Adjustable scaffolding and lift carriage and support member therefor

BACKGROUND OF THE INVENTION

1. 1. Field of the Invention

2. The present application relates generally to an adjustable support apparatus including an adjustable lift carriage and support member, and more particularly to an adjustable scaffolding structure including an adjustable lift carriage and platform support and a support tower for use therewith.

3. 2. Description of the Prior Art

4. Various types of adjustable scaffolding exist in the art. Such adjustable scaffolding commonly is used in the construction industry for supporting construction workers and/or materials during the construction, maintenance or demolition of a structure. A common scaffolding structure currently existing in the art includes a cable and winch assembly for raising and lowering a carriage and associated platform support along a plurality of generally vertical tower supports. Although the cable and winch systems have performed generally satisfactorily, cables require a great deal of care and maintenance to maintain their strength. The failure to properly care and maintain cables and the winch assembly in such a system has resulted in system failure and personal injury.

5. Various types of adjustable scaffolding and lift systems exist in the art. These function primarily to support worker and/or material platforms for use during construction, repair, maintenance or demolition of a structure. Examples include non-cable systems such as those described in the Maack U.S. Pat. No. 3,946,836. Maack discloses the use of a rotatable endless belt with a plurality of regularly spaced openings that sequentially engage lugs protruding from a vertical structure. The belt is supported by two vertically spaced sprockets in which one or more teeth are purposely deleted so that the sprocket teeth do not make contact with the lugs while the sprockets are rotating. A requirement of the Maack disclosure is that the spacing of the lugs must be an integral multiple of the spacing between the belt openings.

6. The Pujol U.S. Pat. No. 4,534,446, the Patnode U.S. Pat. No. 5,487,446, the Schernekau U.S. Pat. No. 2,007,480, the Knechtel U.S. Pat. No. 1,442,075, the Beck U.S. Pat. No. 3,071,205 and the Allen UK Patent No. 150,011 also disclose non-cable means for moving a platform up and down a vertical structure. The Pujol patent discloses the use of a wheel with radial projections that sequentially engage perforations in the vertical structure and in which the wheels are rotated by a rotatable worm drive and crown gear assembly. The Patnode patent discloses the use of a sprocket with peripheral teeth that sequentially engage apertures in the vertical structure in order to move the attached platform up and down the structure. In Patnode, with the sprocket is rotated by means of a bevel gear assembly. The Schemekeau and Knechtel patents disclose the use of two sets of staggered radial pins which sequentially engage perforations in their respective vertical structures. The Beck and Allen patents disclose using conventional rack and pinion means.

7. One of the most commonly used adjustable scaffolding systems involves the use of a winch and cable for raising and lowering a support platform relative to a pair of support towers. In these systems one end of the cable is hooked to the top or an upper portion of the tower and the other end is wound onto a winch which is mounted to the carriage. Rotation of the winch causes the carriage and its related structure to be pulled up the tower by the cable. While winch and cable systems function generally satisfactorily, such systems have several limitations. First, cables require a great deal of care and maintenance to maintain their strength. Second, the lift capacity of a winch and cable system is related directly to the size and strength of the cable. For most applications this has practical limitations. Third, use of winch and cable systems is labor intensive in that it requires extensive time for handling and maintaining the cable and dealing with broken, rusted, frayed or otherwise damaged cable. Fourth, when utilizing cable and winch systems, it is necessary to align and re-hook the cable as additional tower sections are added or removed.

8. Accordingly, there is a need in the art for a lift system, and particularly an adjustable scaffolding system, which improves lift capacity, minimizes care and maintenance, and totally eliminates the cable and winch and the various limitations thereof.

SUMMARY OF THE INVENTION

9. In accordance with the present invention, an improved cableless lift system or adjustable scaffolding system is provided. Such system eliminates the cable and winch and provides a structure which increases the lift capacity of the lift carriage and significantly reduces, care, maintenance, handling and other time consuming tasks commonly associated with cable and winch systems.

10. The present invention includes an improved carriage assembly which is designed to move up and down a vertical support member without the use of cable and winch elements. The preferred embodiment of the lift system of the present invention further includes a plurality of support members with a series of spaced first support surfaces positioned along the longitudinal axis of the support members. The improved carriage assembly includes a pair of rotatable members with an endless band such as a chain, belt or the like extending between and around the rotatable members. The band carries a plurality of spaced lift members each having a second support surface for engagement with the first support surfaces of the support member as the rotatable members are rotated. In the preferred embodiment, the spacing between adjacent first support surfaces on the support member is greater than the spacing between the second support surfaces of adjacent lift members.

11. Because of this spacing difference, the lift carriage and its associated platform and platform supports are supported primarily by engagement between one first support surface and one second support surface at any one time. This spacing relationship also enables the second support surface of the non-engaged lift members to clear the first support surface during their movement around and between the rotatable members. In the preferred embodiment, the rotatable members comprise a pair of spaced toothed sprockets carrying an endless roller chain and being rotatably supported within an elongated support housing. The support housing includes a wall portion functioning as a band or chain support to ensure engagement between the first and second support surfaces during operation of the system. The preferred embodiment of the carriage assembly is also provided with a ratchet dog, a speed regulating dog and a safety catch to prevent the carriage from falling in the event of a lift system failure. A plurality of platform supports similar to those which are common in the art are also provided.

12. The vertical support or tower members in accordance with the present invention comprise at least a pair of generally parallel, support posts with a plurality of support braces functioning both to interconnect and brace the support posts and to provide the plurality of spaced first support surfaces. The support members may be comprised of single elongated structures or of a plurality of support member sections connected to one another in end to end relationship. In both embodiments, consistent longitudinal spacing of the support braces, and thus the first support surfaces, is maintained throughout the entire support member length.

13. Accordingly it is an object of the present invention to provide an improved cableless adjustable scaffolding or lift system.

14. Another object of the present invention is to provide an adjustable scaffolding or lift system with improved lift capacity.

15. Another object of the present invention is provide an adjustable scaffolding lift carriage which is free of the conventional cable and winch members and which eliminates limitations of such cable and winch systems.

16. A still further object of the present invention is to provide an improved support or tower member for use with the above described lift system.

17. A still further object of the present invention is to provide an improved adjustable scaffolding assembly comprising an improved cableless lift carriage, a plurality of tower supports and a supporting platform.

18. These and other objects of the present invention will become apparent with reference to the drawings, the description of the preferred embodiment and the appended claims.

DESCRIPTION OF THE DRAWINGS

19.FIG. 1 is an isometric view of an adjustable scaffolding assembly in accordance with the present invention.

20.FIG. 2 is an isometric view of the lift carriage assembly in accordance with the present invention and its relationship to a portion of the support tower.

21.FIG. 3 is a further isometric view of the lift carriage assembly of the present invention similar to FIG. 2 with portions broken away and showing the carriage drive mechanism separated from the carriage housing.

22.FIG. 4 is comprised of FIGS. 4A, 4B, <b>4</b>C and <b>4</b>D and shows sequences of operation of the lift carriage assembly in accordance with the present invention.

23.FIG. 5 is a view, partially in section, as viewed along the section line <b>5</b>—<b>5</b> of FIG. 2.

24.FIG. 6 is a view, partially in section, as viewed along the section line <b>6</b>—<b>6</b> of FIG. 5 showing a portion of the lift carriage assembly and the relationship between the roller chain, the carriage support housing and the lift members.

25.FIG. 7 is a side elevational view of a further embodiment of the support surfaces and lift members in accordance with the present invention.

26.FIG. 8 is a top elevational view of the embodiment of FIG. 7.

27.FIG. 9 is a side elevational view of a still further embodiment of the support surfaces and lift members in accordance with the present invention.

28.FIG. 10 is a top elevational view of the embodiment of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENT

29. The present invention relates generally to a lift assembly of the type having one or more elongated support frame members and a lift carriage moveable along each frame member. The preferred embodiment of the present invention is described with reference to what is commonly referred to as adjustable scaffolding comprising two or more vertically positioned support towers and a lift carriage moveable up and down along the support towers. Unless otherwise specifically limited, it is intended that the scope and benefits of the present invention are applicable not only to an adjustable scaffolding application, but to any other lift apparatus or assembly as well.

30. Further, the description of the preferred embodiment discloses details of the entire lift assembly as well as details of the improved lift carriage and the support tower or support frame, both individually as well as in combination. It is intended that the improved lift carriage in accordance with the present invention may be usable with support towers other than those specifically described in the present application and that similarly, the support tower or frame members will be useful with lift carriages other than those specifically described herein.

31. With reference first to FIG. 1, the lift assembly of the present invention is shown in the form of an adjustable scaffolding assembly <b>10</b>. The adjustable scaffolding assembly <b>10</b> includes a pair of support towers or support members <b>11</b>. Where shorter scaffolding is needed, these members <b>11</b> can be of a single length. For taller scaffolding, however, as shown in the preferred embodiment, the members <b>11</b> are comprised of a plurality support tower or support member sections <b>11</b><i>a</i>, <b>11</b><i>b </i>and <b>11</b><i>c</i>. These sections <b>11</b><i>a</i>, <b>11</b><i>b</i>, and <b>11</b><i>c </i>are connected in end to end relationship with one another to form the elongated support tower <b>11</b> with a longitudinal axis. The pair of support towers <b>11</b> are supported at their bottom ends by a base <b>12</b> in a manner well known in the art and are stabilized throughout their length and at their free end by a plurality of cross braces <b>14</b> and/or a panel brace <b>15</b>. It is also common for multiple support towers or pairs of support towers to be interconnected with one another by cross braces or stringer braces as known in the art to span greater distances.

32. A carriage assembly <b>13</b> is associated with each of the support towers <b>11</b>. Each carriage assembly includes a material or material/laborer platform bracket <b>18</b> and a workman platform bracket <b>19</b>. As shown, a major portion of the material platform bracket <b>18</b> extends outwardly from the side of the support towers <b>11</b> opposite the building structure, while a major portion of the workman support bracket <b>19</b> extends outwardly from the support tower <b>11</b> adjacent to the building structure. A plurality of planks are extended between adjacent material platform brackets <b>18</b> to provide a material or material/laborer platform <b>20</b>. Similarly, a plurality of planks are provided between the workman support brackets <b>19</b> to provide a workman platform <b>21</b>. A plurality of guard rails or railing sections <b>22</b> are connected with the material platform brackets <b>18</b>. It should be noted that the structural details relating to the base <b>12</b>, the material and workman platform brackets <b>18</b> and <b>19</b>, the planks and their platforms <b>20</b> and <b>21</b>, and the guard rails <b>22</b> are well known to those skilled in the art.

33. Each carriage assembly <b>13</b> further includes a lift carriage <b>16</b> associated with one of the frame members <b>11</b>. Each of the carriages <b>16</b> is connected with the platform brackets <b>18</b> and <b>19</b> as described below and includes raising and lowering means to facilitate the selective raising and lowering of the brackets <b>18</b> and <b>19</b>, and thus the material and workman platforms <b>20</b> and <b>21</b>, along the support members <b>11</b>.

34. Reference is next made to FIGS. 2 and 3 illustrating enlarged isometric views of the carriage <b>16</b> and a portion of the support tower <b>11</b>, with portions broken away. As shown, the support tower <b>11</b> includes a pair of laterally spaced support posts <b>24</b>,<b>24</b>. These posts <b>24</b>,<b>24</b>, when the carriage assembly is erected, extend vertically in a direction generally parallel to one another and to the longitudinal axis of the support tower <b>11</b> and define a support post plane. In the preferred embodiment, the support posts <b>24</b>,<b>24</b> are formed from rigid angle members having a pair of outer faces <b>25</b> and <b>26</b> positioned at right angles to one another. As shown in FIGS. <b>2</b> and <b>3</b>, as well as in FIG. 5, the side surfaces <b>26</b>,<b>26</b> of the support posts <b>24</b>,<b>24</b> are laterally spaced and generally parallel to one another, while the surfaces <b>25</b>,<b>25</b> are laterally spaced from one another and lie substantially in a common plane. A plurality of laterally extending brace members <b>28</b> are rigidly secured to the support posts <b>24</b> by welding or the like. The brace members <b>28</b> are spaced vertically along the entire length of the support posts <b>24</b>,<b>24</b>. As will be discussed in greater detail below, the spacing of these brace members <b>28</b> throughout the entire length of the support towers <b>11</b> is constant whether the tower <b>11</b> is a single length or is comprised of sections <b>11</b><i>a</i>, <b>11</b><i>b</i>, <b>11</b><i>c</i>. The brace members <b>28</b> can have a variety of configurations; however, in the preferred embodiment, the brace members <b>28</b> comprise an angle member welded to the inner surfaces of the support posts <b>24</b> opposite the outer faces <b>25</b> and <b>26</b>. As shown, one leg <b>29</b> of the member <b>28</b> is welded to an inside surface of the posts <b>24</b> opposite the face <b>25</b> and the other leg extends generally laterally and at right angles to the longitudinal axis of the support tower <b>11</b> to form a first support surface <b>30</b>.

35. Each support tower <b>11</b> is also provided with a third support post <b>31</b> extending the entire length of the support tower <b>11</b>. When the support tower <b>11</b> is comprised of a plurality of support tower sections <b>11</b><i>a</i>, <b>11</b><i>b </i>and <b>11</b><i>c </i>(FIG. 1), the first and second support posts <b>24</b>,<b>24</b> and the third support post <b>31</b> comprise support post sections extending the entire length of the sections <b>11</b><i>a</i>, <b>11</b><i>b </i>and <b>11</b><i>c</i>. Brace members <b>32</b> and <b>34</b> are provided between the support posts <b>24</b>,<b>24</b> and <b>31</b> as shown to provide proper spacing between such support posts and to ensure rigidity of the entire support tower <b>11</b>. In the preferred embodiment, the brace members <b>32</b> and <b>34</b> are elongated, bent brace members which are welded to inner facing surfaces of the support posts <b>24</b>,<b>24</b> and <b>31</b>. In the preferred embodiment, the cross sectional configuration of the support post <b>31</b> is square to provide a pair of generally planar side roller guide surfaces <b>35</b>,<b>35</b> generally perpendicular to the support post plane and a rear roller guide surface <b>36</b> generally parallel to the support post plane. The outer surfaces <b>25</b> and <b>26</b> of the posts <b>24</b>,<b>24</b> are also generally planar to provide roller guide surfaces as discussed in greater detail below. FIGS. 2 and 3 show the tower <b>11</b> with the top portions of the posts <b>24</b>,<b>24</b> and the post <b>31</b> broken away for clarity. In actuality, these posts <b>24</b>,<b>24</b> and <b>31</b> extend to the top of the tower <b>11</b> as shown in FIG. 1. Although the preferred embodiment shows the support post <b>31</b> as square, it could also be angled, with rollers engaging the two angled surfaces. Further, although the preferred embodiment discloses the support tower <b>11</b> as comprising first, second and third support posts, any number can be used. For example, a support tower with two support posts or with four or more support posts is possible as long as the structure includes the spaced first support surfaces <b>30</b> as described.

36. With continuing reference to FIGS. 2 and 3, the carriage <b>16</b> includes an elongated generally tubular rigid housing <b>38</b> having back and front walls <b>39</b> and <b>42</b>, respectively and a pair of side walls <b>40</b> and <b>41</b>. Although the preferred embodiment shows the tubular carriage housing of the preferred embodiment to be a four sided housing with a generally rectangular cross section, it is intended that the term “tubular housing” as used in describing the housing <b>38</b> of the present invention could also be a three sided housing comprised of the wall <b>39</b> and the side walls <b>40</b> and <b>41</b>.

37. As shown best in FIG. 2 and <b>3</b>, a pair of rotatable members <b>44</b> and <b>45</b> are rotatably supported on shafts <b>46</b> and <b>48</b>, respectively, between the side walls <b>40</b> and <b>41</b> of the carriage housing <b>38</b>. The shafts <b>46</b> and <b>48</b> are supported by suitable bearings within bearing blocks/housings <b>49</b> and <b>50</b> in a manner known in the art. The vertical position of the shaft <b>46</b>, and thus the rotatable member <b>44</b>, is adjustable via a threaded adjustment member <b>51</b>. As shown, the adjustment member <b>51</b> is associated with an adjustment bracket <b>52</b> connected with each of the side walls <b>40</b> and <b>41</b>. Vertical adjustment of the rotatable member <b>44</b> facilitates corresponding adjustment of the endless band <b>54</b> extending between the members <b>44</b> and <b>45</b>.

38. As shown, the endless band <b>54</b> extends around and between the pair of rotatable members <b>44</b> and <b>45</b> so that rotation of the members <b>44</b> and <b>45</b> causes corresponding movement of the band <b>54</b>. It is intended that the benefits of the present invention can be realized regardless of the type of endless band or rotatable members that are utilized. For example, the endless band <b>54</b> could be a chain, a belt or some other endless member and the rotatable members <b>44</b> and <b>45</b> could be a toothed sprocket, a pulley or some other rotatable member cooperating with the band member either by friction or positive engagement. Thus, unless otherwise specifically stated, the terms “band” and “rotatable member” as used in describing the present invention is intended to cover not only a roller chain for use with a toothed sprocket as described in the preferred embodiment, but a belt and pulley as well as any other endless member and corresponding rotating member.

39. In the preferred embodiment, the rotatable members <b>44</b> and <b>45</b> are toothed sprockets and the endless band member <b>54</b> is a roller chain. The roller chain <b>54</b> includes a plurality of rollers <b>55</b> and connecting links <b>56</b> and lift member support links <b>57</b>. As known in the art, the rollers <b>55</b> are connected with the links <b>56</b> and <b>57</b> by pins <b>58</b>. The size and load rating of the chain should be selected to provide sufficient capacity in its use for the adjustable scaffolding applications of the preferred embodiment. Preferably the roller chain size should be at least #80. Positioned along the endless chain <b>54</b> in equally spaced relationship and connected with the support links <b>57</b> are a plurality of lift members <b>59</b>. In the preferred embodiment, each of the lift members <b>59</b> includes a narrow section <b>60</b> and a wide section <b>61</b>. The narrow section <b>60</b> is rigidly secured between spaced attachment ears <b>62</b>,<b>62</b> of the links <b>57</b>. In the preferred embodiment, the narrow portion <b>60</b> is rigidly secured to the attachment ears <b>62</b>,<b>62</b> by a pair of threaded members or rivets <b>64</b>. The wide section <b>61</b> includes a bottom surface defining a bottom second support surface <b>65</b> for engagement with the first support surface <b>30</b>. In the preferred embodiment, the distance between the lift members <b>57</b> along the chain <b>54</b>, and thus the distance between adjacent second support surfaces <b>65</b>, is constant. As shown and described in greater detail below, the distance between adjacent second support surfaces <b>65</b> must be less than the distance between adjacent first support surfaces <b>30</b>. Further, because the distance between adjacent lift members <b>57</b> must be the same, the length of the chain <b>54</b> must be integral multiples of that distance.

40. As shown, the attachment ears <b>62</b>, <b>62</b> of the support links <b>57</b> are positioned on opposite sides of the lift member <b>59</b> and support the lift member <b>59</b>, and thus the second support surface <b>65</b>, outwardly of the chain <b>54</b> and the rollers <b>55</b>. As understood best with reference to FIG. 3, the chain <b>54</b>, and thus the lift members <b>59</b>, travel around and between the sprockets <b>44</b> and <b>55</b> as the sprockets <b>44</b> and <b>45</b> rotate.

41. With continuing reference to FIGS. 2 and 3, and more specific reference to FIGS. 5 and 6, the sprockets <b>44</b> and <b>45</b> are mounted between the side walls <b>40</b> and <b>41</b> in a position such that a portion of the sprockets and a portion of the chain <b>54</b> that extends between the sprockets <b>44</b> and <b>45</b> are outside of, or on the tower side of, the wall <b>39</b> of the tubular housing <b>38</b>. To accommodate this, the wall <b>39</b> is provided with upper and lower band or chain access openings <b>66</b> and <b>68</b>, respectively. Thus, the sprockets <b>44</b> and <b>45</b> are mounted between the walls <b>40</b> and <b>41</b> on one side of the wall <b>39</b>, with a portion of the roller chain <b>54</b> which extends between the sprockets <b>44</b> and <b>45</b> positioned on the other side of the wall <b>39</b>.

42. During movement of the chain <b>54</b> and the lift members <b>59</b> between the sprockets <b>44</b> and <b>45</b> on the outside of the wall <b>39</b>, the wall <b>39</b> functions as a chain or band support to maintain movement of the chain <b>54</b> in a generally straight line path between the sprockets <b>44</b> and <b>45</b>. Although the wall <b>39</b> is capable of providing this support as a result of sliding engagement between the inside surfaces of the link members <b>56</b> and <b>57</b> and the outer surface of the wall <b>39</b>, the preferred embodiment of the present invention includes a chain support or slide member in the form of the chain support <b>69</b> shown best in FIGS. 5 and 6. This chain support <b>69</b> comprises a metal bar or the like having a width slightly less than the width between corresponding link members <b>56</b> and <b>57</b> and having a thickness dimension which allows the member <b>69</b> to engage the rollers <b>55</b> and prevent the links <b>56</b> from sliding engagement with the outer surface of the wall <b>39</b>. In the preferred embodiment, the chain or roller support <b>69</b> extends substantially the entire distance between the band openings <b>66</b> and <b>68</b> to provide rolling engagement with the rollers <b>55</b>. With this structure, the support <b>69</b> maintains the band or chain <b>54</b> in a straight line, or a desired path, between the sprockets <b>44</b> and <b>45</b>.

43. The carriage <b>16</b>, and specifically the tubular housing <b>38</b>, is mounted relative to the support tower <b>11</b> to provide the desired engaging relationship between the first support surface <b>30</b> and the second support surface <b>65</b>. Specifically, as the chain <b>54</b> and lift members <b>59</b> move between the sprockets <b>44</b> and <b>45</b>, the second support surface <b>65</b> on the bottom of the lift member <b>59</b> is positioned to engage the first support surface <b>30</b> on top of the brace member <b>28</b> as shown. This causes the carriage <b>16</b> and thus its associated platforms <b>19</b> and <b>20</b> and platform brackets <b>18</b> and <b>19</b> to move upwardly or downwardly along the tower <b>11</b>. A plurality of roller members <b>70</b> and <b>72</b> are rotatably supported relative to the tubular housing <b>38</b>. These rollers <b>70</b> and <b>72</b> are designed for engagement with outer planar surfaces of the support posts <b>24</b>,<b>24</b> and function to provide the desired spacing and orientation between the carriage <b>16</b> and the support tower <b>11</b>. Specifically, a pair of rollers <b>70</b> near the top of the housing <b>38</b> and a pair of rollers <b>70</b> near the bottom of the housing <b>38</b> are mounted in roller supports <b>71</b> which in turn are rigidly secured to the wall <b>39</b> of the housing <b>38</b>. As shown, the rollers <b>70</b> engage the outer surfaces <b>25</b>, <b>25</b> of the support post <b>24</b>,<b>24</b> in rolling engagement to maintain the wall <b>39</b> in proper spaced relationship relative to the support tower <b>11</b>. Similarly, one or more rollers <b>72</b> are rotatably supported within the roller supports <b>74</b> which are rigidly connected to the side walls of the housing <b>38</b>. These rollers <b>72</b> engage the outer surface <b>26</b> of the posts <b>24</b>,<b>24</b> to maintain the tubular housing <b>38</b> and carriage <b>16</b> in a proper side to side orientation. In an alternate embodiment it is contemplated that the rollers could be replaced by Teflon or other low friction material to reduce friction during movement of the carriage <b>16</b> up and down the support tower.

44. The lower end of the carriage <b>16</b> as shown in FIGS. 2 and 3 is provided with a support bracket portion <b>75</b> rigidly secured to the outer side wall <b>41</b> by welding or the like. The bracket portion <b>75</b> extends generally horizontally, is hollow, and is intended to receive material and workman platform support brackets <b>18</b> and <b>19</b> (FIG. 1) in a manner known in the art. Rigidly secured to the bracket portion <b>75</b> on the outward side of the post <b>31</b> is a support stub <b>76</b> for supporting the plank support bracket <b>78</b>, the roller support brackets <b>79</b>,<b>79</b> and the roller support bracket <b>80</b>. The roller support brackets <b>79</b>, <b>79</b> and <b>80</b> are provided with rollers <b>81</b>,<b>81</b> and <b>82</b>, respectively, for rolling engagement with the side surfaces <b>35</b>,<b>35</b> and the rear or outer surface <b>36</b>, respectively, of the support post <b>31</b>.

45. A plank support bracket <b>84</b> is also rigidly secured to the lower outer surface of the inner wall <b>40</b> as shown to provide a support for a platform plank. As shown, the plank supporting surfaces of the support brackets <b>78</b> and <b>84</b> are at the same level. Further, it should be noted that the adjacent ends <b>77</b> and <b>83</b> of the brackets <b>78</b> and <b>84</b> are sufficiently spaced from one another to allow the carriage assembly to pass a brace members <b>14</b> (FIG. 1) as the carriage moves up and down the support towers <b>11</b>.

46. The upper end of the tubular carriage housing <b>38</b> is provided with a mounting arm <b>85</b> for supporting the rotation and drive assembly <b>86</b>. Specifically, the mounting arm <b>85</b> is rigidly secured to the outer surface of the side wall <b>41</b> by welding or the like. Mounted at the outer end of the mounting arm <b>85</b> is a support bracket <b>88</b>. The rotation and drive assembly <b>86</b> is rigidly connected with the support bracket <b>88</b> and includes a pair of side members <b>89</b>,<b>89</b> and a shaft <b>90</b> rotatably supported therebetween. Each end of the shaft is provided with a rotation shaft end <b>91</b>,<b>91</b> (FIG. 2). The ends <b>91</b>,<b>91</b> can be rotated either manually with a hand crank <b>92</b> or the like by any electrically driven member such as an electric drill (not shown) with a socket adapted to mate with the ends <b>91</b>,<b>91</b>.

47. The rotation and drive assembly <b>86</b> further includes a pair of safety dogs mounted on the shaft <b>90</b> to prevent the carriage from accidentally dropping. Specifically, one safety dog includes the ratchet dog <b>96</b> which contacts the gear teeth on the toothed flange <b>98</b> to prevent the shaft <b>90</b> from rotating in a direction which would cause the carriage to move downwardly, unless manually disengaged. The dog <b>96</b> is gravity operated. The other safety dog comprises the speed regulating dog <b>94</b> which oscillates over the ratchet teeth on the flange <b>95</b> to positively control the rotation speed of the shaft <b>90</b>. The operation of these safety features and particularly operation of the safety dogs <b>96</b> and <b>94</b> is known in the art.

48. The gear assembly for driving the sprockets <b>44</b> and <b>45</b> is illustrated best in FIGS. 2 and 3. In FIG. 2 the assembly is connected with the carriage <b>16</b>, while in FIG. 3 the assembly is separated from the main carriage housing. One end of the drive gear assembly, namely the initial toothed drive sprocket <b>99</b> is connected with the shaft <b>90</b> for rotation by the hand crank <b>92</b> or other rotation means. The toothed sprocket <b>99</b> is in turn connected with the sprockets or gears <b>100</b>, <b>102</b> and <b>104</b> by the roller chains <b>105</b>, <b>106</b> and <b>108</b>. As shown, the gear <b>100</b> is an idler gear provided with the smaller diameter companion gear <b>101</b> on a common hub, while the gear <b>102</b> is an idler gear provided with the smaller diameter companion gear <b>103</b> on a common hub. The gear <b>104</b> is mounted on the shaft <b>48</b> (FIGS. 2 and 3) which directly drives the lower sprocket <b>45</b>. With the drive mechanism as shown, a 32:1 reduction gear ratio is achieved. It is contemplated, however, that the present invention could use other gear and drive mechanisms for rotating the members <b>44</b> and <b>45</b>.

49. Positioned near the top of the carriage housing <b>38</b> is a spring-loaded safety latch <b>109</b> which includes a beveled top surface <b>110</b> and a flat bottom surface <b>111</b>. The safety latch <b>109</b> extends through an opening <b>112</b> in the housing wall <b>39</b> and extends outwardly a sufficient distance to facilitate engagement with the support surface <b>30</b> of the brace members <b>28</b>. The safety latch <b>109</b> is spring mounted and is thus biased in an outward or engagement direction. The safety latch <b>109</b> allows the carriage <b>16</b> to move upwardly relative to the support tower <b>11</b>, but prevents downward movement of the carriage <b>16</b> without first manually releasing the latch <b>109</b>. During upward movement, engagement between the bottom edge of the brace member <b>28</b> and the beveled top surface <b>110</b> causes the latch <b>109</b> to be moved inwardly against the spring force to release the latch <b>109</b> from engagement with the brace <b>28</b>. During downward movement, however, the bottom flat surface <b>111</b> engages the first support surface <b>30</b> and prevents further downward movement unless the latch is manually released. The manual release includes a rotatable release arm <b>115</b> and a cable <b>114</b> connected to the rearward end of the latch <b>109</b>. Forward rotational movement of the release arm <b>115</b> causes retraction and manual release of the latch <b>109</b>.

50. The operation and operational concept of the lift assembly and carriage of the present invention can be understood best with reference to FIG. 4 comprising FIGS. 4A, 4B, <b>4</b>C and <b>4</b>D. FIGS. 4A through 4D represent various stages of rotation of the sprockets <b>44</b> and <b>45</b> and thus various rotational positions of the lift members <b>56</b>. FIGS. 4A through 4D also show the relative positions between the second support surfaces <b>65</b> of the members <b>59</b> and the first support surfaces <b>30</b> of the braces <b>28</b>. In the preferred embodiment, the distance between the first support surfaces <b>30</b> of adjacent brace members <b>28</b> is greater than the distance between the second support surfaces <b>65</b>,<b>65</b> of adjacent lift members <b>59</b>,<b>59</b>. As shown in FIG. 4D, the distance between adjacent first support surfaces <b>30</b> is a first distance D₁, while the distance between the second support surfaces <b>65</b> of adjacent lift members <b>59</b> is a second distance D₂. The amount of this difference in distance which is needed for proper functioning of the lift assembly of the preferred embodiment is primarily a function of several factors. These include among possible others, the size of the rotatable sprockets <b>44</b> and <b>45</b>, the distance which the second support surface <b>65</b> extends outwardly from the outer periphery of the sprockets and the distance between the rotational axis of the sprockets and the first support surfaces <b>30</b>. In the preferred embodiment, the rotatable sprockets <b>44</b> and <b>45</b> have a pitch diameter in the range of about 3 to 6 inches, with a preferred diameter of about 3.2 to 5.5 inches. This provides a preferred distance D₁between adjacent first support surfaces <b>30</b> of about 12½inches and a distance D₂between adjacent second support surfaces <b>65</b> of about 12 inches. Thus, in the preferred embodiment, the distance between the second support surfaces <b>65</b> of adjacent lift members <b>59</b> is ½inch shorter than adjacent first support surfaces <b>30</b>.

51. Although the preferred embodiment shows the sprockets <b>44</b> and <b>45</b> as being of equal diameter, this is not a requirement. Further, the preferred distances of D₁and D₂and the difference between them can vary as long as D₁is greater than D₂and the other factors are such as to facilitate the functioning of the invention as described below.

52. With the above defined relationship, the operation of the invention is as follows. At the beginning of operation when the carriage assembly is supported independently of its respective support tower, the carriage <b>16</b> is positioned so that one of its lift members <b>59</b> is between two of the first support surfaces <b>30</b> of the brackets <b>28</b>. The sprockets <b>44</b> and <b>45</b> are then rotated in a clockwise direction as shown in FIG. 4A-4D. This causes the chain <b>54</b> and the lift members <b>59</b> to move around the sprockets and to ultimately cause a second support surface <b>65</b> of one of the lift members <b>59</b> to engage the higher of the two first support surfaces <b>30</b> as shown in FIGS. 4C or <b>4</b>D. Continued rotation of the sprockets <b>44</b> and <b>45</b> then causes the second support surfaces <b>65</b> of the lift members <b>58</b> sequentially engage the first support surfaces <b>30</b> of the brackets <b>28</b> to lift or lower the carriage <b>16</b> and its associated structure. In FIG. 4A, the carriage <b>16</b> is supported entirely by the lower lift member <b>59</b>.

53. As the sprockets <b>44</b> and <b>45</b> continue to rotate in a clockwise direction, the second support surface of the next (or upper) lift member <b>59</b> as shown in FIG. 4B begins to engage the upper first support surface <b>30</b>. Thus, in FIG. 4B, the carriage <b>16</b> is supported partly by engagement between the lower first and second support surfaces <b>30</b> and <b>65</b> and partly by engagement between the upper first and second support surfaces <b>30</b> and <b>65</b>.

54. As the sprockets <b>44</b> and <b>45</b> continue to rotate further in a clockwise direction, the second support surface <b>65</b> of the upper lift member <b>59</b> becomes fully supported by the upper first support surface <b>30</b> and the second support surface <b>65</b> of the lower lift member <b>59</b> begins to lift off and become disengaged from the lower first support surface <b>30</b>. Thus, in FIG. 4C, the carriage <b>16</b> is supported solely by engagement between the second support surface <b>65</b> of the upper lift member <b>59</b> and the upper first support surface <b>30</b>.

55. As the sprockets <b>44</b> and <b>45</b> continue to rotate further as shown in FIG. 4D, the carriage <b>16</b> continues to be fully supported by engagement between the upper second support surface <b>65</b> and the upper first support surface <b>30</b>, while the lower lift member <b>59</b> and its second support surface <b>65</b> moves further away from the lower first support surface <b>30</b>. Further rotation of the sprockets <b>44</b> and <b>45</b> results in the lower lift member <b>59</b> and its second support surface <b>65</b> moving entirely away from the lower support surface <b>30</b> as it travels around the lower sprocket <b>45</b> as shown in FIG. 4A. Continued rotation of the sprockets <b>44</b> and <b>45</b> causes the above process to be repeated, thereby causing the carriage <b>16</b> and its associated platforms and platform brackets to move upwardly relative to the support tower <b>11</b> and its first support surfaces <b>30</b>.

56. When it is desired for the carriage <b>16</b> is to be lowered, the above described process is reversed. Thus, as viewed in FIGS. 4A through 4D, the sprockets <b>44</b> and <b>45</b> would rotate in a counterclockwise direction and the sequence of engagement of and disengagement from the various first and second support surfaces is from FIGS. <b>4</b>D, to <b>4</b>C, to <b>4</b>B and to <b>4</b>A.

57. In the preferred embodiment, various links of the chain <b>54</b> are provided with lift members <b>59</b> having a second support surface <b>65</b> extending outwardly from the chain for engagement with a first support surface <b>30</b> of the brace <b>28</b>. It is also possible, however, to use hooks or lugs which are welded to and extended outwardly from the support tower <b>11</b> to engage the rollers on the climbing chain instead of using attachment links <b>56</b> in accordance with the preferred embodiment. Two alternative embodiments are illustrated in FIGS. 7 and 8 and in FIGS. 9 and 10. In the embodiment of FIGS. 7 and 8, a plurality of spaced hooks <b>120</b> are rigidly secured to longitudinally spaced brace members <b>121</b> connected between the support posts <b>24</b> of the tower <b>11</b>. These hooks <b>120</b>, like the first support surfaces <b>30</b> in the preferred embodiment are spaced apart a first distance. In the embodiments of FIGS. 7 and 8, the carriage is provided with a drive sprocket <b>122</b> having sprocket teeth for engagement with the roller chain <b>126</b> and a pair of non-toothed idler rollers <b>124</b> and <b>125</b> for guiding the chain <b>126</b> in the area where the lifting is accomplished. Other than this, the function of the embodiment illustrated in FIGS. 7 and 8 is essentially the same as that illustrated in FIGS. 1-6. The embodiment of FIGS. 9 and 10 is similar to that of the embodiments of FIGS. 7 and 8 except that the embodiment of FIGS. 9 and 10 includes a pair of longitudinally spaced hooks <b>128</b>,<b>128</b> (FIG. 10) which engage an extension of the roller pin <b>129</b>.

58. Although the description of the preferred embodiment has been quite specific, it is contemplated that various modifications could be made without deviating from the spirit of the present invention. Accordingly, it is intended that the present invention be dictated by the appended claims rather than by the description of the preferred embodiment.