Title:
DOCKBOARDS
United States Patent 3662416


Abstract:
A dockboard comprises a main plate hinged at its rear edge to a frame and having a lip plate hinged at its front edge. Upwardly acting springs beneath the main plate are sufficiently strong to move the board upwards in the absence of a weight thereon. A cable is connected between the frame and the board, one end of the cable being wound around a ratchet-controlled reel which holds the board in any position to which it is set; a manually controlled release is provided for the ratchet. The lip plate is automatically elevated as the main plate rises by a snatch chain acting on one end of an articulated linkage which just reaches top dead center as the lip plate reaches the elevated position and locks it in that position. The linkage is mounted to move backward and thereby trip the latch upon an impact applied to the elevated lip, for example by a transport backing into the lip.



Inventors:
Brooks, David (Stoney Creek, CA)
Reteff, Arthur L. (Hamilton, both of Ontario, CA)
Application Number:
05/102442
Publication Date:
05/16/1972
Filing Date:
12/29/1970
Assignee:
SERCO ENGINEERING LTD.
Primary Class:
International Classes:
B65G69/28; (IPC1-7): B65G11/00
Field of Search:
14/71
View Patent Images:
US Patent References:
3500486BALANCING MEANS,LIP ACTUATING,LOCKING AND SUPPORTING MEANS FOR DOCKBOARD ASSEMBLY1970-03-17Le Clear
3475778DOCKBOARD1969-11-04Merrick
3335442Dock levelling units1967-08-15Kumpolt
3316575Dock levellers1967-05-02Larsen
3249956Manually operated dockboard1966-05-10Zajac



Primary Examiner:
Nackenoff, Jacob L.
Claims:
We claim

1. A dockboard comprising frame means, a main plate having front and rear edges, means pivotally connecting the main plate with said frame means adjacent said rear edge for pivoting movement about a respective first pivot axis, a lip plate, means pivotally connecting the lip plate with the main plate front edge for pivoting movements relative to the main plate about a respective second pivot axis between a dependent position and an extended position, characterized by lip elevating and latching means comprising an extension arm movable with the lip plate, a lip-elevating articulated linkage constituted by pivotally connected first and second latch arms, the first latch arm being pivotally connected to the extension arm and the second latch arm being pivotally connected to the underside of the main plate to have a portion thereof extending rearwardly from its pivotal connection with the main plate, the two latch arms having respective engaging latching faces operative when the arms reach a relative neutral position with the lip plate in said extended position to latch the arms against pivotal movement and thereby latch the lip plate in the extended position, and a snatch connection between the rearwardly extending portion of said second latch arm and the frame means and operative upon upward movement of the main plate beyond a predetermined position to move the said two latch arms into latching position with simultaneous elevation of the lip plate.

2. A dockboard as claimed in claim 1, and comprising an assist spring means operatively connected between one latch arm and the main plate, the said pring means urging the latch arms toward the latched position and the lip plate away from its dependent position.

3. A dockboard as claimed in claim 2, wherein the assist spring means is connected between the main plate and the second latch arm and there is provided a lost-motion link connected between the spring means and the arm and permitting application of the spring force to the arm to urge latching movement of the latch arms only up to a predetermined position adjacent the fully latched position, the arms moving to the fully latched position without assist from the spring means.

4. A dockboard as claimed in claim 1, and comprising bracket means pivotally mounting the second latch arm to the main plate for movement toward and away from the main plate front edge, spring means operative between the main plate and the bracket means and urging the said bracket means to a predetermined forward position, and cooperating cam means carried by the main plate and the articulated linkage and operative upon rearward movement of the bracket means upon application of a rearwardly operating force to the lip plate and thence to the bracket means through the articulated linkage to unlatch the latch arms and permit the lip plate to move to its dependent position.

5. A dockboard as claimed in claim 1, wherein the said rearwardly extending portion of the second latch arm is cranked to have its rear end extending downwards and means for unlatching the latch arms to permit the lip plate to move to its dependent position upon additional movement of the main plate below a predetermined position comprise a stop on the frame means engaging the said rear end to rotate the second latch arm out of latching engagement with the first latch arm upon said additional movement.

6. A dockboard as claimed in claim 1, and comprising spring means operatively connected between the frame means and the main plate and of sufficient strength to move the dockboard upward in the absence of additional weight thereon and to cause automatic elevation of the lip plate by said upward movement.

7. A dockboard as claimed in claim 6, and comprising an operator-controlled ratchet device operatively connected between the frame means and the main plate for control of the upward movement of the dockboard.

8. A dockboard as claimed in claim 7, wherein the said ratchet device comprises a spring wound ratchet-controlled drum mounted to the underside of the main plate, a buffer spring having one end connected to the frame means, and a flexible cable connected to the other end of the buffer spring and wound upon the drum by the action of the spring thereof.

Description:
IMPROVEMENTS IN DOCKBOARDS

1. Field of the Invention

This invention is concerned with improvements in or relating to dockboards, and especially to dockboards of the type comprising a main plate having a lip plate hinged to its front edge and movable between a stored dependent position and an extended position.

2. Review of the Prior Art

Dockboards of the type specified are well known, and it is usual to provide them with mechanism that will automatically raise the lip plate from the stored to the extended position as the board is moved into a position in which it is ready for use. In one type of dockboard the elevation of the lip plate accompanies the upward movement of the main plate about its pivot axis; an example thereof is shown in U.S. Pat. No. 3,249,956 issued May, 1966. In another type of dockboard the lip plate is moved to the position as the main plate is moved from an uppermost position downward toward the normal operating position; an example is shown in U.S. Pat. No. 3,475,778 issued 4th November, 1969.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a new dockboard of the type specified. It is a more specific object to provide such a dockboard having new means for elevating the lip plate to the said extended position, and for thereafter latching it in that position.

It is another specific object to provide such a dockboard wherein the lip plate latching means are released automatically upon a heavy impact (e.g. by a backward moving transport) with the lip plate while it is latched in the extended position.

In accordance with the present invention there is provided a dockboard comprising frame means, a main plate having front and rear edges, means pivotally connecting the main plate with said frame means adjacent said rear edge for pivoting movement about a respective first pivot axis, a lip plate, means pivotally connecting the lip plate with the main plate front edge for pivoting movements relative to the main plate about a respective second pivot axis between a dependent position and an extended position, characterized by lip-elevating and latching means comprising an extension arm movable with the lip plate, a lip-elevating articulated linkage constituted by pivotally connected first and second latch arms, the first latch arm being pivotally connected to the extension arm and the second latch arm being pivotally connected to the underside of the main plate to have a portion thereof extending rearwardly from its pivotal connection with the main plate, the two latch arms having respective engaging latching faces operative when the arms reach a relative neutral position with the lip plate in said extended position to latch the arms against pivotal movement and thereby latch the lip plate in the extended position, and a snatch connection between the rearwardly extending portion of said second latch arm and the frame means and operative upon upward movement of the main plate beyond a predetermined position to move the said two latch arms into latching position with simultaneous elevation of the lip plate.

DESCRIPTION OF THE DRAWINGS

A dockboard which is a particular preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein

FIG. 1 is a perspective view showing the dockboard mounted in a loading dock with its lip plate in an elevated operative position,

FIG. 2 is a plane section taken on the line 2 -- 2 of FIG. 1,

FIG. 3 is a section similar to that of FIG. 2, but showing the dockboard lip plate in its dependent position,

FIG. 4 is a part section similar to FIG. 2 to show the operation of a safety device, and

FIGS. 5 and 6 are respectively sections taken on the lines 5 -- 5 and 6 -- 6 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The particular kind of dockboard illustrated herein as a specific embodiment is adapted to be mounted as an integral unit into a prepared recess in a loading dock or platform 10, so that with the dockboard in the position shown in FIG. 3 (usually called herein its stored position), the main plate 11 is approximately horizontal and level with the top surface of the dock, while the lip plate 12 hinged to the front edge of the main plate is an approximately vertical dependent position, in which it is generally flush with the front face of the dock. It will be understood that the term "stored position" is used for convenience in terminology, and under some conditions the board will be used for loading and unloading while in this position.

The dockboard has a box-like frame means comprising a bottom 13, side walls 14, and rear wall 15 the frame means being formed of welded sheet metal and made sufficiently rigid, for example by means of cross braces such as 16, for transport installation and subsequent use.

When installed this particular frame means is supported by the surrounding concrete of the dock and a minimum of additional strengthening means and especially thickened edges, is required. The invention is, however, also applicable to other kinds of dockboard, such as a free-standing unit without a surrounding dock, which will require such additional strengthening means, and a unit of the type especially adapted for use with a "step-down" dock.

The term "frame means" is used herein for convenience in terminology in describing the box-like frame assembly; in other embodiments the frame means may instead comprise, for example, only the fastening means by which the main plate and its associated latching mechanism are fastened to a suitable supporting structure, which may be the dock.

The main plate 11 has its rear edge pivotally connected to the frame assembly about a first pivot 17, the first axis thereof being shown as horizontal. Normally the pivot is arranged to permit side-to-side tilting of the main plate, but such arrangements are well known in the art and are not illustrated herein, since they form no part of this invention. The lip plate 12 is pivotally connected to the front edge of the main plate about a second pivot 18, having its respective second axis parallel to the said first axis. Referring especially to FIG. 3, with the board in the stored position the lip plate front edge is engaged inside stop means comprising a pair of spaced stops 19.

The dockboard is of the general type which is urged upwards by spring means, the spring force being sufficient to lift both plates, whether or not the lip plate is in the extended or dependent position, unless some additional weight (such as an operator) is on the main plate, or unless it is positively restrained by some other means. The spring means comprise one or more heavy helical compression springs 20, which are mounted between a member 21 and a bracket 22, the latter being fixed to the underside of the main plate. The member 21 is pivotally connected to another member 23 fixed to the frame means rear wall 15. The springs 20 are so mounted that, as they shorten and provide more spring force, the upwardly acting force component is reduced. Thus, in all positions of the dockboard, whatever the lip position, the upward force component is sufficient to overcome the effective weight of the board, and is made as constant as possible over the full range of the movement of the board. With the lip plate in the extended position, as shown in FIGS. 1 and 2, the effective downward movement of the dockboard about the first pivot and acting against the spring means is increased, whereupon the force required to move the ramp assembly downward is decreased.

The dockboard of this embodiment does not require any lifting action at all by the operator, but instead requires some means to control the board upward movement, and to hold the dockboard in a position to which it has been set. Such means comprise a flexible steel cable 24 having its lower end passing around a pulley 25, which is mounted in a channel 26 fixed at the bottom of the frame means. This lower end is fastened to one end of a tension spring 27 disposed in the channel, the other end of the spring being fastened to the frame means adjacent the rear wall 15.

The other upper end of the cable is connected to a ratchet assembly, indicated generally by the reference 28, the assembly comprising a drum 29 around which the cable is wound. The drum is urged by an internal spring for rotation in the direction to wind the cable thereon, unwinding being prevented as long as a ratchet, also disposed within the drum, is engaged. Ratchet assemblies of this type are well known to those skilled in the art and specific details thereof will not be given, since they form no essential part of the invention. Disengagement of the ratchet is obtained by moving a lever 30 extending from the assembly, the lever being connected by a rod 31 to a bell crank lever 32 pivoted to the underside of the main plate at the rear thereof. A handle 33 for engagement by the hand of the operator is connected to the bell crank lever and is reached through an opening 34 in the main plate. An operator wanting the board to lift merely pulls on the handle 33, which then releases the ratchet and permits the springs 20 to move the main plate upwards. If the main plate is moved downwards by an extra weight, for example by an operator walking on the upper face thereof, the spring-rotated ratchet drum 29 gathers in the slack cable and prevents any upward movement of the main plate upon removal of the extra weight. The board will therefore remain in any position to which it has been set by the operator in this manner.

The usual protective side plates 11a are provided to ensure than an operator cannot be trapped between the dock and the board while the latter is above the dock. The front of the dock is provided in conventional manner on both sides with protective bumpers 35.

Novel lip-elevating and latching means for the lip plate 12 are constituted by an extension arm 36 which is fixed to the underside of the lip plate adjacent the second pivot 18 and projects approximately at a right angle to the plane of the plate. A first latch arm 37 has its forward end pivotally connected to the extension arm 36 at 38, while its other rear end is engaged between two spaced parallel side members of a second latch arm 39, the two latch arms being pivotally connected together at 40 and together constituting an articulated linkage. The second latch arm is angled or cranked in shaped in a vertical plane and is pivoted intermediate its ends at 41 to a mounting structure indicated by 42, this structure being fastened to the underside of the main plate. The portion of the first latch arm projecting beyond the pivot 41 is provided with a downwardly rearwardly inclined latch surface 43, which can engage with a correspondingly inclined mating latch surface 44 on the second latch arm when the two arms are in a latching position, in which position the two latch arms form essentially an extension of one another. A snatch chain 45 of predetermined length has its upper end connected to the rear end of the second latch arm 39, while its other lower end is fastened to a convenient anchor member 46 on the frame means through a shock-absorbing tension spring 47.

With the dockboard in its stored position the two latch arms assume the position illustrated by FIG. 3, in which they are both inclined downwardly with the latch faces 43 and 44 out of engagement with one another. When the operator releases the ratchet mechanism and the dockboard moves upward, at some point in that upward movement the chain 45 becomes taut. Further upward movement is accompanied by corresponding rotational movement of the latch arms about their respective pivots in the direction of the arrows 48, with consequent elevation of the lip plate to the extended position shown in FIGS. 1 and 2. At this point the inclined latch faces 43 and 44 are in engagement with one another, and the linkage has reached approximately a neutral position, so that the weight of the lip plate now holds the latch faces in engagement, maintaining the latch engaged.

The second latch arm 39 is urged at all times towards the latching position by a tension spring 49 connected at one end to the mounting structure 42 by a bolt 50, and at the other end to a freely telescoping lost-motion link, which comprises an inner rod-like member 51 pivotally connected at 52 to the rear end of the second latch arm 39, and an outer tubular member 53 which slides freely over the inner member, is operatively engageable with a shoulder 54 on the rod, and is connected via a link 55 to the spring 49. The spring 49 is also effective to urge the lip plate away from its fully dependent position, and is found in practice to ensure that that automatic elevation of the lip plate is virtually always obtained. The connection provided by the telescoping linkage is only operative one-way to provide that the spring 49 cannot prevent further rotation of the arm 39 when the spring has reached its fully retracted position.

With the main plate inclined upward and the lip plate resting on a transport during the loading and/or unloading operation the weight of the lip plate is removed from the latch links 37 and 39, and they tend to droop downward under their own weight a distance sufficient for the latch to be in unlatched condition. As the transport moves away the usual action is therefore for the lip plate to drop immediately to the fully dependent position; the operator can then walk or drive onto the main plate to return the dockboard to the stored position.

It does sometimes happen, however, that the catch remains sufficiently well engaged for the lip plate to stay elevated when the transport moves away. This will also happen with a transport having a platform below dock level, so that the main plate is inclined downward. In these circumstances the operator unlatches the latch by walking onto the main plate and moving it down until the angled rear end of the latch arm 39 engages a stop member 56 on the frame means, whereupon the latch arms are rotated out of the "neutral" plane, so that the weight of the lip plate can automatically disengage the latch and return the plate to the dependent position. The dockboard is then allowed to return to its stored position by the action of the springs 20 and control of the ratchet by the operator. The same sequence is of course employed to unlatch the latch at any time from any position of the dockboard, whether or not is has been used for a loading/unloading operation.

It can sometimes happen that a transport moves backwards against the front edge of the lip plate while the latch is positively engaged. Such reverse movement may seriously damage the plate, or the whole board, and an automatic release is therefore provided to avoid such damage. The pivot 41 for the second latch arm 39 is provided by a bracket member 57 which is mounted for forward and backward sliding movement in a channel 58 fastened to the under side of the main plate. This bracket carries a tube 59 in which the spring 49 is mounted, while a rod 60 is rigidly connected to the bracket, extends through a stop plate 61, and carries a stiff coiled compression spring 62 operative between an adjusting nut 63 and the stop plate 61; the spring is therefore operative to urge the whole bracket structure 42 forwardly. Any force applied to the lip plate with a rearward component sufficient to overcome the urge of the spring 62 will move the latch arms and the bracket assembly backward, until the rear cam face of a cam member 64 on the second latch arm engages a co-operating stationary cam member 65 fixed to the stop plate 61; further rearward movement of the latch arms forces the front end of the second latch arm downward to release the latch and the lip plate will now drop to its dependent position.

It will be understood that particular preferred embodiments only of the invention have been described and variations and modifications within the scope of the appended claims will be apparent to those skilled in the art.