WO1993003636A1

WO1993003636A1 - Welding helmet with controllable protective lens

Info

Publication number: WO1993003636A1
Application number: PCT/US1992/004888
Authority: WO
Inventors: Richard D. Bean
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-08-19
Filing date: 1992-06-09
Publication date: 1993-03-04
Anticipated expiration: 1994-02-19
Also published as: CA2094033A1; AU2266492A

Abstract

A welding helmet (10) includes a breath activated protective lens assembly (17, 90) which can replace a standard lens assembly of a conventional helmet. A new lens structure (18, 91) with a pneumatic device (20, 110) operates the protective lens (40, 100) within the lens structure (18, 91) and replaces the standard lens. The lens structure includes a slidably mounted frame (42, 102) with the protective lens (40, 100) mounted within the frame (42, 102) and encompassed by safety lenses and placed together in a package. A pneumatic device (20, 110) operated by the breath of the welder pushes the protective lens (40, 100) to cover an opening (88, 97) in the housing (34, 92) of the lens structure (18, 91) to protect the eyes of the welder during welding. Sucking on the mouthpiece (24, 122) or gravity allows the frame (42, 102) to drop and thereby leaves a clear view for the welder to see the fixture that is to be welded. The breath activated lens assembly (17, 90) can be added as a kit to a standard conventional welding helmet.

Description

DESCRIPTION

WELDING HELMET WITH CONTROLLABLE PROTECTIVE LENS

TECHNICAL FIELD

This invention relates generally to welding helmets and more particularly to a welding helmet including a breath controlled sliding protective lens.

BACKGROUND ART

It has long been a problem for welders using electric arc welding apparatus to properly position the electrode before striking the electric arc and yet establish the protective lens in front of their eyes before the arc is established. The welding helmets are required to protect the face and the eyes of the welder. Not only does the helmet protect against the heat, sparks and debris from hitting the face of the welder, an eyeshield is also required to filter out or reduce the intensity of the light produced by the electric arc. Conventionally, the welder's head by adjustable straps or a cage. The eyeshield or lens is required to be made of very dark glass to filter out the intensity of the light produced by the electric arc. It is generally impossible to see out of the mask and eyeshiuld without the electric arc. Traditional welding helmets are pivotable upon the head strap to allow the welder to flip the mask up to see the material that is to be welded and yet to flip the mask down to position the helmet and the protective lens when arc welding. This is, of course, time consuming and cumbersome because the welder must use his free hand to operate the helmet.

Some welding helmets have independently pivotable eyeshields which only require the pivoting of the eyeshield rather than the entire mask. This still requires keeping one hand free tυ move the lens. There have been several attempts to utilize a mechanically operated eyeshield. Motors and other apparatus have been connected to the lens in order to move the lens into and out of position. But the added apparatus only added weight to the helmet and this weight could encumber the welder while in a bent over position during the welding process.

Other prior art have attempted to use the breath of the welder to open and close the _ens as the welder blows or sucks into a hose attached to the lens opening apparatus. All of the prior art apparatus required the addition of apparatus to a standard helmet and all added additional weight to what is already a cumbersome helmet. An object of the present invention, therefore, is to provide a lens which can be easily substituted for the standard protective lens of the welding helmet while providing a simple means using the breath of the operator to control the positioning of the protective lens.

DISCLOSURE OF THE INVENTION

The present invention relates to a welding helmet having a breath activated eyeshield. A welding helmet includes a mask casing having a viewing opening. Means are including for mounting the helmet to the head of a welder. The casing viewing opening includes a lens mounting frame formed around the periphery of the casing viewing opening. In particular, the lens assembly includes an eye protective darkened lens structure operated by a pneumatic device controlled by a mouthpiece placed adjacent to the mouth of the welder. The lens assembly is provided as a kit for replacement of the standard lens structure and is an improvement to a standard welding helmet. The lens structure is mounted within the lens mounting frame. A clip holds the lens structure in place within the lens mounting frame.

The present invention replaces to protective darkened glass lens and its mounting with the lens assembly that includes a protective darkened welding lens slidably mounted within a housing that includes a viewing opening. Clear safety lenses are mounted to the housing with the housing supporting the safety lens and holding the structure assembly together. The pneumatic device includes a cylinder and a piston that is connected to the movable protective lens. The piston is movable within the pneumatic device to cause the protective lens to slide within the housing by air pressure or vacuum, as supplied by the welder by blowing or sucking air through the mouthpiece.

An object of the present invention, therefore, is to provide a structure which can replace the standard protective lens in a welding helmet.

Another object of the present invention is to provide an improvement to a conventional welding helmet that enhances the operation of the protective lens within a welding helmet.

A principle object of the present invention is to provide a welding helmet with an easily replaceable eyeshield that is controlled by the breath of the welder to raise and lower the protective lens as the welder moves between a welding and assembly operation.

Another object of the present invention is to provide a welding helmet which can be easily added to a conventional welding helmet and which relies completely on the inhaling and exhaling of breath to control the positioning of the protective lens into and out of the viewing opening of a welding helmet. Yet another object of the present invention is to provide an enhanced welding helmet that can control the positioning of the protective lens in front of the welder's view without requiring the handling of the helmet or the lens by the hands of the welder.

These and other objects will become clearer as the description of the present invention continues.

BRIEF DESCRIPTION OF THE DRAWINGS

The various novel features of this invention along with the foregoing and other objects, as well as the invention itself, both as to its organization and method of operation, may be more fully understood from the following description of illustrated embodiments when read in conjunction with the accompanying drawings wherein:

Fig. 1 is a perspective view of a welding helmet containing the present invention;

Fig. 2 is a perspective view of the rear of the welding helmet as shown in Fig. 1;

Fig. 3 is a sectional view taken along lines 3-3 of Fig. 1;

Fig. 4 is an exploded view of the present invention as added to the helmet shown in Fig. 1;

Fig. 5 is a plan view showing the completed assembly of the invention as shown in Fig. 4;

Fig. 6 is a sectional view taken along lines 6-6 of Fig. 5; δ

Fig. 7 is a sectional view taken along lines 7-7 of Fig. 5;

Fig. 8 shows a second embodiment of the present invention useful with the welding helmet as shown in Fig. 1;

Fig. 9 is an exploded view of an alternate embodiment of the present invention;

Fig. 10 is a partial sectional side view of the upper portion of the embodiment illustrated in Fig. 9;

Fig. 11 is a partial sectional view of the pneumatic assembly of the embodiment illustrated in Fig. 9;

Fig. 12 is a perspective view of the rear of a welding helmet containing the embodiment of the present invention illustrated in Fig. 9; and

Fig. 13 is a partial sectional top view illustrating the retention of the lens assembly in the helmet. BEST MODES FOR CARRYING OUT THE INVENTION

As shown in Figs. 1 and 2, a welding helmet 10 includes a casing 11 and a standard headband 12 which is adjustable to fit a variety of heads and includes an over the top of the head stabilizing strap and a behind the head adjustment section 14. The casing 11 is generally secured to the strap by a hinge means (not shown) which allows helmet 10 to be tilted out of the way without requiring complete removal from the head of the welder. The casing 11 itself generally comprises a heavy paperboard shell or formed plastic material which essentially covers the front half of the head of the welder. The front of casing 11 includes a casing viewing opening 16. The casing viewing opening 16 is configured to provide a line of sight for the welder when the helmet 10 is positioned on the welder's head. A lens structure 18 is placed within the casing viewing opening 16. The lens assembly of this invention generally designated 17 includes the lens structure 18 having a darkened protective lens, as will be discussed in a later figure, operable by a pneumatic device 2 d connected by a tubing 22 to a mouthpiece 24. Openings are provided in helmet 10 in this embodiment of the present invention, thus an opening 25 is provided for the pneumatic device 20 to actuate the lens structure 18 as will be discussed later. Openings 26 and 28 are also provided for tubing 22 for this embodiment to place mouthpiece 24 adjacent to the mouth of the welder. A clip 30 holds the lens structure 18 into place in viewing opening 16 as is shown in Fig. 2. A better view of the interconnection of the present invention with helmet 10 is shown in Fig. 3.

In Fig. 3, the interior of helmet 10 is shown with lens structure 18 held in place within a lens mounting frame structure 19 viewing opening 16 by the clip 30 engaging a retaining member 31. A seal 32 generally encompasses the periphery of viewing opening 16 to prevent the welding gases from entering the interior of helmet 10 and thereby disturbing the breathing and health of the welder. An exploded view of lens structure 18 and the operation portions of the pneumatic device 20 is shown in Fig. 4.

In the first embodiment of the present invention as shown in Fig. 4, lens structure 18 includes a housing 34 having a cut-out section 36 with an opening 38 formed in cut-out section 36. A conventional darkly colored protective lens 40 is held in place within a frame 42. The protective lens 40 can be made of glass or plastic such as is conventional in welding helmets.

The frame 42 has a width dimension that permits an up and down slideable motion within the width of cut-out section 36 of housing 34. The cut-out section 36 has a height dimension that permits tire complete covering of opening 38 with protective lens 40 when positioned in its upward most travel within cut-out section 36. The frame 42 includes a linkage connection 44. Clear safety lenses 46 and 48 are positioned on opposite sides of housing 34 to provide protection to protective lens 40 and the user when lens 40 is in a lowered position. The aluminum frame 50 fits within seal 32 as was discussed in Fig. 3. An optional pair of U-shaped brackets 52 and 54 encompass safety lens 46 to hold lens structure 18 into place as one assembly.

The pneumatic device 20 includes a standard 56 which permits the attachment of the pneumatic device 20 to housing 34 by screws 58, for irstance. The pneumatic device 20 includes a piston 60 and a shaft 62 that are held in place within a cylinder 64 of pneumatic device 20 by a plug 66. The tubing 22 attaches to plug 66 at one end of the tubing. The mouthpiece 24 is attached to the other end of tubing 22. The shaft 62 protrudes through an opening 68 in standard 56 and an opening 70 in housing 34. A flattened section 72 of the shaft 62 protrudes through the openings 68 and 70 and interfaces with linkage connection 44 of frame 42. A cotter pin 74, for instance, can be used to connect shaft 62 to frame 42. A plan view of lens structure 18 is shown in Fig. 5. The completed lens structure 18 and its attachment to pneumatic device 20 is shown in Fig. 5. The brackets

52 and 54 as shown at the outer edges of lens structure

18 holds the entire assembly together. The pneumatic device 20 has its cylinder 64 attached to housing 34 by screws 58. The shaft 62 of pneumatic device 20 is attached by cotter pin 72 to frame 42. As was stated previously, frame 42 is mounted for slidably operation within cut-out section 36 of housing 34. The lens 42 is of a size to completely cover opening 38 within housing

34. A sectional view from the top is shown in Fig. 6.

In Fig. 6, brackets 52 and 54 encompass the clear safety lenses 46 and 48 together with housing 34 and frame 42. The aluminum frame 50 is not captured by brackets 52 and 54 and is positioned within the viewing opening 16 of helmet 10 as was shown in Fig. 3. A side view of lens assembly 17 is shown in the cross-sectional view of Fig. 7.

In Fig. 7, lens assembly 17 of the present invention including lens structure 18 and pneumatic device 20 is shown in section view to show the interconnection between the two assemblies. The housing 34 has frame 42 and protective lens 40 enclosed within its cut-out section 36 for slidable operation up and down in the figure. The linkage connection 44 of housing 42 is connected to shaft 62 of pneumatic device 20. The shaft 62 in turn is connected to piston 60 all within cylinder 64 of pneumatic device 20. The plug 66 is fastened to the bottom of cylinder 64 while allowing air from tubing 22 to enter within cylinder 64 and either push piston 60 upwards if air pressure is applied or to pull the piston downward if a vacuum is applied. Moving of the piston up and down causes shaft 62 to move up and down which in turn will slide frame 42 and lens 40 up and down to cover and uncover opening 38 in housing 34. If pressure is applied to the interior of cylinder 64 the piston 60 and shaft 62 will move frame 42 and lens upward such that protective lens 40 completely covers opening 38 to protect the eyes of the welder when the arc welding is actually taking place. When piston 60 and shaft 62 is moved downward, frame 42 and protective lens 40 are dropped away from opening 38 thereby allowing a clear view of the assembly as it is being welded by the welder.

In the operation of the present invention, reference is made to Figs. 1-7. In the operation of the present invention, a standard welding helmet 10 is obtained, clip 30 is removed and the standard lenses of conventional welding helmet are removed. A lens structure 18 is assembled as shown in Fig. 4 with frame 42 containing protective lens 40 inserted into cut-out section 36 of housing 34. The standard 56 of pneumatic device 20 is then attached to housing 34 by screws 58. Shaft 62 with flattened section 72 is then passed through holes 68 of standard 56 and hole 70 in housing 34 in order to place flattened section 72 into linka e connection 44. The cotter pin 74 is then fastened through linkage connection 44 and flattened section 72 to hold the shaft to frame 42. The clear safety lens 46 and 48 are then placed over housing 34 and brackets 52 and 54 are placed over safety lenses to hold the entire assembly in place. The plug 66 is passed into cylinder 64 of pneumatic device 20 and tubing 22 and mouthpiece 24 reconnected to pneumatic device 20. The aluminum frame 50 is then placed into viewing opening 16 of casing 11 and the remaining portions of lens structure 18 i-3 then placed into the lens mounting frame structure 19 of helmet 10. Clip 30 is then replaced into casing 11 to hold lens structure 18 in place. Mouthpiece 24 is placed adjacent to the welder's mouth for operation of the movement of protective lens 40 to cover the uncover opening 38 in housing 34. The opening 25 may be formed into helmet 10 for pneumatic device 20. Likewise, openings 26 and 28 may be formed into casing 11 of helmet 10 for tubing 22 in order to easily place mouthpiece 24 into position adjacent to the mouth of the welder. The openings 25, 26 and 28 are optional depending upon the wishes of the welder.

Helmet 10 is then placed over the head of the welder with headband 12 over the head of the welder. The adjusting strap 14 can be tightened or loosened accordingly to hold helmet 10 in place. The welder then places mouthpiece 24 into his mouth and is ready to perform his arc welding duties without further hand adjustment of the protective lens. To remove protective lens 40 from covering opening 38, the welder can either suck onto the mouthpiece to draw the piston downward in the cylinder to pull frame 42 and protective lens 40 downward out of covering of opening 38. The fixture or item to be welded is thus in clear view of the welder since it is only the clear safety lenses 46 and 48 through which the welder needs to look to see the object that is to be welded. By blowing air through mouthpiece 24, piston 16 moves upward in cylinder 64 and through shaft 62, moves the frame 42 and protective lens 40 slidably upward to cover opening 38 in housing 34. The welder does this when he is ready to strike the arc. He can continue to hold the items that need to be welded with his one hand while he holds the arc torch in his other hand.

Thus a standard welding helmet can be improved to include lens assembly 17 of the present invention to thereby permit ease of welding by the welder, especially if many single small tack welds, for instance, need to be taken before the entire fixture can be permanently welded. The welder can use his breath to position the protective lens into and out of his view quickly to perform the tack welds and reposition the arc welding torch easily between many individual welds quickly and without fatigue which could be caused by either flipping a lens up and down using his har.d or moving his entire helmet up and down as the individual welds are required. The invention can be provided as a kit to be assembled directly into the new helmet.

A second embodiment of the lens assembly 17 is shown in Fig. 8. In Fig. 8, similar reference numbers represent parts usable in either embodiment. In Fig. 8, a housing 80 includes housing 34 and brackets 52 and 54 of the prior embodiment all into one assembly. Housing 80 includes a cut-out section 82 ..n the similar manner as the cut-out section 36 in the embodiment of Fig. 4. Frame 42 and protective lens 40 are placed into cut-out section 82 and are connected to shaft 62 of pneumatic device 20 in the same manner as described previously for Fig. 4. The clear safety lenses 46 and 48 slide into formed sections of housing 80 to cover the entire assembly. Housing 80 includes guides 84 and 86. Safety glass 46 slides into guide 84 while safety glass 48 will slide into guide 86. This embodiment includes a lesser number of separate parts anc. provides an easier construction of lens assembly 17 for use with helmet 10 as shown in Fig. 1. Referring now to Fig. 9, a -^:urther embodiment of a lens assembly generally designated 90 is illustrated.

Lens assembly 90 includes a lens structure 91 having a housing 92 with a planar front surface 93 and a planar back surface 94. A cut-out section 95, is inset from back surface 94, with an opening 97 formed therein extending through front surface 93. Housing 92 has a front flange 98 extending along each side and bottom, projecting outward perpendicular ;o front surface 93. A back flange 99 extends from the sides and bottom of housing 92, and projects perpendicularly outward from back surface 94.

A frame 102 containing a conventional darkly colored protective lens 100, is slidably mounted within cut-out section 95. Frame 102 has a width dimension that permits an up and down slidable motion vithin the width of cut out section 95, and has a height dimension that permits the complete covering of opening 97 with protective lens 100 when positioned in its uppermost travel within cut¬ out section 95. Frame 102 includes a linkage connection 103. Protective lens 100 can be easily replaced simply by tilting protective lens 100 out of frame 102 in a direction towards back surface 94. The elements used to prevent protective lens 100 from falling out of frame 102 when in use, will be discussed in greater detail below. Lens assembly 90 also includes a pneumatic device 110 having a piston 112 and a shaft 113 that are held in place within a cylinder 114 of pneumatic device 110 by a plug 115. Cylinder 114 includes a piston bore 117 containing piston 112 and shaft 113. A lateral bore 118 extends through cylinder 114 adjacent to and parallel to piston bore 112. Lateral bore 118 is in fluid communication with piston bore 117 at the lower end of cylinder 114 proximate plug 115. Lateral bore 118 has an outlet 119 proximate housing 92 fitted with a coupling 120 to which a mouth piece 122 at the end of a flexible hose 123 is attached. Cylinder 114 of pneumatic device 110 extends from and is integral with housing 92. In this embodiment, housing 92 and cylinder 114 are molded in a single unit.

Shaft 113 protrudes through an opening 124 which communicates between piston bore 117 of cylinder 114 and cut-out section 95 of housing 92. A flatten section 125 of shaft 113 protrudes through opening 124 and interfaces with linkage connection 103 of frame 102. A cotter pin 127, for instance, can be used to connect shaft 113 to frame 102.

A clear safety lens 104 is mounted inside the perimeter of front flange 98, flush with front surface 93 of housing 92. A second clear safety lens 105 is mounted inside the perimeter of back flange 98, flush with back surface 94. This configuration may be used, as illustrated in Figs. 12 and 13 which will be discussed below, or optionally, U-shaped brackets 128 and 129 may be added to hold clear safety lenses 104 and 105 securely against front surface 93 and back surface 94 respectively. Clear safety lenses 104 and 105 slide into engagement with front surface 93 and back surface 94 to cover the entire assembly. The attachment of U-shaped brackets 128 and 129 to the sides of housing 92 form guides 130 and 132. Clear safety lens 104 slides into guide 130 while clear safety lens slides into guide 132.

With further reference to Fig. 10, it can be seen that when clear safety lenses 104 and 105 are slid into guide 130 and 132 into engagement with front surface 93 and back surface 94, a front tab 107 extending from the upper portion of housing 92 perpendicular to front surface 93 and a back tab 108 extending from the upper portion of housing 92 is perpendicular to back surface 94, prevents clear safety lens 104 and 105 from unintentionally sliding out of guides 130 and 132. To remove safety lenses 104 and 105, each must be bent slightly outward, allowing them to slide past front tab 107 and back tab 108.

In operation, an operator looks through clear safety lens 104 and 105 aligned with opening 97 of housing 92. Air pressure applied to piston 1.12 through mouth piece 122, causes piston 112 to rise in piston bore 117 pushing frame 112 and protective lens 100 over opening 97 in its uppermost travel within cut-out section 95. Frame 102 is held in this position by a magnet 133 affixed to its upper surface, which corresponds to a complemental magnet 134 affixed to the upper portion of cut-out section 95. This allows the operator to concentrate on his welding without maintaining air pressure on mouth piece 122. To lower protective lens 100, a negative air pressure is applied to mouth piece 122, pulling piston 112 downward, and breaking the magnetic engagement between magnet 133 and 134.

Protective lens 100 and clear safety lens 104 and 105 are easily replaced by sliding clear safety lens 104 and 105 out of guides 130 and 132, allowing removal of protective lens 100 from frame 102.

Referring now to Fig. 12, helmet 10 is illustrated with lens assembly 90 of the present embodiment replacing conventional lenses (not shown) , and held in place by clip 30. Clip 30 extends from helmet 10, and pivots down over lens assembly 90 to engage a retaining member 31. Lens assembly 90 may be installed substantially similar to the installation of the lens ^assembly shown in Figs. 1-3. However, in this embodiment lens assembly 90 does not employ a tube 22 and therefore, helmet 10 does not require openings 26 and 28. Instead, mouth piece 122 extends from outlet 119 of cylinder 114 inside helmet 10. Flexible tube 123 coupling mouth -piece 122 to outlet 99, provides mouth piece 122 with some flexibility enabling slight adjustments by the user.

With further reference to Fig. 13, lens assembly 90 is installed on helmet 10 without U-shaped brackets 128 and 129. It will be understood that U-shaped brackets 128 and 129 may be used to hold lens assembly 90 into a single unit, installed in helmet 10, but for purposes of illustration, U-shaped brackets 128 and 129 have not been employed. In this case, clear safety lens 104 is placed in frame 19, housing 92 containing frame 102 and protective lens 100 is placed in position on clear safety lens 104. Finally clear safety lens 105 is placed in engagement with back surface 94 of housing 92. If U- shaped brackets 128 and 129 were being used, the entire lens structure 91 would be placed in bracket 19 of helmet 10. Lens structure 91 is then held in place by engaging clip 30, which presses against safety lens 105, retaining lens assembly 90 securely in plac .

Clip 30 is used on a number of conventional helmets, to hold conventional lens over helmet view opening 16. Therefore, in the preferred embodiment, lens structure 91 is of a size compatible with the conventional lenses used in helmet 10 and may be easily substituted for those lenses. Furthermore, the use of clip 30 allows for quick and simple removal of lens assembly 90 for replacement of protective lens 104 and 105 or protective lens 100.

The principles of the present invention have now been made clear in illustrative embodiments. It will be immediately obvious to those skilled in the art, many modifications of structure, arrangement, proportion, the elements, materials, and components used in the practice of the invention. For instance, helmet 10 may be made of a light weight metal with or without openings 25, 26 and 28 formed therethrough to hold pneumatic device 20 and tubing 22. Likewise, frame 42 with protective lens 40 may be of a width dimension to slidably fit within cut¬ out section 36 of housing 34 and thus the breath of the welder pushes frame 32 and protective lens 42 upward. Gravity can be used to lower lens 42 when the welder no longer is blowing air or holding his breath. Or, frame 42 can be a friction fit within cut-out section 46. In this instance, blowing air will raise protective lens 40, friction holds frame 42 and protective lens 40 covering the housing viewing opening 38, and sucking the air from cylinder 64 through mouthpiece 24 lowers protective lens 40. The appended claims are, therefore, intended to cover and embrace any such modification, within the limits only of true spirit and scope of the invention. Various changes and modifications to the embodiment herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof which is assessed only by a fair interpretation of the following claims.

Having fully described the invention in such clear and concise terms as to enable those skilled in the art to understand and practice the same, the invention claimed is:

Claims

CLAIMS 1. A breath-operated lens assembly comprising:

a housing having a front surface a back surface and a view opening extending therebetween;

a frame containing a protective lens, slidably mounted in said housing, having a raised position wherein said protective lens covers said view opening and a lowered position wherein said view opening is uncovered;

a pneumatic device coupled to said housing, for moving said frame and said protective lens between said lowered position and said raised position;

a safety lens engaging said back surface of said housing, and retaining said protective lens in said frame; and

means for securing said safety lens to said back surface of said housing.

2. A breath-operated lens assembly as claimed in Claim 1 wherein said securing means are guides formed in said housing which slidably receive said safety lens.

3. A breath-operated lens assembly as claimed in Claim 1 for use on a welding helmet having a casing surrounding at least the face of a wearer, a helmet viewing opening extending through said casing, said lens assembly further comprising means for fastening said lens assembly to said casing, covering said helmet viewing opening.

4. A lens assembly as claimed in Claim 3 wherein said fastening means is a clip extending from said casing which contacts said lens assembly and engages a retaining member.

5. A lens assembly as claimed in Claim 4 wherein said securing means are guides formed in said housing which slidably receive said safety lens.

6. A lens assembly as claimed in Claim 4 wherein said clip further acts as said means for securing said safety lens to said housing.

7. A lens assembly as claimed in Claim 2 wherein said pneumatic device including:

a cylinder;

a piston operable within said cylinder;

a shaft attached to said piston, and extending through an opening in said cylinder and said housing, to engage said frame;

an air passage coupled to said cylinder for permitting injection of air thereinto.

8. A lens assembly as claimed in Claim 5 further comprising a second safety lens engaging said front surface of said housing.

9. A lens assembly as claimed in Claim 8 further comprising second guides formed in said housing which slidably receive said safety lens.

10. A lens assembly as claimed in Claim 9 wherein said first guides and said second guides are formed by U- shaped brackets affixed to opposing sides of said housing.