US 3671990 A
A dockboard having a hinged lip which normally hangs down and retains the dockboard in a substantially horizontal position. Linkage connected to the dockboard and the lip locks the latter in its pendent position, and when the dockboard is swung upwardly a predetermined distance and then lowered, the linkage is moved across a toggle line and thereafter swings the lip into an extended position. When the dockboard is released, it swings downwardly until it hits stop means, at which time the momentum causes the lip to swing back towards the pendent position.
Description (OCR text may contain errors)
United States Patent Hovestad [4 1 June 27, 1972 [s41 SELF-EXTENDING DOCKBOARD 3,327,335 6/1967 Beckwith ..14/7|  Inventor: Adrian P. llovestad, 986 Garden City mf gi i Road Richmond, British Columbia Canada Primary Examiner-Jacob L. Nackenoff  Filed: June 23, 1970 Attorney--Fetherstonhaugh & Co.
[ 1 pp 48,994 57 ABSTRACT A dockboard having a hinged lip which normally hangs down  U.S.Cl ..l4/7l and retains the dockboard in a substantially horizontal posi-  Int.Cl. 865g 11/00 tion. Linkage connected to the dockboard and the lip locks  Field of Search ..l4/7l the latter in its pendent position, and when the dockboard is swung upwardly a predetermined distance and then lowered, I 5 References Cited the linkage is moved across a toggle line and thereafter swings the lip into an extended position. When the dockboard is UNITED STATES PATENTS released, it swings downwardly until it hits stop means, at which time the momentum causes the lip to swing back 3,203,002 8/ i965 McGuire ..l4/7l towards the pendent position 3,444,574 5/1969 Le Clear ...l4/71 3,323,158 6/1967 Loomis ..l4/7l l4Clalms,5DrawlngFigum P'A'TE'NTEDJum 1972 SHEET 10F 3 mveMToR ADRIAN P. HOVESTAD ATTORNEY P'ATEmEnJunzv I972 sum 2 or 3 Z jl i INVENTOR ADRIAN P. HOVESTAD ATTORNE SELF-EXTENDING DOCKBOARD This invention relates to a dockboard having a lip which is automatically extended when the dockboard is raised a predetermined distance and then lowered.
Dockboards or loading dock levelers are usually used in docks where trucks and other vehicles draw up to load and unload. The dockboards swing up and down so as to provide ramps between the vehicles and the loading dock. Some ramps have lips hinged to their outer edges which normally hang downwardly out of the way, and when needed are swung upwardly into extended positions so as to rest on the beds of the vehicles to be loaded or unloaded.
Loading dock levelers range from loose plates to complex massive hydraulic boards with complicated lip operating mechanisms. The prior simple mechanical dock levelers having hinged lip plates have a number of disadvantages. The lip must be extended by personal energy, causing considerable difficulty since the lip usually weighs more than the person lift ing it. There is one prior leveler which isbiased upwardly, and which has enough energy stored in its lifting mechanism to raise the lip. As this lip usually weighs more than the operator, the energy stored to actuate the lip to an extended position must not be more than an average person can apply. The difficulty is that if sufficient energy is stored to extend the lip, it is difficult to lower the board to the floor of the truck or vehicle. n the other hand, if there is insufficient energy stored, the lip will not extend without manual help. One attempt to solve the problem has been made by the utilization of a lip assist spring. However, such a spring cannot be in an operative position when the lip is in a pendent position. The lip is easily moved and a spring tension would not allow it to be in a pendent position. 1
Another type of prior dock leveler widely used is the free floating, counterbalanced leveler which requires no holddown mechanism. This type of leveler must latch the lip to the main board section in order to keep the lip in contact with the truck floor. The lip actuating mechanism is very complicated and is subject to damage andconstant adjustment. The lip can be extended by way of lost motion (lifting the board upwards) or by stop motion (downward motion of the main board). The major disadvantage of both ways isthat they are very'difficult to operate.
The object of this invention is to provide a new loading dock leveler having a simple spring assisted mechanism pivotally connected to the lip to lock the lip in a pendent position, automatically unlock the lip from its pendent lock position, and extend the lip to an operative position by the downward uninterrupted motion of the main board. A further feature of the invention is a simple lip actuating means which is free of any adjustment needs. The result is a very reliable andinexpensive dock leveler.
The present invention reduces or eliminates the above problems by providing a loading dock leveler or dockboard which is comparatively simple in construction and operation. The board or ramp has a lip hinged to its outer edge which is swingable from a dependent position to an extended position substantially in line with the ramp. Spring-loaded linkage is connected to the lip and normally locks the lip in the pendent position, at which time the ramp is substantially horizontal. The dockboard includes operating means adapted after the ramp is swung upwardly a predetermined distance and under the action of the ramp moving back towards the horizontal to shift the linkage and to cause it to swing the lip to its extended position. The linkage spring maintains part of the linkage on one side of a toggle line to lock the lip in the pendent position, and when this part of the linkage is shifted to the opposite side of the toggle line, the spring assists in swinging the lip into the extended position. Locking means yieldably locks the lip in the extended position, but if extraordinary force is applied to the lip, such as a truck backing into it, the locking means yields to permit the lip to swing downwardly so that there is no damage done to the mechanism.
A preferred form of the invention is illustrated in the accompanying drawings, in which LII FIG. 1 is a plan view of the improved dockboard, with part of the surface or ramp thereof broken away to show the lip lock-assist mechanism in plan,
FIG. 2 is a longitudinal section taken on the line 2-2 of FIG. 1, showing the lip lock in the pendent position,
FIG. 3 is a view similar to FIG. 2, but showing the dockboard swung upwardly so that the mechanism is cocked and ready to start swinging the lip outwardly,
FIG. 4 is another view similar to FIG. 2, showing the dockboard which has been lowered a bit so that the mechanism has extended the lip, and
FIG. 5 is a cross-section taken on the line 5-5 of FIG. 2.
Referring to the drawings, 10 is a dock having a recess 11 formed therein in which dockboard 12 in accordance with the present invention is mounted. Dockboard 12 consists mainly of a ramp 15 swingably mounted in any desired manner on a suitable frame 17 mounted within recess 11. In this example, frame 17 includes side members 18 having trunnions or pins 19 projecting inwardly therefrom on which the inner edge of ramp l5 rests. There is a pin or'trunnion at each side of the ramp, and the latter has near its inner edge 20 stops 22 and 23 projecting downwardly therefrom which span each trunnion, see FIG. 2, to prevent the ramp from shifting longitudinally in the dock recess. Ramp 15 preferably has a plurality of laterally spaced braces 24 on its under surface and extending longitudinally thereof.
A lip 26 is swingably connected to the outer edge 27 of ramp 15 by means of suitable hinge means, such as a hinge 28. This lip is movable from a pendent position, as shown in FIG. 2, to an extended position, as shown in FIG. 4, which is substantially aligned with ramp 15. When the ramp is in its normal substantially horizontal position and the lip is hanging downwardly, the lower edge of the latter rests on a support 30 which forms part of frame 17, and the lip' supports the outer edge of the ramp at this time.
The weight of ramp l5 and its associated elements keep the ramp in the normal horizontal position, and suitable means is provided for partially counterbalancing this weight when the ramp is swung upwardly. For this purpose there is provided spring means 35, pivoted arm means 36 and cam means 37, the latter being mounted on the underside of ramp l5 and projecting downwardly therefrom. As this counterbalancing equipment is known in the art and does not form part of the present invention, it does not need further description herein.
Linkage generally designated by the numeral 40 includes a, lock and assist spring 41, and is adapted in one position to lock lip 26 in the pendent position, and in another position to assist the movement of the lip to its extended position. This linkage includes a bent link 43 which is fixedly connected to lip 26 adjacent hinge 28. This link extends inwardly beneath ramp I5 and upwardly towards said ramp, as clearly shown in FIGS..2 and 3. A lock-assist member 45 is pivotally connected by a pin 46 to the inner end of link 43, and is nonnally inclined inwardly and downwardly from said link. An actuating member 48 is pivotally connected at one end by a pin 49 to link 43 between the ends thereof. Link 43 is preferably bent into the form of a shallow V, and pin 49 preferably is connected to the link between the bend or bottom 50 of the V and the end of the link connected to lip 26. This member 48 normally is inclined inwardly and downwardly from its connection to the bent link. It will be noted that members 45 and 48 are relatively long, and suitable means is provided for pivotally connecting these members together adjacent the inner ends thereof while permitting one member to slide longitudinally relative to the other. In this examPle, member 48 slidably extends through a sleeve 53. This sleeve is swingably connected to member 45 by a laterally projecting pin 54, see FIG. 1. A rod 57 is connected to the inner end of member 45 and projects laterally therefrom in the direction away from member 48. A lug 58 projects both laterally and downwardly from member 45, see FIGS. 1 and 2, and is located near pivot pin 54 but between the latter and the outer end of said member which is connected to bent link 43. One end of tension spring 41 is connected to lug 58, while the opposite end of said spring is connected to another lug 60 which is connected to the inner surface of ramp near its outer edge 27.
A stop 62 is mounted on the lower edge of member 48, and has a substantially vertical surface 63 facing towards sleeve 53, and an inclined surface 64 facing generally in the opposite direction. A pawl 66 is pivotally mounted at its lower end 67 on part of frame 17, and is inclined upwardly towards member 48. By referring to FIG. 1, it will be seen that the pawl is located a little to one side of member 48, and includes a rod 68 on its upper end projecting laterally beneath said member. Pawl 66 is biased upwardly by a spring 69 connected at one end to the pawl by a lug 70 and its opposite end to .part of frame 17. This spring normally retains pawl rod 68 against the undersurface of member 48, and this rod is normally located between stop 62 and the outer end of the member, as shown in FlG. 2. An over-riding cam 73 is mounted on and projected downwardly from one of the braces 24 of ramp 15. This cam 73 extends downwardly beside member 48, and is located near stop 62 but between the latter and the outer end of member 48. Cam 73 has an inclined surface 74 which faces towards stop 62.
A cam 77 is mounted on the undersurface of ramp 15 near its inner edge 20. This cam projects downwardly, and is in line with rod 57 of member 45. Cam 77 is formed with a forward surface 78 steeply inclined upwardly and facing the outer end 27 of the ramp, and with a rear surface 79 inclined upwardly less steeply than surface 78 and facing in the opposite direction from the latter.
Suitable means is provided by means of which ramp 15 can be manually swung upwardly about trunnions 19. In this example, a hand hole 16 is formed in the ramp near one side thereof. Stops 80 are mounted on the portion of frame 17 extending along the bottom of recess 11, and project upwardly therefrom a short way towards the outer edge 27 of the ramp. Stops 80 are positioned to engage braces 24 of the ramp when the latter is released and swings downwardly below the horizontal.
When dockboard 12 is in its normal position, ramp 15 extends substantially horizontally and is level with the surface of dock 10. The outer edge 27 of the ramp is retained in this position by lip 26 which hangs down therefrom and rests on support 30. There .is an imaginary toggle line 84 extending centrally along member 45 and through pivot pin 46, and at this time, the produced toggle line is above hinge 28 of the lip. As the tension of spring 41 tends to force member 45 longitudinally in an upward direction and keeps toggle line 84 above the hinge, this tends to swing the lower edge of lip 26 inwardly, thereby locking the lip in this position. At the same time, spring 41 provides the only support for the inner ends of members 45 and 48 which are just hanging in the air. The fact that the inner ends of these members tend to rotate downwardly assists in keeping the toggle line above hinge 28. It will be noted that pawl rod 66 is positioned outwardly of stop 62 at this time, see FIG. 2. When it is desired to use the dockboard, the operator inserts his hand into handhole 79 and swings ramp l5 upwardly. This is relatively easy because of the counterbalancing spring means 35. This action clears the lower edge of the lip from support 30, and after the ramp has been swung upwardly a predetermined distance, the mechanism is cocked, that is, pawl 66 has moved behind stop 62 of member 48, as shown in FIG. 3. When the ramp is moved downwardly from the position shown in FIG. 3, pawl 66 which is engaging stop 62'of member 48, forces the inner ends of members 45 and 48 upwardly, thus causing the produced end of toggle line 84 to swing downwardly below lip hinge 28. As the lowering of the ramp continues, pawl 66 pushes member 48 longitudinally in the direction of the lip, at which time said member 48 slides in sleeve 53. The force is now applied to pivot pin 49 which is located. below hinge 28, creating a lever action. As the lip travels towards its extended position, the moment arm between pivot pin 46 and hinge point 28 becomes greater, thus assisting the lip to move towards its extended position. During this movement of pin 46, locking rod 57 rides along cam surface 79. The remaining tension of spring 41 forces rod 57 along the steeply inclined cam surface 78. As rod 57 nears the upper part of cam surface 78, pawl rod 68 comesinto contact with surface 74 of cam 73, and spring 41 continues to pull members 45 and 48 upwardly, leaving the pawl rod to ride over cam 73,'disengaging stop 62. The remaining tension of spring 41 frictionally locks linkage 40 in a yieldable operating position with the lip in its fully extended position. As ramp 15 is urged downwardly by gravity, lip 26 will stay in firm contact with the bed of a truck which has been moved into position relative to the dock, the truck bed being indicated by broken lines 87 in FIG. 4. Cam 77 acts as a stop yieldably to lock the lip in its extended position, The truck can now be loaded or unloaded across the ramp, which moves up and down as the truck load is increased or decreased.
When the truck drives away, ramp l5 swings downwardly under the action of gravity until braces 24 engage stops 80. As the ramp is stopped abruptly, momentum causes the outer edge of lip 26 to continue to swing downwardly, and sufficient force is developed to cause end rod 57 to move down cam surface 78 and over the apex of cam 77. Spring 41 now retains rod 57 against cam surface 79. If nothing further is done to the ramp at this time, it will stay in the downwardly inclined position, but lip 26 has swung to a downwardly-inclined position, as shown in broken lines in FIG. 4, so that if a truck backs towards the dock and hits the lip, linkage 40 will not be damaged. In order to return the dockboard to its normal horizontal position, it is only necessary to raise ramp l5 sufficiently to permit the lip to swing towards its normal dependent position. When the lower edge of the lip isswung inwardly, pivot pin 46 is moved downwardly until toggle line 84 moves above hinge 28, at which time the lip is again locked in its pendent position.
From the above it will be seen that the spring loaded linkage 40 normally locks lip 26 in its pendent position. ln order to extend the lip, it is only necessary to swing the ramp upwardly a predetermined distance and then to move-it back towards the horizontal, at which time the lip automatically is swung to its extended position. The ramp and extended lip swing downwardly until the latter engages the surface of the vehicle which has been moved into position relative to dock 10. If by chance a truck backs into the extended lip, it will force the latter to swing downwardly, end rod 57 riding down cam surface 78 at this time to permit this movement. In other words, although the lip is locked in its extended position, it will swing downwardly under extraordinary force. I
I claim: I
- 1 A- dockboard comprising a ramp adapted to be hingedly mounted ona support, a lip, hinge means mounting the lip on an edge of the ramp, said lip being swingable between a pendent position and an extended position, a toggle arrangement for locking said lip in the pendent position when the ramp is substantially horizontal, said toggle arrangement including linkage connected to the lip at one end and extending inwardly beneath the ramp, a spring retaining the linkage with a toggle line thereof located above said hinge means and thereby locking the lip in the pendent position, and operating means to engage the linkage to shift the latter to start to swing the lip from the pendent position and at the same time to move the toggle line of the linkage below the hinge means when the ramp has been sequentially raised and lowered, at which time said spring acts on the linkage to assist the lip to swing to the extended position, said linkage comprising a bent link connected at one end to the lip near the hinge means thereof and extending therefrom beneath the ramp to an inner end above said toggle line when the lip is in the pendent position, a lockassist first member pivotally connected at an outer end to the inner end of the link and inclined inwardly and downwardly therefrom to an inner end, an actuating second member pivotally connected at an outer end to the link between the ends of the link and inclined inwardly and downwardly therefrom to an inner end, and a sleeve pivotally connected to one of said members remote from said link and through which the other of said member slidable extends, said spring being connected to said first member near the inner end thereof and to the ramp near said link, whereby said spring normally maintains the connection between said first member and the link above said toggle line to lock the lip in the pendent position.
2. A dockboard as claimed in claim 1 in which said operating means comprises a stop on said second member, a pawl biased towards the second member and positioned to engage said stop when the ramp moves downwardly towards the horizontal to move the inner ends of said first and second members upwardly and shift said toggle line beneath the hinge means and unlock the lip, and on continued downward movement of the ramp the engaged stop moves said second member and thereby assisting the swinging movement of the lip.
3. A dockboard as claimed in claim 2 including a cam on the ramp to shift the pawl clear of said stop when the ramp continues to swing downwardly.
4. A dockboard as claimed in claim 2 including a cam on the ramp and having an inclined surface, said cam being positioned so that when the inner end of the first member moves towards the ramp and the lip swings outwardly said inner end engages said inclined surface, the incline of said cam being such as normally to prevent movement of said first member thereby locking the lip in the extended position, and when extraordinary force is applied to swing the lip towards the dependent position, the member end rides along and off said inclined surface. 1
5. A dockboard comprising a ramp adapted to be hingedly mounted on a support, a lip, hinge means mounting the lip on an edge of the ramp, said lip being swingable between a pendent position and an extended position, a toggle arrangement for locking said lip in the pendent position when the ramp is substantially horizontal, said toggle arrangement including linkage swingably connected to the lip at one end and extending inwardly beneath and normally inclined downwardly relative to the ramp to a freely hanging inner end when the lip is in the pendent position, said linkage having a toggle line extending longitudinally thereof, a spring connected to the linkage and normally retaining said linkage with the toggle line thereof extending above said hinge means of the lip and exerting force to lock the lip in the pendent position, and operating means, when the ramp is sequentially raised and lowered, to engage a stop on the linkage and raise the inner end thereof to shift said toggle line below said lip hinge means and at the same time to start to swing the lip through the linkage from the pendent position and to permit said spring to act on the linkage to assist the lip to swing to the extended position.
6. A dockboard as claimed in claim 1 in which said operating means comprises a stop on the actuating member of the linkage. a pawl biased towards the linkage and positioned to engage said stop when the ramp moves downwardly towards the horizontal to shift the linkage.
7. A dockboard as claimed in claim 6 including a cam on the ramp to shift the pawl clear of said stop when the ramp continues to swing downwardly.
8. A dockboard as claimed in claim 5 including a cam mounted on the ramp adjacent an inner end of the linkage and having an inclined surface against which said spring moves the inner end of the linkage when the lip is swung towards the extended position, the incline of said cam being such as normally to prevent movement of the linkage thereby locking the lip in the extended position, and when extraordinary force is applied to swing the lip towards the dependent position, the linkage rides along and off said inclined surface.
9. A dockboard comprising a ramp adapted to be hingedly mounted on a support, a lip, hinge means mounting the lip on an edge of the ramp, said lip being swingable between a pendent position and an extended position, a bent lever link con-, nected to the lip adjacent the hinge means and projecting inwardly and upwardly beneath the ramp when the lip is in the pendent position, linkage swingable connected at one end to the lever link and extending inwardly beneath and normally inclined downwardly relative to the ramp to a freely hanging inner end when the ip is in the pendent position, said linkage having a toggle line extending longitudinally thereof and normally extending generally towards and above the hinge means, spring means connected to the linkage normally retaining said linkage in the normal position thereof and exerting a force on the linkage to lock the lip in the pendent position, latch means for engaging a stop on the linkage to move the inner end of said linkage upwardly to shift the toggle line below the hinge means as the ramp is moving downwardly and to swing the lip out of the pendentposition through said linkage, and stop means on the ramp engaging said inner end of the linkage when the lip approaches the extended position thereof to retain the lip in said extended position.
10. A dockboard as claimed in claim 9 in which said stop means yieldably engages said linkage.
1 l. A dockboard as claimed in claim 10 including means on the ramp at the linkage for disengaging the latch means therefrom when the ramp swings downwardly below a predetermined level.
12. A dockboard as claimed in claim 9 in which said linkage comprises a first member pivotally connected at one end to the lever link near a free end of the latter, said first member extending inwardly beneath the ramp, a second member pivotally connected at one end to the lever link between ends thereof and extending inwardly beneath the ramp, and means swingably and slidably interconnecting the first and second members adjacent ends thereof remote from the lever link.
13. A dockboard as claimed in claim 12 in which said said stop is on said second member, and said latch means comprises a pawl biased against the second member normally on one side of the stop, said pawl engaging the second member on the opposite side of the stop when the ramp is raised and engaging said stop when the ramp moves downwardly.
14. A dockboard as claimed in claim 13 including an overriding cam on the ramp for disengaging the pawl from said stop when the ramp swings downwardly below a predetermined point.