US3570033A - Dockboards - Google Patents

Abstract

IN A DOCKBOARD, ESPECIALLY DOCKBOARDS OF THE "ADD-ON" TYPE THE EFFORT REQUIRED FOR MANUAL HANDLING OF THE BOARD IS REDUCED BY DIVIDING THE BOARD LONGITUDINALLY WHEREBY THE TWO PARTS ARE MOVABLE INDEPENDENTLY BY THEIR OWN MANUAL HANDLING MEANS, ALTERNATIVELY OR IN ADDITION THE BOARD IS PROVIDED WITH A COUNTERBALANCE SPRING COMPRISING A TORSION BAR HAVING TWO GENERALLY PARALLEL PORTIONS CONNECTED TO ONE ANOTHER, SUCH A SPRING GIVING THE NECESSARY COUNTERBALANCE FORCE OVER THE RELATIVELY WIDE ANGLE OF MOVEMENT REQUIRED OF THE DOCKBOARD.

Description

March. 16, 1971 p HQVESTAD ETAL 3,570,033

DOCKBOARDS 2 Sheets-Sheet 1 Filed April 28, 1969 10 I5 14 3O 2O 31 INVENTORS. m a: 25192 W I PATENT AGENTS 'FIGB FIG.2

March 16, 1971 HOVESTAD ET AL 3,570,033

DOCKBOARDS 2 Sheets-Sheet 2 Filed April 28, 1969 INVEN'IORS.

ADRIAN P. HOVESTAD JOHN A. MERRICK BY PATENT AGENTS United States Patent O 3,570,033 DOCKBOARDS Adrian P. Hovestad, 1044 Shepherds Drive, Burlington, Ontario, Canada, and John A. Merrick, .40 Oak Ave., RR. 1, Dundas, Ontario, Canada Filed Apr. 28, 1969, Ser. No. 819,607 Int. Cl. B65g 11/00 US. Cl. 14-71 Claims ABSTRACT OF THE DISCLOSURE FIELD OF THE INVENTION This invention is concerned with improvements in or relating to dockboards, that is to say boards of the type used in connection with a transport loading dock to bridge the gap between the dock and a transport immediately adjacent thereto. The invention is concerned especially but not exclusively with dockboards of the kind described as add-ons, in that they are intended to be readily at tached to and removed from an existing dock.

DESCRIPTION OF THE PRIOR ART Dockboards are now commonly used in the transport industry and range in complexity from a single metal sheet that is dragged into position when required, to a massive motor-operated board with an automatically extended pivoted lip. In many transport operations there is a need for a simple, inexpensive manually-operable, pivoted-lip board that can readily be attached to and removed from an existing dock without requiring substantial modification of the dock, or causing appreciable damage thereto. The usual minimum overall width for such a board in North America is about 36 inches, while a common width is 66 inches, and the usual minimum extension to bridge the space between the dock and the transport is about 28 inches. A minimum practical thickness for the plate or plates constituting the board, even with the use of high structural steel is about /s inch, so that such boards are usually relatively heavy, in the range of about 200-250 pounds.

Such a board usually requires the exertion of a force in the range of 70-90 pounds for its manipulation, but it is desirable that the board should be operable by a single man, preferably by the exertion of a force constituting not more than about 4050 pounds direct pull, both for ease of manipulation and also to ensure such manipulation without undue physical strain. To this end it has been proposed hitherto to provide the board with a spring counterbalance, for example by means of a crank arm mounted on the base plate and rotated by a torque spring mounted around the crank arm.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a new dockboard.

It is a specific object to provide a new dockboard of the add-on kind.

It is a more specific object to provide a new dockboard comprising a spring counterbalance of new form.

Patented Mar. 16, 1971 In accordance with the present invention there is provided a dockboard comprising a base member adapted to be fastened to a dock, a main plate hinged to the base member about a respective first hinge axis, and a counterbalance spring comprising a torsion bar having two generally parallel longitudinal portions, one end of one bar portion being operatively engaged with the said main plate, a corresponding end of the other bar portion being anchored relative to the said base member, and the other two ends of the bar portion operatively connected together for transmission or torque between them.

Preferably, a lip plate is hinged to the said main plate about a respective second hinge axis generally parallel to the first axis.

Also in accordance with the present invention there is provided a dockboard comprising a base member adapted to be fastened to a clock, two separate main plates disposed side by side immediately adjacent one another and hinged to the base member about respective coaxial first hinge axes, two separate lip plates each hinged to a respective main plate about a respective second hinge axis, whereby each main plate and its associated lip plate is movable independently of the other main and lip plates and both said main and lip plates can be disposed sideby-side to constitute a substantially continuous extension of one another, and manual means for each main and lip plates for manipulation thereof independently of the other main and lip plates.

DESCRIPTION OF THE DRAWINGS Particular preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:

FIG. 1 is a perspective view of a dock showing a dockboard which is a first embodiment of the invention, mounted thereon and in operative loading position,

FIG. 2 is a similar view to FIG. 1 with the main and lip plates of the dockboard removed to show the construction of the counterbalance spring,

FIG. 3 is a section generally on the line 3-3 of FIG. 1,

FIG. 4 is a view similar to FIG. 1 showing a dockboard which is a second embodiment of the invention, and

FIG. 5 is a view similar to FIG. 2 of the embodiment of FIG. 4.

Similar parts are given the same reference number in all the figures of the drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 1 to 3, there is illustrated therein a dock providing a flat, horizontal elevated face 10, and a vertical face 11. A transport which has been backed up to the clock for loading and/or unloading is represented by flat truck bed 12 (shown in broken lines). The dockboard illustrated herein as a particular embodiment of the invention is of the so-called add-on" kind and comprises a fiat, steel base plate member 13 which is bolted, screwed, welded or otherwise fastened by means which are not shown, to the vertical front face 11 of the dock. The upper edge of the base member is joined to the rear edge of a steel main plate 14 by means of a conventional piano type hinge, so that the plates are pivoted together about a respective horizontal first hinge axis provided by a pin 15. A lip plate 16 in turn has its rear edge hinged to the front edge of the main plate by a similar hinge about a horizontal second hinge axis provided by a pin 17 parallel to the said first axis. The two ends of the pin 17 extend beyond the side edges of the main and lip plates and may be provided with enlarged heads 18.

The two plates 14 and 16 each pivot freely about their respective hinge axis, so that they are urged downward by their own weight. The downward movement of the main plate -14 is limited by its engagement with the upper edges of a. plurality of spaced horizontally-extending brackets 19 fastened to the base plate 13. In its downward position the plate 14 is inclined slightly downward below horizontal, so that the dockboard is readily usable with transports having a bed just below dock level. In the absence of a transport 12, or some equivalent surface on which to rest, the lip plate 16 hangs vertically downward in a stored position illustrated in FIG. 3. Two boxlike spacing structures 20 are mounted at respective ends of the base plate, and each mounts a resilient bumper 21 that extends beyond the dockboard in its stored position (see FIG. 3) and protects it against damage while in this position by impact or other contact with a rearwardly-moving transport.

Two flexible chain members 22, each having a handle 23 at one end, have their other ends fastened respectively at 24 to the two front corners of the lip plate 16, and are used by an operator for manhandling the dockboard. Although two chain members are illustrated, it will be apparent that one only need be provided, or they may be used alternatively by a single operator. Thus, with the dockboard in the position shown in FIG. 3 one or both of the chain members are engaged over the top of the protruding ends of the hinge pin 17, and pulled upwards; the board will rise up in the right-angle attitude shown with considerbly less physical effort than if it were in the extended position shown in FIG. 1. With the front edge of the lip plate above the level of the truck bed the board can be lowered in any convenient manner into the extended position shown in FIG. 1. When the board is to be returned to the stored position one or both of the chain members 22 is engaged beneath its respective hinge pin end as illustrated in broken lines in FIG. 1, and an upward pull exerted thereon; this pull causes the plates to fold backwards about the hinge pin 17 until the front edge of the lip plate is clear of the truck bed 12, when the board can be lowered to the stored position.

In this embodiment a counterbalance force to reduce the pull forces that must be applied by the operator to the selected member 22 is provided by a folded torsion bar spring indicated generally in FIG. 2 by the reference 27. This spring comprises straight longitudinal portions 28 and 29 which are disposed generally parallel to one another. One end part 30 of the portion 28 is turned generally at right angles to the said portion, and the free end 31 of the part 60 is also turned to provide a relatively smooth curved surface for operative engagement with the underside of the main plate 14. Such a selfprovided bearing surface is found to be quite adequate, the rubbing friction between the bar and the plate being reduced by a suitable lubricant. The bar portion 28 passes transversely of the dockboard through a mounting 32 fastened to the bracket 19 nearest the portion 30, and then through a retaining bracket 33 fastened to the next bracket 19, its other end is connected to the immediately adjacent end of the portion 29 by an integral looped connecting portion 34. The portion 29 passes back transversely of the dockboard through the bracket 33 and then through a mounting 35 closely adjacent the mounting 32. The end 36 of the portion 29 is cranked at right angles and rests upon a stop member 37. The counterbalance force provided by the spring 27 can be adjusted by vertical adjustment of either one or both of the mountings 32 and 35, their connections to the brackets 19 being such as to permit this vertical adjustment. Other means for such adjustment can of course be provided.

It will be appreciated by those skilled in the art that the counterbalance spring means 27 disclosed are especially simple and inexpensive, in that the spring is formed by bending and suitably heat-treating a plain single length of rod. Attempts to provide a torsion bar spring with only one portion 28 or 29 have not been suc cessful in this particular application, in that the rounded end part 31 must be capable of rotation through about -120". If the rod is of sufficiently small diameter to flex through the desired angle then, because of the need to restrict its length to less than the width of the dockboard, the counterbalance force it can provide is too small for practical purposes. A rod which is of sufficiently large diameter to provide the necessary counterbalance force is either too stiff to flex the necessary amount and may disengage from the board in its upper position, suddenly and perhaps dangerously increasing the force that must be provided by the operator, or provides too much force in its lower positions so that the board cannot be lowered onto the transport. The folded torsion bar spring disclosed herein provides counterbalance force which is within the required limits over the full range of movement required. More than two portions 28 and 29 can be provided as necessary, all of the portions being operatively connected together, and it is not necessary for the portions to be of the same length.

In the embodiment illustrated in FIGS. 4 and 5 the manual force required for manipulation of the board is effectively halved by dividing the dockboard longitudinally, so that it comprises two separate main plates 14a and 14b disposed side-by-side immediately adjacent to one another and hinged to the base member about respective second hinge axes provided respectively by separate hinge pins 17a and 17b. Each main plate and its lip plate is movable independently by the respective manual means constituted by the respective chain 22 and bandle 23. In operative position resting on the transport bed the two main plates and the two lip plates are disposed side-by-side to constitute substantially a continuous extension of one another.

An added advantage of the dockboard of FIGS. 4 and 5 is found with transports having relatively narrow doors or gates. Thus, when such a transport is at the dock only one door or gate need be opened and the corresponding part of the dockboard placed in operative position, while the other dockboard part is left in stored position. It will be understood that the dockboard could be divided into more than two parts, provided that manual handling means are provided for each part.

If the forces required for manhandling of the divided dockboard are still larger than is desired, then each part can be provided with a respective torsion bar counterbalance spring means, the spring means of one part being able to extend beneath the other part if necessary, so that the desired counterbalance characteristic can be obtained. In this particular embodiment each of the two spring means 27a and 27b is illustrated as a separate folded torsion bar spring, the corresponding parts 28 to 32, and 34 to 37 of the two Springs being distinguished by use of the sufiixes a and b as required, and the torsion spring of one dockboard part extending beneath the other dockboard part.

What we claim is:

1. A dockboard comprising a base member adapted to be fastened to a dock, a main plate hinged to the base member about a respective first hinge axis, and counterbalance spring comprising a torsion bar having two generally parallel longitudinal portions one end of one bar portion being operatively engaged with the said main plate, a corresponding end of the other bar portion being anchored relative to the said base member, and the other two ends of the bar portions being operatively connected together for transmission of torque between them.

2. A dockboard as claimed in claim 1, wherein the portion of the torsion bar operatively engaging the main plate is an integral portion thereof turned to provide a curved smooth surface engaging the under face of the main plate.

3. A dockboard as claimed in claim 1, wherein the said two ends of the torsion bar spring means are operatively connected by an integral portion of the bar.

4. A dockboard as claimed in any one of claims 1 to 3, and comprising a lip plate hinged to the said main plate about a respective second hinge axis generally parallel to the first axis.

5. A dockboard as claimed in any one of claims 1 to 3, and comprising two separate main plates disposed sideby-side immediately adjacent one another and hinged to the base member about respective coaxial first hinge axes, two separate lip plates each hinged to a respective main plate about a respective Second hinge axis, whereby each main plate and its associated lip plate are movable independently of the other main and lip plate, and both said main and lip plates can be disposed side-by-side to' constitute a substantially continuous extension of one another, and manual means for each main and lip plates for manipulation thereof independently of the other main and lip plates.

6. A dockboard as claimed in claim 5, wherein each main plate and its respective lip plate are provided with a respective counterbalance spring means.

7. A dockboard as claimed in claim 6, wherein the counterbalance spring means for each main plate and lip plate extends beneath the other main and lip plates.

8. A dockboard comprising a base member adapted to be fastened to a dock, two separate main plates disposed side-by-side immediately adjacent one another and hinged to the base member about respective coaxial first hinge axes, two separate lip plates each hinged to a respective main plate about a respective hinge axis, whereby each main plate and its associated lip plate are movable independently of the other main plate and lip plate, and both of the said main plates and lip plates can be disposed side-by-side to constitute a substantially continuous extension of one another, and manual means for each main plate and lip plate for manipulation thereof independently of the other main plate and lip plate.

9. A dockboard as claimed in claim 8, wherein each main plate and its respective lip plate is provided with a respective counterbalance spring means.

10. A dockboard as claimed in claim 9, wherein the counterbalance spring means for each main plate and its respective lip plate extends beneath the other main plate and its respective lip plate.

References Cited UNITED STATES PATENTS 2,639,450 5/1953 Rarner 1471 2,750,609 6/1956 Jaseph 14-71 2,871,505 2/1959 Clark 16-180 3,006,008 10/ 1961 Loomis 147 1 3,288,522 11/1966 Norton 14-71X 3,314,094 4/1967 Moyer 1471 3,426,377 2/1969 Beckwith 14--71 3,486,181 12/1969 Hecker 14-71 NILE C. BYERS, 1a., Primary Examiner

Images