US 3345471 A
Description (OCR text may contain errors)
Oct. 3, 1967 R, J. KILBURG PORTABLE TROLLEY SYSTEM 4 Sheets-Sheet 1 Filed April 2'7, 1964 Oct. 3, 1967 I R. J. KILBURG 3,345,471
PORTABLE TROLLEY SYSTEM Filed April 27, 1964 4 Sheets-Sheet 2 iffd/FA/EKS? Oct. 3, 1967 R. J. KILBURG 3,345,471
PORTABLE TROLLEY SYSTEM Filed April 27, 1964 4 Sheets-Sheet 3 drum/5m Oct. 3, 1967 Filed April 27, 1964 R. JIKILBURG 3,345,471
. PORTABLE TROLLEY SYSTEM 4 Sheets-$heet 4 "'I II 1 I I I I I! I I I I l I I I l II IIII INVENTOR. paw/0 J/Wlflf United States Patent fornia Filed Apr. 27, 1964, Ser. No. 362,730 Claims. (Cl. 191-45) This invention relates to mobile electrification systems, and more particularly to a system for supplying power to portable hand tools.
In many industrial operations, it is necessary to provide a source of power for portable hand tools that are used by the workers at different positions along an assembly line or in different parts of a work area. Conventional wiring and outlets at the different locations is one solution, but it not only requires a.lot of lost motion by the workers in plugging and unplugging the power cords of the hand tools, but creates safety problems due to the indiscriminate draping of power cords along the floor in the work area. These disadvantages, among others, have led many plants to utilize overhead electrification systems.
These overhead electrification systems are normally mounted above the assembly line or over the work area within easy reach of the workers. As a result, the conductors or bus bars are normally supported in a protective housing-one having a minimum opening-to prevent a worker from accidentally touching the current carrying conductors. The hand tools are electricalb co nnected to movable trolleys which are supported inside the housing for movement along the line of the overhead system. Such systems have the advantage of getting the power lines off of the floor and allowing the tools to be moved along the assembly line or around a work area without plugging and unplugging them all the time. In many cases, a support for the hand tool, when it is not being used, is connected to the trolley as well.
In spite of the many advantages that movable trolleys provide, however, those currently available have certain shortcomings. Since the conductor housing must be finger proof, cover plates or drop-out sections in the housing must be provided to get the captive trolley inside the housing, or the required number of trolleys must be placed in the housing when it is assembled. This may not be too inconvenient as long as each hand tool is used along the same part of an assembly line or in the same section of a work area, but often it is most efficient if a worker can pass other workers and plug in a hand tool anywhere along the electrification system. If this is required, drop-out sections must be judiciously provided or, the tool unplugged from the trolley and transferred to another trolley. Whenever this is done, many of the disadvantages that are attributable to conventional wiring outlets are re-introduced. 5
Over and above these restrictions on flexibility created by many prior art systems, captive trolleys mounted inside of protective housing have certain technical drawbacks. In the first place, space is at a premium in most plants so that the protecting housings must be reasonably small. It follows that the trolleys and their mounting wheels must also be small. Small wheels are far more susceptible to jamming and the accumulation of dirt and grease on the supporting tracks takes its toll.
Secondly, this difliculty is compounded since the housing is difficult to clean when it is worker safe. When obstructions occur, it is usually necessary to shut down the electrification system and partially dismantle the housing. Also, inability to visually or physically examine the guide rail area inside the housing to determine the cause of the jamming is no small part of the problem.
The present invention is designed to ameliorate some 3,345,471 Patented Oct. 3, 1967 "ice of these shortcomings, and to do so, by providing a portable trolley system that is flexible, safe, rugged and economical. Generally speaking, this novel portable trolley system realizes a number of advantages over prior systems by placing the guide rails on the outside of the housing, by increasing the size of the supporting wheels substantially, by providing auxiliary wheels which, among other things, stabilize the trolley as it is moved along the rails, by incorporating means in the trolley to enlarge the spacing between the guide wheels so they can clear the rails when the trolley is mounted on the housing, and providing a novel collector shoe assembly.
The over and under wheel arrangement of the present portable trolley and the outer rail offer a number of advantages. The external rails are easier to maintain and clean. Moreover, when dirt and grease or obstructions cause problems, it is easy to see precisely where the trouble is so that the situation can be remedied in a minimum amount of time. Furthermore, such cleaning and repair can be done without shutting down the electrification system or otherwise completely interrupting the operation of the assembly line or work area.
The use of larger wheels in and of itself constitute a substantial benefit over the prior art system inasmuch asthe larger at supporting wheel is, the less likely it will be to be jammed by dirt or grease deposited along the guide rails or between the wheels. Also, the use of a single, relatively large wheel on each side of the portable trolley to cooperate with auxiliary wheels mounted on the trolley body just beneath the tracks or flanges has added advantages. It has been found to be generally superior to the conventional four-Wheel support systems because the single point of support for the trolley means, that when a trolley is pulled in eitherdirection, the stabilizing wheels away from the direction of pull, and those only, cooperate with the guide or support wheels to rotate the trolley downwardly so that it moves along its track easily. The other auxiliary wheels do not engage the rail which reduces the forces opposing the movement of the trolley.
Other advantages also result. The over and under wheel arrangement is desirable because the fore and aft wheels are closely juxtaposed to both surfaces of the rail which provides substantial reinforcement for it so that the rail will not be deformed or pulled out of shape. An ancillary benefit of the open type housing with outwardly projecting flanges also arises because it permits the housing to be reinforced interiorly by struts if needed to support relatively heavy hand tools. In the case of most prior art trolley systems, the trolley support mechanism, of necessity, had to be so small and took up such a large percentage of the interior of the housing that it left little room to reinforce the housing when the need arose. With the present arrangement, except for the spaced apart conductor bars and their supporting brackets, there is nothing in the housings interior to interfere with reinforcing struts. Yet another advantage of the outer track arrangement is that the support points for the portable trolleys are at maximum outward locations which provides better stability for the trolley as it is pulled along the track.
To eliminate the need for drop out sections or substantially disassembling the housing whenever a portable trolley is to be mounted therein, the trolley includes means to move the guide wheels outwardly from their normal position so they can clear the edge of the flange forming the supporting tracks. By this means, it is possible to mount and demount the portable trolley at any point along the overhead electrification system without using any special dropout sections. The assignee of the present application has had occasion in the past to work on the development of portable trolleys which eliminate the need 3 for dropout sections. But one of the difiiculties, where the trolley is captured inside the housing, is the limited space in the housing. Also it does not meet the other needs of a truly versatile portable trolley system.
One of'the things that makes the present system particularly advantageous is the use of insulated conductor bars of the so-called O-bar or figure 8 type wherein each conductor bar is insulated except for an open slot along its lower edge. The uninsulated slot in the insulated conductorbars is too narrow to permit a workers finger to touch the bare conductors. This makes the conductor bars entirely safe and eliminates the need for the substantially closed housing heretofore employed.
Moreover, by using a plurality of parallel conductor bars supported in the housing and vertically oriented colle-ctor shoes in the trolley, it is possible to provide a flexible system adapted to connect one, two, or three or more electrical circuits to portable hand tools associated with a portable trolley. In most prior art systems, the conductor bars are arranged interior of the housing in a Y-configuration which makes it diflicult to provide more than three connections to the portable trolley. A feature related to the use of collector shoes supported in vertical array on the trolley body is the non-symmetrical transverse spacing of the conductor bars and collector shoes so that the portable trolley has to be polarized to fit onto the housing. This assures that the right collector shoes contact the right conductor bars.
Another feature of the present invention pertains to the removable collector shoes vertically supported along the upper part of the body of the trolley and adapted to slidably engage the conductor bars when the trolley is mounted on the housing flange. These collector shoes are easily removed when they become Worn. They can be replaced easily without requiring a shut down of the entire electrification system or without interrupting the operation of the assembly line.
In one of its broader recitations, the present invention provides a portable trolley for supplying power to hand tools from overhead conductors which are mounted along a path defined by a pair of continuous support rails that combines a body member, a plurality of collector shoes carried by the body to slidably engage the overhead conductors when the trolley is supported along the rails, support arms connected to the body, guide wheels rotatably mounted on the arms to engage the rails to support the body adjacent the overhead conductors, auxiliary wheels rotatably mounted on each side of the body with the guide wheels disposed between them and means operable to mount the trolley so that the guide wheels ride on the rails and the auxiliary Wheels are disposed below the rails.
More specifically, the invention is a system for supplying power to portable hand tools that includes a pair of spaced-apart tracks, a plurality of current conductor bars insulatedly supported intermeditae the tracks at spaced intervals and a removable carriage supported on the tracks to transfer current from the conductor bars to the tools. The removable carriage includes a body member, a plurality of collector shoes supported in the top of the body at spaced intervals corresponding to those of conductor bars, a pair of outwardly and upwardly extending arms normally supported by the body in a closed position, relatively large guide wheels rotatably mounted on the outer ends of the arms to ride on the upper surfaces of the track when the arms are in the closed position, pairs of auxiliary wheels rotatably mounted on both sides of the body with the guide wheels between them, and means to change the transverse spacing of the guide wheels so that the carriage can be freely mounted on the tracks with the arms in their closed position.
These and other objects, advantages and features of the present invention may be more fully understood when the following detailed description is read with reference to the drawings in which:
FIG. 1 is a parital perspecitve of an exemplary assembly line with a number of portable trolleys constructed in accordance with the present invention supported therealong;
FIG. 2 is a perspective of a part of a portable trolley system in accordance with the present invention;
FIG. 3 is an end view of the portable trolley suspended on the housing and cooperating with the conductor bars with certain parts broken away to more clearly show its construction;
FIG. 4 is a section taken along line 4-4 of FIG. 3 to illustrate the collector shoe assembly;
FIG. 5 is a side view of the portable trolley mounted on a housing;
FIG. 6 is an end view of the'outwardly projecting hanger arms of the portable trolley with certain parts broken away to illustrate how the mechanical linkage controlling the arms is constructed and with the outermost position of the guide wheels shown by dotted lines;
FIG. 7a is a section taken along line 77 of FIG. 6 to illustrate the mechanical linkage when the arms are in their normal or closed position;
FIG. 7b is a section taken along 77 of FIG. 6 but with the mechanical linkage extended as it is when the arms are in their open or mounting position; and
FIG. 8 is an enlarged partially exploded view of the means to lock an arm either in its closed or mounting position.
The portable trolley system forming the present invention is illustrated adjacent an assembly line in FIG. 1. Housing 10 supports a plurality of portable trolleys or carriages 15 at spaced apart points. Suspended from the trolleys 15 by power cords 16 are various hand tools, illustrated generally at 17. It can be seen that the housing 10 is supported along and above an assembly line or work bench 18.
Looking more particularly to FIGS. 2-5, the cooperat ing parts of the portable trolley system can be readily appreciated. A plurality of conductor bars 13 are supported in spaced apart parallel relation interior of the housing 10. The housing 10 is formed of two pieces of steel to approximate an inverted open box with outwardly projecting flanges or hems 21. The two parts of the housing 10a and 10b are welded or otherwise affixed at surfaces 22 and the housing is connected to overhead support brackets (not shown) by the upper flange 23.
The conductor bars 13 can be the so-called 0 type conductor bars illustrated in FIG. 2 or the figure-8 conductorbars illustrated in FIG. 3. In both cases, they include a conductor bar 26 having an insulated sheath 27 therea-round with an opening along the lower edge of the conductor bars to permit the collector shoes 64 on the portable trolley to contact the conductor bars 26 to transfer power to a hand tool by power cord 16. In some cases, it may be desirable to use uninsulated conductors and insulated hanger clamps, but for maximum safety, insulated conductor bars are to be preferred.
As illustrated particularly in FIG. 3, the insulated conductor bars 13 are supported in parallel array by plurality of supporting hangers 32 which are aflixed to a transverse bracket 33 that is attached to the inside of housing 10.
In the case of both types of conductor bars illustrated in the drawings, the center conductor bar is closer to the one on the left than to the one on the right (with respect to FIGS. 1 and 3). This non-uniformity in the spacing of the conductor bars 13 is to provide a positive polarization of the portable trolley with respect to the conductor bars so that the trolley can only be attached when it is properly oriented.
The portable trolley 15 generally includes a body 41 having two parts, 41a and 41b, which are held together by screw members such as 42; a number of collector shoe assemblies 61; auxiliary wheels 44; guide wheels 50; and hanger arms 48.
The spaced apart auxiliary wheels 44a and 4412 are rotatably supported on each side of the body member 41, and each has an outwardly disposed shoulder 45 which rides adjacent the edge of its rail 21 when the portable trolley is mounted on the housing 10. These wheels 44 provide a stabilizing function for the portable trolley 15 as it is moved along the rails. The auxiliary wheels 44 also act as a stop for upward movement of the body member 41 when the trolly is mounted or demounted as hereinafter explained.
The outwardly and upwardly projecting hanger arms 48 have guide wheels'50 rotatably supported on their uppermost ends. Each guide wheel 50 has an outwardly disposed shoulder 51. In its operatingor closed position.
(illustrated in FIGS 1 and 3), the guide wheels 50 ride on the upper surfaces of the rails 21 and the projecting shoulders 51 are adjacent the outer edge of their rails 21.
It will also be observed that the arms 48 dispose the guide wheels 50 longitudinally between the auxiliary wheels 44a and 44b. This offset and over and under wheel arrangement gives excellent results. As mentioned earlier, if the trolley 15 is to be pulled, say to the right of the FIG. 2 drawing, the right side of the trolley 15 is pulled away from the rail 21 and only auxiliary wheels 44a cooperate with the guide wheels 50 to stabilize the trolley. The wheels 44b do not contact the bottom of the rail 21 at all. The .trolley 15 is canted or tilted forward which places the force of the pull on the guide wheel. The forward auxiliary wheels 4411 in a left to right pull do not impede the movement of the trolley. By the same token, if the trolley is to .be moved from the right to the left of FIG. 2, the auxiliary wheels 44a do not engage the lower part of the rails 21 and the trolley is moved under the control of guide wheels 50 and auxiliary wheels 44b.
A plurality of collector shoe assemblies 61 (FIGS. 3 and 4) are disposed in slots 62 formed longitudinally in the body 41. Each collector shoe assembly 61 includes the rectangular collector shoe 64 supported in a generally U-shaped holder 66 that has a lower plate 67 and a pair of upstanding sides 68. The sides include a neckeddown portion 69 which engages grooves 71 formed on the longitudinal sides of its collector shoe 64. Each plate 67 of the holder 66 has spaced apart depending pins 72 which act as guides for compressed helical springs 73 which are mounted between the lower surface of plate 67 and the lower surface 74 defining the slot 62. The springs 73 urge a holder 66 upwardly to force the contacting surface 65 of the collector shoe 64 against the lower edge of the conductor bar 26. Electrical connections between the holder 66 and the insulated power cord 16 are also provided.
Turning to the means by which the arms 48 are connected in t-hebody 41 and moved outwardly, the rectangular shaped arms 48 fit into slots 81 formed in the lower part of the body member 41. They are connected by way of links 82 and 83 to a drive link'84 which is, in turn, staked to a vertical shaft 86 rotatably mounted in body 41. A handle 87 is connected at the lower end of shaft 86. A rectangular tension plate 91, aflixed to the shaft 86 (by means not shown), and a washer-type spring 94 is interposed between the tension plate 91 and the lower surface 96 of the body member to urge the plate 91, the handle 87 and the shaft 86 to remain in a downward position.
The inner ends of the arms 48 have radially oriented parallel slots 101 formed through them which terminate in recessedcircular shoulders 102. Upstanding parallel sided pins 92 are disposed in the slots 101 and are aflixed at their lower ends to plate 91. The pins terminate in circular shoulders 103, the diameters of which-coincide with the diameters of recessed shoulders 102. With this arrangement, whenever the shaft 86 is in its closed or open position, the circular shoulders 103 move into the recessed shoulders 102 under the force of spring 94 to 6 lock the arms 48 in their instant positions. Only by pushing upwardly (with respect to the orientation of FIG. 2 for example) on the handle 87 and its associated shaft 86 is it possible to move the circular shoulders 103 out of their recesses 102. At this point, the shaft 36 can be rotated to cause link 84 to move the driven links 82 in translation from one position to another. For example, if the guide Wheels are in open posistion, then the arms 48 can be rotated to their closed position or vice versa.
In the mounting operation, the portable trolley 15 having a hand tool 17 connected to it by way of power cord 16 is located beneath the housing 10 with the auxiliary wheels 44 resting against the underside of the rails 21. With the auxiliary wheels 44 preventing the body member 41 from moving too far towards the housing, the handle 87 is moved upwardly to release the shoulders 103 from the recesses 102. Thereafter, the handle 87 and shaft 86 are rotated to move the arms 48 to their closed or normal position, which position places the guide wheels 50 on the upper surfaces of the guide rail 21. Release of the upward pressure on the handle 87 allows the shoulders 103 to fall into the inwardly disposed recesses 102. This locks the portable trolley 15 firmly in place on the housing 10.
As a worker utilizes a connected hand tool along an assembly line, he pulls the portable carriage along with him.
At the end of the assembly line, or anywhere along it, the worker can reverse the process involved in mounting the trolley on the housing to remove it. He pushes upwardly on the handle 87 to unlock the shaft 86 which controls the movement of arms 48 and guide wheels 50 attached thereto. Rotation of the shaft 86 thereafter moves the arm 48 outwardly so that the guide Wheels 50 clear the edges of the rails 21. The portable trolley 15 can then be removed and carried with the hand tool to another point on the assembly line and there re-attached to the housing to provide power for the hand tool as work is continued.
While the invention has been described with respect to an exemplary embodiment, it should be apparent to those skilled in the art that changes can be made in the basic concept without departing from the spirit and scope of the invention. For this reason the invention should be limited only to the extent of the claims.
What is claimed is:
1. A portable trolley for supplying power to hand tools from overhead conductors mounted along a path defined by a pair of continuous support rails comprising, in combination,
a plurality of collector shoes carried by said body to slidably engage the ovehead conductors when the trolley is supported on said rails;
movable support arms mounted on said body;
guide wheels rotatably mounted on said arms to engage the rails to support said body adjacent the overhead conductors;
auxiliary wheels rotatably mounted on each side of said body with the guide wheels therebetween to stabilize the body by selectively engaging the underside of said pails when the portable trolley is mounted -on said rails; and
means operable to extend said arms transverse to the axis of the rails so as to mount the trolley so that the guide wheels ride on said rails.
2. A portable trolley in accordance with claim 1 wherein the spacings between the overhead conductors and the cooperating collector shoes are non-symmetrical to assure correct polarization of the collector shoe circuits and including means associated with the mounting means and interior of said body to lock said arms when the trolley is mounted on the support rails for movement therealong.
tion of said shaft to change the separation between said guide wheels by moving said arms;
said shaft normally occupying an axial position in which the rotation of the shaft is blocked; and
a carrying handle connected to said shaft so that said shaft can be moved axially to free it for rotation and then rotated to position said arms.
4. A system for supplying electrical power to hand tools used along a moving assembly line comprising, in combination,
a housing having uninterrupted flanges extending outwardly from its sides supported adjacent an assembly line;
a plurality of conductor bars insulated except for their lower edges supported in nonsymmetrical relation interior of said housing; and
a portable carriage adapted to be moved along said housing;
said carriage including an insulated body;
a hanger attached to said body;
guide wheels having shoulders rotatably mounted on the one end of said hanger to support said body on said flanges and prevent movement transverse to said flanges;
a pair of stabilizing wheels symmetric-ally mounted fore andaft of said guide wheels to lie just below the bottom of the flanges when the body is sup ported adjacent said housing by said hanger;
means manually operable to move said guide wheels outwardly in translation to clear said flanges when the carriage is to be attached to said housing or removed therefrom;
means enclosed in said body and cooperating therewith to lock said hanger and said guide wheels in their innermost positions after said carriage is mounted on said housing; and
a plurality of vertically oriented collector shoes supported interior of said body to slidably engage the uninsulated edges of said conductor bars.
5. In a system for supplying power to portable hand tools that includes a pair of spaced apart tracks, a plur ality of current conductor bars insulatedly supported intermediate said tracks at spaced intervals and a movable carriage supported on the tracks to transfer current from the conductor bars to the tools, the improvement in the removable carriage comprising, in combination,
a body member;
a plurality of collector shoes supported adjacent the top of said body in parallel relation and at spaced intervals corresponding to those of the conductor bars;
a pair of outwardly projecting arms normally supported by said body in preselected spaced apart relation;
guide Wheels rotatably mounted on the outer ends of said arms to ride on the upper surfaces of said tracks when said arms are in said preselected spaced apart relation;
a pair of auxiliary wheels rotatably mounted on both sides of said body with the guide wheels therebetween; and,
means associated with said body member operable to move the projecting arms in translation to change the spacing between said guide wheels transverse to said tracks so that the carriage can be mounted on said tracks.
6. A portable hand tool carriage in accordance with claim 5 wherein said guide Wheels are relatively large in comparison with said auxiliary wheels and said g auxiliary wheels underlie a substantial transverse part of the lower surface of said tracks when the carriage is supported on said housing and are normally just below the lower surface of said tracks to assist in stabilizing the carriage during movement and to act as a stop to upward movement of said body with respect to said track whenever the body is mounted or demounted from the tracks.
7. A portable hand tool carriage in accordance with claim 5 wherein said means operable to change the transverse spacing of said guide wheels comprises an axially movable shaft having a handle attached thereto rotatably supported in said body;
a first link aflixed to saidshaft;
a pair of links pivot-ally connected at one set of their ends to said first link on opposite sides of said shaft and at their other ends to the inner ends of said projecting arms so that rotation of said shaft moves projecting arms between inwardly and outwardly positions;
transverse slots formed in each of said projecting arms which terminate in circular recesses;
a plate underlying said arms and aflixed to said shaft;
said plate having affixed to it on opposite sides of said shaft spaced apart, upstanding guide pins with circular shoulders at their upper ends, said pins projecting through said slots;
resilient means normally holding said plate away from said body,
the circular shoulders on said pins seating in said recesses to lock said shaft against rotation when said plate is away from said body; and
means to move said plate and shaft axially upward to free said shoulders from one set of said circular terminations so that said shaft can be rotated with the pins moving along said slots to positions overlying the other circular recesses;
said circular shoulders responsive to said resilient means to move into said recesses upon release of said plate.
8. In a system for supplying power to portable hand tools that comprises an inverted open housing having outwardly projecting hems on each of its sides, a plurality of conductor bars insulatedly supported in spaced parallel relation within the housing and a carriage movably suspended from the housing to permit the transfer of current from the conductor bars to the tools as the carriage is moved along the housing, the carriage comprising, in combination,
an insulated body member having a longitudinal axis parallel to the conductor bars and the supporting hems of the housing when the carriage is mounted on said housing;
a plurality ofremovable collector shoes;
means supporting said collector shoes in the top of said body in planes parallel to said axis and at transverse intervals corresponding to the separation between said conductor bars;
a pair of hanger arms connected to said body member for translational movement in a transverse plane between a normal position and an attachment position;
guide wheels rotatably mounted on the ends of said projecting arms to engage the upper surfaces of said hems when said arms are in said normal position;
auxiliary wheels rotatably mounted on said body member fore and aft of each of said guide wheels to underlie said hems when said carriage is mounted on said housing; and
means generally interior of said body member operable to move said arms outwardly to said attachment position so that said guide wheels can clear the outer edges of said hems before being moved inwardly to said normal position to mount said carriage o a d housin 9. A portable hand tool carriage in accordance with claim 8 wherein means are operative to lock said arms in said normal and attachment positions,
said body member is formed in two parts;
said supporting means for the collector shoes are disposed in longitudinal slots formed in the two halves of said body member before it is assembled;
each of the collector shoe supports includes an elongated U-shaped holder having a restricted longitudinal neck portion and resilient means cooperating with said body member to urge said holder toward the upper part of said carriage, and
said collector shoes are generally rectangularly shaped with longitudinal grooves formed in their sides for their retention by the reduced neck portions of their respective support holders and said auxiliary wheels act as a stop for said body member to avoid damage to the collector shoes and supports and so that the means to move said arms can be moved upward with respect to said body member to unlock said arms.
10. In a system for supplying power to portable hand tools that includes an inverted open housing having outwardly projecting flanges on each of its sides, a plurality of figure-8 conductor bars insulated except for their lower edges supported in non-uniform spaced parallel relation Within the housing and a carriage having a hand tool electrically connected to it removably suspended from the housing to permit the transfer of current from the conductor bars to the electrical connector for the tool as the carriage is moved along the housing, the improvement in the portable carriage comprising, in combination,
an insulated body member having a longitudinal axis;
a plurality of collector shoes confined in the upper part of said body member to slidably engage respective ones of said conductor bars when said carriage is mounted on the overhead housing with the longitudinal axis of its body parallel to the lay of the conductor bars;
two stabilizing wheels having outer shoulders rotatably mounted on each side of said body member to underlie said flanges when the carriage is supported on said housing;
a pair of arms extending outwardly from said body member intermediate the stabilizing wheels on each side of said body member for transverse movement between a normal position and a mounting position;
relatively large guide wheels having outer shoulders rotatably mounted on the outer ends of said arms to ride on the upper surfaces of said flanges when said arms are in said normal position and to be spaced apart a distance greater than that between the outer edges of said flanges when said arms are in said mounting position;
control means manually operable to move said arms to said mounting position so that the guide wheels can pass by said flanges and to said normal position in which said guide wheels engage said flanges;
said control means including a shaft rotatably mounted in the lower part of said body member and having a handle atfixed to its lower end and a mechanical linkage responsive to the rotation of said handle and said shaft to move said arms between said mounting and normal positions;
means to lock said shaft in either one of said normal and mounting positions; and
means associated with said arms responsive to the axial movement of said shaft to release said locking means so the shaft can be rotated between said positions.
References Cited UNITED STATES PATENTS Re. 19,513 4/1935 Frank et al. 191-23 2,117,480 5/1938 Harvey 191-45 X 2,170,298 8/1939 Frank 191-45 X 2,645,187 7/ 1953 Guadagna. 2,696,532 12/1954 Herrmann et al. l9156 X 2,830,136 4/1958 Herrmann et'al. 2 19145 X 2,830,137 4/1958 Herrmann et al. 191-45 X 2,912,526 11/1959 Herrmann et al. 191-23 3,017,958 1/1962 Richter 2- 19l150 X 3,206,560 9/1965 Parmenter.
ARTHUR L. LA POINT, Primary Examiner.
S. T. KRAWCZEWICZ, Assistant Examiner.