US3175961A

US3175961A - Adjusting device for springs associated with the buckstays of coke oven batteries

Info

Publication number: US3175961A
Application number: US198291A
Authority: US
Inventors: Olsen Samson
Original assignee: Allied Chemical Corp
Current assignee: Krupp Wilputte Corp; Allied Corp
Priority date: 1962-05-28
Filing date: 1962-05-28
Publication date: 1965-03-30
Anticipated expiration: 1982-03-30

Description

March so, 1965 s; OLSEN 3,175,961

ADJUSTING DEVICE FOR SPRINGS ASSOCIATED WITH THE BUCKSTAYS OF COKE OVEN BATTERIES Filed May 28, 1962 2 Sheets-Sheet 1 FIG. 2

March 30, 1965 s. OLSEN ADJUSTING DEVICE FOR SPRINGS ASSOCIATED WITH THE BUCKSTAYS OF COKE OVEN BATTERIES 2 Sheets-Sheet 2 Filed May 28, 1962 fl (Z/I) 1074.4 004D Mill; can:

INVENTOR. 674/160 015! United States Patent 3,175,961 ADJUSTING DEVICE FOR dlRlNGS ASSOCIATED WITH THE BUCKSTAYS 0F COKE OVEN BATTERIES Samson Olsen, Brooklyn, N.Y., assignor to Allied Chemical Corporation, New York, N.Y., a corporation of New York Filed May 28, 1962, Ser. No. 198,291

3 Claims. (Cl. 202-223) This invention relates to an adjusting device for taking up or releasing the tension or pressure exerted by the springs on the tie rods, anchor bolts or other such members which maintain compressive forces on the buckstays of a coke oven battery to permit adjustment of the tension or pressure exerted by such springs on the buckstays.

Conventional coke oven battery construction involves buckstays on the opposite sides of the battery positioned contiguous to the ends of each crosswiseaextending heating wall and the crosswise-extending regenerator pillar wall thereben eath. In the case of coke oven batteries having crosswise regenerator division walls positioned between the regenerator pillar walls, auxiliary buckstays are usually positioned contiguous to the ends of these division walls. Tie rods extend through the roof of the battery, usually two tie rods for the buckstays at the opposite ends of each heating wall. Springs exerting compressive forces on the oppositely disposed buckstays at the ends of each heating wall are mounted on these tie rods. Tie rods or anchor bolts are positioned at the lower ends of the buckstays and are maintained under spring pressure.

Buckstays are also provided at the opposite ends of the battery having tie rods associated therewith and maintained under spring pressure. The tie rods, anchor bolts and similar members are provided with threaded members, e.g., nuts, which can be adjusted to regulate and control the pressure exerted by the springs associated therewith. In the heating up of a battery it is necessary to adjust the springs from time to time to accommodate expansion which takes place. When cooling down a hot battery for economic reasons, to make repairs, or other reasons, it is necessary to adjust the springs from time to. time to take into account contraction which takes place and thus prevent excessive crack formation from occurring. The springs on the crosswise-extending tie rods or anchor bolts associated with the buckstays are heavy compression springs exerting pressures of the order of 10,000 to 35,000 pounds and more. Those associated with the auxiliary buckstays are somewhat lighter, usually exerting pressure of the order of 5,000 to 10,000 pounds. To turn the threaded members which control the forces exerted by these springs, while under the influence of the spring pressure is an exceedingly difiicult and arduous operation even when using a large wrench or other tool designed for this purpose.

It is a principal object of the present invention to pro vide a device for taking up or relieving the pressure exerted by such spnings on the threaded members such as the nuts or bolts associated therewith, to permit the ready adjustment of these threaded members to increase or decrease the pressure exerted by the springs.

Another object of this invention is to provide such device which can readily be mounted on the free end of a tie rod, anchor bolt or similar member, to permit the desired adjustment to be made, and after this has been accomplished, can readily be removed therefrom and positioned on another tie rod, anchor bolt or such member for use thereon.

Other objects and advantages of the present invention will be apparent from the following description thereof.

The accompanying drawings, forming a part of thi application, shows for purposes of exemplification a coke oven battery having silica brick heating walls and fireclay brick regenerator pillar walls and division walls. The invention, however, is not confined to use on such'eoke oven batteries but is applicable to all batteries having heavy compression springs requiring adjustment.

In the drawings:

FIGURE 1 is a fragmentary front elevation view showing two buckstays at one side of the battery, each opposite a heating wall and a regenerator pillar wall therebeneath, and an auxiliary buckstay positioned therebetween and opposite a regenerator division wall;

FIGURE 2 is a fragmentary vertical section taken crosswise of the battery, in a plane passing through line 22 on FIGURE 1;

FIGURE 3 is a horizontal section, partly in elevation, taken along the line 33 on FIGURE 2, showing the adjusting device of this invention in position to adjust a compression spring on a base tie rod or anchor bolt; FIGURE 4 is a horizontal section through a buckstay and an elevational view of the adjusting device, taken along the line 4-4 of FIGURE 2;

FIGURE 5 is a horizontal section, partly in elevation, showing the adjusting device in position on a bolt carried by a buckstay in the area thereof opposite a regenerator pillar wall; and

FIGURE 6 is a horizontal section through a buckstay and an elevational view of the adjusting device in position to relieve the pressure exerted by the spring on a buckstay when the latter is in the position opposite a regenerator pillar wall of a coke oven battery in its heated up state.

Referring to the drawings, the coke oven battery shown (see FIGURES l and 2), for purposes of exemplification of this invention, rests on a concrete mat 10. The battery proper includes a regenerator section 13, the major portion of which is constituted of fireclay refractory brick, an oven section 14 constituted of silica refractory brick heating walls flanking the coking chambers, and an oven top or roof section 15 constituted of fireclay refractory brick.

FIGURE 2 shows the approximate relative height of each of these sections. The invention, however, is not confined to such oven batteries. It is applicable to batteries of all silica brick and batteries in which the interface between the silica brickwork and the fireclay brick work in the regenerator pillar walls is disposed at a higher level than that indicated in FIGURE 2, including batteries in which the entire height of the regenerator pillar walls is composed of fireclay brick.

In the battery shown in the drawings, the oven section 14 includes a series of crosswise-extending high coking chambers 16, alternating with a series of heating walls having heating flues therein as conventional. Crosswiseextending regenerators 1'7 (FIGURE 2) are positioned in the regenerator section 13. The regenerators can be arranged in pairs, as conventional, with each pair separated from an adjacent pair by a massive regenerator pillar wall positioned directly beneath a heating wall, and the members of each pair separated from each other by a regenerator division wall. The regenerators 17 are each filled with checkers composed of fireclay brick as conventional. Each of the regenerators 17 can be divided into a number of side-by-side compartments separated by compartment division walls 18 (FIGURE 2).

As conventional, the coking chambers are provided with charging holes and gas oil-takes, and the fines are provided with burners to which fuel gas is supplied, and ports through which air is supplied from the regenerators. These regenerators, of course, communicate through suitable ducts with one or more waste heat flues leading to the chimney.

"ID a Vertical buckstays 21 are arranged in pairs on the opposite sides of the battery. The members of each pair of buckstays 2-1 are positioned at the opposite ends of each heating Wall and the regenerator pillar wall therebeneath. Since the structure of the buckstays along the length of and on either side of the battery is the same, two adjacent buckstays 21 (see FIGURE 1) on one and the same side of the battery will be described in detail.

As shown in FIGURES l and 2, each of the buckstays 21 is an- I-beam extending the entire height of the coke oven battery. Each two adjacent buckstays are connee-ted by a pair of spaced channel-shaped horizontal connecting

beams

22 and 23 extending longitudinally of the battery at about the level of the interface 24 thereof.

Intermediate the ends of a connecting beam 25 (FIG- URE 1) an auxiliary buckstay as is positioned and secured at one end to the connecting beam 25. Each auxiliary buckstay is also attached to the connecting beams 22 by a sliding joint.

The auxiliary buckstay 26 is disposed in bearing relation against the silica brickwork end of the regenerator division wall above the interface 24 The auxiliary buckstays 26, together with the buckstays 21, and the corresponding buckstays at the opposite side of the battery, provide unitary grids which, through the associated springs hereinafter described, exert compressive forces on the opposite ends of the silica brick heating walls and the ends of the silica brickwork in the regenerator section 13 (above the silica brick-fireclay brick interface). An auxiliary buckstay 30 is positioned opposite the ends of each regenerator division wall and is secured at its upper end to beam 23. Its lower end is provided with an anchor bolt or tie rod similar to anchor bolts at the base of the buckstays 21.

Each of the buckstays 21, as noted, extends from the base of the battery to the top thereof. Tie rods 28, preferably a pair for each heating wall (FIGURES 1 and 2) extend through the roof section 15 of the battery and protrude through a contact plate 29 secured to each buckstay. At one of the free ends 31 (FIGURE 1) of the tie rods 28 heavy compression springs 32 are mounted; the force exerted by these springs is adjustable by nuts '33 threaded on the ends 31. The opposite free ends of the tie rods are similarly secured against contact plates at the opposite side of the battery. Adjustment of these nuts varies the tension placed upon the tie rods 23 and the force stressing the buckstays on the opposite sides of the battery toward each other. Preferably compression springs 32 exert a compressive force of the order of 10,000 to 15,000 pounds.

Additional springs 34 can be mounted on the buckstays 21 hearing on suitable members adjacent the ends of the roof section 15, when the latter is made of fireclay, to maintain the fireclay roof under compression at all times.

The base of each buckstay 21 is provided with a tie rod or an anchor bolt 35 (FIGURE 1). When an anchor bolt is used, it is fixed in the concrete mat 10 supporting the battery. This bolt passes through a housing 36 formed in the lower end of the buckstay by cutting away, in the area of this housing, a portion of the vertical wall of the buckstay and providing suitable reenforcing beams welded to the I-beam forming the buckstay to provide the Walls 37 (FIGURE 3) of the housing 35. A compression spring 38 is mounted on the free end 39 of each bolt 35 extending through the housing 336 of the bucksta individual thereto. The compressive force exerted by spring 38 bearing against the buckstay can be adjusted by nut 41 which bears against a collar 42. Spring 33, as best shown in FIGURE 3, is confined between

collars

42 and 43, the latter bearing against the lower end of the buckstay 21 in the area thereof containing the housing 36 through which bolt 35 passes. The springs 38 are heavy compression springs exerting forces of the order of 35,000 to 50,000 pounds.

Bearing members 41' (FTGURES 5 and 6) are positioned on the opposite ends of each regenerator pillar wall to exert compressive forces on the opposite ends of the fireclay brick portions of the regenerator pillar walls, pushing the brickwork forming these walls together so that should any cracks or fissures tend to form, they are immediately closed up under the compressive forces exerted on each wall.

Member 41 (FIGURES 5 and 6) comprises a fiat bearing surface 42 positioned against the end of the regenerator pillar wall in the area immediately below the interface 24, and having flanges 43 extending from the ends thereof in a direction away from the face of the battery. A plate 44 has secured there-to members 45 which abut the ends of the flanges 43 and exert pressure through the flanges on the flat surface of the bearing member 42 and thus against the upper fireclay portion of the regenerator pillar wall. The members 45 are disposed at the opposite sides of each buckstay 21, as clearly shown in FIG- URES 5 and 6. Welded, or otherwise suitably secured to the outer flange 46 of each buckstay 2-1 is one end of a bolt 47 which passes through plate 44 and has the other end threaded as at 48. A sleeve 49 having a collar 51 is positioned on the bolt 47. A heavy compression spring 52 is confined between the collar 51 and the plate i t, the s ring force being adjustable by a nut 53 in threaded engagement with the threaded end 48 of bolt 47. The compression spring 52 exerts a force against the hearing member 42 abutting the fireclay brickwork of the regenerator pillar wall of the order of 20,000 to 25,000 pounds.

FIGURE 3 shows the relative position of the buckstay 21, the tie rod 35, spring 33 and the end of the fireclay wall indicated by the legend wall cold when the battery is in the cold condition. FIGURE 4 shows the relative position of these parts when in the heated up condition with the buckstay having been moved away from the end of the fireclay wall due to the differential expansion between the silica brick of the heating walls and the fireclay wall portions.

FIGURE 5 shows the relative position of member 41" bearing against a fireclay regenerator wall, buckstay 21, bolt 47 and the end of a silica heating wall in the cold condition of the battery. FIGURE 6 shows these parts in the heated up condition of the battery. The buckstay moves away from the fireclay pillar wall due to differential expansion of the silica brick and fireclay brick. The portion of each buckstay 21 opposite the end of the silica brick heating wall continues to bear against the ends of the silica heating walls, but the lower portion opposite the fireclay regenerator walls no longer bears against these walls. The structure shown in FIGURES 5 and 6 enables the maintenance of compressive forces against the ends of the fireclay walls from the buckstays notwithstanding the movement of the buckstays away from the ends of the fireclay regenerator walls. This is accomplished by nut 53, spring 52, plate 44, members 45 and flanges 43 of member 41.

A similar structure 54 can be provided for each auxiliary buckstay 30, at the upper end thereof. The base of each auxiliary buckstay can be provided with an anchor bolt and associated spring and adjusting nut similar to bolt 35, spring 38 and nut 41 hereinabove described.

The above description represents one of many different coke oven batteries having tie rods, anchor bolts and similar members equipped with heavy compression springs requiring adjustment during heating up or cooling downt Best practice is to maintain the pressure exerted by these springs substantially constant to keep the brickwork of the battery tight and minimize crack formation. To accomplish this end it is necessary to adjust the threaded members controlling the pressure exerted on the ends of the roof section, heating walls, regenerator pillar walls and regenerator division walls from time to time.

For example, during heating up it is necessary from time.

to time to reduce the tension on the tie rods and/ or bolts to allow for expansion of the brickwork and to maintain the compressive forces exerted through the buckstays 21 and auxiliary buckstays 26 and 30 at substantially the same value considered optimum to prevent excessive crack formation.

When cooling a hot battery the rate of cooling is more rapid in the 1800 F. to 800 F. range than in the 800 F. to 200 F. range. The greatest contraction of the silica brick takes place in the 800 F. to 200 F. range, and hence it is important to cool at a slower rate within this range as compared with the rate of cooling when the battery is at higher temperaures. Throughout the cooling of the battery, the rate of cooling is controlled to obtain substantially the same amount of contraction er day. Operating in this manner, adjustment of the various nuts, e.g., 33, 41 and 53, once a day will sufiice.

The present invention provides an adjusting device which enables ready adjustment of the nuts 33, 41, 53

and other such threaded members, to give the desired sub- H stantially constant compressive force by the springs, the pressure of which is controlled by these threaded members. As the device used for all threaded members is the same, and desirably one and the same device, or a reasonable number of such devices, depending upon the number of operators available, can be used, one will be described in detail with particular reference to FIGURES 3 to 6, inelusive.

It will be noted that the anchor bolt 35 has the free end 39 threaded as clearly shown in FIGURE 3. The bolt 47 has its free end threaded at 48. Similarly the free end of the tie rods 26 are threaded and the nuts 33 which control the pressure exerted by springs 32 are in threaded engagement with these threads on the tie rods.

The adjustable device, generally indicated at 60, comprises a rotatable rod 61 having a threaded end 62 carr ing a nut 63 designed to be placed in threaded engagement with the threaded free end of the anchor bolt 35, bolt 47, or tie rod 23. Device 6G, it will be understood, is mounted by nut 63 on the free threaded end of the member associated with a compression spring to be adjusted and after the desired adjustment of the threaded member, e.g., nuts 33, 41 or 53, has been made, is removed therefrom and then placed on another free end of another threaded memher to enable the desired adjustment to be made of the spring thereon.

Nut 63 desirably is shaped as shown in the drawings having a collar 64 in threaded engagement with one end of rotatable rod 61 and an enlarged nut dimensioned to be placed in threaded engagement with the free end of the rod member carrying the spring which applies tension or pressure to the buckstay. Nut 63 can be locked in place on rod 61 by a lock nut 65 once nut 63 is properly positioned on the end of rod at. This construction enables the use of one and the same rotatable rod 61 to accornmodate different sizes of tie rods 28,

bolts

35 or 47, etc., by simply changing the nut 63 to accommodate the tie rod or bolt, carrying a compression spring requiring adjustment. In this specification and claims the expression rod member is used as a generic term to include tie rods 23, anchor bolts 35, bolts 4-7 and other such members carrying compression springs associated with the buckstays, including auxiliary buckstays. End 66 of rod 61 carries a handle 67 for effecting rotation or turning movement of rod 61 to position the nut 63 into threaded engagement with the free threaded end of the member carrying the compression spring associated with a buckstay. A bearing stop 68 is in threaded engagement with the threads 69 on the end 66 to rod 61. This bearing stop 68 can be adjustably positioned on rod 61 to provide a bearing surface against which end 71 of jack member "/2 bears. Jack member 72 is a conventional pressure fluid cylinder having a piston 73 therein provided with a piston rod 74. Piston 73 and piston rod 74 have an aligned central opening 75 through which rod 61 extends. Jack member 72 has a port 76 for the supply of pressure fluid to actuate the piston 73. Return movement of piston 73 can be effected by a spring (not shown) or jack 72 can have both inlet and exhaust ports for the supply and discharge of pressure fluid to effect the actuation of the piston 73.

A housing 77, desirably cylindrical in shape, but which can be of any desired shape, is mounted on rod 61 between the free end of piston rod 74 and the bearing member controlling the pressure or tension exerted by the spring. In the structure of FIGURES 3 and 4, the bearing member 42 and nut 41 controls spring 38. In FIG- URES 5 and 6, bearing member 51 and nut 53 control spring 52. End wall 78 of housing 77 seats against the bearing member 42 of FIGURES 3 and 4, and 51 of FIGURES 5 and 6. End Wall 78 is formed with an opening 79 dimensioned to receive the nut 41 in FIG- URES 3 and 4 and 53 in FIGURES 5 and 6 so that the spring adjusting nut is disposed within the housing 77. The opposite end wall 81 is formed with a bearing collar 82, desirably formed integral with wall 81 and provided with radial reinforcing vanes 83. The free end of piston rod 74 bears against collar 82.

The side walls 84 of housing 77 are provided with openings 85; desirably two such openings are provided on the opposite sides of the housing 77. These openings are positioned to give access to the nuts requiring adjustment, e.g., nut 41 in FIGURES 3 and 4 and 53 in FIG- URES 5 and 6. They also facilitate mounting of nut 63 in threaded engagement with the threaded end of the rod member, e.g., and 39 of anchor bolt 35.

In operation, with reference to FIGURES 3 and 4, the device 66 is mounted on the threaded end 39 of the anchor bolt 35 carrying compression spring 38 to be adjusted by aligning nut 63 with the threaded end 39 and turning the rotatable rod 61 by means of its handle 67. The device 60 is thus supported on anchor bolt 35 with rotatable rod 61 aligned with anchor bolt 35. The adjustable bearing stop as is then positioned on the rotatable rod 61 to bear against end 71 of jack 72. The latter is then connected to its source of pressure fluid actuating the piston '73 and the piston rod 74 to move the housing 77 to the right viewing FIGURES 3 and 4 compressing the spring 38. Thus the pressure exerted by spring 38 on nut 41 is relieved; the spring 33 then exerts pressure on the buckstay and bearing stop member 68. Nut 41 can then be readily moved by a wrench or other suitable tool inserted through openings 85. When the desired adjustment of nut 41 is made either increasing or decreasing the pressure or tension exerted by spring 38 to accommodate contraction or expansion, as the case may be, and hence maintain the forces exerted by the springs substantially constant, the supply of pressure fluid to the jack is interrupted. By moving the bearing stop 68 just before the pressure fluid supply to the jack member is interrupted, away from end 71 of jack 72, the load is no longer borne by the jack 72 and the adjustable bearing stop 68 when the pressure fluid supply to jack 72 is interrupted, but is transferred to the bearing member 42 and nut 41. Device 60 can then be removed by turning handle 67 to remove nut 63 from threaded end 39 of anchor bolt 35.

T he operation of the device is substantially the same used to facilitate adjustment of nuts 53 on bolts 47 or other threaded members controlling the pressures exerted by the springs on the buckstays of a coke oven battery.

It will be understood that this invention is not to be limited to the description herein, or the showing of the drawings, given for purposes of exemplification except as required by the accompanying claims.

What is claimed is:

1. In a coke oven battery having buckstays on the opposite sides thereof, tie rods associated with said buckstays, at least one end of each of said tie rods being threaded and extending beyond the buckstay, a spring on I each tie rod, a collar on each tie rod against which the spring bears, a nut on the threaded end of each tie rod for adjusting the position of said collar and thus adjust the force exerted by said spring, in combination, a rotatable rod having a nut member at one end thereof for engaging the threaded end of said tie rod to thus align said rotatable rod with and support it on said tie rod, means at the other end of said rotatable rod for rotating said rod to have said nut member engage the said threaded end of said tie rod, jack means on said rotatable rod, with the rod passing therethrough, a movable piston rod in said jack means, an adjustable bearing stop on said rotatable rod for providing a supporting surface cooperating With said jack means and against which said jack means bears to provide a bearing surface for one end of the jack means when the latter is actuated, a housing member movably mounted on said rotatable rod positioned to have one end actuated by said movable piston rod in said jack means and the other end when said one end is actuated positioned to control the force exerted by said spring and to relieve said force, said housing member having an opening therein giving access to said first mentioned nut controlling the position of said collar to permit adjustment of said first mentioned nut while the pressure of said spring thereon is relieved by actuation of said housing by said jack means to move said collar out of bearing engagement with said first mentioned nut under the influence of said spring.

2. In a coke oven battery having buckstays on the opposite sides thereof, tie rods extending across the full width of the battery and associated with said buckstays, the ends of said tie rods being threaded, a compression spring on each tie rod for exerting compressive forces on said buckstays, a collar on each tie rod against which one end of the compression spring bears, a nut in threaded engagement with a threaded end of the tie rod for controlling the position of said collar, in combination, a rotatable rod having a nut at one end thereof for engaging a threaded end of said tie rod, handle means at the other end of said rotatable rod for turning said rod, jack means having a piston therein and a piston rod extending from one end thereof, said piston and piston rod having a central opening passing therethrough, said rotatable rod passing through said central opening, an adjustable bearing nut threaded on said rotatable rod and arranged to be moved to provide a bearing stop for the end of said jack means opposite the end from which the said piston rod extends, and a movable housing mounted on said rotatable rod with its axis coaxial with the axis of said rod, said piston rod engaging one end of said housing and eflfecting movement thereof, the opposite end of said housing being arranged to engage said collar to control the pressure exerted by said spring through said collar on the first mentioned nut, said housing when said device is in position on said rod member enclosing said first mentioned nut, said housing having an opening in the Walls thereof to give access to said first mentioned nut.

3. In a coke oven battery having buckstays on the op posite sides thereof, bolt means associated wih said buckstays, and compression springs on said bolt means for exerting compressive forces on said buckstays, the improvement which comprises, means for adjusting the compressive forces exerted by said springs, said adjusting means comprising:

(a) said bolt means each having a threaded projecting portion;

([2) a nut threaded on said threaded projecting portion with the end of said projecting portion extending beyond said nut;

(c) a collar member adjacent said nut, said collar member controlling the pressure exerted by the compression spring associated with said threaded portion, the said nut being movable on said threaded portion to adjust the position of said collar member on said threaded portion and thus change the compressive forces exerted by said compression spring;

id) a rotatable member having at one end a nut member for threaded engagement with'the end of said threaded portion to support said rotatable member on said threaded projecting portion;

(e) means at the opposite end of said rotatable memher for rotating same;

(f) an adjustable bearing stop at an intermediate point along the length of said rotatable member in threaded engagement with said rotatable member for adjustably positioning said stop on said rotatable member;

(g) a jack member on said rotatable member having one end positioned to bear against said bearing stop;

(h) a piston rod extending from the opposite end of said jack member; and

(i) a housing member on said rotatable member, one end of which housing member is actuated by said piston rod and the other end of which housing member bears against said collar member, said housing member having at least one opening therein to give access to said nut adjacent said collar member.

References Cited in the file of this patent UNITED STATES PATENTS 2,517,494 Kiss Aug. 1, 1950 2,566,460 Mihalic Sept. 4, 1951 2,695,754 Karig Nov. 30, 1954 2,728,978 Birkenmaier et a1. Jan. 3, 1956 2,948,057 Dagenais Aug. 9, 1960 FOREIGN PATENTS 134,596 Australia Oct. 10, 1949 905,347 France Apr. 9, 1945 829,124 Germany Apr. 4, 1955 862,287 Great Britain Mar. 8, 1961

Claims

3. IN A COKE OVER BATTERY HAVING BUCKSTAYS ON THE OPPOSITE SIDES THEREOF, BOLT MEANS ASSOCIATED WIH SAID BUCKSTAYS, AND COMPRESSION SPRINGS ON SAID BOLT MEANS FOR EXERTING COMPRESSIVE FORCES ON SAID BUCKSTAYS, THE IMPROVEMENT WHICH COMPRISES, MEANS FOR ADJUSTING THE COMPRESSIVE FORCES EXERTED BY SAID SPRINGS, AND ADJUSTING MEANS COMPRISING: (A) SAID BOLT MEANS EACH HAVING A THREADED PROJECTING PORTION; (B) A NUT THREADED ON SAID THREADED PROJECTING PORTION WITH THE END OF SAID PROJECTING PORTION EXTENDING BEYOND SAID NUT; (C) A COLLAR MEMBER ADJACENT SAID NUT, SAID COLLAR MEMBER CONTROLLING THE PRESSURE EXERTED BY THE COMPRESSION SPRING ASSOCIATED WITH SAID THREADED PORTION, THE SAID NUT BEING MOVABLE ON SAID THREADED PORTION TO ADJUST THE POSITION OF SAID COLLAR MEMBER ON SAID THREADED PORTION AND THUS CHANGE THE COMPRESSIVE FORCES EXERTED BY SAID COMPRESSION SPRING; (D) A ROTATABLE MEMBER HAVING AT ONE END A NUT MEMBER FOR THREADED ENGAGEMENT WITH THE END OF SAID THREADED PORTION TO SUPPORT SAID ROTATABLE MEMBER ON SAID THREADED PROJECTING PORTION; (E) MEANS AT THE OPPOSITE END OF SAID ROTATABLE MEMBER FOR ROTATING SAME; (F) AN ADJUSTABLE BEARING STOP AT AN INTERMEDIATE POINT ALONG THE LENGTH OF SAID ROTATABLE MEMBER IN THREADED ENGAGEMENT WITH SAID ROTATABLE MEMBER FOR ADJUSTABLY POSITIONING SAID STOP ON SAID ROTATABLE MEMBER; (G) A JACK MEMBER ON SAID ROTATABLE MEMBER HAVING ONE END POSITIONED TO BEAR AGAINST SAID BEARING STOP; (H) A PISTON ROD EXTENDING FROM THE OPPOSITE END OF SAID JACK MEMBER; AND (I) A HOUSING MEMBER ON SAID ROTATABLE MEMBER, ONE END OF WHICH HOUSING MEMBER IS ACTUATED BY SAID PISTON ROD AND THE OTHER END OF WHICH HOUSING MEMBER BEARS AGAINST SAID COLLAR MEMBER, SAID HOUSING MEMBER HAVING AT LEAST ONE OPENING THEREIN TO GIVE ACCESS TO SAID NUT ADJACENT SAID COLLAR MEMBER.