Patent Publication Number: US-7909743-B1

Title: Dual action weightlifting machine

Description:
RELATED APPLICATION 
     The present application is a Continuation of co-pending U.S. patent application Ser. No. 11/929,372 filed on Oct. 30, 2007, which is a Continuation of U.S. patent application Ser. No. 11/363,677 filed on Feb. 28, 2006, now issued as U.S. Pat. No. 7,393,309, the contents of each of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     This invention relates generally to exercise machines, and is particularly concerned with exercise machines of the type which simulate free weight barbell exercise movements. 
     2. Related Art 
     Weightlifting machines with weight bars for simulating barbells, also known as Smith machines, have been a fitness club staple for many years. The basic machine has a barbell attached to slide mechanisms which run on vertical guides on opposite sides of a stationary frame. This allows an exerciser to perform exercises with vertical up and down movement, such as squats, bench press exercises, and the like, but does not permit any horizontal movement. The exerciser does not have to worry about balancing the side-to-side or front-to-back movement of an independent, free weight bar. The premise is that this design provides an additional measure of safety and is easy for the neophyte to use. 
     The first Smith machines had the vertical guides running perpendicular to the floor, which worked well for some exercises such as squats but fought the natural chest-to-chin arcing movement of a bench press. Manufacturers soon started designing Smith machines that placed the vertical guides at a slight (five to seven degrees) angle. These new designs worked better for exercises which involved travel in a slight arc, but not as well for other exercise motions which tended to follow a straight line. 
     The next evolution came with the advent of composite motion or dual action Smith machines that provided simultaneous horizontal and vertical exercise motion. These designs allowed the exercise bar to follow a natural front-to-back exercise motion but still eliminated the side-to-side balancing worries. They provided a halfway point between the balance and coordination needed to perform free weight exercises and the security of a traditional Smith machine. These designs also provided the ability to perform exercises such as lunges which require greater horizontal movement. 
     Dual motion weightlifting machines typically have a horizontal exercise bar which is slidably mounted at its opposite ends on two vertical guide bars. Each vertical guide bar in turn is slidably mounted on horizontal guide bars at its upper and lower ends. This allows the exercise bar to move simultaneously in vertical and horizontal directions, so that the exerciser can perform a more natural feeling weightlifting exercise which allows for the natural horizontal movements of the arms while pushing a weight upwards. The weight bearing bar or exercise bar is normally a standard Olympic bar, which may have hooks attached to it on a rotatable sleeve for hooking onto pinning holes on vertical guides so as to hold the bar in a rest position. The usual weight for an Olympic bar is between forty and fifty pounds. By attaching hooks, bearings, and vertical slides, the weight is dramatically increased. In some cases, counterweights are added to help reduce the weight or inertia required to move the bar from a rest position. While this counterbalance offsets the vertical weight, horizontal weight is increased. It also adds to the complexity and expense of the machine. 
     SUMMARY 
     Embodiments described herein provide for a dual action weightlifting machine which has an exercise bar assembly including slides on vertical guides slidably mounted for horizontal movement along opposite sides of a stationary frame. 
     According to one aspect, the frame has at least one pair of upright struts at one end, each upright strut having a plurality of spaced support or racking portions such as hooks or teeth. The racking portions are designed to receive and support spaced rack engaging portions of the exercise bar in a rest position. When the user is in position gripping the exercise bar, they can place the bar on a pair of aligned hooks or teeth on the two struts. The rack engaging portions comprise cylindrical surfaces outside the vertical guide on each side of the machine, and in one embodiment the cylindrical surfaces are placed directly onto the respective hooks or teeth at the end of an exercise or if a user is unable to finish an exercise. Safety stops are provided on each side of the frame for catching the bar if it is dropped. 
     In one embodiment, the weight bearing exercise bar comprises two end portions each having a vertical slide for slidably engaging a respective vertical guide, a weight receiving end projecting in one, outward direction from the slide and a shaft projecting in an opposite, inward direction from the slide, and a sleeve rotatably engaged on the shafts at its opposite ends. This makes the exercise bar much lighter, and the sleeve does not have any hooks or other devices for engaging on the stationary frame. Instead, each end portion engages directly on hooks provided on upright struts of the frame. The sleeve may have 360 degrees of unobstructed rotation to allow the user to perform a greater variety of exercises. 
     The dual action weightlifting machine allows simultaneous horizontal and vertical movement of an exercise bar and simulates a free barbell exercise. The central sleeve section of the exercise bar provides free rotation, duplicating the feel of a barbell. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The details of the present invention, both as to its structure and operation, may be gleaned in part by study of the accompanying drawings, in which like reference numerals refer to like parts, and in which: 
         FIG. 1  is a top perspective view of a dual action weightlifting machine according to a first embodiment; 
         FIG. 2  is a front perspective view of the machine of  FIG. 1 , with part of the base frame removed to reveal a lower horizontal guide and slide; 
         FIG. 3  is a side elevation view of the machine of  FIGS. 1 and 2 ; 
         FIG. 4  is a bottom plan view of the machine of  FIGS. 1 to 3  with part of the base frame removed to reveal a lower horizontal guide and slide; 
         FIG. 5  is an enlarged perspective view of an upper portion of the machine, showing the rigid attachment of the cross bar to the upper end of the vertical guide; 
         FIG. 6  is an enlarged view of a lower horizontal slide showing its rigid attachment to a vertical guide; 
         FIG. 7  is an enlarged view of an upper part of an upright strut of the frame, showing how the exercise bar racks directly onto a hook on a racking plate; 
         FIG. 8  is a perspective view of part of one side of the machine of  FIGS. 1 to 7 , showing the exercise bar removed from the racking plate; 
         FIG. 9  is a perspective view showing only the components of the movable exercise unit of the machine of  FIGS. 1 to 8 , with stationary components of the machine removed; 
         FIG. 10  is a perspective view of the exercise bar with one end of the bar separated from the rotating sleeve; 
         FIG. 10A  is a perspective view of a modified exercise bar with two rotating hand grip sleeves; 
         FIG. 10B  is an exploded perspective view illustrating the separate components at one end of the exercise bar of  FIG. 10A ; 
         FIG. 11  is an enlarged perspective view of the lower end of the machine of  FIGS. 1 to 10 , illustrating an alternative lower horizontal slide replacing the linear bearing slide of  FIG. 6 ; 
         FIG. 12  is a view similar to  FIG. 11  but with a portion of the stationary frame removed for clarity; 
         FIG. 13  is a side view of the modified lower horizontal slide of  FIGS. 11 and 12 ; 
         FIG. 14  is a bottom perspective view of the lower horizontal slide of  FIGS. 11 to 13 ; 
         FIG. 15  is a perspective view of a dual action weightlifting machine according to a second embodiment; 
         FIG. 16  is a front elevation view of the machine of  FIG. 15 ; 
         FIG. 17  is a top plan view of the machine of  FIGS. 15 and 16 ; 
         FIG. 18  is a top perspective view of the machine of  FIGS. 15 to 17 ; 
         FIG. 19  is an enlarged view of part of the top of the machine of  FIGS. 15 to 18  illustrating the attachment of the upper end of one of the vertical guides to the cross bar and one of the slides on the cross bar engaging one of the upper horizontal guide bars; 
         FIG. 20  is an enlarged view of a lower horizontal slide of the machine of  FIGS. 15 to 19 , showing its rigid, inboard attachment to a vertical guide; 
         FIG. 21  is a view of the slide of  FIG. 20  from a different angle; 
         FIG. 22  is a side perspective view of a dual action weightlifting exercise machine according to another embodiment; 
         FIG. 23  is a bottom perspective view of the machine of  FIG. 22 , illustrating the lower traveling cross bar and lower horizontal guide; 
         FIG. 24  is a front elevation view of the machine of  FIGS. 22 and 23 ; 
         FIG. 25  is a top plan view of the machine of  FIGS. 22 to 24 ; 
         FIG. 26  is an enlarged view illustrating the rigid attachment of the lower cross bar of the machine of  FIGS. 22 to 25  to the vertical guide; 
         FIG. 27  is a side perspective view of a dual action weightlifting exercise machine according to another embodiment; 
         FIG. 28  is a bottom perspective view illustrating the lower cross bar of the machine of  FIG. 27 ; 
         FIG. 29  is a front elevation view of the machine of  FIGS. 27 and 28 ; 
         FIG. 30  is a top plan view of the machine of  FIGS. 27 to 29 ; 
         FIG. 31  is an enlarged perspective view of an upper portion of the machine of  FIGS. 27 to 30 , showing the rigid attachment of the cross bar to the upper end of the vertical guide; 
         FIG. 32  is an enlarged view illustrating one end of the lower horizontal cross bar of  FIG. 28 , illustrating the attachment of the cross bar to a slide at one end, outboard of the vertical guide connection point; 
         FIG. 33  is a side perspective view of another embodiment of a dual action weightlifting exercise machine; 
         FIG. 34  is a bottom perspective view of the machine of  FIG. 33 , illustrating the lower horizontal slide and cross bar; 
         FIG. 35  is a front elevation view of the machine of  FIGS. 33 and 34 ; 
         FIG. 36  is a top plan view of the machine of  FIGS. 33 to 35 ; and 
         FIG. 37  is an enlarged perspective view of the lower end of the machine of  FIGS. 33 to 36 , showing the rigid connection between the lower cross bar and one of the vertical guides. 
     
    
    
     DETAILED DESCRIPTION 
     Certain embodiments as disclosed herein provide for a dual action weightlifting exercise machine having upper and lower horizontal guides and horizontally spaced vertical guides allowing vertical and horizontal movement of a weight bearing exercise bar which has rack engaging portions outside the vertical guides which are coaxial with a user engaging portion of the exercise bar. 
     After reading this description it will become apparent to one skilled in the art how to implement the invention in various alternative embodiments and alternative applications. However, although various embodiments of the present invention are described herein, it is understood that these embodiments are presented by way of example only, and not limitation. 
       FIGS. 1 to 10  illustrate a dual action weightlifting exercise machine  10  according to a first embodiment. The apparatus basically comprises a stationary main frame  12  and an exercise unit  14  movably mounted on the stationary frame. The movable exercise unit  14  is shown separately in  FIG. 9 , with most of the stationary frame parts removed for clarity. 
     The stationary frame  12  has an upper end, a lower end, a front, a rear and opposite left and right sides, and is designed to support the movable exercise unit. Frame  12  has a floor engaging base  15 , first and second pairs of upright struts  16 ,  17  and  18 ,  19 , respectively, upper struts  20 ,  22  extending between the upper ends of each pair of upright struts, and upper cross struts  24 ,  25 , the first upper cross strut  24  extending between the upper ends of the front upright strut  16 ,  18  of each pair, and the second upper cross strut  25  extending between the upper ends of the second upright strut  17 ,  19  of each pair. A lower horizontal guide or guide assembly having a pair of lower horizontal guide bars  26 ,  28  extends between the lower ends of each pair of cross struts at the lower end of the machine. The guide bars  26 ,  28  are located in a channel or shield member  30 ,  32  respectively, forming part of the base of the machine, for shielding users from moving parts of the machine. One of the channel members is removed in  FIG. 2  to reveal the slide mechanism in more detail. A base connecting plate  34  extends between the base channel members  30 ,  32  and engages the floor for added stability. An upper horizontal guide or guide assembly having a single upper horizontal guide bar  35  extends between the two upper cross struts  24 ,  25  at a central position offset from the lower horizontal guide bars  26 ,  28 . The lower guide assembly includes traveling members or slides  40 ,  42  which are slidably or movably engaged with the respective horizontal guide bars  26 ,  28 . The upper guide assembly includes a traveling member or slide  45  movably engaged with upper guide bar  35 . 
     As best illustrated with reference to  FIGS. 1 ,  2  and  9 , the movable exercise unit  14  comprises a pair of vertical guides  36 ,  38  each slidably mounted at their lower ends on a respective horizontal guide bar  26 ,  28  via horizontal slides  40 ,  42 , a cross bar  44  extending between the upper ends of the vertical guides and slidably connected to the upper horizontal guide bar  35  via upper horizontal slide  45 , and a weight bearing exercise bar  46  extending between the vertical guides and slidably linked to the vertical guides by vertical slides  48 ,  50 . This arrangement provides simultaneous vertical and horizontal guided movement of the exercise bar  46 , as indicated by the arrows in  FIG. 9 . Portions of the lower and upper horizontal guide bars of the frame are included in  FIG. 9  for clarity. The vertical guides  36 ,  38  move horizontally back and forth on the lower guide bars  26 ,  28  and upper guide bar  35 , while the exercise bar  46  can move vertically up and down on the vertical guides, providing for simultaneous horizontal and vertical movement of the exercise bar. 
     The main frame includes a rack assembly for supporting the exercise bar in multiple possible positions when not in use. The rack assembly comprises vertical rack plates  52  mounted on each of the upright struts  16 ,  17 ,  18  and  19 , as illustrated in  FIGS. 1 ,  2 ,  3 ,  5 ,  7  and  8 . The vertical rack plate  52  on upright strut  18  is not visible, but is identical in position to the rack plate  52  on the other front upright strut  16 . The rack plates each have a series of spaced teeth or upwardly directed hooks  58 , with the hooks on front upright struts  16  and  18  facing the hooks on the rear upright struts  17  and  19 , and the hooks on the front upright struts and rear upright struts all aligned with one another. When a user wishes to place the exercise bar in a rest position, they simply engage portions  60 ,  62  of the bar  46  in a respective pair of aligned hooks  58  on the two front upright struts  16 ,  18  or the two rear upright struts  17 ,  19 . Hook engaging portions  60 ,  62  are immediately adjacent and outboard of the respective vertical slides  48  and  50 .  FIGS. 1 and 2  illustrate the bar engaged in the two uppermost hooks  58  of the rear upright struts  17 ,  19 , while  FIG. 7  is an enlarged view illustrating the engagement of hook engaging portion  60  in the uppermost hook  58  on the upright strut  17 . Weight plates can be added or removed from the weight receiving ends  72 ,  74  of the exercise bar when it is in the rest position racked onto two of the toothed plates  52 , and the exercise bar can be left in this position for storage purposes when the machine is not in use. 
     A pair of safety tiers  64  is provided for engagement between respective pairs of rack plates  52  on opposite sides of the main frame, as best illustrated in  FIGS. 1 and 2 . The tiers  64  have pins  65  at their ends which can engage on hooks or teeth  58  as illustrated in  FIG. 7 . The safety tiers can be adjusted as necessary, depending on the type of exercise, to provide the user with protection against losing control of a weighted exercise bar. 
     The components of the weighted exercise bar  46  are illustrated in more detail in  FIG. 10 . The exercise bar  46  comprises a central, hollow rotating sleeve  66  which is rotatably mounted at each end on opposite end members  68 ,  69  of the bar. Each end member  68 ,  69  incorporates a respective vertical slide  48 ,  50 , and has an inwardly extending shaft or axle  70  on which a respective end of the sleeve  66  is rotatably engaged. A weight receiving end  72 ,  74  projects outwardly from the respective vertical slide  48 ,  50 , and a rack engaging portion  60 ,  62  between the respective slide  48 ,  50  and end  72 , 74  is designed to engage on aligned hooks  58  when the exercise bar is in the rest position. An annular stop  75  with a bumper is provided between the weight receiving outer end  72 ,  74  of each end member  68 ,  69  and the hook or rack engaging portion  60 ,  62 . The rack engaging end portions  60 ,  62  have a larger diameter than the sleeve or user engaging portion  66  of the exercise bar, as illustrated in  FIG. 10 . A bushing  76  at each open end of the sleeve  66  releasably retains the rotating sleeve on the respective axle  70 . This arrangement provides a freely rotatable sleeve for gripping by a user when performing exercises, with the sleeve having 360 degree, unrestrained rotation. The hollow sleeve construction provides a much lighter weight exercise bar than was used in many previous designs, and the vertical slides  48  and  50  are in line with the axis of the exercise bar, providing better weight distribution since the traveling exercise unit is centered on the exercise bar. 
       FIGS. 10A and 10B  illustrate a modified exercise bar  200 . Rather than a single hollow rotating sleeve  66  extending between the vertical slides  48 ,  50 , as in  FIG. 10 , this embodiment has a bar  202  extending between the vertical slides and rigidly secured to the vertical slide at each end via set screws  204 , and a pair of shorter sleeves  205 ,  206  rotatably mounted on bar  202 . Bar  202  extends through the sleeves and engages in short collar  208  projecting from the respective sleeve, and is secured in position via the set screw  204  extending through the collar and bar. The bar may be a solid bar or may be hollow to reduce the overall weight of the assembly. The sleeves  205 ,  206  are free to slide back and forth along the bar  202  and to rotate through 360 degrees about the bar, as indicated in  FIG. 10A . The bumper of end stop  75  is omitted in  FIGS. 10A and 10B  for clarity but is identical to the bumpers illustrated on end stops  75  in  FIG. 10 . As best illustrated in  FIG. 10B , each weight receiving end portion of the modified exercise bar  200  includes a protective outer sleeve. The rack engaging portions of both bar  46  and modified bar  200  are of substantially the same diameter as the weight receiving end portions, as illustrated in  FIG. 10  and  FIGS. 10A and 10B . 
     The provision of two rotating hand grip sleeves which are slidably mounted on an exercise bar as in  FIGS. 10A and 10B  provides greater versatility in hand grip adjustment both before and during an exercise movement. When the bar is pushed or pulled during a lifting exercise, the hands can diverge or converge in order to duplicate the types of exercises performed with separate dumbbells, such as a dumbbell press. The user can also adjust the width of their handgrip to the most comfortable position. 
     The horizontal and vertical slide connections between the moving exercise unit and the horizontal guide bars are seen in  FIGS. 1 ,  2 ,  5 ,  6  and  9 . As noted above, the exercise unit has two vertical guides  36  and  38  on opposite sides of the machine which are slidably engaged with respective horizontal guides  26 ,  28  at the base of the main frame via horizontal slides  40  and  42 , respectively.  FIG. 6  is a close up of one of the lower horizontal slides  40  showing its rigid attachment to the lower end of the vertical guide  26 . The horizontal slides  40 ,  42  each comprise an outer sleeve housing a linear bearing which is telescopically engaged for smooth sliding motion along the respective horizontal guide  36 ,  38 . A collar  80  projects upwardly from each horizontal slide and the lower end of the vertical guide  36  engages in the collar and is rigidly attached to the collar  80  by a set screw  82 . A bumper  84  at the top of collar  80  provides a stop which engages the vertical slide  48  to prevent further downward movement of the exercise bar beyond this point. The vertical guide  28  is rigidly attached to the other lower horizontal slide  42  in an identical manner, and like reference numerals have been used for like parts in the drawings as appropriate. 
       FIG. 5  illustrates the attachment of the upper end of vertical guide  38  to the traveling cross bar  44 . The upper end of the other vertical guide  36  is attached to the opposite end of the traveling cross bar in an identical manner, as seen in  FIG. 7 . Vertical caps  85  at opposite ends of cross bar  44  engage over the upper ends of the respective vertical guides and are rigidly attached to the vertical guides by bolts  86 . The vertical slide  50  is seen adjacent the upper end of vertical guide  36  in  FIG. 5 . Each vertical slide also comprises a sleeve enclosing a linear bearing, like the lower horizontal slides  40  and  42 . The single upper horizontal slide  45  at the center of cross bar  44  also comprises a sleeve enclosing a linear bearing. As best illustrated in  FIGS. 1 and 2 , the cross bar  44  connecting the upper ends of the two vertical guides has first and second portions extending transversely from slide  45  to the respective vertical guides  36 ,  38 , and is arched upwardly at its center, as are the respective front and rear upper cross struts  24  and  25 . 
     The horizontal movement of the movable exercise unit  14  is controlled by three horizontal guide bars mounted on the stationary main frame with three horizontal slides movably mounted on the respective guide bars and each secured to one or both vertical guides. The horizontal guides are offset from one another, rather than being aligned in the vertical direction as was the case with most prior art Smith machines. This vertical offset provides more stability and less play in the sliding motion of the exercise bar. 
     Once the user engages the weight receiving exercise bar  46  and moves it from a rest position on the toothed plates and into an exercise ready position, as indicated in  FIG. 8 , the entire movable exercise unit  14  acts as one device to provide simultaneous horizontal movement. This allows a large variety of different exercises to be performed. The exercise unit  14  is relatively light weight due to the hollow sleeve design of the exercise bar and the use of only three horizontal slides rather than four which was common in the past, producing a smoother, and more fluid exercise motion. By reducing the weight of the exercise bar below that of a standard Olympic bar, this machine allows a novice user to handle the weight comfortably and safely, without needing the costly inclusion of any counter-balancing means. 
     The machine of  FIGS. 1 to 10  has a reduced number of moving components in order to reduce the weight of the movable exercise unit, thus reducing the inertia required to initiate or change directions on the horizontal plane. Some free weight exercises require the horizontal motion to be paused or the direction of horizontal movement to be changed at the mid point of an exercise. The reduced weight of the movable exercise unit in this machine allows such exercises to be performed more easily. At the same time, the elimination of framework and reduction of the number of components reduces the overall cost and complexity of the machine. 
     The horizontal and vertical slides in the machine of  FIGS. 1 to 10  are all linear bearings enclosed in outer sleeves which are telescopically engaged over the respective horizontal and linear guides. However, other types of slides or traveling members may be used in alternative embodiments, such as roller wheels.  FIGS. 11 to 14  illustrate a modified lower slide comprising a pair of roller wheels  90  mounted in a channel or formed housing  92 . The wheels  90  run on top of the horizontal guide  26  with part  93  of the formed housing  92  wrapping around the lower side of the guide  26 , as best illustrated in  FIGS. 12 and 14 , to prevent the slide from coming off the guide. The lower end of the vertical guide  36  engages in a collar  94  projecting upwardly from an upper wall of housing  92 , and is rigidly secured to the housing by set screws  95 . An end stop bumper  84  is provided on top of collar  94 , as in the previous embodiment. Both of the lower slides  40 ,  42  may be replaced with a modified, roller wheel slide arrangement as illustrated in  FIGS. 11 to 14 . The other linear bearing slides  45 ,  48  and  50  may also be replaced with roller wheel slides in a similar manner, if desired. 
     In each of the embodiments described below and illustrated in  FIGS. 15 to 37 , the horizontal and vertical slides or traveling members are illustrated as sleeves enclosing linear bearings, as illustrated in  FIGS. 1 to 10 . However, the roller wheels of  FIGS. 11 to 14  may alternatively be used in the first embodiment described above or in any of the following embodiments in place of the linear bearings. 
       FIGS. 15 to 21  illustrate a second embodiment of a dual action weightlifting exercise machine  100 . In this embodiment, there are two upper horizontal guides and two upper horizontal slides attached to the traveling cross bar which extends between the upper ends of the vertical guides. There are also two lower horizontal guides and associated horizontal slides. Unlike the previous embodiment, the respective lower horizontal slides are connected to the vertical guides in an offset manner rather than being positioned directly under the lower ends of the vertical guides, as in  FIGS. 1 to 11 . Other parts of the machine  100  are identical to those of  FIGS. 1 to 11 , and like reference numerals have been used for like parts as appropriate. 
     The machine  100  basically comprises a stationary main frame and a movable exercise unit which is movably mounted on the frame. As in the first embodiment, the main frame has a floor engaging base  15 , first and second pairs of upright struts  16 ,  17  and  18 ,  19 , respectively, upper struts  20 ,  22  extending between the upper ends of each pair of upright struts, and upper cross struts  24 ,  25 , the first upper cross strut  24  extending between the upper ends of the front upright strut  16 ,  18  of each pair, and the second upper cross strut  25  extending between the upper ends of the second upright strut  17 ,  19  of each pair. A pair of lower horizontal guide bars  26 ,  28  extends between the lower ends of each pair of cross struts at the lower end of the machine. The guide bars  26 ,  28  are located in a channel or shield member  102 ,  103  respectively, forming part of the base of the machine. The shield member is open on its inner side, as seen in  FIGS. 15 and 18 , to allow for the offset mounting of the vertical guides. Vertical toothed rack plates  52  are mounted on the upright struts in exactly the same manner as the previous embodiment. The single upper horizontal guide bar  44  of the previous embodiment is replaced by two spaced upper horizontal guide bars  104 ,  105  extending between the upper cross struts  24  and  25 . 
     The movable exercise unit has a pair of vertical guides  106 ,  108  each slidably mounted at their lower ends on a respective horizontal guide bar  26 ,  28  via horizontal slides  112 , a cross bar  114  extending between the upper ends of the vertical guides and slidably connected to the upper horizontal guide bars  104 ,  105  via upper horizontal slides  115 ,  116 , and a weight bearing exercise bar  46  extending between the vertical guides and slidably linked to the vertical guides by vertical slides  48 ,  50 . The main difference between this exercise unit and the exercise unit of the previous embodiment is the provision of two horizontal slides  115 ,  116  on the traveling cross bar  114  engaging the associated offset horizontal guides  104 ,  105 , and the offset mounting arrangement of the vertical guides  106 ,  108  which are positioned inboard of the respective guide bars  26 ,  28  rather than directly above the guide bars as in the previous embodiment. The exercise bar  46  is substantially identical to that of the previous embodiment, except that the hook or tooth engaging portions  60 ,  62  outside the vertical slides  48 ,  50  are lengthened to allow for the inwardly offset mount of the vertical guides, so that the portions  60 ,  62  can still engage over the teeth or hooks  58  in the rest position. 
     The inboard mounting of the vertical guides  106 ,  108  can be seen in  FIGS. 16 to 18  and is illustrated in more detail for one of the vertical guides  108  in  FIGS. 20 and 21 . The second vertical guide  106  is mounted inboard of the horizontal guide  26  in an identical manner. Each horizontal slide  112  comprises a sleeve housing a linear bearing telescopically engaged over the respective horizontal guide  26 ,  28 , as in the previous embodiment. However, unlike the previous embodiment, the sleeve of slide  112  has an inwardly directed rod  118  on its inner face terminating in an upwardly directed cup or retainer  120  for receiving the lower end of the respective vertical guide  106  or  108 , which is rigidly secured to the retainer  120  by set screws  122 . As in the previous embodiment, an annular bumper or end stop  124  is provided at the upper end of the cup or retainer  120 . 
     As in the previous embodiment, the vertical guides  106  and  108  are rigidly attached at their upper ends to the traveling upper cross bar  114 . This attachment is illustrated in more detail for one of the vertical guides  108  in  FIG. 19 , it being understood that the attachment of the opposite end of the cross bar  114  to the other vertical guide  106  is identical. As in the previous embodiment, a cup or mounting ring  125  at each end of the cross bar  114  is engaged over the upper end of the respective vertical guide  106 ,  108 , and is rigidly secured to the vertical guide by a bolt  126 . The upper horizontal slides  115 ,  116  are mounted in line with the cross bar  114  as seen in  FIGS. 18 and 19 , with each slide comprising an outer sleeve enclosing a linear bearing which is telescopically engaged over the respective upper horizontal guide bar  104 ,  105 . 
     The inwardly offset mounting of the vertical guides in this embodiment allows the exercise bar  46  to travel lower before it makes contact with the bumper stop  124 , which no longer has to be positioned completely above the horizontal slide. In other words, the distance between the connection points of each vertical guide to the respective cross bar  114  or rod  118  which connects the vertical guide to the respective slide is greater than the vertical distance between the upper and lower horizontal slides. 
     The operation of the weightlifting exercise machine of  FIGS. 15 to 21  is substantially identical to that of  FIGS. 1 to 11 , with the movable exercise unit providing simultaneous horizontal and vertical exercise movement of the weight bearing exercise bar  46 . Although there are two lower horizontal guides and two upper horizontal guides in this embodiment, the vertical guides are offset from all of the horizontal guides, and all of the horizontal guides are offset from one another, i.e. none of the horizontal guides are vertically aligned. This offset arrangement gives less play and provides more stability, allowing a smooth exercise movement with reduced risk of jamming or jarring. 
       FIGS. 22 to 26  illustrate a dual action weightlifting exercise machine  130  according to another embodiment which has an upper traveling cross bar  114  having two horizontal slides  115 ,  116  engaging two horizontal guides  104 ,  105 , similar to the upper horizontal slide arrangement of the embodiment of  FIGS. 11 to 21 , and like reference numbers have been used for like parts as appropriate. Unlike the previous embodiments, this embodiment also has a second or lower traveling cross bar between the vertical guides  106 ,  108 , as best illustrated in  FIG. 23 , the lower horizontal cross bar having a single horizontal slide  134  engaging a single horizontal guide  135  in the base of the machine. The ends of the two traveling cross bars are both rigidly attached to the respective ends of the vertical guides. A platform  136  is mounted on the base of the main frame of the machine, covering the moving lower cross bar and allowing the user to position themselves above the moving lower cross bar and away from any moving parts. This embodiment is otherwise substantially identical to the first embodiment, and like reference numerals have been used for like parts as appropriate. 
     As in the previous embodiments, the main frame of the machine  130  has first and second pairs of upright struts  16 ,  17  and  18 ,  19  each having an attached toothed rack plate  52 , upper struts  20 ,  22  extending between the upper ends of each pair of upright struts, and upper cross struts  24 ,  25 , the first upper cross strut  24  extending between the upper ends of the front upright strut  16 ,  18  of each pair, and the second upper cross strut  25  extending between the upper ends of the second upright strut  17 ,  19  of each pair. The upper horizontal guides  104 ,  105  extend between the upper cross struts  24 ,  25  at locations offset from the center of the machine and from the opposite sides of the machine. Lower cross plates  138 ,  139  extend between the lower ends of each pair of upright struts. The platform  136  has cut outs  140  at each side to provide clearance for the lower ends of the vertical guides  106 ,  108  to extend down for connection to the lower traveling cross bar  132 . Alternatively, the traveling cross bar  132  may be bent upwardly at its opposite ends and extend up through the cut outs  140  to connect to the lower ends of the vertical guides. The lower horizontal guide  135  extends between downwardly bent front and rear end portions  141 ,  142  of the platform  138 , as best seen in  FIG. 23 . 
     As noted above, in this embodiment the moving exercise unit comprises a pair of vertical guides  106 ,  108 , a first or upper traveling cross bar  114  extending between the upper ends of the vertical guides and associated with two horizontal slides  115 ,  116  which are slidably engaged with two upper horizontal guides on the main frame, a second or lower traveling cross bar  132  extending between the lower ends of the vertical guides and associated with a single horizontal slide  134  which is slidably engaged with a lower, centrally located horizontal guide  135  in the base of the frame, and an exercise bar  46  which is slidably engaged with the two vertical guides for sliding vertical movement via two vertical slides  48 ,  50 . The exercise bar  46  is identical to the exercise bar of the previous embodiment, with lengthened portions  60  and  62  due to the inwardly offset position of the vertical guides and associated slides  48 ,  50 . 
     As in the previous embodiment, the vertical and horizontal slides comprise sleeves containing linear bearings telescopically engaged over the respective vertical and horizontal guides. In this embodiment, the vertical guides are mounted outboard from both the upper and the lower horizontal guides, and all three horizontal guides are offset from one another, providing greater stability and less free play when the exercise bar is operated. 
     The upper end of each vertical guide is rigidly attached to the respective end of the upper traveling cross bar  114  via cup  125  and bolt  126 , as in the previous embodiment, as illustrated in  FIGS. 22 and 25 . The attachment of the lower end of the vertical guides to the lower traveling cross bar  132  can be seen in  FIGS. 23 and 26 . As best seen in  FIG. 26 , the lower end of vertical guide  108  engages in a vertical mounting sleeve or cup  145  at the end of lower traveling cross bar  132 , and is rigidly secured to the sleeve  145  by set screws  146 . The lower end of vertical guide  106  is attached to the opposite end of the cross bar  132  in an identical manner. A bumper or end stop  148  is mounted on the lower end of each vertical guide above sleeve  145  to limit downward traveling movement of the exercise bar, as in the previous embodiments. In an alternative arrangement, the ends of the lower cross bar  132  may be bent upwardly and extend through the cut outs, with the lower ends of the vertical guides engaging in the upwardly bent ends of the cross bar and secured in place with set screws. 
       FIGS. 27 to 32  illustrates a modified exercise machine  150  which is a variation of the embodiment of  FIGS. 22 to 26  where the upper cross bar of the moving exercise unit has a single horizontal slide and the lower traveling cross bar has two horizontal slides. The machine is otherwise substantially identical to that of the previous embodiments and like reference numerals have been used for like parts as appropriate. 
     As in the previous embodiments, the main frame of the machine  150  has first and second pairs of upright struts  16 ,  17  and  18 ,  19  each having an attached toothed rack plate  52 , upper struts  20 ,  22  extending between the upper ends of each pair of upright struts, and upper cross struts  24 ,  25 , the first upper cross strut  24  extending between the upper ends of the front upright strut  16 ,  18  of each pair, and the second upper cross strut  25  extending between the upper ends of the second upright strut  17 ,  19  of each pair. In this embodiment, a single upper horizontal guide  152  extends between the front and rear cross struts  24 ,  25  at a central location, similar to the single upper horizontal guide of the first embodiment. Two lower horizontal guide bars  154  (only one of which is visible in the drawings, the other being identical and positioned similarly to the horizontal guide bar  26  of  FIG. 1 ) extend between the lower ends of each pair of upright struts, inboard of the lower shield plates  138 ,  139  of the frame. 
     The moving exercise unit in this embodiment is similar to the previous embodiment, since it has a single upper traveling cross bar  155  and a single lower traveling cross bar  158  extending between the upper and lower ends, respectively, of the vertical guides  106  and  108 . As in the previous embodiments, exercise bar  46  extends between the vertical guides and is associated with vertical slides  48 ,  60  which are slidably engaged on the vertical guides  106 ,  108 , respectively. The exercise bar  46  is identical to the exercise bar of the previous embodiments. The upper traveling cross bar  155  has a single horizontal slide  156  slidably engaged on the upper horizontal guide  152 . A single lower traveling cross bar  158  is rigidly connected to the lower ends of the vertical guides  106  and  108 , and has two lower horizontal slides  162  at its opposite ends which are slidably engaged over the respective lower horizontal guide bars  154 . As in the previous embodiments, the horizontal and vertical slides comprise outer sleeves housing linear bearings and are slidably engaged over the respective horizontal and vertical guides, although they may alternatively comprise wheels, rollers, or other sliding devices. A platform  136  is mounted on the base of the main frame of the machine, covering the moving lower cross bar  158  and allowing the user to position themselves above the moving lower cross bar and away from any moving parts. Cut outs  140  in opposite sides of platform  136  provide clearance for the vertical guides  106 ,  108  to extend past the platform for rigid attachment to the lower traveling cross bar  158 , or for a joint to project upwardly from the traveling cross bar through each cut out for rigid attachment to the lower ends of the vertical guides. 
     The rigid attachment of the upper traveling cross bar  155  to the upper end of one of the vertical guides  106  is illustrated in more detail in  FIG. 31 , it being understood that the attachment of the opposite end of the cross bar  155  to the other vertical guide  106  is identical. A vertical mounting sleeve  165  is welded at each end of the traveling cross bar  155 . Sleeves  165  are engaged over the upper ends of the respective vertical guides  106 ,  108  and secured to the guides  106 ,  108  with set screws  166 , as indicated in  FIG. 31 . 
       FIG. 32  illustrates the attachment of the lower traveling cross bar  158  to the lower end of vertical guide  108  and to the horizontal slide  162 . The attachment of the lower cross bar  158  to the lower end of vertical guide  106  and to the other lower horizontal slide is identical to that illustrated in  FIG. 32 . A vertical mounting sleeve  168  is mounted in line with the lower traveling cross bar  158  at a location spaced from the outer end of cross bar  158 . The outer end of the cross bar  158  is welded to the inner face of horizontal slide  162 . The lower end of the vertical guide  106  engages in vertical mounting sleeve  168  inboard of horizontal slide  162  and is rigidly secured to the sleeve by set screws  170 . Thus, in this embodiment, the horizontal slides of the lower traveling cross bar are mounted outboard of the vertical guide connection points, unlike the horizontal slide of the upper traveling cross bar, and unlike the traveling cross bars of all of the previous embodiments which have horizontal slides mounted inboard of the vertical guides. A bumper  172  is mounted on the vertical guide  108  above sleeve  168  for limiting downward movement of the exercise arm. 
     This embodiment also has a relatively lightweight moving exercise unit with fewer components, making it easier to operate and less expensive. Again, the upper and lower horizontal guides are offset from one another for added stability and reduced free play. 
       FIGS. 33 to 37  illustrate another modified dual action weightlifting exercise machine  180  for simulating free weight or barbell exercises. The traveling exercise unit of this embodiment has even fewer parts than the previous embodiments, since it has a single upper and lower traveling cross bar, each associated with only one horizontal slide which engages respective upper and lower horizontal guides on the main frame of the machine. The machine is otherwise identical to the previous embodiments, and like reference numerals have been used for like parts as appropriate. 
     As in the previous embodiments, the main frame of the machine  180  has first and second pairs of upright struts  16 ,  17  and  18 ,  19  each having an attached toothed rack plate  52 , upper struts  20 ,  22  extending between the upper ends of each pair of upright struts, and upper cross struts  24 ,  25 , the first upper cross strut  24  extending between the upper ends of the front upright strut  16 ,  18  of each pair, and the second upper cross strut  25  extending between the upper ends of the second upright strut  17 ,  19  of each pair. As in the previous two embodiments, a base platform  136  is mounted on the base of the main frame of the machine, covering the moving lower cross bar and allowing the user to position themselves above the moving lower cross bar and away from any moving parts. A single upper horizontal guide  182  extends between the upper cross struts  24 ,  25  and a single lower horizontal guide  184  extends between extends between downwardly bent front and rear end portions  141 ,  142  of the platform  136 , as best seen in  FIG. 34 . 
     The moving exercise unit in this embodiment is similar to the previous embodiment, since it has a single upper traveling cross bar  185  and a single lower traveling cross bar  186  extending between the upper and lower ends, respectively, of the vertical guides  106  and  108 . As in the previous embodiments, exercise bar  46  extends between the vertical guides and is associated with vertical slides  48 ,  50  which are slidably engaged on the vertical guides  106 ,  108 , respectively. The exercise bar  46  is identical to the exercise bar of the previous embodiments. The upper traveling cross bar  185  has a single horizontal slide  188  slidably engaged on the upper horizontal guide  182 . The single lower traveling cross bar  186  has a single horizontal slide  190  slidably engaged on the lower horizontal guide  184 , as seen in  FIG. 34 . Although the upper and lower horizontal guides  182 ,  184  and associated slides  188 ,  190  are centrally positioned and in line with one another in the vertical direction in the illustrated embodiment, they may be offset from one another in alternative embodiments. For example, one of the horizontal guides may be offset to the left of the position in  FIGS. 33 and 34  and the other horizontal guide may remain in the center or be offset to the right of the position shown in  FIGS. 33 and 34 . 
     As in the previous embodiments, the horizontal and vertical slides comprise outer sleeves housing linear bearings and are slidably engaged over the respective horizontal and vertical guides, although they may alternatively comprise wheels, rollers, or other sliding devices. Cut outs  140  in opposite sides of platform  136  provide clearance for the vertical guides  106 ,  108  to extend past the platform for rigid attachment to the lower traveling cross bar  186  (see  FIG. 34 ). The upper ends of the vertical guides  106  and  108  are rigidly connected to the opposite ends of the horizontal traveling cross bar  185  in exactly the same manner as in the previous embodiment. 
       FIG. 37  illustrates the rigid attachment of one end of the lower traveling cross bar  186  to the lower end of one of the vertical guides  108 . This is identical to the rigid attachment of the single lower traveling cross bar  132  to the vertical guides in the embodiment of  FIGS. 22 to 26 , and like reference numerals have been used for like parts as appropriate. Instead of the arrangement shown in  FIG. 37  where the vertical guides extend downwardly through cut outs in the base plate or platform  136 , the traveling cross bar  186  may have upwardly bent ends which project upwardly through cut outs  140  for attachment to the ends of the vertical guides. 
     The machine  180  of  FIGS. 33 to 37  has a lighter weight moving exercise unit than the previous embodiments since there is only one upper and one lower traveling cross bar and only one horizontal slide associated with each traveling cross bar. However, it may be less stable than the previous embodiments. Offsetting the upper and lower horizontal guides would improve stability. The exercise machine  180  works exactly the same as the machines of the previous embodiments, and allows smooth, simultaneous vertical and horizontal motion of the exercise bar  46 . 
     The weightlifting exercise machines described above have a traveling exercise unit of reduced overall weight and provide a smoother, more fluid exercise motion. Each embodiment has at least one horizontal guide offset from the sides of the frame and one or both horizontal guides may also be offset from the vertical guides. The vertical guides may also be offset from opposite sides of the frame. In a number of these machines, at least one of the horizontal guides is a single horizontal guide bar which is offset from the other horizontal guide or guide bars, and is engaged by a single horizontal slide linked to both vertical guides by a traveling cross bar which is rigidly attached to both vertical guides. This arrangement significantly reduces the number of components required, and thus the overall weight and cost of the exercise machine. It is easier for the novice exerciser to overcome inertia and move the exercise bar when the moving unit is of lighter weight. At the same time, the offset between the upper and lower horizontal guides with which the traveling vertical guides are engaged improve stability and reduce free play, as compared with prior art machines where the upper and lower guides were in line in the vertical direction. 
     The machines described above require fewer horizontal slides and guides than many prior art designs, and also requires fewer vertical slides and guides than some prior art arrangements. They also requires less traveling framework than some prior designs. Because of the stability and restricted free play, there is no need for any alignment compensation means, as were necessary in some prior art Smith machines. 
     The exercise bar is also lighter than in prior art machines because of its design as a hollow revolving sleeve. Although some prior art exercise bars do have revolving sleeves, these have limited rotation since they typically have hooks mounted near each end for engaging pinning holes on vertical struts in the rest position. The rotation is therefore limited by a stop mechanism to avoid rotating the hooks into a potentially dangerous position. In contrast, the hollow revolving sleeve of the exercise arm in the above embodiments can rotate freely through 360 degrees. This allows the user to perform exercises such as curls which require different grips on the exercise bar and rotation during the exercise movement. 
     The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, it is to be understood that the description and drawings presented herein represent a presently preferred embodiment of the invention and are therefore representative of the subject matter which is broadly contemplated by the present invention. It is further understood that the scope of the present invention fully encompasses other embodiments that may become obvious to those skilled in the art and that the scope of the present invention is accordingly limited by nothing other than the appended claims.