US 3868034 A
An industrial lift truck in which forks are mounted on a turret carried up and down a mast. An electric motor for moving the turret has a friction brake which is normally engaged: a switch for operating the motor is simultaneously operable with a switch for a solenoid which releases the brake.
Description (OCR text may contain errors)
United States Patent [191 Goodacre et al.
111 3,868,034 1451 Feb. 25,1975
[ INDUSTRIAL LIFT TRUCKS  Inventors: Cecil Goodacre; Peter Alfred Leggett, both of Basingstoke, England  Assignee: Lansing Bagnall Limited,
Hampshire, England  Filed: May 4, 1973  Appl. No.: 357,383
 Foreign Application Priority Data May 8, 1972 Great Britain 21443/72  U.S. Cl 214/730, 188/162  Int. Cl B661 9/14  Field of Search 214/16.4 A, 730, 731; 188/162  References Cited UNITED STATES PATENTS 2,755,081 7/1956 Johnson et al. 188/77 R 2,910,204 10/1959 Wight 214/730 3,106,305 10/1963 Gehring 214/730 3,420,389 1/1969 Gustetic et al 214/730 Primary ExaminerAlbert J. Makay Assistant ExaminerLawrence J. Oresky Attorney, Agent, or Firm-Cushman, Darby & Cushman 4 Claims, 8 Drawing Figures INDUSTRIAL LIFT TRUCKS The invention relates to industrial lift trucks of the kind comprising a load lifting carriage movable up and down a mast structure mounted on the truck, a turret head mounted on the load lifting carriage for sideways movement relatively thereto, a load supporting structure mounted on the turret head for rotation relatively thereto about an upright axis, and an electric motor mounted on the turret head to effect rotation of the load supporting structure.
In lift trucks of this kind it is desirable that the load supporting structure should be capable of being retained in any position to which it is rotated. The effect can be achieved by arranging for the drive to be transmitted through a non-reversible gear system. For example the gear system may incorporate a worm gear. However, such an arrangement suffers from the disadvantage that if the load lifting structure is forcibly moved by an externally applied force, (for example by the truck hitting an obstruction) severe damage to the gear system can result.
According to the invention the electric motor is drivably connected to the load supporting structure through a reversible transmission, there being provided a releasable frictional brake assembly which normally engages a member rotatable with the transmission so as to restrain it against movement, and wherein means controlling the electric motor are coupled with means controlling the brake assembly in such a manner that operation of the first said means to operate the motor also causes the second said means to effect release of the brake assembly.
There may also be provided a further electric motor driving a further reversible transmission to effect sideways movement of the turret head on the load lifting carriage, there being provided a further releasable frictional brake assembly which normally engages a member rotatable with said further transmission so as to restrain it against movement, and wherein means controlling the further electric motor are coupled with means controlling the brake assembly in such manner that operation of the first said means to operate the motor also causes the second said means to effect release of the brake assembly.
In any of the above arrangements the reversible transmission may comprise a reversible gear train.
Release of the brake assembly may be effected by an electrically operated solenoid, and a switch controlling the solenoid may be coupled with a switch controlling the electric motor so that both switches operate simultaneously.
Preferably spring means are provided to engage the brake assembly, energisation of the solenoid being arranged to disengage the brake assembly against the action of the spring means.
The member which the brake assembly engages may be driven directly by the output shaft of the electric motor. For example it may be mounted on that shaft.
The following is a more detailed description of one embodiment of the invention reference being made to the accompanying drawings in which:
FIG. 1 is a diagrammatic side elevation of an industrial lift truck of the kind to which the invention is applied;
FIG. 2 is a plan view of the truck of FIG. 1 in use in conjunction with storage racking;
FIG. 3 is a vertical section through the load lifting carriage, turret head, and load supporting structure of the truck of FIGS. 1 and 2;
FIG. 4 is a diagrammatic perspective view showing the arrangement of the gear assemblies used in the arrangement of FIG. 3;
FIGS. 5 and 6 are diagrammatic plan views of the turret head, load supporting structure and part of the load lifting carriage showing the two alternative positions of the stop device; and
FIGS. 7 and 8 illustrate respectively an end view and a partly sectioned, partly schematic, view of a brake assembly.
Referring to FIGS. 1 and 2 the industrial lift truck 10 has an upright mast structure 11 on which a load lifting carriage 12 is movable up and down. A turret head 13 is mounted on the load lifting carriage 12 for sideways movement relatively thereto and a load supporting structure in the form of lifting forks 14 is mounted on the turret head 13 for rotation about an upright axis.
In FIG. 2 the truck is shown in a narrow aisle between two sets of racking l5 and 16. The truck 10 passes along the aisle and is required to move a load (indicated at 17) into or out of the racking to either side of the truck. As will be seen from FIG. 2 it is necessary for the turret head 13 to be narrow in width to ensure the maximum space for the load 17 between the turret head and the opposite racking when the lifting forks 14 are rotated to face sideways. Also to permit free passage of the truck along the aisle it is necessary for there to be a clearance gap (indicated at 18) between each side of the load lifting carriage l2 and the racking. However, in order to ensure that the lifting forks l4 and the load they carry can be inserted fully within the racking, it is necessary for the turret head to project laterally from the load lifting carriage 12 as shown in chain lines in FIG. 2. It will be seen that this leaves only a small portion of the turret head 13 still in engagement with the load lifting carriage l2 and FIGS. 3 and 4 show the coupling system between the turret head and the load lifting carriage which ensures that the turret head remains stable even when it is projecting laterally from the turret head. It will be appreciated that it is necessary for the turret head to project from the load lifting carriage at both opposite limits of sideways movement of the turret head since the forks 14 can be rotated through from the position shown in FIG. 2 so as to be movable into and out of the racking 16.
Referring to FIGS. 3 and 4 the load lifting carriage 12 is provided with rollers 19 which engage the upright channels of the mast structure 11 so as to guide the load lifting carriage in its up and down movement on the mast structure. The load lifting carriage 12 has upper and lower plates 20 and 21 respectively which project forwardly of the mast structure and extend across the whole width of the carriage. The upper plate 20 has mounted on its upper surface an upwardly facing channel 22 which receives a roller 23 which is mounted for rotation about a vertical axis on the turret head 13. Similarly the underside of the plate 21 has mounted thereon a downwardly facing channel 24 which receives a roller 25 which is also mounted on the turret head.
A front plate 26 of the load lifting carriage 12 carries a forwardly projecting channel 27 which receives a roller 28 mounted on the turret head 13 to rotate about a fore and aft extending horizontal axis. The rollers 23,
and 28 therefore serve to support the turret head 13 on the load lifting carriage 12 and to permit free sliding movement of the turret head from side to side along the channels 22, 24 and 27 which extend across the full width of the turret head 12.
Mounted on the turret head 13 are two similar gear assemblies which serve to stabilise the turret head during its movement on the load lifting carriage 12. Each assembly comprises a vertical shaft 29 which is rotatable in spaced bearings on the turret head 13 and carries on its upper end a pinion 30 and on its lower end a pinion 31. The pinions 30 and 31 are in mesh with horizontal toothed racks 32 and 33 respectively which are mounted on the front plate 26 of the load lifting carriage and which extend across the whole width of the carriage. The upper pinion 30 is in mesh with another pinion 34 which is carried on a stub shaft 35 rotatable in bearings on the turret heat 13. The pinion 34 is in mesh with a further horizontal toothed rack 36 which is opposite to the toothed rack 32 and also extends across the full width of the load lifting carriage 12.
As will be best seen from FIG. 4 the interengagement between the pinions 30 and 34 and between them and the racks 32 and 36 respectively will prevent pivoting movement of the turret head 13, on which the pinions are mounted, relatively to the load lifting carriage 21 about an upright axis. The provision of the further pinion 31 spaced well below the pinion 30 will prevent rocking of the turret head 13 from side to side or backwards and forwards about horizontal axes.
As mentioned above, and as shown in FIG. 4, each gear assembly comprising the shaft 29, pinions 30, 31 and 34, is duplicated, the two gear assemblies being disposed side by side, so that as the turret head reaches one limit of its sideways movement on the load lifting carriage, one of the gear assemblies can come out of engagement with the racks 32, 33 and 36, so that the turret head can project laterally from the load lifting carriage as shown in chain lines in FIG. 2.'In this case however the other gear assembly remains in contact with the racks and maintains the turret head in a stable condition.
The gear assemblies are also used for transmitting a drive to the turret head to move it sideways on the load lifting carriage. An electric motor 37 is mounted vertically on the turret head 13 and is coupled, through a gyral gear box 38 to a gear wheel 39. The gear wheel 39 is in mesh with an idler gear 40 which is in turn in mesh with both of the lower pinions 31 of the two gear assemblies. Actuation of the motor 37 thus rotates the two pinions 31 in the same direction and thus rotates the shafts 29 to propel the turret head sideways due to engagement of the pinions 30 and 31 with the racks 32 and 33 respectively.
As mentioned earlier it is necessary for the turret head 13 to project from the load lifting carriage 12 when it reaches the limit of its sideways movement in the direction in which the lifting forks 14 are facing. This should occur in both directions of movement. However it is important that the turret head should not project from the load lifting carriage 12 when it reaches the limit of its movement in a direction away from the direction in which the lifting forks 14 are facing. This is the position shown in Full line in FIG. 2. The reason for this is that it may be necessary for the truck to travel along the aisle with the lifting forks still facing sideways as shown in FIG. 2 and if the turret head is permitted to project laterally beyond the load lifting carriage at that limit of its movement it could foul the racking 16. It is therefore necessary to adjust the two limiting positions of the turret head 13 depending on the direction in which the lifting forks 14 are facing. A mechanism for achieving this is shown in FIGS. 5 and 6.
Referring to FIGS. 5 and 6: there is mounted on the turret head 13 a bell crank level 41 mounted for pivoting movement about a vertical axis indicated at 41a. Two elongated stop rods 42 and 43 are mounted on the turret head 13 for reciprocal movement. The stop rods are pivotally connected to the bell crank lever 41 on opposite sides of its axis of pivoting. The lengths of the rods 42 and 43 are such that when the bell crank lever 41 is pivoted anti-clockwise (as shown in FIG. 5) the end of the rod 42 projects into a position where it is engageable with a fixed abutment 44 on the load lifting carriage 12 whereas when the lever 41 is pivoted clockwise (as shown in FIG. 6) the rod 43 is moved to a position where it is engageable with the abutment 44. The relative dispositions of the abutment 44 and the rods 42 and 43 are such that when the rod 43 engages the abutment the edge of the turret head 13 is flush with the edge of the load lifting carriage 12 (as shown in FIG. 6) whereas when the rod 42 is in engagement with the abutment 44 the turret head 13 can move further sideways to a position where it projects laterally from the load lifting carriage 12.
The load supporting structure 14 comprises a vertical back plate 45 on which the lifting forks are supported and the bell crank lever 41 is so disposed that it is engaged by an edge of the plate 45 and pivoted clockwise or anti-clockwise depending on the direction in which the forks are turned. It will thus be seen from FIGS. 5 and 6 that the stop arrangement permits the turret head 13 to project laterally beyond the load lifting carriage 12 when the turret head is moving sideways in the same direction as the forks are facing. As mentioned above this permits the forks to be inserted fully into the racking. It will be appreciated that an abutment similar to the abutment 44 is also disposed at the opposite side of the load lifting carriage. Preferably the lengths of the rods 42 and 43 are such that they cannot, at the same time, both be in a position where they will not engage the abutments 44. Thus should the load lifting structure 14 be in an intermediate position so that the bell crank lever 41 is free to pivot it is then impossible for the bell crank lever to pivot to a position where both stop rods 42 and 43 are free of engagement with the abutment 44 and would thus permit the turret head 13 to move sideways out of engagement with the load lifting carriage 12.
Part of the bell crank lever 41 and one of the stop rods 43 is shown in FIG. 3 and it will be seen that the stop rods are reciprocable in bearing blocks 46 mounted on the turret head.
Referring again to FIG. 3 it will be seen that the load supporting structure 14 is carried on the lower end of a vertical shaft 47 mounted in bearings 48 and 49 on the turret head. The load supporting structure is rotated by an electric motor 50 mounted on the turret head which motor drives the shaft 47 through a gyral gear 51 and gear train 52. The gear train is reversible and thus rotation of the load supporting structure 14 by an external force, for example as a result of striking an obstruction, could permit the structure to rotate. It is desirable to provide some restraint against this and for this purpose there is associated with the electric motor 50 a friction brake assembly which is indicated generally at 53 in FIG. 3 and is shown in more detail in FIGS. 7 and 8.
The brake assembly comprises callipers 54, which are engageable with a brake drum 57 mounted on the end of the motor shaft 58, and the callipers 54 are operated by an electric solenoid 55. The callipers 54 have pivots 59 intermediate their ends and each has a shoe 80 which normally engages the brake drum. Between one pair of adjacent ends of the callipers is disposed a compression spring 60. The other ends of the callipers carry respective adjusting screws 61 and 62 which bear on respective balls 63 and 64 which engage opposite sides of a rod 65 which is formed as a toggle, in a brake operating assembly 66.
The assembly 66 is carried on a plate 67 which is fixed to the casing 68 of the motor in a plane normal to the axis of the shaft 58. The solenoid 55 is secured to this plate to be alongside the motor. The solenoid has an armature 69 pivoted to a lever 70 which bears against the plate 67 on the side thereof opposite the side on which the body of the solenoid is carried. The free end of the lever 70 bears on one end of a slot 71 in the rod 65. The end of the rod 65 further from the balls 63 and 64 carries an extension 72 which extends alongside the body of the solenoid. A compression spring 73 is disposed between a head 74 of the extension 72 and the plate 67. On the other side of the plate 67 the rod 65 is carried in a sleeve 75 which has aligned lateral apertures 76 and 77 in which the balls 63 and 64 are mounted.
The brake is normally engaged in this condition the balls 63 and 64 are maintained on the outward taper 178 of the rod 65 and the callipers force the shoes onto the brake drum against the action of the spring 60. The spring 73 biases the rod 65 into the normal position for effecting engagement of the brake. The brake is released by the solenoid, which, when energised, pulls in the armature 69 and thereby causes the rod 65 to move against the action of the spring 73 and to allow the balls 63 and 64 to move inwardly. This movement allows the spring 60 to move the callipers 54 and their shoes away from the brake drum. The electric switch 79 controlling the supply of power to the motor 50 (shown schematically in FIG. 8) is coupled to the switch 78 controlling the solenoid 55 so that when the switch is operated to energise the motor to rotate the load supporting structure the solenoid 55 is simultaneously energised to release the brake. When the motor 50 is stopped by operation of the switch 79 the brake re-engages. In this condition the brake also serves as an overload device since it will yield and permit rotation of the motor gear assembly and load lifting structure should sufficient external force be applied to the structure.
A similar brake assembly indicated generally at 56 is associated with aforementioned motor 57 which effects side shifting movement of the turret head on the load lifting carriage. This again serves as a safety overload device.
The use of electric motors for shifting the turret head sideways and rotating the load lifting structure means that the operation of the whole assembly can radially be made wholly or partly automatic in operation. For example it may be required to rotate a load while the truck is in an aisle between two sets of racking. It will be appreciated that to achieve this it is necessary to effect simultaneous sideways movement of the turret head 13 and rotation of the load supporting structure 14 and to this end there may readily be provided a control system controlling the motors 37 and 40 so that they operate in coordination to match the speed of sideways movement of the turret head 13 with the speed of rotation of the structure 14.
1. An industrial lift truck comprising:
a mast structure;
a load lifting carriage movable up and down said mast structure;
a turret head mounted on said load lifting carriage for sideways movement relative thereto;
a load supporting structure mounted on said turret head for rotation relative thereto about an upright axis;
an electric motor mounted on said turret head;
a switch controlling the operation of said motor;
a reversible transmission, said motor being drivably connected to said load supporting structure for rotating same through said reversible transmission;
a releasable frictional brake assembly comprising a pair of brake callipers, and spring means for biasing said callipers into braking engagement with a cylindrical member which is rotatable with said transmission so as to restrain it against movement; and
means for releasing said brake assembly when said motor is operated, said means comprising an electrically operated solenoid, and a switch controlling the operation of said solenoid, said switch being coupled for simultaneous operation with said firstmentioned switch controlling said motor, so that operation of said solenoid produces movement of said callipers out of braking engagement with said member against the action of said spring means when said motor is operated, whereby the brake assembly is selectively operable to hold said load supporting structure in any desired position, including three working positions whereat said load supporting structure is directed forwardly or to either side, further said brake callipers serving as an overload device to permit frictional rotation of said cylindrical member if sufficient external force is applied to said cylindrical member.
2. An industrial lift truck according to claim 1 comprising:
a further electric motor mounted on said turret head;
a further switch controlling the operation of said further motor;
a further reversible transmission, said further motor being drivably connected to said lifting carriage to effect sideways movement of said turret head with respect thereto through said further transmission;
a further releasable friction brake assembly comprising a further pair of callipers, and further spring means for biasing said further callipers into braking engagement with a further member which is rotatable with said further transmission so as to restrain it against movement; and
further means for releasing said further brake assembly when said further motor is operated, said further means comprising a further electrically operated solenoid, and a further switch controlling the operation of said further solenoid, said further switch being coupled for simultaneous operation with said first-mentioned further switch controlling said further motor, so that operation of said further solenoid produces movement of said further callipers out of braking engagement with said further member against the action of said further spring means when said further motor is operated. 3. An industrial lift truck according to claim 2, said ated electric motor.