Expansion Gap Sealing Device

Abstract

The present sealing device relates to an expansion gap. Such gaps are maintained between adjacent construction members, for example, slabs of concrete forming the roadbed on bridges or the like. A plurality of gap strips are inserted into such gaps and sealing means of elastic material are inserted between adjacent gap strips or between a gap strip and the edges of the construction member which define the gap. In order to improve the positional stability of the gap strips, the invention provides carrier bars which extend directly through apertures in the gap strips and which are supported at their ends in recesses of the edges defining the gap. Bearing means of elastic material are provided between the gap strips and the carrier bars. In one embodiment the bearing means are firmly secured to the carrier bars and to the gap strips. In another embodiment the bearing means comprise the glide pieces permitting a gliding movement between the bearing means proper and the carrier bars.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a sealing device for expansion gaps in bridges, roadbeds, or any other construction members which are subject to expansion and contraction due to temperature changes. Such expansion gaps extend at an angle across the longitudinal direction of the construction members, for example the longitudinal extension of the road. These sealing devices comprise gap strips usually made of steel which are laterally supported relative to each other and to the gap by means of elastic bodies which simultaneously function as sealing strips. The gap strips are usually supported on top of carrier bars which extend laterally relative to the longitudinal extension of the gap and are supported in the edges of the construction members which define the gap.

Swiss Pat. No. 408,089 describes a prior art expansion gap bridging or sealing device in which each gap strip is rigidly connected to several cross carrier bars which are arranged underneath the gap strips. The cross carrier bars to which one gap strip is connected are shiftably supported in the gap edge means so as to be movable relative to the remaining cross carrier bars and the gap strips connected to such remaining cross carrier bars. This known device requires a relatively large number of cross carrier bars because due to static and dynamic reasons several cross carrier bars are required for supporting each gap strip.

It would be possible to reduce the number of cross carrier bars in the just described known device by increasing the rigidity against bending of the gap strips. Such rigidity could, for example be increased by using strips having a larger overall height or a larger width. However, the larger overall height has a disadvantage because it increases the lever arm of the traffic loads which are effective on the sealing or bridging device, whereby undesirably large moments are effective between the point where such traffic loads are applied to the gap strips and the points at which the gap strips are connected to the cross carrier bars. Besides, increasing the overall height of the gap strip is disadvantageous because the depth of the gap may have to be increased in order to provide space for supporting the cross carrier bars which are arranged underneath the gap strips, in lower positions, in order to accommodate such larger height of the gap strips where the top edge of the gap is given or determined by the top surface of the construction members. However, increasing the gap depth is generally impossible without especially considering this problem at the construction site. In those instances where the superstructure has a given height deepening of the gaps is entirely impossible.

On the other hand, making the gap strips wider has the disadvantage that the overall width of the sealing device is increased. This is not desirable from a traffic point of view as it may adversely affect the smoothness of the road surface.

German Pat. No. 933,157 also describes devices of the type described above in which the gap strips are supported on angle brackets cross bars or the like without being rigidly connected thereto. Due to the fact that the cross bars are not rigidly connected to the gap strips the known structures increase the danger that the gap strips may be tilted by vehicles traveling over the sealing structure. The tilting may be to such an extent that a disadvantageous line of contact results between the gap strips and the cross bars. Similar considerations apply to German Patent Publication 1,257,186 wherein a guide thorn is inserted through the gap strips. However, the guide thorn has no supporting functions.

OBJECTS OF THE INVENTION

In view of the foregoing the invention aims at achieving the following objects:

to overcome the disadvantages of prior art devices;

to provide a sealing device of the type described above in which the gap strips have an increased stiffness or stability against bending without increasing the overall height of the entire structure;

to support the gap strips in such a manner that they are secure against tilting to a high degree;

to support the gap strips in such a manner that fewer cross carrier bars are required for each gap strip than heretofore;

to increase the height of the gap strips and thus their stiffness without the increasing the overall height of the entire structure and without increasing the moments to which the sealing device is subjected by the traffic loads as compared to prior art structures;

to arrange the supporting cross bars relative to the gap strips in such a manner that the moments to which the gap and the cross carrier bars are subjected become smaller as compared to prior art devices;

to support the gap strips on cross carrier bars which extend through apertures in the gap strips whereby preferably bearing means of elastic material are arranged between the gap strips and the carrier bars and whereby the carrier bars are supported at their ends in the edges of the adjacent construction member in such a manner that the lower ends of the gap strips may take up space at the bottom of the gap which heretofore has been taken up by the supporting elements;

to provide elastical sliding means between the gap strips and the cross bars;

to slidingly interconnect all gap strips with each carrier cross bar whereby to substantially reduce the total number of required cross bars;

to simplify the assembling and mounting of expansion gap sealing devices;

to arrange the gap strips in such a manner that a tilting of the gap strips as well as a tilting of the carrier cross bars by vehicles travelling over the sealing device, is definitely prevented, whereby such tilting must be prevented where the cross bars are firmly secured to the gap strips as well as in the embodiment wherein relative slidable movement between the cross bars and the gap strips is possible;

to effectively utilize the space underneath the carrier cross bars for increasing the bending resistance or stiffness of the gap strips;

to insert bearing means of elastic material between the carrier cross bars and the gap strips under a biasing force, whereby these elastic bearing means exert a force which opposes any lateral shifting of the gap strips relative to the carrier cross bars;

to employ bearing means between the gap strips and the carrier cross bars of elastic material such as rubber, neoprene or polyurethane in order to compensate for inaccuracies in the machining or to permit larger tolerances, and to absorb small lateral shifting movements in the longitudinal direction of the gap strips;

to employ elastic bearing means or elastic glide bearing means in such a manner that any shock loads caused by the traffic are dampened and the noise generation of the entire structure is reduced;

to facilitate the replacement or repair of individual elements of the entire sealing device; and

to dimension the bearing means as well as the sealing bodies or strips of elastic material in such a manner and to suitably position these elements so that they can cooperate in controlling the position of the gap strips by restoring the gap strips into the desired positions subsequent to a shift resulting from the traffic moving over the sealing device.

SUMMARY OF THE INVENTION

According to the invention there is provided a sealing or bridging device for expansion gaps between construction members such as roadbeds, especially on bridges and the like wherein gap strips which extend across or at an angle relative to the longitudinal direction of the road support each other by means of elastic bodies, such as sealing strips, whereby the gap strips are supported by means of carrier bars which extend across the gap and wherein the ends of the cross bars are supported by means which are located in the edges, preferably in recesses of the edges of the gap so that said cross bars extend through apertures in the gap strips, whereby the latter can now extend into the space which heretofore has been taken up by the supporting cross bars. In one embodiment of the invention the gap strips and the cross bars are firmly secured to each other by means of bearings made of elastic material such as elastomers of the rubber, neoprene, polyurethane type or the like.

In another embodiment of the invention the structure is such that the carrier cross bars are supported in the gap strips by glide bearing means which are secured to the gap strips but which permit a relative sliding movement between the gap strips and the carrier cross bar. For this purpose, preferably gliding pieces made of polyamid, teflon or the like are inserted between the elastic glide means proper and the carrier cross bars.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be clearly understood, it will now be described, by way of example, with reference to the accompanying drawings, wherein:

FIG. 1 is a top view of two construction members, for example, two concrete slabs of a road with the expansion gap extending between the two concrete slabs;

FIG. 2 is a sectional view along the section line 2--2 shown in FIG. 1;

FIG. 3 illustrates a partial sectional view along the section line 3--3 shown in FIG. 1, whereby a cross carrier beam is shown in section;

FIG. 4 is a sectional view through a gap strip according to the invention along the section line 4--4 shown in FIG. 3;

FIG. 5 shows a similar view to that of FIG. 3 however, illustrating a modified embodiment of the invention;

FIG. 6 is a sectional view along the section line 6--6 in FIG. 5;

FIG. 7 illustrates a partial view wherein glide bearing means are employed comprising a body of elastic material and a glide bearing piece firmly secured to each other and to the respective gap strip means;

FIG. 8 shows the embodiment wherein the bearing means are firmly secured to the cross carrier bar as well as to the gap strip means;

FIG. 9 shows the insertion of resilient means between the lower end portion of adjacent gap strips and between the gap strip and the adjacent edge of the expansion gap;

FIG. 10 illustrates an embodiment wherein a firm connection between a glide piece and a bearing body of elastic material as well as between said bearing body and the gap strip permits a gliding movement of the gap strip in its longitudinal direction across the carrier bar; and

FIG. 11 shows a modification similar to that of FIG. 10.

DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 shows a top view of two concrete slabs 1 and 2 forming, for example, the road surface on a bridge. An expansion gap 3 is provided between the edges 4 and 5 of the concrete slabs. The gap 3 accommodates expansions and contractions of the slabs which may result from temperature changes. The longitudinal direction of the road is indicated by the double arrow A. The longitudinal direction of the gap 3 is indicated by the double arrow B.

FIG. 2 shows the sectional view through an expansion gap sealing device wherein a cross carrier bar 6 extends laterally across the gap in the direction of arrow A. The ends of the cross carrier bar 6 are slidably supported in recesses 7 and 8 of the edges 4 and 5, by glide bearing means which comprise glide blocks 9 made of elastic material, such as rubber, polyurethane or neoprene and glide pieces 10 which may be made of a polyamide. The glide blocks 9 are rigidly connected to the edges 4 and 5. These edges may, for example, be made of steel beams having the shown U-profile.

To properly locate the cross carrier bars 6 at the desired elevation so that they may extend through apertures in the gap strips 11, there are preferably provided raiser blocks or ridges 12 inside said recesses 7 and 8 of the profiles forming the edges 4 and 5. The bearing blocks 9 are, for example, glued to the raiser blocks 12. The relative gliding movement between the edges 4 and 5 on the one hand and the carrier bars 6 on the other hand is facilitated by said glide pieces 10 between the bar 6 and the bearing block 9. However, the invention is not limited to this embodiment. It is also possible to insert the glide pieces 10 between the bearing blocks 9 and the raiser blocks or ridges 12, whereby said ridges would be provided with respective gliding surfaces. In the shown example the carrier bar 6 is provided with such gliding surfaces 13.

A plurality of gap strips 11 are held in position in the gap by bearing means 14 and glide pieces 15 which support the gap strips 11 above and below the cross carrier bars 6. The construction of the bearing means such as blocks 14 and the glide pieces 15 may be, for example, substantially the same as described for means 9 and 10. Here again a firm connection 16 is provided between the gap strips 11 and the bearing blocks 14. The glide pieces 15 are, on the one hand firmly connected to the bearing blocks 14 and on the other hand glide on the surfaces 13 of the cross carrier bars 6. It should be mentioned here that the bearing blocks 14 are inserted into their gap strips supporting position under a biasing force which resiliently compresses the elastic bearing blocks 14.

Between adjacent gap strips 11 and between a gap strip and the adjacent edge there are inserted sealing means in the form of elastic or resiliently yielding bodies or strips 17 to form a continuous and smooth surface of the sealing device which surface will be flush with the road surface. These elastic or resiliently yielding means 17 may, for example, be strips of polyamide, Teflon (R.T.M.), or the like which provide a lateral support for the gap strips 11.

The lower ends of the gap strips 11 are also laterally supported relative to the edge profile or relative to the gap and relative to each other by resilient or elastic control means such as steel springs or bodies of elastomer material. In this manner the gap strips are laterally secured in three positions, namely at the top by the sealing strips 17, in the center by the carrier rods 6, and at the bottom by the spring means 18. This structure according to the invention has the important advantage that tilting of the gap strips is excluded because the gap strips may reach deeper down into the expansion gap into a space which heretofore has been taken up by the gap strip supporting means.

The glide pieces 15 improve the relative movability. However, it should be noted that the invention is not limited to the use of such glide pieces. The glide blocks 14 or 9 may directly contact the bars 6 since it is also possible to employ merely the bearing blocks 14 as will be described with reference to FIG. 5.

FIG. 3 illustrates a longitudinal side view in the direction of line 3--3 of FIG. 1 and showing a modified form of gap strip 19. This gap strip comprises an upper rod 20 and a lower rod 21 which are interconnected with each other by means of cross pieces 22. The interconnection between the rods and the cross pieces may be permanent or removable as will be explained with reference to FIG. 4.

The cross pieces 22 are spaced from each other so as to provide apertures 23 through which the carrier cross bars 6 extend. The cross bars 6 may be provided with longitudinal ridges 24 which act to limit any lateral shifting of the cross bar relative to the glide pieces 15 or vice versa.

FIG. 4 illustrates several possibilities of interconnecting the upper and lower rods 20 and 21 with the cross pieces 22 in order to form the gap strips according to the invention. For example, the upper rod 20 is connected to the cross pieces 22 by means of threaded bolts 25. This has the advantage that the upper rods of the gap strips which are subjected to the traffic conditions of the road may be easily replaced when they are worn out.

On the other hand, the lower rod 21 is shown to be connected to the cross pieces 22 by means of weldment 26. It is to be understood that various modifications and combinations of the interconnections between the rods and the cross pieces are within the scope of the present invention. For example, it is possible to provide the cross pieces 22 as elements which are divided along a central line of symmetry extending longitudinally through the gap strips and having lugs 27 which are interconnected with each other by means of nuts and bolts 28.

With regard to FIG. 2 it should be mentioned that due to the resiliency of the sealing strips 17 and due to the resiliency of the bearing means 14 as well as of the spring means 18 the gap strips are always subject to position controlling biasing forces which continuously tend to restore the gap strips into their proper, preferably equally spaced positions.

Preferably, the sealing strip 17 and the spring means 18 are arranged in a mirror symmetrical fashion relative to the longitudinal axis of the carrier cross bar 6 so that the biasing forces will be perfectly balanced. Moreover, the spring means 18 may also be provided in the form of elastically yielding or resilient sealing strips so that the entire device will be sealed not only at the surface of the road but also at the bottom of the expansion gap. In addition to the sealing strips it is possible to insert further elastically supporting bodies between adjacent gap strips and between gap strips and the edge means 4, 5, whereby these additional supporting bodies may operate as buffers and as stop means for limiting the lateral movement of the gap strips.

FIG. 5 illustrates a view similar to that of FIG. 3. However, two gap strips 29 and 30 are shown to extend in parallel one behind the other. Only one half of each gap strip is visible because the left hand portion of the gap strip 30 is broken away along the line 31 in order to expose the gap strip 29 which is located behind the gap strip 30. The gap strip 29 comprises an upper rod 32 and a lower rod 33 interconnected by cross pieces 34, 35 which preferably have a mirror symmetrical shape. The interconnection between the cross pieces on the one hand and the upper and lower rods 32, 33 may, for example, be accomplished as has been described above with reference to FIG. 4.

The cross pieces 34, 35 are shaped and spaced from the adjacent pair of cross pieces 36, 37 so as to provide an aperture comprising an upper trapezoidal half 38 and a lower trapezoidal half 39. It will be noted that the upper half 34 of the cross piece has also a trapezoidal shape in such a manner that it fits into the lower half 39 of the aperture. The same applies to the lower half 35 of the cross piece which will fit into the upper half 38 of the aperture. In this manner there is substantially no waste of any material.

The gap strip 30 is constructed in the same manner as has just been described with reference to gap strip 29. The respective elements 32' to 39' are also arranged relative to an axis of symmetry 40.

A carrier bar 49 extends through the aperture formed by aperture portions 38, 39. A further carrier bar 42 extends through the aperture formed by aperture portions 38', 39'. The gap strip 29 is supported on the carrier bar 41 by means of bearing blocks 43. The gap strip 30 is supported on carrier cross bar 42 by means of bearing bocks 44.

In practice the carrier cross bars 49, 42 will be spaced from each other by approximately 3 to 5 meters. This relatively wide spacing is an advantage of the invention as compared to the prior art since now fewer carrier cross bars are required than heretofore.

Moreover, the arrangement of the cross pieces in spaced relation to each other results in a substantial weight reduction and the construction requires less material than heretofore because due to the above described arrangement of the portions of the cross pieces relative to the axis of symmetry 40 there results a honey comb type of structure which is relatively light but nevertheless has substantial strength.

A honey comb type of gap strip may be, for example, manufactured in the following manner. A single piece profile is first produced, for example by rolling or extruding. The intermediate land or cross piece of the profile will have a height H as shown in FIG. 5. Thereafter, the single piece profile will be cut along the lines 45, 46, 47, 48, to produce two separate pieces which are then shifted longitudinally relative to each other so that they may be connected along lines 45, for example, by welding whereupon the height H of the cross connecting pieces will be substantially doubled.

Another possibility of completing the present gap strips would be to connect them along the axis of symmetry 40 by connecting means which, for example, may be loosened so as to provide the possibility of replacing the upper portion of the gap strip when it is worn out. This could, for example, be accomplished by threaded connecting means and straps 50. This embodiment has substantial advantages with regard to assembling and disassembling the gap strips.

FIG. 6 illustrates a sectional view along line 6--6 of FIG. 5 and the same reference numerals as in FIG. 5 are employed in FIG. 6. Between the carrier cross bar 42 and the upper rod 32' there is inserted under a biasing force a glide piece or bearing block 44 which is firmly secured to the upper rod 32' but permits relative gliding movement between the carrier bar 42 and the gap strip 30. Similar considerations apply to the glide piece or bearing block 44 inserted between the lower rod 33' and the carrier bar 42.

The construction or embodiment which provides for a relative gliding movement between the carrier bars and the gap strips has the additional advantage that the width of the entire sealing device can be easily adapted to the local requirements simply by adding or removing gap strips and by exchanging the carrier bars either by longer or shorter bars. This adaptability is an important advantage of the invention.

The mounting or assembly is relatively simple. For example, it is possible to first place a bearing block of elastic position into position on the top edge of the cross carrier bar where it is to contact the respective gap strip. Thereafter the cross bar is inserted into the respective aperture of the gap strip and an additional bearing block is inserted between the lower edge of the cross bar and the lower portion of the gap strip. By forcing the second bearing block into position, automatically both bearing blocks are subjected to the desired biasing force, whereby the necessary firm connection is accomplished, especially since the established biasing force counteracts any shift of the gap strip relative to the cross bar.

Referring again to FIG. 6 there is shown an elastic body 51 inserted between the upper rods 32 and 32' of the gap strips 29 and 30. This elastic body 51 as well as the respective elastic body 52 which is inserted between the lower rods 33 and 33' are so dimensioned and shaped that they are subjected to a biasing force, whereby not only a sealing is accomplished but the gap strips 29 and 30 are also supported laterally relative to each other in a resilient manner, whereby biasing forces are established which will continuously restore the gap strips to their normal evenly spaced positions.

It is an important advantage of the present invention that it provides the necessary space even in the lower portions of the structure for the insertion of each elastic bodies as shown at 52 in FIG. 6.

FIG. 7 is a view on a slightly enlarged scale of a portion of FIG. 1 in order to illustrate that layers of glue 53 may be provided between the bearing blocks 14 and the glide pieces 15 as well as between the bearing blocks 14 and the gap strips 11.

FIG. 8 illustrates an embodiment without glide pieces 15. Thus it is possible to employ layers of glue 54 between the bearing block 14 and the gap strip 11 and between the cross bar 6 and the bearing block 14 as shown in FIG. 8. However, gluing the bearing block 14 to the bar 6 may be omitted altogether.

The spring means 18 symbolically shown in FIG. 2 may, for example, comprise strips 55 of polyurethane as shown in FIG. 9. These strips may have a width slightly larger than the spacing between the adjacent gap strips 11 so as to press the strips 55 into the spacing, whereby the above described biasing force is provided.

FIGS. 10 and 11 illustrate modified embodiments for firmly interconnecting the gap strips with the bearing means. In FIG. 10 the gap strip 55 is glued to the bearing block 59 by an adhesive 61. A glide piece 57 is provided with a groove 58 in which the bearing block 59 is firmly supported.

In FIG. 11 the glide block 62 is provided with a tongue 63 which is firmly held in a respective groove 64 of the bearing block 65. The bearing block 65 is firmly attached to the gap strip 56 by pressing it between ridges 66 of the gap strip 56, whereby sufficient frictional contact between the bearing block 65 and the gap strip 56 is provided to hold the bearing block 65 in the proper position.

The firm connection of the bearing means to the respective gap strip nevertheless permits a relative gliding movement between the gap strips and the cross bars 60 in the longitudinal direction of the gap strips. However, a movement of the gap strips laterally to the gap strips, that is in the longitudinal direction of the cross bars is prevented, for example, by the tongue 63 and the groove 64, whereby tilting of the gap strips is avoided which is an advantage of the invention.

Although the invention has been described with reference to specific embodiments, it is to be understood that it is intended to cover all equivalents and modifications within the scope of the appended claims.

Claims

What I claim is:

1. An expansion gap sealing device located between edges of adjacent construction members, said edges defining an expansion gap having a given depth, comprising gap strip means extending substantially across the longitudinal extension of said construction members, sealing means extending alongside said gap strip means in said gap for sealing the gap and providing lateral support for the gap strip means, carrier bars for said gap strip means extending across said gap, apertures in said gap strip means through which said carrier bars extend, and supporting means for said carrier bars located in said edges and at such an elevation relative to the depth of the gap to permit alignment of each carrier bar with the respective apertures in the gap strip means, said supporting means for the carrier bars comprising carrier bar bearing means of elastic material, said gap edges comprising means for properly locating said carrier bar bearing means under a biasing force, said bearing means being firmly attached to said locating means and permitting gliding movement between the carrier bar and the carrier bar bearing means.

2. The expansion gap sealing device according to claim 1, wherein said carrier bar bearing means comprise a bearing body of elastic material and a glide piece rigidly connected to said body and permitting said gliding movement between the carrier bar and the carrier bar bearing means.

3. The expansion gap sealing device according to claim 1, comprising further elastic bearing means (14) located between said gap strip means (11) and said carrier bars (6), and means (54) for firmly securing said further elastic bearing means (14) to the gap strip means (11) and to the carrier bars (6).

4. The expansion gap sealing device according to claim 3, wherein said further elastic bearing means (14) have an outer dimension larger than said apertures in said gap strip means (11), said further elastic bearing means having an inner dimension to provide a tight fit relative to the carrier bars, whereby said further elastic bearing means (14) are maintained under a predetermined biasing force.

5. The expansion gap sealing device according to claim 3, wherein said further elastic bearing means (14) are arranged above and below the respective carrier bar, said means for firmly securing being arranged between the elastic bearing means and top and bottom surfaces of the carrier bar inside the apertures.

6. The expansion gap sealing device according to claim 1, wherein said gap strip means comprise upper rods and lower rods and intermediate means for interconnecting the upper and lower rods with each other.

7. The expansion gap sealing device according to claim 6, wherein said intermediate means comprise cross pieces and detachable connecting members for releasably connecting any one of said upper and lower rods with the cross pieces.

8. The expansion gap sealing device according to claim 7, wherein a plurality of said cross pieces is provided for each gap strip means, said cross pieces being spaced from each other to provide said apertures in the gap strip means, said cross pieces having a shape which is symmetrical relative to the longitudinal axis of the gap strip means, said cross pieces having a size corresponding substantially to that of the adjacent aperture.

9. The expansion gap sealing device according to claim 8, wherein any of said cross pieces comprises two members one above and one below said longitudinal axis of the gap strip means, said apertures having a shape corresponding to that of said cross piece members such that a cross piece member above said longitudinal axis fits into the aperture below the axis and vice versa.

10. The expansion gap sealing device according to claim 1, comprising elastic glide bearing means (14, 15) located between said gap strip means (11) and said carrier bars (6), means (16) for securing the gap strip means to the glide bearing means, and a gliding fit between the carrier bars (6) and the glide bearing means to permit a relative gliding movement therebetween.

11. The expansion gap sealing device according to claims 10, wherein said elastic glide bearing means (14, 15) are arranged above and below the respective carrier bar and comprising said gliding fit with top and bottom surfaces of the carrier bar inside the apertures.

12. The expansion gap sealing device according to claim 10, further comprising means for firmly securing said elastic glide bearing means to the gap strip means and means for permitting a gliding movement between the carrier bar and the elastic glide bearing means.

13. The expansion gap sealing device according to claim 10, wherein said elastic glide bearing means comprise a body of elastic material and a glide piece firmly secured to said body of elastic material.

14. The expansion gap sealing device according to claim 10, wherein said carrier bars comprise stop means for limiting the sliding movement of said elastic glide bearing means in the longitudinal direction of said gap strip means and thus laterally relative to the carrier bars.

15. The expansion gap sealing device according to claim 10, wherein said elastic glide bearing means (14, 15) have an outer dimension larger than said apertures in said gap strip means, said elastic glide bearing means having an inner dimension relative to the carrier for maintaining said elastic glide bearing means under a predetermined biasing force while simultaneously assuring said gliding fits.