Information
-
Patent Grant
-
6695917
-
Patent Number
6,695,917
-
Date Filed
Wednesday, November 14, 200123 years ago
-
Date Issued
Tuesday, February 24, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Calfee, Halter and Griswold, LLP
-
CPC
-
US Classifications
Field of Search
US
- 118 106
- 118 257
- 118 268
- 118 70
- 015 971
- 015 102
- 015 103
- 427 429
-
International Classifications
-
Abstract
A flow through felt liquid dispensing apparatus for applying liquids to a receiving surface. The dispensing apparatus may include one or more dispensing heads each including a dispensing gun and an articulated rub block. The articulated rub block includes a recess or galley just behind the felt so as to provide a puddle of liquid material for soaking through the felt during a dispensing operation. The apparatus may be tilted so as to present only one dispensing head at a time to the receiving surface. The galley has a geometry to improve the bead profile of the liquid material dispensed onto the surface. Liquid material is dispensed by relative lateral movement between the apparatus and the receiving surface.
Description
TECHNICAL FIELD OF THE INVENTION
The invention relates generally to apparatus and methods for dispensing fluids onto a surface using a felt applicator. More particularly, the invention relates to a flow through felt dispenser that utilizes one or more dispensing heads and additional features to provide a more uniform and consistent bead or film to the surface.
BACKGROUND OF THE INVENTION
Many industries utilize dispensing systems to apply liquid material to a surface. In the motor vehicle industry, for example, liquid primers are applied to a perimeter region of a windshield as part of the process for installing a windshield in a vehicle body. These primers may be of various types and are preparatory to applying a urethane bead to the windshield that bonds the windshield to the frame. In a typical process, the windshield manufacturer applies a roughened black ceramic frit to a marginal or perimeter region of the windshield on the side of the glass that is bonded to the frame. Before the urethane bonding material can be applied to the frit, a first type of primer must be applied to the surface of the frit with a rubbing action. Often this first type primer is clear in color and is a surface activator that quickly evaporates and prepares the frit surface for application of a second type primer. In order to be effective, however, the clear primer cannot be simply applied but must be applied with a rubbing action as well.
After the clear primer is applied, a second type primer is applied to the frit, again with a rubbing action. Typically the second primer is black in color. The black primer improves adhesion of the urethane to the frit, but more importantly functions to block ultraviolet radiation that would otherwise cause degradation of the urethane. The black primer tends to have a higher viscosity than the clear primer, with the latter having a viscosity about that of water. A typical black primer may have a viscosity, for example, of about 40-100 centipoise.
The primers may be applied to the windshield by manual operations, but more commonly they are applied by dispensing the primer onto the frit using a liquid dispensing gun, and then applying a rubbing action by robotically moving a piece of felt across the frit by relative movement between the windshield and the gun. In a known process commonly referred to as “drip and drag”, the primer is applied onto the frit just ahead of the felt. The primer may be intermittently applied rather than continuously. When the type of the primer is changed, the felt must be changed or an opposite surface of the same felt piece used.
One such system utilizing a drip and drag process is disclosed in U.S. Pat. Nos. 5,277,927 and 5,370,905 which are owned by the assignee of the present invention, the entire disclosures of which are fully incorporated herein by reference. These patents provide a more detailed description of such apparatus and the various technical issues involved with applying these primers to a windshield.
Although the above referenced systems are a significant advance in the art, they as well as other known systems have limitations. For example, the known systems require manual changeover of the felt piece either for each type primer change or after each windshield is completed. This results in a substantial consumption of the felt material. The process of applying the primers to the frit tends to cause splashing of the primer onto surfaces that should not have primer. Still further, most vehicle windshields are not flat panes of glass but rather are curved, some more than others, particularly near the marginal area or perimeter. This can cause a loss of or diminished contact between the felt applicator and the frit, especially as the robotic arm passes around corners. Another drawback to a drip and drag process is an uneven bead profile, particularly of the more viscous black primer. The felt tends to push the primer ahead of it, thereby diverting primer to either side resulting in a “railroad track” profile in which the edges of the bead are thicker than the center region of the bead. Additionally, since the primers are applied by pulsing a dispensing gun on and off, it is difficult to control the amount of liquid material applied to the frit.
The need exists therefore to provide a process and apparatus for applying liquid material to a surface with a rubbing contact or action that overcomes or diminishes the aforementioned limitations of known systems.
SUMMARY OF THE INVENTION
The invention contemplates in one embodiment a liquid dispensing system that utilizes a flow through application process. In accordance with one aspect of the invention, the dispensing system uses two dispensing heads. Each head may dispense a liquid material that is of a different type (for example, possibly a different color or viscosity) than the other dispensing head. Each dispensing head may be presented to a surface, such as a windshield, and placed in contact with the surface, with the other dispensing head out of contact with the surface. The dispensing heads may be disposed side by side on a frame such that by applying a slight tilt or rotation of the frame only one dispensing head at a time contacts the surface.
In accordance with another aspect of the invention, each dispensing head utilizes a flow through process for applying liquid material to the surface. In one embodiment, a flow through process is realized by the use of a porous material, such as a felt web, that is held in position on each dispensing head. Each dispensing head includes a valve that controls flow of liquid material to the porous material. A rub block supports a portion of the porous material proximate to an outlet orifice of the valve. In accordance with another aspect of the invention, the rub block is configured to permit the block to be compliant or adjustable about at least one axis to improve contact between the porous material and an irregular surface. In one embodiment, the valve includes a ball nozzle and the rub block is installed on the ball so as to be able to pivot or swivel as the dispensing head traverses the surface. In accordance with another aspect of the invention, the rub block may further include a recess, pocket or galley between the valve orifice and the porous material to improve the bead profile of the liquid material applied to the surface.
In accordance with another aspect of the invention, a flow through liquid dispensing system is provided with an improved bead profile. The improved bead profile is achieved by use of the rub block galley design, as well as use of a pressure regulator, nozzle orifice size and a flow meter as a system or arrangement for controlling the amount of liquid material dispensed through the nozzle. Accurate volume and pressure control of the liquid material can thus be achieved during a dispensing operation rather than relying on triggering properties of the dispensing valve. The improved bead profile is more consistently produced and includes a greater volume of material near the center of the bead and less volume along the edges of the bead.
Various aspects of the present invention may also be used in a single dispensing head configuration.
These and other aspects and advantages of the present invention will be readily appreciated and understood from the following detailed description of the invention in view of the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is an elevation of a liquid dispensing apparatus in accordance with the invention;
FIG. 2
is a perspective view of the apparatus of
FIG. 1
viewed from below the apparatus and with the porous material web omitted;
FIGS. 3A and 3B
illustrate exemplary dispensing positions for each of the dual heads of
FIG. 1
;
FIG. 4
is an enlarged elevation of a dispensing head section of the apparatus of
FIG. 1
;
FIG. 5
is a nozzle in perspective;
FIG. 6
is the nozzle of
FIG. 5
in longitudinal section along the line
6
—
6
in
FIG. 5
;
FIG. 7
is an enlarged view of a nozzle orifice denoted by the dotted circle in
FIG. 6
;
FIG. 8
is a nozzle and rub block assembly in vertical cross-section;
FIG. 8A
is a rub block and nozzle/dispensing gun assembly in longitudinal cross-section;
FIG. 9
is a lower view perspective of one embodiment of a rub block;
FIG. 10
is a longitudinal cross-section of the rub block of
FIG. 9
taken along the line
10
—
10
;
FIG. 11
is a bottom plan view of the rub block of
FIG. 9
;
FIG. 12
is a perspective of a nozzle and rub block assembly showing a rub block used for a single dispensing head system;
FIGS. 13A and 13B
schematically illustrate operation of an articulated rub block;
FIG. 14A
illustrates a typical bead profile produced by prior art apparatus and
FIG. 14B
illustrates a typical bead profile achieved by the present invention;
FIG. 15
is a flowchart for a control process for the dispensing apparatus of
FIG. 1
;
FIG. 16
is an elevation of a single dispensing head embodiment;
FIG. 17
is a below angle perspective of an alternative rub block embodiment for a single dispensing load application;
FIG. 18
is a longitudinal cross-section of the rub block of
FIG. 17
; and
FIGS. 19A and 19B
illustrate another embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
With reference to
FIGS. 1 and 2
, the numeral
10
generally indicates a flow through liquid dispensing apparatus in accordance with and that embodies various aspects of the present invention. While the invention is described with particular reference to the application of two types of primers such as, for example, clear and black primers to a receiving surface such as a vehicle windshield, such description is intended to be exemplary in nature and should not be construed in a limiting sense. Those in the art will readily appreciate and understand that the invention may be used in other liquid dispensing applications including but not limited to the application of other types of primers or liquids to different types of receiving surfaces or substrates. It is noted that primers may be of different types though not necessarily different in color. Additionally, various aspects of the invention are described herein and are embodied in the exemplary embodiments. These various aspects however may be realized in alternative embodiments either alone or in various combinations thereof. Some of these alternative embodiments will be described herein but such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments. Those skilled in the art may readily adopt one or more of the aspects of the invention into additional embodiments within the scope of the present invention even if such embodiments are not expressly disclosed herein. Additionally, even though some features may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless so expressly stated.
A. General Description
With continued reference to
FIGS. 1 and 2
, the liquid dispensing apparatus
10
includes three basic sections, namely a porous material
12
, at least one dispensing head section
14
and a supply mechanism
16
for feeding an unused portion of the porous material
12
for a dispensing application. In the exemplary embodiment the porous material
12
is in the form of a continuous web, and the supply mechanism
16
includes a supply reel
18
and a take-up reel
20
. This arrangement allows for an automatic advance or indexing of the web
12
prior to each dispensing operation or between a selectable number of dispensing operations. Alternatively, however, a piece of porous material
12
may be manually installed in the apparatus
10
as required and thus the supply mechanism
16
may be omitted. Use of the automatic supply feature however will typically improve throughput speed.
The exemplary embodiment utilizes a pair of dispensing heads
14
a,
14
b
positioned side by side along a direction of travel “Y” of the apparatus
10
. The dual head configuration is used in this case for a typical windshield application of a clear and black primer. The dual head arrangement thus substantially reduces the amount of porous material used during a dispensing operation since the porous material needs to only be advanced or indexed one time for each complete application of a clear and black primer. Single heads may be used for applications requiring only a single liquid application for example.
On the drawings, the XYZ axes are provided as a frame of reference with the Z axis being the vertical axis along which the dispensing section
14
is positioned with pressure against the receiving surface S of the windshield. Pressure and position controls (not shown) may be used to maintain pressure between the dispensing section
14
and the receiving surface S to assure that the primers are dispensed with a good rubbing action between the porous material
12
and the surface as is known. The Y axis represents the direction of relative movement between the dispensing section
14
and the surface of the windshield. In this embodiment the Y axis also corresponds to the direction that the porous material
12
is advanced. The X axis completes the frame of reference such that, as an example, a windshield or other surface onto which liquid material is dispensed would generally lie in the XY plane. Note that
FIG. 2
illustrates the apparatus
10
in perspective by a slight clockwise rotation about the Y axis and the Z axis as compared to FIG.
1
.
The dispensing apparatus
10
is moved relative to the windshield or receiving surface S by any suitable robotic or motion device. For example, the apparatus
10
may be mounted to a robot arm programmed to move the dispensing section
14
along the outer perimeter of a stationary windshield held in a jig or other suitable fixture. Alternatively the dispensing apparatus may be stationary and a robot or other platform used to move the windshield. Both could be moved if so desired. Whatever method is selected, liquid material is dispensed by contact pressure between the dispensing section
14
and the windshield by relative movement there between.
With reference to
FIGS. 3A and 3B
, the use of a dual head dispensing section
14
significantly speeds up a dispensing operation for clear and black primers to a windshield. As illustrated, the dispensing apparatus
10
includes a frame
22
having a suitable robot mounting interface arrangement
24
to mount the apparatus
10
onto the end of a robotic arm R. The robotic arm R not only moves the apparatus
10
along the perimeter of the windshield surface S, but also can pivot or rotate the apparatus
10
about the X axis and hold that position during a dispensing operation so that only one dispensing head
14
a,
14
b
is in contact with and applying liquid material to the receiving surface S at any given time. Techniques other than tilting may be used to present only one dispensing head
14
at a time to the receiving surface S. For example, each head
14
a,
14
b
may be raised or lowered independently along the Z-axis. Other techniques will be readily available as required, and in some applications it may not always be necessary to keep one of the heads
14
out of contact during dispensing operations.
In
FIG. 3A
the dispensing head
14
b
is in contact with the surface S and in
FIG. 3B
the dispensing head
14
a
is in contact with the surface S. The amount of pivoting movement about the X axis will be determined by the size of the dispensing heads
14
a,
14
b
and the desired clearance between the non-contacting dispensing head and the surface S during the time that the other dispensing head is being used. We have found that a rotation of about 10° on either side of vertical (Z axis) provides adequate clearance, however, other pivot angles may be used as required. The clearance is desirable so that black primer does not collect on or cross-over to the clear primer dispensing head.
To further reduce cross-over of one primer type to the adjacent dispensing head, note that the direction of travel of the apparatus
10
is preferably selected so that the active dispensing head (
14
b
in
FIG. 3A and 14
a
in
FIG. 3B
) is the rearward or trailing head relative to the direction of travel. Thus the robotic arm R reverses the direction of travel when switching between dispensing heads
14
a,
14
b.
By having the active head trailing the raised head, the liquid material is dispensed onto the surface S behind the raised dispensing head and cannot come into contact with the raised head.
Although the reverse travel feature and trailing dispensing head arrangement are preferred techniques, they are not required. The active dispensing head could be the leading or forward head. Separately or in combination therewith, the robot could be used to move the apparatus
10
in a single direction if so desired.
With reference again to
FIGS. 1 and 2
, the porous material
12
in this example is a continuous web or loop of material such as a thin web of felt. During each dispensing operation, however, only a small portion
26
of the felt
12
actually is in contact with the surface S. The contact portion
26
of the felt overlays a part of the dispensing head
14
called a rub block
100
. As will be described more fully herein, the rub block
100
presses the felt against the surface S and provides a passageway for a pressurized flow of liquid material to soak the felt during a dispensing operation. For purposes of convenience then, each dispensing head section
14
is considered to include a small felt section
26
that is sandwiched between the corresponding rub block
100
and the receiving surface S because preferably, although not necessarily, only felt contacts the surface S during a dispensing operation.
Unused felt web
12
is stored on the supply reel
18
and used felt is recovered by winding it onto the take-up reel
20
. To reduce the size of the apparatus
10
, the reels
18
,
20
are arranged horizontally and are stacked vertically one above the other on a common axis D. Alternatively, the reels
18
,
20
may be supported side by side much like a reel to reel movie projector or tape player. Other mounting techniques may be use as required for a particular application as will be readily apparent to those skilled in the art.
A suitable number of tensioning rollers
28
are used to support and guide the felt web around the dispensing heads
14
. In this example, at least one of the rollers
28
a
is spring biased by a tensioning spring
30
against a payout roller
32
. In this embodiment, because the supply and take-up reels
18
,
20
are vertically stacked and payout the web
12
in a plane that is transverse to the plane XY, the felt web
12
will include a 90° twist to properly overlay the rub blocks
100
. Alignment rollers
34
may be used to prevent twist of the felt web
12
onto the reels
18
,
20
.
Controlled payout and movement of the felt web
12
may be realized with conventional pneumatic or other suitable drive mechanisms. A small pneumatic motor
36
may be used to oppositely turn the reels
18
,
20
thus placing the web
12
under tension.
The payout roller
32
preferably has a non-slip surface that allows the roller
32
to advance the web
12
when the roller
32
is rotated. The payout roller
32
may be turned by any suitable drive mechanism such as a pneumatic motor. A typical payout for a new dispensing operation may be about two inches but will depend on the size of the dispensing head section
14
and how much liquid materials soaks into the web
12
in the vicinity of the dispensing heads
14
. The felt web
12
is advanced a sufficient amount to assure that a completely new portion
26
of the web
12
is presented at the rub blocks
100
prior to a selected dispensing operation. Note that the felt web
12
is clamped in position relative to the rub blocks
100
during an actual dispensing operation. New or unused felt is advanced by the payout roller
32
before the next dispensing operation by unclamping or releasing the felt web
12
. When a dual dispensing head configuration is used it is contemplated that one complete dispensing operation includes dispensing fluid from a first of the dispensing heads
14
and then the other. The side by side dispensing heads
14
a,
14
b
thus minimize the amount of felt
12
used during a dispensing operation of applying two primers to the receiving surface S.
An optical sensor
38
may be used as part of the web payout control. The optical sensor
38
may be used to detect the presence of black primer on the “used” felt web, and provide a signal corresponding thereto to stop further payout of the felt. The sensor
38
preferably is positioned between the dispensing head section
14
and the take-up reel
20
but fairly close to the dispensing section
14
so as to minimize the amount of felt
12
payed out between dispensing operations. Note that preferably the felt web
12
is only advanced in a single direction across the rub blocks
100
. Furthermore, because the felt web
12
physically contacts the rub blocks
100
, each indexing or advancement of the web
12
produces a wiping action that helps clean the rub blocks between dispensing operations. This is particularly useful for the clear primer dispensing head which preferably is first to encounter a new or clean portion of the felt web
12
. Thus in the exemplary embodiment for example, the clear primer dispensing head would be the left side head
14
a
(as viewed in FIG.
1
).
B. Dispensing Head Section
With reference to
FIG. 4
, the dispensing head section
14
is illustrated in an enlarged view. In this embodiment there are two dispensing heads
14
a,
14
b
that are substantially the same in design and operation, therefore, a detailed description of only one (
14
a
) will be given herein.
The dispensing head
14
a
includes a rub block
100
that is installed on a dispensing nozzle
40
. The nozzle
40
extends from a dispensing gun assembly
42
. Each gun
42
may be, for example, model H200 available from Nordson Corporation of Westlake, Ohio. Any suitable dispensing mechanism may be used, however. The dispensing gun
42
is mounted to a manifold block
44
using bolts
46
. A suitable primer supply fitting
48
provides a liquid material inlet to the gun
42
.
The manifold
44
is mounted on a slide
50
. The slide
50
may be raised or lowered by a suitable pneumatic actuator
52
(
FIG. 2
) as viewed in
FIGS. 1 and 4
to position the dispensing head in contact with the receiving surface S. Conventional pressure and position controls may be used to maintain a fairly constant pressure of the rub block
100
and felt
26
against the surface S during a dispensing operation even for irregular surface contours. A mounting bracket
54
a
extends from a support bracket
54
, which is mounted on the slide
50
and supports the optical sensor assembly
38
thereon.
Although the felt web
12
should have some slack or give to permit the dispensing head section
14
to adjust along the Z axis, it is desirable to maintain the felt portion
26
taut and snug against the rub block
100
. Accordingly, a pair of clamping or gripper jaws
56
are provided. Each jaw
56
includes a gripper pad
58
. An actuator (not shown) is used to move the jaws
56
to the position illustrated in
FIGS. 1 and 4
. In this position, the gripper pads
58
snugly hold the felt web
12
against a pinch block
60
. The jaws
56
may be opened by lateral movement to release the clamping grip of the gripper pads
58
when it is desired to index or advance the felt web
12
. Note from
FIG. 4
that in addition to holding the felt web
12
in place during a dispensing operation, the grippers
58
also apply tension to the web
12
by somewhat tensioning the web against the lower rollers
28
that are adjacent the guns
42
. The pinch block
60
may be moveable along the Y-axis to provide a self-centering function thereby compensating for material build-up on the used portions of the web
12
. In this manner, the web
12
is held in proper alignment on the rub blocks
100
during a dispensing operation.
A valve actuator
62
such as a pneumatic actuator is provided as part of the dispensing gun assembly
42
. In the exemplary embodiment each gun assembly
42
includes a needle valve that is opened and closed under control of the associated valve actuator
62
. The manifold
44
provides an inlet for a pressurized air source used to operate the actuators
62
.
A flow meter
70
may be used to monitor the flow volume of liquid material being dispensed. In one embodiment, the flow meter
70
generates a signal such as an alarm signal if during a dispensing operation the flow volume was too high or low. This signal may be detected by the control electronics or the operator and used either to reject the workpiece or to at least indicate a need for an inspection of the workpiece after a dispensing operation. A flow regulator
72
may be used in a conventional manner to regulate the liquid material pressure supplied to the dispensing guns
42
. The pressure of the liquid material, in combination with the nozzle orifice size (
112
) will determine the flow rate of liquid material dispensed from the gun
42
into the felt web portion
26
and onto the receiving surface S.
It is also contemplated however that a more precise control of the flow volume of liquid material being dispensed be provided in some applications. In accordance with another aspect of the invention, flow volume of liquid material to the felt web
12
may be controlled by use of a flow meter feedback function in combination with the flow regulator
72
and orifice
112
size. By way of contrast, prior art systems typically control the quantity of liquid material dispensed onto the receiving surface S by pulsing the dispensing gun on and off at a selected rate. This prior art technique is not a particularly accurate way to control flow volumes. In accordance with another aspect of the invention, the flow meter
70
generates a signal that corresponds to flow rate, and this signal is used as part of a closed loop feedback control to adjust the flow regulator on a real-time or near real-time basis to assure that proper flow volume of liquid material is dispensed onto the receiving surface S. This technique has the added benefit that a pressurized puddle or reservoir of liquid material is produced at the portion of the felt web
26
that actually contacts the receiving surface S (the design of the rub block
100
facilitates this effect, as will be fully described herein after).
In either case, use of the pressure regulator
72
and the orifice
112
produces a smooth flow of liquid material that soaks through the felt web
12
for application to the receiving surface S, thereby improving the bead profile applied to the receiving surface. This is a significant improvement over controlling flow volumes merely by triggering the dispensing gun on and off at a selected rate.
All of the pneumatic and electrical control functions of the apparatus
10
may be executed using a conventional programmable microprocessor or micro-controller or other suitable control circuits as is well known to those skilled in the art. Pneumatic actuators and controls are not required as any suitable actuator design may be used.
C. Articulated Rub Block
Not all surfaces and substrates onto which liquid material is to be dispensed are flat or planar. For example, vehicle windshields usually have a curvature, particularly about the perimeter or marginal edge. A rigid non-compliant dispensing head is therefore difficult to maintain in good contact with the surface, such as when the dispensing head travels around corner regions. The result of poor contact is an inconsistent bead profile and possibly missed areas.
In accordance with another aspect of the invention, a dispensing head design is used that more readily conforms to the variable contour of a surface. Such a compliant dispensing head produces a more consistent bead profile.
In the exemplary embodiment, a compliant dispensing head
14
is realized in the form of an articulated rub block
100
. By “articulated” is meant that the block
100
has some degree of freedom to pivot about at least one axis so as to be able to maintain alignment with the surface S, thus assuring good contact between the felt section
26
and the surface S. Because the rub block
100
moves relative to the surface S along the axis Y, in the preferred embodiment the block
100
is designed to pivot or roll about the Y axis about 10° either side of normal. The degree of permitted articulation will depend on the extent of curvature present in the surface S. The ability of the block
100
to roll allows for workpiece variation and robot programming errors which typically are not more than about ±10°. The present invention is not limited by any specific degree of articulated movement, but most applications will be about 20° or less either side of normal (normal being 0° referenced to the Z axis). Articulated or pivoting movement about the Z axis (yaw) or X axis (pitch) is not as beneficial and may in some applications be undesirable. If the rub block
100
pivots or yaws about the Z axis, the felt
12
will tend to be oriented on a line other than the Y axis direction of travel, possibly producing an inconsistent bead width or an incorrect orientation of the felt on the rub block
100
. If the rub block
100
pivots or pitches about the X axis the felt web
12
might lose contact or have less pressure against the surface S. Since the apparatus
10
already compensates for Z axis variation, there is no need usually for the rub block
100
to be able to pitch about the X axis. In accordance then with this aspect of the invention, the rub block
100
is designed to articulate primarily about the Y or roll axis, and to be more restricted against pivoting about the X and Z axes.
Achieving a consistent bead pattern is also a function of controlling the flow of liquid material through the felt web
12
as a function of the travel speed of the dispensing head
14
across the surface S. In accordance with this aspect of the invention, the rub block
100
includes a galley or pocket or recess formed in a surface of the rub block
100
against which the felt web
12
is pressed. The galley provides a volume in which the pressurized liquid material collects or puddles adjacent the felt web
12
. This pressurized puddle action improves the flow of the liquid material through the felt
12
onto the receiving surface S to produce a more consistent bead pattern.
Each dispensing head section
14
a,
14
b
includes four basic components, a nozzle
102
, a valve needle
124
, the rub block
100
and the adjacent portion of the felt web
26
. With reference to
FIG. 5
, in this embodiment, the nozzle
102
is a ball type nozzle
106
having a mounting block
108
that is installed by screws or bolts onto the dispensing gun
42
. The ball nozzle
106
depends from the mounting block
108
on a valve stem shaft housing
110
. An outlet orifice
112
is formed at the bottom of the ball nozzle
106
. Preferably but not necessarily the nozzle
102
is a unitary piece such as made, for example, from a machined stainless steel or other suitable material.
As best illustrated in
FIG. 6
, the mounting block
108
includes an upwardly extending nipple
114
having an o-ring or seal groove
116
formed therein. The nipple
114
is inserted into the lower end of the dispensing gun
42
such that liquid material is free to flow from the gun
42
into the material passageway
118
that extends through the nozzle
102
to the orifice
112
. With reference to
FIG. 7
, the orifice
112
opens to an axially tapered passageway
120
. The orifice
112
and the tapered passageway
120
join at a needle valve seat
122
.
FIG. 8
illustrates a valve needle
124
installed in the nozzle
102
. The valve needle
124
includes a tapered tip
126
that opens and closes the valve orifice
112
depending on the position of the needle
124
. The valve needle is installed into the dispensing gun
42
and includes an end
128
that is connected with or operably joined to the valve actuator which controls movement of the valve needle
124
to open and close the valve.
FIG. 8A
illustrates one embodiment of a complete rub block
100
and dispensing gun
42
assembly. The actuator
62
receives the upper end
128
of the valve stem
124
at an actuating piston or plate
64
. A spring
65
biases the valve needle
124
to the closed position (illustrated in FIG.
8
A). An air inlet port
66
is used to supply pressurized air that acts against the underside of the piston
64
and the force of the spring
65
to open the orifice
112
by pulling the tip
126
away from the valve seat
122
. A liquid material inlet port is used to supply liquid material such as a primer to a flow passageway
68
within the dispensing gun
42
. The liquid material flows through the passageway
68
around the stem
124
to the orifice
112
. A weep hole
69
may be provided as required.
FIGS. 9 and 10
illustrate an underside perspective of one embodiment of a rub block
100
. This embodiment may be used, for example, as the rub block
100
design for a dual dispensing head configuration such the embodiment of FIG.
1
. The rub block
100
is a hood-like structure having a main body
130
that is generally U-shaped. The body
130
has an outer rounded surface
132
against which the felt web
12
is positioned and traverses when new felt is advanced by the supply mechanism
16
. The outer surface
132
supports the contact portion
26
of the felt web
12
so that the felt web
12
can be pressed against the receiving surface S during a dispensing operation.
A tapered wall or fence
134
on each side of the felt supporting surface
132
helps maintain the felt web
12
in proper position on the rub block
100
, particularly when the felt is advanced prior to a dispensing operation, and also to help hold the felt web
12
in proper position on the rounded supporting surface
132
during a dispensing operation.
As best illustrated in
FIGS. 10 and 11
, the positioning walls
134
taper to near flush or tangent with the felt supporting surface
132
in the vicinity of a galley or recess
136
formed in the supporting surface
132
. The tangential taper of the walls
134
assure that only felt contacts the receiving surface S. By this arrangement, at the region of contact between the felt
26
and the receiving surface S, the galley
136
is behind the felt portion
26
and provides a volume in which pressurized liquid material flows from the nozzle orifice
112
through the felt. The galley
136
is recessed in the felt supporting surface
132
and extends across much of the surface
132
between the lateral sides
138
a
and
138
b
of the rub block
100
. Note that for some liquids, particularly low viscosity liquids, the pressure of the liquid dispensed and soaked into the felt portion
26
may be very low.
The galley
136
is defined by a recessed inner wall
140
. It is important to note that
FIG. 10
illustrates the rub block in an upright position parallel to the Z axis. During a dispensing operation in the dual head configuration, the dispensing head
14
and hence the rub blocks
100
are tilted from vertical about 10° or so (see FIGS.
3
A and
3
B). Accordingly, in the embodiment of
FIGS. 9-11
, the galley
136
is positioned off center from the Z-axis by about 10°. The degree of off center location will be preferably matched to the degree of tilt applied to the dispensing section
14
by the robotic arm during a dispensing operation. Accordingly, the recessed inner wall
140
forms an angle α of about 10° to horizontal but is generally parallel to the receiving surface S when the dispensing head
14
is tilted during a dispensing operation. The depth of the galley
136
tapers somewhat along the Y axis since it is formed into a curved surface.
As best illustrated in
FIG. 11
, the galley
136
is bounded on one side by the adjacent web supporting surface portion
132
a,
on an opposite side by an adjacent web supporting surface portion
132
b,
and on opposite lateral sides by fairly narrow alleys
132
c
and
132
d.
Thus, the felt web
26
is fully supported along all edges of the galley
136
, particularly when held under tension by the gripper pads
58
(FIG.
4
). But at the region of contact between the felt
26
and the receiving surface S, a puddle or pressurized volume of liquid material is present and soaks through the felt
26
for application to the receiving surface. We have found that the use of such recessed galley
136
helps provide a more uniform and desired bead pattern applied to the receiving surface S.
The galley
136
is formed to an apex
142
at the leading end
137
of the galley
136
. By leading end
137
is simply meant as the end of the galley that is towards the direction of travel as the dispensing head
14
is moved across the receiving surface S. Note that this leading apex
142
also corresponds to the deepest region
144
of the galley
136
.
The aforementioned galley
136
geometry appears to allow more liquid material to be dispensed from the forward end
137
and less from the trailing end
146
of the galley
136
to produce a more consistent bead pattern, as the trailing portion of the felt web
26
may be less saturated and better able to smooth out the bead.
A through port
148
connects the galley
136
in fluid communication with a generally hemispherical cavity
150
formed in the rub block
100
. The port
148
is preferably angled and positioned such that the major axis
148
a
of the port
148
opens to the galley
136
so as to be collinear with the forward ends
133
c
and
133
d
of the rectangular portion of the galley
136
that is further defined by the lateral sides
132
c,
132
d
and the back or trailing end
146
. The port
148
preferably opens to the cavity
150
at the bottom thereof. As best shown in
FIG. 11
, the port
148
preferably is oval shaped and oriented with its major axis
148
a
transverse to the direction of travel along the Y axis. This geometry of the port
148
opening to the galley
136
appears to help produce a consistent bead pattern.
The hemispherical cavity
150
is appropriately sized to receive somewhat more than half of the nozzle ball
106
(FIG.
8
). A seal groove
152
is formed adjacent the cavity
150
and retains a suitable seal such as an o-ring
154
.
FIG. 8
illustrates the rub block
100
installed on the nozzle
102
.
The rub block
100
is installed by inserting the nozzle ball
106
through a bore
156
formed in the block body
130
, past the seal
154
and into the cavity
150
. The seal
154
is sized to have an inner diameter that is somewhat smaller than the outside diameter of the ball
106
so that the block
100
is snapped onto the ball
106
and loosely retained on the ball by the seal
154
. The seal
154
not only retains the rub block on the nozzle ball
106
, but also will help prevent liquid material from flowing around the nozzle ball
106
due to back pressure.
The cavity
150
is sized somewhat larger than the nozzle ball
106
diameter. This assures that the rub block can easily pivot much like a ball and socket arrangement. The port
148
is appropriately dimensional so that the valve outlet orifice
112
is always open directly to the port
148
regardless of the pivoted position of the rub block
100
.
With reference to
FIGS. 9 and 10
, the rub block
100
further includes parallel extending extensions, flaps or ears
160
which extend from respective ends of the felt web supporting surface
132
. These ears
160
engage opposite sides of the nozzle block
108
. The extensions
160
will therefore restrict pivoting or rotation of the rub block
100
about the Z and X axes (yaw and pitch respectively) but permit free pivoting movement about the Y axis (roll).
FIG. 12
illustrates another rub block
182
installed on a nozzle
102
. This rub block
182
is somewhat modified as will be described hereinafter, but nonetheless includes similar ears
194
that are positioned adjacent the nozzle mounting block
108
and restrict pivoting motion of the rub block
182
except about the Y axis.
FIGS. 9 and 10
illustrate that the leading side
162
of the rub block
100
is generally planar and flat compared to the trailing side
164
. This arrangement permits closer positioning of the side by side dispensing heads
14
a
and
14
b
while allowing the felt web
12
to be wrapped around and supported by a curved surface (see FIG.
4
).
FIGS. 13A and 13B
illustrate graphically how the articulated rub block
100
design improves application of liquid material to the receiving surface S. Note that in these figures the path of travel or Y axis is into the plane of the drawing. The robotic arm R generally maintains the dispensing guns
42
in a vertical orientation. However, when the receiving surface S is not horizontal, the rub block
100
can pivot about the Y axis thus maintaining excellent contact between the felt portion
26
and the receiving surface S. Variations in angle relative to the X axis are compensated for by the movement adjustment of the slider so along the Z axis (FIG.
4
). The rub block
100
easily articulates due to its ball and socket type coupling to the ball nozzle
102
without adversely affecting flow of liquid material from the nozzle orifice
112
to the felt portion
26
.
FIG. 14A
illustrates a typical bead profile of liquid material L applied to a receiving surface S′ such as a windshield using a prior art process such as drip and drag. This profile is characterized by a “railroad track” effect wherein the bead has a small thickness in the center but raised edges on either side. By way of contrast,
FIG. 14B
illustrates a typical bead profile achieved by the present invention. The profile is characterized by a thicker middle or center section
1
and a tapering thickness portion
2
on either side to relatively thin edge portions
3
. This profile is desirable for improving adhesion of the urethane to the windshield and more even distribution of the UV blocking layer under the urethane.
FIG. 15
illustrates a typical control process for a control system suitable for use with the present invention. This control process may be realized using conventional computer programming techniques well known to those skilled in the art.
At step
200
a sensor detects that a part such as a windshield has been presented to the dispensing apparatus. At step
202
the gripper jaws
56
are actuated to clamp the felt web
26
in position. The apparatus
10
(tool) is positioned by the robotic arm R near the receiving surface S at step
204
. The needle valve within the nozzle
102
for the clear primer is opened and the associated felt portion is saturated with the clear primer at step
206
. The robotic arm R pivots the dispensing head section
14
and at step
208
the clear primer is applied to the receiving surface S.
After the clear primer is completed, the apparatus
10
is moved to the “ready” position at the start of the bead at step
210
and the black primer needle valve is opened at step
212
to saturate the felt with black primer. At step
214
the robotic arm pivots the dispensing head section
14
in the opposite direction to apply black primer to the receiving surface S. The robotic arm R applies the black primer by traversing the receiving surface S on the opposite direction.
At step
216
the apparatus
10
is returned to a park position away from the part and the gripper jaws are released at step
218
. The payout roller
32
rotates to index or advance the felt web
12
at step
220
. This will cause a blackened portion of the felt to be sensed by the optical sensor
38
at step
222
. If black is detected at step
224
, the felt is stopped at
225
and the system goes into standby mode at step
226
. But prior to standby mode, the system checks at step
228
if the felt has been stationary for more that a prescribed time such as longer than two minutes for example. If not, standby mode is entered.
If the time period exceeds the limit, the felt is advanced a greater distance at step
230
. This it to prevent wet primer saturated felt from drying to the rolling and stationary elements over which it travels.
If at step
224
the black material is not detected, the system increments up to another seven times at step
232
to detect the type change. If after seven increments no change is detected, the felt is stopped at step
234
and an alarm indication at step
236
generated at step
236
to indicate probable depletion of the black primer liquid or a malfunction with the black primer dispensing head.
D. Additional Embodiments
With reference to
FIG. 16
, the invention may also be realized in the form of a single dispensing head arrangement
170
. Most of the features such as the gripper jaws
172
, pinch block
174
, manifold
176
and liquid inlet fitting
178
may be the same as the corresponding elements in the dual dispensing head, embodiment described hereinabove. The liquid dispensing gun
180
may also be the same except that only one is used along with a single rub block
182
.
FIG. 12
illustrates the rub block
182
and nozzle
102
in perspective.
FIGS. 17 and 18
illustrate the rub block
182
design that may be used in a single gun application. In this example, the rub block
182
is generally symmetrical and the galley
184
is formed in the curved felt support surface
186
at the bottom of the block
182
. Because only a single gun is used, there is no need to tilt or pivot the dispensing apparatus
10
, but rather the gun
180
and the rub block
182
are vertically oriented on the Z axis. The galley
184
may be of similar design to the prior described embodiment herein, but the galley
184
is not offset by about 10° since the apparatus will not be tilted during a dispensing operation. A port
188
connects the galley
184
to a hemispherical cavity
190
and the rub block
182
is installed on the nozzle in a similar manner to the prior embodiment herein and retained by a seal (not shown) in a seal groove
192
. The rub block
182
includes the ear extensions
194
to limit pivot movement about the Z and X axes (yaw and pitch) while permitting the rub block
182
to pivot or articulate about the Y axis (roll). Note that the rub block
182
support surface
186
is symmetrical about the Z axis because the felt web
12
will be supported along the curved surface on both sides of the block
182
, in contrast to the dual head embodiment herein.
With reference to
FIGS. 19A and 19B
, the invention may be realized in the form of having the dispensing apparatus
10
remain stationary during a dispensing operation. In such an example, the workpiece, such as a windshield having the receiving surface S thereon, is mounted on a platform
80
that is attached to the robotic arm R. The robotic arm R tilts the workpiece to the appropriate angle such as about 10 degrees and moves the workpiece so as to apply the desired bead. Again, for application of the second type primer, the workpiece is tilted in the opposite direction and the direction of travel is reversed. Operation in all other respects is the same.
It should further be noted that the dual dispensing head aspect may be utilized in a dispensing apparatus that is not tilted and without the use of the articulated rub blocks. Such an embodiment is less preferred in that the rub blocks are not as compliant to the receiving surface, however, some of the benefits of the dual dispensing head arrangement are still realized.
The invention has been described with reference to the preferred embodiment. Modifications and alterations will occur to others upon a reading and understanding of this specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims
- 1. Fluid dispensing apparatus for applying a liquid material to a substrate, comprising:at least two liquid dispensing nozzles each disposed within a respective nozzle block; a web of material that is porous for liquid material dispensed from each said nozzle; said porous material being disposed between each said nozzle block and the substrate; each said nozzle being operable to dispense liquid material onto the substrate by contact between said porous material and the substrate wherein each said nozzle block can pivot about a first axis.
- 2. The apparatus of claim 1 wherein each said nozzle block comprises a surface that supports said porous material against the substrate wit pressure being applied to said porous material when said porous material is in contact with the substrate during a dispensing operation.
- 3. The apparatus of claim 2 wherein each said block is compliant with variations in the substrate by pivoting movement with respect to at least one axis.
- 4. The apparatus of claim 3 wherein each said block is restricted against pivoting movement with respect to two axes that are each orthogonal to said at least one axis.
- 5. The apparatus of claim 2 comprising a channel formed in said surface and that is in fluid communication with a respective nozzle so that when liquid material is dispensed from said nozzle liquid material collects in said channel and is absorbed through said porous material onto the substrate.
- 6. The apparatus of claim 5 wherein liquid material is dispensed through said porous material under pressure.
- 7. The apparatus of claim 1 wherein each nozzle block can be individually positioned against the substrate to dispense liquid material thereon through said porous material.
- 8. The apparatus of claim 7 wherein said dispensing nozzles are mounted on a frame, and comprising a device for moving said frame to present each said nozzle and associated nozzle block against the substrate for dispensing liquid material thereon.
- 9. The apparatus of claim 8 wherein said device comprises a robotic arm and the substrate comprises a glass plate.
- 10. The apparatus of claim 9 wherein said glass plate comprises a motor vehicle windshield.
- 11. The apparatus of claim 7 wherein said device imparts relative motion between said nozzles and to substrate.
- 12. The apparatus of claim 1 wherein said porous material comprises a web of felt.
- 13. The apparatus of claim 1 comprising a flow regulator for controlling quantity of liquid material dispensed from said nozzles.
- 14. The apparatus of claim 1 comprising a supply mechanism for providing an unused portion of said porous material to each said nozzle block prior to a dispensing operation.
- 15. The apparatus of claim 14 wherein said supply mechanism comprises a continuous web of said porous material fed from a supply reel and received by a take-up reel.
- 16. The apparatus of claim 15 wherein said supply mechanism is configured so that each said nozzle dispenses liquid material onto the substrate prior to said supply mechanism feeding an unused portion of said porous material to each said nozzle block.
- 17. The apparatus of claim 1 wherein each said nozzle comprises a ball member that is received within said respective nozzle block.
- 18. The apparatus of claim 17 wherein each said nozzle block comprises a resilient member that slides over said bail when said ball is installed in said block to retain said block on said ball.
- 19. The apparatus of claim 18 wherein said resilient member comprises an -o-ring and seals against back flow of the liquid material.
- 20. Fluid dispensing apparatus for applying a liquid material to a substrate, comprising:at least one liquid dispensing nozzle disposed within a rub block; a web of material disposed against said rub block and that is porous to liquid material dispensed from said nozzle; said porous material being supported on said rub block; said nozzle being operable to dispense liquid material onto a surface of the substrate by contact between said porous material and the substrate with liquid material flowing through said porous material to said substrate; wherein said rub block can pivot relative to said nozzle about a first axis in response to variations in the substrate surface.
- 21. The apparatus of claim 20 wherein said rub block and nozzle form a ball and socket coupling.
- 22. The apparatus of claim 20 wherein said nozzle includes a spherical nozzle body and said nab block includes a partially spherical cavity that receives said nozzle body.
- 23. The apparatus of claim 22 wherein said rub block is retained on said nozzle body by an elastomeric seal.
- 24. The apparatus of claim 20 wherein said nozzle is mounted to a frame that is translated across the surface of the substrate by relative movement therebetween to apply a bead of liquid material to a perimeter portion of the substrate.
- 25. The apparatus of claim 20 wherein said rub block is restricted against pivoting about two other axes normal to said first axis.
- 26. A dispensing head for a liquid dispensing gun, comprising:a nozzle having a main body with an outlet orifice fanned therein; and a rub block mountable on said nozzle main body for relative pivoting movement with respect to each other.
- 27. The assembly of claim 26 wherein said rub block and nozzle main body are coupled together as a ball and socket arrangement.
- 28. The assembly of claim 26 wherein said rub block comprises a surface that supports a porous material and has a recess in said surface adjacent said porous material; said recess being in fluid communication with said nozzle outlet orifice.
- 29. The assembly of claim 26 wherein said outlet orifice is open and closed by a needle valve.
- 30. The assembly of claim 26 wherein said rub block pivots about a first axis and is restricted against pivoting about second and third axes that are normal to said first axis.
- 31. Fluid dispensing apparatus for applying a liquid material to a substrate, comprising:at least two liquid dispensing nozzles each disposed within a respective rub block; a web of material that is porous for liquid material dispensed from each said nozzle; said porous material being disposed between each said rub block and the substrate; each said nozzle being operable to dispense liquid material onto the substrate by contact between said porous material and the substrate; each said nib block being selectively and separately positioned for contacting said porous material with the substrate.
- 32. The apparatus of claim 31 comprising a frame; said nozzles and associated it blocks being disposed on said frame, and a mechanism for positioning said frame to first and second frame positions, wherein when said frame is in said first frame position a first of said rub blocks presses said porous material against the substrate and when said frame is in said second frame position a second of said rub blocks presses said porous material against the substrate.
- 33. Fluid dispensing apparatus for applying a liquid material to a substrate, comprising:at least two liquid dispensing nozzles each disposed within a respective nozzle a web of material that is porous for liquid material dispensed from each said nozzle; said porous material being disposed between each said nozzle block and the substrate; each said nozzle being operable to dispense liquid material onto the substrate by contact between said porous material and the substrate; wherein each nozzle block can be individually positioned against the substrate to dispense liquid material thereon through said porous material.
US Referenced Citations (6)
Foreign Referenced Citations (1)
Number |
Date |
Country |
WO9959739 |
Nov 1999 |
WO |