Balancing system with a force multiplying device

Description

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates generally to balancing systems of the type used in manufacturing facilities.

II. Description of the Prior Art

There are many manufacturing operations which require a heavy load to be lowered from an elevated position and to a lower position in preparation for a manufacturing and/or assembly operation. For example, in the manufacture of automobiles with hoods or rear hatchback doors, it is conventional to utilize a carrier to move the jig fixture centering the closure from an elevated position and to a predetermined lower position where the closure is secured to the vehicle body.

In order to provide a controlled movement of the jig fixture or other load from an elevated position and to a lower position, it has been previously known to utilize one or more pneumatic balancers. Such pneumatic balancers typically have an elongated cable with a free end secured to the load. As the load is lowered from an elevated and to a predetermined lower position, the pneumatic balancers exert an upward force on the load to thereby control and cushion the downward descent of the load as it is moved into its assembly position.

One disadvantage of these previously known balancing systems, however, is that certain vehicle components, such as vehicle hoods or hatchbacks, require a very heavy jig fixture, e.g. 1700 pounds, such that even a pair of pneumatic balancers is inadequate to provide to the jig fixture the vertical compliance required in its lower position to self-locate it onto the vehicle with a low level of constraint transmit to this vehicle. While it is possible to multiply by 2, 3 or 4 the number of these pneumatic balancers in order to increase the upward force exerted on the load during its descent, such pneumatic balancers are relatively expensive and are also subject to periodic maintenance and repair.

The previously known pneumatic balancers conventionally apply a substantially constant force, e.g. 100-300 pounds each, upwardly on the load, e.g. 1800 pounds during the entire descent of the load from its elevated and to its lower position. With two pneumatic balancers, only 30% of the weight can be compensated and the 70% remaining will be supported by the vehicle shell, causing not only some damage on the contact area, but generating also an inaccurate setting of the closure onto its opening.

SUMMARY OF THE PRESENT INVENTION

The present invention provides a force multiplying device for use in conjunction with a balancing system which overcomes all of the above-mentioned disadvantages of the previously known devices.

In brief, the device of the present invention comprises a base which is secured to the load so that the base moves in unison with the load. A lever is pivotally secured about an intermediate point on the lever to the base about a generally horizontal axis.

A fixed length flexible member, such as a chain, has one end secured to a first end of the lever and a second end fixedly secured to a support position above the load. The fixed length flexible member is dimensioned so that it is in a fully extended position when the load is in the predetermined lower position for the assembly and/or manufacturing operation.

An elongated rocker arm has a first end in abutment with the base while the cable from a balancer, such as a pneumatic balancer, is secured to a second end of the rocker arm. The second end of the lever, in turn, is pivotally secured to an intermediate point of the rocker arm. Consequently, as the load nears the predetermined lower position, the first end of the lever pivots upwardly due to the force exerted by the fixed length flexible member. In doing so, the lever simultaneously pivots the second end of the rocker arm, i.e. the end of the rocker arm connected to the balancer cable, downwardly to thereby exert an increased downward stroke on the cable and the corresponding increased upward force on the load. This increased upward force remains directly proportional to initial counterbalancing effort and can be accurately adjusted to exactly match the weight of the jig fixture as the load nears its final lower position.

BRIEF DESCRIPTION OF THE DRAWING

A better understanding of the present invention will be had upon reference to the following detailed description, when read in conjunction with the accompanying drawing, wherein like reference characters refer to like parts throughout the several views, and in which:

FIG. 1

is a side view illustrating a preferred embodiment of the present invention for use with a carrier of the type used in manufacturing operations;

FIG. 2

is an elevational view illustrating the preferred embodiment of the present invention;

FIG. 3

is a side view illustrating the preferred embodiment of the present invention;

FIG. 4

is a top view illustrating the preferred embodiment of the present invention;

FIG. 5

is an end view illustrating the preferred embodiment of the present invention; and

FIG. 6

is a view similar to

FIG. 3

, but illustrating the operation of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PRESENT INVENTION

With reference first to

FIG. 1

, a typical carrier

10

for moving a load

12

between an upper position, illustrated in phantom line, and a predetermined lower position, illustrated in solid line, is shown. As illustrated in

FIG. 1

, the carrier

10

moves an automotive closure panel

14

, such as a vehicle hatchback, between the upper and predetermined lower position. Furthermore, although the carrier

10

is illustrated as utilizing a plurality of scissor arms

16

actuated by an electric hoist

20

for movably securing the load

12

to an upper support

18

, any conventional carrier system may be utilized without deviation from the spirit or scope of the invention. Furthermore, the load

12

includes not only the closure panel

14

, but also a jig fixture

15

on the carrier

10

which releasably holds the closure panel

14

.

Still referring to

FIG. 1

, a pneumatic balancer

21

includes an elongated and extensible cable

22

having a free end

24

secured to the load

12

in a fashion to be subsequently described in greater detail. Such pneumatic balancers

21

are conventional in construction and typically exert a constant upward force on the load

12

, e.g. 300 pounds.

With reference now to

FIGS. 2-5

, a force multiplying device

26

according to the present invention is there shown and includes a base

28

secured to the top of the support

15

of the load

12

in any conventional fashion, such as by bolts

30

. A pair of spaced axle supports

32

are secured to and extend upwardly from the plate

28

.

An elongated lever

34

is pivotally secured by an axle

36

to the axle supports

32

so that the lever

34

is pivotal between a first position, illustrated in

FIG. 3

, and a second position, illustrated in

FIG. 6. A

fixed length flexible member

40

, such as a chain or cable, is secured to a first end

42

of the lever

34

while the opposite end

44

(

FIG. 1

) of the fixed length flexible member is secured to the support

18

. Furthermore, the length of the fixed length flexible member

40

is such that, when the load

14

is in its predetermined lower position, the fixed length flexible member

40

is fully extended and pivots the lever

34

close to the position shown in FIG.

6

.

An elongated rocker arm

50

has a roller

54

rotatably mounted to a first end

52

of the rocker arm

50

and this roller

54

abuts against the plate

28

via a contact plate

27

. The free end

24

of the cable

22

from the pneumatic balancer

20

is secured to a second end

56

of the rocker arm

50

in any conventional fashion, such as by a bracket

58

.

As best shown in

FIGS. 3 and 4

, a second end

60

of the lever

34

is pivotally connected by a pivot pin

62

to the rocker arm

50

at a point intermediate the ends

52

and

56

of the rocker arm

50

. Furthermore, in the preferred embodiment of the invention, the distance between the pivot pin

62

and the end

56

of the rocker arm

50

is greater than the distance between the pivot pin

62

and the first end

52

of the rocker arm

50

. By construction, and as shown in

FIGS. 4 and 6

, the length of each rocker

56

and lever

42

arms is such that the distance between the flexible member

40

and the extended cable

22

is minimal. Furthermore, two systems like that can be symmetrically combined in such a way that the center of gravity of the load

12

to be balanced remains perfectly in the same plane, as shown in

FIG. 6

, that the pair of flexible members

40

, the pair of extended cables

22

, and the pulley of the hoist

20

thereby avoiding any swinging of the load during its entire travel down to its lower position. Preferably, the distance between the pivot pin

62

and rocker arm end

56

is two times greater the distance between the pivot pin

62

and rocker arm end

52

. In such a configuration, the counterbalancing force is multiplied by 4. Different ratios may be employed without deviation from the spirit or scope of the invention.

In operation, as the load

14

is initially lowered from its upper and towards its lower predetermined position, the upward force exerted by the balancer cable

22

on the rocker arm

50

maintains the force multiplying device

26

in the position illustrated in

FIG. 3

in which the first end

42

of the lever

34

abuts against the plate

28

through a rubber damper

43

.

As the load

12

nears its predetermined lower position, however, the fixed length flexible member

40

becomes fully extended thus pivoting the first end

42

of the lever upwardly ultimately close to the position shown in FIG.

6

. Simultaneously, the pivotal action of the lever

34

pivots the second end

56

of the rocker arm

50

downwardly close to the position shown in FIG.

6

. This action effectively increases the downward stroke on the balancer cable

22

and simultaneously increases the upward force exerted by the balancer

20

through the flexible member

40

on the load

14

. This increased upward force on the load

12

to achieve even if needed a 100% counterbalancing just prior to the time the load

12

reaches its lower predetermined position.

From the foregoing, it can be seen that the present invention provides a force multiplying device which effectively permits to achieve even a full balancing of the load around a lower predetermined position. This characteristic allows a perfect vertical compliance of a jig fixture to accurately fit and self-locate onto the vehicle body with a minimum of constraint transmitted to it. Having described my invention, however, many modifications thereto will become apparent to those skilled in the art to which it pertains without deviation from the spirit of the invention as defined by the scope of the appended claims.

Claims

1. A force multiplying device for use in conjunction with a balancing system for moving a load from an elevated position to a predetermined lower position, the balancing system having an extendable cable with a free end adapted to be secured to and exert an upward force on the load, said device comprising:a base secured to the load, a lever pivotally secured at an intermediate point of said lever to said base about a horizontal axis, a fixed length flexible member having one end secured to a first end of said lever and a second end fixedly secured to a support positioned above the load, said fixed length flexible member being in a fully extended position when the load is in said predetermined lower position, an elongated rocker arm having a first end in abutment with said base, the cable being secured to a second end of the rocker arm, and means for pivotally securing a second end of said lever to an intermediate point of said rocker arm so that, as the load nears said predetermined lower position, said first end of said lever pivots upwardly and simultaneously pivots said second end of said rocker arm downwardly to thereby exert an increased downward stroke on the cable.
2. The invention as defined in claim 1 wherein said base is secured to the load in such a way that the center of gravity of the load is substantially vertically aligned with the flexible member.
3. The invention as defined in claim 1 wherein said fixed length flexible member comprises a chain.
4. The invention as defined in claim 1 wherein the distance between said second end of said rocker arm and said pivotal securing means is substantially two times the distance between said first end of said rocker arm and said pivotal securing means.
5. The invention as defined in claim 1 and comprising a roller secured to said first end of said rocker arm about a generally horizontal axis, said roller in abutment with said base.
6. The invention as defined in claim 1 wherein said fixed length flexible member comprises a cable.

US Referenced Citations (2)

Number	Name	Date	Kind
1847819	Davies	Mar 1932
2514307	Boyd	Jul 1950

Foreign Referenced Citations (3)

Number	Date	Country
1439125	Apr 1966	FR
1114348	May 1968	GB
1017647	May 1983	SU

Balancing system with a force multiplying device

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

US Referenced Citations (2)

Foreign Referenced Citations (3)