US2757397A

US2757397A - Rodent-preventive hinged gangplank

Info

Publication number: US2757397A
Application number: US319446A
Authority: US
Inventors: Howard R Valentine
Original assignee: Individual
Current assignee: Individual
Priority date: 1952-11-07
Filing date: 1952-11-07
Publication date: 1956-08-07
Anticipated expiration: 1973-08-07

Description

Aug W, 1956 VALEN'HNE EJ57 397 RODENT-PREVENTIVE HINGED GANGPLANK Filed Nov. 7. 1952 2 Sheets-Sheet l INVENTOR m-mwmm W. I WALEWWWE ATTORNEY 9 1956 H. R. VALENTINE RODENT-PREVENTIVE; HINGED GANGPLANK F. Sheets-Sheet L2 Filed NOV. '7, 1952 WW NW %N .0 O QM m b m w W T J T- Q) M W U Adv wm H INVENTOR ATTORNEY United States Patent 2,757,397 RODENT-PREVENTIVE HINGED GANGPLANK Howard R. Valentine, Honolulu, Territory of Hawaii Application November 7, 1952, Serial No. 319,446 6 Claims. c1. 14-71 (Granted under Title 35, U. s. Code 1952 see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the pay ment of any royalties thereon or therefor.

The invention relates to gangplanks as used for marine and air crafts to facilitate access to or ingress and egress from such craft, and more particularly to that type of gangplank having a pivoted or swinging stairway.

The primary object of this invention is to provide a gangplank of the type and for the purpose above mentioned which will effectively serve to prevent rodents, primarily rats, from gaining ingress to the craft by such gangplank and to this extent may be used to advantage in combating bacteriological warfare.

Another important object of the invention is to provide a novel coacting platform and pivoted stairway combination having associated therewith a simple andeifective operating means whereby the stairway is depressible under the weight of the user and automatically returns to elevated position when relieved of such weight, or the stairway may be secured in the lowered ordepressed position, optionally, to the end that the stairway can be left in a normally lowered position when the gangplank is being constantly used and canbe kept in a floatingly elevated position during periods of sporadic use, thus constituting under such latter conditions an effective guard to preclude the entrance of rodents onto-the craft via the stairway, and consequently preventing the loss, damage, pestilence attributable to suchrodents.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood when the following detailed description thereof is read with reference to the accompanying drawings, in whichis illustrated what is presently considered a preferred embodiment of the invention and wherein:

Fig. 1 is a side elevational view of a gangplank embodying the features of the present invention, with the stairway thereof shown by full lines in depressed or lowered position, and by dotted lines in elevated or guard position;

Fig. 2 is a top plan view of the assembly shown in Fig. l;

Figs. 3 and 4 are fragmentary detail sectional-elevational views taken substantially on the lines 3--3 and 4-4 respectively of Fig. 2; and

Fig. 5 is a fragmentary horizontal sectional view substantially on the line 5-5 of Fig. 4.

Referring now more in detail to the drawings, wherein like reference characters designate like or similar parts, it will be seen that in accordance with this invention the gangplank comprises generally a supporting structure 6 upon which is mounted a platform 10 and to which is pivotally connected as at 19,.by apertured lugs 21, a stairway indicated generally by the reference numeral 20.

Preferably the supporting structure 6 is of skeleton form construction was to be light enough in weight to facilitate movability thereof and which at the same time taken ice will be of suitable strength for the purpose designated. It is also necessary that the supporting structure have no horizontal supports or other appurtenances upon which a rodent can leap that are closer than five feet to the ground since it has been found that rats can leap to that height. To this end the supporting structure 6 comprises base rails 7, corner posts 3 rising from the base rails 7, cross members 9 bracing the corner posts and also serving to support a platform 10, and hand or safety side rails 12 bridging the corner posts 8 at opposite sides of the structure as clearly shown in Figs. 1 and 2. It will of course be understood that the supporting structure 6 may be equipped with casters, wheels, or movability of the gangplank. The stairway 20 comprises a plurality of steps 22 and a pair of side walls greater than the spacing of safety side rails 12 to enable said walls to freely pass said rails when the stairway is elevated. The top edges of side walls 23 form an outset continuation of safety side rails 12 and are usable as hand rails. The steps 22 at the upper end thereof terminate inwardly from the corresponding ends of the side walls 23 and effect a continuation of platform 10.

The stairway 20 being hinged as at 19, by apertured lugs 21, to the supporting structure 6 forms part of the gangplank and can be 6 and platform 10 as a unit into and out of operative position relative to a marine or air craft. It will be noted that the hinge connection is of simple construction and assembly and comprises a pair of apertur'ed lugs 21 provided at opposite sides of stairway 2b in an arrangement permitting the apertures in the lugs aligned with a pair of apertures provided in opposite corner posts 8, such alignment permitting the ready rethe like to facilitate ception of removable hinge pins or bolts 19. Thus it will, be appreciated that the stairway 20 can be readily defor repair, storage tached from the supporting structure 6 or other purposes.

In accordance with this invention the stairway 20 may,

optionally, be floatingly or yieldably held in the elevated or guard position shown by the dotted outline 36 in Fig. 1 to that position when reor placed in the depressed the full lines in Fig. 1

and automatically returnable lieved of the weight of the user, or lowered position shown by depending upon whether the gangplank is being used sporadically at night when rodents would be moving about or is being used during the night that rodents would not be tempted to make use of gangplanh further comprises a manually manipulative connected at one end to the supporting structure 6 and at the opposite end to the stairway 20.

In the preferred embodiment thereof the spring device comprises a cylindrical spring housing 14 provided with an integral lug 15 and pivot pin 13..through the medium of which the spring housing is pivotally mounted on one of the cross members 9 of the supporting structure 6. Mounted in housing 14 is a helical spring 16 which has one end suitably anchored by eye bolt 17 to the housings closed end (see Fig. 3).

Suitably mounted on one of the sidewalls 23 of the stairway 20, as by being bolted or otherwise secured thereto as at 11 is a tubular guide 24 of a crank assembly. Gudgeoned into the apertured lower end of the guide 24 is the actuating screw 25 which is restrained from axial move ment by pin 27 (see Fig.4). The upper end ofscrew 25 is journaled in apertured plug 28 and is surmounted by a handle or crank 29 exteriorly of guide 24 and convenient to a person using the stairway 20 as will be readily appreciated upon reference to Figs. 1 and 4 of the drawings. i

moved with supporting structure 21 to be readily day or so frequently at spring device which is gudgeon or necked down portion 26 of i at the free end of spring housing 14. One end of the tie rod 18 is pivotally connected to the free end of spring 16 and has its other end affixed to a yoke 35 which straddles nut 30 and trunnioned thereto by two stud trunnions 31. The yoke equipped end of tie rod 18 is accommodated by longitudinal opening 33 provided in tubular guide 24 as shown in Figs. 4 and 5.

The location of the uppermost and lowermost adjustments of the link 18 attached to the spring 16 will be determined, in the fabrication of any specific gangplank,

by a consideration of the turning moment values which will be created about the pivot point 19 of the stairway or walkway. The spring 16 exerts a force which acts at a variable distance from the pivot point 19. The algebraic value of this variable distance (positive or negative) will determine the turning moment which this force creates. An adjustment of the position of the yoke end '35 of the link 18 varies the length of this variable distance between the pivot 19 and the line of action of the force I of the spring, thereby changing the turning moment caused by this force. In every instance, the uppermost adjust ment position of the link 18 will always be above the pivot point of the walkway. But the lowermost adjustment position of the link 18 will depend upon the turning moment which must be counterbalanced, i. e. the weight of the walkway and the distance of the center of gravity of the walkway from the pivot point. Algebraically, the perpendicular distance from the pivot point 19 of the walkway to the link 18 in its lowest position of adjustment must be less than the product of the weight of the walkway 20 and the distance from the pivot 19 to the center of gravity of the walkway 20 divided by the force exerted by the spring 16 in that position. This means that as long as the link 18 in its lowest position is below the pivot 19, or through the pivot axis, or above the pivot not over a predetermined distance, the weight of the walkway 20 will always be sufficient to exceed any counterbalancing action of the spring, and the walkway will remain down. Therefore, the lower position of adjustment of the link 18 need not necessarily be below the pivot point 19 of the walkway 20, as long as the limitations described above are satisfied.

In operation, the gangplank is moved into place alongside the passageway of a water or air craft so that the platform is adjacent thereto. During the day and during periods of frequent use the stairway is normally left down since the rodents will remain in hiding during these periods and there is little danger of their using the gangplank as a means of ingress. However, at night when the gangplank is used only occasionally, it provides a ready help for rodents desiring to enter the craft so the stairway must be kept in the raised or guard position.

From the depressed position, the stairway 20 is raised by turning crank 29 and thereby elevating non-rotatably mounted nut 30 which carries therealong tie rod 18 followed by pivoted housing 14 and spring 16. As the 1 tie rod 18 is elevated, the tension of spring 16 comes into play to an increasingly greater extent until it overcomes the weight of stairway 20 causing it to pivot to a horizontal guard position where it rests against a stop means (not,

shown) mounted on supporting structure 6.

The ladder assembly is fioatingly held in the elevated position solelyby the tension of the spring 16 so when a person leaving the craft comes onto steps 22, the added weight will overcome the force of the spring and cause the stairway 20 to be depressed to the ground. When the person steps off of the steps 22 onto the ground the stairway will be spring biased back to the guard position. Likewise, when a party boards the ship or air craft the stairway 20 is first pulled down by hand and after the partys ascension will automatically return to the elevated position.

When it is desired to keep the steps lowered, crank 29 is rotated so as to move tie rod 18 down until the weight of the stairway 2t exceeds the decreasing effect of the tension exerted by spring 16, at which time the stairway will descend to the ground. If tie rod 18 is lowered to a point where it is below pivot 19 as seen in Fig. 1, the force of the spring 16 will apply a force tending to hold down the stairway 20 over and beyond the holding down force of such stairways own weight.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In a gangplank including a platform and a vertically swinging stairway, a device operable to either normally retain the stairway in an elevated position and automatically return the stairwayto said position subsequent to a lowering of the stairway or, optionally, to secure the stairway in lowered position, comprising a spring pivotally anchored to the platform, a guide member mounted on the stairway substantially transverse to the longitudinal axis of the spring, upper and lower ends of said guide member being respectively above and below the pivot of the stairway, a nut mounted in the guide member and constrained to move longitudinally thereof, a handle equipped screw journaled in the guide and threadedly engaged with the nut to cause the latter to move in either of two directions in the guide, and a link connection between said spring and said nut.

2. In a gangplank including a platform, a vertically swinging stairway pivoted to said platform, a device operable to either normally retain the stairway in an elevated position and automatically return the stairway to said position subsequent to a lowering of the stairway or, optionally, to secure the stairway in lowered position, comprising a spring pivotally anchored to the platform, a guide member mounted on the stairway in transverse relationship to the longitudinal centerline of said spring, upper and lower ends of said guide member being respectively above and below the pivot point of the stairway, a nut mounted in the guide member and constrained to move longitudinally thereof, a link connection between said spring and said nut, and a handle equipped screw journaled in the guide and threadedly engaged with the nut to cause the latter to move in either of two directions in the guide so as to move the link connection optionally clockwise or counterclockwise in relation to the pivot between the stairway and the platform.

3. A gangplank comprising a platform, a vertically swinging walkway pivoted intermediate its ends at a pivot point tosaid platform, the weight of said walkway causing a turning moment about said walkway pivot point, spring means pivotally anchored at one end to said platform, a pivotal connection between the other end of said spring means and said walkway, said spring means also exerting a turning moment about said walkway pivot point, adjustable means mounted on said walkway and operatively connected with said spring means to shift said outer end of said spring means to a selected position of angular adjustment, said adjustable means being positioned on said walkway substantially transverse to the longitudinal axis of said spring means so as to control and selectively vary said turning moment caused by said spring means to optionally counteract or supplement the turning moment exerted by the weight of the walkway about said walkway pivot point so as to retain the walkway in either raised, intermediate or lowered position.

4. A gangplank comprising a. platform, a vertically swinging walkway pivoted intermediate its ends to said platform, spring means pivotally anchored at one end to said platform, a pivotal connection between the other end of said spring meansand said walkway, adjustable means mounted on said walkway and operatively connected with said spring means to shift said pivotal connection of said other end of said spring means along the length of said Walkway, said adjustable means comprising an internally threaded slidable nut integral with said pivotal connection, a mating screw mounted substantially transverse to the longitudinal axis of said spring means and rotatably secured through bearings to said walkway and engaging said slidable nut to shift it as aforesaid along tne length of said walkway to upper and lower limits of adjustment, said nut at its uppermost limit of adjustment being located higher than the pivot point between said platform and said hinged walkway, and said nut at its lowermost limit of adjustment being so positioned that the turning moment exerted by said spring means around the walkway pivot is less than the turning moment caused by the weight of the walkway around said walkway pivot.

5. A gangplank comprising a platform, a vertically swinging walkway pivoted intermediate its ends at a pivot point to said platform, the weight of said walkway causing a turning moment about said walkway pivot point, spring means pivotally anchored at one end to said platform, a pivotal connection between the other end of said spring means and said walkway, said spring means also exerting a turning moment about said walkway pivot point, adjustable means mounted on said walkway and operatively connected with said spring means to shift said pivotal connection of said other end of said spring means along the length of said walkway so as to control and selectively vary said turning moment caused by said spring means to optionally counteract or supplement the turning moment exerted by the weight of the walkway about said walkway pivot point so as to retain the walkway in either raised, intermediate or lowered position, said spring means including a spring pivoted at one end to said platform, a link and yoke member joining the outer end of said spring to said pivotal connection between said spring and said walkway to control and selectively vary the turning moment caused by said spring means comprising an internally threaded slidable member joined to said yoke member at said pivotal connection, a support and guide member for guiding said internally threaded slidable member, bearing means fixing said support and guide member to said walkway in a position substantially transverse to the longitudinal axis of said spring, an externally threaded member operatively mounted within said bearing means and engaging said internally threaded slidable member to shift said slidable member along said support and guide member, and crank means to axially rotate said externally threaded member.

6. A gangplank comprising a platform, a vertically swinging walkway pivoted intermediate its ends at a pivot point to said platform, the weight of said walkway causing a turning moment about said walkway pivot point, spring means pivotally anchored at one end to said platform, a pivotal connection between the other end of said spring means and said walkway, said spring means also exerting a turning moment about said walkway pivot point, adjustable means mounted on said walkway and operatively connected with said spring means to shift said pivotal connection of said other end of said spring means along the length of said walkway so as to control and selectively vary said turning moment caused by said spring means to optionally counteract or supplement the turning moment exerted by the weight of the walkway about said walkway pivot point so as to retain the walkway in either raised, intermediate or lowered position; the adjustable means to shift said pivotal connection along the length of said walkway comprising an internally threaded slidable nut integral with said pivotal connection, a screw mating with said nut mounted substantially transverse to the longitudinal axis of said spring means and rotatably secured through bearings to said walkway and engaging said slidable nut to shift it as aforesaid along the length of said walkway to upper and lower limits of adjustment, said nut at its uppermost limit of adjustment being located higher than the pivot point hinging said platform and said walkway, whereby said turning moment exerted by said spring means around said walkway pivot point counteracts and exceeds the turning moment exerted by the weight of said walkway, and said nut at its lowermost limit of adjustment being so positioned that the turning moment exerted by said spring means around said walkway pivot point then supplements the turning moment exerted by the weight of said walkway.

References Cited in the file of this patent UNITED STATES PATENTS 228,779 Perkins June 15, 1880 1,379,836 Rackham May 31, 1921 1,836,453 De Veau Dec. 15, 1931 1,992,099 Smith Feb. l9, 1935 2,233,638 Peck Mar. 4, 1941 2,399,150 Snider Apr. 23, 1946 2,549,140 Svendsen Apr. 17, 1951 2,617,131 Harris Nov. 11, 1952