US 2894605 A
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United States Patent PORTABLE FORK LIFT TRUCK Lester W. Leavitt, Jacksonville, Fla.
Application October 2, 1956, Serial No. 613,471 2 Claims. (Cl. 187-11) This invention pertains to portable fork lift trucks.
A general object of the invention is to provide an improved portable fork lift truck, and more particularly, to provide an easily movable fork lift truck wherein the fork lift carriage is power operated; wherein the carriage will remain in its then position upon the operator removing his hand from the controls; wherein the operator uses only one hand to operate and brake the lift; and wherein manual operation of the operating brake is necessary only to release such brake during the lowering operation.
While power operated fork lifts comprising a movable carriage operating between a pair of vertical uprights have been heretofore suggested, such prior fork lifts have been generally expensive to construct and have contained intricate lifting mechanisms and separate braking devices requiring the operator to manipulate several unrelated controls practically simultaneously. In practice such lifts have been diflicult to operate quickly and safely, and have usually required extensive maintenance, adjustment and servicing to maintain their continued operability.
Further objects of this invention accordingly are to provide a compact portable fork lift truck of simple,
gged and inexpensive construction which requires a of skill for quick, safe, one hand operation and a minimum of adjustments to maintain the device in eflicient working condition. Another object of the invention is to provide a stable portable fork lift truck having a small, inexpensive, self-contained power unit which is arranged to furnish relatively great lifting power to a movable lifting carriage. A still further object of the invention is to provide, in a portable fork lift truck, an improved anti-roll floor brake of simple construction which requires no adjustment and is quickly and easily operable.
The novel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing, in which:
Fig. 1 is a perspective view of a portable fork lift truck embodying the invention;
Fig. 2 is a perspective view of a portion of the truck showing the carriage in an upper position;
Fig. 3 is an enlarged rear view of a portion of the truck showing details of the brake drum, winding reel assembly and the brake band;
Fig. 4 is a sectional view taken along the line 4-4 of Fig. 3; and
Fig. 5 is a rear view on an intermediate scale of a lower portion of the truck showing details of the springloaded anti-roll block floor brake and operating means therefor.
Referring now to the drawing, Fig. 1 shows a portable fork lift truck 1 having a movable carriage 50 located in an intermediate position on a vertical frame 2. As seen, the lift truck comprises, in combination, a vertical frame generally referred to as 2, the frame comprising two oppositely disposed channel bars 3 and 3 spaced in parallel relation. The channel bars have outwardly extending rear flanges 4 and 5 respectively, and like front or forward flanges 6 (see Fig. 2) and 7 respectively which define the outwardly facing channels of the bars. An upper cross member 8 terminally joins the channel bars which are further interconnected by intermediate cross members 9 and 10, which lie substantially in the plane of the front flanges, and by cross member 11, which lies substantially in the plane of the rear flanges. The frame also includes upstanding rear braces: 12 and 13, afi'ixed respectively to the rear flanges of the channel bars, and with the frame, rigidly mounted on a horizontal base 14.
The base 14 includes two oppositely disposed horizontal legs 15 and 16 projecting forwardly from a base plate 17, to which they are joined. Legs 15 and 16 are connected by a front angle bar 18. Base plate 17 preferably has a greater length than the width of the frame and is provided with a pair of caster wheels 19 and 20 which are preferably the same size as but spaced further apart than wheels 21 and 22 supporting each of the forward legs.
The power means for operating the lift mechanism is mounted on base 14 and cross member 11, and comprises an electric drive motor 23, mounted on cross member 11 to extend rearwardly therefrom. Drive shaft 24 (see Fig. 3) of the motor extends forwardly through cross member 11. The motor 23 is energized by a storage battery 25 mounted on base 14 between channel bars 3 and 3.
Motor operating control elements "are provided including a push button switch 26 attached to the frame preferably in a position conveniently proximate to operating brake release handle 40, a limit switch 27 disposed on channel bar 3' in position to be engaged and operated by carriage plate 51 near the desired upper limit of the fork lift travel, and a motor control solenoid operated relay 84. Switch 26, which is spring biased into normally open position and which is manually controlled to closed position by thumb pressure, is connected in series circuit with relay 84 and with normally closed limit switch 27, the circuit being connected to battery 25 and operable, in response to closure of push button switch 26, to close relay 84, thereby to complete the power circuit between battery 25 and motor 23 through power cable and ground, the ground circuit being established by the metal frame.
The motor is belt connected with the brake drum assembly 29, the motor being so connected with the battery that, when energized, the brake drum assembly rotates in a reel winding direction, as is more fully discussed and shown with reference to Figs. 3 and 4 herein.
Referring now to Figs. 3 and 4, in which the reference numerals indicate the same parts referred to in Fig. l, the drive shaft 24 mounting the drive pulley 28, shown in broken lines on Fig. 3, is connected with brake drum assembly 29 by drive belt 30, which couples pulley 28 with a pulley portion 30 of the drum assembly. Cable reel 31 comprises an integral portion of drum assembly 29 and rotates with drum 34 and pulley portion 30'. It will be understood that the motor is so connected with the assembly that, when energized, drive belt 36 rotates brake drum assembly 29 in a reel winding and carriage lifting direction, which will be counterclockwise as viewed in Fig. 3.
The braking function is provided by generally circular brake band 32, having a brake lining 35 attached thereto and being engageable with brake drum 34, and having a stationary end 33 of the band anchored to cross member ll). End 33 encircles a post or bolt 58 and pivots slightly thereon, post 58 being aflixed to cross member 10. The brake band substantially encircles the brake drum and has at its other end 36 a plate 59 aflixed thereto and having a plurality of openings 64 to retain end 38 of a tension spring 37 and to permit adjustment of the spring tension. Tension spring 37 is attached at its other end .39 to the frame and functions to urge end 36 of the brake band in a direction to tighten the band about the brake drum. An operating brake release handle 40 pivotally attached to end 36 of the brake band is provided for manually loosening the brake band on the brake drum. As shown, handle 4 receives a manual hand grip 41 on the rearward or hand engageable end 55 thereof and is pivotally attached at its forward end 42 to cross member Bill by a pivot bolt 56.
As best seen in Fig. 4, brake drum assembly 29 receives and is rotatably mounted on spindle 43. The spindle 43 is rigidly mounted rearwardly on cross member 10, such as by bolts 36, and projects rearwardly therefrom.
Referring now to Fig. l and Fig. 2, in the latter of which the reference numerals indicate the same parts referred to in Fig. l, a flexible element such as steel cable 44 is wound on reel 31 and extends upwardly therefrom over free running back idler pulley 45 and front idler pulley 4 5, both of said idler pulleys being mounted on upper cross member The cable then extends downwardly from idler pulley 46 and passes around carriage pulley 4-7 which is mounted rearwardly on carriage yoke 48. The cable extends upwardly from the carriage pulley and passes over stationary free running upper pulley 49, which may be somewhat larger than the idler and carriage pulleys, and is mounted forwardly on cross member 9. The cable end 4 is fixed to carriage yoke 48. It will be seen that the cable is so wound on reel 31 and threaded on the pulleys and aflixed to carriage yoke 48 that, when the brake drum assembly is rotated by the motor in a reel winding direction, the cable winds on reel 31, thereby imparting a lifting action to the carriage.
The movable fork lift carriage, generally referred to at 59, comprises the yoke 48 spanning the channel bars of flame 2, yoke 43 having rigidly attached thereto two rearwardly projecting yoke plates 51 and 52. An upper pair of rollers 53 and a lower pair of rollers 54 are so affixed inwardly on plate 51 that the rear rollers of each pair engage and roll upon the inner face 7 of front flange 7 of channel bar 3. The forward rollers of each pair are positioned on plate Sl to engage and roll upon the outer face 7" (see Fig. 2) of front flange 7. The construction is duplicated in the roller arrangement of yoke plate 52 permitting this plate to travel along channel bar 3, as revealed by the broken away portion shown in Fig. 2. Pork lift carriage 50 further comprises two L-shaped forks 66 and 61 rigidly mounted on yoke 48 and extending forwardly therefrom in spaced parellel relation, the forward ends 62 and 63 respectively thereof being blunted to avoid injuring the objects to be lifted.
As best seen in Fig. the anti-roll block brake 65 comprises an anti-roll block 66 secured to rods 67 and 63 of yoke 69. The rods are slideably enclosed respectively in tubes 70 and 71, which are rigidly attached to a crossmember 72 of the frame. The lower ends of the tubes such as end 84 of tube 7t) have flanges such as 73 which serve as stops for compression springs 75 and 76 respectively. The springs surround yoke rods 67 and 6% and are compressed between block 66 and flanges 73 and 74. A manually operated floor brake handle 77 is provided which has a hand engageable grip 78 and is pivotally connected to a tubular frame crossmember 79 at point 86. Handle 77 is connected between its ends by means of a link 31 to the midpoint of yoke 69. A hook shaped catch 82 is mounted on frame brace 13 and is engageable by handle 77 when the anti-roll block is disengaged from the floor.
A U-shaped tubular handle 83 is provided intermediate the frame connecting channel bars 3 and 3' and protruding horizontally rearwards therefrom. The handle serves as a grip means for guiding the truck along the floor, as a bumper to protect motor 23 and as a guard for handle 4t) preventing external objects from striking the handle and accidentally releasing the brake.
The operation of the invention is best understood by the following descriptive cycle of the lifting and lowering of a hypothetical box conventionally resting on attached skids at approximately the level of the base of the truck.
The portable fork lift truck is manually rolled into position, using handle 83, with respect to the box to dispose forks 69 and 671 of carriage 5t) sufliciently beneath the box to support it in a stable manner. The motor is operated by push button switch 26 to raise the box with the attached skids to be thus supported solely by the forks. Now the truck may be pushed or pulled by handle 83, pivoting on its rear caster wheels 19 and 20, thus to be propelled to any desired position, such as facing the location in which the box is to be lifted and unloaded.
The operator may next raise the box by depressing the normally open operating switch 26, the motor being so connected with the rotatable brake drum assembly 29 that its driving force rotates the assembly in a reel winding or carriage lifting direction. By the rotation of the assembly in such direction, brake drum 34 exerts an unwinding force against its encircling brake lined band 32. It will be noted that band 32 is attached at end 36 to tension spring 37 thus permitting the band to be loosened from around the drum by this unwinding force and allowing the assembly to rotate freely. This rotation of the assembly, of course, winds the cable 44 on reel 31 thereby elevating fork lift carriage 50 to which the cable is attached.
The upward movement of the load-bearing carriage may be halted at any point, prior to engagement of the carriage with limit switch 27, by releasing the operating switch 26 to permit it to reopen, thereby breaking the circuit and stopping the electric motor.
When the motor is de-energized, the weight of the forks and any load thereon tends to urge the brake drum to rotate in a fork lowering direction. This tendency, together with the tension of spring 37, causes band 32 frictionally to wrap tightly around the drum and elfectively prevent any appreciable unreeling of cable 44 from reel 31, unless and until the braking force is reduced by manual operation of brake release handle 4%. If by any chance, because, for example, of the wearing out of the brake band, or because some grease may have been inadvertently spilled on the drum, the brake hand does not operate automatically to prevent unreeling rotation of the brake drum, brake release handle 40 may be pulled in the direction to additionally tighten the band about the drum. [f it is found that manual tightening of the band by means of handle 40 in this manner is frequently necessary, it may be appropriate to increase the tension of spring 37 by engaging it with a different one of openings 64.
If the operator for any reason fails to stop the lifting action before the maximum upper limit of carriage travel, carriage yoke plate Sll will engage normally closed limit switch 27 at the upper limit position of the carriage on the frame, the circuit will be broken, and the electric motor stopped, preventing damage to the truck. Immediately, of course, the braking action of the band and the drum produce the safe effective braking action as hereinabove described.
If the operator desires to lower the carriage, either loaded or unloaded, he need only urge the operating brake handle 40 in a band loosening direction and maintain the handle in such position, allowing the carriage to gravitate. The carriage may be interrupted in its descent at any point by the operator releasing handle 40 which will permit tension spring 37 to urge brake band 32 into contact with the drum which then tightens the band about the drum effectively braking the assembly as above described.
When the forks bearing the box have been elevated sufficiently permit them to pass above the stack or platform upon which the box is to be deposited, the operator pushes the truck into position to lower the box onto the top of the stack. The motor is then stopped, and, if necessary, the operator releases the operating brake, which allows the forks to be lowered until the skids attached to the bottom of thebox rest on the top of the stack or platform. The forks then may be withdrawn from between the box and the stack by pulling the truck outwardly and away from the stack.
Whenever necessary during the operation the operator may activate the spring-loaded anti-roll block brake 65 by disengaging floor brake handle 77 from its catch 82, permitting the compressed springs 75 and 76 to partially expand downwardly urging block 66 into contact with the floor thus preventing horizontal movement of the truck.
It will be understood that no manual force is applied to the operating brake handle during either the lifting or lowering operation to eflect the braking action as herein described. The manual operation of the brake handle is only necessary to disengage the brake band from about the drum when the motor is inoperative, such as during the lowering operation. It is therefore to be noted that the hereinabove described interrelation of the brake drum and brake band encircling it, together with the predetermined direction of rotation of the drum by the electric motor and the urging force supplied by the tension spring to the brake lband, aflfords an automatic brake disengaging mechanism during the power operation of the lift and an automatic brake engaging mechanism during the lowering operation. It will also be noted that if for any reason the operator removes the manual pressure from switch 26, the switch will reopen, breaking the circuit and stopping the motor, and the braking action herein described will be effected.
While only a certain preferred embodiment of this invention has been shown and described by way of illustration, many modifications will occur to thos skilled in the art and it is, therefore, desired that it be understood that it is intended in the appended claims to cover all such modifications as fall within the true spirit and scope of this invention.
What is claimed as new and what it is desired to secure by Letters Patent of the United States is:
1. A fork lift truck comprising a frame, said frame including a horizontal base having supporting wheels and further including a pair of spaced, parallel channel bars having front and rear flanges defining outwardly facing channels, said bars being attached to and extending upwardly from said base, and four crossmembers, including a top crossmember, a second crossmember disposed below and adjacent said top crossmember, a third crossmember below said second crossmember and a fourth crossmember below said third crossmember and above said base, said crossmembers connecting said bars in spaced parallel relation, one of said third and fourth crossmembers lying substantially in the plane of said front flanges and the other lying substantially in the plane of said rear flanges, a fork lift carriage spanning said bars and having roller means thereon mounted to run on said forward flanges, a spindle rigidly mounted on said one crossmember and extending rearwardly therefrom, a brake drum having a reel attached thereto and rotatably mounted on said spindle, a brake-lined band having two ends, a pivot fixed to said frame pivotally anchoring one said end externally of and adjacent said drum, said band extending from said pivot and engagingly encircling in a predetermined direction at least more than one-half of said drum, a tension spring having its ends respectively connected to a portion of said frame and a portion of said second end of said band urging said band end in said direction into braking engagement with said drum, an adjustable attachment element interposed between one end of said spring and its respective connected portion, a pivot member mounted on said frame, a brake handle pivoted at one end to said pivot member and having an intermediate portion pivotally attached to said second band end, said band being selectively loosenable and tightenable about said drum by manual operation of said handle in respective selected directions, top idler pulleys mounted to said top crossmember, a carriage pulley mounted on said fork lift carriage, an upper stationary pulley mounted forwardly on said second crossmember adjacent the upper end of said frame, a cable 'having an end at said reel and extending upwardly therefrom over said top pulleys and downwardly therefrom around said carriage pulley and upwardly therefrom over said upper pulley and downwardly therefrom and supportingly connected to said carriage, electric motor means mounted on said other crossmember and extending rearwardly therefrom and having a drive shaft extending forwardly through said other crossmember, said shaft mounting a motor pulley disposed forwardly of said other crossmember, flexible drive means connecting said motor pulley with said drum and reel, a storage battery mounted on said base between said bars, a spring-loaded normally closed limit switch mounted adjacent the upper end of said frame and engageable by said carriage in an upper limit position, a spring-loaded normally open operating switch connected in series with said limit switch, a solenoid relay connected in series with said switches between the terminals of said battery, a connection between said battery and said motor through said relay controlled by said relay, said motor being operative when energized through said connection to rotatably drive said drum and reel in the direction opposite to said predetermined direction, said cable end being wound on said reel in the direction to wind further thereon in response to rotation of said reel in said opposite direction and to unwind upon rotation of said reel in said predetermined direction, whereby rotation of said drum in said opposite direction frictionally urges said second band end to move against the force of said spring to loosen said band on said drum and rotation of said drum in said predetermined direction tends frictionally to tighten said band brakingly about said drum, an anti-roll sping-loaded floor brake block mounted on said frame, a floor brake handle attached to said block for manually raising and lowering said block, a hook catch mounted on said frame and engageable by said floor brake handle when said block is in a raised position, and a U-shaped tubular handle connecting said channel bars and protruding horizontally rearwards therefrom and passing outwardly protectingly beyond said drum brake handle.
2. A portable fork lift truck comprising a frame and fork lift carriage movably engaging said frame, a spindle rigidly mounted on said frame, a brake drum having a reel attached thereto rotatably mounted on said spindle, a brake-lined band having two ends, a pivot fixed to said frame pivotally anchoring one said end externally of and adjacent said drum, said band extending from said pivot and engagingly encircling said drum in a predetermined direction, a tension spring having its ends respectively connected to a portion of said frame and a portion of said second end of said band urging said band end in said direction into braking engagement with said drum, an adjustable attachment element interposed between one end of said spring and its respective connected portion, a pivot member mounted on said frame, a brake handle pivoted at one end to said pivot member and having an intermediate portion pivotally attached to said second band end, said band being selectively loosenable and tightenable about said drum by manual operation of 27 said handle in respective selected directions, a cable supportingly connected to said carriage, electric motor means, a flexible drive connection connecting said motor means with said drum, a source of electric power, a control switch, electrical connections connecting said power 5 source in circuit with said switch and with said electric motor means, said control switch being mounted on said frame adjacent said brake release handle and biased into position to disconnect said power source from said motor tion of said reel in said predetermined direction, whereby rotation of said drum in said opposite direction frictionally urges said second band end to move against the force of said spring to loosen said band on said drum and rotation of said drum in said predetermined direction tends frictionally to tighten said band brakingly about said drum, and a U-shaped handle mounted on said frame and protruding horizontally rearwards therefrom and passing outwardly protectingly beyond said means and manually operable to connect said power 10 drum brake handle.
source with said motor means, said electrical and flexible drive connections being oriented to operate said motor means in a direction to rotatably drive said drum and reel in the direction opposite to said predetermined direction, said cable being wound on said reel in the direction 15 to wind further thereon in response to rotation of said reel in said opposite direction and to unwind upon rota- References Cited in the file of this patent UNITED STATES PATENTS 1,781,104 De Lamar Nov. 11, 1930 1,781,700 Payne Nov. 18, 1930 1,875,046 LeTourneau Aug. 30, 1932 2,714,434 Peterson Aug. 2, 1955