GB2088998A

GB2088998A - Caulking Gun

Info

Publication number: GB2088998A
Application number: GB8136172A
Authority: GB
Original assignee: Toray Silicone Co Ltd
Current assignee: DuPont Toray Specialty Materials KK
Priority date: 1980-12-04
Filing date: 1981-12-01
Publication date: 1982-06-16
Also published as: AU7822081A; BE891333A; FR2495502A1

Abstract

A caulking gun for dispensing sealant 2 from a bag 1, is characterised by a frusto-conical piston body 6, Fig. 3, backed by a flexible sealing member 16 which prevents snagging of the bag, a piston/piston rod coupling comprising a nut 17, Fig. 3, and a cotter pin 18, a cylinder 4, of light transparent plastics material and a "detent" 15 to prevent the piston slipping backwards. <IMAGE>

Description

SPECIFICATION Caulking Gun Background of the Invention This invention deals with a caulking gun which extrudes bagged sealant.

Conventionally, sealant is packed in a sausageshaped flexible plastic bag. This bagged sealant is then packed in the cylinder of a caulking gun, the tip of the bag is opened, and then a piston pushes the posterior of the bag forward and thus extrudes the sealant. Compared with conventional cartridge-type caulking guns, the advantage of this type of sealant extrusion is that the bag for the internal packaging can be folded into smaller segments. As a result, waste can be significantly reduced. There are, however, certain drawbacks to the use of such a sealant bag in the caulking gun. The bottom of the bag, when pushed by the tapered piston face, may be caught between the piston and the cylinder thus hampering the smooth motion of the piston, sometimes leading to a failure of extrusion.

Since the sealants are generally high viscosity elastomeric materials, the piston that is used to push the sealant may frequently be pushed back by the internal pressure existing in the sealant.

Backward movement of the piston not only makes the extrusion of sealant from the tip of the nozzle sporadic and unreliable, but also causes other flaws such as the introduction of air. In the sausage-type caulking gun, a threaded attachment is used to attach the piston to the tip of the piston rod and this threaded attachment, coupling the piston rod and the piston, loosens from torque auction during work when the cylinder is rotated, frequently making the gun malfunction and the caulking work more difficult.

Finally, such guns are usually made of metal, they are heavy and become especially inconvenient in high workplaces. In addition, because they are made of metal, it is impossible to know the conditions of the sealant inside them.

At times air may be mixed without notice and the extrusion operation is affected.

The present invention overcomes these problems. It provides a new kind of caulking gun which is lightweight, making it easier to use in high workplaces. In addition, at any time during operation, the condition of the sealant inside may be observed. Further, this invention provides a caulking gun wherein the piston cannot disengage from the piston rod during work. Also, this invention provides a caulking gun wherein retraction of the piston during operation of the gun caused by the internal pressure of the sealant is prevented and, finally, this invention provides a novel two part piston that prevents snagging of the sealant bag and allows smooth uniform extrusion of the sealant.

Summary of the Invention According to this invention, sealant is extruded from a flexible plastic bag through a nozzle at the forward tip of the cylinder. It is characterized by the fact that the surface of the piston in contact with the sealant bag consists of two parts: a truncated conical portion and a planar portion extending from the base of the truncated conical portion in a plane perpendicular to the piston axis; the piston has attached to its rear end a soft, flexible, elastic material that is in tight contact with the surface of the cylinder; the piston and piston rod cannot separate during working because of the presence of a cotter pin and the cylinder of the gun is manufactured from transparent plastic so that the contents of the sealant bag are visible.

Brief Description of the Drawings Figure lisa side view of the sealant bag used in the caulking gun of this invention.

Figure 2 presents a side view of the caulking gun of this invention.

Figure 3 is a detailed vertical cross-sectional view of the fixed piston taken along the longitudinal axis of the piston rod.

Figure 3(A) is an oblique view of the piston.

1-bag; 2-sealant; 4-cylinder; 6nozzle; 6-piston; 6a-cone; 6h-planar portion; 7piston rod; 16-packing material; 17-threaded nut; 18-cotter pin.

This invention therefore consists of a piston actuated caulking gun for extruding sealants through a nozzle from a flexible plastic bag, the improvements comprising mounting the piston on the forward end of the piston rod with a threaded nut locked by a cotter pin, in order to stabilize the piston and piston rod against relative rotation wherein the piston is in contact with the bagged sealant which piston comprises two parts: a truncated conical portion and a planar portion extending circumferentially from the base of the conical portion in a plane perpendicular to the piston axis and wherein there is attached to the back of said piston a flexible packing material such that the packing material positively contacts the internal surface of the cylinder and wherein the cylinder is manufactured from a transparent plastic material.

Description of the Preferred Embodiments Figure 1 shows the sealant bag used in the caulking gun of this invention. Bag 1 is formed from a tube of plastic film and is filled with sealant 2. The two ends of the bag are closed by clamps 3. The following materials can be used as sealants: silicone sealants, polysulfide sealants, polyurethane sealants, acrylic sealants, and oil caulk.

Figure 2 shows the caulking gun of this invention, with the above-mentioned sealant bag ioaded into the cylinder and partially compressed.

This figure shows the process of extrusion when the tip of the bag has been opened. In this figure, 4 represents the cylinder, with nozzle 5 mounted on its front end.

The transparent plastic material of cylinder 4 can be selected from polymethacrylic or polyacetal resins.

It can be seen from the above example that as the body of cylinder 4 is made of plastics with a specific weight much lower than that of metals, this kind of caulking gun is lightweight and can easily be used in high workplaces. In addition, as transparent material is used in making cylinder 4, the condition of sealant 1 can be observed easily.

Therefore, any abnormal situation, such as the presence of mixed air, can be found and the operation stopped until appropriate measures are taken. Inside the cylinder 4 is a piston 6, which is mounted on the head of piston rod 7 and which can move reciprocally along the rod axis. Piston rod 7 penetrates through the rear end of cylinder 4 and the upper portion of grip 8, which is mounted at the rear of the cylinder A handle 9 is fixed at the rear of the piston rod. Metal piece 11 is slideably fitted to the piston rod 7 in the upper portion of grip 8. Metal piece 11 is combined with the upper end of trigger 12. Behind it, a detent 15 is suspended in a movable way by detent mounting 14 with spring 13 at its rear.Therefore, when trigger 12 is pulled into the engaged state of said detent 15 mentioned above, piston rod 7 is pushed forward through the detent toward nozzle 5 via frictional engagement of metal piece 11, and the sealant 2 in bag 1 is extruded by piston 6.

A packing made of soft, elastic materials such as rubber or leather 16 is attached to the rear of the piston 6, and the external peripheral surface of this packing 16 is designed to positively contact the internal surface of the cylinder 4.

When a bagged sealant is pushed by the piston action, the piston 6 will push the rear end of the bagged sealant with the conical portion 6a. On the planar portion below the conical portion, the planar surface part 6b whose plane is perpendicular to the direction of the movement will accept and retain the rear end of the empty bag from the bagged sealant. As a result, the rear end of the bag 1 will be folded onto the planar surface 6b, and therefore it will not be snagged in the space between the piston 6 and cylinder 4.

Moreover, due to pushing by the above said piston 6, an internal pressure is generated in the bagged sealant and a repulsive force to push back the piston 6 will be at work. However, since the soft, elastic packing 16 located at the rear of the piston 6 is tightly contacting the internal surface of the cylinder 4, it works to prevent the backward slippage of the piston 6. Therefore, one can eliminate the introduction of air or sporadic outpouring of the sealant from the tip 5 that might be caused by the retraction of the piston 6.

As illustrated in detail in Figure 3. piston 6 is borne by the forward tip of piston rod 7. The piston 6 is also fixed to the piston rod tip with threaded nut 17. A cotter pin 18 is inset in the surface of piston 6 and inserted into the portion of piston rod 7 to which the piston 6 is rigidly attached, with the cotter pin extending through piston 6, nut 17 and piston rod 7 at the same time to prevent piston rod 7 from rotating around the rod axis. Thus, even if the sealant is extruded with continued rotation of cylinder 4 to move the tip of the nozzle 5 to fit the pattern of the joint at the working site, and even if a certain degree of torque from the rotation of this cylinder 4 is transmitted to the piston 6, such relative rotation of the piston 6 and the piston rod 7 will not loosen the threaded engagement of nut 1 7 with piston 6.

As shown in Figure 3(A), the front surface of piston 6, which is in contact with bag 1, consists of a truncated conical portion 6a and a planar portion 6b, which extends circumferentially from the base of the conical portion 6a and in a plane perpendicular to the piston axis. Piston 6, including truncated conical portion 6a and planar portion 6b, can be made from any plastic or metal material. For example, the following plastics can be used: polyacetals, nylon, polypropylene, phenol resin, or epoxy resins; the following metals can be used: aluminum, alumite, and stainless steel.

When sealant is extruded by the piston of the caulking gun mentioned above, the rear end of the sealant bag is pushed forward by the truncated conical portion 6a. At the same time, the emptied portion of bag 1 is retained by the planar surface 6b, which is at a right angle to the direction of motion. Contrary to what occurs with the use of a prior art piston, the rear end of the emptied bag will never be caught between the cylinder and the piston. Moreover, unlike the prior art piston, which has an acute angle tapered conical face, damage or abrasion from insufficient strength will seldom happen. In addition, from the combination of planar portion 6b and conical portion 6a, dead space will be small and sealant will not be wasted.

Claims

1. A piston actuated caulking gun for extruding bagged sealants through a nozzle from a flexible plastic bag, the gun comprising a removable piston, a piston rod, a cylinder for cooperation with the piston and for supporting the flexible plastic bag, a nozzle on the cylinder, a detent for maintaining the piston position in the cylinder, and a handle, the improvement comprising mounting the piston on the forward end of the piston rod with a threaded nut locked by a cotter pin in order to stabilize the piston and piston rod against relative rotation, wherein the piston is in contact with the bagged sealant which piston comprises two parts: a truncated conical portion and a planar portion extending circumferentially from the base of the conical portion in a plane perpendicular to the piston axis and, wherein there is attached to the back of said piston a flexible packing material such that the packing material positively contacts the internal surface of the cylinder and, wherein the cylinder is manufactured from a transparent plastic material.

2. A caulking gun according to Claim 1, substantially as herein before described with reference to the accompanying drawings.