Mold construction method and apparatus for making plastic backings for skating rink dasher boards

A mold construction, method and apparatus for forming backing shells for skating ring dasher boards out of a single piece of material is disclosed. The mold comprises a vacuum box and oppositely disposed forming members loosely positioned in the box to form a mold cavity. A sheet of plastic material is secured in a frame and is softened by radiant heat. The softened sheet is brought adjacent the mold cavity and is drawn into the cavity to assume the conformation thereof by air being withdrawn from the cavity through cracks therein resulting from the loosely fitting forming members. One or more layers of fiberglass and polyester resinous material applied to a face of the backing shell completes the dasher board.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to dasher boards for skating rinks and more 
particularly to the mold, method of, and apparatus for forming backing 
shells for dasher boards of plastic sheet material and the method of 
making the dasher board itself. 
2. Prior Art and Objects of the Invention 
Applicant is unaware of any mold construction in the prior art such as that 
disclosed or a molding apparatus or method employing such a mold 
construction for making plastic backing shells for fiberglass dasher 
boards for skating rinks or any other object. The dasher boards capable of 
being formed with the backing made by the mold, method, and apparatus 
herein disclosed are shown generally in my U.S. Pat. No. 3,883,120 of May 
13, 1975 entitled "Monolithic Dasher Board for Skating Rinks" and are 
essentially a waist-high retaining wall around the outer periphery of the 
rink when positioned vertically end to end. Heretofore, the dasher boards 
set forth in my afore-mentioned patent were made by placing numerous, 
successive layers of fiberglass and polyester resinous material directly 
on a positive mold coated with a release gel. After the resinous material 
had cured, the completed board could be removed from the mold. This method 
had the serious drawback that numerous positive molds had to be provided 
so that other boards could be in the process of being formed while others 
were curing. Such positive molds were very expensive. The backing shells 
of the present invention provide an inexpensive positive mold which 
becomes an integral part of each completed dasher board, thus speeding up 
production, reducing mold and material costs, and eliminating the 
necessity of a release gel. 
The formation of plastic objects by drawing a heated plastic sheet into a 
negative mold is shown in U.S. Pat. No. 2,749,572 issued June 12, 1956. In 
this type of apparatus, the air is withdrawn from an area proximate to the 
molding surface through a plurality of small holes formed through the 
molding surface. Generally, the more holes present the more uniformly 
distributed the vacuum is and the better the heated plastic can be made to 
conform to the contours of the mold surface. This is particularly true 
when the objects are relatively small and the curved surfaces are gradual 
and not sharp. However, when the object to be formed is large such as a 4 
by 8 foot dasher board for skating rinks which is basically a five sided, 
rectangular shaped box having sharply defined edges, the problems of 
constructing a mold to vacuum form such a board are considerable. Further, 
if parts of the mold itself must be capable of being removed so that the 
completed dasher board can be removed from the mold, the problem of 
providing a mold construction with the proper vacuum distribution is 
magnified. Applicant has discovered that by making all of the forming 
members loosely fitting within a vacuum box and providing a channel in the 
forming members for distributing the vacuum to the cracks formed between 
the forming members themselves as well as between the forming members and 
the vacuum box, a superior mold results and one which is particularly 
suited for use in a method and apparatus for molding large, rectangular 
shape, box-like objects. 
It is therefore the primary object of the present invention to provide a 
novel mold construction, method and apparatus for vacuum forming backing 
shells for skating rink dasher boards and a novel method of making the 
dasher board itself. 
It is another object of the invention to provide an apparatus and mold 
construction which is particularly suited to vacuum forming large objects 
having the walls thereof substantially perpendicular to each other. 
It is a further object of the invention to provide an apparatus and a mold 
for use therewith which is uncomplicated in design and made of inexpensive 
materials. 
It is a still further object of the invention to provide a method of making 
a complete dasher board for skating rinks. 
The novel features which are believed to be characteristic of the invention 
both as to its organization and method of operation, together with further 
objectives and advantages thereof will be better understood from the 
following description considered in connection with the accompanying 
drawings in which a presently preferred embodiment of the invention is 
illustrated by way of example. It is to be expressly understood, however, 
that the drawing is for the purpose of illustration and description only, 
and is not intended as a definition of the limits of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Looking now in greater detail at the accompanying drawings, FIG. 1 
illustrates generally a dasher board backing shell 10 capable of being 
made by the mold, method and apparatus to be hereinafter described. The 
dasher board backing shell 10 is made of a thermoplastic material such as 
an acrylic resin over which is built up successive layers of polyester 
resinous material reinforced with fiberglass to arrive at the completed 
dasher board. As aforementioned, when the dasher boards are placed end to 
end with like boards around the periphery of a skating rink, they act as a 
waist-high wall to retain skaters, hockey pucks and the like. The dasher 
board backing shell sections 10 have rectangular shaped grooves 12 on the 
ends thereof which receive a portion of a stanchion (not shown) for 
supporting the completed board sections in an upright position. The dasher 
board backing shell 10 has a flat front portion 14, a top and bottom 
portion 16, 18 respectively and end portions 20, 22. The portions 16, 18, 
20 and 22 are all perpendicular to the front portion 14 and to the 
portions adjacent each other to thereby form, substantially, a five sided 
box. 
The apparatus for forming the aforedescribed dasher board backing shell 10 
can best be seen by referring to FIGS. 2, 3 and 4. The apparatus comprises 
generally a mold 24, a frame 26 and a heater hood 28. The heater hood 28 
is suitably suspended above the frame 26 and mold 24 and consists of an 
outer housing 30 containing a plurality of rows of elongated electrical 
resistance type heating elements 32. The heat from the hood 28 radiates 
downward toward the frame 26 which holds a sheet of thermoplastic material 
34. The frame 26 comprises a lower frame member 36 which is rectangular in 
shape and formed of L-shaped metal. The lower frame member 36 has four 
rods 38 secured to the lower side thereof. The rods 38 are slidably 
mounted in brackets 39 secured to mold 24 for permitting the frame to move 
relative thereto. The frame 26 also has an upper frame member 38 which is 
constructed in the same manner as the lower member 36. The thermoplastic 
material 34 is maintained between the frame members 36, 38 by means of a 
C-type clamp 40 or the like. 
The mold 24 of the apparatus comprises a vacuum box 44 having a bottom 46, 
side walls 48 and end walls 50. The vacuum box 44 is mounted on wheels 52 
to permit the entire mold 24 and frame 26 to be moved into and out of 
position beneath the heater hood 28. The vacuum box 44 has a plurality of 
apertures 54 through the bottom wall 46 and connected by piping 56 to a 
source of vacuum (not shown). The vacuum box 44 can be made out of wood or 
other suitable, inexpensive material. The areas where the side and end 
walls meet each other and the bottom must be sealed to prevent air 
leakage. 
Positioned within the vacuum box 44 is a mold matrix comprising a first set 
consisting of forming members 58, 60 and a second set consisting of 
forming members 62, 64. The forming members 58, 60 are disposed in the 
vacuum box 44 opposite each other and are slightly shorter than the side 
48 of the box against which they are positioned resulting in a loose fit. 
Similarly, the forming members 62, 64 are disposed in the vacuum box 44 
opposite each other and are slightly shorter than the distance between the 
forming members 58, 60 so that they too loosely fit in the box 44. When 
all of the forming members 58-64 are in position within the vacuum box 44 
a mold cavity 65 results. The forming member 58 is rectangular in 
cross-section whereas the forming members 60, 62, 64 are L-shaped. The 
extended portion 66 of forming members 62, 64 form the grooves 12 of the 
dasher board 10 and the extended portion 67 forms the surface 13 as will 
be more fully described later. As a result of the loose fit of the forming 
members 58, 60, 62, 64 relative to the sides 48, 50 of the box 44, a 
narrow gap 68 is caused to exist therebetween. Similarly, a gap 70 is 
caused to exist between the ends of the forming members 62, 64 and the 
forming members 58, 60 by the loose fit therebetween. Also as the forming 
members 58, 60, 62, 64 rest on the bottom wall 46 a slight gap 72 exists 
therebetween. As can be seen, the gap 68 communicates with the gaps 70 and 
72 leading into the mold cavity 65 as well as with the atmosphere adjacent 
the forming members 58-64 and the open end of the vacuum box 44. 
A substantially rectangular shaped channel 74 is provided in the side of 
the forming members 58-64 positioned opposite the side walls 48, 50. The 
channels 74 of adjacent forming members are in communication with each 
other around the inside of the vacuum box 44 as shown in FIG. 8 and serve 
to withdraw air from the gap 68 when a vacuum is caused to exist in the 
channel 74. The vacuum existing in piping 56 and apertures 54 is 
communicated to channels 74 by means of recesses 76 in forming members 58, 
60, which recesses are located directly above the apertures 54. Thus, when 
the open end of the mold cavity 65 is covered, air in the cavity is 
withdrawn rapidly and uniformly through gaps 70 and 72 into gap 68 and 
from there into vacuum channel 74 and out through recesses 76 and piping 
56. 
The method of operation of the apparatus and the mold will now be discussed 
with reference to FIGS. 9(a)-9(e). A sheet of thermoplastic material 46 is 
clamped between frame members 36, 40 and the entire mold 24 and frame 26 
are moved to a position beneath the heater hood 28. The frame 26 is raised 
and maintained in a position adjacent the heater hood 28 as shown in FIG. 
9(a) until the required degree of plasticity is achieved in the sheet 46. 
After the sheet of plastic material 34 is lowered to cover the opening of 
the mold cavity 65, a strong vacuum is caused to exist in channel 74 from 
a source not shown which vacuum is rapidly transmitted through gap 68 to 
the area adjacent the forming members 58-64 and the open end of the vacuum 
box 44. The vacuum in gap 68 acts adjacent the periphery of the plastic 
sheet 34 and draws it into sealing engagement with the periphery of the 
open end of the vacuum box 44 and the forming members 58-64 as shown in 
FIG. 9(b). With the open end of the mold cavity now sealed, the cavity is 
rapidly and uniformly exhausted of the air therein through gaps 70 and 72. 
Initially, as shown in FIG. 9(c) the plastic sheet material 34 is caused 
to form around the extended portions 66 and then as shown in FIG. 9(d) 
into the remainder of the mold cavity 65 to take the final shape and 
contour of the mold cavity 65. After the heated sheet material 34 has 
cooled the vacuum is terminated and the completed dasher board backing 
shell 10 together with forming members 62, 64 are removed from the vacuum 
box 44. The forming member extended portions 66 are removed from the 
grooves 12 formed thereby, see FIG. 9(e) and are returned to the vacuum 
box 44. The process can then be repeated. The finished dasher board 
backing shell 10 can be quickly trimmed of any excess material to place it 
in finished form. 
My invention further comprises the method of making the complete dasher 
board as partially shown at 80 in FIG. 10. After the dasher board backing 
shell 10 is formed by the mold 24 as hereinbefore described, the outer 
surface of the shell 10 is covered by fiberglass and polyester resinous 
material 82. The fiberglass and polyester material 82 may be in the form 
of one layer, as shown, or it may be in the form of a plurality of layers 
placed one on the other until the desired thickness is achieved. The shell 
10 thus becomes an integral part of the completed dasher board and in 
effect reduces the number of layer of more costly fiberglass and polyester 
resinous material heretofore required when the dasher board was made 
entirely of such fiberglass and polyester resinous material. 
The present invention has been described in detail above for purposes of 
illustration only and is not intended to be limited by this description or 
otherwise to exclude any variation or equivalent arrangement that would be 
apparent from or reasonably suggested by the foregoing disclosure to the 
skilled of the art.