CA1155611A - Bulk loading facility having a drop way - Google Patents

Abstract

TITLE
IMPROVEMENT IN A BULK LOADING FACILITY
HAVING A DROP WAY

ABSTRACT OF THE DISCLOSURE
Improvement in a bulk loading facility having a fixed deck having a drop way projecting from and hinged to the deck so that it can be raised or lowered for loading, the drop way having a handrail assembly, the improvement comprising a safety cage assembly affixed to the front end of the drop way, the safety cage assembly forming an enclosed workspace in front of the front edge of the drop way, the safety cage assembly having a top member of structural truss design affixed to the top rail of the handrail assembly and at least one lower member flexibly supported by the top truss member, whereby the safety cage assembly collapses to minimum profile in the raised position of the drop way.

Description

` 1~55611 SPECIFICATION
My invention relates to bulk loading facilities.
The principal object of my invention is to provide im-provements in drop ways, commonly known as gangways and drop platforms, used on bulk loading facillties.
The forgoing object of my invention and the advantages thereof will become apparent during the course of the following description, taken in conjunction with the accompanying draw-ings in which:
Figs. 1 and 2 are, respectively, top plan and side eleva-1~ tional views of an improved form of a drop way embodying myinvention;
Fig. 3 is a perspective view of the underside of said drop way;
Figs. 4-6 are, respectively, fragmentary perspective, side elevational and vertical sectional views of part of said drop way;
Figs. 7 and 8 are, respectively, fragmentary vertical sect-ional and side elevational views of a modified form of said drop way;
Figs. 9 and 10 are, respectively, side elevational and perspective views of another modified form of a drop way embodying my invention;~
Fig. 11 is a fragmentary elevational view with parts in section of à part of the structure of Figs. 9 and 10;
Fig. 12 is a perspectiveview of another modified form of a drop way embodying my invention;
Figs. 13 and 14 are, respectively perspective and side elevational views of the drop way of Figs 1-8 equiped with an embodiment of my invention; and Figs. 15 and 16 are, respectively, perspective and vertical sectional views of a modified form of handrail for said drop way;
Referring to the drawings in greater detail and first to Figs. 1 through 6, a drop way 50 is illustrated therin which is hinged to a fixed deck 40 via a vertical rotatable xigid subframe. Said fixed deck 40 consists of vertical support ~, columns (not shown), main beams 90, cross beams 60, decking and guard rail assemblies 28 and 30. Said subframe consists of beam 29, rigid uprights 53, pivot guide 61 and tubular posts 59. Pivot guide 61 is rigidly connected to a fixed deck 40 via a cross beam 60. Post 59 is rigidly connected to the subframe beam 29 with a bearing plate 62 therebetween; said beam 29, uprights 53, bearing 62 and post 59 are free to ro-tate about the vertical axis formed by pivot guide 61. The drop way 50 is made up of a mainframe having deck 41 there-on, a pair of hinge elements 31 and a handrail assembly con-sisting of a pair of vertical posts 51, a pair of handrails 52 and a pair of telescoping middle rails 37 and 138. The handrails 52 are pivotally connected to the posts 53 by hinges 34 and the middle rails 37 and are also pivotally connec-ted to the posts 53 by hinges 36. Middle rails 138 are pivotally connected to posts 51 and hinges 35 and the posts 51 are pivotally connected to the drop way mainframe and to the handrails 52 by hinges 32 and 33, respectively. A counter-balance assembly is provided for said drop way 50 comprising a counterweight 56 and a four-bar mechanism consisting of pins 31, 37, 38 and 39, members 57 and 154, the rigid sub-frame 53, 29 and 59 and the drop way mainframe. Member 57 is connected to crossbar 126 by pin 38 and crossbar 126 is rigidly joined at its extreme ends to the drop way main-frame. Because said four bar mechanism is a parallelogram, a torque applied by member 154 at pin 39 is translated to a force on member 57 which in turn acts on member 50 at pin 38 through member 126 and produces on member 50 at pin 31 an identical torque. The force of the counterbalance weight 56 acting at pin 55 produces a torque at pin 39 which is proportional to the length of the moment arm 54 and the mass of the counterbalance weight and which torque is there-- fore transferred by said four bar mechanism to act at pin 1~5~61 1 ~1. Therefore any relationship oE distance, such as posi-tion with respect to the center of gravity of the drop way 97 which exists at pin 31, is efEectively transposed by said four bar mechanism to pi~ 39. Therefore the counterbalance weight 56 has a positive eccentricity since a line drawn through the center of pin 39 having a slope similar to the slope of the line joining the center o pin 31 and the center of gravity of the drop way 97, passes below the center of pin 55. The counterbalance weight 56 is joined to the member 54 by an adjustable retention member 58 and pins 55 and 76; the member 58 being positionable along the lenyth of member 54. The post 59 is slotted to receive the members 54 and 154 which are rigidly joined together and offset from each other; the member 54 being pivotally connected to post 59. The decking 41 has a non-slip surface and load bearing capacity of not less than 100 pounds per square foot and is securely anchored to the mainframe by suitable fasteners (not shown). All hinges (31, 32, 33, 34, 35, 36, 3~, 38, 39, 55, and 76) are conventional pin-in-sleeve type hinges acting in double shear for strength, rigidity,~and increased lubricant life and decreased maintenance.
A frame extension 43 with suitable decking 42 thereon is slideably mounted at the front end of the drop way 50 be-neath the decking 41 and within the drop way mainframe 50 so as to permit horizontal translation thereof. The extension 43 has an angle iron frame which is supported and slides on the horizontal flat bar 125 (Fig. 3) rigidly mounted to the inside of the drop way mainframe 50. A
front cross member 89 of the drop way mainframe limits forward travel of said extension 43. The front end of said extension 43 is provided with spaced apart supports 96 which bear against the vessel to be loaded. The rear end of said extension 43 is connected to an actuating lever 63 by a rigid push c, ~ . .

bar 69 and pin 70. The actuating lever 63 is pivotally connected to midrail 37 by a pin 47 and is secured in place by a cotter pin 45. Differential motion between pin 70 and lever arm 63 is taken up by actuating forks 91. The actuating lever 63 is normally restrained from rotational movement by means of a deadbolt locking mechanism comprising a hand lever 64, a connecting rod 65, cam arms 66, a deadbolt pin 44 and spring 67. The spring is secured at one end to lever arm 63 by a bolt 94. The cam arms 66 are pivotally connected to the lever arm 63 by a pin 93 and to the connecting rod 65 by a pin 92. The spring 67 has affixed thereto a pin 44 and is mechanically interlocked to cam arms 66 by a pin 95. In the at rest position of lever arm 63, the pin 44 engages one of a plurality of holes in a plate 68 which, in turn, is rigidly connected to midrail 37. --In operation, said drop way 50 acts as a hinged exten-sion to the fixed deck 40 and when lowered to the horizontal or near horizontal plane provides access for workmen to the top or side of a vehicle, vessel or container for loading purposes; wheneverthe term loading is used herein it should be understood that it includes unloading or any other activity associated with loading or unloading. The drop way 50 can be raised away from the vehicle or vessel to permit movement of the latter. The drop way is normally stored in its raised - position and is lowered after the vehicle to be loaded is moved into position. The front cross member 89 of the mainframe 50 normally does not reach the vehicle so that the extension 43 is usually extended such that the supports 96 rest on the vehicle or vessel. The workman actuates the ex-tension 43 by squeezing hand lever 64 and lever arm 63 to-gether with one hand which pulls the connecting rod 65 upward-ly and raises cam arms 66. This action lifts the spring-67 and retracts the pin 44 from the plate 68 thus releasing the hand lever 64, the workman either pulls or pushes the upper end of the lever arm 63 which pivots about pin 47 and moves the extension 43 via actuating forks 91, pin 70 and rigid link 69. The extension 43 is thus extended or retracted relative to the drop way mainframe. On releasing the hand lever 64, the deadbolt mechanism is brought into operation by the spring 67 which tends to press the pin 44 into one of the apertures in the plate 68. On continued movement of the lever arm 63, the pin 44 will engage one of the holes in plate 68 and will restrain lever arm 63 from further motion.
The spatial arrangement of the holes in plate 68 is such as to limit the incremental placements of the extension 43 to a distance less than the length of the supports 96. Thus, the extension 43 can always be positioned to bear on the vehicle or vessel being loaded while at the same time it is restrained against movement by the deadbolt locking mechanism. By the arrangement shown, the lever arm 63 can be actuated by an operator without stepping onto the drop way and while the ~ drop way is unsupported at its outboard end. This feature is ;; essential in the use of the extendible deck 43 to enable the operator to extend same as to bear on the vehicle being loaded to assist in support of the weight of the drop way and super-imposed loads. Further, the lever arm 63 as designed will not interfere with the raising of the drop way or its collapse to minimum profile in its raised position.
Since accurate positioning of vehicles is nQt always possible, it may happen that the desired access point is displaced laterally from the drop way 50. Provision is made to rotate the entire drop way 50 about a vertical axis to accomodate small errors in vehicle positioning. The workman accomplishes this by grasping the uprights 53 and applying a rotational force thereto (push on one and pull on the other). The rigid subframe including uprights 53, ~, . .

`-` 1155611 crossbeam 29, bearing 62 and post 59 rotates about vertical ; axis within main pivot 61. The amount of rotation is limited only by the horizontal clearance between the rigid sub-frame assembly 53, 29, 59, and the fixed platform beams 9D
which is predetermined by the positioning of support beam 60.
Once the drop way 50 is rotated, the extension 43 is posi-tioned, as described above, to bear on the vehicle.
The counterbalance mechanism comprising the counter-balance weight 56 and said four-bar mechanism acts through 10 .the horizontal axis 31 of rotation of the drop way 50 and ~ .

. .-5 A-- 1155~11 independantly of the rotation of the drop way 50 about the vertical axis 61. Member 154 is offset from member 54 at pivot 39 to permit full collapse of the drop way 50 when in the raised position. An adjustment mechanism is provided for the counterbalance weight 56 consisting of retention member 58, pivot pins 55 and 76 and an adjusting bolt 46 to adjust the eccentricity of the action of the counterbal-ance weight in respect to the effective line of action through the center of gravity 97 (Fig. 1) of the drop way 50 and through the hinge element 31. Said line of action is offset by said four-bar linkage mechanism acting about pivot pins 39, 37, 38 and 31; such eccentricity is effective in imparting to the drop way 50 the self restraining force desired in the raised position. The self restraining force in the lowered position is adjusted by increasing or decreasing the mass of the counterbalance weight 56.
Referring now to Figs. 7 and 8 a typical application is illustrated in which the extension 43 is supported on roller bearings 48 spaced along and fixed to the inside of the mainframe of the drop way designated 150. Each roller bearing is attached to said mainframe by a threaded axle 98 and a nut 49. Each roller has an inner race 120, a dirt seal 121, a roller bearing 122, an outer race 123 and a spacer washer 124. Fail-safe support blocks 71 and 72 (Fig. ~) are made fast to the inside of the drop way mainframe at the front end thereof between the first and second roller bear-ings 48. The extension 143 normally clears these support blocks 71 and 72 by a small amount but in the event that the roller bearings 48, shaft 98 or retaining nut 49 break or come loose the support blocks 71 and 72 will provide emer-gency support to the extension 43. Full roller support for the extension 43 as shown in Figs. 6 and 7 considerably -6- : - `

` 1 ~5561 1 decreases the frictional resistance with sliding assemblies and permits use of higher leverage ratios in the actuating lever 63. Conse~uently, longer extensions 143 can be employed with the san~e or less operating effort on the part of the workman. The roller bearing support, mounted as shown on the inboard side of the drop way mainframe 50 are not suscept-ible to ice build-up and subsequent jammingas is often experienced in less temperate climates, and avoids the prob-lem of increasing friction forces due to corrosion, scale build-up and build-up of dirt and foreign material on the slideways.

Referring now to Figs. 9-11 a modification is illus-trated in which a spring force is used to counterbalance the drop way 50. This modification includes a torsion bar 78, a torsion arm 77, a tenslon rod 74, a connecting pin 75, a spring housing 73, a spring 80, an adjusting nut 79, and a connectingpin 72. Torsion bar 78 is connected to the cen-tral longitudinal axis of the mainframe of drop way 50 by a lever arm 100 and shear pin 101. The spring force is transmitted to the torsion bar 78 by tension rod 74 acting on torsion arm 77 through connecting pin 75. A slotted hole 102 is provided in torsion arm 77 to enable adjustment of the length of the moment arm through which the spring force acts, thereby adjusting the counterbalancing force. The spring 80 is compressed by the tension rod 74 acting through cap plate 103 and adjusting nut 79.
The length of the moment arm is made variable by the mechanism shown in section in Fig. 11 whereby pin 7~ is retained in sleeve 109 which is secured within a slotted hole 102 in lever arm 74 by retention nuts 108 and where pin 75 is retained by cotter pins 110 and whereby the location of pin 75 along the moment arm 77 establishes the effective length 1 1556 1 ~
of the moment arm and the momen~ of the applied spring force.
When tightened, nuts 108 hold sleeve 109 in slot by frictional retention. The hold-up force imparted to the drop way while in the raised position by the spring action is a function of the precompression of the spring 8~. The precompression of the spring 80 is ad~usted by the adjusting nut 79. The gravity moment of the drop way 50 about the main hinge axis 31 is a function of the fixed weight of the drop way 50 acting at a fixed distance from the main hinge point through an angle C~(Fig. 9). In this modification the torque of the torsion bar 78 is arranged to counterbalance such gravity moment of the drop way 50 by application of a restoring torque through lever arm 100. The restoring moment provided by the spring 80 is a function of the spring force, which is in turn a function of spring travel. Spring travel is linear and a function of the moment arm 77 and the angle c~ (Fig. 9). Since the spring force increases with spring travel and since this is a function of the compound angle (oC-e)~ the resulting moment is a compound function of the angle of inclination of the drop 20 way. It is important to match the restoring moment of the spring to the gravity moment of the drop way to achieve smooth, effortless operation of the drop way and to achieve a gentle transition of unbalanced moments from "hold-up" mode in the raised position to the "hold-down"mode in the low-ered position. It is therefore necessary to make the angle e significant relative to the overall system. Values of ~
which are suitable for manual operation of the drop way lie within the range -20 to -40. The value ofe depends to some degree on the magnitude of any superimposed loads added to the drop way whose gravity moments do not follow the cosine relationship of the drop way. Such loads added out-board to the drop way require that the value of ~ be in-creased. Such loads can be encountered in the form of attachments to retain tools, ope~ating equipment, etc., or 1 15~61 1 as appendages to the drop way such as a safety cage or platform addition. In order to limit travel of the drop way below a predetermined angle the spring may be preselected to come to full compression at the desired travel. Alter-nately the connecting rod can be fitted with suitable collars to limit the angular travel of the drop way to its useful working range and to prevent excessive travel ~f the spring.
Referring now to Fig. 12 a further modification to the spring attachment as discussed above is shown therein which ; 10 eliminates the need for a torsion bar. In this modification the use of two spring assemblies is assumed (one side only shown) disposed on to each side of the drop way in much the same manner as shown in Figs. 9, 10, and 11 except that the tension rod 74 is now pivotally connected by pin 75 to member 111 having a slotted hole 102, fitted with a sleeve 109 having retention nuts 108 and where pin 75 is secured to the drop way main frame by members 112 and 113, respect-ively. Member 111 resides at an angle e below the axis of the drop way mainframe as noted before and has its axis aligned radially to the drop way main hinge 31. The effective length of the moment arm is established by the linear displace-ment of pin 75 from the drop way main hinge 31.
By selection of angle e and adjustment to the moment arm and preset spring travel the spring assemblies illustrated both in Figs. 9-11 and 12 are capable of closely duplicating the gravity moment of the drop way through its entire effective angular motion from -15 to +90. The drop way is bias-balanced by spring 80 when the gravity moment is not exactly duplicated and exhibits desirable and controlled out-of-balance characteristics. My arrangement makes the amountof out-of-balance small throughout the travel of the drop way g `` 1~S5611 to minimize operating effort. However, the out-of-balance is sufficient to hold the drop way up when it is in its raised position and down when it is in its lowered posltion.
Control of "hold-down" and "holcl-up" forces and counterbalancing the gravity moment components of attachments to the drop way (which are articulated relative to the four-bar linkage of the handrails)are possible with the spring counterbalance system described herein. The hold down force is inversely proportional to the length of the moment arm and -9A~

the force imparted by the pretensioning of the spring. The hold-up force is proportional to the pretensioning of the spring and, to a lesser extent, inversely proportional to the length of the moment arm. Increasing the pretension-ing increases the hold-up force and decreases the hold-down force by a similar amount. Increasing the moment arm decreases the hold-down force and has the effect of marginally decreasing the hold-up force by decreasing the pretensioning displacement when the platform is in the raised position.
Referring now to Figs. 13 and 14, a modification is shown in which a safety cage is attached to the drop way.
The safety cage comprises a rigid structural double rail top frame 81 fixed to the top rail 52 of the drop way by members 82. A bottom frame 84 is suspended from and braced to frame 81 by chains 83 and members 104 which are pivotally connected to frame 84 and 81 by pins 105 and 106, respectively. The opening between the frames 81 and 84 is enclosed by a cage or canvas 88. The drop way is strengthened by addition of mem-bers 87 and 85 and pivotally connected to each other by pin 86and rigidly connected to the drop way mainframe 50 and vert-ical post 51. The safety cage, being rigidly connected via top frame 81 to the top rail 52, piVQts in the vertical plane about hinge point 34 on the main subframe 53. The structural frame is generally hoop shaped, open to the drop way and with-out decking. In use, the safety cage assembly surrounds thé
work space, on top of a vehicle, on three sides and provides in conjunction with the drop way handrails, a continuous railing from the fixed platform 40 to the vehicle being loaded, capable of protecting the workman from falling. The frame 84 is free to articulate in a manner to accommodate obstructions on top of the vehicle such as handrailings, pipes - . ~

or other devices without interfering with the positioning of the drop way or extension frame and without loss of protec-tion to the workman. Member 104 provides lateral stiff-ness as a result of the rigidity of the pinned joints 105 and 106. In the raised position the safety cage collapses under its own weight, whereby frame 84 collapses to frame 81, thus presenting the narrowest of possible profiles. The narrow profile most easily accommodates railway specified clearance in éffect in all railcar loading operations and is therefore a unique feature permitting the use of said safety cage with tank cars. Since the safety net angulates with the drop way, no extra considerations are required to ensure the proper operation of the counterbalancing mech-anisms. The netting or canvas 88 is attached to the frames 81 and 84 by removeable fastenings and serves to complete the enclosure of the wor~space regardless of the displace-ment of the lower frame 84.
Referring now to Figs. 15 and 16 another modification is illustrated in which a member 25 is arranged to fit within the top rail 52 in a telescoping manner. The member 25 effectively extends the~useful reach of the top rail. Slots 99 with enlarged holes 26 at predetermined positions are provided in member 25. The slot ~9 is engaged within the top - rail 52, by ~olt 23 but the nut 24 is of sufficient size that it can only engage the holes 26 at their various locations.
Bolt 23 is retained by washer 22 and is restrained in the raised position by spring 20. Spring 20 is spaced from and attached to handrail 52 by block 21. In operation, the nut 24 is normally held against the upper surface of top rail 52 and engages one of the holes 26, thus restraining member 25 from lateral displacement. To reposition member 25, bolt 23 and hence nut 24 is depressed against the spring force.
Once depressed, the nut 24 is disengaged from the hole 26 and member 25 can be displaced laterally except that the engage-~

~ ~ J

-`` 115~611 ment between the slot 99 and the shaft of the bolt 23 limits the total possible displacement of member 25. After member 25 is repositioned, bolt 23 is released and nut 24 re-engages one of the holes 26. The extension 25 to the top rail 52 permits enclosing of the variable gap that often remains between the drop way and the vehicle being loaded a~ter the drop way is positioned. The deadbolt engaging mechanism provided in this modification ensures that the extension will not retract due to human error in positioning or securing of any auxiliary fasteners.
It will thus be seen that there has been provided by my invention improvements in drop ways for bulk loading facili-ties in which the obiect hereinabove set forth, together with many practical advantages, has been successfully achieved.
For example, the operating mechanism for the extension is fitted with a dea~bolt locking device which secures the exten-sion at any number of discrete intervals. By grasping and squeezing the lever 63 and hand lever 64 the operator releases the deadbolt restraint and by pulling or pushing on the lever the operator positions the extension 43 to the desired degree of extension. The hand lever 64 is released and lever 63 moved slightly until the deadbolt is re-engaged in the plate 68, thus securing the extension 43 in the desired position. This mechanism provides a safe positive restraint for the extension 43 against retraction while in use.
Since the drop way is often used in an inclined position to gain access to vehicles which are taller than the top of the fixed platf~m there is a tendency due to gravity for the extension to retract and in doing so would release the frontal support for the drop way. Such a retraction is most likely to occur while the operator is walking on the extendible frame but can also occur while the operator .

`

is on the vehicle. Failure of the restraint mechanism in the f~rst instance may cause the operator to fall, while failure in the second instance will leave the operator stranded on the vehicle and will remove all advantages of having a drop way. The self actuated deadbolt mechanism described herein will prevent failure of the restraint mechanism.
The spring counter~alance which acts at an adjusted angle from ~he mainframe of ~he drop way and acts on the drop way indirectly by way of a torsion bar arrangement, has been incorporated in the drop way. Since the spring acts through an angle which is offset to the drop way in all instances, the counterbalancing force imparted by the spring is always similar to the gravity moment of the drop way except that the spring force can be set by a~justments--~o-b~ u~de-r~dlan~ when-~he dr~ ~ay~
in the lowered position to produce a net "hold down" force and to be over balancing when the drop way is in the raised position to produce a net "hold up" force. The torsion bar attachment causes the counterbalancing force to act along the longitudinal axis of the drop way in a balanced manner for a smooth undistorted motion of the drop way.
The safety cage, which acts as a guardrail around the work area, is attached directly to and is an integral working part of the drop way. This safety cage completely surrounds the work area providing both top and mid rails and intermediate netting or canvas and is required to ~`` 115561 1 prevent falls and related injury to the workman. Slnce the work area is comp~etely surrounded, the use of a safety harness is not required. Since the safety cage acts as an integral part of the drop way, and in addition since the mid rail of the safety cage is free to adjust to any railing or other obstructions which are encountered on the vehicle, the safety cage is always in proper and most effective position whenever the drop way is used. There is no chance of human error to negate th~ usefulness ~f the safety cage. The safety cage herein descri~ed is capable of assuming a compact shap~ of narrow profile when the drop way is in its raised position thus enabling its use with railway tank cars or other situations where it is adjacent to railway tracks without compromise to the features and advantages described above.
;~The ex-tensio~-to the top ~il, which increases the effective length of the top rail, is telescopically and `slideably joined to the top rail. The extension of the top rail when used in conjunction with vehicles having railings, ;20 extends the drop way top rail to overlap the handrail on the vehicle and block any intervening opening which would otherwise exist. Thi effectively provides a continuous barrier around the work space for such vehicles. The extension to the handrail is retracted when not in use.
While preferred embodiments of my invention have been shown and ~escribed, it is to be understood that variations and changes may be resorted to without departing from the spirit of my invention as defined by the appended claims.

Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1.Improvement in a bulk loading facility having a fixed deck, having a drop way projecting from and hinged to said deck so that it can be raised or lowered for loading, said drop way having a handrail assembly, said improvement comprising a safety cage assembly affixed to the front end of said drop way, said safety cage assembly forming an enclosed workspace in front of the front edge of said drop way, said safety cage assembly having a top member of struc-tural truss design affixed to the top rail of said handrail assembly and at least one lower member flexibly supported by said top truss member, whereby said safety cage assembly collapses to a minimum profile in the raised position of said drop way.

2. Improvement as claimed in claim 1, said drop way having a counter balance system having a gravity counter-weight, and a four bar mechanism which augments the moment arm of said gravity counterweight, said four bar mechanism including a pivotally mounted vertically offset moment arm, said moment arm being interconnected between said drop way and said counterbalance, whereby said drop way and counter balance system have a narrow profile in the elevated position of said drop way.

3. Improvement as claimed in claim 1, said drop way having a counter balance system having a spring assembly, a torsion bar and a first lever arm interconnecting said torsion bar and spring assembly and a second lever arm interconnecting said torsion bar and said drop way,said lever arms being angularily displaced from each other and spaced along the length of said torsion bar, whereby said drop way is bias-balanced throughout its angular travel.

4. Improvement as claimed in claim 3, further com-prising means for varying the effective length of said first lever arm including a pivot connection between same and said spring assembly, said pivot connection being moveably adjustable lengthwise of said first lever arm.

5.Improvement as claimed in claim 4, locking means for said pivot connection to secure same against lengthwise displacement along said first lever arm.

6. Improvement as claimed in claim 3, said spring assembly comprising a compression spring, a housing and a tension rod therefor, means for fastening said housing to said handrail assembly, and means for pivotally connecting said tension rod to said first lever arm.

7. Improvement as claimed in claim 6, means for precompressing said spring assembly comprising fastening means on the free end of said tension rod for applying a pre-compression force to said spring.

8. Improvement as claimed in claim 1, said drop way having a counter balance system having a pair of spring assemblies, each spring assembly comprising a compression spring, a housing and a tension rod therefor, means for fastening said pair of spring housings to said handrail assembly, a pair of levers fastened to and disposed at angles to said drop way, and means for pivotally connecting the lower ends of said tension rods to said lever arms, respectively.