Abstract:
A hoist provides high mechanical advantage and accurate positioning, driven by hand or with a powered rotary implement such as a drill. The hoist includes flexible tension members, such as chains, cables or straps, for applying force and tension to a load. A load nut is connected to the tension members for high mechanical advantage from rotational drive input to a load screw threadedly connected to the load nut. Alongside the tension members are guides forming channel-like spaces within which the flexible tension members travel. The guides, or portions of the guides, pass through the load nut in most forms of the invention.

Description:
BACKGROUND OF THE INVENTION 
   This invention concerns a hoist which receives a rotational input and applies tension to a pair of opposed flexible tension members with very high mechanical advantage. Hoists of this type include a screw gear which provides a positive hold of the applied tension force when the screw gear is not being driven. 
   Screw gear hoists are known. The applicant&#39;s own U.S. Pat. No. 5,971,178 shows a hoist of this type employing link-and-pin type chains (roller chains) drawn by a load nut or nut gear which is translated by a load screw or screw gear having a connection for receiving rotary input from a pneumatically powered impact tool or from a hand-powered tool. 
   Hoists of this type, with high mechanical advantage, can be used for lifting or repositioning a heavy load, for fine positional adjustment, or for load binding. Often they can be used in combination with an overhead electric hoist, secured to the bottom hook of such a hoist. The electric hoist lacks precision, and use of the screw hoist enables very precise final adjustment of position of a heavy load. For example, the hoist shown in the above patent can be designed to make an adjustment of about 0.001 inch with input rotation on the order of about one degree. 
   The term “hoist” as used herein and commonly in the industry, applies whether a load is moved vertically, horizontally or otherwise, or is not moved at all but is only subjected to tension. Improved hoists of this general type, using flexible tension members different from the roller chain disclosed in U.S. Pat. No. 5,971,178, and with guide members to maintain position of the tension members in the housing, form the subject matter of the invention described below. 
   SUMMARY OF THE INVENTION 
   Hoists of this invention have various types of flexible tension members, each with appropriate guides or guide channels for maintaining the tension members in position in the housing even when the tension members are slack or are being fed out of the housing without tension. The hoists of the invention have a fitting, accessible from the exterior of the housing, for attaching a hand tool to input rotation to the hoist, or for use of a powered tool such as a drill. 
   The tension members can be wire cables, coil chains, synthetic webbing straps, or other appropriate strong and flexible tension members. These tension members apply force to a load and, with the high mechanical advantage of the hoist, can move and position a load very accurately. 
   In one form of the invention, a pair of cables, or four or more cables, are secured to a load nut gear within the housing of the tool and pass over cable idler pulleys to extend in opposite directions from the housing. Guides for the cables comprise V grooves extending longitudinally in the housing, and preferably with a spring-biased means for pushing the cable into the V groove to maintain the cables in an orderly fashion in the housing, without kinking or twisting, when the wire cables are not in tension. Stationary pulley guides are located in close proximity to the edges flanges of the cable pulleys so that the cables cannot twist out of the pulley groves when not in tension. 
   A minimum of two such cables are included, but there could be two, three or more cables on each side, preferably with a V-groove and pulley for each such cable. 
   In another embodiment of the invention, coil chains are used, one in each side of the housing. Such coil chains generally comprise welded racetrack-shaped links which are interlinked in alternating orientations, the type used for log chains, many chain hoists and other heavy duty applications. In this case the pulleys of the cable embodiment are replaced with idler sprockets designed to smoothly engage with this type of chain. For guidance of chains within the housing, guide channels are provided at each side of the housing, closely guiding each chain within the housing, and with guides actually passing through the nut. The load nut has arms from which pins extend into and through the guide channels, engaging the end links of the chains. When the screw gear is back-rotated to pay chain out of the housing, the guide channels prevent bunching, kinking, or jamming and keep the chains in orderly arrangement for feeding out over the idler sprockets to the exterior of the housing. 
   In a third embodiment, synthetic webbing straps are employed as the tension members. The housing includes idler rollers or pulleys to feed the straps out of the housing in opposite directions, the ends of these straps being secured to arms of the load nut in the housing. As in the coil chain embodiment, the load nut arms have pins which extend into guide channels that maintain the webbing straps in non-kinked, relatively straight and orderly configuration within the housing even without tension in the straps and when the straps are being pushed out of the housing by back-rotation of the screw gear. 
   It is therefore among the objects of the invention to improve over prior high-mechanical-advantage precision screw hoists, with alternate forms of flexible tension members, properly guided within the housing of the tool. These and other objects, advantages and features of the invention will be apparent from the following description of preferred embodiments, considered along with the accompanying drawings. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an elevation or plan view in section showing a first embodiment of a hoist according to the invention, wherein wire ropes cables serve as the tension members. 
       FIG. 2  is a sectional view cut transversely through the longitudinal direction of the apparatus along the line  2 — 2  in  FIG. 1 . 
       FIG. 3  is an elevation or plan view in section, showing a modified embodiment of the device with synthetic web straps as tension members. 
       FIG. 4  is a transverse cross section view of the device of  FIG. 3 , the section being taken along the line  4 — 4  in  FIG. 3 . 
       FIG. 5  is a sectional view similar to  FIGS. 1 and 3  and showing a further embodiment of the invention. 
       FIG. 6  is a sectional view as seen along the line  6 — 6  in  FIG. 5 . 
       FIG. 7  is view similar to  FIG. 5 , showing another form of the hoist with coil chains as flexible tension members. 
       FIG. 8  is a sectional view of the embodiment of  FIG. 7 , as seen along the line  8 — 8  in  FIG. 7 . 
       FIG. 9  is a sectional view similar to  FIG. 7  showing a modification of the hoist shown in  FIG. 7 . 
       FIG. 10  is a sectional view of the  FIG. 9  embodiment as seen along line  10 — 10  in  FIG. 9 . 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1 and 2  show a screw gear hoist  10  of one embodiment of the invention, in this case utilizing wire rope, also known as wire cable or cable, as the tension members  12  of the hoist. In this form of the invention, a housing  14  provides a frame for the device and is generally elongated in shape as shown, providing bearings  16  and  18  at opposite ends for rotation of a screw gear or load screw  20  within the housing. The bearing  18  is a thrust bearing, only schematically shown in the drawings. Typically this will be a cylindrical roller thrust bearing. At a first end of the load screw is a tool head  22  for engagement by a tool for rotational input to the device. This could be a hand tool or a power tool such as a drill, for example. Threadedly connected to the load screw is a load nut  24 , which moves in a longitudinal direction, with great mechanical advantage, when the load screw  20  is rotated. 
   In this embodiment the wire ropes or cables  12  are guided within the housing so as not to twist or kink in the housing when in a slackened condition. This occurs in the down status of the tool, where the operator is essentially trying to push on a rope, back-rotating the load screw  20  to push the cable out of the housing. To prevent twisting or kinking of the cable in this condition, there are provided a pair of V shaped grooves  25 , at opposed sides of the interior of the housing and extending in the longitudinal direction as shown in  FIGS. 1 and 2 . The inner portions of the cables  12  are essentially confined within these V shaped grooves by a spring loaded cable positioner  26  on each side of the housing as shown. These cable positioners  26  are pivotally connected to the load nut  24  and have a spring, such as a coiled wire spring  28  shown in dashed lines, to bias the elements  26  to an outer position pushing the cables  12  toward the sides of the housing and into the V-grooves  25 . These cable positioners  26  are effective only in the slack condition of the cables, when the operator spins the tool head  22  in the back-rotating direction and the load nut  24  pushes the cables out of the housing. On the other hand, under high tension each cable will overcome the spring and assume a taut, straight configuration within the housing. 
   As shown, each cable has a terminal end  30  which is connected to a suitable form of pin or hook  32  on the load nut  24 . Each cable then leads down to an idler pulley  34  near the cable payout end  36  of the hoist device. These idler pulleys each have a peripheral groove  38  within which the cable  12  resides as it passes around approximately ¼ of the circumference of the pulley. Each annular groove  38  is formed by a pair of flanges  40 , one of which is shown on each pulley in the view of  FIG. 1 , both flanges being shown in  FIG. 2 . 
   Closely adjacent to each idler pulley  34 , in the area where the cable passes over the pulley, is a stationary pulley guide wall  42 , formed as a component of the housing or frame. By closely approaching the flanges  40  of the pulleys, the guide wall  42  retains the wire rope or cable  12  within the pulley groove  38 , preventing its escape therefrom even during slackened position or during payout on back-rotation of the load screw  20 . 
   The hoist device of  FIGS. 1 and 2  can employ more than one cable on each side. For two or three or more cables on each side, the housing as shown in  FIG. 2  would become deeper, and the load nut would be secured to multiple cables on each side. Multiple spring-loaded positioners  26  would then be provided, as would multiple V-groove guides  25  on each side. The use of multiple cables on each side enables the load capability of the device to be increased without requiring heavier, stiffer cables, and can make the tool more compact because of commensurate smaller-diameter pulleys required. 
     FIGS. 3 and 4  show another form of the invention  10   a . Taking first  FIG. 3 , this view can be considered as showing an alternative wire cable arrangement to what is shown in  FIG. 1 . In this case the tension members  45  are secured to the load nut  24   a  at or near outer ends of arms  46  of the load nut. A guide  48 , which may be a flat bar, extends longitudinally and in spaced parallel relationship with a side wall  50  of the housing, at each side. This forms a channel-like space  52  within which the tension member moves when under tension and also when paying out the tension members  45  when the load screw  20   a  is back-rotated to move the load nut  24   a  closer to the head  22  of the load screw. Pins  54  extending transversely support the terminal ends  56  of the tension members  45 . The arms  46  of the load nut  24   a  are split and spaced apart, extending at front and back of the flat bar guides  48  as viewed in  FIG. 3 . This is seen in  FIG. 4 , with the pin  54  (dashed lines) extending between the spaced arm sections  46 . 
   Although  FIG. 4  shows an embodiment with a synthetic web straps  45  as the tension members, and  FIG. 3  is a view corresponding to  FIG. 4 ,  FIG. 3  can also be considered to show the wire ropes (cables) of  FIG. 1  as guided in a different way, in the channels  52 . 
   The synthetic webbing straps  45  of  FIG. 4  are also illustrated in  FIG. 3 , as noted above. These straps extend around idler pulleys or rollers  34   a , lying in a groove  38   a  of the pulleys, as in the cable embodiment of  FIGS. 1 and 2 . However, such pulley grooves can be eliminated if desired, relying on adjacent walls  57  to maintain the straps on the rollers  34   a.    
   The straps extend out of the housing in opposite directions. When the load screw  20   a  is back-rotated to retract the load nut  24   a  toward the front of the housing, i.e. toward the screw head  22 , the end sections of the webbing straps  45  are pushed through the channels  52  toward the exterior of the housing. In addition to preventing kinking or twisting during payout, the web guides  48 , along with the housing, prevent the webbing straps from contacting the grease on the screw gear  20   a  and the load nut  24   a , which is important because the webbing straps will be handled and will touch other objects when they are exterior to the hoist. 
   As in  FIG. 1  embodiment, stationary pulley guides  58  preferably are included, essentially formed by curved walls positioned near the periphery of each pulley or roller  34   a , to confine the web straps as illustrated. In this embodiment the strap guides  48  pass through an opening in the load nut  24   a , the opening being defined between the two forks or legs of the load nut arm  46  and the pin  54 . 
     FIGS. 5 and 6  show a hoist apparatus  10   b  with an alternative to the strap guides  48  shown in  FIGS. 3 and 4 . In this case the structure is primarily the same as what is shown in  FIGS. 3 and 4 , except that at each side of the housing  50  the strap guide comprises a pair of elongated, parallel, longitudinally-extending rods  60 .  FIG. 5  shows one of the rods at each side of the housing, and the sectional view of  FIG. 6  shows both rods  60  at each side, in cross section. Since the webbing strap  45  has an appreciable width, a pair of parallel rods  60 , at spacing approximately as shown in the drawings, are sufficient to act as one wall of a channel  52   a  (the housing wall  61  being the other); as in the previous embodiment, the guides pass through an opening in the load nut  24   a . The rods  60  forming the strap guides can be secured to the housing in any appropriate way, and  FIGS. 5 and 6  show generally U-shaped clamps  62  formed on brackets, two each bracket, for clamping these rods in place using a fastener  64  such as a machine screw. 
     FIGS. 7 and 8  show a further form of the invention, in which coil chains  70  serve as the tension members.  FIGS. 9 and 10  show a modified embodiment also with coil chains  70 . In the form shown in  FIGS. 7 and 8 , chain guides within the housing comprise a pair of U-shaped longitudinal members  72  facing each other to capture alternate ones of the chain links  74  between them. The transverse sectional view of  FIG. 8  shows the shape of these members  72  and how they trap the links  74  between them, with just enough space provided that the chain can freely slide through the guides. These elongated guides or channels are formed on both sides of the housing  75  of the hoist  10   c , as shown in  FIGS. 7 and 8 . 
   Near the payout end  36   a  of the hoist unit  10   c  are rotationally-mounted idler sprockets  34   c , of the type which are typically used in hoists that utilize chain of this type. The idler sprockets  34   c  have grooves  38   c  which seat alternate links  74  as show in  FIG. 7 , and bridges  38   d  between adjacent grooves  38   c , to engage the alternating chain links  74   a , as shown in the drawing. 
   The load nut  24   c  for this embodiment is similar to those described above, with one of the U-shaped guide components  72  passing through the load nut as shown particularly in  FIG. 8 . As in the embodiment described above, the left and right ends of the load nut  24   c  are bifurcated, with spaced arms or arm portions  76  extending in front of and behind the guide channel member  72  and a pin  78  extending between the two arms or arm portions  76  to engage with the chain  70 . 
   The U-shaped guide elements  72  can be retained in the housing in any suitable fashion. In  FIG. 7  these are shown retained by machine screws  80  and  82  to portions of the housing or frame. 
   Reviewing  FIG. 7  it can be seen that the coil chains  70  are easily fed out of the housing when the chain is slack and especially during back-rotation of the screw gear  20  to feed chain out. Alternating links  74  of each chain are retained in the desired position and configuration, preventing bunching, kinking or jamming. 
     FIGS. 9 and 10  show an embodiment  10   d  very similar to that of  FIGS. 7 and 8  but with a different type of chain guide. In this case the guides for the coil chain  70  comprise four guide rods  85  at each side of the housing.  FIG. 10  shows the four rods  85  in section, at each side. These guide rods keep all links, both the orientation of the links  74  and the orientation links  74   a , in substantially aligned configuration, as can be seen from the drawings. The guide rods  85  may be retained in the housing  75   a  in any appropriate manner. In  FIG. 9  a plate  86  secured in the housing or frame has bores into which ends of the rods  85  are seated. The other ends of the rods can be secured in any suitable and efficient manner. 
   The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit its scope. Other embodiments and variations to this preferred embodiment will be apparent to those skilled in the art and may be made without departing from the spirit and scope of the invention as defined in the following claims.