CA1214363A

CA1214363A - Method and apparatus for sealing welded seams of automobiles

Info

Publication number: CA1214363A
Application number: CA000452729A
Authority: CA
Inventors: Larry Soutar
Original assignee: Nordson Corp
Current assignee: Nordson Corp
Priority date: 1983-05-11
Filing date: 1984-04-25
Publication date: 1986-11-25
Also published as: JPS6041568A; EP0125771A2; ES532415A0; ES8504521A1; EP0125771A3

Abstract

METHOD AND APPARATUS FOR SEALING WELDED
SEAMS OF AUTOMOBILES

Abstract of the Disclosure There is disclosed a system for applying sealant material to the welded seams of an automobile body. The system includes a reciprocating piston pump for supplying the material under pressure from a reservoir to an overhead distribution manifold. From a manifold the material is supplied to a plurality of extrusion guns through drop lines, each of which includes a volumetric metering gear pump for maintaining a constant flow rate to said guns irrespective of pressure changes which may occur in the distribution manifold.

Description

- This invention relates to the sealing of weld~d seams of automobile bodies wherein finishing requirements dictate that the welded seam be covered with a sealant either before or after the body is primed and painted.
1 At ~he present time, some form of welded seam sealer 1~ is used to cover and protect very nearly every welded seam or joint of an automobile body. This seam sealer is applied for purposes of excluding water or air, preventing leaking, and 1I combating corrosion. Presently, most commercial sealers comprise 1 a vinyl plastisol or epoxy that is pumped via a reciprocating piston pump to a manually operated extrusion gun Depending upon the volume of material con~umed, the sealant is sup~lie~
either from a 55 gallon drum operable to feed a manifold system to which multiple guns are attached, or the sealant material is supplied from a five gallon can operable to supply only a sin~le ' extrusion gun.
Prior art commercial welded seam sealant systems have generally been unsatisfactory because of large variations in the ¦l amount of deposit supplied to a seam. The problem is parLi~ularl~
! acute a~ the beginning or end of each application when the flow ~j control valves of the hand ~uns used for applying the sealant arel I opened or closed. Each opening and closing of the valves of the ¦
extrusion guns results in pump surges and pressure fluctuations which in turn cause wide flow variations of sealant pumpe~ from il the guns. Becausè of these wide flow variations, operators I tend to apply excessive amounts of material in oràer to insure adequate coverage of all areas of the seams. This excessive application of material results in a messy or sloppy appearance which detracts from the quality and appearance of the resulting -1- 1214~ifi3 welded seams. In addition~ the excess material commonly washes off in the phosphate painc priming wash and ~ecomes redeposited jl on exterior surfaces of the automobile thereby causing paint blemishes in the resulting product. In addition, the excess sealant material frequently contaminates the paint primer system.
For some time now automotive company engineers have been engaged in an extensive effort to find some means for pro-1¦ viding a constant bead of sealant material with a predictable ,1 uniform size which would apply a complete covering of the welded II seam without any excess of visible sealant material to mar the ~appearance of the finished product and contaminate subsequent ¦Ifinishing operations. To that end, those engineers have jattempted in one instance to solve the problem by inserting fluid pressure regulators into each extrusion gun supply system immediately upstream of each of the extrusion guns. Those pressure regulators though did not solve this problem, primarily ~¦because the viscosity of the material was too great for regu- !
Illators to operate effectively.
~1 Still another attempt which has been made, but which ¦has so far proven to be a failure, has been the use of a sealant ~tape cut to length and manually placed into the various welded eams. This tape sealant approach has proven to be too expensive to be practical because of the expensive form in which the sealan~
¦is delivered, i.e., the tape. Additionally, the tape requires ¦significantly greater labor time to apply than is required to apply liquid through an extrusion gun.
¦¦ It has therefore been one objective oE this invention 11~ provide an improved method and apparatus for applying sealant Ito a welded seam of an automobile so as to effectively cover I that seam without the use of excessive sealant material.
. ~ 3~3 I Still another objective o.f this lnvention has been 1I to provide an improved m~ethod and apparatus for applying sealant to a welded seam of an automobile in such a manner that sealer redeposition in the phosphate wash or in the primer paint Syst~
i8 avoided.
Still another objective of this invention has been to provide a ~ery accurate method and apparatus ~or applying sealant ¦
to the welded seams oi an automobile such that only so much seal-I ant is ~pplied as is required t~ cover the welded seam without jl thP application of any excess material.
These objectives are accomplished and this invention ~i is predicated upon the concept of utilizing a metering gear pump in the sealant supply system to each of the extrusion guns ¦l of an automobile welded seam sealant applicator system so as to accurately meter and control the volumetric deposition of sealant material from the gun. Ihe sealant material may be either a hot melt sealant which is solid at room temperature and I applied in a molten sta~e or a cold unheated sealant. In either ¦¦event, the metering gear pump in the supply systems to each of ¦I the extrusion guns eliminates pressure surges and uneven flow ¦¦variations from the bead of material applied by the extrusion guns. Thereby, only so much sealant is applied to a welded seam as is requireA to adequately cover that seam without the application of excess material.
~1 In one preferred embodiment, the system for applying ¦ llthe sealant to the welded seam of an automobile comprises a 55 gallon drum from which sealant material is pumped by a convent-ional reciprocating piston pump. This reciprocating piston . pump supplies the sealant material to an overhead manifold line ii 3L~4.~3 1. _3_ 1 .. I, from which there extends a plurality of drop line~. Eac~ ~rop line terminates in a manually or a robotic operated extrusion gun. According to the practice of this invention an electric motor driven metering gear pump is connected to each of the drvp 1 lines so that sealant is ~upplied ~o each of the extrusion gun~ ¦
j through a metering pump at a fixed and constant pressure without any pump surges or pressure fluctuations. Thereby, an even ~n~ i i precis~ am~unt of sealant is extruded from each gun at a pre-¦l determined and accurately controlled rate.
~'i These and other objects and advantages of this inven-l tion will be more readily apparent from the following description I of the drawing in which:
The figure is a partially diagrammatic illustration of a sealant application system for applying sealant to welded seams of an automobile incorporating the invention of this ¦ application.
With reference to the drawing there is diagrammatically illustrated a system 10 for applying sealant to the welde~ seams ¦l of an automobile body and chassis 12. In general, all of the ¦ welded seams of an automobile body ~us~ be cov~red ~ith a 3e~1ant:
material to exclude w~ter or air and to combat corrosion. This sealant is either applied before or after the welding of the ¦¦ seams and either before or af~er any primer paint or any pre-jl paratory coating treatment of the body.
¦¦ The sys~em 10 comprises a reciprocating piston pump 14 for pumping sealant material 16 from a drum or container 18 ¦¦ to a distribution manifold 20. This manifold generally extends ¦I parallel to an automobile production line 13 and is operative ,I to supply pressurized sealant from the pump 14 to a plurality of Il drop lines 22 through which the sealant is distributed to !i multiple extrusion guns 24 located along the production line.
li The guns 24 are illustrated herein as being of the ~' _4_ ~ 2~ ~ 3 ¦I manual type controlled fr~m a manually operated trigger 26. One i suitable gun is disclosed in U.S. Patent No. 4,~45,759. The ¦I guns could as well though be automatically operable guns controlled and moved relative to the body by robots.
There is associated with each drop line 22 a volumetri~l ¦I me~erin8 pump 30. E~ch p~mp 30 comprises a two-speed DC motor driven gear pump. Since the gear pumps 30 and the motor M for driving the gear pumps are conventional commercially available ¦¦ items, they have not been illustrated or disclosed in detail ,¦ herein.
The reciprocating piston pump 14 is a conventional pneumatic motor driven reciprocating pis~on pump. It may be either a single acting or a double acting pump, i.e., a pump ¦ which pumps on one of two strokes or pumps on both strokes.
If the sealant material 16 is a hot melt material then a heated platen 40 will be suspended beneath the pump to heat and melt the hot melt sealant material which is 601id at room temperature.
One appropriate heated pl~ten is disclosed in U.S. Patent No.
1 4,227,069. Alternatively, if the sealant is a cold sealant, ~ i.e., liquid at room temperature, then the heated platen will ¦I be omitted and the pump 14 inlet simply inserted in~o the cold ¦ sealant 16 contained in the drum.
Irrespective of whether the pump 14 is single acting or double acting, there are pressure surges or variances associated with the reciprocation of the piston of the pump.
At the end of each cycle of the piston there are conventional ¦ presssure drops. Heretofore, it has been the practice to supply the sealant material directly from the pump 14 to the extrusion gun 24 without the presence of any volumetric metereing pumps 30 _5 _ As a result, pressure chlanyes effected by reciprocation of the piston of the pump were transmitted through the distribution manifold to the gun. Those pressure changes resulted in varying flows of material from the gun. Additionally, pressure changes ¦, occurred whenever one gun of a plurality of guns operated from ~¦ a common distribution manifGld was opened or closed to initiate ¦ or terminate dispensing of adhesive material from that gun.
These pressure changes, irrespective of their source, resulted I in varying flow rates from the guns. The use of volumetric i metering pumps upstream of the gun in each drop line 22 has been found to eliminate the pressure and flow variance which have ¦ heretofore been characteristic of automobile welded joint sealer ¦l systems.
The metering pumps 30 are conventional motor driven gear pumps such as the gear pump disclosed in U. S. Patent ~o.
¦ 4,009,974. In one preferred embodiment, this pump is motor driven by a two speed DC electric motor M. The use of a two ¦ 3peed motor has been found to be desirable if that motor is ~ controlled from the trigger 26 of a manually operated gu~ 24 I becau~e it enables the operator of the ~un to increase or decrease the rate at which material is dispensed from the gun in accordance with the needs or requirements of the application.
Specifically, it has been found that when applying sealant with a manual gun to a straight welded seam, high speed application may be employed, but when applying the sealant to a rounded corner, a slower speed is required in order to effect complete coverage of the se`am without applica~ion of excessive sealant material Robot controlled guns may use an even greater number ¦ of motor speeds to drive the metering pump 30.
. ~1 I :~2~

~¦ In use, the reciprocating pump 14 is actuated when ¦I the system is turned on and before ~he valves of any of the ¦ extrusion guns are opened. This results in viscous sealant material being supplied at a pressure substantially above that of the atmosphere from the drum 18 into the distribution mani-fold 20 and from the distributlon manifold 20 through the meter-ing pumps 30 to the extrusi~n guns 24. When the trigger 26 of a gun 24 is actuated so as to open the valve V contained inter-I nally of the gun 24, the motor M for driving the ge~r pump 30 1l is actuated and sealant material is dispensed from the gun at a II controlled volumetric rate for so long as the trigger remains ¦ open. That rate will remain constant irrespective of any pressure fluctuations which may occur in the distribution mani-fold 20 because of the presence of the motor driven year pumps 30. If more sealant is required, as for example because the gun ¦ is being moved at a fast rate over a straight section of welded seam, greater quantities of sealant may be obtained by adjusting the trigger 26 of the guns 24 to secure high motor speed. This ~ trigger is preferably connected via a conventional electric I control circuit to the motor M of the gear pump 30 so that by controlling the trigger, the actuation and speed of the motor M is controlled. The control circuit which connects the trigger 26 of each of the guns 24 to the associated motor M of the meter- ¦
¦ ing pump 30 through wh~ch a sealant is supplied to the gun 24 is a conventional electrical control circuit which could readily be supplied by a person skilled in this art. Accordingly, it has only been diagrammatically illustrated and represented by the dashed line 42 and the box labeled CC.
In lieu of a manual gun 24, the sealant may be dis-~0 pensed from a conventional robot controlled automatic gun. In l ~ 3 ,. ' ~ -7- 1 , that event, the control circuit CC would be a part of a progranl-med control for the automatic gun, the robot, and the motor M
I for driving the metering pump 30 or a clutch operable between ¦! the motor M and the metering pump 30 for controlling actuation , of the metering pump 30.
While I have described only a single embodiment of , my invention, persons skilled in the art to which my invention pertains will appreciate numerous modifications and changes 1, which can be made without departing from the spirit of my 1 invention. For example, persons skilled in this art will Il appreciate that in some applications it may be desirable to insert a pressure regulator in line 22 between the distribution manifold 20 and the metering gear pump 30 to drop the liquid pressure to an acceptable inlet pressure for the particular gear pump 30. Therefore, I do not intend to be limited except il by the scope of the following appended claims.
I claim:

.. i ~L21 Il l

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A system for dispensing viscous sealant material onto a welded seam of an automobile, which system comprises a distribution manifold extending generally parallel to an automobile production line, a plurality of extrusion guns, a plurality of drop lines, each of said drop lines having upper ends connected to said distribution manifold and lower ends connected to one of said extrusion guns, a primary pump for supplying sealant to said distribution manifold, and a plurality of volumetric metering pumps, each of said volumetric metering pumps being motor driven and operatively connected to one of said drop lines so as to accurately control the rate of flow of sealant from said distribution manifold to one of said extrusion guns.

(2) The system of Claim 1 wherein said primary pump is a reciprocating piston pump.

(3) The system of Claim 1 wherein each of said volumetric metering pumps is a motor driven gear pump.

(4) The system of Claim 2 wherein each of said volumetric metering pumps is driven by a DC electric motor.

(5) The system of Claim 4 wherein each of said DC electric motors is a two speed electric motor.

(6) The system of Claim 3 wherein said extrusion gun is a manually operated gun having a valve contained therein, said valve being controlled by a trigger associated with said gun.

(7) The system of Claim 6 wherein each of said DC electric motors is a variable speed motor, and said triger controling the speed of said DC electric motor.

(8) A method of applying sealant material to a welded seam of an automobile, which method comprises, supplying sealant material from a bulk sealant reservoir to a distribution manifold at a pressure substantially greater than that of the atmosphere, supplying said sealant material from said distribution manifold to a plurality of sealant dispensing extrusion guns, each of said extrusion guns containing a flow control valve, and metering the flow of sealant material from said distrubition manifold to each of said extrusion guns by means of a motor driven metering pump so as to maintain an even flow of sealant material from said extrusion guns upon actuation of said flow control valves irrespective of pressure changes which may occur in said sealant material contained in said distribution manifold.