US3027127A

US3027127A - Roller trolley apparatus

Info

Publication number: US3027127A
Application number: US819443A
Authority: US
Inventors: Leonard S Suozzo
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-06-10
Filing date: 1959-06-10
Publication date: 1962-03-27
Anticipated expiration: 1979-03-27

Description

March 27, 1962 L. s. suozzo ROLLER TROLLEY APPARATUS 3 Sheets-Sheet 1 Filed June 10, 1959 FIG.|

FIG.'?

INVENTOR. Leonard S. Suozzo ATTORNEY March 27, 1962 1.. s. suozzo 3,027,127

ROLLER TROLLEY APPARATUS Filed June 10, 1959 3 Sheets-Sheet 2 Leonard S. Suozzo ATTORNEY March 27, 1962 s. suozzo ROLLER TROLLEY APPARATUS 3 Sheets-Sheet 3 Filed June 10, 1959 ATTORNEY United States Patent Ofiiicc 3,ll27,l27 Patented Mar. 27, 1932 3,027,127 RGLLER TROLLEY APPARATUS Leonard S. Suozzo, Hachensaclt, NJ. Filed June 10, 1959, Ser. No. 819,443 14 Elaims. (Cl. 248-65) This invention relates to a support structure, and, more particularly, to apparatus for use in supporting a load, such as high temperature piping, and simultaneously allowing horizontal movement of the piping in response to thermal expansion or contraction thereof during use. The invention pertains, in one of its more specific aspects, to roller trolley apparatus which provides adequate vertical support and at the same time permits requisite lateral movement of a load of the character indicated.

As is well known to the art, piping and similar loads expand and contract both horizontally and vertically due to temperature changes therein. Accordingly, it is necessary in properly supporting such a load to provide for and permit of horizontal movement as well as vertical movement of the load.

There have been several important developments in recent years in the field of spring support devices for piping and the like. Such developments include the constructions disclosed in my copending applications, Serial No. 555,010, filed December 23, 1955, now Patent No. 2,903,213, and Serial No. 574,534, filed March 28, 1956, now Patent No. 2,939,663, both entitled Constant Support Device. These devices provide constant lifting forces while permitting vertical movement of the piping.

While these and certain other devices adequately and effectively compensate for vertical movement of the piping, they are neither capable of nor intended to permit horizontal movement of the piping. The horizontal movement may be along a rectilinear path, a simple curvilinear path, or a complex and irregular path depending on the particular piping load under consideration.

My present invention is concerned with an improved roller trolley apparatus for supporting and permitting horizontal movement of the piping. The apparatus may be used alone to permit of such horizontal movement or may be used in combination with a spring support device of the type indicated whereby the combined structure permits of simultaneous horizontal and vertical movement of the piping.

The apparatus of this invention embodies a number of worthwhile features that constitute important and distinct improvements in the art. For one thing, the apparatus includes a novel arrangement of a carriage having rollers, which rotate along rails that define the path of movement of the carriage, and a load-carrying unit having a member which bears directly on the rollers and is movable relative thereto along the path. The rollersare of one piece construction, thereby eliminating the need for separate wheels and axles and substantially reducing friction between the rollers and the rails and between the rollers and the load-carrying unit.

Another feature resides in the configuration and cooperative relationship of the rollers and the referred-to member of the loadcarrying unit. Each roller comprises a pair of outer parts of enlarged diameter which engage the rails and a central part of reduced diameter which defines an annular groove with the outer parts. The member includes a first part which projects into the annular grooves of both rollers and a second part which is positioned between the central parts of the rollers. The

parts are so arranged that for each revolution of the rollers the member moves a linear distance equal to the sum of the circumference of a roller outer part and the circumference of the roller central part.

The apparatus is compact and requires a minimum of space for installation and proper operation. Also, the apparatus has certain of its moving parts positioned Within a housing which provides adequate protection against dust, dirt and the like. This insures proper functioning and minimizes maintenance costs.

Another feature of the invention resides in the fact that the apparatus is capable of adequately supporting either a suspended load or an overhead load. Thus, the apparatus is quite flexible in application and may be uti lized advantageously to meet the requirements of particular conditions.

The roller trolley apparatus of this invention may be readily preset at the time of manufacture. This simplifies proper installation and protects moving parts against damage or tampering during transportation and at the time of installation.

It is the primary object of this invention to provide improved roller trolley apparatus which atfords adequate vertical support and at the same time permits requisite lateral movement of piping and similar loads.

Another object of the invention is to provide improved roller trolley apparatus which permits horizontal movement of a load along a rectilinear path, a curvilinear path or an irregular path.

A further object of the invention is to provide roller trolley apparatus for supporting and permitting horizontal movement of a load, such as piping, the apparatus including a novel and improved arrangement of at least one carriage and a load-carrying unit which are so constructed and arranged as to allow for relative movement therebetween while minimizing friction between rotating parts.

The invention has for a still further object the provision of apparatus of the character indicated that is simple and compact in design; that is sturdy and durable in construction; that is reasonable in manufacturing, installation and maintenance costs; and that is capable of performing its intended functions in an entirely satisfactory manner.

The enumerated objects and features, together with the advantages of the invention, will be readily understood by persons trained in the art from the following detailed description taken in conjunction with the accompanying drawings which describe and illustrate several forms of construction embodying the invention.

In the drawings, wherein like reference numerals denote corresponding parts throughout the several views:

FIG. 1 is a side elevation of one form of roller trolley apparatus that is constructed in accordance with this invention;

FIG. 2 is a bottom plan view of FIG. 1;

FIG. 3 is a view in enlargement taken along line 3-3 of FIG. 2, certain parts being shown in cross-section and other parts in full line;

FIG. 4 is a view taken along line 4-4 of FIG. 3;

FIG. 5 is an enlarged isometric View of a carriage which is one of the devices of the apparatus shown in other views;

FIG. 6 is an enlarged isometric view of a load-carrying unit which is one of the devices of the apparatus shown in other views;

FIG. 7 is a view in side elevation of a modified form of the invention;

FIG. 8 is a view in side elevation of the load-carrying unit of FIG. 7;

FIG. 9 is a top plan view of another modification of the invention;

FIG. 10 is a view in enlargement taken along line 10-10 of FIG. 9 and corresponds to FIG. 3;

SIG. 11 is a view taken along line 1111 of FIG. 10; an

FIG. 12 is a view taken along line 1212 of FIG. 11.

Reference is first had to the form of the invention shown in FIGS. 1 through 6. In this form, the roller trolley apparatus is generally indicated by numeral 15 and, as shown in FIG. 1, is suspended from an overhead support 16. The overhead support preferably consists of an I-beam having a top flange 17 and a bottom flange 18. The roller trolley apparatus is affixed to the I-beam by means of a pair of spaced angle members 20. The angle members are attached to beam flange 18 by bolts 21 and nuts 22 and are attached to the roller trolley apparatus by bolts 23 and nuts 24.

The roller trolley apparatus includes a housing 25 which is best shown in FIGS. 3 and 4. The housing comprises a pair of oppositely disposed, parallel, channel members 26. Each channel member consists of a vertical web 27, an upper horizontal flange 28 and a lower horizontal flange 29. Upper flanges 28 serve as the top wall of the housing while lower flanges 29 serve as its bottom wall. The channel members are spaced apart so that the facing edges of flanges 28 define an elongated housing top slot 30 while the corresponding edges of flanges 29 define a like housing bottom slot 31. A protective cover member 32 is mounted on top of the channel members.

The housing is provided with a pair of

end plates

33 and 34 which extend across and beyond the ends of channel members 26. The end plates, channel members and cover member are joined together, preferably by Welding, to obtain'a sturdy, rigid, unitary housing. Each end plate has at least one drill hole 35 for reception of a connecting bolt 23.

An indicator plate 36 (FIG. 2) is affixed to one of the channel members by means of screws 37. This plate has a series of graduations 38 for indicating travel of parts which will be described further along herein.

An angle member 40 is welded to channel flanges 29 and extends across bottom slot 31. This member is located adjacent housing end plate 33 and serves as a stop for limiting movement of a carriage, hereinafter described, in one direction.

Mounted on and bearing against the upper surfaces of channel flanges 29 is a pair of cold rolled bars 41. These bars are parallel and aligned with bottom slot 31. These bars are also slightly inclined, as shown in FIG. 4, and constitute rails for a carriage 42 which is best shown in FIGS. 4 and and which will next be described.

Carriage 42 comprises a rigid, rectangular, open, metal frame consisting of a pair of parallel sides 43 and a pair of parallel ends 44 which are united, preferably by welding. The carriage also includes a pair of one-piece, parallel rollers 45. Each roller is formed with a pair of outer parts 46 of enlarged diameter that bear on and ride along corresponding rails 41 and a central part 47 of reduced diameter. Each roller has a pair of axial extensions 48 which register with and are rotatable in frame side openings 49. Roller outer parts 46 are frusto-conical to conform to the inclined upper surfaces of rails 41. It is to be understood that roller parts 46 may be right circular cylindrical in configuration, if desired. In that case, the upper surfaces of rails 41 should be horizontal and coplanar. The inner end surface of each roller part 46 is preferably frusto-conical.

A load-carrying unit 51 is mounted on rollers 45. This unit is best shown in FIGS. 3 and 6 and includes a onepiece, generally T-shaped member consisting of a top part 52 having end lugs 53. and a stem part 54 having lateral extensions 55. One of extensions 55 terminates in a depending arm 56 which has a tapped opening 57. Stem part 54 is provided with an integral indicator element 58 which cooperates with graduations 38 to indicate the travel position of the load-carrying unit.

Each lug 53 carries a guide wheel 60. Each extension 56 also carries guide wheel 61.

Guide wheels

66 and 61 are freely rotatable relative to the T-shaped member about corresponding axes which are parallel and coplanar.

When the apparatus is assembled, as shown in FIGS. 3 and 4, the load-carrying unit is positioned on and supported by rollers 45. Part 52 of the T-shaped member projects into the annular groove formed by each roller and bears against roller central parts 47 while stem part 54 is positioned between the rollers. Also, guide wheels 60 register with housing top slot 30 and guide wheels 61 register with housing bottom slot 31. The illustrated arrangement of guide wheels and housing slots prevents undesirable movement of the carriage and load-carrying unit in a direction transverse of the path defined by the rails and eliminates any possibility of binding action between the load-carrying unit and the housing during use.

The T-shaped member ha an opening 62 in part 54 for reception of a bolt (not shown) or other element of a coupling means which is adapted to connect the load-carrying unit directly to piping (not shown) or to a spring support device (also not shown). An arm 63 is Welded to carriage frame end 44 and extends downwardly through housing slot 31 (FIGS. 3 and 5). This arm has a through opening 64 (FIG. 5). Carriage 42 and load-carrying unit 51 are adapted to be preset at zero position of the indicator plate at the time of assembly by means of a screw 65 which extends through an opening in angle member 40, opening 64 in arm 63 and tapped opening 57 in extension 56 (FIG. 3). Screw 65 is removed at the time of installation.

For the purpose of outlining the operation of the apparatus of FIGS. 1 through 6, it is assumed that roller trolley apparatus 15 is assembled and suspended from I-beam flange 18 as illustrated in FIG. 1. It is also assumed that the parts are in the relative position shown in FIGS. 1 and 3. Screw 65 is removed and a spring support device (not shown) i coupled to the load-carrying unit and to the piping system (also not shown). Carriage 42 and load-carrying unit 51 are free to move along the rectilinear path defined by rails 41 in response to corresponding lateral movement of the piping. It will be noted from an examination of FIG. 3 that housing 25, carriage 42 and load-carrying unit 51 are so constructed and arranged that for each revolution of the carriage rollers the load-carrying unit moves a linear distance that is equal to the sum of the mean circumference of a roller outer part 46 and the circumference of roller central part 47. Thus, the load-carrying unit is subjected to the horizontal movement of the carriage as a whole and, by virtue of its direct engagement with the rollers, to the turning action of roller central parts 47.

Housing end plates

33 and 34 limit travel of the load-carrying unit in opposite directions as indicated in FIG. 3.

The modification of the invention shown in FIGS. 7 and 8 is adapted to support an overhead load instead of a suspended load. In this modification, the roller trolley apparatus is generally denoted by numeral 66 and is supported above a floor by means of angle members 67. The housing is essentially the same as earlier described housing 25 but is devoid of a cover member. Also indicator plate 36 is secured to a side of the housing instead of at the bottom.

Roller trolley apparatus 66 includes a load-carrying unit 7% which is cruciform in configuration instead of T- shaped. This unit includes

parts

71 and 72 which correspond to

parts

52 and 54, earlier described, and an integral upwardly projecting part 73 which extends through and above the housing top slot. Part 73 has an opening '74 which serves the same function as opening 62. Part 72 carries an indicator 75 which coacts with graduations 38 on the indicator plate to denote load travel.

The construction illustrated int FIGS. 7 and 8 operates in substantially the same manner as that shown in FIGS. 1 through 6.

The forms of the invention shown in FIGS. 1 through 6 and in FIGS. 7 and 8 allow horizontal movement of the piping only along a rectilinear path. As was pointed out earlier in this description, the actual horizontal movement of the piping is not necessarily along a rectilinear path. Such movement may be along a curvilinear path or an irregular path depending on the particular piping arrangement.

The modification of the invention shown in FIGS. 9 through 12 permits horizontal movement of a piping load along any one of the above-indicated paths, namely a rectilinear path, a curvilinear path or an irregular path.

Referring to FIG. 9, I have illustrated therein a rectangular frame 76 that is adapted to be supported by building columns or the like. Frame 76 includes a pair of parallel side channels 77 and a pair of parallel end plates 78. Extending between and welded to channels '77 are a channel member 80 and an angle member 81. A combined stiffening and bearing plate 82 (FIG. is welded to the upped face of the lower flange of channel member 8%).

A housing 85 is similar to earlier described housing and is provided with a pair of spaced parallel connecting plates 86 which are welded to the top and bottom flanges of channel members 26. Spacing rings 8'7 are positioned against the outer faces of plates 86. A stop element 88" is welded to upper connecting plate 36 and projects into the interior of the housing. The stop element limits travel of load-carrying unit 51 toward the left, as viewed in FIG. 10.

The housing is pivotally connected to channel member 86 by a pivot pin 9% which extends through the flanges of this channel member and through connecting plates as and spacing rings 87, as best shown in FIG. 10. The pivot pin has a head M and is threaded at its lower end to receive a retaining nut 92.

Channel member 89 extends across the left end of the housing as viewed in FIG. 10. The other end of the housing is closed by an angle member which consists of a vertical flange 3 and a horizontal flange ea.

As in the case of the construction shown in FIGS. 1 through 6, the modification under consideration is provided with a carriage 4 2 and a load-carrying unit 51 that are adapted to move along a rectilinear path defined by housing rails 41. By virtue of the pivotal connection between the housing and frame, the housing is adapted to oscillate so that the end thereof remote from pivot pin 96 moves along a curvilinear path through the cooperation of devices which will next be described.

A cold rolled bar 95 is mounted on the horizontal flange of angle 51 and is equipped with an upstanding arcuate guide rail 96. A carriage 1% is mounted for movement along bar 95 as allowed by the guide rail. This carriage is similar to carriage 42 but is somewhat smaller in overall size. Carriage 1% includes a pair of arcuate and parallel sides lltll and a pair of ends 1&2. The carriage is provided with a pair of one-piece rollers Hi3, each of which includes a pair of spaced outer parts 104, a central part End of reduced diameter and endextensions 1% which project through openings in frame sides 1% Welded to the underside of angle flange 94 is a generally T-shaped member 107 which consists of an arcuate upper part 103 and a stem or lower part 169 (FIG. 11). Upper part 163 of the T-shaped member bears against central parts 195 of the rollers While lower part 199 is positioned between the rollers. A pair of plates 11% is welded to the ends of the T-shaped member and angle flange 94. These plates serve to reinforce the connection between the T-shaped member and its supporting angle.

An indicator plate 111 is aflixed to the underside of the housing adjacent angle flange 93. An indicator pointer 112 is secured to and movable with carriage 100. The indicator pointer coacts with the indicator plate to denote arcuate travel of the housing about pivot pin 90. An arm 113 is affixed to angle 81 at a point midway between the ends of track bar 95. The carriage and housing are adapted to be maintained at zero position of arcuate movement by a screw 114 which extends through arm 113 and indicator pointer 112 and into a tapped opening in indicator plate 111.

it will be appreciated from an examination of FIGS. 9 through 12 that the housing is adapted to be pivoted about pin so that T-shaped member 10 7 moves in an arcuate path in response to corresponding movement to the load. Inasmuch as load-carrying unit 51 is movable along a rectilinear path and T-shaped member 107 is simultaneously movable in an arcuate path, the apparatus permits movement of the load along a rectilinear path, a curvilinear path or an irregular path consisting of the sums of any rectilinear and curvilinear movements encountered by the apparatus in response to movement of the piping.

From the foregoing, it is believed that the objects, construction, operation and advantages of my present nvention will be readily comprehended by persons skilled n the art, without further description. Although the invention has been herein shown and described in several simple and practicable forms, it is recognized that certam parts or elements thereof are representative of other parts or elements which may be used in substantially the same manner to accomplish substantially the same results. Therefore, it is to be understood that the invention is not to be limited to the exact details described herein, but is to be accorded the full scope and protection of the following claims.

I claim:

1. In apparatus for supporting a load, such as high temperature piping, a housing, rail means carried by the housing and defining a path of predetermined configura t1on, a carriage movable along the path defined by the rail means and including a frame and a pair of spaced rollers coupled to the frame and rotatable relative to the frame about substantially parallel axes, each roller including a pair of spaced outer parts that engage the rail means and a central part intermediate and coaxial with the outer parts, said outer and central parts defining an annular groove, and a load-carrying unit mounted on the carriage and movable therewith along said path, said unit including a member that projects into the annular groove and bears against the central part of each roller, sard member being movable relative to the carriage, said unit being adapted to be connected to the load.

2. In apparatus for supporting a load, such as high temperature piping, a housing, rail means carried by the housing and defining a substantially rectilinear path, a carriage pos1t1oned within the confines of the housing and movable along the path defined by the rail means, said carriage including a frame and a pair of spaced rollers coupled to the frame and rotatable relative to the frame about substantially parallel axes, each roller including a pair of spaced outer parts that engage the rail means and a central part intermediate and coaxial with the outer parts, said outer and central parts defining an anular groove, and a load-carrying unit mounted on the carriage and movable therewith along said path, said unit comprising a generally T-shaped member including a lateral part which projects into the annular grooves and bears against the central part of each roller and a depending vertical part which is positioned between the central parts of the rollers and is adapted to be connected to the load, said member being movable relative to the carriage.

3. In apparatus for supporting a load, such as high temperature piping, a housing, rail means carried by the housing and defining a substantially rectilinear path, a carriage positioned within the confines of the housing and movable along the path defined by the rail means, said carriage including a frame and a pair of spaced roller-s coupled to the frame and rotatable relative to the frame about substantially parallel axes, each roller including a pair of spaced outer parts that engage the rail means and a central part intermediate and coaxial with the outer parts, said outer and central parts defining an annular groove, and a load-carrying unit mounted on the carriage and movable therewith along said path, said unit comprising a generally cruciform member including a lateral part which projects into the annular grooves and bears against the central part of each roller, a part depending from the lateral part and positioned between the central parts of the rollers and a part projecting above the lateral part and adapted to be connected to the load, said cruciform member being movable relative to the carriage.

4. In apparatus for supporting a load, such as high temperature piping, a housing, rail means carried by the housing and defining a path of predetermined configuration, the housing being provided with a pair of spaced slots which are parallel to each other and to said path, a carriage movable along the path defined by the rail means and including a frame and a pair of spaced rollers coupled to the frame and rotatable relative to the frame about substantially parallel axes, each roller including a pair of spaced outer parts that engage the rail means and a central part intermediate and coaxial with the outer parts, said outer and central parts defining an annular groove, and a load-carrying unit mounted on the carriage and movable therewith along said path, said unit including a member that projects into the annular grooves and bears against the central part of each roller, said member being movable relative to the carriage, and a plurality of pairs of spaced guide Wheels carried byand rotatable relative to the member, said guide wheels extending into corresponding slots and being movable therealong, said unit being adapted to be connected to the load.

5. Apparatus according to claim 4 wherein the axes of the guide wheels are parallel to each other and normal to the axes of the rollers.

6. In apparatus for supporting a load, such as high temperature piping, a support, a housing connected to the support for pivotal movement about a substantially vertical axis, rail means carried by the housing and defining a path of predetermined configuration which lies in a substantially horizontal plane, a carriage movable along the path defined by the rail means and including a frame and a pair of spaced rollers coupled to the frame and rotatable relative to the frame about substantially parallel axes, each roller including a pair of spaced outer parts that engage the rail means and a central part intermediate and coaxial With the outer parts, said outer and central parts defining an annular groove, and a load-carrying unit mounted on the carriage and movable therewith along said path, said unit including a member that projects into the annular groove and bears against the central part of each roller, said member being movable relative to the carriage, said unit being adapted to be connected to the load.

7. In apparatus for supporting a load, such as high temperature piping, a support, a housing connected to the support for pivotal movement about a substantially vertical axis, rail means carried by the housing and defining a substantially rectilinear path which lies in a substantially horizontal plane, a carriage movable along the path defined by the rail means and including a frame and a pair of spaced rollers coupled to the frame and rotatable relative to the frame about substantially parallel axes, each roller including a pair of spaced outer parts that engage the rail means and a central part intermediate and coaxial with the outer parts, said outer and central parts defining an annular groove, and a load-carrying unit mounted on the carriage and movable therewith along said path, said unit comprising a member including a first part which projects into the annular grooves and bears against the central part of each roller and a second part which is positioned between the central parts of the rollers and is adapted to be connected to the load, said member being movable relative to the carriage.

8. In apparatus for supporting a load, such as high temperature piping, a support, a device connected to the support for pivotal movement about a substantially vertical axis, a load-carrying unit carried by the device, rail means carried by the support and defining an arcuate path which lies in a substantially horizontal plane and which constitutes a portion of an arc of a circle having its center on said vertical axis, a carriage movable along the path defined by the rail means and including a frame and a pair of spaced rollers coupled to the frame and rotatable relative thereto, each roller including a pair of spaced outer parts that engage the rail means and a central part intermediate and coaxial with the outer parts, said outer and central parts defining an annular groove, a member secured to the device, said member projecting into the annular groove and bearing against the central part of each roller, said member being movable relative to the carriage.

9. Apparatus according to claim 8 wherein the member comprises a first part which projects into the annular grooves and bears against the central part of each roller and a second part which is positioned between the central parts of the rollers.

10. in apparatus for supporting a load, such as high temperature piping, a support, a housing connected to the support for pivotal movement about a substantially vertical axis, first rail means carried by the housing and defining a substantially rectilinear path Which lies in a substantially horizontal plane, a first carriage movable along the path defined by the first rail means and including a frame and a pair of spaced rollers coupled to the frame and rotatable relative to the frame about substantially parallel axes, each roller including a pair of spaced outer parts that engage the rail means and a central part intermediate and coaxial with the first part, said outer and central parts defining an annular groove, a load-carrying unit mounted on the carriage and movable therewith along said path, said unit including a first member that projects into the annular groove and bears against the central part of each roller, said first member being movable relative to the first carriage, said unit being adapted to be connected to the load, second rail means carried by the support and defining an arcuate path which lies in a substantially horizontal plane and which constitutes a portion of an arc of a circle having its center on said vertical axis, a second carriage movable along said arcuate path and including a second frame and a pair of spaced second rollers coupled to the frame and rotatable relative thereto, each second roller including a pair of spaced outer parts that engage the second rail means and a central part intermediate and coaxial with the outer parts, said outer and central parts of each second roller defining an annular groove, and a second member secured to the housing, said second member projecting into the annular groove and bearing against the central part of each second roller, said second member being movable relative to the second carriage.

11. Apparatus according to claim 10 wherein the first carriage is positioned between said vertical axis and the second carriage.

12. Apparatus according to claim 10 wherein each of said first and second members includes a first part which projects into the annular grooves and bears against the central parts of corresponding rollers and a second part which. is positioned between the central parts of corresponding rollers.

13. Apparatus according to claim 10 wherein the hous- 9 10 ing is provided with at least one elongated slot which is ing into corresponding slots and being movable thereparallel to said first-mentioned path and the load-carryalong.

ing unit includes a pair of spaced guide wheels which R f ence C't d n the file of this atent carried by and rotatable relative to the first member, e H S l e l p said guide Wheels extending into the slot and being 5 UNITED STATES PAThNTS movable therealong. 1,920,744 Webb Aug. 1, 1933 14. Apparatus according to claim 10 wherein the hous- 1,959,172 McIlrath May 15, 1934 ing is provided with a pair of spaced slots which are 2,156,468 Wood May 2, 1939 parallel to each other and to the first-mentioned path FOREIGN PATENTS and the load-carrying unit includes a plurality of pairs 10 l of spaced guide wheels which are carried by and rotat- 191,501 swltlerlapdl P 1937 able relative to the first member, said guide wheels extend- 593,303 Great Britain Oct 14, 1947