US3412423A

US3412423A - Counterbalancing apparatus

Info

Publication number: US3412423A
Application number: US613534A
Authority: US
Inventors: John W Binns
Original assignee: Overhead Door Corp
Current assignee: Overhead Door Corp
Priority date: 1967-02-02
Filing date: 1967-02-02
Publication date: 1968-11-26
Anticipated expiration: 1985-11-26

Description

Nov. 26, 1968 Jlw. BINNS COUNTERBALANCING APPARATUS 2 Sheets-Sheet 1 Filed Feb. 2, 1967 INVENTOR. JO/M/ l1! E/IV/VS BY MM 2 Sheets-Sheet 2 Filed Feb. 2, 1967 mvsm'on. dol/n/ 11/. 5/4/46 A "pe d 6X8 United States Patent 3,412,423 COUNTERBALANCING APPARATUS John W. Binns, Claridon Township, Marion County, Ohio, assignor to Overhead Door Corporation, Dallas, Tex., a corporation of Indiana Filed Feb. 2, 1967, Ser. No. 613,534 8 Claims. (Cl. 16-198) ABSTRACT OF THE DISCLOSURE A counerbalancing mechanism for an upwardly acting door is secured to the frame around a door opening and comprises a pair of coaxial shafts rotatably supported at the ends thereof upon the door frame of a truck, for example, near the upper edge of the opening. Each of the shafts supports a cable drum which is securely fastened thereto, and the cables are connected between said drums and the lower end of said door. The counterbalancing mechanism is provided with coupling means interconnecting said shafts and permitting a limited amount of relative rotation of said shafts. Tension means connected between said shafts and said door urges said shafts to wind the cables on the drums.

Background of the invention This invention relates in general to a counterbalancing mechanism for an upwardly operated door mounted in the rear end of a truck van and, more particularly, to a type thereof having a pair of spring-actuated coaxial cable drums having cables connected to said door and coupled together so that the door can be operated with some counterbalancing effect when one of the springs or one of the cables fails.

Known counterbalancing mechanism for upwardly operated doors comprises a pair of shafts on which are secured a pair of counterbalancing cable drums. The shafts are preloaded by a pair of torsion springs to counterbalance the weight of the door, such as a truck door, to which the cables are attached. Thus, when the door is closed, it may be raised, hence opened, relatively easily due to the fact that much of its weight is counteracted by the torques of the torsion springs. Likewise, the door can be closed at an easily regulatable rate, thereby preventing the door from slamming shut, by applying a relatively small amount of manual force.

This system, however, has several disadvantages which impair the desirability of its use. For example, if one of the cables breaks, it immediately releases the tension or torque on its associated spring which then unwinds rapidly, and usually with sufficient force to damage the spring or its mounting. Thereafter, the door is balanced with only one spring and the remaining cable, which provides only half of the original support. However, by coupling the drums (or shafts) together, both springs operate through the single cable to support the door in a substantially conventional manner until the defective cable can be repaired or replaced.

With an existing counterbalance system having a broken cable, as described in the preceding paragraph, failure of the spring connected to the operative cable will completely immobilize the system. However, if the shafts are coupled, the s ring associated with the damaged cable will still act through the good cable to provide about 50 percent of the normal support. In fact, this further safety factor is provided regardless of which spring or which cable should fail.

It follows from the foregoing that failure of one spring will reduce the support of the counterbalance mechanism by about 50 percent, but both cables will be kept taut, hence away from interference with the normal operation ice of the door. With existing systems, the cable connected to the damaged spring will hang loose in or near the door opening where it can interfere with loading operations and with the movement of the door.

It is difficult to ensure constant and uniform performance between the two, coupled units of a counterbalance system, which are rigidly interlocked for simultaneous rotation, due to variations in spring torque, cable stretch, frame alignment, friction and the like. Thus, it is essential in this system to provide a shaft coupling mechanism which perimts limited relative rotational movement between the shafts (or drums). Moreover, a pair of coupled, but relatively rotatable, shafts as proposed provides cable movement control during the winding and unwinding movement which has not been possible with uncoupled shafts or even with a single shaft for both drums.

Accordingly, the objects of this invention are:

(1) To provide a counterbalancing mechanism including a pair of cable-supporting drums which are connected to independent spring means and which are coupled for limited rotation whereby one cable and/or one spring can fail without completely immobilizing the system.

(2) To provide a door counterbalancing mechanism, as aforesaid, which does not depend on an accurate door installation for proper operation.

(3) To provide a door counterbalancing mechanism, as aforesaid, wherein the door may be tied down upon an irregular load without permitting the cable on the cable drums to jump off the cable drums due to the shocks on the door caused by the vehicle moving over rough roads.

(4) To provide a counterbalancing mechanism, as aforesaid, which is easy to assemble and install.

Other objects and purposes of this invention will become apparent to persons acquainted with apparatus of this general type upon reading the following specification and inspecting the accompanying drawings, in which:

FIGURE 1 is a perspective view of the rear end of a truck enclosure and door structure embodying the invention.

FIGURE 2 is a broken, side elevational view of the counterbalancing mechanism embodying the invention.

FIGURE 3 is a sectional view taken on the line III-III in FIGURE 2.

FIGURE 4 is a sectional view taken on the line IVIV in FIGURE 3.

FIGURE 5 is a sectional view similar to FIGURE 3 with the pin rotated to one of its extreme limits.

Certain terminology will be used in the following description for convenience in reference only and will not be limiting. For example, the words upwardly, downwardly, rightwarclly and leftwardly will designate directions in the drawings to which reference is made. The words inwardly and outwardly will refer to directions toward and away from, respectively, the geometric center of the device and designated parts thereof. Said terminology will include the words above specifically mentioned, derivatives thereof and words of similar import.

Description A counterbalancing mechanism 10 for an upwardly acting door 16 is illustrated in FIGURE 1 for use with a truck 11 having a van or closed compartment 12 having a door opening 13 at its rear end. The door 16 is supported for movement along rails, one of which is shown at 14, mounted to the frame along said door opening. More particularly, and referring to FIGURE 2, the counterbalancing mechanism 10 comprises two shafts 17 and 18 independently and rotatably sup ported on the compartment frame 19 around and above the door opening 13 by

brackets

21, 22, 23, 24 and 25.

The bracket 21 is generally L-shaped and has its leg 27 (FIGURE 2) secured to the frame 19 by a plurality of bolts 28. The other leg 29 of the bracket 21 has an opening therethrough for the reception of the outer end of shaft 17. A bearing 31 is secured to the leg 29 by bolts 32, and the shaft 17 is rotatable therewithin.

The bracket 22 is generally L-shaped having a leg 42 secured to said frame 19 by the bolts 34 and a leg 43 extending perpendicularly away therefrom. The inner end i of the shaft 17 is rotatably supported by the bearing 33 which is secured to the leg 43 by bolts 41. Mounted coaxially on the shaft 17 and extending leftwardly from the bracket 22 is a cable tensioning torsion spring 38 having its left end secured to the shaft 17 by a lock collar having a set screw 39 and having its right end secured to the leg 43 of the bracket 22 by the bearing 33.

Adjacent the bracket 21, a cable drum 34 is securely fastened to the shaft 17 by a set screw 36. The cable drum 34 is provided with a cable 37 wrapped therearound and preferably fastened at its free end to the lower edge of the door 16.

The bracket 24 is generally L-shaped and has a leg 46 secured to the frame 19 by a plurality of bolts 47, of which one is shown in FIGURE 2. The other leg 48 of the bracket 24 extends perpendicularly to the axis of the shaft 18. The leg 48 has an opening therethrough for the reception of the outer end of the shaft 1 8, and a bearing 49 is secured to the leg 48 by bolts 51, so that the shaft 18 is rotatable therewithin.

The shaft 18 supports a cable drum 53 which is securely fastened thereto by a set screw 54 and rotatable therewith. The cable drum 53 is provided with a cable 55 wrapped therearound and fastened at its free end to the lower edge of the door 16.

An intermediate bracket 25 is secured to the frame 19 between the brackets 23 and 24. Bracket 25 is preferably L-shaped having a leg 57 secured to the frame 19 by a plurality of bolts 56, and a leg 59 extending away there- 'from perpendicular to the axis of the shaft 18. A cable tensioning torsion spring 45 extends inwardly away from the leg 59 of the bracket 25 and is preferably identical to the torsion spring 38 on the shaft 17. The torsion spring 45 is secured to the leg 59 by the bearing 60 which sup ports the shaft 18 and is secured to the leg 59 by the bolts 61. The inner end of the torsion spring 45 is secured to the shaft 18 by a lock collar 50 having a set screw 62.

The leg 44 of the bracket 23 has attached thereto a bearing 63 through which the inner end of the shaft 18 is received and is rotatably supported. The bearing is secured to the leg 44 by bolts 64.

In this embodiment, the shafts 17 and 18 are shown as coaxial, abutting and connected together by a coupling 66 (FIGURE 4).

The coupling 66 comprises a cylindrical sleeve 68 having a coaxial opening 67 extending therethrough. The diameter of the opening 67 at the left end of the sleeve 68 is of the same diameter as the shaft 17. However, said opening has a portion 70 of enlarged diameter at the right end of the sleeve 68 which is of a diameter greater than the diameter of the shaft 18.

The sleeve 68 (FIGURE 4) is rigidly secured to the shaft 17 by means of a pin 71 extending through diametrical openings provided in the sleeve 68 and the shaft 17. The inner end of the shaft 18 extends into the opening 70 in the right end of the sleeve 68 to a point adjacent, but axially spaced from, the inner end of the shaft 17. The rightward end of the sleeve 68 (FIGURES 3 and 4) is provided with a pair of diametrically opposed, circumferentially aligned and extending slots 73 and 74 separated by abutments 75 and 76. A pin 72 extends diametrically through the shaft 18 so that its opposite ends extend into the slots 73 and 74, respectively, of the sleeve 68. The pin 72 is arranged so that it engages the corresponding, circumferential sides of the abutments simultaneously.

The shaft 18 and sleeve 68 have diametrically aligned openings 81 and 82 disposed between the shaft 17 and 4 pin 72 through which the shank of an eyebolt 83 is slide ably received for holding said shafts 17 and 18, hence the drums 34 and 53 against relative rotation. The openings 81 and 82 are aligned when the pin 72 is centered between the abutments 75 and 76.

Operation Although the operation of the device embodying the invention has been indicated above, said operation will be detailed hereinbelow to assure a more complete understanding of the invention.

The counterbalancing mechanism 10 is installed, upon the frame 19 of the van 12 with the eyebolt 83 in the openings 81 and 82. The cables 37 and 55 are connected to a door 16 and the torsion springs 38 and 45 are properly adjusted so that the weight of the door is properly balanced. The eyebolt 83 is then removed so that the shafts 17 and 18 can rotate relatively within the limits imposed by the pin 72 and abutments 75 and 76. That is, the amount of relative rotation of the shafts 17 and 18 in either direction is stopped when the pin 72 comes in contact with the abutments 75 and 76.

The slots 73, 74 and abutments 75, 76 are circumferentially arranged so that the opposite ends of the pin 72 will contact the abutments 75 and 76 simultaneously. Thus, the shearing force on the pin will be distributed equally on both ends of pin 72 and both abutments. Variations in the performance of the two parts of the mechanism 10, such as the tension applied to cables 37 and 55, will be compensated for by the coupling 66. That is, the sleeve 68 is able to rotate with respect to the shaft 18 to compensate for differences in tension upon the cable 37 and cable 55. Moreover, if one cable or one spring should break or fail, the other cable or spring will automatically take over, due to the coupling 66. In fact, the counterbalance mechanism will continue to perform at about 50 percent effectiveness even with either cable and either spring disabled.

Although a particular prefered embodiment of the invention has been disclosed above for illustrative purposes, it will be understood that variations or modifications thereof, which lie within the scope of the appended claims, are fully contemplated.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A mechanism secured to the frame around a door opening for counterbalancing the weight of an upwardly acting door mounted adjacent said opening, comprising:

a pair of relatively rotatable shafts rotatably supported upon said door frame near the upper end of said opening;

a cable drum securely fastened to each shaft and having a cable wound thereon and fastened to said door; means interconnecting said shafts for limiting the relative rotation of said shafts; and

torque means connected between said shafts and said frame for opposing rotation thereof in a direction for unwinding said cables from said drums.

2. The device defined in claim 1, wherein said shafts are coaxial and abutting.

3. The device defined in claim 2, wherein said means interconnecting said shafts comprises first stop means secured to one of said shafts and second stop means secured to the other of said shafts, said first and second stop means being adapted to engage each other to limit the relative rotation of said shafts.

4. The device defined in claim 3, wherein said first stop means comprises a sleeve secured to one of said shafts, said sleeve having a pair of circumferentially spaced and circumferentially extending slots; and

wherein said second stop means comprises a pair of projections extending radially outwardly from the other of said shafts and extending into said slots, said projections being adapted to simultaneously engage the corresponding ends of said slots to limit the amount of relative rotation of said shafts.

5. The device defined in claim 4, wherein said other shaft extends into said sleeve and they have diametrically aligned openings which are aligned when said projections are disposed midway between the ends of said slots; and

bolt means adapted for removable insertion into said diametrically aligned openings for holding said shafts against relative rotation.

6. The device defined in claim 4, wherein said pair of radially extending projections comprise the opposite ends of a pin extending diametrically through said other of said shafts, and said slots are diametrically disposed and of equal length.

7. The device defined in claim 4, wherein one end of said other shaft is in a telescoped relation with said sleeve.

8. The device defined in claim 7, wherein said other shaft is received into an opening in one end of said sleeve and said projections extend outwardly through said slots.

References Cited UNITED STATES PATENTS BOBBY R. GAY, Primary Examiner.

I. L. KOHNEN, Assistant Examiner.