Patent Publication Number: US-6986557-B2

Title: Slide segment with integral ball bearing mount

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to telescoping slide assemblies. More particularly, the present invention relates to a slide assembly that occupies a reduced cross-sectional area while maintaining a high load rating. 
   2. Description of the Related Art 
   Slide assemblies are commonly used to support an object, relative to a support structure, for linear motion between an accessible and a stored position. For example, drawers are usually supported by one or more slide assemblies for movement between an open and closed position relative to a cabinet, or other enclosure. Regardless of the application, it is generally desirable for the slide assembly to occupy as small an area as possible, while still providing sufficient strength, in order to maximize the dimensions of the drawer, or other object supported by the slide asembly. 
   One specific application in which a reduction of the cross-sectional area of the slide assembly is especially beneficial is the internet server market. In an internet server, the hardware components comprising the server are arranged and secured within a metal or a plastic enclosure, or chassis. The server/chassis assembly is then typically housed within an enclosed cabinet containing multiple servers arranged in a vertical manner. Each chassis is mounted on a pair of telescoping slides so that the server may be easily withdrawn from the cabinet for inspection, repair or replacement. It is contemplated that 1U and 2U servers will comprise the majority of the future internet server market. 
   A large number of cabinets, each containing multiple internet servers, often covering thousands, or tens of thousands, of square feet of floor space may be found in a single location. Storage costs for internet servers are typically calculated on a basis of square feet of floor space occupied per server. Accordingly, it is highly desirable to reduce the area occupied by the cabinets in order to maximize the number of cabinets, and thus servers, that may be stored in a given area. 
   One impediment to reducing cabinet dimensions has been the cross-sectional size of the available slide mechanism, or “slide”, for short. Additionally, in an effort to reduce design and purchasing costs, it is desirable to provide a single slide that is suitable for both the 1U and 2U server applications. Therefore, a need exists for a slide of reduced cross-sectional area that is structurally capable of supporting a vertical load produced by either a 1U or 2U internet server. 
   In an internet server application, it is desirable to utilize an over-travel type slide assembly, which is capable of extending a distance greater than the length of any of the slide&#39;s individual segments. When utilizing an over-travel slide, the server may be completely withdrawn from the cabinet to permit access to the rearward end of the server where cables, such as power cables or connecting cables, may be located. A typical over-travel slide has three individual slide segments telescopingly engaged with one another. For example, an outer slide segment may be connected to the cabinet and an inner slide segment may be connected to the internet server chassis. An intermediate segment may interconnect the outer slide segment and the inner slide segment. 
   In a three piece slide assembly it is desirable for the individual slide segments to move in a specific sequence relative to one another. Specifically, it is highly undesirable for the inner segment to fully extend alone, before the intermediate slide segment begins to extend. Accordingly, the inner and intermediate slide segments are often coupled to move together, at least initially, when extending from the fully closed position of the slide. The inner and intermediate slide segments may be configured to frictionally engage one another to achieve the desired sequencing. Alternatively, a latch-type mechanism may be used to releasably connect the inner and intermediate slide segments. 
   However, as mentioned above, it is highly desirable to reduce the cross-sectional dimensions of the slide. To be strong enough to withstand the forces from repeated extensions of the slide assembly, latch-type mechanisms may necessarily be prohibitively large and prevent the slide assembly from having desirably small cross-sectional dimensions. Friction-type sequencing mechanisms are often unreliable in operation. For example, frictional forces between the outer and intermediate slide segments, due to the weight of the server, may be larger than the sequencing friction and allow the inner slide segment to extend alone. 
   An alternative method of sequencing extension of the slide segments is disclosed in U.S. Pat. No. 6,056,379 to Weng. The Weng slide assembly  1  is a three-piece, over-travel slide assembly having an inner slide segment  2 , an intermediate slide segment  3  and an outer slide segment  4 . An outer assembly of bearings includes both upper and lower bearings  5  positioned between the intermediate slide segment  3  and outer slide segment  4 . An inner assembly of bearings includes both upper and lower bearings  6  between the intermediate slide segment  3  and inner slide segment  2 . 
   A plurality of spherical members, or transmission members  7 , are fixed for movement with the intermediate slide segment  3  as it extends and retracts. Each transmission member  7  contacts both the inner slide segment  2  and outer slide segment  4 . Upper and lower sets of transmission members  7  are in contact with upper and lower end portions  8  of the inner slide segment  2  and upper and lower end portions  9  of the outer slide segment, respectively. Extension of the inner slide segment  2  results in rotation of the transmission members  7 , as a result of being in contact with the end portions  8 , which then roll on the end portions  9  of the outer slide segment  4 . Because the intermediate slide segment  3  is fixed for movement with the transmission members  7 , the rolling motion of the transmission members  7  causes extension of the intermediate segment  3  along with extension of the inner slide segment  2 . 
   One problem with the Weng slide assembly  1  is that the provision of both outer bearings  5  and inner bearings  6  necessarily increases the height of the slide  1 . As discussed above, a reduced cross-sectional envelope is highly desirable, especially in internet server mounting applications. An additional problem with the Weng slide assembly  1  is that, because both the outer and inner bearings  5 ,  6  and the transmission members  7  are positioned between the inner slide segment  2  and the outer slide segment  3 , the tolerances of both the inner and outer segments  2 ,  3  must be precisely controlled in order to ensure that the transmission members  7  will properly contact both the end portions  8 ,  9  of the inner and outer segments  2 ,  4 , respectively, which necessarily increases manufacturing costs. It may even be necessary to perform an additional manufacturing process step in order to ensure appropriate dimensions of the end portions  8 ,  9 , which may increase the overall cost of the slide assembly  1  to a greater extent. 
   SUMMARY OF THE INVENTION 
   Accordingly, preferred embodiments of the present slide assembly are capable of supporting a 1U or 2U internet server and have a compact cross-sectional area, allowing it to fit within a 1″×⅜″ cross-sectional envelope. Additionally, a single set of upper bearings and a single set of lower bearings desirably support substantially the entire load carried by the slide. Both the upper and lower bearings are carried by an intermediate slide segment and contact both the inner and outer slide segments when the slide is in a fully closed position. Accordingly, with such an arrangement, the bearings cause the intermediate slide segment to extend along with the inner slide segment. In addition, because only a single set of upper and lower bearings are positioned between the inner and outer slide segments, the slide assembly can be manufactured with typical tolerance ranges, thereby keeping the overall cost of the slide assembly low. Desirably, the slide assembly is an over-travel type assembly wherein the inner slide segment may be extended completely from the outer slide segment to permit access to the rearward end of an internet server mounted to the slide assembly. However, advantages of the present invention may also be realized with under-travel slide assemblies. 
   A preferred embodiment is a slide assembly including a first slide segment configured to carry a load and having a web, a first transverse section and a second transverse section spaced from one another along the web. The first transverse section defines a first contact surface and the second transverse section defines a second contact surface. A second slide segment is telescopingly engaged with the first slide segment. A third slide segment is configured to be connected to an object and is telescopingly engaged with the second slide segment. The third slide segment includes a web, a third transverse section and a fourth transverse section spaced from one another along the web. The third transverse section defines a third contact surface and the fourth transverse section defines a fourth contact surface. The slide is movable from a retracted position to an extended position, wherein the second slide segment is at least partially withdrawn from the third slide segment. A plurality of upper bearings and a plurality of lower bearings are carried by the second slide. At least one of the upper plurality of bearings and the lower plurality of bearings support substantially all load carried by the first slide segment. For example, desirably the slide is constructed such that the plurality of upper bearings and the plurality of lower bearings contact both the first and third slide segments in substantially any position of the slide assembly. In such an arrangement, the load carried by the first slide segment is supported by both the upper and lower bearings. However, in some arrangements, one or the other of the upper plurality of bearings or the lower plurality of bearings may primarily, or wholly, support the load carried by the first slide segment. For example, when the slide is in a fully retracted position, the load may be primarily, or wholly, supported by the lower plurality of bearings. Further, the upper bearings desirably contact both of the first contact surface and the third contact surface and the lower bearings contact both of the second contact surface and the fourth contact surface when the slide is in the retracted position. 
   A preferred embodiment is a slide assembly including a first slide segment having a web defining a vertical inner surface, a first transverse section and a second transverse section spaced from one another and extending in a first direction from the web. The first transverse section defines a first contact surface and the second transverse section defines a second contact surface. A second slide segment is telescopingly engaged with the first slide segment. A third slide segment is telescopingly engaged with the second slide segment and includes a web defining a vertical inner surface, a third transverse section and a fourth transverse section spaced from one another and extending from the web in a second direction opposite the first direction. The third transverse section defines a third contact surface and the fourth transverse section defines a fourth contact surface. The slide is movable from a retracted position to an extended position, wherein the second slide segment is at least partially withdrawn from the third slide segment. A plurality of upper bearings and a plurality of lower bearings are carried by the second slide segment and at least one of the upper plurality of bearings and the lower plurality of bearings support substantially all load carried by the first slide segment. The upper bearings contact both of the first contact surface and the third contact surface and the lower bearings contact both of the second contact surface and the fourth contact surface when the slide is in the retracted position. An exposed portion of the upper and lower plurality of bearings are not in contact with either of the first slide segment and the third slide segment when the slide is in the extended position. The second slide segment supports the exposed portion of the bearings. The upper bearings and the lower bearings are spaced inward in the first direction from the inner surface of the web of the first slide segment and the upper bearings and the lower bearings are spaced inward in the second direction from the inner surface of the web of the third slide segment. 
   A preferred embodiment is a slide assembly including a first slide segment configured to carry a load. The first slide segment has a web, a first transverse section and a second transverse section spaced from one another along the web. The first transverse section defines a first contact surface and the second transverse section defines a second contact surface. A second slide segment is telescopingly engaged with the first slide segment. A third slide segment is configured to be connected to an object and is telescopingly engaged with the second slide segment. The third slide segment includes a web, a third transverse section and a fourth transverse section spaced from one another along the web. The third transverse section defines a third contact surface and the fourth transverse section defines a fourth contact surface. The slide is movable from a retracted position to an extended position, wherein the second slide segment is at least partially withdrawn from the third slide segment. A plurality of upper bearings define centers arranged in no more than one plane, said plane being substantially perpendicular to said web of one of said first slide segment and said third slide segment, and a plurality of lower bearings define centers arranged in no more than one plane, said plane being substantially perpendicular to said web of one of said first slide segment and said third slide segment, and support the first slide segment relative to the third slide segment. The upper bearings and the lower bearings support substantially an entire load carried by the slide. 
   A preferred embodiment is a slide assembly including a first slide segment configured to carry a load. The first slide segment has a web, a first transverse section and a second transverse section spaced from one another along the web. The first transverse section defines a first contact surface and the second transverse section defines a second contact surface. A second slide segment is telescopingly engaged with the first slide segment. A third slide segment is configured to be connected to an object and is telescopingly engaged with the second slide segment. The third slide segment includes a web, a third transverse section and a fourth transverse section spaced from one another along the web. The third transverse section defines a third contact surface and the fourth transverse section defines a fourth contact surface. The slide is movable from a retracted position to an extended position, wherein the second slide segment is at least partially withdrawn from the third slide segment. A plurality of upper bearings and a plurality of lower bearings are carried by the second slide segment and at least one of the plurality of upper bearings and the plurality of lower bearings supports substantially all load carried by the first slide segment. The upper bearings contact both of the first contact surface and the third contact surface and the lower bearings contact both of the second contact surface and the fourth contact surface when the slide is in the retracted position. The second slide segment is at least two-thirds of the length of one of the first slide segment and the third slide segment. 
   A preferred embodiment is a slide assembly including a first slide segment configured to carry a load. The first slide segment has a web, a first transverse section and a second transverse section spaced from one another along the web. The first transverse section defines a first contact surface and the second transverse section defines a second contact surface. A second slide segment is telescopingly engaged with the first slide segment. A third slide segment is configured to be connected to an object and is telescopingly engaged with the second slide segment. The third slide segment includes a web, a third transverse section and a fourth transverse section spaced from one another along the web. The third transverse section defines a third contact surface and the fourth transverse section defines a fourth contact surface. The slide is movable from a retracted position to an extended position, wherein the second slide segment is at least partially withdrawn from the third slide segment. A plurality of upper bearings define centers arranged in no more than one plane, said plane being substantially perpendicular to the web of one of the first and third slide segments, and a plurality of lower bearings define centers arranged in no more than one plane, said plane being substantially perpendicular to the web of one of the first and third slide segments. The upper bearings and the lower bearings support the first slide segment relative to the third slide segment and at least one of the plurality of upper bearings and the plurality of lower bearings support substantially all load carried by the slide. The second slide segment is at least two-thirds the length of one of the first slide segment and the third slide segment. 
   A preferred embodiment is a slide assembly having a first slide segment configured to be connected to a first object. The first slide segment has a web, a first transverse section and a second transverse section spaced from one another along the web. The first transverse section defines a first contact surface and the second transverse section defines a second contact surface. A second slide segment is configured to be connected to a second object. The second slide segment is telescopingly engaged with the first slide segment and includes a web, a third transverse section and a fourth transverse section spaced from one another along the web. A plurality of upper bearings are held in a fixed location relative to the third transverse section and are rotatable relative to the third transverse section. A plurality of lower bearings are held in a fixed location relative to the fourth transverse section and are rotatable relative to the fourth transverse section. At least one of the plurality of upper bearings and the plurality of lower bearings support substantially all load carried by the slide assembly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned, and other features of the invention, are described with reference to the drawings of a preferred embodiment of the present invention. The illustrated embodiment of the slide assembly is intended to illustrate, but not to limit, the invention. The drawings contain nine figures. 
       FIG. 1  is a cross-sectional view of a prior art slide assembly; 
       FIG. 2  is a perspective view of an internet server cabinet with one server in a withdrawn position from the cabinet. The server is shown mounted to the cabinet with a pair of preferred slides; 
       FIG. 3  is a cross-sectional view of the slide assembly shown in  FIG. 2 . The slide assembly includes an inner slide segment, an intermediate slide segment and an outer slide segment telescopingly engaged with one another. The inner and outer segments are separated from one another by upper and lower bearings, which are carried by the intermediate slide segment; 
       FIG. 4  is an exploded assembly view of the intermediate slide segment, upper and lower bearings and upper and lower bearing retainers; 
       FIG. 5  is a side view of the slide assembly taken along the line  5 — 5  of  FIG. 3 . In  FIG. 5 , the slide assembly is shown in a closed position; 
       FIG. 6  is a side view of the slide assembly in a partially open position; 
       FIG. 7  is a side view of the slide assembly in a fully open, or extended, position; 
       FIG. 8  is a cross-sectional view of a variation of the slide assembly of  FIGS. 2–7  including a alternate intermediate slide segment; and 
       FIGS. 9A–9C  are a series of cross-sectional views illustrating a method for fabricating the alternate intermediate slide segment of  FIG. 8 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A slide constructed in accordance with the present invention finds utility in a wide variety of applications. As will be appreciated by one of skill in the art, the slide assembly may comprise an under-travel arrangement, or an over-travel arrangement, and may be configured for vertical mounting, or other mounting orientations. However, a preferred embodiment of the slide disclosed herein is particularly well suited for use in computer hardware applications and, in particular, for mounting 1U and 2U internet servers within a server cabinet. Accordingly, the present slide assembly is described in the environment of internet server mounting, however, such a description of use is not intended to limit the present invention. 
   The individual hardware components comprising an internet server are typically housed within a chassis. When the term server is used herein, it is typically intended to include the server/chassis assembly, unless otherwise indicated. A 1U server has approximate dimensions (width×depth×height) of 19″×22½″×1¾″ and may weigh approximately 30–35 pounds. A 2U server is typically 19″×20½″×3½″ and may weigh approximately 60–75 pounds. However, preferably, a slide assembly constructed in accordance with principles disclosed herein is capable of supporting an operating load of approximately 100 pounds. Such an arrangement provides a slide assembly having sufficient strength to permit use with either a 1U or 2U server, and also provides a factor of safety. As a result of the increased volume of slides produced due to providing a single slide design for both the 1U and 2U server markets, design and manufacturing costs may be reduced. 
     FIG. 2  illustrates a plurality of internet servers  10  held within a cabinet  12 . Each server  10  is connected to the cabinet  12  by a pair of slides  14 . The slides  14  are constructed for translation between a fully retracted position and a fully extended position. A single server  10  is illustrated with its related pair of slides  14  in a fully extended position. As discussed above, the slides  14  preferably are constructed such that in their fully extended position the server  10  is completely withdrawn from the cabinet  12 . Advantageously, such an arrangement allows easy access to the server  10  for purposes such as installation, modification or repair. As discussed in detail below, the slides  14  are constructed with sufficient strength to support a 1U or 2U server while, at the same time, occupying a minimum amount of space. Such an arrangement advantageously reduces wasted space (i.e., non-server space) within the cabinet  12 , allows the cabinet  12  to be constructed with reduced dimensions and, thus, maximizes the number of servers that may occupy a given area. 
   With reference to  FIG. 3 , a preferred slide assembly  14  is shown in section. The slide assembly  14  includes an inner slide segment  16 , an intermediate slide segment  18  and an outer slide segment  20 . An upper arrangement of bearings  22  and a lower arrangement of bearings  24  support the outer slide segment  20  relative to the inner slide segment  16 . Desirably, both the upper and lower bearings  22 ,  24  are carried by, or fixed for motion with, the intermediate slide segment  18 . With reference to  FIGS. 4–7 , both the upper and lower bearings  22 ,  24  desirably comprise a plurality of individual bearing members, or ball bearings spaced from one another along the length of the slide  14 . 
   With reference to  FIG. 3 , the inner slide segment  16  includes a substantially vertical web  26  extending between an upper transverse section  28  and a lower transverse section  30 . The upper transverse section  28  desirably is curved and includes an upper curved surface  32  that defines a contact surface, or bearing race, for supporting the upper bearings  22 . Similarly, the lower transverse section  30  desirably is curved and includes a lower curved surface  34  that defines a contact surface, or bearing race, for supporting the lower bearing  24 . In addition, the curved shape of the upper and lower transverse sections  28 ,  30  inhibits lateral, or transverse, movement of the inner slide segment  16  (i.e., movement in the horizontal direction in the vertical slide illustrated in  FIG. 3 ). 
   The outer slide segment  20  also includes a vertical web  36  extending between upper and lower transverse sections  38 ,  40 , respectively. The upper and lower transverse sections  38 ,  40  of the outer slide segment  20  extend in an opposite direction from the transverse sections  28 ,  30  of the inner slide segment  16 . The upper transverse section  38  of the outer slide segment  20  includes a curved lower surface that defines a curved contact surface  42 , or bearing race, for supporting the upper bearings  22 . Similarly, the lower transverse section  40  of the outer slide segment  20  includes a curved upper surface that defines a contact surface  44 , or bearing race, for the lower bearings  24 . The curved shape of the upper and lower transverse sections  38 ,  40  inhibits lateral, or transverse, movement of the outer slide segment  20 . 
   Desirably, strengthening ribs  46  are located generally at the transition between the vertical web  36  and both the upper and lower transverse sections  38 ,  40  of the outer slide segment  20 . Preferably, the strengthening ribs  46  extend approximately the entire length of the outer slide segment  20 . Advantageously, the strengthening ribs  46  increase the resistance of the outer slide segment  20 , and the entire slide assembly  14 , from flexing due to bending and/or torsional forces. In addition, the strengthening ribs  46  inhibit outward flexing of the transverse sections  38 ,  40  of the outer slide segment  20  thereby preventing undesired vertical movement, or play, of the inner and intermediate slide segments  16 ,  18 . 
   The intermediate slide segment  18  also includes a vertical web  48  extending between an upper transverse section  49  and a lower transverse section  51 . Preferably, the upper and lower transverse sections  49 ,  51  of the intermediate slide segment  18  extend away from the vertical web  48  in the same direction as the upper and lower transverse sections  38 ,  40  of the outer slide segment. In addition, the vertical web  48  of the intermediate slide segment  18  is positioned generally between a vertical web  26  of the inner slide segment  16  and the vertical web  36  of the outer slide segment  20 . 
   With reference to  FIGS. 3 and 4 , desirably, the upper transverse section  49  includes a first portion  50  and a second portion  56 , which cooperate to support the upper bearings  22 . That is, the first and second portions  50 ,  56  hold the bearings  22  for movement with the intermediate slide segment  18  and substantially prevent vertical movement of the bearings  22 . Each upper bearing  22  is received within an aperture  54 , which passes vertically through the first portion  50 . The first portion  50  defines the surface of the aperture  54 , which desirably is spherical in shape to generally conform to the outer surface of the upper ball bearing  42 . Preferably, the maximum diameter of the aperture  54  is located at the upper surface of the first portion  50  and is approximately equal to the diameter of the upper bearing  42  such that the upper bearing  42  may only pass approximately halfway through the aperture  54 . That is, approximately one-half of the upper bearing  42  is positioned above the upper surface of the first portion  50 . 
   A second portion  56  of the upper transverse section  49  is attached to the first portion  50  and includes a spherical aperture  58 , which generally corresponds with the aperture  54  of the first portion  50 . The maximum diameter of the aperture  58  desirably is located at the lower surface of the second portion  56  and the diameter reduces when moving upward through the aperture  58 . 
   As described above, the aperture  54  of the first portion  50  and the aperture  58  of the second portion  56  cooperate to retain the upper bearing  22  in substantially all directions, while permitting the bearing to rotate. Thus, the upper bearing  22  may rotate in response to linear movement of the inner slide segment  16 , as is described in greater detail below. 
   Similarly, the lower transverse section  51  of the intermediate slide segment  18  includes a first portion  52  and a second portion  62  which cooperate to support the lower bearings  24  in a manner similar to that described above in relation to the upper transverse section  49 . The first portion  52  includes a spherical aperture  60 , which prevents the lower bearing  24  from moving in an upward direction. The second portion  62  includes a spherical aperture  64  that cooperates with the aperture  60  and prevents the lower bearing  24  from moving in an upward direction. As mentioned above, desirably the upper and lower bearing arrangements  22 ,  24  comprise a plurality of bearings, each retained in their respective apertures. 
   Preferably, the vertical web  26  of the inner slide segment  16  and the vertical web  36  of the outer slide segment  20  define a width W of the slide assembly  14 . The upper transverse section  38  and the lower transverse section  40  of the outer slide segment  20  define a height H of the slide assembly  14 . Advantageously, with the arrangement described above, the slide assembly  14  is capable of supporting a 1U or 2U internet server while fitting within a relatively small cross-sectional envelope. Desirably, the height H is approximately one inch and the width W is approximately three-eighths of an inch. However, as will be appreciated by one of skill in the art, the dimension of the slide assembly  14  may be altered to suit a particular application. 
   As illustrated in  FIGS. 3 and 4 , preferably the upper bearings  22  are aligned with one another in both a vertical direction (i.e., in the direction of the height H) and a lateral direction (i.e., in the direction of the width W). Similarly, it is preferred that the lower bearings  24  are aligned with one another in both a vertical and a lateral direction. Additionally, it is preferred that the upper bearings  22  are aligned with the lower bearings  24  in the lateral direction. Such an arrangement allows the slide assembly to have a compact cross-section. Although the above-described arrangement is preferred, other arrangements may also be utilized wherein the upper and/or lower bearings are not aligned. 
   Desirably, a central portion  66  of the vertical web  48  of the intermediate slide segment  18  is off-set from the remainder of the vertical web  48  and is located approximately an equal distance from the vertical web  26  of the inner slide segment  16  and the vertical web  36  of the outer slide segment  20 . Accordingly, a space  68  is defined between the vertical web  26  and the vertical web  66 . Similarly, a space  70  is defined between the vertical web  66  and the vertical web  36 . Typically, in an internet server environment, the outer slide segment  20  is connected to the server cabinet  12  ( FIG. 2 ) and the inner slide segment  16  is connected to the internet server  10  ( FIG. 2 ). The spaces  68 ,  70  provide clearance for fastening members utilized to connect the server  10  and the cabinet  12  to the slide assembly  14 , as is well known in the art. The above-described arrangement permits the spaces  68 ,  70  to be sized such that common mounting fasteners may be utilized despite the desirably small cross-sectional envelope of the slide assembly  14 . 
     FIG. 4  is an exploded assembly view of the intermediate slide segment  18 . As illustrated, both the upper and lower second portions, or retainers  56 ,  62 , are relatively flat, elongated pieces, which are sized and shaped to generally conform to the upper surface of the upper first portion  50  and lower surface of the lower first portion  52 , respectively. The upper and lower retainers  56 ,  62  may be attached to the intermediate segment  18  by any suitable method. For example, the upper and lower retainers  56 ,  62  may be secured to the intermediate slide segment  18  through a welding process, such as spot welding, for example. Alternatively, mechanical fasteners, such as rivets, may also be used. 
     FIG. 5  is a side plan view of the slide assembly in a fully closed, or retracted position. In the closed position, the slide assembly  14  defines a length L C  approximately equal to the length of the individual segments  16 ,  18 ,  20 . Further, desirably the length of the intermediate slide segment  18  is equal to at least a significant portion of the length of either the inner segment  16  and outer slide segment  20 . With such an arrangement, when the slide is in an over-travel position, the load applied to each of the inner and outer slide segments  16 ,  20  by the intermediate slide segment  18  is spread over a significant length of the inner and outer segments  16 ,  20 . Accordingly, the slide  14  is capable of supporting a relatively large amount of weight in an over-travel position without damaging either the inner or outer slide segments  16 ,  18 . Desirably, the intermediate slide segment  18  is at least two-thirds the length of either the inner or outer slide segments  16 ,  20 . Preferably, the intermediate slide segment  18  is at least three-quarters the length of either the inner or outer slide segments  16 ,  20  and, more preferably, is at least four-fifths the length of either the inner or outer slide segments  16 ,  20 . Most preferably, as illustrated in  FIG. 5 , the intermediate slide  18  is approximately the same length as the inner slide segment  16  and the outer slide segment  20 . 
   In addition, because the load is transmitted between the individual slide segments  16 ,  18 ,  20  by the bearings  22 ,  24 , it is desirable that at least five upper and five lower bearings  22 ,  24  are provided. Such an arrangement spreads the load applied to the inner and outer segments  16 ,  20  over a larger area. Preferably, at least ten each of upper bearings  22  and lower bearings  24  are provided. More preferably, at least fifteen of each upper bearings  22  and lower bearings  24  are provided and, most preferably, at least twenty each of upper bearings  22  and lower bearings  24  are provided. Further, it is also desirable that the bearings  22 ,  24  are spread out over a significant length of the intermediate slide segment  18  in order to spread the load applied to the inner and outer segments  16 ,  20  over a larger area. Desirably, both the upper bearings  22  and lower bearings  24  are spread over at least one half the length of the intermediate slide  18 . More desirably, the bearings are spread over at least two-thirds and, preferably, over at least three-quarters of the slide segment  18 . More preferably, the bearings are spread out over at least four-fifths of the intermediate segment  18  and, in some applications, may even be spread out over the entire length of the intermediate segment  18 . 
     FIG. 6  illustrates the slide assembly  14  in a partially extended position. As the inner slide segment  16  is extended, rotational motion is imparted to the upper and lower bearings  22 ,  24 , due to the contact between the bearing contact surfaces  32 ,  34  ( FIG. 3 ) of the inner slide segment  16 . As a result, the upper and lower bearings  22 ,  24  roll along the bearing contact surfaces  42 ,  44  of the outer slide segment  20 . Because the bearings are held by the intermediate slide segment  18 , as described above, motion is imparted to the intermediate slide segment  18  as the inner slide segment  16  is extended with respect to the outer slide segment  20  due to the rolling motion of the bearings  22 ,  24 . Advantageously, such an arrangement ensures that the inner slide segment  16  does not extend alone. Instead, the intermediate slide segment  18  moves toward an extended position, along with the inner slide segment  16 . 
   As illustrated in  FIG. 6 , because at least a portion of the upper and lower bearings  22 ,  24  contact both of the inner segment  16  and the outer segment  20  (until approximately when over-travel begins), the intermediate slide segment  18  moves about one-half the distance that the inner slide segment  16  moves. For example, if the inner slide segment  16  is extended from a fully closed position of the slide  14  a distance of D, the intermediate slide segment  18  is extended approximately one-half the distance D, or D/2. Once an over-travel position is reached (i.e., the inner segment  16  is completely withdrawn from the outer segment  20 ), no individual bearing  22 ,  24  is in contact with both of the inner and outer segments  16 ,  20  and, as a result, no motion is imparted to the intermediate segment  18  through the bearings  22 ,  24 . 
   With reference to  FIG. 7 , the slide assembly  14  is shown in a fully extended position. In the fully extended position, the slide assembly  14  defines an extended length L E , which desirably is greater than the length of any individual slide segments  16 ,  18 ,  20 . Thus, when the slide assembly  14  is in its fully extended position, a distance O D  is defined between the outer slide segment  20  and the inner slide segment  16 . The distance O D  is referred to as the over-travel distance, as is well known in the art. 
   Although the illustrated slide assembly  14  is an over-travel slide, an under-travel slide assembly may also be provided in accordance with the present invention. In an under-travel slide assembly, the inner slide segment is not completely withdrawn from the outer slide segment when the slide is in a fully extended position. In addition, although a three-piece slide assembly  14  is shown, the slide may comprise additional slide segments. For example, more than one intermediate slide segment may be provided, as will be appreciated by one of skill in the art. 
   As is known in the art, when an over-travel slide assembly is in a fully extended position, the intermediate slide segment must be capable of withstanding substantially the entire load carried by the slide without permanently deforming and, preferably, without significant deflection. Preferably, the intermediate slide segment  18  of the illustrated slide assembly  14  is configured to support an operating load of at least thirty pounds being carried by the slide  14  without permanent deformation. More preferably, the intermediate slide segment  18  is configured to support an operating load of at least seventy five pounds being carried by the slide  14  without permanent deformation. As will be apparent to one of skill in the art, in other slide applications, the intermediate slide segments may be configured to support a lesser, or much greater, load. 
   Advantageously, as described above, the bearings  22 ,  24  are retained in both an upward and downward vertical direction by the upper and lower transverse sections  49 ,  51 . Accordingly, when the slide  14  is in a fully extended position, a portion of the bearings  22   a ,  24  that may not be in contact with the either the inner segment  16  or the outer segment  20  are nonetheless secured to the intermediate slide segment  18  and are prevented from being displaced from the slide assembly  14 . Similarly, the bearings  22   b ,  24   b  that are in contact with the outer slide segment  20 , but not the inner slide segment  16 , are also secured to the intermediate slide segment  18 . 
   As will readily be determined by one of skill in the art, any of a number of suitable stop mechanisms may be utilized to define fully closed and/or fully extended positions of the slide assembly  14 , or any two segments thereof. Additionally, if desired, any suitable type of lock mechanism may be utilized to releasably secure the slide assembly  14 , or any two segments of the slide  14 , in a fully closed and/or fully extended position. 
   With reference to  FIG. 1 , as discussed above, the Weng slide assembly  1  has several disadvantages that make it undesirable for general use, and especially in internet server mounting applications. For example, incorporating both an outer set of bearings  5  and an inner set of bearings  6  increases the overall height of the slide assembly  1 . As a result, it may not be possible for such a slide assembly  1  to both be strong enough to reliably carry the load of a 1U or 2U internet server and fit within the 1″×⅜″ cross-sectional envelope, which is presently preferred within the internet server industry. 
   In addition, as discussed above, the dimensions of the Weng slide assembly  1  must be held within a precise range to ensure appropriate contact between the transmission members  7  and the inner and outer slide segments  2 ,  4 . As a result, it may not be possible to manufacture a slide assembly  1  as shown in the Weng patent at an economically feasible cost. 
   Specifically, both the inner slide segment  2  and the outer slide segment  4  of the Weng slide assembly  1  have two critical vertical dimensions in order to ensure proper functioning of the slide  1 . First, as with many slide assemblies, a vertical distance O 1  between the bearing surfaces of the transverse sections of the outer slide segment  4  and a vertical distance I 1  between the bearing surfaces of the inner slide segment  2  are important to permit proper functioning of the slide assembly  1 . Desirably, the difference between the distances O 1  and I 1  is large enough to accommodate the bearings  5 ,  6  and transverse section of the intermediate slide segment  3  to allow the slide  1  to extend with low resistance, yet not so large as to permit excessive vertical movement of the inner and outer segments  2 ,  4  relative to one another. 
   Unlike many other slide assemblies, however, a distance O 2  between the end portions  9  of the outer segment  4  and a distance I 2  between the end portions  8  of the inner segment  2  are also critical to proper functioning of the sequencing action of the slide assembly  1 . The difference between the distances O 2  and I 2  must be large enough to accommodate the transmission members  7 , yet still permit the members  7  to contact both respective end portions  8 ,  9  of the inner and outer slide segments  2 ,  4 . 
   Common manufacturing methods may be unable to hold the above-described dimensions O 1 , I 1  and O 2 , I 2  within a tolerance range necessary to ensure proper, consistent motion of the slide assembly  1 , at least without necessitating additional process steps, which increase the manufacturing cost. For example, the individual slide segments of a slide assembly are commonly manufactured by a roll-forming process wherein a flat piece of metal is passed through a progression of rollers, which incrementally deform the flat piece of material into the desired final shape. Due to normal variation in the width of the initially flat piece of material and normal variations in the roll-forming process itself, if the first critical dimensions O 1  and I 1  are controlled, it is likely that the second critical dimensions O 2  and I 2  will not be held within the necessary tolerance range to permit proper sequencing action of the slide  1 . It is likely that an additional machining process will be necessary to remove such variation to achieve the desired critical dimensions I 2 , O 2  of one or both of the end portions  8 ,  9  of the inner and outer segments  2 ,  4 . As a result, the overall manufacturing cost of the slide assembly  1  is increased. 
   Another disadvantage of the Weng slide assembly  1  is that no means is disclosed for securing the transmission members  7  vertically with respect to the intermediate slide segment  3 . As a result, when any one of the transmission members  7  is not secured vertically between the inner and outer segments  2 ,  4  (i.e., when the inner slide segment  2  is extended), the transmission member  7  will fall from the intermediate slide segment  3  due to the force of gravity. 
   In contrast, the present slide assembly  14  overcomes the above-described disadvantages of the Weng slide assembly  1 . For instance, by utilizing only a single arrangement each of upper and lower bearings  22 ,  24 , the illustrated slide assembly  14  is capable of both supporting either a 1U or 2U internet server and fitting within the desired 1″×⅜″ cross-sectional envelope. In addition, the bearings  22 ,  24  support the load carried by the slide  14  and cause extension, or sequencing movement, of the intermediate slide segment  18 . 
   Additionally, the inner segment  16  and the outer segment  18  are separated by only the upper and lower bearings  22 ,  24 . Accordingly, with reference to  FIG. 3 , the upper transverse section  28  of the inner segment  16  and the upper transverse section  38  of the outer segment  20  are separated by only two spherical surfaces (i.e., the upper and lower surfaces of the upper bearing  22 ). Similarly, the lower transverse section  30  of the inner segment  16  and the lower transverse section  40  of the outer segment  20  are separated by only two spherical surfaces (i.e., the upper and lower surfaces of the lower bearing  24 ). As a result, normal manufacturing practices may be used to shape the individual segments  16 ,  18 ,  20 , without requiring additional manufacturing steps. That is, there is no critical vertical dimension necessary to accommodate a transmission mechanism in addition to the necessary vertical dimension, common to most slide assemblies, for accommodating the load-carrying bearings. 
   Furthermore, the present slide assembly  14  also secures the bearings  22 ,  24  vertically with respect to the intermediate slide segment  18 , as described above. Such an arrangement prevents the bearings  22 ,  24  from being displaced from the slide assembly  14  when they are not in contact with both of the inner and outer segments  16 ,  20 , such as when the slide  14  is in an over-travel position ( FIG. 7 ). Advantageously, such an arrangement eliminates the need for a separate bearing cage member to secure the bearings in contact with either the inner or outer slide segment, thereby reducing the cost of the final assembly. 
     FIG. 8  illustrates an alternative configuration of the slide assembly  14  of  FIGS. 2–7  and is generally referred to by the reference numeral  14 ′. The slide  14 ′ is substantially similar in construction and operation to the slide  14  of  FIGS. 2–7  and, therefore, like reference numerals are used to describe like components, except that a prime (′) is added. 
   In the intermediate slide segment  18 ′ of  FIG. 8 , both the upper and lower second portions  56 ′,  62 ′ of the upper and lower transverse sections  49 ′,  51 ′ are formed from the same piece of material as the intermediate segment  18 ′, including the first portions  50 ′,  52 ′. Advantageously, such an arrangement reduces the overall number of components in the slide assembly  14 ′, thereby reducing the overall cost. In addition, assembly of the bearings  22 ′,  24 ′ into the intermediate slide segment  18 ′ is simplified in comparison to the arrangement of  FIGS. 2–7 . 
     FIGS. 9A–9C  illustrate one method for fabricating the intermediate slide segment  18 ′ of  FIG. 8  and assembling the bearings  22 ′,  24 ′ into the segment  18 ′. With reference to  FIG. 9A , desirably the intermediate segment  18 ′ is partially shaped by a suitable process, such as a roll-forming process for example, such that the first portions  50 ′,  52 ′ are angled from the second portions  56 ′,  62 ′ a sufficient distance such that the bearings  22 ′,  24 ′ may be positioned therebetween. Preferably, the angle between the first portions  50 ′,  52 ′ and the second portions  56 ′,  62 ′ is small enough such that the bearings  22 ′,  24 ′ are at least partially positioned within one, or both, of the apertures  54 ′,  60 ′ of the first portions  50 ′,  52 ′ and/or apertures  58 ′,  64 ′ of the second portions  56 ′,  62 ′ and are thereby held in a desired position. 
   With reference to  FIG. 9B , the transverse sections  50 ′,  52 ′ are formed in an inward direction toward a position transverse with respect to the web  48 ′ of the intermediate slide segment  18 ′. In addition, desirably the second portions  56 ′,  62 ′ are formed inward toward the first portions  50 ′,  52 ′. Subsequently, and with reference to  FIG. 9C , the second portions  56 ′,  62 ′ are further formed until they are generally adjacent the first portions  50 ′,  52 ′ and the bearings  22 ′,  24 ′ are secured within the apertures  54 ′,  60 ′ of the first portions  50 ′,  52 ′ and the apertures  58 ′,  64 ′ of the second portions  56 ′,  62 ′. If desired, the second portions  56 ′,  62 ′ may then be secured to the first portions  50 ′,  52 ′ by a suitable means, such as welding or mechanical fasteners, for example. 
   Although the present invention has been described in the context of a preferred embodiment, it is not intended to limit the invention to the provided example. Modifications to the slide assembly  14 , or alternative configurations, that are apparent to one of skill in the art are considered to be part of the present invention. For example, although the illustrated slide assembly  14  is arranged for vertical mounting applications, the present invention may also be adapted for horizontal, or other mounting configurations. In addition, the slide assembly  14  may be adapted for uses other than internet server mounting applications and, therefore, may take on alternative cross-sectional dimensions or lengths. Accordingly, the invention should be defined solely by the appended claims in light of the teachings of the disclosure.