Abstract:
A braking mechanism for a winch. The braking mechanism includes a sleeve disposed on a motor shaft. The sleeve has slots at intervals which match and align with the slots in the shaft. The sleeve and the shaft are synchronized by a knob that engages the slots. A sprocket coupler attached to the sleeve has channels along its outer surface. Projections are urged out from the channels to mesh with notches in a gear or sprocket that is disposed on the sprocket coupler. The gear has teeth along the outer circumference, a contact surface and a plurality of spaced apart notches along the inner circumference. The notches are designed to have a gradual compressing and an engaging side such that a force is transmitted against the engaging side to turn the gear when the cable is being unwound. A solenoid having a latch coupled thereto is used to arrest the rotation of the gear. Brake pads engage the contact surface to provide a frictional check on gear movement. The arrestment of the gear causes the projections to be forced down into the channels by the compressing side of notches thereby allowing the sprocket to turn within the stationary gear.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of Ser. No. 27/198, now U.S. Pat. No. 5,486,082, filed Jul. 4, 1994, and is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a braking apparatus associated with a lifting device and more particularly to a braking mechanism for a lifting apparatus for loading and unloading heavy objects to and from a van. 
     2. Description of Related Art 
     The use of vans for service intensive businesses has proliferated due to their great versatility. Plumbing contractors, appliance repair contractors and other labor intensive type of services have long used vans because of their unique convenience. Unlike the open beds of trucks, vans provide a covered enclosure which can be locked and secured, thereby protecting its contents. Shelving and storage containers may be mounted on the interior walls of the van and access to the interior is usually provided from the rear by adjoining doors which swing outward away from the van and by a sliding panel on the side of such vans. Very often, it is desirable to transport heavy machinery, appliances, or other cargo from a remote location back to the main warehouse or shop for further service. 
     There have been many commercial systems available for open trucks and vans which have hoist systems mounted thereto for facilitating the loading and unloading of the aforementioned heavy cargo. Hoist systems, in general, have been bulky thereby utilizing the great majority of a space within the van. One example of an apparatus for loading and unloading a van which includes a framework within the van is shown in U.S. Pat. No. 4,187,048. The hoist mechanism includes a beam which is slidably mounted within the van. The wench is movably disposed on the beam for allowing an object to be loaded by hoisting an object upwardly when the beam and the hoist extend out the rear of the van. The beam may be slid manually to a position within the van once the object is hoisted. Thereafter it can then be lowered to the floor of the van prior to transporting. In operation, the van is backed up to an object where the rear doors of the van are opened and the I-beam slid outwardly along an axis parallel to the length of the van. Both the winch and the sliding of the I-beam are manually operated. The problem with this type of hoist system is that it does not enable an object to be loaded through the side door of a van, and the operation of the winch and the control of the extension of the boom are manually controlled. 
     Another example of a hoist system is disclosed in U.S. Pat. No. 4,252,491. U.S. Pat. No. 4,252,491 shows a hoist for loading and unloading cargo through a side doorway of a van. The hoist system consists of a platform which may be lowered outside the vehicle wherein the object to be hoisted is moved onto the platform and the platform thereafter raised by an electric winch connected to the platform by cables. However, the problem with this type of system is that the object to be loaded into the van must be first positioned over the platform. However, it is often desirable to position the van relative to the object to be moved, to position the boom over the object, to lower a cable down to the object, lift the object, and then move the boom back into the interior of the van where the object can then be lowered. 
     Another exemplary system is U.S. Pat. No. 4,806,060, which is for hoisting a wheelchair for vehicle having a body, a roof, and a door opening. The hoist system comprises a support bar suspended from the roof of the van with a mount tube reciprocally mounted upon the support bar. A boom is mounted to the support tube. A reversible electric motor is supported upon the mount tube and drives a pinion and mesh with a stationary rack gear for reciprocally feeding the boom from its retracted position to an advance position through the door opening. However, this system has the problem that the support for the extendable boom is secured to the roof of the van by spaced hanger brackets. Therefore, the ability to lift heavy objects such as appliances is severely limited. Further the rack gear and motor would not provide sufficient torque to lift heavy appliances. 
     New methods have been devised for lifting and moving heavy objects into vans and the like which include a telescoping boom to facilitate loading and unloading. Further information on a lifting device having an extendable boom mechanism for loading and unloading heavy cargo from the side door of a van while maximizing lift capability, ease of use, and minimization of the interior area of the van is disclosed in the co-pending application Ser. No. 08/271,198 filed on Jul. 7, 1994, by the present applicants entitled &#34;REMOTELY CONTROLLED EXTENDABLE LIFT APPARATUS FOR A VAN&#34;, which application is hereby incorporated by reference. 
     Nevertheless, since the such lifting devices are often used for lifting objects of great weight, inherent danger exits once the objects have been lifted or during the lifting process. For example the motor may fail during the lifting of the objects. In this situation, the object being lifted will crash to the ground possibly injuring the operator who may be trying to guide the object into the van. 
     Accordingly, it can be seen that there is a need for a break mechanism for a lifting apparatus to prevent injury to the operator. 
     SUMMARY OF THE INVENTION 
     To overcome the limitations of prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a brake for an extendable lift apparatus. 
     The present invention solves the above-described problems by providing a braking mechanism which locks the winch upon command. 
     A system in accordance with the principles of the present invention comprises gear means that is coupled to a motor shaft. The motor shaft is also coupled to a winch for winding and unwinding a cable. A latch is pivotably coupled to the gear means for arresting the movement of the gear means thereby halting the rotation of the winch. A solenoid is coupled to the latch for engaging and disengaging the latch which allows the latch to arrest the movement of the gear means as mentioned. 
     One aspect of the present invention is that the gear means allows the rotation of the motor shaft in a first direction for winding the cable while the gear means is restrained by a friction applying device. 
     Another aspect of the present invention is that the gear means opposes the movement of the motor shaft in a second direction for unwinding the cable when the latch is engaged thereby preventing the unwinding of the cable. 
     These and various other advantages and features of novelty which characterize the invention or point out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompany descriptive matter, in which there is illustrated and described specific examples of an apparatus in accordance with the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings in which like reference numbers represent corresponding parts throughout: 
     FIG. 1 is a side view of the loading and unloading apparatus having a first embodiment of the braking system according to the present invention; 
     FIG. 2 is a second embodiment of the braking mechanism according to the present invention; 
     FIG. 3a is a perspective view of the brake sprocket, sleeve and shaft of the present invention; 
     FIG. 3b is a perspective view of the knob having the protruding slot to engage the recessed slots of the sleeve and shaft of FIG. 3a; 
     FIG. 4a is a side view of the gear for the brake of the invention; 
     FIG. 4b is a cross-sectional view taken along line A--A of FIG. 4a; and 
     FIG. 4c is a perspective view of the brake show mechanism for the brake of the invention; 
     FIG. 5 shows a perspective view of a lifting apparatus that the braking system according to the present invention is adapted for; and 
     FIG. 6 is a front view of a lifting apparatus that the braking system according to the present invention is adapted for. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the description of the preferred embodiment, reference is made to the accompanying drawings which form a part hereof and in which is shown by way of illustration specific embodiment in which the invention may be practiced. It should be understood that other embodiments may be utilized as structural changes may be made without departing from the scope of the present invention. The present invention provides a braking mechanism for an extendable boom mechanism for loading and unloading heavy objects through the side door of a van. 
     FIG. 1 shows a side view of the system. Support members 20 are shown holding boom support tube 30 at the anterior end by bracket 40 and at the posterior end by bracket 50. The extendable boom 60 is shown partially extended. Wheels 70 are shown attached to the extendable boom 60. Even in the fully extended position, a substantial portion of boom 60 remains within boom support tube 30. 
     Motor 80 for controlling the extension of boom 60 is shown attached to bracket 90. Cable 100 is shown extending out of the anterior end of extendable boom 60. Motor 80 drives a sprocket (not shown) which is located on the underside of bracket 90 on shaft 200. The sprocket drives chain 210 which in turn drives sprocket 220. Sprocket 220 is coupled to a smaller sprocket (not shown) to drive chain 230. Control unit 130 is attached by coupler 240 to chain 230. Thus as chain 230 travels around sprocket 250 control unit 130 is moved along support tube 30. Since bracket 122 is coupled to the control unit 130 and extension boom 60, chain 230 drives the extension boom 60, control unit 130, and bracket 122 through the full range of motion. 
     Cable 100 extends out the end of the boom for attaching to the object to be raised. A rod 260 extends out from control unit 130. One end of the rod 260 which is disposed internally to the control unit 130 activates a switch for disengaging the winding of the winch. As the object is being raised, the band 270 around cable 100 contacts rod 260 and trips the switch which is internal to control unit 130 thereby terminating power to motor 120. 
     Control unit 130 has indicator lights 300, 310, 320 to indicate whether the boom is being extended or whether the extension of the boom has been terminated. Light 330 attached to control unit 130 provides illumination to the operator outside the van which will be connecting cable 100 to an object to be lifted into the van. Circuit breaker 340 controls power to the control unit 130. 
     A winch may uses a brake 400 according to the present invention for preventing the accidental dropping of an object while being lifted. Although motor 120 may have a high torque, the motor 120 may not resist being turned to effect unwinding of the cable from the winch when the motor 120 is not activated to lift an object or the winch may unwind if the motor malfunctions in any way which would allow the shaft to turn freely. Thus, according to the preferred embodiment, it is desirable to provide a mechanism for resisting rotation of the winch under predetermined conditions. 
     For this purpose, sprocket or gear 410 rotates clockwise when an object is being lowered and latch mechanism 420 is moved away from gear 410 by solenoid 430. Movement of gear 410 is controlled by frictional device or brake pad 440 (shown in greater detail in FIG. 4c). Spring mechanism 450 is compressed by bolt 460 which is held by bracket 462. This creates a force against brake pads 440 which opposes the motion of gear 410. Bolt 470 holds bracket 472 in place which in turn holds knob 480 in operable arrangement with the drive shaft of motor 120 (not shown). The operation of knob 480 will be explained in greater detail in the discussion associated with FIGS. 3a and 3b. Switch 490 on control unit 130 activates solenoid 430 pulling latch 420 away from gear 410, so that when knob 480 is uncoupled from the drive shaft of motor 120 cable 100 can be unwound from the winch by hand. 
     FIG. 2 illustrates a second embodiment of the braking mechanism according to the present invention. In FIG. 2, the solenoid 430 is attached to a lever 492. One end of the lever is fixed 494, and the solenoid 430 may act on the lever 492 to cause the second end 496 to move. The lever 492 is coupled to the latch 420. Thus, when the solenoid 430 is activated, the solenoid 430 pulls latch 420 away from gear 410, so that the cable may be unwound from the winch. However, the deactivation of the solenoid 430 causes the latch 420 to engage the gear 410 thereby preventing the gear 410 from rotating and thereby preventing the unwinding of the cable from the winch. The lever 492 increases the force on the latch 420 thereby ensuring that the latch 420 does not separate from the gear 410. 
     FIG. 3a illustrates the sprocket coupler 500 which gear 410 is mounted to. Drive shaft 510 of motor 120 is shown disposed within sprocket coupler 500. The anterior end of motor drive shaft 510 has a notch 520 cut out at 90° intervals. Sleeve 530 slips over the drive shaft 510. Sleeve 530 also has notches cut in its anterior end at 90° intervals in order to match up with the notches of drive shaft 510. Sprocket coupler 500 may be tightened with screws through holes 550 to secure sprocket coupler 500 to sleeve 530. FIG. 3b shows knob 480 which may then be attached to the end of the arrangement shown in FIG. 3a. Knob 480 has a protrusion 540 which may engage notch 520 thereby causing the entire arrangement to rotate when drive shaft 510 rotates. The removal of knob 480 allows the independent rotation of the drive shaft 510 and the combination of the sleeve 530 and sprocket coupler 500. 
     Referring again to FIG. 3a, sprocket coupler 500 also has rectangular notches 560 cut out of shaft 570 parallel to the axis of shaft 570. Spring mechanisms are inserted into the slot 560 whereupon an engaging protrusion may be inserted over the spring within the slot 560. The spring causes the protrusion to extend beyond the surface of shaft 570 to engage gear sprocket 410. However, when a force is applied to the protrusion it becomes recessed within the notch 560 below or even with the surface of shaft 570. 
     FIGS. 4a-c illustrate the sprocket or gear mechanism 410 and brake pad 440 of the system. FIG. 4a is a side view of gear or sprocket 410. The gear has an opening 600 which allows it to slip over the surface of the shaft 570. Notches 610 are cut into the inner wall 600 of gear 410. The movable protrusion 580 (shown in FIG. 3a) engages these notches 610. As illustrated, the gear rotates clockwise when the cable is being lowered. Accordingly the protrusion 580 extends into the notches and contacts surface 620 which is perpendicular to the inner wall 600. Thus, as coupler 500 rotates clockwise, the protrusion pushes against this perpendicular wall to cause gear mechanisms to rotate clockwise. During this motion, solenoid 430 is activated and pulls latch 420 away from the teeth of the gear 410 (as shown in FIGS. 1 and 2). When coupler 500 rotates counterclockwise, for winding the winch, the protrusions encounters the sloped wall 630. The sloped wall 630 causes the protrusion to be pushed downward into recess 560 (as shown in FIG. 3a). 
     FIG. 4b is a cut-away view of gear 410 along line A. The teeth 650 of gear 410 extend outward on the inner and outer portions of the gear cylinder. A recess 660 extends circumferentially around the gear between the inner and outer teeth protrusions. 
     A brake pad 440 is illustrated in FIG. 4c (only the left brake pad is illustrated). The brake pad 440 consists of a curved metal plate 700 having a frictional brake material 710 on the inner surface. The curvature of plate 700 corresponds to the circumference of recess 600 in gear 410. The width of the brake 440 is also selected to match the recess 660 of gear 410. The upper edge 720 of plate 700 is inserted into a holding fixture (obscured in FIG. 1 by gear 410 and bracket 472). The upper edge 720 may be secured in slots or alternatively the upper edge 720 may have an opening for receiving a bolt for securing the brake pad 440. Plate 700 then wraps around gear 410 so that brake pad 710 engages recess 660. Now referring to FIG. 2 again, bolt 460 is threaded through bracket 462 to compress spring 450 against the bottom prong 730 of plate 700. The threaded portion of bolt 460 then passes through the opening 740 so that the bolt may be tightened thereby compressing spring 450. Thus, when the drive shaft 510 rotates counterclockwise, to wind the cable on the winch, the brake mechanism 440 holds gear 410 in place. Latch mechanism 420 engages the teeth 650 of gear 410 to prevent the object being lifted from falling in the event that motor 120 fails. 
     FIG. 5 illustrates a boom and lift system which may implement a braking system in accordance with the present invention. Support members 20 support generally C-shaped boom receiving tube 30. The open end of the boom receiving tube 30, which is located adjacent the van door (not shown), is supported on support member 20 by bracket 40. The rear end of boom support tube 30 is supported by bracket 50. Extendable boom 60 slides the boom support tube 30. Wheels 70 are attached to the side of the extendable boom 60 to facilitate movement of the extendable boom 60 within boom support tube 30. The extension of boom 60 is controlled by motor 80 (partially obscured) which is attached to bracket 90 at the rear portion of support tube 30. 
     Cable 100 extends throughout the length of the extendable boom 60 and is draped over the roller 110 at the anterior end of extension boom 60. Motor 120 drives a winch (not shown) which is attached under bracket 122. The motor 120 may be a gear motor, such as Model 1L474, manufactured by Dayton Electric Manufacturing Company of Chicago, Ill. However, any type of motor capable of providing sufficient torque could be used. 
     The extendable boom 60 is also coupled to bracket 122. The electronics for controlling the extension of boom 60 and lowering of cable 100 is contained in control unit 130. The power to the system is provided by junction box 140. Cable 142, which may be removable, is connected to control unit 130 and junction box 140 to provide power and communication lines from junction box 140 to the control unit 130. All functions of the system are controlled by remote control 150. Switches 160, 170 control the range of motion for the extendable boom 60. Trigger 180 which is mounted to bracket 122 trips switch 160 when the boom 60 reaches the point of maximum extension and opens a circuit which turns off motor 80. When the boom 60 is being retracted within boom support tube 30, switch 170 is tripped by trigger 180 to again turn off motor 80. 
     FIG. 6 illustrates a frontal view of the system as used in a van having a sliding side door. Support members 20 are shown holding support tube 30 using bracket 40. Extension boom 60 shown within support tube 30 and wheels 70 are shown riding along the cusp of support boom 30. The height of the support members 20 is chosen to allow the object being lifted to be pulled into the interior of the van by the retraction of the boom 60 and thereafter lowered to the floor of the van. 
     Boom drive motor 80 is shown attached to side of bracket 90. Control unit 130 is attached to chain 230 by coupler 240. The end of rod 260 for automatically shutting off winch motor 120 is positioned below boom 60 (cable 100 is not shown). Indicator lights 300, 310, 320 are shown on the front face of control unit 130. Circuit breaker 340 is located above the indicator light. Light 330 is generally disposed in the center of the front face of control unit 130. A portion of the braking mechanism 400 is shown extending behind control unit 130. Bolt 460 for compressing the spring and forcing the brake mechanism against the gear is disposed at the lower left portion of control unit 130. Bolt 470 for securing bracket 472 to hold knob 480 is disposed above control unit 130. 
     The foregoing description in the preferred embodiment of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not with this detailed description, but rather by the claims appended hereto.