck.
The rollers 34, 35 on the bogie 33, in the normal running position of the arm, have their upper edges nearly 3 tangential with the upper surface of the fork arm, as seen in FIGURE 2 and FIGURE 3, and thus they have the maximum diameter which is compatible with the dimensions of the arm.
Above the bogie hinge pin 32 and around the roller 34 there extends a nosepiece 45 for the fork arm, which is detachable. This nosepiece is pierced at 46 to allow the roller 34 on the bogie, which it overlies, to have space for running land it is held by strong set screws 47 on to each of the vertical side members 27 of the fork arm 12.
When assembling the parts the nosepiece 45 is detached and the links 26 can `be pushed through the open free end of the fork arm 12 towards the body of the truck without difliculty. When the various hinge pins and pivots are in place the nosepiece 45 can be screwed down. Round-ended or inclined-'sided or other shapes of nosepiece can be provided as desired and all made interchangeable for fitting on the fork arms by the set screws 47.
A pallet truck having in combination a body, supporting means for the body including a ground-wheel, means for lifting the body relative to the ground wheel, boxsection fork-arms projecting from the body close to ground level, a lever at the outer end of each fork-arm, which lever supports a pivoted cradle carrying a pair of rol-1ers for moving on the ground and two longitudinally movable push-rods within each fork-arm, which pushrods are connected to the said means for lifting the body and to the said lever supporting the pivoted cradle, whereby forward movement of the push-rods effected by lifting the body will lift the fork-arms from the ground, the construction of each fork-arm comprising top and bottom faces made of two pairs of at plates, two side plates and a central web which subdivides the arm into two cham-bers, each chamber housing one of the pushrods, and unites the top and bottom faces together, the web being united to each face by a run of weld that also unites the two plates of that face together, the runs of weld thereby being located on the outside of the web, and the side plates of the arm extending forwardly beyond the top and bottom faces and the central web to provide an extended portion for location of the aforesaid lever supporting the pivoted cradle, which lever extends across the full width of the space between the side plates.
References Cited by the Examiner UNITED STATES PATENTS 2,682,350 6/1954 Garrett 214-750 X 2,796,186 6/1957 Arnot ZBO-43.12 X
3,183,989 5/1965 Trusock et al. 280-43-12 X FOREIGN PATENTS 1,056,722 3/1954 France.
BENJAMIN HERSH, Primary Examinez'.
C. C. PARSONS, Assistant Examiner.